JP4194250B2 - Image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that develops a latent image on a latent image carrier to form an image.
[0002]
[Prior art]
As an image forming apparatus such as a copying apparatus, a printer, or a facsimile, an electrophotographic process is used to form a latent image on a latent image carrier, and a developer (hereinafter referred to as “toner”) is attached to the latent image for development. In some cases, a visible image is formed and the toner image is transferred to a recording medium (transfer paper) to form an image.
[0003]
In such an image forming apparatus, as a developing device for developing a latent image, conventionally, the toner stirred in the developing device is carried on the surface of the developing roller as a developer carrying member, and the developing roller is rotated. The developer or toner that is transported to a position facing the surface of the latent image carrier, develops the latent image on the latent image carrier, and is not transferred to the latent image carrier after completion of development, is rotated by a developing roller. There is a known one in which the developer or toner is newly agitated and charged, and is again carried on the developing roller and transported.
[0004]
Further, as described in JP-A-5-19615, as a developing device, toner is transported by using electrostatic force on the surface of the developing roller, and the developing roller is driven by a suction force generated between the latent image carrier and the developing roller. The toner is separated from the surface and adhered to the surface of the latent image carrier, or as described in Japanese Patent Application Laid-Open No. 59-181375 or the like, using a transport substrate that transports the toner with an electrostatic force. In some cases, the toner is transported to a position facing the latent image carrier, and the toner is separated from the transport surface by the suction force generated between the toner and the latent image carrier, and is attached to the surface of the latent image carrier.
[0005]
[Problems to be solved by the invention]
However, in the image forming apparatus in which the toner is attached to the latent image carrier using the developing roller described above, the toner is attached to the latent image carrier by the toner attraction by a strong electric field or an alternating voltage from the developing roller. Development, the latent image carrier is likely to cause brush marks, spikes, and toner scattering, resulting in scumming. In particular, during development, a small amount of charged toner adheres to the latent image carrier regardless of the amount of charge of the toner, so that the charged toner has a low adhesion to the latent image carrier during the development process. There is a problem that is easily scattered.
[0006]
In addition, when the toner is charged by frictional charging or corona discharge charging, the saturated charged toner and the unsaturated charged toner are mixed and have a large charge distribution. When such toner is forcibly transferred to the developing roller using a magnetic brush, a transfer roller or the like, the developer once carried on the developing roller at a developing speed of the developing roller (linear speed of about 100 cm / sec). Among them, there is a problem that the toner having a small charge is separated, and the toner is scattered or the background of the formed image is easily stained.
[0007]
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that has a simple configuration, has less toner scattering, and provides high image quality.
[0008]
[Means for Solving the Problems]
  In order to solve the above problems, an image forming apparatus according to the present invention provides:
  In an image forming apparatus for supplying toner onto a latent image carrier and developing the latent image on the latent image carrier to form an image,
  ChargedAboveA plurality of electrodes for generating a spatial traveling wave electric field for conveying toner toward the one end side by electrostatic force along the conveying surface;AboveFrom one end sideAboveCausing the toner to fly toward the latent image carrier,A pair of electrode surfaces facing each otherA transfer substrate;
  An alternating electric field is generated between the electrodes at the one end of the pair of transport substrates,Means for generating a toner cloud by toner flying from one end side of the transport substrate; and,With
  The plurality of electrodes on the transport substrate are disposed with increasing density in stages along the toner transport direction.
The configuration.
[0009]
  here,It is preferable that an intermediate transport substrate facing each of the pair of transport substrates facing each other is provided.
[0010]
In addition, it is preferable to have a reverse conveyance substrate that conveys toner toward the other end portion by electrostatic force along the conveyance surface facing the conveyance substrate. Furthermore, it is preferable to have a toner gutter that collects toner that has not been used for development. This toner gutter preferably has a reverse conveying member for conveying the collected toner in the reverse direction.
[0011]
Furthermore, it is preferable that a means for generating a DC electric field is provided between the electrode of the transport substrate and the latent image carrier. It is preferable that a means for generating a direct current electric field is provided between the electrode provided on the outer surface side of the transport substrate and the latent image carrier.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an image forming apparatus according to a first embodiment of the present invention will be described with reference to FIG. FIG. 2 is an overall schematic configuration diagram of the image forming apparatus.
The overall outline and operation of the image forming apparatus will be described. A photosensitive drum 1 (for example, an organic photosensitive member: OPC), which is a latent image carrier, is rotationally driven clockwise in FIG. When a document is placed on the contact glass 2 and a print start switch (not shown) is pressed, the scanning optical system 5 including the document illumination light source 3 and the mirror 4 and the scanning optical system 8 including the mirrors 6 and 7 are moved. The original image is read.
[0013]
Here, the scanned document image is read as an image signal by the image reading element 10 disposed behind the lens 9, and the read image signal is digitized and subjected to image processing. Then, a laser diode (LD) is driven by the signal subjected to the image processing, and laser light from the laser diode is reflected by the polygon mirror 13 and then irradiated onto the photosensitive drum 1 through the mirror 14. The photosensitive drum 1 is uniformly charged by a charging device 15, and an electrostatic latent image is formed on the surface of the photosensitive drum 1 by writing with a laser beam.
[0014]
Then, the electrostatic latent image on the surface of the photosensitive drum 1 is visualized by being attached with toner by the developing device 16 according to the present invention, and this visible image is fed from the paper feeding unit 17A or 17B to the paper feeding roller. The image is transferred to the transfer paper (recording medium) 19 fed by 18A or 18B by corona discharge of the transfer charger 20. The transfer sheet 19 onto which the visible image has been transferred is separated from the surface of the photosensitive drum 1 by the separation charger 21, transported by the transport belt 22, and passes through the pressure contact portion of the fixing roller pair 23 so that the visible image is transferred. The paper is fixed and discharged to a discharge tray 24 outside the apparatus.
[0015]
On the other hand, the toner remaining on the surface of the photosensitive drum 1 after the transfer is removed by the cleaning device 25, and the charge remaining on the surface of the photosensitive drum 1 is erased by the static elimination lamp 26.
[0016]
Next, the developing device 16 will be described with reference to FIG. FIG. 2 is a schematic configuration diagram of the developing device.
The developing device 16 conveys the charged toner toward the one end side (hereinafter also referred to as “flying side”) with electrostatic force along the conveyance surfaces 30a and 30a of the conveyance substrates 30 and 30 facing the charged toner. A toner flying device 31 is provided for flying toner from one end side of 30 and 30 toward the photosensitive drum 1 as a latent image carrier.
[0017]
Then, the conveyance path members 33 and 33 for feeding the charged toner between the conveyance substrates 30 and 30 of the toner flying device 31 from the toner box unit 32, the charging roller 34 for charging the toner supplied to the toner box unit 32, and the charging A charging blade 35 disposed in contact with the peripheral surface of the roller 34 and an agitator 37 that conveys the toner in the toner hopper 36 to the vicinity of the charging roller 34 are provided.
[0018]
Further, toner gutters 38 and 38 that are collection means for collecting unused toner that has been ejected from the transport substrates 30 and 30 of the toner flying device 31, and the toner collected by the toner gutter 38 are supplied to the toner box unit 32. Reverse transport path members 39, 39, etc. for transporting in the reverse direction by electrostatic force and returning.
[0019]
Therefore, the transport substrate 30 constituting the toner flying device 31 in the developing device 6 will be described with reference to FIGS. FIG. 3 is a schematic cross-sectional explanatory view of the carrying substrate, and FIG. 4 is a plan explanatory view of the carrying substrate.
This transport substrate 30 is a set of three electrodes 42, 42,... That generate a space traveling wave electric field for transporting toner with electrostatic force on a long flat support substrate 41. Further, a conveyance surface forming member 43 for forming a conveyance surface is laminated, and a surface coat layer 44 for reducing contact resistance with toner is formed on the surface of the conveyance surface forming member 43, and is formed along the conveyance surface. The toner is transported while being accelerated by electrostatic force.
[0020]
Here, as the support substrate 41, 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 is made of SiO.₂A film formed with an insulating film such as the above can be used. Here, a glass substrate having a thickness of 0.9 to 1.1 mm was used.
[0021]
The electrode 42 is formed by forming a conductive material such as Al or Ni—Cr with a thickness of 0.1 to 0.2 μm on the support substrate 41 and patterning it into an electrode shape using a semiconductor technique such as a photolithography technique. Forming. The arrangement density of the electrodes 42 is preferably 1/3 to 100 times the line diameter / space (L / S) of the toner diameter in order to ensure a good conveyance speed and amount, and in particular, 1 of the toner particle diameter. / 2 to 5 times is preferable. The width of the electrode 42 is preferably 1 to 3 times the toner diameter in order to ensure a good transport speed and transport amount.
[0022]
Therefore, as shown in FIG. 4, the electrodes 42 are arranged in a direction orthogonal to the toner flying conveyance direction, and the arrangement density is increased stepwise along the toner flying conveyance direction (the arrangement interval is narrowed). It is arranged. That is, for example, from the toner supply side to the toner flying side, in the region A, the electrodes 42 are spaced at 100 μm intervals, in the region B, the electrodes 42 are spaced at 20 μm intervals, in the region C, the electrodes 42 are spaced at 10 μm intervals, and in the region D Are arranged at intervals of 5 μm. The width of the electrode 42 is 10 μm with the average particle size of the toner being 8 μm.
[0023]
As the transport surface forming member 43, an insulating film having a large relative dielectric constant, for example, SiO₂(Silicon oxide film) or Ta₂O₅(Tantalum pentoxide, relative dielectric constant 28) is formed to a thickness of 0.5 to 1 μm. When polyimide is used, polyimide has a relative dielectric constant of about 3.6. However, when coating on a substrate, BaTiO.₃The apparent dielectric constant becomes 10 to 12 by adding about 1% of the above fine particles.
[0024]
By increasing the relative dielectric constant of the transport surface forming member 43, the drive voltage can be lowered, and the drive recoil and transport speed of particles (toner) are increased. Therefore, in order to transport the charged toner more reliably at a low voltage and at a speed capable of flying, it is preferable that the transport surface forming member 43 is formed of a material having a relative dielectric constant of 10 or more. When an experiment was conducted using a polyimide film having a thickness of 1 μm, a scanning drive voltage of DC 500 V was required.₃When about 1% of the fine particles were added, considerable results were obtained at a driving voltage of 300V.
[0025]
The surface coat layer 44 is a film having a function of reducing contact resistance between the conveying surface and the charged toner interface, and is formed by coating a fluorine resin material such as PTFE or PFA with a thickness of 0.1 to 0.3 μm. is doing.
[0026]
Here, the number of the transport substrate 30 constituting the toner flying device 31 may be one, but in this embodiment, the transport surfaces 30a and 30a of the transport substrate 30 are opposed to each other (confronting each other) using the two transport substrates 30 and 30. ). At this time, the interval between the two conveyance substrates 30 and 30 is set in a range of 30 to 200 μm.
[0027]
By using a plurality of transport substrates 30 in this way, the amount of toner that can be transported and flying per unit time can be increased, and the amount of toner that can be transported and flying by selecting the transport substrate 30 to be driven. Will be able to control.
[0028]
Further, the transport path member 33 and the reverse transport path member 39 have the same basic configuration as the transport substrate 30 described above. Although not shown here, a large number of electrodes are provided on an insulating flexible substrate as a support substrate. The conveyance surface forming member which forms a conveyance surface arrange | positions at intervals, is laminated | stacked, and the surface coat layer which reduces contact resistance with a toner on the surface of this conveyance surface formation member is formed into a film. In the transport path member 33 and the reverse transport path member 39, the arrangement density of the electrodes is substantially equal.
[0029]
Next, toner conveyance and flying (jetting) operations by the conveyance substrates 30 and 30 of the toner flying device 31 will be described with reference to FIGS.
First, in the toner flying device 31, as shown in FIG. 5, the three electrodes 42, 42, 42 of the transport substrates 30, 30 are set as one set, and a three-phase drive voltage (drive waveform) is applied to each electrode 42. Drive circuits (drivers) 50 and 50 for applying electrodes Va, Vb and Vc, respectively, are provided. The drive waveforms Va, Vb, and Vc output from the drive circuit 50 each have a slight delay time, and the drive waveforms Va, Vb, and Vc are ternary values of + potential, −potential, and 0 potential (non-applied), respectively. Is a voltage waveform.
[0030]
Here, as shown in FIG. 6, there is negatively charged toner T on the transport substrate 30, and “+” and “−” are respectively applied to a plurality of continuous electrodes 42 on the transport substrate 30 as indicated by (1). , “0”, “+”, “−” are applied, and when the negatively charged toner T is positioned on the “0” electrode 42, the negatively charged toner T includes the “−” electrode 42 on the left side in FIG. Therefore, the negatively charged toner T moves to the “+” electrode 42 side.
[0031]
For example, when three-phase drive voltages Va, Vb, and Vc are applied to the three electrodes 42 from the drive circuit 50 in a change pattern as shown in FIG. The voltage applied to 42 changes as “0”, “+”, “−”, “0”, “+”, respectively, as indicated by (2). Therefore, no force acts between the electrode 42 changed from “+” to “0” and the negatively charged toner T, and the negatively charged toner T is between the electrode 42 changed from “0” to “−”. Thus, the attractive force acts between the electrode 42 whose repulsive force has changed from “−” to “+”, and thus the negatively charged toner T further moves to the “+” electrode 42 side.
[0032]
In this way, by changing the potential of the drive waveform applied to the electrode 42 and apparently moving the drive waveform, a spatial traveling wave electric field is generated, and the negatively charged toner T is drawn toward the “+” electrode 42 side. Since it moves, the negatively charged toner T is transported along the transport surface of the transport substrate 30. In the case of positively charged toner, it can be conveyed by reversing the drive waveform change pattern. Hereinafter, the negatively charged toner will be described.
[0033]
Here, since the transfer substrate 30 is formed so that the arrangement interval of the electrodes 42 is narrowed as it goes toward one end side (flying side), the negatively charged toner T has stronger suction force and repulsive force. As the toner T moves toward the flying side, the conveyance speed increases stepwise (in the order of area A → area B → area C → area D in FIG. 4), and the toner T finally becomes the conveyance substrate. It flies (injects) from one end part of 30.
[0034]
Note that the change pattern of the three-phase drive voltages Va, Vb, and Vc applied from the drive circuit 50 to each electrode 42 of the transport substrate 30 is not limited to the above example. For example, as shown in FIG. Even if it is a pattern in which the drive waveform for two consecutive electrodes 42 out of the three electrodes 42 is not used and the drive waveform for the other one electrode 42 is set to “−”, it is negatively charged. The toner T is conveyed to the conveyance substrate 30 while being accelerated along the conveyance surface, and flies from the flying side. When the flying toner speed was measured using the transport substrate 30 of the present embodiment, a flying speed of approximately 0.5 m to 5 m / sec was obtained, depending on the applied voltage and frequency.
[0035]
Therefore, the developing operation using the developing device 16 in the image forming apparatus configured as described above will be described with reference to FIG.
First, as shown in the figure, the negatively charged toner T is conveyed by the conveyance substrates 30 and 30 of the toner flying device 31 of the developing device 16 while being accelerated and is made to fly toward the photosensitive drum 1 from the flying side. As a result, the flying negatively charged toner T adheres to the positively charged portion (image portion) of the surface of the photosensitive drum 1 and the latent image is developed.
[0036]
At this time, an AC voltage from the AC power source 52 is applied to the electrodes 42, 42 on one end (flight side) of the transfer substrates 30, 30, and an AC electric field (AC electric field) is generated between the transfer substrates 30, 30. If generated, a toner cloud 53 in which the toner T flying from the transport substrates 30 and 30 becomes a cloud state by an alternating electric field is generated, and the toner adheres uniformly to the latent image on the photosensitive drum 1. Image quality is improved. That is, in this image forming apparatus, means for applying an AC electric field, which is a means for generating a toner cloud, is formed by the electrodes 42 and 42 on one end (flight side) side of the transport substrates 30 and 30 and the AC power source 52. ing.
[0037]
In this way, the charged toner is transported toward the one end side by electrostatic force along the transport surface of the transport substrate, and the toner is ejected from the one end portion side of the transport substrate toward the latent image carrier. In this case, the toner can be adhered directly, and the apparatus can be simplified and the cost can be reduced. Since electrostatic toner conveyance is based on coulomb force, toners with a small charge amount, uncharged toners, and reverse polarity charged toners are not conveyed in a predetermined direction, and only charged toners above a certain threshold are conveyed. As a result, the charge amount of the toner used for the development is made uniform, the re-detachment of the toner in the development process is reduced, the background stain is reduced, and the image quality is improved.
[0038]
Further, toner deterioration is reduced as compared with the case where the developing roller is used as the developing means. That is, normally, the toner is charged by frictional charging, a film is formed on the developing roller together with the magnetic carrier, and the toner electrostatically attached to the carrier is made into a magnetic brush shape, which is brought into contact with the latent image carrier and developed. For this reason, the toner is kneaded by the developing roller and further pulverized into fine powder,₂, TiO₂For example, additives are imprinted on the resin part of the toner, and the characteristics of the toner are deteriorated, resulting in functional failure. On the other hand, as described above, the toner is further pulverized into a fine powder by being transported and flying on the transport substrate.₂, TiO₂Thus, the additive is not imprinted on the resin part of the toner, and the characteristic deterioration is also reduced.
[0039]
Next, the toner collecting action in this image forming apparatus will be described with reference to FIG. This figure is an explanatory diagram for explaining the toner collecting action.
As described above, the toner flies from the conveyance substrates 30 and 30 and adheres to the latent image area on the photosensitive drum 1, but not all toner is used for development, and the toner flies from the conveyance substrates 30 and 30. However, some toner is not used for development.
[0040]
Therefore, toner gutters 38, 38 are provided on the outer sides of the conveying substrates 30, 30 facing each other, and unused toner to be separated from the developing unit is attached and collected. The toner gutters 38 and 38 are provided with the reverse transport path members 39 and 39 as described above, and the reverse transport path members 39 and 39 are also configured by the spatial traveling wave electric field by the same configuration as the transport substrates 30 and 30 described above. Since the toner can be conveyed to the supply side (the other end side) by the electrostatic force, the toner can be returned to the toner box portion 32 side for reuse.
[0041]
Thus, by providing the collecting means for collecting the unused toner flying from the conveyance substrate 30, the toner can be reliably prevented from scattering, and the collecting means is further provided with means for conveying the toner back to the supply side by electrostatic force. As a result, the toner can be reused, and the cost can be reduced.
[0042]
In addition, when a forward / reverse bias voltage is applied alternately to the toner gutter 38 described above, the toner is sucked and released, and the scattered toner is collected and the collected toner is again applied to the transport substrate 30. It can be returned to the flight side and reused. In this case, it is not always necessary to return the collected toner to the toner box portion 32 by the reverse conveyance path member 39.
[0043]
Next, a second embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. FIG. 2 is a main part explanatory view for explaining a developing device portion of the image forming apparatus.
In this embodiment, as the transport substrates 30 and 30 of the toner flying device 31 of the developing device 16, a substrate in which a large number of electrodes 42 are arranged at substantially equal intervals along the transport direction is used. Further, as the drive circuit 55, three-phase drive waveforms Va1, Vb1, and Vc1 having three types of frequencies f1 and three-phase drive waveforms Va2, Vb2, and Vc2 having a frequency f2 for each electrode 42 of the transport substrate 30; A device that outputs three-phase drive waveforms Va3, Vb3, and Vc3 having a frequency f3 (f1> f2> f3) is used.
[0044]
Then, the three-phase drive waveforms Va1, Vb1, Vc1 of the frequency f1 of the drive circuit 55 are applied to the electrodes 42, 42,... In the required region on the flying side of the transport substrate 30, and the three-phase drive waveforms Va2, Vb2 of the frequency f2. , Vc2 to the electrodes 42, 42... In the middle part of the transport substrate 30, and the three-phase drive waveforms Va3, Vb3, Vc3 of the frequency f3 to the electrodes 42, 42. ... are applied respectively. Other configurations are the same as those in the above embodiment, and the description and illustration are omitted.
[0045]
With this configuration, the electrodes 42 and 42 of the transfer substrates 30 and 30 are arranged at substantially equal intervals, but the frequencies of the drive waveforms Va, Vb, and Vc applied to the electrodes 42 of the transfer substrate 30 are From the supply side to the flight side, the level increases stepwise (in this example, three levels f3, f2, and f1). Here, since the suction force and the repulsive force acting on the charged toner change in a single time as the frequency of the drive waveform increases, the toner supplied from the supply side of the transport substrate 30 is the electrodes 42, 42. As the frequency of the drive waveform applied to the toner increases, the moving speed increases. Therefore, the toner is transported while being accelerated along the transport surface of the transport substrate 30 and travels from the flying side (one end side) toward the photosensitive drum 1. To fly.
[0046]
As described above, when the toner is accelerated by changing the frequency of the drive waveform stepwise, the arrangement of the electrodes on the transport substrate is compared with the case where the arrangement density of the electrodes is changed as in the above embodiment. However, the configuration on the drive circuit side is slightly complicated. Therefore, which form should be adopted may be selected in consideration of the manufacturing cost of the drive circuit and the transfer board, and the arrangement density of the electrodes on the transfer board is made narrower toward the flight side, and the drive waveform A drive circuit that increases the frequency stepwise can also be used.
[0047]
Next, a third embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. This figure is an explanatory view of the main part of the developing device portion of the image forming apparatus.
In this embodiment, as the transport substrates 30 and 30 of the toner flying device 31 of the developing device 6, a plurality of electrodes 42 arranged at substantially equal intervals along the transport direction is used. Further, as the drive circuit 56, three-phase drive waveforms Vap1, Vbp1, and Vcp1 having three kinds of peak values Vp1 and three-phase drive waveforms Vap2, Vbp2, and Vcp2 having peak values Vp2 for each electrode 42 of the transport substrate 30 are used. And three-phase drive waveforms Vap3, Vbp3, and Vcp3 having a peak value Vp3 (Vp1> Vp2> Vp3) are used.
[0048]
Then, the three-phase drive waveforms Vap1, Vbp1, and Vcp1 of the peak value Vp1 of the drive circuit 56 are applied to the electrodes 42, 42,... In the required region on the flying side of the carrier substrate 30, and the three-phase drive waveform Vap2 of the peak value Vp2. , Vbp2, Vcp2 are applied to the electrodes 42, 42. , 42... Are applied respectively. Other configurations are the same as those in the above embodiment, and the description and illustration are omitted.
[0049]
With this configuration, the electrodes 42, 42 of the transport substrates 30, 30 are arranged at substantially equal intervals, but the driving waveforms Va, Vb, Vc applied to each electrode 42 of the transport substrate 30. The high value gradually increases from the supply side to the flight side (in this example, three levels of Vp3, Vp2, and Vp1). Here, since the suction force and the repulsive force acting on the charged toner change in a single time as the peak value of the drive waveform is higher, the toner supplied from the supply side of the transport substrate 30 is the electrodes 42, 42. As the crest value of the drive waveform given to... Increases, the moving speed increases. Therefore, the toner is transported while being accelerated along the transport surface of the transport substrate 30, and from the flying side (one end side) to the photosensitive drum 1. Fly towards.
[0050]
Next, a fourth embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. This figure is an explanatory view of the main part of the developing device portion of the image forming apparatus.
In this embodiment, as the transport substrates 30 and 30 of the toner flying device 31 of the developing device 6, a plurality of electrodes 42 arranged at substantially equal intervals along the transport direction is used. The driving circuit 50 includes the above-described driving circuit 50, and the three-phase driving waveform Va from the driving circuit 50 with respect to any one of the electrodes 42 (here, the supply-side electrode 42) of the transport substrate 30. , Vb, and Vc are provided with a drive circuit 57 that applies drive waveforms Vad, Vbd, and Vcd having a higher duty ratio.
[0051]
With this configuration, by applying drive waveforms Vad, Vbd, and Vcd having a high duty ratio from the drive circuit 57, the toner is given an initial speed of flying from the transport substrate 30, and then the drive waveform from the drive circuit 50. The electrostatic force is applied to the electrodes 42 to which Va, Vb, and Vc are applied, and the sheet is transported in a state where the initial speed is substantially maintained, and then travels from the flying side (one end side) of the transport substrate 30 toward the photosensitive drum 1.
[0052]
Next, an image forming apparatus according to a fifth embodiment of the invention will be described with reference to FIG. This figure is an explanatory view of the main part of the developing device portion of the image forming apparatus.
In the toner flying device 31 in this embodiment, like the above-described transport substrate 30, an intermediate transport substrate 30B having both surfaces as transport surfaces is disposed between transport substrates 30A and 30A having one surface as a transport surface. The toner is transported on the transport surfaces of the transport substrates 30A and 30A and the two transport surfaces of the intermediate transport substrate 30B so as to fly.
[0053]
With this configuration, the amount of toner that can be transported per unit time by the toner flying device 31 is twice that of the above-described embodiments, and the toner amount used for high-speed recording can be sufficiently accommodated. In other words, as the recording speed increases, depending on the image, the amount of toner consumed increases, and the replenishment of toner necessary for development may not be in time. With such a configuration, a large amount of toner can be transported, and the recording speed can be increased.
[0054]
In this case, as shown in the figure, the intermediate transfer board 30B is disposed with the flying side set back from the transfer boards 30A and 30A on both sides, and an AC voltage is applied from the AC power source 52 between the transfer boards 30A and 30A on both sides. Then, an AC electric field is generated, and a toner cloud is generated.
[0055]
Next, a sixth embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. This figure is an explanatory view of the main part of the developing device portion of the image forming apparatus.
In this embodiment, an AC voltage is applied from the AC power source 52 between the electrodes 42, 42 at the flying side end portions of the transport substrates 30, 30 of the toner flying device 31, and one side (here) In this case, a DC voltage is applied from a DC power source 60 that is a means for generating a DC electric field between the electrode 42 at the flying side end of the transport substrate 30 on the lower side.
[0056]
With this configuration, for example, when AC ± 300V is applied from the AC power supply 52 and DC500V is applied from the DC power supply 60, + 500V is always applied to the lower transport substrate 30 between the photosensitive drum 1 and the upper side. A voltage of 200V (= 500 − (+ 300)) and 800V (500 − (− 300)) is alternately applied to the transfer substrate 30, so that the transfer substrate 30 between the upper transfer substrate 30 and the photosensitive drum 1 is applied. Electric field vibration is generated by an alternating electric field.
[0057]
As a result, the toner cloud formed by the charged toner T flying from the transport substrates 30 and 30 of the toner flying device 31 is diffused by the electric field vibration caused by the alternating electric field, and adheres to the photosensitive drum 1. / Increased frequency of withdrawal. Therefore, toner can be attached to the charge of the target photosensitive drum 1 with higher accuracy, and the image quality is improved.
[0058]
Next, a seventh embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. This figure is an explanatory view of the main part of the developing device portion of the image forming apparatus.
In this embodiment, an AC voltage is applied from the AC power supply 52 between the transport substrates 30 and 30 of the toner flying device 31 as described above, and the electrode portions 61 and 61 provided on the outer surfaces of the transport substrates 30 and 30; A DC voltage from a DC power source 60 that is a means for generating a DC electric field is applied to the photosensitive drum 1.
[0059]
With this configuration, a DC bias electric field is generated between each of the transfer substrates 30 and 30 and the photosensitive drum 1, and the flying is performed from the transfer substrates 30 and 30 of the toner flying device 31 to be in a cloud state by the AC electric field. The toner T thus formed is confined between the DC bias electric fields. Therefore, toner scattering is prevented and the image quality is further improved.
[0060]
Next, an image forming apparatus according to an eighth embodiment of the present invention will be described with reference to FIG. This figure is an explanatory view of the main part of the developing device portion of the image forming apparatus.
In this embodiment, the toner flying device 31 is provided with a concave-shaped accumulation portion 70 for accumulating toner on the supply side of the conveyance substrates 30 and 30, and the upper conveyance substrate 30 is shown in FIG. As shown in FIG. 18, the drive waveform Va has a change pattern opposite to that shown in FIG. 7, as shown in FIG. , Vb, and Vc, and a drive circuit 72 that applies the change.
[0061]
With this configuration, the toner is transported from the transport substrate 30 on the upper side of the toner flying device 31 in the same manner as described above, and is ejected toward the photosensitive drum 1, but the transport substrate 30 on the lower side is reversed. Since the drive waveform of the change pattern is applied, the toner is conveyed in the reverse direction (direction from the flying side to the supply side). That is, the lower transfer substrate 30 is a reverse transfer substrate.
[0062]
With this configuration, the toner supplied from the toner box unit 32 of the developing device 6 can be stored in the storage units 70 and 70, and the toner can be transported and transported by the transport substrates 30 and 30 without interruption. Can be made. That is, when the amount of toner used is large, the toner must be continuously transported and flying, but if the toner supply to the transport substrates 30 and 30 is not in time at this time, toner shortage will occur. By transporting and flying while accumulating the toner in the accumulating units 70 and 70, it is possible to carry out and fly the toner continuously and prevent image quality deterioration.
[0063]
In addition, the toner that does not adhere to the photosensitive drum 1 and rebounds is transported to the supply side by the lower transport substrate 30 and returned to the storage unit 70, and returned to the storage unit 70 of the lower transport substrate 30. The transferred toner is transferred to the upper transport substrate 30 and again used for development. As a result, the toner can be used effectively, and splashing of the recoil toner can be prevented to improve the image quality.
[0064]
Next, a ninth embodiment of the image forming apparatus according to the present invention will be described with reference to FIG. This figure is an explanatory view of the main part of the developing device portion of the image forming apparatus.
In this embodiment, a drive circuit 71 that applies the drive waveforms Va, Vb, and Vc by changing the drive waveforms Va, Vb, and Vc in the change pattern as shown in FIG. A mode in which the drive waveforms Va, Vb, and Vc are changed and applied to the transport substrate 30 with a change pattern as shown in FIG. 7 and a drive waveform Va, with a change pattern opposite to that shown in FIG. And a drive circuit 73 having a mode in which Vb and Vc are changed and applied.
[0065]
A mode switching signal for switching modes is given to the drive circuit 73 from a control unit (not shown). This mode switching signal is a signal for selecting a mode to be applied by changing the drive waveforms Va, Vb, and Vc with a change pattern as shown in FIG. 18 when the image forming apparatus is on standby, for example.
[0066]
With this configuration, during recording for forming a normal image, the drive waveforms Va, Vb, and Vc are changed from the drive circuit 73 to the lower transport substrate 30 in a change pattern as shown in FIG. Therefore, the toner can be developed by causing the toner to fly to the flying side on both the upper and lower transport substrates 30, 30, and to fly the toner with a transport amount twice that of the single transport substrate 30.
[0067]
In the standby mode, the drive circuit 73 applies the drive waveforms Va, Vb, and Vc in a change pattern as shown in FIG. 18 to the lower transport substrate 30 so that the lower transport substrate 30 is applied. The toner 30 is transported in the reverse direction. As a result, the toner is circulated between the transport substrates 30 and 30 and does not fly. In this way, since the toner does not fly during standby or the like, toner scattering can be prevented more reliably and image quality can be improved.
[0068]
Further, by providing two transport substrates as described above, one of the transport substrates can be used as a transport substrate for flying toner and also as a reverse transport substrate for transporting toner to the supply side, thereby simplifying the configuration. become.
[0069]
Next, another example of the toner conveyance mode in the toner flying device 31 of each of the above embodiments will be described with reference to FIG.
When the transport surfaces of at least two transport substrates 30 and 30 are arranged to face each other as in the toner flying device 31 in each of the above embodiments, two transports can be performed by setting a drive voltage and a gap between the transport surfaces. When the drive waveforms applied to the electrodes 42 of the substrates 30 and 30 are synchronized, the electric field curtain 81 generated by the upper transfer substrate 30 and the electric field curtain 82 generated by the upper transfer substrate 30 are connected.
[0070]
When the electric field curtains 81 and 82 are connected as described above, the toner does not move, and the toner is layered at a portion where the electric field curtains 81 and 82 are not connected. Therefore, by moving these electric field curtains 81 and 82 in the flying direction with a required time constant while being connected, the toner is conveyed to the flying side in a layered state, and the toner is intermittently transferred. It can be conveyed in layers.
[0071]
In this case, a larger amount of toner is supplied from the transport substrate 30 and the amount of unused toner increases depending on the image. Therefore, the unused toner is collected by the toner gutter 38 and is fed to the supply side by the reverse transport path member 39. Reverse the toner. Here, the configuration of the reverse transport path member 39 will be briefly described. The flexible substrate 91 is provided with a plurality of electrodes 92 for generating a spatial traveling wave electric field, which is covered with a transport surface forming member 93 and has a surface coat layer 94 on the surface. , And a flexible substrate 91 can be used to form a transport surface of an arbitrary shape and can be arranged following the toner gutter 38.
[0072]
In each of the above-described embodiments, the toner is described as being accelerated and flying. However, the toner is ejected from one end portion of the transfer substrate at a constant transfer speed (this is also included in “flying”). You can also. In this case, the plurality of electrodes may be arranged at equal intervals, and the same drive waveform may be applied with the phase shifted.
[0073]
【The invention's effect】
  As described above, according to the image forming apparatus of the present invention,It has a plurality of electrodes that generate a space traveling wave electric field to convey charged toner toward the one end side by electrostatic force along the conveying surface, and the toner flies from one end side toward the latent image carrier. A pair of transport substrates facing each other on the electrode surface side, and a means for generating an alternating electric field between the electrodes at one end of the pair of transport substrates and generating a toner cloud due to toner flying from one end of the transport substrate. Since the plurality of electrodes of the transport substrate are arranged with increasing arrangement density step by step along the toner transport direction,A toner having a uniform charge amount can be transported with a simple configuration to generate a toner cloud, toner scattering is reduced, and image quality is improved.
[0074]
  here,By providing the intermediate transport substrate facing each of the pair of transport substrates facing each other, a larger amount of toner can be transported.
[0075]
In addition, by having a reverse conveyance board that conveys toner toward the other end with electrostatic force along the conveyance surface against the conveyance board, unused toner can be collected with a simple configuration to prevent toner scattering The toner can be easily reused. Furthermore, by having a toner gutter that collects toner that has not been used for development, toner scattering can be more reliably prevented. The toner gutter includes a reverse conveying member that conveys the collected toner in the reverse direction, so that the collected toner can be easily reused.
[0076]
Further, by providing means for generating a DC electric field between the electrode of the transport substrate and the latent image carrier, the toner cloud can be vibrated, and more efficient development can be performed. In addition, by providing means for generating a DC electric field between the electrode provided on the outer surface side of the transport substrate and the latent image carrier, toner can be contained between the DC electric fields to prevent toner scattering more reliably. In addition, the area of the toner cloud is widened and the contact area with the latent image carrier is widened, and good high-density development without toner omission can be performed.
[Brief description of the drawings]
FIG. 1 is an overall schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram illustrating an example of a developing device of the image forming apparatus.
FIG. 3 is a schematic cross-sectional explanatory diagram of a conveyance board of a toner flying device in the developing device.
FIG. 4 is an explanatory plan view of the transfer substrate.
FIG. 5 is an explanatory diagram for explaining the operation of the toner flying device.
FIG. 6 is an explanatory diagram for explaining the principle of toner conveyance by the conveyance substrate.
FIG. 7 is an explanatory diagram for explaining an example of a change pattern of a drive waveform applied to the transport substrate.
FIG. 8 is an explanatory diagram for explaining another example of a change pattern of a drive waveform applied to the transport substrate.
FIG. 9 is an explanatory diagram for explaining the principle of the developing operation in the image forming apparatus.
FIG. 10 is an explanatory diagram for explaining a toner collecting operation in the image forming apparatus.
FIG. 11 is an explanatory view of a main part of a developing device portion of an image forming apparatus according to a second embodiment of the present invention.
FIG. 12 is an explanatory diagram of a main part of a developing device portion of an image forming apparatus according to a third embodiment of the present invention.
FIG. 13 is an explanatory view of a main part of a developing device portion of an image forming apparatus according to a fourth embodiment of the present invention.
FIG. 14 is an explanatory view of a main part of a developing device portion of an image forming apparatus according to a fifth embodiment of the invention.
FIG. 15 is an explanatory view of a main part of a developing device portion of an image forming apparatus according to a sixth embodiment of the present invention.
FIG. 16 is an explanatory view of a main part of a developing device portion of an image forming apparatus according to a seventh embodiment of the present invention.
FIG. 17 is an explanatory view of a main part of a developing device portion of an image forming apparatus according to an eighth embodiment of the present invention.
FIG. 18 is an explanatory diagram for explaining a reverse conveyance drive waveform pattern for explaining the embodiment;
FIG. 19 is a main part explanatory view of a developing device for explaining another example of the embodiment;
FIG. 20 is a main part explanatory view of a developing device part for explaining another example of a toner conveyance mode;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum (latent image carrier), 5, 8 ... Scanning optical system, 13 ... Polygon mirror, 15 ... Charging device, 16 ... Developing device, 17A, 17B ... Paper feeding unit, 20 ... Transfer charger, 21 ... Separation charger 23: Fixing roller pair 30, 30A ... Conveying substrate, 30B ... Intermediate conveying substrate, 33 ... Conveying path member, 38 ... Toner gutter, 39 ... Reverse conveying path member, 31 ... Toner flying device, 41 ... Supporting substrate, 42 ... Electrode, 43 ... Transport path forming member, 44 ... Surface coat layer, 52 ... AC power source, 60 ... DC power source, 70 ... Accumulator.

Claims (7)

In an image forming apparatus for supplying toner onto a latent image carrier and developing the latent image on the latent image carrier to form an image,
A plurality of electrodes for generating a space traveling wave electric field for conveying the charged toner toward the one end side by electrostatic force along the conveying surface, from the one end side toward the latent image carrier; A pair of transport substrates facing the electrode surface side for causing the toner to fly; and
Wherein between the electrodes of the one end of the pair of conveying the substrate to generate an alternating electric field, and means for generating a toner cloud by toner flying from one end of the transfer board,
The image forming apparatus according to claim 1, wherein the plurality of electrodes of the transport substrate are disposed with increasing density in a stepwise manner along a toner transport direction . 2. The image forming apparatus according to claim 1 , further comprising an intermediate transport substrate facing each of the pair of transport substrates facing each other. 2. The image forming apparatus according to claim 1 , further comprising: a reverse conveyance substrate that conveys the toner toward the other end portion by electrostatic force along the conveyance surface facing the conveyance substrate. apparatus. The image forming apparatus according to any one of claims 1 to 3, the image forming apparatus characterized by having a Tonagata for collecting toner which has not been used for development. 5. The image forming apparatus according to claim 4 , further comprising a reverse conveying member that conveys the toner collected in the toner gutter in a reverse direction. The image forming apparatus according to any one of claims 1 to 5, the image forming apparatus characterized by comprising means for generating a DC electric field between the latent image bearing member and the electrode of the transporting substrate. The image forming apparatus according to any one of claims 1 to 5, and characterized in that it comprises means for generating a DC electric field between the electrode provided on the outer surface side of the carrying substrate and said latent image bearing member Image forming apparatus.

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