JP3827279B2 - Electrophotographic equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  This invention uses a two-component or one-component developer such as a copying machine, a printer, a facsimile machine, or a complex machine thereof, and sequentially forms a toner image on a photoreceptor by repeating charging, writing, developing, transferring, cleaning, etc. And its toner imageInThe present invention relates to an electrophotographic apparatus for recording an image on a sheet by transferring indirectly through an intermediary transfer member.The
[0002]
[Prior art]
2. Description of the Related Art Today, electrophotographic apparatuses are increasing in color, such as color copiers and color printers, according to market demands.
[0003]
A color electrophotographic apparatus is provided with a developing device of a plurality of colors around one photosensitive member, and a toner is attached to the developing device to form a composite toner image on the photosensitive member, and the toner image is transferred. A so-called revolver type that records a color image on a sheet, and a plurality of photoconductors arranged side by side are each provided with a developing device, and a single color toner image is formed on each photoconductor, and the single color toner images are sequentially formed. There is a so-called tandem type that transfers and records a composite color image on a sheet.
[0004]
Comparing the revolver type and the tandem type, the former has only one photoconductor, so that there is an advantage that the size can be reduced relatively and the cost can be reduced. Times) Since full-color images are formed by repeating image formation, there is a drawback that speeding up image formation is limited, while the latter has the disadvantage of increasing the size and cost, but speeding up image formation There is an advantage that can be realized.
[0005]
Recently, however, tandem-type cameras have been attracting attention because full-color and monochrome-like speeds are desired.
[0006]
As shown in FIG. 10, the tandem type electrophotographic apparatus includes a direct transfer system that sequentially transfers an image on each photoconductor 1 to a sheet s conveyed by a sheet conveying belt 3 by a transfer apparatus 2. As shown in FIG. 9, the image on each photoconductor 1 is once transferred sequentially to the intermediate transfer body 4 by the primary transfer device 2, and then the image on the intermediate transfer body 4 is transferred to the sheet s by the secondary transfer device 5. There are indirect transfer systems that perform batch transfer.
[0007]
Comparing the direct transfer type and the indirect transfer type, the former has a sheet feeding device 6 arranged upstream of the tandem type image forming apparatus T in which the photoreceptors 1 are arranged, and a fixing device 7 arranged downstream. There is a disadvantage of increasing the size. On the other hand, since the latter can set the secondary transfer position relatively freely, the paper feeding device 6 and the fixing device 7 can be arranged so as to overlap the tandem type image forming apparatus T, and the size can be reduced. There are advantages that are possible.
[0008]
In the former case, the fixing device 7 is disposed close to the tandem image forming apparatus T so as not to increase the size. Therefore, the fixing device 7 can be disposed with a sufficient margin that the sheet s can bend. However, there is a drawback that the fixing device 7 affects the image formation on the rear end side due to an impact when the leading edge of the sheet s enters the fixing device 7 or a difference in sheet conveyance speed when passing through the fixing device 7. . On the other hand, in the latter case, the fixing device 7 can be disposed with a sufficient margin that the sheet s can be bent, so that the fixing device 7 can hardly affect the image formation.
[0009]
For these reasons, attention has recently been paid to an indirect transfer type among tandem type electrophotographic apparatuses.
[0010]
In this type of color electrophotographic apparatus, as shown in FIG. 9, the transfer residual toner remaining on the photoconductor 1 after the primary transfer is removed by the photoconductor cleaning device 8 to clean the surface of the photoconductor 1. In preparation for another image formation. In addition, the transfer residual toner remaining on the intermediate transfer body 4 after the secondary transfer is removed by the intermediate transfer body cleaning device 9 to clean the surface of the intermediate transfer body 4 to prepare for another image transfer.
[0011]
[Problems to be solved by the invention]
However, the toner on the image carrier such as the photoreceptor 1 or the intermediate transfer body 4 cannot be sufficiently cleaned only by mechanically scraping off the toner by the photoreceptor cleaning device 8 or the intermediate transfer body cleaning device 9. . Some toners are electrostatically attracted by a cleaning member by applying a bias, but since toners having various charging characteristics remain on the image carrier, it has been difficult to remove all of them cleanly.
[0013]
In particular, in the indirect transfer type tandem type electrophotographic apparatus, since the transfer is repeated, the charged state becomes unstable, and various toners having different charging characteristics remain on the intermediate transfer body 4. Become.
[0014]
  Therefore, the first of the present invention1The challenge of electrophotographyIn placeRemove various toners with different charging characteristics remaining on the intermediate transfer member.In addition, the toner remaining on the intermediate transfer member that cannot be removed by the two cleaning members is also removed neatly.There is to do.
[0019]
  No. 1 of this invention2In addition, in the electrophotographic apparatus, it is necessary to remove the toner on the intermediate transfer member more neatly by removing it with two cleaning members.
[0020]
  No. 1 of this invention3In addition, in the electrophotographic apparatus, there is a problem in that the toner remaining on the intermediate transfer member that cannot be removed by the two cleaning members is more neatly removed.
[0023]
[Means for Solving the Problems]
  Therefore, the invention according to claim 1 is to achieve the above first problem.The image on the photoreceptor is primarily transferred to the intermediate transfer member by the primary transfer device, and then the image on the intermediate transfer member is secondarily transferred to the sheet by the secondary transfer device, while remaining on the photoreceptor after the primary transfer. An electrophotographic apparatus comprising a photoconductor cleaning device for removing residual toner to be removed and an intermediate transfer body cleaning device for removing residual toner remaining on an intermediate transfer body after secondary transfer.Two cleaning members that apply biases of different polarities are provided as cleaning membersOf these cleaning members, a bias having the same polarity is applied to the cleaning member on the downstream side in the rotation direction of the intermediate transfer member at the primary transfer position.It is characterized by.
[0028]
  Claim2The invention according to the above-mentioned2Claims to achieve1In the electrophotographic apparatus described inIntermediate transfer memberIn the direction of rotationSecondaryDownstream of the transcription positionpositionBecauseIntermediate transfer memberIn the upstream position of the cleaning device,Intermediate transfer memberA bias applying member for aligning the polarity of the upper toner is provided.
[0029]
  Claim3The invention according to the above-mentioned3Claims to achieve1In the electrophotographic apparatus described inIntermediate transfer memberA bias applying member that aligns the toner on the intermediate transfer body with the same polarity as the bias applied at the primary transfer position is provided downstream of the cleaning device and upstream of the primary transfer position. And
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of the present invention and is an overall schematic configuration diagram of a color copying machine of a tandem type indirect transfer system.
[0033]
In the figure, reference numeral 100 is a copying machine main body, 200 is a paper feed table on which it is placed, 300 is a scanner mounted on the copying machine main body 100, and 400 is an automatic document feeder (ADF) further mounted thereon.
[0034]
The copying machine main body 100 is provided with an endless belt-shaped intermediate transfer member 10 in the center. As shown in FIG. 2, in the intermediate transfer member 10, the base layer 11 is made of a material that is difficult to stretch, such as a fluororesin or a canvas, and an elastic layer 12 is provided thereon. The elastic layer 12 is made of, for example, fluorine rubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer 12 is coated with, for example, a coating layer 13 having good smoothness by coating a fluorine resin.
[0035]
As shown in FIG. 1, in the illustrated example, it is wound around three support rollers 14, 15, and 16 so that it can be rotated and conveyed clockwise in the figure.
[0036]
In this illustrated example, an intermediate transfer body cleaning device 17 that removes residual toner remaining on the intermediate transfer body 10 after image transfer is provided to the left of the second support roller 15 among the three.
[0037]
Further, four images of black, cyan, magenta, and yellow are formed on the intermediate transfer member 10 stretched between the first support roller 14 and the second support roller 15 among the three along the conveyance direction. The tandem image forming apparatus 20 is configured by arranging the forming units 18 side by side.
[0038]
An exposure device 21 is further provided on the tandem image forming apparatus 20 as shown in FIG.
[0039]
On the other hand, a secondary transfer device 22 is provided on the side opposite to the tandem image forming apparatus 20 with the intermediate transfer body 10 interposed therebetween. In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24, which is an endless belt, between two rollers 23, and is pressed against the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to a sheet.
[0040]
A fixing device 25 for fixing the transfer image on the sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt.
[0041]
The secondary transfer device 22 described above is also provided with a sheet transport function for transporting the sheet after image transfer to the fixing device 25. Of course, a non-contact charger may be arranged as the secondary transfer device 22, and in such a case, it is difficult to provide this sheet conveyance function together.
[0042]
In the illustrated example, a sheet reversing device 28 for reversing the sheet so as to record an image on both sides of the sheet is provided below the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming device 20 described above. Is provided.
[0043]
Now, when making a copy using this color copying machine, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it.
[0044]
When a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the other contact glass 32. At that time, the scanner 300 is immediately driven to travel the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34, and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read.
[0045]
When a start switch (not shown) is pressed, one of the support rollers 14, 15, and 16 is driven to rotate by a drive motor (not shown), and the other two support rollers are driven to rotate to convey the intermediate transfer member 10. To do. At the same time, the individual image forming means 18 rotates the photosensitive member 40 to form black, yellow, magenta, and cyan single-color images on each photosensitive member 40, respectively. Then, along with the conveyance of the intermediate transfer member 10, the single color images are sequentially transferred to form a composite color image on the intermediate transfer member 10.
[0046]
On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 44 provided in multiple stages in the paper bank 43, and the separation roller 45. Then, the sheets are separated one by one into the paper feed path 46, transported by the transport roller 47, guided to the paper feed path 48 in the copying machine main body 100, and abutted against the registration roller 49 and stopped.
[0047]
Alternatively, the sheet feed roller 50 is rotated to feed out the sheets on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped.
[0048]
Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer member 10, the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is recorded on the sheet.
[0049]
The image-transferred sheet is conveyed by the secondary transfer device 22 and sent to the fixing device 25. The fixing device 25 applies heat and pressure to fix the transferred image, and then the switching roller 55 is used to switch the discharge roller. The paper is discharged at 56 and stacked on the paper discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and guided again to the transfer position, and the image is recorded also on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56.
[0050]
On the other hand, the intermediate transfer body 10 after the image transfer is removed by the intermediate transfer body cleaning device 17 to remove residual toner remaining on the intermediate transfer body 10 after the image transfer, so that the tandem image forming apparatus 20 can prepare for another image formation.
[0051]
Here, a conductive rubber roller is used as the registration roller 49, and a bias is applied. The surface is a conductive NBR rubber having a diameter of 18 mm and a thickness of 1 mm. The electrical resistance is about 10E9 Ωcm in volume resistance of the rubber material, and the applied voltage is about −850 V applied to the toner transfer side (front side).
[0052]
Although a voltage of about +200 V is applied to the back side of the paper, it may be grounded especially when there is little need to consider paper dust transfer on the back side. Further, a DC bias is applied as the applied voltage, but this may be an AC voltage having a DC offset component.
[0053]
The AC superimposed DC bias can uniformly charge the paper surface. The paper surface after passing through the registration roller 49 is slightly negatively charged. Therefore, in transferring from the intermediate transfer body 10 to the sheet, care should be taken because the transfer conditions may change compared to when the voltage is not applied to the registration roller 49.
[0054]
In the tandem image forming apparatus 20 described above, the individual image forming means 18 includes, for example, a charging device 60, a developing device 61, and a primary device around a drum-shaped photoconductor 40 as shown in FIG. The image forming apparatus includes a transfer device 62, a photoconductor cleaning device 63, a charge removal device 64, and the like. In the illustrated example, the photosensitive member 40 has a drum shape in which a photosensitive organic photosensitive material is applied to a base tube such as aluminum to form a photosensitive layer. However, the photosensitive member 40 may have an endless belt shape.
[0055]
Although not shown in the drawing, at least the photoconductor 40 is provided, and a process cartridge is formed by all or a part of the part forming the image forming unit 18 so that it can be attached to and detached from the copying machine main body 100 in a lump to improve maintainability. You may do it.
[0056]
Of the portions constituting the image forming unit 18, the charging device 60 is formed in a roller shape in the illustrated example, and charges the photosensitive member 40 by applying a voltage in contact with the photosensitive member 40.
[0057]
The developing device 61 may use a one-component developer. However, in the illustrated example, a two-component developer composed of a magnetic carrier and a nonmagnetic toner is used. The agitation unit 66 conveys the two-component developer while stirring and adheres to the developing sleeve 65, and the developing unit 67 transfers the toner of the two-component developer attached to the developing sleeve 65 to the photoreceptor 40. The stirring unit 66 is positioned lower than the developing unit 67.
[0058]
The stirring unit 66 is provided with two parallel screws 68. The two screws 68 are partitioned by a partition plate 69 except for both ends (see FIG. 6). A toner concentration sensor 71 is attached to the developing case 70.
[0059]
On the other hand, the developing portion 67 is provided with a developing sleeve 65 facing the photoreceptor 40 through the opening of the developing case 70, and a magnet 72 is fixedly provided in the developing sleeve 65. Further, a doctor blade 73 is provided with the tip approaching the developing sleeve 65. In the illustrated example, the distance at the closest portion between the doctor blade 73 and the developing sleeve 65 is set to 500 μm.
[0060]
Then, the two-component developer is conveyed and circulated while being stirred by the two screws 68 and supplied to the developing sleeve 65. The developer supplied to the developing sleeve 65 is drawn up and held by the magnet 72 to form a magnetic brush on the developing sleeve 65. The magnetic brush is trimmed to an appropriate amount by the doctor blade 73 as the developing sleeve 65 rotates. The developer that has been cut off is returned to the stirring unit 66.
[0061]
On the other hand, of the developer on the developing sleeve 65, the toner is transferred to the photoreceptor 40 by the developing bias voltage applied to the developing sleeve 65, and the electrostatic latent image on the photoreceptor 40 is visualized. After the visualization, the developer remaining on the developing sleeve 65 leaves the developing sleeve 65 and returns to the stirring unit 66 where there is no magnetic force of the magnet 72. When the toner concentration in the stirring unit 66 becomes light by this repetition, it is detected by the toner concentration sensor 71 and the stirring unit 66 is replenished with toner.
[0062]
Incidentally, in the illustrated example, the linear velocity of the photosensitive member 40 is 200 mm / s, and the linear velocity of the developing sleeve 65 is 240 mm / s. The developing process is performed with the diameter of the photoreceptor 40 being 50 mm and the diameter of the developing sleeve 65 being 18 mm. The toner charge amount on the developing sleeve 65 is in the range of −10 to −30 μC / g. Development gap G, which is the gap between the photoreceptor 40 and the development sleeve 65_PCan be set in the range of 0.8 mm to 0.4 mm, and development efficiency can be improved by decreasing the value.
[0063]
The thickness of the photoreceptor 40 is 30 μm, the beam spot diameter of the optical system is 50 × 60 μm, and the light quantity is 0.47 mW. Further, the charging (pre-exposure) potential V of the photosensitive member 40.₀-700V, post-exposure potential V_LThe development process is performed with a development bias voltage of −470V, that is, a development potential of 350V.
[0064]
Next, the primary transfer device 62 is formed in a roller shape and is pressed against the photoconductor 40 with the intermediate transfer body 10 interposed therebetween. Separately, it is not limited to a roller shape, and may be a non-contact corona charger or the like.
[0065]
The photoconductor cleaning device 63 is provided with a cleaning blade 75 made of polyurethane rubber, for example, with its tip pressed against the photoconductor 40, and the outer periphery of the photoconductor cleaning device 63 contacts the photoconductor 40 and rotates the conductive fur brush 76 in the direction of the arrow. Prepare freely. Further, a metal electric field roller 77 for applying a bias to the fur brush 76 is rotatably provided in the direction of the arrow, and the tip of the scraper 78 is pressed against the electric field roller 77. Further, a collection screw 79 for collecting the removed toner is provided.
[0066]
Then, residual toner on the photoconductor 40 is removed by a fur brush 76 that rotates in the counter direction with respect to the photoconductor 40. The toner adhering to the fur brush 76 is removed by applying a bias by the electric field roller 77 that contacts the fur brush 76 and rotates in the counter direction. The electric field roller 77 is cleaned by a scraper 78. The toner collected by the photoconductor cleaning device 63 is brought to one side of the photoconductor cleaning device 63 by a collection screw 79, and returned to the developing device 61 by a toner recycling device 80, which will be described in detail, for reuse.
[0067]
The static eliminator 64 is a lamp, for example, and initializes the surface potential of the photoreceptor 40 by irradiating light.
[0068]
Then, along with the rotation of the photosensitive member 40, the surface of the photosensitive member 40 is first uniformly charged by the charging device 60, and then the writing light L from the exposure device 21 described above is emitted from the exposure device 21 according to the reading content of the scanner 300. Irradiation forms an electrostatic latent image on the photoreceptor 40.
[0069]
Thereafter, toner is attached by the developing device 61 to visualize the electrostatic latent image, and the visible image is transferred onto the intermediate transfer member 10 by the primary transfer device 62. The surface of the photoconductor 40 after the image transfer is cleaned by removing residual toner with the photoconductor cleaning device 63, and is neutralized with the static eliminator 64 to prepare for another image formation.
[0070]
4 is an enlarged view of a main part of the color copying machine shown in FIG. In the figure, each image forming unit 18 of the tandem image forming apparatus 20, each photoconductor 40 of the image forming unit 18, each developing device 61, each photoconductor cleaning device 63, and each photoconductor 40 of each image forming unit 18. After the respective symbols of the primary transfer devices 62 provided opposite to each other, BK is indicated for black, Y is indicated for yellow, M is indicated for magenta, and C is indicated for cyan. .
[0071]
4 is a conductive roller provided in contact with the base layer 11 side of the intermediate transfer body 10 between the primary transfer devices 62, although not shown in FIGS. This conductive roller 74 prevents the bias applied by each primary transfer device 62 during transfer from flowing into the adjacent image forming means 18 via the intermediate resistance base layer 11.
[0072]
Next, FIGS. 5 and 6 show the toner recycling apparatus 80. As shown in FIG. 5, the recovery screw 79 of the photoconductor cleaning device 63 is provided with a roller portion 82 having a pin 81 at one end. Then, one side of the belt-like collected toner conveying member 83 of the toner recycling device 80 is hung on the roller portion 82, and a pin 81 is inserted into the long hole 84 of the collected toner conveying member 83. The outer periphery of the collected toner conveying member 83 is provided with blades 85 at regular intervals, and the other side is hung on the roller portion 87 of the rotating shaft 86.
[0073]
The collected toner conveyance member 83 is placed in the conveyance path case 88 shown in FIG. The conveyance path case 88 is formed integrally with the cartridge case 89, and one of the above-described two screws 68 of the developing device 61 is placed at the end of the developing device 61 side.
[0074]
Then, the driving force is transmitted from the outside to rotate the collection screw 79, and the collection toner conveying member 83 is rotated and conveyed, and the toner collected by the photoconductor cleaning device 63 is conveyed to the developing device 61 through the conveyance path case 88. Then, the screw 68 is rotated into the developing device 61. Thereafter, as described above, the two screws 68 are conveyed and circulated while being stirred together with the developer already in the developing device 61, supplied to the developing sleeve 65 and cut off by the doctor blade 73, and then the photoreceptor 40. And the latent image on the photoreceptor 40 is developed.
[0075]
The toner is mixed with a charge control agent (CCA) and a colorant in a resin such as polyester, polyol, and styrene acrylic, and by adding a substance such as silica and titanium oxide around the resin, its charging characteristics and fluidity. Is increasing. The particle size of the additive is usually in the range of 0.1 to 1.5 [μm]. Examples of the colorant include carbon black, phthalocyanine blue, quinacridone, and carmine. The charging polarity is negative charging in the illustrated example.
[0076]
As the toner, a toner obtained by externally adding the above kind of additive to a base toner in which wax or the like is dispersed and mixed can be used. In the description so far, the toner is prepared by a pulverization method, but a toner prepared by a polymerization method or the like can also be used. In general, a toner prepared by a polymerization method, a heating method, or the like can be formed with a shape factor of 90% or more, and the coverage of the additive depending on the shape is extremely high.
[0077]
Here, the shape factor is originally sphericity and is defined as “the surface area of a sphere having the same volume as a particle / the surface area of an actual particle * 100%”. Calculate with The definition is “circumference of circle having the same projected area as the particle / projection contour length of the actual particle * 100%”. Then, the closer the projected circle is to a perfect circle, the closer to 100%.
[0078]
The range of the volume average particle diameter of the toner is preferably 3 to 12 μm. In the illustrated example, it is possible to sufficiently cope with a high resolution image of 1200 μm or more with 6 μm.
[0079]
The magnetic particles contain a magnetic material such as ferrite with a metal or resin as a core, and the surface layer is coated with a silicon resin or the like. The particle size is preferably in the range of 20-50 μm. The resistance is a dynamic resistance of 10⁴-10⁶The range of Ω is optimal. However, the measurement method is to support a roller (φ20; 600 RPM) enclosing a magnet, contact an electrode having a width of 65 mm and a length of 1 mm with a gap of 0.9 mm, and set the upper limit voltage level (high resistance silicon coating). It is a measured value when an applied voltage of 400 V is applied to the carrier and several volts is applied to the iron powder carrier.
[0080]
The developing sleeve 65 has a non-magnetic rotatable sleeve shape, and a plurality of magnets 72 are disposed therein. Since the magnet 72 is fixed, a magnetic force can be applied when the developer passes through a predetermined place. In the illustrated example, the diameter of the developing sleeve 65 is φ18, and the surface is sandblasted or processed to form a plurality of grooves having a depth of 1 to several mm so as to fall within the range of 10 to 30 μm RZ.
[0081]
The magnet 72 is N in the rotational direction of the developing sleeve 65 from the position of the doctor blade 73₁, S₁, N₂, S₂, S₃5 poles. (Toner + magnetic particles) formed by the magnet 72 is carried on the developing sleeve 65 as a developer, and the toner is mixed with the magnetic particles to obtain a specified charge amount. In the illustrated example, a range of −10 to −30 [μC / g] is preferable. The developing sleeve 65 is disposed opposite to the photoreceptor 40 in the S1 side region of the magnet 72 where a magnetic brush for developer is formed.
[0082]
Incidentally, in the illustrated example, as shown in FIG. 4, two fur brushes 90 and 91 are provided in the cleaning device 17 as cleaning members. Fur brush 90/91, φ20mm, acrylic carbon, 6.25D / F, 100,000 / inch²E + 7Ω, and is provided so as to contact the intermediate transfer member 10 and rotate in the counter direction. Then, biases of different polarities are applied to the fur brushes 90 and 91 from a power source (not shown).
[0083]
Such fur brushes 90 and 91 are provided so as to rotate in the forward direction in contact with metal rollers 92 and 93, respectively. In this example, a (−) voltage is applied from the power source 94 to the metal roller 92 on the upstream side in the rotation direction of the intermediate transfer body 10, and a (+) voltage is applied from the power source 95 to the metal roller 93 on the downstream side. The tips of the blades 96 and 97 are pressed against the metal rollers 92 and 93, respectively.
[0084]
Then, along with the rotation of the intermediate transfer member 10 in the direction indicated by the arrow, the surface of the intermediate transfer member 10 is cleaned by applying a bias (−), for example, using the fur brush 90 on the upstream side. If -700V is applied to the metal roller 92, the fur brush 90 becomes -400V, and the (+) toner on the intermediate transfer member 10 is transferred to the fur brush 90 side. The removed toner is further transferred from the fur brush 90 to the metal roller 92 due to a potential difference, and scraped off by the blade 96.
[0085]
Now, the toner on the intermediate transfer member 10 is removed by the fur brush 90, but a lot of toner still remains on the intermediate transfer member 10. Those toners are charged (−) by a (−) bias applied to the fur brush 90. This is considered to be charged by charge injection or discharge.
[0086]
However, the toner can be removed by performing cleaning by applying a bias (+) this time using the fur brush 91 on the downstream side. The removed toner is transferred from the fur brush 91 to the metal roller 93 due to a potential difference, and scraped off by the blade 97.
[0087]
The toner scraped off by the blades 96 and 97 is collected in a tank (not shown). You may make it return to the image development apparatus 61 using a toner recycling apparatus.
[0088]
Now, after cleaning with the fur brush 91, most of the toner is removed, but a little toner still remains on the intermediate transfer member 10. These toners are charged to (+) by a (+) bias applied to the fur brush 91. However, even if the toner remains on the intermediate transfer member 10 without being removed by the two fur brushes 90 and 91, the toner is reversely transferred to the photosensitive member 40BK at the black primary transfer position and collected by the photosensitive member cleaning device 63BK. can do.
[0089]
According to the experiment, about 50% of the toner remaining without being removed by the upstream fur brush 90 was also removed by 90% with the downstream fur brush 91. The toner that cannot be removed by the two fur brushes 90 and 91 but remains on the intermediate transfer member 10 can be almost reversely transferred to the photosensitive member 40BK side at the black primary transfer position, and an afterimage is seen on the sheet. There wasn't. Even when 50,000 full-color copies were made, no deterioration in image quality was observed.
[0090]
Incidentally, in the illustrated example described above, the toner remaining on the intermediate transfer body 10 without being transferred by the secondary transfer device 22 is charged from neutral to (+), but is extremely unstable. Therefore, much toner cannot be removed by the upstream fur brush 90.
[0091]
Therefore, in the example shown in FIG. 7, the bias applying member is in contact with the outside of the intermediate transfer member 10 at a position downstream of the secondary transfer device 22 and upstream of the cleaning device 17 in the rotation direction of the intermediate transfer member 10. As shown in FIG. Then, for example, (+) 700 V is applied to the bias roller 102 to uniformly (+) charge the toner remaining on the intermediate transfer body 10, for example.
[0092]
The (+) charged toner is removed by the upstream fur brush 90 to which the (−) bias is applied. According to experiments, about 90% of the transfer residual toner could be removed. The toner that has not been removed by the upstream fur brush 90 is almost removed by the downstream fur brush 91 to which the next (+) bias is applied.
[0093]
Even when it cannot be removed by the two fur brushes 90 and 91, the surface of the intermediate transfer body 10 can be cleaned by reverse transfer at the primary transfer position as described above, and a sufficient margin for cleaning can be provided. .
[0094]
In FIG. 7, parts corresponding to those in FIG. 4 are denoted by the same reference numerals as those used in FIG.
[0095]
In the example shown in FIG. 7, the bias roller 102 is arranged at the upstream position of the cleaning device 17. However, as shown in FIG. 8, the bias roller 102 is located downstream of the cleaning device 17 and upstream of the primary transfer position. A bias roller 104 may be provided as a bias application member in contact with the outside of the intermediate transfer member 10.
[0096]
Then, for example, a (+) bias is applied by the bias roller 104 so that the toner on the intermediate transfer body 10 has the same polarity as the bias applied at the primary transfer position, and the photoreceptor 40BK side at the primary transfer position. It is possible to reliably perform reverse transfer and to collect the photoconductor cleaning device 63BK.
[0097]
In FIG. 8, the same reference numerals as those used in FIG. 4 are assigned to portions corresponding to those in FIG.
[0099]
【The invention's effect】
  As explained above, according to the invention of claim 1,Intermediate transfer body cleaning deviceAs the cleaning member, two cleaning members that apply biases of different polarities are provided,Intermediate transfer memberFirst, apply a bias using the upstream cleaning member.Intermediate transfer memberThe surface is cleaned, and then the cleaning member on the downstream side is used to apply a bias having a polarity opposite to that of the previous one.Intermediate transfer memberEven if the toner remains on the surface, not only the toner is mechanically scraped off, but also electrostatically adsorbed and removed cleanly, and the occurrence of an afterimage can be prevented.
[0102]
  AlsoSince the bias having the same polarity as the bias applied at the primary transfer position is applied to the cleaning member on the downstream side in the rotation direction of the intermediate transfer member, it cannot be removed by the two cleaning members.Intermediate transfer memberEven when the toner remains on the surface, the remaining toner can be charged with the same polarity as the bias applied at the primary transfer position, reversely transferred to the photoreceptor side at the primary transfer position, and collected by the photoreceptor cleaning device. .
[0104]
  Claim2According to the invention according toIntermediate transfer memberIn the direction of rotationSecondaryDownstream of the transcription positionpositionBecauseIntermediate transfer memberA bias applying member is provided at an upstream position of the cleaning device,Intermediate transfer memberIn front of the cleaning deviceIntermediate transfer memberSince the polarity of the upper toner is aligned, reverse polarity is applied by the upstream cleaning member.Intermediate transfer memberThe upper toner can be removed efficiently, and even if it cannot be completely removed, a reverse polarity bias is further applied by the next downstream cleaning member.Intermediate transfer memberMost of the toner on the top can be removed.
[0105]
  Claim3According to the invention related toIntermediate transfer memberDownstream of the cleaning devicepositionA bias applying member is provided upstream of the primary transfer position;Intermediate transfer memberSince the toner remaining on the intermediate transfer member after cleaning by the cleaning device is aligned with the same polarity as the bias applied at the primary transfer position, it is reliably reverse-transferred to the photoconductor side at the primary transfer position and recovered by the photoconductor cleaning device. be able to.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention and is an overall schematic configuration diagram of a color copying machine of a tandem type indirect transfer system.
FIG. 2 is a partially enlarged cross-sectional view showing a cross-sectional configuration of an intermediate transfer member used in the color copying machine.
FIG. 3 is a partially enlarged configuration diagram of a dandem image forming apparatus used in the color copying machine.
FIG. 4 is an enlarged configuration diagram of a main part of the color copying machine.
FIG. 5 is an exploded perspective view illustrating a toner recycling apparatus used in the color copying machine.
FIG. 6 is a cutaway perspective view of the developing unit side of the toner recycling apparatus.
FIG. 7 is a partially enlarged configuration diagram of a dandem image forming apparatus showing another example of an intermediate transfer member cleaning apparatus used in the color copying machine.
FIG. 8 is a partially enlarged configuration diagram of a dandem image forming apparatus showing still another example.
FIG. 9 is a configuration diagram around a dandem image forming apparatus in a conventional tandem type indirect transfer type color copier.
FIG. 10 is a configuration diagram around a dandem image forming apparatus in a conventional tandem direct transfer type color copier.
[Explanation of symbols]
10 Intermediate transfer member (image carrier)
17 Intermediate transfer member cleaning device
18 Image forming means
20 Tandem image forming apparatus
22 Secondary transfer device
40 photoconductor (image carrier)
62 Primary transfer device
63 Photoconductor cleaning device
80 Toner recycling device
90 fur brush
91 Fur Brush
102 Bias roller (bias application member)
104 Bias roller (Bias application member)

Claims (3)

The image on the photoconductor is primarily transferred to the intermediate transfer member by the primary transfer device, and then the image on the intermediate transfer member is secondarily transferred to the sheet by the secondary transfer device, while the image is transferred onto the photoconductor after the primary transfer. An electrophotographic apparatus comprising a photosensitive member cleaning device for removing residual toner remaining and an intermediate transfer member cleaning device for removing residual toner remaining on the intermediate transfer member after secondary transfer.
As the cleaning member of the intermediate transfer member cleaning device, two cleaning members for applying different polar biases are provided,
Among these cleaning members, a bias having the same polarity is applied to the cleaning member on the downstream side in the rotation direction of the intermediate transfer member at the primary transfer position.
Electrophotographic device.   A bias applying member that aligns the polarity of toner on the intermediate transfer body is provided at a position downstream of the secondary transfer position in the rotation direction of the intermediate transfer body and upstream of the intermediate transfer body cleaning device. Item 2. The electrophotographic apparatus according to Item 1. A bias applying member for aligning the toner on the intermediate transfer body with the same polarity as the bias applied at the primary transfer position is provided at a position downstream of the intermediate transfer body cleaning device and upstream of the primary transfer position. becomes, electrophotographic equipment according to claim 1.

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