Patent Grant
8630561
Embodiments described herein below relate to an image forming apparatus that forms an image on a recording medium such as s sheet of paper, and a cleaning method of removing foreign matter such as sheet residuum or toner dust attached to a charging device upon forming an image.
Generally, in an electrophotographic recording type of an image forming apparatus, a photoconductive drum is irradiated with a laser beam to form an electrostatic latent image. The photoconductive drum forms a toner image by a developing device and transfers the toner image onto a sheet of paper to obtain an image. Furthermore, the image forming apparatus includes a charging device, thereby uniformly charging an electric charge to an outer peripheral surface of the photoconductive drum by the charging device in an axial direction.
Incidentally, in the image forming apparatus of the related art, foreign matter and the like such as discharge products or toner dust that is attached to a discharge electrode of the charging device, sheet fiber and floating matter floated by the flow of wind in a device body are attached to the charging device. When foreign matter is attached to the charging device, an image noise occurs, which causes a decline in the printing quality.
An image forming apparatus according to an embodiment including:
an image carrier which is irradiated with a laser beam to form an electrostatic latent image,
a charging device which is disposed in parallel to the image carrier and includes an electrode that charges an electric charge to the image carrier,
a cleaning device which includes a container accommodating a first cleaning member abutting an end portion of a discharge side of the electrode, enables the container to move along the longitudinal direction of the electrode, removes foreign matter attached to the electrode by the cleaning member, and accommodates the foreign matter in the container,
a developing device that supplies the image carrier with a developer, and
a transfer device that transfers a toner image formed on the image carrier by the developing device onto a recording medium.
Hereinafter, an image forming apparatus according to an embodiment will be described with reference to the drawings. Furthermore, the same parts in each drawing will be denoted by the same reference numerals.
On an upper part of the image forming apparatus (MFP) 10, an automatic document feeding device (ADF) 11, a transmitting document table 12, and an operation panel 13 are included. Furthermore, a plurality of sheet feeding devices 14 are provided on a lower part of the MFP 10, and a tray 15 for stacking the sheet is provided on a side surface of the MFP 10.
Furthermore, the MFP 10 includes a scanner unit 20, and a printer unit 30. The scanner unit 20 reads an image of a document, and the printer unit 30 forms an image on a recoding medium such as a sheet of paper based on the read data. In the following description, an example will be described in which the sheet S is used as the recording medium.
The scanner unit 20 includes a carriage 21, an exposure lamp 22, a reflection mirror 23, a lens 24, a CCD (Charge Coupled Device) 25, and a laser unit 26. The scanner unit 20 radiates light from the exposure lamp 22 provided in the carriage 21 to the document from the lower part of the document table 12 so as to scan and read the document transported by the ADF 11 or the document placed on the document table 12. Moreover, the reflected light from the document is put into a CCD 25 via the reflection mirror 23 and the lens 24.
Image information input to the CCD 25 is output as an analog signal. The analog signal is converted to a digital signal and is subjected to an image process, whereby image data is created. The image data is supplied to the laser unit 26, and a laser beam is generated from the laser unit 26 depending on the image data.
Since the printer unit 30 constitutes an image forming unit, the printer unit 30 has a rotatable photoconductive drum 31. The photoconductive drum 31 is an image carrier. In the periphery of the photoconductive drum 31, a charging device 32, a developing device 33, a transfer device 34, a cleaner 35, and a neutralization lamp 36 are included along a rotation direction. The laser beam from the laser unit 26 is radiated to the photoconductive drum 31, and an electrostatic latent image corresponding to the image information of the document is formed on the outer peripheral surface of the photoconductive drum 31.
When the image formation is started, the charging device 32 is discharged in a predetermined discharge position, uniformly charges the electric charge on the outer peripheral surface of the rotating photoconductive drum 31 in the axial direction, and gives the surface of the photoconductive drum 31 (−) electric charge.
Next, a laser beam is radiated from the laser unit 26 to the photoconductive drum 31. The charging surface of the photoconductive drum 31 is scanned and exposed, and the electrostatic latent image relative to the scanning exposure pattern is formed and held on the surface of the photoconductive drum 31.
The developer (for example, toner) is supplied from the developing device 33 onto the outer peripheral surface of the photoconductive drum 31, and the electrostatic latent image is converted to a toner image and is developed. The toner image formed on the outer peripheral surface of the photoconductive drum 31 is electrostatically transferred onto the sheet S by the transfer device 34. The sheet S is transported from the sheet feeding device 14 via a transport path 37.
Foreign matter such as sheet residue remaining on the photoconductive drum 31 is removed by a cleaner 35 disposed in a post-process of the transfer device 34. The neutralization lamp 36 removes a (−) residual electric charge of the outer peripheral surface of the photoconductive drum 31.
Furthermore, the configuration of the printer unit 30 can use another method, for example, a method of using an intermediate transfer belt or the like, without being limited to the example shown. Furthermore, in
The sheet S, onto which the toner image was transferred by the printer unit 30, is transported to the fixing device 38. The fixing device 38 includes a fixing roller and a pressing roller disposed opposite to each other, and fixes the toner image transferred onto the sheet S to the sheet S by transporting the sheet S between the fixing roller and the pressing roller. The sheet S, in which the toner image is fixed and the image formation is completed, is discharged by a sheet discharging roller 39 to the tray 15.
The developing device 33 adopts a two component developing method, and includes a magnet roller 331, and a developing sleeve 332 that rotates around the outer periphery of the magnet roller 331. The magnet roller 331 selectively provides the toner moving on the surface of the developing sleeve 332 to the latent image of the surface of the photoconductive drum 31 while magnetically adsorbing the toner.
The transfer device 34 includes a transfer roller 341, a sheet transport belt 342, a driven roller 343 and a peeling device 344. The sheet transport belt 342 is rotated by the transfer roller 341 and the driven roller 343 to transport the sheet S. Furthermore, the toner image is transferred onto the sheet S transported on the sheet transport belt 342 by an electric field to be supplied by the transfer roller 341. The peeling device 344 separates the sheet S with the toner attached thereon from the surface of the photoconductive drum 31.
The cleaner 35 includes, for example, seal materials 351 and 352 or a cylindrical brush 353, and forcibly scrapes off foreign matter such as sheet residue or residual toner attached to the surface of the photoconductive drum 31. The neutralization lamp 36, for example, drops (−) electric charge on the photoconductive drum 31 onto an earth by causing light to touch the whole photoconductive drum 31 (the image forming range) by the LED.
The fixing device 38 includes a fixing roller 381 and a pressing roller 382. The fixing roller 381 has a heater 383 for heating therein, and the fixing roller 381 and the pressing roller 382 are rotated in a mutually contacting state. Moreover, the sheet S passes through a portion between the fixing roller 381 and the pressing roller 382, thereby fixing the toner on the sheet S to the sheet S.
Hereinafter, the charging device 32 according to an embodiment will be described with reference to
In the charging device that uses the needle-shaped electrode, silicon as a discharge product is attached to the periphery of the needle-shaped electrode, and grows as the discharge is repeated, and discharge irregularity occurs according to the growth of silicon. Furthermore, as time passes, toner dust or sheet powder is attached to the electrode and discharge irregularity occurs. When foreign matter such as silicon, toner dust, sheet powder or the like is attached to the needle-shaped electrode, the attachment is a cause of image noise, and thus, the cleaning device is provided in the charging device 32.
Furthermore, a grid 45 is disposed in an opening portion of the shield plate 41 of the charging device 32. The (−) electric charge is similarly given to the surface of the photoconductive drum 31 by the corona discharge and the grid 45. The grid 45 is used to control the passage of electrically charged particles and cause the charge electric potential to converge to a certain value. The grid 45 is mounted so as not to damage a mesh portion or a fine portion or so that contaminants (fingerprints of a person and the like) are not attached thereto.
As shown in
Insulation terminals 42 and 43 are provided in both ends of the shield plate 41, and both ends of the electrode 44 are supported by the insulation terminals 42 and 43. Furthermore, on the bottom surface of the insulation terminals 42 and 43, a concave portion 47 for attaching the grid 45 is provided (
The electrode 44 is formed of an electrically conductive member extended in the axial direction of the photoconductive drum 31, for example, stainless steel, and forms a plurality of charging needles 44A at one side thereof facing the grid 45. The electrode 44, for example, forms the charging needles 44A having a thickness of 0.1 mm and a height of 2 mm at a gap of 2 mm. Furthermore, the electrode 44 is disposed so that a portion between the charging needles 44A and the surface of the photoconductive drum 31 maintains a gap of, for example, 9.2 mm. Furthermore, be desirable that a front end of the charging needle 44A has a curvature (R) equal to or less than 30 μmm.
The electrode 44 is supported by the insulation terminals 42 and 43, and as shown in
A cleaning device 52 of the charging device 32 includes a cleaning member 53 that cleans the charging needles 44A of the electrode 44, and a container 54 that accommodates the cleaning member 53. The container 54 is movable along the longitudinal direction of the shield plate 41. When the container 54 is moved, the cleaning member 53 scrapes off the foreign matter attached to the plurality of charging needles 44A and accommodates the fallen foreign matter in the container 54.
A guide 55 is provided in the ceiling portion of the container 54, and the guide 55 is adapted to be protruded through the slit 46 of the shield plate 41 (
Thus, by pushing or pulling the movement rod 57 by a user operation, the container 54 is moved to arrows X1-X2 along the electrode 44, thereby cleaning the charging needles 44A by the cleaning member 53.
The cleaning member 53 can be attached to and detached from the container 54 and can be exchanged. The cleaning member 53 has a U-shaped cross-section so as to surround the charging needles 44A of the electrode 44. As the cleaning member 53, for example, a material such as polyimide or polyamide represented by Kapton Sheeting™ may be used.
In the end portion of the lower holder 54A in the movement direction, a slit 60 is formed through which the electrode 44 passes. The lower holder 54A has a space that accommodates the foreign matter near both sides of the cleaning member 53, and can accommodate the foreign matter fallen upon cleaning the electrode 44.
The upper holder 54B inserts the guide 55 into the ceiling portion, and fixes the front end of the movement rod 57 to the guide 55. Furthermore, in the end portion of the upper holder 54B in the movement direction, a slit is formed through which the electrode 44 passes. Furthermore, in order to combine and fix the lower holder 54A and the upper holder 54B, for example, a window 62 is formed on the side surface of the lower holder 54A, and a hook 63 is provided in a position that faces the window 62 of the upper holder 54B. If the lower holder 54A and the upper holder 54B are combined with each other so that the hook 63 is fitted into the window 62, the container 54 can be assembled.
Thus, the user causes the movement rod 57 to exit and enter, whereby the container 54 is moved in the axial direction (arrows X1-X2 direction) of the photoconductive drum 31, and the cleaning member 53 is moved while coming into contact with the charging needles 44A of the electrode 44. Foreign matter such as silicon, toner dust or sheet powder attached to the charging needles 44A of the electrode 44 is scrapped off by the cleaning member 53 and can be accommodated in the container 54 (the lower holder 54A).
Furthermore, in regard to the cleaning member 53 of
Furthermore, the electrode 44 may use a corona wire instead of the needle-shaped electrode. An example of the cleaning member 53 when using the electrode of the corona wire is illustrated in
According to a first embodiment, a user can securely remove silicon, toner, sheet residue or the like attached to the electrode 44 of the charging device 32 by pushing or pulling the movement rod 57.
The cleaning device 52 of
That is, the foreign matter (*) attached to the electrode 44 in the container 54 is scrapped off by the cleaning member 53 and is accommodated in the container 54. Furthermore, as shown in
Although
Generally, since the urethane-based adhesive has an excellent re-peeling property, such an adhesive is used for a protective sheet of a mobile phone, a dust removal roll or the like. Thus, as the adhesive 70 of the auxiliary cleaning members 68A and 68B, urethane-based adhesive may be used. Furthermore, surfaces, to which the auxiliary cleaning members 68A and 68B of the insulation terminals 42 and 43 are pressed, are minute convex and concave surfaces 42A, and may have shapes to which the adhesive 70 hardly sticks to and has a satisfactory peeling property. The convex and concave surfaces 42A may have shapes in which a plurality of multi-pyramids, cones, cylinders having round front ends are arranged in a row at equal distances, for example, having heights equal to or less than 2 mm.
Furthermore, as shown in
In the state in which contaminants such as the discharge product, dust, and toner are attached to the front end portion of the electrode 44, an image irregularity occurs in a white background portion of the printed image. However, immediately after the front end portion of the electrode 44 is cleaned by the cleaning device 52 of the present embodiment, images of the white background and a intermediate tone (half tone) are printed, an occurrence situation of the image irregularity (a discharge irregularity) was confirmed, and the result showed that the image irregularity (the discharge irregularity) does not occur even after 5,000 sheets of image sheet of printing rate 10% pass, and a satisfactory result was obtained.
Furthermore, although, as the movement mechanism of the container 54, a mechanism was described which is moved by the operation of the movement rod 57 by the user, the movement mechanism may be electrically moved by a motor and the like.
Thus, by rotating the motor 76 in response to the operation of a user or rotating the motor 76 at the predetermined timing, the electrode 44 can be cleaned. Moreover, the mechanism, which moves the container 54 using the motor 76, is not limited to an example of
Furthermore, the cleaning member 53 fixed to the lower holder 54A of the container 54 is exchangeable, and when a lot of foreign matter is stacked in the container 54, the lower holder 54A may be pulled out to remove the foreign matter and may be exchanged for a new cleaning member 53. Furthermore, the auxiliary cleaning members 68A and 68B may also be exchangeable.
According to the aforementioned embodiments, be possible to reliably remove silicon, toner, sheet residue or the like attached to the discharge electrode of the charging device 32. Furthermore, the foreign matter floating in the charging device 32 can be captured and there is an effect of preventing image noise.
Moreover, various modifications can be made without being limited to the aforementioned embodiments. For example, the shape or the material of the cleaning member 53 can use other shapes or other materials without being limited to the aforementioned examples.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel apparatus and methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatus and methods described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and the spirit of the inventions.
This application is based upon and claims the priority of U.S. Provisional Application No. 61/332,689, filed on May, 7, 2010, the entire contents of which are incorporated herein by reference.
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