JP5230540B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to a charger for charging the surface of a photoreceptor and a cleaner unit for cleaning the surface of the photoreceptor.

  An image forming apparatus that forms an image on a sheet includes a cleaner unit that cleans toner adhering to the surface of the photoreceptor after transfer with a blade such as urethane rubber.

  However, when printing is repeated for a long time, the toner remains on the blade surface, and the residual toner may adhere to the photosensitive member, which may cause a printing defect.

  Therefore, a cleaning device has been proposed in which a conductive sheet is attached to the blade surface and an AC voltage is applied to remove the toner on the blade surface and prevent the toner from adhering to the photoreceptor (Patent Document 1). See).

JP-A-1-179978

  In the non-contact type charger, a shield case is provided so that the discharge does not leak. Therefore, as shown in Patent Document 1, the cleaner unit is separately provided on the upstream side of the shield case (upstream side in the moving direction of the photosensitive member surface).

  However, if the cleaner unit is separately provided on the upstream side of the shield case, a large space is required. In particular, when forming a color image, it is necessary to provide a plurality of photoreceptors, cleaner units, and chargers for each color. If a cleaner unit is provided separately on the upstream side of the shield case, a very large space is required. It was.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that realizes space saving of a cleaner unit and a charger.

  The image forming apparatus of the present invention is characterized in that a part of the shield case of the charger is made of a sheet metal for fixing a cleaning blade for the photosensitive member. The cleaning blade is provided on the upstream side of the shield case in the moving direction of the photoreceptor surface.

  Thus, by attaching the cleaning blade to a part of the sheet metal of the shield case, the sheet metal for fixing the blade and a part of the shield case can be used together, and space saving can be realized. In addition, a part of the storage case for storing the scraped toner can be a part of the shield case (or a part of the shield case can be a part of the storage case), and further space saving can be realized. Can do.

  Further, in the above configuration, a mode in which the surface of the cleaning blade that faces the electrode of the charger is made conductive and grounded is also possible. As a result of a part of the shield case of the charger being made of a sheet metal for fixing the cleaning blade of the photosensitive member, the surface of the cleaning blade may be exposed to the discharge of the charger and the discharge product may adhere. Since the discharge product attracts moisture, water may adhere to the surface of the cleaning blade. Then, the surface of the photosensitive drum may be locally charged through the surface of the cleaning blade. Therefore, the surface of the cleaning blade facing the electrode is made conductive and grounded so that the charge on the surface of the cleaning blade is released.

  In this case, a mode in which the cleaning blade itself is made of conductive rubber is also possible, and a mode in which a conductive sheet is attached to the surface facing the electrode of the charger and the conductive sheet is electrically connected to the sheet metal. Is also possible.

  The conductive sheet preferably has a surface layer of ethylene / propylene rubber.

  According to this invention, space saving of the charger and the cleaner unit can be realized.

1 is a schematic front sectional view of an image forming apparatus according to an embodiment of the present invention. It is a perspective view which shows the structure of a cleaner unit and a charger. It is front sectional drawing which shows the structure of a cleaner unit and a charger. It is front sectional drawing which shows the structure of the cleaner unit which concerns on another example, and a charger.

  FIG. 1 is a schematic front sectional view of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus 100 includes an apparatus main body 110 and an automatic document processing apparatus 120, and forms a multicolor or single color image on a sheet according to image data transmitted from the outside.

  The apparatus main body 110 includes an exposure unit 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, a fixing unit 7, a paper feed cassette 81, and a manual feed tray 82.

  On the upper part of the apparatus main body 110, a document placing table 92 made of transparent glass on which a document is placed is provided. An automatic document processing device 120 is attached to the upper side of the document table 92. The automatic document processor 120 automatically conveys the document on the document table 92. The automatic document processing device 120 is supported so as to be rotatable in the direction of arrow M in the figure, and the document can be placed manually by opening the upper surface of the document table 92.

  The image forming apparatus 100 forms a color image by performing electrophotographic image formation using four color toners of black (K), cyan (C), magenta (M), and yellow (Y). For this reason, the developing device 2, the photosensitive drum 3, the cleaner unit 4, and the charger 5 are provided for each color.

  The charger 5 uniformly charges the surface of the photosensitive drum 3 to a predetermined potential. The charger 5 of the present embodiment uses a non-contact type charger.

  As an example, the exposure unit 1 is a laser scanning unit (LSU) provided with a laser emitting portion, a reflection mirror, and the like. The exposure unit 1 scans the surface of the photosensitive drum 3 corresponding to each color with a laser beam modulated and emitted from the semiconductor laser corresponding to each color in accordance with the image data of each color to form an electrostatic latent image. To do. In addition to the LSU shown in FIG. 1, the exposure unit 1 can use, for example, an EL or LED writing head in which light emitting elements are arranged in an array.

  The developing device 2 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 3 for each color with toner.

  An intermediate transfer belt unit 6 is disposed above the photosensitive drum 3. The intermediate transfer belt unit 6 includes an intermediate transfer belt 61, an intermediate transfer belt drive roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and a cleaner unit 65. Four intermediate transfer rollers 64 are provided for each color.

  The intermediate transfer belt driving roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 rotate the intermediate transfer belt 61. The intermediate transfer belt 61 is provided so as to contact the surface of each photosensitive drum 3.

  The intermediate transfer roller 64 is applied with a high-voltage transfer bias (voltage having a polarity opposite to the toner charging polarity (−) and a polarity (+)) in order to transfer the toner image. As a result, the toner images of the respective colors formed on the photosensitive drum 3 are sequentially transferred onto the intermediate transfer belt 61 by the intermediate transfer roller 64. Note that a transfer brush or a transfer charger may be used instead of the transfer roller.

  The toner remaining on the surface of the photosensitive drum 3 after the intermediate transfer process is removed from the surface of the photosensitive drum 3 by the cleaner unit 4.

  The color toner image formed on the intermediate transfer belt 61 is transferred onto the sheet by the rotation of the intermediate transfer belt 61 and the transfer roller 10 disposed at the contact position of the sheet and the intermediate transfer belt 61.

  At this time, the intermediate transfer belt 61 and the transfer roller 10 are pressed into contact with each other at a predetermined nip, and the transfer roller 10 has a voltage for transferring the toner onto the sheet (a toner having a high polarity (-) and reverse polarity (+)). Voltage) is applied.

  Further, in order to obtain the nip constantly, the transfer roller 10 uses either the transfer roller 10 or the intermediate transfer belt drive roller 62 as a hard material (metal or the like) and the other as a soft material (such as an elastic roller). An elastic rubber roller or a foaming resin roller).

  The toner remaining on the intermediate transfer belt 61 causes toner color mixture in the next process, and is therefore removed and collected by the cleaner unit 65.

  A paper feed cassette 81 provided on the lower side of the apparatus main body 110 stores paper before image formation. Further, the paper before image formation can be placed on the manual feed tray 82 as well.

  The apparatus main body 110 is provided with a paper conveyance path S for conveying the paper stored in the paper feed cassette 81 or the manual feed tray 82. The paper transport path S is a path for transporting paper from the transfer roller 10 through the fixing unit 7 to a paper discharge tray 91 provided above the apparatus main body 110. In the sheet conveyance path S, a pickup roller 11A, a pickup roller 11B, a plurality of conveyance rollers 12A to 12D, a registration roller 13, a transfer roller 10, and a fixing unit 7 are arranged.

  The transport rollers 12A to 12D are small rollers for promoting and assisting the transport of the paper. The pickup roller 11 </ b> A is provided in the vicinity of the paper feed cassette 81, picks up paper one by one from the paper feed cassette 81, and supplies it to the paper transport path S. The pickup roller 11 </ b> B is provided in the vicinity of the manual feed tray 82, picks up the paper one by one from the manual feed tray 82, and supplies it to the paper transport path S.

  The registration roller 13 once holds the sheet conveyed through the sheet conveyance path S, and then conveys the sheet to the transfer roller 10 at a timing when the leading edge of the toner image on the photosensitive drum 3 coincides with the leading edge of the sheet.

  During single-sided image formation (single-sided printing), the paper is transported between the intermediate transfer belt 61 and the transfer roller 10 by the transport roller 12A and the registration roller 13 from the paper feed cassette 81 or the manual feed tray 82. Thereafter, the sheet passes through the fixing unit 7 and is discharged onto the sheet discharge tray 91 through the conveyance roller 12B.

  During double-sided image formation (double-sided printing), after the toner image is transferred to one side of the sheet and passes through the fixing unit 7, the conveyance roller 12B is moved when the trailing edge of the sheet reaches the final conveyance roller 12B. Reverse rotation. Thereafter, the sheet is guided between the intermediate transfer belt 61 and the transfer roller 10 through the registration roller 13 with the front and back surfaces reversed through the transport roller 12C and the transport roller 12D. Then, after an image is formed on the other side of the sheet, the sheet is discharged to the discharge tray 91 via the transport roller 12B.

  Next, the cleaner unit and the charger of this embodiment will be described. FIG. 2 is a perspective view showing a part of the structure of the cleaner unit 4 and the charger 5. FIG. 3 is a cross-sectional view (a cross-sectional view in a plane parallel to the rotation axis of the photosensitive drum 3) showing a part of the structure of the cleaner unit 4 and the charger 5.

  The charger 5 includes an electrode (discharge needle) 51 for discharging, a frame 52 having an L-shaped cross section, and a screen grid 53 made of a mesh-like metal plate. The cleaner unit 4 includes a cleaning blade 41 made of urethane rubber, a sheet metal 42 for fixing the cleaning blade 41, a conductive fitting 43 attached to the sheet metal 42 and grounded, and a conductive sheet 44. Yes. The tip of the cleaning blade 41 is in contact with the surface of the photosensitive drum 3 and scrapes off the residual toner adhering to the surface of the photosensitive drum 3.

  The electrode 51 is disposed so as to be surrounded by the frame 52 and a part of the sheet metal 42. One surface of the L-shaped inner surface of the frame 52 faces the surface of the photosensitive drum 3, and the other surface faces a part of the sheet metal 42. A cleaning blade 41 is fixed to a part of the surface of the sheet metal 42. The cleaning blade 41 is provided on the upstream side (upstream side in the moving direction of the surface of the photosensitive drum 3). The screen grid 53 is provided between the electrode 51 and the surface of the photosensitive drum 3. The sheet metal 42 is a part of a storage case that stores the toner scraped off by the cleaning blade 41.

  As described above, the cleaner unit and the charger of this embodiment form a shield case of the charger 5 using the frame 52 having an L-shaped cross section and the sheet metal 42 which is a part of the toner storage case. . That is, a part of the shield case of the charger 5 is configured by a sheet metal for fixing the cleaning blade for the photosensitive member.

  In the case of the structure described above, the surface of the cleaning blade 41 that faces the electrode 51 is exposed to discharge. Then, discharge products (particularly conductive substances) such as ozone, NOx, and SOx generated by the discharge may adhere to the surface of the cleaning blade 41. In this case, moisture in the air is attracted to the discharge product, and water may adhere to the surface of the cleaning blade 41. In particular, there is a high possibility that water will adhere in a humid environment. Then, negative charges are transmitted along the surface of the cleaning blade 41 and flow to the surface of the photosensitive drum 3. In this case, the surface of the photosensitive drum 3 is locally strongly negatively charged, which may cause printing defects such as white stripes.

  Therefore, in the present embodiment, a conductive sheet 44 is attached to the surface of the cleaning blade 41 that faces the electrode 51, and the conductive sheet 44 is electrically connected to the sheet metal 42. The structure is such that the charge generated on the surface is released to the sheet metal 42 side.

  In addition, as for the electroconductive sheet 44, it is desirable for the surface layer to be EPEM (ethylene propylene rubber). If it is ethylene propylene rubber, the conductive effect is high and the surface is hardly oxidized. In this case, the conductive sheet 44 is adhered to the cleaning blade 41 and the sheet metal 42 with a conductive double-sided tape.

  Further, the conductive sheet 44 need not cover the entire surface of the cleaning blade 41. For example, the vicinity of the front end that contacts the surface of the photosensitive drum 3 (for example, about 9 mm from the front end) is less affected by the discharge and may not be covered with the conductive sheet 44.

  When the cleaning blade 41 itself has conductivity, is resistant to ozone, and has high mechanical strength, the conductive sheet 44 is not essential.

  As described above, according to the cleaner unit 4 and the charger 5 in the image forming apparatus of the present embodiment, the cleaning blade is attached to a portion of the sheet metal of the shield case of the charger, so that the blade fixing sheet metal and A part of the shield case can also be used, and space saving can be realized. In particular, in the above example, a part of the storage case that stores the scraped toner can be a part of the shield case, and further space saving can be realized. In addition, when the blade surface facing the electrode is made conductive and grounded, local charging of the surface of the photosensitive drum can be prevented, and the occurrence of printing defects can be prevented.

  The structure shown in FIGS. 2 and 3 is an example for carrying out the present invention, and is not limited to this example as long as the cleaning blade is attached to a part of the sheet metal of the shield case. . For example, the following structure may be used.

  FIG. 4 is a cross-sectional view (a cross-sectional view in a plane parallel to the rotation axis of the photosensitive drum 3) showing the structure of the cleaner unit 4 and the charger 5 according to another example. Components that are the same as those in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted.

  In the example shown in the figure, the charger 5 forms a shield case using a U-shaped frame 55. The cleaning blade 41 is fixed to a part of the surface of the frame 55. The conductive sheet 44 is attached to the cleaning blade 41 and the frame 55. Although not shown, a conductive metal fitting is attached to the frame 55 and is grounded. Therefore, the surface of the cleaning blade 41 that faces the electrode has conductivity and is grounded.

  The surface on the back side of the surface of the frame 55 that fixes the cleaning blade 41 is covered with a frame 45 for a storage case. That is, a part of the shield case of the charger 5 is a part of the toner storage case of the cleaner unit 4.

  Also in this case, a part of the shield case of the charger 5 has a structure made of a sheet metal for fixing the cleaning blade 41 of the photosensitive member, and space saving can be realized. Also in this case, since the blade surface facing the electrode is made conductive and grounded, local charging on the surface of the photosensitive drum can be prevented, and printing failure can be prevented. Can do.

DESCRIPTION OF SYMBOLS 3 ... Photosensitive drum 4 ... Cleaner unit 5 ... Charger 41 ... Cleaning blade 42 ... Sheet metal 43 ... Conductive metal fitting 44 ... Conductive sheet 45 ... Frame 51 ... Electrode 52 ... Frame 53 ... Screen grid 55 ... Frame

Claims (3)

A part of the shield case of the charger is composed of a sheet metal that fixes the cleaning blade of the photoreceptor ,
The cleaning blade has a conductive surface facing the electrode of the charger, and is grounded.
An image forming apparatus , wherein a conductive sheet is attached to a surface facing the electrode of the charger, and the conductive sheet is electrically connected to the sheet metal .   The image forming apparatus according to claim 1, wherein the cleaning blade is provided upstream of the shield case in a moving direction of the surface of the photoreceptor. The conductive sheet, the image forming apparatus according to claim 1 or 2 surface layer comprising an ethylene-propylene rubber.

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