JP3795763B2 - Image forming apparatus and image carrier unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an image forming apparatus including an image carrier having a photosensitive layer and a charging unit having a charging member for charging the image carrier, and an image carrier unit attached to the image forming apparatus.
[0002]
[Prior art]
  2. Description of the Related Art Conventionally, a charging member having an effective charging width is placed close to the surface of a photoconductor as an image carrier, and a voltage is applied between the charging member and the photoconductor to charge the surface of the photoconductor. There are non-contact charging devices. Such a charging device has an advantage that the charging member is not easily soiled because the effective charging width portion of the charging member does not contact the surface of the photoreceptor.
[0003]
  In such a non-contact type charging device, for example, a convex portion is formed by attaching a tape member to both ends of a roller portion of a charging roller, which is a charging member, so that other portions excluding both ends of the charging roller are formed. The surface of the photoconductor, which is an image carrier, is not contacted.
  An example of the charging roller is shown in FIG. The charging roller 114 is provided with, for example, an elastic portion 117 having conductivity on the outer periphery of a stainless steel core 116, and resin tape members 118, 118 are wound in the circumferential direction around both ends of the elastic portion 117. It is fixed together.
[0004]
  Then, both end portions of the core metal 116 are pressed by the pressurizing springs 119 and 119 to the photosensitive drum 105 side through the sliding bearings 130 and 130 with a predetermined pressing force. As a result, the charging roller 114 has the portions of the tape members 118, 118 on both sides in contact with the surface of the photosensitive drum 105, and the portion of the elastic portion 117 having the effective charging width Wac is not in contact with the surface of the photosensitive drum 105. Contact (forms a gap G corresponding to the thickness of the tape member 118).
[0005]
[Problems to be solved by the invention]
  However, a tape member having a predetermined thickness is integrally fixed to both ends of the charging roller in this way, and the portion of the tape member is brought into contact with the photosensitive drum, whereby the charging roller and the surface of the photosensitive drum are brought into contact with each other. In a non-contact type charging device in which a predetermined gap is formed in a portion having an effective charging width therebetween, wear of the tape member sometimes becomes a problem.
[0006]
  That is, if the gap G shown in FIG. 14 is too wide, a predetermined charging performance cannot be obtained. Therefore, the gap G needs to be about 100 μm or less, for example. For this reason, the thickness of the tape member is as extremely thin as about 100 μm or less.
  However, since the outer peripheral surface of the tape member continues to rotate while being in contact with the surface of the photosensitive drum, it is inevitable that the outer peripheral surface is worn over time.
[0007]
  If the tape member is worn out at an early stage, the charging roller comes into contact with the surface of the photosensitive drum at the portion of the effective charging width (zero gap). In this case, residual toner or the like on the photosensitive drum is transferred to the charging effective width portion of the charging roller, so that charging failure occurs due to the contamination.
[0008]
  The present invention has been made in view of the above-mentioned problems, and maintains high charging performance over a long period of time by making gap management members such as tape members less likely to wear, thereby achieving high image quality. Is intended to be obtained.
[0009]
[Means for Solving the Problems]
  In order to achieve the above-mentioned object, the present invention provides an image bearing member having a coated portion for forming a photosensitive layer and an uncoated portion formed of a material harder than the coated portion on both sides thereof, In an image forming apparatus comprising a charging unit having a charging member for charging the coating part, the image bearing member is connected to the non-charged area of the coating part of the image carrier through a gap management member. A predetermined gap is formed between the surface of the image bearing member and the charging member in the charging effective width portion of the charging means in contact with the surface.
[0010]
  Also,Provided with cleaning means for cleaning with a predetermined cleaning width by sliding contact with the coating portion of the image carrier, and the cleaning meansThe cleaning width ofSo as to be located inside the gap management memberIs.
[0011]
  Image forming apparatusA cleaning member oscillating mechanism for oscillating the cleaning member of the cleaning means in a direction orthogonal to the sliding contact direction of the cleaning member with respect to the image carrier, and the cleaning member oscillating by the cleaning member oscillating mechanism is provided. The cleaning rocking region width may be the cleaning width.
[0012]
  The cleaning means may be a means for cleaning the coating portion by bringing the cleaning blade into sliding contact with the coating portion of the image carrier.
  In any one of the above image forming apparatuses, a transfer member for transferring a visible image formed on the surface of the image carrier to a transfer material is provided, and an effective transfer width by the transfer member is narrower than an effective charge width of the charging unit. Good.
  The image forming apparatus further includes a developing device that develops the latent image on the image carrier with a developer to form a visible image, and the developing width of the developing device is larger than the effective charging width of the charging unit. Narrow.
[0013]
  In the image forming apparatus provided with a developing device that develops the latent image on the image carrier with a developer to make it a visible image, the developing width by the developing device may be narrower than the effective transfer width.
  The image forming apparatus is more effective when a two-component developer using toner and carrier is used as the developer.It is.
[0014]
  The charging member is a charging roller in which an elastic portion is formed on a portion excluding both ends of the outer peripheral surface of the metal shaft, and the gap management member is a pair of tape members fixed to both ends of the elastic portion, respectively. It is preferable that the width between the insides of the tape member is the above effective charging width.
  And the tape member is good to make thickness into 100 micrometers or less.
[0015]
  Further, the pair of tape members are wound around the both ends of the elastic portion in the circumferential direction, and the tape members do not exist in the axial direction of the roller at all the positions without overlapping both ends in the circumferential direction. It is good to fix each so that there is no part.
  Further, both ends of the pair of tape members may be cut obliquely so that the edges of the cut end face each other, and a gap is formed between the edges of the cut ends. Moreover, it is good to form the inclination | tilt angle with respect to the side edge of the tape member of the cut line of the part cut diagonally of each both ends of the pair of tape members at about 45 degree | times.
[0016]
  In the charging roller, when a voltage is applied between the metal shaft and the image carrier, the both ends of the metal shaft are placed at positions where no leakage occurs from the both ends of the metal shaft to the non-coated portion of the image carrier. When placed away from the non-coated partGood.
  Furthermore, an image carrier unit in which the image carrier and the charging member are integrally provided is provided as an image carrier unit mounted on any of the image forming apparatuses.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
  FIG. 1 is a schematic view showing a charging roller and a photosensitive drum provided in an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view showing one end side of the charging roller. FIG. 3 is an overall configuration diagram showing a small color printer as the image forming apparatus.
[0018]
  A small color printer as an image forming apparatus shown in FIG. 3 is a four-drum full-color electrophotographic image forming apparatus. Within the apparatus main body 1, there are four image bearing unit units, ie, photosensitive unit 2A, 2B, 2C, and 2D are detachably attached to the apparatus main body 1, respectively.
  In this small printer, a transfer belt 3 is stretched between a plurality of rollers so as to be rotatable in a direction indicated by an arrow A at a substantially central position in the apparatus main body 1.
[0019]
  Then, the photosensitive unit 2A to the photosensitive drum 5 provided on each of the four photosensitive units 2A, 2B, 2C, and 2D are in contact with the upper surface of the transfer belt 3 in FIG. Each 2D is arranged.
  In correspondence with the photoreceptor units 2A to 2D, developing devices 10A to 10D having different toner colors are disposed.
[0020]
  A writing unit 6 is disposed above the photoreceptor units 2A to 2D, and a duplex unit 7 is disposed below.
  Further, this small printer is equipped with a reversing unit 8 that inverts and discharges the transfer paper P after image formation or conveys it to the duplex unit 7 on the left side of the apparatus main body 1 in FIG.
[0021]
  Between the transfer belt 3 and the reversing unit 8, there is provided a fixing device 9 for fixing the image of the transfer paper onto which the image has been transferred.
  A reversal conveyance path 20 is formed on the downstream side of the fixing device 9 in the conveyance direction of the transfer sheet, and the transfer sheet P conveyed there can be discharged onto a discharge tray 26 by a discharge roller pair 25. .
[0022]
  Further, in the lower part of the apparatus main body 1, paper feed cassettes 11 and 12 that can store transfer papers P of different sizes are arranged in two upper and lower stages.
  Further, a manual feed tray 13 is provided on the right side surface of the apparatus main body 1 so as to be openable and closable in the direction indicated by the arrow B, and the manual feed tray 13 is opened so that manual feeding can be performed therefrom.
[0023]
  The photoconductor units 2A to 2D are units having the same configuration, the photoconductor unit 2A forms an image corresponding to yellow, and the photoconductor unit 2B forms an image corresponding to magenta. 2C forms an image corresponding to the cyan color, and the photoreceptor unit 2D forms an image corresponding to the black color. They are arranged at intervals in the transfer paper conveyance direction.
[0024]
  As shown in FIG. 4, the photoreceptor units 2 </ b> A to 2 </ b> D are each charged by the charging roller 14 included in the charging device 4 as a charging unit and the charging roller 14, and an electrostatic latent image is formed by exposure. The photosensitive drum 5 which is an OPC drum type image carrier, and a cleaning blade 47 and a brush roller 15 constituting a cleaning device (cleaning means) for cleaning the surface of the photosensitive drum 5 are configured as an integrated unit. It is made detachable from the apparatus main body 1 shown in FIG.
[0025]
  As shown in FIG. 1, the charging device 4 is arranged such that the charging effective width Wac portion of the charging roller 14 as a charging member is placed close to the charged surface (front surface) of the photosensitive drum 5 by a configuration described later. A voltage is applied between the charging roller 14 and the photosensitive drum 5 to charge the surface to be charged of the photosensitive drum 5.
[0026]
  The charging roller 14 of the charging device 4 is made of, for example, epichlorohydrin rubber at a portion excluding both ends of the outer peripheral surface of the cored bar 16 which is a metal shaft formed by, for example, SUM-Ni plating (steel surface is nickel-plated). The conductive rubber roller portion 17 which is an elastic portion having a volume specific resistance value of 1 × 10 3 to 1 × 10 8 Ω · cm is formed.
[0027]
  At both ends of the conductive rubber roller portion 17, there is an adhesive sheet in which one side made of, for example, polyester or polyethylene terephthalate is formed on the adhesive surface, and the tape members 18, 18 as gap management members are placed with the adhesive surface side down. Wound in the circumferential direction.
[0028]
  Then, the tape members 18 and 18 on both sides of the both sides of the tape member 18 on one side are shown in FIG. The adhesive surface side is fixed by sticking so that there is no portion where the tape member 18 does not exist in the axial direction of the roller indicated by arrow E in the position of.
[0029]
  Therefore, as shown in the drawing, both end portions of each tape member 18 are cut obliquely, the end edges 18a and 18b of the respective cut ends face each other, and between the cut end edges 18a and 18b. A gap S is formed.
  In addition, the inclination angles θ1 and θ2 of the edges 18a and 18b serving as the cut lines of the diagonally cut portions at both ends of the pair of tape members 18 and 18 with respect to the side edges of the tape member 18 are both approximately 45 degrees. Forming.
[0030]
  As described above, when the inclination angles θ1 and θ2 of the cut line of the tape member 18 are set to about 45 degrees, the tips at both ends in the winding direction of the tape member 18 can be made difficult to peel off from the elastic portion 17. Further, since the contact width with the photosensitive drum at the joint portion (the portion where the gap S is formed) of the tape member 18 can be increased, the tip portions at both ends are compared with the case where the inclination angles θ1 and θ2 are made acute. The sticking force to the elastic part 17 increases. Therefore, it is possible to make it difficult for the tip portions at both ends of the tape member 18 to be peeled off.
[0031]
  As shown in FIG. 4, the charging roller 14 has a tape member 18, 18 at both ends in contact with the photosensitive drum 5, and a power source (not shown) is interposed between the charging roller 14 and the photosensitive drum 5. A charging device 4 is configured to charge the surface of the photosensitive drum 5 by applying a voltage.
[0032]
  As shown in FIG. 1, the charging roller 14 is pressed at a predetermined pressure on both ends of the cored bar 16 by the pressure springs 19 and 19 through the slide bearings 30 and 30 to the photosensitive drum 5 side. ing.
  The charging roller 14 may make the tape members 18, 18 at both ends contact the photosensitive drum 5 by its own weight without using the pressure spring 19.
[0033]
  A driving gear 40 is fixed to one end of the metal core 16 on the right side in FIG. 1, a driving force from a motor (not shown) is transmitted thereto, and the charging roller 14 is rotated at the same linear velocity as the photosensitive drum 5. I try to let them.
  As for the application of the voltage to the charging roller 14, for example, DC-700V is applied to the portion of the core metal 16 by constant voltage control, and an AC voltage is applied by constant current control.
[0034]
  In the charging roller 14, for example, the outer diameter of the cored bar 16 is formed to 9 mm, and the conductive rubber roller portion 17 is formed in a rubber layer made of the above-described epichlorohydrin rubber having a wall pressure of 1.5 mm. In this embodiment, the tape member 18 wound around both ends of the conductive rubber roller portion 17 has a tape width of 8 mm and a thickness of 25 to 125 μm, for example. In addition, if the thickness of the tape member 18 is 100 μm or less, more stable charging performance can be obtained.
  Further, the conductive rubber roller portion 17 is used having a rubber hardness of about 77 degrees according to the old JIS-A and a rubber test piece hardness of 50 degrees or more.
[0035]
  The photosensitive drum 5 is rotationally driven in a direction indicated by an arrow C in FIG. 4 by a motor that is rotationally driven via a drum driving timing belt and a drum driving pulley (both not shown).
  Each of the photosensitive units 2A to 2D provided with the photosensitive drum 5 is attached to the coating unit 61 with its tip slidably contacted with a coating unit 61 (to be described later) on the surface of the photosensitive drum 5. A cleaning blade 47 that scrapes off and removes residual toner or the like for cleaning is provided. The toner scraped off by the cleaning blade 47 is moved to the toner transport auger 48 side by the brush roller 15, and the toner transport auger 48 is rotated. Thus, the collected waste toner is conveyed to a predetermined waste toner storage unit.
[0036]
  Further, the photoreceptor units 2A to 2D have a charging roller cleaner 49 made of, for example, a sponge in contact with the surface of the conductive rubber roller portion 17 of the charging roller 14 so that toner, dust, etc. floating in the apparatus are conductive rubber roller portions. Even when it adheres to the surface of 17, it can be cleaned.
[0037]
  The photoreceptor units 2A to 2D are provided with a positioning main reference portion 51 as a reference for attaching and detaching the photoconductor units 2A to 2D with respect to the apparatus body 1 (see FIG. 3). When the photoconductor units 2A to 2D are mounted on the apparatus main body 1, the photoconductor units 2A to 2D are attached to the bracket 50 by a predetermined mounting position. So that positioning can be performed reliably.
[0038]
  Each of the photosensitive drums 5 of the photosensitive units 2A to 2D rotates in the direction indicated by the arrow C as described above, and the linear speeds thereof are monochrome speed priority mode, monochrome image quality priority mode, color speed priority mode, color speed. It can be adjusted in three stages of 185 mm / sec, 125 mm / sec, and 62.5 mm / sec according to several modes such as an image quality priority mode and a cardboard / OHP paper passing mode.
  Note that this photosensitive unit may be configured such that the brush roller 15 is removed from the configuration and the charging roller 14 and the photosensitive drum 5 are integrated.
[0039]
  The developing devices 10A to 10D shown in FIG. 3 have the same configuration, and they differ only in the color of the toner used. The developing device 10A uses yellow toner, the developing device 10B uses magenta toner, the developing device 10C uses cyan toner, and the developing device 10D uses black toner. .
[0040]
  The writing unit 6 shown in FIG. 5 is a writing unit of a 1 polygon motor having two 6-sided rotary polygon mirrors 22a and 22b, which is a laser diode (LD) type color 1 beam and monochrome 2 beam.
  The writing unit 6 emits yellow scanning light, magenta scanning light, and cyan scanning light by rotating polygon mirrors 22a and 22b emitted from a laser diode (not shown) serving as a light source and rotated by a polygon motor 21. And the black scanning light is reflected separately on the right and left.
[0041]
  The scanning light for yellow and the scanning light for magenta pass through the two-layer fθ lens 23, respectively, and the scanning light for yellow is reflected by the mirror 27, passes through the long WTL 24, and is exposed through the mirrors 28 and 29. Irradiated onto the photosensitive drum 5 of the body unit 2A.
  The magenta scanning light is reflected by the mirror 31, passes through the long WTL 32, and is irradiated onto the photosensitive drum 5 of the photosensitive unit 2B via the mirrors 33 and 34.
[0042]
  Further, the cyan scanning light and the black scanning light pass through the two-layer fθ lens 35, respectively, and the cyan scanning light is reflected by the mirror 36, passes through the long WTL 37, and passes through the mirrors 38 and 39. Irradiated onto the photosensitive drum 5 of the photosensitive unit 2C.
  Further, the scanning light for black is reflected by the mirror 41, passes through the long WTL 42, and is irradiated onto the photosensitive drum 5 of the photosensitive unit 2D via the mirrors 43 and 44.
[0043]
  A duplex unit 7 shown in FIG. 3 includes a pair of conveyance guide plates 45a and 45b and a pair of (four sets in this example) conveyance rollers 46, and forms a duplex image on both sides of a transfer sheet. In the formation mode, an image is formed on one side, conveyed to the reversing conveyance path 54 of the reversing unit 8, and transferred back-switched. The transfer paper P is received, and the image forming unit on which the photosensitive units 2A to 2D are provided. Re-carry toward the part.
[0044]
  The reversing unit 8 includes a plurality of paired transport rollers and a plurality of paired transport guide plates. As described above, the reversing unit 8 reverses the transfer paper P when double-sided image formation is carried out to the double-sided unit 7. The transfer paper P after image formation is discharged out of the machine in the same orientation, or the paper is reversed outside and turned out of the machine.
  Separating sheet feeding units 55 and 56 for separating and feeding the transfer sheets P one by one are provided in the sheet feeding unit in which the sheet feeding cassettes 11 and 12 are provided.
[0045]
  This small printer employs a roller curvature separation method using the transfer belt 3, and four transfer brushes 57 are provided inside the transfer belt 3 in correspondence with the four photosensitive drums 5, respectively. .
[0046]
  In this small printer, when the image forming operation is started, each photosensitive drum 5 rotates in the clockwise direction in FIG. The surface of each photosensitive drum 5 is uniformly charged by applying a voltage between the photosensitive drum 5 and the charging roller 14 of each charging device.
  The charging unit 6 irradiates the charged surface of the photosensitive drum 5 of the photosensitive unit 2A with laser light corresponding to the yellow image.
[0047]
  Further, a laser beam corresponding to a cyan image is written on the charging surface of the photosensitive drum 5 of the photosensitive unit 2B by the writing unit 6, and a magenta image is applied to the charging surface of the photosensitive drum 5 of the photosensitive unit 2C. Further, a laser beam corresponding to a black image is irradiated on the charging surface of the photosensitive drum 5 of the photosensitive unit 2D, and a latent image corresponding to each color is formed thereon.
  Each latent image reaches the position of the developing devices 10A, 10B, 10C, and 10D by the rotation of the photosensitive drum 5, and is developed there by toners of yellow, magenta, cyan, and black, and then is divided into four colors. Toner image.
[0048]
  On the other hand, the transfer paper P is fed from the selected paper feed stage of the paper feed cassette 11 or 12 by the separation paper feed unit 55 or 56, and the pair of registration rollers provided immediately before the photosensitive unit 2A. 59, the toner image is conveyed between the photosensitive drum 5 of the photosensitive unit 2A and the transfer belt 3 at an accurate timing coincident with the toner image formed on each photosensitive drum 5.
[0049]
  At that time, the transfer paper P is charged to a positive polarity by a paper suction roller 58 disposed in the vicinity of the entrance of the transfer belt 3, and thereby electrostatically attracted to the surface of the transfer belt 3.
  Then, while the transfer paper P is attracted to the transfer belt 3 and is conveyed in the same direction by the rotation of the transfer belt 3 in the direction of arrow A, yellow, magenta, cyan, and cyan are transferred to the upper surface in FIG. Each black toner image is sequentially transferred, and when passing through the photoreceptor unit 2D, a full-color toner image of four colors superimposed is formed.
[0050]
  The transfer paper P is heated and pressed by the fixing device 9 to melt and fix the toner image, and then passes through the paper discharge system corresponding to the designated mode, and then the paper discharge tray 26 at the upper part of the apparatus main body. Or the paper is fed straight from the fixing device 9 and passes through the reversing unit 8 and is ejected straight.
[0051]
  Alternatively, when the double-sided image forming mode is selected, the sheet is sent to the reversing conveyance path 54 in the reversing unit 8 described above, then switched back and conveyed to the double-sided unit 7, and is fed again from there to the photosensitive unit. The image forming unit provided with 2A to 2D is discharged after an image is formed on the back surface.
  Thereafter, when two or more image formations are instructed, the above-described image forming process is repeated.
[0052]
  By the way, this small printer is provided with the photosensitive drum 5 as described with reference to FIG. 1, and the photosensitive drum 5 has a coating portion 61 for forming a photosensitive layer, and a coating portion 61 on both sides thereof. It has non-coating parts 62 and 62 made of a hard material, and the charging device 4 charges the portion of the coating part 61 having the effective charging width Wac.
  Then, the charging roller 14 of the charging device 4 is brought into contact with the surface of the photosensitive drum 5 via the tape members 18 and 18 brought into contact with the non-charging area of the coating portion 61 of the photosensitive drum 5, and the charging device 4. A predetermined gap G is formed between the charging roller 14 in the portion of the effective charging width Wac and the surface of the photosensitive drum 5.
[0053]
  Therefore, the wear and damage of the tape member 18 can be reduced as compared with the case where each tape member 18 is in contact with the non-coated portion 62 formed of a material harder than the coated portion 61.
  Therefore, even if the tape member 18 has a thickness of 100 μm or less so that good charging performance can be obtained, it is difficult to wear, so the gap G between the charging roller 14 and the surface of the photosensitive drum 5 is increased. In addition, it is possible to continue to maintain a predetermined gap amount that provides good charging performance over a long period of time. Thereby, good image quality can be maintained over time.
[0054]
  FIG. 6 constitutes the image forming system of the small printer of FIG.As a reference technologyIt is the schematic which compared the width relationship of each part relatively.
  thisEach part constituting the image forming system of the small printer has a width relationship as shown in FIG. 6 and a total width Wdo in the longitudinal direction of the photosensitive drum 5 and a coating width Wt of the coating part 61 of the photosensitive drum 5. The non-coating width Wnt of the non-coating portion 62 of the photosensitive drum 5, the effective charging width Wac of the charging device 4, the tape widths Wta of the left and right tape members 18 and 18, and the developing devices 10A to 10D. There are a developing width Wde, a transfer effective width Wte of the transfer device having the transfer belt 3, and a cleaning width Wc of the cleaning blade 47 (see also FIGS. 3 and 4).
[0055]
  That is, a pair of tape members 18, 18 (located at the position of the tape width Wta) is within the cleaning width Wc of the cleaning blade 47 that is in sliding contact with the coating portion 61 on the surface of the photosensitive drum 5 to clean the coating portion 61. Is located).
  As a result, even if the coating portion 61 of the photosensitive drum 5 is worn with time by the sliding contact of the cleaning blade 47 (see FIG. 4), the pair of tape members 18, By contacting 18 together, the gap G between the portion of the charging effective width Wac of the charging roller 14 shown in FIG. 1 and the surface of the photosensitive drum 5 can always be kept constant. Thereby, a good image can be obtained over time.
  In addition, thisSmall printerThen, the width between the insides of the pair of tape members 18 and 18 becomes the effective charging width Wac (see also FIG. 1 if necessary).
[0056]
  The transfer belt 3 (see FIG. 3) is a transfer member that contacts the coating portion 61 of the photosensitive drum 5 and transfers a visible image formed on the surface of the photosensitive drum 5 onto a transfer sheet (transfer material). ) Is made narrower than the effective charging width Wac of the charging device 4.
  As a result, the charging potential becomes unstable near the outside of both ends of the effective charging width Wac on the surface of the photosensitive drum 5, so that the developer tends to adhere, but the effective transfer width Wte is made narrower than the effective charging width Wac. As a result, it is possible to prevent the developer (toner and carrier in the case of a two-component developer) adhering to the vicinity of the outer sides of both ends of the effective charging width Wac from being transferred to the transfer belt 3.
[0057]
  Further, the developing widths Wde of the developing devices 10A to 10D that develop the latent image on the photosensitive drum 5 with a developer to form a visible image are narrower than the effective charging width Wac.
  Accordingly, it is possible to prevent the developer from adhering to the vicinity of both end portions of the effective charging width Wac on the photosensitive drum 5. Accordingly, the developer enters between the tape member 18 described in FIG. 1 and the surface of the photosensitive drum 5 to increase the gap G, or the developer adheres to both ends of the effective charging width Wac. It is possible to prevent the adverse effects that occur when this occurs.
[0058]
  Further, the developing width Wde is made narrower than the transfer effective width Wte. Thereby, it is possible to make it more difficult for the developer to adhere to both ends of the effective charging width Wac on the photosensitive drum 5.
  When the developer is a two-component developer that uses toner and a carrier, both the toner and the carrier can be prevented from adhering to both ends of the effective charging width Wac on the photosensitive drum 5.
[0059]
  Further, the cleaning width Wc is made wider than the effective charging width Wac. As a result, even if deposits such as developer adhere to portions located at both ends of the effective charging width Wac on the photosensitive drum 5, the portions can be cleaned by the cleaning blade 47 (see FIG. 4). Therefore, it is possible to prevent adverse effects due to the attached matter.
[0060]
  FIG.Reference technology related to the small printer in Fig. 6FIG. 7 is a schematic view similar to FIG. 6 in which the width relations of each part of the image forming system in FIG.
  This small printerExplained in FIG.Small printerHowever, the only difference is that the cleaning blade 47 shown in FIG. 8 swings in the direction of arrow F perpendicular to the sliding contact direction with respect to the photosensitive drum 5. Since the configuration of the other parts is the same as that of the small printer described in FIGS. 1 to 6, the illustration and description of the entire small printer are omitted.
[0061]
  thisSmall printerAs shown in FIG. 8, the cleaning member rocking mechanism for rocking the cleaning blade 47, which is a cleaning member of the cleaning means, in the direction indicated by the arrow F perpendicular to the sliding direction of the cleaning blade 47 with respect to the photosensitive drum 5. 70 is provided.
[0062]
  The cleaning member swinging mechanism 70 includes a blade holding member 71 that holds the cleaning blade 47 and is supported so as to be swingable in the direction of arrow F, and the tip of a protrusion 71 a formed at the left end of the blade holding member 71. A cam 72 whose cam surface is in sliding contact with the hemispherical portion, a compression coil spring 73 that presses and urges the blade holding member 71 so as to press the hemispherical portion at the tip of the projecting portion 71a against the cam surface of the cam 72, and the cam 72 And a motor 74 for rotating the motor.
[0063]
  When the cam 72 is rotated once, the cleaning blade 47 swings together with the blade holding member 71 and reciprocates once. Then, the cleaning swing region width Wsc of the cleaning blade 47 swung by the cleaning member swinging mechanism 70 is defined as a cleaning width, and the cleaning width is located in the coating portion 61 of the photosensitive drum 5, and the cleaning swing width is set. As shown in FIG. 7, a pair of tape members 18 and 18 (arranged at the positions of the respective tape widths Wta) are disposed in the moving region width Wsc.
[0064]
  thisSmall printerAccording to the above, the cleaning blade 47 does not slidably contact the joint portion of the photosensitive drum 5 with the non-coated portion 62 and the non-coated portion, so that the cleaning blade 47 is prevented from being turned over. Can be prevented, and it can be prevented from wearing out early.
[0065]
  Also thisSmall printerThen, the movement limit positions (left and right positions of the cleaning rocking region width Wsc) on both sides of the cleaning blade 47 swung by the cleaning member rocking mechanism 70 are positioned outside the effective charging width Wac. I have to.
  Therefore, even if a deposit such as a developer adheres to portions located at both ends of the effective charging width Wac on the photosensitive drum 5, it can be cleaned by the cleaning blade 47. , Adverse effects due to the deposits can be prevented.
[0066]
  Figure 9This is a feature of a small printer which is an image forming apparatus according to the present invention.The cleaning width of the cleaning means is positioned inside each of the pair of tape membersTo explain the pointFIG. 7 is a schematic view similar to FIG. 6. The small printer as the image forming apparatus according to this embodiment is different from the small printer described in FIGS. 1 to 6 only in the positional relationship in the width direction of the pair of tape members 18 and 18 with respect to the cleaning width Wc. Since other configurations are the same, illustration of the configuration of each part is omitted, and description will be made using the reference numerals used in FIGS. 1 to 6 as necessary.
[0067]
  In the small printer according to this embodiment, the cleaning width Wc of the cleaning blade 47 is positioned inside the paired tape members 18 and 18 (disposed at the positions of the left and right tape widths Wta in FIG. 9). Like to do.
  Therefore, in this embodiment, the coating portion 61 (located in the portion of the coating width Wt) forming the photosensitive layer on the surface of the photosensitive drum 5 is an area of the cleaning width Wc by sliding contact with the cleaning blade 47. Wears over time. On the other hand, since the tape members 18 and 18 on both sides are respectively positioned outside the cleaning width Wc by the cleaning blade 47, the coating portion 61 at the portion where the tape members 18 and 18 are in contact is formed by the cleaning blade 47. I can't cut it.
[0068]
  Therefore, when the area of the cleaning width Wc of the coating unit 61 is gradually scraped by the cleaning blade 47, the gap G between the charging roller 14 and the surface of the photosensitive drum 5 described with reference to FIG. It spreads to the gap where charging failure occurs. Therefore, in this small printer, it is possible to determine that the photosensitive drum 5 has reached the end of its life by using the time when the charging failure occurs.
  It should be noted that transfer residual toner or the like collected from the photosensitive drum 5 is likely to spill from both ends of the cleaning blade 47, and when it adheres to the photosensitive drum 5 again and then adheres to the tape member 18, the photosensitive drum 5 and the charging roller 14 may become large.
  However, when the cleaning width Wc is positioned inside the tape members 18 and 18 on both sides as described above, the collected toner spilled from the cleaning blade 47 is difficult to adhere to the tape member 18. It is possible to prevent the gap G from increasing.
[0069]
  FIG. 10 is a schematic view similar to FIG. 7 showing a relative comparison of the width relationship of each part of the image forming system in still another embodiment of the image forming apparatus according to the present invention.
  The compact printer which is the image forming apparatus in this embodiment is described in FIG. 8 with respect to the embodiment described in FIG.Small printerThe cleaning blade 47 is swung in a direction perpendicular to the sliding contact direction with respect to the photosensitive drum 5 by the cleaning member rocking mechanism 70 similarly to the cleaning blade 47, and the cleaning blade 47 is swung by the cleaning member rocking mechanism 70. The area width Wsc is defined as the cleaning width, and the cleaning width is located in the coating portion 61 (located at the coating width Wt) of the photosensitive drum 5 as shown in FIG. The left end and the right end of the region width Wsc are positioned inside the paired tape members 18 and 18 (disposed at the positions of the left and right tape widths Wta in FIG. 10), respectively.
[0070]
  Also in this embodiment, since the cleaning blade 47 does not slidably contact the joint portion of the photosensitive drum 5 with the non-coated portion 62 and the non-coated portion, the cleaning blade 47 is worn out early. Can be prevented.
[0071]
  Further, the movement limit positions on the both sides of the cleaning blade 47 oscillated by the cleaning member oscillating mechanism 70 (the positions of the left end and the right end of the cleaning oscillating region width Wsc) are respectively inside the tape members 18 and 18 on both sides. Therefore, as in the embodiment of FIG. 9, the portion of the coating portion 61 having the cleaning swing region width Wsc is gradually scraped by the cleaning blade 47, so that the charging roller 14 and the photosensitive member described in FIG. The gap G with the surface of the drum 5 is gradually increased.
  Therefore, it is possible to determine that the photosensitive drum 5 has reached the end of its life by using the time when the charging failure occurs as the gap G increases.
[0072]
  FIG. 11 shows an image forming apparatus in which the cleaning width extends beyond the outer edges of the pair of tape members.Reference technologyFIG. 7 is a schematic view similar to FIG.
  This image forming apparatus6 is different from the small printer described with reference to FIG. 6 only in that the cleaning width Wc extends outside the outer edges of the pair of tape members 18, 18. Since the configuration is the same, the illustration of the configuration of each part is omitted, and description will be made using the reference numerals used in FIGS. 1 to 6 as necessary.
[0073]
  In this way, if the cleaning width Wc is set to the outside of the outer edges of the pair of tape members 18, 18, the coating portion 61 of the photosensitive drum 5 can be formed as in the small printer described in FIG. Even if the region of the cleaning width Wc is worn over time due to the sliding contact of the cleaning blade 47 (see FIG. 4), the worn portions are respectively disposed at the positions indicated by the tape width Wta in FIG. The tape members 18 and 18 contact each other with a margin in the width direction (left and right direction in the figure).
  Therefore, the gap G between the charging effective width Wac portion of the charging roller 14 shown in FIG. 1 and the surface of the photosensitive drum 5 can always be kept constant, whereby a good image can be obtained over time. .
[0074]
  FIG. 12 shows an image forming apparatus in which the cleaning width of the oscillating cleaning blade extends beyond the outer edges of the pair of tape members.Reference technologyIt is the schematic similar to FIG.
  This image forming apparatusThe small printer is described with reference to FIG.Small printerThe cleaning blade 47 is swung in a direction perpendicular to the sliding contact direction with respect to the photosensitive drum 5 by the cleaning member rocking mechanism 70 similarly to the cleaning blade 47, and the cleaning blade 47 is swung by the cleaning member rocking mechanism 70. The area width Wsc is defined as a cleaning width, and the cleaning width extends beyond the outer edge of each of the pair of tape members 18 and 18 (disposed at the positions of the left and right tape widths Wta in FIG. 12). Only the points described above are explained in FIG.Small printerAnd different.
[0075]
  If such a cleaning swing region width Wsc is set as the cleaning width, the coating portion 61 of the photosensitive drum 5 is cleaned by the sliding contact of the cleaning blade 47 (see FIG. 4) as in the small printer described in FIG. Even if the region of the width Wc is worn over time, the pair of tape members 18 and 18 come into contact with the worn portion with a margin in the width direction (left and right direction in FIG. 11).
  So thisSmall printerIn this case, the gap G between the charging effective width Wac portion of the charging roller 14 shown in FIG. 1 and the surface of the photosensitive drum 5 can always be kept constant, whereby a good image can be obtained over time. It is done.
[0076]
  FIG. 13 shows the gap management member as a roller.Reference technologyFIG.
  This gap management memberAre rollers 81, 81 respectively attached to both ends of the cored bar 16 formed by the metal shaft of the charging roller 14 '. The roller 81 is made of, for example, rubber and has an outer diameter D2 larger than the outer diameter D1 of the conductive rubber roller portion 17 ′ of the charging roller 14 ′. A gap G (for example, 100 μm or less) is determined by the difference between the outer diameters D1 and D2. Is forming.
[0077]
  In addition, thisReference technologyThe pair of rollers 81 and 81 are both in contact with the non-charged area of the coating part 61 that is softer than the non-coating part 62 of the photosensitive drum 5. Therefore, even if the gap G is set to 100 μm or less, for example, the rollers 81 are not easily worn, and therefore the gap G can be maintained at a gap amount that allows good charging over a long period of time.
[0078]
  As described above, various embodiments of the image forming apparatus according to the present invention have been described. In each of the embodiments, the charging rollers 14 and 14 ′ have a voltage between the metal core 16 and the photosensitive drum 5. The both ends of the cored bar 16 may be arranged away from the non-coated part 62 at a position where no leakage occurs in the non-coated part 62 of the photosensitive drum 5 from both ends of the cored bar 16 when applied.
[0079]
【The invention's effect】
  As described above, according to the present invention, the following effects can be obtained.
  According to the image forming apparatus of the first to thirteenth aspects, the gap management member is in contact with the coating portion of the image carrier and forms a predetermined gap between the charging member and the surface of the image carrier. Compared with the case where the management member is brought into contact with the non-coating portion formed of a material harder than the coating portion, wear and damage of the gap management member can be reduced. Therefore, the gap between the charging member and the surface of the image carrier can be kept substantially constant over a long period by the amount that the gap management member is not easily worn.it can.
[0080]
  Also,The coated portion forming the photosensitive layer of the image carrier is worn over time by the sliding width of the cleaning means so that the image carrier reaches the end of its service life when a predetermined usage time is reached. However, in this image forming apparatus, since the cleaning width of the cleaning unit is located inside the gap management member, the coating portion in contact with the gap management member is not worn by the cleaning unit.
[0081]
  Accordingly, as the cleaning width region of the coating portion is gradually scraped by the cleaning means, the gap between the charging member and the surface of the image carrier gradually increases and the time for charging failure occurs. Therefore, it is possible to determine that the image carrier has reached the end of its life by using the occurrence timing of the charging failure.
  In general, when the cleaning width reaches the position of the gap management member, when transfer residual toner or the like collected from the image carrier spills from both ends of the cleaning means, When attached to the management member, the gap between the image carrier and the charging member may become large. However, if the cleaning width is positioned inside the gap management member as described above, the cleaning means may have spilled. Since the collected toner or the like can be made difficult to adhere to the gap management member, an increase in the gap can be prevented.
[0082]
  Claim 2According to the image forming apparatus, since the cleaning member is swung by the cleaning member swinging mechanism, it is possible to prevent paper dust and the like from continuing to collect between the cleaning member and the surface of the image carrier, Even if the cleaning member is swung, the cleaning member does not come out of the region of the coating portion, so that the cleaning member slides on the joint portion between the coating portion and the non-coating portion of the image carrier or the non-coating portion. It is possible to prevent the cleaning member from being turned up and prematurely worn out.
[0083]
  Claim 3According to the image forming apparatus, since the cleaning blade of the cleaning means does not slidably contact the joint portion of the image carrier and the non-coated portion or the non-coated portion, the cleaning blade is turned over. It is possible to prevent the premature wear of the cleaning blade.
[0084]
  Claim4 and 7According to the image forming apparatus, in general, the charging potential becomes unstable near both ends of the effective charging width on the surface of the image carrier, so that the developer is likely to adhere thereto. Is made narrower than the effective charging width of the charging means, it is possible to prevent the developer attached near the outside of both ends of the effective charging width from being transferred to the transfer member.
[0085]
  Claim 5According to this image forming apparatus, since the developing width of the developing device is narrower than the effective charging width of the charging unit, it is possible to prevent the developer from adhering to both ends of the effective charging width on the image carrier. . Therefore, it is possible to prevent the developer from entering between the gap management member and the surface of the image carrier and increasing the gap, and the developer adheres to both ends of the effective charging width. It is possible to prevent problems that occur in some cases.
[0086]
  Claim 6In this image forming apparatus, the developing width is narrower than the effective transfer width, and the effective transfer width is narrower than the effective charging width, so that one layer of developer adheres to both ends of the effective charging width on the image carrier. Hard to doBecome.
[0087]
  Claim 8According to this image forming apparatus, since the gap management member is a pair of tape members, they can be easily fixed by winding them around both ends of the elastic portion of the charging member. Therefore, the workability at the time of attaching the gap management member can be improved.
[0088]
  Claim 9According to the image forming apparatus, since the tape member is formed to have a very thin plate thickness of 100 μm or less, if the tape member is worn by contact with the surface of the image carrier, the thickness reduction rate with respect to the initial thickness is reduced. The degree of influence becomes very large. Therefore, the effect of reducing wear is great by bringing the tape member into contact with the coated part that is softer than the non-coated part.
[0089]
  Claim 10According to the image forming apparatus, the pair of tape members are wound around the both ends of the elastic portion so that there is no portion where the tape member does not exist in the axial direction of the roller at all the positions of the circumference. Even if the portions of the film material are brought into contact with the image carrier and are brought into rolling contact with each other, it is possible to prevent the image carrier from periodically falling between the edges of both ends in the circumferential direction of each film material.
  Therefore, it is possible to prevent the occurrence of fine vibration that occurs when the image carrier falls between the edges.
[0090]
  Claim 11According to the image forming apparatus, since both ends of the pair of tape members are cut obliquely, the edges of the cut edges face each other, and a gap is formed between the edges of the cut ends. Even if the dimensional control of the length in the winding direction of the film material is not so strict, both ends of the film material in the circumferential direction can be prevented from overlapping each other.
[0091]
  Claim 12According to the image forming apparatus, since the angle of inclination of the cut line of each of the pair of tape members cut obliquely with respect to the side edge of the tape member is approximately 45 degrees, While the tip can be made difficult to peel off, the contact width with the image carrier at the joint portion of the film material can be increased.
[0092]
  Claim 13According to this image forming apparatus, the charging roller is disposed at a position where no leakage occurs from the both ends of the metal shaft to the non-coated portion of the image carrier, and the both ends of the metal shaft are separated from the non-coated portion. , Preventing leakage from the metal shaft of the charging roller to the non-coated portion of the image bearing member to obtain good charging performanceit can.
[0093]
  Claim 14According to this image carrier unit, since the image carrier and the charging member are formed as an integral unit, maintenance of the image carrier and the charging member can be easily performed.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a charging roller and a photosensitive drum provided in an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is an enlarged view showing an enlarged side of one end of the charging roller.
FIG. 3 is an overall configuration diagram showing a small color printer which is also the image forming apparatus.
FIG. 4 is a configuration diagram showing a photosensitive unit provided in the small printer.
FIG. 5 is a configuration diagram showing a writing unit provided in the small printer of FIG. 3;
6 constitutes an image forming system of the small printer of FIG.As a reference technologyIt is the schematic which compared the width relationship of each part relatively.
[Fig. 7]Reference technology related to the small printer in Fig. 6FIG. 7 is a schematic view similar to FIG. 6 in which the width relations of each part of the image forming system in FIG.
FIG. 8 is a schematic view for explaining a cleaning member swinging mechanism included in the image forming apparatus.
FIG. 9This is a feature of a small printer which is an image forming apparatus according to the present invention.The cleaning width of the cleaning means is positioned inside each of the pair of tape membersTo explain the pointFIG. 7 is a schematic view similar to FIG. 6.
FIG. 10 is a schematic view similar to FIG. 7 showing a relative comparison of the width relationship of each part of the image forming system in still another embodiment of the image forming apparatus according to the present invention.
FIG. 11 illustrates an image forming apparatus in which the cleaning width extends beyond the outer edges of a pair of tape members.Reference technologyFIG. 7 is a schematic view similar to FIG.
FIG. 12 shows an image forming apparatus in which the cleaning width of the oscillating cleaning blade is extended to the outside of the outer edges of the pair of tape members.Reference technologyIt is the schematic similar to FIG.
FIG. 13 uses a roller as a gap management member.Reference technologyFIG.
FIG. 14 is a schematic diagram illustrating an example of a conventional charging roller.
[Explanation of symbols]
2A, 2B, 2C, 2D: Photosensitive unit (image carrier unit)
3: Transfer belt (transfer member)
4: Charging device (charging means)
5: Photosensitive drum (image carrier)
10A, 10B, 10C, 10D: Development device
14, 14 ': Charging roller (charging member)
16: Metal core (metal shaft)
17, 17 ': Conductive rubber roller part (elastic part)
18: Tape member (gap management member)
47: Cleaning blade (cleaning member)
61: Coating part 62: Non-coating part
70: Cleaning member swing mechanism 81: Roller

Claims (14)

An image carrier having a coating part for forming a photosensitive layer and a non-coating part formed of a material harder than the coating part on both sides thereof, and a charging member for charging the coating part of the image carrier. In an image forming apparatus provided with a charging unit having
The charging member is brought into contact with the surface of the image carrier through a gap management member that is brought into contact with a non-charged region of the coating portion of the image carrier, and the charging member in the charging effective width portion of the charging unit. A cleaning device is provided for cleaning with a predetermined cleaning width by sliding the coating portion of the image carrier in sliding contact with the surface of the image carrier. An image forming apparatus, wherein the cleaning width is positioned inside the gap management member . 2. The image forming apparatus according to claim 1 , further comprising a cleaning member swinging mechanism that swings the cleaning member of the cleaning unit in a direction orthogonal to a sliding contact direction of the cleaning member with respect to the image carrier. An image forming apparatus, wherein a cleaning swing region width of the cleaning member swinged by a mechanism is set as the cleaning width. The cleaning unit is an image forming apparatus according to claim 1 or 2, wherein the by sliding the cleaning blade on the coated portion of the image bearing member is a means for cleaning the coating coated portion. The image forming apparatus according to any one of claims 1 to 3, a transfer member for transferring a transfer material a visible image formed on the surface of the image bearing member is provided, the transfer effective width by the transfer member An image forming apparatus characterized in that it is narrower than the effective charging width of the charging means. The image forming apparatus according to any one of claims 1 to 4, a developing apparatus for visual image the latent image on the image bearing member with a developer, a developing width by developing device An image forming apparatus characterized in that it is narrower than the effective charging width of the charging means. 5. The image forming apparatus according to claim 4 , further comprising: a developing device that develops the latent image on the image carrier with a developer to make a visible image, and a developing width by the developing device is made narrower than an effective transfer width. An image forming apparatus. 7. The image forming apparatus according to claim 5 , wherein the developer is a two-component developer using toner and a carrier. The charging member is a charging roller in which an elastic portion is formed in a portion excluding both ends of the outer peripheral surface of the metal shaft, and the gap management member is a pair of tape members fixed to both ends of the elastic portion, respectively. the image forming apparatus according to any one of claims 1 to 7 width between the inner pair of tape members is characterized by comprising the charging effective width. 9. The image forming apparatus according to claim 8, wherein the tape member has a thickness of 100 [mu] m or less. 10. The image forming apparatus according to claim 8 , wherein the pair of tape members are wound around both ends of the elastic portion in the circumferential direction, and both ends of the circumferential direction do not overlap with each other, and the roller is disposed at all positions around the circumference. An image forming apparatus, wherein the tape member is fixed so that there is no portion where the tape member does not exist in the axial direction. 11. The image according to claim 10, wherein both ends of the pair of tape members are cut obliquely, the edges of the cut end face each other, and a gap is formed between the edges of the cut ends. Forming equipment. 12. The image forming apparatus according to claim 11 , wherein an angle of inclination of the cut line of each of the pair of tape members, which is cut obliquely, with respect to a side edge of the tape member is approximately 45 degrees. The charging roller has both ends of the metal shaft at positions where no leakage occurs from the both ends of the metal shaft to the non-coated portion of the image carrier when a voltage is applied between the metal shaft and the image carrier. The image forming apparatus according to any one of claims 8 to 12 , wherein a portion is disposed apart from the non-coated portion. A image bearing member unit to be attached to the image forming apparatus according to any one of claims 1 to 13, the image carrier unit provided integrally with said charging member and said image bearing member.

Images