JP4279001B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention provides an image forming unit that is provided in the cleaning unit between a transfer belt unit and a cleaning unit that are arranged adjacent to each other around the image carrier, and has a charge eliminating unit that irradiates light onto the image carrier after transfer. It relates to the device.
[0002]
[Prior art]
Conventionally, image forming apparatuses such as copiers, printers, and fax machines are provided with a photosensitive drum as an image carrier for image formation, and a charging unit, a cleaning unit, a charge eliminating unit, and the like are formed around the photosensitive drum. A transfer belt that is in contact with the photosensitive drum is disposed below the cleaning unit. In recent years, from the viewpoint of preventing potential unevenness on the surface of the photosensitive drum, a configuration is known in which a charge removal unit is disposed between the cleaning unit and the transfer belt in order to ensure the distance between the charging unit and the charge removal unit (for example, a patent). Reference 1).
[0003]
In the photosensitive drum, an electrostatic image is formed on the surface uniformly charged by the charging unit, a toner image is formed by applying toner to the electrostatic image, and the toner image is transferred onto a recording sheet. Later, the residual charge on the surface is removed by the light applied to the static elimination unit, and then the residual toner is removed by the cleaning unit, so that the next toner image can be formed.
[0004]
[Patent Document 1]
Japanese Patent Laid-Open No. 11-133824
[Problems to be solved by the invention]
However, in the conventional image forming apparatus described above, all of the light emitted from the static eliminating unit to the photosensitive drum does not go to the surface of the photosensitive drum, and some diffused light is reflected by other members, Alternatively, it may be directed directly toward the transfer belt, and this light may be reflected by the transfer belt to partially irradiate the photosensitive drum. There are two types of transfer belts: a direct transfer method in which recording paper is conveyed and an indirect transfer method in which toner images are applied. In the former, while recording paper is being conveyed, in the latter, a toner image is applied, The surface is not necessarily the same as the color of the transfer belt itself. Accordingly, since the amount of light reflected from the transfer belt and directed to the photosensitive drum is not constant, the surface potential of the photosensitive drum may be uneven due to the influence of this unstable amount of light.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus that can effectively prevent potential unevenness from occurring on the surface of a photosensitive drum.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a static elimination unit that is provided in the cleaning unit between a transfer belt and a cleaning unit that are arranged adjacent to each other around the image carrier, and irradiates the image carrier after transfer with light. An image forming apparatus having a sheet-like light shielding member for restricting an optical path of irradiation light from the charge removal unit to the transfer belt is attached to the cleaning unit, and the cleaning unit holds a cleaning tool. The case has an installation surface on the side facing the transfer belt, and a protruding portion is formed on a part of the case opposite to the image carrier. Provided on an installation surface, the light shielding member is interposed between the charge eliminating portion and the transfer belt, a base end is fixed to the projecting portion, and the case is on the image carrier side of the installation surface In a direction perpendicular to the axial direction of the image carrier. Ribs is more Hon'nami set at predetermined intervals in the axial direction of said image bearing member, said light blocking member is characterized in that the distal end side is in contact with the top of the rib.
[0008]
According to this, the light path of the transfer belt of the irradiation light from the charge eliminating portion is restricted by the light shielding member, so that the reflected light toward the image carrier after being reflected by the transfer belt is effectively prevented. Here, the reflected light reflected from the transfer belt is not constant when toner is applied to the transfer belt or when the recording paper is conveyed, but it is not affected by the state of the transfer belt. Further, since the residual charge on the image carrier can be eliminated, it is possible to effectively prevent unevenness in the surface potential of the image carrier after neutralization.
[0009]
Further, a static elimination lamp is formed on the installation surface on the side of the cleaning unit case facing the transfer belt, and the base end of the sheet member is fixed to a protrusion formed on the installation surface on the side opposite to the image carrier. Accordingly, it is possible to secure an optical path of the irradiation light from the charge eliminating portion toward the image holding member, and to effectively prevent the reflected light reflected by the transfer belt and toward the image carrier. In particular, if the protrusions have the same height and extend in parallel to the axial direction of the image carrier, the dimensions of the part of the protrusions to which the sheet member is fixed can be sufficiently secured. By fixing the light shielding member over the portion, it is possible to effectively secure the optical path of the irradiation light from the charge eliminating portion toward the image carrier.
[0010]
Furthermore, since the front end side of the light shielding member is in contact with the top of a plurality of ribs arranged in parallel at a predetermined interval, a slit-like optical path can be formed by the light shielding member and the rib, and the light shielding member Since the base end side and the front end side are stably supported, the height of the slit-shaped optical path is stabilized.
[0011]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the installation surface has a recess extending in the axial direction of the image carrier, and the end side (both ends and A protrusion extending toward the inside of the recess is formed on the edge of the side wall of the first end (including the one end), the charge eliminating portion is fitted into the recess and sandwiched between the protrusion and the bottom of the recess, and the light shielding member and the bottom It is characterized by being pinched and supported.
[0012]
The static eliminator is fitted in this recess and is supported by being sandwiched between the protrusion and the bottom of the recess, and is supported by being sandwiched between the light shielding member and the bottom, thereby eliminating the static eliminator without using a fixing member. Can be fixed to the installation surface.
[0013]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , the light shielding member is bonded to the protruding portion via an adhesive member.
[0014]
That is, when fixed by a fixing member or the like, the distance between the adhesive member and the transfer belt is narrowed by the fixing tool or the like, but when the adhesive member is bonded to the protruding portion via the adhesive member, the light shielding member is attached to the case without using the fixing member or the like. It is attached.
[0015]
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the light shielding member is a resin film.
[0016]
According to this, since an extremely thin resin film is used, it is possible to secure a sufficient distance between the transfer belt and the light shielding member.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment in which the image forming apparatus according to the present invention is applied to a printer will be described with reference to FIGS. FIG. 1 is a schematic side view of the printer 1. In FIG. 1, a printer 1 has a recording paper storage unit 2 in which recording papers are stacked on the bottom side of the main body, and is fed out from the recording paper storage unit 2 positioned on the upper side of the main body, and the recording paper after image formation is discharged. Conveying section 4 having a conveying path 41 for conveying the recording paper over the discharge section 3 and an endless transfer belt 42 for conveying the recording paper at positions of image forming sections 5 to 8 to be described later, a transfer belt The image forming units 5 to 8 are provided in series in the transport direction in the upper part of 42 to form an image of each color on the recording paper, and the fixing unit 10 provided downstream of the transfer belt 42 in the paper transport direction. Prepare.
[0018]
The transport unit 4 has a required number of transport roller pairs 43 disposed at required positions along the transport path 41 from the upstream side, and these transport roller pairs 43 are rotationally driven by a motor or the like (not shown). ing.
[0019]
The image forming units 5 to 8 are disposed along the sheet conveyance surface of the transfer belt 42 and form cyan (C), magenta (M), yellow (Y), and black (K) images from the upstream side. The details will be described later. The transfer belt 42 is stretched between rollers 44 and 45 on the upstream side and the downstream side, and a tension roller 46 is disposed at an appropriate position on the lower side therebetween. The roller 44 forms a roller pair together with the pressure roller 44 a so that the conveyed paper can be guided onto the transfer belt 42.
[0020]
The fixing unit 10 includes a heat roller 101 having a heater source therein and a pressure roller 102, and fuses toner of a given color transferred onto a recording sheet by the image forming units 5-8. The image forming units 5 to 8 have the same structure except that the color of the toner is different. Hereinafter, the image forming unit 5 will be described as an example.
[0021]
FIG. 2 is a side view for explaining the structure of the image forming unit 5. In FIG. 2, the image forming unit 5 includes a photosensitive drum 51 as a carrier at the center, and a charging unit 52, an exposure unit 53, a developing unit 54, a transfer roller 55, a cleaning unit around the photosensitive drum 51 from the upstream side in the drum rotation direction. A part 56 (cleaning part) is provided. A transfer belt 42 is disposed between the developing unit 54 and the cleaning unit 56.
[0022]
The photosensitive drum 51 has a cylindrical shape with a photosensitive layer formed on the surface thereof, and is rotated at a constant speed by a driving mechanism (not shown). The charging unit 52 applies a predetermined potential to the surface of the photoreceptor using a corona discharge phenomenon. The exposure unit 53 includes a light emitting unit such as an LED and a polygon mirror for scanning, for example, modulates image data transferred from an external memory or the like and emits it as light, and the photosensitive drum 51 from below through the polygon mirror. By scanning in the length direction, an electrostatic latent image is formed on the surface of the photosensitive drum 51.
[0023]
The developing unit 54 exposes the electrostatic latent image by applying cyan toner to the surface of the photosensitive drum 51 using an electric field. The transfer roller 55 is for transferring the toner image onto the recording paper, and the cleaning unit 56 is for removing residual toner. The cleaning unit 56 includes a blade 560 for removing residual toner, a case 562 that holds a cleaning member 561, a collecting member, and the like, and a transfer belt 42 of the case 562. A neutralization portion 57 for removing residual charges is provided on the installation surface 563 formed on the bottom surface.
[0024]
On the installation surface 563 of the case 562, a protruding portion 564 is formed at a portion opposite to the photosensitive drum 51 so as to extend at the same height, and the photosensitive drum 57 is sandwiched between the charge eliminating portion 57. On the 51 side, a plurality of ribs 565 parallel to the direction orthogonal to the axial direction of the photosensitive drum 51 are provided in parallel in the axial direction of the photosensitive drum 51. An opaque resin sheet 58 is installed between the charge eliminating portion 57 and the transfer belt 42, and the base end of the resin sheet 58 is bonded to the protruding portion 564 by an adhesive member, and the tip end side is the top of the rib 565. Is abutted against and supported.
[0025]
3 is a perspective view of the bottom surface of the case 562 of the cleaning unit 56 shown in FIG. 2, with the upper side showing the photosensitive drum 51 side and the front side of the drawing showing the bottom surface side. FIG. 4 is a cross-sectional view of the case 562 shown in FIG. As shown in FIG. 3, the case 562 has an installation surface 563 on the bottom surface, and the charge removal portion 57 is fitted in a recess 563 a formed at the center position of the installation surface 563. In addition, the protrusion which goes inside the recessed part 563a is formed in the edge of the side wall of this both ends of this recessed part 563a, and the static elimination part 57 is engage | inserted by the recessed part 563a, and is clamped and supported by the protrusion and the bottom part of the recessed part 563a. The configuration is preferable because the static eliminating unit 57 can be attached without using a fixture.
[0026]
The neutralization unit 57 is a state in which a plurality of small LED elements 571 (lamps) arranged in a line shape at predetermined intervals in the longitudinal direction (left and right in the drawing) are exposed from the base 570 embedded in the recess 563a. And is electrically connected to a power source as shown in the figure. In the static eliminating portion 57, the height positions of the tip of the protruding portion 564 and the tip of the rib 565 are substantially the same, and this height is at least based on the sum of the exposed dimensions of the base portion 570 of the static eliminating portion 57 and the LED element 571. It is large and the static elimination part 57 is made into the attitude | position lower than the protrusion part 564 and the rib 565. FIG.
[0027]
In the above configuration, the light emitted from the LED element 571 passes between the ribs 565 toward the photosensitive drum 51, and the light directed toward the transfer belt 42 is directed toward the transfer belt 42 by the resin sheet 58. The optical path is interrupted, that is, reflected and travels toward the photosensitive drum 51.
[0028]
Therefore, by providing the resin sheet 58 between the static elimination unit 57 and the transfer belt 42, it is possible to effectively prevent the irradiation light of the static elimination unit 57 from being irradiated in the direction of the transfer belt 42. The amount of reflection on the resin sheet 58 can always be kept constant. Accordingly, it is possible to irradiate the photosensitive drum 51 with constant irradiation light without being affected by the presence or absence of toner applied to the transfer belt 42 or the state in which the recording paper is conveyed. Therefore, it is possible to sufficiently prevent unevenness in the potential of the surface of the photosensitive drum 51 and effectively prevent unevenness in image density during image formation. Here, since the neutralization unit 57 is not a laser as a light source but an LED element and has light diffusion, there is a great problem that the irradiation light of the neutralization unit 57 is irradiated in the direction of the transfer belt 42 and is particularly effective. .
[0029]
Further, since the resin sheet 58 is bonded to the protruding portion 564, the resin sheet 58 can be attached to the case 562 without using a fixture or the like, and the interval between the transfer belt 42 and the resin sheet 58 can be increased. Can be taken as wide as the fixture. Further, since the resin sheet 58 is supported with the tip side being in contact with the top of the rib 565, the tip of the resin sheet 58 is not directed upward or downward, and is directed from the static elimination unit 57 to the photosensitive drum 51. Blocking the optical path of the reflected light also does not make it difficult to regulate the reflected light traveling from the charge removal unit 57 to the transfer belt 42. Even when the resin sheet 58 is deformed due to a change over time, a temperature change, or the like, it is possible to effectively prevent the interval between the resin sheet 58 and the charge removal unit 57 from being affected.
[0030]
In addition, it can also be set as the structure which attaches the static elimination part 57 to the case 562 by contact | abutting the front-end | tip of the resin sheet 58 to which the base part adhere | attached the protrusion part 564, and the rib 565, By doing in this way, static elimination part 57 and the like are not necessary, and the manufacturing cost can be reduced. Further, the resin sheet 58 may be bonded to the rib 565 at the front end side, or may be extended to the vicinity of the surface of the photosensitive drum 51. Note that the resin sheet 58 is not required to be completely opaque as long as it can reflect the light emitted from the charge removal unit 57. The resin sheet 58 can be used in an image forming apparatus that does not include the case 562, and may be provided on a member other than the case 562.
[0031]
The installation surface 563 of the case 562 may have a shape that does not form the concave portion 563a, and may be, for example, a planar shape.
[0032]
【The invention's effect】
According to the first aspect of the present invention, unevenness in the surface potential of the image bearing member after static elimination can be effectively prevented, so that unevenness in image density caused by the unevenness in potential is sufficiently prevented during image formation. be able to.
[0033]
Furthermore, it is possible to secure an optical path of the irradiation light from the charge eliminating portion to the image holding member, and to sufficiently prevent the reflected light toward the image carrier, so that the irradiation light toward the image carrier can be reduced. Irradiation light toward the transfer belt can be regulated without hindering.
[0034]
Furthermore, since the light shielding member can be stably supported on the proximal end side and the distal end side, it is possible to effectively prevent the height dimension of the optical path from changing even when the light shielding member is deformed from the initial shape. Become.
[0035]
According to the second aspect of the present invention, since the static eliminator can be attached to the case without using a fixture, the manufacturing cost can be reduced.
[0036]
According to the third aspect of the present invention, when the light shielding member can be attached to the case without using a fixture or the like when adhered to the case through the adhesive member, the light shielding member and the transfer belt are provided by the amount of the fixture. The distance can be secured, and the recording paper can be effectively prevented from being clogged between the transfer belt and the static elimination lamp.
[0037]
According to the fourth aspect of the present invention, a sufficient distance between the light shielding member and the transfer belt can be ensured, so that a paper jam at this portion can be effectively prevented.
[Brief description of the drawings]
FIG. 1 is a schematic side view of a printer.
FIG. 2 is a side view for explaining the structure of an image forming unit.
3 is a perspective view of a bottom surface of a case of the cleaning unit shown in FIG. 2. FIG.
4 is a cross-sectional view of the case shown in FIG. 2 as viewed from the side of the photosensitive drum as viewed from a position X. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Printer 42 Transfer belt 5-8 Image formation part 51 Photosensitive drum (Image carrier)
56 Cleaning section (cleaning section)
562 Case 563 Installation surface 564 Projection portion 565 Rib 57 Static elimination portion 58 Resin sheet

Claims (4)

An image forming apparatus provided with the cleaning unit between a transfer belt and a cleaning unit disposed adjacent to each other around the image carrier, and having a charge eliminating unit that irradiates light to the image carrier after transfer, A sheet-shaped light blocking member that regulates the optical path of the irradiation light from the static elimination unit to the transfer belt is attached to the cleaning unit ,
The cleaning section includes a case for holding a cleaning tool, and the case has an installation surface on the side facing the transfer belt, and a protruding portion at a part of the case opposite to the image carrier. Formed, the static elimination part is provided on the installation surface, the light shielding member is interposed between the static elimination part and the transfer belt, and a base end is fixed to the protruding part,
The case includes a plurality of ribs parallel to a direction orthogonal to the axial direction of the image carrier at a predetermined interval in a part of the installation surface on the image carrier side. An image forming apparatus in which the light shielding members are arranged side by side and the front end side is in contact with the top of the rib . The installation surface has a concave portion extending in the axial direction of the image carrier, and a protrusion toward the inside of the concave portion is formed on the edge of the side wall on the end portion side of the concave portion, and the charge eliminating portion is fitted into the concave portion, The image forming apparatus according to claim 1, wherein the image forming apparatus is sandwiched between and supported by the protrusion and the bottom of the recess, and is sandwiched and supported by the light shielding member and the bottom . The image forming apparatus according to claim 1, wherein the light shielding member is bonded to the protruding portion via an adhesive member . The image forming apparatus according to claim 1, wherein the light shielding member is a resin film .

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