SHEET CONVEYING APPARATUS, IMAGE READING APPARATUS, AND IMAGE FORMING APPARATUS

A sheet conveying apparatus which conveys a sheet includes: a first rotating member made of a material which is positive with respect to the sheet in a triboelectric series; and a second rotating member made of a material which is negative with respect to the sheet in the triboelectric series, wherein the first and second rotating members are arranged in a conveyance direction of the sheet and arranged to be contact with the same surface of the sheet, and a foreign material is removed from the conveyed sheet by the first and second rotating members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet conveying apparatus which conveys a sheet, and an image reading apparatus and an image forming apparatus including the sheet conveying apparatus.

2. Description of the Related Art

A sheet conveying apparatus that conveys a sheet has been provided in an image forming apparatus such as a copying machine, facsimile equipment, or a compound machine. For example, there is a known image reading apparatus which includes an automatic original conveying apparatus (hereinafter referred to as an auto document feeder (ADF)) that conveys an original corresponding to a sheet to be read.

An image reading apparatus has had a problem that a stripe-shaped image defect is generated on a read image when sheet dust generated from an original or a contaminant such as dust inside the apparatus is attached to platen glass provided in an original reading portion. In the image forming apparatus, there is concern that an image defect may be generated by a foreign material (sheet dust) attached to a conveyed recording medium (sheet).

Japanese Patent Laid-Open No. 2010-160402 proposes a configuration below as a solution to the problem due to the sheet dust generated from the original. That is, in Japanese Patent Laid-Open No. 2010-160402, an original guide portion includes a static electricity generating member that generates static electricity by friction due to contact with a conveying roller, and a cleaning member charged with static electricity generated by the static electricity generating member. In addition, the cleaning member is charged with static electricity generated by the static electricity generating member in order to electrostatically adsorb the foreign material attached to the original, thereby cleaning the foreign material such as sheet dust attached to the original during conveyance.

However, in the configuration of Japanese Patent Laid-Open No. 2010-160402, foreign materials are insufficiently removed.

SUMMARY OF THE INVENTION

It is desirable to provide a sheet conveying apparatus which conveys a sheet including: a first rotating member made of a material which is positive with respect to the sheet in a triboelectric series; and a second rotating member made of a material which is negative with respect to the sheet in the triboelectric series, wherein the first and second rotating members are arranged in a conveyance direction of the sheet and arranged to be contact with the same surface of the sheet, and a foreign material is removed from the conveyed sheet by the first and second rotating members.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the invention will be illustratively described in detail with reference to drawings. However, dimensions, materials, shapes, relative configurations, etc. of component parts described in embodiments below should be appropriately changed according to a configuration or various conditions of an apparatus to which the invention is applied. Therefore, the scope of the invention is not intended to be restricted only thereto unless a specific description is particularly given.

First Embodiment

First, a description will be given of a schematic configuration of an image reading apparatus205including a sheet conveying apparatus according to a first embodiment of the invention usingFIG. 2andFIG. 3. Herein, an auto document feeder201that conveys an original (paper, for example) corresponding to a sheet to be read is illustrated as the sheet conveying apparatus.

As illustrated inFIG. 2, the auto document feeder201which serves as an original conveying apparatus for separately feeding a plurality of originals and reading an original image includes an original placing portion202, a separately feeding portion (not illustrated), an original feeding portion203, an original reading portion311, and an original discharge portion204. The original placing portion202is a portion for placing a fed original. The separately feeding portion is a portion that separately feeds originals placed on the original placing portion one by one using a roller or a belt (not illustrated). The original feeding portion203is a portion that conveys the originals separately fed by the separately feeding portion. The original reading portion311is a portion that reads an image of an original conveyed by the original feeding portion203. The original discharge portion204is provided at a downstream of the original reading portion311in a conveyance direction to place an original after reading.

In addition, as illustrated inFIG. 3, members below are provided inside the original feeding portion203which serves as a conveying portion in order from an upstream side to a downstream side in the conveyance direction of the original corresponding to the sheet. A pair of conveying rollers305conveys an original separately fed by the separately feeding portion. A pair of registration rollers306is provided at a downstream of the pair of conveying rollers305in the conveyance direction to correct skew feeding of the fed original. Two pairs of foreign material removing rollers307are provided at a downstream of the pair of registration rollers306in the conveyance direction. Furthermore, the pairs of foreign material removing rollers307are provided at an upstream in the conveyance direction of a first platen glass311corresponding to a first original reading portion which is provided on a side of an image reading apparatus302for reading an image of a surface corresponding to one surface of the fed original. A first platen roller308is provided on a side opposing the first platen glass311to apply a force to the fed original to the first platen glass311when the image on the surface of the fed original is read. A pair of conveying rollers309is provided at a downstream of the first platen roller308in the conveyance direction to convey the fed original whose image on the surface is read. Second platen glass312is provided at a downstream of the pair of conveying rollers309in the conveyance direction, and is a second original reading portion for reading an image on a rear surface corresponding to the other surface of the fed original. A second platen roller310is provided on a side opposing the second platen glass312to apply a force to the fed original to the second platen glass312when the image on the rear surface of the fed original is read. A second image reading portion304reads the image on the rear surface of the fed original at a position of the second platen glass312. Although not illustrated, a pair of discharge rollers is provided at a downstream of the second platen roller310in the conveyance direction to discharge the original to the original discharge portion204(see FIG.2).

In addition, the image reading apparatus302for reading the image of the surface of the original conveyed by the auto document feeder201is provided below the auto document feeder201. The first platen glass311corresponding to the first original reading portion is provided in the image reading apparatus302at a position opposing the first platen roller308. In addition, a first image reading portion303for reading the image on the surface of the conveyed original through the first platen glass311is provided inside the image reading apparatus302.

Herein, the above-described two pairs of foreign material removing rollers (pairs of rotating members)307include conveying rollers307aand307bcorresponding to driven rotating members, and foreign material removing follower rotating members103aand103bwhich convey a sheet by nipping the sheet with the opposing conveying rollers307aand307b.The conveying rollers307aand307bare disposed on the rear surface side of the original, and the foreign material removing follower rotating members103aand103bare disposed on the surface side of the original (the first original reading portion side) corresponding to the same surface side of the sheet.

According to the above-described configuration, since the two pairs of foreign material removing rollers307are disposed at an immediate upstream of the first platen glass311corresponding to the first original reading portion, a foreign material such as sheet dust attached to the surface of the fed original may be removed. In this way, it is possible to remove the foreign material such as sheet dust regarded as a main factor of an image defect such as a stripe, and to provide stable image reading.

Next, a description will be given of an outline of a foreign material removing unit101including the two pairs of foreign material removing rollers307usingFIGS. 1A and 1B. A conveyance guide102, which is provided from the pair of registration rollers306up to an immediate upstream of the first platen glass311to guide the same surface side (surface side) of the original, is disposed in the foreign material removing unit101. The foreign material removing follower rotating members103aand103bare provided in the conveyance guide102over a region including dimensions of the original in a width direction (main scanning direction) perpendicular to the conveyance direction (substantially whole region of the original in the width direction) so as to be rubbed with the whole fed original. Further, scrape members104aand104babut on the conveyance guide102to scrape the foreign material (extraneous matter) such as sheet dust attached to the foreign material removing follower rotating members103aand103b.The scrape members104aand104bare attached to a pressure member105that allows the foreign material removing follower rotating members103aand103bto apply pressure to the opposing conveying rollers307aand307b(seeFIG. 3), respectively.

A foreign material removing follower rotating member103includes a first foreign material removing follower rotating member103aserving as a first rotating member, and a second foreign material removing follower rotating member103bserving as a second rotating member. The first foreign material removing follower rotating member103ais made of a material which is positive with respect to the fed original in a triboelectric series. For example, one of ABS resin, PET resin, PC+AS resin, PA resin, POM resin, and PET+ABS resin is used as the material (quality of material) which is positive with respect to the original in the triboelectric series as illustrated inFIG. 8. The second foreign material removing follower rotating member103bis made of a material which is negative with respect to the fed original in the triboelectric series. For example, one of PTFE resin, PVC resin, PS resin, PP resin, PPE+PS resin, and PE resin is used as the material (quality of material) which is negative with respect to the original in the triboelectric series as illustrated inFIG. 8. In this way, the foreign material removing follower rotating members103aand103binclude resin members. The foreign material removing follower rotating members103aand103bmay have opposite-polarities in the triboelectric series. That is, the foreign material removing follower rotating member103amay be made of a material which is negative with respect to the fed original in the triboelectric series, and the foreign material removing follower rotating member103bmay be made of a material which is positive with respect to the fed original in the triboelectric series. In addition, order of a plus sign and a minus sign of the triboelectric series is not an issue in the conveyance direction of the original.

Further, the two pairs of foreign material removing rollers307are disposed in parallel at positions adjacent to each other in the conveyance direction of the original, and the two foreign material removing follower rotating members103aand103bare disposed on the same surface side of the original (herein, the surface side of the original). This disposition allows the original to be conveyed to the first platen glass311corresponding to the original reading portion without the removed foreign material flowing out, and it is possible to reduce the image defect such as the strip generated by the foreign material.

According to the above-described configuration, the fed original plunges into the pairs of foreign material removing rollers307by passing through the pair of conveying rollers305and the pair of registration rollers306. Frictional electrification occurs by the conveyed original and the pairs of foreign material removing rollers307, and the original and the pairs of foreign material removing rollers307are charged. In this way, a foreign material having one polarity (herein, a positive polarity) is removed by the first foreign material removing follower rotating member103athat abuts on the surface of the conveyed original. Subsequently, a foreign material having the other polarity (herein, a negative polarity) unable to be removed in the first foreign material removing follower rotating member103ais removed by the second foreign material removing follower rotating member103b. Thereafter, the conveyed original passes through the first platen glass311corresponding to the original reading portion in a state in which foreign materials having both polarities are reduced. Further, an image of the original is read, and the original is discharged to the original discharge portion204. This operation allows stripe-shaped images mainly caused by a foreign material such as sheet dust to be reduced, and thus it is possible to provide stable image reading.

In addition, in the above-described embodiment, a description has been given using, as an example, the pairs of foreign material removing rollers307which nips the original with the foreign material removing follower rotating members abutting on the original on a read surface side (the surface side) and the conveying rollers abutting on the original on the rear surface side. However, the invention is not limited thereto. For example, as illustrated inFIG. 4, it is possible to employ a configuration including a guide member which guides the rear surface side of the original, and a foreign material removing follower rotating member which is provided to oppose the guide member and abuts on the original on the read surface side (surface side). This configuration achieves compactness, does not incur a problem in terms of control with previous and subsequent rollers, and does not generate nip. Thus, it is possible to suppress generation of a foreign material such as sheet dust.

In addition, the above-described embodiment illustrates a configuration in which the scrape members104are provided for the first foreign material removing follower rotating member103aand the second foreign material removing follower rotating member103b, respectively. However, the invention is not limited thereto. For example, as illustrated inFIG. 5, it is possible to employ a configuration in which a single scrape member104cabuts on the respective foreign material removing follower rotating members103aand103b.This configuration has effect that a configuration may be simplified, which leads to a cost reduction.

Second Embodiment

A description will be given of an image forming apparatus including a sheet conveying apparatus according to a second embodiment usingFIG. 6.FIG. 6is a schematic cross-sectional view illustrating a schematic configuration of the image forming apparatus. Herein, a sheet conveying apparatus that conveys a sheet corresponding to a recording target (recording medium) is given as an example of the sheet conveying apparatus, and a full color laser beam printer (hereinafter referred to as a printer) is given as an example of the image forming apparatus.

Referring toFIG. 6, a printer1corresponds to the image forming apparatus, a main printer body1A corresponds to a main apparatus body of the image forming apparatus, an image forming portion1B forms an image on a sheet, and a fixing portion20is provided. An image reading apparatus2corresponds to an upper apparatus substantially horizontally installed above the main printer body1A. A sheet feeding device30is provided below the image reading apparatus2and the main printer body1A. A toner cartridge15is detachably attachable with respect to the main printer body.

Image information read by the image reading apparatus2or image information input from external equipment such as a personal computer (not illustrated) is subjected to image processing, and then converted into an electric signal and transmitted to a laser scanner10of the image forming portion1B. In addition, in the image forming portion1B, a surface of a photosensitive drum12of each process cartridge11is scanned by a laser beam corresponding to image information of yellow, magenta, cyan, and black component colors emitted from the laser scanner10. In this way, the surface of the photosensitive drum12equally charged at a predetermined polarity and electric potential by a charging unit13is successively exposed, and each electrostatic latent image of yellow, magenta, cyan, and black is successively formed on the photosensitive drum12of each process cartridge11.

Thereafter, when the electrostatic latent image is developed and visualized by each color toner of each development device14of yellow, magenta, cyan, and black, a toner image of each color is formed on each photosensitive drum. The toner image of each color formed on each photosensitive drum is successively superposed on and transferred to an intermediate transfer belt16stretched on a driving roller16aand a tension roller16bby a primary transfer bias applied to a primary transfer roller19. In this way, the toner image is formed on the intermediate transfer belt (image bearing member)16.

Meanwhile, a sheet S (paper, for example) sent from the sheet feeding device30passes through a pair of registration rollers40, and is sent to a secondary transfer portion including the driving roller16aand a secondary transfer roller (transfer portion)17. In the secondary transfer portion, toner images formed in the image forming portion1B are collectively transferred onto the sheet S.

Subsequently, the sheet S onto which the toner image is transferred in this way is conveyed to the fixing portion20, and the toner image is fixed as a color image on the sheet S by receiving heat and pressure in the fixing portion20. Thereafter, the sheet S on which the image is fixed is discharged to a discharge space P by a pair of first discharge rollers25aor a pair of second discharge rollers25b,and is stacked on a protruding stacking portion23at a bottom of the discharge space P.

As illustrated inFIG. 7, in the secondary transfer portion, a first foreign material removing follower rotating member60and a second foreign material removing follower rotating member61serving as conveying apparatuses that convey the sheet S to the secondary transfer roller17are disposed in parallel in a conveyance direction. The first foreign material removing follower rotating member60and the second foreign material removing follower rotating member61are disposed at an immediate upstream (close to an upstream in the conveyance direction) of the secondary transfer roller17, and are disposed on a surface side (toner transfer surface side) of the sheet S. Further, a first scrape member64and a second scrape member65abut on the first foreign material removing follower rotating member60and the second foreign material removing follower rotating member61, respectively. The first scrape member64and the second scrape member65may not be provided for the first foreign material removing follower rotating member60and the second foreign material removing follower rotating member61, respectively. A single scrape member may abut on the respective rotating members.

In addition, as illustrated inFIG. 7, referring to the fixing portion, a first foreign material removing follower rotating member62and a second foreign material removing follower rotating member63serving as conveying apparatuses that convey the sheet S to the fixing portion20are disposed in parallel in the conveyance direction. The first foreign material removing follower rotating member62and the second foreign material removing follower rotating member63are disposed at an immediate upstream (close to an upstream in the conveyance direction) of the fixing portion20, and are disposed on a rear surface side (an opposite side from the toner transfer surface side) of the sheet S. Further, a first scrape member66and a second scrape member67abut on the first foreign material removing follower rotating member62and the second foreign material removing follower rotating member63, respectively. The first scrape member66and the second scrape member67may not be provided for the first foreign material removing follower rotating member62and the second foreign material removing follower rotating member63, respectively. A single scrape member may abut on the respective rotating members.

According to the above-described configuration, the conveyed sheet S plunges into the first foreign material removing follower rotating member60and the second foreign material removing follower rotating member61in order by passing through the pair of registration rollers40. Frictional electrification occurs by the conveyed sheet S and the first and second foreign material removing follower rotating members60and61, and the conveyed sheet S and the first and second foreign material removing follower rotating members60and61are charged. In this way, a foreign material having one polarity is removed by the first foreign material removing follower rotating member60that abuts on the conveyed sheet S. Subsequently, a foreign material having the other polarity unable to be removed in the first foreign material removing follower rotating member60is removed by the second foreign material removing follower rotating member61.

Thereafter, the conveyed sheet S passes by the secondary transfer roller17, and is directed to the fixing portion20to fix the sheet S on which a toner is carried. In this instance, frictional electrification occurs by the first and second foreign material removing follower rotating members62and63and the sheet S, and the sheet S and the first and second foreign material removing follower rotating members62and63are charged. In this way, a foreign material having one polarity is removed by the first foreign material removing follower rotating member62that abuts on the conveyed sheet S. Subsequently, a foreign material having the other polarity unable to be removed in the first foreign material removing follower rotating member62is removed by the second foreign material removing follower rotating member63. In addition, a toner is fixed on the sheet S in the fixing portion20, and the sheet S is discharged to the discharge space P.

This operation allows a reduction in image defect such as a stripe generated by a foreign material. Specifically, when a foreign material such as sheet dust is interposed in a cleaning blade in the intermediate transfer belt16of the transfer portion, it is possible to reduce a problem that a toner slips from the cleaning blade or a problem that a pressure roller of the fixing portion is contaminated.

Other Embodiments

The above-described first embodiment illustrates a configuration, in which two rotating members having different polarities with respect to an original in a triboelectric series are disposed immediately before a first original reading portion, as a conveying apparatus that conveys the original to a first original reading portion. However, the invention is not limited thereto. For example, it is possible to employ a configuration in which two rotating members having different polarities with respect to an original in a triboelectric series are similarly provided as a conveying apparatus that conveys an original to a second original reading portion on a downstream side from a first original reading portion. In this case, the two rotating members are disposed on a rear surface side (second original reading portion side) of the original corresponding to the same surface side of the original.

In addition, the above-described second embodiment illustrates a configuration, in which two rotating members having different polarities with respect to a sheet in a triboelectric series are disposed immediately before a secondary transfer portion and a fixing portion, as a conveying apparatus that conveys a sheet to the secondary transfer portion and the fixing portion. However, the invention is not limited thereto. The conveying apparatus can immediately previously remove an extraneous matter such as sheet dust attached to a sheet. However, the conveying apparatus may be appropriately disposed as necessary.

Further, the above-described embodiments illustrate a copying machine as an image forming apparatus. However, the invention is not limited thereto. For example, it is possible to employ another image forming apparatus such as a printer or facsimile equipment or to employ another image forming apparatus such as a compound machine obtained by combining functions thereof. The same effect may be obtained by applying the invention to a sheet conveying apparatus in the image forming apparatus.

Furthermore, the above-described embodiments illustrate a sheet conveying apparatus integrally included in an image reading apparatus or an image forming apparatus. However, the invention is not limited thereto. For example, it is possible to employ a sheet conveying apparatus which is detachably attachable to the image reading apparatus or the image forming apparatus. The same effect may be obtained by applying the invention to the sheet conveying apparatus.

This application claims the benefit of Japanese Patent Application No. 2015-174814, filed Sep. 4, 2015, which is hereby incorporated by reference herein in its entirety.