Patent Application
20070290435
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
In this embodiment, a case will be described in which the invention is applied to a compound machine (image forming apparatus) provided with a copy function, a print function, and a facsimile function.
Overall Configuration of Image Forming Apparatus
As shown in
Image Capturing System
A scanner portion 101 creates original image data by capturing an image of an original placed on an original stage (not shown) configured using a transparent glass or the like or an image of originals supplied one by one by an unshown auto document feeder. The scanner portion 101 is provided with an exposing light source 101a, a plurality of reflecting mirrors 101b, an imaging lens 101c, and a photoelectric transducer (CCD: Charge Couple Device) 101d.
The exposing light source 101a irradiates light to an original placed on the original stage or an original transported through the auto document feeder. The reflecting mirrors 101b reflect reflected light from the original, and reflect the light from the exposing light source 101a toward the imaging lens 101c. As an original image capturing operation, when an original has been placed on the original stage (usage as a “sheet-fixing type”), the exposing light source 101a and the reflecting mirrors 101b scan in the horizontal direction along the original stage to capture an image of the entire original. On the other hand, when capturing an original transported through the auto document feeder (usage as “sheet moving-type”), the exposing light source 101a and the reflecting mirrors 101b are fixed at positions that have been set in advance, and when the original passes through an original capturing portion of the auto document feeder, an image of that original is captured. Light that has been reflected by the reflecting mirrors 101b and passed through the imaging lens 101c is guided to the CCD 101d, and in the CCD 101d the reflected light is converted into an electrical signal (original image data).
Image Forming System and Paper Transport System
As shown in
The original image data handled in the image forming apparatus 100 corresponds to a color image using the colors black (K), cyan (C), magenta (M), and yellow (Y). Accordingly, as shown in
The image forming apparatus 100 is configured as a color image forming apparatus employing an intermediate transfer method in which, as described below, after image information that has been color-separated into a plurality of colors (four colors in this example) is, using a plurality of the photosensitive drums 103 (four in this example), transferred in layers to the intermediate transfer belt 107, which rotates in contact with each of the photosensitive drums 103 at a predetermined pressure, a color image is formed on paper by transferring that image information all at once onto paper transported from a paper storage portion such as the supply trays 110.
The photosensitive drums 103 are disposed inside the image forming apparatus 100. Disposed around the circumference of each photosensitive drum 103 is a development unit 102, a cleaning unit 104, a charging unit 105, and the like.
With toner of the colors (K, C, M, Y), the development unit 102 makes visible the electrostatic latent image formed on each photosensitive drum 103, thus forming a toner image of each color.
The cleaning unit 104 removes and recovers toner remaining on the surface of the photosensitive drum 103 after development and image transfer.
The charging unit 105 is a charging means for charging the surface of the photosensitive drum 103 to a predetermined potential. In this example, a contact roller-type charging unit is used. A brush-type charging unit or a charger-type charging unit may also be used.
The exposing unit 111 has a function to, by exposing the photosensitive drums 103 that have been charged by the charging unit 105 according to input image data, form an electrostatic latent image corresponding to the image data on the surface of the photosensitive drums 103. A laser scanning unit (LSU) provided with a laser irradiating portion and a reflecting mirror 111a and the like is used as the exposing unit 111. An EL or LED write head in which emitting elements are aligned in an array may for example also be used as the exposing unit 111.
The intermediate transfer belt unit 108 forms a color image or monochrome image on paper using an intermediate transfer method, and is provided with the intermediate transfer belt 107, an intermediate transfer belt drive roller 171, an intermediate transfer belt idler roller 172, an intermediate transfer belt tension mechanism 173, intermediate transfer rollers 174, and an intermediate transfer belt cleaning unit 175.
The intermediate transfer rollers 174 are rotatably supported by an intermediate transfer roller installation portion (not shown) of the intermediate transfer belt tension mechanism 173 of the transfer belt unit 108, and provide a transfer bias for transferring the toner image on the photosensitive drum 103 onto the intermediate transfer belt 107.
The intermediate transfer belt 107 is stretched across the intermediate transfer belt drive roller 171, the intermediate transfer belt idler roller 172, an intermediate transfer belt tension roller of the intermediate transfer belt tension mechanism 173, the intermediate transfer rollers 174, and the like, and is rotatably driven in the direction of arrow A. The intermediate transfer belt 107 is provided so as to make contact with (be sandwiched by) the respective photosensitive drums 103, and by transferring, sequentially layered, the toner images of each color formed on each of the photosensitive drums 103 to the intermediate transfer belt 107, a color toner image (multicolor or single color image) is formed on the intermediate transfer belt 107. The intermediate transfer belt 107 is formed to be endless using a film with a thickness of about 100 to 150 mm.
The transfer of a toner image from the photosensitive drums 103 to the intermediate transfer belt 107 is performed by the intermediate transfer rollers 174, which make contact with the back side of the intermediate transfer belt 107. A high voltage transfer bias (a high voltage with a polarity (+) opposite to the charging polarity (−) of the toner) is applied to the intermediate transfer rollers 174 in order to transfer the toner image.
The intermediate transfer rollers 174 use a metal shaft (for example, stainless steel) with a diameter of 8 to 10 mm as a base, with the surface of that shaft being covered with electrically conductive elastic material (for example, such as EPDM or urethane foam). With this electrically conductive elastic material, it is possible to uniformly apply a high voltage to the intermediate transfer belt 107. In this example, the intermediate transfer rollers 174 are used as transfer electrodes, but a brush or the like may by used instead.
In the above manner, latent images that have been made visible on the photosensitive drums 103 corresponding to each color are layered on the intermediate transfer belt 107, and become the image information input to the apparatus. The image information layered in this manner is, due to rotation of the intermediate transfer belt 107, transferred onto paper by a transfer roller 113 disposed at a contact position of the paper and the intermediate transfer belt 107, described later.
At this time, the intermediate transfer belt 107 and the transfer roller 113 are pressed against with a predetermined nip, and a voltage for transferring toner to the paper is applied to the transfer roller 113 (a high voltage with a polarity (+) opposite to the charging polarity (−) of the toner). Further, in order for the transfer roller 113 to constantly obtain that nip, it is preferable that a hard material (such as metal) is used for either the transfer roller 113 or the intermediate transfer belt drive roller 171, and for the other, a soft material such as an elastic roller or the like (for example, such as an elastic rubber roller or a foam resin roller) is used.
Also, as stated above, toner affixed to the intermediate transfer belt 107 due to contact with the photosensitive drums 103, or toner remaining on the intermediate transfer belt 107 without being transferred onto the paper by the transfer roller 113, will cause mixing of toner colors in the next step, so a configuration is provided in which such toner is removed and recovered by the intermediate transfer belt cleaning unit 175.
A member that makes contact with the intermediate transfer belt 107, for example a cleaning blade provided as a cleaning member, is provided in the intermediate transfer belt cleaning unit 175, and the intermediate transfer belt 107, contacted by that cleaning blade, is supported by the intermediate transfer belt drive roller 171 from the back side.
The supply trays 110 are for storing paper (recording sheets) used for image forming, and two of the supply trays 110 are provided in the lower portion of the image forming apparatus 100. Also, paper for which printing is finished is placed in the discharge tray 115 provided in the paper post-processing portion 109 added to the image forming apparatus 100. Further, a manual feed tray 120 is provided in the body of the image forming apparatus 100, and by using the manual feed tray 120 it is not necessary to perform an operation of opening or closing the supply trays 110. The manual feed tray 120 supplies paper by feeding the paper to the transport path S page by page using a pickup disposed at the end of the manual feed tray 120.
The transport path S is provided in the image forming apparatus 100 in order to feed paper of the supply trays 110 to the discharge tray 115 by way of the transfer roller 113 and the fixing unit 112. Also, the switchback transport path S′ is provided in the image forming apparatus 100 so that duplex printing (transfer of developer to both faces of the paper) is possible. Near the transport path S from the supply trays 110 to the discharge tray 115, and the switchback transport path S′ for allowing duplex printing, are provided the fixing unit 112, the transfer roller 113, a registration roller 114, pickup rollers (paper transport rollers) 116 and 117, and transport mechanisms 121 to 123 that transport the paper.
The fixing unit 112 (fixing portion) is provided with a hot roller, a pressure roller, and the like. The hot roller and the pressure roller rotate while sandwiching the paper.
Also, the hot roller is set to a predetermined fixing temperature by a control based on a signal from a temperature detector that is not shown, and the hot roller, by applying heat and pressure to the paper, melts, mixes, and applies pressure to the multicolor toner image transferred to the paper, thus fixing the image with heat and pressure. After the multicolor toner image has been fixed, the paper is transported to the transport path S by transport rollers 122, and in a reversed state (with the multicolor/single color toner image pointed downstream), the paper is discharged onto the discharge tray 115.
The pickup rollers 116 are provided at the end of the supply trays 110. The pickup rollers 116 supply paper page by page to the transport path S. The registration roller 114 temporarily holds the paper transported through the transport path S, and transports the paper to the transfer roller 113 at a timing that matches the leading edge of the toner image on the intermediate transfer belt 107 to the leading edge of the paper.
The transport mechanisms 121 to 123 are small rollers used in order to promote and assist paper transport, and a plurality of the transport mechanisms 121 to 123 are provided along the transport paths S and S′. Specifically, the transport mechanisms 121 are provided on the transport upstream side of the fixing unit 112, the transport mechanisms 122 are provided on the transport downstream side of the fixing unit 112, and the transport mechanisms 123 are provided in the switchback transport path S′.
Added to the image forming apparatus 100 having the characteristics described above is the paper post-processing portion 109, which performs paper post-processing for paper on which developer has been fixed (printing has been performed) in the fixing unit 112. The functions of the paper post-processing portion 109 include, for example, a stapling function, a hole-punching function, and a binding function. Also, the transport path S is provided in the paper post-processing portion 109, formed continuous from the body of the image forming apparatus 100, and the plurality of transport mechanisms 122 are provided in the transport path S. Of these transport mechanisms 122, the transport mechanism according to the invention is applied to a transport mechanism 122e immediately before the discharge tray 115.
The transport mechanism 122e makes contact with the paper to transport the paper downstream in the transport path, and as shown in
In the transport mechanism 122e, the five transport rollers 201 are provided on one shaft 209 in the direction perpendicular to the transport direction of the paper, and the five idler rollers 202 that form pairs with the transport rollers 201 are provided on one idler shaft (not shown). Thus, the transport rollers 201 and the idler rollers 202 that form five pairs, each with the same operation, make contact with the paper and transport the paper downstream in the transport path. That is, as shown in
The transport rollers 201 are configured with a side face of their cylindrical body perpendicular to the vertical direction, and the shaft 209 piercing through the transport rollers 201 from the upper face to the lower face. In the side face portion of the body of the transport rollers 201, contact portions 203 to 205 are provided that make contact with the paper. Also, a hollow portion 206 is formed in the vicinity of the contact portions 203 to 205. The contact portions 203 to 205 are provided at three points, and of those, two of the contact portions 204 and 205 are deformable in the direction that releases pressing force received from the paper when transporting the paper. The amount of deformation of the contact portions 204 and 205 of the five transport rollers 201 on the single shaft 209 is the same for all of the contact portions.
Incidentally, in the transport rollers 201, around the entire circumference of the end face portion of the body of the transport rollers 201, two protruding portions 207 are formed that protrude in the direction perpendicular to the axis direction of the shaft 209, at the top face side and the bottom face side of the side face portion, and tips 208 of these protruding portions 207 are respectively bent so as to face each other. These tips 208 of the protruding portions 207 are used as the two contact portions 204 and 205. Also, due to the bent formation of the tips 208 of the protruding portions 207, the hollow portion 206 is formed in the vicinity of the contact portions 204 and 205. The one remaining contact portion 203 is provided in the center of the side face portion that faces the hollow portion 206, and this contact portion 203 is used as the nip portion, which is the contact region of the transport roller 201 and the idler roller 202.
In the transport mechanism 122e described above, when the paper is transported, there is a change from the state shown in
Next is a detailed description of the paper transport paths of the above image forming apparatus 100, with reference to
First, disposed in the image forming apparatus 100 of this example are the supply trays 110, where paper is stored in advance, and the manual feed tray 120, whereby when the user prints a small number of sheets, it is not necessary to perform an operation of opening or closing the supply trays 110. The supply trays 110 and the manual feed tray 120 feed paper to the transport path page by page, the pickup rollers 116 and 117 respectively disposed at the end of the trays 110 and 120.
The paper transported from the paper tray 110 is transported to the registration roller 114 by the transport mechanism 121 in the transport path S, then transported to the transfer roller 113 at a timing that coordinates the leading edge of the paper with the leading edge of the image information on the intermediate transfer belt, and the image information is written onto the paper. Afterward, by passing through the fixing unit 112, unfixed toner on the paper is melted and fixed with heat, and then the paper travels through the transport path S and is discharged onto the discharge tray 115 by a discharge roller, which is the final transport mechanism 122e (in the case of a request for one-sided printing).
On the other hand, paper that has been stacked in the manual feed tray 120 is supplied by the pickup roller 117, reaches the registration rollers 114 via the plurality of transport mechanisms 121, and then is discharged to the discharge tray 115 via the same path as paper supplied from the supply trays 110 (in the case of a request for one-sided printing).
Here, when the content of the print request is a request for duplex printing, after one-sided printing in the above manner has been completed, the trailing edge of paper that has passed through the fixing unit 112 is chucked by a reverse roller 122r among the transport mechanisms 122, and in this state the reverse roller 122r rotates in reverse and thus the paper is guided into the reverse transport path S′. In the reverse transport path S′, after being transported by the transport mechanism 123, the paper is again guided into the transport path S. Then, after printing has been performed on the rear face via the registration roller 114, the paper is discharged by the transport mechanism 121 to the discharge tray 115.
In the embodiment described above, there are contact portions at three points, but the invention is not limited to such a configuration; there may be contact portions at a plurality of points, with at least one of the contact portions being deformable.
Also, in this embodiment, the paper post-processing portion 109 was added to the image forming apparatus 100, but the invention is not limited to such a configuration; for example, it is possible that the paper post-processing portion 109 is not added, as shown in
Also, in this embodiment, a color tandem-type image forming apparatus that forms multicolor and single color images on paper is used, but the invention is not limited to such a configuration; for example, as shown in
Also, in this embodiment, as shown in
Also, in the embodiments shown in
Also, in this embodiment, five of the transport rollers 201 are provided for one shaft 209, but the invention is not limited to such a configuration; the number of transport rollers 201 may be set as desired. It is preferable to provide a plurality of the transport rollers 201 for one shaft 209.
Also, in this embodiment, the amount of deformation is the same for all of the contact portions 204 and 205 of the plurality of transport rollers 201 for one shaft 209, but the invention is not limited to such a configuration; the amount of deformation may differ between respective contact portions 204 and 205 of the plurality of transport rollers 201 for one shaft 209, and in the transport mechanism 122e, the amount of deformation of the contact portions 204 and 205 may be set so as to become smaller from, of the plurality of transport rollers 201, a transport roller 201 disposed at an end of the shaft 209 toward a transport roller 201 disposed in the center of the shaft 209. For example, the amount of deformation of the contact portions 204 and 205 may be varied by varying the protrusion length of the protruding portions 207 such that the amount of deformation of the contact portions 204 and 205 becomes smaller from a transport roller 201 disposed at an end of the shaft 209 toward a transport roller 201 disposed in the center of the shaft 209. Alternatively, the amount of deformation of the contact portions 204 and 205 may be varied by varying the thickness of the tips 208 of the protruding portions 207. Alternatively, the amount of deformation of the contact portions 204 and 205 may be varied by using a plurality of materials of differing hardness for the materials of the respective protruding portions 207. In these cases, paper curling is not corrected at each of the plurality of transport rollers 201; rather, it is possible to correct curling of an entire sheet of paper as a single target with the plurality of transport rollers 201 for the one shaft 209. As a result, it is possible to prevent wrinkles in the center of the paper, tears at the ends of the paper, or the like that occur when the paper is transported by the transport mechanism 122e. An embodiment of this configuration is shown in
In the transport mechanism 122e of the embodiment shown in
In the transport mechanism 122e shown in
(t-1)=(t-6)>(t-2)=(t-5)>(t-3)=(t-4) Formula 1
From the above configuration, in the transport mechanism 122e shown in
As described above, with the transport rollers 201, the contact portions 204 and 205 that make contact with the paper are provided, and the contact portions 204 and 205 are deformable in the direction that releases pressing force received from the paper when the paper is transported, so when transporting the paper, it is possible to correct curling of a desired paper without damaging the paper, regardless of the thickness or stiffness of the paper. More specifically, it is possible to vary the amount of deformation in the direction that releases pressing force received from the paper when transporting the paper, and as a result, it is possible to deform the contact portions 204 and 205 according to the thickness or stiffness of the paper.
Also, the contact portions 203 to 205 are provided at three points, and two of the contact portions 204 and 205 are deformable, so it is possible to disperse the pressing force received from the paper among the contact portions 203 to 205 at three points. Thus, the pressing force applied to the individual contact portions 203 to 205 can be suppressed, so that not only does it become possible to correct curling of a desired paper regardless of the thickness or stiffness of the paper, it is also possible to perform paper transport while maintaining a transport force that is appropriate to the thickness and stiffness of the paper. As a result, the pressing force received from the paper is dispersed by increasing the contact points, so that it becomes possible to transport any paper with a maximum amount of transport force for that paper, and moreover, it becomes possible to suppress the occurrence of creases or other damage in comparison to a configuration with one contact point.
Also, the hollow portion 206 is formed near the contact portions 203 to 205 of the body of the transport roller 201, so the hollow portion 206 can be used as a part that releases the pressing force received when transporting the paper.
Also, the protruding portions 207 with the tips 208 bent is formed, these tips 208 being used as the contact portions 204 and 205, so it is possible to insure that the tip 208 vicinity is a part that releases the pressing force received when transporting the paper.
Also, according to the transport mechanism 122e as described above, the five transport rollers 201 are provided to the one shaft 209, and the five transport rollers 201 are capable of correcting curling of an entire sheet of paper transported downstream in the transport path by making contact with the paper.
Also, paper is transported to the nip portion configured from the aforementioned transport rollers 201 and idler rollers 202, and transported downstream in the transport path by the driving rotation of the transport rollers 201 and the idling rotation of the idler rollers 202, so it is possible to transport paper with a nip force appropriate to the thickness and stiffness of the paper. More specifically, for any paper it is possible to transport that paper with a minimum of nip force, and as a result, it is possible to obtain a maximum of paper transport force. Also, because it is possible to transport the paper with a minimum of nip force, it is possible to attain a longer operating life for the transport rollers 201 and the idler rollers 202.
Also, as described above, according to the image forming apparatus 100, the transport mechanism 122e is provided in the transport paths S and S′ downstream in the transport path from the fixing unit 112, so it is particularly possible to have an effect of correct curling that occurs in paper that has passed through the fixing unit 112. For example, when the transport mechanism 122e has been provided in the discharge stage of the transport path S after fixing of developer to the paper, it is possible to improve the stackability of the discharged paper. Also, when the switchback transport path S′ is provided in order to allow duplex printing (transfer of developer to both faces of the paper) in the image forming apparatus 100, and the transport mechanism 122e has been provided in the switchback transport path S′, it is possible to suppress paper transport jams. Further, with the conventional technology, the paper is curled, so there may be cases in which when performing duplex printing, the face on which developer has already been fixed attaches to the intermediate transfer belt 107 (the photosensitive drum 103 in
Also, the paper post-processing portion 109, which performs paper post-processing for paper to which developer has been fixed, is added to or provided in the image forming apparatus, and the transport mechanism 122e is provided in the paper post-processing portion 109, so it is possible to improve stackability when performing paper post-processing in the paper post-processing portion 109.
The transport roller and the transport mechanism according to the invention are applicable in the body of an image forming apparatus provided with a copy function, print function, facsimile function, or the like, and also applicable in a paper post-processing portion added to an image forming apparatus.
The present invention may be embodied in various other forms without departing from the gist or essential characteristics thereof. The embodiments disclosed in this application are to be considered in all respects as illustrative and not limiting. The scope of the invention is indicated by the appended claims rather than by the foregoing description, and all modifications or changes that come within the meaning and range of equivalency of the claims are intended to be embraced therein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-168958 | Jun 2006 | JP | national |
