JP5601719B2 - Sheet transport mechanism, image forming apparatus including the same, and label sheet used therefor - Google Patents

Description

  The present invention relates to a sheet conveying mechanism used in an image forming apparatus such as a digital copying machine or a laser printer, and more particularly to a countermeasure for peeling off a label portion when conveying a label sheet.

  Conventionally, in an electrophotographic image forming apparatus, a transfer roller is pressed against a photosensitive drum, a recording medium (transfer material) is conveyed to the transfer nip portion, and a transfer bias having a polarity opposite to that of toner is applied from the back surface of the recording medium. A direct transfer method in which the toner image formed on the photosensitive drum is directly transferred to a transfer material by being applied to a transfer roller, or after the toner image on the photosensitive drum is primarily transferred onto the intermediate transfer belt, the intermediate transfer belt The recording medium is conveyed to the transfer nip between the toner and the secondary transfer roller, and a transfer bias having a polarity opposite to that of the toner is applied to the secondary transfer roller from the back surface of the recording medium, and the toner image on the intermediate transfer belt is applied to the recording medium. An intermediate transfer system for secondary transfer is widely used.

  In order to allow the recording medium to enter the transfer nip portion, a guide member consisting of a pre-transfer upper (recording medium surface side) guide and a pre-transfer lower (recording medium rear surface) guide is provided at the entrance of the transfer nip portion. In this section, the recording medium is attached (contacted) to the photosensitive drum or the intermediate transfer belt (secondary transfer counter roller) just before the transfer bias is applied, thereby preventing toner scattering and toner reversal.

  In the above-described image forming apparatus, the tip of the lower guide before transfer is disposed on the image carrier side of the tangent of the image carrier such as the photosensitive drum or the intermediate transfer belt in the transfer nip, and the tip of the lower guide before transfer is By supporting the recording medium, a predetermined transfer property can be obtained even if the trailing edge of the recording medium passes through the registration roller pair and the pressing force of the recording medium does not act. However, in such a configuration, the recording medium is conveyed in a bent state toward the image carrier by the transfer guide.

  In addition, when the recording medium is caused to enter the transfer nip portion between the image carrier and the transfer roller from the registration roller pair, the image carrier and the developing device are vibrated by the contact of the recording medium, and transfer deviation, lateral stripe, and color misregistration are caused. Such an image defect may occur. For this reason, it is preferable to enter the transfer nip portion as close as possible to the tangential direction (shallow entry angle). However, in a downsized image forming apparatus, the registration roller pair is arranged in the tangential direction of the transfer nip portion. In order to ensure the separation of the recording medium from the image carrier, it is not preferable to dispose the transfer roller downstream, so it is eventually provided between the registration roller pair and the transfer nip portion. The recording medium is bent by the guide member thus formed and enters the transfer nip portion.

  As a method for stabilizing the conveyance of the recording medium to the transfer nip portion and suppressing the occurrence of image defects, for example, Patent Document 1 discloses a first guide member that introduces a recording material conveyed by a conveying unit to a transfer position. An image forming apparatus having a second guide member for guiding the introduced recording material along the image carrier and an adjustment member for adjusting the positional relationship between the first guide member and the second guide member is disclosed. .

  On the other hand, a label sheet used for physical distribution or the like has a configuration in which a label part having an adhesive (glue) applied to the back surface is bonded to a base material (mounting paper) having a releasable surface. As for this label part, what was affixed on the single side | surface or both surfaces with respect to the base material, and what the label part became not only one layer but the multilayer were marketed. Conventionally, such a label sheet is often printed by a printer dedicated to the label sheet, but recently, there is an increasing demand for printing with a general-purpose printer.

  Since the label sheet is used by peeling the label part from the substrate, the label part needs to be easily peelable. Therefore, when printing using a general-purpose printer, the edge of the label part rises from the substrate due to the bending of the label sheet during conveyance (particularly between the resist roller pair and the transfer nip part), and the label part peels off. There was a risk of jamming. Further, when the pressure-sensitive adhesive adheres to an image carrier such as a photoconductor, foreign matter such as paper dust adheres to the surface of the image carrier using the pressure-sensitive adhesive as a binder, and vertical stripes may occur in the image.

  As a method for preventing the separation of the label portion during the conveyance of the label sheet, for example, Patent Documents 2 and 3 provide perforations in a direction perpendicular to the conveyance direction of the cut line for separating the label portion. A label sheet is disclosed. Further, Patent Document 4 discloses a label paper side half-cut portion obtained by cutting only label paper in a label piece non-arrangement region corresponding to one or more corners of a label piece arrangement region of a label sheet. And a label sheet provided non-parallel to the edge.

JP 2001-166607 A JP-A-10-140105 JP 2003-288021 A JP 2006-917779 A

  According to the configuration of Patent Document 1, by appropriately adjusting the distance between the image carrier and the guide member, it is possible to stabilize the conveyance performance of the recording material to the transfer position and suppress transfer deviation. However, since the appropriate distance between the image carrier and the guide member varies depending on the type of the recording medium, it is difficult to adjust the distance to be compatible with all recording media. Therefore, for example, when adjustment corresponding to the label sheet is performed, there is a possibility that the conveyance of the plain paper may be hindered.

  On the other hand, in the methods of Patent Documents 2 and 3, since a part of the cut line for separating the label portion is perforated, the label portion cannot be smoothly peeled during use. Moreover, in the method of Patent Document 4, although peeling at the time of conveyance of the label paper side half-cut portion formed in the label piece non-arrangement region can be suppressed, there is a possibility that peeling of the outline portion of the label piece may occur.

  Further, even when a label sheet as disclosed in Patent Documents 2 to 4 is used, the label portion may be peeled off depending on the degree of bending of the conveyance path of the image forming apparatus, and a paper jam or an adhesive There is a risk that image defects or the like due to the adhesion of the toner may occur.

  SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a sheet transport mechanism that does not cause image defects due to peeling of a label portion, paper jam caused by the labeling, and adhesion of an adhesive when a label sheet is transported, and an image forming apparatus including the sheet transport mechanism. An object is to provide a device and a label sheet used therefor.

  In order to achieve the above object, the present invention provides a first sheet conveying unit that conveys a sheet conveyed from a sheet feeding device, and a second sheet disposed downstream in the conveying direction of the first sheet conveying unit. Sheet conveying means, an arch-shaped upper conveying guide that is provided between the first and second sheet conveying means and holds the surface side of the sheet, and is disposed opposite to the upper conveying guide. A sheet conveying path configured to include a lower conveying guide that holds the back surface side, and includes a label paper on the front surface side and a base material on the back surface side that releasably supports the label paper, and the label When transporting the label sheet, when transporting a sheet other than the label sheet, in a sheet transport mechanism capable of transporting a label sheet formed by imprinting a contour line consisting of half-cut lines from the paper side Compared to is characterized by narrowing the transport path width of the sheet front-back direction at the bent portion of the sheet conveying path.

  According to the present invention, in the sheet conveyance mechanism having the above-described configuration, the lower conveyance guide is disposed upstream of the bent portion with respect to the sheet conveyance direction, and is movable in a direction approaching and separating from the upper conveyance guide. A guide member and a second guide member disposed downstream of the bent portion, and when the sheet other than the label sheet is conveyed, the first guide member is separated from the upper conveyance guide. When the label sheet is conveyed at the position 1, the first guide member is disposed at a second position close to the upper conveyance guide.

  According to the present invention, in the sheet transport mechanism having the above-described configuration, when the label sheet is transported, the sheet transport speed by the first sheet transport unit is relatively faster than the sheet transport speed by the second sheet transport unit. It is characterized by having become.

  According to the present invention, in the sheet transport mechanism configured as described above, the lower transport guide includes a guide roller disposed to face a bent portion of the upper transport guide, and the upper transport guide is formed on an outer peripheral surface of the guide roller. A pressing roller disposed to be able to contact and separate from the sheet support region, and when the sheet other than the label sheet is conveyed, the pressing roller is disposed at a first position separated from the guide roller; When the sheet is conveyed, the pressing roller is arranged at a second position in contact with the guide roller.

  According to the present invention, in the sheet transport mechanism having the above-described configuration, the first sheet transport unit is a registration roller pair, and the second sheet transport unit rotates while contacting the image carrier and the image carrier. It is a member, and the upper conveyance guide is bent so that the image carrier side is convex.

  The present invention also provides an image forming apparatus including the sheet conveying mechanism having the above-described configuration.

  The present invention also provides a label sheet used in the sheet transport mechanism having the above-described configuration, wherein an edge on the leading end side in the sheet transport direction of the label portion surrounded by the contour line is predetermined with respect to a direction perpendicular to the sheet transport direction. It is characterized by having an angle of.

  According to the present invention, in the label sheet configured as described above, a corner of the label portion on the rear end side in the sheet conveying direction is formed in an arc shape.

  According to the present invention, in the label sheet configured as described above, the corner portion on the leading end side in the sheet conveying direction of the label portion has an arc shape having a larger curvature than the corner portion on the rear end side in the sheet conveying direction.

  According to the first configuration of the present invention, when the label sheet is conveyed, the conveyance path width in the sheet front and back direction at the bent portion of the sheet conveyance path is narrowed, so that the label sheet is bent at the bent portion of the sheet conveyance path. At this time, it is possible to effectively prevent the peeling of the label portion due to the rising edge of the label portion from the base material, the paper jam resulting from it, and the image defect due to the adhesion of the adhesive. Further, when a sheet other than the label sheet is conveyed, the conveyance path width in the sheet front / back direction is restored, so that the conveyance performance of the sheet other than the label sheet is not impaired.

  According to the second configuration of the present invention, in the sheet transport mechanism according to the first configuration, the lower transport guide includes a first guide member upstream of the bent portion with respect to the sheet transport direction, and a bent portion. The second guide member on the downstream side, and when transporting a sheet other than the label sheet, when the first guide member is disposed at the first position separated from the upper transport guide and the label sheet is transported, By disposing the first guide member at the second position close to the upper conveyance guide, the label sheet is pressed by the upper conveyance guide along the arch-shaped upper conveyance guide. It is conveyed in the state. Thereby, the lifting of the edge of the label part from a base material can be prevented effectively. Further, since the sheets other than the label sheet pass between the upper conveyance guide and the lower conveyance guide and are conveyed to the second sheet conveyance means, the conveyance performance of the sheets other than the label sheet is not impaired.

  Further, according to the third configuration of the present invention, when the label sheet is transported in the sheet transport mechanism of the second configuration, the sheet transport speed by the first sheet transport unit is the sheet by the first sheet transport unit. Since it is set to be relatively faster than the conveyance speed, a slack in the upper conveyance guide direction is formed on the label sheet, so that the label sheet can be surely aligned with the upper conveyance guide.

  Further, according to the fourth configuration of the present invention, in the sheet conveyance mechanism of the first configuration, the lower conveyance guide is provided with a guide roller disposed to face the bent portion of the upper conveyance guide, A pressing roller is provided in the sheet support area on the outer peripheral surface of the guide roller so as to be able to come into contact with and separate from it. When a sheet other than the label sheet is conveyed, the pressing roller is arranged at a first position separated from the guide roller, When the sheet is transported, the label sheet is transported downstream while being sandwiched between the guide roller and the pressing roller at the bent portion of the sheet transport path by arranging the pressing roller at the second position in contact with the guide roller. Therefore, the lifting of the edge of the label portion from the base material can be more effectively prevented. In addition, since the arrangement of the guide rollers does not change, even when a label sheet is transported, it can be transported in substantially the same path as other sheets than the label sheet, and the transportability of both the label sheet and other sheets is stable. Can be made.

  According to the fifth configuration of the invention, in the sheet transport mechanism having any one of the first to fourth configurations, the first sheet transport unit is a pair of registration rollers, and the second sheet transport unit is An image carrier and a transfer member that rotates while being in contact with the image carrier, and the upper conveyance guide is bent so that the image carrier side is convex, so that the label sheet is bent in an arch shape. Along the guide, the sheet is conveyed to the transfer nip while the upper surface side (label portion side) is pressed. Thereby, the lifting of the edge of the label part from a base material can be prevented effectively. Further, since sheets other than the label sheet enter the transfer nip from the direction close to the tangential direction in the transfer nip of the image carrier along the lower conveyance guide, an image such as a transfer deviation or a horizontal stripe due to the contact of the sheet with the image carrier. Problems can be suppressed.

  Further, according to the sixth configuration of the present invention, by mounting the sheet transport mechanism having any one of the first to fifth configurations, peeling of the label portion when the label sheet is transported or caused by the peeling. Thus, an image forming apparatus that can suppress the occurrence of image defects due to paper jams and adhesion of an adhesive, and maintain the transportability of sheets other than the label sheet can be obtained.

  According to the seventh configuration of the present invention, the label sheet is used in the sheet transport mechanism having any one of the first to fifth configurations, and the front end side in the sheet transport direction of the label portion surrounded by the contour line When the label sheet is conveyed along the upper conveyance guide, the end of the label portion in the sheet conveyance direction on the front end side is formed so that the edge of the label sheet has a predetermined angle with respect to a direction perpendicular to the sheet conveyance direction. Since the timing at which the edge passes through the bent portion is shifted in the width direction of the label portion, there is no possibility that the edge of the label portion on the front end side in the sheet conveying direction is rolled at a time. Therefore, the label sheet can be more effectively prevented from rising of the edge of the label portion from the substrate.

  Further, according to the eighth configuration of the present invention, in the label sheet of the seventh configuration, a label at the time of transporting the label sheet is formed by making the corner portion on the rear end side in the sheet transport direction of the label portion into an arc shape. In use, the label portion can be smoothly peeled off from the corner on the rear end side in the sheet conveying direction while preventing the edge of the portion from being peeled off.

  According to the ninth configuration of the present invention, in the label sheet of the eighth configuration, the corner on the front end side in the sheet conveyance direction of the label portion has a larger curvature than the corner on the rear end side in the sheet conveyance direction. By using an arc shape, the label portion is smoothly peeled off from either the rear end side or the front end side corner in the sheet transport direction during use while preventing the edge of the label portion from being peeled off during the conveyance of the label sheet. be able to.

1 is a schematic configuration diagram illustrating an overall configuration of an image forming apparatus including a sheet conveyance mechanism according to the present invention. 1 is a schematic cross-sectional view showing the periphery of an image forming unit 9 in the image forming apparatus of FIG. 1 is a schematic sectional view of a sheet conveying mechanism 60 according to a first embodiment of the present invention. Schematic sectional view of the sheet transport mechanism 60 of the first embodiment when transporting plain paper Schematic sectional view of the sheet transport mechanism 60 of the first embodiment when transporting a label sheet Schematic sectional view showing a modification of the sheet conveying mechanism 60 of the first embodiment Schematic sectional view of a sheet conveying mechanism 60 according to a second embodiment of the present invention. Partial enlarged view of the vicinity of the guide roller 45 and the pressing roller 51 in FIG. Schematic sectional view of the sheet transport mechanism 60 of the second embodiment when transporting plain paper Schematic sectional view of the sheet transport mechanism 60 of the second embodiment when transporting a label sheet The top view which shows an example of the label sheet used for the sheet conveying apparatus of this invention FIG. 6 is a plan view showing another configuration example of the label sheet used in the sheet conveying apparatus of the present invention, in which the corner portion 69a on the rear end side in the sheet conveying direction of the label portion 63 is formed in an arc shape. It is another structural example of the label sheet used for the sheet conveying apparatus of the present invention, and only the edge of the label portion 63 at the front end side in the sheet conveying direction has an angle θ with respect to the direction perpendicular to the sheet conveying direction. Plan view showing configuration It is the other structural example of the label sheet used for the sheet conveying apparatus of the present invention, and both the corner portion 69a on the rear end side in the sheet conveying direction and the corner portion 69b on the front end side in the sheet conveying direction of the label portion 63 have an arc shape. Plan view showing configuration

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating the overall configuration of an image forming apparatus on which the sheet conveying mechanism of the present invention is mounted, and the right side is illustrated as the front side of the image forming apparatus. As shown in FIG. 1, an image forming apparatus 100 (here, a monochrome printer) includes a paper feed cassette 2 that accommodates sheets (sheets) stacked at the bottom of the main body. Above the sheet feeding cassette 2 is formed a sheet conveying path 4 that extends substantially horizontally from the front of the main body to the rear of the main body and further extends upward to reach the sheet discharge portion 3 formed on the upper surface of the main body. A pickup roller 5, a feed roller 6, an intermediate transport roller 7, a registration roller pair 8, an image forming unit 9, a fixing unit 10, and a discharge roller pair 11 are arranged in order from the upstream side along the transport path 4. Further, in the image forming apparatus 100, a control unit (CPU) 30 for controlling operations of the above-described rollers, the image forming unit 9, the fixing unit 10, and the like is disposed.

  The sheet feeding cassette 2 is provided with a sheet stacking plate 12 that is rotatably supported with respect to the sheet feeding cassette 2 by a rotation fulcrum 12a provided at the rear end portion in the sheet conveying direction. The paper stacked on the paper 12 is pressed by the pickup roller 5. A retard roller 13 is disposed on the front side of the paper feed cassette 2 so as to be in pressure contact with the feed roller 6. When a plurality of sheets are fed simultaneously by the pickup roller 5, these feed rollers 13 are fed. The sheet is rolled by the roller 6 and the retard roller 13 so that only the uppermost sheet is conveyed.

  The sheet rolled by the feed roller 6 and the retard roller 13 is conveyed to the registration roller pair 8 by changing the conveyance direction to the rear of the apparatus by the intermediate conveyance roller 7, and the timing is adjusted by the registration roller pair 8. Are supplied to the image forming unit 9.

  The image forming unit 9 forms a predetermined toner image on a sheet by an electrophotographic process. The image forming unit 9 is a photosensitive drum 14 that is an image carrier that is rotatably supported in the clockwise direction in FIG. Above the charging drum 15, the developing device 16, the cleaning device 17, the transfer roller 18 arranged to face the photosensitive drum 14 across the sheet conveyance path 4, and the photosensitive drum 14. A toner container 20 for supplying toner to the developing device 16 is disposed above the developing device 16.

  The charging device 15 includes a conductive rubber roller 15 a to which a power source (not shown) is connected, and the conductive rubber roller 15 a is disposed so as to contact the photosensitive drum 14. When the photosensitive drum 14 rotates, the conductive rubber roller 15a comes into contact with the surface of the photosensitive drum 14 and is driven to rotate. At this time, by applying a predetermined voltage to the conductive rubber roller 15a, the photosensitive drum The surface of the drum 14 is uniformly charged.

  Next, an electrostatic latent image based on the image data input on the photosensitive drum 14 is formed by the laser beam from the exposure unit (LSU) 19, and the electrostatic latent image is developed by the developing roller 16a (see FIG. 2) of the developing device 16. The toner adheres to the image to form a toner image on the surface of the photoconductive drum 14, and the transfer roller 18 forms a toner image on the surface of the photoconductive drum 14 at the nip portion between the photoconductive drum 14 and the transfer roller 18. The image is transferred to the sheet supplied to the transfer position.

  The sheet onto which the toner image has been transferred is separated from the photosensitive drum 14 and conveyed toward the fixing unit 10. The fixing unit 10 is disposed on the downstream side of the image forming unit 9 with respect to the sheet conveyance direction, and the sheet on which the toner image is transferred in the image forming unit 9 includes a heating roller 22 provided in the fixing unit 10, and The toner image heated and pressed by the pressure roller 23 pressed against the heating roller 22 is fixed on the toner image transferred onto the sheet.

  Then, the sheet on which the image is formed in the image forming unit 9 and the fixing unit 10 is discharged to the sheet discharge unit 3 by the discharge roller pair 11. On the other hand, the toner remaining on the surface of the photosensitive drum 14 after the transfer is removed by the cleaning roller 17a and the cleaning blade 17b (see FIG. 2) of the cleaning device 17. The photosensitive drum 14 is charged again by the charging device 15 and image formation is performed in the same manner.

  Next, the sheet conveyance path of the image forming apparatus 100 will be described in detail with reference to FIG. FIG. 2 is a schematic cross-sectional view showing the periphery of the image forming unit 9 in the image forming apparatus of FIG. Portions common to FIG. 1 are denoted by the same reference numerals and description thereof is omitted. The registration roller pair 8 and the photosensitive drum 14 and the transfer roller 18 are spaced apart from the pre-transfer upper guide 40, which is bent in an arch shape with the convex on the photosensitive drum 14 side, with a predetermined interval from the pre-transfer upper guide 40. Are connected to each other by a sheet conveyance path 42 composed of a lower guide 41 before transfer. The registration roller pair 8, the photosensitive drum 14, the transfer roller 18, and the sheet conveyance path 42 constitute a sheet conveyance mechanism 60.

  The pre-transfer lower guide 41 includes a first guide member 43 on the upstream side in the sheet conveyance direction (right to left in FIG. 2), a second guide member 44 disposed on the downstream side of the first guide member 43, The guide roller 45 is disposed between the first guide member 43 and the second guide member 44.

  A static eliminator 47, a conveyance guide 48, and a pre-fixing guide 49 are disposed on the downstream side of the photosensitive drum 14 and the transfer roller 18 with respect to the sheet conveyance direction. The sheet that has passed through the nip portion (transfer nip portion N1) between the photosensitive drum 14 and the transfer roller 18 is subjected to charge removal by the static eliminator 47, and then sequentially passes through the conveyance guide 48 and the pre-fixing guide 49, and the heating roller 22 and It is conveyed to the nip portion (fixing nip portion N2) of the pressure roller 23.

  FIG. 3 is a schematic cross-sectional view of the sheet conveying mechanism according to the first embodiment of the present invention disposed between the registration roller pair 8 and the photosensitive drum 14 and the transfer roller 18. In the present embodiment, the first guide member 43 constituting the pre-transfer lower guide 41 is disposed so as to be able to swing up and down with an upstream end (right side in FIG. 3) as a fulcrum. An eccentric cam 50 rotated by a motor (not shown) is in contact with the lower surface of the first guide member 43, and the first guide member 43 is biased downward by a spring member (not shown). That is, the first guide member 43 can approach or be separated from the pre-transfer upper guide 40 by rotating the eccentric cam 50.

  When a sheet to be used is set by an operation panel (not shown) of the image forming apparatus 100 or a printer driver of a personal computer, the control unit 30 determines whether the set sheet is plain paper or a label sheet. The rotation angle of the lead cam 50 is controlled. Thus, the first guide member 43 is selected at a position where the downstream end 43a is separated from the pre-transfer upper guide 40 (first position) or a position close to the pre-transfer upper guide 40 (second position). Be placed.

  Next, a method for transporting plain paper and a label sheet using the sheet transport mechanism 60 of the present embodiment will be specifically described. FIG. 4 is a schematic cross-sectional view of the sheet transport mechanism 60 when transporting plain paper. The small diameter portion of the eccentric cam 50 is in contact with the first guide member 43. As a result, the first guide member 43 is disposed at the first position, and the downstream end portion 43 a of the first guide member 43 is separated from the pre-transfer upper guide 40. When the plain paper P (indicated by a solid line) is passed in this state, the plain paper P sent out from the registration roller pair 8 is the downstream end 43a of the first guide member 43, the guide roller 45, and the second guide member 44. , And enters the transfer nip N1 along the pre-transfer lower guide 41.

  FIG. 5 is a schematic cross-sectional view of the sheet conveying mechanism 60 when conveying the label sheet. The large diameter portion of the eccentric cam 50 is in contact with the first guide member 43. Accordingly, the first guide member 43 is disposed at the second position, and the downstream end 43a of the first guide member 43 is close to the pre-transfer upper guide 40. When the label sheet R (indicated by a broken line) is passed in this state, the label sheet R fed from the registration roller pair 8 is supported by the downstream end 43a of the first guide member 43 and the second guide member 44, The toner enters the transfer nip N1 along the pre-transfer upper guide 40.

  That is, when the plain paper P is transported, it enters the transfer nip N1 from the direction close to the tangential L direction in the transfer nip N1 of the photosensitive drum 14 along the pre-transfer lower guide 41. Image defects such as transfer deviation and horizontal stripes due to contact with the paper P can be suppressed.

  On the other hand, when the label sheet R is conveyed, it enters the transfer nip N <b> 1 along the pre-transfer upper guide 40, so that the upper surface side (label part side) of the label sheet R is pressed by the pre-transfer upper guide 40. As a result, when the label sheet R is bent at the bent portion 42a of the sheet conveying path 42, the label portion is peeled off due to the edge of the label portion floating from the base material, and the paper jam or adhesive is caused by the peeling. It is possible to effectively prevent image defects caused by the above.

  FIG. 6 is a schematic cross-sectional view showing a modification of the sheet conveying mechanism 60 of the first embodiment. In FIG. 6, the pre-transfer lower guide 41 is composed only of the first guide member 43 and the second guide member 44, and the guide roller 45 is not disposed. In the configuration of FIG. 6 as well, by rotating the eccentric cam 50, the first guide member 43 is disposed at the first position when the plain paper P is conveyed, and the first guide when the label sheet R is conveyed. By disposing the member 43 at the second position, the plain paper P can be transported while preventing the label portion R from being peeled off during the transport of the label sheet R, paper jam caused by the labeling, and image defects due to adhesion of adhesive. It is possible to suppress conveyance failure and image failure at the time.

  In the sheet conveyance mechanism of the first embodiment described above, when the label sheet R is conveyed, the sheet conveyance speed in the registration roller pair 8 may be relatively higher than the sheet conveyance speed in the transfer nip portion N1. preferable. By controlling the sheet conveying speed in this way, the label sheet R is slackened in the direction of the pre-transfer upper guide 40, so that the label sheet R can be surely aligned with the pre-transfer upper guide 40. As a method for controlling the sheet conveyance speed, the linear speed of the registration roller pair 8 may be increased, or the linear speed of the photosensitive drum 14 and the transfer roller 18 may be decreased.

  FIG. 7 is a schematic cross-sectional view of the sheet conveying mechanism according to the second embodiment of the present invention, and FIG. 8 is a partially enlarged view of the vicinity of the guide roller 45 and the pressing roller 51 in FIG. In the present embodiment, the first guide member 43 that constitutes the pre-transfer lower guide 41 is fixed, and a pressing roller 51 that can contact and separate from the guide roller 45 is disposed on the pre-transfer upper guide 40 side. Since the configuration of other parts is the same as that of the first embodiment, description thereof is omitted.

  As shown in FIG. 8, the pressing roller 51 is disposed so as to be able to swing up and down at a fulcrum 51a on the downstream side in the transport direction. Further, a tangent line L1 connecting the sheet contact portion 44a at the tip of the second guide member 44 and the outer peripheral surface of the guide roller 45, and a tangent line L2 connecting the outer peripheral surface of the guide roller 45 through the nip outlet of the registration roller pair 8, Are the points P1 and P2 that contact the outer peripheral surface of the guide roller 45, respectively, the pressing roller 51 contacts between P1 and P2 of the outer peripheral surface of the guide roller 45 (the sheet support region on the outer peripheral surface of the guide roller 45). Are arranged as follows.

  When a sheet to be used is set by an operation panel (not shown) of the image forming apparatus 100 or a printer driver of a personal computer, the control unit 30 presses depending on whether the set sheet is plain paper or a label sheet. The roller 51 is selectively arranged at a position separated from the guide roller 45 (first position) or a position in contact with the guide roller 45 (second position). As the swing mechanism of the pressing roller 51, a configuration using an eccentric cam and a spring member similar to the moving mechanism of the first guide member 43 shown in the first embodiment can be given.

  Next, a method for transporting plain paper and a label sheet using the sheet transport mechanism 60 of the present embodiment will be specifically described. FIG. 9 is a schematic cross-sectional view of the sheet transport mechanism 60 when transporting plain paper, and the pressing roller 51 is disposed at the first position. When the plain paper P (indicated by a solid line) is passed in this state, the plain paper P sent out from the registration roller pair 8 is the downstream end 43a of the first guide member 43, the guide roller 45, and the second guide member 44. , And enters the transfer nip N1 along the pre-transfer lower guide 41.

  FIG. 10 is a schematic cross-sectional view of the sheet transport mechanism 60 when transporting the label sheet, and the pressing roller 51 is disposed at the second position. When the label sheet R (indicated by a broken line) is passed in this state, the label sheet R sent out from the registration roller pair 8 is supported by the downstream end portion 43a of the first guide member 43 and the second guide member 44, and It is sandwiched between the guide roller 45 and the pressing roller 51 and enters the transfer nip N1.

  That is, when the plain paper P is transported, it enters the transfer nip N1 from the direction close to the tangential L direction in the transfer nip N1 of the photosensitive drum 14 along the pre-transfer lower guide 41. Image defects such as transfer deviation and horizontal stripes due to contact with the paper P can be suppressed.

  On the other hand, when the label sheet R is conveyed, the label sheet R is conveyed downstream while being sandwiched between the guide roller 45 and the pressing roller 51 in the bent portion 42 a of the sheet conveying path 42. As a result, when the label sheet R is bent at the bent portion 42a, the label portion is lifted off from the base material, and the label portion is peeled off. Can be prevented.

  In addition, since the arrangement of the first guide member 43 and the guide roller 45 does not change, when the label sheet R is transported, the photosensitive drum along the pre-transfer lower guide 41 is transported as in the case of transporting the plain paper P. It is possible to enter the transfer nip N1 from a direction close to the tangential L direction in the 14 transfer nips N1. Accordingly, it is possible to prevent image defects such as transfer deviation and lateral stripes due to the contact of the label sheet R with the photosensitive drum 14 while preventing the label portion from being peeled off when the label sheet R is conveyed.

  Next, the structure of the label sheet R suitably used for the sheet conveying mechanism of the present invention will be described. FIG. 11 is a plan view showing an example of a label sheet R used in the sheet conveying mechanism of the present invention. The label sheet R has a two-layer structure including a label paper on the front surface side and a base material on the back surface side that supports the label paper so that the label paper can be peeled off. An outline 61 composed of a half-cut line is imprinted from the label paper side. By doing so, the label part 63 inside the outline 61 and the frame part 65 outside the outline 61 are formed. In addition, the contour line 61 on the rear end side and the front end side with respect to the sheet conveying direction (arrow A direction), that is, the edge of the label portion 63 in the sheet conveying direction is perpendicular to the sheet conveying direction (the end of the label sheet R). An angle θ is formed with respect to the edge 67), and the label portion 63 is formed in a parallelogram.

  When the label sheet R shown in FIG. 11 is conveyed using the sheet conveying mechanism 60 of the first embodiment, as shown in FIG. 5, when the label sheet R is conveyed along the pre-transfer upper guide 40, the label The timing at which the end edge of the portion 63 in the sheet conveying direction passes through the bent portion 42 a is shifted in the width direction of the label portion 63. As a result, there is no possibility that the edge of the label part 63 on the front end side in the sheet conveying direction is rolled at a time.

  When the label sheet R shown in FIG. 11 is conveyed using the sheet conveying mechanism 60 of the second embodiment, the label sheet R is sandwiched between the guide roller 45 and the pressing roller 51 as shown in FIG. When being conveyed downstream, the timing at which the edge of the label portion 63 on the leading end side in the sheet conveying direction passes between the guide roller 45 and the pressing roller 51 is shifted in the width direction of the label portion 63. As a result, the edge of the label portion 63 on the front side in the sheet conveying direction can be sequentially pressed using the pressing roller 51.

  Therefore, as compared with the case where the normal label sheet R is used, the label portion 63 is peeled off due to the rising edge of the label portion 63 on the front side in the sheet conveyance direction, and the paper jam or adhesive is caused due to the peeling. It is possible to more effectively suppress image defects due to the above. Although there is no particular limitation on the size of the angle θ, if the angle θ is too large, the label portion 63 is liable to be peeled off. There is. In FIG. 11, the trailing edge and the leading edge of the label portion 63 with respect to the sheet conveying direction have an angle θ with respect to the edge 67 of the label sheet R, but at least with respect to the sheet conveying direction. Any configuration may be used as long as the edge on the front end side of the label portion 63 has an angle θ.

  12-14 is a top view which shows the other structural example of the label sheet R used for the sheet | seat conveyance mechanism of this invention. In FIG. 12, an arc shape is provided at a corner portion 69 a of the label portion 63 on the rear end side in the sheet conveying direction. With this configuration, the label portion 63 can be smoothly peeled from the corner portion 69a during use while preventing the edge of the label portion 63 from being peeled when the label sheet R is conveyed.

  In FIG. 13, only the outline 61 on the leading end side in the sheet conveying direction (direction of arrow A), that is, the edge on the leading end side in the sheet conveying direction of the label portion 63 is the direction perpendicular to the sheet conveying direction (the end of the label sheet R). It has an angle θ with respect to the edge 67). Even with such a configuration, it is possible to more effectively suppress the peeling of the label part 63 due to the rising edge of the label part 63 as in FIGS. 11 and 12.

  In FIG. 14, an arc shape is provided at both the corner 69a on the rear end side in the sheet conveyance direction of the label portion 63 and the corner 69b on the front end side in the sheet conveyance direction. Further, the arc shape of the corner portion 69b has a larger curvature than the arc shape of the corner portion 69a. With this configuration, the label portion 63 can be smoothly peeled from either the corner portion 69a or the corner portion 69b during use while preventing the edge of the label portion 63 from being peeled when the label sheet R is conveyed.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. In each of the above embodiments, the swing mechanism of the first guide member 43 and the pressing roller 51 is not limited to the mechanism using the eccentric cam 51 and the spring member, and is a swing mechanism using a gear or a solenoid, for example. Also good.

  The sheet conveying mechanism of the present invention is not limited to the sheet conveying path from the registration roller pair 8 to the transfer nip portion N1, but can be used for other sheet conveying paths having a bent portion. Further, the sheet conveying mechanism of the present invention is not limited to the monochrome printer as shown in FIG. 1, but other image forming apparatuses such as monochrome and color copying machines, color printers, ink jet printers, facsimiles, and punch holes are formed in the sheet. Of course, the present invention can also be applied to a sheet post-processing apparatus that performs stapling and sorting.

  The present invention is applicable to a sheet conveying mechanism that conveys both a sheet such as plain paper and a label sheet. By using the present invention, when a label sheet is conveyed, a sheet conveying apparatus that does not cause image defects due to peeling of a label portion, paper jam caused by the labeling, and adhesion of an adhesive, an image forming apparatus including the same, and an image forming apparatus including the same A label sheet to be used can be provided.

8 Registration roller pair (first sheet conveying means)
14 Photosensitive drum (second sheet conveying means)
16 Developing device 18 Transfer roller (second sheet conveying means)
40 Pre-transfer upper guide (upper conveyance guide)
41 Lower guide before transfer (lower transfer guide)
42 Sheet conveying path 42a Bending portion 43 First guide member 44 Second guide member 45 Guide roller 51 Pressing roller 60 Sheet conveying mechanism 61 Contour line 63 Label portion 65 Frame portion 69a, 69b Corner portion 100 Image forming apparatus P Plain paper R Label Sheet

Claims (9)

A first sheet conveying means for conveying the sheet conveyed from the sheet feeding device;
A second sheet conveying means disposed downstream in the conveying direction of the first sheet conveying means;
An upper conveying guide that is provided between the first and second sheet conveying means and that is bent in an arch shape that holds the front side of the sheet, and a lower side that is disposed opposite to the upper conveying guide and holds the back side of the sheet A sheet conveying path composed of a conveying guide, and
Consists of a label paper on the front side and a base material on the back side that releasably supports the label paper, and can convey a label sheet formed by imprinting a contour line consisting of a half cut line from the label paper side In the sheet transport mechanism
When the label sheet is conveyed while being bent along the upper conveyance guide so that the label paper side is convex, the front and back sides of the sheet in the bent portion of the sheet conveyance path are compared with the case of conveying a sheet other than the label sheet. A sheet conveyance mechanism characterized by narrowing the conveyance path width in the direction. The lower conveyance guide is arranged on the upstream side of the bent portion with respect to the sheet conveyance direction, and is movable downstream in the direction approaching and separating from the upper conveyance guide, and arranged on the downstream side of the bent portion. A second guide member,
When transporting a sheet other than the label sheet, the first guide member is disposed at a first position separated from the upper transport guide, and when transporting the label sheet, the first guide member is the upper transport guide. The sheet conveying mechanism according to claim 1, wherein the sheet conveying mechanism is disposed at a second position close to the sheet. The sheet conveying speed by the first sheet conveying means is relatively faster than the sheet conveying speed by the second sheet conveying means when conveying the label sheet. The sheet conveying mechanism as described. The lower transport guide has a guide roller disposed to face the bent portion of the upper transport guide,
The upper conveyance guide has a pressing roller arranged so as to be able to come into contact with and separate from the sheet support region on the outer peripheral surface of the guide roller,
When transporting a sheet other than the label sheet, the pressing roller is disposed at a first position spaced from the guide roller, and when transporting the label sheet, the pressing roller contacts the guide roller. The sheet conveying mechanism according to claim 1, wherein the sheet conveying mechanism is disposed at a position.   The first sheet conveying means is a pair of registration rollers, the second sheet conveying means is an image carrier and a transfer member that rotates while contacting the image carrier, and the upper conveyance guide is the image carrier. The sheet conveying mechanism according to claim 1, wherein the sheet conveying mechanism is bent so that the body side is convex.   An image forming apparatus comprising the sheet conveying mechanism according to claim 1.   6. The label sheet used in the sheet conveyance mechanism according to claim 1, wherein an edge on a leading end side in a sheet conveyance direction of a label portion surrounded by the outline is perpendicular to the sheet conveyance direction. A label sheet having a predetermined angle with respect to any direction.   The label sheet according to claim 7, wherein a corner portion on the rear end side in the sheet conveying direction of the label portion has an arc shape.   The label sheet according to claim 8, wherein a corner portion of the label portion on the front side in the sheet conveyance direction has an arc shape having a larger curvature than a corner portion on the rear end side in the sheet conveyance direction.

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