JP2006111364A - Sheet carrying device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve both improvement of reliability in carrying and downsizing in a sheet carrying device provided with a lateral registration correction mechanism for correcting the width direction position of sheets by carrying the sheets while abutting their side ends to a reference surface, and an image forming device. <P>SOLUTION: A curved reversal part 40 is provided between a switch-back roller 14 and the lateral registration correction part 23. In a guide rib 50 for guiding the sheet to the curved reversal part 40, outside ribs 50a provided on both sides are set to be higher than inside ribs 50b provided at the center side of in the width direction of the sheets. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet, and relates to an apparatus that is applied to an image forming apparatus such as a printer, a facsimile, and a copying machine.

  In a sheet conveying apparatus applied to a reconveying section of an image forming apparatus capable of forming a double-sided image of a sheet, in order to maintain good printing accuracy on the second side, a sheet generated during conveyance in image formation on the first side Generally, “horizontal registration correcting means” for correcting a shift in the width direction is provided.

  As an example of a conventional sheet conveying apparatus including a lateral registration correcting unit, a configuration known from Patent Document 1 will be described with reference to FIGS.

  6 is a main cross-sectional view of a laser beam printer as an example of a conventional image forming apparatus, and FIG. 7 is a plan view of the sheet conveyance path of the sheet re-conveyance unit 103 from the post-fixing roller 117 to the re-feed roller 122. It is the figure seen from the top. FIG. 8 is a diagram for explaining the lateral registration correcting operation when viewed from the same viewpoint as that in FIG.

  The laser beam printer 101 can form images not only on one side of a sheet but also on both sides. The laser beam printer 101 includes an image forming unit 102 that performs image formation and a sheet reconveying unit 103 that serves as a sheet conveying device that performs sheet reversal.

  When images are formed on both sides of the sheet S, the sheet S is conveyed to the switchback roller 114 after the image is formed by the image forming unit 102. When the trailing edge of the sheet S passes through the nip formed by the post-fixing roller 117 and the first roller 118, the switchback roller 114 reverses, and the sheet S continues to the sheet re-conveying unit 103 with the leading edge and trailing edge reversed. Sent. From the upstream, the sheet re-conveying unit 103 is a post-fixing roller 117 serving as a nipping and conveying unit, a second roller 119 that forms a nip N1 ′ facing the post-fixing roller 117, and the conveyance direction of the sheet S from the substantially vertical direction to the horizontal direction. The curve reversing unit 140 for guiding the direction of the sheet to be changed, the lateral registration correcting unit 123 for correcting the position in the width direction of the conveyed sheet, the refeed roller 122 disposed downstream of the lateral registration correcting unit 123, and the re-feeding roller 122. A re-feed roller 130 that forms a nip N <b> 3 ′ facing the paper feed roller 122 is mainly configured. The sheet S sent to the sheet re-conveying unit 103 is corrected in position in the width direction by the lateral registration correcting unit 123 and then sent again to the image forming unit 102 by the re-feed roller 122 to perform image formation on the second side. Then, the sheet is discharged from the sheet discharge unit 113 to the outside of the apparatus.

  Next, the configuration and operation of the lateral registration correction unit 123 in the sheet re-conveying unit 103 will be described.

  The lateral registration correction unit 123 includes a reference plate 124 including a reference surface 124a, a pair of conveyance rollers including a lateral registration correction roller 125 and a skew feeding roller 126 as a lateral registration correction roller, and a conveyance lower guide 127. It is.

  The reference plate 124 is fixed to the main body of the laser beam printer 101, and includes a lateral registration correction roller 125, a skew feeding roller holding portion 124g, a sheet side end guide 124d including a reference surface 124a and a tapered surface 124b, a sheet lower surface guide 124f, This is a member that includes a sheet upper surface guide 124e and the like. The sheet-side end guide 124d has a tapered surface 124b from the intersection 124c on the upstream side of the lateral registration correction roller 125.

  The lateral registration correction roller 125 is held by the reference plate 124 via a bearing (not shown), and sandwiches the sheet in a predetermined region in the width direction. Further, it is arranged so that its rotation axis is perpendicular to the transport direction.

  The skew feeding roller 126 is rotatably held by the reference plate 124 and is urged by the lateral registration correction roller 125 by a spring (not shown) to form a nip N2 '. Further, the rotation axis of the oblique feeding roller 126 is disposed so as to have an inclination of about 7 ° toward the reference surface 124 a with respect to the rotation axis of the lateral registration correction roller 125.

  The positions of the lateral registration correction roller 125 and the skew feeding roller 126 in the sheet width direction are closer to the right end as viewed from the front of the apparatus, the same as the reference surface 124a. In this case, the position closer to the right end portion is at least the right end portion side of the sheet width 1/3.

  The lower conveyance guide 127 is provided in the lateral registration correction unit 123 so as to guide most of the lower side of the sheet conveyance surface excluding the portion of the sheet lower surface guide 124f of the reference plate 124.

  On the downstream side of the lateral registration correcting unit 123, a refeeding unit that refeeds the refeed roller 122 and the roller 130 facing the refeed roller 122 is provided.

  Next, the lateral registration correction operation when the sheet S is conveyed away from the reference surface 124a to the lateral registration correction unit 123 will be described with reference to FIG.

  The leading edge of the sheet S conveyed to the lateral registration correcting unit 123 by the post-fixing roller 117 is guided to the curve reversing unit 140, and eventually the leading edge reaches the nip N2 'formed by the lateral registration correcting roller 125 and the oblique feeding roller 126. In a state where the trailing edge of the sheet S is held between the nip N1 ′ of the fixing roller 117 and the second roller 119, only the leading edge of the sheet S approaches the reference surface 124a due to the oblique feeding force of the oblique feeding roller 126 (FIG. 8). (A)).

  Thereafter, when the trailing edge of the sheet S passes through the nip N1 ′ of the post-fixing roller 117 and the second roller 119, the sheet S receives the conveyance resistance by the conveyance lower guide 127 and the curve reversing unit 140, and the sheet S has the trailing edge toward the reference surface 124a. Rotate to get closer. Since the sheet S is tilted by this rotation, the sheet S becomes closer to the reference plane 124a (FIG. 8B).

The sheet S abuts on the intersection 124c of the reference surface 124a and the tapered surface 124b, and the reaction force causes reverse rotation to bring the front end of the sheet S closer to the reference surface 124a. The sheet S is aligned at a position along the reference surface 124a. (FIG. 8C).
JP 2000-233850 A

  However, the following problems remain in the conventional sheet conveying apparatus described above.

  As described above, the laser beam printer 101 is provided with the post-fixing roller 117 and the second roller 119 on the conveyance path from the switchback roller 114 to the curve reversing unit 140, and forms a nip N1 '.

  As described above, the lateral registration correction operation is started when the leading edge of the sheet S reaches the nip N2 ′ by the lateral registration correction roller 125 and the skew feeding roller 126, and the nip by the refeed roller 122 and the refeed roller 130. It must be completed before N3 'is reached.

  In the lateral registration correction operation, in the first operation (the state shown in FIG. 8A), since the rear end portion of the sheet S is constrained by the nip N1 ′, it contributes only slightly to the actual lateral registration correction. The substantial lateral registration correction is started after the trailing edge of the sheet S passes through the nip N1 ′. Accordingly, after the leading edge of the sheet S reaches the nip N2 ′, the path length required for the lateral registration correction operation, that is, N2 ′ to N3, is set as the upstream side is installed so that the trailing edge of the sheet S exits the nip N1 ′ as soon as possible. 'It is possible to reduce the distance between the devices, and the entire device can be downsized.

  However, if the nip N1 'is arranged as upstream as possible, the distance between N1' and N2 'is naturally increased. The curved reversing unit 140 exists on the path between N1 ′ and N2 ′, and the waist in the conveyance direction of the sheet S is lost by the curved reversing unit 140. Is difficult to transmit the conveying force applied by the nip N1 ′. When the nip N1 ′ is disposed on the upstream side, the conveyance force at the leading edge of the sheet S is further weakened. Therefore, in the case of thin paper with a weak sheet S, a slight conveyance resistance from the reference plate 124 or the like before reaching the nip N2 ′. Even just receiving it will buckle and become jammed.

  Therefore, in consideration of transportability, the nip N1 ′ cannot be arranged on the upstream side, and a long path (N2 ′ to N3 ′) is necessary for the lateral registration correction operation. It was not possible to achieve both.

  In order to solve the above-described problems in the prior art, in the sheet conveying apparatus and the image forming apparatus of the present invention, a reference plane that regulates a sheet to a predetermined width direction position by regulating a sheet side end, and the reference A reference plate having a tapered surface arranged on the upstream side in the sheet conveying direction of the surface and continuing from the outer side in the width direction to the reference surface, and the sheet is moved downstream in the sheet conveying direction while bringing the sheet toward the reference surface side. A correction unit configured to correct a position in the width direction of a sheet to be conveyed, which is composed of a pair of skew feeding rollers for nipping and conveying, a nipping and conveying unit for nipping and conveying a sheet upstream in the conveying direction of the correction unit, and the nipping and conveying unit Bending guide means for guiding the sheet to be bent in the conveyance direction along the guide surface from the correction means to the correction means, and the sheet is proposed from the holding conveyance means to the bending portion of the bending guide means Guide surface for the end portions in the sheet width direction, characterized in that the curvature center of the curved portion of the curved guide means than the central portion.

  By adopting the above configuration, even when the sheet to be conveyed is thin and the waist is weak, the downstream end of the sheet is not bent by the conveyance resistance received from the side edge guide of the lateral registration correction unit downstream of the curve inversion unit. It is possible to reach the nipping and conveying means on the side and realize stable conveying performance.

  Further, it becomes possible to provide the holding and conveying means on the upstream side of the curve reversing portion far from the bending reversing portion, and the sheet trailing edge can quickly pass through the holding and conveying means on the upstream side of the bending reversing portion. Lateral registration correction can be performed. Accordingly, it is possible to reduce the size of the apparatus by shortening the conveyance path of the lateral registration correction unit and to reduce the cost by simplifying the configuration.

  Based on FIGS. 1-5, embodiment which concerns on this invention is described in detail.

  FIG. 1 is a main cross-sectional view of a laser beam printer which is an example of a double-sided image forming apparatus according to an embodiment. The laser beam printer 1 includes an image forming unit 2 that forms an image on both sides as well as a sheet, and a sheet re-conveying unit 3 that is an example of a sheet conveying device that performs lateral registration correction and performs sheet reversal. .

  First, the operation of the image forming unit 2 will be described.

  When the image forming unit 2 receives a print command, the sheets S stacked on the cassette 4 are separated and fed one by one by the paper feed roller 6 and between the photosensitive drum 8 and the transfer roller 9 in the process cartridge 7 ( Nip). The print command is generated via the controller board 11 when image information is sent from a personal computer (not shown).

  Along with this print command, the laser scanner unit 12 irradiates the photosensitive drum 8 with a bit image of the image information (laser light), and a toner image is formed on the photosensitive drum 8 by developing means according to the bit image.

  The toner image formed on the photosensitive drum 8 is transferred to the sheet S at the nip between the photosensitive drum 8 and the transfer roller 9.

  Then, the sheet S on which the toner image is transferred is sent to the fixing unit 10 and heated and pressed by the fixing unit 10. As a result, the toner image is fixed on the sheet S semi-permanently.

  After being fixed by the fixing unit 10, the sheet S is sent to the nip of the post-fixing roller 18 facing the post-fixing roller 17 and further sent to the sheet discharge unit 13.

  When the controller board 11 receives a single-sided image formation signal, the sheet S is nipped and conveyed by the switchback roller 14 and the discharge roller 15 and discharged to the discharge stacking table 16.

  Here, the single-sided image formation signal is a signal sent to the controller board 11 from a personal computer (not shown) as in the case of the print signal and the image signal.

  When the controller board 11 has received a double-sided image formation signal, the switchback roller 14 rotates reversely after the trailing edge of the sheet has passed through the nip formed by the post-fixing roller 17 and the post-fixing roller 18. Accordingly, the sheet S is continuously sent to the sheet re-conveying unit 3.

  Next, the configuration of the sheet re-conveying unit 3 will be described with reference to FIGS. FIG. 2 is a plan view of the sheet conveyance path of the sheet re-conveyance unit 3 from the switchback roller 14 to the refeed roller 22 as viewed from above, and FIG. 4 is a perspective view showing a guide rib 50 for guiding a sheet S. FIG.

  Here, the sheet re-conveying unit 3 starts from a nip N1 composed of the switchback roller 14 and the discharge roller 15, passes through the curve reversing unit 40 and the lateral registration correcting unit 23, and reaches the junction 21 with the conveying path from the cassette 4. Consists mainly of the transport path leading up to.

  Four switchback rollers 14 and discharge rollers 15 as nipping and conveying means of the present invention are arranged in the sheet width direction to suppress the rotational movement of the sheet S during conveyance, and each forms a nip N1. is doing.

  The conveyance path from the nip N1 to the lateral registration correction unit 23 is provided with a curve reversing unit 40 as a guide unit for changing the sheet conveyance direction from a substantially vertical direction to a horizontal direction. A guide rib 50 is provided as a guide member for guiding the sheet S to the reversing unit 40.

  As shown in FIG. 3, the guide ribs 50 are 15 ribs constituting the conveyance surface, and guide the four outer guide ribs 50 a that guide both ends of the sheet S in the width direction and the center portion in the width direction of the sheet S. 11 inner guide ribs 50b. Further, when viewed from the side as shown in FIG. 1, the outer side rib 50 a of the guide rib 50 is higher than the inner rib 50 b, and the conveyance surface is configured to lift both ends in the width direction of the sheet S. . That is, the guide ribs 50 serving as guide surfaces for guiding the sheet from the switchback roller 14 and the discharge roller 15 to the curved reversing portion 40 are located at both ends in the sheet width direction closer to the center of curvature of the curved reversing portion 40 than the central portion.

  The lateral registration correcting unit 23 as the correcting means of the present invention includes a reference plate 24 including a reference surface 24a, a pair of conveying rollers including a lateral registration correcting roller 25 and an oblique feeding roller 26 as a lateral registration correcting roller, and a conveying roller pair. And a lower guide 27.

  The reference surface 24a is a surface that coincides with the right end position (as viewed from the front of the apparatus) of the maximum width sheet conveyed to the sheet reconveying unit 3. For example, when the size of the sheet S conveyed to the sheet reconveying unit 3 is limited to A4 / LTR / LGL, the reference surface 24a is at the same position as the right end of the LTR or LGL size.

  The lateral registration correction unit 23 is provided for the purpose of correcting the posture of the sheet S that has shifted in the sheet width direction during conveyance to a predetermined position in the width direction along the reference surface 24a before forming the second image. It has been.

  In the present embodiment, since the reference of the first surface is the center reference, the A4 size sheet side end and the reference surface 24a (LTR / LGL end) are different by 3 mm. Accordingly, the lateral registration correction unit 23 always has a role of moving an A4 size sheet by 3 mm in the sheet width direction.

  The reference plate 24 is fixed to the main body of the laser printer 1 and includes a lateral registration correction roller 25, a skew feeding roller holding portion 24g, a sheet side end guide 24d including a reference surface 24a and a tapered surface 24b, and the like. It is a member.

  The lateral registration correction roller 25 is held by the reference plate 24 via a bearing (not shown), and sandwiches the sheet in a predetermined region in the width direction. Further, it is arranged so that its rotation axis is perpendicular to the transport direction.

  The oblique feeding roller 26 is rotatably held by the reference plate 24 and is urged by the lateral registration correction roller 25 by a spring (not shown) to form a nip N2. Further, the rotation axis of the oblique feeding roller 26 is disposed so as to have an inclination of about 7 ° with respect to the rotation axis of the lateral registration correction roller 25 toward the reference surface 24a.

  The position of the lateral registration correction roller 25 and the skew feeding roller 26 in the sheet conveyance direction is such that the path length between N1 and N2 is slightly shorter than the minimum conveyance direction length of the sheet S. As a result, the trailing edge of the sheet S passes through the nip N1 immediately after the leading edge of the sheet S bites into the nip N2.

  Further, the positions of the lateral registration correction roller 25 and the skew feeding roller 26 in the sheet width direction are close to the right end when viewed from the front of the same apparatus as the reference surface 24a. In this case, the position closer to the right end portion is at least the right end portion side of the sheet width 1/3. In this embodiment, the reference plate 24 is on the right side when viewed from the front of the apparatus. However, the reference plate 24 may be disposed on the left side when viewed from the front of the apparatus together with the lateral registration correction roller 25 and the oblique feeding roller 26.

  The lower conveyance guide 27 is provided in the lateral registration correction section 23 so as to guide most of the lower side of the sheet conveyance surface excluding the portion of the sheet lower surface guide 24f of the reference plate 24.

  Further, on the downstream side of the lateral registration correction unit 23, a refeeding unit is provided in which the refeed roller 22 and the refeed roller 30 facing the refeed roller 22 form a nip N3 to refeed.

  Two or more re-feed rollers 22 are arranged in the sheet width direction so that the sheet S subjected to the lateral registration correction is not skewed again. Downstream of the re-feed roller 22, there is a junction 21 with the first cassette feed path, from which it is sent again to the image forming unit 2 to form the second image.

  Next, the operation of the sheet re-conveying unit 3 will be described with reference to FIGS.

  4 is a perspective view showing the conveyance state of the sheet S when viewed from the same viewpoint as FIG. 3, and FIG. 5 is a diagram for explaining a series of operations in the lateral registration correction when viewed from the same viewpoint as FIG.

  When the double-sided image formation signal is received, the switchback roller 14 rotates in the reverse direction after the trailing edge of the sheet S on which the single-sided image has been formed is removed from the post-fixing roller 17, and the switchback roller 14 rotates in the state where the trailing edge of the sheet S is reversed. And is conveyed by a nip N1 including the discharge roller 15. The leading edge of the sheet S sandwiched and conveyed by N1 advances along the guide rib 50, is guided by the curve reversing unit 40 to change the direction from the substantially vertical direction to the horizontal direction, and reaches the lateral registration correcting unit 23.

  At this time, when the leading end of the sheet S has been transported to the side close to the reference plate 24 in the width direction, the leading end corner of the sheet S is guided by the sheet-side end guide 24d including the tapered surface 24b, and at the same time the transport resistance is reduced. receive. Here, since the outer guide rib 50a of the guide rib 50 is higher than the inner guide rib 50b, as shown in FIG. 4, the waist is given in the transport direction of the sheet S, and the transport force by the switchback roller 14 is increased. The leading end of the sheet S reaches the nip N2 without being bent to the conveyance resistance.

  Next, the operation of the lateral registration correction when the sheet S is conveyed away from the reference surface 24a to the lateral registration correction unit 23 will be described with reference to FIG.

  After the leading edge of the sheet S reaches the nip N2 of the lateral registration correction roller 25 and the skew feeding roller 26, the skew feeding roller 26 is between the time when the trailing edge of the sheet S passes through the nip N1 of the switchback roller 14 and the discharging roller 15. Only the leading edge of the sheet S approaches the reference surface 24a in response to the oblique feeding force (FIG. 5A).

  After the trailing edge of the sheet passes through the nip N1 between the switchback roller 14 and the discharge roller 15, the sheet S is rotated so that the trailing edge approaches the reference surface 24a because it receives conveyance resistance by the conveyance lower guide 27. Since the sheet S is tilted by this rotation, the sheet S becomes closer to the reference surface 24a (FIG. 5B).

  Eventually, the sheet S comes into contact with the intersection 24c of the reference surface 24a and the taper surface 24b, and the reaction force causes a reverse rotation to bring the front end of the sheet S closer to the reference surface 24a side, and the sheet S is in a position along the reference surface 24a. Are matched (FIG. 5C).

  The sheet S that has been subjected to the lateral registration correction as described above is sent again to the image forming unit 2 by the refeed roller 22, and a second image whose write start position is adjusted based on the reference surface 24 a is formed. The sheet is sent to the discharge unit 13 and stacked on the sheet discharge table 16.

  As described above, in the laser beam printer 1 according to the present embodiment, the trailing edge of the sheet S passes through the nip N1 immediately after the leading edge of the sheet S engages with the nip N2. The correction can be completed. Accordingly, the path from the nip N2 of the lateral registration correction roller 25 and the skew feeding roller 26 to the nip N3 of the refeed roller 22 and the refeed roller 30 is shorter than before, and the apparatus main body is also downsized. ing.

1 is a side sectional view showing an image forming apparatus according to a first embodiment of the present invention. It is a figure which shows the horizontal registration correction | amendment part which concerns on the 1st Embodiment of this invention. It is a perspective view which shows the guide rib which concerns on the 1st Embodiment of this invention. It is a figure explaining the lateral registration correction operation concerning a 1st embodiment of the present invention. It is a perspective view explaining the role of the guide rib which concerns on the 1st Embodiment of this invention. It is a sectional side view which shows the image forming apparatus of a prior art. It is a figure which shows the horizontal registration correction | amendment part of the image forming apparatus of a prior art. It is a figure explaining the horizontal registration correction | amendment operation | movement of a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser beam printer 2 Image forming part 3 Sheet re-conveying part 14 Switchback roller 15 Discharge roller 22 Refeed roller 23 Horizontal registration correction part 24 Reference plate 24a Reference surface 24b Tapered surface 24d Sheet side edge part guide 25 Horizontal registration correction roller 26 Inclined feeding roller 30 Re-feed roller 40 Curve reversing part 50 Guide rib 50a Outer guide rib 50b Inner guide rib S Sheet N1 Nip between switchback roller 14 and discharge roller 15 N2 Nip between lateral registration correction roller 25 and oblique feeding roller 26 N3 Refeed Nip formed by paper roller 22 and refeed roller 30

Claims (2)

A reference surface that regulates the sheet-side end portion and corrects the sheet to a predetermined position in the width direction; a tapered surface that is disposed upstream of the reference surface in the sheet conveyance direction and continues from the outer side in the width direction to the reference surface; A reference plate having
A correction unit configured to correct a width direction position of a sheet to be conveyed, and a pair of skew feeding rollers that sandwich and convey the sheet to the downstream side in the sheet conveyance direction while bringing the sheet to the reference surface side;
Nipping and conveying means for nipping and conveying the sheet upstream of the correction means in the conveying direction;
Bending guide means for guiding the sheet to be bent in the conveyance direction along the guide surface from the holding conveyance means to the correction means,
The guide surface for guiding the sheet from the holding and conveying means to the curved portion of the curved guide means is such that both ends in the sheet width direction are closer to the center of curvature of the curved portion of the curved guide means than the central portion. Sheet transport device.   An image forming apparatus comprising: the sheet conveying apparatus according to claim 1; and an image forming unit that forms an image on a sheet.

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