JP5350115B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet conveying device smoothly correcting distortion of a sheet when correcting bias feeding of the sheet and preventing deterioration of image quality due to a conveyance error in right and left of the sheet. <P>SOLUTION: This sheet conveying device includes: a conveying roller 8; a paper feeding part including a paper feeding roller 5 arranged upstream of the conveying roller; and a resist roller 11 arranged downstream of the conveying roller. The paper feeding part has a bias feeding function for feeding sheets, inclining them against the resist roller, and the conveying roller movable in a predetermined range in the axial direction is elastically urged toward one side in the axial direction. The bias feeding direction of the sheet by the paper feeding part is a direction in which an end of the conveying roller is elastically urged precedes. The conveying roller is moved resisting the elastic urging force by the force of the sheet which abuts on the resist roller with bias feeding corrected. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet from a sheet feeding unit, and an image forming apparatus using the sheet conveying apparatus.

  Image forming apparatuses such as printers, copiers, and facsimiles are configured to form an image on a sheet as a recording medium that is conveyed based on image information. At this time, the skew of the sheet is corrected and aligned by abutting the leading end of the conveyed sheet against the abutting means disposed in front of the image forming means. This abutting means includes a configuration in which a stopped conveyance roller (sub-scanning roller) is used as a registration roller. FIG. 8 is a plan view showing the skew feeding correcting means described in Patent Document 1. FIG. In this configuration, the rotational force in the direction indicated by the arrow M in FIG. 8 acts due to the twisting of the sheet when correcting the skew of the conveyed sheet, and the rotational force causes each of the transport rollers R1, R2, and R3 to have a shaft. Directional thrust force F acts.

  In order to release this thrust force F, the transport rollers R1, R2, and R3 on the upstream side of the registration roller A are attached to the support shaft C so as to be integrated in the rotational direction and movable in the axial direction. Then, the skew of the sheet is corrected by moving the conveying roller in the axial direction by the thrust force F generated when correcting the skew of the sheet. In FIG. 8, the transport rollers R1, R2, and R3 are urged from both sides in the axial direction by the elastic members S1 to S6, and the transport rollers moved by the thrust force F are returned to their original intermediate positions by the elastic members. I am letting.

Japanese Patent Laid-Open No. 02-018244

  However, in the above conventional example, it is difficult to manage the position of the transport roller, and there are problems such as the transport roller being shifted to one side and the movement range being insufficient. In addition, when the sheet is conveyed by the conveying roller, it is necessary to set the spring force high in order to stabilize the axial position of the conveying roller. Therefore, the torsional force of the sheet is defeated by the spring force, and an appropriate skew is applied. Line correction could be difficult. And, due to these factors, there is a shortage in correcting the twist of the sheet, a difference in the left and right transport distance occurs during image formation due to the twist of the sheet, image distortion when main scanning with the recording head to form an image, Color unevenness and density unevenness may occur.

  The present invention has been made in view of such technical problems. SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying apparatus that can smoothly correct the twist of a sheet when correcting the skew of the sheet and can prevent image quality deterioration due to a left and right conveyance error of the sheet. That is.

  The present invention provides a sheet conveying apparatus comprising: a conveying roller; a sheet feeding unit having a sheet feeding roller disposed on an upstream side of the conveying roller; and a registration roller disposed on a downstream side of the conveying roller. The sheet feeding unit has a skew feeding function of transporting the sheet while inclining the sheet with respect to the registration roller, and the transport roller is movable in a predetermined range in the axial direction and elastically biased to one axial side, The skew feeding direction of the skew feeding function of the sheet feeding unit is a direction in which the end of one side of the axial direction of the sheet, which is elastically biased by the sheet feeding roller, precedes, and the sheet is in contact with the registration roller. Then, it is moved in the axial direction against the elastic biasing force by the force generated when the skew correction is performed.

  According to the present invention, there is provided a sheet conveying apparatus capable of smoothly correcting the twisting of the sheet when correcting the skew of the sheet and preventing image quality deterioration due to a difference in conveyance between the left and right sides of the sheet. The

1 is a perspective view of an image forming apparatus including a sheet conveying device according to an embodiment. 1 is a longitudinal sectional view of an image forming apparatus including a sheet conveying device according to an embodiment. The perspective view which shows the arrangement | positioning relationship of the registration roller and conveyance roller means of the sheet conveying apparatus which concerns on one Embodiment. The fragmentary top view which shows the conveyance roller and driven roller of the conveyance roller means of the sheet conveyance apparatus which concerns on one Embodiment Schematic plan view when correcting the skew feeding by abutting the sheet against the registration roller by the conveying roller means The perspective view which shows the arrangement | positioning relationship between a registration roller and a conveyance roller means at the time of making the conveyance roller and driven roller of a conveyance roller means into one in the sheet conveyance apparatus which concerns on one Embodiment. 1 is a plan view of a sheet skew feeding mechanism in a sheet feeding unit of a sheet conveying apparatus according to an embodiment. Plan view showing sheet twist correction in a conventional sheet conveying apparatus

  Embodiments of the present invention will be specifically described below with reference to the drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings. In this embodiment, the case where the image forming apparatus is a facsimile in which an image reading apparatus and an inkjet recording apparatus are integrated is illustrated. 1 to 3, an image forming apparatus 100 is configured to record an image on a sheet 2 as a recording medium conveyed from a sheet feeding unit by a sheet conveying apparatus by an image forming unit including a recording head. ing. The sheet conveying device of the image forming apparatus according to the present embodiment includes two sheet feeding units, an upper sheet feeding unit and a lower sheet feeding unit, and 18A and 18B can stack a plurality of sheets 2A and 2B, respectively. The upper and lower cassettes are shown. These cassettes are detachably attached to the lower part of the apparatus main body.

  Each of the cassettes 18A and 18B is provided with pressure plates 3A and 3B, and these pressure plates are urged by the pressure plate springs 4A and 4B to the upper sheet feeding roller 5A and the lower sheet feeding roller 5B, respectively. The upper sheet feed roller 5A separates and feeds the uppermost sheet 2A stacked and stored in the upper cassette 18A by the cooperative action with the separation claws 19a and 19a that are locked to the leading end of the sheet. The lower feed roller 5B separates and feeds the uppermost sheet 2B stacked and stored in the lower cassette 18B by the cooperative action with the separation claws 20a and 20a that are locked to the leading end of the sheet. Each of the paper feed rollers 5A and 5B has a half-moon shape, and includes an arcuate surface that contacts and conveys the sheets 2A and 2B on the pressure plates 3A and 3B, and a flat portion that faces the sheet at a predetermined distance. Have. In the standby state, each sheet feeding roller is in a state where the flat surface portion is opposed to the sheet, and when the sheet is fed, the sheet is rotated by one rotation by a one-rotation spring clutch or the like. Note that the separation method for separating sheets in cooperation with the sheet feeding roller is not limited to the nail separation method shown in FIG. 2, and includes a retard separation method, a Duplo separation method, a swing arm separation method, and the like. Any other separation method may be adopted.

  An image forming unit D is disposed above the sheet feeding unit. The image forming unit D is provided with a carriage 31 that is mounted with the recording head 17 and reciprocates in the main scanning direction. The image forming apparatus according to the present embodiment constitutes an ink jet recording apparatus, and an ink jet recording head that performs recording by ejecting ink from a discharge port to a sheet based on image information is used as the recording head 17. A platen 45 for supporting the sheet 2 on which an image is formed is disposed at a position facing the ink ejection surface of the recording head 17. On the upstream side of the image forming unit D, a main conveyance roller unit including a main conveyance roller 11 as a driving roller and a main conveyance roller (pinch roller) 12 as a driven roller is disposed. As will be described later, the main conveyance roller 11 is also used as a registration roller for correcting skew feeding of a sheet.

  The sheet 2A sent out by the sheet feeding roller 5A of the upper sheet feeding section is conveyed to the means conveying roller means by the upper conveying roller means. The sheet 2B sent out by the sheet feeding roller 5B of the lower sheet feeding unit is conveyed to the main conveying roller means by the lower conveying roller means and the upper conveying roller means. The upper transport roller means includes upper transport rollers 8a and 8b, which are driving rollers, and upper upstream transport rollers 9a and 9b and upper downstream transport rollers 10a and 10b that are driven and rotated around the upper transport rollers. The lower transport roller means includes lower transport rollers 6a and 6b that are driving rollers, and lower transport rollers 7a and 7b that are driven and rotated around the lower transport rollers. That is, the lower transport rollers 6a and 6b transport the sheet 2B separated and fed by the lower paper feed roller 5B to the upper transport rollers 8a and 8b.

  On the downstream side of the image forming unit D, a first paper discharge roller 13 and a second paper discharge roller 15 that are driven in synchronization with the main transport roller 11 are disposed. A paper discharge roller as a driven rotator is pressed against the first paper discharge roller 13, and a spur 16 as a driven rotator is engaged with the second paper discharge roller 15 with a light pressing force. The sheet 2 (2a or 2b) conveyed to the main conveying roller means is conveyed to the recording start position on the platen 45 by the rotation of the main conveying roller 11. By alternately repeating the image formation for one line by the recording head 17 and the paper feeding by the main conveying roller 11, the entire sheet is recorded. Sheet conveyance at this time is performed by the main conveyance roller 11 and the discharge rollers 13 and 15. The sheet on which the image has been formed is discharged onto the discharge tray 21 through the discharge rollers 13 and 15.

  The image reading device 50 arranged at the upper part of the apparatus main body is configured to read an image of the original 52 supplied from the manual feed tray 51 by the reading means 53 and discharge the read original on the tray 54.

  3 to 5, the sheet conveyed by the conveying rollers 8a and 8b is inclined (skewed) by abutting the leading edge of the sheet against the main conveying roller 11 with the main conveying roller 11 stopped. Skew correction is performed to correct this. More specifically, the leading edge of the sheet is abutted against the nip between the stopped main conveyance roller 11 and the driven roller 12. That is, the main transport roller 11 also serves as a registration roller for correcting the skew of the sheet 2. FIG. 4 shows the relationship between the upper transport roller (upper drive roller) 8a and the upper downstream transport roller (upper downstream driven roller) 10a. Here, the relationship between the transport roller and transport roller of the upper transport means, that is, the relationship between the upper transport rollers 8a and 8b and the upper upstream transport rollers 9a and 9b and the upper downstream transport rollers 10a and 10b is shown in FIG. It is the same as the relationship between 8a and the conveyance roller 10a. Further, the relationship between the lower transport rollers 6a and 6b and the lower transport rollers 7a and 7b is the same as the relationship between the transport rollers 8a and the transport rollers 10a shown in FIG.

  In FIG. 4, the conveying roller 8a, which is a driving rotating body, is fitted to the roller shaft 25 so as to be movable in the axial direction, and is elastically provided in one axial direction by a compression spring 23a fitted between the retaining ring 27a. It is energized. Further, by inserting a pin 24a press-fitted into the roller shaft 25 into the opening E formed in the conveyance roller 8a, the conveyance roller 8a can move in a predetermined range in the axial direction and the rotation direction with respect to the roller shaft 25. It is supported. The transport roller 10a, which is a driven rotating body, is supported so as to be movable in the axial direction within a predetermined range with respect to the frame body 41 via the shaft portion 26a, and is axially supported by a compression spring 22a mounted between the frame body 41 and the shaft. It is elastically biased toward one side of the direction. As described above, the relationship between the transport roller 8a and the transport roller 9a in the upper transport unit, the relationship between the transport roller 8b and the transport rollers 10b and 9b, the relationship between the transport roller transport roller 6a and the transport roller 7a in the lower transport unit, and The relationship between the conveyance roller 6b and the conveyance roller 7b is also the same as the configuration described in FIG.

  Next, the skew of the sheet 2a conveyed by the upper conveying means or the leading edge of the sheet 2b conveyed by the lower conveying means and the upper conveying means abuts against the registration roller (stopped main conveying roller) 11 to correct the skew. The operation will be described. 3 to 5, when the conveyed sheet hits the registration roller 11 and skew correction is performed, a rotational force of twisting is generated on the sheet. On the other hand, each conveyance roller and each conveyance roller are provided with a certain degree of freedom (movable range) in the axial direction and the rotation direction. For this reason, the conveyance roller and the conveyance roller can be moved in the axial direction and the rotation direction by the rotational force of the twist generated in the sheet. Here, when the twisting force generated in the axial direction due to the correction of the twisting of the sheet is Fp and the pressing force of the compression spring is Fs, the relationship is Fs <Fp. That is, the transport roller and the transport roller move in the axial direction against the elastic biasing force of the compression spring by the force generated when the sheet is in contact with the registration roller and skew correction is performed. Thereby, the twist of the sheet can be corrected.

  In the present embodiment, the conveyance roller and the conveyance roller (driven roller) are elastically urged toward one side in the axial direction by a spring to ensure the axial movement range of the conveyance roller and the conveyance roller. At the same time, a load necessary for conveyance is applied to the conveyance roller and the driven roller by a spring. According to such a configuration, the spring constant can be set lower than in the configuration in which the spring is urged from both sides of the conveyance roller as in the conventional example shown in FIG.

  FIG. 6 is a perspective view showing the positional relationship between the registration roller and the conveyance roller means when the conveyance roller and the driven roller of the conveyance roller means are one. 2 to 5, the transport rollers and the transport rollers are provided at a plurality of locations (two locations) in the axial direction, but this may be configured at one location as shown in FIG. 6. As described above, in the configuration in which the upper conveyance rollers 8a and the conveyance rollers 9a and 10a and the lower conveyance rollers 6a and the conveyance rollers 7a are individually arranged in the axial direction, the contact point between each conveyance roller and the sheet is a single point. It becomes. For this reason, the sheet can be easily rotated around the contact point during skew correction, and the sheet twist can be easily corrected.

  According to the configuration of FIG. 6, if the axial movement range of the upper transport roller 8a and the lower transport roller 6a is restricted by the retaining rings 27a, 27c and 28a, 28c on both sides, the shafts of the upper transport roller 8a and the lower transport roller 6a The structure of each opening E and each pin (24a, 24c) for giving the freedom of a direction and a rotation direction can be abbreviate | omitted. The other configuration of the sheet conveying apparatus of FIG. 6 is the same as that of FIG.

  In the sheet conveying apparatus according to the present embodiment, the conveyance driving roller and the conveyance driven roller are elastically biased to one side in the axial direction within a predetermined movement range by the compression spring, and the movement to one side in the axial direction is restricted ( Has been stopped). Therefore, the twist correction function works only in one twist direction of the sheet. For this reason, the sheet feeding unit is provided with a skew feeding function generating unit that tilts and feeds the sheet so that the one side end of the sheet precedes in order to limit the twisting direction to one direction. In other words, the paper feeding unit has a configuration that has a skew feeding function that conveys (or feeds) the sheet 2 in an inclined manner with respect to the registration roller 11. FIG. 7 is a plan view of a sheet skew feeding mechanism in the sheet feeding unit. FIG. 7 shows the sheet skew feeding mechanism of the upper sheet feeding unit, but the same sheet skew feeding mechanism is also provided in the lower sheet feeding unit.

  Accordingly, the skew feeding direction of the skew feeding function of the sheet feeding unit is such that, in the case of using the conveyance roller elastically biased toward the one axial side described above, the end of the sheet on the conveyance roller biasing direction side is Selected in the preceding direction. That is, the sheet from the sheet feeding unit is conveyed in an inclined posture so that the end in the same direction as the direction in which the conveying roller is urged contacts the registration roller 11 first. In the configuration of FIG. 7, in a direction crossing the transport direction, the sheet is placed at a position where the half-moon shaped paper feed roller 5 a disposed in the paper feed unit is displaced in the biasing direction of the transport roller relative to the transport rollers 8 a and 8 b. It is comprised so that 2a may be contacted. Thereby, a conveyance force is applied to the sheet at a position near the conveyance roller urging direction, and the sheet can be conveyed while being inclined as indicated by a two-dot chain line. When the conveying roller is elastically biased in the direction opposite to that illustrated, the sheet is conveyed while being inclined in the direction opposite to that illustrated.

  In this way, by bringing the sheet into contact with the registration roller 11 with the one end on the one side leading, the conveying roller is elasticized by the force generated when the sheet is in contact with the registration roller and skew correction is performed. It can be moved in the axial direction against the urging force. Accordingly, it is possible to smoothly correct the twist of the sheet when correcting the skew of the sheet, and it is possible to prevent image quality deterioration due to the conveyance error by eliminating the conveyance error on the left and right sides of the sheet. Regarding the sheet skew feeding mechanism for feeding the sheet obliquely from the sheet feeding unit, various configurations are used in addition to the configuration in which the sheet feeding roller is arranged close to one side of the sheet as shown in FIG. Can do. For example, a configuration may be adopted in which rollers are arranged at a plurality of positions and the effective diameter of each roller is changed to perform oblique feeding. Further, a configuration may be adopted in which a sheet set in advance in an inclined posture or a sheet supplied in a skewed state is conveyed by a sheet feeding roller.

  According to the embodiment described above, high positioning accuracy of the transport roller and the transport roller can be realized regardless of the fluctuation of the load tolerance of the elastic biasing force. In addition, the biasing spring constant can be set to an appropriate value, and the accuracy of sheet twist correction can be improved. As a result, by correcting the twist of the sheet, it is possible to eliminate the left and right conveyance errors caused by the twist of the sheet, and to realize a high-accuracy image quality in which image distortion, color unevenness, density unevenness and the like are reduced as much as possible. it can. Further, compared to the conventional example, it is possible to achieve cost reduction and high productivity by reducing parts and assembling man-hours.

  In the embodiment described above, a serial type image forming apparatus using a carriage mounted with a recording head and reciprocally moved is taken as an example. The present invention can be similarly applied to an image forming apparatus of another scanning method such as a line type that records only by sub-scanning in the sheet conveyance direction. In addition, as the material of the sheet as the recording medium, various materials such as paper, plastic sheet, photographic paper, and cloth can be used as long as image formation is possible.

5 (5a, 5b) Feed roller 6 (6a, 6b) Lower transport roller (drive roller)
7 (7a, 7b) Lower transfer roller (driven roller)
8 (8a, 8b) Upper transport roller (drive roller)
9 (9a, 9b) Upper stage upstream transport roller (driven roller)
10 (10a, 10b) Upper stage downstream transport roller (driven roller)
11 Registration roller (main transport roller)
12 Main transport roller 17 Recording head 18A Upper cassette 18B Lower cassette 22 (22a, 22b, 22c, 22d, 22e, 22f) Compression spring 23 (23a, 23b) Compression spring 30 (30a, 30b) Compression spring 31 Carriage 45 Platen 50 Image reading apparatus 100 Image forming apparatus

Claims (5)

In a sheet conveying apparatus comprising a conveying roller, a sheet feeding unit having a sheet feeding roller arranged on the upstream side of the conveying roller, and a registration roller arranged on the downstream side of the conveying roller,
The sheet feeding unit has a skew feeding function of transporting the sheet while tilting the sheet with respect to the registration roller,
The transport roller is movable in a predetermined range in the axial direction and elastically biased to one axial side;
The skew feeding direction of the skew feeding function of the sheet feeding unit is a direction in which the end of one side of the axial direction of the sheet that is elastically biased by the conveying roller precedes.
The sheet conveying apparatus, wherein the conveying roller moves in an axial direction against the elastic urging force by a force generated when a sheet is in contact with the registration roller and skew correction is performed.   The sheet conveying apparatus according to claim 1, wherein the driven roller that rotates following the conveying roller is elastically biased so as to be movable in the axial direction together with the conveying roller.     3. The sheet conveying apparatus according to claim 1, wherein a plurality of the conveying rollers are arranged in the axial direction, and each conveying roller is movable within a predetermined range in the rotation direction. 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 conveyed by the sheet conveying apparatus.
The image forming apparatus, wherein the image forming unit is arranged downstream of a registration roller of the sheet conveying device and forms an image on a sheet by moving in an axial direction of the registration roller.   The image forming apparatus according to claim 4, wherein the image forming unit forms an image by ejecting ink from an ejection port of a recording head.

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