JP2007001749A - Paper sheet carrying mechanism and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate slack of a continuous form by a rotary encoder. <P>SOLUTION: In a paper sheet carrying mechanism, the rotary encoder 61 for measuring a retreat amount of the continuous form P is disposed between a drive roller 32 and a back tension drive roller 44A. Therefore, the slack of the continuous form P occurring between the drive roller 32 and the back tension drive roller 44A can be detected when an actual retreat amount of the continuous form P measured by the rotary encoder 33 is short with respect to a retreat amount of the continuous form P retreated by the drive roller 32. Based on the detection result, the slack can be eliminated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a paper transport mechanism for transporting continuous paper on which an image is formed, and an image forming apparatus provided with the paper transport mechanism.

  As a paper transport mechanism for transporting continuous paper on which an image is formed, there is known a paper transport mechanism for sandwiching and transporting continuous paper without a feed hole between a drive roller and a pinch roller (so-called pinless transport) (for example, Patent Document 1).

  In a paper transport mechanism that performs pinless transport, a drive roller provided downstream of the image transfer unit in the paper transport direction controls the transport amount of continuous paper, and a back tension roller provided upstream of the image transfer unit in the paper transport direction Thus, a mechanism has been proposed in which a sheet is conveyed so that an image can be transferred to a correct transfer position on the continuous sheet by an image transfer unit by applying a tension due to a sliding frictional force to the continuous sheet.

  In this mechanism, the transferred image is fixed on a continuous sheet by a fixing device, and after the image formation is completed, in order to prepare for the transfer of the next image, the drive roller and the back tension roller are reversed so that the image is reversed. The next page of the last page formed is retracted to the front of the image transfer unit.

At this time, if the tension of the continuous paper fluctuates and the sag is generated in the continuous paper, an unfixed image between the image transfer unit and the fixing device may come into contact with the paper guide or the like, resulting in an image defect. Also, when the next image transfer starts, the transfer position may not match.
JP 2003-146502 A

  In consideration of the above-described facts, an object of the present invention is to provide a paper transport mechanism that can eliminate the slack of continuous paper and an image forming apparatus provided with the paper transport mechanism.

  The paper transport mechanism according to claim 1 of the present invention is provided downstream of the image transfer unit in the paper transport direction, transports continuous paper, and retreats the continuous paper with the image transferred upstream in the paper transport direction. 1 conveying means and provided upstream of the image transfer section from the sheet conveying side, apply tension to the continuous sheet conveyed by the first conveying means, and move the continuous sheet with the image transferred upstream in the sheet conveying direction. And a second conveying unit that moves backward, and a measuring unit that is provided between the first conveying unit and the second conveying unit and that measures a retraction amount of the continuous paper.

  In this configuration, the first transport unit provided on the downstream side in the paper transport direction from the image transfer unit transports the continuous paper, and the second transport unit provided on the upstream side of the paper transport from the image transfer unit is the first transport. Tension is applied to the continuous paper transported by the means so that no slack occurs in the continuous paper.

  The continuous paper on which the image is transferred by the image transfer unit is retracted upstream in the paper conveyance direction by the first conveyance means and the second conveyance means.

  The amount of retraction of the retreated continuous paper is directly measured by a measuring unit provided between the first conveying unit and the second conveying unit.

  For this reason, when the actual amount of retraction of the continuous sheet measured by the measuring unit is insufficient with respect to the amount of retraction of the continuous sheet that the first conveying unit is retreated, the first conveying unit and the second conveying unit It is possible to detect the occurrence of sagging of continuous paper between the two, and based on the detected result, the sagging of continuous paper can be eliminated.

  According to a second aspect of the present invention, there is provided a sheet conveying mechanism according to the first aspect, wherein the measuring means is provided upstream of the image transfer unit in the sheet conveying direction.

  In this configuration, since the measuring unit is provided on the upstream side in the paper conveyance direction from the image transfer unit, it is possible to accurately detect the sag of the continuous paper generated on the downstream side in the paper conveyance direction from the image transfer unit.

  According to a third aspect of the present invention, there is provided the sheet conveying mechanism according to the second aspect, wherein the measuring means is provided in the vicinity of the second conveying means.

  In this configuration, since the measuring unit is provided in the vicinity of the second conveying unit, it is possible to accurately detect the sag of the continuous sheet generated between the second conveying unit and the first conveying unit.

  According to a fourth aspect of the present invention, there is provided the paper transport mechanism according to any one of the first to third aspects, wherein the continuous paper retraction amount measured by the measurement means is the continuous retreat amount of the first transport means. Control means is provided for increasing the retraction amount of the continuous paper that the second conveying means retreats when the retraction amount is smaller than the paper retraction amount.

  In this configuration, when the retraction amount of the continuous sheet measured by the measuring unit is smaller than the retraction amount of the continuous sheet retreated by the first conveying unit, the control unit retreats the continuous sheet retreated by the second conveying unit. Increase.

  When the retraction amount of the continuous paper measured by the measuring unit is smaller than the retraction amount of the continuous paper retreated by the first conveyance unit, the slack of the continuous paper occurs between the first conveyance unit and the second conveyance unit. By increasing the retraction amount of the continuous sheet that the second transport unit retracts, it is possible to apply tension to the continuous sheet and eliminate the slack of the continuous sheet.

  An image forming apparatus according to a fifth aspect of the present invention includes the paper transport mechanism according to any one of the first to fourth aspects.

  Since the present invention is configured as described above, it is possible to eliminate the sag of continuous paper.

  Hereinafter, an exemplary embodiment according to an image forming apparatus of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the image forming apparatus 10 according to the present embodiment includes a paper transport mechanism 12 that transports continuous paper P in the direction of arrow F.

  The paper transport mechanism 12 includes a drive roller 32 (first transport means) and a pinch roller 34 provided on the downstream side in the paper transport direction from an image transfer unit T described later.

  The drive roller 32 is configured to rotate (forward rotation, reverse rotation) by a drive roller motor (not shown) connected to the drive roller 32. The drive roller motor controls the number of rotations of the drive roller 32, whereby the transport amount of the continuous paper P transported by the drive roller 32 is controlled.

  The drive roller 32 is attached with a rotary encoder 33 that measures the conveyance amount of the drive roller 32 by measuring the rotation speed of the drive roller 32. The rotary encoder 33 is connected to the control unit 16, and information on the conveyance amount of the drive roller 32 measured by the rotary encoder 33 is input to the control unit 16.

  The pinch roller 34 is provided at an opposing position above the drive roller 32, and is configured to pinch (pinch) the continuous paper P with the drive roller 32. The pinch roller 34 is driven and rotated at the same peripheral speed as the drive roller 32, and the pinch pressure is adjusted so that the pinched continuous paper P does not slip between the drive roller 32 and the pinch roller 34. .

  When the continuous paper P is sandwiched between the drive roller 32 and the pinch roller 34 and the drive roller 32 rotates forward, the continuous paper P is sandwiched and transported in the paper transport direction F, and the drive roller 32 reverses to rotate the continuous paper P. P moves backward in the B direction.

  The rotary encoder 33 is configured to measure the amount of retreat even when the drive roller 32 retreats the continuous paper P.

  A photosensitive drum 20 that rotates in the direction of arrow A is provided upstream of the drive roller 32 in the paper conveyance direction. Around the photosensitive drum 20, in order from the upstream side in the rotation direction of the photosensitive drum 20, a charging corotron 24 that charges the surface of the photosensitive drum 20 and the photosensitive drum 20 are exposed to the photosensitive drum 20. An LED exposure optical system 26 that forms a latent image, a developing unit 28 that attaches toner to the latent image formed on the photoconductive drum 20 by the LED exposure optical system 26 and develops the image, and a photoconductive drum 20. The toner is removed from the transfer corotron 22 for transferring the toner image to the continuous paper P by the image transfer portion T, the static elimination corotron 27 for neutralizing the surface of the photosensitive drum 20, and the surface of the photosensitive drum 20 neutralized by the static elimination corotron 27. A cleaner 29 is provided.

  A flash fixing device 21 that fixes the transferred toner image onto the continuous paper P is provided downstream of the image transfer unit T in the paper transport direction and upstream of the drive roller 32 in the paper transport direction. Between the image transfer portion T and the flash fixing device 21, a guide roller group 52 that guides the continuous paper P that has passed through the image transfer portion T to the flash fixing device 21 is provided.

  In addition, a guide roller group 54 is provided between the flash fixing device 21 and the drive roller 32 to guide the continuous paper P that has passed through the flash fixing device 21 to the drive roller 32. Each of the guide roller group 52 and the guide roller group 54 includes a group of transport rollers that are disposed along the paper transport direction F and that are driven to rotate about a rotation axis that is perpendicular to the paper transport direction F. .

  A side guide unit 14 is provided on the upstream side of the image transfer unit T in the sheet conveyance direction. As shown in an enlarged view in FIG. 2, the side guide unit 14 includes a partial cylindrical R guide portion 48 that guides the continuous paper P along a conveyance path curved in a substantially cylindrical shape. The R guide portion 48 constitutes the R portion in the image forming apparatus 10. A fan-shaped side guide plate 47 is provided on one side (the front side in FIG. 2) of the R guide portion 48.

  An aligning roller 42A is pivotally supported on the outer peripheral surface side of the R guide portion 48. On the inner peripheral surface side of the R guide portion 48, an opening 48A provided in the R guide portion 48 is coupled to the aligning roller 42A. A backup roller 42B is pivotally supported so as to contact.

  Both of the aligning roller 42A and the backup roller 42B are driven to rotate in contact with one end of the continuous paper P in the width direction, and are inclined with respect to the paper transport direction F (the downstream portion of the roller in the paper transport direction is the side). It is tilted toward the guide plate 47 side.

  As a result, when the continuous paper P passes between the aligning roller 42A and the backup roller 42B, the aligning roller 42A and the backup roller 42B are driven to rotate, and between the aligning roller 42A and the backup roller 42B and the continuous paper P. Due to this friction, a force in the direction toward the side guide plate 47 is exerted on the continuous paper P. Therefore, the continuous paper P abuts on the side guide plate 47 to correct the skew, and the continuous paper P is transported along the correct transport path.

  Under the backup roller 42B and the aligning roller 42A (upstream side in the sheet conveyance direction), a back tension unit 44 is provided as a tension applying unit that applies tension to the continuous sheet P conveyed by the drive roller 32 and the pinch roller 34. It has been.

  The back tension unit 44 includes a back tension drive roller 44A (second conveying means) and a back tension pinch roller 44B, and the back tension drive roller 44A is pivotally supported on the inner peripheral surface side of the R guide unit 48, and back tension The pinch roller 44 </ b> B is pivotally supported on the outer peripheral surface side of the guide portion 48.

  The back tension drive roller 44A is composed of a group of rollers arranged in a direction perpendicular to the paper transport direction F. The back tension motor 18 has a rotation axis perpendicular to the paper transport direction F by the back tension motor 18. It rotates at a predetermined rotational speed (forward rotation, reverse rotation). The back tension motor 18 is connected to a control unit 16 that controls the transport amount of the continuous paper P transported by the back tension drive roller 44A by controlling the rotation speed of the back tension drive roller 44A.

  On the other hand, the back tension pinch rollers 44B are a group of driven rollers arranged in a plurality along a direction perpendicular to the paper conveyance direction F, and open along a direction perpendicular to the paper conveyance direction F. The portion 48B is in contact with the back tension drive roller 44A and is pressed by the back tension drive roller 44A with a predetermined pressing force.

  The continuous paper P is sandwiched between the back tension drive roller 44A and the back tension pinch roller 44B, and the back tension drive roller 44A rotates forward at a peripheral speed lower than the peripheral speed of the drive roller 32, whereby tension is applied to the continuous paper P. Then, the back tension driving roller 44A reverses and the continuous paper P moves backward in the B direction.

  A plurality of aging rollers 46 for feeding the continuous paper P is provided upstream of the side guide unit 14 in the paper conveyance direction, and the side guide unit 14 is provided between the image transfer unit T and the side guide unit 14. A plurality of guide rollers 38 for guiding the passed continuous paper P to the image transfer unit T are provided. Further, as the continuous paper P, roll paper, continuous paper that has been folded a plurality of times, or the like is used, and is conveyed from a paper supply unit (not shown) to a stacker (not shown).

  Next, a series of printing operations (image forming operations) of the image forming apparatus according to the present embodiment will be described.

  When the image forming apparatus 10 according to the present embodiment receives a print command (image formation command) from an operator or the like, the surface of the photosensitive drum 20 is charged by the charging corotron 24 and is exposed by the LED exposure optical system 26 to the surface. A latent image is formed. Then, in the developing unit 28, toner is attached to the latent image, and a toner image is formed in which the transfer corotron 22 is transferred onto the continuous paper P.

  The photosensitive drum 20 after transferring the toner image on the surface to the continuous paper P is neutralized by the static eliminating corotron 27, and the toner remaining on the surface without being transferred to the continuous paper P is removed by the cleaner 29.

  On the other hand, the continuous paper P set on the transport path by an operator or the like is nipped by the drive roller 32 and the pinch roller 34 so as not to slip, and is transported in the paper transport direction F. At this time, the upstream portion of the continuous paper P in the paper conveyance direction is sandwiched by the back tension pinch roller 44B and the back tension drive roller 44A and is conveyed at a peripheral speed lower than the peripheral speed of the drive roller 32. . For this reason, the continuous paper P is pulled in a direction opposite to the paper transport direction F, and tension is applied to the continuous paper P.

  Further, one side edge of the continuous paper P on the upstream side in the paper conveyance direction is in contact with the side guide plate 47, the conveyance path is moved so as to be parallel to the side guide plate 47, and the skew is corrected.

  As described above, each page of the conveyed continuous paper P passes through the plurality of aging rollers 46, the side guide unit 14, and the plurality of guide rollers 38 in this order, and is introduced into the image transfer unit T.

  The continuous paper P introduced into the image transfer portion T is charged by the transfer corotron 22 with a polarity opposite to that of the toner forming the toner image. As a result, the toner image on the surface of the photosensitive drum 20 is transferred to the continuous paper P.

  The continuous paper P onto which the toner image has been transferred in the image transfer portion T is guided to the flash fixing device 21 by the guide roller group 52 and is instantaneously heated by being irradiated with flash light in the flash fixing device 21. As a result, the toner is melted and the toner image is fixed on the surface of the continuous paper P.

  The continuous paper P on which the toner image is fixed by the flash fixing device 21 is introduced between the drive roller 32 and the pinch roller 34 by the guide roller group 54 and is sent to a stacker (not shown).

  When the series of printing operations is completed, the drive roller 32 and the back tension drive roller 44A are reversed to prepare for the start of the next printing, so that the next page of the last page on which the image has been transferred is transferred to the image transfer unit T. Retreat to before this.

  Here, a configuration for measuring the amount of retraction of the continuous paper P will be described.

  A rotatable roller 60 is provided between the drive roller 32 and the back tension drive roller 44A and in the vicinity of the back tension drive roller 44A upstream of the image transfer unit T in the paper transport direction. The roller 60 is made of a highly rigid material such as metal. The vicinity of the back tension drive roller 44A is, for example, a distance within a range where the continuous paper P is guided in an R shape.

  A pinch roller 62 that sandwiches (pinches) the continuous paper P with the roller 60 is provided at an opposing position above the roller 60. The pinch roller 62 is formed of an elastic material, and the pinch pressure is adjusted so that the pinched continuous paper P does not slide between the drive roller 32 and the pinch roller 34. The roller 60 and the pinch roller 62 are configured to rotate following as the continuous paper P moves.

  A rotary encoder 61 is attached to the roller 60 as a measuring unit that measures the amount of retraction of the continuous paper P. The rotary encoder 61 is configured to measure the retraction amount of the continuous paper P at the position where the roller 60 is provided by measuring the rotation speed of the roller 60.

  Further, the rotary encoder 61 is connected to the control unit 16, and information on the retreat amount of the continuous paper P measured by the rotary encoder 61 is input to the control unit 16.

  Next, a control procedure of the control unit 16 will be described.

  In the image forming apparatus 10 of the present embodiment, when a series of printing operations is completed, the drive roller 32 and the back tension drive roller 44A are reversed to prepare for the start of the next printing. The next page is moved back to the front of the image transfer portion T.

  At this time, the rotary encoder 33 measures the retraction amount of the continuous paper P retreated by the drive roller 32, and information on the retraction amount is input to the control unit 16. On the other hand, the rotary encoder 61 measures the retreat amount of the continuous sheet in the vicinity of the back tension drive roller 44 </ b> A, and information on the retreat amount is input to the control unit 16.

  The control unit 16 compares the input reverse amount value, and if the reverse amount value in the vicinity of the back tension drive roller 44A is smaller than the reverse amount value that the drive roller 32 has retracted, the control unit 16 As shown in FIG. 3, it is possible to detect that slack has occurred in the continuous paper P between the back tension drive roller 44A and the drive roller 32 (see the dotted line portion Y).

  In this embodiment, since the retreat amount of the continuous paper P is measured in the vicinity of the back tension drive roller 44A, the slack of the continuous paper P between the back tension drive roller 44A and the drive roller 32 accurately. Can be detected.

  When the detected sag of the continuous paper P is small, that is, the difference between the value of the retraction amount in the vicinity of the back tension drive roller 44A and the value of the retraction amount retracted by the drive roller 32 is within a predetermined amount range. In this case, a drive command is issued to the back tension motor 18 of the back tension drive roller 44A to increase the retreat amount that the back tension drive roller 44A is retreated, and the shortage of the retreat amount of the continuous paper P is compensated.

  Thereby, tension is applied to the continuous paper P, and the sag of the continuous paper P is eliminated. Therefore, it is possible to prevent the transfer position from being shifted due to the slack of the continuous paper P when the next printing operation is started.

  Further, when the slack of the continuous paper P is large, that is, the difference between the value of the retraction amount in the vicinity of the back tension drive roller 44A and the value of the retraction amount retreated by the drive roller 32 is out of the predetermined range. In such a case, the operation of the entire apparatus is stopped, an error is displayed, and the operator is notified.

  For example, when the unfixed image is a sag amount that causes an image defect when the unfixed image comes into contact with a paper guide of the flash fixing device 21 or the like, the predetermined amount can be defined as outside the predetermined amount range.

  In the above-described embodiment, the rotary encoder 61 is described as a measurement unit that measures the retraction amount of the continuous paper P. However, the measurement unit of the present invention is not limited to this, and for example, a continuous paper by a laser. The retraction amount may be measured, and any means capable of measuring the retraction amount by which the continuous sheet is retracted may be used.

  In the above embodiment, the rotary encoder 61 as the measuring means is provided in the vicinity of the back tension drive roller 44A. However, the position where the measuring means of the present invention is provided is not limited to this, and the drive roller 32 and the back tension drive roller 44A.

FIG. 1 is an overall schematic diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram illustrating the side guide unit according to the present embodiment. (A) shows the entire configuration of the side guide unit, and (B) is an enlarged view of a portion surrounded by a circle in (A). FIG. 3 is a diagram illustrating a case where sagging occurs in continuous paper in the image forming apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Paper conveyance mechanism 16 Control part (control means)
32 Drive roller (first conveying means)
44A Back tension drive roller (second transport means)
61 Rotary encoder (measuring means)

Claims (5)

A first conveying unit that is provided downstream of the image transfer unit in the sheet conveyance direction, conveys the continuous sheet, and retracts the continuous sheet onto which the image has been transferred upstream in the sheet conveyance direction;
A second transport that is provided upstream of the image transfer section from the paper transport, applies tension to the continuous paper transported by the first transport means, and retracts the continuous paper with the image transferred upstream in the paper transport direction. Means,
A measuring means provided between the first conveying means and the second conveying means for measuring the retreat amount of the continuous paper;
A paper transport mechanism comprising:   The paper transport mechanism according to claim 1, wherein the measurement unit is provided upstream of the image transfer unit in a paper transport direction.   The paper transport mechanism according to claim 2, wherein the measurement unit is provided in the vicinity of the second transport unit.   Control means for increasing the retraction amount of the continuous paper retreated by the second conveyance means when the retraction amount of the continuous paper measured by the measurement means is smaller than the retraction amount of the continuous paper retreated by the first conveyance means. The paper transport mechanism according to claim 1, wherein the paper transport mechanism is provided.   An image forming apparatus comprising the paper transport mechanism according to claim 1.

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