JP2008304751A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device, capable of surely carrying a sheet within a device body to an ejectable position, in the event of its stoppage during image forming operation. <P>SOLUTION: A sheet P is pulled to an iversion position 100 by normal rotation of an inversion roller pair 53, provided to be normally reversely rotatable in an inversion path 103, and the sheet P pulled by the reverse rotation is set longitudinally in reverse at that position and is sent out. When stoppage during image forming operation, the rotation of the inversion roller pair 53 is controlled to pull and the sheet P is inverted at the inversion position 100, even if a sheet detection sensor 54 does not detect the sheet P. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an apparatus for conveying a sheet in an apparatus main body when stopped during an image forming operation.

  2. Description of the Related Art Conventionally, image forming apparatuses such as copying machines, printers, facsimiles, and the like perform double-sided printing and double-sided copying, so that a sheet with an image formed on one side is conveyed again to the image forming unit with the front and back sides reversed. There is something that was made. In addition, in the conventional image forming apparatus, when an image-formed sheet is conveyed, the order is switched, or the sheet is conveyed with the front and back reversed.

  Here, in order to switch the order or to reverse the front and back, the so-called switchback transport system, in which the sheet is once pulled by the reversing roller and then transported by reversing the front and back or the front and back directions. Is used.

  By the way, in a conventional image forming apparatus, there are cases in which image formation cannot be continued, for example, a sheet jam, an image forming system abnormality, a door open error, a power interruption, and the like. When such a situation occurs, the image forming apparatus may stop during the image forming operation. In this case, the conveyance of the sheet is immediately stopped.

  Here, recovery of these errors and the like is usually performed manually. For example, when a plurality of sheets are jammed, some of the jammed sheets may be forgotten. Alternatively, when the sheet conveyance is stopped, the sheet may remain in the sheet conveyance path provided inside the image forming apparatus main body.

  In this case, for example, when the sheet remains in the switchback conveyance path for switchback conveyance of the sheet, after the error is restored, when the switchback conveyance of the sheet is resumed along with the resumption of the image forming operation, the sheet again in the switchback conveyance path. A jam occurs.

  For this reason, conventionally, a sheet presence / absence detection sensor is provided in the vicinity of the reverse roller provided in the switchback conveyance path in order to prevent occurrence of a jam in the switchback conveyance path due to resumption of sheet conveyance. The residual sheet is manually removed based on a signal from the sheet presence / absence detection sensor.

  At this time, if the remaining sheet is at a position where it is difficult to take out, the sheet may be conveyed by the sheet conveying device to a position where the jammed sheet can be taken out in the apparatus main body, and the sheet may be removed at this position. .

  Further, a sheet presence / absence sensor and a sheet discharge port are provided behind the reversing roller, the reversing roller is driven based on a signal from the sheet presence / absence sensor, and the remaining sheet is discharged from the sheet discharge port to a take-out position behind the reversing roller. Some have been made (see Patent Document 1).

JP-A-3-174170

  However, in the conventional image forming apparatus that drives the reverse roller based on the signal from the sheet presence / absence detection sensor, the sheet presence / absence detection sensor does not detect the sheet depending on the position of the sheet when the image forming operation is stopped. There is a case. For example, when the image forming operation is stopped, if the sheet has already passed the sheet presence / absence detection sensor, the sheet presence / absence detection sensor does not detect the sheet.

  In this case, the sheet is not transported (discharged) to the take-out position, and after that, when the image forming operation is restarted and the sheet is transported to the switchback transport path, jamming occurs again in the switchback transport path.

  Accordingly, the present invention has been made in view of such a current situation, and provides an image forming apparatus capable of reliably transporting a sheet in the apparatus main body to a position where it can be taken out when stopped during an image forming operation. It is for the purpose.

  The present invention includes an image forming unit and a sheet conveying device that conveys a sheet on which an image is formed by the image forming unit. When the sheet conveying device stops during an image forming operation, the sheet conveying device removes a sheet in the apparatus main body. In the image forming apparatus configured to convey, the sheet conveying device is provided with a reversing path that guides a sheet that is pulled in and reverses the front-rear direction, and a reversal that is provided in the reversing path and reverses the sheet by normal rotation. A sheet conveying member capable of reversing forward and backward to pull the sheet to a position and reversing the front and rear direction of the drawn sheet by reverse rotation, and to be provided upstream of the reversing path in the sheet conveying direction, the sheet conveying member A detection unit that detects the sheet so as to control rotation of the sheet, and the detection unit detects the sheet when stopped during the image forming operation. Even without knowledge, and it is characterized in that for controlling the rotation of the sheet transport member to invert draws sheet to the reversing position.

  As in the present invention, when the sheet is stopped during the image forming operation, even if the detection unit does not detect the sheet, the sheet in the apparatus main body can be reliably taken out by pulling the sheet to the reversal position and inverting it. Can be transported to a position.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the scope to the following embodiments.

  FIG. 1 is a schematic diagram showing an overall configuration of a color laser printer which is an example of an image forming apparatus according to an embodiment of the present invention.

  In FIG. 1, reference numeral 200 denotes a color laser printer, and 201 denotes a color laser printer main body (hereinafter referred to as a printer main body). The printer main body 201 includes an image forming unit 202 that forms an image on a sheet, a feeding unit 203 that feeds the sheet to the image forming unit 202, and a sheet fed from the feeding unit 203 to the image forming unit 202. A sheet conveying unit 204 for conveying is provided. Further, a fixing device 6 for fixing an image formed on the sheet is provided.

  The image forming unit 202 includes photosensitive drums 21 (21a to 21d) that are arranged in the vertical direction and are image carriers that respectively support toner images of four colors of yellow, magenta, cyan, and black. The photosensitive drum 21 is rotated counterclockwise by a rotating means (not shown).

  Further, a charging device 23 (23a to 23d) that is arranged around the photosensitive drum along the rotation direction and uniformly charges the surface of the photosensitive drum, and the photosensitive drum is irradiated with a laser beam based on image information. A scanner unit (not shown) for forming an electrostatic latent image is provided thereon.

  Furthermore, toner of each color of yellow, cyan, magenta, and black is attached to the electrostatic latent image so as to be visualized as a toner image, and toner remaining on the surface of the photosensitive drum after the transfer is transferred to the developing device 22 (22a to 22d). A cleaning means (not shown) for removal is provided. In the present embodiment, the photosensitive drum 21, the charging device 23, the developing device 22, and the cleaning unit are integrally formed as a cartridge to form a process cartridge 724 (24a to 24d).

  A transfer roller 34 (34a) that holds the transfer conveyance belt 35 together with the four photosensitive drums 21 (21a to 21d) is disposed inside the transfer conveyance belt 35 that is an endless sheet conveyance member that conveys a sheet to be described later. To 34d) are provided.

  These transfer rollers 34 are connected to a power supply for transfer bias (not shown), and positive charges are applied to the sheet from the transfer roller 34 via the transfer conveyance belt 35. By thus applying the transfer bias, the negative color toner images on the photosensitive drum are sequentially transferred to the sheet in contact with the photosensitive drum 21 to form a multicolor image.

  The feeding unit 203 stores a plurality of sheets P, the sheet feeding cassette 11 loaded on the bottom of the printer main body, the pickup roller 9 that feeds the sheet P stored in the sheet feeding cassette 11, and one sheet P. It consists of a separation unit (not shown) that separates each one. At the time of image formation, the sheet P is separated and fed one by one from the paper feed cassette 11 by the pickup roller 9, and then the sheet P is conveyed to the sheet conveying unit 204 by the registration roller pair 12 at a predetermined timing. The

  The sheet conveying unit 204 is provided with a transfer conveying belt 35 as a sheet carrier that is stretched over the driving roller 37 and the driven roller 33 and arranged to face all the photosensitive drums 21. The transfer conveyance belt 35 electrostatically attracts the sheet to the outer peripheral surface facing the photosensitive drum 21, and is circulated and moved clockwise by a driving roller 37 so as to bring the sheet into contact with the photosensitive drum 21.

  Then, the sheet P is conveyed to the transfer position T by the transfer conveyance belt 35 by being electrostatically attracted to the transfer conveyance belt 35 that circulates in this way, and the toner image on the photosensitive drum 21 is transferred.

  A suction roller 36 is disposed at the most upstream position of the transfer conveyance belt 35 and is in pressure contact with the driven roller 33 via the transfer conveyance belt 35. The suction roller 36 brings the sheet P into pressure contact with the outer periphery of the transfer conveyance belt 35 and applies a voltage to the transfer conveyance belt 35 to electrostatically adsorb the sheet P to the transfer conveyance belt 35.

  Next, an image forming operation of the color laser printer 200 configured as described above will be described.

  First, each process cartridge 24 is sequentially driven in accordance with the print timing, and the photosensitive drum 21 is driven to rotate counterclockwise in accordance with the drive. Then, the scanner units corresponding to the respective process cartridges 24 are sequentially driven. By this driving, the charging device 23 applies a uniform charge to the peripheral surface of the photoconductive drum 21, and the scanner unit exposes the peripheral surface of the photoconductive drum 21 in accordance with an image signal, and rotates the photoconductive drum 21. An electrostatic latent image is formed on the surface.

  Further, the latent image is developed by the developing device 22 to form toner images of four colors of yellow, magenta, cyan, and black on the surface of the photosensitive drum.

  In parallel with this toner image forming operation, the sheets P stored in the paper feed cassette 11 are picked up by the pickup roller 9 and separated and fed one by one by the separation unit. Thereafter, the leading edge of the sheet P hits the registration roller pair 12 that has stopped rotating, and a loop is formed. The skew of the sheet P is corrected by forming a loop in this way.

  Thereafter, at the timing when the leading edge of the toner image on the most upstream photosensitive drum 21d is rotated and conveyed to the contact point (transfer position) T with the transfer conveyance belt 35, the printing of the sheet P is performed at the contact point. The registration roller pair 12 starts to rotate so that the start positions coincide.

  As the registration roller pair 12 rotates, the sheet P is conveyed to the nip between the suction roller 36 and the transfer conveyance belt 35, and is attracted to the transfer conveyance belt 35 by the adsorption roller 36, and the photosensitive drum 21 and the transfer conveyance belt 35. Are conveyed to the transfer section where they are in pressure contact.

  Next, the toner images of the respective colors on the photosensitive drum 21 are formed on the photosensitive drum 21 by the action of the transfer roller 34 which is disposed in each transfer unit and applied with a voltage having a polarity opposite to that of the toner. The images are sequentially superimposed and transferred on the sheet.

  Then, the sheet P onto which the four color toner images are transferred in this way is separated from the transfer conveyance belt 35 by the curvature of the driving roller 37 and is carried into the fixing device 6. Thereafter, the toner image is fixed on the sheet P in the fixing device 6, and the sheet P on which the toner image is fixed is conveyed to the sheet conveying device 5 by the intermediate roller 51, and then the sheet is placed with the image forming surface facing down. It is discharged to a discharge tray 58.

  The color laser printer 200 can form a double-sided image. When the double-sided image is formed, the sheet P is conveyed to the double-sided conveyance path 110 by switching the switching flapper 71. Thereafter, the sheet P is re-fed to the registration roller pair 12 and a toner image is formed by the above-described image forming operation as in the case of image formation on the first side.

  By the way, the sheet conveying apparatus 5 is a second conveying path 102 that is a sheet discharging path for discharging a sheet to the sheet discharging tray 58, and a sheet conveying path that is a sheet conveying path for conveying a sheet on which an image is formed to the second conveying path 102. One transport path 101 is provided. Further, a reversing path 103 that is a reversing path for guiding the sheet that is drawn through the first conveying path 101 and is reversed in the front-rear direction to the second conveying path 102 is provided.

  Further, the reversing path 103 is provided with a reversing roller pair 53 which is a sheet conveying member capable of forward and reverse rotation, and the reversing roller pair 53 can be switched in the sheet conveying direction by forward / reverse rotation of the drive motor 90. It has become.

  By rotating the reversing roller pair 53 in the forward direction, the sheet that has passed through the first conveyance path 101 is drawn to a reversing position 100 where the sheet is reversed. Further, after pulling the sheet to the reversal position 100 in this way, the reverse roller pair 53 is reversed to feed the pulled sheet to the second conveyance path 102 with its front-rear direction reversed.

  The reversing roller pair 53 includes a driving roller pair 53a and a driven roller pair 53b facing the driving roller pair 53a, and the drive from the driving motor 90 is transmitted to the driving roller pair 53a.

  Here, the drive motor 90 is a pulse motor, and the transport distance of the sheet P can be controlled by counting the pulses. In FIG. 1, reference numeral 54 denotes a sheet detection sensor which is a detection unit disposed in the first conveyance path 101 located on the upstream side in the sheet conveyance direction of the reverse path 103, and a detection signal from the sheet detection sensor 54 is This is input to the controller 250 that controls the driving of the drive motor 90.

  The control unit 250 detects the presence / absence of the sheet P and the leading and trailing edges of the sheet P passing through the first conveyance path 101 based on the detection signal from the sheet detection sensor 54. Further, the control unit 250 pulls the sheet to the reverse position 100 based on the information on the trailing edge of the sheet P obtained by the sheet detection sensor 54, and then the timing at which the drive motor 90, that is, the reverse roller pair 53 stops and reverses. To control.

  Reference numeral 55 denotes a branch flapper provided at the junction of the first transport path 101 and the reverse path 103, and the branch flapper 55 allows a sheet that is switched back and transported by the reverse roller pair 53 to reverse to the first transport path 101. It can be prevented from being sent. In other words, the branch flapper 55 serves as a check valve for preventing the sheet from being fed back to the first conveyance path 101 when the sheet is switched back, and a swing plate, a sheet, or the like is used. Yes.

  Depending on the type of sheet to be transported and the transport conditions, only the shape of the joining portion of the first transport path 101 and the reversing path 103 can avoid back feeding of the sheet to the first transport path 101. It is not always necessary.

  Next, a sheet conveyance (discharge) operation by the sheet conveyance device 5 configured as described above will be described.

  When the sheet P on which image formation has been completed is transported from the first transport path 101 to the reverse roller pair 53 by the intermediate roller 51, the sheet P is first drawn into the reverse path 103 by the normal rotation of the reverse roller pair 53. Next, when the trailing edge of the sheet passes the branch flapper 55 and then reaches the reversal position 100, the reversing roller pair 53 stops, and then reversely conveys the sheet P to the second conveying path 102. .

  The timing of stopping the reversing roller pair 53 at the reversing position 100 counts the driving pulse applied to the driving motor 90 based on the information on the trailing edge of the sheet obtained by the sheet detecting sensor 54 as described above. It is controlled by doing.

  Next, the sheet P conveyed to the second conveyance path 102 by the reverse rotation of the reverse roller pair 53 is conveyed by the intermediate roller 56 and the discharge roller 57 and is discharged and stacked on the discharge tray 58 in the order of pages.

  In the case of double-sided image formation, the sheet P is transported from the second transport path 102 to the double-sided transport path 110 by switching of the switching flapper 71 and is transferred to the registration roller pair 12 by the double-sided roller 72. Thereafter, the sheet P follows the same conveyance path as in the case of single-sided printing, an image is formed on the second side of the sheet P, and is discharged and stacked on the discharge tray 58 in page order.

  By the way, in such a color laser printer 200, a situation where image formation cannot be continued, for example, a sheet jam, an abnormality in an image forming system, a door open error, a power interruption, or the like may occur. When such a situation occurs, the color laser printer 200 may stop during the image forming operation. In this case, the conveyance of the sheet is immediately stopped.

  Here, these error recovery is usually performed manually, but after the error recovery and before the image forming operation is started, for example, at the time of resumption of conveyance, a sheet (part of) remains in the reversing path 103. There may be. Such residual sheet positions are shown in FIGS. 2 and 3.

  In the case of FIG. 2, the case where the sheet detection sensor 54 detects that there is no sheet and the rear end of the sheet P remains in the first conveyance path 101 when resuming conveyance after error recovery. Show. That is, the case where the sheet P remains between the first conveyance path 101 and the reverse path 103 is shown.

  In FIG. 2, La is a distance from the detection position of the sheet detection sensor 54 to the reversal position 100, and Lb is a distance from the reversal position 100 to the nip position of the reversal roller pair 53. In this case, when the conveyance of the sheet is started, the reversing roller pair 53 first rotates normally, and the sheet P is drawn into the reversing path 103.

  Here, the distance Lt for drawing the sheet P by the forward rotation of the pair of reversing rollers 53 is not less than the distance La and less than the distance Lb. That is, the distance (sheet pull-in distance) Lt for pulling the sheet P is longer than the distance La between the sheet detection sensor 54 and the reverse position 100 and shorter than the distance Lb between the reverse roller pair 53 and the reverse position 100.

  In the present embodiment, La = 40.2 mm, Lb = 58.9 mm, and Lt = 42 mm. In this embodiment, the sheet transfer amount per pulse of the drive motor 90 is 0.244 mm, and in order to pull the sheet P by the distance Lt, a pulse of Lt / 0.244≈172 steps is given. I have to.

  Then, after pulling the sheet P by the distance Lt in this way, the reversing roller pair 53 is reversed, whereby the sheet P is conveyed to the second conveyance path 102.

  In the case of FIG. 3, when the conveyance is resumed after the error is restored, the sheet detection sensor 54 detects that there is no sheet, and the sheet P remains between the reverse path 103 and the second conveyance path 102. Shows the case. That is, a case where the drawn sheet P is reversed and passes through the reversal position 100 is shown.

  Also in this case, after pulling the sheet P by the distance Lt, the reversing roller pair 53 reverses, so that the sheet P is conveyed to the second conveyance path 102. After that, the sheets are discharged and stacked in the page order by the intermediate roller 56 and the discharge roller 57 on the discharge tray 58 that is the take-out position.

  As described above, in the present embodiment, even in the case shown in FIGS. 2 and 3 or the case in which there is no remaining sheet, the sheet detection sensor 54 is used when the conveyance is restarted after error recovery. Even if not detected, the reversing roller pair 53 is controlled as described above.

  As a result, even if the sheet P remains in the first conveyance path 101, the second conveyance path 102, or the reversal path 103, the sheet P moves from the reversal path 103 to the second conveyance path 102 and thereafter. , Conveyed without jamming.

  As described above, when the sheet detection sensor 54 stops during the image forming operation, even if the sheet detection sensor 54 does not detect the sheet, the sheet P in the printer main body is reliably secured by pulling the sheet up to the reversal position 100 and inverting it. It can be conveyed to a take-out position. Further, with such a configuration, the remaining sheet can be reliably conveyed to a position where it can be taken out without causing a secondary conveyance jam using the minimum number of sheet detection sensors 54.

  In the above description, in the case shown in FIG. 3, after the sheet P is pulled by the distance Lt, the reverse roller pair 53 is reversed to convey the sheet P to the second conveyance path 102. . However, the present invention is not limited to this.

  In the case shown in FIG. 3, for example, when it is determined that the drawn sheet is reversed and passes the reversal position 100 based on a signal from the sheet detection sensor 54, the sheet is reversed without being pulled. You may make it send out from the path | pass 103.

  In this case, the time (the number of pulses of the pulse motor) for the trailing edge of the sheet to reach the reverse position 100 from the detection of the trailing edge of the sheet by the sheet detection sensor 54 is calculated from the sheet conveyance speed. It is determined whether or not the reversal position 100 has been passed. In such a configuration, the sheet can be discharged to the discharge tray 58 in a shorter time.

  Further, in the description so far, when a sheet remains in the reversing path 103, the sheet is discharged to the discharge tray 58. However, the present invention is not limited to this.

  For example, as shown in FIG. 4, by switching the switching flapper 71, the sheet P is transported from the second transport path 102 to the double-sided transport path 110 and transported to a take-out position (not shown) provided in the double-sided transport path 110. You may do it. The sheet P thus transported to the take-out position can be taken out by opening the double-sided transport path 110 thereafter.

1 is a schematic diagram illustrating an overall configuration of a color laser printer that is an example of an image forming apparatus according to an embodiment of the present invention. FIG. 6 is a first diagram illustrating a remaining sheet conveying operation of a sheet conveying apparatus provided in the color laser printer. FIG. 6 is a second diagram illustrating a remaining sheet conveying operation of the sheet conveying apparatus. FIG. 9 is a third diagram for explaining the remaining sheet conveying operation of the sheet conveying apparatus.

Explanation of symbols

5 Sheet conveying device 53 Reverse roller pair 54 Sheet detection sensor 58 Sheet discharge tray 90 Drive motor 100 Reverse position 101 First conveying path 102 Second conveying path 103 Reverse path 110 Double-sided conveying path 200 Color laser printer 201 Color laser printer main body 202 Image Forming unit 250 Control unit La Distance Lb between sheet detection sensor and reverse position Distance Lt between reverse roller pair and reverse position Lt

Claims (3)

An image forming unit and a sheet conveying device that conveys a sheet on which an image is formed by the image forming unit, and when stopped during an image forming operation, the sheet conveying device conveys a sheet in the apparatus main body. In the image forming apparatus,
The sheet conveying apparatus is
A reversing passage that guides the seat that is pulled in and the front-rear direction is reversed;
A sheet conveying member that is provided in the reversing path, draws the sheet to a reversing position that reverses the sheet by normal rotation, and reverses the front-rear direction of the pulled-in sheet and feeds it from the reversing path;
A detection unit that is provided upstream in the sheet conveyance direction of the reversing path and detects a sheet so as to control rotation of the sheet conveyance member;
An image forming apparatus that controls rotation of the sheet conveying member so that the sheet is pulled to the reversal position and reversed even when the detection unit does not detect the sheet when stopped during the image forming operation. .   The sheet pull-in distance when stopped during the image forming operation is longer than a distance between the detection unit and the reversal position, and shorter than a distance between the sheet conveying member and the reversal position. Image forming apparatus.   Based on the signal from the detection unit, when it is determined that the drawn sheet is reversed and passes the reversing position, the sheet conveying member is rotated so as to be sent out from the reversing path without being pulled in. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled.

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