JP5899987B2 - Image forming apparatus - Google Patents

Description

  The present invention forms an image on one side of a sheet, then reverses the front and back of the sheet by a twisting method, and forms an image on the other side of the sheet with the front and back reversed. The present invention relates to a printer, a copying machine, and an image forming apparatus applicable to these multifunction devices.

  In recent years, in the image forming field, color and monochrome printers, copiers, and complex machines having a duplex printing mode are increasingly used. In the duplex printing mode, an image is formed on one side of the paper, and then the front and back sides of the paper are reversed, and an image is formed on the other side of the paper with the front and back sides reversed.

  This type of paper reversing method is a switchback type that includes a reversing conveyance path and reverses the paper conveyance direction by 180 °, or the paper in the direction perpendicular to the paper conveyance direction without changing the paper conveyance direction. There is a same edge method that reverses the front and back by rotating 180 degrees. Furthermore, in the method of rotating the paper by 180 ° without changing the paper transport direction, the paper rotation axis along the paper transport direction is set at a position that divides the paper width direction orthogonal to the paper transport direction into approximately ½. There is a twist reversal method that sets and twists the sheet itself with reference to the sheet rotation axis (see Patent Documents 1 and 2).

JP 2002-020000 A JP 2003-146490 A

By the way, there is the following problem when an attempt is made to construct a double-sided image forming apparatus by combining the torsion type front / back reversing mechanism according to the conventional example.
i. In order to avoid a malfunction caused by some cause in the middle of turning the paper in the turning apparatus as seen in Patent Document 1 or the medium transport apparatus as seen in Patent Document 2, When the turning device or the like is stopped, the paper during the reversing operation is displaced, bent, bent or the like, and the paper is damaged.

  ii. Further, a double-sided image forming apparatus of serial connection type is configured by providing a torsion type front / back reversing mechanism between the first image forming part and the second image forming part, and the double-sided printing mode is executed in this double-sided image forming apparatus. If a jam occurs after the second image forming unit (when paper conveyance abnormality is detected), stopping the front / back reversing mechanism during the torsion / reversing operation may damage the paper due to paper misalignment or the like. There is a problem.

  iii. In addition to the above-mentioned problem ii, when paper conveyance abnormality is detected, if the conveyance of the paper after image formation in the middle of the subsequent fixing, or the paper in the middle of image formation by the subsequent first image forming unit is stopped, fixing failure or There is a problem that image formation defects are caused and the number of torn papers is increased.

  iv. In addition, when a booklet creation mode is set in which an image corresponding to a plurality of pages is created on both the front and back sides (both sides) of a plurality of sheets P to create a booklet as an image forming job, There is a problem that it takes time for printing, and the downtime from the occurrence of a jam to the return to the image forming job becomes long.

Therefore, the present invention solves the above-mentioned problems, and reduces damage to the paper, such as reducing torn paper, without stopping the operation of the paper reversing portion of the twisting method when a paper conveyance abnormality is detected. An object of the present invention is to provide an image forming apparatus.

In order to solve the above-described problem, an image forming apparatus according to claim 1 includes a first image forming unit that forms an image on one side of a sheet, and a sheet on which an image is formed by the first image forming unit. A paper reversing portion of a torsion method for reversing the front and back, a second image forming portion for forming an image on the other surface of the paper whose front and back are reversed by the paper reversing portion, and when a paper conveyance abnormality occurs, And a sheet retracting section that is branched from a sheet transport path from the sheet reversing section to the second image forming section, and is provided with a transport retracting path capable of retracting the sheet after reversing the front and back sides. .

According to the image forming apparatus of the first aspect, the first image forming unit forms an image on one side of the sheet. The torsion type paper reversing unit reverses the front and back of the paper on which the image is formed by the first image forming unit. The second image forming unit forms an image on the other side of the paper whose front and back are reversed by the paper reversing unit. Based on these assumptions, the paper evacuation unit branches from the paper conveyance path from the paper reversing unit to the second image forming unit when a paper conveyance abnormality occurs, so that the paper after reversing the front and back can be retreated. A road is provided.

  With this configuration, it is possible to change the paper conveyance after the front / back inversion to the second image forming unit and temporarily retract the paper after the front / back inversion to the paper retracting unit. In addition, when a sheet conveyance abnormality (such as a jam) is detected in the sheet conveyance path and the sheet conveyance path after the second image forming unit, and there is a sheet that is being twisted by the sheet reversing unit, The paper after the end of the twisting operation can be retracted to the paper retracting unit without stopping the twisting operation.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the sheet retracting unit may be configured such that the sheet after reversing the front and back that has been retracted in the conveyance retracting path does not pass through the sheet reversing unit. It is characterized by having a non-reversing path for merging with the paper conveyance path leading to the image forming unit.

  According to a third aspect of the present invention, the image forming apparatus according to the second aspect further includes a first branch switching unit that branches a paper conveyance path from the first image forming section to the paper reversing section to the non-reversing path. It is what.

  An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the first aspect, wherein the abnormality detecting unit detects an abnormality in conveying the sheet in the sheet conveying path and the sheet conveying path after the second image forming unit, and the sheet inversion. And a second branch switching unit for branching a sheet transport path from the first section to the second image forming section to the transport retreat path.

  An image forming apparatus according to a fifth aspect of the present invention is the image forming apparatus according to the fourth aspect, wherein abnormality detection information is input from the abnormality detection unit, and when the abnormality in the conveyance of the sheet is detected by the abnormality detection unit, the sheet that has been turned upside down is removed. A control unit that controls the second branch switching unit so as to switch from the paper transport path to the transport retreat path is provided.

The image forming apparatus according to claim 6, according to claim 5, wherein, in a case where an image forming job that constitute form images corresponding to a plurality of pages into a plurality of sheet is set, the In the case where a conveyance abnormality is detected by the abnormality detection unit on the sheet of the page in the middle of executing the image forming job, the image of the page is first displayed after the sheet of the page where the conveyance abnormality is detected is removed. The paper is re-formed on the new paper by the image forming unit, the front and back sides of the re-formed paper are reversed, and the front and back sides of the paper that have been turned upside down are transported to the second image forming unit, The reversed paper is sequentially conveyed from the conveyance evacuation unit to the second image forming unit.

  An image forming apparatus according to a seventh aspect is the image forming apparatus according to the first to sixth aspects, wherein the first image forming section and the second image forming section are the same image forming section, and are downstream of the image forming section. The torsion-type sheet reversing unit is connected to the sheet conveying path, and the sheet conveying path on the downstream side of the sheet reversing unit is joined to the sheet conveying path on the upstream side of the image forming unit. Is.

  According to the image forming apparatus of the first aspect of the present invention, there is provided a conveyance evacuation path that branches off from the paper conveyance path from the torsion type paper reversing unit to the second image forming unit and can retreat the sheet after the front and back are reversed. is there.

With this configuration, it is possible to change the paper conveyance after the front / back inversion to the second image forming unit and temporarily retract the paper after the front / back inversion to the paper retracting unit. In addition, when a sheet conveyance abnormality (such as a jam) is detected in the sheet conveyance path and the sheet conveyance path after the second image forming unit, and there is a sheet that is being twisted by the sheet reversing unit, The paper after the end of the twisting operation can be retracted to the paper retracting unit without stopping the twisting operation. As a result, in the serial tandem type double-sided image forming apparatus, it is possible to reduce damage to the paper, such as torn paper, without stopping the operation of the twisting type paper reversing unit when a paper conveyance abnormality is detected. I can do it .

  According to the image forming apparatus of the second aspect, the sheet evacuation unit has the non-inversion path, and the second and second inverted sheets evacuated to the conveyance evacuation path are not passed through the sheet inverting unit. Since the paper is merged with the paper conveyance path that reaches the image forming unit, the paper that has been evacuated to the conveyance retraction path can be conveyed and supplied to the second image forming unit again without passing through the paper reversing unit (twisting reversing unit). It becomes like this.

  According to the image forming apparatus of the third aspect, the first branch switching unit is provided, and the sheet transport path from the first image forming unit to the sheet reversing unit is branched to the non-reversing path, so that the sheet is printed in the single-sided printing mode. The retracting portion can be used as a non-reversing conveyance path.

  According to the image forming apparatus of the fourth aspect, when a paper transport abnormality is detected, the second branch switching unit branches the paper transport path from the paper reversing unit to the second image forming unit to the transport retreat path. Therefore, when a paper conveyance abnormality is detected, it is possible to change the paper conveyance after reversing the front and back to the second image forming unit, and temporarily retreat the paper after reversing the front and back to the paper retraction unit.

  According to the image forming apparatus of the fifth aspect, when the paper conveyance abnormality is detected, the control unit causes the second branch switching unit to branch the reversed paper from the paper conveyance path to the conveyance retraction path. Therefore, when a paper conveyance abnormality is detected, it is possible to change the paper conveyance after reversing the front and back to the second image forming unit and temporarily retreat the paper after reversing the front and back to the paper retraction unit.

  According to the image forming apparatus of the sixth aspect, the control unit re-forms the image of the page on a new sheet by the first image forming unit after removing the sheet of the page where the conveyance abnormality is detected, and re-forms the image. After reversing the front and back of the subsequent paper and transporting the paper after reversing the front and back to the second image forming unit, the paper after reversing the front and back retreated by the transport retreating unit from the transport retreating unit to the second image forming unit Since the sheets are sequentially conveyed, no-damaged paper that has been evacuated to the paper evacuation unit can be used for booklet creation. Therefore, even when a jam occurs during the execution of an image forming job, it is possible to avoid the use of all JOBs as compared with the conventional method, and to reduce torn paper as much as possible.

  According to the image forming apparatus of the seventh aspect, the first image forming unit and the second image forming unit are the same image forming unit, and the twist type paper reversing unit is connected to the downstream paper transport path. Since the downstream sheet conveyance path merges with the upstream sheet conveyance path of the image forming unit, in the image forming apparatus having a double-sided image forming function other than the serial tandem type, A sheet on which a single-sided image is formed, which is retracted and placed in the retracting section, can be used after the jam processing.

1 is a cross-sectional view illustrating a configuration example of an image forming apparatus 100 as a first embodiment according to the present invention. 3 is a cross-sectional view illustrating a configuration example of a color printer 80. FIG. 3 is a perspective view illustrating a configuration example of a sheet twisting unit 31. FIG. FIGS. 4A to 4C are perspective views illustrating an example of the operation of the paper twisting unit 31. FIG. 3 is a block diagram illustrating a configuration example of a control system of the image forming apparatus 100. FIG. 4A and 4B are cross-sectional views illustrating a first example of paper conveyance in the image forming apparatus 100. FIG. FIG. 6 is a cross-sectional view illustrating a second example of paper conveyance in the image forming apparatus. 6 is a flowchart illustrating an example (part 1) of conveyance control when a jam occurs in the image forming apparatus 100 according to the first embodiment. It is a flowchart which shows the conveyance control example (the 2) at the time of jam occurrence. 12 is a flowchart illustrating an example (part 3) of conveyance control when a jam occurs. FIGS. 9A and 9B are cross-sectional views illustrating a recovery operation example (part 1) when a jam occurs in the image forming apparatus 100 according to the second embodiment. (A) And (B) is sectional drawing which shows the recovery operation example (the 2) at the time of jam generation. 12 is a flowchart illustrating an example of recovery control (part 1) when a jam occurs in the image forming apparatus according to the second embodiment. It is a flowchart which shows the recovery control example (the 2) at the time of jam occurrence. It is a flowchart which shows the recovery control example (the 3) at the time of jam occurrence. FIG. 10 is a cross-sectional view illustrating an operation example in a single-sided printing mode of an image forming apparatus 100 according to a third embodiment. FIG. 6 is a cross-sectional view illustrating a configuration example of an image forming apparatus 200 as a second embodiment. 6 is a flowchart illustrating a conveyance control example (part 1) when a jam occurs in the image forming apparatus. It is a flowchart which shows the conveyance control example (the 2) at the time of jam occurrence.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. The descriptions in this section do not limit the technical scope described in the claims or the meaning of terms.

<First Embodiment>
Next, the image forming apparatus 100 as the first embodiment will be described with reference to FIGS. 1 forms an image on one side of a sheet of paper, and then reverses the front and back of the paper by a twisting method. The present invention can be applied to color or black and white printers, copiers, and complex machines that form images on the other side.

  The image forming apparatus 100 includes a first image forming unit 101, a second image forming unit 102, and a paper front / back twisting unit 103. The first image forming unit 101 forms an image on one surface of the paper P, in addition to the registration roller 11 and the first print engine 80a, the fixing device 17a, the paper discharge roller 25, and the first paper transport unit 61. have. The first image forming unit 101 is provided with a paper carry-in path I (shown by a white arrow in FIG. 1) to a paper feeding system (not shown) and a paper discharge port 21 for discharging the paper P after image formation. Yes.

  The registration roller 11 aligns the leading ends of the paper P fed from the paper carry-in path I, and discharges the paper P to the first print engine 80a based on a predetermined timing. The first print engine 80 a is disposed on the downstream side of the registration roller 11 and forms an image on one surface (front surface) of the paper P. As the first print engine 80a, a tandem electrophotographic color printer 80 as shown in FIG. 2 is used.

  According to the color printer 80 shown in FIG. 2, an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and a cyan (C) image. And an image forming unit 10K that forms a black (K) color image. In this example, common function names, for example, Y, M, C, and K indicating colors to be formed are added to the back of the reference numeral 10.

  The image forming unit 10Y includes a photosensitive drum 1Y, and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a cleaning unit 8Y are disposed around the photosensitive drum 1Y. The image forming unit 10M includes a photosensitive drum 1M, and a charging unit 2M, an optical writing unit 3M, a developing device 4M, and a cleaning unit 8M are disposed around the photosensitive drum 1M. The image forming unit 10C includes a photosensitive drum 1C, and a charging unit 2C, an optical writing unit 3C, a developing device 4C, and a cleaning unit 8C are disposed around the photosensitive drum 1C. The image forming unit 10K includes a photosensitive drum 1K, and a charging unit 2K, an optical writing unit 3K, a developing device 4K, and a cleaning unit 8K are disposed around the photosensitive drum 1K.

  Respective photosensitive drums 1Y, 1M, 1C, and 1K in the image forming units 10Y, 10M, 10C, and 10K, charging units 2Y, 2M, 2C, and 2K, optical writing units 3Y, 3M, 3C, and 3K, and developing devices 4Y and 4M , 4C, 4K and the cleaning units 8Y, 8M, 8C, 8K have the same contents. In the following description, Y, M, C, and K are not used unless particularly distinguished.

  In the image forming unit 10, the charging unit 2 charges the photosensitive drum 1. For the optical writing unit 3, for example, an LED print head (hereinafter referred to as LPH) type exposure scanning apparatus is used. The light writing unit 3 scans the photosensitive drum 1 with laser beam light based on the image data for each image forming color, and operates so as to simultaneously write information for every plurality of lines. An electrostatic latent image is formed on the photosensitive drum 1 by the laser beam scanned by the optical writing unit 3. The developing device 4 develops the electrostatic latent image. As a result, a toner image which is a visible image is formed on the photosensitive drum 1.

  In the color printer 80, images of Y color, M color, C color, and BK color are formed on the respective photosensitive drums 1Y, 1M, 1C, and 1K of the image forming units 10Y, 10M, 10C, and 10K. The toner images of the respective colors formed on the respective photosensitive drums 1 are intermediated by operating the primary transfer rollers 7Y, 7M, C, and K corresponding to the photosensitive drums 1 for Y, M, C, and BK colors. Transfer is performed on the transfer belt 6 (primary transfer).

  The intermediate transfer belt 6 has an endless belt. Toner images on the photosensitive drums 1Y, 1M, 1C, and 1K are transferred to the intermediate transfer belt 6. The intermediate transfer belt 6 is wound around a plurality of rollers and supported so as to be able to run. The color image formed on the intermediate transfer belt 6 is conveyed toward the secondary transfer portion 7A as the intermediate transfer belt 6 rotates clockwise. The secondary transfer portion 7A is disposed below the color printer 80 and at the lowest position of the intermediate transfer belt 6. The toner image on the intermediate transfer belt 6 is transferred to the paper P sent from the paper transport unit (secondary transfer) in the secondary transfer unit 7A.

  In addition, cleaning units 8Y, 8M, 8C, and 8K corresponding to the Y, M, C, and K color photosensitive drums 1 are provided below the left side of each of the above-described photosensitive drums 1, and the previous writing is performed. Then, the toner agent remaining on the photosensitive drum 1 is removed (cleaned). A cleaning unit 8A is provided above the left side of the intermediate transfer belt 6 and operates to clean the toner agent remaining on the intermediate transfer belt 6 after the secondary transfer. As a result, a toner image based on the image data can be formed.

  A fixing device 17a is disposed on the downstream side of the first print engine 80a, and heat-fixes the paper P (transfer paper) onto which the toner image is transferred. In the fixing device 17a, the toner image on the paper P is thermally fixed by passing the paper P between a fixing roller and a pressure roller heated by a heater (not shown). A paper discharge roller 25 is disposed on the downstream side of the fixing device 17 a, and the heat-fixed transfer paper P ′ is discharged to the paper front / back twisting unit 103 through the paper discharge port 21.

  A first paper transport unit 61 is disposed at a predetermined position of the first image forming unit 101 and controls the transport speed of the paper P by controlling the rotation speeds of the registration roller 11 and the paper discharge roller 25. For example, the first paper transport unit 61 transports the paper P so as to maintain a predetermined interval so that the subsequent paper (following paper) does not collide with the preceding paper (leading paper).

  A sheet front / back twisting unit 103 constituting an example of a sheet reversing unit is connected to the downstream side of the first image forming unit 101. The sheet front / back twisting unit 103 includes a twisting-type sheet reversing unit (hereinafter referred to as a sheet twisting unit 31) and a sheet retracting unit (hereinafter referred to as a sheet stacking unit 32), and an image is formed by the first image forming unit 101. The front and back of the formed paper P are reversed. The sheet front / back twisting unit 103 has a sheet twist reversing path II. In this example, the paper carrying path I of the first image forming unit 101 and the paper twisting / reversing path II are connected in a substantially straight line to form the paper carrying path 13.

  A paper twisting section 31 is disposed in the paper twisting reversal path II and reverses the front and back of the paper P on which an image is formed by the first image forming unit 101. The sheet twisting unit 31 includes, for example, a motor 37, driving rollers 301 and 302, driven rollers 303 and 304, a first belt 305, a second belt 306, a guide plate 307 (large), and a guide plate 308 (small) shown in FIG. And a paper end locus guide bar 309.

  A motor 37 is engaged with the drive rollers 301 and 302. The first belt 305 is hung between the driving roller 301 and the driven roller 303 while being twisted by a rotation angle of 180 °. The second belt 306 is hung between the driving roller 302 and the driven roller 304 in a state where the second belt 306 is twisted by a rotation angle of 180 °.

  The paper P enters from the direction (paper transport direction) indicated by the white arrow in FIG. The paper P is sandwiched between nip portions of the driving roller 301 and the driving roller 302 that are rotated by the motor 37, and is conveyed while being twisted along the paper conveying direction by the first belt 305 and the second belt 306. In this example, the posture of the paper P is twisted clockwise through the guide plates 307 and 308 and the paper edge locus guide bar 309 shown in FIG.

  For example, when a rotation axis in the sheet conveyance direction is set at a position that divides the width direction of the sheet P in the sheet twist reversal path II, as shown in FIG. 4B, the rotation axis is used as a reference. Rotate 180 ° and reverse the front and back. As shown in FIG. 4C, the paper P after the front and back sides are separated from the driven rollers 303 and 304, and the paper transport control is taken over by a downstream paper transport system (not shown).

  A paper stack unit 32 is disposed below the paper twisting unit 31 described above, and the paper stack unit 32 branches from a paper transport path 13 from the paper front / back twisting unit 103 to the second image forming unit 102. A path III (conveyance retreat path) is provided. The paper stack path III is provided with a predetermined interval (space) where the paper after reversing the front and back sides can be retracted. In this example, two to three sheets that have been turned upside down are allowed to stay.

  In this example, the sheet stack path III includes a front stack path IIIa and a single-sided transport path IIIb. The pre-stack path IIIa is a portion from the branch point p1 of the paper transport path 13 shown in FIG. The single-sided conveyance path IIIb constitutes an example of a non-inversion path and is a portion on the downstream side from the non-inversion junction p2.

  The one-side conveyance path IIIb is a sheet conveyance path that reaches the second image forming unit 102 without allowing the sheet P (see FIG. 6) that has been turned upside down retracted to the sheet stack path III to pass through the sheet front / back twist unit 103. 13 is merged. By disposing this single-sided conveyance path IIIb, it is possible to convey and supply the sheet evacuated to the sheet stacking path III to the second image forming unit 102 without passing it again through the sheet front / back twisting unit 103. become.

  Note that a first branching portion 33 is provided in the paper twist reversal path II in a portion near the paper discharge port 21 of the first image forming unit 101. The first branching unit 33 is controlled so as to branch from the sheet twist reversal path II to the single-sided conveyance path IIIb. Further, a second branch portion 34 is provided in the paper twist reversal path II in the downstream portion of the paper twist portion 31. The second branching unit 34 is controlled so as to branch from the paper twisting / reversing path II to the preceding stack path IIIa.

  The second image forming unit 102 is connected to the downstream side of the sheet front / back twisting unit 103, and in order to form an image on the other side (back side) of the paper whose front and back are reversed by the paper twisting unit 31, the loop roller 22, In addition to the registration roller 23 and the second print engine 80b, the image forming apparatus includes a fixing device 17b, a paper discharge roller 26, and a second paper conveyance unit 62. The second image forming unit 102 has a paper carry-in port 12.

  The loop roller 22 takes into the second image forming unit 102 the paper P that has been turned upside down and is transported from the paper transport path 13 through the paper transport inlet 12. The registration roller 23 aligns the leading edge of the paper P taken into the second image forming unit 102 together with the loop roller 22 and discharges the paper P to the second print engine 80b based on a predetermined timing. .

  A second print engine 80 b is disposed on the downstream side of the registration roller 23 and forms an image on the other surface of the paper P. As the second print engine 80b, a tandem-type electrophotographic color printer 80 as shown in FIG. 2 is used, but the description thereof is omitted.

  A fixing device 17b is disposed on the downstream side of the second print engine 80b, and heat-fixes the paper P (transfer paper) onto which the toner image is transferred. Since the same fixing device 17b as the fixing device 17a is used, the description thereof is omitted. A paper discharge roller 26 is disposed on the downstream side of the fixing device 17b, and the heat-fixed paper P is discharged to the paper discharge path IV. A post-processing system (not shown) is connected to the downstream side of the paper discharge path IV, and the above-described paper transport path 13 is connected to the upstream side thereof.

  A second paper conveyance unit 62 is disposed at a predetermined position of the second image forming unit 102, and the conveyance speed of the paper P is controlled by controlling the rotation speed of the loop roller 22, the registration roller 23, the paper discharge roller 26, and the like. To do. Since the function of the second paper transport unit 62 is the same as that of the first paper transport unit 61, the description thereof is omitted. Thus, the image forming apparatus 100 including the first image forming unit 101, the second image forming unit 102, and the sheet front / back twisting unit 103 is configured.

  Next, a configuration example of a control system of the image forming apparatus 100 will be described with reference to FIG. According to the control system of the image forming apparatus 100 shown in FIG. 5, the overall control unit 50 and the first control unit 51 are provided in the first image forming unit 101, and the torsion control unit 30 is provided in the sheet front / back twisting unit 103. The second image forming unit 102 is provided with a second control unit 52.

  The overall control unit 50 controls the entire image forming apparatus 100 including the first image forming unit 101, the second image forming unit 102, and the sheet front / back twisting unit 103. The overall control unit 50 includes, for example, a work RAM 53, a memory unit 54, and a central processing unit (hereinafter referred to as a CPU 55).

  In addition to control data for controlling the first image forming unit 101, the second image forming unit 102, and the paper front / back twisting unit 103, the memory unit 54 stores a system program. For example, when the power is turned on and the power-on information is detected, the CPU 55 reads the system program from the memory unit 54 and develops it in the RAM 53, starts the system, and controls the entire image forming apparatus 100. .

  For example, the overall control unit 50 reads the control data D30, D51, D52 from the memory unit 54 and outputs the control data D30, D51, D52 to each of the corresponding torsion control unit 30, the first control unit 51, and the second control unit 52. The control data D30 is data for controlling the timing when the torsion controller 30 twists the front and back of the paper P. The control data D51 is data for controlling the timing when the first image forming unit 101 transports the paper P and forms an image on the paper P. The control data D52 is data for controlling the timing when the second image forming unit 102 transports the paper P and forms an image on the paper P, for example.

  A first control unit 51 is connected to the overall control unit 50, and a first print engine 80 a and a first paper transport unit 61 are connected to the first control unit 51. The first control unit 51 decodes the control data D51 to generate an image formation control signal S51 and a conveyance control signal S61. The first control unit 51 outputs an image formation control signal S51 to the first print engine 80a together with the image data Dy, Dm, Dc, Dk. The first print engine 80a forms a color image on the paper P based on the image data Dy, Dm, Dc, Dk and the image formation control signal S51.

  The torsion control unit 30 is connected to the overall control unit 50. A paper twisting unit 31, a first branch switching unit 35, and a second branch switching unit 36 are connected to the twist control unit 30. The twist control unit 30 controls the paper twist unit 31, the first branch switching unit 35, and the second branch switching unit 36 based on the control data D30.

  For example, the twist control unit 30 decodes the control data D30 to generate a twist control signal S31 and branch switching signals S35 and S36. The torsion control signal S31 is a signal for controlling the rotation of the motor 37 shown in FIG. 3, and is output from the torsion control unit 30 to the paper torsion unit 31. The paper twisting unit 31 drives the motor 37 based on the twist control signal S31.

  The torsion control unit 30 outputs a branch switching signal S35 to the first branch switching unit 35. The branch switching signal S35 is a signal for switching the sheet conveyance by selecting the one-side conveyance path IIIb from the sheet conveyance path 13. The first branch switching unit 35 operates the first branch unit 33 based on the branch switching signal S35, and switches the conveyance path so as to branch the paper conveyance path 13 to the one-side conveyance path IIIb. The sheet conveyance path 13 includes a conveyance path from the first image forming unit 101 to the sheet front / back twisting unit 103.

  By switching the transport path, the sheet stack unit 32 can be used as a non-reverse transport path in the single-sided printing mode. In this single-sided printing mode, the paper P on which an image is formed on one side by the first image forming unit 101 is conveyed to the second image forming unit 102 as it is face up.

  In this example, the abnormality detection unit 41 is connected to the overall control unit 50. The abnormality detection unit 41 detects a paper conveyance abnormality (jam) in the paper conveyance path 13 and the paper conveyance path 13 after the second image forming unit 102 and generates an abnormality detection signal S41. The abnormality detection signal S41 is output from the abnormality detection unit 41 to the overall control unit 50, for example. The overall control unit 50 performs analog / digital processing on the abnormality detection signal S41 and outputs jam occurrence information D41 (abnormality detection information) to the torsion control unit 30.

  The torsion control unit 30 inputs the jam occurrence information D41 when the paper conveyance abnormality is detected, decodes the jam occurrence information D41, generates the branch switching signal S36, and sends the branch switching signal S36 to the second branch switching unit 36. Output. The branch switching signal S36 is a signal for selecting the preceding stack path IIIa from the paper transport path 13 and switching the paper transport.

  The second branch switching unit 36 operates the second branch unit 34 based on the branch switching signal S36, selects the previous stack path IIIa from the sheet transport path 13, and switches the sheet transport. The sheet conveyance path 13 includes a conveyance path from the sheet front / back twisting unit 103 to the second image forming unit 102. By switching the transport path, when a paper transport abnormality is detected, the transport of the paper after reversing the front and back to the second image forming unit 102 can be changed, and the paper after reversing the front and back can be temporarily retracted to the paper stack unit 32. become.

  In addition to the first control unit 51 and the torsion control unit 30, the second control unit 52 is connected to the overall control unit 50, and the second print engine 80 b and the second paper transport unit 62 are connected to the second control unit 52. Has been. The second controller 52 decodes the control data D52 to generate an image formation control signal S52 and a conveyance control signal S62. The second control unit 52 outputs an image formation control signal S52 to the second print engine 80b together with the image data Dy, Dm, Dc, Dk.

  The second print engine 80b forms a color image on the paper P that has been turned upside down based on the image data Dy, Dm, Dc, Dk and the image formation control signal S52. Thus, a control system of the image forming apparatus 100 is configured, and the first image forming unit 101, the second image forming unit 102, and the sheet front / back twisting unit 103 are controlled.

  In addition to the abnormality detection unit 41, an operation display unit 48 is connected to the overall control unit 50 described above. The operation display unit 48 is operated when setting an image forming job, image forming conditions, and the like. For example, the booklet creation mode is set as an image forming job by operating the operation display unit 48. In the booklet creation mode, a booklet is created by forming images corresponding to a plurality of pages on the front and back sides (both sides) of a plurality of sheets P.

  Further, when a jam occurs, the CPU 55 outputs display data D18 for notifying the operation display unit 48 of the occurrence of the jam. A message screen such as “Jam has occurred” is displayed on the monitor of the operation display section 48 based on the display data D18 (jam occurrence notification display). This message screen displays a procedure for removing the jam.

  Further, the CPU 55 outputs display data D18 for notifying the removal of the transfer sheet to the operation display unit 48. A message screen such as “Please remove the transfer paper in the stack” is displayed on the monitor of the operation display unit 48 based on the display data D18 (stack paper removal notification display).

  Next, with reference to FIGS. 6 to 10, a conveyance control example (Nos. 1 to 3) in the image forming apparatus 100 according to the first embodiment when a jam occurs will be described. In this embodiment, when a paper conveyance abnormality is detected in the paper conveyance path 13 for conveying the paper after reversing the front and back, and a paper conveyance abnormality is detected, the CPU 55 of the overall control unit 50 controls the torsion control unit 30. By controlling, the paper after the front and back being reversed is switched from the paper transport path 13 to the paper stack path III, and the paper after the front and back reversal is retracted to the paper stack unit 32.

  According to the sheet conveyance example in the image forming apparatus 100 shown in FIG. 6A, the duplex printing mode based on a predetermined image forming job is executed. For example, five transfer sheets (1) to (5) are sheets. This is a case where the user stays on the transport path 13. In the first transfer paper (1), images are formed on the front and back (both sides) of the paper P, and the transfer paper (1) is in contact with the fixing device 17b of the second image forming unit 102. In addition, regarding the paper P in the drawing, a portion indicated by a bold line is one side, and a white portion is the other side.

  The second transfer paper (2) is in a state where the paper P after the front and back are reversed is taken into the second image forming unit 102 and is approaching the loop roller 22. The third transfer sheet (3) is in a state immediately after the paper P after the image formation is completed by the paper front / back twist unit 103. In the fourth transfer sheet (4), an image is formed on one surface of the sheet P, and the sheet P is taken into the sheet front / back twisting unit 103 from the first image forming unit 101. The fifth transfer sheet (5) is in a state where an image is formed on one surface of the sheet P by the first image forming unit 101. Note that image forming jobs such as the duplex printing mode are set in the CPU 55 of the overall control unit 50 by operating the operation display unit 48.

  Based on these assumptions, in step ST1 shown in FIG. 8, the CPU 55 detects the occurrence of a jam and acquires jam occurrence information D41. In this example, in the sheet conveyance path 13 and the sheet conveyance path 13 after the second image forming unit 102, the abnormality detection unit 41 shown in FIG. 5 detects a sheet conveyance abnormality (jam), and an abnormality detection signal S41 is generated. Occur.

  According to the sheet conveyance example in the image forming apparatus 100 shown in FIG. 6A, the first transfer sheet (1) and the second transfer sheet (2) are abnormal on the sheet conveyance path 13. Is detected. The abnormality detection signal S41 is output from the abnormality detection unit 41 to the overall control unit 50. The overall control unit 50 performs analog / digital processing on the abnormality detection signal S41 to obtain jam occurrence information D41 (abnormality detection information).

  In step ST <b> 2, the CPU 55 branches the control based on whether the jam is on the downstream side of the sheet front / back twisting unit 103 or on the upstream side. In this example, the abnormality detection unit 41 detects an abnormality in the sheet conveyance path 13 after the sheet conveyance path 13 and the second image forming unit 102.

  In step ST3, the CPU 55 branches the control in accordance with whether or not there is a transfer sheet in the sheet front / back twisting unit 103. In the example shown in FIG. 6A, the third transfer paper (3) to the fifth transfer paper (5) are twisted and reversed by the paper front / back twisting unit 103.

  This corresponds to the case where there are three transfer sheets (3) to (5) in the sheet front / back twisting unit 103, and therefore the CPU 55 executes gate switching control in step ST4. According to the gate switching control, the CPU 55 outputs the jam occurrence information D41 to the torsion control unit 30. The torsion control unit 30 decodes the jam occurrence information D41 and generates a branch switching signal S36.

  The branch switching signal S36 is output from the torsion control unit 30 to the second branch switching unit 36. The second branch switching unit 36 operates the second branch unit 34 based on the branch switching signal S36, disconnects the twist-reverse transport path II from the paper transport path 13, and connects the twist-reverse transport path II and the previous stack path IIIa. The paper conveyance is switched as follows.

  Thereafter, in step ST5, the CPU 55 retracts the transfer paper to the paper stack unit 32. In this example, first, the third transfer paper (3) that has been twisted and reversed by the paper front / back twisting unit 103 moves to and stays in the preceding stack path IIIa of the paper stack unit 32.

  In step ST6, the CPU 55 branches the control depending on whether or not there is a transfer sheet sent to the sheet front / back twisting unit 103. If there is a transfer sheet sent to the sheet front / back twisting unit 103, the process returns to step ST5 and the CPU 55 retracts the transfer sheet to the sheet stack unit 32. In this example, the sheet front / back twisting unit 103 causes the fourth transfer sheet (4) that has been torsionally reversed to move to the front stack path IIIa of the sheet stack unit 32 and stay there. During this time, the third transfer sheet (3) withdrawn first moves from the front stack path IIIa to the one-side transport path IIIb.

  Further, returning to step ST5, the CPU 55 retracts the transfer paper to the paper stack unit 32. In this example, the fifth transfer paper (5) that has been torsionally reversed by the paper front / back twisting unit 103 moves and stays on the preceding stack path IIIa of the paper stack unit 32. During this time, the fourth transfer sheet (4) withdrawn first moves from the front stack path IIIa to the one-side transport path IIIb.

  By this gate switching control, the third transfer paper (3) to the fifth transfer paper (5), which are sequentially twisted and reversed, can be retracted to the paper stack section 32. 6B shows a state in which the third transfer paper (3) to the fifth transfer paper (5) are retracted to the paper stack section 32. FIG. In this example, the fourth transfer paper (4) is the paper P after image formation in the middle of fixing when a jam occurs, and the fifth transfer paper (5) is the first paper when the jam occurs. 1 is a sheet P in the middle of image formation by the image forming unit 101. In any case, fixing is performed without stopping the sheet conveyance when a jam occurs, and image formation is continued. Thereby, torn paper can be reduced.

  If there is no transfer sheet sent to the sheet front / back twisting unit 103, the process proceeds to step ST7, and the CPU 55 executes gate switching control. In this gate switching control, the second branch switching unit 36 operates the second branch unit 34 based on the branch switching signal S36, disconnects the previous stack path IIIa from the twist-reverse transport path II, and turns the twist-reverse transport path II and the sheet. The sheet conveyance is switched so as to connect the conveyance path 13 (return).

  Thereafter, returning to step ST3, the CPU 55 branches the control in accordance with whether or not there is transfer paper in the paper front / back twisting unit 103. In the above example, since the three transfer papers (3) to (5) are retracted, the subsequent transfer paper is not sent, and the process proceeds to step ST8 shown in FIG.

  In step ST8, the CPU 55 notifies the occurrence of a jam. For example, the CPU 55 outputs display data D18 for notifying the occurrence of a jam to the operation display unit 48. A message screen such as “Jam has occurred” is displayed on the monitor of the operation display section 48 based on the display data D18 (jam occurrence notification display). This message screen displays a procedure for removing the jam. At this time, the user confirms the paper jam location while referring to the message screen, and removes the jam.

  Thereafter, the process proceeds to step ST9, where the CPU 55 branches based on whether or not the jam processing is completed. Whether or not the jam processing is completed is determined by well-known techniques, for example, a method in which the user presses a predetermined push button of the operation display unit 48 to instruct the CPU 55, or a door that is opened and closed to confirm a paper jam location. A method of instructing the CPU 55 from a switch mechanism that is automatically detected by closing and closing is adopted. In either method, a signal indicating the end of jam processing is output to the CPU 55. The CPU 55 decodes the logic of the signal and determines whether or not the jam processing is finished.

  If the jam processing has not ended, the process returns to step ST8, and the CPU 55 continues the jam occurrence notification display. A message screen such as “Jam has occurred” is displayed on the monitor of the operation display section 48 based on the display data D18 (jam occurrence notification display).

  When a signal indicating the end of jam processing is detected, the process proceeds to step ST10, and the CPU 55 branches the control based on whether or not JOB is continued. When continuing the JOB, the CPU 55 discharges the transfer paper of the paper stack unit 32 in step ST11. According to the sheet conveyance example in the image forming apparatus 100 shown in FIG. 7, the third transfer sheet (3) to the fifth sheet that have been retracted to the sheet stack path III after completion of the jam processing and the like are transferred. In this state, the paper (5) is discharged from the paper stack unit 32 to the second image forming unit 102.

  Thereafter, in step ST12, the CPU 55 continues the job. In the above example, the third transfer sheet (3) has already formed images on the front and back (both sides) of the sheet P, and the transfer sheet (3) has reached the fixing device 17b of the second image forming unit 102. It is in a state. The fourth transfer sheet (4) is in a state of reaching a portion where the sheet stack path III joins the sheet transport path 13. The fifth transfer sheet (5) is in a state of moving from the preceding stack path IIIa to the one-side transport path IIIb of the sheet stack path III. In this example, the sheet placed in the sheet stack path III while being retracted can be conveyed and supplied to the second image forming unit 102 without passing the sheet front / back twisting unit 103 again.

  In step ST13, the CPU 55 monitors the occurrence of a jam and branches the control in response to the detection of the jam. When the occurrence of a jam is detected, the process returns to step ST1 and the CPU 55 repeats the above-described steps ST1 to ST13. If the occurrence of a jam is not detected, the CPU 55 determines the end of JOB in step ST14.

  The job end determination is performed, for example, by detecting an end-of-flag (EOP signal) indicating the last page at the time of image formation in a data format for managing an image formation job. When the EOP signal is detected, the paper conveyance control related to the JOB is terminated. When the EOP signal is not detected, the process returns to step ST13 to monitor the occurrence of the jam, and the control branches in response to the detection of the jam.

  If JOB is not continued in step ST10 described above, the process proceeds to step ST15 and the CPU 55 notifies the removal of the transfer paper in the paper stack unit 32. For example, the CPU 55 outputs display data D18 for informing the operation display unit 48 of the transfer paper removal. On the monitor of the operation display section 48, a message screen such as “Please remove the transfer paper in the paper stack section” is displayed based on the display data D18 (stack paper removal notification display).

  On this message screen, a procedure for removing the transfer paper in the paper stack unit 32 is displayed. At this time, the user confirms the installation location of the stack unit while referring to the message screen, and removes the transfer paper from the sheet stack unit 32.

  Thereafter, in step ST16, the CPU 55 branches the control based on whether or not the process for removing the transfer paper in the stack is completed. When the transfer paper removal process in the stack is not completed, the process returns to step ST15, and the CPU 55 continues the stack paper removal notification display.

  Further, regarding the jam on the upstream side of the sheet front / back twisting unit 103 in step ST2, the process proceeds to step ST17 shown in FIG. In step ST17, the CPU 55 notifies the occurrence of a jam (jam occurrence notification display). Since the jam occurrence notification display has the same contents as in step ST8, the description thereof is omitted.

  Thereafter, the process proceeds to step ST18, and the CPU 55 branches the control based on whether or not the jam processing is completed. Whether or not the jam processing has been completed is the same as that in step ST9, and the description thereof is omitted. If the jam processing has not ended, the process returns to step ST17 and the jam occurrence notification display is continued.

  When a signal indicating the end of jam processing is detected, the process proceeds to step ST19, and the CPU 55 continues the job. Thereafter, in step ST20, the CPU 55 monitors the occurrence of a jam and branches the control in response to the detection of the jam occurrence. When the occurrence of jam is not detected, the CPU 55 determines the end of JOB in step ST21. When the job end signal is detected, the paper conveyance control related to the job is ended. If the JOB end signal is not detected, the process returns to step ST20 to monitor the occurrence of jam, and control is executed in response to the detection of jam occurrence.

  As described above, according to the sheet conveying method of the image forming apparatus 100 according to the first embodiment, the sheet conveying abnormality (jam or the like) occurs in the sheet conveying path 13 and the sheet conveying path 13 downstream of the second image forming unit 102. Is detected, and when there is a paper P that is being twisted by the paper front / back twisting unit 103, the paper P after the twisting operation is retracted to the paper stack unit 32 without stopping the twisting operation. become able to.

  As a result, in a serial tandem type image forming apparatus 100 (system), an image forming apparatus having a double-sided image function, or the like, a sheet on which a single-sided image has been formed is retracted and placed in the paper stack unit 32 when a paper conveyance abnormality is detected After jamming P, an image can be formed on the other side and used. In addition, it becomes possible to reduce torn paper as much as possible, and downtime can be reduced.

  Next, a recovery operation example in the image forming apparatus 100 according to the second embodiment when a jam occurs will be described with reference to FIGS. In this embodiment, when an image forming job for creating a booklet by forming images corresponding to a plurality of pages on the front and back surfaces (both sides) of a plurality of sheets P is set to the booklet creation mode, the booklet creation mode is set. This is a case where a conveyance abnormality is detected by the abnormality detection unit 41 in a page (paper P) in the middle of executing an image forming job.

  In this case, after removing the sheet P of the page on which the conveyance abnormality is detected, the CPU 55 re-forms the image of the page on a new sheet by the first image forming unit 101, and changes the front and back of the sheet P after the re-formation. After reversing and conveying the paper P after the front / back reversal to the second image forming unit 102, the paper P after the front / back reversal saved in the paper stacking unit 32 is transferred from the paper stacking unit 32 to the second image forming unit 102. It was made to carry in order.

  Based on these assumptions, the CPU 55 detects the occurrence of a jam and acquires the jam occurrence information D41 in step ST31 shown in FIG. Also in this example, in the sheet conveyance path 13 and the sheet conveyance path 13 after the second image forming unit 102, the abnormality detection unit 41 shown in FIG. 5 detects a sheet conveyance abnormality (jam), and the abnormality detection signal S41 is generated. Occur.

  According to the sheet conveyance example in the image forming apparatus 100 shown in FIG. 11A, the first transfer sheet (1) to the third transfer sheet (3) are abnormal on the sheet conveyance path 13. Detected as The abnormality detection signal S41 is output from the abnormality detection unit 41 to the overall control unit 50. The overall control unit 50 performs analog / digital processing on the abnormality detection signal S41 to obtain jam occurrence information D41 (abnormality detection information).

  In step ST32, the CPU 55 branches the control based on whether the jam is on the downstream side of the sheet front / back twisting unit 103 or on the upstream side. Also in this example, the abnormality detection unit 41 detects an abnormality in the sheet conveyance path 13 after the sheet conveyance path 13 and the second image forming unit 102.

  In step ST <b> 33, the CPU 55 branches the control in accordance with whether or not there is transfer paper in the paper front / back twisting unit 103. In the example shown in FIG. 11A, the fourth transfer sheet (4) to the sixth transfer sheet (6) are twisted and reversed by the sheet front / back twisting unit 103.

  This corresponds to the case where there are three transfer sheets (4) to (6) in the sheet front / back twisting unit 103, and thus the CPU 55 executes gate switching control in step ST34. According to the gate switching control, the CPU 55 outputs the jam occurrence information D41 to the torsion control unit 30. The torsion control unit 30 decodes the jam occurrence information D41 and generates a branch switching signal S36.

  The branch switching signal S36 is output from the torsion control unit 30 to the second branch switching unit 36. The second branch switching unit 36 operates the second branch unit 34 based on the branch switching signal S36, disconnects the twist-reverse transport path II from the paper transport path 13, and connects the twist-reverse transport path II and the previous stack path IIIa. The paper conveyance is switched as follows.

  Thereafter, in step ST <b> 35, the CPU 55 retracts the transfer paper to the paper stack unit 32. In this example, the fourth transfer paper (4) that is torsionally reversed by the paper front / back twisting unit 103 first moves and stays on the preceding stack path IIIa of the paper stack unit 32.

  In step ST <b> 36, the CPU 55 branches the control depending on whether there is a transfer sheet sent to the sheet front / back twisting unit 103. If there is a transfer sheet sent to the sheet front / back twisting unit 103, the process returns to step ST35 and the CPU 55 retracts the transfer sheet to the sheet stack unit 32. In this example, by the sheet front / back twisting unit 103, the fifth transfer sheet (5) that has been twisted and reversed moves to the upstream stack path IIIa of the sheet stack unit 32 and stays there. During this time, the fourth transfer sheet (4) withdrawn first moves from the front stack path IIIa to the one-side transport path IIIb.

  Furthermore, returning to step ST35, the CPU 55 retracts the transfer paper to the paper stack unit 32. In this example, the sixth transfer sheet (6) that has been rotated and reversed by the sheet front / back twisting unit 103 moves to the previous stack path III a of the sheet stack unit 32 and stays there. During this time, the fifth transfer sheet (5) withdrawn first moves from the front stack path IIIa to the one-side transport path IIIb.

  By this gate switching control, the fourth transfer paper (4) to the sixth transfer paper (6), which are sequentially twisted and reversed, can be retracted to the paper stack section 32. FIG. 11B shows a state in which the fourth transfer sheet (4) to the sixth transfer sheet (6) are retracted to the sheet stack section 32. FIG.

  If there is no transfer sheet sent to the sheet front / back twisting unit 103, the process proceeds to step ST37, and the CPU 55 executes gate switching control. In this gate switching control, the second branch switching unit 36 operates the second branch unit 34 based on the branch switching signal S36, disconnects the previous stack path IIIa from the twist-reverse transport path II, and turns the twist-reverse transport path II and the sheet. The sheet conveyance is switched so as to connect the conveyance path 13 (return).

  Thereafter, returning to step ST33, the CPU 55 branches the control in accordance with whether or not there is a transfer sheet in the sheet front / back twisting unit 103. In the above example, since the three transfer sheets are retracted, the subsequent transfer sheets are not sent, and the process proceeds to step ST38 shown in FIG.

  In step ST38, the CPU 55 notifies the occurrence of a jam. For the jam occurrence notification display, refer to step ST8 described in the first embodiment. Also in this example, the user confirms the jammed portion while referring to the message screen, and removes the jam.

  Thereafter, the process goes to step ST39, and the CPU 55 branches the control based on whether or not the jam processing has been completed. When the jam processing is completed, the CPU 55 is instructed to end the jam processing as described in the first embodiment. If the jam processing has not ended, the process returns to step ST38 and the jam occurrence notification display is continued (see steps ST8 and ST9).

  When a signal indicating the end of the jam processing is detected, the process proceeds to step ST40, and the CPU 55 branches the control based on whether or not JOB is continued. When continuing the job, the CPU 55 executes reprinting of the transfer paper at the time of jam removal, unlike the first embodiment, in step ST41.

  In the above-described example, the first transfer sheet (1) to the third transfer sheet (3) are targets for reprinting. According to the paper conveyance example in the image forming apparatus 100 shown in FIG. 12A, the jam processing or the like is completed and the process returns to the image forming job. In this case, the first transfer paper (1) to the third transfer paper (3) relating to the booklet formation mode that has been lost due to jamming or the like is the fourth transfer paper (4) being retracted. The second image forming unit 102 forms an image in preference to the sixth transfer sheet (6).

  In the first transfer paper (1) ′ for compensation shown in FIG. 12A, an image is formed on one surface by the first image forming unit 101, and the paper P after the image formation is the front and back of the paper. This is a state immediately after the torsion unit 103 is torsionally reversed and the torsional inversion is completed. The second transfer paper (2) ′ for compensation is a state in which the paper P after image formation is taken into the paper front / back twisting unit 103 from the first image forming unit 101. The third transfer paper (3) ′ for compensation is in a state where an image is formed on one surface of the paper P by the first image forming unit 101.

  Thereafter, in step ST <b> 42, the CPU 55 branches the control based on whether or not all the paper P (reprinted paper) related to reprinting has passed through the paper front / back twisting unit 103. If all the reprinted paper has not passed through the paper front / back twisting unit 103, the passage of the reprinted paper is awaited.

  In this example, instead of the first transfer paper (1) to the third transfer paper (3) that are lost due to jamming or the like, the first transfer paper (1) ′ to be supplemented instead of the first transfer paper (1) ′ to the third transfer paper (3). After the third transfer sheet (3) ′ is fed to the second image forming section 102, the fourth transfer sheet is retracted to the sheet stack section 32 shown in FIG. (4) to the sixth transfer sheet (6) is fed to the second image forming unit 102.

  In this example, the reprinted paper is three sheets of transfer paper (1) ′ to (3) ′ for compensation, and when the transfer paper (3) ′ for compensation passes the paper front / back twisting unit 103, step ST43. Then, the CPU 55 sequentially discharges the transfer sheets (4) to (6) from the sheet stack unit 32 to the sheet transport path 13. According to the sheet conveyance example in the image forming apparatus 100 shown in FIG. 12B, the third transfer sheet (3) ′ to the eighth transfer sheet (8) after returning to the image forming job. It is a state.

  On the third transfer sheet (3) ′, images are already formed on the front and back surfaces (both sides) of the sheet P by the second image forming unit 102. Thereafter, the fixing by the fixing device 17b is finished and the sheet is discharged. It is in a state of moving to route IV. The fourth transfer sheet (4) returns to the image forming job from the sheet stack section 32 shown in FIG. 12A, and the second image forming section 102 transfers the other sheet P of the sheet P that has been turned upside down. In this state, an image is formed on the surface.

  The fifth transfer sheet (5) is in a state immediately before the sheet P after the front / back inversion is discharged from the sheet stack section 32 through the sheet transport path 13. The sixth transfer sheet (6) is in a state of moving from the preceding stack path IIIa to the one-side transport path IIIb of the sheet stack path III.

  Thereafter, in step ST44, the CPU 55 continues the job. In the above example, the seventh transfer sheet (7) shown in FIG. 12B has an image formed on one side, and then the sheet P is twisted from the first image forming unit 101 to the front and back of the sheet. It is in a state of being taken into the unit 103. The eighth transfer sheet (8) is in a state immediately before an image is formed on one side of the sheet P by the first image forming unit 101. In this example, the fourth sheet of transfer paper (4) to the sixth sheet of transfer (6) having no damage and retracted and placed in the paper stack unit 32 can be used for booklet creation.

  In step ST45, the CPU 55 monitors the occurrence of a jam and branches the control in response to the detection of the jam occurrence. When the occurrence of a jam is detected, the process returns to step ST31 and the CPU 55 repeats the above-described steps ST31 to ST45. When the occurrence of jam is not detected, the CPU 55 determines the end of JOB in step ST46. The job end determination is described in the first embodiment, so please refer to it. If the EOP signal is not detected, the process returns to step ST43 to monitor the occurrence of a jam, and the control branches in response to the detection of the jam occurrence.

  If JOB is not continued in step ST40 described above, the process proceeds to step ST47, and the CPU 55 notifies the removal of the transfer paper in the paper stack unit 32. For the stack paper removal notification display, refer to steps ST15 and ST16 of the first embodiment. At this time, the user confirms the installation location of the stack unit while referring to the message screen, and removes the transfer paper from the sheet stack unit 32.

  Thereafter, in step ST48, the CPU 55 branches based on whether or not the removal process of the transfer paper in the stack is completed. When the transfer paper removal process in the stack is not completed, the process returns to step ST47, and the CPU 55 continues the stack paper removal notification display.

  Further, regarding the jam on the upstream side of the sheet front / back twisting unit 103 in step ST32 described above, the process proceeds to step ST49 shown in FIG. In step ST49, the CPU 55 notifies the occurrence of a jam (jam occurrence notification display). The jam occurrence notification display has the same contents as in step ST38, and thus the description thereof is omitted.

  Thereafter, the process proceeds to step ST50, where the CPU 55 branches based on whether or not the jam processing is completed. Whether or not the jam processing has ended is the same as that in step ST39, and thus the description thereof is omitted. If the jam processing has not ended, the process returns to step ST49 and the jam occurrence notification display is continued.

  When a signal indicating the end of jam processing is detected, the process proceeds to step ST51, and the CPU 55 continues the job. Thereafter, in step ST52, the CPU 55 monitors the occurrence of a jam and branches the control in response to the detection of the jam occurrence. If the occurrence of a jam is not detected, the CPU 55 determines the end of JOB in step ST53. When the job end signal is detected, the paper conveyance control related to the job is ended. If the JOB end signal is not detected, the process returns to step ST31 to monitor the occurrence of jam, and control is executed in response to the detection of the jam occurrence.

  As described above, according to the image forming apparatus 100 according to the second embodiment, the CPU 55 of the overall control unit 50 removes the sheet of the page on which the conveyance abnormality is detected, and then transfers the image of the page to the first image forming unit 101. Is re-formed on a new sheet, the front and back of the re-formed paper P is reversed, and the front and back of the paper P after being reversed is conveyed to the second image forming unit 102 and then retreated by the paper stack unit 32. Since the subsequent sheets P are sequentially conveyed from the sheet stacking section 32 to the second image forming section 102, a booklet is created of the no-damaging sheets P = transfer sheets (4) to (6) that have been evacuated to the sheet stacking section 32. Can be used. Therefore, even when a jam occurs during execution of an image forming job such as a booklet creation mode, it is possible to avoid using all JOBs as compared with the conventional method, and to reduce torn paper as much as possible.

  Next, with reference to FIG. 16, an operation example of the image forming apparatus 100 in the single-sided printing mode according to the third embodiment will be described. According to the paper conveyance example in the image forming apparatus 100 in the single-sided printing mode shown in FIG. 16, an image forming job based on the single-sided printing mode is executed. For example, six transfer sheets (1) to (6) are conveyed. This is a case where the user is staying on the route 13. When the operation display unit 48 sets the single-sided printing mode, the CPU 55 of the overall control unit 50 shown in FIG. 5 moves the sheet conveyance path 13 from the first image forming unit 101 to the sheet front / back twisting unit 103 for non-single-sided use. The first branch switching unit 35 is controlled to switch to the inversion path.

  In this example, the CPU 55 outputs control data D30 indicating that the paper front / back surface twisting unit 103 is passed to the twisting control unit 30. The torsion control unit 30 decodes the control data D30 and generates a branch switching signal S35. The torsion control unit 30 outputs to the first branch switching unit 35 a branch switching signal S35 indicating that the sheet front / back twisting unit 103 is passed. The first branch switching unit 35 operates the first branch unit 33 based on the branch switching signal S35, and switches the conveyance path so as to branch the paper conveyance path 13 to the one-side conveyance path IIIb.

  By switching the transport path, the sheet P = transfer sheets (1) to (6) on which one surface is formed by the first image forming unit 101 is transported to the second image forming unit 102 in a face-up state. become able to.

  In the first transfer paper (1), an image is already formed only on the front surface (one side) of the paper P, and the transfer paper (1) is approaching the fixing device 17b of the second image forming unit 102. It is. The second transfer sheet (2) is in a state immediately before the non-inverted sheet P passes through the sheet front / back twisting unit 103 and is taken into the second image forming unit 102 via the one-side conveyance path IIIb. . The third transfer sheet (3) is also in a state where the non-inverted sheet P passes through the sheet front / back twisting unit 103 and passes through the one-side conveyance path IIIb.

  An image is formed on one surface of the fourth transfer sheet (4), and the sheet P after fixing is taken in from the sheet conveyance path 13 to the one-side conveyance path IIIb by receiving the operation of the first branch portion 33. It is a state that has been. The fifth transfer sheet (5) is in a state where an image is formed on one side of the sheet P by the first image forming unit 101 and then fixed. The sixth transfer sheet (6) is in a state immediately before the first image forming unit 101 forms an image on one surface of the sheet P.

  As described above, according to the image forming apparatus as the first embodiment, the paper stack unit 32 has the paper stack path III that can branch from the paper transport path 13 from the paper front / back twisting unit 103 to the second image forming unit 102. The sheet stack path III is provided with a predetermined interval at which the sheet after reversing the front and back sides can be retracted. The paper stack path III includes a front stack path IIIa and a single-side transport path IIIb. With this configuration, it is possible to change the paper conveyance after the front / back reversal to the second image forming unit 102 and temporarily retract the paper P after the front / back reversal to the paper stack unit 32.

  In addition, according to the image forming apparatus 100 according to the third embodiment, when the single-sided printing mode is set, the single-sided conveyance path IIIb extends from the first image forming unit 101 to the sheet front / back twisting unit 103. Since the first branch switching unit 35 is controlled so as to switch to, it can be used as a detour path (one-side non-inverted path) that passes the sheet front / back twisting unit 103. The single-sided printing mode can be executed even in the duplex-only machine.

  In the first to third embodiments described above, the overall control unit 50 is provided in the first image forming unit 101. However, the present invention is not limited to this, and the overall control unit 50 is provided in the second image forming unit 102. The sheet front / back twisting unit 103 may be controlled. Further, the abnormality detection unit 41 is connected to the overall control unit 50. However, the present invention is not limited to this, and the abnormality detection unit 41 may be connected to the torsion control unit 30 to perform sheet retraction control.

<Second Embodiment>
Next, an image forming apparatus 200 according to the second embodiment will be described with reference to FIGS. In the image forming apparatus 200 with the double-sided image forming function shown in FIG. 17, the first image forming unit 101 and the second image forming unit 102 as described in the first embodiment are not separated, and FIG. The same color printer 80 shown is also used. The registration roller 11 and the loop roller 22 are also used.

  According to the image forming apparatus 200, the torsion type paper front / back twist unit 103 is disposed below the color printer 80. The upstream side of the sheet front / back twist unit 103 is connected to the sheet conveyance path 13 on the downstream side of the fixing device 17. A structure is adopted in which the downstream side of the sheet front / back twisting unit 103 joins the sheet conveyance path 13 on the upstream side of the color printer 80.

  According to the sheet conveyance example in the image forming apparatus 200 shown in FIG. 17, the duplex printing mode based on a predetermined image forming job is executed. For example, three transfer sheets (1) to (3) are placed on the sheet conveyance path 13. If you are staying in. The first transfer sheet (1) is in a state immediately after an image is formed on the surface (one side) of the sheet P and the transfer sheet (1) is twisted and inverted by 180 ° by the sheet front / back twisting unit 103. The second transfer paper (2) is in a state in which an image is formed on the surface (one side) of the paper P and the transfer paper (2) is fixed by the fixing device 17. The third transfer sheet (3) is in a state in which the sheet P is fed from a sheet feeding system (not shown) and fed to the color printer 80. At the time of jam detection, for example, three transfer sheets (1) to (3) are retracted to the sheet stack unit 32. In addition, since the thing of the same name and code | symbol as 1st Embodiment has the same function, the description is abbreviate | omitted.

  18 and 19 is different from the first embodiment in the conveyance control example (Nos. 1 and 2) at the time of paper front / back twisting in the image forming apparatus 200 shown in FIG. 18 and FIG. In the meantime, the step of discriminating “is it a downstream jam?” Relating to step ST2 described in FIG. 8 is omitted.

  Step ST61 shown in FIG. 18 corresponds to step ST1 shown in FIG. 8, step ST62 corresponds to step ST3, and step ST63 corresponds to step ST4. Similarly, step ST64 to step ST73 correspond to each of step ST5 to step ST14, and a description thereof will be omitted. At that time, the first image forming unit 101 and the second image forming unit 102 should be read as the color printer 80, the fixing devices 17a and 17b should be read as the fixing device 17, and the registration roller 23 should be read as the registration roller 11. .

  As described above, according to the image forming apparatus as the second embodiment, the first image forming unit 101 and the second image forming unit 102 are the same color printer 80, and the downstream side of the sheet conveying path 13 is provided. Since a twist-type paper front / back twist unit 103 is mounted (connected) and the downstream paper transport path 13 joins the upstream paper transport path 13 of the color printer 80, a structure other than the series tandem type is adopted. In the image forming apparatus 200 having the double-sided image forming function, the paper P on which the single-sided image is formed that is retracted and placed in the paper stack unit 32 can be used after the jam processing when the paper conveyance abnormality is detected.

  The present invention forms an image on one side of a sheet, then reverses the front and back of the sheet by a twisting method, and forms an image on the other side of the sheet with the front and back reversed. The present invention is extremely suitable when applied to a printer, a copying machine, or a multifunction machine.

1Y, 1M, 1C, 1K Photosensitive drum 2Y, 2M, 2C, 2K Charging unit 3Y, 3M, 3C, 3K Optical writing unit 4Y, 4M, 4C, 4K Developing device 6 Intermediate transfer belt 7A Secondary transfer unit 7Y, 7M , 7C, 7K Primary transfer unit 8A, 8Y, 8M, 8C, 8K Cleaning unit 10Y, 10M, 10C, 10K Image forming unit 11, 23 Registration roller 13 Paper transport path 15 Control unit 17, 17a, 17b Fixing device 22 Loop roller 25, 26 Paper discharge roller 31 Paper twisting part 32 Paper stacking part (paper retraction part)
33 First branch unit 34 Second branch unit 35 First branch switching unit 36 Second branch switching unit 41 Abnormality detection unit 48 Operation display unit 50 Overall control unit 51 First control unit 52 Second control unit 53 RAM (overall control unit) )
54 Memory part (overall control part)
55 CPU (overall control unit)
61 First paper transport unit 62 Second paper transport unit 80 Color printer (image forming unit)
80a First print engine (image forming unit)
80b Second print engine (image forming unit)
DESCRIPTION OF SYMBOLS 100 Double-sided image forming apparatus 101 1st image forming part 102 2nd image forming part 103 Paper front / back twist unit 200 Image forming apparatus

Claims (7)

A first image forming unit that forms an image on one side of the paper;
A torsion type paper reversing unit for reversing the front and back of the paper on which an image is formed by the first image forming unit;
A second image forming unit that forms an image on the other side of the paper whose front and back are reversed by the paper reversing unit;
A paper evacuation section provided with a conveyance evacuation path that branches off from a paper conveyance path from the paper reversing section to the second image forming section when a paper conveyance abnormality occurs and can retreat the paper after the front and back are reversed; ,
An image forming apparatus comprising: The paper evacuation unit is
It has a non-inversion path for joining the paper after reversing the front and back that has been retreated to the conveyance retreat path to the paper conveyance path to the second image forming unit without passing through the paper reversing unit. The image forming apparatus according to claim 1.   3. The image forming apparatus according to claim 2, further comprising a first branch switching unit that branches a sheet conveyance path from the first image forming section to the sheet reversing section to the non-reversing path. An abnormality detection unit that detects a paper conveyance abnormality in the paper conveyance path and a paper conveyance path downstream of the second image forming unit; and
A second branch switching unit for branching a sheet conveyance path from the sheet reversing unit to the second image forming unit to the conveyance retraction path;
The image forming apparatus according to claim 1, further comprising:   When the abnormality detection information is input from the abnormality detection unit and a paper conveyance abnormality is detected by the abnormality detection unit, the second reversal is performed so that the paper after reversing the front and back is switched from the paper conveyance path to the conveyance retraction path. The image forming apparatus according to claim 4, further comprising a control unit that controls the branch switching unit. The controller is
In a case where the image forming job that constitute form images corresponding to a plurality of pages into a plurality of sheet is set,
When a conveyance abnormality is detected by the abnormality detection unit on a sheet of a page in the middle of executing the image forming job,
After removing the sheet of the page where the conveyance abnormality is detected, the image of the page is re-formed on a new sheet by the first image forming unit,
After reversing the front and back of the paper after re-formation, and transporting the paper after reversing the front and back to the second image forming unit,
6. The image forming apparatus according to claim 5, wherein the sheets that have been turned upside down that are retracted in the transport retracting unit are transported in order from the transport retracting unit to the second image forming unit. The first image forming unit and the second image forming unit are the same image forming unit,
The paper reversing unit is connected to a paper transport path downstream of the image forming unit;
The image forming apparatus according to claim 1, wherein the sheet conveyance path on the downstream side of the sheet reversing unit joins the sheet conveyance path on the upstream side of the image forming unit.

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