JP4844248B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  As one of conventional techniques related to an image forming apparatus such as a copying machine or a printer that forms an image on a sheet by an electrophotographic method, for example, Patent Document 1 discloses that an image-formed sheet heated by a fixing device is discharged. In order to prevent image defects (image unevenness, image peeling, etc.) due to the fusion of the developer on the paper loaded on the discharge tray, the paper discharge time may be temporarily delayed or Techniques have been proposed in which the rotational drive is temporarily stopped, the interval between sheets is increased, or the length of the discharge path is changed.

JP 2003-248349 A

  An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of an image defect due to fusion of a developer when discharging a sheet on which an image has been formed.

The image forming apparatus according to claim 1, wherein an image is formed by an image forming unit that forms an image on a sheet, a sheet discharging unit that discharges a sheet on which an image is formed by the image forming unit, and the image forming unit. A plurality of branch conveyance paths provided on a discharge conveyance path for guiding the discharged paper to the sheet discharge means, and a conveyance path switching means for switching the path of the sheet sent to the discharge conveyance path between the plurality of branch conveyance paths; a sheet transport members provided in the plurality of branch conveying path, when the length of the paper on which the image is formed is less than half the maximum sheet length, the sheet to the plurality of branched transport path 2 with temporarily stopping capture one by sheets, to deliver the paper by two sheets to the sheet discharge means from said plurality of branched transport path according to the captured sequence, wherein said transport path switching means paper It is characterized in further comprising a conveyance control means for controlling the operation of the feed member.

  According to the image forming apparatus of the first aspect, when the sheet on which the image is formed by the image forming unit is guided to the sheet discharging unit through the discharge conveying path, the image forming apparatus does not reduce the productivity of image formation. Thus, it is possible to secure a long cooling time for the paper. For this reason, when the paper on which the image has been formed is discharged, it is possible to prevent image defects due to the fusion of the developer.

  According to the image forming apparatus of the second aspect, when the length of the sheet to be image-formed is half or less of the maximum sheet length, the cooling time of the sheet is ensured longer on the discharge conveyance path. Can do.

  Hereinafter, specific embodiments in which the present invention is applied to a color image forming apparatus will be described in detail with reference to the drawings. The present invention can be applied not only to a color image forming apparatus but also to a black and white image forming apparatus.

  FIG. 1 is a schematic diagram showing the overall configuration of a color image forming apparatus to which the present invention is applied. The illustrated color image forming apparatus 1 forms an image on a sheet by an electrophotographic method, and generally includes an image reading device 2, an image forming unit 3, and a sheet conveying device 4.

  The image reading device 2 reads an image of a document placed on a transparent document table (platen glass). The image reading device 2 includes, for example, an optical scanning system including a lamp, a mirror, a carriage, and the like, a lens system that forms an optical image read and scanned by the optical scanning system, and an optical image formed by the lens system. An image reading sensor that receives an image and converts it into an electrical signal is provided.

  The image forming unit 3 includes four photosensitive drums 5, 6, 7, and 8 corresponding to K (black), Y (yellow), M (magenta), and C (cyan), and each photosensitive drum. A four-tandem structure including four corresponding primary transfer rolls 9, 10, 11, 12, an intermediate transfer belt 13, a secondary transfer roll 14, a vacuum transport unit 15, and a fixing device 16 is provided. ing.

  A charging device, an image writing device, a developing device, a cleaner, and the like are disposed around each of the photosensitive drums 5, 6, 7, and 8. The charging device uniformly charges the surface of the photosensitive drum, and the image writing device forms an electrostatic latent image by scanning the surface of the photosensitive drum charged by the charging device with a laser beam. . The developing device supplies toner as a developer to the surface of the photosensitive drum to visualize (develop) the electrostatic latent image to form a toner image. The cleaner remains on the photosensitive drum after development. Unnecessary toner is removed.

  On the other hand, the primary transfer rolls 9, 10, 11, and 12 are arranged in opposition to each other in the vicinity of the corresponding photosensitive drums 5, 6, 7, and 8 via the intermediate transfer belt 13. . These primary transfer rolls 9, 10, 11, and 12 transfer (primary transfer) the toner images formed on the photosensitive drums 5, 6, 7, and 8 onto the intermediate transfer belt 13 as described above. is there. The intermediate transfer belt 13 is supported in a loop by a plurality of (five in the illustrated example) belt support rolls.

  The secondary transfer roll 14 is disposed so as to face the intermediate transfer belt 13. The secondary transfer roll 14 transfers (secondary transfer) the toner image formed on the intermediate transfer belt 13 to a sheet (sheet) as described above. The transfer position (secondary transfer position) of the toner image ) Is an image transfer position in the image forming unit 3. The vacuum conveyance unit 15 conveys the sheet on which the toner image is transferred by the secondary transfer roll 14 to the fixing device 16. The fixing device 16 fixes the toner image on the paper by heating and pressing.

  On the other hand, the paper transport device 4 is a paper selected by a user operation among the papers stored in the first paper storage unit 17, the second paper storage unit 18, and the third paper storage unit 19. Each of the sheets selected by the automatic sheet selection function is conveyed along a predetermined route. In the vicinity of each of the paper storage units 17, 18, and 19, corresponding feeding rolls 20, 21, and 22 are disposed. Each of the delivery rolls 20, 21, and 22 sandwiches the called paper one by one from the corresponding paper storage units 17, 18, and 19 to temporarily stop the paper on the paper conveyance path and generate a predetermined start signal. The paper is sent to the downstream side in the paper transport direction at the timing based on the timing. An operation panel 23 that is operated by a user is provided in the vicinity of the image reading apparatus 2.

  Here, the sheet transport path having each of the sheet storage units 17, 18, and 19 as the starting point of the sheet transport and the discharge sheet stacking storage unit 24 as the end point of the sheet transport is configured by a plurality of sheet transport paths R1 to R5. Yes. On the paper transport paths R1 to R5, transport rolls are arranged at predetermined intervals. The paper stored in the first paper storage unit 17 is sent out by the feed roll 20 and then sent to the merging transport unit 25 via the first paper transport path R1. The paper stored in the second paper storage unit 18 is sent out by the feed roll 21 and then sent to the merging transport unit 25 via the first paper transport path R1. On the other hand, the paper stored in the third paper storage unit 19 is sent directly to the merging / conveying unit 25 by the delivery roll 22.

  The sheet sent to the merging / conveying section 25 is sent to the image transfer position in the image forming section 3 through the second sheet conveying path R2. Further, the sheet that has passed the image transfer position is sent to the fixing device 16 by the vacuum conveyance unit 15 and then discharged to the discharge sheet stacking and accommodating unit 24 via the third sheet conveyance path R3. On the other hand, the sheet on which images are formed on both sides (the first side and the second side) passes through the fixing device 16 and then is sent to the double-side reversing unit 28 via the fourth sheet conveyance path R4. Then, after being turned upside down, the paper is again fed into the merging and conveying unit 25 via the fifth sheet conveying path R5.

  In such sheet conveyance paths R1 to R5, the posture correction unit 26 and the registration roll 27 are arranged in the second sheet conveyance path R2. The posture correction unit 26 is a portion that corrects the posture (such as skew correction) of the paper transported through the second paper transport path R2. The registration roll 27 is composed of a pair of rolls that come into contact with each other with a predetermined pressure. The registration roll 27 feeds the paper to the image transfer position by rotating the pair of rolls while sandwiching the paper between the pair of rolls. .

  When the sheet is fed by the registration roll 27, the timing of the sheet reaching the image transfer position is adjusted by a timing adjusting unit (not shown). The timing adjustment means, for example, by changing (shift control) the sheet conveyance speed by the registration roll 27 based on the timing at which a registration sensor (not shown) provided upstream of the registration roll 27 detects the passage of the sheet. The arrival timing of the paper at the image transfer position is adjusted in accordance with the arrival timing of the toner image at the image transfer position.

  The third paper conveyance path R3 is a discharge conveyance path for discharging the image-formed paper formed in the portion from the fixing device 16 to the discharge paper stacking and accommodating portion 24. Accordingly, the sheet on which the image is formed by the image forming unit 3 is guided to the discharged sheet stacking and storing unit 24 through the third sheet transport path R3. A branch conveyance unit 29 is provided on the third sheet conveyance path R3. Further, a curl correction unit 30 is provided on the fifth paper transport path R5. The curl correction unit 30 corrects paper curl.

  Next, the operation of the color image forming apparatus 1 having the above configuration will be described. First, when an image of a document is read by the image reading device 2, a toner image is formed by the image forming unit 3 based on an image signal obtained thereby. In this image forming unit 3, while rotating the four photosensitive drums 3, 4, 5 and 6, the photosensitive drums 5, 6, 7 and 8 are respectively charged by the charging device, the image writing device and the developing device corresponding thereto. K, Y, M, and C toner images are sequentially formed on the surface. The toner images of the respective colors formed in this manner are sequentially transferred onto the intermediate transfer belt 13 by the primary transfer rolls 9, 10, 11, and 12. As a result, a multicolor (full color) toner image in which four color toners are superimposed is formed on the intermediate transfer belt 13. The toner image formed on the intermediate transfer belt 13 in this way is held on the intermediate transfer belt 13 and sent to the image transfer position (secondary transfer position).

  On the other hand, the paper in the paper storage unit selected by the user using the operation panel 23 or the paper in the paper storage unit selected by the automatic selection function is registered by the registration roll 27 in accordance with the timing at which the toner image reaches the image transfer position. It is sent. For example, if the paper storage unit selected as described above is the first paper storage unit 17, the paper fed by the feed roll 20 is transferred to the merging transport unit 25 via the first paper transport path R1. Then, the sheet is further fed to the image transfer position by the registration roll 27 via the second sheet conveyance path R2.

  As a result, at the image transfer position of the image forming unit 3, the toner image (color image) held on the intermediate transfer belt 13 is collectively transferred (secondary transfer) onto the sheet by the secondary transfer roll 14. Thereafter, the sheet is sent to the fixing device 16 by the vacuum conveyance unit 15, where the toner image is fixed, and then discharged to the discharged sheet stacking unit 24 via the third sheet conveyance path R3. At that time, the sheet is sent to the discharge roll 32 through the branch conveyance unit 29 provided on the third sheet conveyance path R 3, and is discharged to the discharge sheet stacking / accommodating unit 24 by the rotation of the discharge roll 32. Further, the sheets discharged by the discharge roll 32 are stacked and stored in order on the discharged sheet stacking and storing unit 24. At this time, the position of the discharged paper stacking and storing unit 24 is controlled so as to gradually move downward as the stacking height of the sheets stored in the discharged paper stacking and storing unit 24 increases.

  On the other hand, the paper on which image formation is performed on both sides is sent from the fixing device 16 to the double-side reversing unit 28 via the fourth paper conveyance path R4, where the paper is reversed and sent to the fifth paper conveyance path R5. It is done. Thereafter, the sheet is transported along the fifth sheet transport path R5, and then is abutted against a feed roll 31 provided near the end of the sheet transport path R5, and temporarily stops. Then, the sheet is fed again into the merging / conveying section 25 by the rotation of the feeding roll 31 based on a predetermined restart signal. Thereafter, the toner image is transferred and fixed on the paper in the same procedure as described above, and then the paper is discharged to the discharged paper stacking storage section 24 via the third paper transport path R3. Further, when the image-formed paper is reversed and discharged, the paper is once sent from the fixing device 16 to the fourth paper transport path R4, and then the third paper transport is performed by the reversing operation of the paper reversing unit 33. By feeding the sheet to the path R3, the sheet is discharged to the discharged sheet stacking storage unit 24 via the third sheet transport path R3. At that time, the sheet is fed to the discharge roll 32 through the branch conveyance unit 29 provided in the middle of the third sheet conveyance path R 3, and is discharged to the discharge sheet stacking and storing unit 24 by the rotation of the discharge roll 32.

[First Embodiment]
FIG. 2 is a schematic diagram illustrating a configuration example of the branch conveyance unit 29 according to the first embodiment of the present invention. The branch transport unit 29 is provided with two branch transport paths 34 and 35. The two branch conveyance paths 34 and 35 are provided on a third sheet conveyance path R3 extending from the fixing device 16 to the discharged sheet stacking storage unit 24. The discharge roll 32 is disposed at the end of the third paper transport path R3 in the paper transport direction. Each of the branch conveyance paths 34 and 35 branches from a first position (hereinafter referred to as a “branch position”) P1 on the third sheet conveyance path R3, and a second position (on the downstream side of the branch position P1 ( Hereinafter, “merge position”) P2 merges. The branch position P1 is set on the downstream side of the fixing device 16 and on the downstream side of the joining position of the sheets fed from the reverse conveying unit 33. The merge position P <b> 2 is set on the upstream side of the discharge roll 32. The conveyance path lengths of the respective branch conveyance paths 34 and 35 are set to the same length. Further, the length of the conveyance path of each of the branch conveyance paths 34 and 35 is set to be equal to or longer than the maximum sheet length. The maximum paper length refers to the maximum paper length that can be handled by the color image forming apparatus 1. The length of the paper refers to the size of the paper in the paper transport direction.

  On one branch conveyance path (hereinafter, referred to as “first branch conveyance path”) 34, two branch conveyance rolls 36 and 37 are arranged at a predetermined interval in the sheet conveyance direction. Similarly, on the other branch conveyance path (hereinafter referred to as “second branch conveyance path”) 35, two branch conveyance rolls 38 and 39 are arranged at a predetermined interval in the sheet conveyance direction. The branch transport rolls 36 and 37 transport paper along the first branch transport path 34, and the branch transport rolls 38 and 39 transport paper along the second branch transport path 35. . On the first branch transport path 34, the branch transport roll 36 (hereinafter referred to as “first branch transport roll”) is upstream of the branch transport roll (hereinafter referred to as second branch transport roll) 37. Arranged on the side. On the second branch transport path 35, a branch transport roll (hereinafter referred to as “third branch transport roll”) 38 is from a branch transport roll (hereinafter referred to as fourth branch transport roll) 29. Is also arranged upstream.

  Further, on the third paper transport path R3, a paper passage sensor 40 is disposed on the upstream side of the branch position P1. The sheet passage sensor 40 detects the passage of the sheet fed from the fixing device 16 or the sheet reversing unit 33 to the branch conveyance unit 29 through the third sheet conveyance path R3 on the upstream side from the branch position P1.

  The paper passage sensor 40 is configured using, for example, a photosensor having a light emitting element and a light receiving element, and the output signal of the sensor is turned on when the leading edge of the paper passes the detection position (sensor optical axis) of the sensor. The output signal of the sensor is switched from the off state to the on state when the rear end of the sheet passes the detection position of the sensor. Therefore, whether or not the leading edge of the sheet has passed the detection position of the sensor on the third sheet conveyance path R3 can be determined by whether or not the output signal of the sensor has been switched from the on state to the off state. Further, whether or not the trailing edge of the sheet has passed the detection position of the sensor on the third sheet conveyance path R3 can be determined by whether or not the output signal of the sensor has been switched from the off state to the on state.

  Further, on the third paper transport path R3, a transport path switching member 41 is provided at the branch position P1. The conveyance path switching member 41 is configured so that the path of the sheet fed to the branch conveyance unit 29 through the third sheet conveyance path R3 is between the first branch conveyance path 34 and the second branch conveyance path 35. It switches to the branch conveyance path. For this reason, in a state where the conveyance path switching member 41 switches the paper path to the first branch conveyance path 34, the sheet fed into the third sheet conveyance path R3 is moved from the branch position P1 to the first branch conveyance path 34. Led to. Further, in a state in which the transport path switching member 41 switches the paper path to the second branch transport path 35, the paper fed into the third paper transport path R3 is transferred from the branch position P1 to the second branch transport path 35. Led.

  A paper passage sensor 42 is provided in the first branch conveyance path 34, and a paper passage sensor 43 is provided in the second branch conveyance path 35. The paper passage sensor 42 is provided on the first branch conveyance path 34 in the middle of the conveyance path from the second branch conveyance roll 37 to the joining position P2. The paper passage sensor 43 is provided on the second branch transport path 35 in the middle of the transport path from the fourth branch transport roll 39 to the joining position P2. Each of the paper passage sensors 42 and 43 is configured using, for example, a photosensor in the same manner as the paper detection sensor 40.

  FIG. 3 is a block diagram showing a schematic configuration of a control system of the image forming apparatus according to the first embodiment of the present invention. The main control unit 50 controls the overall processing operation of the image forming apparatus 1. The main control unit 50 is largely configured to include an image formation control unit 51 and a sheet conveyance control unit 52. The image forming control unit 51 mainly controls the image forming operation by the image forming unit 3. The paper transport control unit 52 mainly controls the paper transport operation by the paper transport device 4.

  The paper transport control unit 52 includes the above-described paper passage sensors 40, 42, 43, the discharge roll 32, the first branch transport roll 36, the second branch transport roll 37, and the third branch transport roll 38. And the 4th branch conveyance roll 39 and the conveyance path switching member 41 are connected. As a result, the output signals of the paper passage sensors 40, 42, and 43 are individually taken into the paper conveyance control unit 52. The rotation operation of the discharge roll 32 and each of the branch conveyance rolls 36 to 39 is individually controlled by the paper conveyance control unit 52, and the conveyance path switching operation by the conveyance path switching member 41 is also controlled by the paper conveyance control unit 52. It is the composition which becomes. In FIG. 3, among the components of the sheet conveying device 4, in particular, components for conveying the sheet on the third sheet conveying path R <b> 3 are extracted and displayed, and other components are displayed. Is omitted.

  In the image forming apparatus according to the first embodiment of the present invention, when the image forming conditions applied to the image forming process satisfy a predetermined condition that is set in advance and when the predetermined condition is not satisfied, the sheet is conveyed. The applied paper transport process changes. Whether the image forming condition satisfies a predetermined condition is determined by the main control unit 50 according to a procedure as shown in FIG. 19, for example.

  As a criterion for determination, whether the paper type is an OHP sheet (step S101), whether the paper type is thick paper (step S102), or a job for forming an image on both sides of the paper (step S103). The determination steps such as whether the density of the image is equal to or higher than the predetermined density (step S104) and whether the number of formed images is equal to or higher than the predetermined number (step S105) are combined. When the image forming condition satisfies the predetermined condition (Yes in step S105), the first sheet conveying process is applied and the sheet conveying control unit 52 controls the sheet conveying so that the image forming condition is predetermined. If the above condition is not satisfied (No in Step S103, Step S104, or Step S105), the second paper transport process is applied and the paper transport control unit 52 controls the transport of the paper. .

  FIGS. 4 to 6 are schematic views of the image forming apparatus according to the first embodiment of the present invention. When the sheet fed to the branch conveyance unit 29 through the third sheet conveyance path R3 is discharged to the discharge sheet stacking storage unit 24, FIGS. 6 is a flowchart illustrating a procedure of a first paper conveyance process performed by a paper conveyance control unit. The contents of the second paper transport process will be described after the procedure of the first paper transport process is described.

  First, the paper conveyance control unit 52 determines whether or not the leading edge of the paper has passed the detection position of the paper passage sensor 40 while monitoring the output signal of the paper passage sensor 40 (step S1). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the first branch conveyance path 34 by the operation of the conveyance path switching member 41. (Step S2), rotation of the first branch transport roll 36 and the second branch transport roll 37 is started (Step S3).

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed the detection position of the paper passage sensor 42 while monitoring the output signal of the paper passage sensor 42 (step S4). When it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 42, the sheet conveyance control unit 52 determines that the first branch conveying roll 36 and the second branching roller 36 and the second branching roller 52 before the leading edge of the sheet reaches the merging position P2. The rotation of the branch conveyance roll 37 is stopped (step S5). As a result, as shown in FIG. 7A, the first sheet 46-1 stops in a state where it is taken into the first branch conveyance path.

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed the detection position of the paper passage sensor 40 while monitoring the output signal of the paper passage sensor 40 (step S6). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the second branch conveyance path 34 by the operation of the conveyance path switching member 41. (Step S7), rotation of the third branch transport roll 38 and the fourth branch transport roll 39 is started (Step S8).

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed through the detection position of the paper passage sensor 43 while monitoring the output signal of the paper passage sensor 43 (step S9). When it is determined that the leading edge of the sheet has passed through the detection position of the sheet passage sensor 43, the sheet conveyance control unit 52 determines whether the third branch conveying roll 38 and the fourth branch roller 38 are in contact with each other before the leading edge of the sheet reaches the merging position P2. The rotation of the branch conveyance roll 39 is stopped (step S10). Accordingly, as shown in FIG. 7B, the second sheet 46-2 stops in a state where it is taken into the second branch conveyance path 35.

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed the detection position of the paper passage sensor 40 while monitoring the output signal of the paper passage sensor 40 (step S11). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the first branch conveyance path 34 by the operation of the conveyance path switching member 41. (Step S12), rotation of the first branch transport roll 36, the second branch transport roll 37, and the discharge roll 32 is started (Step S13).

  As a result, as shown in FIG. 8A, the first sheet 46-1 is sent out from the first branch conveyance path 34 toward the discharge roll 32, and then discharged by rotation of the discharge roll 32. It is discharged to the loading storage unit 24. In addition, the third sheet 46-3 is taken into the first branch conveyance path 34 in the form of being replaced with the first sheet 46-1. At this time, the conveyance speed of the first sheet 46-1 between the first branch conveyance path 34 and the conveyance roll 32 may be reduced to a speed at which it does not contact the third sheet 46-3.

  Next, the paper conveyance control unit 52 determines whether or not the leading edge of the paper has passed the detection position of the paper passage sensor 42 while monitoring the output signal of the paper passage sensor 42 (step S14). When it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 42, the sheet conveyance control unit 52 determines that the first branch conveyance roll 36, the second branching roller 36, and the second branching roller 36 before the leading edge of the sheet reaches the merge position P2. The rotation of the branch conveyance roll 37 and the discharge roll 32 is stopped (step S15). As a result, the third sheet 46-3 stops in a state of being taken into the first branch conveyance path 34.

  Next, the sheet conveyance control unit 52 determines whether or not the sheet stopped on the first branch conveyance path 34 in step S15 is the last sheet (step S16). The last sheet refers to the last sheet on which an image is formed by one image forming process (image forming job). For example, when the color image forming apparatus 1 forms an image on 100 sheets in one image forming process, the 100th sheet is the last sheet.

  If it is determined in step S16 that the sheet is not the last sheet, the sheet conveyance control unit 52 determines whether the leading edge of the sheet has passed the detection position of the sheet passage sensor 40 while monitoring the output signal of the sheet passage sensor 40. (Step S17). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the second branch conveyance path 35 by the operation of the conveyance path switching member 41. (Step S18), rotation of the third branch transport roll 38, the fourth branch transport roll 39, and the discharge roll 32 is started (Step S20).

  As a result, as shown in FIG. 8B, the second sheet 46-2 is sent out from the second branch conveyance path 35 toward the discharge roll 32, and then discharged by the rotation of the discharge roll 32. It is discharged to the loading storage unit 24. Further, the fourth sheet 46-4 is taken into the second branch conveyance path 35 in the form of being replaced with the second sheet 46-2. At this time, the conveyance speed of the second sheet 46-2 between the second branch conveyance path 35 and the conveyance roll 32 may be reduced to a speed at which the second sheet 46-4 does not contact the fourth sheet 46-4.

  Next, the paper conveyance control unit 52 determines whether or not the leading edge of the paper has passed through the detection position of the paper passage sensor 43 while monitoring the output signal of the paper passage sensor 43 (step S20). When it is determined that the leading edge of the sheet has passed through the detection position of the sheet passage sensor 43, the sheet conveyance control unit 52 determines that the third branch conveying roll 38, the fourth branching roller 38, and the fourth branch roller before the leading edge of the sheet reaches the joining position P2. The rotation of the branch conveyance roll 39 and the discharge roll 32 is stopped (step S21). As a result, the fourth sheet 46-4 stops in a state of being taken into the second branch conveyance path 35.

  Next, the sheet conveyance control unit 52 determines whether or not the sheet stopped on the second branch conveyance path 35 in step S21 is the last sheet (step S22). If it is determined in step S22 that the sheet is not the last sheet, the process returns to step S11 and the conveyance of the fifth and subsequent sheets is continued.

  On the other hand, if it is determined in step S16 that the sheet is the last sheet, the sheet conveyance control unit 52 rotates the third branch conveyance roll 38, the fourth branch conveyance roll 39, and the discharge roll 32 to perform the second branch conveyance. After the sheet is discharged from the path 35 to the discharged sheet stacking / accommodating section 24 (step S23), the first branch transport path 36, the second branch transport roll 37, and the discharge roll 32 are rotated to rotate the first branch transport path 34. The paper is discharged to the discharged paper stacking / accommodating section 24 (step S24), and a series of processing is completed.

  If it is determined in step S22 that the sheet is the last sheet, the sheet conveyance control unit 52 rotates the first branch conveyance roll 36, the second branch conveyance roll 37, and the discharge roll 32 to rotate the first branch conveyance. After discharging the sheet from the path 34 to the discharged sheet stacking / accommodating section 24 (step S25), the third branch transport roll 38, the fourth branch transport roll 39, and the discharge roll 32 are rotated to rotate the second branch transport path 35. The paper is discharged to the discharged paper stacking storage unit 24 (step S26), and a series of processing is completed.

  On the other hand, when the sheet conveyance control unit 52 controls the conveyance of the sheet by applying the second sheet conveyance process, the sheet path is fixed by the conveyance path switching member 41 and the first branch conveyance path 34 is fixed. In this state, the sheet that has passed the detection position of the sheet detection sensor 40 is always guided to the first branch conveyance path 34 and the sheet is not temporarily stopped on the first branch conveyance path 34 (in other words, Then, the first branch transport roll 36, the second branch transport roll 37, and the discharge roll 32 are continuously rotated), and the discharge paper stacking storage section is passed from the first branch transport path 34 via the discharge roll 32. The paper is discharged to 24.

[Second Embodiment]
FIG. 9 is a schematic diagram illustrating a configuration example of the branch conveyance unit 29 according to the second embodiment of the present invention. FIG. 10 is a block diagram showing a schematic configuration of a control system of the image forming apparatus according to the second embodiment of the present invention. In the second embodiment of the present invention, compared to the first embodiment, a paper passage sensor 44 is additionally provided in the first branch conveyance path 34 in addition to the paper passage sensor 42, and the paper passage sensor 44 is provided. Is connected to the conveyance control unit 52, and a sheet passage sensor 45 is additionally provided in the second branch conveyance path 35 in addition to the sheet passage sensor 43, and the sheet passage sensor 45 is connected to the conveyance control unit 52. Is different.

  The paper passage sensor 42 is provided in the middle of the conveyance path from the branch conveyance roll 37 to the joining position P2 on the first branch conveyance path 34, and the paper passage sensor 44 passes the paper on the first branch conveyance path 34. It is provided on the upstream side of the sensor 42 and in the middle of the transport path from the branch transport roll 36 to the branch transport roll 37. Further, the paper passage sensor 42 is disposed upstream of the merging position P2 in the paper transport direction, and the paper passage sensor 44 is disposed upstream of the intermediate point of the first branch transport path 34 in the paper transport direction. ing.

  On the other hand, the sheet passage sensor 43 is provided in the middle of the conveyance path from the branch conveyance roll 39 to the joining position P2 on the second branch conveyance path 35, and the sheet passage sensor 45 is disposed on the second branch conveyance path 35. It is provided on the upstream side of the paper passage sensor 43 and in the middle of the transport path from the branch transport roll 38 to the branch transport roll 39. Further, the paper passage sensor 43 is arranged upstream of the merging position P2 in the paper conveyance direction, and the paper passage sensor 45 is arranged upstream of the intermediate point of the second branch conveyance path 35 in the paper conveyance direction. ing.

  In the image forming apparatus according to the second embodiment of the present invention, as in the first embodiment, the image forming condition applied to the image forming process satisfies the predetermined condition and the predetermined condition. If the condition is not satisfied, the sheet conveyance process applied to the sheet conveyance changes. Further, when the image forming condition satisfies a predetermined condition, and the length of the sheet to be image formed (paper feeding target) exceeds half of the maximum sheet length, it is described in the first embodiment. The sheet conveyance control unit 52 controls the conveyance of the sheet by applying the first sheet conveyance process. If the length of the sheet to be image-formed is less than or equal to half the maximum sheet length, the first sheet conveyance process is performed. The sheet conveyance control unit 52 controls sheet conveyance by applying a third sheet conveyance process different from the one sheet conveyance process.

  Incidentally, the case where the length of the sheet to be image-formed exceeds half of the maximum sheet length is, for example, the maximum sheet length is equivalent to the A3 longitudinal dimension = 420 mm and the length of the sheet to be image-formed is set. Is equivalent to A4 longitudinal dimension = 297 mm. Further, the case where the length of the sheet to be image formed exceeds half of the maximum sheet length is, for example, the maximum sheet length is equivalent to the A3 longitudinal dimension = 420 mm, and the length of the sheet to be image formed is Is equivalent to A4 short dimension = 210 mm.

  The length of the sheet to be image-formed is set, for example, by providing a sheet passage sensor on the second sheet conveyance path R2 upstream from the image transfer position, and this sheet passage sensor detects the passage of the leading edge of the sheet. May be detected by measuring the time from when the trailing edge is detected until the trailing edge is detected, or the paper sheets 17, 18, and 19 that store sheets used for image formation may be individually set. You may detect based on attribute information (paper size information).

  FIGS. 11 to 14 are schematic views of the image forming apparatus according to the second embodiment of the present invention, when discharging the sheet fed to the branch conveyance unit 29 through the third sheet conveyance path R3 to the discharge sheet stacking unit 24. 10 is a flowchart illustrating a procedure of a third paper transport process performed by the paper transport control unit 52.

  First, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed through the detection position of the paper passage sensor 40 while monitoring the output signal of the paper passage sensor 40 (step S31). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the first branch conveyance path 34 by the operation of the conveyance path switching member 41. (Step S32), rotation of the first branch transport roll 36 and the second branch transport roll 37 is started (Step S33).

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed the detection position of the paper passage sensor 42 while monitoring the output signal of the paper passage sensor 42 (step S34). If it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 42, the sheet conveyance control unit 52 stops the rotation of the second branch conveyance roll 37 after T1 (sec) (step S35). T1 (sec) is a time set in advance so that the leading edge of the paper that has passed the detection position of the paper passage sensor 42 stops at a position slightly upstream of the merging position P2. As a result, as shown in FIG. 15A, the first sheet 46-1 stops in a state where it is taken into the downstream side of the first branch conveyance path.

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed the detection position of the paper passage sensor 44 while monitoring the output signal of the paper passage sensor 44 (step S36). When it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 44, the sheet conveyance control unit 52 stops the rotation of the first branch conveyance roll 36 after T2 (sec) (step S37). T2 (sec) is a time set in advance so that the leading edge of the paper that has passed the detection position of the paper passage sensor 44 stops at a position slightly upstream of the intermediate point of the first branch conveyance path 34. . As a result, as shown in FIG. 15B, the second sheet 46-2 stops in a state where it is taken into the upstream side of the first branch conveyance path. Therefore, the first sheet 46-1 and the second sheet 46-2 are taken into the first branch conveyance path 34 in a line.

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed through the detection position of the paper passage sensor 40 while monitoring the output signal of the paper passage sensor 40 (step S38). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the second branch conveyance path 35 by the operation of the conveyance path switching member 41. (Step S39), rotation of the third branch transport roll 38 and the fourth branch transport roll 39 is started (Step S40).

  Next, the paper conveyance control unit 52 determines whether the leading edge of the paper has passed the detection position of the paper passage sensor 43 while monitoring the output signal of the paper passage sensor 43 (step S41). When it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 43, the sheet conveyance control unit 52 stops the rotation of the fourth branch conveyance roll 39 after T3 (sec) (step S42). T3 (sec) is a time set in advance so that the leading edge of the paper that has passed the detection position of the paper passage sensor 43 stops at a position slightly upstream of the merging position P2. Accordingly, as shown in FIG. 16A, the third sheet 46-3 stops in a state where it is taken in the downstream side of the second branch conveyance path 35.

  Next, the paper conveyance control unit 52 determines whether or not the leading edge of the paper has passed the detection position of the paper passage sensor 45 while monitoring the output signal of the paper passage sensor 45 (step S43). If it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 45, the sheet conveyance control unit 52 stops the rotation of the third branch conveyance roll 38 after T4 (sec) (step S44). T4 (sec) is a time set in advance so that the leading edge of the paper that has passed the detection position of the paper passage sensor 45 stops at a position slightly upstream of the intermediate point of the second branch conveyance path 35. . Accordingly, as shown in FIG. 16B, the fourth sheet 46-4 stops in a state where it is taken in the upstream side of the second branch conveyance path 35. Therefore, the third branch sheet 46-3 and the fourth sheet 46-4 are taken into the second branch transport path 35 in a line.

  Next, the paper conveyance control unit 52 determines whether or not the leading edge of the paper has passed the detection position of the paper passage sensor 40 while monitoring the output signal of the paper passage sensor 40 (step S45). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the first branch conveyance path 34 by the operation of the conveyance path switching member 41. (Step S46), rotation of the first branch transport roll 36, the second branch transport roll 37, and the discharge roll 32 is started (Step S47).

  Thus, as shown in FIG. 17A, after the first sheet 46-1 and the second sheet 46-2 are sent out from the first branch conveyance path 34 toward the discharge roll 32. Then, the paper is sequentially discharged to the discharge paper stacking and storing unit 24 by the rotation of the discharge roll 32. Further, the fifth sheet 46-5 is taken into the first branch conveyance path 34 in such a manner that the first sheet 46-1 and the second sheet 46-2 are replaced. At that time, the conveyance speed of the first sheet 46-1 and the second sheet 46-2 is brought into contact with the fifth sheet 46-5 between the first branch conveyance path 34 and the conveyance roll 32. It may be slowed down to a speed that does not.

  Next, the paper transport control unit 52 determines whether the leading edge of the next paper has passed through the detection position of the paper passage sensor 42 while monitoring the output signal of the paper passage sensor 42 (step S48). When it is determined that the leading edge of the next sheet has passed the detection position of the sheet passage sensor 42, the sheet conveyance control unit 52 stops the rotation of the second branch conveyance roll 37 after T1 (sec) (step S49). The “next sheet” described here means that when the rotation of the first branch transport roll 36, the second branch transport roll 37, and the discharge roll 32 is started in step S47, the first branch transport path 34 A sheet fed to the first branch conveyance path 34 from the branch position P1 following the two sheets fed to the discharge roll 32. As a result, the fifth sheet 46-5 stops in a state where it is taken in the downstream side of the first branch conveyance path 34.

  Next, the sheet conveyance control unit 52 determines whether or not the sheet stopped on the first branch conveyance path 34 in step S49 is the last sheet (step S50). If it is determined in step S50 that the sheet is not the last sheet, the sheet conveyance control unit 52 determines whether the leading edge of the sheet has passed the detection position of the sheet passage sensor 44 while monitoring the output signal of the sheet passage sensor 44. (Step S51). If it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 44, the sheet conveyance control unit 52 stops the rotation of the first branch conveyance roll 36 after T2 (sec) (step S52). Accordingly, as shown in FIG. 17B, the sixth sheet 46-6 stops in a state where it is taken in the upstream side of the first branch conveyance path 34. Therefore, the first branch conveyance path 34 is in a state where the fifth sheet 46-5 and the sixth sheet 46-6 are taken in a line.

  Next, the sheet conveyance control unit 52 determines whether or not the sheet stopped on the first branch conveyance path 34 in step S52 is the last sheet (step S53). If it is determined in step S53 that it is not the last sheet, the sheet conveyance control unit 52 determines whether the leading edge of the sheet has passed through the detection position of the sheet passage sensor 40 while monitoring the output signal of the sheet passage sensor 40. (Step S54). When it is determined that the leading edge of the paper has passed the detection position of the paper passage sensor 40, the paper conveyance control unit 52 switches the paper path to the second branch conveyance path 35 by the operation of the conveyance path switching member 41. (Step S55), the third branch transport roll 38, the fourth branch transport roll 39, and the discharge roll 32 are started to rotate (Step S56).

  As a result, as shown in FIG. 18A, after the third sheet 46-3 and the fourth sheet 46-4 are sent out from the second branch conveyance path 35 toward the discharge roll 32. Then, the paper is sequentially discharged to the discharge paper stacking and storing unit 24 by the rotation of the discharge roll 32. Further, the seventh sheet 46-7 is taken into the second branch conveyance path 35 in such a manner that the third sheet 46-3 and the fourth sheet 46-4 are replaced. At that time, the transport speed of the third sheet 46-3 and the fourth sheet 46-4 is brought into contact with the seventh sheet 46-7 between the second branch transport path 35 and the transport roll 32. It may be slowed down to a speed that does not.

  Next, the paper transport control unit 52 determines whether the leading edge of the next paper has passed through the detection position of the paper passage sensor 43 while monitoring the output signal of the paper passage sensor 43 (step S57). When it is determined that the leading edge of the next sheet has passed the detection position of the sheet passage sensor 43, the sheet conveyance control unit 52 stops the rotation of the fourth branch conveyance roll 39 after T3 (sec) (step S58). The “next sheet” described here means that when the rotation of the third branch transport roll 38, the fourth branch transport roll 39, and the discharge roll 32 is started in step S56, the second branch transport path 35 A sheet that is fed from the branch position P1 to the second branch conveyance path 35 following the two sheets fed to the discharge roll 32. As a result, the seventh sheet 46-7 stops in a state where it is taken into the downstream side of the second branch conveyance path 35.

  Next, the paper transport control unit 52 determines whether or not the paper stopped on the second branch transport path 35 in the above step S58 is the last paper (step S59). If it is determined in step S59 that the sheet is not the last sheet, the sheet conveyance control unit 52 determines whether the leading edge of the sheet has passed the detection position of the sheet passage sensor 45 while monitoring the output signal of the sheet passage sensor 45. (Step S60). When it is determined that the leading edge of the sheet has passed the detection position of the sheet passage sensor 45, the sheet conveyance control unit 52 stops the rotation of the third branch conveyance roll 38 after T4 (sec) (step S61). As a result, as shown in FIG. 18B, the eighth sheet 46-8 stops in a state where it is taken in the upstream side of the second branch conveyance path 35. Accordingly, the seventh paper 46-7 and the eighth paper 46-8 are taken into the second branch conveyance path 35 in a line.

  Next, the sheet conveyance control unit 52 determines whether or not the sheet stopped on the second branch conveyance path 35 in step S61 is the last sheet (step S62). If it is determined in step S62 that the sheet is not the last sheet, the process returns to step S45 to continue transporting the ninth and subsequent sheets.

  On the other hand, if it is determined in step S50 or step S53 that the sheet is the last sheet, the sheet conveyance control unit 52 rotates the third branch conveyance roll 38, the fourth branch conveyance roll 39, and the discharge roll 32 to rotate the second sheet. After the sheet is discharged from the branch conveyance path 35 to the discharged sheet stacking storage unit 24 (step S63), the first branch conveyance roll 36, the second branch conveyance roll 37, and the discharge roll 32 are rotated to form the first branch. The sheet is discharged from the conveyance path 34 to the discharged sheet stacking and storing unit 24 (step S64), and a series of processing is finished.

  If it is determined in step S59 or step S62 that the sheet is the last sheet, the sheet conveyance control unit 52 rotates the first branch conveyance roll 36, the second branch conveyance roll 37, and the discharge roll 32 to rotate the first sheet. After the sheet is discharged from the branch conveyance path 34 to the discharged sheet stacking storage unit 24 (step S65), the third branch conveyance roll 38, the fourth branch conveyance roll 39, and the discharge roll 32 are rotated to form the second branch. The paper is discharged from the conveyance path 35 to the discharged paper stacking / accommodating section 24 (step S66), and a series of processing is finished.

  In the first and second embodiments, the two branch transport paths 34 and 35 are provided in the middle of the third paper transport path R3. However, three or more branch transport paths may be provided. . Further, a cooling means (for example, a blower fan) for cooling the paper taken into each branch conveyance path may be provided.

1 is a schematic diagram illustrating an overall configuration of a color image forming apparatus to which the present invention is applied. It is the schematic which shows the structural example of the branch conveyance part which concerns on 1st Embodiment of this invention. 1 is a block diagram showing a schematic configuration of a control system of an image forming apparatus according to a first embodiment of the present invention. 6 is a flowchart (part 1) illustrating a procedure of a sheet conveyance process performed by the image forming apparatus according to the first embodiment of the present invention. 6 is a flowchart (No. 2) illustrating a procedure of a sheet conveyance process performed by the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is a flowchart (No. 3) illustrating a procedure of sheet conveyance processing performed by the image forming apparatus according to the first embodiment of the present invention. FIG. FIG. 3 is an image diagram (part 1) illustrating a flow of a sheet conveyance process performed by the image forming apparatus according to the first embodiment of the present invention. FIG. 6 is an image diagram (part 2) illustrating a flow of a sheet conveyance process performed in the image forming apparatus according to the first embodiment of the present invention. It is the schematic which shows the structural example of the branch conveyance part which concerns on 2nd Embodiment of this invention. It is a block diagram which shows schematic structure of the control system of the image forming apparatus which concerns on 2nd Embodiment of this invention. 10 is a flowchart (part 1) illustrating a procedure of a sheet conveyance process performed in an image forming apparatus according to a second embodiment of the present invention. 12 is a flowchart (No. 2) illustrating a procedure of a sheet conveyance process performed by the image forming apparatus according to the second embodiment of the present invention. 12 is a flowchart (No. 3) illustrating a procedure of a sheet conveying process performed by the image forming apparatus according to the second embodiment of the present invention. 12 is a flowchart (No. 4) illustrating a procedure of a sheet conveyance process performed by the image forming apparatus according to the second embodiment of the present invention. FIG. 9 is an image diagram (part 1) illustrating a flow of a sheet conveyance process performed in an image forming apparatus according to a second embodiment of the present invention. FIG. 9 is an image diagram (part 2) illustrating a flow of a sheet conveyance process performed in an image forming apparatus according to a second embodiment of the present invention. FIG. 12 is an image diagram (part 3) illustrating the flow of a sheet conveyance process performed by the image forming apparatus according to the second embodiment of the present invention. FIG. 14 is an image diagram (part 4) illustrating a flow of a sheet conveyance process performed by the image forming apparatus according to the second embodiment of the present invention. 6 is a flowchart illustrating a flow of processing for determining whether or not an image forming condition satisfies a predetermined condition when applying a paper conveyance process.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Color image forming apparatus, 3 ... Image forming part, 4 ... Paper conveying apparatus, 16 ... Fixing apparatus, 24 ... Discharged paper stacking accommodation part, 29 ... Branch conveyance part, 32 ... Discharge roll, 34, 35 ... Branch conveyance path , 36 to 39 ... branch conveyance rolls, 40, 42, 43, 44, 45 ... paper passage sensor, 41 ... conveyance path switching member, 52 ... paper conveyance control unit, R1 to R5 ... paper conveyance path

Claims (1)

Image forming means for forming an image on paper;
Paper discharge means for discharging the paper on which the image is formed by the image forming means;
A plurality of branch conveyance paths provided on a discharge conveyance path for guiding the paper on which an image is formed by the image forming means to the paper discharge means;
A transport path switching means for switching the path of the sheet sent to the discharge transport path between the plurality of branch transport paths;
A sheet conveying member provided on the plurality of branch conveying paths;
When the length of the paper on which the image is formed is less than half of the maximum paper length, the paper is taken into the plurality of branch conveyance paths two by two in order and paused, and according to the order of taking in the paper An image forming apparatus comprising: the conveyance path switching unit and a conveyance control unit configured to control the operation of the sheet conveyance member so as to feed two sheets from the plurality of branch conveyance paths to the sheet discharge unit. .

Images