JP6911357B2 - Control method of printing system, medium transfer mechanism, medium transfer mechanism - Google Patents

Description

The present invention relates to a printing system having a printing device such as an inkjet printer that prints on paper such as a conveyed medium, a medium conveying mechanism used in the printing system, and a control method thereof .

Conventionally, as an example of a printing device included in a printing system, an image forming device that records (prints) an image on a conveyed paper (medium) has been known. Further, some of these image forming devices are provided with a switchback mechanism (reversing portion) for reversing the paper (for example, Patent Document 1).

That is, the switchback mechanism includes a roller, and by rotating the roller in the forward and reverse directions, the paper fed from the upstream side transport path (first transport path / pre-reverse path) is transferred to the downstream transport path (second transport path). / Send to the path after inversion) and invert.

In this image forming apparatus, two switchback mechanisms are provided, and a roller for feeding paper to one switchback mechanism and a roller for feeding paper from the other switchback mechanism are shared by one roller. That is, when the roller rotates in the normal direction, the paper is fed to one switchback mechanism and the paper is fed from the other switchback mechanism. Then, when the rollers are reversed, the paper is fed from one switchback mechanism and the paper is fed to the other switchback mechanism.

Therefore, the roller feeds the paper from the switchback mechanism to the downstream transport path at the same speed as the paper is fed from the upstream transport path to the switchback mechanism.

Japanese Unexamined Patent Publication No. 9-12198

By the way, when printing is performed by adhering a liquid such as ink to the surface of the paper, the paper may be curled so as to be curled. It is considered that this curl is caused by the difference in expansion coefficient between the front side portion where the adhered liquid permeates and the back surface side where the ink does not permeate. Then, as time passes after the liquid adheres to the paper, the liquid permeates the back surface side or the liquid evaporates, and the curl is gradually reduced.

Further, the shape of the swelled paper that has absorbed the liquid is fixed as the liquid evaporates and dries. That is, for example, when the paper is dried in a state where the transport of the paper is interrupted, the paper is fixed in the shape of the transport path. Therefore, it is preferable that the paper is conveyed and changed in shape until the attached liquid dries.

In the case of the image forming apparatus of Patent Document 1, the speed at which the paper is fed from the switchback mechanism is determined by the speed at which the paper is fed into the switchback mechanism. Therefore, in order to lengthen the transport time, the paper transport path must be lengthened, which causes a problem that the apparatus becomes large in size.

It should be noted that these problems are generally common not only in the image forming apparatus for recording on paper but also in the printing apparatus for printing on the medium.
The present invention has been made in view of such circumstances, and an object of the present invention is to provide a printing system having a printing device capable of securing a required transport time while suppressing an increase in size of the device.

Hereinafter, means for solving the above problems and their actions and effects will be described.
A printing system that solves the above problems includes a printing unit that prints by adhering a liquid to a medium, an upstream transfer path that conveys the medium printed by the printing unit, and a printing device that has the upstream transfer. The intermediate transport path has an intermediate transport path in which the medium is conveyed from the path, and the intermediate transfer path includes a switchback path for switching back the medium, an inversion path for reversing the medium conveyed from the switchback path, and the inversion path. After the intermediate device including the inverted path for transporting the medium inverted in, the downstream transport path in which the medium is transported from the intermediate transport path, and the medium transported from the downstream transport path. The second transport speed, which is the transport speed of the medium in the post-reversal path, includes a post-processing unit that performs processing and a post-processing device having a discharge unit that discharges the medium that has been post-processed by the post-processing unit. The distance between the rear end of the preceding medium and the tip of the medium following the preceding medium is slower than the first transport speed, which is the transport speed of the medium in the upstream transport path. It is shorter when the preceding medium is conveyed at the second transfer speed than when it is conveyed at the first transfer speed.

According to this configuration, the medium before being inverted is conveyed at the first conveying speed, and the medium after being inverted is conveyed at a second conveying speed slower than the first conveying speed. Therefore, the time required for transporting the route after reversal can be longer than the time required for transporting the route after reversal at the first transport speed. Therefore, it is possible to secure the required transport time while suppressing the increase in size of the apparatus. Further, by reducing the transport speed of the media after the inversion and shortening the distance between the media before the inversion, it is possible to prevent the media from unintentionally contacting each other.

The printing system further includes a transport control unit that controls the transport of the medium, and the printing device in the printing system includes a cassette on which the medium is placed and a feed unit that feeds the medium from the cassette. When the unit adhesion amount, which is the amount of liquid that the printing unit adheres to per unit region of the medium, is smaller than a preset threshold value, the transport control unit has the preceding medium and the successor. The feeding unit is controlled so that the distance between the printing medium and the medium is the first, and when the unit adhesion amount is larger than the threshold value, the first distance between the preceding medium and the succeeding medium is used. When the feeding unit is controlled so that the second interval is wider than the interval, and the interval between the preceding medium and the succeeding medium is the first interval as the transport speed of the medium in the post-reversal path. The fourth transport speed is controlled so as to be the second transport speed, and when the distance between the preceding medium and the succeeding medium is the second spacing, the fourth is slower than the second transport speed. It is preferable to control the transport speed so as to be the transport speed.

According to this configuration, the larger the unit adhesion amount, the longer the required transport time. Further, the slower the transport speed of the media, the narrower the distance between the media. In that respect, according to this configuration, the interval between the media at the time of feeding is changed according to the unit adhesion amount. Therefore, even when the unit adhesion amount is large, by widening the distance between the media in advance, it is possible to suppress the occurrence of stains due to the overlap of the media even if the media are transported at a sufficiently slow transfer speed. can. Further, when transporting a medium having a large amount of unit adhesion and a long required transport time, the medium is transported along the inversion path at a fourth transport speed slower than the second transport speed. Therefore, the time required for transporting the path after inversion can be made longer than in the case of transporting the medium at the second transport speed.

In the printing system, it is preferable that the transport control unit controls the transport speed of the medium so as to have a third transport speed higher than the second transport speed in the downstream transport path.

In the post-processing unit that processes media, for example, if the distance between a plurality of conveyed media is narrow, the next medium is conveyed before the processing of the previously conveyed medium is completed, resulting in erroneous processing. There is a risk that it will end up. In that respect, according to this configuration, the medium is conveyed at a third transfer speed higher than the second transfer speed in the downstream transfer path. Therefore, even if the distance between the media is narrowed in the process of being conveyed along the path after inversion, the distance between the media can be widened, so that the post-processing unit can appropriately perform the processing.

In the printing system, the transport control unit sets the interval between the preceding medium and the succeeding medium as the interval after switching back each of the media rather than the interval before switching back each of the media. It is preferable to control the transfer so that the width is narrower, and the interval when the preceding medium is conveyed at the third transfer rate is wider than the interval after the switchback. ..

According to this configuration, it is possible to promote the drying of the medium in the intermediate transport path, and it is possible to secure the space between the media for appropriately performing the post-treatment in the post-treatment section.

In the printing system, the intermediate transport path includes a plurality of pairs of the switchback path and the reversal path, and the plurality of reversal paths merge with the post-reversal path, and the reversal path joins the reversal path. It is preferable that the transport speed of the medium is the second transport speed or the fourth transport speed.

In the upstream side transport path in the printing system, the upstream end of the preceding medium and the downstream end of the succeeding medium are transported in a separated state, and in the post-reversal path, the upstream end of the preceding medium and the upstream end of the preceding medium are transported. The downstream end of the following medium is transported in an overlapping state, and in the downstream transport path, the upstream end and the downstream end are separated again after the preceding medium reaches the third transport speed. Is preferable.

According to this configuration, while improving the transport efficiency of the medium in the post-reversal path, the medium can be separated in the downstream transport path, so that the post-processing in the post-processing unit can be appropriately executed.

The schematic diagram of one Embodiment of a printing system. Schematic diagram of the intermediate device. Block diagram of the control unit. The schematic diagram of the intermediate device which conveys the 1st sheet medium. The schematic diagram of the intermediate device which carries the 1st sheet and the 2nd sheet medium. The schematic diagram of the intermediate device which carries the 1st to 3rd sheets of a medium. The schematic diagram of the intermediate device which carries the 1st to 4th sheets of a medium.

Hereinafter, an embodiment of the printing system will be described with reference to the drawings.
As shown in FIG. 1, the printing system 11 includes a device main body 13 which is an example of a first device such as a printing device that prints on a medium 12 such as paper, and a second device that processes the printed medium 12. It includes a post-processing device 14 which is an example, and an intermediate device 15 which is an example of a third device located between the device main body 13 and the post-processing device 14.

The apparatus main body 13 is provided with an upstream transport path 17, and the intermediate device 15 is provided with an intermediate transport path 18. Further, the post-processing device 14 is provided with a downstream transfer path 19. Then, the upstream transfer path 17, the intermediate transfer path 18, and the downstream transfer path 19 continue from the device main body 13 on the upstream side in the transfer direction Y to the post-processing device 14 via the intermediate device 15. The transport route indicated by the dotted chain line is configured.

The apparatus main body 13 is detachably provided with at least one cassette 21 (four in FIG. 1) capable of accommodating the medium 12 in a stacked state. Then, the apparatus main body 13 is conveyed by the feeding section 22 that feeds the medium 12 housed in the cassette 21, the upstream transport section 23 that transports the fed medium 12, and the upstream transport section 23. It is provided with a printing unit 24 for printing on the medium 12.

The feeding unit 22 is a pair of separation rollers that separate the pickup roller 26 that sends out the highest-level medium 12 and the medium 12 that is sent out by the pickup roller 26 one by one among the media 12 arranged in a stacked state on the cassette 21. It has 27 and. Further, the feeding unit 22 includes a feeding motor 28 for rotationally driving the pickup roller 26.

The upstream transport unit 23 rotates with the drive of the upstream transport motor 29 to transport the medium 12 along the upstream transport path 17 (two in FIG. 1) of the upstream transport roller. It has a pair of 30. Further, a drive pulley 32 and a driven pulley 33 on which an endless transport belt 31 is hung are provided at a position along the upstream transport path 17. Then, the medium 12 is conveyed with the rotation of the transfer belt 31 in a state of being electrostatically attracted to the support surface (outer peripheral surface) of the transfer belt 31.

The printing unit 24 is provided at a position facing the transport belt 31 with the upstream transport path 17 interposed therebetween. Then, the printing unit 24 prints by injecting a liquid such as ink onto the medium 12 supported by the transport belt 31 and transported, so that the liquid adheres to the medium 12 transported by the upstream transport unit 23. The printing unit 24 of the present embodiment is a so-called line head capable of simultaneously injecting ink in a width direction intersecting (for example, orthogonal to) the transport direction Y of the medium 12.

Further, the post-processing apparatus 14 has a downstream transport unit 35 that transports the medium 12 along the downstream transport path 19, and a post-processing unit 36 that processes the medium 12 that has been transported along the downstream transport path 19. It is provided with a discharge unit 37 from which the discharged medium 12 is discharged.

The downstream transfer unit 35 rotates with the drive of the downstream transfer motor 38 to convey at least one (one in FIG. 1) downstream transfer roller along the downstream transfer path 19. It has a pair of 39. Then, the post-processing unit 36 performs, for example, stapler processing for binding a plurality of media 12 with staples (needle).

Next, the intermediate device 15 will be described.
As shown in FIG. 1, the intermediate device 15 includes at least one reversing section (two first reversing sections 41 and a second reversing section 42 in the present embodiment) that reverses the conveyed medium 12. That is, the first reversing section 41 and the second reversing section 42 are located on the downstream side of the printing section 24 in the transport direction Y in the transport path, and reverse the printed medium 12.

Further, the intermediate transport path 18 includes an introduction path 43 whose upstream end is connected to the upstream transport path 17, and a first branch path 44 and a second branch path 45 branched at a branch point A which is a downstream end of the introduction path 43. And have. That is, the downstream end of the introduction path 43, the upstream end of the first branch path 44, and the upstream end of the second branch path 45 are connected to the branch point A, respectively. The introduction path 43 is formed in a substantially linear shape, whereas the first branch path 44 and the second branch path 45 are formed in a meandering manner. The path lengths of the first branch path 44 and the second branch path 45 in the transport direction Y are substantially the same as each other.

Further, the intermediate transport path 18 is connected to the first inversion path 46 connected to the first connection point B, which is the downstream end of the first branch path 44, and the second connection point C, which is the downstream end of the second branch path 45. It has a second inversion path 47 that is connected. The path lengths of the first inversion path 46 and the second inversion path 47 in the transport direction Y are substantially the same as each other.

Further, the first switchback path 48 of the first inversion unit 41 is connected to the first connection point B, and the second switchback path of the second inversion unit 42 is connected to the second connection point C. 49 is connected. That is, the downstream end of the first branch path 44, the upstream end of the first inversion path 46, and one end of the first switchback path 48 are connected to the first connection point B. Further, the second connection point C is connected to the downstream end of the second branch path 45, the upstream end of the second inversion path 47, and one end of the second switchback path. The path lengths of the first switchback path 48 and the second switchback path 49 are set to be equal to or longer than the medium length of the medium 12 that can be printed by the apparatus main body 13 in the transport direction Y.

Further, the intermediate transport path 18 has a lead-out path 50 connected to a confluence point D where the first reversal path 46 and the second reversal path 47 merge. That is, the downstream end of the first reversing path 46, the downstream end of the second reversing path 47, and the upstream end of the derivation path 50 are connected to the confluence point D. The derivation path 50 is curved downward in a meandering manner between the first switchback path 48 and the second switchback path 49 toward the aftertreatment device 14, and then extends downward, and then the other of the first switchback path 48. It wraps around the end side and extends upward. The downstream end of the lead-out path 50 is connected to the downstream transfer path 19 of the aftertreatment device 14.

Then, in the present embodiment, the introduction path 43, the first branch path 44, and the second branch path 45 constitute the pre-reversal path 18a, and the first reversal path 46, the second reversal path 47, and the derivation path 50 form the post-reversal path. 18b is configured. The pre-reversal path 18a functions as an example of a first transfer path located upstream of the first reversal section 41 or the second reversal section 42 in the transport direction Y. Further, the post-reversal path 18b functions as an example of a second transport path located downstream of the first reverse section 41 or the second reverse section 42 in the transport direction Y. That is, the intermediate transport path 18 includes a pre-reversal path 18a located upstream of the first reversal section 41 and the second reversal section 42 in the transport direction Y, and a post-reversal path 18b located downstream of the transport direction Y. have. The downstream transport path 19 functions as an example of a third transport path located downstream of the reverse path 18b in the transport direction Y.

As shown in FIG. 2, the intermediate device 15 includes an intermediate transport unit 52 that transports the medium 12 along the intermediate transport path 18. That is, the first inversion unit 41 and the second inversion unit 42 invert the medium 12 conveyed by the intermediate transfer unit 52.

The intermediate transport unit 52 includes a first transport roller pair 54 driven by the first transport motor 53 and a second transport roller pair 56 driven by the second transport motor 55. A plurality of first transport roller pairs 54 are provided in the pre-reversal path 18a (three pairs in FIG. 2), and a plurality of second transport roller pairs 56 are provided in the post-reversal path 18b (14 pairs in FIG. 2). It is provided.

Then, in the printing system 11, the upstream side transport unit 23, the downstream side transport unit 35, and the intermediate transport unit 52 constitute a transport unit that transports the medium 12 from the upstream side to the downstream side in the transport direction Y along the transport path. Has been done. That is, the transport section is a transport path by rotationally driving one roller (the drive roller shown by the double circle in FIGS. 1 and 2) while each roller pair sandwiches and supports the medium 12 from both the front and back sides. The medium 12 is conveyed along the above.

Further, the introduction path 43 is provided with an introduction sensor 58 for detecting the medium 12, and a guide flap 59 is provided at a branch point A on the downstream side of the introduction sensor 58. The guide flap 59 is driven by a solenoid (see FIG. 3) 60 to switch which of the first branch path 44 and the second branch path 45 guides the medium 12 conveyed through the introduction path 43. That is, the guide flap 59 is positioned between the first position P1 that guides the medium 12 to the first branch path 44 and the second position (see FIG. 5) P2 that guides the medium 12 to the second branch path 45. Can be switched.

Further, at the downstream end of the first branch path 44, the medium 12 is allowed to move from the first branch path 44 to the first switchback path 48, while the medium 12 is allowed to move from the first switchback path 48 to the first branch path 44. A first regulation flap 61 that regulates the movement of the medium 12 is provided. Further, at the downstream end of the second branch path 45, the medium 12 is allowed to move from the second branch path 45 to the second switchback path 49, while the medium 12 is allowed to move from the second switchback path 49 to the second branch path 45. A second regulation flap 62 that regulates the movement of the medium 12 is provided. The first regulation flap 61 and the second regulation flap 62 are urged so as to block the downstream end of the first branch path 44 or the second branch path 45 by an urging force by an urging member (not shown).

The first inversion unit 41 includes a first inversion sensor 64 that detects the medium 12 sent to the first switchback path 48, and a plurality of (two pairs in FIG. 1) provided on both sides of the first inversion sensor 64. It is equipped with one reversing roller vs. 65. The first reversing roller pair 65 is driven in the forward rotation or the reverse rotation by the first reversing motor 66 based on the signal transmitted when the first reversing sensor 64 detects the medium 12.

Further, the second inversion unit 42 includes a second inversion sensor 67 that detects the medium 12 sent to the second switchback path 49, and a plurality of second inversion units 42 provided on both sides of the second inversion sensor 67 (two pairs in FIG. 1). It is equipped with a second reversing roller pair 68. The second reversing roller pair 68 is driven in the forward rotation or the reverse rotation by the second reversing motor 69 based on the signal transmitted when the second reversing sensor 67 detects the medium 12.

As shown in FIG. 3, the printing system 11 includes a control unit 71 that comprehensively controls the driving of each mechanism in the printing system 11. The control unit 71 controls the drive of various motors and solenoids 60 based on the detection results of the introduction sensor 58, the first reversing sensor 64, and the second reversing sensor 67, thereby controlling the upstream side transport unit 23 and the intermediate transport unit 52. , The medium 12 is conveyed to the downstream side conveying unit 35.

Further, the control unit 71 has a calculation unit 72 that calculates a unit adhesion amount that is the amount of liquid that the printing unit 24 adheres to per unit area of the medium 12 based on the print data, and a preset threshold value for the unit adhesion amount. It is provided with a storage unit 73 for storing the above. That is, when the print data is input to the printing system 11, the calculation unit 72 calculates the unit adhesion amount based on the print data.

The threshold value is set according to the type of the medium 12, the liquid, the length of the transport path, and the like. That is, when the printing unit 24 adheres a liquid to the surface (printing surface) of the medium 12 to perform printing, curls may occur in which the surface has a convex shape. This curl is considered to be caused by the difference in expansion coefficient between the front and back surfaces because the front surface side that has absorbed the liquid swells, while the back surface side that does not permeate the liquid does not swell. Therefore, the larger the unit adhesion amount, the more likely the curl is to occur. Then, the curl is reduced as the liquid adhering to the front surface permeates the back surface side or the liquid evaporates to reduce the swelling on the front surface side.

Therefore, for example, in the case of a medium in which a liquid easily permeates, the time required for curl reduction is shorter than in a medium in which a liquid does not easily permeate. The threshold value is set smaller for a medium in which the liquid is less likely to permeate or a liquid in which the liquid is less likely to permeate or evaporate.

Next, the feeding interval of the medium 12 by the feeding section 22 and the feeding speed at which the upstream transport section 23, the intermediate transport section 52, and the downstream transport section 35 transport the medium 12 will be described.
When the unit adhesion amount calculated by the calculation unit 72 is smaller than the threshold value stored in the storage unit 73, the feeding unit 22 feeds the media 12 to each other at the first interval, and the unit adhesion amount is less than this threshold value. If there are many, the media 12 are fed at a second interval wider than the first interval.

The transport speed referred to here may be the maximum transport speed in the section of the predetermined transport route or the average transport speed in the section of the predetermined transport route. Further, in the case of continuously transporting the media 12 to each other, the case where the speed is any of the media 12 is shown. However, for a very short period of time, the preceding medium 12 may be slower than the succeeding medium 12. For example, when the switchback path is used as a boundary, there is a moment when the preceding medium 12 is slower than the succeeding medium 12. Therefore, when comparing the speeds of the preceding medium 12 and the succeeding medium 12, it is necessary to be aware of whether each medium 12 is before or after the switchback.
The section of the predetermined transport path referred to here is, for example, a section defined by an arbitrary start point and an arbitrary end point in the upstream transport path 17 in the upstream transport path 17, and is an intermediate transport path 18 Is a section defined by an arbitrary start point and an arbitrary end point in the intermediate transport path 18, and is defined by an arbitrary start point and an arbitrary end point in the downstream transport path 19 in the downstream transport path 19. It is a section.
Further, it may be a section defined by an arbitrary start point in the upstream transfer path 17 and an arbitrary end point in the intermediate transfer path 18, or an arbitrary start point in the intermediate transfer path 18 and the downstream transfer path 19 It may be a section defined by an arbitrary end point in. Further, in the intermediate transport path 18, an arbitrary start point upstream from the first switchback path 48 and the second switchback path 49, and an arbitrary end point downstream from the first switchback path 48 and the second switchback path 49. It may be a section specified by.

The first interval and the second interval are intervals between the media 12 in the transport direction Y. That is, for example, the interval between the media 12 is increased by setting the time from the feeding of the first medium to the feeding of the second medium to the second interval time longer than the first interval time. The second interval can be wider than the first interval.

Then, the upstream side transport unit 23 transports the fed medium 12 along the upstream side transport path 17 at the pre-reversal speed (an example of the first transport speed). Further, the intermediate transport unit 52 transports the medium 12 on the pre-reversal path 18a at the pre-reversal speed, and conveys the post-reversal path 18b at a post-reversal speed slower than the pre-reversal speed. Further, the downstream transport unit 35 transports the medium 12 on the downstream transport path 19 at a processing speed (an example of a third transport speed) faster than the speed after reversing.

The intermediate transport unit 52 changes the speed after reversal according to the unit adhesion amount calculated by the calculation unit 72. That is, when the unit adhesion amount is smaller than the threshold value stored in the storage unit 73, the intermediate transport unit 52 transports the medium 12 through the reverse path 18b at the first reverse speed (an example of the second transport speed). do. Then, when the unit adhesion amount is larger than the threshold value stored in the storage unit 73, the intermediate transport unit 52 sets the post-reversal path 18b to a second post-reversal speed (fourth transport speed) slower than the first reversal speed. The medium 12 is conveyed by one example).

That is, the medium 12 fed at intervals according to the amount of adhesion is conveyed on the upstream side transport path 17 and the pre-reversal path 18a at the pre-reversal speed regardless of the unit amount of adhesion, and is also conveyed on the downstream side transfer path 19. It is transported at the processing speed. Then, in the inversion path 18b, the medium 12 fed at the first inversion is conveyed at the speed after the first inversion, and the medium 12 fed at the second interval is conveyed at the speed after the second inversion.

The processing speed is the fastest among the pre-reversal speed, the first post-reversal speed, the second post-reversal speed, and the processing speed. The processing speed is substantially the same as the pre-reversal speed or faster than the pre-reversal speed. The speed after the first inversion is slower than the speed before the inversion, and the speed after the second inversion is slower than the speed after the first inversion (processing feed ≥ speed before inversion> speed after first inversion> after second inversion). speed). The transport speed of the medium 12 may satisfy the above-mentioned inequality, and the medium 12 may be transported at a constant speed in a section of a predetermined transport path, or the medium 12 may be transported while accelerating or decelerating. good.

Next, the operation when the printing system 11 performs printing will be described.
In the following description, the medium 12 fed to and conveyed to the feeding unit 22 is referred to as the first medium 12a, the second medium 12b, and the third medium 12c in order from the first sheet, and the fourth medium 12 is used. This will be described as the fourth medium 12d.

When printing is executed, the control unit 71 drives the feed motor 28 and the second transfer motor 55 depending on whether or not the calculated unit adhesion amount is larger than the threshold value stored in the storage unit 73. To control. Further, the control unit 71 drives the upstream side transfer motor 29, the first transfer motor 53, the first reversing motor 66, the second reversing motor 69, and the downstream side transfer motor 38 in the forward rotation.

That is, the medium 12 is fed by the feeding unit 22 and is also transported by the transporting unit. Further, the printing unit 24 injects a liquid onto the medium 12 at the timing when the medium 12 passes between the printing unit 24 and the transport belt 31 to perform printing.

As shown in FIG. 4, the first medium 12a conveyed through the upstream transfer path 17 at the speed before reversal is delivered to the introduction path 43 at substantially the same speed. Then, when the introduction sensor 58 detects the tip of the first medium 12a, the control unit 71 drives the solenoid 60 to position the guide flap 59 at the first position P1. That is, the guide flap 59 guides the first medium 12a to the first branch path 44. Then, when the tip of the first medium 12a conveyed to the first connection point B comes into contact with the first regulation flap 61, the first regulation flap 61 is moved so as to resist the urging force of the urging member. .. That is, the first regulation flap 61 moves so as to open the downstream end of the first branch path 44. Therefore, the first medium 12a is sent to the first switchback path 48 at the speed before reversal by the first reversing roller pair 65 that drives the forward rotation. Then, when the first medium 12a passes through the first regulation flap 61, the first regulation flap 61 moves from the position where the downstream end of the first branch path 44 is opened to the position where the first branch path 44 is closed.

As shown in FIG. 5, when the first reversing sensor 64 detects the rear end of the first medium 12a, the control unit 71 switches the first reversing motor 66, which has been driven in the normal rotation, to the reverse driving. Then, the first reversing unit 41 sends the first medium 12a from the first switchback path 48 to the first connection point B side at the speed after reversing. At this time, the first regulation flap 61 guides the first medium 12a to the first reversal path 46. That is, the first reversing unit 41 reverses (switches back) the direction of the first medium 12a by sending the first medium 12a sent from the first branch path 44 to the first reversing path 46.

When the introduction sensor 58 detects the tip of the second medium 12b, the control unit 71 drives the solenoid 60 to change the position of the guide flap 59. That is, the control unit 71 moves the guide flap 59 located at the first position P1 to the second position P2. Then, the guide flap 59 guides the second medium 12b to the second branch path 45.

Then, when the tip of the second medium 12b conveyed to the second connection point C comes into contact with the second regulation flap 62, the second regulation flap 62 is moved so as to resist the urging force of the urging member. .. That is, the second regulation flap 62 moves so as to open the downstream end of the second branch path 45. Therefore, the second medium 12b is sent to the second switchback path 49 at the speed before reversal by the second reversing roller pair 68 that drives the normal rotation. Then, when the second medium 12b passes through the second regulation flap 62, the second regulation flap 62 moves from the position where the downstream end of the second branch path 45 is opened to the position where the second regulation flap 62 is closed.

As shown in FIG. 6, the first medium 12a inverted by the first inversion unit 41 is conveyed in the inversion path 18b at the inversion speed. Then, when the first medium 12a passes through the first connection point B, the control unit 71 drives the first reversing motor 66 in the forward rotation.
Further, when the second reversing sensor 67 detects the rear end of the second medium 12b, the control unit 71 reversely drives the second reversing motor 69. That is, the second inversion unit 42 inverts the second medium 12b in the same manner as the first inversion unit 41 and sends the second medium 12b to the second inversion path 47 at the speed after inversion.

The speed after inversion in which the first inversion unit 41 sends the first medium 12a from the first switchback path 48 to the first connection point B side, and the second inversion unit 42 sends the second medium 12b to the second switchback path 49. It is preferable that the speed after inversion sent from the second connection point C to the second connection point C side is the same. According to this configuration, in the transport after inverting each medium, the distance between the rear end of the preceding medium and the front end of the succeeding medium can be made constant.

Further, when the introduction sensor 58 detects the tip of the third medium 12c, the control unit 71 drives the solenoid 60 to change the position of the guide flap 59. That is, the control unit 71 moves the guide flap 59 located at the second position P2 to the first position P1. That is, the guide flap 59 alternately guides the conveyed medium 12 to the first branch path 44 and the second branch path 45.

As shown in FIG. 7, the second medium 12b that has been inverted by the second inversion unit 42 and sent out to the second inversion path 47 is conveyed along the lead-out path 50 via the confluence point D. At this time, the intermediate transport unit 52 transports the first medium 12a and the second medium 12b at a speed after reversal, which is slower than the speed before reversal. Therefore, the distance between the first medium 12a and the second medium 12b in the transport direction Y is narrower than that when the pre-reversal path 18a is transported at the pre-reversal speed.

Then, when the first reversing sensor 64 detects the rear end of the third medium 12c, the control unit 71 reversely drives the first reversing motor 66 and sends the third medium 12c to the first reversing path 46. When the introduction sensor 58 detects the tip of the fourth medium 12d, the control unit 71 drives the solenoid 60 to change the position of the guide flap 59 to the second position P2.

Then, the intermediate device 15 sends out the first medium 12a introduced earlier to the post-processing device 14 in order. That is, the medium 12 is sent to the aftertreatment device 14 with the printed surface facing the gravity direction side. Further, since the downstream transport unit 35 transports the medium 12 at a processing speed faster than the speed after inversion, the distance between the media 12 is widened. Then, the post-processing unit 36 performs processing such as staples on the medium 12 conveyed through the downstream transfer path 19, and discharges the medium 12 to the discharge unit 37.

The distance between the rear end of the preceding medium 12 and the front end of the succeeding medium 12 in the apparatus main body 13, that is, the distance before switching back is defined as the distance S1. Further, in the intermediate device 15, the interval between the rear end of the preceding medium 12 and the tip of the succeeding medium 12 after the preceding medium 12 and the succeeding medium 12 are both switched back, that is, the interval after the so-called switchback is set. The interval is S2. Further, when the rear end of the preceding medium 12 passes through the downstream side transport roller pair 39 of the aftertreatment device 14, the distance between the rear end of the preceding medium 12 and the front end of the succeeding medium 12 is defined as the interval S3.

At this time, the following inequality holds at each interval.
Equation 1: Interval S1> Interval S3> Interval S2
or,
Equation 2: Interval S3> Interval S1> Interval S2
The magnitude relationship between the interval S1 and the interval S3 can be appropriately adopted based on the transport path of the device. For example, when it is necessary to secure a sufficiently wide space between the media 12 in the apparatus main body 13, it is preferable to adopt the formula 1. On the other hand, if the post-processing by the post-processing unit 36 of the post-processing device 14 cannot be sufficiently performed at the interval S1, the equation 2 may be adopted. Alternatively, the interval S1 and the interval S3 may be the same as long as there is no inconvenience in the various processes in the apparatus.

In any case, the interval S2 is narrower than the interval S1 and the interval S3. As a result, in the intermediate device 15, the distance between the media 12 can be narrowed, and the medium 12 can be transported slower than the transport speed before the switchback, so that the time for drying the medium 12 in the intermediate device 15 is secured. be able to.

By the way, in order to make the interval S3 wider than the interval S2, the transfer speed of the downstream transfer roller pair 39 is made faster than the transfer speed of the transfer roller pair (for example, the second transfer roller pair) of the intermediate device 15. do it. In this case, if the transport roller pair of the intermediate device 15 is provided with a friction clutch or the like, even in a situation where the tip of the medium 12 is nipped into the downstream transport roller pair 39 to start transport, the intermediate device 15 Since the generation of back tension caused by the portion of the medium 12 nipped by the transport roller pair can be reduced, the transport is not disturbed.

The rotation speed of the downstream transfer roller pair 39 is faster than the rotation speed of the transfer roller pair of the intermediate device 15. Therefore, the interval S3 varies depending on the size of the conveyed medium 12 in the conveying direction. That is, when transporting the medium 12 so that the long side of the medium 12 and the transport direction are parallel to each other, the case of transporting the A3 size and the case of transporting the A4 size are accelerated by the downstream side transport roller pair 39. Since the time is longer in the A3 size, the interval S3 is longer when the A3 size is transported than when the A4 size is transported.

As described above, the reason why the difference in the interval S3 is required depending on the size of the medium 12 is that the larger the size in the transport direction, the more the plurality of media 12 are stapled (needle) in the post-processing unit 36. This is because it takes a lot of time to align the ends of the plurality of media 12 which are the processing parts when performing the stapler processing or the like. That is, since the surface area of the medium 12 is larger in the A3 size than in the A4 size, it takes a lot of time to align the end portions, which are the processing portions, due to the friction between the plurality of media 12.

There is another method for defining the interval S1, the interval S2, and the interval S3. That is, as the interval S1, the time difference between the time when the rear end of the preceding medium 12 arrives and the time when the rear end of the succeeding medium 12 arrives with respect to the upstream side transport roller pair 30 of the apparatus main body 13 is set. , Can be considered as the interval S1. Further, as the interval S2, after the preceding medium 12 and the succeeding medium 12 are both switched back, the medium following from the time when the rear end of the preceding medium 12 arrives at the confluence D in the intermediate transport path 18. The time difference from the time when the rear end of 12 arrives can be considered as the interval S2. Further, as the interval S3, the difference time from the time when the rear end of the preceding medium 12 arrives to the time when the rear end of the succeeding medium 12 arrives with respect to the downstream side transport roller pair 39 of the aftertreatment device 14. Can be considered as the interval S3.

In addition, various positions can be considered as reference positions for the distance between the preceding medium 12 and the succeeding medium 12. That is, the interval S1 is the time when the rear end of the preceding medium 12 arrives from the time when the rear end of the preceding medium 12 arrives with respect to the introduction sensor 58 located near the branch point A in the intermediate transport path 18. The time of the difference up to may be considered as the interval S1. Further, the interval S2 is set with respect to the second inversion sensor 67 of the second switchback path 49 from the time when the rear end of the medium 12 preceding the first inversion sensor 64 of the first switchback path 48 arrives. The time difference from the time when the rear end of the subsequent medium 12 arrives may be considered as the interval S2. That is, from the viewpoint of improving the transport efficiency, the first switchback path 48 and the second switchback path 49 switch back the preceding medium 12 branched from the branch point A and the succeeding medium 12 separately. It is a route to do. Therefore, as a design concept of the intermediate transport path 18, the first switchback path 48 and the second switchback path 49 are designed to have the same transport distance. By doing so, even if the preceding medium 12 and the succeeding medium 12 are branched and conveyed to different switchback paths, the distance between the preceding medium 12 and the succeeding medium 12 after the switchback is appropriately managed. be able to. Therefore, if the transfer path is based on such a design concept, the reference position of the interval S2 may be a different position as in the case where the first inversion sensor 64 and the second inversion sensor 67 are used. good.

In the above, the time interval until the rear end of the preceding medium 12 and the rear end of the succeeding medium 12 pass at each of the reference positions of the interval is set. Instead of this, it may be an interval of time until the tip of the preceding medium 12 and the tip of the succeeding medium 12 pass at the reference position of each interval.

By the way, before and after the switchback in the first switchback path 48 or the second switchback path 49, the start point and the end point of the physical interval between the media 12 are different. That is, before the switchback, it is the distance between the rear end of the preceding medium 12 and the front end of the succeeding medium 12. On the other hand, if it is after the switchback, it is the distance between the rear end of the preceding medium 12 after the switchback and the tip of the succeeding medium 12 after the switchback. Further, if the timing is after the preceding medium 12 has switched back and before the succeeding medium 12 has switched back, the distance between the media 12 is the rear end of the preceding medium 12 after the switchback. This is the distance from the tip of the subsequent medium 12 before the switchback.

According to the above embodiment, the following effects can be obtained.
(1) The intermediate transport unit 52 transports the medium 12 before being inverted at the speed before inversion, and the medium 12 after being inverted by the first inversion unit 41 or the second inversion unit 42 is slower than the speed before inversion. Transport at speed after inversion. Therefore, the time required for transporting the reverse path 18b can be longer than the time required for transporting the reverse path 18b at the pre-reversal speed. Therefore, it is possible to secure the required transport time while suppressing the increase in size of the apparatus.

(2) In the post-processing unit 36 that processes the medium 12, for example, if the distance between the plurality of conveyed media 12 is narrow, the next medium 12 is conveyed before the processing of the previously conveyed medium 12 is completed. There is a risk of erroneous processing. In that respect, the downstream transport unit 35 transports the medium 12 in the downstream transport path 19 at a processing speed faster than the speed after reversal. Therefore, even if the distance between the media 12 is narrowed in the process of being conveyed through the path 18b after inversion, the distance between the media 12 can be widened.

(3) The larger the unit adhesion amount, the longer the required transport time. Further, the slower the transport speed of the media 12, the narrower the distance between the media 12. In that respect, the interval between the media 12 at the time of feeding is changed according to the unit adhesion amount. Therefore, even when the unit adhesion amount is large, the medium 12 can be conveyed at a sufficiently slow transfer speed while suppressing the generation of stains and the like due to the overlapping of the media 12.

(4) When transporting the medium 12 having a large unit adhesion amount and a long required transport time, the downstream transport unit 35 follows the post-reversal path 18b at a second post-reversal speed slower than the first post-reversal speed. 12 is transported. Therefore, the time required for transporting the path 18b after reversing can be made longer than in the case of transporting the medium 12 at the speed after the first reversal.

(5) Since the printing system 11 includes the apparatus main body 13, the post-processing apparatus 14, and the intermediate apparatus 15, the combination of the apparatus can be easily changed. Therefore, for example, by exchanging the post-processing apparatus 14, the processing performed by the post-processing unit 36 on the medium 12 can be easily changed.

(6) The medium 12 is dried while being conveyed by the conveying unit. Therefore, by transporting the post-reversal path 18b at a slower post-reversal speed than the pre-reversal path 18a to prolong the transport time, for example, even if the medium 12 is curled due to printing, the curl is reduced. The medium 12 can be discharged. Therefore, for example, it is possible to reduce the occurrence of media clogging and processing defects that occur when the curled medium 12 is processed by the post-processing unit 36.

(7) The overlap between the media 12 can be reduced by changing the distance between the media 12 when the feeding unit 22 feeds the medium 12 and the speed after inversion according to the unit adhesion amount. Therefore, it is possible to reduce the occurrence of medium clogging caused by the media 12 coming into contact with each other.

The above embodiment may be changed as follows.
-In the above embodiment, three or more reversing portions may be provided.
-In the above embodiment, a motor for driving the second transport roller pair 56 located on the most downstream side in the transport direction Y may be separately provided. That is, the speed at which the medium 12 is sent from the after-reversal path 18b to the downstream transport path 19 may be different from the after-reversal speed. For example, the intermediate transport unit 52 may feed the medium 12 from the reverse path 18b at a delivery speed faster than the first reverse speed (an example of the fifth transport speed) (first modification). The delivery speed is preferably faster than the first inversion speed, and is preferably the same as or slower than the processing speed (processing speed ≥ transmission speed ≥ pre-reversal speed> first inversion speed> second post-reversal speed. ).

According to this first modification, the medium 12 is conveyed through the inversion path 18b at the first inversion post-speed and is sent out from the inversion path 18b at a delivery speed faster than the first inversion post-speed. Therefore, for example, even if the media 12 overlap each other when the reverse path 18b is conveyed, the media 12 can be separated from each other and sent out from the reverse path 18b. That is, the media 12 can be separated from each other and delivered to the downstream transport path 19.

-In the above embodiment, the intermediate transport unit 52 may transport the path 18b after inversion in a state where a part of the media 12 is overlapped with each other. At this time, the overlapping portion is preferably a margin portion that is not printed. Then, when the medium 12 on the downstream side in the transport direction Y is pulled out by the downstream transport portion 35 in a state where the overlapped portion is sandwiched by the second transport roller pair 56, the second transport roller pair 56 is formed. The driving roller and the driven roller may be separated from each other.

-In the above embodiment, the transport speed of the medium 12 in the upstream transport path 17 and the pre-reversal path 18a may be different. For example, the upstream transport unit 23 may transport the medium 12 through the upstream transport path 17 at a printing speed slower or faster than the pre-reversal speed.

-In the above embodiment, one motor may drive rollers on different paths. For example, the upstream transfer roller pair 30 may be driven by the first transfer motor 53 without the upstream transfer motor 29.

-In the above embodiment, the threshold value regarding the unit adhesion amount stored in the storage unit 73 may be set or selected according to the environment in which the printing system 11 is installed. That is, the curl generated on the printed medium 12 also depends on the environment. Specifically, for example, in a low-humidity environment, the amount of water contained in the medium 12 before printing is small, so that the curl associated with printing tends to be large. Further, in a low temperature environment, the fluidity of the liquid is lowered and the liquid is hard to evaporate, so that it takes time to reduce the curl. Therefore, in an environment where curl is difficult to reduce, the threshold value may be reduced.

-In the above embodiment, a plurality of threshold values regarding the unit adhesion amount may be set, and the interval between the media 12 to be fed by the feeding unit 22 and the speed after reversal may be changed stepwise.
-In the above embodiment, the medium 12 may be conveyed on the post-reversal path 18b at a post-reversal speed (second transport speed) slower than the pre-reversal speed (first transport speed) regardless of the unit adhesion amount. That is, it is not necessary to set the speed after the second inversion.

In the above embodiment, the feeding unit 22 feeds the media 12 to each other at the first interval by rotating the pickup roller 26 at the first rotation speed, and rotates at the second rotation speed slower than the first rotation speed. The media 12 may be fed at a second interval wider than the first interval.

-In the above embodiment, the feeding unit 22 may feed the medium 12 at regular intervals regardless of the unit adhesion amount.
-In the above embodiment, the printing system 11 does not have to include the feeding unit 22. For example, the printing system 11 may include a feeding port, and the upstream transporting unit 23 may transport the medium 12 inserted one by one from the feeding port. That is, the printing system 11 may print on the medium 12 fed by the feeding device provided separately from the printing system 11. Further, the feeding unit 22 may feed the media 12 set in the feeding tray one by one.

In the above embodiment, the post-processing unit 36 has a punch process for making a hole in the medium 12, a shift process for shifting the medium 12 in units of copies, a cutting process for cutting the medium 12, a binding process for folding the medium 12, and a medium. Arbitrary processing such as a bookbinding process or a collating process for binding 12 may be performed.

-In the above embodiment, the printing system 11 may be configured not to include the post-processing device 14.
-The liquid can be arbitrarily selected as long as it can be printed on the medium 12 by adhering to the medium 12. The liquid may be in the state when the substance is in the liquid phase, and is a highly viscous or low-viscosity liquid, sol, gel water, other inorganic solvent, organic solvent, solution, liquid resin, liquid metal. It shall contain a liquid such as (metal melt). Further, it includes not only a liquid as a state of a substance but also a particle of a functional material made of a solid substance such as a pigment or a metal particle dissolved, dispersed or mixed in a solvent. Ink is a typical example of a liquid. The ink includes general water-based inks, oil-based inks, and various liquid compositions such as gel inks and hot melt inks.

-The medium 12 may be paper, resin, metal, cloth, ceramic, rubber, a natural material (wood, stone, etc.) or a composite thereof. Further, the thickness of the medium may be a plate, a sheet, a film, a foil or the like. Further, the shape of the medium may be any shape such as a rectangle or a circle. That is, for example, a paper-resin composite film (resin-impregnated paper, resin-coated paper, etc.), a resin-metal composite film (laminate film), a woven fabric, a non-woven fabric, a disk, a circuit board, or the like may be used. Then, in the case of a medium such as paper that swells due to adhesion of a liquid, curl can be reduced while being conveyed through the intermediate transfer path 18. Further, in the case of a medium that does not swell, curling does not occur, but the medium can be dried while being conveyed through the intermediate transfer path 18. Therefore, the medium 12 transported through the intermediate transport path 18 can be appropriately processed by the post-processing unit 36.

The printing system 11 is a device that prints images such as characters, pictures, and photographs by adhering a liquid such as ink to a medium, and may be a serial printer, a lateral printer, a line printer, a page printer, or the like. Further, it may be an offset printing device, a printing printing device, or the like. Further, the printing apparatus may have at least a printing function for printing on a medium, and may be a multifunction device having a function other than the printing function.

A ... branch point, B ... first connection point, C ... second connection point, D ... confluence point, P1 ... first position, P2 ... second position, Y ... transport direction, 11 ... printing system, 12 ... medium, 12a ... 1st medium, 12b ... 2nd medium, 12c ... 3rd medium, 12d ... 4th medium, 13 ... Device body (example of 1st device), 14 ... Post-processing device (example of 2nd device), 15 ... Intermediate device (an example of a third device), 17 ... Upstream transfer path, 18 ... Intermediate transfer path, 18a ... Pre-reversal path (an example of a first transfer path), 18b ... Post-reversal path (an example of a second transfer path) ), 19 ... Downstream transport path (an example of a third transport path), 21 ... Cassette, 22 ... Feeding section, 23 ... Upstream transport section (an example of a transport section), 24 ... Printing section, 26 ... Pickup roller, 27 ... Separation roller pair, 28 ... Feeding motor, 29 ... Upstream transfer motor, 30 ... Upstream transfer roller pair, 31 ... Transfer belt, 32 ... Drive pulley, 33 ... Driven pulley, 35 ... Downstream transfer section (conveyance) Example of part), 36 ... post-processing part, 37 ... discharge part, 38 ... downstream side transfer motor, 39 ... downstream side transfer roller pair, 41 ... first reversing part, 42 ... second reversing part, 43 ... introduction path, 44 ... 1st branch path, 45 ... 2nd branch path, 46 ... 1st reversal path, 47 ... 2nd reversal path, 48 ... 1st switchback path, 49 ... 2nd switchback path, 50 ... Derivation path (reversal) Rear path), 52 ... Intermediate transport section (an example of transport section), 53 ... 1st transport motor, 54 ... 1st transport roller pair, 55 ... 2nd transport motor, 56 ... 2nd transport roller pair, 58 ... Introduction sensor , 59 ... Guide flap, 60 ... Solenoid, 61 ... 1st regulation flap, 62 ... 2nd regulation flap, 64 ... 1st reversing sensor, 65 ... 1st reversing roller pair, 66 ... 1st reversing motor, 67 ... 2nd Reversing sensor, 68 ... 2nd reversing roller pair, 69 ... 2nd reversing motor, 71 ... Control unit (conveying control unit), 72 ... Calculation unit, 73 ... Storage unit.

Claims (7)

A printing unit that prints by adhering a liquid to a medium, and a printing device that has an upstream transfer path for transporting the medium printed by the printing section.
The intermediate transport path has an intermediate transport path in which the medium is transported from the upstream transport path, and the intermediate transport path includes a switchback path for switching back the medium and an inversion path for reversing the medium transported from the switchback path. An intermediate device including a post-reversal path for transporting the medium inverted by the reversal path, and
Discharges a downstream transport path in which the medium is transported from the intermediate transport path, a post-processing unit that performs post-treatment on the medium transported from the downstream transport route, and a medium that has been post-treated by the post-processing unit. An aftertreatment device having a discharge unit
A transport control unit that controls the transport of the medium,
A cassette on which the medium is placed and a feeding unit for feeding the medium from the cassette are provided.
The second transport speed, which is the transport speed of the medium in the post-reversal path, is slower than the first transport speed, which is the transport speed of the medium in the upstream transport path.
The distance between the rear end of the preceding medium and the tip of the medium following the preceding medium is such that the preceding medium is conveyed in the second transport more than when the preceding medium is transported at the first transport speed. It is shorter when transporting at speed,
The transport control unit
When the unit adhesion amount, which is the amount of liquid adhered to the unit area of the medium by the printing unit, is smaller than a preset threshold value, the first interval is used as the interval between the preceding medium and the succeeding medium. When the unit adhesion amount is larger than the threshold value, the distance between the preceding medium and the succeeding medium is a second interval wider than the first interval. To control the feeding unit,
When the distance between the preceding medium and the succeeding medium is the first distance, the transport speed of the medium in the post-reversal path is controlled to be the second transport speed. A printing system that controls the transfer speed so that when the interval between the preceding medium and the succeeding medium is the second interval, the fourth transfer speed is lower than the second transfer speed. The transport control unit
The printing system according to claim 1, wherein the transport speed of the medium is controlled so as to be a third transport speed faster than the second transport speed in the downstream transport path. The transfer control unit sets the distance between the preceding medium and the succeeding medium so that the distance after switching back each of the media is narrower than the distance before switching back each of the media. The printing according to claim 2, wherein the transfer is controlled so that the interval when the preceding medium is conveyed at the third transfer speed is wider than the interval after the switchback. system. In the upstream transport path, the upstream end of the preceding medium and the downstream end of the succeeding medium are transported in a separated state.
In the post-reversal path, the upstream end of the preceding medium and the downstream end of the succeeding medium are conveyed in an overlapping state.
The printing system according to claim 2 or 3, wherein in the downstream transport path, the upstream end and the downstream end are separated again after the preceding medium reaches the third transport speed. The intermediate transport path includes a plurality of pairs of the switchback path and the reverse path.
The plurality of reversal paths merge with the post-reversal path,
The printing system according to any one of claims 1 to 4 , wherein the transport speed of the medium in the post-reversal path is the second transport speed or the fourth transport speed. An introduction path configured to carry the medium recorded by the printing unit that ejects droplets, and
A first switchback path configured to switch back the medium conveyed from the introduction path, and
A second switchback path configured to switch back the medium transferred from the introduction path,
A first branch path configured to transport the medium from the introduction path to the first switchback path, and
A second branch path configured to transport the medium from the introduction path to the second switchback path, and
A first inversion path configured to invert and convey the medium switched back from the first switchback path, and
A second inversion path configured to invert and convey the medium switched back from the second switchback path, and
It is provided with a derivation path configured so that the upstream end is connected to the confluence point where the downstream ends of the first reversal path and the second reversal path merge with each other and the medium is conveyed to the post-processing unit.
The second transport speed, which is the transport speed of the medium in the lead-out path, is slower than the first transport speed, which is the transport speed of the medium in the introduction path.
The second distance between the trailing end of the leading medium and the trailing end of the trailing medium in the derivation path is shorter than the first distance between the trailing end of the leading medium and the trailing end of the trailing medium in the introduction path. A medium transport mechanism characterized by. It is a control method of the medium transfer mechanism.
The medium transfer mechanism is
An introduction path configured to carry the medium recorded by the printing unit that ejects droplets, and
A first switchback path configured to switch back the medium conveyed from the introduction path, and
A second switchback path configured to switch back the medium transferred from the introduction path,
A first branch path configured to transport the medium from the introduction path to the first switchback path, and
A second branch path configured to transport the medium from the introduction path to the second switchback path, and
A first inversion path configured to invert and convey the medium switched back from the first switchback path, and
A second inversion path configured to invert and convey the medium switched back from the second switchback path, and
It is provided with a derivation path configured so that the upstream end is connected to the confluence point where the downstream ends of the first reversal path and the second reversal path merge with each other and the medium is conveyed to the post-processing unit.
The control method is
The second transport speed, which is the transport speed of the medium in the lead-out path, is slower than the first transport speed, which is the transport speed of the medium in the introduction path, and
The second distance between the trailing end of the leading medium and the trailing end of the trailing medium in the derivation path is shorter than the first distance between the trailing end of the leading medium and the trailing end of the trailing medium in the introduction path. , Control method.

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