Printing System

Abstract

To provide a printing system that suppresses the occurrence of an inappropriate oblique motion in a printing part on a downstream side even when a delay occurs in conveying a medium on which printing has been performed by the printing part on an upstream side.SOLUTION: A printing system 1 includes: printing parts 16 and 66 (an example of a first printing part and a second printing part) that print on paper P (an example of a medium); and a conveyance mechanism that conveys paper P printed by the printing part 16 to the printing part 66. The conveyance mechanism includes a registration roller 64 that is arranged on a downstream side in a conveyance direction from a re-feed sensor 63 (an example of a passage detection sensor) and a re-feed roller 61 (an example of a conveyance roller). The printing system 1 includes a second printing device control part 71 (an example of a control part) that controls the re-feed roller 63 so that the sagging amount of subsequent paper P is constant, based on a conveyance situation of preceding paper P (time t11) and a detection time (time t12) of the leading edge of the subsequent paper P detected by the re-feed sensor 63.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a printing system. [Background technology]

[0002] A printing system is known that includes two printing devices and an intermediate device that is disposed between the two printing devices and turns the paper over. This printing system can improve the productivity of printed matter compared to a case where double-sided printing is performed by a single printing device. In the above-mentioned printing system, for example, a printing device is used that abuts the paper against a registration roller disposed upstream of the printing unit to form slack and correct skew, and then drives the registration roller to transport the paper to the printing unit and print it.

[0003] In a printing system in which multiple printing devices are connected, the transported paper is likely to be delayed or advanced at the connection between the devices. When the paper is delayed or advanced, a jam occurs due to a collision of the paper. In order to prevent the collision of the paper, a printing system has been disclosed that prevents the collision of the paper by controlling the transport between the transport roller at the connection and the transport roller of the downstream printing device (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-119563 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the printing system that prevents paper collisions described above, slippage of printing paper can cause variations in the spacing between sheets during transport and the amount of slack based on this to be inappropriate, which does not take into consideration the occurrence of skew defects. In other words, if the amount of slippage of the paper at the joint varies from sheet to sheet, the timing of arrival at the registration roller differs for each sheet, and the amount of slack may be inappropriate. Specifically, when a sheet with a low printing rate is transported to the joint after a sheet with a high printing rate, the ease of slipping of the sheets differs (sheets with a high printing rate are more slippery), and the amount of slack is likely to vary. Furthermore, as will be described later with reference to FIG. 6, there are cases in which the leading edge of the paper that should be abutted against the registration roller slips through the registration roller, and no slack is formed, resulting in skew defects.

[0006] In addition, at the connection part, the speed difference between the entrance transport roller and the downstream transport roller, or the difference in paper size or printing rate may cause transport back tension, and the arrival timing of each paper at the registration roller may differ. Note that the transport delay of the paper may also be caused by other factors such as curling of the paper.

[0007] FIG. 6 is an explanatory diagram for explaining the drive control of the paper re-feed motor and the registration motor in the reference technology.

[0008] The refeed motor drives a refeed roller that transports paper toward a printing section of a downstream printing device in a printing system that includes an upstream printing device and a downstream printing device.

[0009] The re-feed sensor is disposed near the re-feed roller, downstream in the transport direction of the re-feed roller.

[0010] The registration motor drives the registration roller. This registration roller is located downstream of the refeed sensor and upstream of the printing unit. The drive time of the registration motor (time t64 to time t67) is always constant because it is controlled by a specified amount converted into an encoder. The start time of the registration motor (time t64, time t68) is determined based on the ON timing of the refeed sensor (times t62, t66).

[0011] The registration sensor is disposed upstream of and in the vicinity of the registration rollers.

[0012] For example, if the printing rate is high and the transport of slippery paper is delayed, the timing (time t62) at which the leading edge of the paper is detected by the re-feed sensor will be delayed, and the paper gap, which is the period between the timing (time t61) at which the trailing edge of the preceding paper is detected by the re-feed sensor, will become longer.

[0013] On the other hand, if the paper conveyed after the slippery paper is not delayed, the paper interval (time t65 to time t66) between these two papers at the refeed sensor becomes short. Therefore, the leading edge of the next paper enters the registration roller before the driving time (time t64 to time t67) of the registration motor for conveying the slippery paper ends, specifically, before the registration roller stops rotating. In this case, the paper stops with its leading edge passing the registration roller, so slack is not formed and skew failure occurs as described above.

[0014] The object of the present invention is to provide a printing system that can suppress the occurrence of skew defects in a downstream printing unit even if a delay occurs in the transport of a medium printed by an upstream printing unit. [Means for solving the problem]

[0015] In one aspect, a printing system includes a first printing unit that prints on a medium, a second printing unit that is located downstream of the first printing unit in the transport direction of the medium and prints on the medium, and a transport mechanism that transports the medium printed by the first printing unit to the second printing unit, wherein the transport mechanism includes a passing detection sensor that detects the passage of the medium, a transport roller that transports the medium, and a registration roller that is located downstream of the passing detection sensor and the transport roller in the transport direction and transports the medium that has been abutted against it and has become slack due to the abutment, and the printing system is characterized in that it includes a control unit that controls the transport roller so that the amount of slack in the subsequent medium is constant based on the transport status of the preceding medium and the detection time of the leading edge of the subsequent medium detected by the passing detection sensor. Effect of the Invention

[0016] According to this aspect, even if a delay occurs in the transport of a medium printed by an upstream printing unit, it is possible to prevent the occurrence of skew defects in the downstream printing unit. [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic configuration diagram of a printing system according to an embodiment. [Diagram 2] FIG. 1 is a control block diagram of a printing system according to an embodiment. [Diagram 3] 5 is a time chart showing the operations of a relay roller, a paper re-feed roller, and a registration roller in the embodiment. FIG. [Figure 4] FIG. 2 is an explanatory diagram for explaining a calculation method of a first period, a second period, etc. in one embodiment. [Diagram 5] 5 is a flowchart showing operation control of a paper re-feed roller and a registration roller in the embodiment. [Figure 6] 11A and 11B are explanatory diagrams for explaining drive control of a paper re-feed motor and a registration motor in the reference technology. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A printing system according to an embodiment of the present invention will now be described with reference to the drawings.

[0019] The present embodiment described below is an example of an apparatus for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the material, shape, structure, arrangement, etc. of each component to those described below. The technical idea of ​​the present invention can be modified in various ways within the scope of the claims.

[0020] FIG. 1 is a schematic diagram of a printing system 1 according to an embodiment of the present invention.

[0021] FIG. 2 is a control block diagram of the printing system 1.

[0022] In the following description, the direction perpendicular to the paper surface of Fig. 1 is referred to as the front-rear direction, and the directions up, down, left, and right on the paper surface of Fig. 1 are referred to as the up, down, left, and right directions.

[0023] 1, the path indicated by the thick line is the transport path along which paper P, which is an example of a medium, is transported. Among the transport paths, the paths indicated by the solid lines are the upstream transport path RU and the downstream transport path RD, the path indicated by the dashed lines is the reversing path RR, and the path indicated by the dashed and dotted lines is the non-reversing middle path RC. In the following description, upstream and downstream refer to upstream and downstream in the transport direction on the transport path.

[0024] As shown in FIG. 1 and FIG. 2, the printing system 1 includes a first printing device 2, an intermediate device 3, and a second printing device 4. Note that the printing system according to the present embodiment may be omitted as long as it includes a first printing unit, an example of which is the printing unit 16 described later, a second printing unit, an example of which is the printing unit 66 described later, and a transport mechanism that transports paper P (medium) printed by the first printing unit to the second printing unit. In addition, the first printing device 2 and the second printing device 4 do not have to be disposed independently. Therefore, a printing device that includes the first printing unit and the second printing unit, for example, in a single housing also functions as a printing system.

[0025] The first printing device 2 prints an image on paper P and sends the paper P to the intermediate device 3. The first printing device 2 includes a paper feed tray 11, a paper feed roller 12, a paper feed motor 13, a registration roller 14, a registration motor 15, a printing unit 16, paper discharge rollers 17 and 18, a paper discharge motor 19, and a first printing device control unit 20. The first printing device 2 can be considered as an external device of the second printing device 4.

[0026] The paper feed tray 11 is a tray on which paper P to be used for printing is stacked.

[0027] The paper feed rollers 12 take out the paper sheets P stacked on the paper feed tray 11 one by one and transport them to the registration rollers 14. The paper feed rollers 12 also perform an assisting operation to assist the registration rollers 14 in transporting the paper sheets P. The paper feed rollers 12 are disposed at the upstream end of the upstream transport path RU.

[0028] The paper feed motor 13 drives the paper feed roller 12 to rotate.

[0029] The registration rollers 14 are abutted against the paper P conveyed from the paper feed rollers 12, and after the paper P is loosened, the registration rollers 14 convey the paper P toward the printing unit 16.

[0030] The registration motor 15 drives the registration rollers 14 to rotate.

[0031] The printing unit 16 prints an image on the paper P while transporting the paper P. The printing unit 16 includes a belt platen unit 21 and a head unit 22. The printing unit 16 is an example of a first printing unit that prints on the paper P (medium).

[0032] The belt platen unit 21 attracts and holds the paper P conveyed from the registration rollers 14 on the belt and conveys it.

[0033] The head unit 22 prints an image by ejecting ink onto the paper P transported by the belt platen unit 21. The head unit 22 has an inkjet head (not shown) having a plurality of nozzles arranged along the front-rear direction, and ejects ink onto the paper P from the nozzles of the inkjet head.

[0034] The paper discharge rollers 17 and 18 discharge the paper P conveyed from the belt platen unit 21 to the intermediate device 3.

[0035] The paper discharge motor 19 drives the paper discharge rollers 17 and 18 to rotate.

[0036] The first printing device control unit 20 controls the operation of each unit of the first printing device 2. The first printing device control unit 20 has a processor (e.g., CPU: Central Processing Unit). The first printing control unit 20 also has memories such as ROM (Read Only Memory), which is a read-only semiconductor memory in which a specific control program is pre-recorded, and RAM (Random Access Memory), which is a semiconductor memory that can be written and read at any time and is used as a working memory area as necessary when the processor executes various control programs.

[0037] The first printing device control unit 20 is capable of communicating with a terminal device 7, such as a personal computer, via a first network 5, such as a LAN. The first printing device control unit 20 is also capable of communicating with a second printing device control unit 71 of the second printing device 4, which will be described later, via a second network 6, such as a LAN. The first printing device control unit 20 is also capable of communicating with an intermediate device control unit 51 of the intermediate device 3, which will be described later, and a second printing device control unit 71 of the second printing device 4, via a communication line 8.

[0038] When printing is performed by the first printing device 2, the first printing device control unit 20 controls the paper feed roller 12 to take out the paper P from the paper feed tray 11 and to abut the paper P against the registration roller 14. After that, the first printing device control unit 20 controls the paper feed roller 12 to assist the registration roller 14 in driving the paper P and to transport the paper P to the printing unit 16. Then, the first printing device control unit 20 controls the printing unit 16 to print an image on the paper P by the head unit 22 while transporting the paper P by the belt platen unit 21.

[0039] The intermediate device 3 transports the paper P between the first printing device 2 and the second printing device 4. The intermediate device 3 is disposed adjacent to the downstream side (right side) of the first printing device 2. The intermediate device 3 includes an entrance roller 31, an entrance motor 32, an entrance sensor 33, a path switching flipper 34, a path switching solenoid 35, reversing rollers 36 and 37, a reversing sensor 38, and a switchback roller 39. The intermediate conveying device includes a switchback motor 39, a switchback motor 40, a switchback sensor 41, intermediate rollers 42, 43, an intermediate conveying motor 44, a face-up roller 45, a lifting roller 46, a lifting motor 47, a relay roller 48, a relay motor 49, a relay sensor 50, and an intermediate device control unit 51.

[0040] Here, the intermediate device 3 functions as an example of a transport mechanism together with the discharge rollers 17, 18 and discharge motor 19 of the first printing device 2, and the re-feed roller 61, re-feed motor 62, re-feed sensor 63, registration roller 65, and registration motor 66 of the second printing device 4 described below. This transport mechanism transports the paper P (medium) printed by the printing unit 16 (first printing unit) of the first printing device 2 to the printing unit 66 (second printing unit) of the second printing device 4.

[0041] The entrance rollers 31 take in the paper P discharged from the first printing device 2 into the intermediate device 3. The entrance rollers 31 are disposed at the downstream end of the upstream transport path RU and at the upstream end of the transport path within the intermediate device 3.

[0042] The approach motor 32 drives the approach roller 31, the reversing roller 36, and the face-up roller 45 to rotate.

[0043] The entry sensor 33 detects the paper P that has entered the intermediate device 3 from the first printing device 2. The entry sensor 33 is disposed in the vicinity of the entry rollers 31 on the downstream side.

[0044] The path switching flipper 34 switches the path of the paper P transported along the upstream transport path RU between a reversing path RR and a non-reversing intermediate path RC.

[0045] The path switching solenoid 35 drives the path switching flipper 34 .

[0046] The reversing rollers 36 and 37 convey the sheet P, which has been guided to the reversing path RR by the path switching flipper 34, to a switchback roller 39.

[0047] The reversing sensor 38 detects the paper P being transported to the switchback rollers 39 by the reversing rollers 36 and 37. The reversing sensor 38 is disposed between the entrance sensor 33 and the switchback rollers 39, and between the reversing rollers 36 and 37.

[0048] The switchback roller 39 switches back the sheet P conveyed by the reversing rollers 36, 37 and conveys it to the intermediate roller 42. The switchback roller 39 is configured to be capable of rotating forward and backward in order to switch back the sheet P.

[0049] The switchback motor 40 drives the switchback roller 39 in the forward and reverse directions.

[0050] The switchback sensor 41 detects the paper P being switched back by the switchback roller 39 .

[0051] The intermediate rollers 42 and 43 transport the paper P switched back by the switchback roller 39 to the lifting roller 46 .

[0052] The intermediate conveying motor 44 drives the reversing roller 37 and the intermediate rollers 42 and 43 to rotate.

[0053] The face-up roller 45 conveys the paper P, which has been guided to the non-reversing intermediate path RC by the path-switching flipper , to the lifting roller .

[0054] The lifting roller 46 transports the paper P transported from the intermediate roller 43 or the face-up roller 45 to the relay roller 48. The lifting roller 46 is disposed on the downstream transport path RD near the downstream side of the junction of the reversing path RR and the non-reversing intermediate path RC.

[0055] The lifting motor 47 drives the lifting roller 46 to rotate.

[0056] The relay roller 48 transports the paper P transported from the lift roller 46 to the second printing device 4.

[0057] The relay motor 49 drives the relay roller 48 to rotate.

[0058] The relay sensor 50 detects the paper P being transported to the second printing device 4 by the relay rollers 48. The relay sensor 50 is disposed near the downstream side of the relay rollers 48, which is near the exit of the paper P from the intermediate device 3.

[0059] The intermediate device control unit 51 controls the operation of each unit of the intermediate device 3. The intermediate device control unit 51 has a processor (e.g., a CPU), memories such as RAM and ROM, etc. The intermediate device control unit 51 is capable of communicating with the first printing device control unit 20 of the first printing device 2 and a second printing device control unit 71 of the second printing device 4 (described later) via the communication line 8.

[0060] The second printing device 4 prints on the paper P transported from the intermediate device 3. The second printing device 4 is disposed adjacent to the downstream side (right side) of the intermediate device 3. The second printing device 4 includes a re-feed roller 61, a re-feed motor 62, a re-feed sensor 63, a registration roller 64, a registration motor 65, a printing unit 66, paper discharge rollers 67 and 68, a paper discharge motor 69, a paper discharge tray 70, and a second printing device control unit 71.

[0061] The re-feed roller 61 transports the paper P transported from the relay roller 48 of the intermediate device 3 to the registration roller 64. The re-feed roller 61 also performs an assisting operation to assist the registration roller 64 in transporting the paper P. The re-feed roller 61 is disposed at the upstream end of the downstream transport path RD in the second printing device 4. The re-feed roller 61 is an example of a transport roller that transports the paper P (medium). It is desirable for this transport roller to be a roller that is closest to the registration roller 64 on the upstream side of the registration roller 64, like the re-feed roller 61.

[0062] The sheet re-feed motor 62 rotates and drives the sheet re-feed roller 61. The sheet re-feed motor 62 is an example of a transport drive unit that drives the sheet re-feed roller 61 (transport roller).

[0063] The paper re-feed sensor 63 detects the paper P transported from the paper re-feed rollers 61 to the registration rollers 64. The paper re-feed sensor 63 is disposed upstream of the registration rollers 64 and in the vicinity of the downstream side of the paper re-feed rollers 61. The paper re-feed sensor 63 is an example of a passage detection sensor that detects the passage of the paper P (medium).

[0064] The registration roller 64 is disposed downstream of the re-feed sensor 63 and the re-feed roller 61, and is abutted against the paper P transported from the re-feed roller 61, and transports the paper P that has become slack due to the abutment toward the printing section 66.

[0065] The registration motor 65 rotates and drives the registration roller 64. The registration motor 65 is an example of a registration driving unit that drives the registration roller.

[0066] The printing unit 66 prints an image on the paper P while transporting the paper P. The printing unit 66 includes a belt platen unit 76 and a head unit 77. The printing unit 66 is disposed downstream of the printing unit 16 (first printing unit) in the transport direction of the paper P, and is an example of a second printing unit that prints on the paper P (medium).

[0067] The belt platen section 76 and the head unit 77 have the same configurations as the belt platen section 21 and the head unit 22 of the first printing device 2 described above, respectively.

[0068] The paper discharge rollers 67 and 68 discharge the paper P conveyed from the belt platen unit 76 onto the paper discharge tray 70 .

[0069] The paper discharge motor 69 drives the paper discharge rollers 67 and 68 to rotate.

[0070] The paper discharge tray 70 holds the paper P discharged by the paper discharge rollers 67 and 68 .

[0071] The second printing device control unit 71 controls the operation of each unit of the second printing device 4. The second printing device control unit 71 has a processor (e.g., a CPU), and memories such as RAM and ROM. The second printing device control unit 71 is capable of communicating with the first printing device control unit 20 of the first printing device 2 via the second network 6. The second printing device control unit 71 is also capable of communicating with the first printing device control unit 20 of the first printing device 2 and the intermediate device control unit 51 of the intermediate device 3 via the communication line 8.

[0072] Although details will be described later, when printing is performed by the second printing device 4, the second printing device control unit 71 causes the re-feed roller 61 to abut the paper P transported from the intermediate device 3 against the registration roller 64 to stop the re-feed roller 61. Thereafter, the second printing device control unit 71 controls the registration roller 64 to be driven and the re-feed roller 61 to assist the registration roller 64 to transport the paper P to the printing unit 66. Then, the second printing device control unit 71 controls the printing unit 66 to print an image on the paper P by the head unit 77 while transporting the paper P by the belt platen unit 76. Here, the second printing device control unit 71 is an example of a control unit that controls the re-feed roller 61 so that the amount of slack in the subsequent paper P is constant based on the transport status of the preceding paper P and the detection time of the leading edge of the subsequent paper P detected by the re-feed sensor 63, as will be described later.

[0073] Next, the operation of the printing system 1 when performing double-sided printing will be described.

[0074] The double-sided printing operation in the printing system 1 is started when the first printing apparatus control unit 20 receives a print job for double-sided printing from the terminal apparatus 7 via the first network 5 .

[0075] When the first printing apparatus control unit 20 receives the print job, it starts driving the belt platen unit 21 and the paper discharge rollers 17 and 18.

[0076] Furthermore, when the first printing device control unit 20 receives the print job, it transmits the print job to the second printing device control unit 71 via the second network 6. Furthermore, the first printing device control unit 20 transmits a preparation signal to the intermediate device control unit 51 via the communication line 8 to instruct the intermediate device control unit 51 to start preparations for double-sided printing.

[0077] When the second printing apparatus control unit 71 receives the print job, it starts driving the paper re-feed roller 61, the belt platen unit 76, and the paper discharge rollers 67, 68.

[0078] When the intermediate device control unit 51 receives the preparation signal, it starts driving the entry roller 31, the reversing rollers 36, 37, the switchback roller 39, the intermediate rollers 42, 43, the lifting roller 46, and the relay roller 48. In addition, the intermediate device control unit 51 sets the path switching flipper 34 in a direction that leads the paper P from the upstream transport path RU to the reversing path RR.

[0079] The first printing device control unit 20 starts driving the belt platen unit 21 and the paper discharge rollers 17, 18, and then starts feeding the paper from the paper feed tray 11 to the printing unit 16. Then, the paper P hits the registration rollers 14 and stops in a slack state. As a result, the skew of the paper P is corrected.

[0080] When a predetermined time has elapsed after the paper feed roller 12 has stopped, the first printing apparatus control unit 20 starts driving the registration roller 14. Also, at the same time as starting to drive the registration roller 14, the first printing apparatus control unit 20 starts an assisting operation by the paper feed roller 12. Thereafter, the first printing apparatus control unit 20 controls the registration roller 14 to transport the paper P to the printing unit 16. The assisting operation ends before the rear end of the paper P passes through the paper feed roller 12. This is to prevent the paper feed roller 12 from accidentally transporting the next paper P. By repeating such operations of the paper feed roller 12 and the registration roller 14, the paper P is transported sequentially to the printing unit 16.

[0081] The paper P transported to the printing unit 16 is printed on its front side by the head unit 22 while being transported by the belt platen unit 21. The paper P printed in the printing unit 16 is discharged to the intermediate device 3 by the paper discharge rollers 17 and 18.

[0082] The paper P discharged to the intermediate device 3 is switched back at the intermediate device 3.

[0083] In the intermediate device 3, the sheet P is received by the entrance rollers 31 and transported, and is guided from the upstream transport path RU to a reverse path RR by a path switching flipper 34. The sheet P guided to the reverse path RR is transported to a switchback roller 39 by reverse rollers 36 and 37.

[0084] When the sheet P reaches the switchback rollers 39, the sheet P is received by the switchback rollers 39 and transported at a preset reversal transport speed.

[0085] When a predetermined stop time has elapsed since the switchback rollers 39 stopped, the intermediate device control section 51 starts driving the switchback rollers 39 in the reverse direction.

[0086] The switched-back paper P is transported by intermediate rollers 42 and 43, a lift roller 46, and a relay roller 48, and is sent to the second printing device 4. Having been switched-back by the intermediate device 3, the paper P is sent to the second printing device 4 in an inverted state.

[0087] The paper P sent from the intermediate device 3 to the second printing device 4 is received and transported by the paper re-feed rollers 61, and is abutted against the registration rollers 64. The paper P is then transported by the registration rollers 64 to the printing unit 66. At this time, the paper re-feed rollers 61 perform an assisting operation to assist the registration rollers 64 in transporting the paper P.

[0088] The operations of the re-feed roller 61 and the registration roller 64 are controlled based on the timing when the leading edge of the paper is detected by the re-feed sensor 63. Furthermore, if the size of the paper P is equal to or larger than a predetermined size, the relay roller 48 performs a deceleration abutment operation and an assist operation in synchronization with the re-feed roller 61. Specifically, if the size of the paper P is such that the trailing edge does not come out of the relay roller 48 (is nipped by the relay roller 48) when the paper P abuts against the registration roller 54, the relay roller 48 operates in synchronization with the re-feed roller 61 until the paper P comes out.

[0089] Here, the operations of the relay roller 48, the paper re-feed roller 61, and the registration roller 64 will be described.

[0090] FIG. 3 is a time chart showing the operations of the relay roller 48, the paper re-feed roller 61, and the registration roller 64. In FIG.

[0091] FIG. 4 is an explanatory diagram for explaining a method of calculating the first period Tx, the second period Ty, and the like.

[0092] FIG. 5 is a flow chart showing the operation control of the paper re-feed rollers 61 and the registration rollers 64. As shown in FIG.

[0093] First, when the intermediate device control unit 51 receives a LOW level signal (downstream I / F signal) from the second printing device control unit 71, it starts driving the relay roller 48, the re-feed roller 61, and the registration roller 64 (time t10 in FIG. 3, step S1 in FIG. 5). The operation of the relay roller 48 and the re-feed roller 61 is an assist operation that assists the registration roller 64 in transporting the paper P. The relay roller 48, the re-feed roller 61, and the registration roller 64 accelerate to a predetermined speed and then decelerate to transport the paper P at the printing speed.

[0094] Then, the relay sensor 50 detects the trailing edge of the first sheet of paper P, and thereafter, the re-feed sensor 63 detects the trailing edge of the first sheet of paper P (time t11 after the time Ts has elapsed). Note that the time Ts can be calculated as a theoretical value (fixed value) for each printing condition.

[0095] When the re-feed sensor 63 detects the leading edge of the second sheet of paper P (time t12, step S2: YES), the second printing device control unit 71 acquires the sensor-off period Ta since the re-feed sensor 63 detected the trailing edge of the first sheet of paper P (step S3).

[0096] In addition, based on the sensor-off period Ta, the second printing device control unit 71 determines a first period Tx during which the reverse conveying speed V1 (an example of a first conveying speed) of the re-feed roller 61 at the detection time (time t12) of the leading edge of the second sheet of paper P detected by the re-feed sensor 63 is maintained after this detection time, and determines a second period Ty during which abutment speed V2 (an example of a second conveying speed), which is the conveying speed when the second sheet of paper P is abutted against the registration roller 64 and is slower than the reverse conveying speed V1, is maintained (step S4).

[0097] FIG. 4 is an explanatory diagram for explaining a method of calculating the first period Tx, the second period Ty, and the like.

[0098] 4, the feed amount (conveyance amount) during a first period Tx during which the refeed roller 61 maintains the leading edge reversing transport speed V1 from the time (time t12) when the refeed sensor 63 detects the leading edge of the paper P to time t13 is set to L1, and the feed amount (conveyance amount) during a second period Ty during which the refeed roller 62 maintains the abutment speed V2 from time t13 until time t14 after the leading edge reversing transport speed V1 is decelerated is set to L2. The sum of the feed amounts L1 and L2 is set to Lconst, and the deceleration acceleration of the refeed roller 61 is set to αdn.

[0099] The feed amount Lstrike (shaded portion) from time t12 to time t15 is constant, for example, in order to maintain a constant amount of slackness formed in the paper P. If the feed amount Lstrike of the refeed roller 61 is constant, slippery paper P is more likely to have less slack than non-slippery paper P. Therefore, the feed amount Lstrike may be increased as the actual transport time from the predetermined position of the paper P to time t12 increases (as the paper P becomes more slippery).

[0100] Lconst can be expressed as Lstrike-V1^2 / 2 / αdn.

[0101] Time Tkr from time t11 when the trailing edge of the preceding (first) sheet of paper P is detected by the re-feed sensor 63 to the start of driving of the registration rollers 64 can be expressed as the difference between time Tcyc from time t11 to the time when the trailing edge of the succeeding (second) sheet of paper P is detected by the re-feed sensor 63, and time Tsr from time t20 to the time when the trailing edge of the succeeding (second) sheet of paper P is detected by the re-feed sensor 63. If the time Tkr minus the sensor-off period Ta is time Ttr, the drive cycle of the registration rollers 64 can be expressed as the sum of time Tsr, sensor-off period Ta, and time Ttr.

[0102] The time Tconst, which is the sum of the first period Tx and the second period Ty, can be expressed as the value obtained by subtracting V1 / αdn and the sensor-off period Ta from the time T3 from time t11 to time t15, and can also be expressed as Tkr-Ta-V1 / αdn-T5.

[0103] Using the above-mentioned values, the feed amount L1 can be calculated as shown in the lower right column of Fig. 4. Therefore, the feed amount L2 can be calculated in the same manner. If the feed amounts L1 and L2 can be calculated, the first period Tx and the second period Ty can be calculated by dividing the feed amounts L1 and L2 by the conveying speeds V1 and V2.

[0104] The above-mentioned time Tcyc can be expressed as P / Vg+Tpp, where P is the length of the paper P in the transport direction, Vg is the transport speed (print speed) of the belt platen unit 76, and Tpp is the paper interval time. If B is the distance from the refeed sensor 63 to the registration roller 64, and Drb is the distance from the registration roller 64 to the belt platen unit 76, the time Tsr can be expressed as the sum of the total time Ttop of the acceleration time of the registration roller 64 at the acceleration αr1, the transport time at the maximum speed Vtop, and the deceleration time at the deceleration acceleration αr2, and (PB-Drb) / Vg. The above-mentioned first period Tx and second period Ty may be calculated appropriately using the time T2r from time t11 until the trailing edge of the preceding paper P leaves the registration roller 64, the time T1s from when the trailing edge of the preceding paper P leaves the registration roller 64 until time t15, the time T2s from when the trailing edge of the preceding paper P leaves the registration roller 64 until time t20, etc.

[0105] Here, the slippery paper P has its leading edge detected by the refeed sensor 63 at a later time t12. As the time t12 is later, the first period Tx becomes longer and the second period Ty becomes shorter. However, when the sensor-off period Ta reaches Tmax and the time t12 is later by a time Th, the second period Ty becomes zero. Therefore, when the sensor-off period Ta exceeds Tmax, the refeed roller 61 cannot be controlled by adjusting the first period Tx and the second period Ty. In this case, the subsequent time T5 cannot be secured. Therefore, when the synchronization control of the registration roller 64, the refeed roller 61, etc. cannot be stably performed because the time T5 cannot be secured, it is advisable to delay the drive start time (time t20) of the registration roller 64. After that, when the paper P reaches the refeed sensor 53, etc., the control returns to that shown in FIG. 3.

[0106] The above calculation is performed, for example, by the second printing apparatus control unit 71. The second printing apparatus control unit 71 calculates the first period Tx and the second period Ty based on the time t11, which is the detection time of the trailing edge of the preceding (first) sheet of paper P detected by the refeed sensor 63 (passage detection sensor), and the time t12, which is the detection time of the leading edge of the following (second) sheet of paper P detected by the refeed sensor 63, thereby controlling the refeed roller 61 via the intermediate apparatus control unit 51 so that the amount of slack in the following sheet of paper P is constant. Note that, instead of time t11, the time when the trailing edge of the preceding sheet of paper P is detected by the relay sensor 50, the drive start time of each roller of the preceding sheet of paper P, etc. may be used. Therefore, time t11 can be said to be an example of the transport status of the preceding sheet of paper P. However, it is preferable to use the time t11 closest to the time t12 when the leading edge of the following sheet of paper P is detected by the refeed sensor 63.

[0107] In the present embodiment, the first period Tx and the second period Ty are calculated based on the detection time of the refeed sensor 63, which is an example of a passing detection sensor. However, as another example of the passing detection sensor, another sensor arranged on the upstream side of the registration roller 64 may be used to calculate the first period Tx and the second period Ty based on the detection time of this sensor. In addition, instead of at least one of the first period Tx and the second period Ty, the deceleration acceleration αdn of the refeed roller 61 may be adjusted. In addition, in the present embodiment, the control of the refeed roller 61, which is an example of a conveying roller, is described. However, the conveying roller to be controlled is not limited to the refeed roller 61, and other conveying rollers such as the relay roller 48 may be used. In addition, the calculation of the first period Tx and the second period Ty and the control of the refeed roller 61 may be performed by another control unit such as the intermediate device control unit 51.

[0108] Based on the first period Tx calculated as described above, the second printing device control unit 71 repeats the judgment from the time when the re-feed sensor 63 detects the second sheet of paper P until the deceleration start timing (time t13) after the first period Tx has elapsed (step S5).

[0109] When the second printing apparatus control unit 71 reaches the deceleration start timing (step S5: YES), it switches the signal to the intermediate apparatus control unit 51 to a LOW level signal (time t13). As a result, the intermediate apparatus control unit 51 starts decelerating the relay roller 48 and the re-feed roller 61, and when it decelerates to the abutment speed V2, it maintains the abutment speed V2 for the second period Ty until it receives a HIGH level signal (time t14) from the second printing apparatus control unit 71. Then, in the middle of the second period Ty, the leading edge of the second sheet P abuts against the registration rollers 64 in a stopped state, slack is formed in the sheet P, and the skew is corrected (step S6).

[0110] Thereafter, when the slack formation ends, the relay roller 48 and the re-feed roller 61 stop (time t15), and after the time T5 has elapsed, the second printing apparatus control unit 71 transmits a LOW level signal. Upon receiving this LOW level signal (step S7: YES), the intermediate apparatus control unit 51 starts driving the registration roller 64, and also starts driving the relay roller 48 and the re-feed roller 61 for the assist operation (time t20, step S8).

[0111] When the intermediate conveying device control unit 51 receives a HIGH level signal from the second printing device control unit 71 (time t21), it temporarily decelerates the speeds of the relay roller 48, the re-feed roller 61, and the registration roller 64 from the predetermined speed after acceleration to the printing speed.

[0112] Thereafter, the intermediate conveying device control unit 51 determines whether the second sheet of paper P is the last sheet of paper P in the printing job being executed (step S9), and if the sheet of paper P being conveyed is the second and last sheet of paper P (step S9: YES), it stops the relay roller 48 and the re-feed roller 61 (step S10), as shown by dotted lines in FIG. 3, after a predetermined time has elapsed since the above-mentioned LOW level signal (time t20) of the second printing device control unit 71, and terminates the processing shown in FIG. 5.

[0113] On the other hand, if the paper P being transported is the second sheet and not the last (step S9: NO), the intermediate transport device control unit 51 accelerates the relay roller 48 and the re-feed roller 61 to the reversal transport speed V1 (acceptance speed) (step S11) after a predetermined time has elapsed since the above-mentioned LOW level signal (time t20) from the second printing device control unit 71, and returns to the processing of the above-mentioned step S2.

[0114] Here, the above-mentioned "after the specified time has elapsed" refers to, for the relay roller 48, the timing (time t22) when the trailing end of the subsequent sheet P passes through the relay roller 48 just before it passes through the relay sensor 50, which can be determined based on the drive start time (time t20) of the registration roller 64, and for the re-feed roller 61, the timing (time t23) after the trailing end of the subsequent sheet P passes through the re-feed sensor 63.

[0115] In addition, if the printing process of the first printing device 2 is delayed and the above-mentioned sensor-off period Ta becomes too long, the second period Ty of the abutting speed V2 becomes zero, and the paper P may be abutted against the registration rollers 64 at a conveying speed faster than the abutting speed V2. Therefore, when the sensor-off period Ta is a predetermined time or more, the re-feed rollers 61 may be controlled so that the conveying speed when the following (second) paper P is abutted against the registration rollers 64 is a predetermined speed or less (for example, the abutting speed V2). For example, when the sensor-off period Ta is a predetermined time or more, the first period Tx and the second period Ty may be set to predetermined values, time T5 may be secured, and the drive start time of the registration rollers 64 (time t20) may be delayed.

[0116] The paper P transported to the printing unit 66 is printed on the back side by the head unit 77 while being transported by the belt platen unit 76. The paper P printed by the printing unit 66 is discharged onto the paper discharge tray 70 by paper discharge rollers 67, 68.

[0117] In the above description of the double-sided printing operation, the case where the size of the paper P is equal to or larger than a predetermined size has been described, but if the size of the paper P is less than the predetermined size, the deceleration abutment operation and assist operation of the relay roller 48 synchronized with the re-feed roller 61 are not performed. Specifically, if the size of the paper P is such that it is removed from the relay roller 48 (not nipped by the relay roller 48) when it abuts against the registration roller 64, the relay roller 48 continues to be driven at the reverse conveying speed V1. In other words, the intermediate device control unit 51 controls the relay roller 48 to perform the deceleration abutment operation and assist operation in synchronization with the re-feed roller 61 according to the paper size.

[0118] When single-sided printing is performed in the printing system 1, the first printing device 2 prints on the front side of the paper P in the same manner as in the double-sided printing operation described above. The printed paper P is transported to the second printing device 4 via the reversing path RR of the intermediate device 3. In the second printing device 4, the paper P is transported along the downstream transport path RD without being printed on, and is discharged to the paper discharge tray 70. It is also possible to print in the second printing device 4 without printing in the first printing device 2. Also, the paper P discharged from the first printing device 2 may be transported to the second printing device 4 without being reversed by passing through the non-reversing intermediate path RC of the intermediate device 3.

[0119] In the present embodiment described above, the printing system 1 includes a printing unit 16 (an example of a first printing unit) that prints on paper P (an example of a medium), a printing unit 66 (an example of a second printing unit) that is arranged downstream of the printing unit 16 in the transport direction of the paper P and prints on the paper P, and a transport mechanism that transports the paper P printed by the printing unit 16 to the printing unit 66. The transport mechanism includes a refeed sensor 63 (an example of a passage detection sensor) that detects the passage of the paper P, a refeed roller 61 (an example of a transport roller) that transports the paper P, and a registration roller 64 that is arranged downstream of the refeed sensor 63 and the refeed roller 61 in the transport direction and transports the paper P that has become slack due to the abutment against the paper P. In addition, the printing system 1 is equipped with a second printing device control unit 71 (an example of a control unit) that controls the re-feed roller 61 so that the amount of slack in the subsequent paper P is constant based on the transport status of the preceding paper P and the detection time (time t12) of the leading edge of the subsequent paper P detected by the re-feed sensor 63.

[0120] As a result, even if the detection time (time t12) at which the leading edge of the paper P is detected by the refeed sensor 63 is delayed due to slippage of the paper P when the printing rate of the paper P is high, the amount of slack formed by the paper P hitting the registration roller 64 can be made constant. In addition, the end time of the conveyance of the refeed motor 61 (time t15) and therefore the start time of conveyance of the paper P by the registration roller 64 (time t20) can be made constant. Therefore, when the conveyance of the preceding paper P is delayed and the conveyance of the succeeding paper P is not delayed, it is possible to avoid a delay in the end time of the drive of the registration roller 64 for conveying the preceding paper P. This makes it possible to avoid a situation in which the succeeding medium M reaches the registration roller 64 before the end time of the drive of the registration roller 64, and the leading edge of the succeeding medium M passes through the registration roller 64, resulting in no slack being formed in the succeeding medium M. As described above, by forming a constant amount of slack in the paper P, the occurrence of skew of the paper P can be suppressed. Therefore, according to this embodiment, even if there is a delay in the transport of the paper P printed by the upstream printing unit 16, it is possible to suppress the occurrence of skew defects in the downstream printing unit 66. In addition, by setting the time (time t20) when the registration rollers 64 start transporting the paper P at regular intervals, it is also possible to maintain the productivity of the paper P.

[0121] In the present embodiment, the transport state of the preceding sheet P is the detection time of the rear end of the preceding sheet P detected by the re-feed sensor 63 (time t11).

[0122] Therefore, the transport status of the preceding sheet P can be accurately determined at time t11 close to the detection time (time t12) when the leading edge of the succeeding sheet P is detected by the refeed sensor 63. This makes it possible to more reliably suppress the occurrence of skew defects, and more reliably prevent the leading edge of the succeeding medium M from passing through the registration rollers 64, resulting in no slack being formed in the succeeding medium M.

[0123] In addition, in this embodiment, when the difference (sensor off period Ta) between the detection time (time t11) of the rear end of the preceding paper P detected by the re-feed sensor 63 and the detection time (time t12) of the leading end of the succeeding paper P detected by the re-feed sensor 63 is greater than a predetermined time, the second printing device control unit 71 controls the re-feed rollers 61 so that the conveying speed when the succeeding paper P hits the registration rollers 62 is less than or equal to a predetermined speed.

[0124] Incidentally, when the first printing device 2 is connected upstream of the transport mechanism, the interval between the sheets P arriving at the second printing device 4 may widen beyond a predetermined value depending on the transport status (empty transport, etc.) of the first printing device 2. In such a case, it is disadvantageous to the productivity of the sheets P to stop the printing system 1 by determining that a jam has occurred. In addition, in such a case, if the speed at which the succeeding sheets P strike the registration rollers 64 is increased in order to make the transport start time (time t20) of the succeeding sheets P by the registration rollers 64 closer to a constant, the collision sound becomes louder and the damage to the sheets P also becomes greater. As a result, even if the transport start time (time t20) of the registration rollers 20 is delayed and the transport interval between the sheets P to the second printing device 4 becomes wider than usual, it is possible to achieve appropriate skew correction and reduction in collision sound by ensuring the amount of bending in the registration rollers 64 without significantly reducing the productivity of the sheets P.

[0125] In this embodiment, the second printing apparatus control unit 71 adjusts the first period Tx to control the refeed rollers 61. This first period Tx is a period during which the refeed rollers 61 maintain the reverse conveying speed V1 (an example of the first conveying speed) from the detection time (time t12) of the leading edge of the succeeding paper P detected by the refeed sensor 63.

[0126] Therefore, by simply controlling the period of the re-feed roller 61 at the reverse conveying speed V1, which is, for example, the maximum speed, and by using a simple configuration that does not use the re-feed motor 62 that enables a conveying speed faster than the reverse conveying speed V1, the time (time t20) at which the registration roller 64 starts conveying the paper P can be made constant.

[0127] Furthermore, in this embodiment, the second printing apparatus control unit 71 controls the re-feed rollers 61 so that the conveying speed of the re-feed rollers 61 becomes abutment speed V2 (an example of a second conveying speed) that is slower than the reverse conveying speed V1 when the succeeding paper P abuts against the registration rollers 64. Furthermore, the second printing apparatus control unit 71 controls the re-feed rollers 61 by adjusting the first period Tx and the second period Ty during which the re-feed rollers 61 maintain the abutment speed V2.

[0128] Therefore, by simply controlling the period between the reverse conveying speed V1, which is, for example, the maximum speed of the re-feed roller 61, and the collision speed V2, which is slower than the first conveying speed V1 and thereby can reduce collision noise, the time (time t20) at which the registration roller 64 starts conveying the paper P can be made constant, and the collision noise caused by the paper P being abutted when slack is formed can be reduced.

[0129] The present invention is not limited to the above-described embodiment as it is, and the components can be modified and embodied without departing from the gist of the invention in the implementation stage. In addition, various inventions can be formed by appropriate combinations of the multiple components disclosed in the above-described embodiment. For example, all the components shown in the embodiment may be appropriately combined. Of course, various modifications and applications are possible without departing from the spirit of the invention. The invention described in the claims at the time of filing of this application is appended below.

[0130] [Appendix 1] A printing system including a first printing unit that prints on a medium, a second printing unit that is disposed downstream of the first printing unit in a transport direction of the medium and prints on the medium, and a transport mechanism that transports the medium on which the printing has been performed by the first printing unit to the second printing unit, The transport mechanism includes: a passage detection sensor that detects the passage of the medium; A conveying roller for conveying the medium; a registration roller that is disposed downstream in the transport direction from the passage detection sensor and the transport roller, against which the medium is abutted and which transports the medium that has become loose due to the abutment; The printing system includes: a control unit that controls the transport rollers so that the amount of slack in the trailing medium is constant based on the transport status of the leading medium and the detection time of the leading edge of the trailing medium detected by the passage detection sensor; A printing system comprising: [Appendix 2] The transport status of the preceding medium is the detection time of the trailing edge of the preceding medium detected by the passage detection sensor. 2. The printing system according to claim 1 . [Appendix 3] When a difference between a detection time of the rear end of the preceding medium detected by the passage detection sensor and a detection time of the front end of the following medium detected by the passage detection sensor is equal to or greater than a predetermined time, the control unit controls the conveying rollers so that a conveying speed of the following medium when it abuts against the registration rollers is equal to or less than a predetermined speed. 3. The printing system according to claim 2. [Appendix 4] The control unit controls the transport roller by adjusting a first period during which the transport roller maintains a first transport speed from the detection time of the leading edge of the subsequent medium. 4. The printing system according to claim 1, [Appendix 5] the control unit controls the conveying rollers so that a conveying speed of the conveying rollers becomes a second conveying speed slower than the first conveying speed when the succeeding medium abuts against the registration rollers; The control unit controls the transport roller by adjusting the first period and a second period during which the transport roller maintains the second transport speed. 5. The printing system according to claim 4. [Explanation of symbols]

[0131] 1 Printing System 2 1st printing device 3 Intermediate device 4 2nd printing device 16 Printing Department 48 Relay Roller 50 Relay Sensor 51 Intermediate device control section 61 Refeed roller 62 Refeed motor 63 Refeed sensor 64 Registration roller 65 Resist motor 66 Printing Department 71 Second printing device control section

Claims

[Claim 1] A printing system including a first printing unit that prints on a medium, a second printing unit that is disposed downstream of the first printing unit in a transport direction of the medium and prints on the medium, and a transport mechanism that transports the medium on which the printing has been performed by the first printing unit to the second printing unit, The transport mechanism includes: a passage detection sensor that detects the passage of the medium; A conveying roller for conveying the medium; a registration roller that is disposed downstream in the conveying direction from the passage detection sensor and the conveying roller, against which the medium is abutted and which conveys the medium that has become loose due to the abutment; The printing system includes: a control unit that controls the conveyance rollers so that an amount of slack in the trailing medium is constant based on a detection time of the trailing end of the preceding medium detected by the passage detection sensor and a detection time of the leading end of the following medium detected by the passage detection sensor; When a difference between a detection time of the rear end of the preceding medium detected by the passage detection sensor and a detection time of the front end of the following medium detected by the passage detection sensor is equal to or greater than a predetermined time, the control unit delays a drive start time of the registration rollers and controls the transport rollers so that a transport speed of the following medium when it abuts against the registration rollers is equal to or less than a predetermined speed. A printing system comprising:

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