Printing system

Abstract

The present invention provides a printing system. In the printing system, even if there is a conveyance delay of a medium printed by an upstream printing unit, skewing defects occurring in a downstream printing unit thereof will be suppressed. The printing system includes a printing unit (an example of a first printing unit and a second printing unit) that prints on a sheet (an example of a medium), and a conveyance mechanism that conveys the sheet printed by the printing unit to the printing unit. The conveyance mechanism includes a positioning roller disposed at a position downstream of a refeeding sensor (an example of a detection sensor) and a refeeding roller (an example of a conveyance roller) in the conveyance direction. The printing system includes a second printing device control unit (an example of a control unit) that controls the refeeding roller based on the conveyance state of a preceding sheet (time t11) and the detection time (time t12) when the front end of a subsequent sheet is detected by the refeeding sensor so that the bending amount of the subsequent sheet is fixed.

Description

Technical Field

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

[0002] There is known a printing system including two printing devices and an intermediate device disposed between the two printing devices and configured to flip the front and back sides of a sheet. This printing system can improve the productivity of printed matter compared to the case of performing double-sided printing using a single printing device. In the printing system as described above, for example, the following printing device is used: a sheet is brought into contact with a registration roller disposed on the upstream side of a printing unit to form a bend in the sheet for skew correction, and then the registration roller is driven to convey the sheet to the printing unit for printing.

[0003] In a printing system in which a plurality of such printing devices are connected, delays or advances of the conveyed sheets are likely to occur at the connection portions between the devices. If a delay or advance of the sheet occurs, paper jams occur due to collisions of the sheets or the like. Therefore, in order to prevent collisions of the sheets, a printing system that prevents sheet collisions by conveyance control between a conveyance roller in a connection portion and a conveyance roller of a downstream printing device has been disclosed (see Patent Document 1).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-119563 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] In the above-described printing system for preventing sheet collisions, the following situations are not considered: changes in the interval of the conveyed sheets due to sliding of the printed sheets, and inappropriate bending amounts based on such changes, resulting in skew defects. That is, if the sliding amount of the sheets in the connection portion varies from sheet to sheet, the arrival timing at the registration roller differs from sheet to sheet, and inappropriate bending amounts occur. Specifically, when a sheet with a low printing rate is conveyed to the connection portion after a sheet with a high printing rate, the ease of sliding of the sheets is different (the sheet with the high printing rate is more likely to slide), so that the bending amount is likely to deviate. Furthermore, as will be described later, there is also a case where the leading edge of the sheet that should come into contact with the registration roller passes through the registration roller without forming a bend, resulting in a skew defect. Figure 6 As will be described later, there is also a case where the leading edge of the sheet that should come into contact with the registration roller passes through the registration roller without forming a bend, resulting in a skew defect.

[0009] In addition, in the connecting section, conveyance reverse tension is also generated due to the speed difference between the conveyance roller at the inlet and the conveyance roller downstream thereof, as well as differences in paper size or printing rate, and thus the arrival timing at the registration roller varies depending on the paper. In addition, conveyance delay of the paper may also occur due to other factors such as curling of the paper.

[0010] Figure 6 It is an explanatory diagram for explaining the drive control of the refeeding motor and the registration motor in the related art.

[0011] The refeeding motor drives the refeeding roller. In the downstream printing device in a printing system having an upstream printing device and a downstream printing device, the refeeding roller conveys the paper toward the printing unit.

[0012] The refeeding sensor is disposed downstream in the conveyance direction of the refeeding roller and near the refeeding roller.

[0013] The registration motor drives the registration roller. The registration roller is disposed at a position downstream of the refeeding sensor and upstream of the printing unit. Regarding the drive time of the registration motor (time t64 to time t67), control of a specified amount is performed by encoder conversion, and thus it is always fixed. The start time of the registration motor (time t64, time t68) is determined based on the ON timing (time t62, t66) of the refeeding sensor.

[0014] The registration sensor is disposed upstream of the registration roller and near the registration roller.

[0015] For example, when the conveyance of a paper with a high printing rate and easy to slip is delayed, the timing (time t62) at which the leading edge of the paper is detected by the refeeding sensor becomes later, and the paper interval, that is, the period between this timing and the timing (time t61) at which the trailing edge of the preceding paper is detected by the refeeding sensor, becomes longer.

[0016] On the other hand, when the conveyance of the paper conveyed after the easy-to-slip paper is not delayed, the paper interval (time t65 to time t66) between these two papers at the refeeding sensor becomes shorter. Therefore, before the drive time (time t64 to time t67) of the registration motor for conveying the easy-to-slip paper ends, specifically, before the rotation of the registration roller stops, the leading edge of the next paper enters the registration roller. In this case, the paper stops in a state where the leading edge of the paper has passed through the registration roller, and thus, as described above, no bending occurs and skew defects do not occur.

[0017] An object of the present invention is to provide a printing system that can suppress the occurrence of skew defects in the downstream printing unit even when conveyance delay of a medium printed by the upstream printing unit occurs.

[0018] Solution for solving problems

[0019] In one mode, a printing system includes: a first printing unit that prints on a medium; a second printing unit that is disposed at a position downstream of the first printing unit in the conveyance direction of the medium and prints on the medium; and a conveyance mechanism that conveys the medium printed by the first printing unit to the second printing unit. The printing system is characterized in that the conveyance mechanism includes: a passage detection sensor for detecting the passage of the medium; conveyance rollers for conveying the medium; and positioning rollers that are disposed at a position downstream of the passage detection sensor and the conveyance rollers in the conveyance direction, the positioning rollers abut against the medium and convey the medium that has been bent by the abutment. The printing system further includes a control unit that controls the conveyance rollers based on the conveyance state of the preceding medium and the detection time of the front end of the subsequent medium detected by the passage detection sensor so that the amount of bending of the subsequent medium is fixed.

[0020] Effects of the invention

[0021] According to the above mode, even when there is a conveyance delay of the medium printed by the upstream printing unit, it is possible to suppress the occurrence of skew defects in the downstream printing unit. Description of the drawings

[0022] Figure 1 It is a schematic configuration diagram of a printing system according to an embodiment.

[0023] Figure 2 It is a control block diagram of a printing system according to an embodiment.

[0024] Figure 3 It is a timing chart showing the operations of a relay roller, a re-feeding roller, and a positioning roller in an embodiment.

[0025] Figure 4 It is an explanatory diagram for explaining the calculation method of a first period, a second period, etc. in an embodiment.

[0026] Figure 5 It is a flowchart showing the operation control of a re-feeding roller and a positioning roller in an embodiment.

[0027] Figure 6 It is an explanatory diagram for explaining the drive control of a re-feeding motor and a positioning motor in the related art. Detailed description of the invention

[0028] Next, a printing system according to an embodiment of the present invention will be described with reference to the drawings.

[0029] The embodiment shown below exemplifies a device or the like for embodying the technical idea of the present invention. The technical idea of the present invention does not specify the material, shape, structure, arrangement, etc. of each component as the following material, shape, structure, arrangement, etc. The technical idea of the present invention can be variously modified in the claims.

[0030] Figure 1 is a schematic configuration diagram of a printing system 1 according to an embodiment of the present invention.

[0031] Figure 2 is a control block diagram of the printing system 1.

[0032] In the following description, the direction orthogonal to the Figure 1 paper surface is set as the front-rear direction. In addition, the upper, lower, left, and right of the Figure 1 paper surface are set as the upper direction, lower direction, left direction, and right direction.

[0033] In Figure 1 , the path indicated by the thick line is a conveyance path for conveying a sheet of paper P as an example of a medium. Among the conveyance paths, the path indicated by the solid line is the upstream conveyance path RU and the downstream conveyance path RD, the path indicated by the dashed line is the reverse path RR, and the path indicated by the dotted line is the non-reverse intermediate path RC. In the following description, upstream and downstream refer to upstream and downstream along the conveyance direction on the conveyance path.

[0034] As Figure 1 and Figure 2 show, the printing system 1 includes a first printing device 2, an intermediate device 3, and a second printing device 4. In addition, as the printing system according to the present embodiment, as long as it includes a first printing unit exemplified by the printing unit 16 described later, a second printing unit exemplified by the printing unit 66 described later, and a conveyance mechanism for conveying the sheet of paper P (medium) printed by the first printing unit to the second printing unit, the intermediate device 3 can be omitted. In addition, the first printing device 2 and the second printing device 4 may not be independently arranged. Therefore, for example, a printing device having a first printing unit and a second printing unit in a single housing also functions as a printing system.

[0035] The first printing device 2 prints an image on the sheet of paper P and sends out the sheet of paper P to the intermediate device 3. The first printing device 2 includes a paper supply tray 11, a paper supply roller 12, a paper supply motor 13, a registration roller 14, a registration motor 15, a printing unit 16, discharge rollers 17, 18, a discharge motor 19, and a first printing device control unit 20. In addition, the first printing device 2 can be regarded as an external device of the second printing device 4.

[0036] The paper supply tray 11 is used for stacking the sheets of paper P used for printing.

[0037] The paper feed roller 12 picks up the sheets of paper P stacked on the paper feed table 11 one by one and conveys them to the registration roller 14. In addition, the paper feed roller 12 performs an auxiliary action for assisting the registration roller 14 in conveying the paper P. The paper feed roller 12 is disposed at the upstream end of the upstream conveyance path RU.

[0038] The paper feed motor 13 rotationally drives the paper feed roller 12.

[0039] The registration roller 14 abuts against the paper P conveyed from the paper feed roller 12, and after the paper P is bent, the paper P is conveyed toward the printing unit 16.

[0040] The registration motor 15 rotationally drives the registration roller 14.

[0041] The printing unit 16 conveys the paper P and prints an image on the paper P. The printing unit 16 includes a belt pressing portion 21 and a head unit 22. In addition, the printing unit 16 is an example of a first printing unit that prints on the paper P (medium).

[0042] The belt pressing portion 21 adsorbs and holds the paper P conveyed from the registration roller 14 on the belt and conveys it.

[0043] The head unit 22 ejects ink onto the paper P conveyed by the belt pressing portion 21 to print an image. The head unit 22 includes an inkjet head (not shown) having a plurality of nozzles arranged in the front-rear direction, and ejects ink from the nozzles of the inkjet head onto the paper P.

[0044] The paper discharge rollers 17 and 18 discharge the paper P conveyed by the belt pressing portion 21 to the intermediate device 3.

[0045] The paper discharge motor 19 rotationally drives the paper discharge rollers 17 and 18.

[0046] The first printing device control unit 20 controls the operations of the respective parts of the first printing device 2. The first printing device control unit 20 includes a processor (e.g., CPU: Central Processing Unit). In addition, the first printing device control unit 20 includes memories such as a ROM (Read Only Memory) and a RAM (Random Access Memory). The ROM is a read-only semiconductor memory in which a predetermined control program is pre-recorded, and the RAM is a semiconductor memory that can be read and written at any time and is used as a work storage area as needed when the processor executes various control programs.

[0047] The first printing device control unit 20 can communicate with a terminal device 7 composed of a personal computer or the like via a first network 5 including a LAN or the like. In addition, the first printing device control unit 20 can communicate with a second printing device control unit 71 of a second printing device 4 described later via a second network 6 including a LAN or the like. In addition, the first printing device control unit 20 can communicate with an intermediate device control unit 51 of an intermediate device 3 and the second printing device control unit 71 of the second printing device 4 via a communication line 8.

[0048] When printing is performed using the first printing device 2, the first printing device control unit 20 controls to take out a sheet P from a paper feed table 11 by a paper feed roller 12 and bring the sheet P into contact with a registration roller 14. After that, the first printing device control unit 20 controls to drive the registration roller 14 and use the paper feed roller 12 to assist the registration roller 14 to convey the sheet P to a printing unit 16. Then, the first printing device control unit 20 controls so that in the printing unit 16, the sheet P is conveyed by a belt pressing unit 21 and an image is printed on the sheet P by a head unit 22.

[0049] The intermediate device 3 conveys the sheet P between the first printing device 2 and the second printing device 4. The intermediate device 3 is arranged 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, turning rollers 36, 37, a turning sensor 38, a switch back roller 39, a switch back motor 40, a switch back sensor 41, intermediate rollers 42, 43, an intermediate conveyance motor 44, a face up roller 45, a rising roller 46, a rising motor 47, a relay roller 48, a relay motor 49, a relay sensor 50, and an intermediate device control unit 51.

[0050] Here, the intermediate device 3 functions as an example of a conveyance mechanism together with the paper discharge rollers 17, 18 and the paper discharge motors 19 of the first printing device 2, and the re-feed rollers 61, the re-feed motors 62 and the re-feed sensors 63, the registration rollers 64 and the registration motors 65 of the second printing device 4 described later. This conveyance mechanism conveys the sheet P (medium) that has been 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.

[0051] The entrance roller 31 guides the sheet P discharged from the first printing device 2 into the intermediate device 3. The entrance roller 31 is arranged at the downstream end of the upstream conveyance path RU and at the upstream end of the conveyance path inside the intermediate device 3.

[0052] The entry motor 32 rotationally drives the entry roller 31, the turning roller 36, and the face-up roller 45.

[0053] The entry sensor 33 detects the sheet P that has entered the intermediate unit 3 from the first printing device 2. The entry sensor 33 is disposed near the downstream side of the entry roller 31.

[0054] The path switching fin 34 switches the traveling path of the sheet P conveyed along the upstream conveyance path RU between the turning path RR and the non-turning intermediate path RC.

[0055] The path switching solenoid 35 drives the path switching fin 34.

[0056] The turning rollers 36 and 37 convey the sheet P guided to the turning path RR by the path switching fin 34 to the reverse roller 39.

[0057] The turning sensor 38 detects the sheet P conveyed from the turning rollers 36 and 37 to the reverse roller 39. The turning sensor 38 is disposed between the entry sensor 33 and the reverse roller 39 and between the turning roller 36 and the turning roller 37.

[0058] The reverse roller 39 reverses the sheet P conveyed by the turning rollers 36 and 37 and then conveys the sheet P to the intermediate rollers 42. The reverse roller 39 is configured to be capable of forward rotation and reverse rotation to reverse the sheet P.

[0059] The reverse motor 40 rotationally drives the reverse roller 39 for forward rotation and reverse rotation.

[0060] The reverse sensor 41 detects the sheet P reversed by the reverse roller 39.

[0061] The intermediate rollers 42 and 43 convey the sheet P reversed by the reverse roller 39 to the ascending roller 46.

[0062] The intermediate conveyance motor 44 rotationally drives the turning roller 37 and the intermediate rollers 42 and 43.

[0063] The face-up roller 45 conveys the sheet P guided to the non-turning intermediate path RC by the path switching fin 34 to the ascending roller 46.

[0064] The ascending roller 46 conveys the sheet P conveyed from the intermediate roller 43 or the face-up roller 45 to the relay roller 48. The ascending roller 46 is disposed near the downstream side of the confluence point of the turning path RR and the non-turning intermediate path RC on the downstream conveyance path RD.

[0065] The ascending motor 47 rotationally drives the ascending roller 46.

[0066] The relay roller 48 conveys the sheet P conveyed from the ascending roller 46 to the second printing device 4.

[0067] The relay motor 49 rotationally drives the relay roller 48.

[0068] The relay sensor 50 detects the sheet P conveyed by the relay roller 48 to the second printing device 4. The relay sensor 50 is disposed near the outlet of the sheet P from the intermediate device 3, that is, near the downstream side of the relay roller 48.

[0069] The intermediate device control unit 51 controls the operations of the respective parts of the intermediate device 3. The intermediate device control unit 51 includes a processor (e.g., a CPU) and memories such as a RAM and a ROM. The intermediate device control unit 51 can communicate with the first printing device control unit 20 of the first printing device 2 and the second printing device control unit 71 of the second printing device 4 described later via the communication line 8.

[0070] The second printing device 4 prints on the sheet P conveyed 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-feeding roller 61, a re-feeding motor 62, a re-feeding sensor 63, a registration roller 64, a registration motor 65, a printing unit 66, discharge rollers 67, 68, a discharge motor 69, a discharge tray 70, and a second printing device control unit 71.

[0071] The re-feeding roller 61 conveys the sheet P conveyed from the relay roller 48 of the intermediate device 3 to the registration roller 64. In addition, the re-feeding roller 61 performs an auxiliary operation for assisting the conveyance of the sheet P by the registration roller 64. The re-feeding roller 61 is disposed at the upstream end of the downstream conveyance path RD in the second printing device 4. The re-feeding roller 61 is an example of a conveyance roller that conveys the sheet P (medium). As such a conveyance roller, it is desirable that the roller be located upstream of the registration roller 64 and closest to the registration roller 64, like the re-feeding roller 61.

[0072] The re-feeding motor 62 rotationally drives the re-feeding roller 61. The re-feeding motor 62 is an example of a conveyance driving unit that drives the re-feeding roller 61 (conveyance roller).

[0073] The re-feeding sensor 63 detects the sheet P conveyed from the re-feeding roller 61 to the registration roller 64. The re-feeding sensor 63 is disposed near the upstream side of the registration roller 64 and the downstream side of the re-feeding roller 61. The re-feeding sensor 63 is an example of a passage detection sensor that detects the passage of the sheet P (medium).

[0074] The registration roller 64 is disposed at a position downstream of the re-feeding sensor 63 and the re-feeding roller 61. The registration roller 64 abuts against the sheet P conveyed from the re-feeding roller 61 and conveys the sheet P that has been bent by the abutment toward the printing unit 66.

[0075] The positioning motor 65 rotationally drives the positioning roller 64. The positioning motor 65 is an example of a positioning drive unit that drives the positioning roller.

[0076] The printing unit 66 conveys the sheet P and prints an image on the sheet P. The printing unit 66 includes a belt pressing plate unit 76 and a head unit 77. In addition, the printing unit 66 is disposed at a position downstream of the printing unit 16 (first printing unit) in the conveyance direction of the sheet P, and is an example of a second printing unit that prints on the sheet P (medium).

[0077] The structures of the belt pressing plate unit 76 and the head unit 77 are the same as those of the belt pressing plate unit 21 and the head unit 22 of the first printing apparatus 2 described above.

[0078] The paper discharge rollers 67 and 68 discharge the sheet P conveyed from the belt pressing plate unit 76 to the paper discharge tray 70.

[0079] The paper discharge motor 69 rotationally drives the paper discharge rollers 67 and 68.

[0080] The paper discharge tray 70 is used to hold the sheet P discharged by the paper discharge rollers 67 and 68.

[0081] The second printing apparatus control unit 71 controls the operations of the respective units of the second printing apparatus 4. The second printing apparatus control unit 71 includes a processor (e.g., CPU) and memories such as RAM and ROM. The second printing apparatus control unit 71 can communicate with the first printing apparatus control unit 20 of the first printing apparatus 2 via the second network 6. In addition, the second printing apparatus control unit 71 can communicate with the first printing apparatus control unit 20 of the first printing apparatus 2 and the intermediate apparatus control unit 51 of the intermediate apparatus 3 via the communication line 8.

[0082] When printing is performed by the second printing apparatus 4, the second printing apparatus control unit 71 abuts the sheet P conveyed from the intermediate apparatus 3 against the positioning roller 64 using the re-feed roller 61 and stops the re-feed roller 61, details of which will be described later. After that, the second printing apparatus control unit 71 controls such that the positioning roller 64 is driven and the re-feed roller 61 assists the positioning roller 64 to convey the sheet P to the printing unit 66. Then, the second printing apparatus control unit 71 controls such that in the printing unit 66, the belt pressing plate unit 76 conveys the sheet P and the head unit 77 prints an image on the sheet P. Here, the second printing apparatus control unit 71 is an example of a control unit that controls the re-feed roller 61 based on the conveyance state of the preceding sheet P and the detection time of the front end of the subsequent sheet P detected by the re-feed sensor 63 so that the bending amount of the subsequent sheet P is fixed, details of which will be described later.

[0083] Next, the operation when double-sided printing is performed by the printing system 1 will be described.

[0084] The operation of double-sided printing in the printing system 1 starts when the first printing device control unit 20 receives a double-sided printing job from the terminal device 7 via the first network 5.

[0085] When the first printing device control unit 20 receives a printing job, it starts driving the platen unit 21 and the paper discharge rollers 17, 18.

[0086] In addition, when the first printing device control unit 20 receives a printing job, it sends the printing job to the second printing device control unit 71 via the second network 6. In addition, the first printing device control unit 20 sends a preparation signal for instructing the start of preparation for double-sided printing to the intermediate device control unit 51 via the communication line 8.

[0087] When the second printing device control unit 71 receives a printing job, it starts driving the refeed rollers 61, the platen unit 76, and the paper discharge rollers 67, 68.

[0088] When the intermediate device control unit 51 receives the preparation signal, it starts driving the entrance roller 31, the inversion rollers 36, 37, the reverse roller 39, the intermediate rollers 42, 43, the ascending roller 46, and the relay roller 48. In addition, the intermediate device control unit 51 sets the path switching fin 34 to the direction of guiding the paper P from the upstream conveyance path RU to the inversion path RR.

[0089] After the first printing device control unit 20 starts driving the platen unit 21 and the paper discharge rollers 17, 18, it starts feeding paper from the paper supply tray 11 to the printing unit 16. Then, the paper P abuts against the registration roller 14 and stops in a bent state. As a result, the skew of the paper P is corrected.

[0090] When a predetermined time has elapsed after the paper supply roller 12 stops, the first printing device control unit 20 starts driving the registration roller 14. In addition, at the same time as starting the driving of the registration roller 14, the first printing device control unit 20 makes the paper supply roller 12 start an auxiliary operation. After that, the first printing device control unit 20 controls the registration roller 14 to convey the paper P to the printing unit 16. The auxiliary operation ends before the rear end of the paper P has disengaged from the paper supply roller 12. This is to prevent the paper supply roller 12 from erroneously conveying the next paper P. By repeating the operations of the paper supply roller 12 and the registration roller 14 like this, the paper P is sequentially conveyed to the printing unit 16.

[0091] Regarding the paper P conveyed to the printing unit 16, the platen unit 21 conveys the paper P and the head unit 22 prints on the surface. The paper P printed by the printing unit 16 is discharged to the intermediate device 3 by the paper discharge rollers 17, 18.

[0092] The paper P discharged to the intermediate device 3 is reversed in the intermediate device 3.

[0093] In the intermediate device 3, the paper P is received and conveyed by the inlet roller 31, and the paper P is guided from the upstream conveyance path RU to the reverse path RR by the path switching fin 34. The paper P guided to the reverse path RR is conveyed to the reverse roller 39 by the reverse rollers 36 and 37.

[0094] When the paper P reaches the reverse roller 39, the reverse roller 39 receives the paper P and conveys the paper P at a preset reverse conveyance speed.

[0095] When a predetermined stop time has elapsed since the reverse roller 39 stopped, the intermediate device control unit 51 starts the reverse drive of the reverse roller 39.

[0096] The paper P that has been reversed is conveyed by the intermediate rollers 42 and 43, the lifting roller 46, and the relay roller 48 and is sent out to the second printing device 4. Since the paper P is reversed in the intermediate device 3, it is sent out to the second printing device 4 in a state where the front and back sides are reversed.

[0097] The paper P sent from the intermediate device 3 to the second printing device 4 is received and conveyed by the re-feeding roller 61 and abuts against the registration roller 64. Thereafter, the paper P is conveyed to the printing unit 66 by the registration roller 64. At this time, the re-feeding roller 61 performs an auxiliary action for assisting the conveyance of the paper P by the registration roller 64.

[0098] Based on the timing when the leading edge of the paper is detected by the re-feeding sensor 63, the operations of the re-feeding roller 61 and the registration roller 64 are controlled. Further, when the size of the paper P is equal to or larger than a predetermined size, the relay roller 48 performs a deceleration abutting action and an auxiliary action synchronously with the re-feeding roller 61. Specifically, when the paper P is of a size such that the rear end does not separate from the relay roller 48 (is being held by the relay roller 48) when abutting against the registration roller 64, the relay roller 48 operates synchronously with the re-feeding roller 61 until the paper P separates.

[0099] Here, the operations of the relay roller 48, the re-feeding roller 61, and the registration roller 64 will be described.

[0100] Figure 3 is a timing chart showing the operations of the relay roller 48, the re-feeding roller 61, and the registration roller 64.

[0101] Figure 4 is an explanatory diagram for explaining the calculation methods of the first period Tx, the second period Ty, and the like.

[0102] Figure 5 is a flowchart showing the operation control of the re-feeding roller 61 and the registration roller 64.

[0103] 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-feeding roller 61, and the registration roller 64 ( Figure 3 at time t10, Figure 5 step S1). The operations of the relay roller 48 and the re-feeding roller 61 are auxiliary operations for assisting the registration roller 64 in transporting the paper P. The relay roller 48, the re-feeding roller 61, and the registration roller 64 accelerate to a specified speed and then decelerate to transport the paper P at the printing speed.

[0104] Then, the relay sensor 50 detects the rear end of the first sheet of paper P, and then the re-feeding sensor 63 detects the rear end of the first sheet of paper P (at time t11 after the elapsed time Ts). In addition, regarding the time Ts, it can be calculated as a theoretical value (fixed value) according to the printing conditions.

[0105] When the re-feeding sensor 63 detects the front end of the second sheet of paper P (at time t12, step S2: "Yes"), the second printing device control unit 71 obtains the sensor-off period Ta from when the re-feeding sensor 63 detected the rear end of the first sheet of paper P (step S3).

[0106] In addition, the second printing device control unit 71 determines the first period Tx and determines the second period Ty based on the sensor-off period Ta (step S4). The first period Tx is the period during which the re-feeding roller 61 maintains the reverse transport speed V1 (an example of the first transport speed) at the detection time (at time t12) after detecting the front end of the second sheet of paper P by the re-feeding sensor 63. The second period Ty is the period during which the transport speed when the second sheet of paper P abuts against the registration roller 64, that is, the abutment speed V2 (an example of the second transport speed) slower than the reverse transport speed V1, is maintained.

[0107] Figure 4 is an explanatory diagram for explaining the calculation methods of the first period Tx, the second period Ty, etc.

[0108] As Figure 4 shown, the feed amount (transport amount) of the first period Tx during which the re-feeding roller 61 maintains the reverse transport speed V1 from the detection time (at time t12) when the re-feeding sensor 63 detects the front end of the paper P to time t13 is set as L1, and the feed amount (transport amount) of the second period Ty during which the re-feeding roller 61 maintains the abutment speed V2 after the reverse transport speed V1 decelerates from time t13 to time t14 is set as L2. In addition, the sum of the feed amounts L1 and L2 is set as Lconst, and the deceleration acceleration of the re-feeding roller 61 is set as αdn.

[0109] In order to fix the amount of bending of the bend formed by the sheet P, the feed amount Lstrike (the shaded portion) from time t12 to time t15 is fixed, for example. In addition, if the feed amount Lstrike of the re-feeding roller 61 is fixed, the bend of the sheet P that is likely to slide is more likely to become smaller than that of the sheet P that is difficult to slide. Therefore, it is also possible that the later (the easier to slide) the actual conveyance time from the specified position of the sheet P to time t12 is, the larger the feed amount Lstrike is.

[0110] Lconst can be expressed as Lstrike - V1^2 / 2 / αdn.

[0111] The time Tkr from the time t11 when the rear end of the preceding (first) sheet P is detected by the re-feeding sensor 63 until the start of driving of the registration roller 64 can be expressed as the difference between the time Tcyc from time t11 until the rear end of the subsequent (second) sheet P is detected by the re-feeding sensor 63 and the time Tsr from time t20 until the rear end of the subsequent (second) sheet P is detected by the re-feeding sensor 63. In addition, when the time obtained by subtracting the sensor off period Ta from the time Tkr is set as the time Ttr, the driving cycle of the registration roller 64 can be expressed as the sum of the time Tsr, the sensor off period Ta, and the time Ttr.

[0112] 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.

[0113] The above-mentioned respective values can be used to calculate the feed amount L1 as shown in the lower right column of Figure 4 Therefore, the feed amount L2 can also be calculated in the same manner. As long as 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 conveyance speeds V1 and V2.

[0114] In addition, when the length in the conveyance direction of the sheet P is denoted as P, the conveyance speed (printing speed) of the belt platen portion 76 is denoted as Vg, and the sheet interval time is denoted as Tpp, the above-mentioned time Tcyc can be expressed as P / Vg + Tpp. Further, when the distance from the re-feeding sensor 63 to the registration roller 64 is denoted as B, and the distance from the registration roller 64 to the belt platen portion 76 is denoted as Drb, the time Tsr can be expressed as the sum of the acceleration time of the acceleration αr1 of the registration roller 64, the conveyance time at the maximum speed Vtop, and the deceleration time of the deceleration acceleration αr2, which is Ttop, plus (P - B - Drb) / Vg. Additionally, in the calculation of the above-mentioned first period Tx and second period Ty, the time T2r from the time t11 until the rear end of the preceding sheet P disengages from the registration roller 64, the time T1s from the rear end of the preceding sheet P disengaging from the registration roller 64 until the time t15, the time T2s from the rear end of the preceding sheet P disengaging from the registration roller 64 until the time t20, etc. can also be appropriately used for the calculation.

[0115] Here, the time t12 when the leading end of the easily slidable sheet P is detected by the re-feeding sensor 63 is delayed. In this way, the later the time t12 is, the longer the first period Tx is and the shorter the second period Ty is. However, when the sensor off period Ta becomes Tmax and the time t12 is delayed by the time Th, the second period Ty becomes zero. Therefore, if the sensor off period Ta exceeds Tmax, the re-feeding 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 ensured. Therefore, in cases where the synchronous control of the registration roller 64, the re-feeding roller 61, etc. cannot be stably performed due to the inability to ensure the time T5, etc., it is preferable to delay the drive start time (time t20) of the registration roller 64. After that, when the sheet P reaches the re-feeding sensor 63, etc., return to Figure 3 such control.

[0116] For example, the above calculation is performed by the second printing apparatus control unit 71. It can be said that the second printing apparatus control unit 71 calculates the first period Tx and the second period Ty based on the detection time t11 of the rear end of the preceding (first) sheet P detected by the re-feeding sensor 63 (through-detection sensor) and the detection time t12 of the front end of the subsequent (second) sheet P detected by the re-feeding sensor 63, and thereby controls the re-feeding roller 61 via the intermediate apparatus control unit 51 to fix the bending amount of the subsequent sheet P. In addition, instead of the time t11, the time when the rear end of the preceding sheet P is detected by the relay sensor 50, the driving start time of each roller for the preceding sheet P, etc. may be used. Therefore, the time t11 can be said to be an example of the conveyance state of the preceding sheet P. However, it is desirable to use the time t11 that is closest to the time t12 when the front end of the subsequent sheet P is detected by the re-feeding sensor 63.

[0117] In addition, in the present embodiment, the first period Tx and the second period Ty are calculated based on the detection time of the re-feeding sensor 63 as an example of the through-detection sensor. However, other sensors disposed upstream of the registration roller 64 may be used as another example of the through-detection sensor, and the first period Tx and the second period Ty may be calculated based on the detection time of this sensor. Further, instead of at least one of the first period Tx and the second period Ty, the deceleration acceleration αdn of the re-feeding roller 61 may be adjusted. In addition, in the present embodiment, the control of the re-feeding roller 61 as an example of the conveyance roller is described. However, the conveyance roller to be controlled is not limited to the re-feeding roller 61, and for example, other conveyance rollers such as the relay roller 48 may be used. Further, the calculation of the first period Tx and the second period Ty and the control of the re-feeding roller 61 may be performed by other control units such as the intermediate apparatus control unit 51.

[0118] The second printing apparatus control unit 71 repeatedly makes a determination based on the first period Tx calculated as described above until the deceleration start timing (time t13) after the elapse of the first period Tx from when the second sheet P is detected by the re-feeding sensor 63 is reached (step S5).

[0119] When the deceleration start timing is reached (step S5: "Yes"), the second printing apparatus control unit 71 switches the signal to the intermediate apparatus control unit 51 to a low-level signal (time t13). Thereby, the intermediate apparatus control unit 51 starts to decelerate the relay roller 48 and the re-feeding roller 61, and when the deceleration reaches the contact speed V2, the contact speed V2 is maintained for the second period Ty until a high-level signal from the second printing apparatus control unit 71 is received (time t14). Moreover, in the middle of the second period Ty, the front end of the second sheet P comes into contact with the stopped registration roller 64, and the sheet P forms a bend, thereby correcting the skew (step S6).

[0120] After that, at the end time of the bend formation, the relay roller 48 and the re-feed roller 61 are stopped (time t15), and after a time T5 has passed from this time, the second printing device control unit 71 sends a low level signal. When the intermediate device control unit 51 receives the low level signal (step S7: "Yes"), it starts driving the registration roller 64, and starts driving the relay roller 48 and the re-feed roller 61 to perform the auxiliary operation (time t20, step S8).

[0121] When the intermediate device control unit 51 receives a high level signal from the second printer control unit 71 (time t21), it temporarily decelerates the speeds of the relay roller 48, re-feed roller 61, and registration roller 64 from the accelerated predetermined speed to the printing speed.

[0122] After that, the intermediate device control unit 51 determines whether the second sheet of paper P is the last sheet of paper P in the print job being executed (step S9). If the sheet of paper P being conveyed is the second and last sheet of paper (step S9: "Yes"), then after a predetermined time has passed since the low-level signal (time t20) from the second printing device control unit 71 is received, the intermediate device control unit 51 performs the following operations: Figure 3 As shown by the dotted line in FIG. 1 , the relay roller 48 and the re-feed roller 61 are stopped (step S10), and the process ends. Figure 5 Processing shown.

[0123] On the other hand, if the paper P being conveyed is the second sheet and not the last sheet (step S9: "No"), the intermediate device control unit 51 accelerates the relay roller 48 and the re-feed roller 61 to the flipping conveying speed V1 (receiving speed) (step S11) after a prescribed time has passed since the above-mentioned low-level signal (time t20) is received from the second printing device control unit 71, and returns to the processing of the above-mentioned step S2.

[0124] Here, with respect to the relay roller 48, the above-mentioned after the prescribed time refers to the timing (time t22) when the rear end of the subsequent paper P is about to separate from the relay roller 48 before it separates from the relay sensor 50, which can be judged based on the drive start time of the positioning roller 64 (time t20). With respect to the re-feed roller 61, the above-mentioned after the prescribed time refers to the timing (time t23) when the rear end of the subsequent paper P separates from the re-feed sensor 63.

[0125] In addition, if the printing process of the first printing device 2 is delayed and the above-described sensor-off period Ta is too long, the second period Ty of the abutment speed V2 becomes zero, and it may happen that the sheet P abuts against the registration roller 64 at a conveying speed faster than the abutment speed V2. Therefore, when the sensor-off period Ta is longer than a prescribed time, it is preferable to control the re-feeding roller 61 so that the conveying speed when the subsequent (second) sheet P abuts against the registration roller 64 is equal to or lower than a prescribed speed (for example, the abutment speed V2). For example, when the sensor-off period Ta is longer than a prescribed time, it is preferable to set the first period Tx and the second period Ty to prescribed values to ensure the time T5, thereby delaying the drive start time (time t20) of the registration roller 64.

[0126] Regarding the sheet P conveyed to the printing unit 66, the sheet P is conveyed by the belt platen unit 76 and the back surface is printed by the head unit 77. The sheet P printed by the printing unit 66 is discharged to the discharge tray 70 by the discharge rollers 67 and 68.

[0127] In the description of the above double-sided printing operation, the case where the size of the sheet P is equal to or larger than a prescribed size has been described. However, when the size of the sheet P is smaller than the prescribed size, the deceleration abutment operation and the auxiliary operation of the relay roller 48 synchronized with the re-feeding roller 61 are not performed. Specifically, when the sheet P is sized such that it disengages from the relay roller 48 (is not clamped by the relay roller 48) when abutting against the registration roller 64, the relay roller 48 is continuously driven at the reverse conveying speed V1. That is, the intermediate device control unit 51 controls according to the sheet size to perform the deceleration abutment operation and the auxiliary operation of the relay roller 48 synchronized with the re-feeding roller 61.

[0128] In addition, when performing single-sided printing using the printing system 1, the front surface of the sheet P is printed in the first printing device 2 by the same operation as in the above double-sided printing operation. The printed sheet P is conveyed to the second printing device 4 via the reverse path RR of the intermediate device 3. In the second printing device 4, the sheet P is conveyed along the downstream conveying path RD without being printed and is discharged to the discharge tray 70. In addition, printing may not be performed in the first printing device 2 and may be performed in the second printing device 4. Alternatively, the sheet P discharged from the first printing device 2 may be conveyed to the second printing device 4 through the non-reverse intermediate path RC of the intermediate device 3 without front and back surface inversion.

[0129] In the embodiment described above, the printing system 1 includes: a printing unit 16 (an example of a first printing unit) that prints on a sheet P (an example of a medium); a printing unit 66 (an example of a second printing unit) that is disposed at a position downstream of the printing unit 16 in the conveyance direction of the sheet P and prints on the sheet P; and a conveyance mechanism that conveys the sheet P printed by the printing unit 16 to the printing unit 66. The conveyance mechanism includes: a re-feeding sensor 63 (an example of a detection sensor) that detects the passage of the sheet P; a re-feeding roller 61 (an example of a conveyance roller) that conveys the sheet P; and a registration roller 64 that is disposed at a position downstream of the re-feeding sensor 63 and the re-feeding roller 61 in the conveyance direction, and the registration roller 64 abuts against the sheet P and conveys the sheet P that has been bent by the abutment. In addition, the printing system 1 includes a second printing device control unit 71 (an example of a control unit), and the second printing device control unit 71 controls the re-feeding roller 61 based on the conveyance state of the preceding sheet P and the detection time (time t12) when the front end of the subsequent sheet P is detected by the re-feeding sensor 63 so that the amount of bending of the subsequent sheet P is fixed.

[0130] Accordingly, even when the detection time (time t12) when the front end of the sheet P is detected by the re-feeding sensor 63 is delayed due to sliding of the sheet P or the like in a case where the printing rate of the sheet P is high, the amount of bending of the sheet P formed by abutting against the registration roller 64 can be made fixed. In addition, the conveyance end time (time t15) of the re-feeding motor 62 can be made fixed, and further, the conveyance start time (time t20) of the registration roller 64 for conveying the sheet P can be made fixed. Therefore, it is possible to avoid a delay in the drive end time of the registration roller 64 for conveying the preceding sheet P in a case where the conveyance of the preceding sheet P is delayed and the conveyance of the subsequent sheet P is not delayed. As a result, it is possible to avoid the subsequent medium M reaching the registration roller 64 before the drive end time of the registration roller 64 and the front end of the subsequent medium M passing through the registration roller 64 without forming a bend in the subsequent medium M. As described above, by forming a fixed amount of bending in the sheet P, the occurrence of skew of the sheet P can be suppressed. Therefore, according to the present embodiment, even in a case where the conveyance of the sheet P printed by the upstream printing unit 16 is delayed, it is possible to suppress the occurrence of skew defects in the downstream printing unit 66. In addition, by making the conveyance start time (time t20) of the registration roller 64 for conveying the sheet P at a fixed interval, it is also possible to maintain the productivity of the sheet P.

[0131] In addition, in the present embodiment, the conveyance state of the preceding sheet P is the detection time (time t11) when the rear end of the preceding sheet P is detected by the re-feeding sensor 63.

[0132] Therefore, it is possible to accurately determine the conveyance state of the preceding sheet P at a time t11 close to the detection time (time t12) when the front end of the subsequent sheet P is detected by the re-feeding sensor 63. As a result, it is possible to more reliably suppress the occurrence of skew defects and more reliably prevent the front end of the subsequent medium M from passing through the registration roller 64 without forming a bend in the subsequent medium M.

[0133] In addition, in the present embodiment, when the difference (sensor off period Ta) between the detection time (time t11) when the rear end of the preceding sheet P is detected by the re-feeding sensor 63 and the detection time (time t12) when the front end of the subsequent sheet P is detected by the re-feeding sensor 63 is equal to or longer than a specified time, the second printing apparatus control unit 71 controls the re-feeding roller 61 so that the conveyance speed when the subsequent sheet P abuts against the registration roller 64 is equal to or lower than a specified speed.

[0134] In addition, when the first printing apparatus 2 is connected upstream of the conveyance mechanism, the interval between the sheets P reaching the second printing apparatus 4 may become larger than a specified value depending on the conveyance state (such as air feeding) of the first printing apparatus 2. In such a case, it is not beneficial to the productivity of the sheet P to determine that a paper jam has occurred and stop the printing system 1. In addition, in such a case, when the abutment speed at which the subsequent sheet P abuts against the registration roller 64 is increased to make the conveyance start time (time t20) of the registration roller 64 for conveying the subsequent sheet P approach a fixed value, the collision sound is large and the damage to the sheet P is also large. As a result, even if the conveyance start time (time t20) of the registration roller 64 is delayed and the conveyance interval for conveying the sheet P to the second printing apparatus 4 becomes larger than in the normal case, it is possible to keep the productivity of the sheet P from being too low and to achieve appropriate skew correction and reduction of the collision sound by ensuring the amount of deflection at the registration roller 64.

[0135] In addition, in the present embodiment, the second printing apparatus control unit 71 controls the re-feeding roller 61 by adjusting a first period Tx. This first period Tx is a period during which the re-feeding roller 61 maintains the reverse conveyance speed V1 (an example of the first conveyance speed) from the detection time (time t12) when the front end of the subsequent sheet P is detected by the re-feeding sensor 63.

[0136] Therefore, it is possible to fix the conveyance start time (time t20) of the registration roller 64 for conveying the sheet P by a simple control such as adjusting the period of, for example, the maximum speed of the re-feeding roller 61, i.e., the reverse conveyance speed V1, and by a simple structure that does not use a re-feeding motor 62 capable of making the conveyance speed higher than the reverse conveyance speed V1.

[0137] Further, in the present embodiment, the second printing apparatus control unit 71 controls the re-feeding roller 61 such that the conveying speed of the re-feeding roller 61 is a contact speed V2 (an example of the second conveying speed) slower than the flipping conveying speed V1 when the subsequent sheet P comes into contact with the positioning roller 64. Further, the second printing apparatus control unit 71 controls the re-feeding roller 61 by adjusting a first period Tx and a second period Ty during which the re-feeding roller 61 maintains the contact speed V2.

[0138] Therefore, by simple control of adjusting, for example, the period of the highest speed of the re-feeding roller 61, i.e., the flipping conveying speed V1, and the period of the contact speed V2 at which the collision sound can be reduced because it is lower than the flipping conveying speed V1, the conveying start time (time t20) of the positioning roller 64 for conveying the sheet P can be fixed, and the collision sound generated when the sheet P comes into contact during the formation of the bend can be reduced.

[0139] In addition, the present invention is not limited to the above-described embodiment, and at the implementation stage, the components can be deformed without departing from the gist thereof. Further, 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 can be appropriately combined. Of course, various deformations and applications can be made within the scope not departing from the gist of the invention. Hereinafter, the invention described in the original claims of the Japanese application of this application is annexed.

[0140] [Annex 1]

[0141] A printing system, comprising: a first printing unit that prints on a medium; a second printing unit that is disposed at a position downstream of the first printing unit in the conveying direction of the medium and prints on the medium; and a conveying mechanism that conveys the medium that has been printed by the first printing unit to the second printing unit, wherein the printing system is characterized in that

[0142] the conveying mechanism includes:

[0143] a passing detection sensor for detecting the passing of the medium;

[0144] a conveying roller for conveying the medium; and

[0145] a positioning roller that is disposed at a position downstream of the passing detection sensor and the conveying roller in the conveying direction, the positioning roller comes into contact with the medium, and conveys the medium that has been bent due to the contact.

[0146] The printing system further includes a control unit that controls the conveyance roller based on the conveyance state of the preceding medium and the detection time of detecting the front end of the subsequent medium by the detection sensor, so that the bending amount of the subsequent medium is fixed.

[0147] [Supplementary Note 2]

[0148] The printing system according to Supplementary Note 1 is characterized in that

[0149] The conveyance state of the preceding medium is the detection time of detecting the rear end of the preceding medium by the detection sensor.

[0150] [Supplementary Note 3]

[0151] The printing system according to Supplementary Note 2 is characterized in that

[0152] When the difference between the detection time of detecting the rear end of the preceding medium by the detection sensor and the detection time of detecting the front end of the subsequent medium is equal to or longer than a specified time, the control unit controls the conveyance roller so that the conveyance speed when the subsequent medium abuts against the positioning roller is equal to or lower than a specified speed.

[0153] [Supplementary Note 4]

[0154] The printing system according to any one of Supplementary Notes 1 to 3 is characterized in that

[0155] The control unit controls the conveyance roller by adjusting a first period during which the conveyance roller maintains a first conveyance speed from the detection time of detecting the front end of the subsequent medium.

[0156] [Supplementary Note 5]

[0157] The printing system according to Supplementary Note 4 is characterized in that

[0158] The control unit controls the conveyance roller so that the conveyance speed of the conveyance roller when the subsequent medium abuts against the positioning roller is a second conveyance speed slower than the first conveyance speed.

[0159] The control unit controls the conveyance roller by adjusting the first period and a second period during which the conveyance roller maintains the second conveyance speed.

[0160] Explanation of Reference Numerals

[0161] 1: Printing system; 2: First printing device; 3: Intermediate device; 4: Second printing device; 16: Printing unit; 48: Relay roller; 50: Relay sensor; 51: Intermediate device control unit; 61: Re-feeding roller; 62: Re-feeding motor; 63: Re-feeding sensor; 64: Registration roller; 65: Registration motor; 66: Printing unit; 71: Second printing device control unit.

Claims

1. A printing system includes: a first printing unit that prints on a medium; A second printing unit, which is disposed at a position downstream of the first printing unit in the conveyance direction of the medium and prints on the medium; and a conveyance mechanism that conveys the medium printed by the first printing unit to the second printing unit, wherein the printing system is characterized in that the conveyance mechanism includes: a passage detection sensor for detecting the passage of the medium; conveyance rollers for conveying the medium; and positioning rollers disposed at a position downstream of the passage detection sensor and the conveyance rollers in the conveyance direction, the positioning rollers abut against the medium and convey the medium that has been bent by the abutment; the printing system further includes a control unit that controls the conveyance rollers based on the difference between the detection time of the rear end of the preceding medium detected by the passage detection sensor and the detection time of the front end of the subsequent medium detected by the passage detection sensor, so that the amount of bending of the subsequent medium is fixed.

2. The printing system according to claim 1, wherein when the difference between the detection time of the rear end of the preceding medium detected by the passage detection sensor and the detection time of the front end of the subsequent medium detected by the passage detection sensor is a predetermined time or more, the control unit controls the conveyance rollers so that the conveyance speed when the subsequent medium abuts against the positioning rollers is a predetermined speed or less.

3. The printing system according to claim 1 or 2, wherein the control unit controls the conveyance rollers by adjusting a first period during which the conveyance rollers maintain a first conveyance speed from the detection time of the front end of the subsequent medium.

4. The printing system according to claim 3, wherein the control unit controls the conveyance rollers such that the conveyance speed of the conveyance rollers when the subsequent medium abuts against the positioning rollers is a second conveyance speed slower than the first conveyance speed, and the control unit controls the conveyance rollers by adjusting the first period and a second period during which the conveyance rollers maintain the second conveyance speed.

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