Printing apparatus

Abstract

To improve the productivity of double-side printing, with a simple configuration, in a printer.SOLUTION: A printer 1 comprises: a printing unit 40; a print conveyance unit 50 which conveys a sheet P which is one example of a medium in the printing unit 40; an equal speed conveyance unit 33 which conveys the sheet P at an equal speed of a variable conveyance speed in a circulating route R2 for side printing; a resist roller pair 31 to which the sheet P conveyed toward the printing unit 40 is abutted; and a control unit 81 which determines a conveyance schedule of the sheet P, on the basis of a first conveyance route length L1 between a conveyance direction downstream side end part (guide roller 55) of the print conveyance unit 50 and a conveyance direction upstream side end part (equal speed roller pair 33a) of the equal speed conveyance unit 33 (and at least one of a second conveyance route length between the conveyance direction downstream side end part of the equal speed conveyance unit and the resist roller pair), and a sheet length L0 in the conveyance direction of the sheet P.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a printing apparatus.

Background Art

[0002] Conventionally, in a printing apparatus that performs double-sided printing in an interleaving method in which a sheet is circulated and conveyed in a conveyance path, by providing an acceleration / deceleration section between a printing section and a constant-speed section that performs constant-speed conveyance in a circulation path, a technique has been proposed for efficiently re-supplying paper to the printing section and improving productivity (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when performing double-sided printing of a long sheet in a printing apparatus provided with a constant-speed conveyance section in a circulation path for double-sided printing, for example, if the sheet length is such that it is simultaneously nipped by the rear-end roller (roller on the downstream side) of the printing section and the inlet roller (roller on the upstream side) of the constant-speed conveyance section, the conveyance speed of the constant-speed conveyance cannot be made faster than the conveyance speed in the printing section. In this case, it becomes impossible to convey a plurality of sheets in the circulation path, and the productivity of printing cannot be improved.

[0005] Furthermore, when performing double-sided printing on long sheets of paper, if, for example, the path length between the exit roller (the roller at the downstream end) of the constant-speed transport section and the pair of registration rollers is insufficient to decelerate the paper to the specified stopping speed for skew correction, the rollers will not be able to decelerate and stop synchronously, which can damage the paper through pulling and bending, and can also lead to jams. Therefore, if the path length for deceleration cannot be secured, the transport speed of the constant-speed transport cannot be increased in order to transport multiple sheets of paper in the circulation path. In this case as well, the productivity of printing cannot be improved.

[0006] Furthermore, extending the acceleration / deceleration section allows multiple sheets of paper to be transported through the circulation path, even for long paper rolls. However, this increases the overall size of the printing apparatus and the number of rollers to control, leading to higher costs.

[0007] The objective of the present invention is to provide a printing apparatus that can improve the productivity of double-sided printing with a simple configuration. [Means for solving the problem]

[0008] In one embodiment, the printing apparatus includes a printing unit, a printing transport unit for transporting a medium in the printing unit, a constant-speed transport unit for transporting the medium at a constant speed at a variable transport speed in a circulation path for double-sided printing, a pair of registration rollers against which the medium being transported toward the printing unit abuts, and a control unit that determines the transport schedule for the medium based on at least one of a first transport path length between the downstream end of the printing transport unit in the transport direction and the upstream end of the constant-speed transport unit in the transport direction, and a second transport path length between the downstream end of the constant-speed transport unit in the transport direction and the pair of registration rollers, and the length of the medium in the transport direction. [Effects of the Invention]

[0009] According to the above embodiment, the productivity of double-sided printing can be improved with a simple configuration. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram showing the internal structure of a printing apparatus according to the first embodiment. [Figure 2] This is a diagram showing the control configuration of the printing apparatus according to the first embodiment. [Figure 3] This figure shows an example in the first embodiment where the paper length is longer than the first transport path length. [Figure 4] This figure illustrates the transport speed when the paper length is longer than the first transport path length in the first embodiment. [Figure 5] This figure illustrates an example in the first embodiment where the paper length is shorter than the first transport path length. [Figure 6] This figure illustrates the transport speed in the first embodiment when the paper length is shorter than the first transport path length. [Figure 7] This table shows the relationship between the number of sheets in the circulation path for each paper length and the productivity of double-sided printing in the first embodiment. [Figure 8] This is a diagram illustrating a printing apparatus equipped with a discharge device, which is a modified example of the first embodiment. [Figure 9] This figure shows the internal structure of the printing apparatus according to the second embodiment. [Figure 10] This figure shows the control configuration of the printing apparatus according to the second embodiment. [Figure 11] This figure illustrates the transport speed when the paper length is shorter than the second transport path length in the second embodiment. [Modes for carrying out the invention]

[0011] The printing apparatus according to the first and second embodiments of the present invention will be described below with reference to the drawings.

[0012] <First Embodiment> Figure 1 shows the internal structure of the printing apparatus 1 according to the first embodiment.

[0013] Figure 2 shows the control configuration of the printing device 1.

[0014] As shown in FIGS. 1 and 2, the printing apparatus 1 includes an external paper feeding unit 10, an internal paper feeding unit 20, a printing unit 40, a printing conveyance unit 50, a paper discharging unit 60, and a paper detection sensor S. Further, as shown in FIG. 1, the printing apparatus 1 includes a resist roller pair 31, an acceleration conveyance unit 32, a constant-speed conveyance unit 33, a reverse conveyance unit 34, a re-feeding unit 35, a paper discharging conveyance unit 36, a straight conveyance unit 37, and path switching units 38 and 39. Further, as shown in FIG. 2, the printing apparatus 1 includes a conveyance drive unit 70, a control unit 81, a storage unit 82, and an interface unit 83.

[0015] In FIG. 1, the straight path R1 of the paper P continuing from the external paper feeding unit 10 or the internal paper feeding unit 20 is indicated by a solid line, the path continuing from the circulation path R2 for double-sided printing located above the printing unit 40 to the paper discharging path R3 is indicated by a two-dot chain line, and the reverse path R2a of the circulation path R2 is indicated by a broken line. Note that the paper P is an example of a medium. In this specification, paper feeding is an example of supply, and paper discharging is an example of discharge. Therefore, paper feeding can be replaced with supply, and paper discharging can be replaced with discharge. The medium may be a sheet-like material made of a material other than paper, or may have a folded portion such as an envelope. <​​​​​​​​​​The first paper feeding unit 21, the second paper feeding unit 22, and the third paper feeding unit 23 are arranged in this order from top to bottom inside the printing device 1. Each of the first paper feeding unit 21, the second paper feeding unit 22, and the third paper feeding unit 23 has paper trays 21a, 22a, and 23a on which paper sheets P are loaded before printing, and paper feeding rollers 21b, 22b, and 23b that feed and transport the topmost sheet of paper P from among the multiple sheets of paper P loaded in the paper trays 21a, 22a, and 23a. Although not shown in the figures, the internal paper feeding unit 20 also has actuators such as motors that drive the paper feeding rollers 21b, 22b, and 23b. The internal paper feeding unit 20 is an example of a supply unit that supplies a medium (e.g., paper P) to the printing unit 40, similar to the external paper feeding unit 10.

[0019] The registration roller pair 31 is positioned upstream of the printing unit 40 and the printing transport unit 50 in the transport direction, in a straight path R1 that continues from the external paper feed unit 10 or the internal paper feed unit 20. The registration roller pair 31 is struck by the paper P being transported toward the printing unit 40. As a result, the registration roller pair 31 corrects the skew of the paper P and transports the paper P while nipping it. A paper detection sensor S is positioned downstream of the registration roller pair 31 in the transport direction and upstream of the transport direction of the printing unit 40. This paper detection sensor S is an example of a medium detection sensor that detects a medium (e.g., paper P), and for example, it outputs an ON signal while detecting paper P and an OFF signal when not detecting paper P.

[0020] The accelerated transport unit 32 is capable of accelerating and transporting the paper P in the circulation path R2. The accelerated transport unit 32 has pairs of accelerating rollers 32a, 32b, and 32c that transport the paper P while nipping it.

[0021] The constant-speed transport section 33 transports the paper P at a constant speed at a variable transport speed downstream of the accelerated transport section 32 in the transport direction of the circulation path R2. The constant-speed transport section 33 has pairs of constant-speed rollers 33a, 33b, and 33c that transport the paper P while nipping it.

[0022] The reversal transport section 34 is a pair of switchback rollers that reverse the front and back sides of the paper P by nipping and switching back transporting the paper P in the reversal path R2a, which is located downstream in the transport direction from the constant-speed transport section 33 of the circulation path R2.

[0023] The refeeding unit 35 refeeds the paper P toward the printing unit 40 downstream of the constant-speed transport unit 33 in the transport direction of the circulation path R2. The refeeding unit 35 decelerates the transport of the paper P when it comes into contact with the pair of registration rollers 31.

[0024] The paper discharge transport section 36 is a pair of paper discharge rollers that transport the paper P toward the paper discharge section 60 while nipping it in the paper discharge path R3, which is connected to the circulation path R2 upstream of the reversal path R2a in the transport direction.

[0025] The straight-line transport section 37 is located at the downstream end of the transport direction of the straight-line path R1 and is a pair of straight-line rollers that transport the paper P while nipping it towards a paper discharge section, transport section, post-processing device, etc. (not shown) connected to the printing device 1.

[0026] The route switching unit 38 switches the transport path of the paper P, which has been printed on by the printing unit 40, between the straight path R1 and the circulating path R2. The route switching unit 38 is, for example, a flipper.

[0027] The route switching unit 39 switches the transport route of the paper P being transported along the circulation route R2 between the reversal route R2a and the paper discharge route R3. The route switching unit 39 is, for example, a flipper.

[0028] The printing unit 40 has, for example, linehead-type inkjet heads (not shown) for each color used in printing. The printing method of the printing unit 40 may be a printing method other than inkjet printing.

[0029] The printing transport unit 50 is positioned opposite the printing unit 40 and transports the paper P in the printing unit 40. The printing transport unit 50 includes a plurality of pulleys 51, a belt 52 stretched across these pulleys 51, a suction fan 53 that sucks air through a plurality of holes in the belt 52 to attract the paper P to the belt 52, a guide roller 54 positioned opposite the pulley 51 at the upstream end of the printing transport unit 50 in the transport direction, and a guide roller 55 positioned opposite the pulley 51 at the downstream end of the printing transport unit 50 in the transport direction. Note that the printing transport unit 50 is not limited to transporting the paper P while attracting it.

[0030] The paper discharge unit 60 is positioned to be exposed to the outside of the printing device 1. The paper discharge unit 60 includes a paper discharge tray 61 on which the printed paper P is loaded, and a pair of paper discharge rollers 62 that transport the paper P toward the paper discharge tray 61.

[0031] The transport drive unit 70 shown in Figure 2 includes a resist drive unit 71 that drives the resist roller pair 31, an acceleration drive unit 72 that drives the acceleration transport unit 32, a constant speed drive unit 73 that drives the constant speed transport unit 33, a reverse drive unit 74 that drives the reverse transport unit 34, a refeed drive unit 75 that drives the refeed unit 35, a paper discharge drive unit 76 that drives the paper discharge transport unit 36, a straight-line drive unit 77 that drives the straight-line transport unit 37, and a switching drive unit 78, 79 that drives the path switching units 38, 39. Each drive unit includes one or more actuators such as motors. A single actuator may also serve as multiple drive units.

[0032] The control unit 81 has a processor (e.g., CPU: Central Processing Unit) that functions as an arithmetic processing unit that controls the operation of the entire printing apparatus 1. As will be described in detail later, the control unit 81 determines the transport schedule for the paper P based on the first transport path length L1 between the downstream end of the print transport unit 50 (guide roller 55) and the upstream end of the constant-speed transport unit 33 (constant-speed roller pair 33a) in the transport direction, and the paper length L0 in the transport direction of the paper P. This transport schedule includes the transport speed and transport timing of the paper P in each part of the printing apparatus 1. Therefore, the printing timing in the printing unit 40 is determined by the transport schedule. The transport schedule can be adjusted by, for example, the transport speed on the reverse side of the reversal transport unit 34 (transport speed of the re-feed unit 35), the amount by which the rear end of the paper P protrudes from the reversal path R2a when the reversal transport unit 34 switches back, the stop time of the paper P when switching back, the amount of slack when the paper P abuts against the registration roller pair 31, the low abutting speed, and the period for which this abutting speed is maintained. Furthermore, the control unit 81 calculates the paper length L0 based on the output value of the paper detection sensor S when the paper length L0 is unknown at the start of paper feeding by the external paper feed unit 10 or the internal paper feed unit 20. For example, the control unit 81 may calculate the paper length L0 based on the amount transported by the encoder of the print transport unit 50 (belt 52) ​​during the period when the paper detection sensor S detects the paper P (the period when the output signal of the paper detection sensor S is ON).

[0033] The storage unit 82 includes, for example, a ROM (Read Only Memory), which is a read-only semiconductor memory in which a predetermined control program is pre-recorded; a RAM (Random Access Memory), which is a semiconductor memory that can be written to and read at any time and used as a working memory area as needed when the processor executes various control programs; and a hard disk drive.

[0034] The interface unit 83 exchanges various types of information with external devices. For example, the interface unit 83 receives print jobs, including print data, from a user terminal.

[0035] Next, we will describe the normal printing operation of the printing device 1.

[0036] As shown in Figure 2, the control unit 81 controls each part of the printing device 1 to feed and transport paper P when a print job is input. The control unit 81 also controls the printing unit 40 to print on the paper P transported by the print transport unit 50 after performing predetermined image processing on the image data included in the print job.

[0037] In the case of single-sided printing, as shown in Figure 1, unprinted paper P is sequentially fed from either the external paper feed unit 10, the first paper feed unit 21, the second paper feed unit 22, or the third paper feed unit 23, and fed sequentially to the print transport unit 50 at timings such that each sheet of paper P is transported between predetermined sheets. The fed paper P is transported at a predetermined transport speed in the print transport unit 50, and printing is performed by the print unit 40. The printed paper P is then discharged from the paper discharge unit 60.

[0038] If the destination for the printed paper is a post-processing device, the transport path for the printed paper P is set by the path switching unit 38 to continue along the straight path R1. The paper P is then discharged to the post-processing device by the straight transport unit 37. On the other hand, if the destination for the printed paper is the paper discharge unit 60, the transport path for the printed paper P is guided to the circulating path R2 by the path switching unit 38, and then to the paper discharge path R3 by the path switching unit 39. The paper P is then discharged to the paper discharge unit 60 by the paper discharge transport unit 36.

[0039] In the case of double-sided printing, for example, unprinted sheets of paper P are sequentially fed at a timing that is twice as long as the feeding timing for each sheet of paper P in single-sided printing. The fed sheets of paper P are transported by the print transport unit 50 and printed by the print unit 40, just as in single-sided printing.

[0040] After single-sided printing, the paper P is guided by the path switching unit 38 to the circulating path R2 for double-sided printing, transported by the accelerated transport unit 32 and the constant-speed transport unit 33, and then transported to the reverse path R2a by the path switching unit 39. The paper P that reaches the reverse transport unit 34 is switched back.

[0041] Next, the paper P is transported to the registration roller pair 31 by the refeeding unit 35. Then, after the paper P's skew is corrected by the registration roller pair 31 as described above, it is refeed into the printing unit 40.

[0042] Here, the paper P after single-sided printing is re-fed to the printing unit 40 at a timing that alternates with the unprinted paper P being fed sequentially. As mentioned above, in double-sided printing, the time between the feeding timings of each paper P is twice as long as in single-sided printing. For this reason, it is possible to insert the paper P after single-sided printing between the unprinted paper P and re-fed the paper P after single-sided printing alternately with the feeding of the unprinted paper P.

[0043] After single-sided printing, the paper P is switched back by the reversal transport unit 34 and then sent to the printing unit 40 with the unprinted side facing upwards. The paper P after single-sided printing is transported by the print transport unit 50, and printing is performed on the unprinted side by the printing unit 40. The double-sided printed paper P is then discharged to the paper discharge unit 60 or the post-processing device.

[0044] The following explains how to determine the transport schedule for non-standard paper sizes P, where the paper length L0 in the transport direction exceeds the long side length (420 mm) of A3 size (420 mm x 297 mm), for example, 450 mm, using Figures 3 to 7.

[0045] Figure 3 shows an example where the paper length L0 is longer than the first transport path length L1.

[0046] Figure 4 is a diagram illustrating the transport speed when the paper length L0 is longer than the first transport path length L1.

[0047] As shown in Figure 3, if the paper length L0 is longer than the first transport path length L1 between the downstream end of the print transport unit 50 (guide roller 55) and the upstream end of the constant-speed transport unit 33 (constant-speed roller pair 33a) in the transport direction (L0 > L1), the transport speed of the constant-speed transport unit 33 cannot be made faster than the transport speed v1 of the print transport unit 50. Therefore, the control unit 81 sets the transport speed of the constant-speed transport unit 33 to be equal to the transport speed v1 of the print transport unit 50. When the transport speed v1 of the constant-speed transport unit 33 is the same as the transport speed v1 of the print transport unit 50, multiple sheets of paper P cannot be transported in the circulation path R2, and only one sheet of paper P is transported.

[0048] Furthermore, as shown in Figure 4, the accelerating roller pairs 32a, 32b, and 32c of the accelerating transport unit 32 are unable to accelerate the transport of the paper P, and instead transport the paper P at the transport speed v1 of the printing transport unit 50 (the transport speed v1 of the constant-speed roller pair 33a).

[0049] Figure 5 shows an example where the paper length L0 is shorter than the first transport path length L1.

[0050] Figure 6 is a diagram illustrating the transport speed when the paper length L0 is shorter than the first transport path length L1.

[0051] As shown in Figure 5, when the paper length L0 is shorter than the first transport path length L1, and the sum of the distance required to accelerate the transport speed v1 in the print transport unit 50 to the transport speed v2 in the constant-speed transport unit 33 and the paper length L0 is equal to or less than the first transport path length L, the control unit 81 shown in Figure 2 increases the number of sheets of paper P in the circulation path R2 (for example, to 2 sheets) compared to when the transport speed in the constant-speed transport unit 33 is the same as the transport speed v1 in the print transport unit 50 (for example, 1 sheet in the examples of Figures 3 and 4), by making the transport speed v2 in the constant-speed transport unit 33 faster than the transport speed v1 in the print transport unit 50.

[0052] Here, just as when the transport speed in the constant-speed transport unit 33 is the same as the transport speed v1 in the printing transport unit 50, it is possible to simply increase the transport speed of the constant-speed transport unit 33 while keeping the number of sheets of paper P in the circulation path R2 at 1. However, as shown in Figure 7 which will be described later, printing productivity can be dramatically improved by increasing the number of sheets of paper P in the circulation path R2 from 1 to 2.

[0053] As shown in Figure 7, when the paper length L0 is 210 mm, for example, in the long side direction of A5 or the short side direction of A4, and there are 4 sheets of paper P in the circulation path R2, 83.3 sheets of double-sided printing can be performed per minute. Also, when the paper length L0 is 420 mm, for example, in the long side direction of A3, and there are 2 sheets of paper P in the circulation path R2, the paper length L0 is longer and the number of sheets in the circulation path R2 decreases compared to the case where the paper length L0 is 210 mm, but the transport speed can be increased, so 43.9 sheets of double-sided printing can be performed per minute.

[0054] Consider the case where, as shown in Figure 5, the transport speed in the constant-speed transport unit 33 is the same as the transport speed v1 in the print transport unit 50, even though the sum of the distance required to accelerate the transport speed v1 in the print transport unit 50 to the transport speed v2 in the constant-speed transport unit 33 and the paper length L0 is equal to or less than the length of the first transport path L (paper length L0 is 450 mm). In this case, the number of sheets of paper P in the circulation path R2 becomes 1, and only 10.7 sheets of double-sided printing can be performed per minute.

[0055] On the other hand, for paper P with a paper length L0 of 450 mm, if the transport speed v2 in the constant-speed transport unit 33 is set to be, for example, more than twice as fast as the transport speed v1 in the print transport unit 50, so that the number of sheets of paper P in the circulation path R2 is 2, then 42.7 sheets of double-sided printing can be performed per minute.

[0056] Next, a modified example of the first embodiment will be described.

[0057] Figure 8 is a diagram illustrating a modified example of the first embodiment, which includes a printing apparatus 1 equipped with a discharge device 90.

[0058] In particular, if the paper output unit 60 shown in Figure 1 is replaced with, for example, an optional device such as the ejection device 90 shown in Figure 8, the transport speed of the ejection device 90 may be limited when the paper P is long.

[0059] If the transport speed of the discharge device 90 is limited, the transport speed of the paper discharge transport unit 36 ​​will be matched to the transport speed of the discharge device 90. Also, the transport speed of the constant-speed transport unit 33 will be matched to the transport speed of the paper discharge transport unit 36. As a result, it may be difficult to increase the transport speed of the constant-speed transport unit 33 to a speed sufficient to transport two sheets of paper P into the circulation path R2 as described above.

[0060] Therefore, when the transport speed of the constant-speed transport unit 33 is matched to the transport speed of the paper discharge transport unit 36, and as described above, when the transport speed in the constant-speed transport unit 33 is faster than the transport speed v1 in the print transport unit 50, the control unit 81 should determine the transport schedule for the paper P so as to increase the number of sheets of paper P in the circulation path R2 from one sheet (when the transport speed in the constant-speed transport unit 33 is the same as the transport speed in the print transport unit 50) to two sheets. For example, the control unit 81 should determine the transport schedule for the paper P by adjusting the stopping time of the paper P in the reversing transport unit 34 (the stopping time at the timing when the transport direction of the paper P is reversed), the spacing between sheets of paper P, etc.

[0061] In the first embodiment described above, the printing apparatus 1 comprises a printing unit 40, a printing transport unit 50 that transports paper P (an example of a medium) in the printing unit 40, a constant-speed transport unit 33 that transports paper P at a constant speed at a variable transport speed in a circulation path R2 for double-sided printing, and a control unit 81 that determines the transport schedule for paper P based on the first transport path length L1 between the downstream end of the printing transport unit 50 in the transport direction (guide roller 55) and the upstream end of the constant-speed transport unit 33 in the transport direction (a pair of constant-speed rollers 33a), and the paper length L0 (an example of a medium length) of paper P in the transport direction.

[0062] As a result, even in a simple printing apparatus 1 that does not unnecessarily lengthen the circulation path R2, for example, as shown in Figure 5, if the paper length L0 is shorter than the first transport path length L1, the transport speed of the constant-speed transport unit 33 can be made faster than the transport speed of the printing transport unit 50. Therefore, in particular, if the number of sheets of paper P in the circulation path R2 can be increased by making the transport speed of the constant-speed transport unit 33 faster than the transport speed of the printing transport unit 50, the productivity of double-sided printing can be improved.

[0063] Furthermore, in this first embodiment, the control unit 81 increases the transport speed v2 in the constant-speed transport unit 33 to faster than the transport speed v1 in the print transport unit 50 when the sum of the distance required to accelerate the transport speed v1 in the print transport unit 50 to the transport speed v2 in the constant-speed transport unit 33 and the paper length L0 is equal to or less than the length of the first transport path L1, so as to increase the number of sheets of paper P in the circulation path R2 (for example, from one sheet to two sheets) compared to when the transport speed in the constant-speed transport unit 33 is the same as the transport speed in the print transport unit 50.

[0064] Therefore, by making the transport speed v2 of the constant-speed transport unit 33 faster than the transport speed v1 of the print transport unit 50, and consequently increasing the number of sheets of paper P in the circulation path R2, the productivity of double-sided printing of paper P is dramatically improved, for example, from 10.7 ppm to 42.7 ppm, as shown in Figure 7.

[0065] Furthermore, in this first embodiment, the printing apparatus 1 includes a paper discharge transport unit 36 ​​(an example of a discharge transport unit) that transports paper P in a paper discharge path R3 (an example of a discharge path) connected to the circulation path R2. When the transport speed of the constant-speed transport unit 33 is matched to the transport speed of the paper discharge transport unit 36, and the transport speed in the constant-speed transport unit 33 is faster than the transport speed in the printing transport unit 50, the control unit 81 determines the transport schedule for paper P so as to increase the number of sheets of paper P in the circulation path R2 compared to when the transport speed in the constant-speed transport unit 33 is the same as the transport speed v1 in the printing transport unit 50.

[0066] Therefore, even if it becomes difficult to increase the transport speed of the constant-speed transport unit 33 to a speed sufficient to increase the number of sheets of paper P in the circulation path R2 as described above, by matching the transport speed of the constant-speed transport unit 33 to the transport speed of the paper discharge transport unit 36, the number of sheets of paper P in the circulation path R2 can be increased by determining the transport schedule for paper P, for example by adjusting the stopping time of paper P in the reversing transport unit 34 and the spacing between sheets of paper P. This improves the productivity of double-sided printing of paper P.

[0067] Furthermore, in this first embodiment, if the sum of the distance required to accelerate the transport speed v1 in the print transport unit 50 to the transport speed v2 in the constant-speed transport unit 33 and the paper length L0 exceeds the first transport path length L1, the control unit 81 sets the transport speed in the constant-speed transport unit 33 to be equal to the transport speed v1 in the print transport unit 50.

[0068] This prevents the paper P from being pulled and damaged when the transport speed in the constant-speed transport section 33 is set to be faster than the transport speed v1 in the printing transport section 50, in cases where the transport speed in the accelerated transport section 32 cannot be accelerated.

[0069] Furthermore, in this first embodiment, the printing apparatus 1 further includes an external paper feed unit 10 and an internal paper feed unit 20, which are examples of supply units that supply medium (paper P) to the printing unit 40, and a paper detection sensor S, which is an example of a medium detection sensor that is located upstream of the transport direction of the printing unit 40 and detects the paper P. When the paper length L0 is unknown at the start of paper supply by the external paper feed unit 10 and the internal paper feed unit 20, the control unit 81 calculates the paper length L0 based on the output value of the paper detection sensor S.

[0070] Therefore, especially when the paper P is of a non-standard size, calculating the paper length L0 makes it possible to determine whether the transport speed v2 of the constant-speed transport unit 33 can be made faster than the transport speed v1 of the print transport unit 50, or whether the number of sheets of paper P in the circular path R2 can be increased.

[0071] <Second Embodiment> Figure 9 shows the internal structure of the printing apparatus 101 according to the second embodiment.

[0072] Figure 10 shows the control configuration of the printing device 1.

[0073] The printing apparatus 101 according to this second embodiment differs from the printing apparatus 1 according to the first embodiment described above mainly in that the circulation path R12 is located below the printing unit 140, the reversal path R12a is located upstream of the constant-speed transport unit 133 in the transport direction, and the paper discharge transport unit 136 is provided outside the circulation path R12. Each part of the printing apparatus 101 according to this second embodiment is denoted by adding 100 (10 for paths starting with R) to the reference numeral of the corresponding part of the printing apparatus 1 according to the first embodiment, and explanations of common matters are omitted as appropriate.

[0074] As shown in Figures 9 and 10, the printing device 101 includes an external paper feed unit 110, an internal paper feed unit 120, a printing unit 140, a print transport unit 150, a paper discharge unit 160, and a paper detection sensor S. Also, as shown in Figure 9, the printing device 101 includes a registration roller pair 131, an accelerated transport unit 132, a constant-speed transport unit 133, a reverse transport unit 134, a re-feed unit 135, a paper discharge transport unit 136, a straight transport unit 137, and path switching units 138, 139. Also, as shown in Figure 10, the printing device 101 includes a transport drive unit 170, a control unit 181, a storage unit 182, and an interface unit 183.

[0075] In Figure 9, the transport path from the registration roller pair 131 to the print transport unit 150 within the straight transport path R11 is shown with a solid line, the circulation path R12 including the reversal path R12a is shown with a dashed line, the straight transport path R11 and the paper discharge path R13 downstream of the print transport unit 150 in the transport direction are shown with a dashed line, and the transport paths from the external paper feed unit 110 and the internal paper feed unit 120 to the registration roller pair 131 are shown with a double dashed line.

[0076] The external paper feed unit 110 is positioned to be exposed to the outside of the printing device 101. The external paper feed unit 110 has a paper feed tray 111 on which sheets of paper P are loaded before printing, and a paper feed roller 112 that feeds and transports the top sheet of paper P from among the multiple sheets of paper P loaded in the paper feed tray 111. The external paper feed unit 110 is an example of a supply unit that supplies a medium (e.g., paper P) to the printing unit 140.

[0077] The internal paper feeding unit 120 has a first paper feeding unit 121 and a second paper feeding unit 122.

[0078] The first paper feed unit 121 and the second paper feed unit 122 are arranged in this order from top to bottom inside the printing device 101. Each of the first paper feed unit 121 and the second paper feed unit 122 has a paper feed tray 121a, 122a on which paper P is loaded before printing, and a paper feed roller 121b, 122b that feeds and transports the topmost sheet of paper P from among the multiple sheets of paper P loaded in the paper feed trays 121a, 122a. The internal paper feed unit 120 is an example of a supply unit that supplies a medium (e.g., paper P) to the printing unit 140, similar to the external paper feed unit 110.

[0079] The registration roller pair 131 is positioned upstream of the printing unit 140 and the printing transport unit 150 in the transport direction, along the straight path R11 that continues from the external paper feed unit 110. The registration roller pair 131 is abutted against by the paper P being transported toward the printing unit 140. A paper detection sensor S is positioned downstream of the registration roller pair 131 in the transport direction and upstream of the transport direction of the printing unit 140. This paper detection sensor S is an example of a medium detection sensor that detects a medium (e.g., paper P). For example, it outputs an ON signal while detecting paper P and an OFF signal when not detecting paper P.

[0080] The accelerated transport unit 132 is capable of accelerating and transporting the paper P in the circulation path R12. The accelerated transport unit 132 has a pair of accelerating rollers 132a and 132b that transport the paper P while nipping it.

[0081] The constant-speed transport section 133 transports the paper P at a constant speed at a variable transport speed downstream of the accelerated transport section 132 in the transport direction of the circulation path R12. The constant-speed transport section 133 has a pair of constant-speed rollers 133a and 133b that transport the paper P while nipping it.

[0082] The reversal transport section 134 is a pair of switchback rollers that reverse the front and back sides of the paper P by transporting it in a switchback manner in the reversal path R12a, which is located upstream of the constant-speed transport section 133 in the circulation path R12.

[0083] The refeeding unit 135 refeeds the paper P toward the printing unit 140 downstream of the constant-speed transport unit 133 in the transport direction of the circulation path R12. The refeeding unit 135 has pairs of refeeding rollers 135a, 135b, and 135c that transport the paper P while nipping it. The refeeding unit 135 slows down the transport of the paper P, causing it to abut against the registration roller pair 131 at a low speed.

[0084] The paper discharge transport unit 136 transports the paper P toward the paper discharge unit 160 in a paper discharge path R13 connected to the straight path R11. The paper discharge transport unit 136 has a pair of paper discharge rollers 136a and 136b that transport the paper P while nipping it.

[0085] The straight-line transport unit 137 is located at the downstream end of the straight-line path R11 in the transport direction and transports the paper P toward a paper discharge unit, transport unit, post-processing device, etc. (not shown) connected to the printing device 101. The straight-line transport unit 137 has a pair of straight-line rollers 137a and 137b that transport the paper P while nipping it.

[0086] The route switching unit 138 switches the transport path of the paper P printed by the printing unit 140 between a straight path R11 and a circulating path R12. The route switching unit 138 is, for example, a flipper.

[0087] The route switching unit 139 switches the transport path of the paper P printed by the printing unit 140 between the straight path R11 and the paper discharge path R13. The route switching unit 139 is, for example, a flipper.

[0088] The printing unit 140 has, for example, linehead type inkjet heads (not shown) for each color used in printing.

[0089] The printing transport unit 150 is positioned opposite the printing unit 140 and transports the paper P in the printing unit 140. The printing transport unit 150 has a plurality of pulleys 151 and a belt 152 stretched across these pulleys 151. Although not shown in the figures, similar to the printing transport unit 50 shown in Figure 1, the printing transport unit 150 may have a suction fan that sucks air through a plurality of holes in the belt 152 to attract the paper P to the belt 152, a guide roller positioned opposite the pulley 151 at the upstream end of the printing transport unit 150 in the transport direction, and a guide roller positioned opposite the pulley 151 at the downstream end of the printing transport unit 150 in the transport direction.

[0090] The paper discharge unit 160 is positioned to be exposed to the outside of the printing device 101. The paper discharge unit 160 includes a paper discharge tray 161 on which the printed paper P is loaded, and a pair of paper discharge rollers 162 that transport the paper P toward the paper discharge tray 161.

[0091] The transport drive unit 170 shown in Figure 10 includes a resist drive unit 171 that drives the resist roller pair 131, an acceleration drive unit 172 that drives the acceleration transport unit 132, a constant speed drive unit 173 that drives the constant speed transport unit 133, a reverse drive unit 174 that drives the reverse transport unit 134, a refeed drive unit 175 that drives the refeed unit 135, a paper discharge drive unit 176 that drives the paper discharge transport unit 136, a straight-line drive unit 177 that drives the straight-line transport unit 137, and a switching drive unit 178, 179 that drives the path switching units 138, 139. Each drive unit includes one or more actuators such as motors. A single actuator may also serve as multiple drive units.

[0092] The control unit 181 has a processor (e.g., a CPU) that functions as an arithmetic processing unit that controls the operation of the entire printing apparatus 101. As will be described in detail later, the control unit 181 determines the transport schedule for the paper P based on the second transport path length L2 between the downstream end of the constant-speed transport unit 133 (the pair of constant-speed rollers 133b) and the pair of registration rollers 131, and the paper length L0 in the transport direction of the paper P. In this second embodiment as well, if the paper length L0 is unknown when the paper feeding of the paper P by the external paper feeding unit 110 or the internal paper feeding unit 120 starts, the control unit 181 may calculate the paper length L0 based on the output value of the paper detection sensor S.

[0093] The memory unit 182 includes, for example, a ROM, which is a read-only semiconductor memory in which a predetermined control program is pre-recorded; a RAM, which is a semiconductor memory that can be written to and read at any time and used as a working memory area as needed when the processor executes various control programs; and a hard disk drive.

[0094] The interface unit 183 exchanges various types of information with external devices. For example, the interface unit 183 receives print jobs, including print data, from a user terminal.

[0095] The following explanation, using Figure 11, describes how to determine the transport schedule for non-standard paper sizes P, where the paper length L0 in the transport direction exceeds the long side length (420 mm) of A3 size (420 mm x 297 mm).

[0096] Figure 11 is a diagram illustrating the transport speed when the paper length L0 is shorter than the second transport path length L2.

[0097] By the way, if the sum of the distance required to reduce the transport speed in the constant-speed transport unit 133 to a specified contact speed (low speed) with the registration roller pair 131 and the media length L0 exceeds the second transport path length L2, the constant-speed transport unit 133 cannot perform decelerated transport. If the re-feed unit 135 performs decelerated transport, it will not only damage the paper P due to pulling and folding, but will also lead to jams. Therefore, if the above sum exceeds the second transport path length L2, the transport speed of the constant-speed transport unit 133 cannot be increased in order to transport multiple sheets of paper P in the circulation path, and the productivity of printing cannot be improved. In this case, for example, the transport speed of the constant-speed transport unit 133 is set to be the same as the transport speed of the printing transport unit 150.

[0098] On the other hand, if the sum of the distance required for deceleration and the media length L0 is equal to or less than the second transport path length L2, the transport speed of the constant-speed transport unit 133 can be made faster than, for example, the transport speed of the printing transport unit 150, so as to increase the number of sheets of paper P in the circulation path R2 to two.

[0099] As shown in Figure 10, the control unit 181 sets the transport speed in the print transport unit 150 and the registration roller pair 131 to transport speed v11, as shown in Figure 11. The control unit 181 also sets the forward-side transport speed of the reversing transport unit (switchback roller pair) 134, which corresponds to the transport speed of the accelerating transport unit 132, to a transport speed v12 that is faster than the transport speed v13 in the constant-speed transport unit 133 and the transport speed v11 in the print transport unit 150, which corresponds to the reverse-side transport speed after the reversing transport unit 134 switches back. Furthermore, the control unit 181 reduces the transport speed of the re-feed unit 35 (re-feed roller pair 135c) from the same transport speed v13 as the constant-speed transport unit 133 to a specified abutment speed v14 before the paper P abuts against the registration roller pair 131. The transport speed v13 of the constant-speed transport unit 133 is set such that the sum of the distance required for deceleration and the media length L0 is equal to or less than the length of the second transport path L2, within a range that allows for two sheets of paper P in the circulation path R12 instead of one. In order to satisfy this relationship, there is a limit to how fast the transport speed v13 of the constant-speed transport unit 133 can be made. Therefore, it is preferable to determine the transport schedule of the paper P in order to suppress this transport speed v13. For example, the transport schedule may be determined by increasing the transport speed v12 on the forward side of the reversing transport unit (switchback roller pair) 134, increasing the amount that the rear end of the paper P protrudes from the reversing path R12a when the reversing transport unit 134 switches back, shortening the stopping time of the paper P when it switches back, reducing the amount of slack when the paper P abuts against the registration roller pair 131, increasing the abutting speed v14, or shortening the time that this abutting speed v14 is maintained.

[0100] In this second embodiment, unlike the first embodiment, the control unit 181 determines the paper transport schedule for the paper P based on the second transport path length L2 between the downstream end of the constant-speed transport unit 133 (constant-speed roller pair 133b) and the registration roller pair 131, and the paper length L0. However, the transport schedule for the paper P may also be determined based on the first transport path length between the downstream end of the printing transport unit 150 and the upstream end of the constant-speed transport unit 133 (constant-speed roller pair 133a). However, in the printing apparatus 101 shown in Figure 9, since the reversing transport unit 134 is located downstream of the printing transport unit 150 in the transport direction and upstream of the constant-speed transport unit 133 in the transport direction, the paper length L0 cannot be longer than the first transport path length L1, as shown in Figure 3 of the first embodiment described above. Similarly, in the printing apparatus 1 according to the first embodiment shown in Figure 1 above, since the reversing transport unit 34 is located downstream of the constant-speed transport unit 33 in the transport direction and upstream of the printing transport unit 50, the paper length L0 will not be longer than the second transport path length.

[0101] In the second embodiment described above, the printing apparatus 101 includes a printing unit 140, a printing transport unit 150 that transports paper P (an example of a medium) in the printing unit 140, a constant-speed transport unit 133 that transports paper P at a constant speed at a variable transport speed in a circulation path R12 for double-sided printing, and a control unit 181 that determines the transport schedule for paper P based on the second transport path length L2 between the downstream end of the constant-speed transport unit 133 (a pair of constant-speed rollers 133b) and the pair of registration rollers 131, and the paper length L0 (an example of a medium length) in the transport direction of paper P. This makes it possible to improve the productivity of double-sided printing with a simple configuration, similar to the first embodiment described above.

[0102] Furthermore, in this second embodiment, the control unit 181 increases the number of sheets of paper P in the circulation path R12 when the sum of the distance required to decelerate the transport speed v13 in the constant-speed transport unit 133 to a specified abutment speed v14 against the register roller pair 131 and the media length L0 is equal to or less than the second transport path length L2, compared to when the sum exceeds the second transport path length L2.

[0103] Therefore, when the paper P can be slowed down to a specified contact speed v14 with the registration roller pair 131, the transport speed v13 of the constant-speed transport unit 133 can be increased compared to when it is not possible to slow it down, thereby increasing the number of sheets of paper P in the circulation path R12. This makes it possible to improve the productivity of double-sided printing while avoiding damage to the paper P due to pulling or folding, or causing jams.

[0104] Furthermore, in this second embodiment, the control unit 181 sets the transport speed v13 in the constant-speed transport unit 133 equal to the transport speed v11 in the printing transport unit 150 if the sum of the distance required to reduce the transport speed v13 in the constant-speed transport unit 133 to a specified abutment speed v14 against the registration roller pair 131 and the media length L0 exceeds the second transport path length L2.

[0105] This prevents damage to the paper P due to pulling or folding, or jams occurring, which can result from the transport speed v13 in the constant-speed transport unit 133 being faster than the transport speed v11 in the print transport unit 150 when the transport speed cannot be reduced in the re-feed unit 135.

[0106] Furthermore, in this second embodiment, similar to the first embodiment described above, the printing apparatus 101 further includes an external paper feed unit 110 and an internal paper feed unit 120, which are examples of supply units that supply medium (paper P) to the printing unit 140, and a paper detection sensor S, which is an example of a medium detection sensor that is located upstream of the transport direction of the printing unit 140 and detects the paper P. The control unit 181 calculates the paper length L0 based on the output value of the paper detection sensor S when the paper length L0 is unknown at the start of paper supply by the external paper feed unit 110 and the internal paper feed unit 120.

[0107] Therefore, especially when the paper P is of a non-standard size, calculating the paper length L0 makes it possible to determine whether the transport speed v13 of the constant-speed transport unit 133 can be increased, or whether the number of sheets of paper P in the circulation path R12 can be increased.

[0108] It should be noted that the present invention is not limited to the embodiments described above, and the components can be modified and implemented in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the embodiments described above. For example, all the components shown in the embodiments may be combined as appropriate. It goes without saying that various modifications and applications are possible without departing from the spirit of the invention. The invention described in the original claims of this application is listed below.

[0109] [Note 1] The printing department, The printing unit includes a printing transport unit that transports the medium, A constant-speed transport unit that transports the medium at a constant speed at a variable transport speed in a circulation path for double-sided printing, A pair of registration rollers against which the medium being transported toward the printing section is brought, A control unit that determines the transport schedule for the medium based on at least one of the first transport path length between the downstream end of the printing transport unit in the transport direction and the upstream end of the constant-speed transport unit in the transport direction, and the second transport path length between the downstream end of the constant-speed transport unit in the transport direction and the pair of resist rollers, and the length of the medium in the transport direction of the medium. A printing apparatus characterized by comprising:

[0110] [Note 2] The control unit, when the sum of the distance required to accelerate the transport speed in the printing transport unit to the transport speed in the constant-speed transport unit and the length of the media is equal to or less than the length of the first transport path, increases the number of media sheets in the circulation path compared to when the transport speed in the constant-speed transport unit is the same as the transport speed in the printing transport unit, by making the transport speed in the constant-speed transport unit faster than the transport speed in the printing transport unit. The printing apparatus described in Appendix 1, characterized by the features described herein.

[0111] [Note 3] The discharge transport section further comprises a discharge path connected to the aforementioned circulation path for transporting the medium, When the control unit matches the transport speed of the constant-speed transport unit to the transport speed of the discharge transport unit, and the transport speed in the constant-speed transport unit is faster than the transport speed in the printing transport unit, the control unit determines the transport schedule for the media so as to increase the number of media sheets in the circulation path compared to when the transport speed in the constant-speed transport unit is the same as the transport speed in the printing transport unit. A printing apparatus as described in Appendix 1 or 2, characterized by the above.

[0112] [Note 4] The control unit increases the number of media sheets in the circulation path when the sum of the distance required to reduce the transport speed in the constant-velocity transport section to a specified contact speed with the pair of resist rollers and the length of the media is equal to or less than the length of the second transport path, compared to when the sum exceeds the length of the second transport path. The printing apparatus described in Appendix 1, characterized by the features described herein.

[0113] [Note 5] The control unit sets the transport speed in the constant-speed transport unit to be equal to the transport speed in the printing transport unit when the sum of the distance required to accelerate the transport speed in the printing transport unit to the transport speed in the constant-speed transport unit and the length of the media exceeds the length of the first transport path, and when the sum of the distance required to decelerate the transport speed in the constant-speed transport unit to a specified abutment speed against the registration roller pair and the length of the media exceeds the length of the second transport path, in at least one of these cases. The printing apparatus described in Appendix 1, characterized by the features described herein.

[0114] [Note 6] A supply unit that supplies the medium to the printing unit, The printing section is further equipped with a media detection sensor, which is positioned upstream in the transport direction of the printing section and detects the medium. The control unit calculates the medium length based on the output value of the medium detection sensor when the medium length is unknown at the start of supply by the supply unit. The printing apparatus described in Appendix 1, characterized by the features described herein. [Explanation of symbols]

[0115] 1 Printing device 10 External paper feed section 11 Paper feed tray 12 Paper feed rollers 20 Internal paper feed section 21 1st paper feed section 22 2nd paper feed section 23 3rd paper feed section 21a, 22a, 23a Paper feed tray 21b, 22b, 23b Paper feed rollers 31 Resistola vs. 32 Accelerated transport section 32a, 32b, 32c Accelerating Roller 33 Constant Speed ​​Conveyor Unit 33a, 33b, 33c Constant Speed ​​Roller Pair 34 Reversal and conveying section (switchback roller pair) 35 Refeed section (refeed roller pair) 36 Paper output transport section (paper output roller pair) 37. Straight-line conveying section (pair of straight-line rollers) 38,39 Route switching section 40 Printing Department 50 Printing and transport section 51 Pulley 52 belts 53 Suction fan 54, 55 Guide rollers 60 Paper output section 61 Paper Output Tray 62 Paper output roller pair 70 Conveyor drive unit 71 Resist drive unit 72 Acceleration drive unit 73 Constant Speed ​​Drive Unit 74 Reversing drive unit 75 Re-feed drive unit 76 Paper output drive unit 77 Straight-line drive unit 78,79 Switching drive unit 81 Control Unit 82 Memory section 83 Interface section 90 Ejector 101 Printing device 110 External paper feed section 111 Paper feed tray 112 Paper feed roller 120 Internal paper feed section 121 1st paper feed section 122 2nd paper feed section 121a, 122a Paper feed tray 121b, 122b Paper feed roller 131 Resistola vs 132 Accelerated transport section 132a, 132b Accelerating roller pair 133 Constant Speed ​​Conveying Unit 133a, 133b Constant Speed ​​Roller Pair 134 Reversal and conveying section (switchback roller pair) 135 Paper refeed section 135a, 135b, 135c Refeed Roller Pair 136 Paper output and transport section 136a, 136b Paper output roller pair 137 Straight-line transport section 137a, 137b Straight-moving roller pair 138,139 Route switching section 140 Printing Department 150 Printing and transport section 151 Pulley 152 belts 160 Paper output section 161 Paper Output Tray 162 Paper output roller pair 170 Conveyor drive unit 171 Resist drive unit 172 Acceleration drive unit 173 Constant Speed ​​Drive Unit 174 Reversing drive unit 175 Re-feed drive unit 176 Paper output drive unit 177 Straight-line drive unit 178,179 Switching drive unit 181 Control Unit 182 Memory section 183 Interface section L0 Paper length L1 First transport path length L2 Second transport path length P Paper Routes R1 and R11: Straight Route R2, R12 Circulation Route R2a, R12a Reversal Path R3, R13 Paper Output Route S Paper detection sensor

Claims

1. The printing department, The printing unit includes a printing transport unit that transports the medium, A constant-speed transport unit that transports the medium at a constant speed at a variable transport speed in a circulation path for double-sided printing, A pair of registration rollers against which the medium being transported toward the printing section is brought, A control unit that determines the transport schedule for the medium based on the first transport path length between the downstream end of the printing transport unit in the transport direction and the upstream end of the constant-speed transport unit in the transport direction, and the length of the medium in the transport direction of the medium. Equipped with, The control unit, when the sum of the distance required to accelerate the transport speed in the printing transport unit to the transport speed in the constant-speed transport unit and the length of the medium is equal to or less than the length of the first transport path, increases the number of sheets of the medium in the circulation path compared to when the transport speed in the constant-speed transport unit is the same as the transport speed in the printing transport unit, by making the transport speed in the constant-speed transport unit faster than the transport speed in the printing transport unit. The control unit, when the sum of the distance required to accelerate the transport speed in the printing transport unit to the transport speed in the constant-speed transport unit and the length of the media exceeds the length of the first transport path, sets the transport speed in the constant-speed transport unit to be equal to the transport speed in the printing transport unit. A printing apparatus characterized by the following features.

2. The discharge transport section further comprises a discharge path connected to the aforementioned circulation path for transporting the medium, When the control unit matches the transport speed of the constant-speed transport unit to the transport speed of the discharge transport unit, and the transport speed in the constant-speed transport unit is faster than the transport speed in the printing transport unit, the control unit determines the transport schedule for the media so as to increase the number of media sheets in the circulation path compared to when the transport speed in the constant-speed transport unit is the same as the transport speed in the printing transport unit. The printing apparatus according to claim 1, characterized in that it is a printing apparatus.

3. Printed section and The printing unit includes a printing transport unit that transports the medium, A constant-speed transport unit that transports the medium at a constant speed at a variable transport speed in a circulation path for double-sided printing, A pair of registration rollers against which the medium being transported toward the printing section is brought, A control unit that determines the transport schedule for the medium based on the second transport path length between the downstream end of the constant-velocity transport unit in the transport direction and the pair of resist rollers, and the length of the medium in the transport direction. Equipped with, The control unit increases the number of media sheets in the circulation path when the sum of the distance required to reduce the transport speed in the constant-velocity transport section to a specified contact speed with the pair of register rollers and the length of the media is equal to or less than the length of the second transport path, compared to when the sum exceeds the length of the second transport path. A printing apparatus characterized by the following features.

4. The control unit, if the sum of the distance required to reduce the transport speed in the constant-speed transport unit to a specified abutment speed against the registration roller pair and the length of the media exceeds the length of the second transport path, sets the transport speed in the constant-speed transport unit equal to the transport speed in the printing transport unit. The printing apparatus according to claim 3, characterized in that it is as described above.

5. A supply unit that supplies the medium to the printing unit, The printing section is further equipped with a media detection sensor, which is positioned upstream in the transport direction of the printing section and detects the medium. The control unit calculates the medium length based on the output value of the medium detection sensor when the medium length is unknown at the start of supply by the supply unit. The printing apparatus according to claim 1 or 3, characterized in that it is the same as described in claim 1 or 3.

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