Medium transport device

Abstract

To easily resume conveyance of a medium whose floating is detected in a medium conveying device.SOLUTION: The medium transport device includes a registration roller pair 31 (an example of a transport member) that transports a sheet P (an example of a medium) so as to enable forward transport and reverse transport, a floating detection sensor FS that is disposed downstream of the registration roller pair 31 in a transport direction and detects floating of the sheet P, and a controller (81) that causes the registration roller pair 31 to perform reverse transport of the sheet P whose floating is detected by the floating detection sensor FS and causes the registration roller pair 31 to perform forward transport of the sheet P that has been subjected to the reverse transport.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a medium transport device equipped with a float detection sensor that detects float of a medium. [Background technology]

[0002] Conventionally, when paper floating is detected, a method is known in which the transport operation is stopped, all of the inkjet heads are moved away from the paper transport belt, and then the paper on which paper floating is detected is transported (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-136726 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when floating of a medium such as paper is detected, the user must stop the transport operation of the printing device, open the device door, and remove the medium, which is a time-consuming task for the user.In addition, transport cannot be continued until the medium is removed, which reduces transport efficiency.

[0005] As described above, if a floating portion of the medium is detected, the transport operation is stopped, the inkjet head is retracted, and the medium with the floating portion detected is then transported, which requires time to raise and lower the inkjet head and requires an elevation mechanism to raise and lower the inkjet head.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a medium transport device that can easily resume transport of a medium after a floating has been detected. [Means for solving the problem]

[0007] In one aspect, the media transport device includes a transport member that transports media in both forward and reverse directions, a float detection sensor that is positioned downstream of the transport member in the transport direction and detects floatation of the media, and a control unit that causes the transport member to reverse transport the media whose floatation is detected by the float detection sensor, and causes the transport member to forward transport the reverse-transported media. [Effects of the Invention]

[0008] According to this aspect, the transport of the medium in which the floating has been detected can be easily resumed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing the internal structure of a printing device including a medium transport device according to an embodiment; [Figure 2] FIG. 2 illustrates a control configuration of a printing apparatus according to an embodiment. [Figure 3] 10 is a flowchart illustrating an operation of the medium conveying device according to the embodiment. [Figure 4] 10A and 10B are enlarged explanatory views for explaining the operation of the pair of registration rollers and the like when lifting occurs in the embodiment. [Figure 5A] FIG. 10 is a first explanatory diagram illustrating an operation of the medium conveyance device when floating occurs in one embodiment. [Figure 5B] FIG. 10 is a second explanatory diagram illustrating the operation of the medium conveyance device when floating occurs in one embodiment. [Figure 5C] FIG. 10 is a third explanatory diagram illustrating the operation of the medium conveyance device when floating occurs in one embodiment. [Figure 5D] FIG. 10 is a fourth explanatory diagram illustrating the operation of the medium conveyance device when floating occurs in one embodiment. [Figure 5E] FIG. 5 is a fifth explanatory diagram illustrating the operation of the medium conveyance device when floating occurs in one embodiment. [Figure 5F]FIG. 10 is a sixth explanatory diagram illustrating the operation of the medium conveyance device when floating occurs in one embodiment. [Figure 6A] FIG. 10 is an explanatory diagram (part 1) for explaining the operation of the medium conveyance device when floating occurs in the comparative example. [Figure 6B] FIG. 10 is a second explanatory diagram for explaining the operation of the medium conveyance device when floating occurs in the comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A medium transport device according to an embodiment of the present invention will now be described with reference to the drawings.

[0011] FIG. 1 is a diagram showing the internal structure of a printing device 1 equipped with a medium transport device according to one embodiment.

[0012] FIG. 2 is a diagram showing the control configuration of the printing device 1.

[0013] 1 and 2, the printing apparatus 1 includes an external paper feed unit 10, an internal paper feed unit 20, a printing unit 40, a printing conveyance unit 50, a paper discharge unit 60, a registration sensor RS, a top edge sensor TS, and a lift detection sensor FS. Also, as shown in FIG. 1, the printing apparatus 1 includes a pair of registration rollers 31, an ascending conveyance unit 32, a duplex conveyance unit 33, a reverse conveyance unit 34, a paper re-feed unit 35, a paper discharge conveyance unit 36, a straight conveyance unit 37, and path switching units 38 and 39. Also, as shown in FIG. 2, the printing apparatus 1 includes a conveyance drive unit 70, a control unit 81, a memory unit 82, and an interface unit 83.

[0014] In FIG. 1, a straight path R1 of paper P continuing from the external paper feed unit 10 or the internal paper feed unit 20 is indicated by a solid line, a path continuing from a circulation path R2 for double-sided printing (an example of double-sided processing) located above the printing unit 40 to a paper discharge path R3 is indicated by a two-dot chain line, and a reversal path R2a of the circulation path R2 is indicated by a dashed line. Note that paper P is an example of a medium. In this specification, paper feed is an example of supply, and paper discharge is an example of ejection. Therefore, paper feed can be substituted for supply, and paper discharge can be substituted for ejection. The medium may be a sheet-like object made of a material other than paper, or an object with a folded portion such as an envelope.

[0015] The external paper feed unit 10 is disposed so as to be exposed to the outside of the printing device 1. The external paper feed unit 10 has a paper feed tray 11 on which paper sheets P before printing are stacked, two paper feed rollers 12 that feed and transport the uppermost paper sheet P among the multiple sheets of paper P stacked in the paper feed tray 11, and a separation plate 13 that faces the downstream one of the two paper feed rollers 12 and sandwiches the paper sheet P between the paper feed roller 12 and the separation plate 13 to prevent double feeding of the paper sheets P. Although not shown, the external paper feed unit 10 also has actuators such as motors that drive the paper feed tray 11 and the paper feed rollers 12.

[0016] The paper feed roller 12 is an example of an upstream transport member that transports the paper P (medium) upstream in the transport direction from the registration roller pair 31. The external paper feed unit 10 is an example of a supply unit that supplies the paper P (medium) to the registration roller pair 31. Another example of this supply unit is the internal paper feed unit 20, which will be described later.

[0017] The internal paper feed unit 20 has a first paper feed unit 21, a second paper feed unit 22, and a third paper feed unit .

[0018] The first paper feed unit 21, the second paper feed unit 22, and the third paper feed unit 23 are arranged in this order from top to bottom inside the printing device 1. The first paper feed unit 21, the second paper feed unit 22, and the third paper feed unit 23 each have a paper feed tray 21a, 22a, 23a on which unprinted paper P is stacked, two paper feed rollers 21b, 22b, 23b that respectively feed and transport the uppermost paper P among the multiple sheets of paper P stacked in the paper feed trays 21a, 22a, 23a, and a separation plate (not shown) that faces the downstream one of the two paper feed rollers 21b, 22b, 23b and sandwiches the paper P between the paper feed roller 21b, 22b, 23b to prevent double feeding of the paper P. Although not shown, the internal paper feed unit 20 also includes actuators such as motors that drive the paper feed rollers 21b, 22b, and 23b.

[0019] The registration roller pair 31 is disposed on the straight path R1 continuing from the external paper feed unit 10 or the internal paper feed unit 20, downstream of the external paper feed unit 10 and the internal paper feed unit 20 in the transport direction and upstream of the printing unit 40 and the print transport unit 50 in the transport direction. The registration roller pair 31 is an example of a transport member that transports the paper P (medium) in both forward and reverse directions. As this transport member, a transport belt or the like may be used instead of the roller pair. Furthermore, the transport member may be a member disposed at a different position from the registration roller pair 31.

[0020] The pair of registration rollers 31 is abutted against the sheet P being transported toward the printing unit 40. As a result, the pair of registration rollers 31 corrects skew of the sheet P and transports the sheet P while nipping it.

[0021] A lift detection sensor FS that detects lifting of the paper P is disposed downstream of the pair of registration rollers 31 in the transport direction and upstream of the printing unit 40 in the transport direction. This lift detection sensor FS may be a contact type that includes, for example, a detectable piece such as a metal plate that is located at a position away from the transport path of the paper P and is pressed only by the paper P in which lifting has occurred, and a sensor that detects that the detectable piece has been pressed by the paper P. However, the lift detection sensor FS may also be a transmission or reflection type optical sensor.

[0022] A registration sensor RS, which is, for example, a transmission or reflection optical sensor, for detecting that the paper P has arrived, is disposed near the upstream side of the registration roller pair 31 in the conveying direction.

[0023] The ascending conveying section 32 conveys the sheet P while lifting it from the straight path R1 to the circulation path R2. The ascending conveying section 32 has a pair of acceleration rollers 32a and 32b that nip the sheet P while conveying it.

[0024] The double-sided conveying section 33 conveys the paper P downstream in the conveying direction of the circulation path R2 from the ascending conveying section 32. The double-sided conveying section 33 has constant speed roller pairs 33a, 33b, 33c, and 33d that nip and convey the paper P.

[0025] The reverse conveying unit 34 performs switchback conveyance, in which the sheet P is reversed and conveyed upside down, on a reverse path R2a provided downstream of the double-sided conveying unit 33 on the circulation path R2. The reverse conveying unit 34 has a pair of switchback rollers 34a, 34b that nip and convey the sheet P, and an accumulation unit 34c provided below a sheet output tray 61 (described later). The accumulation unit 34c is provided at the tip of the reverse path R2a. The accumulation unit 34c accumulates sheets P to be discarded inside the sheet output tray 61, which has a rectangular parallelepiped shape, for example. The sheet output tray 61 may be provided with a gap to allow the user to remove the sheets P from the accumulation unit 34c. The accumulation unit 34c may be provided independently of the sheet output tray 61, or may be provided in a position different from the reverse conveying unit 34.

[0026] The paper re-feeding unit 35 re-feeds the paper P toward the printing unit 40 downstream in the conveying direction from the double-sided conveying unit 33 and the reverse conveying unit 34. The paper re-feeding unit 35 is an example of a re-supply conveying unit that re-supplies the paper P (medium) from the circulation path R2 to the registration roller pair 31.

[0027] The paper discharge conveyance section 36 is a pair of paper discharge rollers that nip and convey the paper P toward the paper discharge section 60 on a paper discharge route R3 connected to the circulation route R2 upstream of the reversal route R2a in the conveyance direction.

[0028] The straight conveying section 37 is a pair of straight rollers that are arranged at the downstream end of the straight path R1 in the conveying direction and nip and convey the paper P toward an external paper output section, conveying device, post-processing device, etc. (not shown) that are connected to the printing device 1.

[0029] The path switching unit 38 switches the transport path of the paper P from the straight path R1 on which printing has been performed by the printing unit 40 to the straight path R1 or the circulation path R2. The path switching unit 38 is, for example, a flipper.

[0030] The path switching unit 39 switches the transport path of the paper P transported on the circulation path R2 between the reversing path R2a and the paper discharge path R3. The path switching unit 39 is, for example, a flipper.

[0031] The printing unit 40 has, for example, a line-head type inkjet head (not shown) for each color used for printing. The printing method of the printing unit 40 may be a printing method other than the inkjet printing method.

[0032] Here, the printing unit 40 is an example of a processing unit that prints (processes) on paper P (medium). This processing unit may be an inspection unit that performs inspection (processing) or a punch that performs punch hole processing (processing), and is not limited to the printing unit 40. The printing device 1 is an example of a processing unit that includes a processing unit (printing unit 40) and a medium conveying device. This processing unit is not limited to the printing device 1, and may also be an inspection device, etc. Furthermore, the medium conveying device may have the configuration of the printing device 1 excluding the printing unit 40, but may be a device that does not include a processing unit as long as it includes at least a conveying member (one example is the pair of registration rollers 31), a lift detection sensor FS, and a control unit 81.

[0033] The print transport unit 50 is disposed opposite the printing unit 40 and transports the paper P. The print transport unit 50 is disposed downstream of the registration roller pair 31 in the transport direction and is an example of an adsorption transport unit that adsorbs and transports the paper P (medium) by suction.

[0034] For example, the printing conveying section 50 has a plurality of pulleys 51, a belt 52 stretched over these pulleys 51, a suction fan 53 (an example of a suction means) that sucks air through a plurality of holes provided in the belt 52 to adsorb the paper P to the belt 52, a guide roller 54 arranged opposite the pulley 51 at the upstream end of the printing conveying section 50 in the conveying direction, and a guide roller 55 arranged opposite the pulley 51 at the downstream end of the printing conveying section 50 in the conveying direction.

[0035] A top edge sensor TS is disposed upstream in the conveying direction of the guide roller 54 and downstream in the conveying direction of the registration roller pair 31. This top edge sensor TS is, for example, a transmissive or reflective optical sensor that detects that the paper P has arrived.

[0036] The print transport unit 50 can be called a belt platen, for example, when it has a platen located inside the belt 52 and below the printing unit 40. Note that the print transport unit 50 can have any configuration, and as a unit that transports the paper P (medium) while adsorbed, instead of a unit that transports the paper P (medium) while adsorbed by air suction using the suction fan 53, it may be a unit that transports the paper P while adsorbed by electrostatic adsorption, for example.

[0037] The paper discharge unit 60 is disposed so as to be exposed to the outside of the printing device 1. The paper discharge unit 60 has a paper discharge tray 61 on which printed paper P is stacked, and a pair of paper discharge rollers 62 that transports the paper P toward the paper discharge tray 61.

[0038] 2 includes a registration drive unit 71 that drives the registration roller pair 31, an elevation drive unit 72 that drives the elevation conveyance unit 32, a duplex drive unit 73 that drives the duplex conveyance unit 33, a reversal drive unit 74 that drives the reversal conveyance unit 34, a refeed drive unit 75 that drives the refeed unit 35, a discharge drive unit 76 that drives the discharge conveyance unit 36, a straight drive unit 77 that drives the straight conveyance unit 37, and switching drive units 78 and 79 that drive the path switching units 38 and 39. Each drive unit includes one or more actuators such as motors. A single actuator may also serve as multiple drive units.

[0039] The control unit 81 has a processor (e.g., CPU: Central Processing Unit) that functions as an arithmetic processing device that controls the overall operation of the printing device 1, and controls each part, such as the registration roller pair 31 (conveying member), printing unit 40, printing conveying unit 50 (suction conveying unit), and conveying drive unit 70. In this way, the control unit 81 or the printing device 1 (control unit 81 and memory unit 82) functions as a computer that executes a program. As will be described in detail later, the control unit 81 causes the registration roller pair 31 to convey the paper P in the reverse direction when a lift is detected by the lift detection sensor FS, and causes the registration roller pair 31 to convey the reverse-conveyed paper P in the forward direction.

[0040] The storage unit 82 has, for example, memory such as a ROM (Read Only Memory), which is a read-only semiconductor memory in which a predetermined control program is pre-recorded, and a RAM (Random Access Memory), which is a semiconductor memory that can be written to and read at any time and is used as a working memory area as needed when the processor executes various control programs.

[0041] The interface unit 83 exchanges various types of information with external devices. For example, the interface unit 83 receives a print job including print data from a print control device or a user terminal.

[0042] Next, a normal printing operation in the printing device 1 will be described.

[0043] 2, when a print job is input, controls each part of the printing device 1 to feed and transport paper P. The control part 81 also controls the printing part 40 to perform predetermined image processing on the image data included in the print job, and then print on paper P transported by the print transport part 50.

[0044] In the case of single-sided printing, as shown in FIG. 1, unprinted sheets P are sequentially fed from one of external sheet feeder 10, first sheet feeder 21, second sheet feeder 22, and third sheet feeder 23, and are sequentially fed in a timing such that each sheet P is transported at a predetermined interval in print transport section 50. After skew of the fed sheets P is corrected by registration roller pair 31, the sheets are transported at a predetermined transport speed in print transport section 50 and printed by printing section 40. After printing, the sheets P are guided to circulation path R2 by path switching section 38 and then to discharge path R3 by path switching section 39. The sheets P are then discharged to discharge section 60 by discharge transport section 36. Alternatively, the printed sheets P are transported directly along straight path R1 to a discharge device (not shown) or the like.

[0045] In the case of double-sided printing, for example, unprinted sheets P are sequentially fed at a timing where the time between the feeding timings of each sheet P is twice as long as the feeding timing in single-sided printing. The fed sheets P are printed by the printing unit 40 while being transported by the print transport unit 50, just like in single-sided printing.

[0046] After printing on one side, the paper P is guided by the path switching unit 38 to the circulation path R2 for double-sided printing, and is transported by the ascending transport unit 32 and the double-sided transport unit 33, and then transported to the reversing path R2a by the path switching unit 39. When the paper P reaches the reversing transport unit 34, it is switched back and transported by the switchback roller pair 34a, 34b, and is reversed.

[0047] Next, the sheet P is re-fed by the sheet re-feeding section 35 to the pair of registration rollers 31. Then, the sheet P is conveyed to the printing section 40 after the skew of the sheet P is corrected by the pair of registration rollers 31 as described above.

[0048] Here, the paper P after single-sided printing is refed at a timing such that it is sent to the printing unit 40 alternately with the unprinted paper P that is fed sequentially. As described above, in double-sided printing, the time between the paper feed timing of each paper P is twice as long as in single-sided printing. For this reason, it is possible to insert a paper P after single-sided printing between unprinted paper P, and refed the paper P after single-sided printing alternately with the feeding of the unprinted paper P.

[0049] After printing on one side, the paper P is switched back by the reverse conveyance section 34 and sent to the printing section 40 with the unprinted side facing up. After printing on one side, the paper P is conveyed by the print conveyance section 50, while the printing section 40 prints on the unprinted side. Then, the paper P that has been printed on both sides is conveyed along the straight path R1 and is either conveyed to a paper discharge device (not shown) or discharged to the paper discharge section 60.

[0050] Next, the operation of the medium transport device (mainly when floating occurs) in this embodiment will be described.

[0051] The process of the flowchart shown in FIG. 3 is performed by the control unit 81, for example, upon receiving a print job.

[0052] First, the control unit 81 causes the external paper feed unit 10 to start feeding the paper P, causes the pair of registration rollers 31 and the like to transport the paper P, and causes the printing unit 40 to start printing (step S1).

[0053] Next, the control unit 81 determines whether the floating detection sensor FS has detected floating of the paper sheet P (step S2).

[0054] 4(a), when the leading edge of the sheet P becomes lifted and the lift detection sensor FS detects the lift of the sheet P (step S2: YES), the control unit 81 determines whether the conveying speed of the sheet P by the pair of registration rollers 31 and the like is at its lowest and the suction force of the print conveying unit 50 (suction fan 53) is at its highest (step S3). The minimum and maximum values ​​of the conveying speed and suction force are determined in advance depending on the configuration of the printing device 1, the print settings for the sheet P, etc.

[0055] If the conveying speed of the paper P is the lowest and the suction force of the printing conveying unit 50 is the highest (step S3: YES), the control unit 81 determines that a floating error has occurred and ends the process shown in Fig. 3. In this case, the control unit 81 may stop the conveyance and printing of the paper P and notify the user by voice or the like.

[0056] On the other hand, if the conveyance speed of the sheet P is not the lowest and the suction force of the print conveyance unit 50 is not the highest (step S3: NO), the control unit 81 reverses the sheet P for which lifting has been detected and stops it at the registration roller pair 31, as shown in FIG. 4(b) (step S4). In this case, the control unit 81 may stop the paper feed roller 12 on the upstream side of the registration roller pair 31 in the conveyance direction, and the print conveyance unit 50 may continue conveying the sheet. As a result, the sheet P becomes slack while being sandwiched between the paper feed roller 12 and the separation board 13. Here, the reverse conveyance distance of the sheet P may be a distance that allows the lifting detection sensor FS to detect the sheet P even if the sheet P is subsequently conveyed forward. Note that even if the print conveyance unit 50 continues conveying the sheet P and the registration roller pair 31 conveys the sheet P in the reverse direction, the reverse conveyance of the sheet P is not hindered because the nip pressure of the sheet P between the guide roller 54 and the pulley 51 is weaker than the nip pressure of the registration roller pair 31.

[0057] Next, the control unit 81 determines whether the conveying speed of the paper P is the minimum (step S5). If the conveying speed of the paper P is not the minimum (step S5: NO), the control unit 81 reduces the conveying speed of the paper P by one stage (step S6). Therefore, as shown in FIG. 4(c), when the reversely conveyed paper P is conveyed forward by the registration roller pair 31, the conveying conditions are changed by slowing down the conveying speed of the registration roller pair 31 etc. (speed v1 → v2).

[0058] Furthermore, the control unit 81 determines whether the suction force of the print transport unit 50 is at its maximum (step S7). If the suction force of the print transport unit 50 is not at its maximum (step S7: NO), the control unit 81 increases the suction force of the print transport unit 50 by one level (step S8). Therefore, as shown in FIG. 4(c), when the reversely transported paper P is transported forward by the registration roller pair 31, the transport conditions are changed by increasing the suction force of the print transport unit 50 (air A1 → A2).

[0059] Then, the control unit 81 controls the pair of registration rollers 31 to forwardly convey the reversed sheet P, and starts (resumes) conveyance as shown in FIG. 4(c) (step S9). Thereafter, the control unit 81 repeats the process from the step of determining whether the lifting detection sensor FS has detected the lifting of the sheet P (step S2). Therefore, even if the lifting detection sensor FS again detects the lifting of the sheet P conveyed in the forward direction after the reverse conveyance, the control unit 81 reversely conveys the sheet P as shown in FIG. 4(d), and further changes the conveyance conditions, such as the conveyance speed and suction force (conveyance speed v3, air A3), as shown in FIG. 4(e), and conveys the sheet P in the forward direction. Note that the control unit 81 may forwardly convey the reversed sheet P to the pair of registration rollers 31 at least once without changing the conveyance conditions, and resume conveyance. This is because the lifting of the sheet P may be resolved without changing the conveyance conditions. Therefore, the process shown in FIG. 3 may not be immediately terminated due to the above-mentioned lifting error, and reverse conveyance (step S4) and forward conveyance (step S9) may be performed. Furthermore, although the transport speed and suction force have been mentioned as transport conditions, the transport condition to be changed may be only one of the transport speed and suction force, or may be another transport condition.

[0060] Returning to the process of determining whether the lifting detection sensor FS has detected lifting of the sheet P (step S2), the control unit 81 determines whether lifting has occurred continuously (step S10) if the lifting detection sensor FS does not detect lifting (step S2: NO), as shown in Fig. 4(e). For example, the control unit 81 may determine that lifting has occurred continuously in the following cases: when lifting is detected for a single sheet P a specified number of times (multiple times) or more and then no longer detected; when lifting is detected for a specified number of sheets P in succession in the past; when the percentage of sheets in which lifting was detected among a specified number of sheets P in the past is equal to or greater than a specified percentage; or when the number of times (or percentage) that lifting was detected during a certain period in the past is equal to or greater than a specified number of times (or specified percentage).

[0061] If floating has not occurred continuously (step S10: NO), the control unit 81 returns the transport conditions to the initial conditions (original transport conditions) (step S11) if the transport conditions (steps S6, S8) have been changed as described above. Note that the control unit 81 may return only some of the transport conditions, such as the transport conditions changed by one step in the above-mentioned change process (steps S6, S8), to their original state, or may change the degree to which the transport conditions are returned depending on the occurrence of floating.

[0062] Furthermore, if floating continues to occur (step S10: YES), the control unit 81 does not perform the process of restoring the transport conditions to their original state (step S11). However, the control unit 81 may restore some or all of the changed transport conditions to their original state even if floating continues to occur (step S10: YES).

[0063] Thereafter, the control unit 81 determines whether printing has finished (step S12), and if not finished (step S12: NO), repeats the process from the process of determining whether the lift detection sensor FS has detected lifting of the paper P (step S2). On the other hand, if printing has finished (step S12: YES), the control unit 81 ends the process shown in FIG.

[0064] 3 and 4, the control unit 81 causes the registration roller pair 31 to reversely convey the sheet P whose floating has been detected by the floating detection sensor FS, and then causes the registration roller pair 31 to forwardly convey the reversely conveyed sheet P. The movement of other sheets P in the printing device 1 during this operation will be described with reference to FIGS. 5A to 5F.

[0065] As shown in FIG. 5A, consider the case where the preceding sheets P1 to P4 are being transported in the printing device 1 when the lifting of sheet P5 is detected by the lifting detection sensor FS.

[0066] 5B, while paper P5 is being conveyed in the reverse direction as described above, the print conveying unit 50 and other units continue conveying the paper P1-P4 in the printing device 1, for example, to the accumulation unit 34c described above and become targets for disposal. Note that paper P on which printing has been completed may be conveyed to the paper discharge unit 60 to avoid being discarded.

[0067] Then, as shown in FIG. 5C, the conveying conditions are changed and paper P5 is conveyed in the forward direction again. If no floating of paper P5 is detected, paper P5 is also conveyed to the accumulation unit 34c as shown in FIGS. 5D and 5E. In this case, based on the fact that no floating of paper P5 is detected, the control unit 81 stops the conveyance of the registration roller pair 31, and the print conveying unit 50 returns the conveying speed and suction force to the original conveying conditions while continuing conveyance. Therefore, since no paper P remains in the printing device 1, the user does not need to open the door of the printing device 1 to remove the paper P. Furthermore, it is possible to automatically resume conveyance (printing) of paper P. Furthermore, even if a floating error occurs when the conveying speed of paper P is lowest and the suction force of the print conveying unit 50 is highest (step S3: YES in FIG. 3) when floating is detected, paper P5 is the only paper P remaining in the printing device 1, and paper P5 can be removed only from the paper feed section, as shown in FIG. 5F. It should be noted that the printing transport section 50 may be stopped after the floating detection sensor FS detects floating of the paper P, until the pair of registration rollers 31 transports the paper P in the reverse direction and then transports it in the forward direction again, but from the viewpoint of transporting the preceding paper P quickly, it is preferable for the printing transport section 50 to continue transporting.

[0068] Consider a comparative example shown in FIG. 6A in which the pair of registration rollers 31 and the print transport unit 50 are stopped when the floating detection sensor FS detects floating of sheet P15 while the preceding sheets P11-P14 are being transported within the printer 1. In this example, as shown in FIG. 6B, even if the duplex transport unit 33, the ascending transport unit 32, and the like continue transport, sheets P13-P15 remain at the pair of registration rollers 31 and the print transport unit 50, and only sheets P11 and P12 are transported to the accumulation unit 34c. This requires time and effort to open the door of the printer 1 and remove the remaining sheets P13-P15. Furthermore, printing cannot be automatically resumed.

[0069] In the present embodiment described above, the medium conveying device includes a pair of registration rollers 31 (an example of a conveying member) that conveys paper P (an example of a medium) in both forward and reverse directions, a float detection sensor FS that is positioned downstream of the pair of registration rollers 31 in the conveying direction and detects float of paper P, and a control unit 81 that reversely conveys paper P whose float is detected by the float detection sensor FS to the pair of registration rollers 31, and causes the pair of registration rollers 31 to convey the reversely conveyed paper P in the forward direction.

[0070] In this way, by conveying the paper P in the reverse direction for which floating has been detected, the presence or absence of floating in the paper P can be detected again by the floating detection sensor FS. Therefore, even in cases where a complex configuration such as a decurler for eliminating floating is not required, the work of stopping the conveyance of the paper P and having the user remove the paper P from the medium conveyance device (printing device 1) can be eliminated with a simple operation. Therefore, according to this embodiment, the conveyance of the paper P for which floating has been detected can be easily resumed. Note that the medium conveyance device may be equipped with a floating elimination unit such as a decurler for eliminating floating, but if this floating elimination unit is not provided, costs and installation space can be saved.

[0071] In addition, in this embodiment, when the control unit 81 causes the registration roller pair 31 to forwardly convey the reversely conveyed sheet P, the control unit 81 changes the conveying conditions by causing the registration roller pair 31 to slow down the conveying speed.

[0072] This makes it possible to prevent floating of the paper P, which tends to occur at the leading edge when transported at high speed, by transporting at low speed. Therefore, transport of the paper P after floating is detected can be more reliably resumed. Furthermore, compared to a mode in which the transport speed is slowed down in advance, the transport efficiency of the paper P can be improved.

[0073] In this embodiment, the medium transport device further includes a print transport unit 50 (an example of an adsorption transport unit) that is disposed downstream in the transport direction of the registration roller pair 31 and adsorbs and transports the paper P by suction. When the control unit 81 causes the reversely transported paper P to be transported forward by the registration roller pair 31, the control unit 81 changes the transport conditions by increasing the suction force of the print transport unit 50.

[0074] Therefore, the suction of the paper P can make it difficult for the paper P to float. Therefore, the transport of the paper P that has been detected to be floating can be more reliably resumed. Also, power consumption can be reduced compared to a mode in which the suction force is already strong.

[0075] Furthermore, in this embodiment, if the float detection sensor FS again detects float of the paper P that has been transported in the forward direction after being transported in the reverse direction, the control unit 81 further changes the transport conditions, and if the float detection sensor FS does not detect float, the control unit 81 returns the transport conditions to the transport conditions before the change.

[0076] This makes it even more difficult for the paper sheet P to float, and therefore makes it possible to more reliably resume conveyance of the paper sheet P for which floating has been detected.

[0077] The present invention is not limited to the above-described embodiments, and can be embodied by modifying the components without departing from the spirit of the invention in the implementation stage. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiments. For example, all the components shown in the embodiments may be appropriately combined. Naturally, various modifications and applications are possible without departing from the spirit of the invention. Below, some of the inventions described in the specification of this application are additionally noted.

[0078] [Appendix 1] a conveying member that conveys a medium in a forward direction and a reverse direction; a float detection sensor disposed downstream in the transport direction of the transport member and configured to detect float of the medium; a control unit that causes the conveying member to convey the medium in a reverse direction when a lift is detected by the lift detection sensor, and causes the conveying member to convey the reversely conveyed medium in a forward direction; A medium transport device comprising:

[0079] [Appendix 2] When the control unit causes the conveying member to convey the reversely conveyed medium in the forward direction, the control unit changes the conveying conditions by slowing down the conveying speed of the conveying member. 2. A medium transport device according to claim 1.

[0080] [Appendix 3] a suction conveyance unit that is disposed downstream of the conveyance member in the conveyance direction and that suctions and conveys the medium, When the control unit causes the conveying member to convey the reversely conveyed medium in the forward direction, the control unit changes the conveying conditions by increasing the suction force of the suction conveying unit. 3. A medium transport device according to claim 1 or 2.

[0081] [Appendix 4] When the float detection sensor detects float again in the medium transported in the forward direction after the reverse transport, the control unit further changes the transport conditions, and when the float detection sensor does not detect float again, the control unit returns the transport conditions to the transport conditions before the change. 4. A medium transport device according to claim 2 or 3. [Explanation of symbols]

[0082] 1 Printing device 10 External paper feed section 11 Paper tray 12 Paper feed roller 13 Sabaki board 20 Internal paper feed section 21 1st paper feed section 22 2nd paper feed section 23 3rd paper feed section 21a, 22a, 23a Paper tray 21b, 22b, 23b Paper feed roller 31 Registration roller pair 32 Elevating conveyor section 32a, 32b Acceleration roller pair 33 Double-sided conveying section 33a, 33b, 33c, 33d uniform speed roller pairs 34 Reversing conveying section 34a, 34b Switchback roller pair 34c storage section 35 Paper refeed section 36 Paper ejection transport section 37 Straight transport 38,39 Route switching section 40 Printing Department 50 Printing transport unit 51 Pulley 52 Belt 53 Suction fan 54,55 Guide roller 60 Paper output section 61 Paper output tray 62 Paper ejection roller pair 70 Conveyor drive unit 71 Resist drive unit 72 Lifting drive unit 73 Double-sided drive unit 74 Reversing drive unit 75 Refeed drive unit 76 Paper ejection drive unit 77 Straight drive unit 78,79 Switching drive unit 81 Control Unit 82 Memory section 83 Interface section FS Float Detection Sensor P paper R1 Straight route R2 Circulation Route R2a Reversal Path R3 paper output path RS Resist Sensor TS Top Edge Sensor

Claims

1. a conveying member that conveys a medium in a forward direction and a reverse direction; a float detection sensor disposed downstream in the transport direction of the transport member and configured to detect float of the medium; a control unit that causes the conveying member to convey the medium in a reverse direction when a lift is detected by the lift detection sensor, and causes the conveying member to convey the reversely conveyed medium in a forward direction; A medium transport device comprising:

2. When the control unit causes the conveying member to convey the reversely conveyed medium in the forward direction, the control unit changes the conveying conditions by slowing down the conveying speed of the conveying member.

2. The medium transport device according to claim 1.

3. a suction conveyance unit that is disposed downstream of the conveyance member in the conveyance direction and that suctions and conveys the medium, When the control unit causes the conveying member to convey the reversely conveyed medium in the forward direction, the control unit changes the conveying conditions by increasing the suction force of the suction conveying unit.

2. The medium transport device according to claim 1.

4. When the float detection sensor detects float again in the medium transported in the forward direction after the reverse transport, the control unit further changes the transport conditions, and when the float detection sensor does not detect float again, the control unit returns the transport conditions to the transport conditions before the change.

4. The medium transport device according to claim 2 or 3.

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