Conveyor

Abstract

To provide a transport apparatus by which it is possible to reduce unnecessary cleaning of a medium detection part while preventing a large-sized apparatus and a complicated circuit design.SOLUTION: A paper sensor 28C includes a light-receiving part 28b to receive light emitted from light-emitting parts 28a and 28a. Paper sensors 28A to 28L detect a paper P. If an amount of light by a light-receiving part 28b is attenuated due to a paper transport operation, a control part calculates, on the basis of an attenuation amount D in the paper transport operation and a direction of the paper sensor 28 subjected to a paper feed, a determination addition value C for each of the paper sensors 28 subjected to the paper feed, and makes a determination that the paper sensor 28 in which a determination value H obtained by accumulating the determination addition values C exceeds a determination threshold value Ht needs cleaning.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a transport device that transports a medium. [Background technology]

[0002] There is known a printing device that prints on paper as a medium while transporting the paper. In such a printing device, a plurality of paper sensors (medium detection units) are arranged along the paper transport path to detect paper jams, etc.

[0003] In such a printing device, paper dust generated during paper transport can adhere to and accumulate on the paper sensor. Such accumulation of paper dust can cause the paper sensor to remain in the on state or cause chattering in the paper sensor, which can lead to erroneous detection of paper by the paper sensor.

[0004] A technology for dealing with problems caused by paper dust in printing devices is disclosed in Patent Document 1. In this technology, multiple sensors for detecting paper dust are arranged on the paper transport path, and a message is displayed on an operation panel encouraging cleaning of the area where paper dust has accumulated, based on the amount of accumulated paper dust detected by the paper dust detection sensors. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2009-20370 A Summary of the Invention [Problem to be solved by the invention]

[0006] As with the technology of Patent Document 1, by arranging multiple sensors for detecting paper dust, it is possible to determine the timing when each of the multiple paper sensors needs cleaning. This allows the paper sensors to be cleaned at the appropriate timing, reducing false detection of paper by the paper sensors. However, providing multiple sensors for detecting paper dust leads to an increase in the size of the device and a complex circuit design.

[0007] On the other hand, if only one sensor for detecting paper dust is provided and the timing for cleaning all paper sensors is determined based on the amount of accumulated paper dust detected by that sensor, there is a risk that paper sensors that do not need cleaning will be cleaned, because the amount of accumulated paper dust in each paper sensor may differ depending on conditions such as the orientation of each paper sensor.

[0008] The present invention has been made in consideration of the above, and has an object to provide a transport device that can reduce unnecessary cleaning of a media detection unit while suppressing an increase in size of the device and a complex circuit design. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the conveying device of the present invention is characterized in that it comprises a dust detection unit having an light-emitting unit arranged along a conveying path along which a medium is conveyed and a light-receiving unit that receives light emitted by the light-emitting unit, a plurality of media detection units arranged along the conveying path and detecting media, and a judgment unit that, when the amount of light received by the light-receiving units is attenuated due to a media conveying operation, calculates a judgment addition value for each media detection unit through which the medium has passed based on the amount of attenuation in the amount of light received by the light-receiving units during the media conveying operation and the installation conditions of the media detection units through which the medium has passed, and judges that cleaning is required for the media detection units whose judgment value, obtained by accumulating the judgment addition values, exceeds a predetermined judgment threshold. Effect of the Invention

[0010] According to the transport device of the present invention, it is possible to reduce unnecessary cleaning of the medium detection unit while suppressing an increase in size of the device and an increase in the complexity of the circuit design. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic configuration diagram of a printing device according to an embodiment. [Diagram 2] 2 is a control block diagram of the printing apparatus shown in FIG. 1. [Diagram 3] FIG. 13 is a diagram showing a sensor table. [Figure 4] 4 is a flowchart illustrating an operation of the printing device. [Diagram 5] 4 is a flowchart illustrating an operation of the printing device. [Figure 6] 4 is a flowchart illustrating an operation of the printing device. [Figure 7] 4 is a flowchart illustrating an operation of the printing device. [Figure 8] 4 is a flowchart illustrating an operation of the printing device. [Figure 9] 4 is a flowchart illustrating an operation of the printing device. [Figure 10] 11 is a diagram showing an example of a transition of a determination value of a paper sensor. FIG. [Figure 11] 13 is a view showing a sensor table for explaining an example of a calculation result of a determination value of a paper sensor through which a paper has passed during a paper transport operation; FIG. [Figure 12] 13 is a diagram showing an example of a sensor table when a determination value of a paper sensor exceeds a determination threshold value for the first time; FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The same or equivalent parts and components are denoted by the same or equivalent reference numerals throughout the drawings.

[0013] The following embodiments are examples of devices for embodying the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the material, shape, structure, arrangement, etc. of each component to those described below. The technical idea of ​​the present invention can be modified in various ways within the scope of the claims.

[0014] Fig. 1 is a schematic diagram of a printing device provided with a conveying device according to an embodiment of the present invention. Fig. 2 is a control block diagram of the printing device shown in Fig. 1. In the following description, the top, bottom, left, and right directions on the paper surface of Fig. 1 are defined as the top, bottom, left, and right directions.

[0015] 1, the path indicated by the thick line is the transport path along which the paper (corresponding to the medium) P is transported. Of the transport paths, the path indicated by the solid line is the normal path RC, the path indicated by the dashed line is the reversing path RR, the path indicated by the dashed line is the paper discharge paths RD1 and RD2, and the path indicated by the two-dot chain line is the paper feed path RS. In the following description, upstream and downstream refer to the upstream and downstream of the transport path.

[0016] 1 and 2, the printing device 1 according to this embodiment includes a paper feed section 2, a print transport section 3, a printing section 4, a first paper discharge section 5, an upper transport section 6, a second paper discharge section 7, an inversion section 8, an operation panel 9, a storage section 10, a control section (corresponding to a determination section) 11, and a housing 12 that houses or holds each of the sections. Note that the sections of the printing device 1 other than the printing section 4 form a transport device.

[0017] The paper feed unit 2 feeds paper P. The paper feed unit 2 includes an external paper feed tray 21, an external paper feed roller 22, an internal paper feed tray 23, an internal paper feed roller 24, a vertical transport roller 25, an external paper feed motor 26, an internal paper feed motor 27, and paper sensors 28A and 28B (corresponding to a medium detection unit). Note that the alphabetical suffixes in the reference symbols of the paper sensors 28A, 28B, etc. may be omitted to collectively indicate the components.

[0018] The external paper feed tray 21 is provided on which paper sheets P to be used for printing are stacked. The external paper feed tray 21 is provided so that a portion of the external paper feed tray 21 is exposed to the outside of the housing 12.

[0019] The external paper feed rollers 22 take out the paper sheets P stacked on the external paper feed tray 21 one by one, and transport the paper sheets P along a paper feed path RS toward a registration roller 31, which will be described later.

[0020] The internal paper feed tray 23 is disposed inside the housing 12 and supports paper P to be used for printing.

[0021] The internal paper feed roller 24 takes out the paper sheets P stacked on the internal paper feed tray 23 one by one and sends them out to the paper feed path RS.

[0022] The vertical transport rollers 25 transport the paper P taken out from the internal paper feed tray 23 along the paper feed path RS toward the registration rollers 31, which will be described later.

[0023] The external paper feed motor 26 rotates and drives the external paper feed rollers 22 and the vertical transport rollers 25. The external paper feed motor 26 can be connected / disconnected to the external paper feed rollers 22 and the vertical transport rollers 25 via a clutch (not shown). The drive of the external paper feed rollers 22 and the vertical transport rollers 25 is switched by the clutch.

[0024] The internal paper feed motor 27 drives the internal paper feed rollers 24 and the vertical transport rollers 25 to rotate.

[0025] The paper sensor 28A detects the paper P taken out from the external paper feed tray 21 and transported along the paper feed path RS. The paper sensor 28B detects the paper P taken out from the internal paper feed tray 23 and transported along the paper feed path RS. The paper sensors 28A and 28B are reflective optical sensors, and are digital sensors that output a signal indicating the presence or absence of paper. The paper sensor 28A is installed facing downward along the paper feed path RS near the upstream side of the junction of the path from the external paper feed rollers 22 to the registration rollers 31 and the path from the internal paper feed rollers 24 to the registration rollers 31 in the paper feed path RS. The paper sensor 28B is installed horizontally (facing right) along the paper feed path RS near the upstream side of the vertical transport rollers 25.

[0026] The print transport unit 3 transports the paper P transported from the paper feed unit 2 or the reversing unit 8. The print transport unit 3 includes a registration roller 31, a registration motor 32, a belt platen unit 33, a belt platen motor 34, and paper sensors 28C and 28D.

[0027] The registration rollers 31 temporarily stop the paper P conveyed from the paper feed unit 2 or the inversion unit 8, and then convey the paper P toward the belt platen unit 33. The registration rollers 31 are disposed along the normal path RC, downstream of the joining point of the paper feed path RS and the inversion path RR.

[0028] The registration motor 32 drives the registration rollers 31 to rotate.

[0029] The belt platen unit 33 transports the paper P transported from the registration rollers 31 along the horizontal portion in the upstream area of ​​the normal path RC.

[0030] The belt platen motor 34 drives the belt platen unit 33 .

[0031] Paper sensor 28C (corresponding to the medium detection section and dust detection section) detects paper P transported from registration rollers 31 toward belt platen section 33. Paper sensor 28C is also used to determine whether or not cleaning is required due to accumulation of paper powder (dust) in paper sensors 28A-D and paper sensors 28E-L described below. Paper sensor 28C is a transmissive optical sensor having light-emitting section 28a and light-receiving section 28b, and is composed of an analog sensor that outputs a signal indicating the amount of light received by light-receiving section 28b.

[0032] The light-emitting unit 28a emits light upward along the normal path RC. The light-receiving unit 28b receives the light emitted by the light-emitting unit 28a. The light-receiving unit 28b is disposed facing downward and opposite the light-emitting unit 28a across the normal path RC.

[0033] The paper sensor 28C is disposed along the normal path RC in the vicinity of the downstream side of the registration rollers 31. The vicinity of the downstream side of the registration rollers 31 is the position on the transport path of the paper P where paper dust is most likely to accumulate.

[0034] Paper sensor 28D (corresponding to a medium detection unit) detects paper P transported from belt platen unit 33 toward switching unit 36, which will be described later. Paper sensor 28D is made up of a digital sensor similar to paper sensors 28A and 28B. Paper sensor 28D is installed facing downward along normal path RC near the downstream side of belt platen unit 33.

[0035] The printing unit 4 has a plurality of inkjet heads (not shown), and performs printing by ejecting ink from the inkjet heads onto the paper P transported by the belt platen unit 33. The printing unit 4 is disposed above the belt platen unit 33.

[0036] The first paper discharge section 5 guides printed paper P to a post-processing device (not shown) connected downstream of the printing device 1. The first paper discharge section 5 includes a switching section 36 and a paper sensor 28E (corresponding to a medium detection section).

[0037] The switching unit 36 ​​switches the transport path of the paper P between the normal path RC and the paper discharge path RD1. The switching unit 36 ​​is disposed at a branch point between the normal path RC and the paper discharge path RD1.

[0038] The paper sensor 28E detects the paper P transported along the paper discharge path RD1. The paper sensor 28E is a digital sensor similar to the paper sensors 28A and 28B. The paper sensor 28E is installed downstream of the switching unit 36 ​​and facing downward along the paper discharge path RD1.

[0039] The upper surface transport section 6 transports the paper P transported from the belt platen section 33 to the second paper discharge section 7 or the inversion section 8. The upper surface transport section 6 includes two pairs of upward transport rollers 41, an upward transport motor 42, four pairs of horizontal transport rollers 43, a horizontal transport motor 44, and paper sensors 28F to 28J (corresponding to medium detection sections).

[0040] The upward transport rollers 41 transport the paper P transported by the belt platen unit 33 to the upper horizontal transport rollers 43. The upward transport rollers 41 are disposed along the upward portion of the middle stream area of ​​the normal route RC.

[0041] The lifting conveying motor 42 drives the two pairs of lifting conveying rollers 41 to rotate.

[0042] The horizontal transport rollers 43 transport the paper P transported by the ascending transport rollers 41 to the paper discharge section 5 or the inversion section 8. The most downstream horizontal transport rollers 43 are disposed in the upstream area of ​​the inversion route RR. The other horizontal transport rollers 43 are disposed in the horizontal parts of the downstream area of ​​the normal route RC.

[0043] The horizontal conveying motor 44 drives the four pairs of horizontal conveying rollers 43 to rotate.

[0044] Paper sensors 28F-28I detect paper P transported along the upward portion in the middle stream area and the horizontal portion in the downstream area of ​​normal route RC. Paper sensor 28J detects paper P transported from the most downstream horizontal transport roller 43 to reversing rollers 61, which will be described later. Paper sensors 28F-28J are composed of digital sensors similar to paper sensors 28A and 28B.

[0045] The paper sensor 28F is installed horizontally (facing left) along the normal path RC between the upstream ascending conveying rollers 41 and the downstream ascending conveying rollers 41. The paper sensor 28G is installed facing downward along the normal path RC between the downstream ascending conveying rollers 41 and the most upstream horizontal conveying rollers 43.

[0046] Paper sensor 28H is installed facing downward along normal path RC between the most upstream horizontal transport roller 43 and the second most upstream horizontal transport roller 43. Paper sensor 28I is installed facing downward along normal path RC near the downstream side of the third most upstream horizontal transport roller 43. Paper sensor 28J is installed facing downward along reversing path RR near the downstream side of the most downstream horizontal transport roller 43.

[0047] The second paper discharge section 7 discharges the printed paper P. The second paper discharge section 7 includes a switching section 51, a paper discharge roller 52, a paper discharge motor 53, a paper discharge tray 54, and a paper sensor 28K (corresponding to a medium detection section).

[0048] The switching unit 51 switches the transport path of the paper P between the paper discharge path RD2 and the reverse path RR. The switching unit 51 is disposed at a branch point of the paper discharge path RD2 and the reverse path RR.

[0049] The paper discharge rollers 52 transport the paper P guided to the paper discharge path RD2 by the switching unit 51, and discharge the paper P onto the paper discharge tray 54. The paper discharge rollers 52 are disposed between the switching unit 51 and the paper discharge tray 54 along the paper discharge path RD2.

[0050] The paper discharge motor 53 drives the paper discharge rollers 52 to rotate.

[0051] The paper discharge tray 54 is configured to stack the paper sheets P discharged in the second paper discharge section 7. The paper discharge tray 54 is disposed at the downstream end of the paper discharge path RD2.

[0052] The paper sensor 28K detects the paper P being transported to the paper discharge tray 54 by the paper discharge rollers 52. The paper sensor 28K is composed of a digital sensor similar to the paper sensors 28A and 28B. The paper sensor 28K is installed facing downward along the paper discharge path RD2 between the paper discharge rollers 52 and the paper discharge tray 54.

[0053] When performing double-sided printing, the reversing unit 8 reverses the paper P that has been printed on one side and transports it to the print transport unit 3. The reversing unit 8 includes a reversing roller 61, a reversing motor 62, a paper re-feed roller 63, a paper re-feed motor 64, a switching gate 65, and a paper sensor 28L (corresponding to a medium detection unit).

[0054] The reversing rollers 61 switch back the paper P conveyed by the horizontal conveying rollers 43 and convey it to the paper re-feed rollers 63. The reversing rollers 61 are disposed downstream of the horizontal conveying rollers 43 located at the most downstream side along the reversing path RR.

[0055] The reversing motor 62 drives the reversing roller 61 to rotate.

[0056] The sheet re-feed rollers 63 transport the sheet P, which has been switched back and inverted by the reversing rollers 61, to the registration rollers 31. The sheet re-feed rollers 63 are disposed on the reversing route RR between the reversing rollers 61 and the registration rollers 31.

[0057] The re-feed motor 64 drives the re-feed roller 63 to rotate.

[0058] The switching gate 65 guides the paper P conveyed by the horizontal conveying rollers 43 to the reversing rollers 61. The switching gate 65 also guides the paper P switched back by the reversing rollers 61 to the re-feed rollers 63. The switching gate 65 is disposed near the center of gravity of the three points of the most downstream horizontal conveying rollers 43, the reversing rollers 61, and the re-feed rollers 63.

[0059] Paper sensor 28L detects paper P being switched back by reversing rollers 61 and transported to re-feed rollers 63. Paper sensor 28L is a digital sensor similar to paper sensors 28A and 28B. Paper sensor 28L is installed near the upstream side of re-feed rollers 63 and facing horizontally (to the left) along reversing path RR.

[0060] The operation panel 9 receives input operations from a user and displays various screens etc. The operation panel 9 includes a display unit 71 and an input unit 72.

[0061] The display unit 71 displays various screens, etc. The display unit 71 has a liquid crystal display panel, etc.

[0062] The input unit 72 receives an input operation by a user and outputs an operation signal corresponding to the operation. The input unit 72 has various operation keys, a touch panel, and the like.

[0063] The storage unit 10 stores a sensor table 81 shown in Fig. 3. The storage unit 10 is composed of a HDD (Hard Disk Drive) or the like.

[0064] As shown in FIG. 3, the sensor table 81 holds the orientation of each paper sensor 28 (sensor orientation coefficient K), the judgment value H, the judgment threshold value Ht, the number of passed sheets N (corresponding to the number of passing sheets), and the number of passed sheets threshold value Nt.

[0065] The orientation of the paper sensor 28 is set so as to detect the paper P transported along the transport path at the position where the paper sensor 28 is installed. For example, as described above, the orientation of the paper sensor 28A is downward.

[0066] The sensor orientation coefficient K is a coefficient by which the attenuation D of the amount of light received by the light receiving section 28b of the paper sensor 28C before and after the paper transport operation (corresponding to the medium transport operation) is multiplied when calculating the determination addition value C described below. The sensor orientation coefficient K is set to a larger value in the direction in which paper dust is more likely to accumulate on the paper sensor 28. In the example of Fig. 3, the sensor orientation coefficients K for the upward, horizontal, and downward directions are set to 1.0, 0.5, and 0.25, respectively.

[0067] It should be noted that the value of the sensor orientation coefficient K is not limited to the above example, and the orientation of the paper sensor 28 is not limited to upward, horizontal, and downward, but may be further classified, for example.

[0068] The judgment value H is a value for judging whether or not cleaning of the paper sensor 28 is necessary. The judgment value H is a value obtained by accumulating the judgment addition values ​​C from the first paper transport operation after cleaning of the paper sensor 28 to the most recent paper transport operation. If the paper sensor 28 has never been cleaned, the judgment value H is a value obtained by accumulating the judgment addition values ​​C from the first paper transport operation after starting to use the paper sensor 28 (after starting to use the printing device 1) to the most recent paper transport operation. The judgment value H of each paper sensor 28 is reset when the paper sensor 28 is cleaned, and H=0 is set.

[0069] The judgment addition value C indicates the degree of increase in the amount of accumulated paper dust on the paper sensor 28 due to a series of paper transport operations. When the amount of light received by the light receiving portion 28b is attenuated by the paper transport operation, the judgment addition value C is calculated for the paper sensor 28 through which paper passed (paper P passed) during the paper transport operation, based on the amount of attenuation D and the orientation of the paper sensor 28 (sensor orientation coefficient K), which is an installation condition of the paper sensor 28.

[0070] Specifically, the determination addition value C of the paper sensor 28 where paper has passed (paper P has passed) during the paper transport operation in which the amount of light received by the light receiving section 28b has attenuated is calculated by the following formula (1).

[0071] C = K × D … (1) Whether or not paper passes through each paper sensor 28 is determined by the settings of single-sided / double-sided printing, the paper feed source (external paper feed tray 21 or internal paper feed tray 23), and the paper discharge destination (whether the paper P is discharged from the first paper discharge section 5 or the second paper discharge section 7) during the paper transport operation (printing operation), as described below.

[0072] The judgment threshold Ht is a threshold for judging whether or not cleaning of the paper sensor 28 is necessary from the judgment value H. The judgment threshold Ht of each paper sensor 28 is set in advance based on experiments, etc. As will be described later, the judgment threshold Ht of each paper sensor 28 is changed if a false detection of paper P occurs in the paper sensor 28 before the judgment value H exceeds the judgment threshold Ht.

[0073] The number of sheets of paper P passed by the paper sensor 28 from the first paper transport operation after the paper sensor 28 is cleaned to the most recent paper transport operation. If the paper sensor 28 has never been cleaned, the number of sheets of paper P passed by the paper sensor 28 from the first paper transport operation after the paper sensor 28 has started to be used (after the printing device 1 has started to be used) to the most recent paper transport operation. The number of sheets of paper P passed by each paper sensor 28 is reset to N=0 when the paper sensor 28 is cleaned.

[0074] The passing sheet count threshold Nt is a value for determining whether or not cleaning of the paper sensor 28 is necessary from the passing sheet count N. In each paper sensor 28, the passing sheet count N when the judgment value H exceeds the judgment threshold Ht for the first time after the paper sensor 28 starts to be used (after the printing device 1 starts to be used) is set as the passing sheet count threshold Nt. After the passing sheet count threshold Nt is set, if the passing sheet count N exceeds the passing sheet count threshold Nt even if the judgment value H does not exceed the judgment threshold Ht, it is determined that the paper sensor 28 needs cleaning.

[0075] The control unit 11 controls the operation of each unit of the printing device 1. The control unit 11 includes a CPU, a RAM, a ROM, and the like.

[0076] The control unit 11 executes a printing operation in which the printing unit 4 prints on the paper P while the print transport unit 3 transports the paper P. Here, the printing operation includes a paper transport operation. When the amount of light received by the light receiving unit 28b of the paper sensor 28C is attenuated by the paper transport operation, the control unit 11 calculates a judgment addition value C for each paper sensor 28 through which paper has passed, based on the amount of attenuation D during the paper transport operation and the orientation of the paper sensor 28 through which paper has passed, and calculates a judgment value H by accumulating the judgment addition values ​​C. Then, the control unit 11 determines that the paper sensor 28 whose judgment value H has exceeded the judgment threshold Ht needs to be cleaned.

[0077] Next, the operation of the printing device 1 will be described with reference to the flowcharts of FIGS.

[0078] When a print job is input, in step S1 of Fig. 4, control unit 11 acquires the amount of light received by light receiving unit 28b of paper sensor 28C. The amount of light received by light receiving unit 28b acquired by control unit 11 here is the amount of light received at the start of a series of paper transport operations (printing operations), and is the amount of light received in a state in which paper sensor 28C does not detect paper P (there is no paper P between light emitting unit 28a and light receiving unit 28b).

[0079] Next, in step S2, the control unit 11 starts a printing operation. Here, the control unit 11 executes single-sided printing or double-sided printing according to the single-sided / double-sided printing setting in the print job.

[0080] In the case of single-sided printing, the control unit 11 controls the paper feed unit 2 to sequentially take out unprinted paper P from the external paper feed tray 21 or the internal paper feed tray 23 and feed it to the print transport unit 3. Here, the control unit 11 controls the paper feed unit 2 to sequentially feed the paper at a timing according to the drive timing of the registration rollers 31 that send out each paper P so that each paper P is transported at a predetermined interval between sheets on the belt platen unit 33. As a result, multiple sheets of paper P are transported simultaneously on the transport path.

[0081] The fed paper P is sent to the belt platen unit 33 by the registration rollers 31, and is transported by the belt platen unit 33. At this time, the paper P is printed with ink ejected from the inkjet head of the printing unit 4.

[0082] In single-sided printing, when paper P is discharged by the first discharge section 5, the printed paper P is transported by the belt platen section 33, guided to the discharge path RD1 by the switching section 36, and transported along the discharge path RD1 until it is discharged.

[0083] In single-sided printing, when the paper P is discharged by the second discharge unit 7, the printed paper P is transported by the belt platen unit 33 and guided by the switching unit 36 ​​along the normal path RC to the upper surface transport unit 6. In the upper surface transport unit 6, the paper P is transported by the upward transport rollers 41 and the horizontal transport rollers 43. The paper P is then guided by the switching unit 51 to the paper discharge path RD2 and discharged by the paper discharge rollers 52 to the paper discharge tray 54.

[0084] In the case of double-sided printing, the control unit 11 controls the paper feed unit 2 to sequentially feed unprinted paper P at a timing that doubles the time between the paper feed timings of each paper P compared to the paper feed timing in single-sided printing.

[0085] The fed paper P is printed by the printing unit 4 while being transported by the belt platen unit 33, in the same manner as in single-sided printing. After single-sided printing, the paper P is transported from the belt platen unit 33 to the upper surface transport unit 6, and is transported by the ascending transport rollers 41 and the horizontal transport rollers 43 in the upper surface transport unit 4. The paper P is then guided by the switching unit 51 to the reversing route RR.

[0086] The paper P guided to the reversing path RR is guided to the reversing rollers 61 by the switching gate 65 in the reversing unit 8, switched back by the reversing rollers 61, and guided to the re-feed rollers 63 by the switching gate 65. The paper P is then re-fed to the printing transport unit 3 by the re-feed rollers 63, and sent to the belt platen unit 33 by the registration rollers 31 in the printing transport unit 3.

[0087] Here, the paper P after single-sided printing is refed at a timing such that it is sent to the belt platen unit 33 alternately with the unprinted paper P that is fed in sequence. As described above, in double-sided printing, the time between the feeding timing of each paper P is twice as long as the feeding timing 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 to refed the paper P after single-sided printing alternately with the feeding of the unprinted paper P.

[0088] After single-sided printing, the paper P is inverted by the inversion unit 8 and sent to the belt platen unit 33 with the unprinted side facing up. Then, while the paper P is transported by the belt platen unit 33, the unprinted side is printed by the printing unit 4. The paper P that has been printed on both sides is discharged by the first paper discharge unit 5 or the second paper discharge unit 7 in the same manner as the printed paper P during single-sided printing described above.

[0089] In double-sided printing, as described above, the feeding of unprinted paper P and the re-feeding of paper P after single-sided printing are alternately performed, so that printing on one side of unprinted paper P and printing on the unprinted side of paper P after single-sided printing are alternately performed on the belt platen unit 33. This allows double-sided printing to be performed with the same productivity per side as when printing on one side.

[0090] Here, since the printing operation is performed as described above, the path that the paper P passes through is determined by the settings of single-sided / double-sided printing, the paper feed source (external paper feed tray 21 or internal paper feed tray 23), and the paper discharge destination (whether the paper P is discharged from the first paper discharge section 5 or the second paper discharge section 7). Therefore, in a series of paper transport operations (printing operations), the paper P passes through some of the paper sensors 28 among the paper sensors 28A-28L, and whether or not the paper passes through each paper sensor 28 is determined by the settings of single-sided / double-sided printing, the paper feed source, and the paper discharge destination.

[0091] Specifically, in single-sided printing, when the paper feed source is the external paper feed tray 21 and the paper P is discharged by the first paper discharge unit 5, the paper sensors 28A, 28C to 28E pass paper, but the other paper sensors 28 do not.

[0092] In single-sided printing, when the paper source is the external paper feed tray 21 and paper P is discharged by the second paper discharge section 7, paper sensors 28A, 28C, 28D, 28F to 28I, and 28K pass paper, but other paper sensors 28 do not.

[0093] In single-sided printing, when the paper feed source is the internal paper feed tray 23 and the paper P is discharged by the first paper discharge section 5, the paper sensors 28B to 28E pass paper, but the other paper sensors 28 do not.

[0094] In single-sided printing, when the paper feed source is the internal paper feed tray 23 and paper P is discharged by the second paper discharge section 7, paper sensors 28B to 28D, 28F to 28I, and 28K pass paper, but other paper sensors 28 do not.

[0095] In double-sided printing, when the paper source is the external paper feed tray 21 and paper P is discharged by the first paper discharge unit 5, paper passes through paper sensors 28A, 28C to 28J, and 28L, but not through the other paper sensors 28. One sheet of paper P passes through paper sensors 28C and 28D twice.

[0096] In double-sided printing, when the paper feed source is the external paper feed tray 21 and paper P is discharged by the second paper discharge unit 7, paper passes through paper sensors 28A, 28C, 28D, 28F to 28L, but not through the other paper sensors 28. One sheet of paper P passes twice through paper sensors 28C, 28D, 28F to 28I.

[0097] In double-sided printing, when the paper feed source is the internal paper feed tray 23 and paper P is discharged by the first paper discharge unit 5, paper passes through paper sensors 28B to 28J, 28L, but not through the other paper sensors 28. One sheet of paper P passes twice through paper sensors 28C, 28D.

[0098] In double-sided printing, when the paper feed source is the internal paper feed tray 23 and paper P is discharged by the second paper discharge unit 7, paper passes through paper sensors 28B to 28D, 28F to 28L, but not through the other paper sensors 28. One sheet of paper P passes twice through paper sensors 28C, 28D, 28F to 28I.

[0099] 4, control unit 11 determines whether or not a jam has been detected in paper P. Specifically, control unit 11 determines that a jam has been detected when an error between the detection timing of paper P and its theoretical value is equal to or greater than a threshold value in at least one of paper sensors 28A-28L.

[0100] If it is determined that a jam has not been detected (step S3: NO), in step S4, the control unit 11 determines whether the printing operation has ended. Here, when printing and paper ejection for the number of prints in the print job are completed, the printing operation ends, and the paper transport operation also ends. If it is determined that the printing operation has not ended (step S4: NO), the control unit 11 returns to step S3.

[0101] If it is determined that the printing operation has ended (step S4: YES), in step S5, the control unit 11 updates the number of passed sheets N in the sensor table 81 for each sheet sensor 28 through which a sheet passed in the most recent sheet transport operation.

[0102] Specifically, for each paper sensor 28 through which paper passed in the most recent paper transport operation, the control unit 11 calculates the number of passed papers N at the end of the paper transport operation by adding the number of passed papers N at the start of the paper transport operation (the number of passed papers N in the sensor table 81). Then, the control unit 11 updates the number of passed papers N in the sensor table 81 for each paper sensor 28 through which paper passed to the calculated number of passed papers N. Here, for paper sensors 28 through which one sheet of paper P passes twice in double-sided printing, each pass is counted as one pass.

[0103] Next, in step S6, the control unit 11 acquires the amount of light received by the light receiving unit 28b of the paper sensor 28C. The amount of light received by the light receiving unit 28b acquired by the control unit 11 here is the amount of light received at the end of a series of paper transport operations, and is the amount of light received in a state in which the paper sensor 28C has not detected the paper P.

[0104] Next, in step S7, the control unit 11 determines whether the amount of light received by the light receiving unit 28b has attenuated due to the paper transport operation. If the amount of light received by the light receiving unit 28b at the end of a series of paper transport operations is smaller than the amount of light received by the light receiving unit 28b at the start of the series of paper transport operations, the control unit 11 determines that the amount of light received by the light receiving unit 28b has attenuated.

[0105] If it is determined that the amount of light received by the light receiving unit 28b has attenuated (step S7: YES), in step S8, the control unit 11 calculates the determination value H at the end of the most recent paper transport operation for each paper sensor 28 through which paper passed. Then, the control unit 11 updates the determination value H in the sensor table 81 for each paper sensor 28 through which paper passed.

[0106] Specifically, the control unit 11 calculates the attenuation D by subtracting the amount of light received by the light receiving unit 28b at the end of the most recent paper transport operation from the amount of light received by the light receiving unit 28b at the start of the most recent paper transport operation. Next, the control unit 11 calculates the judgment addition value C for each paper sensor 28 through which paper has passed, using the above-mentioned formula (1). Then, the control unit 11 adds the calculated judgment addition value C for each paper sensor 28 through which paper has passed to the judgment value H (judgment value H in the sensor table 81) at the start of the most recent paper transport operation to calculate the judgment value H at the end of the paper transport operation. Then, the control unit 11 updates the judgment value H in the sensor table 81 for each paper sensor 28 through which paper has passed to the calculated judgment value H.

[0107] Next, in step S9, the control unit 11 determines whether or not there is a paper sensor 28 whose determination value H has exceeded the determination threshold value Ht.

[0108] If it is determined that there is a paper sensor 28 whose judgment value H has exceeded the judgment threshold Ht (step S9: YES), in step S10, the control unit 11 determines whether or not there is a paper sensor 28 whose judgment value H has exceeded the judgment threshold Ht and whose passing paper count threshold Nt has not been set. Here, when the paper sensor 28 starts to be used (when the printing device 1 starts to be used), the passing paper count threshold Nt has not been set.

[0109] If it is determined that among the paper sensors 28 whose judgment value H exceeds the judgment threshold Ht, there is a paper sensor 28 for which the paper passing number threshold Nt has not been set (step S10: YES), in step S11, the control unit 11 sets the paper passing number N of the paper sensor 28 to the paper passing number threshold Nt.

[0110] Thus, the control unit 11 sets, in each paper sensor 28, the number of passed sheets N when the determination value H first exceeds the determination threshold value Ht after the start of use of the paper sensor 28 as the passed sheet number threshold value Nt.

[0111] Next, in step S12 of FIG. 5, the control unit 11 determines whether or not there is a paper sensor 28 whose judgment value H exceeds the judgment threshold Ht and whose number of passed sheets N is different from the number of passed sheets threshold Nt.

[0112] When it is determined that the paper sensor 28 whose judgment value H exceeds the judgment threshold Ht includes a paper sensor 28 whose number of passed sheets N is different from the number of passed sheets threshold Nt (step S12: YES), in step S13, the control unit 11 changes the number of passed sheets threshold Nt of the paper sensor 28. Specifically, the control unit 11 sets the number of passed sheets N of the paper sensor 28 to the new number of passed sheets threshold Nt.

[0113] As a result, after setting the paper count threshold Nt in each paper sensor 28, if the number of sheets N passed when the judgment value H exceeds the judgment threshold Ht is different from the paper count threshold Nt, the control unit 11 sets the number of sheets N passed as a new paper count threshold Nt.

[0114] Next, in step S14, the control unit 11 instructs the user to clean the paper sensor 28 whose judgment value H has exceeded the judgment threshold Ht. Specifically, the control unit 11 causes the display unit 71 to display a message urging the user to clean the paper sensor 28 whose judgment value H has exceeded the judgment threshold Ht, as well as the position of the paper sensor 28, etc.

[0115] In this way, the control unit 11 determines that cleaning is required for the paper sensor 28 whose determination value H has exceeded the determination threshold value Ht, and instructs the user to clean it.

[0116] Next, in step S15, the control unit 11 determines whether or not cleaning of the paper sensor 28 is complete. Here, the control unit 11 determines that cleaning of the paper sensor 28 is complete when a user operation is performed on the input unit 72 to notify the printing device 1 that cleaning of the paper sensor 28 is complete. If the control unit 11 determines that cleaning of the paper sensor 28 is not complete (step S15: NO), the control unit 11 repeats step S15.

[0117] When it is determined that cleaning of the paper sensor 28 is completed (step S15: YES), in step S16, the control unit 11 resets the determination value H and the number of passed sheets N in the sensor table 81 for the paper sensor 28 that has been cleaned. This ends the series of processes.

[0118] In step S10, if it is determined that there is no paper sensor 28 for which the passed paper count threshold Nt has not been set among the paper sensors 28 for which the determination value H has exceeded the determination threshold Ht (step S10: NO), the control unit 11 proceeds to step S12 in FIG.

[0119] In step S12, if it is determined that there is no paper sensor 28 whose judgment value H exceeds the judgment threshold Ht and whose number of passed sheets N is different from the number of passed sheets threshold Nt (step S12: NO), the control unit 11 proceeds to step S14.

[0120] If it is determined in step S7 that the amount of light received by the light receiving unit 28b has not attenuated (step S7: NO), and if it is determined in step S9 that there is no paper sensor 28 whose judgment value H has exceeded the judgment threshold value Ht (step S9: NO), then in step S17, the control unit 11 determines whether there is a paper sensor 28 whose number of sheets of paper N has exceeded the number of sheets of paper threshold value Nt.

[0121] If it is determined that there is a paper sensor 28 whose number of passed sheets N has exceeded the number of passed sheets threshold Nt (step S17: YES), the control unit 11 proceeds to step S14 in FIG. 5 and instructs the user to clean the paper sensor 28 whose number of passed sheets N has exceeded the number of passed sheets threshold Nt.

[0122] In this way, when the number of sheets N passing through each paper sensor 28 exceeds the number of sheets N passing through threshold Nt, even if the judgment value H does not exceed the judgment threshold Ht, the control unit 11 judges that cleaning of the paper sensor 28 is necessary and instructs the user to clean it.

[0123] When the control unit 11 determines that there is no paper sensor 28 in which the number of passed sheets N exceeds the number of passed sheets threshold Nt (step S17: NO), the series of processes ends.

[0124] In step S3, if it is determined that a jam has been detected (step S3: YES), the control unit 11 stops the printing operation in step S18 in Fig. 6. This also stops the paper transport operation.

[0125] Next, in step S19, the control unit 11 updates the number of passed sheets N in the sensor table 81 for each sheet sensor 28 through which a sheet passed in the most recent sheet transport operation.

[0126] Here, when the paper transport operation is stopped due to the detection of a jam, the series of paper transport operations up to the stop is the most recent paper transport operation. The method for calculating the number of passed sheets N is the same as the method described in step S5 above. The paper P stopped at a position detected by the paper sensor 28 at the time when the paper transport operation is stopped due to the detection of a jam may or may not be included in the paper P that has passed the paper sensor 28.

[0127] After step S19, the control unit 11 proceeds to step S20. The processes of steps S20 to S22 are similar to the processes of steps S6 to S8 described above.

[0128] After step S22, in step S23, the control section 11 determines whether the jam has been detected due to erroneous detection of the paper P by the paper sensor 28 or not.

[0129] Specifically, the control unit 11 causes the display unit 71 to display a message instructing the user to check whether or not there is paper P at the position of the paper sensor 28 where the jam was detected. Then, when a user operates the input unit 72 to notify the printing device 1 that there is no paper P at the position instructed to be checked, the control unit 11 determines that the jam was detected due to erroneous detection of paper P by the paper sensor 28. Note that the method of determining erroneous detection is not limited to this.

[0130] If it is determined that the jam was detected due to a mistaken detection of paper P by the paper sensor 28 (step S23: YES), then in step S24 of FIG. 7, the control unit 11 determines whether the judgment value H of the paper sensor 28 that mistakenly detected the paper P is less than the judgment threshold value Ht.

[0131] When it is determined that the determination value H of the paper sensor 28 that erroneously detected the paper P is less than the determination threshold Ht (step S24: YES), in step S25, the control unit 11 changes the determination threshold Ht of the paper sensor 28. Specifically, the control unit 11 sets the determination value H of the paper sensor 28 to the new determination threshold Ht.

[0132] As a result, when a false detection of paper P occurs in the paper sensor 28 before the judgment value H reaches the judgment threshold Ht, the control unit 11 sets the judgment value H in the paper sensor 28 at the time when the false detection of paper P occurred as the new judgment threshold Ht for the paper sensor 28.

[0133] After step S25, the control unit 11 proceeds to step S26. If the control unit 11 determines in step S24 that the determination value H of the paper sensor 28 that erroneously detected the paper P is equal to or greater than the determination threshold value Ht (step S24: YES), the control unit 11 proceeds to step S26. The processes of steps S26 to S34 are the same as the processes of steps S9 to S17 described above.

[0134] Here, in step S31, when instructing the user to clean paper sensor 28, control unit 11 also instructs the user to remove paper P remaining in printing device 1 due to the stop of the printing operation. As a result, when cleaning paper sensor 28, paper P remaining in printing device 1 is also removed, and when cleaning of paper sensor 28 is completed, removal of paper P remaining in printing device 1 is also completed.

[0135] After step S33, the control unit 11 proceeds to step S35. Also, in step S34, if it is determined that there is no paper sensor 28 in which the number of sheets N passed exceeds the number of sheets Nt threshold (step S34: NO), the control unit 11 proceeds to step S35.

[0136] In step S35, the control unit 11 acquires the amount of light received by the light receiving unit 28b of the paper sensor 28C. The amount of light received by the light receiving unit 28b acquired by the control unit 11 here is the amount of light received at the start of a series of paper transport operations (printing operations) after the printing operation is resumed, and is the amount of light received in a state in which the paper sensor 28C has not detected the paper P.

[0137] Next, in step S36, the control unit 11 restarts the printing operation based on the print job that was stopped due to the detection of the jam. After that, the control unit 11 returns to step S3 in FIG.

[0138] In step S21 of FIG. 6, if it is determined that the amount of light received by the light receiving unit 28b has not attenuated (step S21: NO), in step S37 of FIG. 8, the control unit 11 determines whether the detection of the jam is due to a false detection of the paper P by the paper sensor 28.

[0139] When it is determined that the jam was detected due to erroneous detection of paper P by the paper sensor 28 (step S37: YES), in step S38 of Fig. 8, the control unit 11 changes the judgment threshold Ht of the paper sensor 28 that erroneously detected the paper P. Specifically, the control unit 11 sets the judgment value H of the paper sensor 28 to the new judgment threshold Ht. After this, the control unit 11 proceeds to step S31 of Fig. 7.

[0140] Here, if the determination in step S21 of FIG. 6 is "NO" and the determination in step S37 of FIG. 8 is "YES," the determination value H of the paper sensor 28 that erroneously detected the paper P remains the determination value H at the start of the most recent paper transport operation. Therefore, the erroneous detection of the paper P occurred before the determination value H of the paper sensor 28 exceeded the determination threshold Ht. Through the process of step S38 described above, the control unit 11 sets the determination value H at the time when the erroneous detection of the paper sensor 28 that erroneously detected the paper P occurred before the determination value H exceeded the determination threshold Ht as the new determination threshold Ht of the paper sensor 28.

[0141] If it is determined in step S37 that the jam is not due to erroneous detection of paper P by the paper sensor 28 (step S37: NO), then in step S39, the control unit 11 determines whether there is a paper sensor 28 in which the number of sheets of paper N has exceeded the paper number threshold value Nt.

[0142] When it is determined that there is a paper sensor 28 in which the number of passed sheets N has exceeded the number of passed sheets threshold Nt (step S39: YES), the control unit 11 proceeds to step S31 in FIG.

[0143] If it is determined that there is no paper sensor 28 in which the number of sheets N passed exceeds the number of sheets Nt passed threshold (step S39: NO), in step S40, the control unit 11 instructs the user to clear the jam (remove the paper P remaining in the printing device 1). Specifically, the control unit 11 causes the display unit 71 to display a message instructing the user to clear the jam, as well as the position of the paper P remaining in the printing device 1, etc.

[0144] Next, in step S41, the control unit 11 determines whether or not jam removal is complete. Here, the control unit 11 determines that jam removal is complete when a user operation is performed on the input unit 72 to notify the printing device 1 that jam removal is complete. If the control unit 11 determines that jam removal is not complete (step S41: NO), it repeats step S41. If the control unit 11 determines that jam removal is complete (step S41: YES), it proceeds to step S35 in FIG. 7.

[0145] In step S23, when it is determined that the jam is not due to erroneous detection of paper P by paper sensor 28 (step S23: NO), control unit 11 proceeds to step S42 in Fig. 9. The processes of steps S42 to S47 are similar to the processes of steps S9 to S13 and S17 described above.

[0146] In step S45, if it is determined that there is no paper sensor 28 in which the number of sheets N passed exceeds the number of sheets Nt (step S45: NO), the control unit 11 proceeds to step S31 in Fig. 7. Also, after step S46, the control unit 11 proceeds to step S31 in Fig. 7.

[0147] In step S47, if it is determined that there is a paper sensor 28 whose number of sheets passed N exceeds the number of sheets passed threshold Nt (step S47: YES), the control unit 11 proceeds to step S31 in Fig. 7. If it is determined that there is no paper sensor 28 whose number of sheets passed N exceeds the number of sheets passed threshold Nt (step S47: NO), the control unit 11 proceeds to step S40 in Fig. 8.

[0148] By processing the flowcharts of Figures 4 to 9 as described above, when the amount of light received by the light receiving portion 28b of the paper sensor 28C is attenuated due to the paper transport operation, as described above, a judgment addition value C is calculated for each paper sensor 28 through which paper passed during the paper transport operation, and a judgment value H is calculated by accumulating the judgment addition values ​​C.

[0149] An example of the transition of the determination value H of the paper sensor 28 calculated in this manner is shown in Fig. 10. In Fig. 10, a positive value of the attenuation amount D indicates that the amount of light received by the light-receiving portion 28b has attenuated, and a negative value of the attenuation amount D indicates that the amount of light received by the light-receiving portion 28b has increased.

[0150] One paper transport operation is made up of a continuous series of paper transport operations. For example, if the paper transport operations for the number of sheets printed in a print job are performed without stopping midway, the series of paper transport operations is considered to be one paper transport operation. Also, for example, if the paper transport operation stops once midway during a print job due to detection of a jam, the series of paper transport operations up to the stop is considered to be one paper transport operation, and the series of print transport operations from restart to end is also considered to be one paper transport operation. The same applies if the paper transport operation stops multiple times midway.

[0151] In the example of FIG. 10, the determination value H exceeds the determination threshold value Ht at the end of the 28th paper transport operation, so it is determined at this point that cleaning of the paper sensor 28 in the example of FIG. 10 is necessary.

[0152] Here, due to the influence of the transport air current generated by the paper transport, the amount of paper dust accumulated on the paper sensor 28C may decrease, and the amount of light received by the light receiving section 28b may increase before and after the paper transport operation. That is, as described above, the attenuation amount D may become a negative value. However, even if the amount of paper dust accumulated on the paper sensor 28C has decreased, it does not necessarily mean that the amount of paper dust has also decreased in the other paper sensors 28. For this reason, the printing device 1 calculates the judgment addition value C of each paper sensor 28 through which paper has passed only when the amount of light received by the light receiving section 28b has decreased, and calculates the judgment value H by accumulating the judgment addition values ​​C. The judgment value H of the paper sensor 28C is calculated in the same manner. This makes it possible to prevent a delay in the time when it is determined that the paper sensor 28 needs to be cleaned.

[0153] Next, an example of the calculation results of the determination value H of each paper sensor 28 through which a paper sheet has passed during a certain paper transport operation will be described.

[0154] The paper transport operation in this example is a paper transport operation in a printing operation in which, in single-sided printing, the paper source is the external paper feed tray 21 and paper P is discharged by the second paper discharge section 7. In this case, as described above, paper passes through paper sensors 28A, 28C, 28D, 28F to 28I, and 28K, but no paper passes through the other paper sensors 28.

[0155] Moreover, the number of printed sheets in this example is 10. The determination value H of each paper sensor 28 at the start of the paper transport operation in this example is assumed to be that shown in Fig. 3. The amount of attenuation due to this paper transport operation is assumed to be D=15.

[0156] In this example, the judgment addition value C of paper sensor 28A is calculated as C=3.75 using the above-mentioned formula (1). Then, by adding the judgment addition value C=3.75 to the judgment value H=5 of paper sensor 28A in FIG. 3, the judgment value H=8.75 of paper sensor 28A is calculated as shown in FIG.

[0157] Similarly, for the paper sensors 28C, 28D, 28F to 28I, and 28K, the respective judgment values ​​H are calculated as shown in Fig. 11. Also, "10" is added to the number of sheets of paper N of the paper sensors 28A, 28C, 28D, 28F to 28I, and 28K in Fig. 3, respectively, to obtain the value of the number of sheets of paper N shown in Fig. 11.

[0158] Next, an example of the sensor table 81 when the determination value H of the paper sensor 28 exceeds the determination threshold value Ht for the first time is shown in FIG.

[0159] In this example, at the end of a certain paper transport operation, the judgment value H of each of the paper sensors 28G-28I exceeds the judgment threshold Ht for the first time after the paper sensors 28G-28I start to be used. As a result, it is determined that the paper sensors 28G-28I require cleaning. Also, for each of the paper sensors 28G-28I, the number of sheets of paper passed at the end of this paper transport operation is N=10,000.

[0160] In this example, after the paper transport operation is completed, the determination values ​​H and the number of passed sheets N of the paper sensors 28G-28I in the sensor table 81 are reset (H=0, N=0) as shown in Fig. 12. In addition, the number of passed sheets threshold values ​​Nt of the paper sensors 28G-28I are set to 10,000.

[0161] In this example, in the paper sensors 28 other than the paper sensors 28G to 28I, the determination value H has never exceeded the determination threshold value Ht since the start of use, and the passed paper count threshold value Nt has not been set, as shown in FIG.

[0162] As described above, in the printing device 1, when the amount of light received by the light receiving section 28b of the paper sensor 28C is attenuated by the paper transport operation, the control unit 11 calculates the judgment addition value C for each paper sensor 28 through which paper has passed, based on the attenuation amount D during the paper transport operation and the orientation of the paper sensor 28 through which paper has passed, and calculates the judgment value H by accumulating the judgment addition values ​​C. Then, the control unit 11 determines that the paper sensor 28 whose judgment value H exceeds the judgment threshold value Ht needs to be cleaned. This makes it possible to determine the timing when cleaning is required for each of the multiple paper sensors 28, with only one analog sensor for measuring the degree of accumulation of paper dust, the paper sensor 28C. Therefore, it is possible to reduce unnecessary cleaning of the paper sensor 28 while suppressing the increase in size of the device and the complication of the circuit design. In addition, since unnecessary cleaning of the paper sensor 28 can be reduced, maintenance time can be shortened.

[0163] In addition, in the printing device 1, the orientation of the paper sensor 28 is used as an installation condition of the paper sensor 28 for calculating the judgment value H, so that in a printing device 1 equipped with multiple paper sensors 28 installed in various orientations, the timing when each paper sensor 28 needs to be cleaned can be determined.

[0164] Furthermore, in the printing device 1, the control unit 11 sets the number of passed sheets N when the judgment value H first exceeds the judgment threshold Ht as the passed sheet number threshold Nt for each paper sensor 28. After setting the passed sheet number threshold Nt, the control unit 11 determines that cleaning is required for a paper sensor 28 whose number of passed sheets N exceeds the passed sheet number threshold Nt even if the judgment value H does not exceed the judgment threshold Ht. In this way, by also using the passed sheet number threshold Nt to determine whether cleaning of the paper sensor 28 is required, the timing when cleaning of each paper sensor 28 is required can be determined with higher accuracy.

[0165] Furthermore, in the printing device 1, after setting the sheet-passing-number threshold Nt in each paper sensor 28, if the number of sheets N passed when the judgment value H exceeds the judgment threshold Ht differs from the sheet-passing-number threshold Nt, the control unit 11 sets the number of sheets N passed as a new sheet-passing-number threshold Nt. By updating the sheet-passing-number threshold Nt in this manner, it is possible to further increase the accuracy of determining when each paper sensor 28 needs to be cleaned.

[0166] Furthermore, in the printing device 1, when a paper sensor 28 erroneously detects paper P before the determination value H reaches the determination threshold Ht, the control unit 11 sets the determination value H of the paper sensor 28 at the time the erroneous detection of paper P occurred as the new determination threshold Ht for the paper sensor 28. By updating the determination threshold Ht in this way, it is possible to further increase the accuracy of determining when each paper sensor 28 needs to be cleaned.

[0167] Furthermore, in the printing device 1, the paper sensor 28C, which functions as a sensor for measuring the degree of accumulation of paper dust, also serves as a sensor for detecting the paper P. This allows the number of paper sensors 28 to be reduced, thereby preventing the device configuration from becoming complicated.

[0168] The paper sensor 28C may be a dedicated sensor for measuring the degree of accumulation of paper dust.

[0169] A condition other than the orientation of the paper sensor 28 may be used as the installation condition of the paper sensor 28 for calculating the judgment value H. For example, if the degree of generation of the transport airflow differs depending on the position of the paper sensor 28 on the transport path and the ease of accumulation of paper dust differs depending on the position of the paper sensor 28 on the transport path, the position of the paper sensor 28 on the transport path may be used as the installation condition of the paper sensor 28 for calculating the judgment value H. The orientation of the paper sensor 28 may be combined with other conditions as the installation condition of the paper sensor 28 for calculating the judgment value H.

[0170] The present invention is not limited to the above-described embodiment, and the components can be modified and embodied in the implementation stage without departing from the gist of the invention. In addition, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiment. For example, some components may be deleted from all the components shown in the embodiment.

[0171] [Note] This application discloses the following inventions.

[0172] (Appendix 1) a dust detection unit having a light emitting unit disposed along a transport path along which a medium is transported and a light receiving unit that receives light emitted by the light emitting unit; a plurality of medium detection units arranged along the transport path and configured to detect the medium; a determination unit that, when the amount of light received by the light receiving unit is attenuated by a medium transport operation, calculates a determination sum value for each medium detection unit through which the medium has passed based on the amount of attenuation of the amount of light received by the light receiving unit during the medium transport operation and an installation condition of the medium detection unit through which the medium has passed, and determines that cleaning is required for the medium detection unit when a determination value obtained by accumulating the determination sum values ​​exceeds a predetermined determination threshold; A conveying device comprising:

[0173] (Appendix 2) 2. The conveying device according to claim 1, wherein the installation conditions include an orientation of the medium detection unit.

[0174] (Appendix 3) The conveying device described in Appendix 1 or 2, characterized in that the judgment unit resets the judgment value and the number of media that have passed in the media detection unit that has been cleaned, and in each of the media detection units, the number of passed sheets when the judgment value first exceeds the judgment threshold is set as the passing sheet threshold, and after the passing sheet threshold is set, if the passing sheet number exceeds the passing sheet threshold even if the judgment value does not exceed the judgment threshold, it is determined that cleaning of the media detection unit is necessary.

[0175] (Appendix 4) The conveying device described in Appendix 3, characterized in that in each of the media detection units, after setting the passing number threshold, if the number of passing sheets when the judgment value exceeds the judgment threshold is different from the passing number threshold, the judgment unit sets the passing number to a new passing number threshold.

[0176] (Appendix 5) The conveying device described in any of Appendices 1 to 4, characterized in that the judgment unit resets the judgment value in the media detection unit after cleaning, and if a false detection of a medium occurs in the media detection unit before the judgment value reaches the judgment threshold, the judgment value in the media detection unit at the time the false detection of the medium occurred is set as a new judgment threshold for the media detection unit.

[0177] (Appendix 6) 6. The conveying device according to claim 1, wherein the dust detection unit also serves as one of the plurality of medium detection units. [Explanation of symbols]

[0178] 1 Printing device 2 Paper feed section 3 Printing transport section 4 Printing Department 5 First paper exit section 6 Upper conveyor section 7 Second paper ejection section 8 Reversal section 9 Operation Panel 10 Storage section 11 Control section 28A~28L Paper sensor 28a Light emitting part 28b Light receiving section 81 Sensor Table P paper RC Normal Route RD1,RD2 paper ejection path RR Reverse Route RS Paper Path

Claims

1. a dust detection unit having a light emitting unit disposed along a transport path along which a medium is transported and a light receiving unit that receives light emitted by the light emitting unit; a plurality of medium detection units arranged along the transport path and configured to detect a medium; a determination unit that, when the amount of light received by the light receiving unit is attenuated by a medium transport operation, calculates a determination sum value for each medium detection unit through which the medium has passed based on the amount of attenuation of the amount of light received by the light receiving unit during the medium transport operation and an installation condition of the medium detection unit through which the medium has passed, and determines that cleaning is required for the medium detection unit when a determination value obtained by accumulating the determination sum values ​​exceeds a predetermined determination threshold; A conveying device comprising:

2. The transport device according to claim 1 , wherein the installation conditions include an orientation of the medium detection unit.

3. The conveying device described in claim 1 or 2, characterized in that the judgment unit resets the judgment value and the number of media sheets passing through the media detection unit after cleaning, and in each media detection unit, the number of sheets passing when the judgment value first exceeds the judgment threshold is set as the passing number threshold, and after the passing number threshold is set, if the passing number exceeds the passing number threshold even if the judgment value does not exceed the judgment threshold, it judges that cleaning of the media detection unit is necessary.

4. The conveying device described in claim 3, characterized in that in each of the media detection units, after setting the passing number threshold, if the number of passing sheets when the judgment value exceeds the judgment threshold is different from the passing number threshold, the judgment unit sets the passing number to a new passing number threshold.

5. A conveying device as described in any one of claims 1 to 4, characterized in that the judgment unit resets the judgment value in the media detection unit after cleaning, and if a false detection of a medium occurs in the media detection unit before the judgment value reaches the judgment threshold, the judgment value in the media detection unit at the time the false detection of the medium occurred is set as a new judgment threshold for the media detection unit.

6. 6. The transport device according to claim 1, wherein the dust detection unit also serves as one of the plurality of medium detection units.

Images