Conveyor

Abstract

To accurately perform error determination based on the amount of light received by a light reception unit of a medium detection sensor during conveyance.SOLUTION: A printer 1 (example of conveyance device) comprises a sheet detection sensor S (example of medium detection sensor) and a control unit 81. The sheet detection sensor S has a light projection unit Sa that projects light to a sheet P (example of medium) and a light reception unit Sb that receives the light projected from the light projection unit Sa, and detects the sheet P. The control unit 81 compares the detected transmission amount (example of detected amount of received light) of the light projected to the sheet P and received by the light reception unit Sb with a reference transmission amount (example of reference received light amount) corresponding to the type of the sheet P detected by the sheet detection sensor S, and determines a deposition error indicating deposition of paper powder (example of dust) in the sheet detection sensor S on the basis of continuous dropping of the detected transmission amount below the reference transmission amount from the first sheet P of a plurality of continuously conveyed sheets P (step S15).SELECTED DRAWING: Figure 5A

Description

[Technical Field]

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

[0002] 2. Description of the Related Art In a printing device that prints on paper, a plurality of sensors that detect paper are arranged along a paper transport path to detect paper jams and the like.

[0003] In such printing devices, paper dust generated during paper transport can adhere to and accumulate on the sensor, causing the sensor to remain in an on state or causing sensor chattering, which can lead to false paper detection.

[0004] As a printer that detects the accumulation of paper dust on a sensor, a printer has been proposed that displays a cleaning message when the sensor level falls below a threshold value stored for each type of paper, in order to display a warning message urging the user to clean the sensor before a sensor error occurs even if dust or paper dust has adhered to the sensor (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-107281 Summary of the Invention [Problem to be solved by the invention]

[0006] In a conveying device (e.g., a printing device) that conveys media such as paper, a media detection sensor that detects the media has a light-emitting unit that emits light onto the media and a light-receiving unit that receives the light emitted by the light-emitting unit. This media detection sensor is, for example, a transmission sensor or a reflection sensor.

[0007] In such media detection sensors, the amount of light received by the light receiving unit decreases when dust such as paper powder accumulates. However, this is not limited to when dust accumulates, and the amount of light received by the light receiving unit of the media detection sensor also decreases when, for example, multiple media are fed or a different type of media than expected is being transported.

[0008] Therefore, if a cleaning message is displayed when the sensor level falls below a threshold, as in the printer described above, the user will be presented with incorrect information if the sensor level has fallen due to a different factor, such as a double feed or the wrong type of media.

[0009] The present invention provides a transport device that can accurately perform error determination based on the amount of light received by the light receiving portion of a medium detection sensor. [Means for solving the problem]

[0010] In one aspect, the conveying device has a light-emitting unit that emits light onto a medium and a light-receiving unit that receives the light emitted by the light-emitting unit, and is equipped with a medium detection sensor that detects the medium, and a control unit that compares a reference amount of received light corresponding to the type of medium detected by the medium detection sensor with the detected amount of received light of light emitted onto the medium and received by the light-receiving unit, and determines that an accumulation error has occurred, that is, dust has accumulated on the medium detection sensor, based on the fact that the detected amount of received light has fallen below the reference amount of received light by a specified amount for multiple media that are transported consecutively, starting with the first media transported. [Effects of the Invention]

[0011] According to this aspect, an error determination can be accurately performed based on the amount of light received by the light receiving portion of the medium detection sensor. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an internal structure of a printing device according to an embodiment. [Figure 2]FIG. 2 illustrates a control configuration of a printing apparatus according to an embodiment. [Figure 3] 10A and 10B are explanatory diagrams for explaining a reference transmission amount acquisition process according to an embodiment. [Figure 4] 10A and 10B are explanatory diagrams for explaining a process of comparing a detected transmittance with a reference transmittance in an embodiment. [Figure 5A] 10 is a flowchart (part 1) for explaining a paper dust accumulation determination process according to an embodiment. [Figure 5B] 10 is a flowchart (part 2) illustrating the paper dust accumulation determination process according to an embodiment. [Figure 6] 10 is a flowchart illustrating another factor determination process according to an embodiment. [Figure 7] FIG. 10 is an explanatory diagram for explaining each error in one embodiment. [Figure 8A] 1 is a flowchart (part 1) for explaining automatic light amount adjustment processing according to an embodiment. [Figure 8B] 10 is a flowchart (part 2) for explaining the automatic light amount adjustment process according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A conveying device according to an embodiment of the present invention will be described below with reference to the drawings, taking a printing device as an example.

[0014] FIG. 1 is a diagram showing the internal structure of a printing device 1 according to an embodiment.

[0015] FIG. 2 is a diagram showing the control configuration of the printing device 1.

[0016] As shown in FIGS. 1 and 2, the printing device 1 includes an external paper feed unit 10, an internal paper feed unit 20, a printing unit 40, a print transport unit 50, a paper discharge unit 60, and a paper detection sensor S. Also, as shown in FIG. 1, the printing device 1 includes transport members (a pair of registration rollers 31, an accelerated transport unit 32, a constant-speed transport unit 33, a reverse transport unit 34, a paper re-feed unit 35, a paper discharge transport unit 36, a straight transport unit 37, and path switching units 38 and 39). Also, as shown in FIG. 2, the printing device 1 includes a transport drive unit 70, a control unit 81, a memory unit 82, and an interface unit 83. The print transport unit 50 and transport members such as the pair of registration rollers 31 function as an example of a transport unit that transports paper P. Paper P is an example of a medium, and the medium may be a sheet-like medium made of a material other than paper, or a medium with a folded portion such as an envelope.

[0017] 1, a solid line indicates a straight path R1 of paper P continuing from the external paper feed unit 10 or the internal paper feed unit 20, a two-dot chain line indicates a path continuing from a circulation path R2 for double-sided printing located above the printing unit 40 to a paper discharge path R3, and a dashed line indicates a reversal path R2a of the circulation path R2. In this specification, paper feed is an example of supply, and paper discharge is an example of discharge. Therefore, paper feed can be substituted with supply, paper discharge with discharge, and paper with medium (for example, paper detection sensor S can be substituted with medium detection sensor).

[0018] 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, and a paper feed roller 12 that feeds and conveys the uppermost paper sheet P among the multiple sheets of paper sheets P stacked on the paper feed tray 11. Although not shown, the external paper feed unit 10 also has actuators such as motors that drive the paper feed tray 11 and paper feed roller 12.

[0019] 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 .

[0020] The first paper feed unit 21, the second paper feed unit 22, and the third paper feed unit 23 are arranged inside the printing device 1, lined up in this order from top to bottom. 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, and paper feed rollers 21b, 22b, 23b that feed and transport the uppermost paper P among the multiple sheets of paper P stacked in the paper feed trays 21a, 22a, 23a. Although not shown, the internal paper feed unit 20 also includes actuators such as motors that drive the paper feed rollers 21b, 22b, 23b.

[0021] The registration roller pair 31 is disposed on the upstream side of the printing unit 40 and the print transport unit 50 in the transport direction on the straight path R1 continuing from the external paper feed unit 10 or the internal paper feed unit 20. The registration roller pair 31 is abutted against the paper P being transported toward the printing unit 40. In this way, the registration roller pair 31 corrects skew of the paper P and transports the paper P while nipping it.

[0022] The acceleration conveyance section 32 is capable of accelerating and conveying the paper sheet P on the circulation path R2. The acceleration conveyance section 32 has acceleration roller pairs 32a, 32b, and 32c that nip and convey the paper sheet P.

[0023] The constant speed conveying section 33 conveys the paper P at a constant speed at a variable conveying speed on the downstream side of the accelerating conveying section 32 in the conveying direction of the circulation path R2. The constant speed conveying section 33 has constant speed roller pairs 33a, 33b, and 33c that nip and convey the paper P.

[0024] The reverse conveying section 34 is a pair of switchback rollers that nip and switchback convey the paper P on a reverse path R2a located downstream in the conveying direction from the constant speed conveying section 33 of the circulation path R2, thereby reversing the front and back of the paper P.

[0025] The paper re-feeding unit 35 re-feeds the paper P toward the printing unit 40 on the downstream side of the constant speed transport unit 33 in the transport direction of the circulation path R2. The paper re-feeding unit 35 decelerates and transports the paper P when the paper P abuts against the pair of registration rollers 31.

[0026] 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.

[0027] 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 a paper discharge section, conveying section, post-processing device, etc. (not shown) that are connected to the printing device 1.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] The print transport unit 50 is disposed opposite the print unit 40 and transports the paper P in the print unit 40. The print transport unit 50 has a plurality of pulleys 51, a belt 52 stretched across these pulleys 51, a suction fan 53 that sucks air through a plurality of holes provided in the belt 52 to cause the paper P to adhere to the belt 52, a guide roller 54 disposed opposite the pulley 51 at the upstream end of the print transport unit 50 in the transport direction, and a guide roller 55 disposed opposite the pulley 51 at the downstream end of the print transport unit 50 in the transport direction. Note that the print transport unit 50 is not limited to one that transports the paper P while adsorbing it.

[0032] 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.

[0033] The paper detection sensor S is disposed on the straight path R1 downstream of the pair of registration rollers 31 in the transport direction and upstream of the printing unit 40 and print transport unit 50 in the transport direction. The paper detection sensor S has a light-projecting unit Sa located, for example, above the straight path R1 and a light-receiving unit Sb located, for example, below the straight path R1, and detects the paper P. The light-projecting unit Sa projects light onto the paper P. The light-receiving unit Sb receives the light projected by the light-projecting unit Sa.

[0034] The paper detection sensor S is, for example, a transmission sensor. Therefore, the light receiving unit Sb receives the transmitted light that is emitted by the light emitting unit Sa and transmitted through the paper P. However, the paper detection sensor S is not limited to a transmission sensor, and may be another sensor such as a reflection sensor. If the paper detection sensor S is a reflection sensor, the light receiving unit Sb receives the reflected light that is reflected by the paper P. Therefore, the transmitted amount of light received by the light receiving unit Sb, which will be described later, is merely one example of the amount of received light, and if the paper detection sensor S is a reflection sensor, the amount of reflected light is one example of the amount of received light.

[0035] In the present embodiment, an example will be described in which the paper detection sensor S is disposed downstream in the transport direction of the registration roller pair 31 and upstream in the transport direction of the printing unit 40 and the print transport unit 50, but the paper detection sensor S can be disposed at any position in the printing device 1. Furthermore, the medium detection sensor, of which the paper detection sensor S is an example, is not limited to being disposed in the printing device 1, but may also be disposed in other transport devices that transport media, such as a post-processing device that performs post-processing on the medium after printing.

[0036] 2 includes a registration drive unit 71 that drives the registration roller pair 31, an acceleration drive unit 72 that drives the acceleration conveyance unit 32, a constant speed drive unit 73 that drives the constant speed conveyance unit 33, a reversal drive unit 74 that drives the reversal conveyance unit 34, a re-feed drive unit 75 that drives the re-feed 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. Note that a single actuator may serve as multiple drive units.

[0037] The control unit 81 has a processor (for example, a CPU (Central Processing Unit)) that functions as an arithmetic processing device that controls the overall operation of the printing device 1. As will be described in detail later, the control unit 81 determines errors such as accumulation errors caused by dust accumulation on the paper detection sensor S.

[0038] The storage unit 82 includes, for example, a memory such as a ROM (Read Only Memory), which is a read-only semiconductor memory in which a predetermined control program is pre-recorded, a RAM (Random Access Memory), which is a semiconductor memory that can be written and read at any time and is used as a working memory area as needed when the processor executes various control programs, a hard disk drive, etc.

[0039] The interface unit 83 exchanges various information with external devices. For example, the interface unit 83 receives a print job including print data from a user terminal.

[0040] Here, the process of acquiring a reference transmission amount (an example of a reference received light amount) to be compared with the detected transmission amount (an example of a detected received light amount) of the light receiving section Sb of the sheet detection sensor S will be described with reference to FIG.

[0041] As a premise, the light receiving section Sb of the paper detection sensor S receives a reduced amount of transmitted light (amount of received light) due to, for example, the accumulation of paper powder (an example of dust), the occurrence of double feeding of paper P, or the conveyance of a different type of paper P than the expected type. Therefore, based on the detected transmittance (AD value) of the light receiving section Sb, it is possible to determine errors such as paper powder accumulation errors, double feeding errors, and paper (medium) wrong type errors.

[0042] First, the control unit 81 acquires a reference transmittance to be used for comparison. For example, the paper detection sensor S detects, for example, five sheets of paper P that are printed in a test mode, separate from normal printing based on a print job or the like. The control unit 81 calculates the average transmittance received by the light receiving unit Sb in each of blocks 1 to N, which are divided into blocks each including, for example, eight detection locations, excluding the leading edge to prevent erroneous detection, for each of the five sheets of paper P. The control unit 81 also calculates the average transmittance for all N blocks (5 × N) of the five sheets of paper P. The control unit 81 stores this average in the storage unit 82 as the reference transmittance corresponding to the type of paper P. For example, when printing is performed on multiple types of paper P, printing may be performed in test mode for each paper type, and the control unit 81 may calculate the reference transmittance for each paper type (for example, plain paper X1, inkjet (inkjet) paper X2, matte inkjet paper X3, inkjet postcard X4, high-quality paper X5, lightweight paper X6, and recycled paper X7).

[0043] The reference transmission amount does not have to be calculated after actually transporting the paper P in a test mode or the like, but may be stored in the storage unit 82 as a predetermined numerical value, such as a numerical value obtained from another device via the interface unit 83. Furthermore, if the average value for each block is not used in the comparison process described below, the control unit 81 does not calculate the average value for each block, but may instead calculate the average value of all detection locations for all (e.g., five) sheets of paper P printed in the test mode as the reference transmission amount. Furthermore, if the number of detection locations in the above-mentioned Nth block is less than the specified number (e.g., eight locations), the numerical value for the Nth block is not used.

[0044] 5A and 5B are flowcharts for explaining the paper dust accumulation determination process.

[0045] The processing of the flowcharts shown in FIGS. 5A and 5B is performed by the control unit 81 when printing (transportation) is started.

[0046] First, the control unit 81 repeatedly determines whether the sheet detection sensor S is ON until the sheet detection sensor S is ON, that is, until the sheet P is detected (step S1).

[0047] When the paper detection sensor S is turned ON (step S1: YES), the control unit 81 performs a detected transmittance sampling process in units of blocks (step S2). This detected transmittance sampling process is the same as that shown in Fig. 3, and calculates the average value of the detected transmittance for each block of paper P (e.g., eight detection locations) on which normal printing is performed, as shown in Fig. 4.

[0048] 4, the control unit 81 compares the calculated detected transmittance (average value) for each block with the above-mentioned reference transmittance (X1 to X7) (step S3). The reference transmittance to be compared is a single value that is the average value for all blocks of all sheets printed in the above-mentioned test mode, but it may also be, for example, the average value for all sheets in the test mode that include only the block corresponding to the detected transmittance. Furthermore, the control unit 81 may calculate the detected transmittance of the sheet P from the average of detection locations on any part or all of the sheet P, rather than using a method of calculating the average value for each block, and compare the detected transmittance thus obtained with the reference transmittance.

[0049] Next, the control unit 81 determines whether the paper sheet P detected by the paper sheet detection sensor S is the first paper sheet P to be transported (step S4). Note that the first paper sheet P refers to the first paper sheet P when printing based on a print job starts after a predetermined time interval, and does not refer to the second or subsequent paper sheets P to be transported consecutively.

[0050] When the control unit 81 determines that the paper P detected by the paper detection sensor S is the first paper P to be conveyed (step S4: YES), it determines whether the detected transmittance is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S5). Note that the control unit 81 may omit the criterion of whether the detected transmittance is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks, and instead perform processing to determine whether the average value of the detected transmittance for the entire detected paper P is lower than the reference transmittance by a specified amount. The fact that the criterion of a certain number of consecutive blocks can be omitted also applies to the following explanation.

[0051] If the detected transmittance is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S5: YES), the control unit 81 turns on the "possibility of paper dust accumulation" flag (step S6). On the other hand, if the detected transmittance is not lower than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S5: NO), the control unit 81 turns off the "possibility of paper dust accumulation" flag (step S7).

[0052] Next, the control unit 81 determines whether the paper detection sensor S has turned OFF, i.e., whether the paper P is no longer being detected (step S8). If the paper detection sensor S has not turned OFF (step S8: NO), the paper detection sensor S is still detecting the paper P, and the control unit 81 repeats the process from step S2 described above. Note that in this case, when the "possibility of paper dust accumulation" flag was OFF (step S7), if the number of consecutive blocks in which the detected transmittance is lower than the reference transmittance by a specified amount (step S5) reaches a certain number of blocks in the subsequent sampling process (step S2), the control unit 81 may change the "possibility of paper dust accumulation" flag from OFF (step S7) to ON (step S6), but not the other way around.

[0053] If the paper detection sensor S turns OFF (step S8: YES), the control unit 81 determines whether printing has finished (step S9), for example, based on the detection results of a sensor (not shown) upstream of the paper detection sensor S or the print job, and if printing has not finished (step S9: NO), it performs processing on the next paper P to be transported, starting from the processing in step S1 described above.

[0054] When printing is completed (step S9: YES), the control unit 81 determines whether a "paper dust accumulation error" (step S15) described below has occurred (step S10), and if a "paper dust accumulation error" has occurred (step S10: YES), it causes a notification unit such as a display unit or audio output unit (not shown) to notify the user that "cleaning is required" (step S11). Note that instead of "cleaning is required," the notification content may be other content such as "paper dust has accumulated," or "paper dust accumulation may have occurred."

[0055] If there is no "paper dust accumulation error" (step S10: NO) and if the control unit 81 has notified the user (step S11), the control unit 81 ends the processing shown in FIGS. 5A and 5B.

[0056] Returning to the process of determining whether the paper P detected by the paper detection sensor S is the first paper P to be transported (step S4), even if it is determined that it is not the first paper P (step S4: NO), the control unit 81 determines whether the detected transmittance for that paper P is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks, as shown in Figure 5B (step S12).

[0057] If the detected transmittance is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S12: YES), the control unit 81 determines whether the "possible paper dust accumulation" flag (step S6) is ON, i.e., whether the detected transmittance of the first sheet of paper P is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S13).

[0058] If the "Possible Paper Dust Accumulation" flag is ON (Step S13: YES), it is determined whether the detected transmittance amount was lower than the reference transmittance amount by a specified amount for a certain number of consecutive blocks (Steps S5, S12: YES) for a specified number of consecutive sheets of paper P (Step S14). This specified number can be any number equal to or greater than two. If the "Possible Paper Dust Accumulation" flag is not ON (Step S13: NO), another factor determination process (Step S18), which will be described later, is performed.

[0059] If the detected transmittance is detected to be lower than the reference transmittance by a specified amount for a certain number of consecutive blocks for a specified number of consecutive sheets of paper P (step S14: YES), it can be said that the detected transmittance has been lower than the reference transmittance by a specified amount for consecutive sheets of paper P, starting from the first sheet of paper P (for example, consecutively for the first through third sheets of paper P, whose detected transmittances are indicated by thick lines in FIG. 7), and the control unit 81 determines that dust has accumulated on the paper detection sensor S, resulting in a "paper dust accumulation error," and stores this determination in the memory unit 82 (step S15). The control unit 81 then turns OFF the "possible paper dust accumulation" flag (step S16) and repeats the process from step S8 described above. Furthermore, if the detected transmittance is not lower than the reference transmittance by a specified amount for a certain number of consecutive blocks for a specified number of consecutive sheets of paper P (step S14: NO), the process also repeats the process from step S8 described above. The paper dust determination threshold shown in FIG. 7 is a value that is below the reference transmittance by a specified amount and is indicated by a dotted line.

[0060] The process returns to the process of determining whether the detected transmission amount is lower than the reference transmission amount by a specified amount for a certain number of consecutive blocks (step S12), and if the case where the detected transmission amount is lower than the reference transmission amount by a specified amount for a certain number of consecutive blocks does not apply (step S12: NO), it is determined whether the detected transmission amount is higher than the reference transmission amount by a specified amount for a certain number of consecutive blocks (step S17). Note that the specified amount in the process of determining whether the detected transmission amount is higher than the reference transmission amount by a specified amount (steps S5, S12) may be the same value as or different from the specified amount in the process of determining whether the detected transmission amount is lower than the reference transmission amount by a specified amount.

[0061] If the detected transmittance exceeds the reference transmittance by a specified amount for a certain number of consecutive blocks (step S17: YES), the control unit 81 determines that the error is due to a cause other than the paper dust accumulation error (step S18), and performs the other cause determination process shown in Fig. 6, which will be described later. On the other hand, if the detected transmittance does not exceed the reference transmittance by a specified amount for a certain number of consecutive blocks (step S17: NO), the process is repeated from step S8 described above.

[0062] After performing the other-cause determination process, the control unit 81 clears the "paper dust accumulation error" (step S15) (step S19). Then, since an error caused by a cause other than the paper dust accumulation error is of high urgency, the control unit 81 stops printing (step S20), unlike when the control unit 81 notifies the user that "cleaning is required" based on the paper dust accumulation error (step S11) as described above, and causes a notifying unit such as a display unit or audio output unit (not shown) to notify the user of the error caused by a cause other than the paper dust accumulation error (step S21). Thereafter, the control unit 81 repeats the process from step S9 described above. Note that the content of the notification for an error caused by a cause other than the paper dust accumulation error may be determined appropriately depending on the content of the error.

[0063] FIG. 6 is a flowchart for explaining the other cause determination process corresponding to the other cause error determination (step S18) in FIG. 5B.

[0064] First, the control unit 81 determines whether the detected transmittance exceeds the reference transmittance by a specified amount for a certain number of consecutive blocks (step S31). If the detected transmittance exceeds the reference transmittance by a specified amount for a certain number of consecutive blocks (step S31: YES), it can be said that the detected transmittance exceeds the reference transmittance by a specified amount from the second sheet of paper P onwards (for example, the Nth sheet whose detected transmittance is indicated by a thick line in FIG. 7), and the control unit 81 determines that a "wrong paper type" error has occurred, meaning that a different type of paper P has been conveyed (step S32).

[0065] If the detected transmittance is higher than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S31: NO) and if a "wrong paper type" error is determined (step S12), the control unit 81 determines whether the detected transmittance is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S33).

[0066] If the detected transmittance amount is not less than the reference transmittance amount by a specified amount for a certain number of consecutive blocks (step S33: YES), the control unit 81 determines whether the detected transmittance amount is less than the detected transmittance amount of the previously transported paper P by a specified amount for a certain number of consecutive blocks (step S34). This "specified amount" may be the same as or different from the "specified amount" in the process of determining whether the detected transmittance amount is less than or greater than the reference transmittance amount by a specified amount (steps S5, S12, S17, S31, S33).

[0067] If the detected transmittance is not less than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S33: NO), or if the detected transmittance is less than the detected transmittance of the previously transported paper P by a specified amount for a certain number of consecutive blocks (step S34: YES), it is determined that the detected transmittance of the second or subsequent paper P (for example, the Pth paper, whose detected transmittance is indicated by a thick line in FIG. 7) is less than the reference transmittance by a specified amount, or that the detected transmittance of the second or subsequent paper P (for example, the Xth paper, whose detected transmittance is indicated by a thick line in FIG. 7) is less than the detected transmittance of the previously transported paper P (for example, the X-1th paper, whose detected transmittance is indicated by a thick line in FIG. 7), and a "double feed" error in which the papers P are overlapping has occurred (step S35), and the processing shown in FIG. 6 is terminated. In addition, even if the detected transmittance amount is not lower than the specified amount for a certain number of consecutive blocks than the detected transmittance amount of the paper P transported immediately before (step S34: NO), the control unit 81 also terminates the processing shown in Figure 6.

[0068] Next, the automatic light amount adjustment process will be described with reference to Figures 8A and 8B. Note that the process of the flowcharts shown in Figures 8A and 8B can be performed in parallel with the process of the flowcharts shown in Figures 5A and 5B.

[0069] First, when printing is completed (step S41), the control unit 81 determines whether a paper dust accumulation error notification such as "cleaning required" (step S11 in FIG. 5A) has been issued within a predetermined period of time (step S42). If a paper dust accumulation error notification has been issued (step S42: YES), the control unit 81 increases the light emission amount of the light-emitting unit Sa of the paper detection sensor S and turns on the light emission amount increase flag (step S43).

[0070] When the control unit 81 has performed a process of increasing the light emission amount of the light-emitting unit Sa of the paper detection sensor S (step S43), and when the paper dust accumulation error notification (step S11 in Figure 5A) has not been performed (step S42: NO), once printing starts (step S44), it repeatedly determines whether the paper detection sensor S is ON until the paper detection sensor S is ON (step S45).

[0071] When the sheet detection sensor S is turned ON (step S45: YES), the control unit 81 performs a detected transmittance sampling process for each block (step S46), similar to the process of step S2 shown in Fig. 5A described above. Also, the control unit 81 compares the calculated detected transmittance (average value) for each block with the reference transmittances (X1 to X7) (step S47), similar to the process of step S3 shown in Fig. 5A described above.

[0072] Next, the control unit 81 determines whether the detected transmittance is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks (step S48).

[0073] If the detected transmission amount is not lower than the reference transmission amount by a specified amount for a certain number of consecutive blocks (step S48: YES), the control unit 81 determines whether the detected transmission amount is higher than the reference transmission amount by a specified amount for a certain number of consecutive blocks (step S49).

[0074] If the detected transmittance exceeds the reference transmittance by a specified amount for a certain number of consecutive blocks (step S49: YES), it is possible that the paper detection sensor S was cleaned or replaced after the process of increasing the light emission amount of the light-emitting section Sa of the paper detection sensor S (step S43) was performed, so the control unit 81 sets the counter that returns the light emission amount to +1 (step S50).

[0075] On the other hand, if the detected transmittance is lower than the reference transmittance by a specified amount for a certain number of consecutive blocks, the control unit 81 performs a process of increasing the light emission amount of the light-emitting unit Sa of the paper detection sensor S (step S43), and since it is unlikely that the paper detection sensor S has been cleaned or replaced, sets the counter that resets the light emission amount to -1 (step S51). Also, since there is a possibility that paper dust has accumulated, the control unit 81 may perform the process of the flowchart shown in Figures 5A and 5B (step S52) and determine whether a "paper dust accumulation error" (step S15 in Figure 5B) has occurred.

[0076] If the determination process in step S49 is NO, and if the processes in steps S50 and S52 have been performed, the control unit 81 determines whether the paper detection sensor S has turned OFF (step S53), as shown in Fig. 8B. If the paper detection sensor S has not turned OFF (step S52: NO), the paper detection sensor S continues to detect the paper P, and the control unit 81 repeats the process from the process in step S46 described above.

[0077] If the paper detection sensor S turns OFF (step S53: YES), the control unit 81 determines whether printing has finished (step S54), and if not (step S54: NO), the control unit 81 performs processing on the next paper P to be transported, starting from the processing in step S45 described above.

[0078] When printing is completed (step S54: YES), the control unit 81 determines whether there is a "paper dust accumulation error" (step S55), and if there is no "paper dust accumulation error" (step S55: YES), it determines whether the light projection amount increase flag is ON (step S56). Furthermore, if the light projection amount increase flag is ON (step S56: YES), the control unit 81 determines whether the counter that returns the light projection amount is equal to or greater than a specified number (step S57). This specified number can be any number equal to or greater than 1.

[0079] If the counter for resetting the light emission amount is equal to or greater than the specified number of times (step S57), the control unit 81 resets (decreases) the increased light emission amount of the light-emitting unit Sa of the paper detection sensor S, turns off the light emission amount increase flag (step S58), and ends the processing shown in Figures 8A and 8B. Note that if the control unit 81 determines whether there is a "paper dust accumulation error" (step S55), whether the light emission amount increase flag is ON (step S56), or whether the counter for resetting the light emission amount is equal to or greater than the specified number of times (step S57) as NO, it does not reset the light emission amount and ends the processing shown in Figures 8A and 8B. Thereafter, the control unit 81 restarts the processing shown in Figures 8A and 8B at the end of printing (step S41 in Figure 8A), etc.

[0080] In the present embodiment described above, the printing device 1 (an example of a conveying device) includes a paper detection sensor S (an example of a medium detection sensor) and a control unit 81. The paper detection sensor S has a light-projecting unit Sa that projects light onto paper P (an example of a medium) and a light-receiving unit Sb that receives the light projected by the light-projecting unit Sa, and detects the paper P. The control unit 81 compares a reference transmittance (an example of a reference received light amount) corresponding to the type of paper P detected by the paper detection sensor S with a detected transmittance (an example of a detected received light amount) of light projected onto the paper P and received by the light-receiving unit Sb, and determines that an accumulation error has occurred, that is, paper powder (an example of dust) has accumulated on the paper detection sensor S, based on the detected transmittance being lower than the reference transmittance by a specified amount for consecutive sheets of paper P, starting from the first sheet of paper P (step S15 in FIG. 5A).

[0081] In this way, the control unit 81 determines that a paper dust accumulation error has occurred based on the detected transmittance falling below the reference transmittance by a specified amount for successive sheets of paper P, starting from the first sheet of paper P being transported among the multiple sheets of paper P being transported in succession, so that it is possible to prevent erroneous determination of a paper dust accumulation error in cases where the detected transmittance has decreased for the second or subsequent sheets of paper P among the multiple sheets of paper P being transported in succession due to the occurrence of double feeding or transport of the wrong type of paper P. Therefore, according to this embodiment, it is possible to accurately perform error determination based on the detected transmittance of light received by the light receiving unit Sb of the paper detection sensor S.

[0082] Furthermore, in this embodiment, when the control unit 81 determines that a stacking error has occurred, it controls the paper detection sensor S to increase the amount of light emitted by the light-emitting unit Sa (step S43 in Figure 8A), and then, based on the fact that the detected transmittance exceeds the reference transmittance by a specified amount (step S49), it controls the paper detection sensor S to decrease the amount of light emitted by the light-emitting unit Sa (step S58 in Figure 8B).

[0083] Therefore, by increasing the amount of light emitted, it is possible to prevent the paper detection sensor S from failing to detect the paper P due to an insufficient amount of detected transmission caused by the paper dust accumulation not being resolved even after the user has been notified of the accumulation error. Also, if the paper dust accumulation is resolved by cleaning or replacing the paper detection sensor S and the amount of detected transmission increases, the amount of light emitted can be restored.

[0084] In addition, the control unit 81 determines that a double feed error has occurred for the paper P (step S35) based on at least one of the following: the detected transmittance of the second or subsequent paper P among the multiple sheets of paper P being transported continuously is lower than the reference transmittance by a specified amount (step S18 in Figure 5B, step S33 (NO) in Figure 6) and the detected transmittance of the paper P transported immediately before is lower than the detected transmittance of the paper P transported immediately before (step S34: YES).

[0085] This makes it possible to determine not only paper dust accumulation errors but also double feed errors based on the detected transmittance amount received by the light receiving section Sb of the paper detection sensor S, thereby making it possible to more accurately determine errors based on the detected transmittance amount.

[0086] Furthermore, in this embodiment, the control unit 81 determines that a different type of paper P has been transported, that is, a wrong paper type error (step S32), based on the fact that the detected transmittance amount exceeds the reference transmittance amount by a specified amount (step S18 in FIG. 5B, step S31 (YES) in FIG. 6).

[0087] Therefore, based on the detected transmittance amount received by the light receiving section Sb of the paper detection sensor S, not only paper dust accumulation errors but also paper type errors can be determined, thereby making it possible to more accurately determine errors based on the detected transmittance amount.

[0088] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiments. For example, all of 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. The invention as originally claimed in the present application is described below.

[0089] [Appendix 1] a medium detection sensor that detects the medium and has a light-projecting unit that projects light onto the medium and a light-receiving unit that receives the light projected by the light-projecting unit; a control unit that compares a reference amount of received light corresponding to the type of medium detected by the medium detection sensor with the detected amount of received light of light projected onto the medium and received by the light receiving unit, and determines that an accumulation error has occurred due to dust accumulation on the medium detection sensor when the detected amount of received light falls below the reference amount of received light by a specified amount for the first medium among the plurality of media that are continuously transported, starting from the first medium; A conveying device comprising:

[0090] [Appendix 2] When the control unit determines that a deposition error has occurred, the control unit controls the medium detection sensor to increase the amount of light projected by the light projecting unit, and thereafter controls the medium detection sensor to decrease the amount of light projected by the light projecting unit based on the fact that the detected amount of received light has exceeded the reference amount of received light by a specified amount. 2. The conveying device according to claim 1.

[0091] [Appendix 3] The control unit determines that a media multifeed error has occurred based on at least one of the following: the detected amount of received light being lower than the reference amount of received light by a specified amount from the second or subsequent media conveyed among the plurality of media being conveyed continuously; and the detected amount of received light being lower than the detected amount of received light of the previously conveyed medium by a specified amount. 3. The conveying device according to claim 1 or 2.

[0092] [Appendix 4] The control unit determines that a different type of medium is being conveyed, that is, a wrong medium type error, based on the detected amount of received light exceeding the reference amount of received light by a specified amount. 4. The conveying device according to any one of claims 1 to 3. [Explanation of symbols]

[0093] 1 Printing device 10 External paper feed section 11 Paper tray 12 Paper feed roller 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 Acceleration conveying section 32a, 32b, 32c Acceleration roller pair 33 Constant speed conveying section 33a, 33b, 33c uniform speed roller pair 34 Reversing conveying section (switchback roller pair) 35 Re-feed unit (re-feed roller pair) 36 Paper discharge transport section (paper discharge roller pair) 37 Straight conveying section (straight roller pair) 38,39 Route switching section 40 Printing Department 50 Printing transport section 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 Acceleration drive unit 73 Constant velocity 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 P paper R1 Straight route R2 Circulation Route R2a Reversal Path R3 paper output path S Paper detection sensor Sa Light projector Sb light receiving section

Claims

1. a medium detection sensor that detects the medium and has a light-projecting unit that projects light onto the medium and a light-receiving unit that receives the light projected by the light-projecting unit; a control unit that compares a reference amount of received light corresponding to the type of medium detected by the medium detection sensor with a detected amount of received light of light projected onto the medium and received by the light receiving unit, and determines that an accumulation error has occurred due to dust accumulation on the medium detection sensor only when the detected amount of received light is lower than the reference amount of received light by a specified amount from the first medium conveyed to a specified number of two or more media consecutively among the plurality of media conveyed continuously, from the first medium conveyed to the specified number of media, or when the detected amount of received light is lower than the reference amount of received light by a specified amount from the second medium onwards; A conveying device comprising:

2. When the control unit determines that a deposition error has occurred, the control unit controls the medium detection sensor to increase the amount of light projected by the light projecting unit, and thereafter controls the medium detection sensor to decrease the amount of light projected by the light projecting unit based on the detected amount of received light exceeding the reference amount of received light by a specified amount.

2. The conveying device according to claim 1.

3. The control unit determines that a media multifeed error has occurred based on at least one of the following: the detected amount of received light being lower than the reference amount of received light by a specified amount from the second or subsequent media conveyed among the plurality of media conveyed continuously; and the detected amount of received light being lower than the detected amount of received light of the previously conveyed medium by a specified amount.

3. The conveying device according to claim 1 or 2.

4. The control unit determines that a different type of medium is being conveyed, that is, a wrong medium type error, based on the detected amount of received light exceeding the reference amount of received light by a specified amount.

4. The conveying device according to claim 1, wherein the conveying device is a conveying device for conveying a plurality of objects.

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