Sheet feeding device

Abstract

To provide a sheet feeding device capable of reducing double feeding of sheets while suppressing complication and enlargement of a device configuration.SOLUTION: The scraper roller 12 feeds and conveys the sheets P stacked on the sheet feed tray 11. The registration rollers 16 convey the sheet P conveyed from the scraper roller 12 to the conveyor 21 that conveys the sheet P at the printing conveyance speed. The control part 4 controls the scraper roller 12 and the resist roller 16 so that the paper P conveyed by the resist roller 16 passes through the scraper roller 12 in a drive stop state where the scraper roller 12 is rotated together with the paper P conveyed by the resist roller 16. The controller 4 controls the registration rollers 16 such that the sheet P reaches the conveyor 21 at a speed higher than the printing conveyance speed, the sheet P having reached the conveyor 21 is conveyed at a speed higher than the printing conveyance speed, and the sheet P is conveyed at a conveyance speed equal to or lower than the printing conveyance speed at a timing when the sheet P passes through the scraper roller 12.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sheet feeding device that feeds sheets. [Background technology]

[0002] A known sheet supplying device for supplying sheets is one that uses a scraper roller to feed paper stacked on a paper feed tray one sheet at a time from above, and then transports the paper fed from the paper feed tray using a registration roller to feed it to the printing section of a printing device.

[0003] In such a paper feeder, after the driving of the scraper roller is stopped, the scraper roller continues to rotate along with the paper until the paper being transported by the registration roller passes through the scraper roller.

[0004] After the paper passes through the scraper roller, the scraper roller continues to rotate for a while due to inertia. As a result, the scraper roller, rotating due to inertia, may unintentionally transport the following paper, causing a double feed of paper. The faster the paper transport speed by the registration roller is increased to improve productivity, the more likely this double feed of paper occurs.

[0005] Incidentally, Patent Document 1 discloses a technology that prevents transport problems caused by differences in the shape of the sag in the width direction by releasing the nip of the paper by an upstream roller located upstream of the registration roller during transport after the paper is pushed against the registration roller to create sag in the paper and correct the skew.

[0006] Using a technique similar to this technology, it is possible to prevent the above-mentioned double-feeding of sheets. Specifically, before the sheet conveyed by the registration roller passes through the scraper roller, the scraper roller is moved away from the sheet. This prevents double-feeding of sheets caused by the scraper roller continuing to rotate due to inertia even after the sheet has passed through the scraper roller. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-51699 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in order to separate the scraper roller from the paper as described above, a mechanism for doing so is required, and providing such a mechanism leads to a complicated and large-sized device configuration.

[0009] The present invention has been made in view of the above, and has an object to provide a sheet feeding device that can reduce the occurrence of double sheet feeding while preventing the device configuration from becoming complicated and large in size. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the sheet supply device of the present invention comprises a supply roller that unwinds and transports a sheet loaded on a supply table, a registration roller that transports the sheet transported from the supply roller to a transport mechanism that transports the sheet at a predetermined speed, and a control unit that controls the supply roller and the registration roller so that the sheet transported by the registration roller passes through the supply roller when the supply roller is in a drive-stop state in which the supply roller rotates along with the sheet transported by the registration roller, and the control unit controls the registration roller so that the sheet reaches the transport mechanism at a speed faster than the predetermined speed, transports the sheet that has reached the transport mechanism at a speed faster than the predetermined speed, and transports the sheet at a transport speed lower than the predetermined speed when the sheet passes through the supply roller. [Effects of the Invention]

[0011] According to the sheet feeding device of the present invention, it is possible to reduce the occurrence of double sheet feeding while preventing the device configuration from becoming complicated and large in size. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a printing device according to an embodiment. [Figure 2] FIG. 2 is a control block diagram of the printing apparatus shown in FIG. [Figure 3] 1. FIG. 4 is a diagram showing an example of conveyance speed control waveforms of a registration roller, a scraper roller, and a pickup roller during secondary paper feeding by the printing device shown in FIG. [Figure 4] 2 is a diagram showing how a sheet is transported in secondary paper feeding of the printing device shown in FIG. 1. FIG. [Figure 5] 10A and 10B are diagrams showing conventional examples of control waveforms of conveying speeds of a registration roller, a scraper roller, and a pickup roller during secondary paper feeding. [Figure 6] 6 is a diagram showing how a sheet is transported in the secondary sheet feeding of the conventional example shown in FIG. 5. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The same or equivalent parts and components are designated by the same or equivalent reference numerals throughout the drawings.

[0014] The following embodiments are examples of devices that embody the technical idea of ​​the present invention, and the technical idea of ​​the present invention does not limit the materials, shapes, structures, arrangements, 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.

[0015] Fig. 1 is a schematic diagram of a printing 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 in Fig. 1 are defined as the top, bottom, left, and right directions. The direction from left to right in Fig. 1 is the paper transport direction. In the following description, upstream and downstream refer to upstream and downstream in the paper transport direction.

[0016] 1 and 2, the printing device 1 according to this embodiment includes a paper feed unit 2, a printing unit 3, and a control unit 4. The paper feed unit 2 and the control unit 4 form a paper feed device (corresponding to a sheet supply device).

[0017] The paper feed unit 2 feeds paper (corresponding to a sheet) P, which is a printing medium, to the printing unit 3. The paper feed unit 2 includes a paper feed tray (corresponding to a supply tray) 11, a scraper roller (corresponding to a supply roller) 12, a pickup roller 13, a paper feed motor 14, a separation plate 15, a registration roller 16, a registration motor 17, and a paper sensor 18.

[0018] The paper feed tray 11 is a tray on which the paper sheets P are stacked.

[0019] The scraper roller 12 picks up and transports the sheets P stacked on the sheet feed tray 11. The scraper roller 12 presses against the uppermost sheet P among the sheets P on the sheet feed tray 11, and sends the sheet P downstream by friction.

[0020] When the paper P in contact with the scraper roller 12 is being transported by the registration roller 16 in a drive-stop state where the drive by the paper feed motor 14 is stopped, the scraper roller 12 rotates along with the paper P due to the frictional force between the scraper roller 12 and the paper P.

[0021] The pickup roller 13 separates the paper P sent by the scraper roller 12 between itself and a separation plate 15 and sends the paper P downstream. The pickup roller 13 is disposed adjacent to the scraper roller 12 on the downstream side.

[0022] Like the scraper roller 12, when the pickup roller 13 is in a stopped state and a sheet of paper P in contact with the pickup roller 13 is being transported by the registration roller 16, the pickup roller 13 rotates along with the sheet of paper P due to the frictional force between the pickup roller 13 and the sheet of paper P.

[0023] The paper feed motor 14 drives the pickup roller 13. The driving force of the paper feed motor 14 is transmitted from the pickup roller 13 to the scraper roller 12 by a driving force transmission mechanism (not shown), so that the scraper roller 12 is driven together with the pickup roller 13. The paper feed motor 14 is made up of a pulse motor.

[0024] The separation plate 15 separates the sheets P so that the sheets P are conveyed one by one by the pickup roller 13. The separation plate 15 is in pressure contact with the pickup roller 13 from below.

[0025] The registration rollers 16 are abutted against the sheet P conveyed from the scraper roller 12 and the pickup roller 13, and after a slack is formed in the sheet P, the registration rollers 16 convey the sheet P to a conveying section 21, which will be described later. The registration rollers 16 are disposed downstream of the pickup roller 13.

[0026] The registration motor 17 drives the registration rollers 16 .

[0027] The paper sensor 18 detects the paper P being transported from the pickup roller 13 to the registration rollers 16. The paper sensor 18 is disposed at a predetermined position between the pickup roller 13 and the registration rollers 16. The paper sensor 18 is used to detect double feeding of the paper P, etc. The paper sensor 18 includes a light-emitting unit 18a and a light-receiving unit 18b.

[0028] The light-emitting unit 18a and the light-receiving unit 18b are disposed opposite each other with the transport path of the paper P in between. The light-emitting unit 18a emits light toward the light-receiving unit 18b. The light-receiving unit 18b receives the light from the light-emitting unit 18a and outputs an electrical signal according to the amount of light received. When the amount of light received by the light-receiving unit 18b is equal to or less than a threshold for paper detection, the paper P is detected. When the amount of light received by the light-receiving unit 18b is equal to or less than a threshold for detecting multiple feeds, which is smaller than the threshold for detecting paper, multiple feeds of the paper P are detected.

[0029] The printing unit 3 prints by ejecting ink onto the paper P while transporting the paper P. The printing unit 3 is disposed downstream of the paper feed unit 2. The printing unit 3 includes a transport unit (corresponding to a transport mechanism) 21 and a plurality of inkjet heads 22.

[0030] The transport unit 21 transports the paper P fed from the paper feed unit 2 at a predetermined print transport speed Vg (corresponding to a predetermined speed). The transport unit 21 includes a transport belt 31, a drive roller 32, driven rollers 33 to 35, pressure rollers 36 and 37, a transport motor 38, and a fan 39.

[0031] The conveyor belt 31 attracts and holds the paper sheet P conveyed by the registration rollers 16 and conveys the paper sheet P. The conveyor belt 31 is a circular belt that is stretched over a drive roller 32 and driven rollers 33 to 35. The conveyor belt 31 has a large number of belt holes (not shown) that are through holes for suctioning air. The conveyor belt 31 attracts and holds the paper sheet P by the suction force generated in the belt holes by the drive of the fan 39. The conveyor belt 31 rotates (moves endlessly) clockwise in FIG. 1, thereby conveying the attracted and held paper sheet P in a conveyance direction from left to right.

[0032] The drive roller 32 rotates the conveyor belt 31 in the clockwise direction in FIG.

[0033] The driven rollers 33 to 35 support the conveyor belt 31 together with the drive roller 32. The driven rollers 33 to 35 are rotated by the rotating conveyor belt 31. The driven roller 33 is disposed at the same height as the drive roller 32 and to the left of the drive roller 32. The driven rollers 34 and 35 are disposed below the drive roller 32 and the driven roller 33, spaced apart from each other in the left-right direction, and at the same height.

[0034] The pressure rollers 36 and 37 are rollers for pressing the paper P against the conveyor belt 31. The pressure rollers 36 and 37 are rotated following the rotation of the conveyor belt 31. The pressure rollers 36 and 37 are disposed above the conveyor belt 31 at the upstream end and downstream end of the conveyor section 21, respectively.

[0035] The transport motor 38 drives the drive roller 32 .

[0036] The fan 39 generates a downward airflow, which causes the fan 39 to suck air through the belt holes of the conveyor belt 31, generating negative pressure in the belt holes and causing the paper P to be adsorbed and held on the conveyor belt 31.

[0037] The inkjet heads 22 perform printing by ejecting ink onto the paper P transported by the transport unit 21. In this embodiment, four inkjet heads 22 are provided. The four inkjet heads 22 are arranged side by side in the left-right direction above the transport unit 21. The four inkjet heads 22 each eject ink of a different color (for example, black, cyan, magenta, or yellow).

[0038] The control unit 4 controls the operation of each unit of the printing device 1. The control unit 4 is configured with a CPU, RAM, ROM, a hard disk, and the like.

[0039] Specifically, the control unit 4 controls the paper feed unit 2 to feed the paper P to the printing unit 3, and controls the inkjet head 22 to eject ink to print on the paper P while the transport unit 21 transports the paper P.

[0040] During the paper feeding operation by the paper feeder 2, the control unit 4 drives the scraper roller 12 and the pickup roller 13, and causes the paper P conveyed by the scraper roller 12 and the pickup roller 13 to abut against the registration roller 16. When a predetermined amount of slack is formed in the paper P that has abutted against the registration roller 16, the control unit 4 stops the scraper roller 12 and the pickup roller 13.

[0041] After stopping the scraper roller 12 and the pickup roller 13, the control unit 4 starts driving the registration rollers 16. In addition, the control unit 4 causes the scraper roller 12 and the pickup roller 13 to perform an assist operation to assist the registration rollers 16 in conveying the paper P.

[0042] The control unit 4 terminates the assisting operation of the scraper roller 12 and the pickup roller 13 before the paper P being transported by the registration roller 16 passes through the scraper roller 12. As a result, the paper P being transported by the registration roller 16 passes through the scraper roller 12 while the scraper roller 12 is not being driven.

[0043] In addition, the control unit 4 controls the registration rollers 16 so that the paper P reaches the conveying unit 21 at a conveying speed V1 that is faster than the printing conveying speed Vg, and after conveying the paper P that has reached the conveying unit 21 at the conveying speed V1, the paper P is conveyed at a conveying speed V2 that is faster than the printing conveying speed Vg, and at the time the paper P passes through the scraper rollers 12, the paper P is conveyed at a conveying speed V3 that is equal to or lower than the printing conveying speed Vg.

[0044] Next, the paper feeding operation of the printing device 1 will be described.

[0045] When a print job is input, the control unit 4 acquires information indicating the paper type and information indicating the paper size from the print setting information included in the print job.

[0046] Then, the control unit 4 sets the conveying speed V3 of the paper P by the registration rollers 16 at the timing when the paper P passes through the scraper rollers 12 based on the paper type and paper size.

[0047] As will be described later, in a state where the scraper roller 12 is stopped after the assist operation is completed, the scraper roller 12 rotates together with the paper P being transported by the registration rollers 16. After the paper P passes through the scraper roller 12, the scraper roller 12 continues to rotate by inertia for a while and then stops rotating.

[0048] The faster the conveying speed V3, the greater the amount of rotation due to inertia of the scraper roller 12 after the paper P has passed through it. Also, the ease with which the subsequent paper P moves due to the rotation of the scraper roller 12 after the paper P has passed through it varies depending on the paper type (paper quality). Also, for the same paper type, the smaller the paper size, the easier the subsequent paper P will move. The greater the amount of conveyance of the subsequent paper P due to the rotation of the scraper roller 12 after the paper P has passed through it, the more likely it is that multiple paper P will be fed.

[0049] Therefore, the control unit 4 sets the conveying speed V3 based on the paper type and paper size so that the conveying speed V3 does not become excessively slow, while keeping the conveying amount of the subsequent paper P due to the rotation by the inertia of the scraper roller 12 after the paper P has passed below a predetermined conveying amount. Here, the predetermined conveying amount is a value less than the distance between the position of the leading edge (downstream end) of the paper P loaded on the paper feed tray 11 and the nip point between the pickup roller 13 and the separation board 15. In the printing device 1, the conveying speed V3 for each combination of paper type and paper size is determined in advance by experiment or the like and stored in the control unit 4.

[0050] Furthermore, the control unit 4 starts driving the transport unit 21. Then, the control unit 4 drives the transport unit 21 so that the paper P can be transported at the printing transport speed Vg.

[0051] Next, the control unit 4 starts the primary paper feeding. Specifically, the control unit 4 starts driving the scraper roller 12 and the pickup roller 13. As a result, the topmost paper P stacked on the paper feed tray 11 is fed by the scraper roller 12 and transported by the scraper roller 12 and the pickup roller 13 toward the registration rollers 16.

[0052] When the leading edge of the paper P being conveyed by the scraper roller 12 and the pickup roller 13 hits the registration roller 16 and a predetermined amount of slack is formed in the paper P, the control unit 4 stops the scraper roller 12 and the pickup roller 13. This corrects the skew of the paper P and ends the primary paper feeding.

[0053] Here, the control unit 4 corrects the transport amount according to the paper transport rate of the scraper roller 12 and the pickup roller 13 in the primary paper feed.

[0054] Specifically, when the leading edge of paper P is detected by paper sensor 18, control unit 4 acquires a count value of the number of drive pulses of paper feed motor 14 from the start of driving scraper roller 12 and pickup roller 13 to the time when the leading edge of paper P is detected by paper sensor 18. Next, control unit 4 calculates the paper conveyance rate by dividing the theoretical value of the number of drive pulses of paper feed motor 14 from the start of driving scraper roller 12 and pickup roller 13 to the time when the leading edge of paper P is detected by paper sensor 18 by the count value.

[0055] Then, based on the calculated paper transport rate, the control unit 4 adjusts the number of drive pulses of the paper feed motor 14 from the time the leading edge of the paper P is detected by the paper sensor 18 until the scraper roller 12 and the pickup roller 13 are stopped so that the leading edge of the paper P hits the registration roller 16 and a predetermined amount of slack is formed in the paper P.

[0056] 3, which is a predetermined time after the leading edge of the paper P abuts against the registration rollers 16 and the scraper roller 12 and pickup roller 13 are stopped as described above, the control unit 4 starts the secondary paper feeding. Specifically, the control unit 4 starts driving the registration rollers 16. After this, when the conveying speed of the registration rollers 16 reaches a conveying speed V1 that is faster than the printing conveying speed Vg, the control unit 4 maintains the conveying speed V1.

[0057] Also, at time t1, the control unit 4 starts the assisting operation of the scraper roller 12 and the pickup roller 13. Specifically, the control unit 4 starts driving the scraper roller 12 and the pickup roller 13. After that, when the conveying speed of the scraper roller 12 and the pickup roller 13 reaches a conveying speed V4 that is faster than the printing conveying speed Vg but slower than the conveying speed V1, the control unit 4 maintains the conveying speed V4.

[0058] After the registration rollers 16, scraper roller 12, and pickup roller 13 start to be driven at time t1, the slack in the paper P between the registration rollers 16 and pickup roller 13 gradually decreases and is eliminated. Note that the slack in the paper P may be eliminated during the assisting operation of the scraper roller 12 and pickup roller 13, or may be eliminated after the assisting operation is completed.

[0059] At time t2 after the registration rollers 16 have reached the conveying speed V1, the leading edge of the paper P being conveyed at the conveying speed V1 reaches the conveying section 21. The leading edge of the paper P that has reached the conveying section 21 is conveyed by the conveying section 21 at the print conveying speed Vg, so that from time t2, slack begins to form in the paper P between the conveying section 21 and the registration rollers 16. By forming slack in the paper P between the conveying section 21 and the registration rollers 16, back tension is applied to the paper P, which prevents the conveying section 21 from vibrating and causing disturbances in the printed image.

[0060] After the leading edge of the paper P reaches the conveying section 21 at time t2, the control section 4 decelerates the registration rollers 16 from the conveying speed V1 to a conveying speed V2 that is slightly faster than the printing conveying speed Vg.

[0061] Furthermore, the control unit 4 stops the scraper roller 12 and the pickup roller 13 to end the assisting operation at a predetermined timing before the paper P passes through the scraper roller 12. From time t3 when the assisting operation ends, the scraper roller 12 and the pickup roller 13 are stopped and rotate together with the paper P being transported by the registration rollers 16.

[0062] After the assist operation is completed, the control unit 4 decelerates the registration rollers 16 from conveying speed V1 to conveying speed V3 before the paper P passes through the scraper rollers 12. At time t5 after the registration rollers 16 have been decelerated to conveying speed V3, the paper P passes through the scraper rollers 12. As shown in FIG. 4, after the paper P passes through the scraper rollers 12, the scraper rollers 12 continue to rotate due to inertia for a while.

[0063] Due to the rotation due to inertia as described above, the scraper roller 12 unintentionally transports the succeeding sheet P of paper P that has passed through the scraper roller 12. The area of ​​region A in FIG. 3 indicates the transport amount of the succeeding sheet P due to the rotation due to inertia of the scraper roller 12.

[0064] As described above, in the printing device 1, the conveying speed V3 is set so that the conveying amount of the succeeding paper P due to the rotation by the inertia of the scraper roller 12 is kept below a predetermined conveying amount. As a result, the conveying amount indicated by the area of ​​region A is kept to a level that prevents the succeeding paper P from reaching the nip point between the pickup roller 13 and the separation plate 15.

[0065] After the paper P passes through the scraper roller 12, the control unit 4 accelerates the registration rollers 16 from the conveying speed V3 back to the conveying speed V2.

[0066] Here, as described above, the registration rollers 16 are decelerated to the conveying speed V3, which reduces the amount of slack in the sheet P between the conveying unit 21 and the registration rollers 16. In response to this, the control unit 4 accelerates the registration rollers 16 from the conveying speed V3 to the conveying speed V2 at a timing that does not eliminate the slack in the sheet P between the conveying unit 21 and the registration rollers 16.

[0067] Specifically, the control unit 4 accelerates the registration rollers 16 from the conveying speed V3 to the conveying speed V2 so that the area of ​​the region C in FIG.

[0068] Here, the area of ​​region B indicates the amount of slack in the paper P formed from time t2 when the leading edge of the paper P reaches the conveying section 21 to time t4 when the registration rollers 16 reach the printing conveying speed Vg while decelerating from conveying speed V2 to conveying speed V3. The area of ​​region C indicates the amount of reduction in the amount of slack in the paper P from time t4 to time t6 when the registration rollers 16 reach the printing conveying speed Vg while accelerating from conveying speed V3 to conveying speed V2.

[0069] As described above, by controlling the registration rollers 16 so that the area of ​​region C is less than the area of ​​region B, the slack in the sheet P can be left even after the period from time t4 to time t6 in which the amount of slack in the sheet P decreases has ended.

[0070] After time t6, when the registration rollers 16 reach the conveying speed V2, the registration rollers 16 convey the sheet P at the conveying speed V2 until the sheet P passes through the registration rollers 16. Therefore, the amount of slack in the sheet P increases from time t6 until the sheet P passes through the registration rollers 16. Therefore, by controlling the registration rollers 16 so that the area of ​​region C is less than the area of ​​region B as described above, it is possible to prevent the slack in the sheet P between the conveying section 21 and the registration rollers 16 from disappearing until the sheet P passes through the registration rollers 16.

[0071] The timing for starting the acceleration of the registration rollers 16 from the conveying speed V3 to the conveying speed V2 may be either before or after the sheet P passes through the pickup roller 13. If the acceleration of the registration rollers 16 from the conveying speed V3 to the conveying speed V2 starts after the sheet P passes through the pickup roller 13, when the following sheet P has reached the nip point between the pickup roller 13 and the separation board 15 at the time the following sheet P passes through the pickup roller 13, it is possible to reduce the occurrence of double feeding of the following sheets P, which is caused by the separation board 15 being unable to separate the following sheet P.

[0072] Furthermore, the timing at which the registration rollers 16 complete the acceleration from the conveying speed V3 to the conveying speed V2 may be before the leading edge of the paper P reaches the inkjet head 22 on the most upstream side (before printing by the printing unit 3 starts).

[0073] After returning the registration rollers 16 to the conveying speed V2, the control unit 4 stops the registration rollers 16 when the sheet P passes through the registration rollers 16. This completes the feeding of one sheet of sheet P.

[0074] Here, after the paper P passes through the pickup roller 13, the control unit 4 starts driving the scraper roller 12 and the pickup roller 13 to feed the next paper P before stopping the registration roller 16.

[0075] When the number of sheets P to be printed in the print job has been fed, the series of paper feeding operations is completed.

[0076] Here, an example of a conventional paper feeding operation in which, unlike this embodiment, the registration rollers 16 are not decelerated when the paper P passes through the scraper rollers 12 will be described.

[0077] In this example, as in the example of the present embodiment described above, first, the control unit 4 executes primary paper feeding using the scraper roller 12 and the pickup roller 13. Next, at time t11 in FIG. 5, the control unit 4 starts secondary paper feeding. Specifically, the control unit 4 starts driving the registration rollers 16. When the registration rollers 16 reach the conveying speed V2, the control unit 4 maintains the conveying speed V2. In this example, the control unit 4 maintains the conveying speed V2 of the registration rollers 16 until the sheet P passes through the registration rollers 16. This conveying speed V2 is the same as that in the example of FIG. 3 of the present embodiment described above.

[0078] Also, at time t11, the control unit 4 starts the assisting operation of the scraper roller 12 and the pickup roller 13. Specifically, the control unit 4 starts driving the scraper roller 12 and the pickup roller 13. After that, when the conveying speed of the registration rollers 16 reaches a conveying speed V5 that is slower than the printing conveying speed Vg, the control unit 4 maintains the conveying speed V5.

[0079] After the registration rollers 16, the scraper roller 12, and the pickup roller 13 start to be driven at time t11, the slack in the sheet P between the registration rollers 16 and the pickup roller 13 gradually decreases and is eliminated.

[0080] At time t12 after the registration rollers 16 reach the conveying speed V2, the leading edge of the paper P being conveyed at the conveying speed V2 reaches the conveying section 21, and slack begins to form in the paper P between the conveying section 21 and the registration rollers 16.

[0081] The control unit 4 stops the scraper roller 12 and the pickup roller 13 to end the assisting operation at a predetermined timing before the paper P passes through the scraper roller 12. From time t13 when the assisting operation ends, the scraper roller 12 and the pickup roller 13 are stopped and rotate together with the paper P being transported by the registration rollers 16.

[0082] After the assist operation is completed, the sheet P, which is being transported by the registration rollers 16 at transport speed V2, passes through the scraper roller 12. After the sheet P passes through the scraper roller 12, the scraper roller 12 continues to rotate by inertia for a while, as in the example of Figure 3, and unintentionally transports the succeeding sheet P. The area of ​​region D in Figure 5 indicates the transport distance of the succeeding sheet P due to the rotation by inertia of the scraper roller 12.

[0083] 5, the sheet P is being transported at transport speed V2 when it passes through the scraper roller 12, and therefore the amount of rotation due to the inertia of the scraper roller 12 after the sheet P passes through the scraper roller 12 is greater than in the example of FIG. 3. Therefore, the transport amount indicated by the area of ​​region D in FIG. 5 is greater than the transport amount indicated by the area of ​​region A in FIG. 3. As a result, the example of FIG. 5 is more susceptible to double feeding of sheets P than the example of FIG. 3.

[0084] 6, when multiple succeeding sheets P move simultaneously due to the rotation of the scraper roller 12 due to inertia, it is difficult for the separation board 15 to separate the sheets P between the sheet P being transported by the registration roller 16 and the bottommost sheet of the multiple sheets P being transported due to the rotation of the scraper roller 12 due to inertia. This can result in multiple sheets P being fed.

[0085] In contrast, in this embodiment, as described above, the amount of transport of the subsequent sheets P due to the rotation of scraper roller 12 under inertia is limited to an extent that the subsequent sheets P do not reach the nip point between pickup roller 13 and separation plate 15. Therefore, even if multiple subsequent sheets P move simultaneously due to the rotation under inertia of scraper roller 12, the number of these sheets P reaching the nip point between pickup roller 13 and separation plate 15 is reduced, and double feeding of sheets P is reduced.

[0086] As described above, in the printing device 1, the control unit 4 controls the registration rollers 16 to transport the paper P at a transport speed V3 that is equal to or lower than the printing transport speed Vg when the paper P passes through the scraper roller 12. This reduces the transport amount of the subsequent paper P caused by the rotation due to the inertia of the scraper roller 12 after the paper P passes through the scraper roller 12, thereby reducing double feeding of the paper P.

[0087] Furthermore, since there is no need to provide a dedicated mechanism for preventing the occurrence of double feeding of the paper sheets P, the device configuration can be prevented from becoming complicated and large in size.

[0088] Therefore, according to the printing device 1, it is possible to reduce the occurrence of multiple feeding of the paper sheets P while preventing the device configuration from becoming complicated and large in size.

[0089] Furthermore, the printing device 1 can reduce skew of the paper P. The reason for this is as follows.

[0090] After the paper P passes through the scraper roller 12, the subsequent paper P is transported by the inertial rotation of the scraper roller 12, and the paper P moves downstream, which may cause the paper transport rate of the scraper roller 12 and the pickup roller 13 calculated during the first paper feed of the paper P to be higher than the actual value. Then, when the calculated paper transport rate is higher than the actual value, the correction amount of the transport amount according to the paper transport rate becomes insufficient, and the paper P may not reach the registration roller 16 during the first paper feed.

[0091] Even if the paper P does not reach the registration rollers 16 in the primary paper feed, the scraper roller 12 and the pickup roller 13 assist the paper P in the secondary paper feed, causing the paper P to reach the registration rollers 16, thereby preventing empty feeding of the paper P. However, since the paper P does not abut against the registration rollers 16 in the primary paper feed, skew correction is not performed.

[0092] In contrast to this, in this embodiment, the transport amount of the paper P due to the rotation by the inertia of the scraper roller 12 can be reduced, so that the amount of correction of the transport amount according to the paper transport rate can be reduced. This reduces the occurrence of a situation where the skew correction is not performed as described above, so that the skew of the paper P can be reduced.

[0093] Unlike the present embodiment, when the assisting operation of scraper roller 12 and pickup roller 13 is not performed, empty feeding of paper P occurs if paper P does not reach registration roller 16 in the primary paper feed. In contrast, as in the present embodiment, by controlling registration roller 16 to convey paper P at conveying speed V3 when paper P passes through scraper roller 12, it is possible to reduce insufficient correction of the conveyance amount according to the paper conveyance rate of scraper roller 12 and pickup roller 13, as described above, and therefore empty feeding of paper P can be reduced.

[0094] Furthermore, in the printing device 1, the control unit 4 controls the registration rollers 16 so that the slack in the paper P formed between the conveying unit 21 and the registration rollers 16 does not disappear until the paper P passes through the registration rollers 16. This prevents back tension from being applied to the paper P, causing the conveying unit 21 to vibrate and disrupting the printed image.

[0095] Furthermore, in the printing device 1, the control unit 4 sets the conveying speed V3 of the paper P by the registration rollers 16 at the time when the paper P passes through the scraper rollers 12, based on the paper type and paper size. This prevents the conveying speed V3 from becoming excessively slow, making it easier to control the conveying speed of the registration rollers 16.

[0096] In the embodiment described above, the registration rollers 16 are controlled so that the sheet P reaches the conveying section 21 at the conveying speed V1, the sheet P that has reached the conveying section 21 is conveyed at the conveying speed V1, and then the speed is decelerated to the conveying speed V2, and the sheet P is conveyed at the conveying speed V3 when the sheet P passes through the scraper rollers 12. However, this is not limiting, and for example, the registration rollers 16 may be decelerated from the conveying speed V1 to the conveying speed V2 before the sheet P reaches the conveying section 21, and the sheet P may reach the conveying section 21 at the conveying speed V2. It is only necessary to control the registration rollers 16 so that the sheet P reaches the conveying section 21 at a speed faster than the printing conveying speed Vg, the sheet P that has reached the conveying section 21 is conveyed at a speed faster than the printing conveying speed Vg, and the sheet P is conveyed at a conveying speed equal to or lower than the printing conveying speed Vg when the sheet P passes through the scraper rollers 12.

[0097] In the above-described embodiment, the registration rollers 16 are controlled so that the slack in the sheet P formed between the conveying section 21 and the registration rollers 16 does not disappear until the sheet P passes through the registration rollers 16. However, this is not limiting, and there may be a timing at which the slack in the sheet P between the conveying section 21 and the registration rollers 16 disappears.

[0098] In the above-described embodiment, the conveying speed V3 is set based on the paper type and paper size. However, the conveying speed V3 may be set based on only either the paper type or the paper size. Alternatively, a common conveying speed V3 may be set for each paper type and each paper size used for the printing paper 1.

[0099] In the above-described embodiment, the printing device 1 is described as having the pickup roller 13 and separation plate 15 that separate and transport the paper sheets P downstream of the scraper roller 12. However, even in a configuration without the pickup roller 13 and separation plate 15, by controlling the registration roller 16 to transport the paper sheets P at a transport speed V3 that is equal to or lower than the printing transport speed Vg when the paper sheets P pass through the scraper roller 12, the transport amount of the subsequent paper sheets P due to the rotation of the scraper roller 12 due to inertia after the paper sheets P pass through the scraper roller 12 can be reduced, thereby reducing double feeding of the paper sheets P.

[0100] Furthermore, in the above-described embodiment, the printing device 1 that feeds paper P has been described, but the present invention can also be applied to devices that feed sheets other than paper.

[0101] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be created by appropriately combining multiple components disclosed in the above-described embodiments. For example, some components may be omitted from all the components shown in the embodiments.

[0102] [Note] The present application discloses the following inventions.

[0103] (Appendix 1) a supply roller that feeds and conveys the sheets loaded on the supply table; a registration roller for conveying the sheet conveyed from the supply roller to a conveying mechanism for conveying the sheet at a predetermined speed; a control unit that controls the supply roller and the registration roller so that the sheet conveyed by the registration roller passes through the supply roller under a drive-stop state in which the supply roller rotates together with the sheet conveyed by the registration roller, The control unit controls the registration rollers to make the sheet reach the conveying mechanism at a speed faster than the predetermined speed, to convey the sheet that has reached the conveying mechanism at a speed faster than the predetermined speed, and to convey the sheet at a conveying speed lower than the predetermined speed when the sheet passes through the supply rollers.

[0104] (Appendix 2) The sheet supply device described in Appendix 1 is characterized in that the control unit controls the registration rollers so that the slack in the sheet formed between the conveying mechanism and the registration rollers after the sheet reaches the conveying mechanism does not disappear until the sheet passes through the registration rollers.

[0105] (Appendix 3) The sheet supply device described in Appendix 1 or 2, characterized in that the control unit sets the sheet conveying speed by the registration roller at the time the sheet passes through the supply roller based on at least one of the type and size of the sheet. [Explanation of symbols]

[0106] 1 Printing device 2 Paper feed section 3 Printing Department 4. Control section 11 Paper feed tray 12 Scraper roller 14 Paper feed motor 13 Pickup roller 14 Paper feed motor 15 Sabaki board 16 Registration roller 17 Resist motor 21 Conveyor 22 Inkjet head

Claims

1. a supply roller that feeds and conveys the sheets loaded on the supply table; a registration roller for conveying the sheet conveyed from the supply roller to a conveying mechanism for conveying the sheet at a predetermined speed; a control unit that controls the supply roller and the registration roller so that the sheet conveyed by the registration roller passes through the supply roller under a drive-stop state in which the supply roller rotates together with the sheet conveyed by the registration roller, The control unit controls the registration rollers to make the sheet reach the conveying mechanism at a speed faster than the predetermined speed, to convey the sheet that has reached the conveying mechanism at a speed faster than the predetermined speed, and to convey the sheet at a conveying speed lower than the predetermined speed when the sheet passes through the supply rollers.

2. The sheet supply device according to claim 1, characterized in that the control unit controls the registration rollers so that the slack in the sheet formed between the conveying mechanism and the registration rollers after the sheet reaches the conveying mechanism does not disappear until the sheet passes through the registration rollers.

3. 3. The sheet supply device according to claim 1, wherein the control unit sets a sheet conveying speed by the registration rollers at the timing when the sheet passes through the supply rollers, based on at least one of a type and a size of the sheet.

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