Sheet conveying device

Abstract

To provide a sheet conveying device capable of performing highly accurate skew correction regardless of the size of a sheet SOLUTION: The sheet conveying device includes the registration portion 31 having the plurality of nip rollers arranged at intervals in the direction orthogonal to the sheet conveying direction, and the controller 70 that selects one nip roller pair capable of nipping a position close to the end portion of the sheet in the direction orthogonal to the sheet conveying direction from among the plurality of nip rollers 31a to 31f according to the size of the sheet in the direction orthogonal to the sheet conveying direction, and controls the selected nip roller pair to perform the skew correction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying device that conveys a sheet while correcting skew. [Background technology]

[0002] 2. Description of the Related Art In a conventional printing apparatus that performs printing processing on a sheet such as printing paper transported on a transport path, the sheet may be transported skewed, which may affect the printing processing or cause a jam.

[0003] For example, a printing apparatus has been proposed in which a sheet fed from a paper feed unit is corrected for skew by a registration roller, and then the sheet is sent from the registration roller to a conveyance unit such as a conveyor belt, and a printing process is performed while the sheet is being conveyed by the conveyance unit.

[0004] It has also been proposed to separate the registration rollers in a direction perpendicular to the sheet conveying direction and to independently control each of the separated registration rollers, thereby correcting skew while the sheet is being conveyed.

[0005] For example, Patent Document 1 proposes arranging two sets of independently controlled separate registration rollers in the conveying direction, and if the skew correction by the upstream registration roller set is insufficient, re-correction is performed by the downstream registration roller set. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5355021 Summary of the Invention [Problem to be solved by the invention]

[0007] However, arranging multiple registration rollers in the conveying direction as in Patent Document 1 results in a longer conveying path and an increased size of the device. Also, when skew correction is performed by independently controlling two registration rollers, the positions of the two registration rollers are fixed, so depending on the size of the printing paper, the registration rollers may not be able to nip the edge of the printing paper, preventing sufficient skew correction and reducing correction accuracy.

[0008] SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a sheet transport device that can perform skew correction with high accuracy regardless of the size of the sheet. [Means for solving the problem]

[0009] The sheet conveying device of the present invention includes a registration unit having a plurality of nip rollers arranged at intervals in a direction perpendicular to the sheet conveying direction, and a control unit that selects from the plurality of nip rollers a pair of nip rollers that can nip a position near the end of the sheet in the direction perpendicular to the sheet conveying direction, depending on the size of the sheet in the direction perpendicular to the sheet conveying direction, and controls the selected pair of nip rollers to correct skew. [Effects of the Invention]

[0010] According to the sheet conveying device of the present invention, a pair of nip rollers capable of nipping a position close to the edge of the sheet is selected from among a plurality of nip rollers depending on the size of the sheet, and the selected pair of nip rollers is controlled to perform skew correction, thereby enabling highly accurate skew correction regardless of the size of the sheet. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram showing a schematic configuration of an inkjet printing apparatus using an embodiment of a sheet conveying device of the present invention; [Figure 2] An example of a resist section viewed from above [Figure 3] An example of a resist section viewed from the front [Figure 4] Diagram showing the state of the cam when the shaft rotation angle is 0° [Figure 5] Diagram showing the state of the cam when the shaft is rotated 90° [Figure 6] Diagram showing the state of the cam when the shaft is rotated 180° [Figure 7] Diagram showing the state of the cam when the shaft is rotated 270° [Figure 8] A flowchart for explaining a nip roller selection process in a registration unit. [Figure 9] A block diagram showing the configuration of a control system of the inkjet printing apparatus shown in Figure 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] An inkjet printing apparatus using an embodiment of a sheet conveying device of the present invention will be described in detail below with reference to the drawings. The inkjet printing apparatus of this embodiment is characterized by the configuration of a registration unit that corrects skew of a sheet being conveyed, but first, its overall configuration will be described. FIG. 1 is a diagram showing a schematic configuration of an inkjet printing apparatus 1 of this embodiment. Note that the up-down, front-rear directions shown in FIG. 1 are the up-down, front-rear directions of the inkjet printing apparatus 1 of this embodiment, with the front side of the paper in FIG. 1 being the right direction and the back side being the left direction. The front side shown in FIG. 1 is the conveying direction of a sheet P, with the rear side being the upstream side in the conveying direction and the front side being the downstream side in the conveying direction.

[0013] The inkjet printing device 1 of this embodiment includes a paper feed section 30, a registration sensor RS, a registration section 31, a right-side skew correction sensor CSR and a left-side skew correction sensor CSL, a conveying roller 32, four line heads 33, a conveying section 34, a circulating conveying path CR, first to fifth circulating conveying rollers 35 to 39, a paper discharge roller 40, a first reversing conveying roller 41, a reversing roller 42, and a second reversing conveying roller 44.

[0014] The paper feed unit 30 includes a paper feed tray 30a, a scraper 30b, a separating plate 30c, and a pickup roller 30d.

[0015] A plurality of sheets P (e.g., printing paper) are stacked on the paper feed tray 30a. The scraper 30b rotates while contacting the upper surfaces of the sheets P stacked on the paper feed tray 30a. The separation plate 30c is made of a high-friction member such as a rubber plate and is provided downstream of the scraper 30b in the conveying direction of the sheets P. The pickup roller 30d is rotatably provided above and opposite the separation plate 30c, and separates and conveys the sheets P between itself and the separation plate 30c.

[0016] The scraper 30b and the pickup roller 30d are driven by a first paper feed drive motor 50 (see FIG. 9).

[0017] Scraper 30b presses against the top sheet P stacked on paper feed tray 30a with a predetermined pressure, and the resulting frictional force causes sheet P to flow downstream. Even if scraper 30b picks up multiple sheets P, separator plate 30c and pickup roller 30d separate only one sheet and transport it further downstream to registration unit 31. In this way, paper feed unit 30 picks up sheets P stacked on paper feed tray 30a one by one and transports them to registration unit 31.

[0018] The scraper 30b and the pickup roller 30d are rotated by the first paper feed drive motor 50 in the direction of conveying the sheet P, but are under assist control when the sheet P is conveyed by the registration unit 31. Under assist control, while the sheet P is being conveyed by the registration unit 31, the sheet P is conveyed at a conveying speed faster than that of the registration unit 31, thereby forming slack in the sheet P. Then, the conveying speed is reduced thereafter so that the slack is gradually eliminated.

[0019] The registration unit 31 is provided downstream of the pickup roller 30d in the conveying direction of the sheet P, and has a plurality of nip rollers 31a to 31f that sandwich the sheet P. Fig. 2 is a view of the registration unit 31 as seen from above.

[0020] 2, the registration unit 31 of this embodiment includes a right registration unit 31R and a left registration unit 31L. The right registration unit 31R and the left registration unit 31L are provided separately in two in a direction perpendicular to the conveying direction of the sheet P.

[0021] The right registration section 31R has three nip rollers 31a to 31c and a drive shaft 31gR on which the three nip rollers 31a to 31c are arranged at predetermined intervals in a direction perpendicular to the conveying direction.

[0022] The left registration section 31L has three nip rollers 31d to 31f and a drive shaft 31gL on which the three nip rollers 31d to 31f are arranged at predetermined intervals in a direction perpendicular to the conveying direction.

[0023] The right registration section 31R and the left registration section 31L are controlled independently, and the nip rollers 31a to 31c of the right registration section 31R are driven by a right roller drive motor 51R (see Figure 9), and the nip rollers 31d to 31f of the left registration section 31L are driven by a left roller drive motor 51L (see Figure 9).

[0024] The registration section 31 of this embodiment is configured to be switchable between a first skew correction, which performs skew correction by independently controlling the conveying speeds of the right registration section 31R and the left registration section 31L depending on the skew state of the sheet P, and a second skew correction, which performs skew correction by temporarily stopping all nip rollers 31a to 31f and abutting the leading edge of the sheet P.

[0025] When performing the first skew correction, the registration unit 31 selects one pair of nip rollers to nip the sheet P from among the six nip rollers 31a to 31f in accordance with the size of the sheet P in the direction perpendicular to the conveying direction. Specifically, the registration unit 31 selects a pair of nip rollers that are positioned inside the sheet P with respect to a position with a predetermined margin from the edge of the sheet P in the direction perpendicular to the conveying direction of the sheet P and that can nip the position closest to the edge of the sheet P in the direction perpendicular to the conveying direction.

[0026] For example, when the paper width of sheet P is W1 shown in Fig. 2, registration unit 31 selects nip roller 31c and nip roller 31d as one nip roller pair. When the paper width of sheet P is W2 shown in Fig. 2, registration unit 31 selects nip roller 31b and nip roller 31e as one nip roller pair. When the paper width of sheet P is W3 shown in Fig. 2, registration unit 31 selects nip roller 31a and nip roller 31f as one nip roller pair.

[0027] The registration unit 31 is controlled so that the sheet P is nipped by one pair of nip rollers selected in accordance with the paper width of the sheet P, and the other nip rollers are released from the nip.

[0028] Next, when the second skew correction is performed, the registration unit 31 puts all six nip rollers 31a to 31f into a state in which the sheet P can be nipped.

[0029] The registration unit 31 has a nip roller selection unit 60 for selecting nip rollers and for nipping and releasing the nip in the first and second skew corrections described above. Fig. 3 is a view of the registration unit 31 as seen from the front. The nip roller selection unit 60 has a plurality of cam portions 61a-61f provided for the nip rollers 31a-31f, respectively, and a shaft 62 on which the plurality of cam portions 61a-61f are provided. Also, GD shown in Fig. 3 is a paper conveyance unit cover that supports the sheet P.

[0030] Cam portions 61a-61f are provided so as to be able to come into contact with the driven rollers of the corresponding nip rollers 31a-31f. When each cam portion 61a-61f rotates, the driven rollers of nip rollers 31a-31f move up and down, thereby switching nip rollers 31a-31f between a nipped state and a released nip state.

[0031] In the state shown in Figure 3, the driven rollers of nip roller 31a and nip roller 31f are lifted upward by cam portion 61a and cam portion 61f, creating a nip state, while the driven rollers of nip rollers 31b to 31e are lowered, creating a nip-release state.

[0032] 4A to 4C are views of cam portions 61a to 61c corresponding to nip rollers 31a to 31c of right-side registration portion 31R shown in Fig. 3, viewed from the right side (the direction of arrow A in Fig. 4). Each of cam portions 61a to 61c has two cams Ca and two cams Cb, and each of the two cams Ca and Cb is attached to shaft 62 with the two cams Ca and Cb combined at a predetermined angle.

[0033] As shown in Figures 4A and 4C, cam portion 61a and cam portion 61c are combined so that the longitudinal axes of cam Ca and cam Cb are perpendicular to each other. Cam portion 61a and cam portion 61c are attached to shaft 62 so that cam portion 61c is rotated 90° relative to cam portion 61a. As shown in Figure 4B, cam portion 61b is combined so that the longitudinal axes of cam Ca and cam Cb are in the same direction and the cam lift portions are located on opposite sides of shaft 62. Cam portion 61b is attached to shaft 62 so that the longitudinal axis direction of cam Cb of cam portion 61a, the longitudinal axis direction of the two cams Ca and Cb of cam portion 61b, and the longitudinal axis direction of cam Cb of cam portion 61c are aligned.

[0034] 4A to 4C show the states of cam portions 61a to 61c when nip roller 31a of right-side registration portion 31R shown in FIG. 3 is in a nip state and nip rollers 31b and 31c are in a nip-release state.

[0035] 5A to 5C show a state in which shaft 62 is rotated 90° from the state of cam portions 61a to 61c shown in Figures 4A to 4C. When cam portions 61a to 61c are in the state shown in Figures 5A to 5C, nip roller 31b of right-side registration portion 31R shown in Figure 3 is in a nip state, and nip rollers 31a, 31c are in a nip-release state.

[0036] 6A to 6C show a state in which shaft 62 is rotated 180° from the state of cam portions 61a to 61c shown in Figures 4A to 4C. When cam portions 61a to 61c are in the state shown in Figures 6A to 6C, nip roller 31c of right-side registration portion 31R shown in Figure 3 is in a nip state, and nip rollers 31a, 31b are in a nip-release state.

[0037] 7A to 7C show a state in which shaft 62 has been rotated 270° from the state of cam portions 61a to 61c shown in Figures 4A to 4C. When cam portions 61a to 61c are in the state shown in Figures 7A to 7C, all nip rollers 31a to 31c of right-side registration portion 31R shown in Figure 3 are in a nip state.

[0038] Furthermore, cam portions 61d-61f corresponding to nip rollers 31d-31f of left-side registration portion 31L shown in Fig. 3 are configured symmetrically to cam portions 61a-61c. That is, a view of cam portion 61f from the left side (the direction of arrow B shown in Fig. 3) is similar to cam portion 61a shown in Fig. 4A, a view of cam portion 61d from the left side is similar to cam portion 61b shown in Fig. 4B, and a view of cam portion 61d from the left side is similar to cam portion 61c shown in Fig. 4C.

[0039] Furthermore, when shaft 62 is rotated 90°, 180°, or 270° from the state shown in Figures 4A to 4C, cam portions 61d to 61f have a configuration symmetrical to cam portions 61a to 61c. That is, Figures 5A to 5C are views of cam portions 61d to 61f as viewed from the left side when shaft 62 has rotated 90°, Figures 6A to 6C are views of cam portions 61d to 61f as viewed from the left side when shaft 62 has rotated 180°, and Figures 7A to 7C are views of cam portions 61d to 61f as viewed from the left side when shaft 62 has rotated 270°.

[0040] As described above, the nip roller selection unit 60 of this embodiment can select the nip roller that will nip the sheet P from among the nip rollers 31a to 31c of the right registration unit 31R and the nip rollers 31d to 31f of the left registration unit 31L, simply by rotating the shaft 62 in one direction. The shaft 62 is rotationally driven by a shaft drive motor 80 (see FIG. 9).

[0041] Next, the nip roller selection process in the registration unit 31 will be described with reference to the flowchart shown in Fig. 8. The nip roller selection process is performed by the shaft drive motor 80 being rotationally driven under the control of the control unit 70 (see Fig. 9), which will be described later. The initial states of the cam portions 61a to 61f are assumed to be the states shown in Figs. 4A to 4C.

[0042] First, the control unit 70 acquires information about the type and size of the sheet P to be printed (S10). Next, the control unit 70 checks whether the size (paper width) of the sheet P is equal to or smaller than W1 shown in Fig. 2 (S12). If the size of the sheet P is equal to or smaller than W1 (S12, YES), the control unit 70 notifies the control unit 70 that the sheet P (paper) is of an incompatible size (S14).

[0043] On the other hand, if the size (paper width) of the sheet P is larger than W1 (S12, NO), the control unit 70 selects whether to perform the first skew correction or the second skew correction based on the information on the type of the sheet P (S16).

[0044] Here, for example, if the type of sheet P is slippery paper or thin paper, the second skew correction, which uses all of the nip rollers, is more likely to achieve accurate skew correction than the first skew correction, which controls two nip rollers independently. Conversely, if the type of sheet P is neither slippery paper nor thin paper, the first skew correction can shorten the conveyance time and improve productivity compared to the second skew correction, which temporarily stops the leading edge of the sheet P.

[0045] Therefore, the control unit 70 selects the second skew correction when the type of sheet P is slippery paper or thin paper, and selects the first skew correction when the type of sheet P is other than that. Note that the type of sheet P is not limited to the above-mentioned differences in slipperiness or thickness, and the relationship between the type of sheet P and the type of skew correction corresponding to that type (first skew correction or second skew correction) is assumed to be set in advance.

[0046] When the control unit 70 selects the second skew correction according to the type of sheet P (S16, second skew correction), it controls the drive of the shaft drive motor 80 to rotate the shaft 62 by 270° from the state shown in Figures 4A to 4c (S18), bringing the cam portions 61a to 61f into the state shown in Figures 7A to 7C, and making all of the nip rollers 31a to 31f into a state where they can nip the sheet P.

[0047] On the other hand, when the control unit 70 selects the first skew correction (S16, first skew correction), it checks whether the paper width of the sheet P is equal to or greater than W3 shown in FIG. 2 (S20).

[0048] If the paper width of sheet P is equal to or greater than W3 (S20, YES), control unit 70 selects nip roller 31a and nip roller 31f as the nip roller pair. In this case, cam portions 61a to 61f can remain in the states shown in Figures 4A to 4C, so control unit 70 does not rotate shaft 62 (shaft rotation angle 0 degrees) (S22), and sets sheet P in a state where it can be nipped by nip rollers 31a and 31f.

[0049] On the other hand, if the paper width of sheet P is smaller than W3 (S20, NO), control unit 70 checks whether the paper width of sheet P is equal to or larger than W2 shown in FIG. 2 (S24). If the paper width of sheet P is equal to or larger than W2 (S24, YES), control unit 70 selects nip roller 31b and nip roller 31e as the nip roller pair. In this case, cam portions 61a to 61f must be in the states shown in FIGS. 5A to 5C, so control unit 70 rotates shaft 62 by 90° (shaft rotation angle 90 degrees) (S26) to bring sheet P into a state where nip rollers 31b and 31e can nip it.

[0050] On the other hand, if the paper width of sheet P is smaller than W2 (S24, NO), that is, if the paper width of sheet P is greater than W1 and smaller than W2, control unit 70 selects nip roller 31c and nip roller 31d as the nip roller pair. In this case, cam portions 61a to 61f must be in the states shown in FIGS. 6A to 6C, so control unit 70 rotates shaft 62 by 180° (shaft rotation angle 180°) (S28) to bring sheet P into a state where nip rollers 31c and 31d can nip sheet P. This concludes the description of the nip roller selection process in registration unit 31.

[0051] Next, the registration sensor RS is disposed between the pickup roller 30d and the registration unit 31, and detects the conveyed sheet P. A detection signal by the registration sensor RS is output to the control unit 70, and the control unit 70 controls the start and stop of rotation of the nip rollers 31a to 31f of the registration unit 31 based on the detection signal from the registration sensor RS.

[0052] During the second skew correction, the leading edge of the sheet P in the conveying direction conveyed from the paper feed section 30 contacts the nip rollers 31a to 31f, and after correcting the skew of the sheet P by this contact, the registration section 31 conveys the sheet P toward the conveying rollers 32 located downstream in the conveying direction at a predetermined timing.

[0053] The right-side skew correction sensor CSR and the left-side skew correction sensor CSL are disposed between the registration unit 31 and the conveying rollers 32, and detect the sheet P being conveyed.

[0054] 3, the right-side skew correction sensor CSR is provided downstream of the right-side registration unit 31R, and the left-side skew correction sensor CSL is provided downstream of the left-side registration unit 31L. The right-side skew correction sensor CSR and the left-side skew correction sensor CSL are provided at a predetermined interval in a direction perpendicular to the conveying direction of the sheet P.

[0055] The detection signals from the right-side skew correction sensor CSR and the left-side skew correction sensor CSL are output to the control unit 70, and the control unit 70 controls the rotation speeds of the right-side registration unit 31R and the left-side registration unit 31L based on the detection signals from the right-side skew correction sensor CSR and the left-side skew correction sensor CSL to perform skew correction.

[0056] The control unit 70 calculates the correction distance D based on the difference Tsnr in detection time between the detection signal of the right-side skew correction sensor CSR and the detection signal of the left-side skew correction sensor CSL, using the following formula: ROL Calculate. D ROL = Transfer speed V1 × Tsnr × (D1 / D2) Conveying speed V1: Conveying speed of pickup roller 30d D1: distance between the right registration section 31R and the left registration section 31L (distance in a direction perpendicular to the conveying direction) D2: Distance between the right-side skew correction sensor CSR and the left-side skew correction sensor CSL (distance in the direction perpendicular to the conveying direction)

[0057] Then, the control unit 70 calculates the correction distance D ROL Based on this, the conveying speed of the right registration unit 31R or the left registration unit 31L is reduced, etc., to form slack so that the leading ends of the sheets P are aligned. The slack is eliminated by the subsequent assist control.

[0058] The conveying rollers 32 nip the sheet P whose skew has been corrected by the registration unit 31, and convey the sheet P toward the conveying unit 34. The conveying rollers 32 are driven by a conveying roller drive motor 53 (see FIG. 9).

[0059] The conveying unit 34 includes a conveying belt 34a and a platen roller 34b. The conveying belt 34a is formed of a circular endless belt and has many suction holes formed therein. The conveying belt 34a is stretched over four platen rollers 34b extending in a direction perpendicular to the conveying direction. The sheet P conveyed by the conveying rollers 32 is conveyed to the circular conveying belt 34a. The sheet P is then attracted to the conveying belt 34a by the suction of a suction fan (not shown) installed on the back side of the conveying path surface of the conveying belt 34a, and is conveyed at a predetermined conveying speed. While the sheet P is conveyed by the conveying belt 34a, ink is ejected from the line head 33 onto the sheet P, thereby performing a printing process on the sheet P. The platen roller 34b is driven by a platen roller drive motor 54 (see FIG. 9).

[0060] Each line head 33 is an array of inkjet heads in a direction perpendicular to the conveyance direction of the sheet P. As shown in Fig. 1, the four line heads 33 are arranged at predetermined intervals along the conveyance path of the sheet P. The four line heads 33 eject ink of C (cyan), M (magenta), Y (yellow), and K (black), respectively.

[0061] The sheet P that has been subjected to printing processing by the four line heads 33 is transported on the circulating transport path CR by first to fifth circulating transport rollers 35 to 39 that are arranged on the circulating transport path CR.

[0062] Ahead of the fifth circulating conveying rollers 39, a switching mechanism 43 is provided which switches between guiding the sheet P to the discharge rollers 40 side and guiding the sheet P to the first reverse conveying rollers 41 side.

[0063] When performing single-sided printing, the sheet P with one side printed is guided by the switching mechanism 43 to the discharge roller 40 side and discharged onto the discharge tray 45. On the other hand, when performing double-sided printing, the sheet P with one side printed is guided by the switching mechanism 43 to the first reverse conveying roller 41 side.

[0064] The sheet P guided to the first reverse conveying rollers 41 by the switching mechanism 43 is conveyed by the first reverse conveying rollers 41 toward the reverse rollers 42.

[0065] The reversing rollers 42 transport the sheet P toward the reversing table 46 and then return it from the reversing table 46, thereby transporting the sheet P in an inverted state toward the second reversing transport rollers 44.

[0066] Then, the sheet P, whose front and back sides have been inverted, is conveyed again to the registration unit 31 by the second inversion conveying roller 44, and is conveyed again by the registration unit 31 toward the conveying unit 34 at a predetermined timing. Then, the line head 33 performs printing on the back side of the sheet P.

[0067] The sheet P, the back side of which has been printed, is conveyed by the first to fifth circular conveying rollers 35 to 39, passes through the switching mechanism 43, and is conveyed to the sheet receiving tray 45 by the sheet discharging rollers 40.

[0068] FIG. 9 is a block diagram showing a schematic configuration of a control system of the inkjet printing apparatus 1 of this embodiment.

[0069] The control unit 70 controls the entire inkjet printing apparatus 1, and includes a CPU (Central Processing Unit), semiconductor memory, a hard disk, etc. The control unit 70 controls the operation of each part of the inkjet printing apparatus 1 by executing a program stored in advance in a storage medium such as the semiconductor memory or the hard disk, and by operating electric circuits.

[0070] In particular, the control unit 70 of this embodiment switches between the first skew correction and the second skew correction depending on the type of sheet P, as described above, and selects the pair of nip rollers to be used during the first skew correction depending on the size of the sheet P.

[0071] According to the inkjet printing device 1 of the above embodiment, a pair of nip rollers capable of nipping a position close to the edge of the sheet P is selected from among the plurality of nip rollers 31a to 31f depending on the size of the sheet P, and the selected pair of nip rollers is controlled to perform skew correction, thereby enabling highly accurate skew correction regardless of the size of the sheet P.

[0072] Furthermore, in the inkjet printing device 1 of the above embodiment, it is possible to switch between a first skew correction in which each nip roller constituting a nip roller pair is independently controlled to perform skew correction, and a second skew correction in which all nip rollers 31a to 31f are temporarily stopped and the leading edge of the sheet P is brought into contact with the rollers to perform skew correction. Therefore, it is possible to perform the first skew correction when productivity is given priority, and the second skew correction when accuracy of the skew correction is given priority.

[0073] Furthermore, when the first skew correction and the second skew correction are switched depending on the type of sheet P, skew correction can be performed appropriately even on slippery or thin sheets P.

[0074] In the inkjet printing apparatus 1 of the above embodiment, it is preferable to control the registration unit 31 so that the nip pressure during the second skew correction is greater than the nip pressure during the first skew correction. One method for changing the nip pressure in this manner is to configure the cam lift of cam Cb to be greater than the cam lift of cam Ca in the cam portions 61a to 61f, for example.

[0075] By controlling the nip pressure during the second skew correction so that it is greater than the nip pressure during the first skew correction, the leading edge of the sheet P abutting against the nip rollers 31a to 31f can be prevented from slipping out of the nip rollers 31a to 31f during the second skew correction, and skew correction can be performed with high accuracy.

[0076] Furthermore, in the above embodiment, the number of nip rollers that nip the sheet P during the second skew correction is greater than the number of nip rollers that nip the sheet P during the first skew correction, so that skew correction of the sheet P can be performed more reliably when the leading edge of the sheet P contacts the nip rollers 31a to 31f.

[0077] Furthermore, in the above embodiment, the nip roller pair that nips the sheet P is selected by rotating the shaft 62 and rotating the cam portions 61a to 61f, so that the nip roller pair can be selected with a simpler and more space-saving configuration.

[0078] In addition, in the above embodiment, a pair of nip rollers is selected that is located inside the sheet P at a position that is a predetermined margin from the edge of the sheet P in a direction perpendicular to the conveying direction, and that can nip the position closest to the edge of the sheet P in a direction perpendicular to the conveying direction.This makes it possible to select a pair of nip rollers that can more appropriately convey the sheet P without causing wrinkles or the like in the sheet P.

[0079] 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 formed by appropriately combining the multiple components disclosed in the above-described embodiments. For example, all of the components shown in the embodiments can be appropriately combined. Naturally, various modifications and applications are possible without departing from the spirit of the invention.

[0080] The present invention further discloses the following supplementary notes.

[0081] (Appendix 1) The sheet conveying device of the present invention includes a registration unit having a plurality of nip rollers arranged at intervals in a direction perpendicular to the sheet conveying direction, and a control unit that selects from the plurality of nip rollers a pair of nip rollers that can nip a position near the end of the sheet in the direction perpendicular to the sheet conveying direction, depending on the size of the sheet in the direction perpendicular to the sheet conveying direction, and controls the selected pair of nip rollers to correct skew.

[0082] (Appendix 2) In the sheet conveying device described in Appendix 1, the control unit can switch between a first skew correction in which each nip roller constituting a nip roller pair is independently controlled to perform skew correction, and a second skew correction in which all nip rollers are temporarily stopped and the leading edge of the sheet is brought into contact with the nip rollers to perform skew correction.

[0083] (Appendix 3) In the sheet conveying device described in Supplementary Note 2, the control unit can switch between the first skew correction and the second skew correction depending on the type of the sheet.

[0084] (Appendix 4) In the sheet conveying device according to Supplementary Note 2 or 3, the control unit can control the registration unit so that the nip pressure during the second skew correction is greater than the nip pressure during the first skew correction.

[0085] (Appendix 5) In the sheet conveying device according to any one of Supplementary Notes 2 to 4, the control unit can increase the number of nip rollers that nip the sheet during the second skew correction compared to the number during the first skew correction.

[0086] (Appendix 6) In the sheet conveying device described in any one of Appendices 1 to 5, the registration section has a plurality of cam sections provided for each nip roller and a shaft on which the plurality of cam sections are provided, and the control section can select the pair of nip rollers that will nip the sheet by rotating the shaft to rotate the cam sections.

[0087] (Appendix 7) In the sheet conveying device described in any one of Appendices 1 to 6, the control unit can select a pair of nip rollers that are located inside the sheet from a position with a predetermined margin from the edge of the sheet in a direction perpendicular to the conveying direction, and that can nip the position closest to the edge of the sheet in the direction perpendicular to the conveying direction. [Explanation of symbols]

[0088] 1. Inkjet printing device 30 Paper feed section 30a Paper feed tray 30b scraper 30c Cutting Board 30d Pickup Roller 31 Resist section 31L Left side registration part 31R Right side registration part 31a~31f Nip rollers 31gL drive shaft 31gR drive shaft 32 Conveyor roller 33 Line Head 34 Conveying section 34a Conveyor belt 34b Platen roller 40 Paper ejection roller 42 Reversing roller 43 Switching mechanism 45 Paper receiving tray 46 Inversion Table 50 First paper feed drive motor 51L Left roller drive motor 51R Right roller drive motor 53 Conveyor roller drive motor 54 Platen roller drive motor 60 Nip roller selection section 61a~61f Cam section 62 Shaft 70 Control Unit 80 shaft drive motor CR Circulation Path CSL Left-side skew correction sensor CSR right-side skew correction sensor Ca,Cb Cam P-sheet RS Resist Sensor

Claims

1. a registration unit having a plurality of nip rollers arranged at intervals in a direction perpendicular to the sheet conveying direction; a control unit that selects, from the plurality of nip rollers, a pair of nip rollers that can nip a position near the end of the sheet in a direction perpendicular to the conveying direction, depending on the size of the sheet in a direction perpendicular to the conveying direction, and controls the selected pair of nip rollers to correct skew.

2. The sheet conveying device of claim 1, wherein the control unit switches between a first skew correction in which each nip roller constituting the nip roller pair is independently controlled to perform skew correction, and a second skew correction in which all nip rollers are temporarily stopped and the leading edge of the sheet is brought into contact with the nip rollers to perform skew correction.

3. The sheet transport device according to claim 2 , wherein the control unit switches between the first skew correction and the second skew correction depending on the type of the sheet.

4. 3. The sheet conveying device according to claim 2, wherein the control unit controls the registration unit so that the nip pressure during the second skew correction is greater than the nip pressure during the first skew correction.

5. 3. The sheet conveying device according to claim 2, wherein the control unit controls the number of nip rollers that nip the sheet during the second skew correction to be greater than the number of nip rollers that nip the sheet during the first skew correction.

6. the registration portion includes a plurality of cam portions provided for each of the nip rollers and a shaft on which the plurality of cam portions are provided, 2. The sheet conveying device according to claim 1, wherein the control unit selects a pair of nip rollers that nip the sheet by rotating the shaft to rotate the cam portion.

7. 2. The sheet conveying device of claim 1, wherein the control unit selects a pair of nip rollers that are located inside the sheet from a position that is a predetermined margin from the edge of the sheet in a direction perpendicular to the conveying direction, and that can nip the position closest to the edge of the sheet in a direction perpendicular to the conveying direction.

Images