Sheet transport device and image forming apparatus

Abstract

To suppress skew and distortion of a sheet portion that is passing through a part or all of a plurality of conveyance roll pairs arranged with an interval on the upstream side in the conveyance direction relative to a movement conveyance roll pair when one set or two sets of movement conveyance roll pairs which can move in the axial direction intersecting the conveyance direction of a sheet are moved in the axial direction in a sheet conveyance device.SOLUTION: A sheet conveyance device comprises: two sets of movement conveyance roll pairs; a second conveyance roll pair which is arranged between the two sets of movement conveyance roll pairs; a plurality of third conveyance roll pairs which are arranged on the upstream side in the conveyance direction relative to the movement conveyance roll pair on the upstream side; and a plurality of conveyance guide pairs which are arranged so as to form a conveyance space of a sheet. At least a part of the plurality of third conveyance roll pairs is separated so as not to sandwich at least a part of a sheet portion being conveyed when the two sets of movement conveyance roll pairs are moved in the axial direction.SELECTED DRAWING: Figure 12

Description

Technical Field

[0001] The present invention relates to a sheet conveying device and an image forming apparatus.

Background Art

[0002] Patent Document 1 describes a skew correction unit that corrects the skew of a sheet by rotating the sheet while conveying it, a lateral registration correction unit that is provided so as to be movable in a direction orthogonal to the sheet conveying direction on the downstream side of the skew correction unit, and corrects the position of the sheet in the direction orthogonal to the sheet conveying direction, and a sheet conveying auxiliary unit that is provided on the upstream side of the skew correction unit and is movable in a direction orthogonal to the sheet conveying direction.

[0003] Patent Document 1 also describes that when the lateral registration correction unit moves the sheet in a direction orthogonal to the sheet conveying direction to perform position correction after the skew correction unit of the sheet conveying device corrects the skew of the sheet, the sheet conveying auxiliary unit moves in the same direction as the lateral registration correction unit in synchronization with the lateral registration correction unit. Furthermore, Patent Document 1 describes that the sheet skew correction unit is two pairs of sheet conveying rotators independently arranged on a line orthogonal to the sheet conveying direction, and the skew of the sheet is corrected by the difference in the sheet conveying speed of each pair of conveying rotators, and the pressure contact of each pair of sheet conveying rotators is released after the skew of the sheet is corrected.

[0004] Patent Document 2 describes a sheet conveying device including two pairs of sandwiching conveying member pairs capable of conveying a sheet while sandwiching it and moving it in a width direction orthogonal to the conveying direction. Patent Document 2 also describes that in the sheet conveying device, while a single sheet is sandwiched between two pairs of sandwiching conveying member pairs, it is moved in the width direction, and after the movement in the width direction, two sandwiching conveying members forming the upstream-side sandwiching conveying member pair located on the upstream side in the conveying direction of the two pairs of sandwiching conveying member pairs are separated, and the sheet is conveyed by the downstream-side sandwiching conveying member pair located on the downstream side in the conveying direction of the two pairs of sandwiching conveying member pairs. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2008-1473 (Claim 1, 2, Figure 2) [Patent Document 2] Japanese Patent Publication No. 2019-147663 (Claim 1, Figure 1) [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention provides a sheet conveying device and an image forming apparatus that, when moving one or two pairs of movable conveying rolls that are movable in an axial direction intersecting the sheet conveying direction, can suppress the slanting or distortion of the sheet portion as it passes through a plurality of conveying roll pairs that are spaced upstream of the movable conveying roll pairs in the conveying direction, compared to a case where the plurality of conveying roll pairs grip the sheet portion being conveyed and convey it without changing the conveying speed. [Means for solving the problem]

[0007] The present invention (1) is, A pair of mobile transport rolls capable of gripping and transporting a sheet, and moving in an axial direction intersecting the transport direction, Multiple pairs of first conveying rolls are arranged at intervals on the upstream side of the moving conveying roll pair in the conveying direction, and are used to grip and convey the sheet. A plurality of transport guide pairs are arranged to form a sheet transport space between the mobile transport roll pair and the plurality of first transport roll pairs and between the plurality of first transport roll pairs, Equipped with, At least a portion of the plurality of first conveyor roll pairs are separated so as not to pinch at least a portion of the sheet being conveyed that is located upstream of the moving conveyor roll pairs when the moving conveyor roll pairs are moved in the axial direction. death, The first conveyor roll pair to be separated is a portion of the first conveyor roll pair that is holding the sheet portion during conveyance, including the downstream first conveyor roll pair. Multiple pairs of first conveyor rolls located upstream of the separating pair of first conveyor rolls, which grip and do not separate the sheet portion, create a difference in conveying speed, causing the sheet portion to be curved within the conveying space during transport. This is a sheet conveying device.

[0008] The present invention (2) is, A pair of movable conveying rolls is provided, which are capable of gripping and conveying a sheet and moving in an axial direction intersecting the conveying direction, and which are spaced apart in the conveying direction. One or more pairs of second conveying rolls are positioned between the two aforementioned pairs of mobile conveying rolls to grip and convey the sheet, Multiple third conveying roll pairs are positioned at a distance upstream of the upstream conveying roll pair, which is located on the upstream side of the two sets of conveying roll pairs, and which grip and convey the sheet. A plurality of transport guide pairs are arranged to form a sheet transport space between the two sets of mobile transport roll pairs and between the plurality of third transport roll pairs, Equipped with, At least a portion of the plurality of third conveying roll pairs is a sheet conveying device that separates at least a portion of the sheet being conveyed that is located upstream of the upstream moving conveying roll pair when the two sets of moving conveying roll pairs are moved in the axial direction, so as not to pinch it.

[0009] The present invention (3) relates to the sheet conveying device of the above invention (1), The aforementioned pair of first conveying rolls to be separated constitutes a sheet conveying device in which all pairs of first conveying rolls are gripping the sheet portion during conveyance.

[0010] The present invention (4) relates to the sheet conveying device of the above invention (2), The aforementioned pair of third conveying rolls to be separated constitutes a sheet conveying device that includes all the pairs of third conveying rolls that are holding the sheet portion during conveyance.

[0012] This invention ( 5 ) is a sheet conveying device of the above invention (2), The third pair of conveying rolls for separation is a part of the third pair of conveying rolls including the lowermost third pair of conveying rolls among the third pair of conveying rolls sandwiching the sheet portion during conveyance. A sheet conveying device in which a plurality of third pairs of conveying rolls that exist upstream of the third pair of conveying rolls for separation, sandwich the sheet portion, and do not separate, cause a difference in conveyance speed, and convey the sheet portion in a curved state within the conveyance space.

[0013] The present invention ( 6 ) is a sheet conveying device according to the above invention (1), The first pair of conveying rolls for separation is a sheet conveying device that is in a normally contacting state when the moving pair of conveying rolls does not move and when the moving pair of conveying rolls has moved and finished conveying the sheet.

[0014] The present invention ( 7 ) is a sheet conveying device according to the above invention (2), The third pair of conveying rolls for separation is a sheet conveying device that is in a normally contacting state when the two pairs of moving conveying rolls do not move and when the moving conveying rolls have moved and finished conveying the sheet.

[0015] The present invention ( 8 ) is a sheet conveying device according to the above invention (1), The conveyance path of the sheet on which the plurality of first pairs of conveying rolls are arranged is a sheet conveying device having at least a partially curved curved section.

[0016] The present invention ( 9 ) is a sheet conveying device according to the above invention (2), [[ID='34']]The conveyance path of the sheet between the two pairs of moving conveying rolls is a sheet conveying device that is curved.

[0017] The present invention ( 10 ) is a sheet conveying device according to the above invention ( 9 ), The sheet conveying path in which the plurality of third conveying roll pairs are arranged is a sheet conveying device consisting of a straight section that extends in a straight line for a certain distance from the upstream moving conveying roll pair.

[0018] Furthermore, the present invention ( 11 )teeth, The system comprises a conveying source unit from which sheets are transported, an image forming unit for forming images on sheets, and a sheet transport device for transporting sheets from the conveying source unit to the image forming unit. At least a part of the sheet conveying device is based on the above inventions (1) and (3), (6) or (8) This is an image forming apparatus consisting of a sheet transport device.

[0019] This invention ( 12 )teeth, The system comprises a conveying unit from which sheets are transported, an image forming unit that forms an image on the sheet, and a sheet transporting device that transports the sheet from the conveying unit to the image forming unit. At least a part of the sheet conveying device is based on the above inventions (2) and (4), (5), (7), (9) or (10) This is an image forming apparatus consisting of a sheet transport device.

[0020] This invention ( 13 ) is the above invention ( 11 )or( 12 In the image forming apparatus of ), The transport source unit is a sheet reversal unit that reverses the front and back surfaces of the sheet after it has passed through the image forming unit. At least a portion of the sheet transport device is an image forming apparatus that includes a retransmission path for retransmitting the sheet transported from the sheet reversing unit to the image forming unit. [Effects of the Invention]

[0021] The above invention (1 )of According to the sheet conveying device, one can move in an axial direction intersecting the sheet conveying direction. groupWhen moving a pair of mobile conveying rolls in the axial direction, the tendency for the sheet portion to become oblique or distorted as it passes through a plurality of conveying roll pairs, which are spaced upstream of the mobile conveying roll pair in the conveying direction, can be suppressed compared to when the plurality of conveying roll pairs grip the sheet portion being conveyed and convey it without changing the conveying speed. Furthermore, according to the sheet conveying device of the above invention (1), compared to the case where multiple pairs of first conveying rolls that do not separate convey the sheet by gripping the sheet portion upstream of the pair of first conveying rolls that is to be separated, and the sheets are conveyed without creating a difference in conveying speed or by pulling the sheets together, it is possible to suppress the sheet portion passing on the upstream side of the moving conveying roll pair from becoming oblique or distorted.

[0022] The above invention ( 2 According to the sheet transport device, When two pairs of movable conveyor rolls capable of moving in an axial direction intersecting the conveying direction of the sheet are moved axially, the sheet portion passing through some or all of the multiple conveyor roll pairs, which are spaced upstream of the movable conveyor roll pairs in the conveying direction, will be obliquely or distorted compared to when the multiple conveyor roll pairs grip the sheet portion being conveyed and convey it without changing the conveying speed. It can be suppressed.

[0023] The above invention ( 3 According to ), separate first Conveyor rolls The move A portion of the sheet that is located upstream of the dynamic conveyor roll pair is being held in place. first Compared to the case of a pair of conveyor rolls, Mobile transport rolls This makes it easy to prevent the sheet portion passing upstream from becoming skewed or distorted.

[0024] The above invention ( 4 According to, Compared to a case where the separated third conveyor roll pair is a portion of the third conveyor roll pair that is gripping the sheet portion located upstream of the upstream moving conveyor roll pair, the number of separated third conveyor roll pairs is kept to the absolute minimum, and the upstream This makes it easy to suppress the slanting or distortion of the sheet portion as it passes upstream of the moving conveyor roll pair.

[0025] The above invention ( 5 According to this method, when multiple pairs of third conveyor rolls that do not separate the sheet portion are held between them on the upstream side of the pair of third conveyor rolls that are separated, and the sheets are conveyed without creating a difference in conveying speed, or when the sheets are pulled together during conveying, it is possible to suppress the sheet portion passing on the upstream side of the upstream moving conveyor roll pair from becoming oblique or distorted.

[0026] The above invention ( 6 According to this, compared to the case where the first pair of conveying rolls that separates is not moving with the moving conveying roll pair, and the case where the separation occurs after the moving conveying roll pair has moved and finished conveying the sheet, stable conveyance of the sheet during normal operation is more easily ensured.

[0027] The above invention ( 7 According to this, the separation of the third transport roll pair is easier to ensure during normal operation compared to when the two sets of mobile transport roll pairs are not moving, or when the separation occurs after the two sets of mobile transport roll pairs have moved and finished transporting the sheet.

[0028] The above invention ( 8 According to the study, compared to a sheet transport path with multiple pairs of first transport rolls arranged without curved sections, the sheet portion passing through the curved section is more likely to become skewed or distorted, but this is a way to suppress the occurrence of such distortion. and It is possible.

[0029] The above invention ( 9 According to the study, compared to a sheet conveying device where the sheet conveying path between two pairs of movable conveying rolls is not curved, the sheet portion passing between the two pairs of movable conveying rolls tends to be more prone to slanting or distortion, but this is a way to suppress the occurrence of such distortion. and It is possible.

[0030] The above invention ( 10 According to this, compared to a system where the sheet transport path with the third transport roll pair is not composed of a straight section for a certain distance from the upstream moving transport roll pair, it becomes easier to suppress the sheet portion passing through that section from becoming oblique or distorted.

[0031] Furthermore, the above invention ( 11 According to the image forming apparatus, when a pair of movable transport rolls in a sheet transport device is moved axially, the sheet portion passing through a plurality of first transport roll pairs, which are spaced upstream of the movable transport roll pair in the transport direction, can be made less likely to be oblique or distorted compared to when the plurality of first transport roll pairs grip the sheet portion being transported and transport it without changing the transport speed, thus facilitating the normal formation of an image on the sheet.

[0032] Furthermore, the above invention ( 12 According to the image forming apparatus, when two pairs of movable transport rolls in a sheet transport device are moved axially, the sheet portion passing through a plurality of third transport roll pairs, which are spaced further upstream in the transport direction than the upstream movable transport roll pair, can be made less likely to be oblique or distorted compared to when the plurality of third transport roll pairs grip the sheet portion being transported and transport it without changing the transport speed, thus facilitating the normal formation of an image on the sheet.

[0033] The above invention ( 13 According to this, compared to a case where the re-feed path is not included as at least part of the sheet conveying device, it becomes easier to align the image formation position on the back surface of the sheet conveyed from the sheet reversal unit with the image formation position on the front surface of the sheet. [Brief explanation of the drawing]

[0034] [Figure 1] This is a schematic diagram of the sheet transport device and image forming apparatus according to Embodiment 1. [Figure 2] This is a schematic diagram of a sheet transport device applied to the image forming apparatus shown in Figure 1. [Figure 3] (A) is a schematic diagram of the first pair of mobile conveying rolls, and (B) is a schematic diagram of the first pair of conveying rolls, etc. [Figure 4] (A) is a schematic diagram of the second pair of mobile transport rolls, and (B) is a schematic diagram of the third pair of transport rolls. [Figure 5] (A) is a schematic diagram of a separable transport roll pair, and (B) is a schematic side view of the transport roll pair in (A). [Figure 6] This is a functional block diagram showing the configuration of the control system for the sheet transport device. [Figure 7] (A) is an explanatory diagram showing the transport state of a sheet that has been transported with an axial offset, and (B) is an explanatory diagram showing the state of the sheet when a pair of mobile transport rolls has been moved. [Figure 8] This flowchart shows the transport operation when there is no reversal transport. [Figure 9] This is a schematic diagram of the main components showing the sheet transport state corresponding to the transport operation performed when a pair of mobile transport rolls is moved. [Figure 10] (A) is an explanatory diagram showing the state of the sheet when the conveying operation in Figure 9 is performed, and (B) is an explanatory diagram showing the state when the rear end of the sheet in (A) passes through the first pair of conveying rolls at the very downstream end. [Figure 11] This is a flowchart illustrating the transport operation during reverse transport. [Figure 12] This is a schematic diagram of the main components showing the sheet transport state corresponding to the transport operation performed when two sets of mobile transport rolls are moved. [Figure 13] (A) is an explanatory diagram showing the state of the sheet when the transport operation shown in Figure 12 is performed, and (B) is an explanatory diagram showing the state when the rear end of the sheet in (A) passes through the third transport roll pair at the downstream end. [Figure 14] This is a flowchart illustrating the transport operation when there is no inversion transport in Embodiment 2. [Figure 15] This is a schematic diagram of the main components showing the sheet transport state corresponding to the transport operation performed when a pair of mobile transport rolls is moved. [Figure 16] (A) is an explanatory diagram showing the state of the sheet when the transport operation shown in Figure 15 is performed, and (B) is an explanatory diagram showing the state when the trailing end of the sheet in (A) passes through the second first transport roll pair from the downstream end. [Figure 17] This is a flowchart illustrating the transport operation when reverse transport is involved. [Figure 18] This is a schematic diagram of the main components showing the sheet transport state corresponding to the transport operation performed when two sets of mobile transport rolls are moved in Embodiment 2. [Figure 19] (A) is an explanatory diagram showing the state of the sheet when the transport operation shown in Figure 18 is performed, and (B) is an explanatory diagram showing the state when the rear end of the sheet in (A) passes through the third transport roll pair, the third from the downstream end. [Figure 20](A) is an explanatory diagram showing an example of a transport failure when transport is continued after moving only one pair of mobile transport rolls, and (B) is an explanatory diagram showing an example of a transport failure when transport is continued after moving only two pairs of mobile transport rolls. [Modes for carrying out the invention]

[0035] Hereinafter, embodiments for carrying out this invention will be described with reference to the drawings.

[0036] Embodiment 1. Figure 1 shows an overview of the sheet transport device 5 and image forming apparatus 1 according to the first embodiment. Figure 2 shows an overview of the sheet transport device 5 applied to the image forming apparatus 1.

[0037] (Image forming apparatus) As shown in Figure 1, the image forming apparatus 1 comprises a transport source unit 3 from which the sheet 9 is transported, an image forming unit 2 for forming an image on the sheet 9, and a sheet transport device 5 for transporting the sheet from the transport source unit 3 to the image forming unit 2. Sheet 9 is a medium in the form of a sheet, which can be transported by the sheet transport device 5 and on which an image can be formed in the image forming unit 2.

[0038] Furthermore, the image forming apparatus 1 is more specifically composed of a main body 10 and an extension 15, as shown in Figure 1.

[0039] The main body 10 has a housing of the required shape. Inside the housing of the main body 10 are the image forming unit 2, the first supply unit 3A which is an example of the transport source unit 3, the final transport path 51, discharge path 52, first transport path 53, reversal path 54, retransmission path 55, and part of the second transport path 56 that constitute the sheet transport device 5, the control device 12, etc. In addition, the main body 10 has a discharge section 11 for receiving the discharged sheets 9 located on the side of the housing, and an operation section, etc. (not shown) is located on the top or front of the housing.

[0040] The extension unit 15 has a housing of the required shape and is connected to the side of the main unit 10. The extension unit 15 has a second supply unit 3B, which is another example of the conveying source unit 3, located on the top of its housing. Inside the housing of the extension unit 15, the extension unit 15 has a third supply unit 3C, which is yet another example of the conveying source unit 3, and the second conveying path 56 and the third conveying path 57, which constitute the sheet conveying device 5, located.

[0041] The image forming unit 2 is a part that has the function of forming a desired image on the sheet 9. The image is not limited in any way in terms of type, material, etc., as long as it can be formed on the sheet 9, and for example, it includes images that are formed in a planar manner on the sheet 9. In Embodiment 1, for example, an image forming unit 2 that forms an image composed of a developer using an electrophotographic method is applied.

[0042] The image forming unit 2, to which electrophotography or the like is applied, is not shown in the diagram, but includes an image holder such as a photoreceptor, a charging device for charging the image holder, and an image exposure device for exposing the charged image holder to light to form an electrostatic latent image. The image forming unit 2 is also not shown in the diagram, but includes a developing device for developing the electrostatic latent image on the image holder with a developer to form an unfixed developer image, a transfer device for directly or indirectly transferring the developer image on the image holder to the sheet 9, and a fixing device for fixing the unfixed developer image transferred to the sheet 9 to the sheet 9.

[0043] Furthermore, the image forming unit 2 includes an image transfer unit 21 that transfers the image formed in the image forming unit 2 to the sheet 9. In addition, as shown in Figure 2, the image forming unit 2 is equipped with a transport support roll 25 and transport guides (not shown) that guide the sheet 9 to the image transfer unit 21 and pass through it. In the image forming apparatus 1, the image is transferred when the sheet 9, which is transported by the sheet transport device 5, passes through the image transfer section 21.

[0044] The transport source unit 3 is the part that receives and sends out the sheets 9 to be transported. In Embodiment 1, the first supply unit 3A, second supply unit 3B, third supply unit 3C, etc., described above are used as an example of the conveying source unit 3. The conveying source unit 3 also includes the sheet reversing unit 3D, which is composed of the reversing path 54 described later.

[0045] The first supply unit 3A consists of a storage unit for loading and storing sheets 9A of the required type and size, a dispensing device for dispensing sheets 9A one by one from the storage unit, etc. The second supply unit 3B consists of a storage unit for loading and placing sheets 9B of the required type and size, a dispensing device for dispensing sheets 9B one by one from the storage unit, etc. The third supply unit 3C consists of a storage unit for loading and storing sheets 9C of the required type and size, a dispensing device for dispensing sheets 9C one by one from the storage unit, etc. Sheets 9A, 9B, and 9C may differ in type and size from each other, but some or all of them may be the same.

[0046] (Sheet transport device) As shown in Figures 1 and 2, the sheet transport device 5 is a device that has the function of unloading sheets 9 of the type and size used in the image forming unit 2 from the transport source unit 3 and transporting them to the image forming unit 2 or other required locations. The sheet conveying device 5 according to Embodiment 1 includes a final conveying path 51, a discharge path 52, a first conveying path 53, a reversing path 54, a retransmission path 55, a second conveying path 56, a third conveying path 57, and the like.

[0047] The final transport path 51 is a route that transports the sheet 9 to the image forming unit 2, adjusting the timing and correcting the transport orientation as the sheet is sent to the image forming unit 2. The final transport path 51 includes a pair of movable transport rolls 61, a plurality of first transport roll pairs 711, 712, a plurality of transport guide pairs 811, 812, etc. A roll pair is a pair of rolls that rotate while forming contacting portions that grip and transport the sheet 9. In Embodiment 1, the final transport path 51 is provided as a transport path that extends in a substantially straight line.

[0048] The mobile transport roll pair 61 is a pair of transport rolls that can grip and transport the sheet 9 and move in the axial direction D intersecting the transport direction C. The mobile transport roll pair 61, as shown in Figure 3(A), has a pair of drive rolls 61a and driven rolls 61b, a drive unit 616 and a mobile unit 617.

[0049] The drive roll 61a is composed of multiple required sections and is fixed to the rotating shaft 611 at required intervals. The driven roll 61b is composed of multiple required sections and is fixed or rotatably mounted to the rotating shaft 612 at required intervals. In Embodiment 1, both the drive rolls 711a, 712a and the driven rolls 711b, 712b are divided into four parts, but the number of divisions is not limited to this. The same applies to other conveying roll pairs other than the moving conveying roll pair 61. The rotating shafts 611 and 612 are rotatably mounted to the support frame 67 via bearings 613 and 614.

[0050] Furthermore, the driven roll 61b receives a biasing force directed toward the driven roll 61a from a biasing member 615 such as a coil spring, via a bearing 614 that is displaceably mounted on the support frame 67. As a result, the driven roll 61b is in contact with the driven roll 61a with the required pressure.

[0051] The drive unit 616 transmits rotational power from the drive motor 616M to a gear 616a attached to one end of the rotating shaft 611 via a transmission gear 616b. This allows the drive unit 616 to rotate the drive roll 61a in the required direction.

[0052] The mobile device 617 includes a rack 617a attached to a support frame 67, a pinion 617b that meshes with the rack 617a, and a drive motor 617M that transmits rotational power to rotate the pinion 617b. The moving device 617 moves the support frame 67 via the rack 617a by a required distance in either direction Da or Db in the axial direction D by rotating the pinion 617b by a required amount in the required direction. The support frame 67 is mounted to the main frame of the sheet conveying device 5 (not shown) so as to be movable in the axial direction D. The mobile device 617 is not limited to the configuration in Embodiment 1.

[0053] The first conveyor roll pair 711, 712 is a plurality of pairs of conveyor rolls that are spaced apart to form a sheet conveying path upstream of the moving conveyor roll pair 61 in the conveying direction C, and that grip and convey the sheet 9. Of these, the first conveyor roll pair 711 is the downstream first conveyor roll pair, initially positioned upstream of the moving conveyor roll pair 61 in the conveying direction C. The first conveyor roll pair 711, 712, as shown in Figure 3(B), has a pair of drive rolls 711a, 712a and driven rolls 711b, 712b, and a drive unit 706. Incidentally, the first transport roll pair is a general term for multiple transport roll pairs positioned to grip the portion 9t of the sheet 9 that is located upstream of the transport direction C from the transport roll 61 (see Figure 9(A), etc.) when the sheet 9 of the maximum transportable length used in the image forming apparatus 1 is transported and gripped by the mobile transport roll pair 61.

[0054] The drive rolls 711a and 712a are composed of multiple divided parts and are fixed to the rotating shaft 701 at required intervals. The driven rolls 711b and 712b are composed of multiple divided parts and are fixed or rotatably mounted to the rotating shaft 702 at required intervals. In Embodiment 1, both the drive rolls 711a and 712a and the driven rolls 711b and 712b are divided into four parts, but the number of divisions is not limited to this. The rotating shafts 701 and 702 are rotatably mounted to the support frame 77 via bearings 703 and 704.

[0055] The driven rolls 711b and 712b receive a biasing force directed toward the driven rolls 711a and 712a from a biasing member 705 such as a coil spring, via bearings 703 and 704 that are displaceably mounted on the support frame 77. As a result, the driven rolls 711b and 712b are in contact with the driven rolls 711a and 712a with the required pressure.

[0056] The drive unit 706 transmits rotational power from the drive motors 707M1 and 707M2 to a gear 706a attached to one end of the rotating shafts 701 and 702 via a transmission gear 706b. This allows the drive unit 706 to rotate the drive roll 61a in the required direction. Incidentally, the drive unit 706 may be configured as a single shared drive unit that drives multiple pairs of conveyor rolls together, except when it is necessary to provide one drive unit for each pair of conveyor rolls when multiple pairs of conveyor rolls are arranged in a continuous manner with intervals between them. This point also applies to the drive units for other pairs of conveyor rolls arranged thereafter.

[0057] The transport guide pairs 811, 812 are a plurality of pairs of guide members arranged to form a transport space 50 for the sheet 9 between the mobile transport roll pair 61 and the first transport roll pairs 711, 712 and between the multiple first transport roll pairs 711, 712.

[0058] As shown in Figure 2, the transport guide pairs 811 and 812 are positioned facing each other with the required spacing between the mobile transport roll pair 61 and the first transport roll pairs 711 and 712, and between multiple first transport roll pairs 711 and 712. In this way, the transport guide pairs 811 and 812 form a transport space 50 with a required height between them. Furthermore, the transport guide pairs 811 and 812 may be composed of a single guide member formed by integrating transport guides that are positioned on the same side between them. Also, a portion of the transport guide pairs 811 and 812 may be configured to utilize a part of another component positioned close to the final transport path 51 as a guide surface, rather than being a dedicated guide member. This configuration applies to other transport guide pairs as well.

[0059] The discharge path 52 is a path for transporting the sheet 9 that has passed through the image forming unit 2 toward the discharge unit 11. As shown in Figure 2, the discharge passage 52 is equipped with multiple conveyor roll pairs 721 to 724 and multiple conveyor guide pairs 820, etc. The conveyor roll pairs 721 to 724 have almost the same configuration as the first conveyor roll pairs 711 and 712. The conveyor guide pair 820 has almost the same configuration as the conveyor guide pairs 811 and 812.

[0060] The first transport path 53 is the route for transporting the sheet 9A, which is sent out from the first supply unit 3A, to the final transport path 51. As shown in Figure 2, the first transport path 53 is equipped with a plurality of transport roll pairs 731 to 734 and transport guide pairs 830, etc. In Embodiment 1, as shown in Figure 9, the first transport path 53 is provided as a transport path consisting of a straight section 53S in which an intermediate section, which is an example of a certain section, extends in a nearly straight line, and as a transport path consisting of a curved section 53C in which an upstream section and a downstream section are curved, which is another example of a certain section.

[0061] The conveyor roll pairs 731-734 are arranged at intervals in the conveying direction C to form the first conveying path 53, and have almost the same configuration as the first conveyor roll pairs 711 and 712. The transport guide pair 830 consists of multiple transport guide pairs 831, 832, etc., which are located on the final transport path 51 side, and has almost the same configuration as the transport guide pairs 811, 812. The transport guide pair 830 is connected to the upstream end of the transport direction C of the final transport path 51 via the transport guide pair 831 at the downstream end of the transport direction C.

[0062] The second transport path 56 is the route for transporting the sheet 9B, which is sent out from the second supply unit 3B, to the final transport path 51. As shown in Figure 2, the second transport path 56 is equipped with a plurality of transport roll pairs 761 to 764 and transport guide pairs 860, etc. In Embodiment 1, the second transport path 56 is provided as a transport path consisting of a curved section 56C in which the upstream section, which is an example of a certain section, is curved, and as a transport path consisting of a straight section 56S in which the intermediate section and the downstream section extend in a nearly straight line, which is another example of a certain section.

[0063] The conveyor roll pairs 761-764 are spaced apart in the conveying direction C to form the second conveying path 56, and have almost the same configuration as the first conveyor roll pair 711-712. The transport guide pair 860 is composed of multiple transport guide pairs and has almost the same configuration as transport guide pairs 811 and 812. The transport guide pair 860 is connected so as to merge with the upstream end of the transport direction C of the final transport path 51 at the downstream end of the transport direction C.

[0064] The third transport path 57 is a route for transporting the sheets 9C sent from the second supply unit 3B toward the final transport path 51. As shown in Figure 2, the third transport path 57 includes multiple transport roll pairs 771 to 773 and transport guide pairs (not shown) except for one transport guide pair 871. In Embodiment 1, the third transport path 57 is provided as a curved transport path throughout its entire length.

[0065] The conveyor roll pairs 771 to 773 are spaced apart in the conveying direction C to form the third conveying path 57, and have almost the same configuration as the first conveyor roll pairs 711 and 712. The conveyor guide pairs (not shown), including conveyor guide pair 871, have almost the same configuration as conveyor guide pairs 811 and 812. The conveyor guide pairs are connected so as to merge with a portion of the second conveying path 56 at the downstream end in the conveying direction C.

[0066] The reversal path 54 is a transport path used to reverse the front and back sides of the sheet 9 after it has passed through the image forming unit 2. In Embodiment 1, the inversion path 54 consists of an inlet path 54a that transports the sheet 9 to be inverted into the inversion path 54, and an inversion / outlet path 54b that transports the sheet 6 that was taken in by the inlet path 54a in an inverted state and sends it out. In the inversion / outlet path 54b, the sheet 9 is temporarily stopped and stored.

[0067] The inlet path 54a of the reversal path 54 is equipped with multiple pairs of conveying rolls 741 to 743, multiple pairs of conveying guides (not shown), and a conveying destination switching material 58a, etc. The conveyor roll pairs 741-743 are arranged at intervals along the conveying direction C to form a pull-in path, and have almost the same configuration as the first conveyor roll pairs 711 and 712. The conveyor guide pairs (not shown) have almost the same configuration as the conveyor guide pairs 811 and 812. The conveyor guide pairs branch off from a portion of the discharge path 52 and form a conveying space that extends below the main body 10.

[0068] The transport destination switching material 58a is positioned at the point where the discharge path 52 branches off to the inlet path 54a, and is a component that can switch the transport destination of the sheet 9 by partially entering both the discharge path 52 and the reversal path 54. The transport destination switching material 58a operates to move to and stop at either a discharge switching position that guides the sheet 9 to the discharge path 52, or a reverse switching position that guides the sheet 9 to the reverse path 54.

[0069] The reversal and discharge path 54b of the reversal path 54 is equipped with a conveying roll pair 744, a plurality of conveying guide pairs (not shown), and a conveying destination switching material 58b, etc. The conveyor roll pair 744 has almost the same configuration as the first conveyor roll pair 711 and 712, and its rotation direction can be switched between forward and reverse. The conveyor guide pair (not shown) is designed to pull the entire length of the sheet 9 from the pull-in path 54a, temporarily store it, and then send the sheet 9 from the rear end in the conveying direction at the time of pull-in to the re-feed path 55, thereby forming a conveying space of a certain length and shape. Furthermore, this conveyor guide pair has almost the same configuration as the conveyor guide pairs 811 and 812. In addition, the conveyor guide pair forms a branch connection section that connects to the re-feed path 55 on the upstream end side in the conveying direction C.

[0070] The destination switching member 58b is positioned at the branching point of the reverse feed path 54b to connect to the re-feed path 55, and is a component that can partially enter the pull-in path 54a to switch the destination of the sheet 9 to the re-feed path 55. The destination switching member 58b operates to move and stop at either a reverse switching position that guides the sheet 9 to be transported to the reverse feed path 54b, or a re-feed switching position that guides the sheet 9 to be transported to the re-feed path 55.

[0071] The retransmission path 55 is a path that transports the sheet 6, which has been inverted on both sides in the reversal path 54, back towards the final transport path 51.

[0072] The re-transfer path 55 includes one pair of movable transport rolls 63, multiple pairs of second transport rolls 711, 712, 731 positioned between the two pairs of movable transport rolls 61, 63, multiple pairs of third transport rolls 751 to 758 positioned upstream of the movable transport rolls 63 in the transport direction C, and multiple pairs of transport guides 811, 812, 831, 832, 851 to 858, etc. In Embodiment 1, the retransmission path 55 is provided as shown in Figure 12, etc., as a transport path consisting of a curved section 55C, which is an example of a certain section, where the upstream section is curved, and as a transport path consisting of a straight section 55S, which is another example of a certain section, where the intermediate section and the downstream section extend in a nearly straight line. The curved section 55C of the retransmission path 55 merges with and overlaps with the curved section 55C of the first transport path 53.

[0073] The mobile transport roll pair 63 is a pair of transport rolls capable of gripping and transporting the sheet 9 and moving in the axial direction D, which intersects the transport direction C. Furthermore, the mobile transport roll pair 63 is also the upstream mobile transport roll pair, positioned upstream of the mobile transport roll pair 61 in the transport direction C.

[0074] The mobile transport roll pair 63, as shown in Figure 4(A), has a pair of drive rolls 63a and driven rolls 63b, a drive unit 636 and a mobile unit 637.

[0075] The drive roll 63a and driven roll 63b have the same configuration as the drive roll 61a and driven roll 63b in the mobile transport roll pair 61. In Figure 4(A), reference numerals 631 and 632 indicate the respective rotation axes of the drive roll 63a and driven roll 63b, reference numeral 635 indicates the biasing member, and reference numeral 67 indicates the support frame.

[0076] The drive unit 636 rotates the drive roll 63a in the required direction by transmitting rotational power from the drive motor 636M to a gear 636a attached to one end of the rotating shaft 613 via a transmission gear 636b.

[0077] The moving device 637 is configured such that a pinion 637b, which receives rotational power from the drive motor 637M, rotates in a required direction by a required amount on a rack 637a attached to the support frame 67, thereby moving the support frame 67 by a required distance in either direction Da or Db along the axial direction D. Note that the moving device 637 is not limited to the configuration in Embodiment 1.

[0078] The second conveyor roll pairs 711, 712, and 731 are conveyor roll pairs positioned between the two sets of mobile conveyor roll pairs 61 and 63. The second conveyor roll pair 711, 712, and 731 has the configuration described above (see Figure 3(B)).

[0079] The third conveyor roll pairs 751-758 are multiple pairs of conveyor rolls that are spaced apart to form a sheet conveying path upstream of the upstream mobile conveyor roll pair 63 in the conveying direction C, and that grip and convey the sheet 9. Of these, the third conveyor roll pair 751 is the downstream third conveyor roll pair, which is the first to be placed upstream of the mobile conveyor roll pair 63 in the conveying direction C. The third conveyor roll pair 751-758, as shown representatively in Figure 4(B) for the third conveyor roll pair 751-754, has a pair of drive rolls 751a, 752a, 753a, 754a and driven rolls 751b, 752b, 753b, 754b, and a drive unit 706. Incidentally, the third transport roll pair is a general term for multiple transport roll pairs positioned to grip the portion 9t of the sheet 9 that is located upstream of the upstream transport roll 63 in the transport direction C (see Figure 13(A), etc.) when the sheet 9 of the maximum transportable length used in the image forming apparatus 1 is transported and gripped by two sets of movable transport roll pairs 61 and 63.

[0080] The driven rolls 751a, 752a, 753a, 754a and the driven rolls 751b, 752b, 753b, 754b have the same configuration as the driven rolls 711a, 712a, 713a and driven rolls 711b, 712b, 731b in the first conveyor roll pair 711, 712 and the second conveyor rolls 711, 712, 713 (see Figure 3(B)). The drive unit 706 has the same configuration as the drive unit 706 in the first conveyor roll pair 711, 712 and the second conveyor rolls 711, 712, 713 (see Figure 3(B)).

[0081] Furthermore, in the sheet conveying device 5, as shown in Figure 5, the conveying roll pairs 711, 712, and 731, which correspond to both the first and second conveying roll pairs, and the downstream third conveying roll pair 751 and 752, etc., are also configured as separate conveying roll pairs that can be separated from their normal contact state. These separating conveyor roll pairs 711, 712, 731, 751, 752, etc. are equipped with a separation device 708.

[0082] The separation device 708 moves the pressing bar 708b, which is fixedly attached to the rotating shaft 708a, downward in the direction indicated by arrow P1 by the eccentric cam 708e, thereby pressing the rotating shaft 702 of the driven rolls 711b, 712b, 731b, 751b, 752b, etc., away from the rotating shaft 701 against the biasing force of the biasing member 705. As a result, the driven rolls 711b, 712b, 731b, 751b, 752b, etc. are separated from the driven rolls 711a, 712a, 731a, 751a, 752a, etc. The oscillating bar 708c is fixedly mounted on the rotating shaft 708a. A cam receiving portion 708g is provided on the free end side of the oscillating bar 708c. The eccentric cam 708e is fixedly mounted on the pivot shaft 708f. The pivot shaft 708f rotates in the required direction by the required angle when rotational power from the drive motors 709M1~M3 and 709M5 is transmitted to it via the gear 708h. When the eccentric cam 708e is rotated by the pivot shaft 708f, its large diameter portion and small diameter portion come into contact with the cam receiving portion 708g.

[0083] In this separation device 708, when the swinging bar 708c is oscillated by the eccentric cam 708e in the direction indicated by arrow S1 against the biasing force of a biasing member (not shown), the pressing bar 708b is moved downward in the direction indicated by arrow P1. This moves the rotation axis 702 away from the rotation axis 701. Furthermore, when the swinging bar 708c of the separation device 708 is swung in the direction indicated by arrow S2 by the eccentric cam 708e, the pressing bar 708b is moved upward in the direction indicated by arrow P2. This moves the rotating shaft 702 closer to the rotating shaft 701, returning it to its normal contact position. Incidentally, the separation device 708 may be configured as a single shared separation device that separates multiple pairs of transport rolls together, except when it is necessary to place one separation device for each pair of transport rolls when multiple pairs of separable transport rolls are arranged in a continuous manner with intervals between them.

[0084] Furthermore, as shown in Figure 2, the sheet transport device 5 is equipped with a first passage sensor 59a, a second passage sensor 59b, a third passage sensor 59c, and a positional misalignment detector 65.

[0085] The first passage sensor 59 is a detector that detects when the leading edge 9s and trailing edge 9e of the sheet 9 being transported along the final transport path 51 have passed the pair of moving transport rolls 61. This first passage sensor 59 is positioned upstream of the pair of moving transport rolls 61 in the transport direction C of the final transport path 51 and in front of the image forming unit 2. The second passage sensor 59b is a detector that detects when the rear end 9e of the sheet 9 being transported along the retransmission path 55 has finished passing the pair of moving transport rolls 63. This second passage sensor 59b is positioned in the retransmission path 55 near the downstream side of the pair of moving transport rolls 63 in the transport direction C. The third passage sensor 59c is a detector that detects when the rear end 9e of the sheet 9 being transported along the reversal path 54 has finished passing the destination switching material 58b. This third passage sensor 59c is positioned in the vicinity of the reversal path 54, downstream of the destination switching material 58b in the transport direction C. For example, optical detection sensors can be used as the first pass sensor 59, the second pass sensor 59b, and the third pass sensor 59c.

[0086] The misalignment detector 65 is a detector that detects the deviation of the sheet 9 being transported along the final transport path 51 from the transport reference line CP in the axial direction (width direction) D. This misalignment detector 65 is positioned in the final transport path 51 between the moving transport roll pair 61 and the first downstream first transport roll pair 711, which is the first to be placed upstream of the moving transport roll pair 61 in the transport direction C. For example, the misalignment detector 65 may be an image reading sensor, an image processing device, or the like.

[0087] Furthermore, the sheet transport device 5 includes a control unit 13, as shown in Figure 6.

[0088] The control unit 13 is composed of a microcomputer or other device consisting of an arithmetic processing unit, a memory unit, an input / output device, etc. The control unit 13 may be configured as an independent control device, or, as shown in Figure 1, it may be configured as a part of the control function of the control device 12, which comprehensively controls the overall operation of the image forming apparatus 1.

[0089] As shown in Figure 6, the control unit 13 is connected to the transport drive control unit 501, the roll-to-move drive control unit 502, the roll-to-separate drive control unit 503, etc., in a way that enables information communication.

[0090] The transport drive control unit 501 is the part that controls the transport operation in each transport path. The transport drive control unit 501 is connected to the following as its control targets: the final transport path drive unit 510, the first transport path drive unit 530, the second transport path drive unit 560, the third transport path drive unit 570, the discharge path drive unit 520, the reversal path drive unit 540, the retransmission path drive unit 550, the transport path switching drive unit 580, and so on.

[0091] The final transport path drive unit 510 is a drive unit related to the transport operation of the final transport path 51. The final transport path drive unit 510 consists of, for example, the drive motor 616M for the mobile transport roll pair 61, and the drive motors 707M1, 707M2 for the first transport roll pairs 711, 712, etc. The first transport path drive unit 530 is a drive unit related to the transport operation of the first transport path 53. The second transport path drive unit 560 is a drive unit related to the transport operation of the second transport path 56. The third transport path drive unit 570 is a drive unit related to the transport operation of the third transport path 57.

[0092] The discharge path drive unit 520 is a drive unit related to the transport operation of the discharge path 52. The reversal path drive unit 540 is a drive unit related to the transport operation of the reversal path 54. The retransmission path drive unit 550 is a drive unit related to the transport operation of the retransmission path 55. The transport path switching drive unit 580 is a drive unit related to the switching operation of the transport destination switching materials 58a and 58b.

[0093] The roll-to-move drive control unit 502 is a drive unit for the movement of two sets of mobile transport rolls 61 and 63. The roll-to-move drive control unit 502 is composed of drive motors 617M, 637M, etc.

[0094] The roll pair separation drive control unit 503 is a drive unit related to the separation operation of separable transport roll pairs 711, 712, 713, 751, 752, etc. The roll pair separation drive control unit 503 is composed of drive motors 709M1, 709M2, 709M3, 709M5, 709M6, etc.

[0095] Furthermore, as shown in Figure 6, the control unit 13 is connected to the sheet size detection unit 14, the first passage sensor 59a, the second passage sensor 59b, the third passage sensor 59c, the positional displacement detector 65, and various other sensors 16, etc., in a manner that enables information communication.

[0096] The sheet size detector 14 is configured as an acquisition unit that acquires size information of the sheet 9 included in the command information for the image forming operation input to the image forming apparatus 1, or as a measuring instrument that measures the sizes of the sheets 9A, 9B, and 9C housed in the supply units 3A, 3B, and 3C. The other various sensors 16 are a group of sensors that detect various types of information necessary for the transport operation of the sheet 9, etc.

[0097] (An action to correct axial misalignment during sheet transport) In the sheet conveying device 5, as illustrated in Figure 7(A), the sheets 9 (9A, 9B, 9C) being conveyed along the final conveying path 51 may be transported with their positions in the axial direction D shifted relative to the conveying reference line CL.

[0098] The sheet conveying device 5 shown in Figure 7(A) employs a center register system, for example, in which the center position in the axial direction D of the final conveying path 51 is set as the conveying reference line CL, and the center position in the width direction of the sheet 9 is aligned with the conveying reference line CL to perform the conveying operation. TaThis scenario is assumed. In Figure 7(A), the sheet 9 sent from the first supply unit 3A is transported via the first transport path 53 to the final transport path 51. The dashed line denoted by Sc in Figure 7(A), etc., indicates the center line connecting the central points in the width direction of the sheet 9 during transport.

[0099] In contrast, the sheet conveying device 5 is configured such that if there is a displacement α in the axial direction D detected by the misalignment detector 65, the pair of moving conveying rolls 61 will move by a required distance α in the required directions Da and Db in the axial direction D while still holding the sheet 9, in order to correct the displacement α. Figure 7(B) illustrates the case when the pair of moving conveying rolls 61 moves in the required direction Db in the axial direction D.

[0100] Furthermore, in the sheet conveying device 5, when the amount of displacement α in the axial direction D of the sheet 9 re-transmitted from the re-transmitting path 55 to the final conveying path 51 exceeds a predetermined value M, the two pairs of movable conveying rolls 61 and 63 are configured to move by a required distance α in the required directions Da and Db in the axial direction D while still holding the sheet 9, as shown in Figures 13(A) and 20(B). Figure 20(B) also illustrates the case where the two pairs of movable conveying rolls 61 and 63 move in the required direction Db in the axial direction D.

[0101] However, in the sheet conveying device 5 that performs this movement operation, if the conveying operation continues with one pair of moving conveying rolls 61 moved by the required distance α in the axial direction D, the sheet 9 may end up in a state of conveyance failure, as illustrated in Figure 20(A). In other words, when the mobile transport roll pair 61 moves, the sheet portion (the rear portion during transport) passing through a portion of the multiple first transport roll pairs 711, 712, 713, which are located upstream of the mobile transport roll pair 61 in the transport direction C, may become oblique or distorted.

[0102] Furthermore, in the sheet conveying device 5, even if the conveying operation continues with the two pairs of movable conveying rolls 61 and 63 moved by the required distance α in the axial direction D, the sheet 9 may still be in a state of conveying failure, as illustrated in Figure 20(B). In this case, the conveying failure may occur when the moving conveying roll pair 61, 63 moves, causing a portion of the sheet passing through some of the multiple third conveying roll pairs 751, 752, 753, which are located upstream of the upstream moving conveying roll pair 63 in the conveying direction C, to become skewed or distorted.

[0103] In these cases, the rear portion of the sheet 9 passes through the moving transport roll pair 61 in an oblique or distorted state, and is then introduced into and passes through the image transfer section 21 of the image forming section 2. As a result, in the image forming apparatus 1, the image on the sheet 9 is not formed properly at the required position.

[0104] (Configuration related to the transport operation when moving a pair of mobile transport rolls) Therefore, as shown in Figures 8 to 10, the sheet conveying device 5 according to Embodiment 1 is configured such that at least a portion of the first conveying roll pair 711, 712, 731-734, which is located upstream of the moving conveying roll pair 61 in the conveying direction C, separates from at least a portion of the sheet portion 9t being conveyed, which is located upstream of the moving conveying roll pair 61, when the moving conveying roll pair 61 is moved in the axial direction D.

[0105] Furthermore, as shown in Figures 11 to 13, the sheet conveying device 5 is configured such that at least a portion of the third conveying roll pair 751 to 757, which is located upstream of the upstream moving conveying roll pair 63 in the conveying direction C, separates from at least a portion of the sheet portion 9t being conveyed, which is located upstream of the upstream moving conveying roll pair 63, when the two sets of moving conveying roll pairs 61 and 63 are moved axially D.

[0106] The first pair of conveying rolls to be separated is the first pair of conveying rolls positioned to grip the sheet portion 9t located upstream of the moving conveying roll pair 61. Here, we will explain assuming that the sheet portion 9t, which is being transported in a transport section upstream of the mobile transport roll pair 61 in the transport direction C, is scheduled to be held between the first transport roll pair 711 and 712, as shown in Figure 10. Therefore, in the scenario shown in Figure 10, the first pair of conveying rolls that separate the 9t sheet portion during transport without pinching it would be all (both) of the first pair of conveying rolls 711 and 712.

[0107] Furthermore, the third pair of conveying rolls that are separated are the first pair of conveying rolls, which are positioned to grip the sheet portion 9t located upstream of the upstream moving conveying roll pair 63. Furthermore, this explanation assumes that the sheet portion 9t, which is being transported in a transport section upstream of the upstream mobile transport roll pair 63 in the transport direction C, is scheduled to be held between the third transport roll pair 751 and 752, as shown in Figure 13. Therefore, in the scenario shown in Figure 13, the third transport roll pair that separates the 9t sheet portion during transport without pinching it would be both of the third transport roll pairs 751 and 752.

[0108] In the sheet conveying device 5, when the mobile conveying roll pair 61 moves in the axial direction D, the control unit 13 calculates and identifies the target first conveying roll pair that will grip the sheet portion 9t being conveyed upstream of the mobile conveying roll pair 61, based on information such as the size of the sheet 9 and the distance from the mobile conveying roll pair 61 to each first conveying roll pair. Furthermore, in the sheet conveying device 5, when the two pairs of movable conveying rolls 61 and 63 move in the axial direction D, the control unit 13 calculates and identifies the third conveying roll pair that will grip the sheet portion 9t being conveyed upstream of the upstream movable conveying roll pair 63, based on information such as the size of the sheet 9, the distance from one pair of movable conveying rolls 61 to the other pair of movable conveying rolls 63, and the distance from the other pair of movable conveying rolls 61 to each third conveying roll pair.

[0109] Incidentally, the degree to which the driving roll and the driven roll in the first or third pair of conveying rolls are separated is sufficient if the gripping force applied by the pair of conveying rolls does not reach the sheet 9 during transport, and a gap is formed that allows the sheet 9 to move arbitrarily in the axial direction.

[0110] (Sheet transport device transport operation) Next, we will explain the main conveying operations of the sheet conveying device 5.

[0111] In the sheet transport device 5, image formation is performed by the image forming device 1. re Then, the sheet 9 of the type and size used for image formation is sent out from the sheet storage section of the transport source section 3 (Figure 8: Step S110). In Embodiment 1, the drawing shows the case in which the sheet 9 (9A) is sent out from the first supply section 3A, but this is for convenience only. 、 The sheet 9 that is fed out is not limited to the sheet 9A fed out from the first supply unit 3A. The sheet 9 (9A) sent from the first supply unit 3A is transported via the first transport path 53 to the final transport path 51. In the drawings from Figure 7 onward, the sheet 9 shown is one of sheets 9A, 9B, or 9C.

[0112] Next, the control unit 13 acquires the size information of the sheet 9 (step S111), and when the sheet 9 passes through the final transport path 51, the misalignment detector 65 detects the amount of misalignment α of the sheet 9 in the axial direction D (step S112).

[0113] The detection of the displacement amount α at this time is performed when the leading edge 9s of the sheet 9 passes through the measurement area of ​​the misalignment detector 65. The information detected by the misalignment detector 65 is sent to the control unit 13. While this detection of the displacement amount α is taking place, the transport operation of the first transport path 53 and the final transport path 51 is temporarily stopped.

[0114] Furthermore, the sheet 9, once transported to the final transport path 51, is straightened so that its leading edge 9s abuts against the space between the two moving transport rolls 61 and becomes nearly parallel to the axial direction D, and then transported a short distance so that it is held between the two moving transport rolls 61.

[0115] Almost simultaneously with the detection of the displacement amount α in step S112, the control unit 13 performs calculations regarding the first transport roll pair to be separated (step S113). In Embodiment 1, the first transport roll pair 711, 712, which are positioned to grip the sheet portion 9t as described above, are calculated.

[0116] and, vinegar If a displacement amount α is detected in step S112, one pair of mobile transport rolls 61 is moved by the required distance α in the axial direction D (step S114). This movement of the mobile transport rolls 61 is performed by the control unit 13 controlling the drive of the drive motor 617M via the roll pair movement drive control unit 502. re ru.

[0117] Furthermore, simultaneously with or immediately before the movement of the moving transport roll pair 61, the first transport roll pair 711 and 712, which are to be separated, are separated (step S115). This separation is performed by the control unit 13 controlling the drive of the drive motors 709M1 and 709M2 in the separation device 708 via the roll pair separation drive control unit 503.

[0118] When the moving transport roll pair 61 moves and the first transport roll pair 711, 712 separates, the sheet 9 is moved axially D while being held between the moving transport roll pair 61, as shown in Figure 10(A). In this case, the portion 9t of the sheet 9 being transported is not gripped by the first transport roll pair 711, 712 and is in an open, easily movable state. As a result, the sheet 9 is as shown in Figure 10. B As shown in ), the entire assembly is moved by the same distance in the axial direction D in synchronization with the moving transport roll pair 61. As a result, the sheet 9, which was being transported with a misalignment in the axial direction D, now has its center line Sc almost coincide with the transport reference line CL, and its misalignment in the axial direction D is corrected.

[0119] Furthermore, once the movement of the mobile transport roll pair 61 is completed, the transport operation of the necessary sheet transport paths, such as the first transport path 53 and the final transport path 51, is resumed. As a result, the sheet 9 is fed out while being held only by the pair of moving transport rolls 61 with the misalignment in the axial direction D corrected, and is transported to be sent to the image forming unit 2.

[0120] Next, after the transport operations of the first transport path 53, the final transport path 51, etc. are resumed, the control unit 13 determines whether or not the rear end 9e of the sheet 9A has passed the pair of moving transport rolls 61 (step S116). At this point, the fact that the rear end 9e of the sheet 9 has passed the moving transport roll pair 61 is confirmed by the detection of the rear end 9e by the first passing sensor 59a.

[0121] If it is confirmed in step S116 that the rear end 9e of the sheet 9 has passed the moving conveyor roll pair 61, the control unit 13 controls the moving conveyor roll pair 61 back to its original position before movement (normal reference position), and the separated first conveyor roll pair 711 and 712 are returned to their normal contact state (step S117). This prepares the machine for the next transport operation.

[0122] Next, the control unit 13 determines whether or not there is any inversion transport of the sheet 9 (step 118).

[0123] If it is determined in step 118 that there is no need for inversion transport to sheet 9, the transport operation to sheet 9 is terminated. In this case, the sheet 9 with the image formed on one side is transported via the discharge passage 52 and finally stored in the discharge section 11.

[0124] (Transport operation when reverse transport is involved) On the other hand, if it is determined in step 119 that there is a reverse transport to sheet 9, that reverse transport will continue.

[0125] In the reverse transport process, the sheet 9, which first passes through the image forming section 2 and has an image formed on one side, is guided to the reverse transport path 54 by a transport destination switching material 58a from the middle of the discharge path 52.

[0126] In this process, the sheet 9 is transported and fed through the inlet path 54a of the reversal path 54 to the reversal discharge path 54b in the forward direction indicated by arrow Cf (see Figures 2 and 12). At this time, when the rear end 9e of the sheet 9 is detected by the third passage sensor 59c, it is temporarily stopped within the reversal discharge path 54b.

[0127] Next, the sheet 9, which has been transported to the reversal path 54, is fed out from its rear end 9e in the reverse direction indicated by arrow Cr (see Figures 2 and 12) as the transport roll pair 744 in the reversal feed path 54b rotates in the reverse direction (Figure 11: Step S120). In this case, the reversal path 54 (specifically the reversal feed path 54b) becomes the source of the sheet 9. As a result, the sheet 9 is sent to the retransmission path 55 with its front and back sides reversed. Subsequently, the reversed sheet 9 is transported via the retransmission path 55 to the final transport path 51.

[0128] Next, in the control unit 13, when the inverted sheet 9 passes through the final transport path 51, the misalignment detector 65 detects the amount of misalignment α of the sheet 9 in the axial direction D (step S121).

[0129] Next, the control unit 13 determines whether the sheet 9 is of a length that can be gripped by the upstream moving transport roll pair 63 (step S122).

[0130] If, in step S122, it is determined that the sheet 9 is of a length that will be gripped by the downstream mobile conveying roll pair 61 but not by the upstream mobile conveying roll pair 63, the process proceeds to step S114 (see Figure 8) as shown in Figure 11. In this case, sheet 9 will undergo the transport operation from steps S114 to S118 shown in Figure 8.

[0131] On the other hand, if in step S122 it is determined that the sheet 9 is of a length that will be gripped by the upstream moving transport roll pair 63, the control unit 13 determines whether or not there is a portion of the sheet 9 (the rear portion during transport) 9t that will be gripped by the third transport roll pair 751 to 757 (step S123).

[0132] In step S123, if it is determined that the sheet 9 has a portion 9t of the sheet that is held between the third conveyor roll pair 751 to 757, the calculation is performed for the third conveyor roll pair that will be subject to increasing the conveying speed (step S124). At this point, the sheet 9 is held between both pairs of moving conveyor rolls 61 and 63, and is also held between a portion of the third conveyor roll pair 751 to 757, making it a relatively long sheet, or what is known as a long sheet. In Embodiment 1, the third transport roll pair 751,752 is calculated, which is positioned to grip the sheet portion 9t as in the above-described assumption.

[0133] After the calculation in step S124 is completed, both sets of mobile conveying rolls 61 and 63 are moved by the required distance α in the axial direction D, and the second conveying rolls 711, 712, and 731 positioned between the two sets of mobile conveying rolls 61 and 63 are separated (step S125). The movement of the two sets of mobile transport roll pairs 61 and 63 is performed by the control unit 13 controlling the drive of the drive motors 617M and 637M in the mobile device 637 via the roll pair movement drive control unit 502. re Furthermore, the separation operation of the second transport roll pair 711, 712, 731 is performed by the control unit 13 controlling the drive of the drive motors 709M1, 709M2, and 709M3 in the separation device 708 via the roll pair separation drive control unit 503. re ru.

[0134] When the two sets of mobile transport rolls 61 and 63 are moved, the second transport rolls 711, 712, and 731 are separated. As a result, the portion of the sheet 9 that was held between the two pairs of mobile conveying rolls 61 and 63 is no longer held between them by the second pair of conveying rolls 711, 712, and 731, and can move smoothly in the axial direction D along with the movement of the two pairs of mobile conveying rolls 61 and 63.

[0135] Furthermore, simultaneously with or immediately before the movement of these two pairs of moving transport rolls 61 and 63, the third transport roll pair 751 and 752, which are to be separated, are separated (step S126). This separation is performed by the control unit 13 controlling the drive of the drive motors 709M5 and 709M6 in the separation device 708 via the roll pair separation drive control unit 503.

[0136] When the moving transport roll pair 61,63 moves, the second transport roll pair 711,712,731 separates, and the first transport roll pair 711,712 separates, the sheet 9 is moved axially D while being held between the two sets of moving transport roll pairs 61,63. In this case, the sheet portion 9t of the sheet 9 that is being transported, located upstream of the upstream moving transport roll pair 63, is not gripped by the third transport roll pair 751, 752, but is in an open and easily movable state. As a result, the entire sheet 9 is moved by the same distance in the axial direction D in synchronization with the moving transport roll pair 61, 63, as shown in Figure 13(A). As a result, the sheet 9, which was being transported with a misalignment in the axial direction D, now has its center line Sc almost coincide with the transport reference line CL, and its misalignment in the axial direction D is corrected.

[0137] Furthermore, once the movement of the moving conveyor rolls 61 and 63 is completed, the conveying operations of the necessary sheet conveyor paths, such as the re-transfer path 55, the first conveyor path 53, and the final conveyor path 51, are resumed. As a result, the sheet 9 is carried while being held between the moving transport roll pair 61 and 63 with the misalignment in the axial direction D corrected, and finally, while being held only by the moving transport roll pair 61, it is sent out from the final transport path 51 and fed to the image forming unit 2.

[0138] Next, after the transport operation of the necessary sheet transport paths, such as the re-transport path 55 and the final transport path 51, is resumed, the control unit 13 determines whether or not the rear end 9e of the sheet 9 has passed the pair of moving transport rolls 61 (step S127). At this point, the fact that the rear end 9e of the sheet 9 has passed the moving transport roll pair 61 is confirmed by the detection of the rear end 9e by the first passing sensor 59a.

[0139] If, in step S123, it is determined that there is no portion of the sheet 9 that is held between the third conveyor roll pair 751 and 757, then, as shown in Figure 11, the process does not proceed to step S124, but to step S125. In this case, after completing the operation of step S125, the process does not proceed to the operation of step S126, but to the operation of step S127, as shown in Figure 11.

[0140] If it is confirmed in step S127 that the rear end 9e of the sheet 9 has passed the pair of moving conveyor rolls 61, the control unit 13 controls the two pairs of moving conveyor rolls 61 and 63 to return them to their original positions before movement (normal reference positions), and the separation of the second pair of conveyor rolls 711, 712, and 731 and the third pair of conveyor rolls 751 and 752 is released, returning them to their normal contact state (step S128). This prepares the machine for the next transport operation.

[0141] As a result, the inverted sheet 9 has an image formed on the back surface of its inverted side in the image forming unit 2. The sheet 9 with the image formed on the opposite side is then transported via the discharge passage 52 and finally stored in the discharge unit 11.

[0142] As explained above, in this sheet conveying device 5, when the sheet 9 is moved axially D by one pair of movable conveying rolls 61 or two pairs of movable conveying rolls 61, 63, the sheet portion 9t passing through part or all of the multiple first conveying roll pairs 711, 712 etc. or third conveying roll pairs 751, 752 etc., which are located upstream of the movable conveying roll pairs 61, 63, is prevented from becoming oblique or distorted. In more detail, compared to the case where the sheet conveying device 5 uses multiple pairs of first or third conveying rolls to grip the sheet portion 9t while it is being conveyed and without changing the conveying speed, the above-mentioned slanting and distortion of the sheet portion 9t as it passes is suppressed.

[0143] Furthermore, in this sheet conveying device 5, the first conveying roll pairs to be separated include all first conveying roll pairs (711, 712) that are gripping the sheet portion 9t located upstream of the moving conveying roll pair 61. In addition, the third conveying roll pairs to be separated include all third conveying roll pairs (751, 752) that are gripping the sheet portion 9t located upstream of the upstream moving conveying roll pair 63. This makes it easier to suppress the slanting and distortion of the sheet portion 9t compared to cases where the separating first conveyor roll pair is only a portion of the first conveyor roll pair (for example, only the first conveyor roll pair 711) that grips the sheet portion 9t located upstream of the moving conveyor roll pair 61, or where the separating third conveyor roll pair is only a portion of the third conveyor roll pair (for example, only the third conveyor roll pair 751) that grips the sheet portion 9t located upstream of the upstream moving conveyor roll pair 63.

[0144] Furthermore, in the image forming apparatus 1 to which this sheet transport device 5 is applied, when one pair of movable transport rolls 61 or two pairs of movable transport rolls 61, 63 are moved in the axial direction D in the sheet transport device 5, the skewing and distortion of the sheet portion passing through some or all of the first transport roll pairs 711, 712 etc. or the third transport roll pairs 751 to 758 can be suppressed as described above. As a result, the image forming unit 2 in the image forming apparatus 1 can more easily perform the normal formation of an image on the sheet 9.

[0145] Furthermore, in the image forming apparatus 1, the sheet transport device 5 is configured to include a re-transport path 55. Therefore, compared to a case where the sheet transport device 5 does not include a re-transport path 55, it becomes easier to align the image formation position on the back surface of the sheet 6 transported from the reversal path 64 (which is the sheet reversal section) with the image formation position on the front surface of the sheet 6.

[0146] Embodiment 2. Figures 14 to 19 show the sheet transport device 5, etc., according to Embodiment 2.

[0147] The sheet conveying device 5 according to the second embodiment differs from the sheet conveying device 5 according to the first embodiment in that some of the conveying operations have been modified, as described below, but the other parts are the same configuration. Therefore, in the following description and drawings, common components will be denoted by the same reference numerals used in the first embodiment, and their descriptions will be omitted unless necessary.

[0148] In the sheet conveying device 5 according to Embodiment 2, the first conveying roll pair to be separated is configured to be a portion of the first conveying rolls, including the downstreammost first conveying roll pair 711, which is located upstream of the moving conveying roll pair 61 and grips the sheet portion 9t. Moreover, in this case, the sheet conveying device 5 is configured so that multiple first conveying roll pairs located upstream of the first conveying roll pair to be separated, which grip the sheet portion 9t and do not separate it, create a difference in conveying speed between the first conveying roll pairs, causing the sheet portion 9t to be curved within the conveying space 50 during conveying. Embodiment 2 will be described assuming that, as shown in Figures 14 and 15, the only first conveyor roll pair to be separated is the upstream first conveyor roll pair 711, and the multiple first conveyor roll pairs that are not separated are the second and third first conveyor roll pairs 712 and 731 from the upstream end.

[0149] Furthermore, in this sheet conveying device 5, the separated third conveying roll pair is configured to include some of the third conveying rolls, including the downstreammost third conveying roll pair 751, which is located upstream of the upstream moving conveying roll pair 63 and grips the sheet portion 9t. Moreover, in this case, the sheet conveying device 5 is configured so that multiple third conveying roll pairs located upstream of the separated third conveying roll pair, which grip the sheet portion 9t and do not separate it, create a difference in conveying speed between the first conveying roll pairs, causing the sheet portion 9t to be curved within the conveying space 50 during transport. Embodiment 2 will be described assuming that, as shown in Figures 18 and 19, the separated third conveyor roll pairs are the upstreammost third conveyor roll pair 751 and the second upstream third conveyor roll pair 752, and the multiple third conveyor roll pairs that do not separate are the third and fourth upstream third conveyor roll pairs 753 and 754.

[0150] Furthermore, in the sheet conveying device 5, the conveying drive control unit 501 controls the difference in conveying speed between the first conveying roll pairs 712 and 731 that do not separate, above flow Second from First conveyor roll vs 71 2 While maintaining the transport speed at the normal transport speed V1, above From the flow 3 The second first conveyor roll vs 7 31 This is pre-configured to be caused by controlling the transport speed to change it to a high-speed transport speed V2 (>V1) which is faster than the normal transport speed V1. Furthermore, in the sheet conveying device 5, the conveying drive control unit 501 controls the difference in conveying speed between the non-separated third conveying roll pairs 753 and 754. Upstream While maintaining the transport speed of the third transport roll to 753 at the normal transport speed V1, above From the flow 2 This is pre-set to be caused by controlling the transport speed of the third transport roll pair 754 to a high transport speed V2 (>V1), which is faster than the normal transport speed V1.

[0151] At this time above Second first conveyor roll from the flow vs. 7 31 The high-speed conveying speed V2 is set to a speed at which the curved sheet portion does not come into contact with the conveying guide pair 831 located between the first conveying roll pair 712, 731, or at a speed at which it comes into only light contact. above From the flow 2 The high-speed transport speed V4 of the third transport roll pair 754 is also set from a similar perspective, based on the transport guide 855 located between the third transport roll pair 753 and 754. The high-speed transport speed V2 for the first transport roll pair 712 and the high-speed transport speed V4 for the third transport roll pair 754 are set to the same speed, but they may be set to different speeds.

[0152] (Sheet transport device transport operation) Next, the main conveying operations of the sheet conveying device 5 according to Embodiment 2 will be described.

[0153] In the sheet transport device 5, image formation is performed by the image forming device 1. re Then, the sheet 9 of the type and size used for image formation is sent out from the sheet storage section of the transport source section 3 (Figure 14: Step S130). In Embodiment 2, as in Embodiment 1, for convenience the drawing shows the case in which the sheet 9 (9A) is sent out from the first supply section 3A. The sheet 9 (9A) sent from the first supply unit 3A is transported via the first transport path 53 to the final transport path 51. In the drawings from Figure 15 onward, the sheet 9 shown is one of sheets 9A, 9B, or 9C.

[0154] Next, the control unit 13 acquires the size information of the sheet 9 (step S131), and when the sheet 9 passes through the final transport path 51, the positional displacement detector 65 detects the amount of displacement α of the sheet 9 in the axial direction D (step S132). While the above-mentioned displacement amount α is being detected, the transport operation of the first transport path 53 and the final transport path 51 is temporarily stopped.

[0155] Next, the control unit 13 determines whether there are three or more pairs of first conveying rolls that grip the sheet portion 9t (step S133).

[0156] If it is determined in step S133 that there are three or more pairs of first conveyor rolls to be gripped, the control unit 13 calculates which pairs of first conveyor rolls will be separated and which will not be separated, and also calculates which pairs of first conveyor rolls will have their conveying speed increased (step S134).

[0157] In Embodiment 2, the first conveying roll pairs that grip the sheet portion 9t consist of three first conveying roll pairs, 711, 712, and 731, based on the assumptions described above. Furthermore, in Embodiment 2, the first conveyor roll pair 711 is calculated as the object to be separated, as in the above-described assumption, while the first conveyor roll pairs 712 and 731 are calculated as the object not to be separated. In addition, in Embodiment 2, the first conveyor roll pair 731 is calculated as the object to be increased in speed.

[0158] Next, one pair of mobile transport rolls 61 is moved a required distance α in the axial direction D (step S135). Furthermore, simultaneously with or immediately before the movement of the moving transport roll pair 61, the first transport roll pair 711 that has become subject to separation is separated (step S136), and the transport speed of the first transport roll pair 712 that has become subject to speed increase is changed to increase speed (step S137).

[0159] The separation operation of the first transport roll pair 711 is performed by the control unit 13 controlling the drive of the drive motor 709M1 via the roll pair separation drive control unit 503. The acceleration of the first transport roll pair 712 is performed by the control unit 13 controlling the drive of the drive motor 709M2 via the transport drive control unit 501. After these operations are completed, the conveying operations of the necessary sheet conveying paths, such as the first conveying path 53 and the final conveying path 51, are resumed.

[0160] As the moving motion of the mobile transport roll pair 61, the separation of the first transport roll pair 711, and the acceleration of the first transport roll pair 731 occur, and the sheet 9 is transported, the sheet 9 is moved axially D while being held between the mobile transport roll pair 61 in the transport space 50 upstream of the first transport roll pair 712, as shown in Figures 15(A) and 16(A), and is also transported in a curved state within the transport space 50 between the first transport roll pairs 712 and 731.

[0161] In this state, the sheet portion 9t being transported is not gripped by the first transport roll pair 711 and is in an open, easily movable state. Furthermore, the sheet portion 9t is in a curved state and easily moves within the transport space 50 between the first transport roll pairs 712 and 731. As a result, the portion of the sheet 9t being transported, as shown in Figure 16(A), begins to move axially D, with the portion located downstream of the first transport roll pair 712 in the transport direction C, so as to closely follow the movement of the moving transport roll pair 61. Furthermore, when the sheet portion 9t being transported has a portion located upstream of the first transport roll pair 712 in the transport direction C, compared to transporting the sheet 9 without creating a difference in transport speed between the unseparated first transport roll pairs 712 and 731, or transporting the sheet 9 by pulling against each other, the portion of the sheet passing between the first transport roll pairs 712 and 731 is less likely to become oblique or distorted.

[0162] Then, as the sheet portion 9t being transported is released from being held by the first transport roll pair 712 and passes through, as shown in Figure 16(B), its rear end 9e moves to the moving transport roll pair 61 with the misalignment in the axial direction D resolved, as shown by the dashed line in the figure, from a state where it is slightly tilted with respect to the axial direction D as illustrated by the solid line in the figure. As a result, the sheet 9, which was being transported with a misalignment in the axial direction D, now has its center line Sc almost coincide with the transport reference line CL, and its misalignment in the axial direction D is corrected. The sheet 9 is then transported last by the moving transport roll pair 61 and fed to the image forming unit 2.

[0163] If it is determined in step S133 that there are fewer than three pairs of first conveying rolls to be gripped, the conveying operation cannot proceed to step S134 and beyond, and the conveying operation proceeds to step S113 as shown in Figure 8.

[0164] Next, after the transport operations of the first transport path 53, the final transport path 51, etc. are resumed, the control unit 13 determines whether or not the rear end 9e of the sheet 9A has passed the pair of moving transport rolls 61 (step S138).

[0165] Step S13 8If it is confirmed that the rear end 9e of the sheet 9 has passed the moving conveyor roll pair 61, the control unit 13 will control the moving conveyor roll pair 61 back to its original position before movement (normal reference position), and the separation of the downstream first conveyor roll pair 711 will be released and returned to its normal contact state, and furthermore, above From the flow 2 The transport speed of the second first transport roll pair 731 is returned to the normal speed (V1) (step S139). This prepares the machine for the next transport operation.

[0166] Next, the control unit 13 determines whether or not there is any inversion transport of the sheet 9 (step 140).

[0167] If it is determined in step 140 that there is no need for inversion transport of sheet 9, the transport operation for sheet 9 is terminated. In this case, the sheet 9, on which an image has been formed on one side in the image forming unit 2, is transported via the discharge passage 52 and finally stored in the discharge unit 11.

[0168] (Transport operation when reverse transport is involved) On the other hand, if it is determined in step 140 that there is a reverse transport of sheet 9, that reverse transport will continue. In the reverse transport process, the sheet 9, which first passes through the image forming section 2 and has an image formed on one side, is guided to the reverse transport path 54 by a transport destination switching material 58a from the middle of the discharge path 52.

[0169] Next, the sheet 9, which has been transported to the reversal path 54, is fed out from its rear end 9e in the reverse direction indicated by arrow Cr (see Figures 2 and 12) as the transport roll pair 744 in the reversal feed path 54b rotates in the reverse direction (Figure 17: step S160). In this case, the reversal path 54 (specifically the reversal feed path 54b) becomes the source of the sheet 9. As a result, the sheet 9 is sent to the retransmission path 55 with its front and back sides reversed. Subsequently, the reversed sheet 9 is transported via the retransmission path 55 to the final transport path 51.

[0170] Next, the control unit 13 detects the amount of displacement α of the sheet 9 in the axial direction D as the inverted sheet 9 passes through the final transport path 51 (step S161).

[0171] Next, the control unit 13 determines whether the sheet 9 is of a length that can be gripped by the upstream moving transport roll pair 63 (step S162).

[0172] If, in step S162, it is determined that the sheet 9 is of a length that will be gripped by the downstream mobile conveying roll pair 61 but not by the upstream mobile conveying roll pair 63, the process proceeds to step S133 (see Figure 14) as shown in Figure 17. In this case, sheet 9 will undergo the transport operation from steps S133 to S140 shown in Figure 14.

[0173] On the other hand, if in step S162 it is determined that the sheet 9 is of a length that can be gripped by the upstream moving conveyor roll pair 63, the control unit 13 determines whether or not there is a sheet portion 9t that can be gripped by the third conveyor roll pair 751 to 757 (step S163). Sheet 9 in this case will also be a long sheet as described above.

[0174] In step S163, if it is determined that the sheet 9 has a sheet portion 9t that is held between the third conveyor roll pair 751 and 757, a determination is made as to whether there are three or more third conveyor roll pairs that hold that sheet portion 9t (step S164).

[0175] If it is determined in step S165 that there are three or more pairs of third conveyor rolls gripping the 9t sheet portion, the number of third conveyor roll pairs to be separated and those not to be separated is calculated, and the number of third conveyor roll pairs to be increased in conveyance speed is also calculated (step S166).

[0176] In Embodiment 2, the first pair of conveying rolls that grip the sheet portion 9t at this time will be four pairs of third conveying rolls, 751 to 754, as in the assumption described above. Furthermore, in Embodiment 2, as in the above-described assumption, third conveyor roll pairs 751 and 752 are calculated as targets to be separated, and third conveyor roll pairs 753 and 754 are calculated as targets not to be separated. In addition, in Embodiment 2, third conveyor roll pair 754 is calculated as a target for speed increase.

[0177] After the calculation in step S166 is completed, both sets of mobile transport rolls 61 and 63 are moved by the required distance α in the axial direction D, and the second transport rolls 711, 712, and 731 positioned between the two sets of mobile transport rolls 61 and 63 are separated (step S166).

[0178] Furthermore, simultaneously with or immediately before the movement of these two pairs of mobile transport rolls 61 and 63, the third transport roll pair 751 and 752, which is to be separated, is separated (step S167), and the most above From the flow 2 The transport speed of the third transport roll against 754 is changed to increase (step S168). After these operations, the conveying operations of the necessary sheet conveying paths, such as the re-transfer path 55 and the final conveying path 51, are resumed.

[0179] When the sheet 9 is transported by the movement of these two sets of mobile transport rolls 61 and 63, the separation of the second transport rolls 711, 712, and 731, the separation of the third transport rolls 751 and 752, and the acceleration of the third transport roll 754, the sheet portion 9t being transported is transported as follows. In other words, as shown in Figures 18 and 19(A), the sheet portion 9t at this time is moved axially D within the transport space 50 between the upstream mobile transport roll pair 63 and the third transport roll pair 752 while being held between the mobile transport roll pair 61, and is transported in a curved state within the transport space 50 between the third transport roll pairs 753 and 754.

[0180] In this state, the sheet portion 9t being transported is not gripped by the third transport roll pair 751, 752 and is in an open, easily movable state. Also, the sheet portion 9t is in a curved state and easily moves within the transport space 50 between the third transport roll pair 753, 754. As a result, the portion of the sheet 9t being transported, as shown in Figure 19(A), begins to move axially D, with the portion located downstream of the third transport roll pair 753 in the transport direction C, so as to closely follow the movement of the moving transport roll pair 61,63. Furthermore, when the sheet portion 9t being transported is located upstream of the third transport roll pair 753 in the transport direction C, compared to transporting the sheet 9 without creating a difference in transport speed between the unseparated third transport roll pair 753 and 754, or transporting the sheet 9 by pulling it, the portion of the sheet passing between the third transport roll pair 753 and 754 is less likely to become oblique or distorted.

[0181] Then, as the sheet portion 9t being transported is released from being held by the third transport roll pair 753 and passes through, as shown in Figure 19(B), its rear end 9e moves toward the upstream moving transport roll pair 63, with the misalignment in the axial direction D being eliminated, as shown by the dashed line in the same figure, from a state where it is slightly tilted with respect to the axial direction D as illustrated by the solid line in the same figure. As a result, the sheet 9, which was being transported with a misalignment in the axial direction D, now has its center line Sc almost coincide with the transport reference line CL, and its misalignment in the axial direction D is corrected. The sheet 9 is then transported last by the moving transport roll pair 61 and fed to the image forming unit 2.

[0182] Furthermore, if it is determined in step S164 that there are fewer than three pairs of third transport rolls to be gripped, the process cannot proceed to the transport operation in step S165, and the process proceeds to the operation in step 166. In this case, after or immediately after the completion of step 167, the third transport roll pair 751, 752 that grip the sheet portion 9t are separated, as shown in Figure 16 (step 167). As a result, the sheet 9 is corrected for any misalignment in the axial direction D, in much the same manner as when the transport operation shown in Figure 11 in Embodiment 1 is performed.

[0183] After the operation in step S167, the transport operation of the necessary sheet transport paths, such as the re-transport path 55 and the final transport path 51, is resumed. Then, the sheet 9 is transported last by the moving transport roll pair 61 and fed to the image forming unit 2.

[0184] Next, after the transport operation of the necessary sheet transport paths, such as the re-transport path 55 and the final transport path 51, is resumed, the control unit 13 determines whether or not the rear end 9e of the sheet 9 has passed the pair of moving transport rolls 61 (step S169).

[0185] If, in step S163, it is determined that there is no portion of the sheet 9 that is held between the third conveyor roll pair 751 and 757, then, as shown in Figure 17, the process does not proceed to step S164, but to step S167. In this case, after completing the operation in step S166, the process does not proceed to the operations in steps S167 and S168, as shown in Figure 17, but proceeds to the operation in step S169.

[0186] If it is confirmed in step S169 that the rear end 9e of the sheet 9 has passed the moving conveyor roll pair 61, the control unit 13 controls the moving conveyor roll pair 61 back to its original position before movement (normal reference position), and the separation of the second conveyor roll pair 711, 712, 731 and the third conveyor roll pair 751, 752 is released and they are brought into contact, and the conveying speed of the third conveyor roll pair 754 is returned to the normal speed (V1) (step S170). This prepares the machine for the next transport operation.

[0187] Through the above operations, the inverted sheet 9 has an image formed on the back surface of its inverted side in the image forming unit 2. The sheet 9 with the image formed on the opposite side is then transported via the discharge path 52 and finally stored in the discharge unit 11.

[0188] As explained above, in this sheet conveying device 5, when the sheet 9 is moved axially D by one pair of movable conveying rolls 61 or two pairs of movable conveying rolls 61, 63, the sheet portion 9t passing through part or all of the multiple first conveying roll pairs 711, 712 etc. or third conveying roll pairs 751, 752 etc., which are located upstream of the movable conveying roll pairs 61, 63, is prevented from becoming oblique or distorted.

[0189] Therefore, in this sheet conveying device 5, the downstream first conveying roll pair 711 is a non-separating roll pair, and compared to a case where a certain section Ea is a section other than the second section Ea2, the sheet portion of the conveyed sheet 9 passing through the first conveying roll pair 711, 712, etc., is suppressed from becoming skewed or distorted.

[0190] Furthermore, in this sheet conveying device 5, the sheet 9 is conveyed in a curved state between multiple pairs of first or third conveying rolls that are not separated and are located upstream of the first or third conveying roll pair that is separated. As a result, the sheet portion passing between these multiple pairs of first or third conveying rolls that are not separated is prevented from becoming oblique or distorted.

[0191] Variant expression. The present invention is not limited to the configuration examples illustrated in each of the above embodiments, and necessary modifications and combinations may be made as long as they do not alter the gist of the invention as described in the claims. The present invention also includes, for example, the following modifications.

[0192] The sheet conveying device 5 may have only one pair of movable conveying rolls 61, without an upstream pair of movable conveying rolls 63. Specifically, for example, it may be a sheet conveying device without a re-feed path.

[0193] The number and configuration of the sheet transport paths may differ from those exemplified in Embodiments 1 and 2. In embodiments 1 and 2, an example was given in which three transport roll pairs 711, 712, and 731 are arranged as the first transport roll pair between two sets of mobile transport roll pairs 61 and 63. However, the number of first transport roll pairs arranged between the two sets of mobile transport roll pairs 61 and 63 may be one (single) or multiple other than three. Furthermore, regarding the sheet transport criteria, instead of the center register system exemplified in Embodiments 1 and 2, a so-called side register system may be adopted, for example. In the side register system, one end of either the left or right end in the axial direction D of the final transport path 51 is set as the end transport reference line, and the transport operation is performed by aligning the left and right ends in the width direction of the sheet 9 with the end transport reference line.

[0194] Furthermore, in Embodiment 2, the downstream pair of first conveyor rolls 711 was exemplified as the pair of first conveyor rolls to be separated from the first conveyor rolls intended to grip the sheet portion 9t during transport. However, in addition to the downstream pair of first conveyor rolls 711, other pairs of first conveyor rolls may also be included as the pair of first conveyor rolls to be separated, depending on conditions such as the length of the sheet portion 9t. Furthermore, in Embodiment 2, the third transport roll pair 751 and 752 are exemplified as the third transport roll pair to be separated from the third transport rolls intended to grip the sheet portion 9t during transport. 。 However, the third roll pair to be separated may be other third conveying roll pairs depending on conditions such as the length of the 9t sheet portion.

[0195] Furthermore, among the first or third conveyor roll pairs intended to grip the 9t sheet portion during transport, there may be two or more pairs that do not separate, depending on conditions such as the length of the 9t sheet portion. In this case, the sheet portion passing through should be transported in a curved state between the multiple such pairs of first or third conveyor rolls that do not separate. Furthermore, in Embodiment 1, the decision in step S123 (Figure 11) may be configured to be predetermined by the control unit 13 when it receives a command for image formation operation. stomach. In this case, the decision in step S123 can be omitted. Furthermore, in the second embodiment, the determination in step S133 (Figure 14) and the determinations in steps S162 and S163 (Figure 17) may be configured to be determined in advance by the control unit 13 when the command for the image forming operation is received. stomach. In this case, the decision in step S133 and the decisions in steps S162 and S163 can be omitted.

[0196] Furthermore, in the sheet conveying device 5, when two pairs of movable conveying rolls 61 and 63 are arranged, the upstream pair of movable conveying rolls 63 may be placed on a conveying path other than the re-conveying path 55. In embodiments 1 and 2, the upstream pair of movable conveying rolls 63 can also be placed on the second conveying path 56 or the third conveying path 57.

[0197] Furthermore, in the sheet conveying device 5, the first conveying roll pair positioned upstream of the moving conveying roll pair 61 in the conveying direction C is not limited to the conveying roll pair positioned in the final conveying path 51 and the first conveying path 53. Specifically, the first conveying roll pair may be the conveying roll pair positioned in the final conveying path 51 and the second conveying path 56, or the conveying roll pair positioned in the final conveying path 51 and the second conveying path 56.

[0198] Furthermore, in the sheet conveying device 5, if a difference in conveying speed is to be created in order to convey the sheet 9 in a curved state, instead of controlling the drive motor (adjusting the rotational speed) of the pair of conveying rolls whose conveying speed is to be increased, the conveying speed may be changed at the stage of the drive transmission mechanism that transmits the rotational power from the drive motor to the pair of conveying rolls whose speed is to be increased. Furthermore, the difference in conveying speed in this case is not limited to a configuration in which the conveying speed of the upstream conveying roll pair, which is located upstream in the conveying direction C, is changed to be faster than the conveying speed of the downstream conveying roll pair, which is initially located downstream of that conveying roll pair. If there are no obstacles to the overall sheet conveying, the configuration may also be such that the difference in conveying speed is created by changing the conveying speed of the downstream conveying roll pair to be slower than the conveying speed of the upstream conveying roll pair.

[0199] The image forming unit 2 in the image forming apparatus 1 only needs to be capable of forming an image on the sheet 9, and its form and other specifications are not particularly limited. Therefore, the image forming unit 2 may, for example, be of a type that sprays or transfers ink constituting the image onto the sheet 9. Furthermore, there are no particular restrictions on the type of image. The image may be, for example, an image that is formed entirely on one or both sides of the sheet 9. [Explanation of symbols]

[0200] 1 ...Image forming apparatus 2 ...Image forming unit 3 ... Source of transport 3A...First containment area (an example of a transport source area) 3B...Second containment section (an example of a transport source section) 3C...Third containment section (an example of a transport source section) 5. Sheet conveying device 9 sheets 9t...the sheet portion being transported 51…Final transport path (an example of a transport path where the first pair of transport rolls are located) 53…Second final conveyance path (an example of a conveyance path where the first conveyance roll pair is arranged) 55…Return path (an example of a conveyance path where the third conveyance roll pair is arranged) 61…Moving conveyance roll pair 63…Upstream moving conveyance roll pair 711…Lowermost first conveyance roll pair or second conveyance roll pair (an example) 711, 712, 731…First conveyance roll pair or second conveyance roll pair for separation (an example) 712, 731…First conveyance roll pair that does not separate (an example) 751, 752…Third conveyance roll pair for separation (an example) 753, 754…Third conveyance roll pair that does not separate (an example) C …Unloading direction D …Axial direction

Claims

1. A pair of mobile transport rolls capable of gripping and transporting a sheet, and moving in an axial direction intersecting the transport direction, Multiple pairs of first conveying rolls are arranged at intervals on the upstream side of the moving conveying roll pair in the conveying direction, and are used to grip and convey the sheet. A plurality of conveying guide pairs are arranged to form a sheet conveying space between the moving conveying roll pair and the plurality of first conveying roll pairs and between the plurality of first conveying roll pairs, Equipped with, At least a portion of the plurality of first conveying roll pairs are separated so as not to pinch at least a portion of the sheet being conveyed that is located upstream of the moving conveying roll pairs when the moving conveying roll pairs are moved in the axial direction. The first conveyor roll pair to be separated is a portion of the first conveyor roll pair that is holding the sheet portion during conveyance, including the downstream first conveyor roll pair. A sheet conveying device in which a plurality of pairs of first conveying rolls located upstream of the separating first conveying roll pair, which grip and do not separate the sheet portion, create a difference in conveying speed between them, thereby conveying the sheet portion in a curved state within the conveying space.

2. A pair of movable conveying rolls is provided, which are capable of gripping and conveying a sheet and moving in an axial direction intersecting the conveying direction, and which are spaced apart in the conveying direction. One or more pairs of second conveying rolls are positioned between the two aforementioned pairs of mobile conveying rolls to grip and convey the sheet, Multiple third conveying roll pairs are positioned at a distance upstream of the upstream conveying roll pair, which is located on the upstream side of the two sets of conveying roll pairs, and which grip and convey the sheet. A plurality of transport guide pairs are arranged to form a sheet transport space between the two sets of mobile transport roll pairs and between the plurality of third transport roll pairs, Equipped with, A sheet conveying device in which at least a portion of the plurality of third conveying roll pairs are separated so as not to pinch at least a portion of the sheet being conveyed that is located upstream of the upstream moving conveying roll pair when the two sets of moving conveying roll pairs are moved in the axial direction.

3. The sheet conveying device according to claim 1, wherein the first conveying roll pairs to be separated are all the first conveying roll pairs that are holding the sheet portion during conveying.

4. The sheet conveying device according to claim 2, wherein the separated third conveying roll pairs are all the third conveying roll pairs that are holding the sheet portion during conveying.

5. The separated third conveyor roll pair is a portion of the third conveyor roll pair that is holding the sheet portion during conveyance, including the downstream third conveyor roll pair. The sheet conveying device according to claim 2, wherein a plurality of third conveying roll pairs located upstream of the separating third conveying roll pair, which do not grip and separate the sheet portion, create a difference in conveying speed between them, thereby conveying the sheet portion in a curved state within the conveying space.

6. The sheet conveying device according to claim 1, wherein the separated first conveying roll pair is in a normal contact state when the moving conveying roll pair is not moving and when the moving conveying roll pair has finished conveying the sheet after moving.

7. The sheet conveying device according to claim 2, wherein the separated third conveying roll pair is in a normal contact state when the two sets of moving conveying roll pairs are not moving and when the moving conveying roll pairs have moved and finished conveying the sheet.

8. The sheet conveying device according to claim 1, wherein the sheet conveying path on which the plurality of first conveying roll pairs are arranged has a curved section in which at least a portion is curved.

9. The sheet conveying device according to claim 2, wherein the sheet conveying path between the two sets of movable conveying rolls is curved.

10. The sheet conveying device according to claim 9, wherein the sheet conveying path on which the plurality of third conveying roll pairs are arranged is a straight section that extends in a straight line for a certain distance from the upstream moving conveying roll pair.

11. A conveying source unit from which the sheet is conveyed, An image forming unit that forms an image on a sheet, A sheet transport device that transports a sheet from the transport source to the image forming unit, Equipped with, An image forming apparatus in which at least a portion of the sheet transport device is configured as the sheet transport device described in claim 1, 3, 6, or 8.

12. The transport source unit from which the sheets are transported, An image forming unit that forms an image on a sheet, A sheet transport device that transports a sheet from the transport source to the image forming unit, Equipped with, An image forming apparatus in which at least a portion of the sheet transport device is configured as the sheet transport device described in claim 2, 4, 5, 7, 9, or 10.

13. The conveying source unit is a sheet reversal unit that reverses the front and back surfaces of the sheet after it has passed through the image forming unit, The image forming apparatus according to claim 11 or 12, wherein at least a part of the sheet transport device includes a retransmission path for retransmitting the sheet transported from the sheet reversing unit to the image forming unit.

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