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 third conveyance guide pairs which are arranged so as to form a conveyance space of a sheet between the plurality of third conveyance roll pairs. At least a partial third conveyance guide pair of the plurality of third conveyance guide pairs is displaced in a direction of spreading the conveyance space when the two sets of movement conveyance roll pairs are moved in the axial direction.SELECTED DRAWING: Figure 13

Description

Technical Field

[0001] The present invention relates to a sheet conveyance 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 conveyance direction on the downstream side of the skew correction unit, and corrects the position of the sheet in the direction orthogonal to the sheet conveyance direction, and a sheet conveyance assist unit that is provided on the upstream side of the skew correction unit and is movable in a direction orthogonal to the sheet conveyance direction.

[0003] Further, Patent Document 1 describes that when the lateral registration correction unit moves the sheet in a direction orthogonal to the sheet conveyance direction to perform position correction after the skew correction unit has corrected the skew of the sheet, the sheet conveyance assist 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 conveyance rotators independently arranged on a line orthogonal to the sheet conveyance direction, and the skew of the sheet is corrected by the difference in the sheet conveyance speed of each pair of conveyance rotators, and the pressure contact of each pair of sheet conveyance rotators is released after the skew of the sheet is corrected.

[0004] Patent Document 2 describes a sheet conveyance device including two pairs of sandwich conveyance member pairs capable of conveying a sheet while sandwiching it and moving it in a width direction orthogonal to the conveyance direction. Further, Patent Document 2 describes that in the sheet conveyance device, while sandwiching one sheet with two pairs of sandwich conveyance member pairs, the sheet is moved in the width direction, and after the movement in the width direction, the two sandwich conveyance members forming the upstream sandwich conveyance member pair located on the upstream side in the conveyance direction of the two pairs of sandwich conveyance member pairs are separated, and the sheet is conveyed by the downstream sandwich conveyance member pair located on the downstream side in the conveyance direction of the two pairs of sandwich conveyance 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 project] [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 some or all of 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 all of the plurality of conveying guide pairs that are arranged to form a sheet conveying space between the movable conveying roll pairs and between the plurality of conveying roll pairs are fixed without displacement. [Means for solving the problem]

[0008] This invention ( 1 )teeth, 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 third conveying guide pairs are arranged to form a sheet conveying space between the plurality of third conveying roll pairs, Equipped with, At least some of the aforementioned plurality of third transport guide pairs are sheet transport devices that are displaced in a direction that expands the transport space when the two sets of movable transport roll pairs are moved in the axial direction.

[0010] This invention ( 2 ) is the above invention ( 1 In a sheet conveying device, The displaceable third transport guide pair is a sheet transport device that is the downstream third transport guide pair positioned between the upstream moving transport roll pair and the first downstream third transport roll pair among the plurality of third transport roll pairs that is upstream of the upstream moving transport roll pair.

[0012] This invention ( 3 ) is the above invention ( 1 In a sheet conveying device, Of the plurality of third conveyor roll pairs, at least the first and most downstream third conveyor roll pair located upstream of the upstream moving conveyor roll pair is a conveyor roll pair that can be separated, The displaceable third transport guide pair is a sheet transport device in which, when the downstreammost third transport roll pair is separated, the downstreammost third transport guide pair is located between the upstream moving transport roll pair and the downstreammost third transport roll pair, and the second downstreamst third transport guide pair is located between the downstreammost third transport roll pair and the first third transport roll pair upstream of that third transport roll pair, either or both.

[0013] This invention ( 4 ) is the above invention ( 3) In a sheet conveying device, The aforementioned lowest downstream The third Of the transport guide pair and the second-to-last-downstream third transport guide pair, the transport guide pair that is displaced is the one at the very bottom The third This sheet conveying device is characterized by the displacement of one of the conveying guide pairs, which is located on the same side as the moving roll, when the two conveying roll pairs separate.

[0014] The present invention ( 5 ) is a sheet conveying device in the above invention ( 3) ) where among the conveyance guide pair at the most downstream The third and the conveyance guide pair that is displaced among the conveyance guide pair at the second from the most downstream third conveyance guide pair, the conveyance guide pair that is displaced is arranged on the same side as the roll on the side that does not move when the conveyance roll pair at the most downstream The third separates.

[0015] The present invention ( 6 ) is a sheet conveying device in the above invention (1 )of ) where the displaced The third conveyance guide pair is The two sets mentioned above in the normal position before expanding the conveyance space when the moving conveyance roll pair of The two sets mentioned above does not move and when the moving conveyance roll pair of

[0016] has finished conveying the sheet after moving. 7 The present invention ( )of ) is a sheet conveying device in the above invention (1 ) where The third the displaced conveyance guide pair is composed of members that are displaced by the force received when a part of the sheet being conveyed comes into contact with the conveyance guide pair on the side where displacement occurs.

[0018] The present invention ( 8 ) is a sheet conveying device in the above invention ( 1 ), where the conveyance path of the sheet between the two sets of moving conveyance roll pairs is curved.

[0019] [[ID=5H]] The present invention ( 9 ) is a sheet conveying device in the above invention ( 8 ), where the conveyance path of the sheet on which the plurality of third conveyance roll pairs are arranged is composed of a straight section in which a certain section extends linearly from the upstream moving conveyance roll pair.

[0020] This invention ( 10 )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 the above invention (1). any of (9) This is an image forming apparatus consisting of a sheet transport device.

[0022] This invention ( 11 ) is the above invention ( 10 In a sheet conveying device, The transport 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]

[0023] The above invention (1 )of According to the sheet conveying device, it is possible to move in an axial direction intersecting the conveying direction of the sheet. na2 When moving a pair of mobile conveying rolls axially, the tendency for the sheet portion to diagonal or distorted as it passes through some or all of the multiple conveying roll pairs, which are spaced upstream of the mobile conveying roll pair in the conveying direction, can be suppressed compared to a case where all of the multiple conveying guide pairs, which are arranged to form a conveying space for the sheet between the mobile conveying roll pair and between multiple conveying roll pairs, are fixed without displacement.

[0025] The above invention ( 2 According to this, compared to cases where the displaced transport guide pair is a transport guide pair other than the first and furthest downstream transport guide pair upstream of the upstream moving transport roll pair, it becomes easier to suppress the slanting and distortion of the sheet portion as it passes through at least a part of the third transport roll pair.

[0027] The above invention ( 3According to this, compared to a case where the downstream third conveyor roll pair is a non-separating conveyor roll pair and the displaced conveyor guide pair is a conveyor guide pair other than the downstreammost conveyor guide pair and the second-to-last downstream conveyor guide pair, it becomes easier to suppress the slanting and distortion of the sheet portion as it passes through at least a part of the third conveyor roll pair.

[0028] The above invention ( 4 According to this, the displaced transport guide pair is configured such that the other transport guide pair, which is located on the same side as the roll that does not move when the transport roll pair separates, is displaced, compared to the case where the other transport guide pair is configured to displace. three This makes it easier to suppress the slanting or distortion of the sheet portion as it passes through at least a portion of the conveyor roll pair.

[0029] The above invention ( 5 According to this, compared to the case where the transport guide pair is fixed without displacement, Third transport This can prevent the sheet portion from becoming skewed or distorted while passing through at least a portion of the roll pair.

[0030] The above invention ( 6 According to this, the displaced transport guide pair, 2 sets Compared to when the pair of mobile conveying rolls does not move and when the conveying space is expanded after the pair of mobile conveying rolls has moved and finished conveying the sheet, this method allows for conveying the sheet without conveying defects or jamming at the leading edge.

[0031] The above invention ( 7 According to this, the displaceable transport guide pair can be made into a simpler structure compared to a case where the displaceable transport guide pair is composed of a member that does not displace due to the force it receives when a part of the sheet comes into contact with it during transport.

[0033] The above invention ( 8 According to the study, compared to the case where the sheet transport path between two pairs of mobile transport rolls is not curved, the sheet portion passing between the two pairs of mobile transport rolls tends to be more prone to slanting or distortion, but this can be suppressed.

[0034] The above invention ( 9 According to this, compared to a system where a certain section of the sheet transport path in which the third transport roll pair is located is not composed of a straight section, it becomes easier to suppress the slanting or distortion of the sheet portion as it passes through that section.

[0036] Furthermore, the above invention ( 10 In the image forming apparatus described above, when two pairs of movable transport rolls in a sheet transport device are moved axially, the sheet portion passing through some or all of the multiple third transport roll pairs, which are spaced further upstream in the transport direction than the upstream movable transport roll pair, can be suppressed compared to the case where all of the multiple transport guide pairs, which are arranged to form a sheet transport space between the movable transport roll pair and the transport roll pair and between the multiple transport roll pairs, are fixed without displacement, making it easier to form an image on the sheet normally.

[0037] The above invention ( 11 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]

[0038] [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] (A) is a schematic diagram of the transport guide pair when it is not displaced, and (B) is a schematic diagram of the transport guide pair when it is displaced. [Figure 9] This flowchart shows the transport operation when there is no reversal transport. [Figure 10] 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 11] (A) is an explanatory diagram showing the state of the sheet when the conveying operation in Figure 10 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 12] This is a flowchart illustrating the transport operation during reverse transport. [Figure 13] 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 14] (A) is an explanatory diagram showing the state of the sheet when the transport operation shown in Figure 13 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 15] This is a flowchart illustrating the transport operation when there is no inversion transport in Embodiment 2. [Figure 16] 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 17](A) is an explanatory diagram showing the state of the sheet when the transport operation shown in Figure 16 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 18] This is a flowchart illustrating the transport operation when reverse transport is involved. [Figure 19] 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 20] (A) is an explanatory diagram showing the state of the sheet when the transport operation shown in Figure 19 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 21] This is an explanatory diagram showing the state of the sheet when the transport operation is performed according to a modified example of Embodiment 2. [Figure 22] This is an explanatory diagram showing the state of the sheet when a transport operation is performed using another modification of Embodiment 2. [Figure 23] (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]

[0039] Hereinafter, embodiments for carrying out this invention will be described with reference to the drawings.

[0040] 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.

[0041] (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.

[0042] Furthermore, the image forming apparatus 1 is more specifically composed of a main body 10 and an extension 15, as shown in Figure 1.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] (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.

[0051] 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.

[0052] 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 first 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.

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] The first conveyor roll pairs 711 and 712 are multiple pairs of conveyor rolls that are spaced apart to form a sheet conveying path upstream of the mobile 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, which is initially positioned upstream of the mobile 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 of a sheet 9 of the maximum transportable length used in the image forming apparatus 1 that is located upstream of the transport direction C from the transport roll 61 when the sheet 9 is transported and gripped by the transport roll pair 61.

[0059] 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.

[0060] 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. 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.

[0061] 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.

[0062] The first 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 movable transport roll pair 61 and the first transport roll pairs 711, 712, and between the multiple first transport roll pairs 711, 712.

[0063] As shown in Figure 2, the first 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 first transport guide pairs 811 and 812 form a transport space 50 with a required height between them. Furthermore, the first transport guide pairs 811 and 812 may be composed of a guide member formed by integrating transport guides that are positioned on the same side between them. Also, a portion of the first 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 the other transport guide pairs as well.

[0064] 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 first conveyor guide pairs 811 and 812.

[0065] 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 conveyor path 53 is equipped with a plurality of conveyor roll pairs 731 to 734 and a first conveyor guide pair 830, etc. In Embodiment 1, as shown in Figure 9, the first conveyor path 53 is provided as a conveyor path consisting of a straight section 53(S) in which an intermediate section, which is an example of a certain section, extends in a nearly straight line, and as a conveyor path consisting of a curved section 53(C) in which an upstream section and a downstream section are curved, which is another example of a certain section.

[0066] 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 first transport guide pair 830 is composed of multiple transport guide pairs 831, 832, etc., arranged on the final transport path 51 side, and has almost the same configuration as the first transport guide pairs 811, 812. The first transport guide pair 830 is connected to the upstream end of the final transport path 51 in the transport direction C via the transport guide pair 831 at the downstream end in the transport direction C.

[0067] 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 a first transport guide pair 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.

[0068] 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 pairs 711 and 712. The first transport guide pair 860 is composed of multiple transport guide pairs and has almost the same configuration as the first transport guide pairs 811 and 812. The first 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.

[0069] 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 a first transport guide pair (not shown) with the exception of one transport guide pair 871. In Embodiment 1, the third transport path 57 is provided as a curved transport path throughout its entire length.

[0070] The conveyor roll pairs 771-773 are spaced apart in the conveying direction C to form a third conveying path 57, and have almost the same configuration as the first conveyor roll pairs 711 and 712. The first conveyor guide pair (not shown), including conveyor guide pair 871, has almost the same configuration as the first 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.

[0071] 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.

[0072] 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 first 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.

[0073] 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.

[0074] 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, 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. This conveyor guide pair also has almost the same configuration as the first conveyor guide pair 811, 812. Furthermore, 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.

[0075] 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.

[0076] 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.

[0077] The re-transfer path 55 includes one pair of movable transport rolls 63, a plurality of second transport roll pairs 711, 712, 731 positioned between the two pairs of movable transport rolls 61, 63, a plurality of third transport roll pairs 751 to 758 positioned upstream of the movable transport roll pair 63 in the transport direction C, a plurality of (second) transport guide pairs 811, 812, 831 positioned between the movable transport roll pairs 61, 63, a plurality of third transport guide pairs 851, 852, 851, 852, 851 to 858 positioned upstream of the upstream movable transport roll pair 63 in the transport direction C, and so on. 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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)).

[0084] 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) with the third conveyor roll pair 751-753, has a drive unit 706 and a pair of drive rolls 751a, 752a, 753a and driven rolls 751b, 752b, 753b. Incidentally, the third transport roll pair is a general term for multiple transport roll pairs positioned to grip the portion of a sheet 9 of the maximum transportable length used in the image forming apparatus 1 that is located upstream of the upstream transport roll 63 in the transport direction C when the sheet 9 is transported and gripped by two sets of movable transport roll pairs 61 and 63.

[0085] The driven rolls 751a, 752a, 753a and the driven rolls 751b, 752b, 753b have the same configuration as the driven rolls 711a, 712a, 713a and driven rolls 711b, 712b, 71b 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)).

[0086] Furthermore, as shown in Figure 5, the sheet conveying device 5 is also configured as a separable conveying roll pair in which 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 can be separated. These transport roll pairs 711, 712, 731, and 751 are equipped with a separation device 708.

[0087] 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 shafts 702 of the driven rolls 711b, 712b, 731b, and 751b away from the rotating shaft 701 against the biasing force of the biasing member 705. As a result, the driven rolls 711b, 712b, 731b, and 751b are separated from the driven rolls 711a, 712a, 731a, and 751a. 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] Furthermore, the sheet transport device 5 includes a control unit 13, as shown in Figure 6.

[0093] 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.

[0094] 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.

[0095] 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 roll pair drive unit 510, the transport path switching drive unit 580, and other components as its control targets. The roll pair drive unit 510 is a drive unit consisting of a drive motor and the like that rotates each pair of conveying rolls. The conveying path switching drive unit 580 is a drive unit related to the switching operation of the conveying destination switching materials 58a and 58b.

[0096] 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. 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, etc. The roll pair separation drive control unit 503 is composed of drive motors 709M1, 709M2, 709M3, 709M5, etc.

[0097] 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., so that information can be communicated.

[0098] 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 contained 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.

[0099] (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.

[0100] The sheet conveying device 5 shown in Figure 7(A) assumes, for example, that a center register system is employed 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 for conveying operation. Also, in Figure 7(A), it is assumed that the sheet 9 sent out from the first supply unit 3A is conveyed to the final conveying path 51 via the first conveying path 53. The dashed line denoted by Sc in Figure 7(A), etc., indicates the center line connecting the center points in the width direction during conveying of the sheet 9.

[0101] In contrast, the sheet conveying device 5 is configured such that, as illustrated in parts of Figure 7(B) and Figure 8, when the displacement amount α in the axial direction D is detected by the displacement detector 65 and exceeds a predetermined value (threshold: M), the pair of moving conveying rolls 61 moves 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 amount α. Figure 7(B) illustrates the case where the pair of moving conveying rolls 61 moves in the required direction Db in the axial direction D.

[0102] Furthermore, in the sheet conveying device 5, if 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 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 23(B). Figure 23(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.

[0103] 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 23(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.

[0104] 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 23(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 a plurality of 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.

[0105] 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.

[0106] (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 some of the multiple pairs of first conveying guides 811, 812, 831, 832, ... which are located upstream of the pair of moving conveying rolls 61 in the conveying direction C, are displaced in a direction that widens the conveying space 50 formed by the first conveying guide pairs 811, etc., when the pair of moving conveying rolls 61 is moved in the axial direction D.

[0107] Furthermore, as shown in Figures 8, 12, 13, etc., this sheet conveying device 5 is located upstream of the upstream moving conveying roll pair 63 in the conveying direction C, and at least some of the third conveying guide pairs 852, 813, 834, 835, ... However, 2 When the pair of movable transport rolls 61 and 63 of the set are moved axially D, they are configured to be displaced in a direction that widens the transport space 50 formed by the third transport guide pair 852, etc.

[0108] In Embodiment 1, the displaceable first transport guide pair is the downstream first transport guide pair 811, which is positioned between the movable transport roll pair 61 and the downstream first transport roll pair 711, which is the first one upstream of the movable transport roll pair 61 in the transport direction C, among the multiple first transport roll pairs 711, 712, 731, ... In Embodiment 1, the displaceable third transport guide pair is the downstream third transport guide pair 852, which is positioned between the upstream moving transport roll pair and the first downstream third transport roll pair that is upstream of the upstream moving transport roll pair among the plurality of third transport roll pairs.

[0109] Both the first transport guide pair 811 and the third transport guide pair 852, which are displaced, are composed of a pair of guide bodies 802a and 802b, as shown in Figure 8. The guide bodies 802a and 802b are rotatably mounted on the mounting shafts 802c and 802d at the upstream or downstream end of the sheet 9 in the transport direction C, so as to allow the transport space 50 to be expanded. In addition, the guide bodies 802a and 802b are in contact with positioning pins 802e and 802f at the downstream or upstream end opposite to the mounting shafts 802c and 802d in the transport direction C, which stop the transport space 50 in its normal position before expansion.

[0110] The first transport guide pair 811 and the third transport guide pair 852, which are displaced, are configured to be displaced in the following manner. In other words, Seat 9 is, As shown in Figure 8(B), when the mobile transport roll pair 61 moves in the axial direction D, the mobile transport roll pair 61 and the first transport roll pair 711 located upstream of it move in a state of being gripped by them. Distorted It deforms (changes) in a certain way. Therefore, the displaced first transport guide pair 811 and the third transport guide pair 852 are moved around the mounting shaft 802c as a fulcrum by receiving an external force when the distorted portion 9m of the sheet 9 comes into contact with one of the guide bodies 802a. In addition, the displaced first transport guide pair 811 and the third transport guide pair 852 are also moved around the mounting shaft 802d as a fulcrum when the distorted portion 9m of the sheet 9 comes into contact with the other guide body 802b, depending on the direction of deformation of that portion 9m.

[0111] Then, the transport space 50 consists of a transport space 50n, which is the normal size before expansion as shown in Figure 8(A), and a transport space 50p, which is larger than the normal size when expanded as shown in Figure 8(B).

[0112] Furthermore, in Embodiment 1, the guide bodies 802a and 802b are composed of members that displace due to the force they receive when a portion 9m of the sheet 9 comes into contact with them during transport. These displaced members include not only displacement to a different position, but also displacement by deforming to bend when subjected to an external force. These displaced members are made of an elastically restorable film material such as synthetic resin.

[0113] (Sheet transport device transport operation) Next, we will explain the main conveying operations of the sheet conveying device 5.

[0114] In the sheet transport device 5, once image formation is performed by the image forming device 1, 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 9: Step S110). In Embodiment 1, the drawing shows the case where the sheet 9 (9A) is sent out from the first supply section 3A, but this is for convenience only, and the sheet 9 sent out is not limited to the sheet 9A 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 7 onward, the sheet 9 shown is one of sheets 9A, 9B, or 9C.

[0115] 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).

[0116] 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. Furthermore, the sheet 9 transported to the final transport path 51 is straightened so that its leading edge 9s abuts against the rollers of the pair of moving transport rolls 61 and becomes approximately parallel to the axial direction D. After that, it is transported a short distance so that it is held between the rollers of the pair of moving transport rolls 61, and then temporarily stops. Until the results of the detection of the above-mentioned displacement amount α are obtained, the transport operation of the first transport path 53 and the final transport path 51 is temporarily stopped.

[0117] Next, one pair of mobile transport rolls 61 is moved a required distance α in the axial direction D (step S113). The movement of the mobile transport roll pair 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.

[0118] At this time, the sheet 9 is held between the moving conveyor roll pair 61 and the first conveyor roll pair 711, 712, and its leading edge 9s is moved axially D by the moving conveyor roll pair 61. As a result, when the sheet 9 moves in accordance with the axial movement D of the mobile conveying roll pair 61, it deforms (fluctuations) by bending upward or in other directions between the mobile conveying roll pair 61 and the downstream first conveying roll pair 711, as shown in Figures 10 and 11(A). The part indicated by the reference numeral 9m in Figures 10 and 11(A) is the part that has been distorted and deformed.

[0119] Furthermore, at this time, the distorted and deformed portion 9m of the sheet 9 comes into contact with the downstream first conveyor guide pair 811, which is positioned between the moving conveyor roll pair 61 and the downstream first conveyor roll pair 711. As a result, the downstream first transport guide pair 811 is displaced upward (step S114) when the deformed portion 9m, which is bent and distorted above the sheet 9, comes into contact with one of the guide bodies 902a (see Figure 8) in a way that pushes it upward from below. Consequently, the transport space 50 in the downstream first transport guide pair 811 becomes a transport space 50p that is wider than the transport space 50n before the displacement by the amount of the displacement, as shown in Figures 8 and 10. As a result, the deformed portion 9m of sheet 9 has more space to move within the transport space 50p, increasing the degree of freedom to adjust its state.

[0120] Ultimately, Sheet 9 at this point is shown in Figure 1. 1 As shown in (B), when the rear portion of the conveying material is released from being gripped by the first conveying roll pair 711 at the very bottom and passes through, the rear end 9e moves to the moving conveying roll pair 61 within the expanded conveying space 50p, from a state in which it is slightly tilted with respect to the axial direction D as illustrated by the solid line in the figure, to a state in which the misalignment in the axial direction D is eliminated as shown by the dashed line in the figure. As a result, the rear portion of sheet 9 during transport will also be positioned so that its center line Sc is approximately aligned with the transport reference line CL.

[0121] Furthermore, once the movement of the pair of moving transport rolls 61 in the axial direction D is completed, the transport operations of the first transport path 53, the final transport path 51, etc. are resumed. As a result, the sheet 9 is transported by the pair of moving transport rolls 61, which are in a state where they have moved in the axial direction D, and is ultimately fed to the image forming unit 2.

[0122] 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 S115). 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.

[0123] If it is confirmed in step S115 that the rear end 9e of the sheet 9 has passed the pair of moving conveyor rolls 61, the control unit 13 controls the pair of moving conveyor rolls 61 back to its original position before movement (normal reference position) (step S117). In addition, when the sheet 9 passes over the first conveyor guide pair 811 at the very downstream end, the guide body 802a of the first conveyor guide pair 811 descends due to gravity and returns to its normal position. This prepares the machine for the next transport operation.

[0124] Next, the control unit 13 determines whether or not there is any inversion transport of the sheet 9 (step 117).

[0125] If it is determined in step 117 that there is no need for inverted transport of sheet 9, the transport operation for sheet 9 at this time is terminated. In this case, the sheet 9 on which the 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.

[0126] (Transport operation when reverse transport is involved) On the other hand, if it is determined in step 117 that there is a reverse transport to sheet 9, that reverse transport will continue.

[0127] 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.

[0128] At this time, 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 13). Also 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.

[0129] 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 13) as the transport roll pair 744 in the reversal feed path 54b rotates in the reverse direction (Figure 12: 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.

[0130] 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).

[0131] 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).

[0132] 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, then the process proceeds to step S113 (see Figure 9) as shown in Figure 12. In this case, sheet 9 will undergo the transport operation from steps S113 to S117 shown in Figure 9.

[0133] 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 that will be gripped by the third transport roll pair 751 to 757 (the rear portion during transport) (step S123).

[0134] In step S123, if it is determined that there is a portion of the sheet 9 that is held between the third conveyor roll pair 751 and 757, both sets of two mobile conveyor roll pairs 61 and 63 are moved by the required distance α in the axial direction D, and the second conveyor roll pair 711, 712, and 731 positioned between the two sets of mobile conveyor roll pairs 61 and 63 are separated (step S124).

[0135] The movement of the two sets of mobile transport roll pairs 61 and 63 is performed by the control unit 13 controlling the drives of the drive motors 617M and 637M in the transport device 637 via the roll pair movement drive control unit 502. The separation of the second transport roll pair 711, 712, and 731 is performed by the control unit 13 controlling the drives of the drive motors 709M1, 709M2, and 709M3 in the separation device 708 via the roll pair separation drive control unit 503.

[0136] At this time, the sheet 9 is held between two pairs of moving conveyor rolls 61 and 63 and a part of the third conveyor roll pair (third conveyor roll pair 751 and 752 in Embodiment 1), and its leading edge 9s side is moved axially D by the moving conveyor roll pair 61. As a result, when the sheet 9 moves in accordance with the axial movement D of the moving conveyor roll pair 61, it deforms (changes) by bending upward or in other directions between the upstream moving conveyor roll pair 63 and the downstream third conveyor roll pair 751, as shown in Figures 13 and 14(A). The part indicated by the reference numeral 9m in Figures 13 and 14(A) is the part that has been distorted and deformed.

[0137] Furthermore, at this time, the distorted and deformed portion 9m of the sheet 9 comes into contact with the downstream third conveyor guide pair 852, which is positioned between the upstream moving conveyor roll pair 63 and the downstream third conveyor roll pair 751.

[0138] As a result, the downstream third transport guide pair 852 is displaced upward (step S125) when a portion 9m that has deformed to bend and distort above the sheet 9 comes into contact with one of the guide bodies 902a (see Figure 5) in a way that pushes it upward from below. Consequently, the transport space 50 in the downstream third transport guide pair 852 becomes a transport space 50p that is wider than the transport space 50n before the displacement by the amount of the displacement, as shown in Figures 5 and 13. As a result, the deformed portion 9m of sheet 9 has more space to move within the transport space 50p, increasing the degree of freedom to adjust its state.

[0139] Finally, as shown in Figure 14(B), when the rear portion of sheet 9 is released from being gripped by the third pair of transport rolls 751 at the very bottom and passes through, its rear end 9e moves to the pair of transport rolls 63 within the expanded transport space 50p, from a state where it is slightly tilted with respect to the axial direction D as illustrated by the solid line in the figure, to a state where the misalignment in the axial direction D is eliminated as shown by the dashed line in the figure. As a result, the rear portion of sheet 9 during transport will also be positioned so that its center line Sc is approximately aligned with the transport reference line CL.

[0140] Furthermore, once the movement of the two pairs of mobile transport rolls 61 and 63 in the axial direction D is completed, the transport operations of the first transport path 53, the final transport path 51, etc. are resumed. As a result, the sheet 9 is transported by the pair of moving transport rolls 61, which are in a state where they have moved in the axial direction D, and is ultimately fed to the image forming unit 2.

[0141] 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 S126). 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.

[0142] If it is confirmed in step S126 that the rear end 9e of the sheet 9 has passed the pair of moving conveyor rolls 61, the control unit 13 controls the pair of moving conveyor rolls 61 back to their original position before movement (normal reference position) (step S127). When the sheet 9 passes over the third transport guide pair 852 at the downstream end, its guide body 802a descends due to gravity and returns to its normal position. This prepares the machine for the next transport operation.

[0143] 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.

[0144] As described 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 passing through some 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 a case where all of the multiple first transport guide pairs 811, 812, ... and the multiple third transport guide pairs 852, 853, ... are fixed without displacement, the sheet transport device 5 suppresses the slanting and distortion of the sheet portion as it passes through.

[0145] Furthermore, in this sheet conveying device 5, the displaceable first conveying guide pair is the downstream first conveying guide pair 811 and the downstream third conveying guide pair 852. Therefore, compared to cases where the displaceable conveying guide pair is a first conveying guide pair other than the downstream first conveying guide pair 811, or a third conveying guide other than the downstream third conveying guide pair 852, it is easier to suppress the slanting or distortion of the sheet portion as it passes through at least a part of the first conveying roll pair or the third conveying roll pair.

[0146] 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.

[0147] 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.

[0148] Embodiment 2. Figures 15 to 20 show the sheet transport device 5 and other components according to Embodiment 2.

[0149] 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.

[0150] In the sheet conveying device 5 according to Embodiment 2, as shown in Figures 15 and 16, the downstream first conveying roll pair 711 is a conveying roll pair that can be separated, and the first conveying guide pair that is displaced in correspondence with separating the downstream first conveying roll pair 711 is changed.

[0151] In other words, the displaceable first transport guide pair in this case is both the downstream first transport guide pair 811 located between the moving transport roll pair 61 and the downstream first transport roll pair 711, and the second downstream first transport guide pair 812 located between the downstream first transport roll pair 711 and the first first transport roll pair 712 upstream of the first transport roll pair 711.

[0152] Furthermore, in this sheet conveying device 5, as shown in Figures 18 and 19, the downstream third conveying roll pair 751 is a conveying roll pair that can be separated, and the third conveying guide pair that is displaced in correspondence with separating the downstream third conveying roll pair 751 is modified. In other words, the displaceable third transport guide pair in this case is both the downstream third transport guide pair 852 located between the upstream moving transport roll pair 63 and the downstream third transport roll pair 751, and the second downstream third transport guide pair 853 located between the downstream third transport roll pair 751 and the first third transport roll pair 752 upstream of the third transport roll pair 751.

[0153] (Sheet transport device transport operation) Next, the main conveying operations of the sheet conveying device 5 according to Embodiment 2 will be described.

[0154] In the sheet transport device 5, once image formation is performed by the image forming device 1, 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 15: 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 assumed to be one of sheets 9A, 9B, or 9C.

[0155] 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 misalignment detector 65 detects the amount of misalignment α of the sheet 9 in the axial direction D (step S132). Until the result of the detection of the amount of misalignment α is obtained, the transport operation of the first transport path 53 and the final transport path 51 is temporarily stopped.

[0156] Next, the control unit 13 determines whether or not the second-to-last first conveyor roll pair 712 grips the sheet 9 (step S133).

[0157] Furthermore, if it is determined in step S134 that the first conveyor roll pair 712 is gripping the sheet 9, the downstream first conveyor roll pair 711 is separated (step S135), and one pair of moving conveyor rolls 61 is moved by a required distance α in the axial direction D (step S136). Embodiment 2 illustrates the case in which the sheet 9 is gripped by the two first conveyor roll pairs 712 and 731.

[0158] The separation 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. At this time, the separation of the first transport roll pair 711 occurs when the driven roll 711b moves downward. 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.

[0159] At this time, the sheet 9 is held between the moving conveyor roll pair 61 and the first conveyor roll pair 712,731, and its leading edge 9s is moved axially D by the moving conveyor roll pair 61.

[0160] As a result, when the sheet 9 moves in accordance with the axial movement D of the moving conveyor roll pair 61, it deforms (fluctuations) by bending downward between the moving conveyor roll pair 61 and the second-to-last downstream first conveyor roll pair 712, as shown in Figures 16 and 17(A). The reason the sheet 9 deforms downward is that the driven roll 711b of the first conveyor roll pair 711 separates downward, creating a gap on the lower side and making it easier to move. In Figures 16 and 17(A), the part indicated by the reference numeral 9m is the part that has been bent and deformed.

[0161] Furthermore, at this time, the distorted and deformed portion 9m of the sheet 9 comes into contact with the downstream first conveyor guide 851 and the second downstream first conveyor guide pair 812, which are positioned between the moving conveyor roll pair 61 and the second downstream first conveyor roll pair 712.

[0162] As a result, the two first transport guide pairs 811 and 812 are displaced downward (step S136) because the deformed portion 9m of the sheet 9, which is bent and distorted downward, comes into contact with the other guide body 902a (see Figure 5), which is located on the same side as the driven roll 711b that moves when the first transport roll pair 711 is separated, and pushes downward from above. As a result, each transport space 50 in the two first transport guide pairs 811 and 812 becomes a transport space 50p that is wider than the transport space 50n before the displacement by the amount of the displacement, as shown in Figures 8 and 16.

[0163] Therefore, compared to the first embodiment, the deformed portion 9m of the sheet 9 has a wider range of movement in the transport space 50p, even in the transport direction C, and the degree of freedom to adjust its state is further increased.

[0164] Finally, as shown in Figure 17(B), when the rear portion of sheet 9 is released from being gripped by the second-to-last third conveyor roll pair 752 during transport and passes through, its rear end 9e moves to the moving conveyor roll pair 61 within the transport space 50p, which is also extended in the transport direction C, from a state where it is slightly tilted with respect to the axial direction D as illustrated by the solid line in the figure, to a state where the misalignment in the axial direction D is eliminated as shown by the dashed line in the figure. As a result, the rear portion of sheet 9 during transport will also be positioned so that its center line Sc is approximately aligned with the transport reference line CL.

[0165] Furthermore, once the movement of the pair of moving transport rolls 61 in the axial direction D is completed, the transport operations of the first transport path 53, the final transport path 51, etc. are resumed. As a result, the sheet 9 is transported by the pair of moving transport rolls 61, which are in a state where they have moved in the axial direction D, and is ultimately fed to the image forming unit 2.

[0166] Furthermore, if it is determined in step S133 that the second-to-last first conveyor roll pair 712 does not grip the sheet 9, the operation does not proceed to step S134, and the operation of step S135 (movement of the mobile conveyor roll pair 61) is performed. Also, once the movement of the mobile conveyor roll pair 61 is completed, the conveying operations of the first conveyor path 53, the final conveyor path 51, etc. are resumed. In this case as well, the sheet 9 is transported by the pair of moving transport rolls 61, which are in a state of being moved in the axial direction D, and is ultimately fed to the image forming unit 2.

[0167] 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 moving transport roll pair 61 (step S137).

[0168] If it is confirmed in step S137 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 downstream first conveyor roll pair 711 is released from separation and returned to its normal contact state (step S138). As the sheet 9 passes over it, the two first transport guide pairs 811 and 812 have their guide bodies 802a rise due to the restoring force after elasticity, returning to their normal positions. This prepares the machine for the next transport operation.

[0169] Next, the control unit 13 determines whether or not there is any inversion transport of the sheet 9 (step 139).

[0170] If it is determined in step 139 that there is no need for inverted transport of sheet 9, the transport operation for sheet 9 at this time is terminated. In this case, the sheet 9 on which the 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.

[0171] (Transport operation when reverse transport is involved) On the other hand, if it is determined in step 139 that there is a reverse transport to 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.

[0172] 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 18: Step S150). 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.

[0173] 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 S151).

[0174] 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 S152).

[0175] If, in step S152, 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 15) as shown in Figure 18. In this case, sheet 9 will undergo the transport operation from steps S133 to S139 shown in Figure 15.

[0176] On the other hand, if in step S152 it is determined that the sheet 9 is long enough to be gripped by the upstream moving conveyor roll pair 63, the control unit 13 determines whether or not the second downstream third conveyor roll pair 752 grips the sheet 9 (step S153). Sheet 9 in this case will also be a long sheet as described above.

[0177] In step S153, if it is determined that the third conveyor roll pair 752 is gripping the sheet 9, the downstream third conveyor roll pair 751 is separated (step S154). The separation of the third transport roll pair 751 is performed by the control unit 13 controlling the drive of the drive motor 709M5 via the roll pair separation drive control unit 503. At this time, the separation of the third transport roll pair 751 occurs when the driven roll 751b moves downward.

[0178] Next, both sets of mobile transport rolls 61 and 63 are moved a 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 S155).

[0179] Then, as shown in Figure 20(A), the sheet 9 is held between the upstream moving conveyor roll pair 63 and the third conveyor roll pair 753, 754, and its tip 9s side is moved axially D by the moving conveyor roll pair 61. As a result, when the sheet 9 moves in accordance with the axial movement D of the two pairs of movable conveying rolls 61 and 63, it deforms (fluctuations) by bending downward between the upstream pair of movable conveying rolls 63 and the second-to-last third pair of conveying rolls 752, as shown in Figure 19. The part indicated by the reference numeral 9m in Figure 19, etc., is the part that has been distorted and deformed.

[0180] Furthermore, at this time, the distorted and deformed portion 9m of the sheet 9 comes into contact with the downstream third transport guide pair 852 and the second downstream third transport guide pair 852, which are positioned between the moving transport roll pair 63 and the second downstream third transport roll pair 752.

[0181] As a result, the two third transport guide pairs 852 and 853 are displaced downward (step S156) as they come into contact with the other guide body 902a (see Figure 5), which is located on the same side as the driven roll 711b that moves when the first transport roll pair 711 is separated, and the deformed portion 9m that bends and distorts downwards from above the sheet 9 comes into contact with it and pushes downwards. As a result, each transport space 50 in the two third transport guide pairs 852 and 853 becomes a transport space 50p that is wider than the transport space 50n before the displacement by the amount of the displacement, as shown in Figures 8 and 19. Therefore, compared to the first embodiment, the deformed portion 9m of the sheet 9 has a wider range of movement in the transport space 50p, even in the transport direction C, and the degree of freedom to adjust its state is further increased.

[0182] Finally, as shown in Figure 20(B), when the rear portion of sheet 9 is released from being gripped by the second-to-last third conveyor roll pair 753 during transport and passes through, its rear end 9e moves to the upstream moving conveyor roll pair 63 within the transport space 50p, which is also extended in the transport direction C, from a state where it is slightly tilted with respect to the axial direction D as illustrated by the solid line in the figure, to a state where the misalignment in the axial direction D is eliminated as shown by the dashed line in the figure. As a result, the rear portion of sheet 9 during transport will also be positioned so that its center line Sc is approximately aligned with the transport reference line CL.

[0183] Once the movement of the two pairs of mobile transport rolls 61 and 63 in the axial direction D is completed, the transport operations of the re-transport path 55, the final transport path 51, etc. are resumed. As a result, the sheet 9 is transported by the pair of moving transport rolls 61, which are in a state where they have moved in the axial direction D, and is ultimately fed to the image forming unit 2.

[0184] Furthermore, if it is determined in step S153 that the second-to-last third conveyor roll pair 752 does not grip the sheet 9, the process does not proceed to step S154, and the process of step S155 (movement of the two sets of mobile conveyor roll pairs 61 and 63) is performed. After the movement of the two sets of mobile conveyor roll pairs 61 and 63 is completed, the conveying operations of the re-transport path 55, the final conveyor path 51, etc. are resumed. In this case as well, the sheet 9 is transported by the pair of moving transport rolls 61, which are in a state of being moved in the axial direction D, and is ultimately fed to the image forming unit 2.

[0185] 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 S157).

[0186] If it is confirmed in step S157 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 downstream third conveyor roll pair 751 is released and they are returned to a contact state (step S158). 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, this sheet conveying device 5 makes it easier to obtain the effects and advantages obtained with the sheet conveying device 5 according to the first embodiment described above.

[0189] In other words, in this sheet conveying device 5, compared to a case where the downstream first conveying roll pair 711 is a non-separating conveying roll pair and the displaceable conveying guide pairs are conveying guides other than the downstream first conveying guide pair 811 and the second downstream conveying guide pair 812, the slanting and distortion of the sheet portion passing through at least a part of the first conveying roll pair (for example, the first conveying roll pair 711, 712) is more suppressed.

[0190] Furthermore, in this sheet conveying device 5, the third conveying roll pair 751 at the very bottom is a non-separating conveying roll pair, and the displaced conveying guide pairs are conveying guides other than the third conveying guide pair 852 at the very bottom and the second-to-last conveying guide pair 853 at the bottom. In this device, the slanting and distortion of the sheet portion passing through at least a portion of the third conveying roll pair (for example, the third conveying roll pair 752, 753) is more effectively suppressed.

[0191] Furthermore, in this sheet conveying device 5, the displaced first conveying guide pair 811, 812 or third conveying guide pair 852, 853 is configured such that the other conveying guides 811b, 812b and conveying guides 852b, 853b (all of which are guide bodies 802b) located on the same side as the roll that moves when the first conveying roll pair 711 or third conveying roll pair 751 is separated (driven roll) are displaced. Therefore, compared to a configuration where the displacing transport guide pair is configured such that the other transport guide, which is located on the same side as the roll that does not move when the transport roll pair separates, is displacing, it is easier to suppress the slanting or distortion of the sheet portion as it passes through the first transport roll pair or at least a portion of the third transport roll.

[0192] 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.

[0193] 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.

[0194] The sheet transport device 5 according to Embodiment 2 may be configured to perform transport operations as shown in Figures 21 and 22.

[0195] The sheet conveying device 5 illustrated in Figure 21 is configured such that when the downstream first conveying roll pair 711 is separated, the downstream first conveying guide pair 811 and the second downstream first conveying guide pair 812 are displaced, with one of the conveying guides 811a and 812a (guide body 802a) located on the same side as the non-moving driven roll 711a (in other words, on the opposite side from the moving driven roll 711b) being displaced. In this modified example, in other words, the conveying guide 811a and 812a located on the opposite side from the moving driven roll 711b is displaced.

[0196] The sheet conveying device 5 illustrated in Figure 22 is configured such that when the downstream third conveying roll pair 751 is separated, the downstream third conveying guide pair 852 and the second downstream third conveying guide pair 853 are displaced, and one of the conveying guides 852a and 853a (guide body 802a) located on the same side as the drive roll 751a, which does not move when the third conveying roll pair 751 is separated, is displaced. In other words, this modified version displaces the one of the conveying guides 852a and 853a located on the opposite side of the moving driven roll 751b.

[0197] Embodiment 2 shows a configuration in which both the downstream first conveyor guide pair 811 and the second downstream first conveyor guide pair 812, which are positioned adjacent to each other on the upstream and downstream sides of the conveying direction C with respect to the downstreammost first conveyor roll pair 711 to be separated, are displaced when the first conveyor roll pair 711 is separated. However, in this case, the system may be configured to displace only one of the two pairs of first transport guides, 811 (the furthest downstream) and 812 (the second furthest downstream). In this case, it is preferable to displace the furthest downstream pair of first transport guides, 811, which is located downstream in the transport direction C, as this makes it easier to suppress the occurrence of the aforementioned slanting and other issues.

[0198] Furthermore, Embodiment 2 shows a configuration in which both the downstream third conveyor guide pair 852 and the second downstream third conveyor guide pair 853, which are positioned adjacent to each other on the upstream and downstream sides of the conveying direction C with respect to the downstreammost third conveyor roll pair 751 to be separated, are displaced when the third conveyor roll pair 751 is separated. However, in this case, the system may be configured to displace only one of the two pairs of third transport guides, 852 (the furthest downstream) and 853 (the second furthest downstream). In this case, it is preferable to displace the furthest downstream pair of third transport guides, 852, which is located on the downstream-upstream side of the transport direction C, as this makes it easier to suppress the occurrence of the aforementioned slanting and other issues.

[0199] Furthermore, in embodiments 1 and 2, the transport guides (guide bodies 802) that constitute the displaceable first transport guide pair or third transport guide pair are exemplified as being made of members that are displaced when a part of the sheet 9 comes into contact with them. However, the displaceable first or third transport guide pair may be configured such that the transport guide (guide body 802) is displaced using the driving force of the drive device. Furthermore, the form of displacement is not limited to the forms exemplified in Embodiments 1 and 2 (a form in which the transport guide is displaced by swinging with one end as a pivot). Other forms of displacement include, for example, a form in which the transport guide on the displaceable side is displaced so as to move in parallel with respect to the transport guide on the non-displaceable side.

[0200] 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.

[0201] 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.

[0202] 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.

[0203] Furthermore, in Embodiment 1, the decision in step S122 (Figure 12) may be made in advance by the control unit 13 when it receives a command for image formation operation, in which case the decision in step S122 can be omitted. Furthermore, in the second embodiment, the decision in step S133 and the decisions in steps 152 and S153 (Figure 18) may be configured to be determined in advance by the control unit 13 when it receives a command for image formation operation. In this case, the decision in step S133 and the decisions in steps S152 and S153 can be omitted.

[0204] 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]

[0205] 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 50…Transportation space 50p, 50q... Expanded transport space 51…Final transport path (an example of a transport path where the first pair of transport rolls are located) 53...Second final transport path (an example of a transport path where the first transport roll pair is located) 55…Re-transport path (an example of a transport path with a third pair of transport rolls) 61... Mobile transport rolls 63…Upstream moving conveyor roll pair 711...The first conveyor roll at the uppermost level 712... The second first conveyor roll from the uppermost position 751...The third conveyor roll at the uppermost level 752...The second third conveyor roll from the uppermost position 802a...One of the guide bodies (an example of one of the transport guides) 802b... The other guide body (an example of the other transport guide) 811...The first transport guide at the uppermost level 852... Third transport guide pair at the uppermost level C…Export direction D…Axial direction

Claims

1. 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, A plurality of third conveying roll pairs are positioned at a distance upstream in the conveying direction from the upstream conveying roll pair of the two sets of conveying roll pairs mentioned above, and are used to grip and convey the sheet. A plurality of third conveying guide pairs are arranged to form a sheet conveying space between the plurality of third conveying roll pairs, Equipped with, A sheet conveying device in which at least some of the plurality of third conveying guide pairs are displaced in a direction that widens the conveying space when the two sets of movable conveying roll pairs are moved in the axial direction.

2. The sheet conveying device according to Claim 1, wherein the displaceable third conveying guide pair is the downstreammost third conveying guide pair, which is positioned between the upstream moving conveying roll pair and the first downstream third conveying roll pair among the plurality of third conveying roll pairs that is upstream of the said upstream moving conveying roll pair.

3. A transport roll pair in which at least the first downstream third transport roll pair upstream of the upstream moving transport roll pair among the plurality of third transport roll pairs is separable, The sheet conveying device according to claim 1, wherein the displaceable third conveying guide pair is, when the downstreammost third conveying roll pair is separated, the downstreammost third conveying guide pair located between the upstream moving conveying roll pair and the downstreammost third conveying roll pair, and the second downstreammost third conveying guide pair located between the downstreammost third conveying roll pair and the first third conveying roll pair upstream of the said third conveying roll pair, or both.

4. The sheet conveying device according to claim 3, wherein, of the downstreammost third conveying guide pair and the second downstreammost third conveying guide pair, the displaced conveying guide pair is one of the conveying guide pairs located on the same side as the roll that moves when the downstreammost third conveying roll pair separates.

5. The sheet conveying device according to claim 3, wherein the displaced conveying guide pair of the downstreammost third conveying guide pair and the second downstreammost third conveying guide pair is such that the other conveying guide pair, which is located on the same side as the roll that does not move when the downstreammost third conveying roll pair separates, is displaced.

6. The sheet conveying device according to Claim 1, wherein the displaceable third conveying guide pair is in the normal position before the conveying space is expanded when the two sets of movable conveying roll pairs are not moving and when the two sets of movable conveying roll pairs have moved and finished conveying the sheet.

7. The sheet conveying device according to claim 1, wherein the displaceable third conveying guide pair is composed of a member that is displaced by the force received when a part of the sheet being conveyed comes into contact with the displaceable conveying guide pair.

8. The sheet conveying device according to claim 1, wherein the sheet conveying path between the two pairs of movable conveying rolls is curved.

9. The sheet conveying device according to claim 8, 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.

10. 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 any one of claims 1 to 9.

11. 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 10, 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.

Images