Sheet transport device and image forming apparatus

Abstract

To prevent switching means, for switching a pair of conveying rolls between a nip state and a nip release state and maintaining a switching function at the time of recovery from an open position by separating means, from becoming inoperative by moving one of the pair of conveying rolls to the open position by the separating means as compared with a case not including the switching means.SOLUTION: A sheet conveyance device comprises: a pair of conveying rolls placed on a conveyance path of a sheet; separating means for moving one conveying roll constituting the pair of conveying rolls to an open position separated from the other conveying roll; and switching means which is the means for switching the pair of conveying rolls between a nip state and a nip release state and maintains a switching function at the time of recovery from the open position by the separating means.SELECTED DRAWING: Figure 9

Description

Technical Field

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

Background Art

[0002] Conventionally, as technologies related to sheet conveying devices, for example, those disclosed in Patent Document 1, Patent Document 2, etc. have already been proposed.

[0003] Patent Document 1 has 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 movably in a direction orthogonal to the sheet conveying direction on the downstream side of the skew correction unit and corrects the position of the sheet in the direction orthogonal to the sheet conveying direction, and a sheet conveying auxiliary unit that is provided on the upstream side of the skew correction unit and is movable in a direction orthogonal to the sheet conveying direction. After the skew correction of the sheet by the skew correction unit, when the lateral registration correction unit moves the sheet in the direction orthogonal to the sheet conveying direction for position correction, the sheet conveying auxiliary unit is configured to move in the same direction as the lateral registration correction unit in synchronization with the lateral registration correction unit.

[0004] Patent Document 2 is a sheet conveying device provided with two pairs of sandwiching conveying members capable of conveying while sandwiching a sheet and moving in the width direction orthogonal to the conveying direction. In this device, while a single sheet is sandwiched by the two pairs of sandwiching conveying members, it is moved in the width direction. After the movement in the width direction, the two sandwiching conveying members forming the upstream sandwiching conveying member pair located on the upstream side in the conveying direction among the two pairs of sandwiching conveying members are separated, and the sheet is conveyed by the downstream sandwiching conveying member pair located on the downstream side in the conveying direction among the two pairs of sandwiching conveying members.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] The object of this invention is to provide a means for switching a pair of conveying rolls between a nip state and a nip release state, and compared to a method that does not include a switching means that maintains the switching function when returning from the open position by a separating means, the invention avoids the switching means becoming inoperable when one of the conveying rolls moves to the open position by a separating means. [Means for solving the problem]

[0007] The invention described in claim 1 comprises a pair of conveying rolls arranged in a sheet conveying path, One of the conveying rolls constituting the pair of conveying rolls has an open pivot point on one end side along the axial direction, and the open pivot point is the center A separation means for moving one of the transport rolls constituting the pair of transport rolls to an open position separated from the other transport roll, It has an eccentric cam that is rotationally driven by a driving means, and an operating arm that follows the eccentric cam, and by the movement of the operating arm A means for switching the aforementioned pair of conveying rolls between a nip state and a nip release state, The operating arm moves along the surface of the eccentric cam before and after moving to the open position by the separating means. When returning from the open position by the aforementioned separation means The aforementioned pair of conveying rolls can be switched between a nip state and a nip release state. Switching mechanism, This is a sheet conveying device equipped with [a specific feature / feature].

[0009] Claim 2 The invention described herein is such that the eccentric cam is extended along the axial direction so as to maintain contact with the operating arm even when the operating arm moves to the open position during the separation operation by the separation means. Claim 1 This is the sheet conveying device described above.

[0013] Claim 3 The invention described herein includes an image forming means for forming an image on a recording medium, A transport means for transporting the recording medium to the image forming means, Equipped with, The conveying means Claim 1 or 2 This is an image forming apparatus that uses the sheet transport device described above. [Effects of the Invention]

[0014] According to the invention described in claim 1, compared to a means for switching a pair of conveying rolls between a nip state and a nip release state, which does not include a switching means that maintains the switching function when returning from the open position by a separation means, it is possible to avoid the switching means becoming inoperable when one of the conveying rolls moves to the open position by the separation means.

[0015] Claim 1 According to the invention described herein, the operating arm moves along the surface of the eccentric cam before and after moving to the open position by the separation means, thereby preventing the switching means from becoming inoperable with a simpler configuration compared to a case where the switching function is not maintained.

[0016] Claim 2 According to the invention described herein, the eccentric cam can be extended axially to maintain contact with the operating arm even when the operating arm moves to the open position during separation operation by the separation means. This simple configuration of extending the eccentric cam axially can prevent the switching means from becoming inoperable.

[0018] Claim 1 According to the invention described herein, the separation means allows one conveyor roll to be moved to an open position separated from the other conveyor roll with a simple configuration, compared to the case where there is no opening pivot point on one end of one of the conveyor rolls constituting the conveyor roll pair along the axial direction.

[0020] Claim 3 According to the invention described above, as a conveying means Claim 1 or 2 Compared to not using the sheet conveying device described above, this method avoids the switching mechanism becoming inoperable when one of the conveying roll pair moves to the open position due to the separation mechanism. [Brief explanation of the drawing]

[0021] [Figure 1]This is an overall configuration diagram showing an image forming apparatus to which the sheet conveying device according to Embodiment 1 of the present invention is applied. [Figure 2] This is a configuration diagram showing a main part of a paper conveying device as an example of the sheet conveying device according to Embodiment 1 of the present invention. [Figure 3] This is a plan configuration diagram showing a pair of paper conveying rolls. [Figure 4] This is a cross-sectional configuration diagram of the main part showing a pair of paper conveying rolls. [Figure 5] This is a plan configuration diagram showing a pair of paper conveying rolls. [Figure 6] This is a cross-sectional configuration diagram of the main part showing a pair of paper conveying rolls. [Figure 7] This is a perspective configuration diagram showing the main part of the paper conveying device according to Embodiment 1 of the present invention. [Figure 8] This is a perspective configuration diagram showing the main part of the paper conveying device according to Embodiment 1 of the present invention. [Figure 9] This is a perspective configuration diagram showing a switching mechanism. [Figure 10] This is a cross-sectional configuration diagram showing a switching mechanism. [Figure 11] This is a cross-sectional configuration diagram showing a switching mechanism. [Figure 12] This is a perspective configuration diagram showing the main part of the paper conveying device according to Embodiment 1 of the present invention. [Figure 13] This is a perspective configuration diagram showing the main part of the paper conveying device according to Embodiment 1 of the present invention.

Mode for Carrying Out the Invention

[0022] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0023] [Embodiment 1] FIG. 1 is a configuration diagram showing an overall overview of an image forming apparatus to which the sheet conveying device according to Embodiment 1 of the present invention is applied.

[0024] [Overall Configuration of Image Forming Apparatus] The image forming apparatus 1 according to Embodiment 1 is configured, for example, as a color printer. As shown in Figure 1, this image forming apparatus 1 broadly comprises an image output device 2 that forms (outputs) full-color images such as yellow (Y), magenta (M), cyan (C), and black (K) onto recording paper 5, which is an example of a recording medium (sheet), and an independent paper feed device 3 that feeds long recording paper (hereinafter referred to as "long paper") to the image output device 2. The paper feed device 3 is located adjacent to the outside of the image output device 2.

[0025] The image output device 2 includes a plurality of image-forming devices 10 that form toner images developed with toner constituting the developer, an intermediate transfer device 20 that holds the toner images formed by each image-forming device 10 and transports them to a secondary transfer position where they are ultimately transferred to recording paper 5, which is an example of a recording medium, a paper feed device 50 that receives and transports the required amount of recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20, a fixing device 40 that fixes the toner image on the recording paper 5 that has been secondarily transferred by the intermediate transfer device 20, and a paper transport device 60, which is an example of a sheet transport device, that transports the recording paper 5 fed from the paper feed device 50 along a required transport path. In the figure, 2a represents the main body of the image output device 2. This main body 2a is composed of support structural members and an exterior cover, etc. The solid lines in the figure indicate the main transport path through which the recording paper 5 is transported inside the main body 2a, etc. In this embodiment, the plurality of image-forming devices 10, the intermediate transfer device 20, and the fixing device 40 constitute the image forming means.

[0026] The imaging device 10 consists of four imaging devices 10Y, 10M, 10C, and 10K, each dedicated to forming toner images of four colors: yellow (Y), magenta (M), cyan (C), and black (K). These four imaging devices 10 (Y, M, C, K) are arranged in a single row horizontally within the internal space of the device body 2a, with the required gaps between them.

[0027] The four imaging devices 10 each include, for example, a photoreceptor drum 11 and a charging device, exposure device, or developing device (not shown) arranged on the outer circumference of the photoreceptor drum 11 to form a toner image of the required color on the surface of the photoreceptor drum 11, and are configured to form images of yellow (Y), magenta (M), cyan (C), and black (K) on the circumferential surface of each photoreceptor drum 11 using an electrophotographic method. The four imaging devices 10 are not limited to those that form images using an electrophotographic method; they may also use inkjet recording methods, electrostatic recording methods, etc., to form images of yellow (Y), magenta (M), cyan (C), and black (K). If the imaging device 10 forms images using an inkjet recording method, the intermediate transfer device 20 is unnecessary, and it is possible to form an image directly from the imaging device 10 to the recording paper 5.

[0028] As shown in Figure 1, the intermediate transfer device 20 is positioned below the yellow (Y), magenta (M), cyan (C), and black (K) imaging devices 10 (Y, M, C, K) in the vertical direction. The intermediate transfer device 20 mainly consists of an intermediate transfer belt 21 that rotates in the direction indicated by the arrow while passing through a primary transfer position between the photoreceptor drum 11 and the primary transfer device 15 (primary transfer roll), a plurality of belt support rolls 22 to 24 that hold the intermediate transfer belt 21 in a desired state from its inner surface and support it so that it can rotate, and a secondary transfer device 30 that is positioned on the outer circumferential surface (image holding surface) side of the intermediate transfer belt 21 supported by the belt support rolls 24 and secondary transfers the toner image on the intermediate transfer belt 21 to the recording paper 5.

[0029] The fixing device 40 is constructed by arranging a heating rotating body 41 in the form of a roll or belt, which rotates in the direction indicated by the arrow and is heated by a heating means so that its surface temperature is maintained at a predetermined temperature, and a pressurizing rotating body 42 in the form of a belt or roll, which rotates in contact with the heating rotating body 41 at a predetermined pressure and is driven to rotate, substantially aligned with the axial direction of the heating rotating body 41. In this fixing device 40, the contact area where the heating rotating body 41 and the pressurizing rotating body 42 come into contact becomes the fixing processing area where the required fixing process (heating and pressurizing) is performed.

[0030] As shown in Figure 1, the paper feeder 50 is positioned below the intermediate transfer device 20 and the secondary transfer device 30. The paper feeder 50 mainly consists of a plurality (or single) of paper containers 51, 51... that hold recording paper 5 of a desired size and type, and a dispensing device (not shown) that feeds out the recording paper 5 one sheet at a time from the paper containers 51. The paper containers 51 are mounted so that they can be pulled out, for example, from the front side (the side that the user faces when operating) of the device body 2a.

[0031] On the other hand, the independent paper feeder 3 includes a paper holder 31 that stores long paper 5a, which is larger in size in the paper feed direction and / or in the direction intersecting the paper feed direction than A3 size recording paper 5, the largest standard-sized recording paper used in a normal image forming apparatus 1, and a large-capacity paper holder 32 that can store more standard-sized recording paper 5 than the normal paper holder 51. In addition, a paper holder 33 for manual feeding of long paper 5a, etc., is located at the upper end of the main body 3a of the paper feeder 3.

[0032] The paper transport device 60 includes a paper feed transport path 61 that transports the recording paper 5 fed from the paper feed device 50 to the secondary transfer position, an intermediate transport path 62 that transports the recording paper 5, on which the toner image has been secondarily transferred at the secondary transfer position, to the fuser device 40, an ejection transport path 63 that transports the recording paper 5, on which the toner image has been fixed by the fuser device 40, to a paper ejection section (not shown), an inversion transport path 64 that reverses the front and back of the recording paper 5, on which the toner image has been fixed by the fuser device 40, without ejecting it as is, and a double-sided transport path 65 that transports the recording paper 5, which has been reversed by the inversion transport path 64, back to the paper feed transport path 61 to form an image on both sides. The paper transport device 60 will be described in detail later.

[0033] Furthermore, the independent paper feeder 3 is equipped with a paper feed path 35 having a pair of paper transport rolls 34 that transports long paper 5a or recording paper 5 fed from the paper container 31, the large-capacity paper container 32, or the manual feed paper container 33 to the external paper feed section 66 of the image output device 2.

[0034] In Figure 1, reference numeral 100 denotes a control device that controls the operation of the entire image forming apparatus 1, including the paper feed device 3.

[0035] <Basic operation of an image forming apparatus> The following describes the basic image forming operation of the image forming apparatus 1.

[0036] This section describes the image formation operation when forming a full-color image by combining four toner images (Y, M, C, K) using the four imaging devices 10 (Y, M, C, K).

[0037] When the control device 100 receives command information requesting an image forming operation (printing), the image forming apparatus 1 starts up the four image forming devices 10 (Y, M, C, K), the intermediate transfer device 20, the secondary transfer device 30, the fixing device 40, the paper feed device 50, and the paper transport device 60, etc.

[0038] Then, in each imaging device 10 (Y, M, C, K), images of each color, such as yellow (Y), magenta (M), cyan (C), and black (K), are first formed on each photoreceptor drum 11. When the toner images of each color formed on the photoreceptor drum 11 of each imaging device 10 (Y, M, C, K) are transported to the primary transfer position, the primary transfer device 15 performs a primary transfer in which the toner images of each color are sequentially superimposed on the intermediate transfer belt 21 of the intermediate transfer device 20, which rotates in the direction indicated by the arrow.

[0039] Next, the intermediate transfer device 20 holds the toner image transferred in the first stage by the rotation of the intermediate transfer belt 21 and transports it to the secondary transfer position. Meanwhile, the paper feed device 50 sends the required recording paper 5 to the paper feed transport path 61 in accordance with the image formation operation. The paper feed transport path 61 supplies the recording paper 5 to the secondary transfer position in accordance with the transfer timing.

[0040] At the secondary transfer position of the intermediate transfer device 20, the secondary transfer roll 30 transfers the toner image on the intermediate transfer belt 21 onto the recording paper 5 in one go. The recording paper 5, on which the toner image has been transferred, is peeled off from the intermediate transfer belt 21 and the secondary transfer roll 30 and then transported to the fixing device 40. In the fixing device 40, the recording paper 5 after secondary transfer is introduced and passed through the fixing processing section between the rotating heating body 41 and the pressing body 42, thereby performing the necessary fixing process (heating and pressing) to fix the unfixed toner image onto the recording paper 5. After fixing is complete, the recording paper 5 is discharged via the discharge transport path 63 to, for example, a paper discharge section (not shown) located outside the image processing device 2.

[0041] Furthermore, when forming an image on both sides of the recording paper 5, the recording paper 5 with the image formed on one side is not discharged directly to a paper discharge unit (not shown) via the discharge transport path 63, but is transported to a reversal transport path 64 by a switching means (not shown), where the front and back sides of the recording paper 5 are reversed in the reversal transport path 64 and then transported again to the paper feed transport path 61 via the double-sided transport path 65, where an image is formed on the back side of the recording paper 5.

[0042] On the other hand, when forming an image on one or both sides of a long sheet of paper 5a or the like fed from an external paper feeder 3, the paper feeder 3 is configured to send the recording paper 5, such as the long sheet of paper 5a, to the paper feed transport path 35 in accordance with the image formation operation, and to feed the paper to the external transport path 66 of the image output device 2 via the paper feed transport path 35.

[0043] Through the above operations, a recording sheet 5 is output, on which a full-color image formed by combining the four toner images is created.

[0044] <Configuration of the sheet conveying device> Figures 1 and 2 are configuration diagrams showing an image forming apparatus to which a paper transport device 60, as an example of a sheet transport device according to Embodiment 1 of the present invention, is applied.

[0045] The paper transport device 60 according to this embodiment 1 is arranged to be located inside the main body 2a of the image output device 2. As shown in Figure 1, the paper transport device 60 is broadly comprised of a paper feed transport path 61 that transports the recording paper 5 fed from the paper feed device 50 to the secondary transfer position of the intermediate transfer device 20; an intermediate transport path 62 that transports the toner image transferred at the secondary transfer position of the intermediate transfer device 20 to the fuser device 40; an discharge transport path 63 that transports the recording paper 5 on which the toner image has been fixed by the fuser device 40 to a paper discharge section (not shown); an inversion transport path 64 that reverses the front and back of the recording paper 5 without discharging it as is; a double-sided transport path 65 that transports the recording paper 5, which has been reversed by the inversion transport path 64, back to the secondary transfer position of the intermediate transfer device 20 via the paper feed transport path 61; and a short external transport path 66 that transports the recording paper 5, including long paper 5a, fed from an external paper feed device 3 to the paper feed transport path 61.

[0046] As shown in Figure 2, the paper feed transport path 61 includes a vertical transport path 67 that is vertically positioned to transport the recording paper 5 supplied from the paper feed device 50 upward along the vertical direction, a curved transport path 68 that changes the transport direction of the recording paper 5, which has been transported upward along the vertical transport path 67, to the horizontal direction, and a horizontal transport path 69 that transports the recording paper 5, whose transport direction has been changed to the horizontal direction along the curved transport path 68, to the secondary transfer position of the intermediate transfer device 20.

[0047] In the vertical transport path 67 of the paper feed transport path 61, a pair of paper transport rolls 671 for transporting the recording paper 5 and a guide member 672 for guiding the front and back surfaces of the recording paper 5 are arranged. In addition, a curved guide member 681 for guiding the front and back surfaces of the recording paper 5 is arranged in the curved transport path 68 of the paper feed transport path 61.

[0048] Meanwhile, the horizontal transport path 69 of the paper feed transport path 61 is equipped with multiple (three in the illustrated example) pairs of paper transport rolls 691 to 693 that transport the recording paper 5 while holding (nipping) it, and a guide member 694 that guides the front and back surfaces of the recording paper 5. Of these three pairs of paper transport rolls 691 to 693, the paper transport roll pair 693 located furthest downstream and immediately before the secondary transfer position of the intermediate transfer device 20 is configured as a first shift roll pair that moves (shifts) the recording paper 5 in parallel along the main scanning direction intersecting the transport direction.

[0049] The first shift roll pair, the paper transport roll pair 693, as shown in Figures 3 and 4, comprises a drive roll 693a that is rotationally driven by a drive motor 70 via a reduction gear train 71, and a driven roll 693b that receives driving force from the drive roll 693a via a transmission gear 72 and is pressed against the drive roll. The drive roll 693a is configured to move along the axial direction together with the driven roll 693b via a bearing portion 73 provided at one end of its rotation axis along the axial direction, with its thrust position restricted, by a moving mechanism consisting of a drive motor 74, a rack gear 75, and a pinion gear 76. On the upstream side of the paper transport roll pair 693 along the transport direction of the recording paper 5, a first detection means 77, consisting of an in-line sensor or the like, is arranged to detect the position of the edge along a direction intersecting the transport direction of the recording paper 5.

[0050] Furthermore, of these three paper transport roll pairs 691 to 693, paper transport roll pair 692, located upstream of paper transport roll pair 693, is configured as a register roll pair that adjusts the timing of transporting the recording paper 5 to the secondary transfer section. In addition, of these three paper transport roll pairs 691 to 693, paper transport roll pair 691, located furthest upstream, works in cooperation with the other paper transport roll pairs 692 and 693 to transport the recording paper 5.

[0051] Furthermore, when the first shift roll pair, the paper transport roll pair 693, adjusts its position along the main scanning direction which intersects the transport direction of the recording paper 5, the transport roll pairs other than the paper transport roll pair 693 are configured to release the nip state of the recording paper 5.

[0052] As shown in Figure 1, the intermediate transport path 62 transports the recording paper 5, which holds an unfixed toner image. Therefore, it is configured to transport the recording paper 5 to the fuser 40 by multiple or a single transport belt (not shown). Downstream of the fuser 40, along the transport direction, is a curl correction device 78 for correcting the curl of the recording paper 5.

[0053] Furthermore, the discharge transport path 63 is equipped with multiple (three in the illustrated example) pairs of paper discharge rolls 631 to 633 that discharge the recording paper 5 that has been fixed by the fixing device 40.

[0054] Of the three paper discharge roll pairs 631 to 633 in the discharge transport path 63, a plurality of paper transport roll pairs 641 to 644 are arranged downstream of the paper discharge roll pair 631, which is located furthest upstream along the transport direction of the recording paper 5. These paper transport roll pairs 641 to 644 transport the recording paper 5 to the reversal transport path 64 by a switching mechanism (not shown) that switches the transport direction of the recording paper 5. The downstream end 645 of the reversal transport path 64, along the transport direction, extends downward to the double-sided transport path 65 along the transport direction of the plurality of paper transport roll pairs 641 to 644. The plurality of paper transport roll pairs 642 to 644 arranged in the reversal transport path 64 are configured so that their rotation direction can be switched between forward and reverse. Once the recording paper 5 has been transported to the reversal transport path 64, it can be discharged to a paper discharge section (not shown) with its front and back sides reversed by the discharge roll pair 645 via the reversal transport path 64, by reversing the rotation direction of the plurality of paper transport roll pairs 642 to 644.

[0055] Furthermore, the recording paper 5, once transported to the reversal transport path 64, is transported to the double-sided transport path 65 by a switching mechanism (not shown) that reverses the rotation direction of the paper transport roll pair 644.

[0056] As shown in Figures 1 and 2, the double-sided transport path 65 is equipped with a plurality of paper transport roll pairs 651 to 659 for transporting the recording paper 5, and a guide member 650 for guiding the front and back surfaces of the recording paper 5. Of these plurality of paper transport roll pairs 651 to 659, the paper transport roll pair 659 located furthest downstream and immediately before the paper feed transport path 61 is configured as a second shift roll pair that moves (shifts) the recording paper 5 in parallel along the main scanning direction which is intersecting the transport direction.

[0057] The second shift roll pair, the paper transport roll pair 659, is configured similarly to the first shift roll pair, the paper transport roll pair 693, as shown in Figures 5 and 6. Specifically, the second shift roll pair, the paper transport roll pair 659, comprises a drive roll 659a that is rotationally driven by a drive motor 78 via a reduction gear train 79, and a driven roll 659b that receives driving force from the drive roll 659a via a transmission gear 80 and is pressed against the drive roll 659a. The drive roll 659a is configured to move along the axial direction together with the driven roll 659b via a bearing portion 81 provided at one end of its rotation axis along the axial direction, with its thrust position restricted, by a moving mechanism consisting of a drive motor 82, a rack gear 83, and a pinion gear 84.

[0058] Furthermore, of these three paper transport roll pairs 657 to 659, paper transport roll pair 658, located upstream of paper transport roll pair 659, is configured as a skew correction roll pair to correct the skew of the recording paper 5. Paper transport roll pair 658 is divided into a first drive roll 658a located on the front side along the axial direction and a second drive roll 658b located on the rear side along the axial direction, and the first drive roll 658a and the second drive roll 658b are configured so that their rotation direction and amount of rotation can be controlled independently. The driven roll 658c located below paper transport roll pair 658 has multiple rolls integrally provided along the axial direction.

[0059] Furthermore, the paper transport roll pair 658 is configured to correct the skew of the recording paper 5 by individually switching the amount and direction of rotation of the first drive roll 658a and the second drive roll 658b while the recording paper 5 is nipped.

[0060] Upstream of the paper transport roll pair 658 along the transport direction of the recording paper 5, a second detection means 85 is positioned, consisting of an in-line sensor or the like, which detects the position of the edge of the recording paper 5 along a direction intersecting the transport direction. The detection signal from the second detection means 85 is input to the control device 100.

[0061] Furthermore, of these three paper transport roll pairs 657 to 659, the paper transport roll pair 657, which is located furthest upstream, works in cooperation with the other paper transport roll pairs 651 to 656, etc., to transport the recording paper 5.

[0062] As shown in Figures 1 and 2, the double-sided transport path 65 is located inside the main body 2 of the image output device 2. Therefore, of the paper transport roll pairs 651 to 659 that make up the double-sided transport path 65, the paper transport roll pairs 654 to 659 located downstream along the transport direction of the recording paper 5 are integrally configured as a paper transport unit 200, as shown in Figures 2 and 7. The paper transport unit 200 is provided so as to be retractable to the front side of the main body 2a by a slide rail (not shown).

[0063] As shown in Figure 7, the paper transport unit 200 is formed in the shape of a long, narrow rectangular frame. The bottom of the paper transport unit 200 has a double structure with first and second bottom plates 201 and 202, which are formed in the shape of long, narrow rectangular plates. As shown in Figure 8, the first bottom plate 201 of the paper transport unit 200 has the drive rolls 654a to 659a, which are located at the top of the paper transport roll pair 654 to 659, rotatably mounted on the drive motor 203 via the drive shaft 203a. The second bottom plate 202 of the paper transport unit 200 has the driven rolls 654b to 659b, which are located at the bottom of the paper transport roll pair 654 to 659, mounted so as to rotate in accordance with the drive rolls 654a to 659a. The second bottom plate 202 of the paper transport unit 200 is configured to be movable (rotatable) to an open position spaced apart from the first bottom plate 201 of the paper transport unit 200, via an opening / closing pivot point 204 provided at the rear end along the depth direction. The second bottom plate 202 of the paper transport unit 200 is provided with an opening / closing handle 205 as an example of a separation mechanism in the center of its front side. The second bottom plate 202 of the paper transport unit 200 can be opened and closed downwards using the opening / closing pivot point 204 as a pivot point by gripping the opening / closing handle 205, which rotates the claw portion 206 of the locking mechanism and releases its engagement with the first bottom plate 201.

[0064] As shown in Figure 7(b), the paper transport unit 200 moves the first bottom plate 201 to the open position, thereby separating the driven rolls 654b to 659b from the upper driven rolls 654a to 659a of the paper transport roll pair 654 to 659. This makes it possible to remove recording paper 5 or long paper 5a that has experienced a transport malfunction (so-called jam) at the position of the paper transport roll pair 654 to 659.

[0065] As shown in Figure 2, the external transport path 66 is equipped with a pair of paper transport rolls 661 that transport the recording paper 5 supplied from the external paper feed device 3 while holding (nipping) it, and a guide member 662 that guides the front and back surfaces of the recording paper 5.

[0066] Incidentally, the image forming apparatus 1 to which the paper transport device 60 configured as described above is applied is configured to be able to form images on long paper 5a fed from an external paper feeder 3 or the like. Long paper 5a, which is an example of recording paper 5, has a longer length along the transport direction compared to ordinary standard paper, so it is prone to skew, or tilting relative to the transport direction, while being transported by the paper transport device 60. In particular, when forming an image on both sides of long paper 5a, it is necessary to transport the long paper 5a with an image formed on one side from the discharge transport path 63 to the reversal transport path 64, in a state where the front and back sides are reversed, and then transport it to the secondary transfer position of the intermediate transfer device 20 via the double-sided transport path 65 and the paper feed transport path 61. As a result, the transport path of the recording paper 5 is very long, and skew is more likely to occur compared to ordinary recording paper 5.

[0067] Therefore, in the paper transport device 60 according to this embodiment 1, as shown in Figure 2, the paper transport roll pair 659 as a second shift roll pair, the paper transport roll pair 658 as a skew correction roll pair, and the paper transport roll pair 657 are provided at the downstream end of the double-sided transport path 65 along the transport direction of the recording paper 5. The paper transport roll pair 659 as the second shift roll pair corrects the skew of the recording paper 5 by the paper transport roll pair 658, and then corrects the edge position by translating the recording paper 5.

[0068] Furthermore, the paper transport device 60 is configured to detect the amount of skew of the long paper 5a by detecting the position of the edge of the long paper 5a using the second detection means 85 while the long paper 5a is being transported by the paper transport roll pair 657 for the required distance.

[0069] If the control device 100 detects that the long paper 5a is skewed, it is necessary to first release the nip state of the long paper 5a using the paper transport roll pair 659 or 657, correct the skew of the long paper 5a using the paper transport roll pair 658 as a skew correction roll pair, correct the end position of the long paper 5a using the paper transport roll pair 659 as a second shift roll pair, and then transport the long paper 5a using the paper transport roll pair 659 or the like.

[0070] Therefore, the paper transport device 60 needs to switch between a first nip state in which both the paper transport roll pair 658, which serves as a skew correction roll pair, and the upstream adjacent paper transport roll pair 657 are nipped; a second nip state in which only the paper transport roll pair 658, which serves as a skew correction roll pair, is nipped and the paper transport roll pair 657 is released from the nip; and a third nip-release state in which both the paper transport roll pair 658 and the paper transport roll pair 657 are released from the nip.

[0071] Similarly, the other paper transport roll pairs 654 to 657 are also configured to be switchable between a nip state and a nip-release state. Therefore, paper transport roll pairs 654 to 658 are provided with a switching mechanism at their ends along their axial direction, which is an example of a switching means for switching the paper transport roll pair 654 to 658 between a nip state and a nip-release state.

[0072] However, as described above, the paper transport roll pairs 654 to 659 are configured such that, by operating the opening / closing handle 205, the first bottom plate 201 of the paper transport unit 200 is moved to the open position, and the driven rolls 654b to 659b are separated from the driven rolls 654a to 659a, which are located at the top of the paper transport roll pairs 654 to 659, so that jammed recording paper 5, etc., can be removed.

[0073] Therefore, if the driven rolls 654b to 659b are separated from the driven rolls 654a to 659a, which are located at the top of the paper transport roll pairs 654 to 659, there is a risk that the switching mechanism that switches the paper transport roll pairs 654 to 658 between the nip state and the nip release state will become inoperable. Furthermore, even when the driven rolls 654b to 659b that make up the paper transport roll pairs 654 to 659b are separated from the driven rolls 654a to 659a and then returned to a state where they are pressed against the driven rolls 654a to 659a, the switching mechanism must be configured to operate, which presents a technical challenge as it complicates the configuration of the switching mechanism.

[0074] Therefore, the paper transport device 60 according to this embodiment 1 is configured to include a separation means for moving one of the transport rolls constituting a transport roll pair to an open position separated from the other transport roll, and a switching means for switching the transport roll pair between a nip state and a nip release state, which maintains the switching function when returning from the open position by the separation means.

[0075] Furthermore, the paper transport device 60 according to this embodiment 1 has an eccentric cam that switches the transport roll pair between a nip state and a nip release state as a switching means, and an operating arm that switches the transport roll pair between a nip state and a nip release state by the eccentric cam, and the operating arm is configured to maintain the switching function by moving along the surface of the eccentric cam before and after moving to the open position by the separation means.

[0076] Furthermore, in the paper transport device 60 according to this embodiment 1, the eccentric cam is extended along the axial direction so as to maintain contact with the operating arm even when the operating arm moves to the open position during separation operation by the separation means.

[0077] In other words, as shown in Figures 9 and 10, the paper transport device 60 according to this embodiment 1 is equipped with a switching mechanism 90 at one end (the rear end) along the axial direction of the paper transport roll pair 654 to 658, which is an example of a switching means for switching the nip state of these paper transport roll pairs 654 to 658. Although Figures 8 and 9 show the paper transport roll pair 654 as an example, the other paper transport roll pairs 655 to 658 are configured similarly.

[0078] The switching mechanism 90 is configured to include an eccentric cam 92 that is rotationally driven by a drive motor 91, and a drive transmission mechanism 93 that transmits the movement of the eccentric cam 92 to the paper transport roll pair 654 to change the nip state.

[0079] The drive transmission mechanism 93 includes an operating arm 932 with a rotatable roller-shaped cam follower 931 attached to its tip that follows the eccentric cam 92, a drive shaft 933 that transmits the inclined movement of the operating arm 932 to the paper transport roll pair 654, and a switching plate 934 fixed to the drive shaft 933 that switches between a nip state and a nip release state by pushing down the rotation shaft 654c of the driven roll 654b of the paper transport roll pair 654. The operating arm 932 is biased to always contact the outer circumferential surface of the eccentric cam 92 by a biasing means such as a spring (not shown).

[0080] The eccentric cam 92 is attached to the drive shaft 95, as shown in Figure 10. The drive shaft 95's rotation direction and amount are switched by the drive motor 91. The eccentric cam 92 is configured to connect, by a smooth curved section, a first eccentric section 921 that switches the driven roll 654b of the paper transport roll pair 654 to a nipped state relative to the drive roll 654a, and a second eccentric section 922 that switches the driven roll 654b of the paper transport roll pair 654 to a nipped-release state, separated from the drive roll 654a, as shown in Figure 11.

[0081] In this embodiment 1, as shown in Figure 9, the eccentric cam 92 is formed to be longer than a normal eccentric cam 92, extending along its axial direction toward the front side of the device body 2a. A normal eccentric cam 92 displaces the cam follower 931 in a direction intersecting the axial direction, so its length along the axial direction is set to be slightly longer than the contact width of the cam follower 931.

[0082] In contrast, the eccentric cam 92 in this embodiment 1, as shown in Figure 9, has an axial length that is approximately 3 to 5 times longer than the contact width of the cam follower 931. Furthermore, the outer surface of the eccentric cam 92 is made of a material with high sliding properties and a relatively low coefficient of friction compared to materials such as rubber, such as Teflon (registered trademark). Therefore, the cam follower 931 can move along the outer surface of the eccentric cam 92 in the axial direction or diagonally in the axial direction. The axial length of this eccentric cam 92 is set to be long enough that, even when the second bottom plate 202 of the paper transport unit 200 is tilted downward, the cam follower 931, which is tilted together with the second bottom plate 202, maintains contact with the outer surface of the eccentric cam 92 without detaching.

[0083] The cam follower 931 is positioned to contact the eccentric cam 92. The cam follower 931 is formed in a cylindrical shape and is rotatably mounted on the tip of the operating arm 932. As shown in Figure 8, the operating arm 933 is fixed to the first bottom plate portion 201 of the paper transport unit 200 so as to be rotatable around the drive shaft 933 at the tip of the drive shaft 933. The drive shaft 933 is supported and positioned so as to be rotatable along the axial direction of the paper transport roll pair 654 from the rear to the front of the device body 2a.

[0084] A switching plate 934 is fixedly attached to the tip of the drive shaft 933, which moves the paper transport roll pair 654 to a nip-release state, separated from the drive roll 654a.

[0085] <Operation of the paper transport device> In the paper transport device 60 according to this embodiment 1, the means for switching the transport roll pair between a nip state and a nip release state is provided in the following manner, and compared to a device that does not have a switching means that maintains the switching function when returning from the open position by the separating means, it is possible to avoid the switching means becoming inoperable when one of the transport roll pair moves to the open position by the separating means.

[0086] In other words, in the paper transport device 60 according to this embodiment 1, if a jam occurs in the double-sided transport path 65 of the paper transport path, such as with recording paper 5 or long paper 5a, the paper transport unit 200 is pulled out to the front side of the main body 2a of the image output device 2, and the opening / closing handle 205 is operated to rotate the second bottom plate 202 of the paper transport unit 200 around the opening / closing pivot point 204 and move it downward to open it.

[0087] At this time, before the second bottom plate 202 of the paper transport unit 200 is opened, the paper transport roll pairs 651 to 658 in the double-sided transport path 65 are in a nipped state.

[0088] By the way, in the paper transport device 60 according to this embodiment 1, as shown in Figure 12(b), by moving the second bottom plate 202 of the paper transport unit 200 to the open state, the operating arm 932 of the switching mechanism 90 attached to the second bottom plate 202 moves to the open state together with the drive shaft 933.

[0089] As a result, the cam follower 931, attached to the tip of the operating arm 932 of the switching mechanism 90, slides downward and to the right in the figure, as shown in Figures 13(a) and (b), to the outer surface 92a of the eccentric cam 92, which is provided to be longer than a normal eccentric cam and whose outer surface is made of a material with high sliding properties, and maintains contact with the outer surface 92a of the eccentric cam 92. Therefore, the outer diameter and length of the eccentric cam 92 are configured so that the cam follower 931 maintains contact with the outer surface 92a of the eccentric cam 92 even when the second bottom plate 202 of the paper transport unit 200 moves to the open position.

[0090] Next, in the paper transport device 60 according to this embodiment 1, after removing the recording paper 5 and long paper 5a that have jammed in the double-sided transport path 65 of the paper transport path, the second bottom plate 202 of the paper transport unit 200 is moved to the closed position by operating the opening / closing handle 205, as shown in Figure 7(a).

[0091] In this embodiment 1, the paper transport device 60 moves the second bottom plate 202 to the closed position, causing the cam follower 931 attached to the operating arm 932 of the switching mechanism 90 attached to the second bottom plate 202 to return to the normal operating position while maintaining contact with the outer peripheral surface 92a of the eccentric cam 92, as shown in Figures 13(a) and (b).

[0092] As a result, the switching mechanism 90 can switch the driven roll 654b of the paper transport roll pair 654 to a nip-release state, which is separated from the drive roll 654a, by driving the drive motor.

[0093] Although this explanation uses the paper transport roll pair 654 of the paper transport device 60 as an example, the same principles apply to the other paper transport roll pairs 655 to 659.

[0094] Furthermore, although the above embodiment described an image forming apparatus that forms full-color images, it is not limited to this, and the same can of course be applied to an image forming apparatus that forms monochrome images.

[0095] Furthermore, although the above embodiment described the case in which the sheet transport device is applied as a paper transport device for an image forming apparatus, it is not limited to this, and of course, any sheet transport device that transports sheets can be similarly applied to devices other than image forming apparatuses. [Explanation of symbols]

[0096] 1…Image forming apparatus 2…Image output device 3…Paper feeder 60...Paper transport device 61... Paper feed path 65... Double-sided transport path 90... Single switching mechanism

Claims

1. A pair of conveyor rolls arranged in the sheet conveying path, The conveying roll pair comprises a means for moving one of the conveying rolls to an open position separated from the other conveying roll, with an open pivot point on one end of the conveying roll along its axial direction, and the means for moving one of the conveying rolls to an open position separated from the other conveying roll, A means for switching the transport roll pair between a nip state and a nip release state, comprising an eccentric cam rotationally driven by a driving means and an operating arm that follows the eccentric cam, wherein the movement of the operating arm switches the transport roll pair between a nip state and a nip release state, The operating arm moves along the surface of the eccentric cam before and after movement to the open position by the separating means, thereby enabling the transfer roll pair to be switched between a nip state and a nip release state when returning from the open position by the separating means. A sheet transport device equipped with the following features.

2. The sheet conveying device according to claim 1, wherein the eccentric cam is extended along the axial direction so as to maintain contact with the operating arm even when the operating arm moves to the open position during separation operation by the separation means.

3. Image forming means for forming an image on a recording medium, A transport means for transporting the recording medium to the image forming means, Equipped with, An image forming apparatus using the sheet conveying device described in claim 1 or 2 as the conveying means.

Images