JP2014005153A - Document conveyance device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a document conveyance device capable of conveying a document by suppressing a rapid variation in a conveyance load.SOLUTION: A document conveyance device includes a driving roller 901 arranged in a direction D2 perpendicular to a document conveyance direction D1 on the upstream side of a document reading unit 201, and driven rollers 902 and 903 arranged to oppose the driving roller 901 for respectively forming nip portions N2 and N3 between the driving roller 901 and themselves. The driven rollers 902 and 903 are supported on a common shaft 905 extending in the direction D2. A position of the nip portion N3 formed by the displacement driven roller 903 is displaced to the downstream side or the upstream side in the document conveyance direction D1 of a position of the nip portion N2 formed by the other driven roller 902. The other driven roller 902 is concentrically penetrated by the common shaft 905 and rotatably supported thereon, and the displacement driven roller 903 is rotatably supported on a supporting member 906 that is arranged while being penetrated by the common shaft 905. The displacement driven roller 903 is urged, to contact the driving roller 901 that opposes the displacement driven roller 903.

Description

  The present invention relates to a document conveying device that conveys a document to a document reading unit, and an image forming apparatus including the document conveying device.

  In general, the document conveying device includes a plurality of driving rollers arranged at a predetermined interval in a direction orthogonal to the document conveying direction and a plurality of driven rollers arranged to face each driving roller. In this apparatus, a document is sandwiched between nip portions formed therebetween, and the document is conveyed to a document reading unit by driving rotation of a driving roller. When a document is transported by such a document transport device, if the nip portion formed between a plurality of opposed roller pairs is formed in a straight line in a direction orthogonal to the document transport direction, the document is transported. The rear end portion of the document comes out of the nip portion simultaneously or substantially simultaneously. In this case, since the conveyance load abruptly varies (decreases) at the moment when the trailing edge of the document comes out of the nip portion, the document conveyance speed temporarily increases. This phenomenon also affects the document conveyance speed in the document reading unit, and as a result, reading failure tends to occur.

  In order to reduce the fluctuations in the conveyance load as described above, conventionally, the nip portion has been arranged by shifting the rotation axis of any one of a plurality of driving rollers and driven rollers in the document conveyance direction. Has been proposed that is formed in a non-straight line in a direction orthogonal to the document conveyance direction (see, for example, Patent Document 1).

JP 2004-277055 A

  However, in the document conveying device described in Patent Document 1, it is necessary to provide the rotation shafts of a plurality of rollers, the support members that support these rotation shafts, and the like separately and separately. Therefore, the number of parts increases, the structure and assembly of the apparatus become very complicated, and the cost increases. Further, since it is necessary to individually assemble a plurality of rollers, there is a problem that the positional accuracy of each roller and the distance (dimension) accuracy between the rollers are likely to vary, and it is difficult to perform stable document conveyance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a document conveying device that can realize stable document conveyance while suppressing rapid fluctuations in conveyance load with a simple structure with a reduced number of parts.
Another object of the present invention is to provide an image forming apparatus provided with the document conveying device.

  The present invention provides a document reading unit that reads a document that is transported in the document transport direction, a drive roller that is disposed on the upstream side of the document read unit in the document transport direction, and that is disposed to face the drive roller, A plurality of driven rollers forming a nip portion with the driving roller, and the plurality of driven rollers are supported by a single common shaft extending in a direction orthogonal to the document conveying direction, The position of the nip portion by at least one driven roller of the plurality of driven rollers is related to a document conveying device that is displaced downstream or upstream in the document conveying direction with respect to the position of the nip portion by another driven roller. .

  The displacement driven roller, which is the driven roller in which the position of the nip portion is displaced, has a smaller diameter than the other driven roller, and the other driven roller penetrates the common shaft concentrically. It is preferable that the displacement driven roller is rotatably supported, and the displacement driven roller is rotatably supported by a support member disposed so as to penetrate the common shaft.

  Further, it is preferable that the driven roller in which the position of the nip portion is displaced is a driven roller disposed at a central position in a direction orthogonal to the document conveying direction among the plurality of driven rollers.

  The document reading unit is preferably composed of two reading units that can read both the front and back sides of the document without turning the document upside down.

  The present invention also relates to an image forming apparatus comprising: the document conveying device; and an image forming unit that forms an image on a sheet-like image forming medium based on image information read from the document by the document reading unit. .

According to the present invention, it is possible to provide a document conveying device that can realize stable document conveyance while suppressing rapid fluctuations in the conveyance load with a simple structure with a reduced number of parts.
Further, according to the present invention, it is possible to provide an image forming apparatus provided with the document conveying device.

1 is a left side view for explaining the arrangement of components in a copying machine 1 as an embodiment of an image forming apparatus of the present invention. FIG. 3 is a schematic diagram showing a positional relationship between the document transport mechanism 44 and the document lift member 32 in a state where the downstream end of the document lift member 32 of the document transport apparatus 700 shown in FIG. 1 is lowered. FIG. 2 is a schematic diagram showing a positional relationship between a document transport mechanism 44 and a document lift member 32 in a state where a downstream end of the document lift member 32 of the document transport apparatus 700 shown in FIG. 1 is raised. FIG. 5 is a perspective view of each roller group arranged along a document reading conveyance path L10 as viewed from the inside of a conveyance mechanism housing 701. FIG. 6 is a plan view showing the overall configuration of a registration roller pair 70 and a first transport roller pair 90 with a cover member 702 removed. 6 is an enlarged cross-sectional view of the vicinity of a first transport roller pair 90. FIG. 4 is an enlarged perspective view of the vicinity of a first transport roller pair 90. FIG. FIG. 4 is an overall perspective view of driven rollers 902 and 903 in a first transport roller pair 90. It is a perspective view which shows the detailed structure of the center driven roller 903 of the driven rollers 902. FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, the overall structure of the copier 1 as an embodiment of the image forming apparatus of the present invention will be described with reference to FIGS. FIG. 1 is a left side view for explaining the arrangement of components in a copier 1 as an embodiment of an image forming apparatus of the present invention. FIG. 2 is a schematic diagram showing the positional relationship between the document transport mechanism 44 and the document lift member 32 in a state where the downstream end of the document lift member 32 of the document transport apparatus 700 shown in FIG. 1 is lowered. FIG. 3 is a schematic diagram showing a positional relationship between the document transport mechanism 44 and the document lift member 32 in a state where the downstream end of the document lift member 32 of the document transport apparatus 700 shown in FIG.

As shown in FIG. 1, the copier 1 of this embodiment includes a document reading device 200 and a device main body M.
The document reading device 200 includes a document reading unit 201 and a document conveying device 700. The document conveying device 700 is disposed above the document reading unit 201 in the vertical direction, and automatically conveys the document G to the document reading unit 201.
The apparatus main body M is disposed on the lower side in the vertical direction of the document reading apparatus 200 and forms a toner image on the paper T (sheet-like image forming medium) based on the image information of the document G read by the document reading unit 201. To do.

First, the document conveying apparatus 700 will be briefly described, the document reading unit 201 and the apparatus main body M of the document reading apparatus 200 will be described, and then the details of the document conveying apparatus 700 will be described.
As shown in FIGS. 1 to 3, the document conveyance device 700 includes a conveyance mechanism housing 701, a document placement unit 710, and a document stacking unit 720.

The transport mechanism housing 701 is a housing that houses a feeding roller unit 40 (described later) and a document transport mechanism 44 (described later) in the document transport apparatus 700.
The document placing portion 710 is a portion where the document G before the document information is read is placed in a stacked state.
The document accumulating unit 720 is a portion that is positioned below the document placing unit 710 in the vertical direction and that accumulates the documents G that have passed predetermined document reading positions J1 and J2 (described later).

In the document conveying device 700 of the present embodiment, the document G placed on the document placing unit 710 is upstream of the document conveying direction D1 by the document conveying mechanism 44 provided in the conveying mechanism housing 701. The document G is sequentially sent to the first document reading position J1 and the downstream document reading position J2, and the document G for which the document image reading processing by the document reading unit 201 has been completed is discharged into the document discharge space K.
The detailed configuration of the document placement unit 710 and the configuration of the feeding roller unit 40 and the document transport mechanism 44 inside the transport mechanism housing 701 will be described after the description of the apparatus main body M.

Next, the document reading unit 201 will be described.
As shown in FIGS. 2 and 3, the document reading unit 201 includes a first reading unit 201A including a contact image sensor (CIS) and a second reading unit 201B. The first reading unit 201A is arranged at the first document reading position J1 on the upstream side in the document conveyance direction D1 by the document conveyance mechanism 44 and reads the image information on the back surface of the document G. The second reading unit 201B is arranged at a second document reading position J2 downstream of the first document reading position J1 in the document transport direction D1, and reads the image information on the surface of the document G. The second reading unit 201B on the downstream side in the document transport direction D1 includes, for example, an illumination unit including a light source, a plurality of mirrors that form an optical path, an imaging lens, a CCD, and a CCD substrate.

  The original reading unit 201 reads the image information on both sides of the original G without inverting the original G by the first reading unit 201A and the second reading unit 201B, and the image information on the front and back sides of the read original G Is configured to perform predetermined processing and to output the processed image information to the image forming unit GK of the apparatus main body M.

Next, the apparatus main body M will be described.
As shown in FIG. 1, the apparatus main body M includes an image forming unit GK that forms a predetermined image on a paper T based on predetermined image information input from a document reading unit 201, and the paper T as an image forming unit GK. And a paper supply / discharge section KH for discharging the paper T after image formation.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2, a charging unit 10, a laser scanner unit 4, a developing device 16, a toner cartridge 5, a toner supply device 6, and a drum cleaning device 11. A transfer roller 8 and a fixing device 9.

  The paper feed / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a registration roller pair 80, and a conveyance path L for the paper T.

  The photosensitive drum 2 is made of a cylindrical member and functions as an image carrier. The photosensitive drum 2 is disposed in the apparatus main body M in a manner that can rotate around a rotation axis perpendicular to the paper surface of FIG. An electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The charging unit 10 is disposed on the upper side (upward) of the photosensitive drum 2 in the vertical direction. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 positively (plus polarity).

  The laser scanner unit 4 is disposed on the upper side (upward) in the vertical direction of the photosensitive drum 2 and is separated from the photosensitive drum 2. The laser scanner unit 4 includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on the image information output from the document reading apparatus 200. By performing scanning exposure with the laser scanner unit 4, electric charges charged on the surface of the photosensitive drum 2 are removed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  The developing device 16 is disposed in front of the photosensitive drum 2 (on the right side in FIG. 1). The developing device 16 develops a monochrome (usually black) toner image on the electrostatic latent image formed on the photosensitive drum 2. The developing device 16 includes a developing roller 17 that can be disposed to face the photosensitive drum 2 and a stirring roller 18 for stirring the toner.

The toner cartridge 5 stores toner supplied to the developing device 16.
The toner supply device 6 supplies the toner stored in the toner cartridge 5 to the developing device 16.

  The drum cleaning device 11 is disposed behind the photosensitive drum 2 (on the left side in FIG. 1). The drum cleaning device 11 removes toner and deposits remaining on the surface of the photosensitive drum 2.

The transfer roller 8 directly transfers the toner image developed on the surface of the photosensitive drum 2 onto the paper T. A transfer bias for transferring the toner image developed on the photosensitive drum 2 to the paper T is applied to the transfer roller 8 by a voltage application unit (not shown).
The toner image developed on the surface of the photosensitive drum 2 can be indirectly transferred onto the paper T via an intermediate transfer belt or the like.

The transfer roller 8 is configured to be movable between a contact position where the transfer roller 8 is in contact with the photosensitive drum 2 and a separation position where the transfer roller 8 is separated from the photosensitive drum 2. Specifically, the transfer roller 8 is moved to the contact position when the toner image developed on the photosensitive drum 2 is transferred to the paper T, and is moved to the separation position in other cases.
Here, the paper T is sandwiched between the photosensitive drum 2 and the transfer roller 8 and pressed against the surface of the photosensitive drum 2 (the side on which the toner image has been developed). In this way, a transfer nip N as a transfer portion is formed, and the toner image developed on the photosensitive drum 2 is transferred to the paper T.

  The fixing device 9 melts the toner constituting the toner image transferred onto the paper T and fixes it on the paper T. The fixing device 9 includes a heating roller 9a heated by a heater and a pressure roller 9b pressed against the heating roller 9a. The heating roller 9a and the pressure roller 9b convey the paper T on which the toner image is transferred so as to be sandwiched. By transporting the paper T so as to be sandwiched between the heating roller 9a and the pressure roller 9b, the toner transferred onto the paper T is melted and fixed on the surface of the paper T.

  The paper feed cassette 52 is disposed below the apparatus main body M (lower side in the vertical direction). The paper feed cassette 52 is arranged on the front side (right side in FIG. 1) of the apparatus main body M so as to be able to be pulled out in the horizontal direction. The paper feed cassette 52 includes a placement plate 60 on which the paper T is placed. The paper feed cassette 52 stores the paper T in a state where the paper T is stacked on the placement plate 60. The cassette paper feed unit 51 is disposed at the paper feed side end (the right side end in FIG. 1) of the paper feed cassette 52. The cassette paper feed unit 51 sends out the paper T stored in the paper feed cassette 52 to the transport path L.

  The cassette paper feeding unit 51 includes a forward feed roller 61 for taking out the paper T placed on the placement plate 60 and a double feed prevention mechanism including a roller pair 63 for feeding the paper T one by one to the transport path L. Prepare.

  A transport path L for transporting the paper T is formed between the cassette paper feed unit 51 or the manual paper feed unit 64 and the paper discharge unit 50. The conveyance path L is transferred from the first conveyance path L1 from the cassette paper feeding unit 51 to the first merge part P1, the second conveyance path L2 from the first merge part P1 to the registration roller pair 80, and the transfer from the registration roller pair 80. A third conveyance path L3 to the roller 8, a fourth conveyance path L4 from the transfer roller 8 to the fixing device 9, a fifth conveyance path L5 from the fixing device 9 to the branching portion P3, and a discharge portion from the branching portion P3. And up to 50 sixth transport paths L6.

Further, the transport path L has a seventh transport path L7 from the manual paper feed unit 64 to the first junction P1. The first merging portion P1 is a merging portion between the first conveyance path L1 that conveys the paper T from the cassette paper feeding section 51 and the seventh conveyance path L7 that conveys the paper T from the manual feed tray 65.
A second junction P2 is disposed in the middle of the second transport path L2. Furthermore, the conveyance path L has a return conveyance path Lb from the branching part P3 to the second joining part P2. The second junction P2 is a junction between the second conveyance path L2 and the return conveyance path Lb.

  Here, on the upstream side (right side in FIG. 1) of the transfer direction of the paper T in the transfer roller 8, a registration roller pair 80 is disposed. The registration roller pair 80 is a roller pair for correcting skew (oblique feeding) of the paper T and adjusting timing with the toner image.

  The return conveyance path Lb is a conveyance path that is provided so that the opposite surface (non-printing surface) to the surface that has already been printed faces the photosensitive drum 2 when performing duplex printing on the paper T. According to the return conveyance path Lb, the sheet T conveyed from the branching section P3 to the paper discharge section 50 side can be reversed and returned to the second conveyance path L2. A predetermined toner image is transferred onto the non-printing surface of the paper T that has been turned upside down by the return conveyance path Lb.

  A manual paper feed unit 64 is provided on the front side of the apparatus main body M (on the right side in FIG. 1) and above the paper feed cassette 52. The manual paper feed unit 64 feeds the paper T placed on the open manual feed tray 65 to the second transport path L2 via the seventh transport path L7 and the first junction P1. The manual paper feed unit 64 includes a manual feed tray 65 and a paper feed roller 66. The base of the manual feed tray 65 is attached to the vicinity of the entrance of the seventh transport path L7 so as to be rotatable (openable and closable). The manual feed tray 65 constitutes a part of the front surface of the apparatus main body M in the closed state. The paper feed roller 66 takes out the paper T placed on the manual feed tray 65 and sends it out toward the seventh transport path L7.

  A paper discharge unit 50 is formed at the end of the sixth transport path L6. The paper discharge unit 50 is disposed on the upper side of the apparatus main body M. The paper discharge unit 50 opens toward the front of the apparatus main body M (to the right in FIG. 1). The paper discharge unit 50 discharges the paper T on which the toner is fixed by the fixing device 9 to the outside of the apparatus main body M.

  On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M. The paper discharge stacking unit M1 is a part formed by recessing the upper surface of the apparatus main body M downward (vertically in the vertical direction). The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, the paper T discharged from the paper discharge unit 50 and having a predetermined image transferred thereon is stacked and stacked.

The image information output from the document reading unit 201 is output from the document reading apparatus 200 to the apparatus main body M.
The image information input to the apparatus main body M is input to an image formation control unit (not shown). The image formation control unit controls the photosensitive drum 2, the charging unit 10, the laser scanner unit 4, the developing device 16, and the like that constitute the image forming unit GK based on the image information. A predetermined toner image is formed on the photosensitive drum 2 based on the image information.

  The same image as the image of the original G is transferred to the paper T conveyed to the transfer nip N formed by the photosensitive drum 2 via the conveyance path L based on the image information. The paper T on which the image is formed is discharged from the paper discharge unit 50 to the paper discharge stacking unit M1.

  Next, the document placement unit 710 of the document transport apparatus 700 according to the present embodiment and the document transport mechanism 44 in the transport mechanism housing 701 will be described with reference to FIGS. First, a schematic configuration of the document conveying device 700 will be described with reference to FIGS. 2 and 3.

  As shown in FIGS. 2 and 3, the document conveying apparatus 700 according to the present embodiment includes a document placing portion 31, a document lift member 32, a lift operation member 35, a feeding roller unit 40, and a document conveyance mechanism 44. And a motor (not shown). The feeding roller unit 40 includes a pickup roller 34 and a belt-type feeding unit 413.

  The document placing portion 31 is a tray body that is a main body of the document placing portion 710 on which the document G before being transported is placed. The document placing portion 31 is rotatably connected to the transport mechanism housing 701 on the downstream end 31b side so that the upstream end 31a side can be retracted upward as indicated by an arrow U1 in FIG.

  The operation of retracting the upstream end 31 a side of the document placement portion 31 upwards facilitates, for example, the work of eliminating JAM when JAM occurs in the document discharge space K located below the document placement portion 31. It is necessary to do.

  As shown in FIGS. 2 and 3, the document lift member 32 is disposed on the downstream side of the document placement portion 31 so as to be disposed on the lower surface side on the downstream side of the document G placed on the document placement portion 31. It is assembled on the top surface. The upper surface 32 a of the document lift member 32 serves as a placement surface on which the downstream side of the document G placed on the document placement portion 31 is placed.

  The document lift member 32 has a pair of movable side walls 321 (only one of the movable side walls is shown in FIGS. 2 and 3) that regulates the positions of both sides in the width direction of the document G to be placed. The pair of movable side walls 321 can move in a direction away from or close to each other, and can position both sides of the document G having various sizes.

  The document lift member 32 is rotated so as to raise the downstream end portion 32b as shown in FIG. As a result, the downstream end of the document G placed on the document placement unit 31 and the document lift member 32 is lifted. Further, the document lift member 32 is rotated so as to lower the downstream end portion 32b as shown in FIG. 2 by the downward rotation of the lift operation member 35. As a result, the downstream end of the document G placed on the document placement unit 31 and the document lift member 32 is lowered. FIG. 2 shows a state in which the document lift member 32 has been lowered to the lowest position.

  Although not shown, the document lift member 32 is rotatably engaged with the document placing portion 31 at the upstream end portion 32c. As shown by an arrow R11 in FIG. 3, the document lift member 32 is moved upward with the upstream end portion 32c as a rotation fulcrum, as shown by the arrow R11 in FIG. Rotate. This rotation is called rotation in the positive direction. That is, the document lift member 32 rises by rotating in the forward direction and descends by rotating in the reverse direction.

  As shown in FIGS. 2 and 3, the pickup roller 34 is provided so as to be opposed to the upper surface of the document lift member 32. When the downstream end 32 b of the document lift member 32 is lifted by the lift operation member 35 and the document G is lifted by the lift of the document lift member 32, the pickup roller 34 is placed on the document lift member 32. It contacts the upper surface of the original G. The pickup roller 34 that is in contact with the upper surface of the document G rotates, so that the document G can be sent from the document lift member 32 to the document transport mechanism 44 in the transport mechanism housing 701. The pickup roller 34 is made of hollow rubber.

  As shown in FIGS. 2 and 3, the feed roller unit 40, the document transport mechanism 44, and the like are disposed in the transport mechanism housing 701. The pickup roller 34 is disposed in the feeding roller unit 40. The document transport mechanism 44 discharges the document G sent out by the feeding roller unit 40 to the document discharge space K via the first document reading position J1 and the second document reading position J2. The configurations of the feeding roller unit 40 and the document transport mechanism 44 in the transport mechanism housing 701 will be described later.

As shown in FIGS. 2 and 3, the lift operating member 35 includes a first rotating shaft member 351 and a lift member 352.
The first rotation shaft member 351 is a shaft member that extends in the width direction of the document G. The first rotating shaft member 351 is rotatably supported by bearing portions 313 provided on the bottom wall 312 of the document placing portion 31 at both ends thereof.

  The lift member 352 is disposed below the document lift member 32. The lift member 352 is connected to the first rotating shaft member 351 at the base end thereof, and rotates around the axis of the first rotating shaft member 351. The lift member 352 is fixed at two locations spaced apart in the axial direction of the first rotating shaft member 351. The lift member 352 rotates to lift the downstream end 32b of the document lift member 32 during normal rotation (when rotating in the direction of arrow R12 in FIG. 3). Further, the lift member 352 rotates so as to lower the downstream end portion 32b of the document lift member 32 during reverse rotation (when rotating in the direction of arrow R13 in FIG. 3).

  That is, the lift member 352 operates to raise the document lift member 32 when operating in the forward direction (when rotating in the direction of arrow R12 in FIG. 3). Further, the lift member 352 operates to lower the document lift member 32 when operated in the reverse direction (when rotating in the direction of arrow R13 in FIG. 3).

In the present embodiment, as shown in FIGS. 2 and 3, the belt-type feeding unit 413 is held at a position downstream of the pickup roller 34.
The belt-type feeding unit 413 includes a pair of rollers 414 and 415 that are spaced apart from each other in the conveyance direction of the document G, a conveyance belt 416 that is stretched between them, and a lower portion of the conveyance belt 416. And a pressing roller 417 pressed against. The belt-type feeding unit 413 conveys the document G downstream by sandwiching the document G between the conveyance belt 416 and the pressing roller 417 and causing the conveyance belt 416 to travel in the direction indicated by the arrow X9 in FIG. To do.

  The document transport mechanism 44 includes a document reading transport path L10 and a document discharge transport path L11 in a transport mechanism housing 701. The document reading transport path L10 passes the document G from the feeding roller unit 40 through the first reading unit 201A (first document reading position J1) of the document reading unit 201, and then to the second reading unit 201B (second document reading). It is a transport path for transporting to position J2). The document discharge transport path L11 is a transport path that transports the document G that has been read from the second reading unit 201B (second document reading position J2) to the document stacking unit 720.

  In the document reading conveyance path L10, along the document conveyance direction D1, a registration roller pair 70 including a first registration roller 71 and a second registration roller 72, a first conveyance roller pair 90, and a first reading unit 201A are provided. An opposing CIS roller 91 and a second transport roller pair 92 are disposed. A third transport roller pair 93 and a discharge roller pair 94 are arranged along the document transport direction D1 in the document discharge transport path L11.

  Next, with reference to FIGS. 4 to 9, the document transport mechanism 44 that is a characteristic configuration of the document transport apparatus 700 in the copier 1 of the present embodiment will be described in detail. FIG. 4 is a perspective view of each roller group arranged along the document reading transport path L10 as viewed from the inside of the transport mechanism housing 701. FIG. FIG. 5 is a plan view showing the entire configuration of the registration roller pair 70 and the first transport roller pair 90 with the cover member 702 removed. FIG. 6 is an enlarged cross-sectional view of the vicinity of the first transport roller pair 90. FIG. 7 is an enlarged perspective view of the vicinity of the first transport roller pair 90. FIG. 8 is an overall perspective view of the driven rollers 902 and 903 in the first transport roller pair 90. FIG. 9 is a perspective view showing a detailed configuration of the central driven roller 903 among the driven rollers 902.

  As shown in FIGS. 4 to 9, the upper portion of the registration roller pair 70 and the first transport roller pair 90 is covered with a cover member 702 that is detachably attached to the inside of the transport mechanism housing 701. A plurality (five) of first conveyance roller pairs 90 positioned upstream of the document reading direction D1 of the first reading unit 201A are arranged at predetermined intervals in a direction D2 orthogonal to the document conveying direction D1. A driving roller 901 and a plurality (five) of driven rollers 902 and 903 arranged to face each driving roller 901 are provided. A nip portion N2 is formed between each drive roller 901 and each driven roller 902, respectively. A nip portion N3 is formed between the center driving roller 901 and the center driven roller 903 as a displacement driven roller.

  The five drive rollers 901 are fixed to one drive shaft 904 extending in a direction D2 orthogonal to the document transport direction D1. One end of the drive shaft 904 projects outward from the side of the transport mechanism housing 701 and is connected to a motor (not shown). When the motor drives the drive shaft 904, the five drive rollers 901 are driven and rotated in the direction of the arrow R1 shown in FIGS.

  As shown in FIG. 8, the five driven rollers 902 and 903 are driven to rotate in the direction of the arrow R2 shown in FIG. Of the five driven rollers 902 and 903, the central driven roller 903 arranged at the center position in the direction D2 orthogonal to the document conveying direction D1 is configured to have a smaller diameter and longer than the other four driven rollers 902. Has been.

  The four driven rollers 902 excluding the central driven roller 903 pass through one common shaft 905 extending in the direction D2 orthogonal to the document conveying direction D1 and are rotatably supported. The common shaft 905 is urged downward by a plurality of coil springs 907 interposed between the cover member 702 and the common shaft 905. As a result, the four driven rollers 902 are elastically pressed against the circumferential surfaces of the four drive rollers 901 facing each other to form a linear nip portion N2.

On the other hand, the center driven roller 903 is rotatably supported by a support member 906 that is disposed so as to penetrate the central portion of the common shaft 905 in the axial direction.
As shown in FIG. 9, the support member 906 includes two side plate portions 906a having a substantially isosceles triangle shape, a connecting plate portion 906b that connects one corner portion of the two side plate portions 906a, and two side plate portions 906a. And a fixed shaft 906c fixed between the other corners.

A through hole 906d through which the common shaft 905 passes is formed at the top of the two side plate portions 906a in the support member 906. A small-diameter central driven roller 903 is rotatably inserted and supported on the fixed shaft 906c of the support member 906.
Further, both ends of a torsion spring 908 wound around the common shaft 905 are in contact with the connecting plate portion 906 b in the support member 906 and the fixed plate portion 703 inside the transport mechanism housing 701. Due to the urging force of the torsion spring 908, the central driven roller 903 is elastically pressed against the peripheral surface of the central driving roller 901 opposite to the central driving roller 901 to form the nip portion N3.

  With the configuration described above, the position of the nip portion N3 formed between the central driven roller 903 and the central driving roller 901 opposite to the central driven roller 903 is the other four driven rollers 902 and the four driving rollers opposed to them. With respect to the position of the nip portion N2 formed between 901 and 901, it is displaced downstream in the document transport direction D1. The amount of displacement between the nip portion N3 and the nip portion N2 is, for example, 1 to 5 mm.

  As shown in FIG. 5, the plurality of coil springs 73 elastically press one (upper) registration roller 72 of the registration roller pair 70 against the other (lower) registration roller 71. The coil spring 73 is interposed between the cover member 702 and a shaft 74 that rotatably supports one registration roller 72.

  In the document transport mechanism 44 of the document transport apparatus 700 configured as described above, the document G sent out from the feed roller unit 40 is the registration roller pair 70, the first transport roller pair 90, and the CIS roller 91. The images are sequentially delivered and sequentially conveyed toward the first document reading position J1 along the document reading transport path L10. Then, when the document G passes through the first document reading position J1, the image on the back surface of the document G is read by the first reading unit 201A.

  Subsequently, the document G is transferred in the order of the CIS roller 91 and the second transport roller pair 92 while the image on the back surface of the document G is read at the first document reading position J1, and is transferred to the document reading transport path L10. And sequentially conveyed toward the second document reading position J2. Then, when the document G passes through the second document reading position J2, the image on the surface of the document G is read by the second reading unit 201B.

  After the reading of the image on the back side of the original G at the first original reading position J1 and the reading of the image on the front side of the original G at the second original reading position J2, the original G is transferred to the third transport roller pair. 93 and the discharge roller pair 94 are sequentially transferred to the document stacking unit 720 along the document discharge transport path L11, and then discharged to the document discharge space K.

  In the transporting and reading operations of the document G as described above, the central driven roller 903 among the five driven rollers 902 and 903 in the first transport roller pair 90 that transports the document G to the first document reading position J1. The position of the nip portion N3 is displaced downstream in the document conveying direction D1 with respect to the position of the nip portion N2 by the other four driven rollers 902. That is, the nip portions N3 and N2 by the first conveying roller pair 90 are formed in a non-linear manner along a direction D2 orthogonal to the document conveying direction D1.

  Therefore, when the rear end of the original G in the transport direction is pulled out from the first transport roller pair 90, all of the rear end in the transport direction does not come out at the same time or substantially simultaneously, and the rear end in the transport direction is the same as the nip portion N2. It comes out with a time difference corresponding to the amount of displacement from the nip portion N3. As a result, it is possible to suppress the fluctuation (decrease) in the conveyance load and the accompanying temporary change (increase) in the document conveyance speed at the moment when the rear end portion in the conveyance direction of the document G comes out of the nip portions N2 and N3. As a result, the original G can be conveyed at a stable speed, and the original G can be read normally and satisfactorily.

According to this embodiment, the following effects are produced, for example.
In the document conveying device 700 of the present embodiment, the first conveying roller pair 90 disposed upstream of the first document reading position J1 in the document conveying direction D1 is predetermined in a direction D2 orthogonal to the document conveying direction D1. A plurality of (five) drive rollers 901 arranged with a gap of 5 and a plurality of nip portions N2 and N3 formed between the drive rollers 901 and the drive rollers 901, respectively. A plurality of (five) driven rollers 902 and 903. The plurality of driven rollers 902 and 903 are supported by one common shaft 905 extending in a direction D2 orthogonal to the document conveying direction D1, and are driven at the center of the plurality of driven rollers 902 and 903. The position of the nip portion N3 by the roller 903 is displaced downstream in the document conveyance direction D1 with respect to the position of the nip portion N2 by the other driven roller 902.

  Therefore, according to the present embodiment, the rotation axes of the plurality of driven rollers 902 and 903 are arranged so as to be shifted in the document transport direction D1, so that the nip portions N2 and N3 are orthogonal to the document transport direction D1. It is not necessary to provide the rotating shaft and its supporting member independently and separately as compared with the prior art formed in a non-linear manner in D2. Further, by using one common shaft 905 and a single support member that supports the common shaft 905, all the driven rollers 902 and 903 can be supported at predetermined positions. Therefore, the number of parts of the apparatus can be reduced, and the structure and assembly of the apparatus can be simplified and simplified, and the manufacturing cost can be reduced.

  Further, the plurality of driven rollers 902 and 903 need not be individually assembled, and only one common shaft 905 needs to be assembled. Therefore, the positional accuracy of each driven roller 902 and 903 and the distance (dimension) accuracy between the rollers can be improved. Therefore, stable document conveyance can be performed by a synergistic effect of the suppression of the conveyance load due to the displacement of the positions of the nip portion N2 and the nip portion N3 and the appropriate conveyance action by the driven rollers 902 and 903.

In the present embodiment, the position of the nip portion N3 by the center driven roller 903 arranged at the center position in the direction D2 orthogonal to the document transport direction D1 among the plurality of driven rollers 902 and 903 is the other driven. The roller 902 is displaced downstream in the document transport direction D1 with respect to the position of the nip portion N2.
Therefore, the central portion in the width direction out of the rear end portion in the conveyance direction D1 of the document G comes out of the driven rollers 902 and 903 later than both side portions. Therefore, as compared with the case where the exit of the position biased from the central portion in the width direction of the document G is delayed, an excessive rotational moment does not act on the document G, and the document G is pulled out of the driven roller while maintaining a straight posture. Therefore, document conveyance can be further stabilized.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
In this embodiment, the monochrome copying machine 1 is described as the image forming apparatus. However, the present invention is not limited to this, and the image forming apparatus is, for example, a color copying machine, a printer, a facsimile machine, or a complex machine thereof. Also good.

  The displacement driven roller in which the position of the nip portion N3 is displaced is not limited to the central driven roller disposed at the center position in the direction D2 orthogonal to the document conveyance direction D1, and for example, in the direction D2 orthogonal to the document conveyance direction D1. One or two or more driven rollers may be arranged other than the central position.

In the present embodiment, the drive roller 901 and the driven rollers (902, 903) are each provided with a predetermined interval in the direction D2 orthogonal to the document conveyance direction, but the present invention is not limited to this. The driven roller may be two or more. There may be one drive roller 901 or two or more drive rollers 901. The driving roller 901 has a length corresponding to the plurality of driven rollers, and is disposed at a position corresponding to the plurality of driven rollers.
In the present embodiment, the position of the nip portion N3 by the central driven roller 903 is displaced downstream in the document transport direction D1 with respect to the position of the nip portion N2 by the other driven roller 902, but is not limited thereto. Instead, it may be displaced upstream in the document conveyance direction D1. In that case, the displacement is, for example, 1 to 5 mm.

  In the present embodiment, the document reading unit 201 sequentially reads the images on both sides of the document G while continuously conveying the document G in one direction without turning the document G upside down. And the second reading unit 201B are arranged at the upstream position and the downstream position in the document transport direction D1, but the present invention is not limited to this. You may comprise so that an image may be read.

  DESCRIPTION OF SYMBOLS 1 ... Copy machine (image forming apparatus), 44 ... Conveyance mechanism, 90 ... Conveyance roller pair, 201 ... Document reading part, 201A ... First reading part, 201B ... Second reading part, 700 ... Document conveying device, 901... Driving roller, 902, 903... Driven roller, 903... Central driven roller (displacement driven roller), D2... Direction orthogonal to document conveying direction, 905. Support member, D1... Original conveying direction, G... Original, GK... Image forming unit, J1... First document reading position, J2... Second document reading position, N2, N3. T: Paper (image forming medium)

Claims (7)

A document reading unit that reads a document conveyed in the document conveyance direction;
A driving roller disposed upstream of the document reading unit in the document transport direction;
A plurality of driven rollers disposed opposite to the drive roller and forming a nip portion with the drive roller,
The plurality of driven rollers are supported by one common shaft extending in a direction orthogonal to the document conveying direction,
The position of the nip portion by at least one driven roller of the plurality of driven rollers is displaced downstream or upstream in the document conveying direction with respect to the position of the nip portion by the other driven rollers,
The displacement driven roller, which is the driven roller in which the position of the nip portion is displaced, has a smaller diameter than the other driven rollers,
The other driven roller is rotatably supported by concentrically penetrating the common shaft,
The displacement driven roller is rotatably supported by a support member disposed through the common shaft,
The displacement driven roller is a document conveying device that is biased and contacts the driving roller facing the displacement driven roller. The document conveying apparatus according to claim 1, wherein the displacement driven roller is longer than the other driven rollers. 3. The document conveying device according to claim 1, wherein the displacement driven roller is a driven roller disposed at a central position in a direction orthogonal to the document conveying direction among the plurality of driven rollers. 4. The document conveying device according to claim 1, wherein the document reading unit includes two reading units that can read both the front and back sides of the document without inverting the document.   5. The document conveying device according to claim 1, wherein the driving roller and the driven roller are a pair of rollers adjacent to the document reading unit on the most upstream side in the document conveying direction. 6. The document conveying device according to claim 1, wherein the common shaft is biased so that the other driven roller contacts the driving roller facing the other driven roller. 7. A document conveying device according to any one of claims 1 to 6,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet-like image forming medium based on image information read from a document by the document reading unit.

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