Sheet conveying device, image reading device, and image forming device

Abstract

To enable more stable conveyance of a small-size sheet.SOLUTION: A sheet conveying device includes a conveying member, a separating member that forms a separating portion between the conveying member and the separating member, a driving source, and a conveying unit disposed downstream of the separating portion, wherein the conveying unit includes a drive roller having a plurality of first roller bodies, a driven roller having a plurality of second roller bodies and a shaft member that supports the plurality of second roller bodies, a holder member that restricts a position of a central second roller body, and a biasing member that biases the holder member. The holder member includes a first side surface portion provided with a first bearing portion and a second side surface portion provided with a second bearing portion, and the first and second side surface portions restrict the position of the central second roller body and transmit a biasing force of the biasing member to the shaft member via the first and second bearing portions.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying device that conveys a sheet, an image reading device that reads an image from a sheet, and an image forming apparatus that forms an image on a recording material. [Background technology]

[0002] Patent Document 1 describes an image reading device capable of reading images of small-sized documents such as business cards while transporting them. In this image reading device, a document fed from a document tray by a feed roller passes through a separation section formed by a separation roller and a separation pad, and is transported toward a reading section by a pair of transport rollers. The pair of transport rollers is composed of a drive roller having three rollers spaced apart in the width direction, and a driven roller having three rollers spaced apart in the width direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-054431 Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned document, a normal-sized document is conveyed while being sandwiched between all three rollers of the drive roller and all three rollers of the driven roller, while a small-sized document is conveyed between only the center roller of the drive roller and the center roller of the driven roller. As a result, the conveying force imparted to a small-sized document by the conveying roller pair is smaller than the conveying force imparted to a normal-sized document by the conveying roller pair. Depending on the relationship between the conveying force imparted to the document by the conveying roller pair and the frictional resistance experienced by the document at the separation section, the stability of document conveyance may be reduced.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet conveying device that can more stably convey small-sized sheets. [Means for solving the problem]

[0006] One aspect of the present invention is a sheet conveying device including a conveying member that conveys a sheet, a separating member that forms a separation section between the conveying member and the separating member and that separates the sheet by applying a frictional force to the sheet in the separation section, a drive source, and a conveying unit that is arranged downstream of the separation section in a sheet conveying direction, wherein the conveying unit has a plurality of first roller bodies arranged in a sheet width direction that is perpendicular to the sheet conveying direction, and includes a drive roller that rotates by a driving force of the drive source, a plurality of second roller bodies that respectively come into contact with the plurality of first roller bodies, and a shaft member that supports the plurality of second roller bodies, and includes a driven roller that rotates following the drive roller, and a central second roller that is arranged in the center of the plurality of second roller bodies in the sheet width direction. a holder member that regulates the position of the central second roller body, and a biasing member that biases the holder member so that the plurality of second roller bodies are pressed against the plurality of first roller bodies, wherein the holder member has a first bearing portion that abuts against the shaft member and a first side portion that faces one end face of the central second roller body in the sheet width direction, and a second bearing portion that abuts against the shaft member and a second side portion that faces the other end face of the central second roller body in the sheet width direction, wherein the first side portion and the second side portion regulate the position of the central second roller body in the sheet width direction, and the biasing force of the biasing member is transmitted to the shaft member via the first bearing portion and the second bearing portion.

[0007] Another aspect of the present invention is a sheet conveying device including a conveying member that conveys a sheet, a separating member that forms a separation section between the conveying member and the separating member and that separates the sheet by applying a frictional force to the sheet in the separation section, a drive source, and a conveying unit that is arranged downstream of the separation section in a sheet conveying direction, wherein the conveying unit has a plurality of first roller bodies arranged in a sheet width direction perpendicular to the sheet conveying direction, and the conveying unit has a drive roller that rotates by a driving force of the drive source, a plurality of second roller bodies that respectively contact the plurality of first roller bodies, and a shaft member that supports the plurality of second roller bodies, and a driven roller that rotates following the drive roller, and a second roller body that is arranged at the center in the sheet width direction among the plurality of second roller bodies. A sheet conveying device comprising: a holder member that regulates the positions of two second roller bodies; and a biasing member that biases the holder member so that the multiple second roller bodies are pressed against the multiple first roller bodies, wherein the holder member has a first bearing portion that abuts against the shaft member, a first side portion that faces one of the two second roller bodies in the sheet width direction, and a second bearing portion that abuts against the shaft member, and a second side portion that faces the other of the two second roller bodies in the sheet width direction, wherein the first side portion and the second side portion regulate the positions of the two second roller bodies in the sheet width direction, and the biasing force of the biasing member is transmitted to the shaft member via the first bearing portion and the second bearing portion. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a sheet conveying device that can more stably convey small-sized sheets. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of an image forming apparatus according to a first embodiment. [Figure 2] FIG. 1 is a perspective view of an image reading apparatus according to a first embodiment. [Figure 3] 1 is a schematic diagram of an image reading apparatus according to a first embodiment. [Figure 4] FIG. 2 is a cross-sectional view of the ADF according to the first embodiment. [Figure 5] FIG. 2 is a diagram showing the inside of the ADF according to the first embodiment. [Figure 6] 1A is a cross-sectional view of an ADF according to a first embodiment, and FIG. 1B is a perspective view of a driven roller holder according to the first embodiment. [Figure 7] FIG. 10 is a cross-sectional view of an ADF according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0011] First Embodiment First, an image forming apparatus 100 and an image reading apparatus 101 according to the first embodiment will be described with reference to FIGS. 1 to 3. The image forming apparatus 100 is an electrophotographic multifunction machine with a copying function that reads an image from an original using the image reading apparatus 101 and forms an image on a recording material P based on the acquired image information. However, the "image forming apparatus" may also be a single-function printer with only a printing function, a facsimile machine, a commercial printing machine, or the like. The "image forming apparatus" may also be, for example, an inkjet printer equipped with an inkjet printing unit as image forming means.

[0012] 1 is a schematic diagram of an image forming apparatus 100 according to a first embodiment. The image forming apparatus 100 has a printer main body 104 as the image forming apparatus main body, and an image reading device 101 arranged above the printer main body 104. The printer main body 104 is equipped with an image forming unit 120, which is an electrophotographic image forming engine, a feed cassette 105 that stores recording material P, a conveying mechanism that conveys the recording material P, and an output tray 119. A variety of sheet materials of different sizes and materials can be used as the recording material P (recording medium), including paper such as plain paper and cardboard, surface-treated sheet materials such as coated paper, specially shaped sheet materials such as envelopes and index paper, plastic film, cloth, etc.

[0013] Image forming section 120 includes image forming units 111, 112, 113, and 114 (process units), exposure units 107, 108, 109, and 110, a transfer unit, and a fixing unit 118. Each of image forming units 111 to 114 has a photosensitive drum as an image carrier (photosensitive member), a charging unit that acts on the photosensitive drum to perform the charging, developing, and cleaning processes in the electrophotographic process, a developing unit, and a cleaning unit. The transfer unit has an intermediate transfer belt 115 as an intermediate transfer member, a secondary transfer roller 116 that forms a secondary transfer section together with intermediate transfer belt 115, and primary transfer rollers that face each photosensitive drum across intermediate transfer belt 115. Fixing unit 118 has, for example, a pair of fixing rollers and a halogen lamp as a heat source.

[0014] The image forming apparatus 100 performs a series of operations (image forming operations) to form an image while conveying the recording material P as follows: For example, when a user presses a print execution button (copy button) on an operation unit with a document set in the document tray 200 of the image reading apparatus 101, the image forming apparatus 100 performs a reading operation by the image reading apparatus 101 and also performs an image forming operation.

[0015] During image formation, the photosensitive drums of each image forming unit 111-114 and the intermediate transfer belt 115 are rotated. The surface of each photosensitive drum is uniformly charged by a charging unit. The exposure units 107-110 expose the surface of the photosensitive drum based on image information received from the image reading device 101 or a host computer connected to the image forming apparatus 100 via a network. This forms an electrostatic latent image corresponding to a monochrome image on the surface of each photosensitive drum. The development units of each image forming unit 111-114 develop the electrostatic latent image into a toner image using yellow, magenta, cyan, or black toner (developer). The toner image is then transferred from the photosensitive drum to the intermediate transfer belt 115 by a primary transfer roller. A full-color toner image (hereinafter simply referred to as the toner image) is formed on the intermediate transfer belt 115 by multiple transfer, with each color toner image overlapping the other. The toner image is then transported toward the secondary transfer unit by the rotation of the intermediate transfer belt 115.

[0016] Meanwhile, a feeding roller 106 feeds a recording material P from a feeding cassette 105 and transports it toward a secondary transfer section. At the secondary transfer section, a toner image is transferred from an intermediate transfer belt 115 to the recording material P by a secondary transfer roller 116 to which a predetermined transfer voltage is applied. After passing through the secondary transfer section, the recording material P is transported to a fixing unit 118 by a pre-fixing transport section 117, where it undergoes a fixing process in which the toner image is heated and pressurized. After passing through the fixing unit 118, the recording material P is discharged as a product and stacked on a discharge tray 119.

[0017] (Image reader) Next, the image reading device 101 will be described with reference to Figures 2 and 3. The image reading device 101 roughly includes a reader 103 and an automatic document feeder 102 (hereinafter referred to as ADF 102) as a sheet conveying device in this embodiment. The reader 103 is fixed to the top of a printer main body 104. The ADF 102 is supported by the reader 103 and is provided so as to be openable and closable relative to the reader 103.

[0018] 2 and 3, the reader 103 has a surface reading unit 306 and a scanning glass 312. The surface reading unit 306 has a light source 310, a substrate 309 on which a CCD (charge-coupled device) serving as a light receiving element is arranged, and an optical system 308 that guides light from the original and forms an image on the light receiving surface of the light receiving element.

[0019] The ADF 102 has a back surface reading unit 307 and a flow reading glass 313. The back surface reading unit 307 is an image sensor unit that includes a light source, a sensor substrate on which a CMOS circuit serving as a light receiving element is formed, and an optical system that forms an image of light from the original on the light receiving surface of the sensor substrate.

[0020] Each of the front surface reading unit 306 and the back surface reading unit 307 is an example of a reading unit that reads an image from a document as a sheet being transported by a transport member of the ADF 101.

[0021] The ADF 102 also has a document tray 200, an opening / closing cover 315, a plurality of transport guides including a separation guide 317, a housing 316, and a discharge tray 201. The ADF 102 also has, as transport members for transporting documents, a pickup roller 300 (feed roller), a separation roller pair 301, a pull-out roller pair 302, a first read roller pair 303, a second read roller pair 304, and a discharge roller pair 305.

[0022] Open-close cover 315 is a second frame (second frame) that is supported by housing 316 as a first frame (first frame) so as to be openable and closable. Open-close cover 315 has top cover portion 315u that forms at least a portion of the top surface of ADF 102, and transport guide 315g (second guide portion) that forms at least a portion of transport path CP together with transport guide 316g (first guide portion) provided in housing 316. Open-close cover 315 is movable (rotatable) relative to housing 316 so as to open at least a portion of transport path CP.

[0023] The pickup roller 300, separation roller pair 301, pull-out roller pair 302, first read roller pair 303, second read roller pair 304, and discharge roller pair 305 are arranged in this order along the conveyance path CP. Hereinafter, the direction in which the document is conveyed along the conveyance path CP will be referred to as the sheet conveyance direction Dc. Also, the direction along the sheet and perpendicular to the sheet conveyance direction will be referred to as the sheet width direction Dw. The sheet width direction Dw is substantially the same as the main scanning direction of the front surface reading unit 306 and the back surface reading unit 307, which are line sensors.

[0024] The document tray 200 is an example of a placement portion on which documents as sheets are placed. The document tray 200 is supported by a housing 316. The pickup roller 300 is an example of a feeding member that feeds documents from the document tray 200. The discharge tray 119 is a placement portion on which documents whose images have been read are stacked. The pair of discharge rollers 305 is an example of a discharge member that discharges documents from inside the ADF 102 to the outside toward the discharge tray 119.

[0025] The document tray 200 is provided with side regulating plates 200a and 200b as a pair of regulating members that regulate the position of the document in the sheet width direction Dw. The side regulating plates 200a and 200b are connected via an interlocking mechanism such as a rack and pinion and are configured to move in conjunction with each other in the sheet width direction Dw. The side regulating plates 200a and 200b move while maintaining a symmetrical positional relationship with respect to the center of the document tray 200 in the sheet width direction Dw (a state in which the distances from the regulating surfaces facing the side edges of the document to the center of the document tray 200 are equal). The ADF 102 is a center-based sheet transport device that transports documents so that the center of the document in the sheet width direction Dw coincides with the transport center Wc (FIGS. 5 and 6), with the center of the document tray 200 in the sheet width direction Dw being the transport center Wc. The transport center Wc is the reference for the sheet position in the sheet width direction Dw of the document transported by the ADF 102.

[0026] In this embodiment, the document tray 200 can accommodate sheets (hereinafter referred to as small-sized documents) with a short length in the sheet width direction Dw (hereinafter referred to as sheet width), such as business cards, and the ADF 102 can transport these small-sized documents. A small-sized document is a sheet smaller than the paper size used for general documents, such as an A6 size or smaller document (sheet width 105 mm or smaller). Small-sized documents include documents with a sheet width of 55 mm and a sheet length of 91 mm, which is the size of a general business card. The side regulating plates 200a and 200b can be moved to positions where they abut both side edges of a business-card-sized document. Instead of using the side regulating plates 200a and 200b, the widthwise position of a small-sized document may be restricted by placing the small-sized document on a dedicated auxiliary tray that is detachable from the document tray 200.

[0027] Separation roller pair 301 includes feed roller 301a (FIG. 3) that conveys the document, and separation roller 301b that forms separation portion Ns (separation nip) between feed roller 301a and feed roller 301a. Feed roller 301a is an example of a conveying member that conveys the document in the sheet conveyance direction. Feed roller 301a and pickup roller 300 are driven to rotate by a common drive source (motor). Separation roller 301b is an example of a separating member that separates the document by applying frictional force to the document at separation portion Ns. Separation guide 317 guides the leading edge of the document fed by pickup roller 300 toward separation portion Ns.

[0028] Separation roller 301b is a roller member connected, for example, via a torque limiter, to a fixed shaft (a non-rotating shaft member) supported by housing 316. The separation member is not limited to this, and for example, a pad-shaped elastic member (rubber pad) that contacts feed roller 301a, or a retard roller to which a driving force (retard drive) in a direction opposite to the sheet conveying direction is input via a torque limiter may be used.

[0029] The pull-out roller pair 302 is a transport unit disposed downstream of the separation roller pair 301 in the sheet transport direction Dc, and transports the document received from the separation roller pair 301 further in the sheet transport direction Dc. In other words, the pull-out roller pair 302 is a transport roller pair that transports the document in the sheet transport direction Dc against the frictional force (frictional resistance) in the opposite direction to the sheet transport direction Dc that the document receives from the separation roller 301b in the separation section Ns.

[0030] The pair of pull-out rollers 302 includes a drive roller 302A that rotates by receiving a driving force from a drive source disposed in a housing 316, and a driven roller 302B that rotates following the drive roller 302A. The detailed configuration of the pair of pull-out rollers 302 will be described later.

[0031] In this embodiment, the opening / closing cover 315 supports the pickup roller 300, the feed roller 301a of the separation roller pair 301, and the driven roller 302B of the pull-out roller pair 302. The housing 316 supports multiple rollers including the separation roller 301b and the drive roller 302A of the pull-out roller pair 302. When the opening / closing cover 315 is closed, a conveying path CP is formed and a nip portion is formed between the separation roller pair 301 and the pull-out roller pair 302. In other words, the ADF 102 is allowed to convey documents when the opening / closing cover 315 is closed.

[0032] The following describes the reading operation (scanning operation) in which the image reading device 101 reads an image while transporting a document using the ADF 1. The user places a document on the document tray 200 and operates the operation unit to issue a command to execute the reading operation, which starts the reading operation. The pickup roller 300 rotates while in contact with the top surface of the top document on the document tray 200, thereby feeding the top document toward the pair of separation rollers 301. The fed document is guided by the separation guide 317 and enters the separation unit Ns, where it is further transported in the sheet transport direction Dc by the feed roller 301a. When multiple documents enter the separation unit Ns, the frictional force applied by the separation roller 301b to the documents prevents documents other than the top document from passing through the separation unit Ns. As a result, each document is transported along the transport path CP in a separated state.

[0033] When the leading edge of the document that has passed through the separation portion Ns reaches the pair of pull-out rollers 302, the document is further conveyed downstream in the sheet conveying direction Dc by the pair of pull-out rollers 302.

[0034] Here, the rotational drive of the pickup roller 300 and the feed roller 301a may be stopped before the trailing edge of the document in the sheet transport direction Dc passes through the separation unit Ns. This prevents the following document from moving together with the document to be fed in the current feeding operation. Furthermore, the transport speed of the pull-out roller pair 302 (the peripheral speed of the drive roller 302A) may be set faster than the transport speed of the separation roller 301b (the peripheral speed of the feed roller 301a). This improves both the separation performance in the separation unit Ns and the throughput of the reading operation. The above configurations may be applied alone or in combination. When the above configurations are applied, it is preferable that the pull-out roller pair 302 can apply a greater transport force to the document in order to stably transport the document against the frictional resistance experienced by the document in the separation unit Ns.

[0035] The document that has passed through the pair of pull-out rollers 302 is transported via the first pair of read rollers 303 and the second pair of read rollers 304. During this process, at a reading position between the first pair of read rollers 303 and the second pair of read rollers 304, a front side reading unit 306 optically scans the first side of the document through a flow reading glass 312 to read image information on the first side. When image information is to be read from both sides of the document, a back side reading unit 307 optically scans the second side of the document through a flow reading glass 313 to read image information on the second side at a reading position between the second pair of read rollers 304 and the pair of discharge rollers 305. The document from which the image information has been read is discharged to the outside of the housing 316 by the pair of discharge rollers 305 and stacked on the discharge tray 201.

[0036] In addition, the image reading device 101 can perform an operation (fixed reading operation) of reading image information while moving the surface reading unit 306 in the sub-scanning direction, with a document placed on the document table glass provided on the top surface of the reader 103 and the ADF 102 closed.

[0037] (Pressure configuration of the pull-out roller pair) The configuration of the pull-out roller pair 302 and its pressure application configuration in this embodiment will be described in detail using FIGS. 4, 5, and 6(a) and 6(b). FIG. 4 is a cross-sectional view showing a portion of the ADF 102 taken along line AA (a virtual plane along the conveyance center Wc) in FIG. 2. FIG. 5 is a top view showing the inside of the open-close cover 315, illustrating the ADF 102 as viewed from above through the top cover portion 315u of the open-close cover 315. FIG. 6(a) is a cross-sectional view showing a portion of the ADF 102 taken along line BB in FIG. 2. FIG. 6(a) shows a cross-section of the ADF 102 taken along a virtual plane including the rotational axis of the drive roller 302A and the rotational axis of the driven roller 302B of the pull-out roller pair 302. FIG. 6(b) is a perspective view of the driven roller holder 320.

[0038] 4 and 6(a), the pull-out roller pair 302 includes a drive roller 302A and a driven roller 302B. The ADF 102 also includes a driven roller holder 320 that contacts the driven roller 302B, and a pressure spring 318 as a biasing member that biases the driven roller holder 320 to apply pressure to the nip portion. The conveying unit in this embodiment includes the pull-out roller pair 302, the driven roller holder 320, and the pressure spring 318.

[0039] The drive roller 302A has drive rollers 331, 332, and 333 as a plurality of first roller bodies arranged in the sheet width direction Dw, and a drive shaft 334 that is a shaft member that supports the drive rollers 331 to 333. The drive rollers 331 to 333 are attached to the drive shaft 334 and rotate integrally with the drive shaft 334. An input gear that receives a driving force from a motor M serving as a drive source is provided at one end of the drive shaft 334. The drive roller 302A is driven to rotate by the driving force of the motor M. Each of the drive rollers 331 to 333 is exposed to the conveyance path CP through an opening formed in the conveyance guide 316g.

[0040] The driven roller 302B has driven rollers 341, 342, and 343 as multiple second roller elements arranged in the sheet width direction Dw, and a driven shaft 344 that is a shaft member that supports the driven rollers 341 to 343. The driven rollers 341 to 343 are rotatably supported by the driven shaft 344. The driven rollers 341 to 343 are loosely fitted to the driven shaft 344 so as to be rotatable, but the driven rollers 341 to 343 may also rotate integrally with the driven shaft 344. Each of the driven rollers 341 to 343 is exposed to the conveying path CP through an opening formed in the conveying guide 315g. The driven rollers 341 to 343 are disposed at positions corresponding to the drive rollers 331 to 333, and abut against the drive rollers 331 to 333, respectively.

[0041] The driven shaft 344 is rotatably supported by the conveying guide 315g on the side opposite to the conveying surface of the conveying guide 315g. The open-close cover 315 has ribs that protrude in the height direction Dh from the surface of the conveying guide 315g on the side opposite to the conveying surface and that are provided with bearings that rotatably support both ends of the driven shaft 344.

[0042] The driving rollers 331-333 and the driven rollers 341-343 are rotating bodies (roller members, roller bodies) having outer circumferential surfaces that can come into contact with the document to be conveyed. The pair of pull-out rollers 302 is configured to convey the document by nipping it in at least one of a plurality of nip portions N1, N2, and N3 formed between the driving rollers 331-333 and the driven rollers 341-343.

[0043] In this embodiment, the drive roller 302A has three drive rollers 331-333, and the driven roller 302B has three driven rollers 341-343. The drive roller 331 is located at the center of the multiple drive rollers 331-333 in the sheet width direction Dw. The drive rollers 332 and 333 are located at both ends of the multiple drive rollers 331-333 in the sheet width direction Dw. Similarly, the driven roller 341 is located at the center of the multiple driven rollers 341-343 in the sheet width direction Dw. The driven rollers 342 and 343 are located at both ends of the multiple driven rollers 341-343 in the sheet width direction Dw.

[0044] In this embodiment, the central drive roller 331 and the central driven roller 341 are disposed on the aforementioned conveyance center Wc in the sheet width direction Dw. Meanwhile, the drive rollers 332 and 333 and the driven rollers 342 and 343 at both ends are positioned outside the area through which small-sized documents pass in the sheet width direction Dw for at least some of the small-sized documents that the ADF 102 can convey. In other words, the sheet width of the smallest-sized document that the ADF 102 can convey is shorter than the distance W1 ( FIG. 5 ) from the driven roller 342 adjacent to one side of the central driven roller 341 to the driven roller 343 adjacent to the other side. Therefore, at least some of the small-sized documents are clamped only by the central nip portion N1 of the three nip portions N1 to N3 of the pull-out roller pair 302. Incidentally, A4-sized documents are clamped by all three nip portions N1 to N3.

[0045] The number of drive rollers (first roller bodies) and driven rollers (second roller bodies) of the drive roller 302A and driven roller 302B is not limited to three each. They may be four each as in the second embodiment described below, or five or more. When there is an odd number of driven rollers, a configuration similar to that of this embodiment can be suitably applied.

[0046] As shown in Figures 5 and 6(a), a driven roller holder 370 (holder member, regulating member, bearing member) is attached to the driven shaft 344 of the driven roller 302B. As shown in Figure 6(b), the driven roller holder 320 has a first side surface portion 320a, a second side surface portion 320b, a base portion 320g, grooves 320e and 320f, a protrusion 320i, a rib portion 320r, bearing holes 320c and 320d, and a spring receiving region 320h. The driven roller holder 320 having the above-mentioned components can be integrally molded from a resin material.

[0047] Hereinafter, the direction perpendicular to both the sheet width direction Dw and the sheet conveying direction Dc at the nip portion of the pull-out roller pair 302 will be referred to as the height direction Dh. The height direction Dh is the direction along the straight line connecting the rotation axis of the drive roller 302A and the rotation axis of the driven roller 302B. In addition, the direction in which the driven roller 302B is located relative to the drive roller 302A in the height direction Dh will be referred to as the "upper side in the height direction Dh," and the opposite direction will be referred to as the "lower side in the height direction Dh."

[0048] The base portion 320g is plate-shaped and extends in the sheet width direction Dw and the sheet conveying direction Dc. The base portion 320g covers the central driven roller 341 when viewed from above in the height direction Dh. The protrusion 320i protrudes upward from the base portion 320g in the height direction Dh. The protrusion 320i is a generally cylindrical or columnar convex portion for holding one end of the pressure spring 318. The spring receiving region 320h is a region of the base portion 320g surrounding the protrusion 320i.

[0049] The first side surface portion 320a and the second side surface portion 320b extend downward in the height direction Dh from both ends of the base portion 320g in the sheet width direction Dw. The first side surface portion 320a and the second side surface portion 320b extend along the sheet conveying direction Dc. The first side surface portion 320a faces one end face of the central driven roller 341 in the sheet width direction Dw (FIG. 6(a)). The second side surface portion 320b faces the other end face of the central driven roller 341 in the sheet width direction Dw. The driven roller holder 320 can regulate the position of the central driven roller 341 in the sheet width direction Dw by the first side surface portion 320a and the second side surface portion 320b.

[0050] A bearing hole 320c serving as a first bearing portion is formed in the first side surface portion 320a, and a bearing hole 320d serving as a second bearing portion is formed in the second side surface portion 320b. The bearing holes 320c and 320d are generally circular holes that penetrate the first side surface portion 320a and the second side surface portion 320b, respectively. A driven shaft 344 is inserted through the bearing holes 320c and 320d. Note that the first bearing portion and the second bearing portion are not limited to through holes, and may be, for example, recessed shapes in which portions of the lower edges of the first side surface portion 320a and the second side surface portion 320b in FIG. 6(b) are recessed upward in a semicircular shape.

[0051] The grooves 320e and 320f are recessed grooves that open toward a direction intersecting the sheet width direction Dw when viewed in the height direction Dh and extend along the height direction Dh. The grooves 320e and 320f are guided portions that engage with two guide shapes 321a and 321b (FIG. 5) provided on the opening / closing cover 315. The guide shapes 321a and 321b extend along a direction intersecting both the sheet width direction Dw and the sheet conveying direction Dc (preferably the height direction Dh). The guide shapes 321a and 321b have widths in the sheet width direction Dw that are approximately equal to (or slightly narrower than) the width of the inner sides of the grooves 320e and 320f and extend in the height direction Dh. The guide shapes 321a and 321b are integrally formed with the conveying guide 315g using, for example, a resin material.

[0052] The guided portion of driven roller holder 320 may be a convex portion that convex toward the upstream side or downstream side in the sheet conveyance direction Dc. In this case, the guide shape of open-close cover 315 may be a concave shape that engages with the convex portion and a groove shape that extends along the height direction Dh.

[0053] The driven roller holder 320 is movable in the height direction Dh relative to the open-close cover 315. That is, the driven roller holder 320 is movable relative to the open-close cover 315 (second frame) so that the rotation axis of the driven roller 302B approaches and moves away from the rotation axis of the drive roller 302A. The grooves 320e and 320f engage with the guide shapes 321a and 321b, thereby regulating the position of the driven roller holder 320 in the sheet width direction Dw.

[0054] Furthermore, by restricting the position of the driven roller holder 320 in the sheet width direction Dw, the position of the central driven roller 341 restricted by the driven roller holder 320 in the sheet width direction Dw relative to the opening / closing cover 315 is restricted. This makes it possible to improve the positioning accuracy (alignment) of the central driven roller 341 in the sheet width direction Dw relative to, for example, the conveyance guide 315g and other conveyance rollers supported by the opening / closing cover 315.

[0055] In the case of small-sized originals, the pair of pull-out rollers 302 only holds the original at the central nip N1, so the original tends to rotate and skew more easily during transport than an A4-sized original, which is held at multiple nip portions N1 to N3. By improving the positioning accuracy of the central driven roller 341, it is possible to make it less likely for the original to skew while being transported by the pair of pull-out rollers 302, especially when transporting small-sized originals.

[0056] The positions of the driven rollers 342, 343 other than the central one in the sheet width direction Dw are restricted by, for example, a rib provided on the opening / closing cover 315. The driven rollers 342, 343 may be positioned relative to the driven shaft 344 in the sheet width direction Dw.

[0057] In this embodiment, two guide shapes 321a and 321b are arranged on the upstream and downstream sides of the driven roller holder 320 in the sheet conveying direction Dc. If one guide shape 321a is defined as a first guide shape, the other guide shape 321b can be considered a second guide shape. The two guide shapes 321a and 321b face the bottoms of the grooves 320e and 320f, thereby restricting the position of the driven roller holder 320 in the sheet conveying direction Dc. Restricting the position of the driven roller holder 320 restricts the positions of the driven shaft 344 and the driven rollers 341 to 343 in the sheet conveying direction Dc.

[0058] In this embodiment, grooves 320e and 320f are arranged on the upstream and downstream sides of the driven roller holder 320 in the sheet conveying direction Dc. Also, in this embodiment, the grooves 320e and 320f and the guide shapes 321a and 321b are all arranged on the conveying center Wc in the sheet width direction Dw. However, the positions and numbers of the grooves 320e and 320f can be changed.

[0059] The rib portion 320r is a protruding portion that protrudes from the base portion 320g in the height direction Dh and extends in the sheet width direction Dw between the first side surface portion 320a and the second side surface portion 320b. While FIG. 6B illustrates only the rib portion 320r provided at the upstream end of the base portion 320g in the sheet conveying direction Dc, a similar rib portion 320r is also provided at the downstream end of the base portion 320g. The rib portion 320r functions as a reinforcing rib that increases the rigidity of the driven roller holder 320, thereby enabling the biasing force of the pressure spring 318 to be efficiently transmitted to the driven shaft 344. It is preferable that the rib portion 320r be continuously formed in the sheet width direction Dw from the first side surface portion 320a to the second side surface portion 320b.

[0060] Next, the pressure applied to the pull-out roller pair 302 by the pressure spring 318 will be described. As shown in Figures 4 and 6(a), the pressure spring 318 is disposed between the open-close cover 315 and the driven roller holder 320, and urges the driven roller holder 320 downward in the height direction Dh. The driven roller holder 320 presses the driven shaft 344 with the wall surfaces of the bearing holes 320c and 320d, thereby transmitting the urging force of the pressure spring 318 to the driven shaft 344. As a result, the driven rollers 341 to 343 are brought into pressure contact with the drive rollers 331 to 333, and nip pressure is generated in the nip portions N1 to N3.

[0061] That is, the biasing force of pressure spring 318 is transmitted to driven shaft 344 that supports the plurality of driven rollers 341 to 343. Therefore, one pressure spring 318 (one pressure member) can bring the plurality of driven rollers 341 to 343 (plurality of second roller bodies) into pressure contact with the plurality of drive rollers 331 to 333 (plurality of first roller bodies).

[0062] Further description will be given of the configuration of the pressure spring 318. The pressure spring 318, which is the biasing member in this embodiment, is a compression coil spring. However, a leaf spring or a rubber member can also be used as the biasing member.

[0063] Pressure spring 318, which is a compression coil spring, is disposed with its central axis facing the height direction Dh. One end of pressure spring 318 in the height direction Dh abuts against spring receiving portion 322 provided on open-close cover 315, and the other end of pressure spring 318 abuts against spring receiving region 320h of driven roller holder 320. Spring receiving region 320h is a pressure-receiving region where driven roller holder 320 receives the force from pressure spring 318. Spring receiving portion 322 of open-close cover 315 is provided on bracket 315A, which is fixed to conveyance guide 315g with screws or the like, for example. Spring receiving portion 322 may be formed integrally with other parts of open-close cover 315. Bracket 315A also has protrusion 323 onto which one end of pressure spring 318 can be press-fitted to attach pressure spring 318.

[0064] The pressure spring 318 is disposed on the conveyance center Wc in the sheet width direction Dw. That is, a part of the pressure spring 318 is located on the conveyance center Wc in the sheet width direction Dw. Preferably, the pressure spring 318, which is a compression coil spring, is configured so that the position of the center axis in the sheet width direction Dw coincides with the conveyance center Wc, excluding unavoidable errors such as assembly tolerances.

[0065] In this embodiment, pressure spring 318 is the only biasing member that biases drive roller 302A or driven roller 302B so that the multiple drive rollers 331 and the multiple driven rollers 341 come into pressure contact with each other. Other than pressure spring 318, no biasing member is provided for biasing driven roller 302B toward drive roller 302A. Nor is there any biasing member provided for biasing drive roller 302A toward driven roller 302B. In other words, pressure spring 318 is the only biasing member that biases the drive roller or driven roller so that the multiple first roller bodies and the multiple second roller bodies come into pressure contact with each other.

[0066] According to this embodiment, a simple configuration using a single pressure spring 318 (biasing member) can apply pressure to the multiple nip portions N1 to N3.

[0067] (Summary of this embodiment) In this embodiment, the biasing force of one pressure spring 318 (biasing member) presses the plurality of driven rollers 341-343 (plurality of second roller elements) against the plurality of drive rollers 331-333 (plurality of first roller elements). The driven roller holder 320 regulates the position of the central driven roller 341 (central second roller element) in the sheet width direction Dw by the first side surface portion 320a and the second side surface portion 320b. Furthermore, the driven roller holder 320 transmits the biasing force of the pressure spring 318 to the driven shaft 344 (shaft member) via bearing holes 320c, 320d (first bearing portion and second bearing portion) of the first side surface portion 320a and the second side surface portion 320b.

[0068] According to the above configuration, the biasing force of the pressure spring 318 is transmitted from the first side surface portions 320a and 320b adjacent to the central driven roller 341 to the driven shaft 344. Therefore, the central driven roller 341 can be pressed against the drive rollers 331 to 333 more strongly than the other driven rollers 342 and 343. This increases the nip pressure at the central nip portion N1, thereby increasing the force applied to the document in the sheet conveyance direction Dc by the central drive roller 331 and driven roller 341. As a result, when the ADF 102 conveys a small-sized document, even if the document is sandwiched between the pull-out roller pair 302 only at the central nip portion N1, the pull-out roller pair 302 can overcome the frictional resistance that the document experiences at the separation portion Ns and convey the document.

[0069] In other words, according to this embodiment, it is possible to provide a sheet conveying device that can convey small-sized sheets more stably. According to this embodiment, it is possible to provide an image reading device 101 that can realize more stable conveyance of small-sized originals.

[0070] While the above description has been given of a small-sized document that is sandwiched only by the central nip portion N1 of the pull-off roller pair 302, the same effect can be achieved for a small-sized document whose side edges are sandwiched by portions of the nip portions N2 and N3 other than the central portion. That is, even in the case of a small-sized document whose sheet width is slightly larger than the distance W1 ( FIG. 6A ) between the nip portions N2 and N3 in the sheet width direction Dw, the conveying force imparted to the document by the pull-off roller pair 302 at the nip portions N2 and N3 is small. Therefore, if the conveying force imparted to the document by the pull-off roller pair 302 at the central nip portion N1 is small, the stability of document conveyance may be reduced. According to this embodiment, the document can be stably conveyed even in such a case.

[0071] One possible method for increasing the conveying force at the central nip portion N1 is to arrange two pressure springs near both ends of the central driven roller 341 (hereinafter referred to as a comparative example). However, with this arrangement, the point of action of the biasing force of the pressure spring is somewhat distant from the conveyance center Wc in order to ensure space for installing the pressure springs, making it difficult to concentrate the pressure force at the central nip portion N1. Here, concentrating the pressure force at the central nip portion N1 means increasing the ratio of the pressure force at the central nip portion N1 to the pressure forces at the end nips N2 and N3.

[0072] In contrast, according to this embodiment, the biasing force is transmitted to the driven shaft 344 from the first side surface portion 320a and the second side surface portion 320b of the driven roller holder 320, which positions the central driven roller 341. Therefore, compared to the above-described comparative example, the points of action p1 and p2 (FIG. 6A) of the biasing force of the pressure spring 318 on the driven shaft 344 can be brought closer to the conveyance center Wc. Therefore, according to this embodiment, the pressure force can be more concentrated at the central nip portion N1, and small-sized documents can be conveyed more stably.

[0073] More specifically, the pressure applied at the central nip N1 is preferably greater than the pressure applied at each of the multiple nips (nip portions N2 and N3 in this embodiment) other than the central nip N1. However, the pressure applied at nip N1 is the magnitude of the force with which drive roller 331 and driven roller 341 press against each other in the height direction Dh, and corresponds to the force obtained by integrating the nip pressure over the entire contact surface of drive roller 331 and driven roller 341. Further, the pressure applied to the central nip portion N1 may be greater than the total pressure applied to all nip portions N2 and N3 other than the central nip portion N1 among the plurality of nip portions.

[0074] Furthermore, in the comparative example described above, due to manufacturing tolerances of the two pressure springs, etc., the distribution of pressure at the nip portions N1 to N3 of the pull-out roller pair 302 may become asymmetric with respect to the conveyance center Wc (hereinafter referred to as a left-right nip pressure difference). For example, if the pressure at the nip portion N2 on one end side is greater than the pressure at the nip portion N3 on the other end side, when the pull-out roller pair 302 conveys an A4-sized document, the document may rotate and become skewed. In contrast, according to this embodiment, the biasing force of a single pressure spring 318 applies pressure to multiple nip portions N1 to N3 via the driven roller holder 320 and the driven shaft 344. This makes it possible to avoid left-right nip pressure differences due to manufacturing tolerances of the pressure springs.

[0075] Second Embodiment A second embodiment will be described, in which the arrangement of driven rollers is different from that of the first embodiment. Below, elements with the same reference symbols as the first embodiment have basically the same configuration and function as those described in the first embodiment unless otherwise specified, and differences from the first embodiment will be mainly described. When there is an even number of driven rollers, a configuration similar to this embodiment can be suitably applied.

[0076] Fig. 7 is a cross-sectional view showing a cross section of the ADF 102 according to this embodiment, and corresponds to Fig. 6(a) of the first embodiment. As shown in Fig. 7, in this embodiment, the drive roller 302A has four drive rollers 351-354 as a plurality of first roller bodies, and a drive shaft 355 that supports the drive rollers 351-354. The driven roller 302B has four driven rollers 361-364 as a plurality of second roller bodies, and a driven shaft 365 (shaft member) that supports the driven rollers 361-364. The drive rollers 351-354 come into contact with the driven rollers 361-364, respectively, to form four nip portions.

[0077] The two central driven rollers 361, 362 (two second roller bodies) are located between the driven rollers 363, 364 at both ends in the sheet width direction Dw. Unlike the first embodiment, the two central driven rollers 361, 362 are both located away from the conveying center Wc and are adjacent to each other across the conveying center Wc.

[0078] A driven roller holder 370 (holder member, regulating member, bearing member) is attached to the driven shaft 365 of the driven roller 302B. The driven roller holder 370 regulates the positions of the two central driven rollers 361 and 362 in the sheet width direction Dw and is configured to transmit the biasing force of the pressure spring 318 to the driven shaft 344.

[0079] Specifically, the driven roller holder 370 of this embodiment has a first side surface portion 370a, a second side surface portion 370b, a third side surface portion 370c, and a fourth side surface portion 370d. The first side surface portion 370a faces the outer end face of the driven roller 361 in the sheet width direction Dw. The second side surface portion 370b faces the outer end face of the driven roller 362 in the sheet width direction Dw. The third side surface portion 370c faces the inner end face of the driven roller 361 in the sheet width direction Dw. The fourth side surface portion 370d faces the inner end face of the driven roller 362 in the sheet width direction Dw. The first side surface portion 370a to the fourth side surface portion 370d regulate the positions of the two central driven rollers 361, 362 in the sheet width direction Dw.

[0080] The first side surface portion 370a is formed with a bearing hole (first bearing portion) into which the driven shaft 365 is inserted. Similarly, the second side surface portion 370b, the third side surface portion 370c, and the fourth side surface portion 370d are formed with bearing holes (second bearing portion, third bearing portion, fourth bearing portion) into which the driven shaft 365 is inserted. The biasing force of the pressure spring 318 is transmitted by the bearing hole coming into contact with the driven shaft 365.

[0081] In this embodiment, the sheet width of the smallest size document that can be conveyed by the ADF 102 is shorter than the distance from the driven roller 363 adjacent to one side of the two central driven rollers 361 and 362 to the driven roller 364 adjacent to the other side. Therefore, at least some small-sized documents are held only by the two central nip portions of the four nip portions of the pull-out roller pair 302. Note that A4-sized documents are held by all four nip portions.

[0082] In this embodiment, the biasing force of the single pressure spring 318 (biasing member) also causes the multiple driven rollers 361-364 (multiple second roller elements) to be pressed against the multiple drive rollers 351-354 (multiple first roller elements). The driven roller holder 370 regulates the positions of the two central driven rollers 361, 262 (two second roller elements) in the sheet width direction Dw by the first side surface portion 370a and the second side surface portion 370b. Furthermore, the driven roller holder 370 transmits the biasing force of the pressure spring 318 to the driven shaft 365 (shaft member) via bearing holes (first bearing portion and second bearing portion) in the first side surface portion 370a and the second side surface portion 370b.

[0083] According to the above configuration, similarly to the first embodiment, the pressure applied by the two central driven rollers 361 and 362 can be made stronger than the pressure applied by the other driven rollers 363 and 364. Therefore, similarly to the first embodiment, according to this embodiment, it is possible to provide a sheet conveying device capable of more stably conveying small-sized sheets. Furthermore, according to this embodiment, it is possible to provide an image reading device 101 capable of more stably conveying small-sized originals.

[0084] (Other embodiments) In the above-described embodiments, a configuration example has been described in which the present technology is applied to the ADF 102, which is a sheet conveying device that conveys documents in the image reading device 101. However, the present technology is not limited to this, and may be applied to, for example, a sheet conveying device that conveys sheets used as recording materials in an image forming device. [Explanation of symbols]

[0085] 301a... conveying member (feed roller) / 301b... separating member (separation roller) / 302A... driving roller / 302B... driven roller / 320, 370... holder member (driven roller holder) / 320a, 370a... first side portion / 320b, 370b... second side portion / 331-333, 351-354... first roller body / 341-343, 361-364... second roller body / 342... second roller body in the center / 344... shaft member (driven shaft) / M... driving source (motor)

Claims

1. a conveying member that conveys a sheet; a separating member that forms a separating portion between itself and the conveying member and that separates the sheets by applying a frictional force to the sheets in the separating portion; A driving source; a conveying unit disposed downstream of the separating unit in a sheet conveying direction; A sheet conveying device comprising: The transport unit includes: a drive roller having a plurality of first roller bodies arranged in a sheet width direction perpendicular to the sheet conveying direction, the drive roller being rotated by a driving force of the drive source; a driven roller having a plurality of second roller bodies respectively contacting the plurality of first roller bodies and a shaft member supporting the plurality of second roller bodies, the driven roller rotating to follow the drive roller; a holder member that regulates the position of a central second roller body that is disposed at the center in the sheet width direction among the plurality of second roller bodies; a biasing member that biases the holder member so that the second roller bodies are brought into pressure contact with the first roller bodies; and The holder member is a first side surface portion provided with a first bearing portion that abuts against the shaft member and that faces an end surface of the central second roller body on one side in the sheet width direction; a second side surface portion provided with a second bearing portion that abuts against the shaft member and that faces the other end surface of the central second roller body in the sheet width direction; the first side surface portion and the second side surface portion regulate the position of the central second roller body in the sheet width direction, and the biasing force of the biasing member is transmitted to the shaft member via the first bearing portion and the second bearing portion. A sheet conveying device characterized by:

2. a conveying member that conveys a sheet; a separating member that forms a separating portion between itself and the conveying member and that separates the sheets by applying a frictional force to the sheets in the separating portion; A driving source; a conveying unit disposed downstream of the separating unit in a sheet conveying direction; A sheet conveying device comprising: The transport unit includes: a drive roller having a plurality of first roller bodies arranged in a sheet width direction perpendicular to the sheet conveying direction, the drive roller being rotated by a driving force of the drive source; a driven roller having a plurality of second roller bodies respectively contacting the plurality of first roller bodies and a shaft member supporting the plurality of second roller bodies, the driven roller rotating to follow the drive roller; a holder member that regulates the positions of two second roller bodies that are arranged at the center in the sheet width direction among the plurality of second roller bodies; a biasing member that biases the holder member so that the second roller bodies are brought into pressure contact with the first roller bodies; and The holder member is a first side surface portion provided with a first bearing portion that abuts against the shaft member and faces one of the two second roller bodies in the sheet width direction; a second side surface portion provided with a second bearing portion that abuts against the shaft member and faces the other of the two second roller bodies in the sheet width direction; the first side surface portion and the second side surface portion regulate the positions of the two second roller bodies in the sheet width direction, and the biasing force of the biasing member is transmitted to the shaft member via the first bearing portion and the second bearing portion. A sheet conveying device characterized by:

3. the biasing member is a sole biasing member that biases the drive roller or the driven roller so that the plurality of first roller bodies and the plurality of second roller bodies are in pressure contact with each other; 3. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

4. the second roller body at the center, the holder member, and the biasing member are disposed at a conveyance center that serves as a reference for a sheet position in the sheet width direction; 2. The sheet transport device according to claim 1.

5. the two second roller bodies are arranged adjacent to each other across a conveyance center that serves as a reference for a sheet position in the sheet width direction, the holder member and the biasing member are disposed at the transport center; 3. The sheet transport device according to claim 2.

6. a pressure applied to a central nip portion among a plurality of nip portions formed by the plurality of first roller bodies and the plurality of second roller bodies is greater than pressure applied to any of the nip portions other than the central nip portion; 2. The sheet transport device according to claim 1.

7. the pressure applied at the central nip portion is greater than the sum of the pressure applied at all nip portions other than the central nip portion; 6. The sheet transport device according to claim 5.

8. a first frame having a first guide portion that forms a sheet conveyance path and that supports the drive roller; a second frame having a second guide portion that forms the transport path together with the first guide portion, the second frame being movable relative to the first frame so as to open the transport path; Further provided with the holder member is supported by the second frame and is movable relative to the second frame so that the rotation axis of the driven roller approaches and moves away from the rotation axis of the drive roller.

3. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

9. the second frame is provided with a guide shape extending in a direction intersecting both the sheet conveying direction and the sheet width direction, the holder member has a guided portion that engages with the guide shape, The position of the holder member in the sheet width direction is regulated by engagement between the guide shape and the guided portion.

9. The sheet transport device according to claim 8.

10. the guide shape is disposed on the upstream side of the holder member in the sheet conveying direction, The second frame is further provided with a second guide shape disposed downstream of the holder member in the sheet conveying direction, the guide shape and the second guide shape regulate the position of the holder member in the sheet conveying direction; 10. The sheet transport device according to claim 9.

11. the holder member has a base portion extending in the seat width direction, the first side surface portion and the second side surface portion extend from both ends of the base portion in the sheet width direction in a direction intersecting both the sheet width direction and the sheet conveying direction, The base portion is provided with a pressed region that receives the biasing force of the biasing member.

3. The sheet conveying device according to claim 1, wherein the sheet conveying device is a sheet conveying device.

12. The holder member further includes a rib portion formed to protrude from the base portion and extend in the seat width direction between the first side surface portion and the second side surface portion.

12. The sheet transport device according to claim 11.

13. a length in the sheet width direction of a sheet having a shortest length in the sheet width direction among sheets that can be conveyed by the sheet conveying device is shorter than a distance in the sheet width direction from a second roller body adjacent to one side of the central second roller body to a second roller body adjacent to the other side of the central second roller body; 2. The sheet transport device according to claim 1.

14. a length in the sheet width direction of a sheet having a shortest length in the sheet width direction among the sheets that can be conveyed by the sheet conveying device is shorter than a distance in the sheet width direction from a second roller body adjacent to one side of the two second roller bodies to a second roller body adjacent to the other side of the two second roller bodies; 3. The sheet transport device according to claim 2.

15. The sheet conveying device according to claim 1 or 2; a reading means for reading an image from the sheet being conveyed by the sheet conveying device; An image reading device comprising:

16. The image reading device according to claim 15; an image forming means for forming an image on a recording material; Equipped with forming an image on the recording material based on the image information acquired by the image reading device; An image forming apparatus characterized by:

Images