Sheet transport device, automatic document transport device, and image forming apparatus

Abstract

To provide a sheet conveying apparatus capable of stably conveying a sheet, an automatic document conveying apparatus, and an image forming apparatus.SOLUTION: In a sheet conveying apparatus according to the present invention, a read outlet driven roller 32b, which is a driven rotating body, is provided in an open / close guide unit, which is an open / close member that can be opened / closed with respect to the main body of the apparatus. The read outlet driven roller 32b has outlet driven roller members 132a to 132d serving as driven roller members on both sides in the axial direction and on the center side in the axial direction. The outer diameters d2 of the outlet driven roller members 132b, 132c disposed on the center side in the axial direction are larger than the outer diameters d1 of the outlet driven roller members 132a, 132b disposed on both sides in the axial direction (d2>d1).SELECTED DRAWING: Figure 9

Description

Technical Field

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

Background Art

[0002] Conventionally, a sheet conveying apparatus having a pair of conveying rotating bodies that nipping and conveying a sheet by a driving rotating body and a driven rotating body is known.

[0003] Patent Document 1 describes, as the above sheet conveying apparatus, a configuration in which a driven roller serving as the driven rotating body is provided in an opening / closing guide unit serving as an opening / closing member arranged to face a back surface reading unit that reads the back surface image of a document sheet.

Summary of Invention

Problems to be Solved by the Invention

[0004] However, there is a risk that stable sheet conveyance cannot be performed due to deflection of the opening / closing member such as the opening / closing guide unit.

Means for Solving the Problems

[0005] In order to solve the above-described problems, the present invention provides a sheet conveying apparatus having a pair of conveying rotating bodies that nip and convey a sheet by a driving rotating body and a driven rotating body, wherein the driven rotating body is provided in an opening / closing member that can be opened and closed relative to the apparatus main body, the driven rotating body has driven roller members at least on both axial sides and on the axially central side, and the outer diameter of the driven roller member on the axially central side is made larger than the outer diameter of the driven roller members on both axial sides The driven rotating body is biased toward the driving rotating body by a biasing member, and the multiple driven roller members of the driven rotating body are mounted on a single driven shaft, and the biasing force of the biasing member toward the driven shaft is set such that the transport force on the central side in the axial direction : the transport force on both sides in the axial direction = 2:1. It is characterized in that.

Effects of the Invention

[0006] According to the present invention, stable sheet conveyance can be performed.

Brief Description of the Drawings

[0007] [Figure 1] Perspective view of an image forming apparatus. [Figure 2] An enlarged diagram showing the main components of the image reading device. [Figure 3] A top view of the opening / closing guide unit. [Figure 4] A view of the opening / closing guide unit from below. [Figure 5] A schematic diagram showing the opening / closing guide unit locked in the closed position by the lock lever on the rear side of the device. [Figure 6] A diagram illustrating the opening and closing of the opening / closing guide unit. [Figure 7] Perspective view of the reader exit roller pair. [Figure 8] A diagram illustrating a conventional reading exit roller pair. [Figure 9] This diagram illustrates the pair of reading exit rollers in this embodiment. [Modes for carrying out the invention]

[0008] The following describes embodiments of the present invention applied to an image forming apparatus equipped with an image reading device. Figure 1 is a perspective view of an image forming apparatus 1, which is an example of such an apparatus. The image forming apparatus 1 shown in Figure 1 combines the functions of a copier, printer, facsimile machine, scanner, etc., and can record and output full-color or monochrome images on recording paper or output them in a predetermined data format based on input data such as scanned image data.

[0009] As shown in Figure 1, the image forming apparatus 1 is equipped with an ADF 20, which is an automatic document transport device, above the paper feed unit, scanner unit 4, and image forming unit 15 (not shown in the figure). The scanner unit 4 and the ADF 20 together constitute the image reading apparatus 5. The paper feeding section of the image forming unit 15 includes, for example, multiple paper feeding cassettes, each storing cut-sheet-shaped recording paper, and multiple sets of paper feeding rollers that pick up and feed recording paper from any of these paper feeding cassettes. The paper feeding section also includes a paper feeding path that transports the recording paper fed from any of the paper feeding rollers to a predetermined image forming position in the image forming unit, including various rollers.

[0010] The image forming unit 15 includes, for example, an exposure unit, a plurality of photosensitive drums, a developing device that uses four toners: cyan (C), magenta (M), yellow (Y), and black (K), a transfer belt, a secondary transfer unit, and a fixing unit. The image forming unit 15, based on the image read by the image reading device 5, for example, exposes each color photoreceptor drum using an exposure unit to form an electrostatic latent image on each photoreceptor drum, and then develops the image by supplying toner to the latent image on each photoreceptor drum using the developing unit for each color. The image forming unit 15 also performs primary transfer of the toner image on each color photoreceptor drum to a transfer belt, secondary transfer by overlaying it onto recording paper in a secondary transfer unit, and then heats and pressurizes the toner image on the recording paper in a fixing unit to fix it, thereby forming a color image. Furthermore, the image forming unit 15 can form external output images such as image files or data that can be output externally, based on the image read by the scanner unit 4 or the back-side image reading module 35 (second image reading unit) described later. Instead of the electrophotographic image forming unit 15 described above, an image forming unit employing another recording method such as an inkjet method may be used.

[0011] Next, the image reading device 5 will be described. Figure 2 is an enlarged diagram showing the main components of the image reading device 5. The image reading device 5 is configured to be switchable between flatbed scanner mode (placed document reading mode) and DF scanner mode (transported document reading mode). The flatbed scanner mode is an operation mode for reading an image of a placed original, which is executed when a reading start request operation such as pressing a copy start button is performed in a state where the original is placed on the flatbed contact glass 13 at the upper part of the scanner unit 4. While moving the image reading unit 16 in the moving reading area 11 directly below the flatbed contact glass 13, light is emitted to the image surface of the original. Then, the reflected light from the image surface of the original is converted into an image signal, thereby reading the image of the original.

[0012] Further, the DF scanner mode is an operation mode in which the image reading unit 16 is stopped in the stop reading area 12 directly below the DF contact glass 14 to read the image of a conveyed original.

[0013] In the DF scanner mode, the ADF 20 separates original sheets one by one from the bundle of original sheets stacked on the original placement tray 21 (original placement table), conveys them into the original conveyance path 22, and conveys them along the original conveyance path 22. During the conveyance, the original sheets sequentially partially face the upper surface of the DF contact glass 14 from the upstream side portion in the conveyance direction.

[0014] The ADF 20 is attached to the rear portion (the portion on the back surface side) on the upper surface side of the scanner unit 4 via an opening / closing mechanism such as a hinge. Further, the ADF 20 can adopt an open position for opening the top of the flatbed contact glass 13 relative to the scanner unit 4, and a closed position capable of pressing the original on the flatbed contact glass 13.

[0015] The image reading unit 16 may be any unit that can repeatedly perform line scanning to read the image on the front surface side of the original at a predetermined image reading position on the contact glasses 13 and 14, such as a CCD module or a CIS module. Further, a fixed image reading unit fixed in the stop reading area 12 and a movable reading unit that moves along the flatbed contact glass 13 in the moving reading area 11 may be respectively provided.

[0016] The document placement tray 21 is equipped with a pair of side fences 23 that are movable in the width direction for positioning the document sheets set in the ADF 20 in the sheet width direction orthogonal to the sheet feeding direction. These side fences 23 can relatively approach and separate from each other so that the centers of the document placement tray 21 and the document sheets in the width direction are aligned.

[0017] The ADF 20 is covered at least by a cover 38 that can be opened and closed from above. Further, the main guide portion forming the document conveyance path 22 of the ADF 20 is formed by ribs or the like formed on the cover 38. On the other hand, the ADF 20 includes a pickup roller 24 that pulls the document set on the document placement tray 21 in the sheet feeding direction, and a feed roller 25 and a separation pad 43 for feeding the document pulled in the sheet feeding direction by the pickup roller 24 toward the document conveyance path 22.

[0018] Further, the ADF 20 is provided with a conveyance unit 27 that conveys the document fed into the document conveyance path 22 by the feed roller 25 onto the DF contact glass 14 in an image readable posture, and conveys the document after image reading to the discharge port 36.

[0019] This conveyance unit 27 reverses the document sheet separated and carried in by the feed roller 25 or the like along the document conveyance path 22, and conveys the document sheet so as to pass a predetermined reading position on the upper surface of the DF contact glass 14. For such document conveyance, a first conveyance roller 28, a second conveyance roller 29, and a registration sensor 31 that detects the leading end of the document sheet in the conveyance direction are provided on the upstream side of the DF contact glass 14 in the document conveyance path 22.

[0020] The document sheet separated by the feed roller 25 or the like is conveyed by the first conveyance roller 28 and the second conveyance roller 29 so as to pass over the DF contact glass 14. Then, based on the timing at which the leading end of the document sheet is detected by the registration sensor 31, the document surface image is read in a timely manner by the image reading unit 16.

[0021] For example, when the leading edge of the document sheet is detected by the resist sensor 31, the timing at which the leading edge position of the document sheet, detectable by the pulse count of the paper feed motor (the drive source), reaches the reading position on the DF contact glass 14 is determined. A gate signal indicating the effective image area in the sub-scanning direction of the surface of the document sheet is started to be transmitted, and the gate signal continues to be transmitted until the trailing edge of the document sheet passes the reading position.

[0022] When it is required to read the image on the back of the original sheet, the back image is read by a back image reading module 35 (second image reading unit) consisting of a contact-type image sensor for back image reading.

[0023] The back-side image reading module 35 includes a light source unit that illuminates the document sheet with light based on a lighting signal from the control unit, a plurality of sensor chips that receive reflected light from the document sheet, and a plurality of amplification units that amplify the signals output from each sensor chip. The back-side image reading module 35 also includes an A / D conversion unit that converts the signals amplified by the amplification units from analog signals to digital signals, and an image processing unit that performs image processing on the digitally converted signals. Furthermore, this back-side image reading module 35 has an output control circuit that controls the output of signals stored in the frame memory based on timing signals from the control unit, and an interface circuit that outputs signals from the output control circuit to the main unit of the device. The timing of back-side image reading by this back-side image reading module 35 is controlled in substantially the same way as the timing of front-side image reading, and the scanned document is ejected into the output tray 39.

[0024] Downstream of the DF contact glass 14 in the document transport path 22, there is a pair of transport rotating bodies, which are a reading exit roller pair 32, that transports the document with the scanned front side image to the back side image reading module 35. Downstream of the reading exit roller pair 32, there is a white guide member 33, which is a guide part that faces the back side image reading module 35. Furthermore, downstream of the back side image reading module 35 and the white guide member 33, there is a pair of transport rotating bodies, which are a paper discharge roller pair 37.

[0025] The white guide member 33 has a guiding function for moving the transport document along the back-side image reading module 35, and also has a white reference surface for shading correction that is positioned to face the back-side image reading module 35 across the entire main scanning direction.

[0026] The number and location of these transport and paper ejection rollers can be arbitrarily set according to the path setting conditions of the document transport path 22, the length of the transport direction of the smallest size document, etc.

[0027] The back-side image reading module 35 uses a contact-type image sensor with a shallow depth of field and transports the back side of the document sheet in contact with the glass surface of the back-side image reading module 35. As a result, paper dust and toner from the document sheet adhere to the glass surface of the back-side image reading module 35, making the glass surface prone to soiling. Therefore, soiling of the glass surface may cause abnormalities such as black streaks in the image read by the back-side image reading module 35. Consequently, periodic cleaning of the glass surface becomes necessary. In this embodiment, an opening / closing guide unit is provided on the main body of the ADF 20 that can be opened and closed, exposing the document transport path 22 from the DF contact glass 14 to the output port, in order to allow cleaning of the glass surface.

[0028] Figure 3 is a top view of the opening / closing guide unit 100, and Figure 4 is a bottom view of the opening / closing guide unit 100. The opening / closing guide unit 100, which is the opening / closing member, has three guide parts. Specifically, these are the lower exit guide plate 101 that guides the document sheet that has passed through the DF contact glass 14 to the back image reading module 35, the white guide member 33, and the lower paper discharge guide plate 102. The opening / closing guide unit 100 also includes the reading exit driven roller 32b, which is the driven rotating body of the reading exit roller pair 32, and the paper discharge driven roller 37b, which is the driven rotating body of the paper discharge roller pair 37.

[0029] As shown in Figure 4, the reading outlet driven roller 32b of the reading outlet roller pair 32 is composed of a driven shaft 131 and a plurality of outlet driven roller members 132a to 132d attached to the driven shaft 131, and is rotatably held by the outlet lower guide plate 101. The reading outlet driven roller 32b is biased toward the reading outlet driven roller 32a by a plurality of pressurizing parts 110a to 110f.

[0030] The paper discharge driven roller 37b of the paper discharge roller pair 37 has the same configuration as the reading exit driven roller 32b, and is composed of a driven shaft and a plurality of paper discharge driven roller members 137a to 137d attached to the driven shaft. The paper discharge driven roller 37b is rotatably held by the paper discharge lower guide plate 102.

[0031] As shown in Figure 3, each of the outlet driven roller members 132a to 132d of the reading outlet driven roller 32b protrudes in part from the roller relief holes provided on the guide surface of the outlet lower guide plate 101. This allows the outlet driven roller members 132a to 132d of the reading outlet driven roller 32b to come into contact with the outlet driven roller members 134a to 134d (see Figure 7) of the reading outlet driven roller 32a. Similarly, the paper discharge driven roller members 137a to 137d of the paper discharge driven roller 37b protrude in part from the roller relief holes provided on the guide surface of the paper discharge lower guide plate 102, allowing them to come into contact with the drive roller members of the paper discharge driven roller 37a.

[0032] Support shafts 107 are provided at both ends of the opening / closing guide unit 100, on the downstream end in the document sheet transport direction. These support shafts 107 are rotatably fitted to each frame 20a, 20b of the ADF 20, and the opening / closing guide unit 100 is mounted to the ADF 20 so as to be rotatable with the support shafts 107 as pivot points.

[0033] Furthermore, the opening / closing guide unit 100 is provided with a locking mechanism that locks the opening / closing guide unit 100 in the closed position. The locking mechanism has a pivot shaft rotatably supported on the lower exit guide plate 101, and lock levers 108a and 108b fixed to both ends of this pivot shaft. The basic configuration of each lock lever 108a and 108b is the same, but the lock lever 108b provided on the front side of the device, which is one end in the axial direction, is provided with an operating part 118 for operation by the user, as shown in Figure 4.

[0034] Figure 5 is a schematic diagram showing the state in which the opening / closing guide unit 100 is locked in the closed position by the lock lever 108a on the rear side of the device. The rear frame 20a of the ADF20 is provided with a hook projection 20d that extends inward towards the inside of the device. By hooking the hook portion of the lock lever 108a onto this hook projection 20d, the opening and closing guide unit 100 is locked in the closed position. The rotating shaft to which the lock lever 108a is attached is biased by a torsion spring to prevent the engagement between the hook portion of the lock lever 108a and the hook projection 20d from disengaging. The front lock lever 108b of the device has a similar configuration.

[0035] To release the lock on the opening / closing guide unit 100, the user operates the operating part 118 (see Figure 4) of the lock lever 108b on the front side of the device to rotate the lock mechanism in the opposite direction to the biasing direction of the torsion spring. This releases the engagement between the hook portion of each lock lever 108a, 108b and the hook projection 20d, allowing the opening / closing guide unit 100 to rotate to the open position.

[0036] Figure 6(a) shows the opening / closing guide unit 100 in the closed position, and Figure 6(b) shows the opening / closing guide unit 100 in the open position. As shown in Figure 6(a), when the opening / closing guide unit 100 is in the closed position, the opening / closing guide unit 100 is housed inside the ADF 20. When the opening / closing guide unit 100 is in the closed position, the reading outlet driven roller 32b (or its roller member) contacts the reading outlet drive roller 32a (or its roller member) to form a transport nip. Also, the paper discharge driven roller 37b (or its roller member) contacts the paper discharge drive roller 37a (or its roller member) to form a transport nip.

[0037] When cleaning the glass surface of the back-side image reading module 35, or when removing a jammed document sheet in the document transport path from the DF contact glass 14 to the output port 36, the opening / closing guide unit 100 is moved to the open position. To move the opening / closing guide unit 100 to the open position, first, the ADF 20 is moved to the open position that opens the flatbed contact glass 13. Next, the lock lever 108b on the front side of the locking mechanism is operated (see Figure 4) to release the lock on the opening / closing guide unit 100. Then, the opening / closing guide unit 100 is rotated counterclockwise in the figure using the support shaft 107 as a pivot point, thereby moving the opening / closing guide unit 100 to the open position shown in Figure 6(b).

[0038] As shown in Figure 6(b), when the opening / closing guide unit 100 is in the open position, the document transport path from the DF contact glass 14 to the output port is opened, and the glass surface of the back-side image reading module 35 is exposed. This allows the glass surface of the back-side image reading module 35 to be cleaned.

[0039] Furthermore, as shown in Figure 6(b), when the opening / closing guide unit 100 is in the open position, the reading outlet driven roller 32b separates from the reading outlet driven roller 32a, and the paper discharge driven roller 37b separates from the paper discharge driven roller 37a. This allows the jammed document sheet in the document transport path from the DF contact glass 14 to the output port to be easily removed without damaging it.

[0040] Figure 7 is a perspective view of the reading exit roller pair 32. The reading exit drive roller 32a, which is the driving rotating body of the reading exit roller pair 32, has a drive shaft 133 and a plurality of exit drive roller members 134a to 134d attached to the drive shaft 133. In this embodiment, one exit drive roller member is provided on each side in the axial direction, and two are provided on the axial center side, and are arranged symmetrically with respect to the axial center. The outer diameters of each exit drive roller member 134a to 134d are the same so that the peripheral speed of each exit drive roller member 134a to 134d is the same. As a result, the document sheet can be transported at a uniform transport speed in the axial direction, the occurrence of wrinkles on the document sheet can be suppressed, and the document sheet can be transported stably.

[0041] The reading outlet driven roller 32b has a driven shaft 131 and four outlet driven roller members 132a to 132d attached to the driven shaft 131 and provided in correspondence with the outlet drive roller members 134a to 134d. Specifically, there is one outlet driven roller member on each side in the axial direction and two on the axial center side, and they are arranged symmetrically with respect to the axial center as the starting point.

[0042] By configuring the reading outlet drive roller 32a and the reading outlet driven roller 32b with multiple roller members arranged at predetermined intervals in the axial direction, the occurrence of skew due to external factors such as conveying load can be suppressed.

[0043] The driven shaft 131 is biased toward the reading exit drive roller 32a by springs 111a to 111f (for example, compression springs), which are biasing members of the pressurizing sections 110a to 110f. Due to this biasing, each exit driven roller member 132a to 132d presses against the corresponding exit drive roller member 134a to 134d, forming a transport nip. The document sheet fed into this transport nip is pressed against the exit drive roller members 134a to 134d by the exit driven roller members 132a to 132d. This generates the desired frictional force (hereinafter referred to as transport force) between the document sheet and the exit drive roller members 134a to 134d, and the document sheet is transported.

[0044] The goal of the conveying force is to ensure that the central roller member is greater than or equal to the end roller member. This is because if the conveying force is less than that of the central roller member, a slight difference between the conveying force at one end and the other may cause skew. In this embodiment, the biasing force of each pressurizing section 110a to 110f on the driven shaft 131 is set so that the central conveying force : end conveying force = 2:1.

[0045] Figure 8 illustrates a conventional reader exit roller pair 32. Figure 8(a) is a schematic diagram of the reader exit driven roller 32b of the conventional reader exit roller pair 32, and Figure 8(b) illustrates a problem with the conventional reader exit roller pair 32. As shown in Figure 8(a), in the conventional reading outlet roller pair 32, the outer diameter d of each outlet driven roller member 132a to 132d of the reading outlet driven roller 32b was the same.

[0046] The opening / closing guide unit 100 is configured to be openable and closable, and is held by the ADF 20 on both axial sides, making the axial center side prone to bending downward. When the opening / closing guide unit 100 bends, the driven shaft 131 of the reading outlet driven roller 32b provided on the opening / closing guide unit 100 bends, as shown in Figure 8(b). As a result, the outlet driven roller members 132b and 132c on the axial center side, and the outlet driven roller members 132a and 132d on the axial end side, are positioned δ away from the reading outlet drive roller 32a. This reduces the contact pressure between the outlet driven roller members 132b and 132c on the axial center side and the outlet drive roller members 134b and 134c. As a result, the transport force becomes such that the central roller members < the end roller members, making skew more likely to occur, and there is a risk that the original sheet cannot be transported stably.

[0047] Similarly, the driven roller 37b on the opening / closing guide unit 100 also experiences bending of its driven shaft due to the deflection of the opening / closing guide unit 100. As a result, the transport force becomes less for the central roller member than for the end roller member, making skew more likely to occur and potentially preventing stable transport of the original sheet.

[0048] Therefore, one might consider increasing the rigidity of the opening / closing guide unit 100 to make it less prone to bending. However, increasing the rigidity of the opening / closing guide unit 100 would increase its thickness (vertical length), leading to an increase in the size of the ADF 20.

[0049] Alternatively, for example, the driven shaft could be divided into at least three parts: a central part and two end parts, and an adjustment mechanism could be provided to adjust the spring biasing force corresponding to each driven shaft. By adjusting the biasing force using the adjustment mechanism in accordance with the deflection of the opening and closing guide unit, it becomes possible to maintain the conveying force at the desired level. However, such a configuration may lead to increased costs due to the increased number of parts and an increase in the size of the ADF.

[0050] Therefore, in this embodiment, the outer diameter of the driven roller member on the axial center side of the reading outlet driven roller 32b and the paper discharge driven roller 37b provided on the opening / closing guide unit 100 is made larger than the outer diameter of the driven roller member on the axial end side. In the following description, the reading outlet driven roller 32b will be described, but the same applies to the paper discharge driven roller 37b.

[0051] Figure 9(a) is a schematic diagram of the reading outlet driven roller 32b of this embodiment, and Figure 9(b) is a diagram illustrating the contact between the reading outlet driven roller 32b and the reading outlet drive roller 32a when the opening / closing guide unit is deflected in this embodiment. As shown in Figure 9(a), in this embodiment, the outer diameter d2 of the outlet driven roller members 132b and 132c on the axial center side of the read outlet driven roller 32b is larger than the outer diameter d1 of the outlet driven roller members 132a and 132d on the axial end side. Therefore, when the driven shaft 131 is not deflected, the outlet driven roller members 132b and 132c on the axial center side protrude by Δd=(d2-d1) / 2 towards the read outlet driven roller 32a compared to the outlet driven roller members 132a and 132d on the axial end side.

[0052] The outer diameters d2 of the axially central outlet driven roller members 132b and 132c and the outer diameters d1 of the axially end outlet driven roller members 132a and 132d are set such that Δd equals the deflection amount δ of the driven shaft 131. With this setting, as shown in Figure 9(b), even if the driven shaft 131 deflects by a deflection amount δ due to the deflection of the opening / closing guide unit 100, the decrease in the contact pressure of the axially central outlet driven roller members 132b and 132c against the outlet drive roller members 134b and 134c can be suppressed. As a result, the transport force of the central roller members can be maintained to be greater than or equal to the transport force of the end roller members. This suppresses the occurrence of skew and allows for stable transport of the document sheet. Furthermore, by adjusting the biasing force with an adjustment mechanism, the transport force can be maintained at the target transport force with a less expensive configuration compared to a system that maintains the transport force so that the transport force of the central roller members is greater than or equal to the transport force of the end roller members.

[0053] For example, in a configuration where the maximum document width that can be transported is 297 mm (A3 width), the outer diameter d2 of the axially central exit driven roller members 132b and 132c is set to φ13 mm. Also, the outer diameter d1 of the end-side exit driven roller members 132a and 132d is set to φ11 mm, increasing the diameter of the central part by approximately 20% compared to the end part. As a result, with the driven shaft 131 deflected, a transport force ratio of 2:1 between the central part and the end part was achieved. Note that this is just one example, and the outer diameter d2 of the axially central exit driven roller members 132b and 132c, the outer diameter d1 of the end-side exit driven roller members 132a and 132d, and the ratio of the transport forces between the end and central parts should be determined appropriately depending on the configuration of the device.

[0054] In the above description, the drive rotating body that the driven roller of the opening / closing guide unit 100 contacts is a roller in which multiple drive roller members are provided at predetermined intervals, but the drive rotating body may be a belt member. In this case, the driven roller is brought into contact with the region between the tension rollers of the belt member stretched between the drive tension roller and the driven tension roller to form a transport nip. By using a belt member as the drive rotating body, the transport nip width can be increased, and the decrease in transport force on the central side due to the deflection of the opening / closing guide unit 100 can be suppressed. This makes it possible to transport the document sheet more stably.

[0055] Although the above describes an example of applying the present invention to the ADF 20, the present invention can also be applied to the transport device that transports the recording paper of the image forming unit 15.

[0056] The above is just one example; each of the following embodiments produces its own unique effects. (Aspect 1) In a sheet conveying device such as a conveying section 27 having a pair of conveying rotating bodies such as a pair of reading outlet rollers 32 that grips and conveys a sheet such as a document sheet with a driving rotating body such as a reading outlet drive roller 32a and a driven rotating body such as a reading outlet driven roller 32b, the driven rotating body is provided on an opening / closing member such as an opening / closing guide unit 100 that can be opened and closed relative to the device body, and the driven rotating body has driven roller members such as outlet driven roller members 132a to 132d on at least both sides in the axial direction and on the axial center side, and the outer diameter of the driven roller member located on the axial center side is larger than the outer diameter of the driven roller members located on both sides in the axial direction. To prevent skew from occurring due to axial load deviations in the transport direction, the driven rotating body is generally designed as a segmented roller, with multiple roller members mounted on the driven shaft at predetermined intervals. Since the opening / closing member is configured to open and close relative to the main body of the device, it is generally held by the main body at only two points on the axial side, and there is a risk that the axial center will bend away from the drive rotating body. Due to this bending of the opening / closing member, there is a risk that the axial center of the driven rotating body provided on the opening / closing member will bend away from the drive rotating body. As a result, the pressure applied by the driven rotating body at the axial center will decrease, and the frictional force between the drive rotating body and the sheet on the axial center side (hereinafter referred to as the conveying force) may become lower than the conveying forces on both axial sides. In this way, if the conveying force on the axial center side of the driven rotating body becomes lower than the conveying forces on both axial sides, even a slight difference between the conveying force on one end and the conveying force on the other end may cause sheet skew, and stable conveying may not be possible. In Embodiment 1, the outer diameter of the driven roller member on the axial center side is larger than the outer diameters of the driven roller members on both axial sides. Therefore, even if the opening and closing member bends, it is possible to suppress the conveying force at the axial center of the driven rotating body from becoming lower than the conveying force on both axial sides, thereby enabling stable conveying of the sheet.

[0057] (Aspect 2) In embodiment 1, the drive rotating body such as the reading outlet drive roller 32a has a plurality of outlet drive roller members 134a to 134d that correspond to roller members such as the outlet driven roller members 132a to 132d of the driven rotating body such as the reading outlet driven roller 32b, and the outer diameter of the plurality of drive roller members is the same. According to this, as described in the embodiment, the peripheral speed of each drive roller member can be made the same, and the transport speed of sheets such as original sheets can be made uniform in the axial direction. As a result, the occurrence of wrinkles and sheet skew on the sheets can be effectively suppressed, and the sheets can be transported stably.

[0058] (Aspect 3) In embodiment 1 or 2, the driven rotating body, such as the reading outlet driven roller 32b, is biased toward the driving rotating body, such as the reading outlet driven roller 32a, by biasing members such as springs 111a to 111f, and the opening / closing member, such as the opening / closing guide unit 100, has a guide portion such as the outlet lower guide plate 101 that guides the conveying sheet. According to this, as described in the embodiment, the sheet can be pressed against the reading outlet drive roller 32a by a driving rotating body such as the reading outlet drive roller 32a, thereby obtaining the desired conveying force. Furthermore, by opening the opening / closing member, the guide section and driven rotating body are retracted, exposing the sheet transport path and making it possible to easily remove jammed sheets.

[0059] (Aspect 4) In any of embodiments 1 to 3, the sheet transport reference is the axial center. According to this, by arranging the roller members symmetrically with the axial center as the pivot point, sheets of various sizes, from small to large, can be transported stably.

[0060] (Appendix 5) In any of embodiments 1 to 4, the multiple driven roller members, such as the outlet driven roller members of the driven rotating body, such as the reading outlet driven roller 32b, are mounted on a single driven shaft. According to this, the number of parts can be reduced compared to a configuration in which the driven shaft is divided into multiple parts, thereby reducing the cost of the device. Furthermore, in a configuration where multiple driven roller members, such as outlet driven roller members, are mounted on a single driven shaft, the driven shaft becomes longer in the axial direction, making it more susceptible to bending due to the deflection of opening and closing members such as the opening and closing guide unit 100. However, by adopting the configuration of Embodiment 1, conveying disturbances such as skew can be effectively suppressed.

[0061] (Aspect 6) An automatic document transport device is provided which includes a document sheet transport unit for transporting document sheets, and which transports the document sheets to an image reading unit 16 by the document sheet transport unit, and a sheet transport device from any of embodiments 1 to 5 is used as the document sheet transport unit. This allows for stable transport of the original document sheets.

[0062] (Aspect 7) In embodiment 6, the device includes a back-side image reading unit, such as a back-side image reading module 35, which reads the image on the back side of the document opposite to the side read by the image reading unit 16. The opening / closing member, such as an opening / closing guide unit 100, opens up the transport path from the transport path in front of the back-side image reading unit, which transports the document sheet toward the back-side image reading unit, to the transport path after the back-side image reading unit, which transports the document sheet that has passed through the back-side image reading unit. According to this, as described in the embodiment, the glass surface of the back-side image reading section, such as the back-side image reading module 35, can be cleaned by opening the opening / closing member, such as the opening / closing guide unit 100. In addition, a jammed document sheet in the transport path before or after the back-side image reading section can be easily removed.

[0063] (Pattern 8) In embodiment 7, the opening / closing member such as the opening / closing guide unit 100 holds the driven rotating body such as the reading outlet driven roller 32b of the transport rotating body pair such as the reading outlet roller pair 32 that transports the original sheet to the back image reading section such as the back image reading module 35, and the driven rotating body such as the paper discharge driven roller 37b of the transport rotating body pair such as the paper discharge roller pair 37 that transports the original sheet after it has passed through the back image reading section. The outer diameter of the driven roller member located on the axial center side of at least one of the driven rotating bodies of the transport rotating body pair that transports the original sheet to the back image reading section and the transport rotating body pair that transports the original sheet after it has passed through the back image reading section is made larger than the outer diameter of the driven roller members located on both sides in the axial direction. According to this, the original document sheet can be stably transported before and after the back-side image reading unit, such as the back-side image reading module 35, and the back-side image reading unit can accurately read the image on the back of the original document sheet.

[0064] (Aspect 9) In embodiment 7 or 8, the back-side image reading unit, such as the back-side image reading module 35, is a contact-type image sensor. According to this, as described in the embodiment, when a contact-type image sensor is used as the back-side image reading unit, such as the back-side image reading module 35, there is a high risk that paper dust and toner will adhere to the glass surface of the back-side image reading unit, causing the glass surface to become dirty. By opening the opening / closing member, the glass surface of the back-side image reading unit is exposed, and the glass surface of the back-side image reading unit can be cleaned. As a result, the back-side image reading unit can read the image on the back side of the document sheet well over time.

[0065] (Aspect 10) In embodiment 9, the document sheet is transported so that it comes into contact with a back-side image reading unit such as a back-side image reading module 35. According to this, a contact-type image sensor can reliably read the image on the back of the document sheet.

[0066] (Aspect 11) An image forming apparatus that forms an image on a sheet transported by a sheet transport unit, comprising a sheet transport device as described in any of embodiments 1 to 5, or an automatic document transport device as described in any of embodiments 6 to 10. According to this, the sheets can be transported stably. [Explanation of symbols]

[0067] 1: Image forming apparatus 4: Scanner section 5: Image reading device 15: Image forming unit 16: Image reading unit 20: ADF 20a: Rear frame 20b: Front frame 20d: Hooked protrusion 27: Conveyor Department 32: Read-out exit roller pair 32a: Read exit drive roller 32b: Read-out exit driven roller 33: White guide member 35: Backside image reading module 36: Outlet 37: Paper output roller pair 37a: Paper output drive roller 37b: Paper ejection driven roller 39: Paper output tray 100: Opening / closing guide unit 101: Exit lower guide plate 102: Paper output guide plate 107: Support shaft 108a: Rear locking lever 108b: Front locking lever 110a~110d: Pressurized section 111a~111f: Spring 118:Operation unit 131: Driven axis 132a~132d: Outlet driven roller member 133: Drive shaft 134a~134d: Outlet drive roller member 137a~137b: Paper discharge driven roller member d1: Outer diameter of the end-side exit driven roller member d2: Outer diameter of the central exit driven roller member δ: Deflection of the driven shaft [Prior art documents] [Patent Documents]

[0068] [Patent Document 1] Japanese Patent Publication No. 2017-130860

Claims

1. In a sheet conveying device having a pair of conveying rotating bodies that grip and convey a sheet between a driving rotating body and a driven rotating body, The driven rotating body is provided on an opening / closing member that can be opened and closed relative to the main body of the device. The driven rotating body has driven roller members on at least both sides in the axial direction and on the central side in the axial direction. The outer diameter of the driven roller member located on the axial center side is larger than the outer diameter of the driven roller members located on both sides in the axial direction. The driven rotating body is biased toward the driving rotating body by a biasing member, The multiple driven roller members of the driven rotating body are mounted on a single driven shaft. A sheet conveying device characterized in that the biasing force of the biasing member on the driven shaft is set such that the conveying force on the central side in the axial direction : the conveying forces on both sides in the axial direction = 2:

1.

2. In the sheet conveying device according to claim 1, The drive rotating body has a plurality of drive roller members provided in correspondence with the roller members of the driven rotating body, A sheet conveying device characterized in that the outer diameters of multiple drive roller members are the same.

3. In the sheet conveying device according to claim 1, The sheet conveying device is characterized in that the opening and closing member has a guide portion for guiding the conveyed sheet.

4. In the sheet conveying device according to claim 1, A sheet conveying device characterized in that the sheet conveying reference is the axial center.

5. A document sheet transport unit for transporting document sheets, In an automatic document transport device that transports a document sheet to an image reading unit using the document sheet transport unit, An automatic document transport device characterized in that the aforementioned document sheet transport unit uses the sheet transport device described in claim 1.

6. In the automatic document transport device according to claim 5, The system includes a back-side image reading unit that reads the image on the back side of the document, which is the opposite side of the document read by the aforementioned image reading unit. The automatic document transport device is characterized in that, when opened, the opening / closing member opens the transport path in front of the back image reading unit, which transports the document sheet toward the back image reading unit, to the transport path after the back image reading unit, which transports the document sheet that has passed through the back image reading unit.

7. In the automatic document transport device according to claim 6, The opening / closing member holds the driven rotating body of the transport rotating body pair that transports the original document sheet to the back-side image reading unit, and the driven rotating body of the transport rotating body pair that transports the original document sheet after it has passed through the back-side image reading unit. An automatic document transport device characterized in that the outer diameter of a driven roller member positioned on the axial center side of at least one of the driven rotating bodies of a pair of transport rotating bodies that transports the document sheet to the back-side image reading unit and the driven rotating body of a pair of transport rotating bodies that transports the document sheet after it has passed through the back-side image reading unit is larger than the outer diameter of driven roller members positioned on both sides in the axial direction.

8. In the automatic document transport device according to claim 6 or 7, The automatic document transport device is characterized in that the back-side image reading unit is a contact-type image sensor.

9. In the automatic document transport device according to claim 8, An automatic document transport device characterized by transporting the document sheet so that the document sheet comes into contact with the reverse side image reading unit.

10. In an image forming apparatus that forms an image on a sheet conveyed by a sheet conveying unit, An image forming apparatus characterized in that the sheet transport unit comprises the sheet transport device described in claim 1, or the automatic document transport device described in claim 5.

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