Sheet carrier and image reading apparatus

Abstract

To provide a sheet carrier that is comparatively simple in construction and made easy for a brochure body to enter a transport roller pair.SOLUTION: A sheet carrier comprises a drive roller that carries a sheet, a guide that is for guiding the sheet toward the drive roller and allowed to retract in a thickness direction of the sheet, and biasing means that biases the guide toward a transport pathway of the sheet. The guide is pushed by a sheet being carried into retraction in the thickness direction of the sheet against a biasing force of the biasing means, thereby increasing the protrusion amount of the drive roller toward the transport pathway from the guides.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a sheet conveying device used in an image reading device such as a scanner, a facsimile, or a copying machine, or an image forming device such as a printer, and also to an image reading device that reads an image from a sheet. [Background technology]

[0002] Some sheet transport devices, such as scanners, are capable of transporting booklets such as passports and bankbooks. However, booklets are thick, and they may not fit between the two rollers (the nip) of the pair of transport rollers that transport the sheet, resulting in a non-feed. Furthermore, if the width between the upper and lower reading units is narrow, the load on the booklet being transported increases, causing the booklet to be non-feedable.

[0003] Therefore, Patent Document 1 discloses a configuration in which a sensor detects the rigidity of the medium being transported, and if the rigidity is high, a motor and a cam unit retract the lower reading unit in the thickness direction of the medium, widening the transport path and making it easier to transport. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6721863 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the configuration described in Patent Document 1 requires a sensor to detect the rigidity of the medium being transported, a motor to retract the lower reading section, and a cam mechanism, which results in a problem of a complex scanner configuration and high costs.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a sheet conveying device that has a relatively simple configuration and that makes it easy for a booklet to enter a pair of conveying rollers. [Means for solving the problem]

[0007] The sheet conveying device of the present invention comprises a drive roller for conveying a sheet, a guide for guiding the sheet toward the drive roller, the guide being capable of retracting in the thickness direction of the sheet, and a biasing means for biasing the guide toward the sheet conveying path, and is characterized in that the guide is pushed by the sheet being conveyed and retracts in the thickness direction of the sheet against the biasing force of the biasing means, thereby increasing the amount by which the drive roller protrudes from the guide toward the conveying path. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a sheet transporting device that has a relatively simple configuration and that allows a booklet to easily enter a pair of transport rollers. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of an image reading device. [Figure 2] FIG. 2 is a control block diagram of the image reading apparatus. [Figure 3] FIG. 2 is a cross-sectional view of the image reading apparatus with the discharge tray closed. [Figure 4] FIG. 2 is a cross-sectional view showing a schematic configuration of the image reading apparatus with an upper unit unfolded. [Figure 5] FIG. 2 is a cross-sectional view showing a schematic configuration of a reading unit of the image reading device. [Figure 6] FIG. 10 is an enlarged cross-sectional view of a schematic configuration of a reading unit of a conventional image reading device. [Figure 7] FIG. 2 is an enlarged cross-sectional view of a schematic configuration of a reading unit of the image reading device. [Figure 8] FIG. 2 is an enlarged cross-sectional view of a schematic configuration of a reading guide unit of the image reading device. [Figure 9] FIG. 2 is an enlarged cross-sectional view of a schematic configuration of a reading unit of the image reading device. [Figure 10] FIG. 2 is an enlarged cross-sectional view of a schematic configuration of a reading unit of the image reading device. [Figure 11]FIG. 2 is a cross-sectional view showing a schematic configuration of a reading unit of the image reading device. [Figure 12] FIG. 2 is a cross-sectional view showing a schematic configuration of a reading unit of the image reading device. [Figure 13] FIG. 2 is a front view of a lower reading unit of the image reading device. [Figure 14] FIG. 10 is a front view of a modified example of the lower reading unit of the image reading device. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described below with reference to Figures 1 to 13. First, a schematic configuration of a sheet conveying device and an image reading device according to this embodiment will be described with reference to Figure 1.

[0011] [Image reader] The image reading device 100 is an apparatus that uses a sheet conveying device to convey one or more sheets (conveying media, originals) S loaded on a feed tray 110 serving as a loading section, one by one along a path RT into the apparatus, reads the images on the sheets, and discharges the sheets onto a discharge tray 2. The sheets S to be read are, for example, office paper, checks, business cards, cards, etc., and may be thick or thin. Cards include, for example, insurance cards, driver's licenses, credit cards, etc. The sheets S also include booklets T (see FIG. 6) such as passports.

[0012] [Feeding] A first conveying unit 10 is provided as a feeding mechanism that feeds sheets S along a path RT. The first conveying unit 10 includes a feed roller 11 as a first roller and a separation roller 12 as a second roller disposed opposite the feed roller 11, and conveys sheets S placed on a feed tray 110 one by one in a conveying direction D1. As shown in FIG. 7, the separation roller 12 is biased toward the feed roller 11 by a separation roller spring 13.

[0013] The conveying direction D1 is inclined at a predetermined angle with respect to the placement surface (surface of a table or the like) of the image reading device 100, and the sheet S placed on the feed tray 110 is supplied to the feed mechanism by its own weight. A driving force is transmitted from a drive unit 3 such as a motor to the feed roller 11 via a transmission unit 5, and the feed roller 11 is driven to rotate in the direction of the arrow in the figure (the forward direction for conveying the sheet S along the path RT). The transmission unit 5 is, for example, an electromagnetic clutch, and is capable of connecting and disconnecting the driving force from the drive unit 3 to the feed roller 11 (transmitting and cutting off the driving force).

[0014] [Drive unit] In this embodiment, the transmission unit 5 connecting the drive unit 3 and the feed roller 11 normally transmits the driving force, and cuts off the driving force when the sheet S is reversed or stopped. When the transmission of the driving force is cut off by the transmission unit 5, the feed roller 11 is allowed to rotate freely. Note that such a transmission unit 5 does not need to be provided when the feed roller 11 is driven in only one direction.

[0015] [Separated structure] The separation roller 12, which is disposed opposite the feed roller 11, is a roller for separating the sheets S one by one, and is pressed against the feed roller 11 at a constant pressure by a separation roller spring 13 (see FIG. 6). To ensure this pressed state, the separation roller 12 is configured to be swingable and to be biased toward the feed roller 11. A driving force is transmitted to the separation roller 12 from the drive unit 3 via a torque limiter 12a, and the separation roller 12 is driven to rotate in the direction of the solid arrow (the opposite direction to the forward direction of the feed roller 11).

[0016] Because the transmission of driving force is restricted by torque limiter 12a, separation roller 12 rotates in a direction (indicated by the dashed arrow) that rotates together with feed roller 11 when in contact with feed roller 11. Furthermore, when multiple sheets S are conveyed to the pressure contact portion (nip portion) between feed roller 11 and separation roller 12, the separation roller blocks all but one sheet S from being conveyed downstream. In other words, separation roller 12 separates the remaining sheets from the multiple sheets S being conveyed toward the nip portion between feed roller 11 and separation roller 12 so that the feed roller 11 can feed the sheets one by one from the multiple sheets S.

[0017] In this embodiment, the separation mechanism is configured by the separation roller 12 and the feed roller 11, but such a separation mechanism is not necessarily provided, and any feed mechanism that sequentially feeds the sheets S one by one to the path RT will suffice. Furthermore, when a separation mechanism is provided, instead of a configuration such as the separation roller 12, a separation pad that applies friction to the sheets S may be pressed against the feed roller 11 to provide a similar separation effect.

[0018] [Transport structure] The second conveying section 20, which serves as a conveying mechanism located downstream of the first conveying section 10 in the conveying direction D1, includes a drive roller 21 and a driven roller 22 driven by the drive roller 21, and conveys the sheet S conveyed from the first conveying section 10 downstream in the conveying direction D1. A driving force is transmitted to the drive roller 21 from a drive section 4 such as a motor, and the drive roller 21 is driven to rotate in the direction of the arrow in the figure. The driven roller 22 is pressed against the drive roller 21 at a constant pressure by a driven roller spring 23 (see FIG. 5), and rotates along with the drive roller 21. A detailed configuration of the periphery of the second conveying section 20 according to this embodiment will be described later.

[0019] The third conveying section 30, which is located downstream of the second conveying section 20 in the conveying direction, includes a drive roller 31 and a driven roller 32 that rotates following the drive roller 31, and conveys the sheet S conveyed from the second conveying section 20 to the discharge tray 2. In other words, the third conveying section 30 functions as a discharge mechanism.

[0020] A driving force is transmitted from a driving unit 4 such as a motor to the driving roller 31, and the driving roller 31 is driven to rotate in the direction of the arrow in the figure. The driven roller 32 is pressed against the driving roller 31 at a constant pressure by a driven roller spring 33 (see FIG. 5), and rotates along with the driving roller 31. The detailed configuration of the third conveying unit 30 and its surroundings according to this embodiment will be described later.

[0021] The discharge tray 2 is pivotally supported via a first hinge 101 provided below the device body 100A so as to be rotatable relative to the device body 100A of the image reading device 100. The discharge tray 2 is made up of a first discharge tray 2a on the first hinge 101 side and a first extension tray 2b connected to its tip end. The first extension tray 2b is supported so as to be slidable relative to the first discharge tray 2a.

[0022] [Image reading structure and control] In the image reading device 100 of this embodiment, an image is read by an image reading unit 70, which serves as an image reading section disposed between the second conveying section 20 and the third conveying section 30, and therefore the second conveying section 20 and the third conveying section 30 convey the sheet S at a constant speed. By always setting the conveying speed of the second conveying section 20 and the third conveying section 30 to be equal to or higher than the conveying speed of the first conveying section 10, it is possible to reliably prevent the subsequent sheet S from catching up with the preceding sheet S. For example, in this embodiment, the conveying speed of the sheet S by the second conveying section 20 and the third conveying section 30 is controlled so as to be faster than the conveying speed of the sheet S by the first conveying section 10.

[0023] [CIS placement] The image reading unit 70, located downstream of the media detection sensor 60, optically scans the image on the sheet, converts it into an electrical signal, and reads it as image data. It includes a light source such as an LED, an image sensor, a lens array, and the like. In this embodiment, one image reading unit 70 is disposed on each of the top and bottom sides of the path RT, and reads both the front and back sides of the document S. However, a configuration in which one image reading unit 70 is disposed on only one side of the path RT and reads only one side of the document S may also be adopted. Furthermore, in this embodiment, the image reading units 70 are disposed on both sides of the path RT, facing each other. However, they may also be disposed, for example, spaced apart in the direction of the path RT. The detailed configuration of the image reading unit 70 and its surroundings according to this embodiment will be described later.

[0024] [Control Unit] The control unit 80 of the image reading device 100 of this embodiment will be described with reference to Fig. 2. Fig. 2 is a block diagram of the control unit 80.

[0025] The control unit 80 includes a CPU 81, a storage unit 82, an operation unit 83, a communication unit 84, and an interface unit 86. The CPU 81 controls the entire image reading device 100 by executing a program stored in the storage unit 82. The storage unit 82 is composed of, for example, RAM, ROM, etc. The operation unit 83 is composed of, for example, switches, a touch panel, etc., and receives operations from an operator.

[0026] The communication unit 84 is an interface for communicating information with an external device. If the external device is a PC (personal computer), the communication unit 84 is, for example, a USB interface or a SCSI interface. In addition to such a wired communication interface, the communication unit 84 may also be a wireless communication interface, or may include interfaces for both wired communication and wireless communication.

[0027] The interface unit 86 is an I / O interface that inputs and outputs data to and from the actuator 85 and the sensor 87. The actuator 85 includes a drive unit 3, a drive unit 4, a transmission unit 5, etc. The sensor 87 includes a double feed detection sensor 40 having a sensor pair 41, 42 for detecting that multiple sheets S have passed through the first conveying unit 10 while overlapping, as well as medium detection sensors 50 and 60 for detecting the position of the sheets S, an image reading unit 70, etc. The medium detection sensor 50 has photointerrupters 51, 52, and the medium detection sensor 60 has photointerrupters 61, 62.

[0028] [Driven by receiving a start command from a PC] Next, a description will be given of the basic operation of the image reading device 100. When the control unit 80 receives an instruction to start image reading from, for example, an external personal computer (PC) to which the image reading device 100 is connected, it starts driving the first conveying unit 10, the second conveying unit 20, and the third conveying unit 30. The sheets S stacked on the feed tray 110 are conveyed one by one, starting with the bottommost sheet S.

[0029] The control unit 80 starts reading the image on the sheet S conveyed by the second conveying unit 20 using the image reading unit 70 at a timing based on the detection result of the medium detection sensor 60, temporarily stores the read image, and sequentially transmits it to the external computer. The sheet S from which the image has been read is discharged onto the discharge tray 2 by the third conveying unit 30, and the image reading process for the sheet S is completed.

[0030] [Details of the upper and lower units] Figures 3 and 4 are schematic cross-sectional views of the image reading device 100 according to this embodiment. Note that the internal configuration of the device is the same as that explained in Figure 1, and therefore some reference numerals and components are omitted in Figures 3 and 4. Also, Figure 3 shows a state in which the upper unit 103 is closed around the hinge 105, and Figure 4 shows a state in which the upper unit 103 is open.

[0031] The device main body 100A of the image reading device 100 is composed of an upper unit 103 as a second unit and a lower unit 104 as a first unit. The lower unit 104 has a feed roller 11 and is a unit below the path RT of the device main body 100A. On the other hand, the upper unit 103 has a separation roller 12 and is a unit above the path RT of the device main body 100A.

[0032] [Details of the Configuration of the Image Reading Unit 70, the Second Conveyor 20, and the Third Conveyor 30] Next, the configuration of the image reading unit 70, the second conveying section 20, and the third conveying section 30 of this embodiment will be described with reference to FIGS.

[0033] 5 shows a schematic cross-sectional view of the image reading unit 70, second conveying section 20, and third conveying section 30 of this embodiment. The image reading unit 70 is made up of an upper reading section 71 and a lower reading section 72, with the upper reading section 71 located on the upper unit 103 side and the lower reading section 72 located on the lower unit 104 side. Furthermore, a driven roller 22 is provided on the upstream side of the upper reading section in the conveying direction, a driven roller 32 is provided on the downstream side of the conveying direction, and a drive roller 21 is provided on the upstream side of the lower reading section 72 in the conveying direction, and a drive roller 31 is provided on the downstream side of the conveying direction.

[0034] In the second conveying section 20, the upper reading section 71 has an upper reading guide (a guide on the driven roller side) 73 integral with the upper reading section 71 on the upstream side in the conveying direction, and the lower reading section 72 has a lower reading guide 74 integral with the lower reading section 72 on the upstream side in the conveying direction. The upper reading guide 73 and the lower reading guide 74 guide the sheet S to the pressure contact portion (nip portion) between the drive roller 21 and the driven roller 22. In addition, the lower reading guide 74 has a surface (tapered guide surface 74a) that is inclined from upstream to downstream in the conveying direction in the direction approaching the conveying path Y.

[0035] 6 shows a schematic cross-sectional view of the periphery of the conventional second conveying section 20. Conventionally, the lower reading section 72 (in the figure, the lower reading guide 74 that is integral with the lower reading section 72) is fixed to the lower unit 104 with the drive roller 21 protruding only slightly from the conveying path Y (distance A).

[0036] As shown in Figure 6, the leading edge X2 of booklet T conveyed by feed roller 11 abuts against tapered guide surface 74a, and booklet T is guided to second conveyance section 20. When leading edge X1 subsequently contacts driven roller 22, booklet T attempts to push up driven roller 22. However, before leading edge X2 of booklet T contacts drive roller 21, it pushes up driven roller 22, causing drive roller 21 and driven roller 22 to separate. As a result, the conveying force of drive roller 21 is not transmitted to booklet T, and booklet T cannot push up driven roller 22 with the conveying force of feed roller 11 alone. As a result, booklet T does not enter the pressure contact portion (nip portion) between drive roller 21 and driven roller 22, resulting in a non-feed. Non-feeding occurs not only in second conveyance section 20, but also in third conveyance section 30 for the same reason.

[0037] 7 shows a schematic cross-sectional view of the second conveying unit 20 and its surroundings in this embodiment. When the booklet T reaches the lower reading guide 74, the leading edge X2 of the booklet T abuts against the tapered guide surface 74a, the lower reading guide 74 is pressed by the booklet T, and the lower reading unit 72, which is integral with the lower reading guide 74, retracts in the medium thickness direction indicated by arrow C against the biasing force of the reading spring 78. This causes the drive roller 21 to protrude a distance B into the conveying path Y. Because distance B is greater than distance A, which is the protrusion amount of the conventional drive roller 21, the protrusion amount of the drive roller 21 toward the conveying path is greater than in the conventional embodiment. As a result, the timing at which end X2 of the booklet T hits the drive roller 21 occurs earlier than or simultaneously with the timing at which end X1 of the booklet T hits the driven roller 22. That is, when the leading edge X1 of the booklet T pushes up the driven roller 22, the leading edge X2 of the booklet T is in contact with the driving roller 21, so that the transport force is transmitted to the booklet T and the booklet can be transported without being stopped.

[0038] An enlarged view of the area around the tapered guide surface 74a is shown in Figure 8. The smaller the angle θ at which the leading edge X2 of the booklet T abuts against the tapered guide surface 74a, the smaller the load on the booklet T when the lower reading guide 74 is retracted in the medium thickness direction. For this reason, it is desirable that the tapered surface D of the tapered guide surface 74a be long and the angle θ' be small.

[0039] The booklet T is further transported and enters between the image reading units as shown in Figure 9. In addition to the lower reading unit 72, the upper reading unit 71 is also pressed by the booklet T and retreats in the direction of arrow E against the biasing force of the reading spring 77. The transport path Y widens, allowing the booklet T to be transported smoothly.

[0040] FIG. 10 shows a schematic cross-sectional view of the third transport unit 30 and its surroundings in this embodiment. When the booklet T reaches the third transport unit 30, the same effect as the second transport unit 20 is achieved. A lower reading guide 76, which is integrated with the lower reading unit 72, and an upper reading guide 75, which is integrated with the upper reading unit 71, are arranged around the third transport unit 30. When the booklet T reaches the lower reading guide 76, the lower reading guide 76 is pushed by the booklet T, and the lower reading unit 72, which is integrated with the lower reading guide 76, retreats in the medium thickness direction indicated by arrow F against the biasing force of the reading spring 78. This causes the drive roller 31 to protrude from the transport path Y. Therefore, the timing at which the end X2 of the booklet T hits the drive roller 31 is earlier than or simultaneous with the timing at which the end X1 of the booklet T hits the driven roller 32. That is, when the leading edge X1 of the booklet T pushes up the driven roller 32, the leading edge X2 of the booklet T is in contact with the drive roller 21, so that the transport force is transmitted to the booklet T and the booklet can be transported without being stopped.

[0041] Furthermore, by retracting the lower reading unit 72 in the medium thickness direction, the transport path Y widens, and the thick paper transported between the lower reading unit 72 and the upper reading unit 71 is transported smoothly without stopping. Therefore, the image on the thick paper does not shrink, and the image can be read stably.

[0042] When transporting thick paper such as booklet T, the lower reading unit 72 can be retracted in the thickness direction of the medium as in this embodiment, and the drive roller 21 can protrude more from the transport path Y, allowing the paper to be transported without being stopped. However, when transporting thin paper as shown in Figure 11, the drive roller 21 can be made to protrude less into the transport path Y, narrowing the transport path Y, allowing the thin paper to be transported by pressing it against the lower reading unit 72, and allowing it to enter the pressure contact area (nip area) between the drive roller 21 and driven roller 22 more smoothly.

[0043] Therefore, as shown in FIG. 12, a reading spring 78 is provided on the opposite side of the reading surface of the lower reading unit 72. The force of the reading spring 78 that biases the lower reading unit 72 in the direction of arrow G is set so that the lower reading unit 72 retracts when thick paper is being transported as shown in FIG. 7, but does not retract when thin paper is being transported as shown in FIG. 11. Therefore, the lower reading unit 72 can be retracted in the thickness direction of the medium by the transported thick paper, without requiring a complex mechanism such as using a motor to retract the reading unit. When thin paper is being transported, the lower reading unit 72 can be transported without retracting, but when thick paper is being transported, the lower reading unit 72 retracts, the drive roller 21 protrudes onto the transport path Y, and the thick paper is more likely to enter the pressure contact area (nip area) between the drive rollers 21, 31 and the driven rollers 22, 32.

[0044] The upper reading unit 71 retracts in the thickness direction of the medium, being pushed out by the medium being transported due to the thickness of the sheet S. The upper reading unit 71 is urged in the direction of arrow H by a reading spring 77 provided on the opposite side of the reading surface. In this case, it is desirable that the reading spring 78 urging the lower reading unit 72 has a stronger elastic force than the reading spring 77 urging the upper reading unit 71. For materials other than thick paper such as booklet T, the lower reading unit 72 does not retract as in the conventional case, and the amount of protrusion of the drive rollers 21 and 31 onto the transport path Y is reduced, allowing thin paper to be transported without jamming.

[0045] In this embodiment, the upper reading unit 71 is supported so as to be retractable in the thickness direction of the sheet S. However, the upper reading unit 71 may be fixed to the upper unit 103.

[0046] Figure 13 is a diagram showing the lower reading unit 72 as seen from the direction of arrow G in Figure 12. One method for making it easier to retract the lower reading unit 72 is to arrange the holding unit 79 that holds the lower reading unit 72 to the lower unit 104 and the reading spring 78 linearly in the document width direction, as shown in Figure 13. Because the rotation axis of the lower reading unit 72 in the document width direction and the biasing position of the reading spring 78 are located on a straight line, when the lower reading unit 72 is pressed by the transported medium, the holding unit 79 is not pried against the lower unit 104, and the lower reading unit 72 retracts smoothly in the medium thickness direction.

[0047] It is preferable that the width 74a of the lower reading guide 74 in the direction perpendicular to the conveying direction is wider than the width of the booklet T. By making the width 74a of the lower reading guide 74 wider than the width of the booklet T, when the booklet T is conveyed, the entire width 74a of the lower reading guide 74 retracts in the thickness direction of the booklet T, making it easier to convey the booklet T stably. For example, when considering the case where a passport is conveyed as the booklet T, it is preferable that the width 74a of the lower reading guide 74 be 130 mm or more.

[0048] However, the width 74a of the lower reading guide 74 is not limited to being wider than the width of the booklet T, and as shown in FIG. 14, the lower reading guide 74 may be separated at the center in the width direction.

[0049] The first transport unit 10 can select between a "first feeding mode" in which the original documents S on the loading platform 110 are separated and fed one by one, and a "second feeding mode" in which the original documents S on the loading platform 110 are fed without separating them. As a variation of this embodiment, a configuration (not shown) may be adopted in which, in the second feeding mode, the lock that secures the lower reading unit 72 to the lower unit 104 is released, allowing the lower reading unit 72 to move down in the thickness direction of the medium. Also, the mechanism that releases the lock that secures the lower reading unit 72 to the lower unit 104 may be integrated with a lever for changing to the second feeding mode. Also, a configuration may be adopted in which, when a sensor detects the second feeding mode, a cam that acts as a lock that secures the lower reading unit 72 to the lower unit 104 moves, causing the lower reading unit 72 to retract.

[0050] <Other embodiments> The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. In addition, the sheet conveying device of the present invention can be applied not only to the above-described image reading device, but also to image forming devices such as copiers, printers, and multifunction peripherals that have an image forming unit that forms an image on a sheet (recording medium). [Explanation of symbols]

[0051] 10 First conveying section 11 Feed roller 12 Separation roller 13 Separation roller spring 20 Second conveying section 21 Drive roller 22 driven roller 23 Follower roller spring 30 Third conveying section 31 Drive roller 32 driven roller 33 Follower roller spring 70 Image reading unit 71 Upper reading section 72 Lower reading section 73,75 Upper reading guide 74,76 Lower reading guide 77,78 Reading spring 79 Holding part 100 Image reader 110 Loading platform 103 Upper Unit 104 Lower unit

Claims

1. a drive roller for conveying a sheet; a guide that guides the sheet toward the drive roller and that can be retracted in a thickness direction of the sheet; and a biasing means for biasing the guide toward the sheet conveyance path, A sheet conveying device characterized in that the guide is pushed by the sheet being conveyed and retreats in the thickness direction of the sheet against the biasing force of the biasing means, thereby increasing the amount by which the drive roller protrudes from the guide toward the conveying path.

2. 2. The sheet transport device according to claim 1, wherein the guide is integral with a reading means for reading an image on the sheet.

3. 3. The sheet conveying device according to claim 2, wherein the biasing means applies a biasing force to a surface of the reading means opposite to a reading surface thereof.

4. 3. The sheet conveying device according to claim 2, wherein the guide has a tapered surface, and when the sheet abuts against the tapered surface, the guide retracts in the thickness direction of the sheet.

5. The sheet conveying device according to claim 2, characterized in that the reading means is composed of a first reading unit arranged on the lower side of the conveying path and a second reading unit arranged on the upper side, and the guide is integrally configured with the first reading unit.

6. 6. The sheet conveying device according to claim 5, wherein the first reading unit and the second reading unit are each biased toward the conveying path, the biasing force of the first reading unit is generated by the biasing means, and the biasing force of the first reading unit is stronger than the biasing force of the second reading unit.

7. 7. The sheet conveying device according to claim 6, wherein the reading means comprises a holding portion that is held by a main body of the image reading device, and the holding portion and the biasing means are arranged linearly in line in the width direction of the sheet.

8. The image reading device has a first feeding mode in which a stack of multiple sheets is separated and fed, and a second feeding mode in which the stack of sheets is fed without separating it, and in the second feeding mode, the guide is pushed by the sheets being transported and retracts in the thickness direction of the sheets against the urging force of the urging means, as described in claim 1.

9. a driven roller that is disposed at a position opposite to the drive roller across a conveyance path for conveying the sheet and that is rotated in response to rotation of the drive roller; 2. The sheet transport device according to claim 1, wherein the drive roller and the driven roller are disposed on the upstream side and downstream side in the transport direction of the sheet.

10. 10. The sheet conveying device according to claim 9, wherein the guide on the driven roller side is pushed by the sheet being conveyed and retreats in the thickness direction of the sheet against the biasing force of the biasing means.

11. 2. The sheet transport device according to claim 1, wherein the sheet is a document on which an image is formed or a recording medium for forming an image.

12. reading means for reading an image on the sheet; The sheet conveying device according to any one of claims 1 to 11, An image reading device comprising:

Images