Medium transfer device and image reading device

Abstract

To easily detach and easily attach a transfer roller 6 from a device main body 2 for replacement, etc.SOLUTION: A medium transfer device 11 includes a transfer roller unit 12 including a transfer roller 6 capable of transferring a medium, and a drive unit 13 that drives the transfer roller 6. The drive unit 13 has a power transmission section 14, and the transfer roller unit 12 has a power transmitted section 15. When the transfer roller unit 12 moves in an approaching direction to the drive unit 13, the power transmission section 14 and the power transmitted section 15 are set to be connected to each other, and when the transfer roller unit 12 moves in a direction away from the drive unit 13, the power transmission section 14 and the power transmitted section 15 are set to be disconnected from each other.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a medium conveying device and an image reading device. [Background technology]

[0002] One example of this type of device is described in Patent Document 1. Patent Document 1 discloses an image reading device equipped with a document transport unit including document transport means such as a first transport roller, a second transport roller, and a feed roller, and drive means such as a motor, pulley, and belt for driving the document transport means. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 5-83491 Summary of the Invention [Problem to be solved by the invention]

[0004] In the device of Patent Document 1, for example, when replacing only the first conveyor roller, it is necessary to remove the pulley and belt. Therefore, after replacing the first conveyor roller, it is necessary to adjust the tension of the belt. The tension adjustment is troublesome and time-consuming. [Means for solving the problem]

[0005] In order to solve the above problems, the media transport device of the present invention comprises a transport roller unit including a transport roller capable of transporting a medium, and a drive unit that drives the transport roller, wherein the drive unit has a power transmission section and the transport roller unit has a power transmitted section, and when the transport roller unit moves in a direction toward the drive unit, the power transmission section and the power transmitted section become connected, and when the transport roller unit moves in a direction away from the drive unit, the power transmission section and the power transmitted section become disconnected.

[0006] An image reading device according to the present invention includes a medium conveying device according to any one of the first to seventh aspects described below, and a reading section that reads an image on the medium. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is an external perspective view of an image reading apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view of the image reading apparatus according to the embodiment with a side cover removed. [Diagram 3] FIG. 3 is a perspective view of the state in which a transport roller unit is removed from the state in FIG. 2 . [Figure 4] FIG. 2 is an overall perspective view of a transport roller unit according to the embodiment. [Diagram 5] FIG. 4 is a perspective view of a main part of a drive unit according to the embodiment. [Figure 6] FIG. 13 is a front view of the state in which insertion of the transport roller unit is started in the embodiment. [Figure 7] FIG. 7 is a front view of a state in which the transport roller unit has moved further from the state in FIG. 6. [Figure 8] 8 is a front view of the state in which the movement of the transport roller unit has been completed from the state in FIG. 7. [Figure 9] 13 is a perspective view showing a modified example of a fixing structure for fixing the second support portion to the second frame. FIG. [Figure 10] FIG. 13 is a perspective view of a structure in which a handle is provided on the second support part. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention will first be briefly described below. In order to solve the above problems, a first aspect of a media transport device according to the present invention comprises a transport roller unit including a transport roller capable of transporting a medium, and a drive unit that drives the transport roller, wherein the drive unit has a power transmission section and the transport roller unit has a power transmitted section, and when the transport roller unit moves in a direction toward the drive unit, the power transmission section and the power transmitted section become connected, and when the transport roller unit moves in a direction away from the drive unit, the power transmission section and the power transmitted section become disconnected.

[0009] According to this aspect, the power transmission part and the power transmitted part are connected by moving the transport roller unit in a direction toward the drive unit, and conversely, the power transmission part and the power transmitted part are disconnected by moving the transport roller unit in a direction away from the drive unit. As a result, when it is desired to remove the transport roller for replacement or the like, the transport roller can be easily removed since the disconnected state is achieved simply by moving the transport roller unit in a direction away from the drive unit. Furthermore, when a new transport roller unit including a different transport roller is to be attached, the connected state is achieved simply by moving the transport roller unit in a direction toward the drive unit, so this can be easily performed. In other words, the transport roller unit can be removed and installed without touching the drive unit, i.e., in its original state, by simply moving the transport roller unit, so that the transport roller can be easily replaced. In addition, tension adjustment, etc., as in the conventional case, is not required for the drive unit, and the replacement time can be shortened.

[0010] A second aspect of the media transport device of the present invention is an aspect dependent on the first aspect, characterized in that the transport roller unit has a first axis supporting the transport roller, a first frame located on one end side of the first axis, and a second frame located on the other end side of the first axis, the drive unit is held by the first frame, and the transport roller unit can take the connected state and the disconnected state by moving in a direction along the first axis through an insertion portion of the second frame.

[0011] According to this aspect, the transport roller unit can take the connected state and the disconnected state by moving in a direction along the first axis through the insertion portion of the second frame, which makes it possible to replace the transport roller with a simple structure.

[0012] A third aspect of the medium conveying device of the present invention is an aspect dependent on the second aspect, and is characterized in that the power transmitted part located at one end of the first shaft is a first gear, and the power transmitting part is a second gear meshing with the first gear.

[0013] According to this aspect, both the power transmitted part and the power transmitting part are configured with gears, which simplifies the structure for realizing the connected state and the disconnected state, and also makes it easy to switch between these states.

[0014] A fourth aspect of the medium conveying device of the present invention is an aspect dependent on the third aspect, and is characterized in that at least one of the first gear and the second gear has an inclined surface formed at a portion where the first gear moves in the approaching direction and the multiple first teeth of the first gear begin to mesh with the multiple second teeth of the second gear, thereby expanding the spacing between adjacent teeth.

[0015] According to this aspect, at least one of the first gear and the second gear has an inclined surface that expands the space between adjacent teeth at a portion where the first gear and the second gear start to mesh with each other by moving in the approaching direction. The inclined surface makes it easy to move the transport roller unit in the approaching direction relative to the drive unit to achieve the connected state.

[0016] A fifth aspect of the media conveying device of the present invention is an aspect dependent on the third aspect, and is characterized in that the drive unit has a toothed belt and a pulley around which the toothed belt rotates, and the second gear is attached to a second shaft which is the center of rotation of the pulley and rotates integrally with the pulley. This aspect can also be subordinate to the fourth aspect.

[0017] In some media transport devices, the drive unit has a structure including a toothed belt and the pulley, and conventionally, when replacing the transport roller, it was necessary to remove the toothed belt from the pulley. However, according to this aspect, the second gear is attached to a second shaft that is the rotation center of the pulley and rotates integrally with the pulley. Therefore, the connected state can be changed to the disconnected state by moving the drive roller unit in a direction away from the drive unit. This makes it easy to remove the drive roller unit from the drive unit, thereby making it easy to replace the transport roller.

[0018] A sixth aspect of the media conveying device of the present invention is an aspect dependent on the second aspect, and is characterized in that the conveying roller unit has a support portion that rotatably supports the first shaft, and has a guide portion between the first frame and the second frame that guides the support portion during the movement. This aspect may be subordinate to any one of the third to fifth aspects.

[0019] According to this aspect, when the transport roller unit is moved from the second frame toward the first frame, the support portion is guided along the guide portion, which makes it possible to easily move the transport roller unit.

[0020] A seventh aspect of the medium conveying device of the present invention is an aspect dependent on the sixth aspect, and is characterized in that the support part is conductive and has a first support part located on one end side of the first shaft and supporting the first shaft via a bearing, a second support part located on the other end side of the first shaft and supporting the first shaft via a bearing, and a base support part connecting the first support part and the second support part, and the first shaft and the support part are connected by a conductive member.

[0021] With continued use, the properties of the lubricating oil inside the bearing deteriorate, and the electrical conductivity decreases, so in a structure in which the first shaft is grounded via the bearing, there is a risk that the earthing properties will also deteriorate. However, according to this aspect, the first shaft and the conductive support part are connected by a conductive member such as brass, etc. This makes it possible to continue earthing the first shaft through the conductive member even if the earthing characteristics of the bearing deteriorate.

[0022] An eighth aspect of the image reading device of the present invention comprises a medium conveying device described in any one of the first to seventh aspects, and a reading unit that reads an image on the medium.

[0023] According to this aspect, it is possible to obtain the same effects as any one of the first to seventh aspects as an image reading device.

[0024] [Embodiment] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a medium conveying device according to the present invention and an image reading device including the medium conveying device will be specifically described with reference to the drawings. In the following explanation, the three mutually orthogonal axes are referred to as the X-axis, Y-axis, and Z-axis, as shown in each figure. The directions indicated by the arrows on the three axes (X, Y, Z) are the + directions of each direction, and the opposite directions are the - directions. The Z-axis direction corresponds to the vertical direction, i.e., the direction in which gravity acts, the +Z direction indicates a vertical upward direction, and the -Z direction indicates a vertical downward direction. The X-axis and Y-axis directions correspond to the horizontal direction. The +Y direction indicates the front direction of the device, and the -Y direction indicates the rear direction of the device. The +X direction indicates the right direction of the device, and the -X direction indicates the left direction of the device.

[0025] [Embodiment 1] <Image reader> As shown in FIGS. 1 to 4, an image reading device 1 of this embodiment includes a device main body 2 and includes a medium conveying device 11 and a reading section 4 therein. The medium transport device 11 has a transport path 3 for transporting a medium such as paper (not shown) in a transport direction F. A plurality of transport rollers 6 are arranged on the transport path 3 along the transport direction F as described below. The transport rollers 6 are supported by a first shaft 7 (FIGS. 2, 3, and 4) and rotate integrally with the first shaft 7. The transport rollers 6 apply a transport force to the medium in the transport direction F by rotating. FIG. 2 shows a portion of the first shaft 7 of one of the plurality of transport rollers 6, and the other transport rollers 6 are not shown. FIG. 2 shows a state in which one side cover 8 (-X side) of the image reading device 1 has been removed. The structure of the medium transport device 11 will be described in further detail below.

[0026] 1, the reading unit 4 is disposed along the transport path 3. The reading unit 4 optically reads an image of the medium transported along the transport path 3 to obtain image information. In this embodiment, the transport path 3 has an inversion unit 5. The front of the image reading device 1 forms a medium placement section 9 on which a medium is placed. The medium placement section 9 is in an open state in which a medium can be placed by rotating the lower end section as a pivot point and positioning the upper end section horizontally with the lower end section open toward the user (in the +Y direction). In FIG. 1, the medium placement section 9 is in a closed state. The media placed on the media loading section 9 in the open state is picked up one by one by a pick roller (not shown), transported along the transport path 3 in the transport direction F, where the media is read by the reading section 4, transported through the inversion section 5, and discharged to the discharge receiving section 10 located at the top of the device main body 2.

[0027] <Medium transport device> 4 and 5, the medium transport device 11 of this embodiment includes a transport roller unit 12 including a transport roller 6, and a drive unit 13 that drives the transport roller 6. The drive unit 13 is driven by rotational power transmitted from a motor (not shown). The drive unit 13 has a power transmission section 14 for transmitting the rotational power to the transport roller unit 12. The transport roller unit 12 has a power transmitted section 15 for receiving the rotational power transmitted from the drive unit 13. Then, as the transport roller unit 12 moves in a direction (+X direction) approaching the drive unit 13, the power transmission part 14 and the power transmitted part 15 become connected. That is, the rotational power is transmitted from the drive unit 13 to the transport roller unit 12. On the other hand, as the transport roller unit 12 moves in a direction (-X direction) away from the drive unit 13, the power transmission part 14 and the power transmitted part 15 become disconnected. That is, the power transmitted part 15 of the transport roller unit 12 is located away from the power transmission part 14 of the drive unit 13.

[0028] 2, in this embodiment, the medium conveying device 11 has a plate-shaped first frame 16 located on one end side (+X side) of the first shaft 7, and a plate-shaped second frame 17 located on the other end side (-X side) of the first shaft 7. The first frame 16 is located inside a side cover (not shown) on the other side (+X side) of the image reading device 1. The drive unit 13 is held by the first frame 16. In other words, the drive unit 13 is attached to the first frame 16 side. 2 to 4, the transport roller unit 12 has a first shaft 7 that supports the transport roller 6. The transport roller unit 12 is configured to be able to take the connected state and the disconnected state by moving in a direction along the first shaft 7 (X-axis direction) through an insertion portion 18 (partially enlarged view in FIG. 2) of a second frame 17.

[0029] 5, in this embodiment, the power receiving part 15 located at one end (+X side) of the first shaft 7 is a first gear 20, and the power transmitting part 14 is a second gear 21 that meshes with the first gear 20. Here, as shown in the partially enlarged view in FIG. 5, the second gear 21 is formed with an inclined surface 25 that widens the space between adjacent teeth 23 at a portion where the transport roller unit 12 moves in the approaching direction (+X direction) and the multiple first teeth 22 of the first gear 20 start to mesh with the multiple second teeth 23 of the second gear 21. The inclined surface 25 may be formed on the first gear 20 instead of the second gear 21, or on both the first gear 20 and the second gear 21.

[0030] 5, in this embodiment, the drive unit 13 has a toothed belt 26 and a pulley 27. The toothed belt 26 is wound around the pulley 27, and rotates when rotational power is transmitted from a motor (not shown) to the toothed belt 26. The second gear 21 is attached to a second shaft 28 that is the center of rotation of the pulley 27, and is configured to rotate integrally with the pulley 27.

[0031] As shown in FIG. 4, in this embodiment, the transport roller unit 12 includes a support portion 30 that rotatably supports the first shaft 7. The support portion 30 is made of a conductive material such as sheet metal. The support portion 30 includes a first support portion 301 that is located on one end side (+X side) of the first shaft 7 and supports the first shaft 7 via a bearing 32, a second support portion 302 that is located on the other end side (-X side) of the first shaft 7 and supports the first shaft 7 via a bearing 33, and a base support portion 303 that connects the first support portion 301 and the second support portion 302. In FIG. 2, reference numeral 38 denotes a C-ring. In this embodiment, the first shaft 7 and the support portion 30 are connected by a conductive member 34. Here, the conductive member 34 is made of a material with good conductivity, such as brass.

[0032] 6 to 8, the medium transport device 11 is provided with a guide portion 31 between the first frame 16 and the second frame 17 that guides the support portion 30 when the transport roller unit 12 moves in the X-axis direction. Here, the base support portion 303 of the support portion 30 is guided by the guide portion 31. Here, the guide portion 31 is formed in a rib shape. It is configured so that the base support portion 303 moves and is guided in the X-axis direction with the lower surface of the base support portion 303 in contact with the upper surface of the rib-shaped guide portion 31. In this embodiment, the rib-like guide portion 31 has the same height from the second frame 17 side to the front near the first frame 16, but an upward guide inclined surface 35 is formed in the area from the front position of the first frame 16 toward the second gear 21 of the drive unit 13. When the first gear 20 is connected to the second gear 21, the guide inclined surface 35 functions to easily reach a state in which the first gear 20 and the second gear 21 mesh with each other, that is, the connected state, by approaching each other obliquely from below to above. In addition, the guide inclined surface 35 also functions to keep the lower surface of the base support portion 303 away from the upper surface of the guide portion 31 on the rib in the connected state.

[0033] In the connected state of the first gear 20 and the second gear 21, as described above, the lower surface of the base support part 303 is separated from the upper surface of the guide part 31 on the rib. As shown in the partially enlarged view of Fig. 2, in the separated state of the transport roller unit 12, the second support part 302 of the support part 30 is fastened and fixed to the second frame 17 by the screws 36 and 37. The transport roller unit 12 is configured to be fixed in a position where the transport roller 6 can apply a transport force to the medium in the fastened and fixed state. The second frame 17 is provided with a positioning portion (not shown) for positioning so that it can be fixed in the above-mentioned position. The transport roller unit 12 is fastened and fixed with screws 36 and 37 in the above-mentioned positioned state. The second frame 17 is formed with holes into which the screws 36 and 37 are inserted, although they are hidden and not visible in the partially enlarged view of FIG.

[0034] 9 shows a modified fixing structure for fixing the second support part 302 to the second frame 17. In this modified structure, the screws 36, 37 are not used, and the movable locking part 40 is attached to the second frame 17 so as to rotate about a shaft 41 as a rotation fulcrum. The shaft 41 is attached to the second frame 17. The movable locking part 40 has a concave locking recess 42 formed on the side opposite the shaft 41. As shown in Fig. 9, a protrusion 43 is provided on the second frame 17. The protrusion 43 is formed in a shape that engages with the locking recess 42. When the movable locking part 40 rotates in the direction of the arrow from the state shown in the upper diagram of Fig. 9, it reaches the state shown in the lower diagram of Fig. 9, where the locking recess 42 of the movable locking part 40 engages with the protrusion 43, and in this state the second support part 302 is fixed. The second support part 302 is positioned and fixed in the Y-axis direction and the Z-axis direction by positioning parts not shown.

[0035] <Replacing the transport roller> (1) Installation of new transport rollers First, the installation of a new transport roller 6 in the apparatus body 2 will be described with reference to FIGS. As shown in FIG. 6, with the side cover 8 of the device body 2 removed, the transport roller unit 12 is aligned with the insertion portion 18 of the second frame 17 and insertion in the +X direction is started. Next, as shown in FIG. 7, the transport roller unit 12 is moved so as to be pushed in while being guided in the +X direction with the lower surface of the base support portion 303 of the support portion 30 in contact with the rib-shaped guide portion 31.

[0036] When moved further, the leading end of the base support part 303 in the moving direction reaches the position of the inclined guide surface 35 of the guide part 31, and moves in the +X direction while ascending obliquely along the inclined guide surface 35. At the end point of the movement, the first gear 20 of the transport roller unit 12 meshes with the second gear 21 of the drive unit 13, thus achieving the connected state. In this state, the second support part 302 is fastened and fixed to the second frame 17 by the screws 36 and 37. This state is shown in FIG. In Fig. 8, reference numeral 45 denotes a driven roller. As shown in Fig. 8, in the fastened and fixed state, the transport rollers 6, 6 and the driven rollers 45, 45 are in contact with each other. When the transport rollers 6, 6 rotate in this state, the driven rollers 45, 45 are rotated to apply a transport force to the medium.

[0037] (2) Removing the transport rollers 2, first, the side cover 8 is removed from the apparatus body 2. Next, the screws 36 and 37 are removed from the second support portion 302. This makes it possible to remove the transport roller unit 12 in the -X direction. 3, the transport roller unit 12 is pulled out in the -X direction. The lower surface of the base support part 303 of the support part 30 moves obliquely downward along the guide inclined surface 35, comes into contact with the upper surface of the guide part 31, and moves in the -X direction. Finally, the entire unit is pulled out from the device body 2.

[0038] <Explanation of Effects of First Embodiment> (1) In the medium transport device 11 of the present embodiment, the power transmission section 14 and the power transmitted section 15 are connected when the transport roller unit 12 moves in a direction toward the drive unit 13, and conversely, the power transmission section 14 and the power transmitted section 15 are disconnected when the transport roller unit 12 moves in a direction away from the drive unit 13. As a result, when it is desired to remove the transport roller 6 for replacement or the like, the transport roller unit 12 can be easily removed since it is in the disconnected state simply by moving the transport roller unit 12 in a direction away from the drive unit 13. Furthermore, when a new transport roller unit 12 including a different transport roller 6 is to be attached, the transport roller unit 12 can be easily removed since it is in the connected state simply by moving the transport roller unit 12 in a direction toward the drive unit 13. In other words, the transport roller unit 12 can be removed and installed without touching the drive unit 13, i.e., without changing the drive unit 13, by simply moving the transport roller unit 12, so that the transport roller 6 can be easily replaced. In addition, tension adjustment, etc., as in the conventional method, is not required for the drive unit 13, and the replacement time can be shortened.

[0039] (2) In addition, in this embodiment, the transport roller unit 12 can take the connected state and the disconnected state by moving in a direction along the first shaft 7 through the insertion portion 18 of the second frame 17. This makes it possible to replace the transport roller 6 with a simple structure. (3) In this embodiment, both the power transmitted part 15 and the power transmitting part 14 are made up of gears. This simplifies the structure for achieving the connected state and the disconnected state, and also makes it easy to switch between these states.

[0040] (4) In this embodiment, at least one of the first gear 20 and the second gear 21 has an inclined surface 25 that expands the spacing between adjacent teeth 23, 23, ... at the portion where they move in the approaching direction and start to mesh with each other. This inclined surface 25 makes it easy to move the transport roller unit 12 in the direction approaching the drive unit 13 to achieve the connected state.

[0041] (5) In the medium transport device 11, the drive unit 13 has a structure including a toothed belt 26 and a pulley 27. Conventionally, when replacing the transport roller 6, it was necessary to remove the toothed belt 26 from the pulley 27. However, in this embodiment, the second gear 21 is attached to a second shaft 28 which is the rotation center of the pulley 27, and rotates integrally with the pulley 27. Therefore, the connected state can be changed to the disconnected state by moving the transport roller unit 12 in a direction away from the drive unit 13. This allows the transport roller unit 12 to be easily removed from the drive unit 13, and therefore the transport roller 6 can be easily replaced. (6) In addition, in this embodiment, when transport roller unit 12 moves from second frame 17 toward first frame 16, support portion 30 is guided along guide portion 31. This allows transport roller unit 12 to move easily.

[0042] (7) The first shaft 7 is supported by the second support part 302 via the bearing 33. With continued use, the characteristics of the lubricant inside the bearing 33 deteriorate, and the electrical conductivity decreases. Therefore, in a structure in which the first shaft 7 is grounded via the bearing 33, there is a risk that the earthing characteristics will also deteriorate. However, in this embodiment, the first shaft 7 and the conductive support part 30 are connected by a conductive member 34 such as brass. This allows the first shaft 7 to continue to be grounded by the conductive member 34 even if the earthing characteristics of the bearing 33 deteriorate.

[0043] Other Embodiments The medium conveying device 11 and the image reading device 1 equipped with the medium conveying device 11 according to the present invention are based on the configuration of the embodiment described above, but it is of course possible to modify or omit some of the configuration within the scope that does not deviate from the gist of the present invention. 10, it is preferable to provide a handle 39 on the second support portion 302 of the drive roller unit 12. The presence of this handle 39 allows the user to move the drive roller unit 12 by holding the handle 39, improving operability. Furthermore, in the above embodiment, the drive roller unit 12 has been described as having a structure including the support portion 30, but the support portion 30 may be omitted and the first shaft 7 may be moved directly in the X-axis direction. [Explanation of symbols]

[0044] 1: image reading device; 2: device body; 3: conveying path; 4: reading section; 5: reversing section; 6: conveying roller; 7: first shaft; 8: side cover; 9: medium placement portion; 10: discharge receiving portion, 11: medium transport device, 12: transport roller unit, 13: drive unit; 14: power transmission part; 15: power transmitted part; 16...first frame, 17...second frame, 18...insertion portion, 20...first gear, 21... second gear, 22... first tooth, 23... second tooth, 25... inclined surface, 26... toothed belt, 27... pulley, 28... second shaft, 30... support portion, 301...first support portion, 302...second support portion, 303...base support portion, 31: guide portion; 32: bearing; 33: bearing; 34: conductive member; 35...guide inclined surface, 36...screw, 37...screw, 38...C-ring, 39...handle, 40: movable locking portion, 41: shaft, 42: locking recess, 43: protrusion, 45: driven roller, F...Transport direction

Claims

1. a transport roller unit including a transport roller capable of transporting a medium; A drive unit that drives the transport roller, The drive unit has a power transmission section, The transport roller unit has a power receiving part, When the transport roller unit moves in a direction approaching the drive unit, the power transmission unit and the power transmitted unit are brought into a connected state, When the transport roller unit moves in a direction away from the drive unit, the power transmission unit and the power transmitted unit are disconnected from each other. A medium transport device comprising:

2. The medium transport device according to claim 1 , the transport roller unit has a first shaft supporting the transport roller, A first frame located on one end side of the first shaft; a second frame located on the other end side of the first shaft, The drive unit is held by the first frame, the transport roller unit can take the connected state and the disconnected state by moving in a direction along the first axis through an insertion portion of the second frame; A medium transport device comprising:

3. The medium transport device according to claim 2 , the power transmitted part located at one end of the first shaft is a first gear, The power transmission unit is a second gear that meshes with the first gear. A medium transport device comprising:

4. The medium transport device according to claim 3 , At least one of the first gear and the second gear has an inclined surface formed at a portion where the first gear moves in the approaching direction and the first teeth of the first gear start to mesh with the second teeth of the second gear, the inclined surface expanding a space between adjacent teeth. A medium transport device comprising:

5. The medium transport device according to claim 3 , The drive unit includes: A toothed belt; The toothed belt has a pulley around which the toothed belt rotates, The second gear is attached to a second shaft that is a rotation center of the pulley and rotates integrally with the pulley. A medium transport device comprising:

6. 3. The medium transport device according to claim 2, the transport roller unit includes a support portion that rotatably supports the first shaft, a guide portion that guides the support portion during the movement is provided between the first frame and the second frame; A medium transport device comprising:

7. 7. The medium transport device according to claim 6, The support portion is It is electrically conductive, a first support portion located on one end side of the first shaft and supporting the first shaft via a bearing; a second support portion located on the other end side of the first shaft and supporting the first shaft via a bearing; a base support portion connecting the first support portion and the second support portion, The first shaft and the support portion are connected by a conductive member. A medium transport device comprising:

8. The medium transport device according to any one of claims 1 to 7; A reading unit that reads an image on the medium; An image reading device comprising:

Images