Document transport device, image reading device, and image forming device

Abstract

The present invention provides a document transport device that can suppress wear between the separation roller and the separation pad. [Solution] The document transport device 16 comprises a separation roller 47, a transport roller 41, a drive motor 45, a drive transmission unit 60, an upstream actuator 70, a downstream actuator 72, and a lock arm 74. When the upstream actuator 70 is positioned at the upstream detection position P2 and the downstream actuator 72 is positioned at the downstream non-detection position P3, the lock arm 74 is positioned at the transmission position P6, and the planetary gear unit 63 transmits rotational force to both rollers 41 and 47. When the upstream actuator 70 is positioned at the upstream detection position P2 and the downstream actuator 72 is positioned at the downstream detection position P4, the lock arm 74 is positioned at the non-transmission position P5, and the planetary gear system 63 does not transmit rotational force to the separation roller 47 but transmits rotational force to the transport roller 41.

Description

Technical Field

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[0001] The present invention relates to a document conveying device, an image reading device, and an image forming device.

Background Art

[0002] A sheet conveying device for conveying a document sheet on a document feed tray is known (Patent Document 1). The sheet conveying device is provided with a paper feed roller pressed against a separation pad by a spring member. The paper feed roller rotates around its axis while sandwiching a document between itself and the separation pad, separating the uppermost document sheet from the underlying document sheets and sending it out downstream of the conveyance path.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described sheet conveying device, after the document sheet (the trailing edge thereof) passes between the paper feed roller and the separation pad, the paper feed roller may continue to rotate while contacting the separation pad. Then, the paper feed roller (separation roller) and the separation pad may rub against each other and wear, so there is a risk that the overlapping document sheets cannot be properly separated.

[0005] In view of the above circumstances, the present invention provides a document conveying device, an image reading device, and an image forming device that can suppress wear between a separation roller and a separation pad.

Means for Solving the Problems

[0007] In this case, the separation roller preferably includes a separation shaft portion that is rotationally driven by the drive motor, a separation cylindrical portion that is rotatably supported on the outer circumferential surface of the separation shaft portion, and a one-way clutch that allows the separation cylindrical portion to rotate in the direction of transporting the document and restricts rotation in the opposite direction to the rotation of the separation cylindrical portion in the direction of transporting the document.

[0008] In this case, it is preferable to further include an upstream biasing member that biases the upstream actuator toward the upstream non-detection position, and a downstream biasing member that biases the downstream actuator toward the downstream non-detection position.

[0009] The image reading device of the present invention comprises a document transport device as described above, and a reading unit that reads an image on the document being transported along the document transport path.

[0010] The image forming apparatus of the present invention is equipped with the image reading apparatus described above. [Effects of the Invention]

[0011] According to the present invention, wear between the separation roller and the separation pad can be suppressed. [Brief explanation of the drawing]

[0012] [Figure 1]This is a schematic diagram (front view) showing the internal structure of an image forming apparatus according to one embodiment of the present invention. [Figure 2] This is a front view showing a document transport device according to one embodiment of the present invention. [Figure 3] This is a rear view showing a document transport device (wear suppression mechanism) according to one embodiment of the present invention. [Figure 4] This is a perspective view showing a wear suppression mechanism for a document transport device according to one embodiment of the present invention. [Figure 5] This is a perspective view showing a part of the wear suppression mechanism of a document transport device according to one embodiment of the present invention, specifically the drive transmission section. [Figure 6] This is an exploded perspective view showing a planetary gear system of the drive transmission section, which is part of a wear suppression mechanism for a document transport device according to one embodiment of the present invention. [Figure 7] This is a rear view illustrating the process of transporting the first document in a document transport device wear suppression mechanism according to one embodiment of the present invention. [Figure 8] This is a rear view illustrating the process of transporting a second document in a document transport device wear suppression mechanism according to one embodiment of the present invention. [Figure 9] This is a rear view illustrating a wear suppression mechanism for a document transport device according to one embodiment of the present invention, showing the state after the transport of the second document has been completed. [Modes for carrying out the invention]

[0013] Embodiments of the present invention will be described below with reference to the attached drawings. In the drawings, Fr, Rr, L, R, U, and D indicate front, rear, left, right, top, and bottom, respectively. Furthermore, the front-to-back, left-to-right, and up-to-down directions are mutually orthogonal. While this specification uses terms to indicate direction and position, these terms are used for convenience of explanation and do not limit the technical scope of the present invention. Also, in each figure, the shapes and dimensions of the members are not precise but are schematic representations for illustrative purposes.

[0014] Referring to FIGS. 1 and 2, an image forming apparatus 1 according to an embodiment will be described. FIG. 1 is a schematic diagram (front view) showing the internal structure of the image forming apparatus 1. FIG. 2 is a front view showing the document conveying apparatus 16.

[0015] [Overview of Image Forming Apparatus] As shown in FIG. 1, the image forming apparatus 1 includes an image forming device 1A that forms an image on a sheet S by an electrophotographic method, and an image reading device 1B that optically reads an image of a document M and converts it into digital data.

[0016] [Image Forming Device] A paper feed cassette 3 for accommodating a bundle of sheets S (paper, resin film, etc.) is detachably attached to the lower side of the apparatus main body 2 of the image forming device 1A. A paper discharge tray 4 for receiving the sheet S on which an image is formed is provided on the upper surface of the apparatus main body 2. The image forming device 1A includes a paper feed unit 5, an image forming unit 6, and a fixing unit 7 inside the apparatus main body 2. The paper feed unit 5 is provided on the upstream side of a conveyance path 8 extending from the paper feed cassette 3 to the paper discharge tray 4, and the fixing unit 7 is provided on the downstream side of the conveyance path 8.

[0017] The image forming unit 6 includes an intermediate transfer belt 10, four image forming units 11, four toner containers 12, and an exposure unit 13. The four image forming units 11 are provided below the intermediate transfer belt 10, and the exposure unit 13 is provided below the four image forming units 11. The four toner containers 12 contain toner (developer) for replenishing four colors (yellow, magenta, cyan, black). In this specification, one image forming unit 11 will be described.

[0018] The image forming unit 11 includes a photoreceptor drum 20, a charging device 21, a developing device 22, a primary transfer roller 23, a cleaning device 24, and a charge removing device 25. The photoreceptor drum 20 contacts the intermediate transfer belt 10, and the charging device 21, the developing device 22, the primary transfer roller 23, the cleaning device 24, and the charge removing device 25 are arranged around the photoreceptor drum 20 in the order of the image forming process. The primary transfer roller 23 faces the photoreceptor drum 20 with the intermediate transfer belt 10 interposed therebetween. On the right side of the intermediate transfer belt 10, a secondary transfer roller 26 is in contact.

[0019] The image forming apparatus 1 includes a control unit 14 that performs overall control. The control unit 14 may be constituted by a processor or may be constituted by a logic circuit formed in an integrated circuit or the like. When constituted by a processor, various processes are implemented by the processor reading and executing a program stored in a memory. As the processor, for example, a CPU (Central Processing Unit) is used. The memory is constituted by one or a plurality of storage devices such as a ROM (Read Only Memory) and a RAM (Random Access Memory) according to the application.

[0020] [Image Forming Process] Here, the operation of the image forming apparatus 1A will be described. The image forming apparatus 1A forms an image on a sheet S based on the image data read by the image reading device 1B or the image data transmitted from an external terminal (such as a personal computer). The control unit 14 controls the image forming apparatus 1A based on the input image data, and the image forming process is executed as follows.

[0021] The charging device 21 charges the surface of the photoreceptor drum 20. The exposure unit 13 exposes the photoreceptor drum 20 to the image data, forming an electrostatic latent image on the surface of the photoreceptor drum 20. The developing device 22 develops the electrostatic latent image on the photoreceptor drum 20 into a toner image using toner supplied from the toner container 12. The four toner images supported on the four photoreceptor drums 20 are sequentially transferred to the intermediate transfer belt 10 by the primary transfer roller 23 to which a primary transfer bias is applied. As a result, a full-color toner image is formed on the surface of the intermediate transfer belt 10.

[0022] The paper feed unit 5 feeds the paper S from the paper feed cassette 3 onto the transport path 8. The secondary transfer roller 26 transfers the toner image on the intermediate transfer belt 10 onto the paper S. The fuser unit 7 heat-fixes the toner image onto the paper S. After that, the paper S is discharged into the output tray 4. The cleaning device 24 removes waste toner remaining on the surface of the photoreceptor drum 20, and the static elimination device 25 removes the charge from the photoreceptor drum 20 by irradiating it with static elimination light.

[0023] [Image reading device] As shown in Figure 1, the image reading device 1B comprises a reading unit 15 and a document transport device 16. The reading unit 15 reads, for example, an image on a document M being transported along a document transport path 39. The document transport device 16 is located above the reading unit 15 and automatically feeds the documents M one by one into the document transport path 39.

[0024] <Reading Section> The reading unit 15 includes a contact glass 30, a platen glass 31, an optical scanning unit 32, a reflection unit 33, and an image sensor 34.

[0025] The contact glass 30 is located on the upper left side of the housing of the reading unit 15, and the platen glass 31 is located to the right of the contact glass 30. The optical scanning unit 32 irradiates light onto the document M being transported on the contact glass 30, and irradiates light onto the document M on the platen glass 31 while moving to the right. The reflection unit 33 reflects the light reflected by the document M towards the focusing lens 34A. When the optical scanning unit 32 irradiates light onto the document M on the platen glass 31, the reflection unit 33 moves in the same direction as the optical scanning unit 32 to keep the optical path length from the document M to the focusing lens 34A constant. The image sensor 34 converts the light input through the focusing lens 34A into photoelectric energy.

[0026] <Document transport device> As shown in Figure 1, the document transport device 16 includes a document holder 35, a supply tray 36, an output tray 37, and a transport unit 38. In the following description, "upstream" and "downstream" refer to the upstream (right) and downstream (left) directions of the document M transport.

[0027] (Manuscript holding section) The document holder 35 is rotatably (opens and closes) attached to the upper rear of the main body 2 of the imaging device 1A via a hinge (not shown). When the front side of the document holder 35, which covers each glass 30, 31, is lifted, each glass 30, 31 is exposed.

[0028] (Supply tray, discharge tray) The supply tray 36 extends diagonally upward and to the right from the transport unit 38. The supply tray 36 is located above the document holder unit 35. Documents M (a stack of documents M) are placed on the supply tray 36. The supply tray 36 is provided with a pair of cursors 36A (see Figure 2) for aligning the front and rear ends of the stacked documents M. The output tray 37 is located above the document holder unit 35 and below the supply tray 36. The output tray 37 receives the documents M that have been transported to the transport unit 38 and output.

[0029] (Transportation section) As shown in Figures 1 and 2, the transport unit 38 is located on the left side of the upper surface of the document holder unit 35. Inside the transport unit 38, a roughly U-shaped document transport path 39 is formed, connecting the supply tray 36 to the discharge tray 37. The transport unit 38 feeds the documents M on the supply tray 36 one by one into the document transport path 39, and discharges the documents M that have passed through the document transport path 39 into the discharge tray 37. The downstream side of the supply tray 36 (the position opposite the document supply unit 40, which will be described later) may be considered as the upstream end of the document transport path 39.

[0030] As shown in Figure 2, the transport unit 38 includes a document supply unit 40, a transport roller 41, a supply roller 42, a discharge roller 43, a pair of intermediate transport rollers 44, and a drive motor 45 (see Figure 5, which will be described later).

[0031] The document feeding unit 40 is located on the top surface of the upstream end of the document transport path 39. The transport roller 41 and the supply roller 42 are located adjacent to the downstream side of the document feeding unit 40. The transport roller 41 is located on the bottom surface of the upstream side of the document transport path 39, and the supply roller 42 is located on the top surface of the upstream side of the document transport path 39. The discharge roller 43 is located on the bottom surface of the downstream end of the document transport path 39. The intermediate transport roller pair 44 is located downstream of the transport roller 41 and upstream of the reading position on the contact glass 30. Each roller constituting the transport roller 41, the supply roller 42, the discharge roller 43, and the intermediate transport roller pair 44 has multiple rollers fixed to a shaft that extends in the front-rear direction, and these shafts are rotatably supported by the housing (not shown) of the transport unit 38.

[0032] The conveyor roller 41 is sandwiched between the supply roller 42 and the discharge roller 43. The conveyor roller 41 is paired with the supply roller 42 and also with the discharge roller 43. The drive motor 45 rotates the conveyor roller 41 and one of the rollers of the intermediate conveyor roller pair 44 around its axis. The supply roller 42 and the discharge roller 43 rotate in conjunction with the conveyor roller 41. The other roller of the intermediate conveyor roller pair 44 rotates in conjunction with the other roller.

[0033] (Manuscript Submission Department) The document feeding unit 40 includes a pickup roller 46, a separation roller 47, and a separation pad 48.

[0034] The pickup roller 46, separation roller 47, and separation pad 48 are positioned approximately in the center of the document transport path 39 in the front-to-back direction. The pickup roller 46 is positioned on the top surface of the upstream end of the document transport path 39, and the separation roller 47 is provided adjacent to the downstream side of the pickup roller 46. The pickup roller 46 and separation roller 47 each include cylindrical rollers and are rotatably supported by a support frame 40A. A drive motor 45 rotates the separation roller 47 around its axis. The pickup roller 46 is connected to the separation roller 47 via a gear train or the like and rotates in accordance with the separation roller 47. The support frame 40A is supported by the housing of the transport unit 38 in a state that it can swing around the same axis as the separation roller 47. The separation pad 48 is formed in a thick plate shape and is provided in a position opposite to the lower side of the separation roller 47. The separation roller 47 is in contact with the upper surface of the separation pad 48.

[0035] When the document feeding unit 40 (support frame 40A) rotates downward, the pickup roller 46 contacts the document M on the supply tray 36 (the topmost document M if multiple documents M are stacked). After contacting the document M, the pickup roller 46 is driven to rotate and remove (pull out) the document M from the supply tray 36. The separation roller 47 feeds the document M removed from the supply tray 36 onto the document transport path 39, sandwiching it between the separation pad 48. Even if two or more documents M are pulled out by the pickup roller 46, the transport speed of documents M other than the topmost one is reduced by the frictional force with the separation pad 48, and the topmost document M is transported first (preventing double feeding). The transport roller 41 described above transports the document M fed out by the separation roller 47 along the document transport path 39, sandwiching it between the supply roller 42.

[0036] [Image reading process] The operation of the image reading device 1B will now be explained with reference to Figures 1 and 2. Note that the original documents M placed on the supply tray 36 are formed as single sheets. In contrast, the original documents M stacked on the platen glass 31 are not limited to sheets; they may be booklets, cards, or the like.

[0037] When a user places a document M (or a stack of documents M) in the supply tray 36 and inputs a scan command, the control unit 14 controls the image reading device 1B, and the image reading process is executed as follows: The pickup roller 46 picks up the document M placed in the supply tray 36, and the separation roller 47 works in cooperation with the separation pad 48 to send the documents M one by one to the downstream side of the document transport path 39. The transport rollers 41 and the like transport the documents M onto the contact glass 30, and the optical scanning unit 32 irradiates light onto the documents M as they pass over the contact glass 30. The light reflected by the documents M is input to the image sensor 34 and converted into an electrical signal, and the image of the documents M is read as image data. The transport roller 41 sends the documents M to the discharge tray 37 while holding them between itself and the discharge roller 43.

[0038] Next, when the user opens the document holder 35, places the document M on the platen glass 31, and inputs a scan command, the optical scanning unit 32 moves to the right and illuminates the document M on the platen glass 31 with light. The light reflected by the document M is input to the image sensor 34 and converted into an electrical signal, and the image of the document M is read as image data.

[0039] The read image data is stored in the memory of the control unit 14, and the control unit 14 performs the image formation process (printing) described earlier. Note that the image data may also be transmitted (stored) to an external terminal instead of being printed.

[0040] Incidentally, if the separation roller 47 continues to rotate while in contact with the separation pad 48 after the rear end of the original document M has passed between the separation roller 47 and the separation pad 48, the separation roller 47 and the separation pad 48 will rub against each other and wear down. When the separation roller 47 and the separation pad 48 wear down, there is a risk that the overlapping original documents M will not be able to be properly separated. In addition, replacing the separation roller 47 and other parts will be costly, and the image forming apparatus 1 will be unusable until the replacement work is completed. Therefore, the original document transport device 16 according to this embodiment is equipped with a wear suppression mechanism 17 that suppresses wear of the separation roller 47 and the separation pad 48.

[0041] [Wear suppression mechanism] The wear suppression mechanism 17 will be described with reference to Figures 2 to 6. Figure 3 is a rear view showing the document transport device 16 (wear suppression mechanism 17). Figure 4 is a perspective view showing the wear suppression mechanism 17. Figure 5 is a perspective view showing the drive transmission section 60 etc. of the wear suppression mechanism 17. Figure 6 is an exploded perspective view showing the planetary gear device 63 of the drive transmission section 60.

[0042] As shown in Figures 2 and 3, the wear suppression mechanism 17 includes a document feeding unit 40, a transport roller 41, a drive motor 45, a drive transmission unit 60, an upstream actuator 70, a downstream actuator 72, and a lock arm 74. The document feeding unit 40, the transport roller 41, and the drive motor 45 are components of the transport unit 38, but are also components of the wear suppression mechanism 17.

[0043] <Separation roller in the manuscript feeding section> As shown in Figure 4, the separation roller 47 has a separation shaft portion 50, a separation cylindrical portion 51, and a one-way clutch 52. The separation shaft portion 50 is formed in the shape of a rod extending in the front-rear direction and is rotatably supported on the support frame 40A. The separation shaft portion 50 extends rearward through the rear plate of the support frame 40A. A separation input gear 53 is fixed to the tip (rear end) of the separation shaft portion 50. The separation cylindrical portion 51 is formed in the shape of a cylinder and is rotatably supported on the outer circumferential surface of the separation shaft portion 50 inside the support frame 40A. The one-way clutch 52 is interposed between the separation shaft portion 50 and the separation cylindrical portion 51. The one-way clutch 52 allows the rotation of the separation cylindrical portion 51 in the direction of transporting the document M (counterclockwise in Figure 3) and restricts rotation in the opposite direction to the rotation of the separation cylindrical portion 51 in the direction of transporting the document M (clockwise in Figure 3). The separation cylinder 51 rotates counterclockwise in Figure 3, in conjunction with the separation shaft 50, due to the function of the one-way clutch 52. Also, due to the function of the one-way clutch 52, the separation cylinder 51 rotates freely counterclockwise relative to the stationary separation shaft 50 in Figure 3, but does not rotate clockwise in Figure 3.

[0044] <Conveyor rollers> As shown in Figure 4, the transport roller 41 has a transport shaft portion 54 and a plurality (for example, two) transport cylindrical portions 55. The transport shaft portion 54 is formed in the shape of a rod extending in the front-rear direction and is rotatably supported by the housing of the transport unit 38. The transport shaft portion 54 is provided downstream of the separation roller 47 and parallel to the separation shaft portion 50. A transport input gear 56 is fixed to the tip (rear end) of the transport shaft portion 54. The two transport cylindrical portions 55 are each formed in the shape of a cylinder and are fixed to the transport shaft portion 54 at intervals in the front-rear direction (axial direction).

[0045] <Drive motor> The drive motor 45 is, for example, a DC motor that rotates the output shaft around its axis, and is fixed to the rear of the housing of the transport unit 38. As shown in Figure 5, the output shaft protrudes forward from the front end surface of the drive motor 45 body, and a pinion gear 57 is fixed to the tip of the output shaft. The drive motor 45 is electrically connected to the control unit 14 and a power supply (not shown), and its drive is controlled by the control unit 14.

[0046] <Drive transmission section> The drive transmission unit 60 is located at the rear of the housing of the transport unit 38. As shown in Figures 3 to 5, the drive transmission unit 60 includes a first transmission gear unit 61 connected to the drive motor 45, a second transmission gear unit 62 connected to the separation roller 47, and a planetary gear device 63 interposed between the first transmission gear unit 61 and the second transmission gear unit 62. The drive transmission unit 60 transmits the rotational force of the drive motor 45 to the separation roller 47 and the transport roller 41.

[0047] (First transmission gear section) The first transmission gear section 61 is, for example, a gear train having a first input gear 61A and a first output gear 61B. The first input gear 61A and the first output gear 61B are rotatably supported in the housing of the transport section 38. The first input gear 61A is a so-called two-stage gear, and the large-diameter portion of the first input gear 61A meshes with the pinion gear 57 of the drive motor 45. The first output gear 61B is a spur gear, and meshes with the small-diameter portion of the first input gear 61A.

[0048] (Second transmission gear section) The second transmission gear section 62 is located upstream (to the right) of the first transmission gear section 61, with the planetary gear device 63 in between. The second transmission gear section 62 is, for example, a gear train having a second input gear 62A, a second intermediate gear 62B, and a second output gear 62C. The second input gear 62A, the second intermediate gear 62B, and the second output gear 62C are each spur gears and are rotatably supported in the housing of the conveying section 38. The second intermediate gear 62B meshes with both gears 62A and 62C between the second input gear 62A and the second output gear 62C. The second output gear 62C meshes with a separation input gear 53 fixed to the separation shaft portion 50 of the separation roller 47.

[0049] (Planetary gear system) As shown in Figure 6, the planetary gear system 63 includes a sun gear 63A, an internal gear 63B, a plurality (e.g., two) of planetary gears 63C, and a planetary carrier 63D.

[0050] (Sun gear) The sun gear 63A is a spur gear and is rotatably supported in the housing of the transport unit 38. The sun shaft portion 64 of the sun gear 63A extends rearward, and a stopper portion 65 is fixed to the rear end of the sun shaft portion 64. The stopper portion 65 is formed in a generally spur gear shape and is provided on the same axis as the sun gear 63A.

[0051] (Internal gears) The internal gear 63B is a gear with teeth arranged on the inner circumferential surface of a cylinder (the teeth on the inner circumferential surface are not shown), and is rotatably supported in the housing of the conveying unit 38. The internal gear 63B is provided on the outer circumference of the sun gear 63A and rotates coaxially with the sun gear 63A. A first external gear 66 is fixed to the front end face of the internal gear 63B. The first external gear 66 is a spur gear and is provided on the same axis as the internal gear 63B. The second input gear 62A of the second transmission gear section 62 meshes with the first external gear 66 (see Figure 5). The separation roller 47 (separation shaft section 50) is connected to the first external gear 66, which is provided on the same axis as the internal gear 63B, via the second transmission gear section 62 (see Figures 4 and 5).

[0052] (Planetary gears) The two planetary gears 63C are each spur gears and are rotatably supported on two planetary support shafts 67 provided on the planetary carrier 63D. Each planetary gear 63C is positioned between the sun gear 63A and the internal gear 63B and meshes with the sun gear 63A and the internal gear 63B (the meshing state is not shown).

[0053] (Planetary Carrier) The planetary carrier 63D has two planetary support shafts 67 that rotatably support two planetary gears 63C. The planetary carrier 63D is formed in a disc shape, and each planetary support shaft 67 extends forward from the front end surface of the planetary carrier 63D. The planetary carrier 63D is rotatably supported by the sun gear 63A and the internal gear 63B via each planetary gear 63C. The planetary carrier 63D rotates coaxially with the sun gear 63A, thereby causing each planetary gear 63C to revolve. A second external gear 68 is fixed to the rear end surface of the planetary carrier 63D. The second external gear 68 is a spur gear and is mounted coaxially with the planetary carrier 63D. The second external gear 68 meshes with the first output gear 61B of the first transmission gear section 61 and the transport input gear 56 fixed to the transport shaft section 54 of the transport roller 41 (see Figures 3 to 5). A second external gear 68, which is arranged on the same axis as the planetary carrier 63D, is connected to a transport roller 41 via a transport input gear 56, and a drive motor 45 is connected to it via a first transmission gear section 61 (see Figures 3 to 5).

[0054] <Upstream Actuator> The upstream actuator 70 is positioned behind the document feeding unit 40 (see Figure 4). As shown in Figures 3 and 4, the upstream actuator 70 has an upstream shaft portion 70A and an upstream contact 70B. The upstream shaft portion 70A is formed in the shape of a rod extending in the front-rear direction and is rotatably supported by the housing of the transport unit 38. The upstream shaft portion 70A is positioned upstream of the separation roller 47 and below the downstream side of the supply tray 36 (or the upstream side of the document transport path 39), and is provided parallel to the separation shaft portion 50. An upstream projection 70C protrudes radially outward from the rear end of the upstream shaft portion 70A (see Figure 4). The upstream projection 70C is a fan-shaped projection when viewed from the rear (axial direction). The upstream contact element 70B is fixed to the front end of the upstream shaft portion 70A and extends radially outward (upward in Figures 3 and 4) from the upstream shaft portion 70A.

[0055] (Upstream biasing member) As shown in Figure 4, an upstream biasing member 71 is provided at the front end of the upstream shaft portion 70A. The upstream biasing member 71 is, for example, a torsion coil spring, which is wound around the upstream shaft portion 70A in front of the upstream contact 70B. One arm of the upstream biasing member 71 engages with the upstream contact 70B, and the other arm engages with the housing of the transport unit 38 (not shown). The upstream biasing member 71 biases the upstream actuator 70 counterclockwise in Figure 3 so that the upstream contact 70B is in an upright position.

[0056] The upstream actuator 70 is provided to swing between an upstream non-detection position P1 (see Figures 3 and 4) in which the upstream contact element 70B is in an upright position and protrudes from the upper surface of the supply tray 36 (or the bottom surface of the document transport path 39), and an upstream detection position P2 (see Figure 7, described later) in which the upstream contact element 70B is tilted downstream (to the left) and embedded in the lower side of the supply tray 36 (or the document transport path 39).

[0057] The upstream contactor 70B of the upstream actuator 70, positioned at the upstream non-detection position P1, is positioned to interfere with the document M placed (set) on the supply tray 36. As a result, the document M placed on the supply tray 36 pushes the upstream contactor 70B downstream against the biasing force of the upstream biasing member 71, causing the upstream actuator 70 to rotate from the upstream non-detection position P1 to the upstream detection position P2. In other words, the upstream actuator 70 is positioned at the upstream detection position P2, which detects the document M placed on the supply tray 36 (see Figure 7, described later). As long as the document M is in the supply tray 36, the document M continues to tilt the upstream contactor 70B, and the upstream actuator 70 is maintained in the upstream detection position P2.

[0058] When all the documents M placed in the supply tray 36 have been transported, in other words, when the last document M has passed over the upstream contactor 70B, the upstream biasing member 71 rotates the upstream actuator 70 from the upstream detection position P2 to the upstream non-detection position P1. That is, the upstream actuator 70 is biased by the upstream biasing member 71 and positioned at the upstream non-detection position P1, where it does not detect any documents M on the supply tray 36 (see Figure 3).

[0059] <Downstream Actuator> The downstream actuator 72 is positioned behind the document feeding unit 40 (see Figure 4). As shown in Figures 3 and 4, the downstream actuator 72 has a downstream shaft portion 72A, a downstream contact 72B, and a release piece 72C. The downstream shaft portion 72A is formed in a rod shape extending in the front-rear direction and is rotatably supported by the housing of the transport unit 38. The downstream shaft portion 72A is positioned downstream of the transport roller 41 and below the document transport path 39, and is provided parallel to the transport shaft portion 54. The downstream contact 72B is fixed to the front end of the downstream shaft portion 72A and extends radially outward from the downstream shaft portion 72A (upward in Figures 3 and 4). The release piece 72C is fixed to the rear end of the downstream shaft portion 72A and protrudes radially outward from the downstream shaft portion 72A (upstream (to the right) in Figures 3 and 4). The unlocking piece 72C is bent in a roughly L-shape when viewed from the rear (axial direction) and is positioned approximately 90 degrees in the circumferential direction relative to the downstream contact 72B.

[0060] (Downstream biasing member) As shown in Figure 4, a downstream biasing member 73 is provided at the front end of the downstream shaft portion 72A. The downstream biasing member 73 is, for example, a torsion coil spring, which is wound around the downstream shaft portion 72A in front of the downstream contact 72B. One arm of the downstream biasing member 73 engages with the downstream contact 72B, and the other arm engages with the housing of the transport unit 38 (not shown). The downstream biasing member 73 biases the downstream actuator 72 counterclockwise in Figure 3 so that the downstream contact 72B is in an upright position.

[0061] The downstream actuator 72 is provided so as to be able to swing between a downstream non-detection position P3 (see Figures 3 and 4) in which the downstream contact element 72B is in an upright position and protruding from the bottom surface of the document transport path 39, and a downstream detection position P4 (see Figure 7, described later) in which the downstream contact element 72B is tilted downstream (to the left) and embedded in the bottom surface of the document transport path 39.

[0062] With the downstream actuator 72 positioned in the downstream non-detection position P3, the document M, passing between the transport roller 41 and the supply roller 42, collides with the downstream contact 72B. As the document M is transported, it pushes the downstream contact 72B downstream against the biasing force of the downstream biasing member 73, causing the downstream actuator 72 to rotate from the downstream non-detection position P3 to the downstream detection position P4. In other words, the downstream actuator 72 is positioned in the downstream detection position P4, which detects the document M being transported by the transport roller 41 (see Figure 7, described later). Since the document M continues to tilt the downstream contact 72B while being transported by the transport roller 41, the downstream actuator 72 is maintained in the downstream detection position P4.

[0063] When the original document M passes between the transport roller 41 and the supply roller 42, in other words, when the original document M passes over the downstream contactor 72B, the downstream biasing member 73 rotates the downstream actuator 72 from the downstream detection position P4 to the downstream non-detection position P3. That is, the downstream actuator 72 is biased by the downstream biasing member 73 and positioned at the downstream non-detection position P3, where it does not detect the original document M being transported by the separation roller 47 (see Figure 3).

[0064] <Lock Arm> As shown in Figures 3 to 5, the lock arm 74 is formed in the shape of a rod extending in the left-right direction and is pivotably connected to the rear end of the upstream actuator 70 (upstream shaft portion 70A). A locking claw 74A protrudes downward from the tip side (left side) of the lock arm 74. The locking claw 74A is formed in the shape of a roughly triangular prism so as to mesh with (engage with) the stopper portion 65 of the planetary gear device 63. The lock arm 74 is slightly bent at the position where the locking claw 74A is formed and extends further toward the tip. The lock arm 74 is pivotably provided between a transmission position P6 (see Figure 7, described later) in which the locking claw 74A meshes with the stopper portion 65 and a non-transmission position P5 (see Figure 3) in which the locking claw 74A is separated from the stopper portion 65.

[0065] As shown in Figures 4 and 5, the base end (right end) of the lock arm 74 has a lock cylinder portion 74B into which the rear end of the upstream shaft portion 70A is inserted. A lock projection 74C protrudes forward from the lock cylinder portion 74B. When the rear end of the upstream shaft portion 70A is inserted into the lock cylinder portion 74B, the lock projection 74C is located to the right (upstream) of the upstream projection 70C of the upstream shaft portion 70A (see Figure 4). When the upstream actuator 70 is positioned in the upstream non-detection position P1, the upstream projection 70C abuts against the left surface of the lock projection 74C, holding the lock arm 74 in the non-transmission position P5 (see Figure 4). In other words, when the upstream actuator 70 is positioned in the upstream non-detection position P1, the lock arm 74 is fixed in the non-transmission position P5. In contrast, when the upstream actuator 70 is positioned at the upstream detection position P2, the upstream protrusion 70C separates from the locking protrusion 74C, and the lock arm 74 becomes able to swing between the transmission position P6 and the non-transmission position P5 (see Figure 7, described later). In practice, when the upstream actuator 70 is positioned at the upstream detection position P2, the lock arm 74 rotates from the non-transmission position P5 to the transmission position P6 due to its own weight.

[0066] Furthermore, the lock arm 74 is provided so as to be able to engage with the downstream actuator 72 located at the downstream detection position P4. Specifically, when the downstream actuator 72 is located at the downstream detection position P4, the tip of the release piece 72C contacts the lock arm 74 from below, closer to the tip than the lock claw 74A (see Figure 7, described later). When the lock arm 74 is located at the transmission position P6, the release piece 72C of the downstream actuator 72 located at the downstream detection position P4 lifts the tip of the lock arm 74, causing the lock arm 74 to rotate from the transmission position P6 to the non-transmission position P5. The release piece 72C of the downstream actuator 72 located at the downstream detection position P4 contacts the lower surface of the lock arm 74 located at the non-transmission position P5, preventing the lock arm 74 from rotating from the non-transmission position P5 to the transmission position P6 by its own weight.

[0067] [Operation of wear suppression mechanism] The operation of the wear suppression mechanism 17 will be explained with reference to Figures 7 to 9. In the following explanation, as an example, two documents M are stacked on the supply tray 36 and the document transport device 16 transports the two documents M one at a time. Figure 7 is a rear view illustrating the process of the document transport device 16 (wear suppression mechanism 17) transporting the first document M. Figure 8 is a rear view illustrating the process of the document transport device 16 (wear suppression mechanism 17) transporting the second document M. Figure 9 is a rear view illustrating the state after the transport of the second document M by the document transport device 16 (wear suppression mechanism 17) has been completed.

[0068] As shown in the upper part of Figure 7, when a user places two documents M in the supply tray 36, the documents M push the upstream contactor 70B downstream, causing the upstream actuator 70 to rotate from the upstream non-detection position P1 to the upstream detection position P2. As the upstream actuator 70 rotates, the lock arm 74 rotates by its own weight from the non-transmission position P5 to the transmission position P6, engaging the lock claw 74A with the tooth stop 65 of the sun gear 63A. The downstream actuator 72 is positioned in the downstream non-detection position P3. As described above, when the upstream actuator 70 is positioned in the upstream detection position P2 and the downstream actuator 72 is positioned in the downstream non-detection position P3, the lock arm 74 is positioned in the transmission position P6 to restrict the rotation of the sun gear 63A (fixing the sun gear 63A).

[0069] <Transporting the first page of the manuscript> When the control unit 14 starts the image reading process, the support frame 40A rotates downward, and after the pickup roller 46 makes contact with the uppermost (first) document M, the drive motor 45 is driven. The planetary gear system 63, to which the sun gear 63A is fixed, transmits the rotational force of the drive motor 45 to the separation roller 47 and the transport roller 41. In detail, the driving force (rotational force) of the drive motor 45 is transmitted to the planetary carrier 63D (second external gear 68) via the first transmission gear section 61, and then to the transport input gear 56 (transport roller 41) connected to the second external gear 68. In addition, the rotational force of the planetary carrier 63D is transmitted to the internal gear 63B (first external gear 66) via each planetary gear 63C, and then to the separation input gear 53 (separation roller 47) connected to the first external gear 66 via the second transmission gear section 62. As described above, the planetary gear system 63 with the sun gear 63A fixed becomes a planetary gear mechanism that approximates a solar type, with the planetary carrier 63D (second external gear 68) as the drive shaft and the internal gear 63B (first external gear 66) as the driven shaft. As a result, the separation roller 47 (separation shaft portion 50) and the transport roller 41 (transport shaft portion 54) are rotationally driven by the drive motor 45.

[0070] The pickup roller 46 rotates while in contact with the topmost (first) document M on the supply tray 36, and picks up the topmost document M from the supply tray 36. The separation roller 47 rotates while sandwiching the document M between itself and the separation pad 48, and feeds the document M downstream.

[0071] As shown in the middle of Figure 7, when the document M passes between the separation roller 47 and the separation pad 48, it collides with the downstream contact 72B of the downstream actuator 72, pushing the downstream contact 72B downstream and rotating the downstream actuator 72 from the downstream non-detection position P3 to the downstream detection position P4. Then, the release piece 72C of the downstream actuator 72 lifts the tip of the lock arm 74, rotating the lock arm 74 from the transmission position P6 to the non-transmission position P5. The lock claw 74A of the lock arm 74 disengages from the stopper portion 65 of the sun gear 63A, releasing the sun gear 63A from its fixed position. As described above, when the upstream actuator 70 is positioned at the upstream detection position P2 and the downstream actuator 72 is positioned at the downstream detection position P4, the lock arm 74 is pushed by the downstream actuator 72 positioned at the downstream detection position P4 to the non-transmission position P5, allowing the sun gear 63A to rotate. Furthermore, even if the end (right edge) of the first document M passes between the separation roller 47 and the separation pad 48, the upstream actuator 70 remains positioned at the upstream detection position P2 because the second document M is on the upstream contactor 70B.

[0072] The planetary gear system 63, which allows the sun gear 63A to rotate, does not transmit the rotational force of the drive motor 45 to the separation roller 47, but transmits the rotational force of the drive motor 45 to the transport roller 41. Specifically, the driving force (rotational force) of the drive motor 45 is transmitted to the planetary carrier 63D (second external gear 68) via the first transmission gear section 61, and then to the transport input gear 56 (transport roller 41) connected to the second external gear 68. Here, since the first external gear 66 of the internal gear 63B is connected to the separation input gear 53 (separation roller 47 in contact with the separation pad 48) via the second transmission gear section 62, the torque required to rotate the internal gear 63B is greater than the torque required to rotate the sun gear 63A. Therefore, the internal gear 63B remains fixed, and the rotational force of the planetary carrier 63D is transmitted to the sun gear 63A via each planetary gear 63C (rotating the sun gear 63A). As described above, the planetary gear unit 63 with the internal gear 63B fixed becomes a planetary gear mechanism that approximates a planetary type, with the planetary carrier 63D (second external gear 68) as the drive shaft and the sun gear 63A as the driven shaft. As a result, the separation roller 47 (separation shaft portion 50) is not rotationally driven, and only the transport roller 41 (transport shaft portion 54) is rotationally driven by the drive motor 45.

[0073] Incidentally, there is a period during which the document M is transported while being sandwiched between the separation roller 47 and the separation pad 48, and between the transport roller 41 and the supply roller 42, even when the separation roller 47 (separation shaft portion 50) is not being driven to rotate. Even during such a period, the separation cylindrical portion 51 of the separation roller 47 rotates freely relative to the separation shaft portion 50 due to the frictional force between it and the document M, thanks to the function of the one-way clutch 52 (see the dashed arrow in the middle of Figure 7). This prevents the separation roller 47, which is not being driven to rotate, from obstructing the transport of the document M.

[0074] As shown in the lower part of Figure 7, when the end (right edge) of the first document M passes between the separation roller 47 and the separation pad 48, the separation roller 47, whose rotational force transmission is cut off, stops rotating. Since the end (right edge) of the first document M and the leading edge (left edge) of the second document M that is to be transported are separated from each other in the transport direction (left-right direction), when the first document M has completely passed between the separation roller 47 and the separation pad 48, the separation roller 47 comes into contact with the upper surface of the separation pad 48 while it is stopped rotating. The separation roller 47 remains in a non-rotating state on the separation pad 48 until the transport of the second document M begins.

[0075] <Transporting the second page of the manuscript> As shown in the upper part of Figure 8, when the end (right end) of the first document M passes over the downstream contact 72B of the downstream actuator 72, the downstream actuator 72 is biased by the downstream biasing member 73 and rotates from the downstream detection position P4 to the downstream non-detection position P3. Then, the lock release piece 72C of the downstream actuator 72 separates from the tip of the lock arm 74, and the lock arm 74 rotates by its own weight from the non-transmission position P5 to the transmission position P6, engaging the lock claw 74A with the tooth stop 65 of the sun gear 63A (restricting the rotation of the sun gear 63A). In this state, the upstream actuator 70 is positioned at the upstream detection position P2, the downstream actuator 72 is positioned at the downstream non-detection position P3, and the lock arm 74 is positioned at the transmission position P6, just as when the first document M is transported. Then, the planetary gear system 63 transmits the rotational force of the drive motor 45 to the separation roller 47 and the transport roller 41, and the transport of the second document M begins.

[0076] Similar to the transport of the first document M, the pickup roller 46 picks up the second document M from the supply tray 36, and the separation roller 47 feeds the document M downstream while sandwiching it between itself and the separation pad 48. As shown in the middle of Figure 8, the document M passes between the separation roller 47 and the separation pad 48, pushing the downstream contact 72B downstream and rotating the downstream actuator 72 from the downstream non-detection position P3 to the downstream detection position P4. As the downstream actuator 72 rotates to the downstream detection position P4, the lock arm 74 rotates from the transmission position P6 to the non-transmission position P5, disengaging the lock claw 74A from the tooth stop 65 of the sun gear 63A (allowing the sun gear 63A to rotate). In this state, the upstream actuator 70 is positioned at the upstream detection position P2, the downstream actuator 72 is positioned at the downstream detection position P4, and the lock arm 74 is positioned at the non-transmission position P5. Furthermore, the planetary gear system 63 does not transmit the rotational force of the drive motor 45 to the separation roller 47, but transmits the rotational force of the drive motor 45 to the conveying roller 41.

[0077] As shown in the lower part of Figure 8, when the end (right end) of the second document M passes over the upstream contact 70B of the upstream actuator 70, the upstream actuator 70 is biased by the upstream biasing member 71 and rotates from the upstream detection position P2 to the upstream non-detection position P1. The upstream projection 70C of the upstream actuator 70 abuts against the lock projection 74C of the lock arm 74, which is positioned in the non-transmission position P5, thereby restricting the rotation of the lock arm 74 to the transmission position P6. As described above, when the upstream actuator 70 is positioned in the upstream non-detection position P1, the lock arm 74 is positioned in the non-transmission position P5, regardless of the position of the downstream actuator 72, allowing the rotation of the sun gear 63A. The planetary gear system 63 does not transmit the rotational force of the drive motor 45 to the separation roller 47, but transmits the rotational force of the drive motor 45 to the transport roller 41.

[0078] The second document M is transported by the transport roller 41, and the separation cylindrical portion 51 of the separation roller 47 rotates freely while in contact with the transported document M. When the second document M has completely passed between the separation roller 47 and the separation pad 48, the separation roller 47, whose transmission of rotational force has been cut off, stops rotating (see the lower part of Figure 8). As shown in the upper part of Figure 9, when the end (right end) of the second document M passes over the downstream contact 72B of the downstream actuator 72, the downstream actuator 72 is biased by the downstream biasing member 73 and rotates from the downstream detection position P4 to the downstream non-detection position P3.

[0079] With the above steps completed, the transport (image reading process) of the two documents M placed in the supply tray 36 is finished. As shown in the lower part of Figure 9, the two transported documents M are stacked on the output tray 37.

[0080] As described above, with the document transport device 16 according to this embodiment, the separation roller 47 does not rotate when there is no document M between the separation roller 47 and the separation pad 48, thus suppressing wear on the separation roller 47 and the separation pad 48. As a result, the separation roller 47 and the separation pad 48 can perform their function of separating overlapping documents M for a long period of time. Furthermore, by suppressing wear on the separation roller 47 and the like, the effort and cost associated with replacing the separation roller 47 and the like can also be reduced.

[0081] Furthermore, in the document transport device 16 according to this embodiment, the one-way clutch 52 is configured to allow the separation cylindrical portion 51 to rotate in the direction of transporting the document M, and to restrict the rotation of the separation cylindrical portion 51 in the opposite direction. With this configuration, even when rotational force is not transmitted to the separation shaft portion 50, the separation cylindrical portion 51 in contact with the transported document M can be rotated. As a result, the document M can be transported by the transport roller 41 while the separation cylindrical portion 51 rotates freely relative to the separation shaft portion 50.

[0082] Furthermore, in the document transport device 16 according to this embodiment, the upstream biasing member 71 biases the upstream actuator 70 toward the upstream non-detection position P1, and the downstream biasing member 73 biases the downstream actuator 72 toward the downstream non-detection position P3. With this configuration, when the document M is removed from the supply tray 36, the upstream actuator 70 can be automatically returned from the upstream detection position P2 to the upstream non-detection position P1. Also, when the document M passes through the transport roller 41, the downstream actuator 72 can be automatically returned from the downstream detection position P4 to the downstream non-detection position P3.

[0083] In this embodiment, the document transport device 16 is provided with a one-way clutch 52 on the separation roller 47, and the separation cylindrical part 51 rotates freely relative to the separation shaft part 50 while in contact with the document M being transported. However, the present invention is not limited to this. For example, the one-way clutch 52 may be omitted, and the document M being transported may slide on the surface of the separation cylindrical part 51.

[0084] Furthermore, in the document transport device 16 according to this embodiment, the upstream biasing member 71 biases the upstream actuator 70 to the upstream non-detection position P1, and the downstream biasing member 73 biases the downstream actuator 72 to the downstream non-detection position P3. However, the present invention is not limited to this configuration. For example, the upstream biasing member 71 may be omitted, and the upstream actuator 70 may be manually rotated from the upstream detection position P2 to the upstream non-detection position P1. Similarly, the downstream biasing member 73 may be omitted, and the downstream actuator 72 may be manually rotated from the downstream detection position P4 to the downstream non-detection position P3.

[0085] Furthermore, in the document transport device 16 according to this embodiment, the first transmission gear section 61 has two gears 61A and 61B, and the second transmission gear section 62 has three gears 62A to 62C, but the present invention is not limited thereto. The number of gears included in the first transmission gear section 61 and the second transmission gear section 62 may be appropriately changed considering the rotation direction of the output shaft (pinion gear 57) of the drive motor 45, the rotation direction of the separation roller 47 and transport roller 41, the transport direction of the document M, etc. Also, the number of teeth of each gear should be set considering the transport speed of the document M.

[0086] Furthermore, in the document transport device 16 according to this embodiment, the locking claw 74A of the locking arm 74 engages with the stopper portion 65 of the sun gear 63A, but the present invention is not limited to this. For example, the locking claw 74A and the stopper portion 65 may be omitted, and the rotation of the sun gear 63A may be restricted by pressing the tip of the locking arm 74 against the sun shaft portion 64 (not shown). In this case, a spring or the like may be provided to press the tip of the locking arm 74 against the sun shaft portion 64 (not shown).

[0087] Furthermore, while this embodiment describes the application of the present invention to an image forming apparatus 1 (multifunction printer) as an example, it is not limited to this, and the present invention may also be applied to, for example, a copier, a facsimile, or a dedicated image reader.

[0088] The above description of embodiments illustrates one aspect of the document transport device, image reading device, and image forming device according to the present invention, and the technical scope of the present invention is not limited to the above embodiments. The present invention may be modified, substituted, or transformed in various ways without departing from the spirit of the technical idea, and the claims include all embodiments that may fall within the scope of the technical idea. [Explanation of Symbols]

[0089] 1. Image forming apparatus 1B Image reading device 15 Reading section 16. Document transport device 36 supply trays 39. Manuscript transport path 41 Conveyor rollers 45 Drive motor 47 Separation roller 48 Separation Pads 50 Separation shaft part 51 Separation cylindrical section 52 One-way clutch 60 Drive transmission section 61 First transmission gear section 62 Second transmission gear section 63 Planetary gear system 63A Sun Gear 63B Internal Gear 63C Planetary gear 63D Planetary Carrier 65 Wheel stop 66 First external gear 68 Second external gear 70 Upstream actuator 71 Upstream biasing member 72 Downstream actuator 73 Downstream biasing member 74 Lock Arm M Manuscript P1 Upstream undetected location P2 Upstream detection position P3 Downstream undetected location P4 Downstream detection position P5 Non-transmission position P6 Transmission location

Claims

1. A separation roller that feeds the document removed from the supply tray into the document transport path while sandwiching it between the separation pad, A transport roller that transports the document fed out by the separation roller along the document transport path, A drive motor that rotates the separation roller and the transport roller around their axes, A drive transmission unit that transmits the rotational force of the drive motor to the separation roller and the transport roller, An upstream actuator is provided so as to be able to swing between an upstream detection position that detects the document placed on the supply tray and an upstream non-detection position that does not detect the document, A downstream actuator is provided so as to be able to swing between a downstream detection position that detects the document being transported by the transport roller and a downstream non-detection position that does not detect the document. The system includes a lock arm that is pivotably connected to the upstream actuator and is provided to be engageable with the downstream actuator positioned at the downstream detection location, The drive transmission unit is A first transmission gear section connected to the drive motor, A second transmission gear section connected to the separation roller, It has a planetary gear system interposed between the first transmission gear section and the second transmission gear section, The aforementioned planetary gear system is A sun gear having a stopper portion for engaging the aforementioned lock arm on the same axis, An internal gear having a first external gear on the same axis as the sun gear, which is provided on the outer circumference of the sun gear and to which the separation roller is connected via the second transmission gear section, A planetary gear that meshes with the aforementioned sun gear and the aforementioned internal gear, The planetary carrier has a second external gear on the same axis to which the transport roller is connected and to which the drive motor is connected via the first transmission gear section, and the planetary gear is rotatably supported, The lock arm is provided so as to be swingable between a transmission position in which it engages with the stopper and a non-transmission position away from the stopper. When the upstream actuator is positioned at the upstream detection position and the downstream actuator is positioned at the downstream non-detection position, the lock arm is positioned at the transmission position to restrict the rotation of the sun gear, and the planetary gear system transmits the rotational force of the drive motor to the separation roller and the transport roller. When the upstream actuator is positioned at the upstream detection position and the downstream actuator is positioned at the downstream detection position, the lock arm is pushed by the downstream actuator positioned at the downstream detection position to the non-transmission position, allowing the rotation of the sun gear, and the planetary gear system does not transmit the rotational force of the drive motor to the separation roller, but transmits the rotational force of the drive motor to the transport roller. A document transport device characterized in that, when the upstream actuator is positioned in the upstream non-detection position, the lock arm is positioned in the non-transmission position regardless of the position of the downstream actuator, allowing the rotation of the sun gear, and the planetary gear system does not transmit the rotational force of the drive motor to the separation roller, but transmits the rotational force of the drive motor to the transport roller.

2. The separation roller is A separation shaft portion that is rotationally driven by the aforementioned drive motor, A separation cylindrical portion is rotatably supported on the outer circumferential surface of the separation shaft portion, The document transport device according to claim 1, further comprising a one-way clutch that allows the separation cylindrical portion to rotate in the direction of transporting the document and restricts rotation in the opposite direction to the rotation of the separation cylindrical portion in the direction of transporting the document.

3. An upstream biasing member that biases the upstream actuator toward the upstream non-detection position, The document transport device according to claim 1, further comprising a downstream biasing member that biases the downstream actuator toward the downstream non-detection position.

4. A document transport device according to any one of claims 1 to 3, An image reading device characterized by comprising: a reading unit that reads an image on the document being transported along the document transport path.

5. An image forming apparatus characterized by comprising the image reading device described in claim 4.

Images