Document transport device and image forming apparatus

Abstract

To provide a document transport device that allows documents to be smoothly placed into the paper tray. [Solution] The document transport device comprises a paper tray on which documents are loaded, a device body having a document transport path, a document feeding unit 70 having a feed roller 72 that feeds documents on the paper tray into the document transport path and which is movable between a first position where the feed roller 72 is separated from the document and a second position where the feed roller 72 is in contact with the document, an opening / closing cover 51 attached to the device body so as to be openable and closable, a drive shaft 61 that moves the document feeding unit 70 from the first position to the second position, and a biasing member 74 attached to the opening / closing cover 51 and the document feeding unit 70. When the opening / closing cover 51 is opened, the document feeding unit 70 is moved to the first position by the biasing force of the biasing member 74, and even when the opening / closing cover 51 is closed, the state in which it is held in the first position is maintained.

Description

Technical Field

[0001] The present disclosure relates to a document conveying device that feeds a document on a paper feed tray into a document conveying path, and an image forming apparatus.

Background Art

[0002] Conventionally, in a document conveying device provided in an image forming apparatus, documents (paper sheets) stacked on a paper feed tray are drawn in, the documents are read, and then discharged onto a discharge tray. Since a plurality of paper sheets are stacked on the paper feed tray, a paper separating device having a configuration combining a feed roller and a reverse roller is adopted. In the paper separating device, in order to avoid conveying two or more paper sheets together (double feeding), a high-load torque limiter is required to apply high torque to the rollers. In this case, there is a problem that unnecessary power must be consumed, so a method for reducing the power consumption of the drive source has been proposed (for example, refer to Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A conventional paper separating device has a feed roller that rotates in a paper feeding direction to feed paper, and a reverse roller that is in pressure contact with the feed roller and to which rotational torque is applied in a paper return direction via a torque applying unit, and is provided with a paper double feed detecting unit that detects double feeding of paper on the downstream side of a paper separating portion where the feed roller and the reverse roller are in pressure contact. The torque applying unit is configured to be capable of selectively switching the limit value of the torque applied to the reverse roller, and controls the driving torque of the feed roller according to the detection output of the paper double feed detecting unit or the switching of the limit value in the torque applying unit.

[0005] The aforementioned paper separation device uses multiple torque limiters to selectively switch the torque limit value, resulting in a complex structure and raising concerns about increased size and cost. Additionally, while a pickup roller is provided to retrieve paper from the stack of paper loaded on the paper tray, a narrow gap between the pickup roller and the paper tray makes it difficult to load paper onto the tray.

[0006] This disclosure is made to solve the above-mentioned problems and aims to provide a document transport device and an image forming apparatus that can smoothly set documents in the paper feed tray. [Means for solving the problem]

[0007] The document transport device according to this disclosure includes a paper feed tray on which documents are loaded, a main body having a document transport path on which documents are transported, a document feeding unit having a feed roller for feeding documents on the paper feed tray into the document transport path, the feed roller being movable between a first position where it is spaced apart from the documents loaded on the paper feed tray and a second position where it is in contact with the documents loaded on the paper feed tray, and an opening / closing cover on which the document feeding unit is provided and which is attached to the main body of the device so as to be openable and closable, and which opens a part of the document transport path when open, and the opening / closing cover The device comprises a drive shaft that, when the cover is closed, receives rotational force from a drive unit and rotates in a predetermined first rotational direction, moving the document feeding unit from the first position to the second position; and a biasing member, one end of which is attached to the opening / closing cover and the other end of which is attached to the document feeding unit, wherein when the opening / closing cover is opened from the closed position, the document feeding unit is moved to the first position by the biasing force of the biasing member, and even when the opening / closing cover is returned to the closed position, the state in which it is held in the first position by the biasing force of the biasing member is maintained.

[0008] In the document transport device according to this disclosure, the document feeding unit is rotatable about the rotation axis of the drive shaft and is supported by the opening / closing cover such that a rotational force is generated in a first rotational direction, which is a rotational direction from the first position to the second position, by its own weight, and the biasing direction of the biasing force that the biasing member applies to the document feeding unit is a second rotational direction opposite to the first rotational direction, and the magnitude of the biasing force may be greater than the rotational force in the first rotational direction due to the weight of the document feeding unit.

[0009] The document transport device according to this disclosure may be configured to include a torque limiter provided between the drive shaft and the document feeding unit, which stops the transmission of rotational force from the drive shaft to the document feeding unit when the torque exceeds a predetermined value, and when the drive unit is driven and the drive shaft rotates in the first rotational direction, the document feeding unit rotates in the first rotational direction against the biasing force of the biasing member, and when the feed roller comes into contact with the paper feed tray or a document on the paper feed tray, the torque limiter stops the transmission of rotational force to the document feeding unit and holds it in the second position.

[0010] In the document transport device according to this disclosure, the predetermined value of the torque limiter may be configured to be greater than the biasing force of the biasing member.

[0011] In the document transport device according to this disclosure, the feed roller may be configured to apply pressure to the document on the paper tray with a force that combines the force received from the drive shaft and the biasing member and the force that causes it to rotate in the first rotational direction due to its own weight, when the document feeding unit is in the second position due to the rotational force of the drive shaft.

[0012] In the document transport device according to this disclosure, the drive shaft may be attached to the opening / closing cover, connected to the drive unit when the opening / closing cover is closed, and disconnected from the drive unit when the opening / closing cover is open, allowing it to rotate freely.

[0013] In the document transport device according to this disclosure, the feed roller may be configured to receive the rotational force of the drive shaft and rotate in a direction that feeds the document to the document transport path when the drive shaft is rotating in the first rotational direction.

[0014] The image forming apparatus relating to this disclosure is characterized by comprising a document transport device relating to this disclosure. [Effects of the Invention]

[0015] According to this disclosure, the document feeding unit is held in a position separated from the paper tray, so that it does not get in the way when setting documents (paper) into the paper tray. [Brief explanation of the drawing]

[0016] [Figure 1] This is a schematic side view of an image forming apparatus according to an embodiment of the present disclosure. [Figure 2] This is a perspective view showing a document transport device according to an embodiment of the present disclosure. [Figure 3] This is a plan view showing the opening and closing cover. [Figure 4] This is a schematic side view showing the vicinity of the document feed unit in its raised and separated position. [Figure 5] This is a schematic side view showing the vicinity of the document feed unit in its lowered position and in contact with the surface. [Modes for carrying out the invention]

[0017] The image forming apparatus according to the embodiments of this disclosure will be described below with reference to the drawings.

[0018] Figure 1 is a schematic side view of an image forming apparatus according to an embodiment of the present disclosure.

[0019] The image forming apparatus 100 is a multifunction peripheral having a scanner function, a copy function, a printer function, a facsimile function, and the like, and includes an image reading unit 41 and an image forming unit 90. The image forming apparatus 100 transmits an image of a document read by the image reading unit 41 to the outside (corresponding to the scanner function), and forms an image on a sheet in color or monochrome by the image forming unit 90 based on the image of the document read by the image reading unit 41 or an image received from the outside (corresponding to the copy function, the printer function, and the facsimile function).

[0020] The image reading unit 41 includes a transparent document placement table 44 on which a document is placed, and a reading scanning unit 42 that scans the document placed on the document placement table 44 in the sub-scanning direction X1 to cause the image sensor 43 to read the document. The document placed on the document placement table 44 is imaged by the image sensor 43 by moving the reading scanning unit 42 in the sub-scanning direction X1, and is converted into image data.

[0021] Above the image reading unit 41, a document conveyance device 50 (ADF) is provided which is supported to be openable and closable relative to the image reading unit 41 and is movable between a position where the document placement table 44 is closed and a position where the document placement table 44 is opened.

[0022] The document conveyance device 50 includes a device main body 59, a sheet feeding tray 52 on which documents are stacked, a document conveyance path 58 that is a conveyance path for conveying documents and is provided midway with a conveyed document reading unit 55 where the conveyed document is read by the reading scanning unit 42, a document feeding unit 70 that feeds the documents on the sheet feeding tray 52 to the document conveyance path 58, a discharge tray 53 to which the document read by the conveyed document reading unit 55 is discharged, and an opening / closing cover 51 that is attached to the device main body 59 to be openable and closable.

[0023] The document transport device 50 feeds documents placed on the paper tray 52 one by one into the document transport path 58. Documents transported along the document transport path 58 are captured by the image sensor 43 via the reading and scanning unit 42 in the document transport reading unit 55 and converted into image data. When the open / close cover 51, which is attached to the main body of the device 59 so as to be openable and closable, is opened, a part of the document transport path 58 is opened. Therefore, even if a document jams in the document transport path 58 while being transported, it can be easily removed from the document transport path 58. The document transport device 50 will be described in detail with reference to Figure 2, which will be described later.

[0024] The image forming apparatus 100 includes an optical scanning device 1, a developing device 2, a photoreceptor drum 3 (an example of a photoreceptor), a drum cleaning device 4, a charger 5, an intermediate transfer belt 7, a fixing unit 12, a paper transport path S, a paper feed cassette 10, a loading tray 15, and the like.

[0025] The image forming apparatus 100 handles image data corresponding to color images using black (K), cyan (C), magenta (M), and yellow (Y), or monochrome images using a single color (for example, black). Therefore, the image forming apparatus 100 is equipped with four developing devices 2, four photoreceptor drums 3, four drum cleaning devices 4, and four chargers 5 for forming four types of toner images, each corresponding to black, cyan, magenta, and yellow, forming four image stations Pa, Pb, Pc, and Pd.

[0026] The charger 5 uniformly charges the surface of the photoreceptor drum 3 to a predetermined potential. The light scanning device 1 exposes the surface of the photoreceptor drum 3 to form an electrostatic latent image. The developing device 2 develops the electrostatic latent image on the surface of the photoreceptor drum 3 to form a toner image on the surface of the photoreceptor drum 3. The toner image formed on the surface of the photoreceptor drum 3 is intermediately transferred to the intermediate transfer belt 7 by the transfer belt device 8, which will be described later. The drum cleaning device 4 removes and collects any remaining toner on the surface of the photoreceptor drum 3 after the toner image has been intermediately transferred. In addition, the surface of the photoreceptor drum 3, which has been cleaned by the drum cleaning device 4, is irradiated with light by a static elimination device (not shown) to erase the electrostatic latent image. By repeating the above series of operations, toner images of each color are formed on the surface of each photoreceptor drum 3.

[0027] The transfer belt device 8 includes a transfer drive roller 21, a transfer driven roller 22, and an intermediate transfer belt 7 stretched between the transfer drive roller 21 and the transfer driven roller 22. A portion of the surface of the intermediate transfer belt 7 is positioned above the photoreceptor drum 3 so as to face the photoreceptor drum 3. An intermediate transfer roller 6 is provided inside the intermediate transfer belt 7, and the intermediate transfer belt 7 is brought into contact with the corresponding surface of the photoreceptor drum 3 by the intermediate transfer roller 6. When the transfer drive roller 21 is rotated by a drive source (not shown), the intermediate transfer belt 7 moves in a circular motion in the direction of arrow C, and the toner images of each color formed on the surface of each photoreceptor drum 3 are sequentially transferred and superimposed, forming a color toner image on the surface of the intermediate transfer belt 7.

[0028] The transfer roller 11a of the transfer unit 11 is positioned to contact the intermediate transfer belt 7, and in the contact nip area (transfer position), which is the area in contact with the intermediate transfer belt 7, it grips and transports the paper that has been transported through the paper transport path S with the intermediate transfer belt 7. As the paper that has been transported through the paper transport path S passes through the contact nip area, the toner image on the surface of the intermediate transfer belt 7 is transferred to the paper and it is transported to the fixing unit 12. Any remaining toner or other deposits on the surface of the intermediate transfer belt 7 that were not transferred in the contact nip area are removed and collected by the belt cleaning device 9.

[0029] The fuser unit 12 includes a fuser roller 31 and a pressure roller 32 that rotate with the paper in between. The fuser unit 12 places the paper with the toner image transferred to it between the fuser roller 31 and the pressure roller 32, heats and pressurizes it, and fixes the toner image to the paper with heat and pressure.

[0030] The paper feed cassette 10 is a cassette for storing paper used for image formation and is located on the lower side of the optical scanning device 1. The paper is pulled out of the paper feed cassette 10 by the paper pickup roller 16, transported through the paper transport path S, passes through the transfer unit 11 and the fixing unit 12, and is delivered to the stacking tray 15 via the paper discharge roller 17. The paper transport path S is equipped with a paper register roller 14 that temporarily stops the paper, aligns the leading edge of the paper, and then starts transporting the paper in accordance with the timing of toner image transfer in the nip area between the intermediate transfer belt 7 and the transfer roller 11a, a transport roller 13 that promotes paper transport, and a paper discharge roller 17.

[0031] Furthermore, if image formation is to be performed on the back side of the paper as well as the front side, the paper is transported in the reverse direction from the paper output roller 17 to the paper reversal path Sr. In the paper reversal path Sr, the front and back sides of the paper are reversed via the reversal roller 18, and the paper is guided back to the paper registration roller 14. After that, image formation is performed on the back side in the same way as on the front side, and the paper is discharged to the stacking tray 15.

[0032] Figure 2 is a perspective view showing a document transport device according to an embodiment of the present disclosure. In Figure 2, a portion of the exterior has been removed so that the internal structure of the document transport device 50 can be seen.

[0033] As shown in Figure 2, the document transport device 50 has an opening / closing cover 51 on one end (upper left side in Figure 2), and on the other end (lower right side in Figure 2), there is a paper feed tray 52 on which documents are loaded and an output tray 53 on which documents are discharged. The paper feed tray 52 and the output tray 53 are arranged side by side in the height direction (up and down direction), with the paper feed tray 52 positioned on the upper level and the output tray 53 positioned on the lower level.

[0034] The paper feed tray 52 is sloped so that the end facing the opening / closing cover 51 is lower. In other words, when a document is placed on the paper feed tray 52, the slope is designed so that the document slides towards the opening / closing cover 51 due to its own weight. A guide plate may also be provided at the end of the paper feed tray 52 on the opening / closing cover 51 side to lift the leading edge of the loaded document and bring it into contact with the document feeding unit 70.

[0035] Below the opening / closing cover 51, a document transport path 58 is provided, through which documents loaded in the paper feed tray 52 are transported toward the paper output tray 53. The document transport path 58 is located on the main body 59 of the device.

[0036] The opening / closing cover 51 has a document guide section (not shown) formed on the side of the document transport path 58, which forms part of the document transport path 58. The opening / closing cover 51 is pivotally supported at its end on the main body of the device 59 and is configured to be attached to the main body of the device 59 so as to be able to open and close. In other words, the opening / closing cover 51 is provided on the main body of the device 59 so as to be movable between an open position in which part of the document transport path 58 is opened and a closed position in which the document transport path 58 is formed, and is configured so that when it is open, part of the document transport path 58 is opened. Therefore, when the opening / closing cover 51 is opened, part of the document transport path 58 that was covered by the opening / closing cover 51 is exposed, so that when a paper jam occurs, the document that has stopped in the document transport path 58 can be easily removed.

[0037] Figure 3 is a plan view showing the opening / closing cover, and shows the side of the opening / closing cover 51 facing the document transport path 58 when it has been removed from the main body 59 of the device. Here, the left side of Figure 3 is the front side of the image forming apparatus 10, and the right side of Figure 3 is the rear side of the image forming apparatus 10.

[0038] Inside the opening / closing cover 51 (on the side of the document transport path 58), there is a document feeding unit 70 that feeds documents from the paper tray 52 one by one into the document transport path 58, and a drive shaft 61.

[0039] The drive shaft 61 is held by the opening / closing cover 51 so as to be rotatable. When the opening / closing cover 51 is closed, that is, when the document transport path 58 is formed, the drive gear 63 provided at the end of the drive shaft 61 is configured to mesh with a transmission gear (not shown) provided on the main body of the device 59. The transmission gear is connected to a drive unit 54 which includes a drive source (motor), a gear train or belt that transmits the rotational force of the drive source, and a clutch for temporarily stopping the transmission of rotational force from the drive source. Therefore, when the drive source of the drive unit 54 rotates with the opening / closing cover 51 closed, the drive shaft 61 rotates by receiving rotational force from the transmission gear. On the other hand, when the opening / closing cover 51 is opened, the drive gear 63 provided on the drive shaft 61 is disengaged from the transmission gear, and the drive shaft 61 is configured to rotate freely. In other words, the drive shaft 61 is attached to the opening / closing cover 51, connected to the drive unit 54 when the opening / closing cover 51 is closed, and disconnected from the drive unit 54 when the opening / closing cover is open, allowing it to rotate freely.

[0040] The document feeding unit 70 has a feed roller 72 that feeds documents on the paper tray 52 into the document transport path 58, and is provided on the opening / closing cover 51 so that the feed roller 72 can move between a separated position (first position) where it is separated from the paper tray 52 or the documents loaded in the paper tray 52, and a contact position (second position) where it is in contact with the paper tray 52 or the documents loaded in the paper tray 52 (see Figures 4 and 5 described later).

[0041] Furthermore, since the document feeding unit 70 is provided on the opening / closing cover 51, when the opening / closing cover 51 is open, even if the document feeding unit 70 is in contact with the document, the feed roller 72 will be separated from the document on the paper tray 52. ​​In this disclosure, even when the opening / closing cover 51 is open, if the document feeding unit 70 is in contact with the document on the paper tray 52 when the cover is closed, it may be said that the document feeding unit 70 is in contact with the document.

[0042] The detailed configuration of the document feeding unit 70 will now be described. The document feeding unit 70 includes a unit housing 71 with an opening on the lower side, which is on the document transport path 58 side, and having a space inside, a feed roller 72, a paper feed roller 73, and a transmission belt 75. The feed roller 72, the paper feed roller 73, and the transmission belt 75 are arranged in the space inside the unit housing 71, and the feed roller 72 and the paper feed roller 73 are rotatably supported on the unit housing 71. Here, the lower parts of the feed roller 72 and the paper feed roller 73 protrude below the housing and can come into contact with documents passing below.

[0043] The paper feed roller 73 has its own rotation axis (paper feed shaft 73a) pivotally supported by the unit housing 71. The end of the paper feed shaft 73a on the drive shaft 61 side is connected to the end of the drive shaft 61 opposite to the drive gear 63. Therefore, when the drive shaft 61 rotates, the paper feed roller 73 rotates integrally with the drive shaft 61. In other words, as shown in Figure 3, when the drive shaft 61 rotates in a predetermined rotational direction, a first direction R1, the paper feed roller 73 also rotates in the first rotational direction R1. In this way, the paper feed roller 73 is pivotally supported by the unit housing 71 so as to be rotatable integrally with the drive shaft 61 around the rotation axis α.

[0044] The feed roller 72 has its own rotation axis (feed axis 72a) supported by the document feeding unit 70. The transmission belt 75 is stretched between the feed axis 73a and the feed axis 72a. Therefore, when the feed axis 73a rotates due to the rotational force of the drive axis 61, the feed roller 72 rotates via the transmission belt 75. In this way, when the drive axis 61 is rotating, the feed axis 73a of the feed roller is also rotating, so the feed axis 72a also rotates via the transmission belt 75, and consequently the paper intake roller 73 rotates.

[0045] The document feeding unit 70 is positioned at the end of the document transport path 58 on the paper tray 52 side, straddling the paper tray 52 (see, for example, Figure 4). More specifically, the feed roller 72 is located above the paper tray 52, and the paper feed roller 73 is located above the main body of the device 59, on the document transport path 58.

[0046] Here, the drive shaft 61 side of the unit housing 71 is connected to the drive shaft 61 via a torque limiter 62. The torque limiter 62 stops transmitting rotational force when a torque (limit value) exceeding a predetermined value is applied. In other words, a torque limiter 62 is provided between the drive shaft 61 and the document feeding unit 70, which stops the transmission of rotational force from the drive shaft 61 to the document feeding unit 70 when the torque exceeds a predetermined limit value. Therefore, when the drive shaft 61 rotates, the unit housing 71 (document feeding unit 70) also rotates around the rotation axis α of the drive shaft 61 until the torque acting on the torque limiter 62 exceeds the limit value.

[0047] For example, when the opening / closing cover 51 is closed and the document feeding unit 71 is in a separated position (first position) (Figure 4), when the drive shaft 61 receives rotational force from the drive unit 54 and rotates in the first rotational direction R1, the document feeding unit 71 (its unit housing 71) rotates integrally with the drive shaft 61 in the first rotational direction R1 via the torque limiter 62, and the feed roller 72 moves toward the contact position (second position) where it contacts the document on the paper tray 52.

[0048] As will be explained in more detail later, the unit housing 71 is configured so that once it rotates to a predetermined contact position, it will not rotate any further due to the action of the torque limiter 62.

[0049] Thus, the document feeding unit 70 is mounted on the opening / closing cover 51 such that the end on the feed roller 72 side swings up and down due to the rotation of the drive shaft 61. In other words, when the opening / closing cover 51 is closed, the drive shaft 61 receives rotational force from the drive unit 54 and rotates in a predetermined first rotational direction R1, moving the document feeding unit 70, which is in a separated position, to a contact position. The rotation (swinging) operation of the document feeding unit 71 by the drive shaft 61 will be explained in detail with reference to Figures 4 and 5 described later.

[0050] A biasing member 74 is installed between the document feeding unit 70 and the opening / closing cover 51. Specifically, the biasing member 74 is a spring, with one end attached to the opening / closing cover 51 and the other end attached to the document feeding unit 70.

[0051] Next, the movement of each part of the document transport device 50 will be explained with reference to Figures 4 and 5. Note that Figures 4 and 5 show only the essential parts of the document transport device 50 in a schematic manner, omitting other parts.

[0052] Figure 4 is a schematic side view showing the vicinity of the document feed unit in its raised and separated position.

[0053] The document feeding unit 70 is pivotally supported by the opening / closing cover 51 such that its own weight Wr acts as a rotational force (self-oscillating force) that moves the document feeding unit 70 in the direction from the separated position to the contact position (the direction of arrow D2 in Figure 5 or the first rotational direction R1 in Figure 4). In other words, the document feeding unit 70 is rotatable around the rotation axis α of the drive shaft 61 and is supported by the opening / closing cover 51 such that its own weight generates a rotational force in the first rotational direction R1, which is the direction of rotation from the separated position (first position) to the contact position (second position).

[0054] Furthermore, a biasing member 74 is attached to the biasing mounting portion 71a provided at the end of the document feeding unit 70 on the side of the paper feed roller 73. The biasing force Fs exerted by the biasing member 74 acts in the direction that moves the document feeding unit 70 from the contact position to the separation position (the direction of arrow D1, or the second rotational direction R2 shown in Figure 4). In other words, the biasing direction of the biasing force Fs exerted by the biasing member 74 on the document feeding unit 70 is the second rotational direction R2, which is opposite to the first rotational direction R1. The magnitude of the biasing force Fs exerted by the biasing member 74 is configured to be greater than the rotational force (self-oscillating force) in the first rotational direction R1 due to the weight of the document feeding unit 70.

[0055] As described above, when the opening / closing cover 51 is opened, the connection between the drive gear 63 and the transmission gear provided on the main body 59 of the device is released, and the drive shaft 61 becomes freely rotatable relative to the opening / closing cover 51. In this state, the document feeding unit 70 rotates together with the drive shaft 61 in the second rotation direction R2 by the biasing force Fs of the biasing member 74, and a part (not shown) comes into contact with a stopper part (not shown) provided on the opening / closing cover 51, and comes to rest in the separated position. The document feeding unit 70, which is resting in the separated position, is then maintained in the separated position by the biasing force Fs of the biasing member 74. In other words, when the opening / closing cover 51 is opened from the closed state, the document feeding unit 70 is moved to the separated position by the biasing force Fs of the biasing member 74, and even when the opening / closing cover 51 is returned to the closed state, it is maintained in the separated position by the biasing force Fs of the biasing member 74.

[0056] When the opening / closing cover 51 is opened in this manner, even if the document feeding unit 70 is in the contact position, the biasing member 74 moves it to the separated position and maintains that position. Specifically, if a document stops for any reason during document transport (i.e., a jam occurs), even if the opening / closing cover 51 is opened to remove the jammed document and then the opening / closing cover 51 is closed again, the document feeding unit 70 will remain in the separated position. As a result, there will be space between the document remaining on the paper tray 51 and the feed roller 72, allowing the jammed document to be inserted between the document remaining on the paper tray 51 and the pull-in roller 73, and document transport can be easily resumed.

[0057] Furthermore, as described above, since the document feeding unit 70 is held in a position separated from the paper tray 52, it is possible to avoid the document feeding unit 70 getting in the way when setting documents (paper) in the paper tray 52. ​​Here, the biasing force Fs is set to be greater than the weight Wr, so it is sufficient to use a biasing member 74 with a weak biasing force Fs, and a simple structure can be made. Since the document feeding unit 70 is biased by the biasing member 74 attached to the opening / closing cover 51, the document feeding unit 70 can maintain its raised position even when subjected to the impact of closing the opening / closing cover 51.

[0058] Next, the movement (rotation) of the document feeding unit 70 when the drive shaft 61 rotates in the first rotational direction R1 in response to the rotational force from the drive unit 54 will be described. As mentioned above, a torque limiter 62 is provided between the drive shaft 61 and the unit housing 71 of the document feeding unit 70. The limit value of the rotational torque that the torque limiter 62 can transmit (the limit value of the torque limiter 62) is configured to be greater than the biasing force Fs of the biasing member 74. Therefore, when the opening / closing cover 51 is closed and the drive shaft 61 rotates in the first rotational direction R1 in response to the rotational force from the drive unit 54, the rotational force of the drive shaft 61 is transmitted to the document feeding unit 71 via the torque limiter 62, causing it to rotate toward the first rotational direction R1 against the biasing force Fs of the biasing member 74. In other words, the document feeding unit 70 rotates toward the contact position. Thus, the driving force (first driving force Tr1) transmitted from the drive shaft 61 to the document feeding unit 70 via the torque limiter 62 acts in a direction that causes the document feeding unit 70 to move toward the contact position.

[0059] As described above, the document feeding unit 70 oscillates in accordance with the combined force of the biasing force Fs, its own weight Wr, and the driving force transmitted from the drive shaft 61 (first driving force Tr1 in Figure 4).

[0060] Figure 5 is a schematic side view showing the vicinity of the document feed unit in its lowered position and in contact with the surface.

[0061] Figure 5 shows the state with the opening / closing cover 51 closed and the document feeding unit 70 in the lowered position. When the drive shaft 61 is rotated by the drive unit 54, the document feeding unit 70 rotates in the first rotational direction R1 and reaches the contact position where the feed roller 72 contacts the document on the paper tray 52. ​​At this time, the contact position of the document feeding unit 70 is maintained by the action of the torque limiter 62 as described above.

[0062] The operation of the torque limiter 62 will now be explained. When the document feeding unit 70 reaches the contact position, it attempts to rotate further in the first rotational direction R1 in accordance with the rotation of the drive shaft 61, but it is unable to rotate any further because the document on the paper tray 52 and the feed roller 72 are in contact. At this time, a torque exceeding the limit value is applied to the torque limiter 62, so the rotation of the document feeding unit 70 stops and it is held in the contact position. In other words, when the drive unit 54 is driven and the drive shaft 61 rotates in the first rotational direction R1, the document feeding unit 70 rotates in the first rotational direction R1 against the biasing force Fs of the biasing member 74, and when the feed roller 72 comes into contact with the paper tray 52 or the document on the paper tray 52, the torque limiter 72 stops transmitting rotational force to the document feeding unit 70 and holds it in the contact position.

[0063] At this time, the drive shaft 61 maintains a rotating state, and since the feed roller 72 and the paper feed roller 73 are also rotating, the document that comes into contact with the feed roller 72 is fed towards the paper feed roller 73 by the feed roller 72, and then further fed into the document transport path 58 by the feed roller 72. Since the paper feed roller 73 is positioned to come into contact with the transport surface of the document transport path 58, even if the document stacked below (the lower document) is transported together with the document that comes into contact with the feed roller 72 (the upper document), the lower document will come into contact with the transport surface of the document transport path 58 and stop. Therefore, only the upper document is fed into the document transport path 58. In this way, even if multiple documents are stacked on the paper tray 52, the document feeding unit 70 can feed the documents one by one into the document transport path 58. In other words, when the drive shaft 61 is rotating in the first rotational direction R1, the feed roller 72 receives the rotational force of the drive shaft 61 and rotates in a direction that feeds the document on the paper tray 52 into the document transport path 58.

[0064] Furthermore, when the drive shaft 61 is rotating and the document feed unit 70 is in contact position, a force (second drive force Tr2) corresponding to the limit value of the torque limiter 62 is transmitted to the document feed unit 70. In other words, when the opening / closing cover 51 is closed and the document feed unit 70 is in contact position, the feed roller 72 contacts the document on the paper feed tray 52 with a force obtained by subtracting the biasing force Fs of the biasing member 74 from the force due to its own weight Wr and the second drive force Tr2. In other words, when the document feed unit 70 is in contact position due to the rotational force of the drive shaft 61, the feed roller 72 applies pressure to the document on the paper feed tray 52 with a force which is the sum of the force received from the drive shaft 61 and the biasing member 74 (biasing force Fs) and the force that causes it to rotate in the first rotational direction R1 due to its own weight Wr.

[0065] Here, the limit value of the torque limiter 62, when combined with the weight Wr of the document feeding unit 70, is set to exceed the biasing force Fs of the biasing member 74, allowing the limit value of the torque limiter 62 to be set to a sufficiently small value. Therefore, a small motor can be used in the torque limiter 62 that uses a motor. In addition, the operation of the drive unit 54 allows the document feeding unit 70 to be oscillated as appropriate.

[0066] As described above, when the drive shaft 61 rotates in the first rotational direction R1 and is in contact position, the document feeding unit 70 applies pressure to the document P with a force (applied pressure Fr) which is the sum of a predetermined torque transmitted from the rotating drive shaft 61 via the torque limiter 62, the force received from the biasing member 74, and the self-oscillating force directed toward the contact position due to its own weight. In this way, when the document feeding unit 70 is in the lowered position and in contact position, the feed roller 72 applies pressure to the document P with a constant force, so that the document P can be stably transported toward the document transport path 58.

[0067] Regarding the document feeding unit 70, it is desirable that it be lowered to a contact position when feeding the document P, and raised to a separated position when setting the document in the paper tray 52, and that it be oscillated appropriately depending on the situation. Conventionally, sensors or the like were used as triggers to oscillate the document feeding unit 70, but the cost increases as the number of parts increases.

[0068] In contrast, in this embodiment, when the opening / closing cover 51 is opened or closed, the connection state between the drive shaft 61 and the drive unit 54 can be switched without any extra effort. Furthermore, when the opening / closing cover 51 is opened, the drive shaft 61 is disconnected from the drive unit 54, so the document feeding unit 70 can be raised to the separated position without the need for a sensor or the like to detect it and provide a trigger.

[0069] In this disclosure, when the document transport is completed, the drive source of the drive unit 54 is rotated in the opposite direction, and the drive shaft 61 is rotated in the second rotation direction R2, thereby moving the document feeding unit 70 to the separated position. At this time, as described above, a part of the document feeding unit 70 (not shown) comes into contact with a stopper part (not shown) provided on the opening / closing member 51, but the torque limiter 62 stops the transmission of rotational force from the drive shaft 61 to the document feeding unit 70. After that, when the rotation of the drive source is stopped, the separated position is maintained by the biasing force Fs of the biasing member 74.

[0070] Therefore, even if some kind of impact is applied to the opening / closing cover 51 in the document transport device 50 where no abnormality such as a document jam has occurred, it is possible to effectively prevent the document feeding unit 70 from moving to the contact position.

[0071] In this embodiment, in order to clearly illustrate the operation of the image forming apparatus 100, the paper before image formation is simply called "paper," and the paper after image formation is called "original," and the original document transport device 50 that transports the original has been described. However, the embodiment is not limited to this, and a paper transport device that feeds the paper used for image formation may be configured similarly to the original document transport device 50.

[0072] Furthermore, the embodiments disclosed herein are illustrative in all respects and do not constitute a limiting interpretation. Accordingly, the technical scope of this disclosure is not to be interpreted solely by the embodiments described above, but is defined based on the claims. This includes all modifications within the meaning and scope of equivalents to the claims. [Explanation of Symbols]

[0073] 50 Document transport device 51 Opening and closing cover 52 Paper feed tray 54 Drive unit 58 Manuscript transport path 59 Main unit of the device 61 Drive shaft 62 Torque Limiter 70 Document feeding unit 74. Biasing member 100 Image forming apparatus

Claims

1. The paper tray on which the documents are loaded, A device body having a document transport path through which documents are transported, A document feeding unit having a feed roller for feeding documents on the paper feed tray into the document transport path, the feed roller being movable between a first position where it is spaced apart from the documents loaded in the paper feed tray and a second position where it is in contact with the documents loaded in the paper feed tray, The aforementioned document feeding unit is provided, and an opening / closing cover is attached to the main body of the device so as to be openable and closable, and when open, it opens a part of the document transport path, When the opening / closing cover is closed, the drive shaft rotates in a predetermined first rotational direction upon receiving rotational force from the drive unit, moving the document feeding unit from the first position to the second position. A biasing member having one end attached to the opening / closing cover and the other end attached to the document feeding unit, The document feeding unit is moved to the first position by the biasing force of the biasing member when the opening / closing cover is opened from the closed position, and the state in which it is held in the first position by the biasing force of the biasing member is maintained even when the opening / closing cover is returned to the closed position. A document transport device characterized by the following.

2. A document transport device according to claim 1, The document feeding unit is rotatable around the rotation axis of the drive shaft and is supported by the opening / closing cover such that its own weight generates a rotational force in a first rotational direction, which is a rotational direction from the first position to the second position. The biasing direction of the biasing force that the biasing member applies to the document feeding unit is a second rotational direction opposite to the first rotational direction. The magnitude of the biasing force is greater than the rotational force in the first rotational direction due to the weight of the document feeding unit. A document transport device characterized by the following.

3. A document transport device according to claim 2, A torque limiter is provided between the drive shaft and the document feeding unit, which stops the transmission of rotational force from the drive shaft to the document feeding unit when the torque exceeds a predetermined value. When the drive unit is driven and the drive shaft rotates in the first rotational direction, the document feeding unit rotates in the first rotational direction against the biasing force of the biasing member, and when the feed roller comes into contact with the paper tray or a document on the paper tray, the torque limiter stops transmitting rotational force to the document feeding unit and holds it in the second position. A document transport device characterized by the following.

4. The document transport device according to claim 3, The predetermined value of the torque limiter is greater than the biasing force of the biasing member. A document transport device characterized by the following.

5. A document transport device according to claim 3, The feed roller, when the document feeding unit is in the second position due to the rotational force of the drive shaft, applies pressure to the document on the paper tray with a force that combines the force received from the drive shaft and the biasing member and the force that causes it to rotate in the first rotational direction due to its own weight. A document transport device characterized by the following.

6. A document transport device according to claim 1, The drive shaft is attached to the opening / closing cover, and when the opening / closing cover is closed, it is connected to the drive unit, and when the opening / closing cover is open, the connection to the drive unit is released, allowing it to rotate freely. A document transport device characterized by the following.

7. A document transport device according to claim 1, The feed roller, when the drive shaft is rotating in the first rotational direction, receives the rotational force of the drive shaft and rotates in a direction that feeds the document to the document transport path. A document transport device characterized by the following.

8. An image forming apparatus comprising the document transport device described in claim 1.

Images