Document transport device

Abstract

To provide a document conveyance device capable of solving a problem caused by taking-out of a document stacked on a paper feed tray.SOLUTION: This document conveyance device comprises: a document detection sensor 123 that detects a document on a paper feed tray 43; a discharge tray 45 provided below the paper feed tray 43; a lifting mechanism 125 for lifting the paper feed tray 43 between an upper limit position where the document is pressed to a delivery roller 103 to raise the delivery roller 103 to a prescribed paper height and a lower limit position separated downward from the delivery roller 103; and an upper limit position detection sensor 115 that detects rising of the paper feed tray 43 to the upper limit position. When the document detection sensor 123 detects the document in a standby state, the lifting mechanism 125 raises the paper feed tray 43 to the upper limit position and then lowers it, and the paper feed tray 43 is stopped with the passage of prescribed time after the upper limit position detection sensor 115 no longer detects the paper feed tray 43.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a document transport device that transports a document to a document reading device. [Background technology]

[0002] In recent years, with the shift to paperless systems, the conversion of various documents (originals) into electronic data has led to improvements in the quality and functionality required of document feeders in multi-function peripherals (MFPs). One of the required functions is the ability to read large volumes of originals at high speed. This requirement is met by increasing the reading speed and increasing the document load capacity. Furthermore, to ensure the reliability of scanned data, new functions have been added, such as the inclusion of sensors to detect double feeds, preventing skipped documents, and protecting the originals in the event of a paper jam.

[0003] For example, Patent Document 1 proposes a document feeder (corresponding to a document transport device) that includes a lifting means for lifting a paper feed tray and a lifting control means for lifting the paper feed tray in response to the feeding of documents from the paper feed tray, and is configured so that the discharge outlet of the paper output tray is lifted and lowered the same amount in response to the lifting and lowering of the paper feed tray. Specifically, the paper feed tray is set to its lowest position based on a detection signal from a lower limit sensor that detects that the paper feed tray has reached the lower limit position with no documents placed on it, and when a document presence / absence sensor detects that a document has been placed on it, the paper feed tray is lifted based on this detection signal until the topmost document abuts against a pickup roller. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-8283 Summary of the Invention [Problem to be solved by the invention]

[0005] In a document feeder such as that described in Patent Document 1, when a document presence sensor detects that a document has been placed, the paper feed tray rises until the top document abuts the pickup roller. Then, for example, when a document is to be added, and the document is then temporarily removed from the paper feed tray, friction occurs between the top document and the pickup roller, resulting in damage to the document and wear on the pickup roller.

[0006] SUMMARY OF THE INVENTION In consideration of the above circumstances, an object of the present invention is to provide a document transport device that can eliminate problems that occur when removing documents stacked on a paper feed tray. [Means for solving the problem]

[0007] In order to achieve the above object, the document transport device of the present invention includes a paper feed tray on which documents are stacked and which is provided so as to be able to be raised and lowered, a document detection sensor which detects the presence or absence of the documents on the paper feed tray, a discharge tray provided below the paper feed tray, a transport path along which the documents are transported from the paper feed tray to the discharge tray via a reading position, a feed roller which rotates in contact with the documents stacked on the paper feed tray to feed the documents into the transport path, and a feed roller which presses the stacked documents against the feed roller to raise the feed roller to a predetermined paper feed height. and an upper limit position detection sensor that detects that the paper feed tray has risen to the upper limit position, and when the document detection sensor detects the document during standby when the document transport operation is not being performed, the lifting mechanism raises the paper feed tray to the upper limit position and then lowers it, and the lifting mechanism stops the paper feed tray after a predetermined time has elapsed since the upper limit position detection sensor no longer detects the paper feed tray.

[0008] In the document transport device of the present invention, the specified time may be the time from when the upper limit position detection sensor no longer detects the paper feed tray until the document on the paper feed tray separates from the feed roller.

[0009] In the document transport device of the present invention, the predetermined time period may be changeable. [Effects of the Invention]

[0010] According to the present invention, by appropriately selecting the predetermined time after the upper limit position detection sensor no longer detects the paper feed tray, after documents are placed on the paper feed tray, the top document can be separated from the feed roller before the document transport operation begins, thereby preventing friction between the document and the feed roller when removing the document from the paper feed tray. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a front view schematically illustrating an internal configuration of a multifunction peripheral including a document transport device according to an embodiment of the present invention; [Figure 2] 1 is a perspective view showing a document transport device (with an outer cover removed) according to an embodiment of the present invention; [Figure 3] 1 is a cross-sectional view showing a document transport device according to an embodiment of the present invention. [Figure 4] FIG. 2 is a front view showing a lifting mechanism for a paper feed tray in a document transport device according to an embodiment of the present invention. [Figure 5] 2 is a perspective view mainly showing a lifting arm of a lifting mechanism for a paper feed tray in a document transport device according to an embodiment of the present invention; FIG. [Figure 6] 3 is a perspective view mainly showing a lower limit sensor of a lifting mechanism of a paper feed tray in a document transport device according to an embodiment of the present invention; FIG. [Figure 7] 2 is a block diagram showing a control unit of the document transport device according to the embodiment of the present invention; FIG. [Figure 8] 5 is a flowchart showing an example of a document transport process in the document transport device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a multifunction peripheral including a document transport device according to an embodiment of the present invention will be described with reference to the drawings.

[0013] The multifunction device 1 will be described with reference to Fig. 1. Fig. 1 is a front view showing a schematic internal configuration of the multifunction device 1. In each figure, Fr, Rr, L, and R indicate the front, rear, left, and right sides of the multifunction device 1, respectively.

[0014] The multifunction device 1 includes an image forming device 3, a document reading device 5, and a document transport device 7. The image forming device 3 forms an image on a sheet based on the image of a document G read by the document reading device 5. The document transport device 7 transports the document G to the document reading device 5.

[0015] First, a brief description will be given of the image forming apparatus 3. The image forming apparatus 3 includes a paper feed unit 11, an image forming unit 13, and a fixing unit 15. The paper feed unit 11 feeds sheets stored in a paper feed cassette 17 and transports the sheets to a transport path 19. The image forming unit 13 forms a toner image on the sheets transported along the transport path 19 by electrophotography, based on the image of the original G read by the original reading device 5. The fixing device 15 fixes the toner image formed on the sheets to the sheets. The sheets with the fixed toner image are stacked on a discharge tray 21.

[0016] Next, we will explain the document reading device 5. The document reading device 5 includes a contact glass 31 on which a document G can be placed, and a scanner unit 33 that is arranged below the contact glass 31 and reads an image of the placed document G. The scanner unit 33 includes a first carriage 35 and a second carriage 37 that move in conjunction with each other in a predetermined direction (left and right direction), and an imaging unit 39 that is fixed at a predetermined position.

[0017] The first carriage 35 accommodates a light source 35a and a first mirror 35b. The first carriage 35 is movable to the right from a home position below the left end of the contact glass 31. The second carriage 37 accommodates second and third mirrors 37a and 37b. The second carriage 37 is movable to the right below the first carriage 35 from a home position to the left of the home position of the first carriage 35.

[0018] The imaging unit 39 includes a CCD sensor 39a and an imaging lens 39b that forms an optical image on the CCD sensor 39a. The imaging unit 39 is fixed below the right end of the contact glass 31 at the same height as the third mirror 37b of the second carriage 37.

[0019] When reading an original G placed on the contact glass 31, the first carriage 35 moves rightward from its home position at a predetermined speed while emitting light from the light source 35a, and the second carriage 37 moves rightward from its home position at half the speed of the first carriage 35. This moves the reading position of the original G (the position where the light emitted from the light source 35a is reflected by the first mirror 35b of the first carriage 35 toward the contact glass 31) and reads the image of the entire surface of the original G. The light reflected by the original G is reflected leftward by the first mirror 35b and further reflected by the second and third mirrors 37a and 37b of the second carriage 37, and is imaged on the CCD sensor 39a by the imaging lens 39b. The formed optical image is converted into an electrical signal and transmitted to the control unit 201 (see FIG. 7).

[0020] On the other hand, when reading the document G transported by the document transport device 7 described below, the first carriage 35 and the second carriage 37 are stopped at their home positions and read the image of the document G transported to the reading position P. As the document G passes through the reading position P, the image of the entire surface of the document G is read.

[0021] Next, the document transport device 7 will be described with reference to Fig. 1, Fig. 2, and Fig. 3. Fig. 2 is a perspective view showing the document transport device 7 (with the outer cover 63 removed), and Fig. 3 is a cross-sectional view showing the document transport device 7.

[0022] The document transport device 7 includes a main body 41 (see FIGS. 2 and 3), a paper feed tray 43 on which documents G whose images are to be read are placed, a discharge tray 45 provided below the paper feed tray 43 and on which the documents G whose images have been read are stacked, a transport unit 47 which transports the documents G from the paper feed tray 43 to the discharge tray 45 via a reading position P, and a feed-out unit 49 which feeds the documents G from the paper feed tray 43 to the transport unit 47. As described above, the reading position P is a position where light emitted from the light source 35a of the first carriage 35 is reflected by the first mirror 35b onto the contact glass 31 when the first carriage 35 and the second carriage 37 of the document reading device 5 are stopped at their home positions.

[0023] 2, the main body 41 has a rectangular bottom plate 51, a front wall 53 extending along the left half of the front edge of the bottom plate 51, and a rear wall 55 extending along the entire rear edge of the bottom plate 51. The left and right rear corners of the main body 41 are rotatably supported by the document reading device 5. By rotating the main body 41 upward, a document can be placed on or removed from the contact glass 31 of the document reading device 5. Furthermore, by rotating the main body 41 downward, the bottom plate 51 presses the document on the contact glass 31 against the contact glass 31, thereby positioning it.

[0024] Next, we will explain the conveying unit 47. The conveying unit 47 has an inner guide 61 and an outer cover 63 that covers the upper surface and left side surface of the inner guide 61, and is provided on the bottom plate 51 of the main body 41, between the front wall 53 and the rear wall 55.

[0025] 3, the transport section 47 is provided with a transport path 69 extending from the receiving opening 65 toward the reading position P, and a discharge path 73 extending from the reading position P toward the discharge opening 71. The transport path 69 is formed between the outer cover 63 and the inner guide 61. The discharge path 73 is disposed inside the inner guide 61 and is formed between upper and lower plate-shaped guide members 75 and 77 that face each other with a gap therebetween that allows the document G to pass through.

[0026] The transport path 69 is formed to extend substantially linearly from the receiving opening 65 to the left, then curve downward and head toward the reading position P. The discharge path 73 is formed to extend diagonally upward to the right from the reading position P toward the discharge opening 71. In this way, the original G is transported along the transport path 69 from the receiving opening 65 to the reading position P, and is transported along the discharge path 73 from the reading position P to the discharge opening 71, and as the original G passes the reading position P, the image of the original G is read by the original reading device 5. In the following description, the upstream side and the downstream side refer to the upstream side and the downstream side in the transport direction of the original G. The direction intersecting with the transport direction is defined as the width direction.

[0027] In the conveying path 69, first to fourth conveying roller pairs 81, 83, 85, and 87 are arranged in this order from the upstream side.

[0028] The first to fourth transport roller pairs 81, 83, 85, and 87 are arranged at predetermined intervals along the transport direction. Each transport roller pair has a drive roller and a driven roller that rotates in contact with the drive roller. Each drive roller is supported by the inner guide 61 so as to be rotatable about a drive shaft parallel to the width direction. Each driven roller is supported by the outer cover 63 so as to be rotatable about a rotation shaft parallel to the width direction.

[0029] An opening 51a corresponding to the reading position P is formed in the bottom plate 51 of the main body 41. A shading plate 91 is disposed in the inner guide 61 so as to face the opening 51a. A gap is provided between the shading plate 91 and the contact glass 31 of the document reading device 5, allowing the document G to pass through. The shading plate 91 performs shading correction for the CCD sensor 39a.

[0030] In the discharge path 73, a fifth conveying roller pair 95 and a discharge roller pair 97 are arranged in this order from the upstream side.

[0031] The fifth conveying roller pair 95 is disposed downstream of the shading plate 91 and includes a drive roller and a driven roller that rotates in contact with the drive roller. The drive roller is supported by the upper guide member 75 so as to be rotatable about a drive shaft parallel to the width direction. The driven roller is supported by the lower guide member 77 so as to be rotatable about a rotation shaft parallel to the width direction.

[0032] The discharge roller pair 97 is disposed upstream of the discharge port 71 and includes a drive roller and a driven roller that rotates in contact with the drive roller. The drive roller is supported by the upper guide member 75 so as to be rotatable about a drive shaft that is parallel to the width direction. The driven roller is supported by the lower guide member 77 so as to be rotatable about a rotation shaft that is parallel to the width direction.

[0033] Next, the payout unit 49 will be described. The payout unit 49 is disposed downstream of the receiving port 65 and includes a payout roller 103 and a conveyor belt 105 housed in a holder 101, and an auxiliary roller 107. The holder 101 has a box shape with an open bottom. A protrusion 101a protrudes from the upper surface of the top plate of the holder 101. The payout roller 103 is disposed upstream inside the holder 101 and is supported rotatably around a rotation axis parallel to the width direction. The conveyor belt 105 is disposed downstream of the payout roller 103 inside the holder 101 and is wound around a drive roller 109 and a driven roller 111. The drive roller 109 is disposed downstream of the driven roller 111 and rotates around a drive axis and a rotation axis parallel to the width direction, respectively. 2, the holder 101 is disposed at the center in the width direction, and both ends of the drive shaft 109a of the drive roller 109 are rotatably supported by the front wall 53 and the rear wall 55 of the main body 41. The rear end of the drive shaft 109a is connected to a drive motor 113 (see FIG. 3).

[0034] A one-way clutch (not shown) is disposed between the drive shaft 109a and the holder 101. When the drive shaft 109a rotates counterclockwise in FIG. 3, the holder 101 together with the drive shaft 109a swings upward around the drive shaft 109a. On the other hand, when the drive shaft 109a rotates clockwise, the drive shaft 109a rotates relative to the holder 101. This causes the drive roller 109 to rotate, and the conveyor belt 105 runs in the clockwise direction in FIG. 3. Furthermore, the clockwise rotation of the drive shaft 109a is transmitted to the feed roller 103 via a gear (not shown), causing the feed roller 103 to rotate in the clockwise direction in FIG. 3.

[0035] The auxiliary roller 107 is disposed in the inner guide 61 so as to contact the lower running surface of the conveyor belt 105, and is supported rotatably about a rotation axis parallel to the width direction.

[0036] As described above, holder 101 swings up and down around drive shaft 109a. When holder 101 swings all the way up to its upper limit position, feed roller 103 rises to a predetermined paper feed height. When holder 101 swings all the way down to its lower limit position, holder 101 is supported by a stopper (not shown). Conveyance unit 47 is provided with upper limit position detection sensor 115 that detects when holder 101 has risen to its upper limit position.

[0037] The upper limit position detection sensor 115 is, for example, a transmissive optical sensor. A transmissive optical sensor has a light-emitting element and a light-receiving element, and outputs an ON signal when the optical path formed between the light-emitting element and the light-receiving element is interrupted, and outputs an OFF signal when the optical path is established. The upper limit position detection sensor 115 is supported by the outer cover 63 above the holder 101. When the holder 101 rotates to the upper limit position, the protrusion 101a enters between the light-emitting element and the light-receiving element of the upper limit position detection sensor 115, interrupting the optical path, and the upper limit position detection sensor 115 outputs an ON signal.

[0038] Next, we will explain the paper feed tray 43 and the discharge tray 45. The paper feed tray 43 is a plate-shaped member that can hold the largest size document G. As shown in Fig. 2, the paper feed tray 43 supports a pair of side cursors 121 that position the document G placed thereon in the width direction so as to be movable in the width direction.

[0039] The paper feed tray 43 is also provided with a document detection sensor 123 that detects the presence or absence of a document G. The document detection sensor 123 is, for example, a reflective optical sensor having a light-emitting element and a light-receiving element. An opening is formed in the upper plate of the paper feed tray 43 at the downstream end. The document detection sensor 123 is disposed below the opening. When a document G is placed on the paper feed tray 43, light emitted from the light-emitting element through the opening is reflected by the document G. When the reflected light passes through the opening and is received by the light-receiving element, the document detection sensor 123 outputs an ON signal. On the other hand, when a document G is not placed on the paper feed tray 43, the light emitted from the light-emitting element is not reflected by the document G and is not received by the light-receiving element, and the document detection sensor 123 outputs an OFF signal.

[0040] The sheet feed tray 43 is disposed above the right half of the bottom plate 51 of the main body 41, and is supported by a lifting mechanism 125 (see FIG. 4) so as to be able to move up and down in an attitude inclined downward toward the receiving opening 65. The lifting mechanism 125 will be described later.

[0041] The discharge tray 45 is formed in the right half of the bottom plate 51 of the main body 41. The discharge tray 45 is inclined upward from below the discharge outlet 71 toward the side away from the discharge outlet 71 (right side).

[0042] Next, the lifting mechanism 125 of the paper feed tray 43 will be described with reference to Figures 4 to 6. Figure 4 is a front view showing the lifting mechanism 125, Figure 6 is a perspective view mainly showing the lifting arm 133 of the lifting mechanism 125, and Figure 7 is a perspective view mainly showing the lower limit position detection sensor 177 of the lifting mechanism 125.

[0043] The lifting mechanism 125 includes a rail 131 extending in the vertical direction, a lifting arm 133 that supports the paper feed tray 43 and engages with the rail 131, and a drive unit 135 that raises and lowers the lifting arm 133 along the rail 131. The lifting mechanism 125 is provided on the front wall 53 and the rear wall 55 of the main body 41 below the feeding unit 49. More specifically, the front wall 53 has a front side plate and a front cover that covers the front surface of the front side plate, and the rear wall 55 has a rear side plate and a rear cover that covers the rear surface of the rear side plate. The lifting mechanism 125 is provided on the front surface of the front side plate and the rear surface of the rear side plate. Hereinafter, for ease of explanation, the front side plate will be referred to as the front wall 53, and the rear side plate will be referred to as the rear wall 55. FIGS. 3 and 4 show the lifting mechanism 125 provided on the front wall 53, and FIG. 5 shows the lifting mechanism 125 provided on the rear wall 55.

[0044] The rail 131 is formed on the front wall 53 (and rear wall 55) along the vertical direction and has a pair of parallel rail pieces 131a along the vertical direction. The lifting arm 133 has an engaging portion 141 that engages with the rail 131, a support portion 143 that is provided upstream of the engaging portion 141 and supports the downstream end of the paper feed tray 43, and a connecting portion 145 that is provided downstream of the engaging portion 141 and connects to the drive unit 135. The engaging portion 141 has upper and lower bearings 151 (see FIGS. 5 and 6). The upper and lower bearings 151 are supported between the pair of rail pieces 131a of the rail 131. The connecting portion 145 has a protruding piece 155 that protrudes outward.

[0045] The drive unit 135 is disposed downstream of the rail 131. The drive unit 135 includes a drive sprocket 161 that rotates about a drive shaft parallel to the width direction, a plurality of sprockets 163 (163A, 163B) that rotate about rotation shafts parallel to the width direction, and a timing belt 167 that is wound around the drive sprocket 161 and the plurality of sprockets 163.

[0046] The drive sprocket 161 is disposed downstream of the upper end of the rail 131, and its drive shaft is rotatably supported on the front wall 53 (and rear wall 55). An elevator motor 173 (see FIG. 4) is connected to one end of the drive shaft. The elevator motor 173 is, for example, a DC motor. The elevator motor 173 is supported by a bracket 171 (see FIG. 6) fixed to the front wall 53 (and rear wall 55).

[0047] One of the multiple sprockets 163, sprocket 163A, is disposed below drive sprocket 161, with its rotation shaft rotatably supported on front wall 53 (and rear wall 55). The other sprocket 163B is disposed downstream of drive sprocket 161, with its rotation shaft rotatably supported on front wall 53 (and rear wall 55). Timing belt 167 is wound around these sprockets 161, 163.

[0048] The drive shaft is driven by the lift motor 173, causing the drive sprocket 161 to rotate, causing the timing belt 167 to run in both directions. At this time, the linear portion 167x of the timing belt 167 between the drive sprocket 161 and the sprocket 163A disposed below it runs in the vertical direction parallel to the rail 131.

[0049] The connecting portion 145 of the lifting arm 133 is connected to the linear portion 167x of the timing belt 167. As a result, when the timing belt 167 runs, the lifting arm 133 moves up and down along the rail 131. More specifically, the upper and lower bearings 151 of the engaging portion 141 of the lifting arm 133 slide along the inner surfaces of the pair of rail pieces 131a of the rail 131. When the lifting arm 133 moves up and down in this way, the paper feed tray 43 moves up and down.

[0050] The sheet feed tray 43 is raised and lowered between an upper limit position and a lower limit position by the lifting mechanism 125. The lower limit position is a position where, for example, a large volume of documents G (e.g., 500 sheets) can be placed. The lifting mechanism 125 is provided with a lower limit position detection sensor 177 (see FIG. 6) that detects when the sheet feed tray 43 has reached the lower limit position. The lower limit position detection sensor 177 is supported by the bracket 171. The lower limit position detection sensor 177 is, for example, a transmissive optical sensor having a light-emitting element and a light-receiving element. When an optical path is formed between the light-emitting element and the light-receiving element, the lower limit position detection sensor 177 outputs an ON signal, and when the optical path is interrupted, the lower limit position detection sensor 177 outputs an OFF signal. When the sheet feed tray 43 reaches the lower limit position, the protrusion 155 of the connecting portion 145 of the lifting arm 133 enters between the light-emitting element and the light-receiving element, interrupting the optical path, and the lower limit position detection sensor 177 outputs an ON signal.

[0051] On the other hand, when the paper feed tray 43 is raised, the topmost document G stacked on the paper feed tray 43 comes into contact with the feed roller 103 (see FIGS. 2 and 3) of the feed unit 49. When the paper feed tray 43 is further raised, the document G pushes up the feed roller 103, causing the holder 101 to rotate upward around the drive shaft 109a. The paper feed tray 43 rises until the holder 101 swings to the upper limit position, that is, until the feed roller 103 rises to a predetermined paper feed height. In this way, the paper feed tray 43 rises to the upper limit position where the protrusion 101a of the holder 101 blocks the optical path of the upper limit position detection sensor 115, causing the upper limit position detection sensor 115 to send an ON signal.

[0052] At this upper limit position, as described above, the feed roller 103 is raised to a predetermined paper feed height, so that by rotating the drive shaft 109a of the drive roller 109 of the feed section 49, the document G placed on the paper feed tray 43 is appropriately fed by the feed roller 103, and the fed document G is transported to the transport path 69 by the conveying belt 105 and the auxiliary roller 107.

[0053] Next, the control unit 201 of the document transport device 7 will be described with reference to the block diagram of Fig. 7. The control unit 201 receives detection results (ON signal or OFF signal) from the document detection sensor 123 (see Figs. 2 and 3), the upper limit position detection sensor 115 (see Fig. 3), and the lower limit position detection sensor 177 (see Fig. 6). The control unit 201 also controls the driving of the drive motor 113 (see Fig. 3) of the feed unit 49 and the lifting motor 173 (see Fig. 4) of the lifting mechanism 125.

[0054] When the control unit 201 receives an ON signal from the document detection sensor 123 , it determines that the document G has been placed on the paper feed tray 43 .

[0055] Furthermore, when the control unit 201 receives an ON signal from the upper limit position detection sensor 115, it determines that the holder 101 has rotated to the upper limit position, i.e., that the paper feed tray 43 has risen to the upper limit position. Furthermore, when the control unit 201 receives an ON signal from the lower limit position detection sensor 177, it determines that the paper feed tray 43 has descended to the lower limit position.

[0056] An example of a document transport process in the document transport device 7 having the above configuration will be described with reference to the flowchart in Fig. 8. During standby when no document transport operation is being performed, the document feed tray 43 is lowered to its lowest position to accommodate a large number of documents G, such as about 500 sheets, placed on the document feed tray 43.

[0057] In step S1, control unit 201 determines whether an ON signal has been received from document detection sensor 123, i.e., whether a document G has been placed on paper feed tray 43. If it is determined in step S1 that an ON signal has been received from document detection sensor 123, i.e., that a document G has been placed on paper feed tray 43, the process proceeds to step S2. If it is not determined that an ON signal has been received from document detection sensor 123, the process of step S1 is repeated.

[0058] In step S2, control unit 201 drives lift motor 173 to lift paper feed tray 43. This lifts documents G placed on paper feed tray 43. When paper feed tray 43 is lifted in this manner, as described above, the topmost document G pushes up feed roller 103, causing holder 101 to rotate upward (see FIG. 3).

[0059] Thereafter, in step S3, the control unit 201 determines whether an ON signal has been received from the upper limit position detection sensor 115, i.e., whether the paper feed tray 43 has risen to the upper limit position. In step S3, the control unit 201 repeats the process of step S3 until an ON signal is received from the upper limit position detection sensor 115.

[0060] If it is determined in step S3 that an ON signal has been received from upper limit position detection sensor 115, i.e., that paper feed tray 43 has risen to the upper limit position, the process proceeds to step S4. In step S4, control unit 201 stops driving lift motor 173. This causes paper feed tray 43 to stop with the uppermost document G remaining in contact with feed roller 103. Thereafter, the process proceeds to step S5.

[0061] In step S5, the control unit 201 drives the lift motor 173 to lower the paper feed tray 43. As a result, the document G is lowered and the holder 101 is rotated downward.

[0062] Thereafter, in step S6, the control unit 201 determines whether an OFF signal has been received from the upper limit position detection sensor 115, i.e., whether the paper feed tray 43 has been lowered from the upper limit position. If an OFF signal has been received from the upper limit position detection sensor 115, i.e., if it is determined that the paper feed tray 43 has been lowered from the upper limit position, the process proceeds to step S7. The control unit 201 repeats the process of step S6 until an OFF signal is received from the upper limit position detection sensor 115.

[0063] In step S7, the control unit 201 determines whether a predetermined time has elapsed since it determined that an OFF signal was received from the upper limit position detection sensor 115, i.e., that the paper feed tray 43 has been lowered from the upper limit position. The predetermined time is, for example, 300 ms. As a result, the topmost document G is spaced downward from the feed roller 103 by a predetermined distance. The control unit 201 repeats the process of step S7 until the predetermined time has elapsed. Note that, if the paper feed tray 43 has been lowered to the lower limit position before the predetermined time has elapsed in step S7, the lower limit position detection sensor 177 sends an ON signal to the control unit 201. Upon receiving the ON signal, the control unit 201 stops driving the lift motor 173.

[0064] When a predetermined time has elapsed in step S7, the process proceeds to step S8. In step S8, the control unit 201 stops driving the lift motor 173 and ends the process.

[0065] After the above process is completed, the document conveyance operation can be started. For example, the user presses a start key provided on an operation panel (not shown) of the image forming apparatus 3 (see FIG. 1) to start the document conveyance operation.

[0066] When the start key is pressed, the control unit 201 drives the lift motor 173 to raise the paper feed tray 43 to the upper limit position. Thereafter, the control unit 201 drives the drive motor 113 to rotate the drive shaft 109a (see FIG. 3), which causes the feed roller 103 to feed out the document G, and the feed-out document G is transported to the transport path 69 by the transport belt 105 and the auxiliary roller 107. The document G transported to the transport path 69 is transported to the reading position P by the first to fourth transport roller pairs 81, 83, 85, and 87. Then, as the document G passes through the reading position P, the image of the document G is read by the document reading device 5. The document G is then transported along the discharge path 73 by the fifth transport roller pair 95, and is discharged from the discharge opening 71 by the discharge roller pair 97 and stacked on the discharge tray 45.

[0067] As described above, according to the present invention, by appropriately selecting the time after upper limit position detection sensor 115 no longer detects paper feed tray 43, it is possible to move the topmost document G downward away from feed roller 103 before the document transport operation is started (before the start key is pressed) after the documents G are placed on paper feed tray 43. Therefore, for example, when a document is removed from paper feed tray 43 to add or replace a document before the start key is pressed, the document G does not come into contact with feed roller 103, and therefore damage to the document G and wear on feed roller 103 can be prevented.

[0068] Furthermore, when the start key is pressed to start the document transport operation, the document feed tray 43 has been raised to a position where the top document G is slightly below the feed roller 103. In this way, the distance between the feed roller 103 and the document G is shortened, and the distance by which the document feed tray 43 is raised can be shortened, so that the document transport operation can be started promptly.

[0069] Furthermore, since lift motor 173 generally uses a DC motor, it is difficult to control the number of rotations and therefore precisely control the position (height) of paper feed tray 43. Therefore, by determining when to stop the lowering of paper feed tray 43 based on the elapsed time after receiving an OFF signal from upper limit position detection sensor 115, paper feed tray 43 can be stopped at an appropriate position away from feed roller 103.

[0070] Furthermore, as described above, because holder 101 of feed-out unit 49 swings between an upper limit position and a lower limit position, when paper feed tray 43 descends from the upper limit position, it is possible that the uppermost document G placed on paper feed tray 43 remains in contact with feed-out roller 103 within the swing range of holder 101. In other words, it is possible that the uppermost document G placed on paper feed tray 43 remains in contact with feed-out roller 103 even after an OFF signal is received from upper limit position detection sensor 115.

[0071] Therefore, by setting the time (predetermined time) from receiving an off signal from the upper limit position detection sensor 115 to stopping the paper feed tray 43 to about 300 ms, the paper feed tray 43 can be lowered below the lower limit position of the holder 101, and the topmost document can be separated from the feed roller 103.

[0072] In this embodiment, the predetermined time may be changeable according to user settings. In this case, for example, an input unit for inputting the predetermined time is provided on the operation panel of the image forming apparatus 1, and the desired elapsed time is input into the input unit. Alternatively, an adjustment unit for lengthening or shortening the predetermined elapsed time is provided. For example, if the predetermined time is set to 0, the feed tray 43 stops with the feed roller 103 remaining in contact with the document G. Alternatively, even if the feed tray 43 stops within the swing range of the holder 101, the feed roller 103 remains in contact with the document G. In this case, there is no need to raise the feed tray 43 when starting the document transport operation, so the document transport operation can be started more quickly.

[0073] Although the present invention has been described with reference to specific embodiments, the present invention is not limited to the above embodiments, and those skilled in the art may modify the above embodiments without departing from the scope and spirit of the present invention. [Explanation of symbols]

[0074] 7 Document transport device 43 Paper tray 45 Output tray 69 Transport Path 103 Feed roller 115 Upper limit position detection sensor 123 Document detection sensor 125 Lifting mechanism

Claims

1. a paper feed tray on which documents are loaded and which is provided so as to be movable up and down; a document detection sensor that detects whether or not the document is on the paper feed tray; an ejection tray provided below the paper feed tray; a transport path along which the document is transported from the paper feed tray to the discharge tray via a reading position; a feed roller that rotates in contact with the document stacked on the paper feed tray to feed the document to the transport path; an elevating mechanism that raises and lowers the paper feed tray between an upper limit position where the stacked documents are pressed against the feed roller to raise the feed roller to a predetermined paper feed height, and a lower limit position where the feed roller is spaced downward from the feed roller; an upper limit position detection sensor that detects that the paper feed tray has risen to the upper limit position; a control unit that receives detection results from the document detection sensor and the upper limit position detection sensor and controls the lifting mechanism based on the detection results; The control unit, when the document detection sensor detects the document during standby when the document transport operation is not being performed, controls the lifting mechanism to raise the paper feed tray from the lower limit position to the upper limit position and then lower it, and controls the lifting mechanism to stop the paper feed tray after a predetermined time has elapsed since the upper limit position detection sensor no longer detects the paper feed tray.

2. 2. The document transport device according to claim 1, wherein the predetermined time is the time from when the upper limit position detection sensor no longer detects the paper feed tray until when the document on the paper feed tray separates from the feed roller.

3. 2. The document transport device according to claim 1, wherein the predetermined time is changeable.

4. The document transport device described in Claim 1, characterized in that the control unit controls the lifting mechanism to stop the paper feed tray if the paper feed tray descends to the lower limit position before a predetermined time has elapsed since the upper limit position detection sensor no longer detects the paper feed tray.

Images