Document Feeder

Abstract

To maintain an appropriate interval between sheets (interval between document and document) without hitting documents to a registration roller pair and temporarily stopping the documents at the registration roller pair.SOLUTION: A document conveying device includes a document tray, a first rotating body (paper feed roller, separation paper feed unit), a first motor, a second rotating body, a second motor, a paper feed sensor, and a control unit (conveyance control unit). The control unit measures a measurement time that is the time from the start of rotation of the first motor until a leading end of a document reaches the paper feed sensor. When a time obtained by subtracting the measurement time from a predetermined necessary time between sheets is longer than a time required for speed change, the control unit decelerates the first motor and accelerates the motor after the deceleration to adjust the interval between a document being conveyed and a preceding document. The time required for speed change is the time required for changing the speed from a first rotation speed to a second rotation speed.SELECTED DRAWING: Figure 6

Description

[Technical field]

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

[0002] There are devices that transport paper to perform jobs. One such device is an image forming device. The transported paper may be skewed. For example, if the paper transported by the image forming device is skewed, the printed image will be skewed. Conventionally, the paper is often abutted against a roller called a registration roller to correct the skew (oblique movement). On the other hand, there are also devices that intentionally prevent the paper from abutting against the roller. An example of a technology that prevents the paper from abutting against the registration roller is described in Patent Document 1.

[0003] Specifically, Patent Document 1 describes an image forming apparatus that includes a transfer section that transfers an image onto a sheet, a registration roller provided upstream of the transfer section in the sheet transport direction, and a control section that controls the operation of the registration roller, and the control section controls the oscillation of the registration roller so that the position of the transferred image in the sheet transport direction is correct after performing a registrationless operation in which the leading edge of the sheet in the transport direction is not abutted against the registration roller, and performs either the registrationless operation or the registration operation based on the shape of the sheet. The registration roller is oscillated in the width direction (direction perpendicular to the sheet transport direction) to accurately transfer the image (Patent Document 1: see claims 1, 4, 5, paragraphs

[0007] ,

[0048] , etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-081623 A Summary of the Invention [Problem to be solved by the invention]

[0005] An image sensor may be used to read an original document and obtain image data of the original document. For example, a multifunction peripheral that can use a copy function reads an original document, generates image data, and prints based on the generated image data.

[0006] Furthermore, a document transport device may be used that continuously and automatically transports documents one by one toward the reading position. By using such a document transport device, multiple documents can be read continuously. The document being transported may be tilted. In this case, the image in the image data obtained by reading is tilted. Therefore, a pair of registration rollers is conventionally provided in the document transport device. In such a document transport device, the leading edge of the document is abutted against the pair of registration rollers that are in a stopped state. As a result, the leading edge of the document is aligned with the nip of the pair of registration rollers. Then, the skew of the document is corrected. After the skew is corrected, the pair of registration rollers starts to rotate, and the document is sent out without skew.

[0007] Another advantage of using a pair of registration rollers is that it is easier to maintain the gap between documents (paper gap). For example, the pair of registration rollers can be started to rotate at regular intervals. For example, if 30 sheets of documents are sent per minute, the pair of registration rollers can be started to rotate once every two seconds. Since the documents are sent out at regular intervals, the gap between the documents does not become too narrow.

[0008] If the document is not abutted against the pair of registration rollers (if the document is not stopped by the pair of registration rollers), the gap between the sheets may become too narrow. Specifically, the preceding document may drag the next document, causing the next document to protrude downstream in the document transport direction. How easily the document protrudes downstream depends on the paper quality of the document and how the document is set. If the next document protrudes downstream in the document transport direction, the gap between the preceding document and the next document becomes narrow. If the document is not stopped by the pair of registration rollers, the gap between the sheets cannot be adjusted. If the document is not stopped by the pair of registration rollers, there is a problem that the appropriate gap between the sheets may not be maintained.

[0009] The above-mentioned patent documents do not include any description of the gap between sheets. There is no description of the case where the next sheet is dragged by the preceding sheet. The image forming device described in the above-mentioned patent document 1 cannot control the gap between sheets, and the gap between sheets may become too narrow. The image forming device described in the patent document 1 cannot solve the above problems.

[0010] The present invention makes it possible to maintain an appropriate paper interval (gap between documents) without abutting a document against a pair of registration rollers and without temporarily stopping the document with the pair of registration rollers. [Means for solving the problem]

[0011] In order to achieve the above object, the document transport device according to the present invention includes a document tray, a first rotating body, a first motor, a second rotating body, a second motor, a paper feed sensor, and a control unit. A plurality of documents can be set on the document tray. The first rotating body sends out the documents set on the document tray one by one. The first motor rotates the first rotating body. The second rotating body is provided downstream of the first rotating body in the document transport direction and sends the documents toward a reading position. The second motor rotates the second rotating body so as to transport the documents at a second transport speed determined in advance. The paper feed sensor is provided downstream of the first rotating body in the document transport direction and upstream of the second rotating body in the document transport direction. The control unit recognizes the arrival of the leading edge of the document at the paper feed sensor and the passing of the trailing edge of the document from the paper feed sensor based on the output of the paper feed sensor. The control unit starts the rotation of the first motor when the transport of the document starts. After the first motor starts rotating, until the leading edge of the document reaches the paper feed sensor, the control unit rotates the first motor at a rotation speed equal to or lower than a first rotation speed for transporting the document at a predetermined first transport speed. After the leading edge of the document reaches the paper feed sensor, until the trailing edge of the document passes the paper feed sensor, the control unit changes the rotation speed of the first motor to a second rotation speed for transporting the document at a second transport speed. After the second rotation speed is reached, until the next document feed start time, the control unit stops the first motor. The control unit measures a measurement time that is a time from the start of rotation of the first motor to the arrival of the leading edge of the document at the paper feed sensor. When a time obtained by subtracting the measured time from a predetermined required paper interval time is longer than a required time for speed change, the control unit decelerates the first motor and accelerates it after the deceleration to adjust the paper interval between the document being fed and the preceding document. The required speed change time is the time required to change the speed from the first rotation speed to the second rotation speed. Effect of the Invention

[0012] According to the present invention, it is possible to maintain an appropriate paper interval (gap between documents) without abutting the document against the pair of registration rollers and without temporarily stopping the document with the pair of registration rollers. This makes it possible to improve the quietness and productivity of the document transport device and stabilize productivity. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating a multifunction peripheral according to an embodiment. [Diagram 2] 2 is a diagram illustrating an example of a document transport unit and a document reading unit according to the embodiment; [Diagram 3] 2 is a diagram illustrating an example of a document transport unit and a document reading unit according to the embodiment; [Figure 4] 11A and 11B are diagrams illustrating an example of document transport in a registration mode according to the embodiment. [Diagram 5] 10 is a diagram showing an example of second conveying speed definition data according to the embodiment. FIG. [Figure 6] 5A and 5B are diagrams illustrating an example of document transport according to the embodiment. [Figure 7] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. [Figure 8] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. [Figure 9] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. [Figure 10] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. [Figure 11] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. [Figure 12] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. [Figure 13] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. [Figure 14] 6A to 6C are diagrams illustrating an example of rotation control of a first motor according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, an embodiment of the present invention will be described with reference to Figs. 1 to 14. In this description, a multifunction device 100 will be taken as an example of a document transport device. The multifunction device 100 is also an image forming device. Specifically, the multifunction device 100 transports a document D that has been set. The multifunction device 100 reads the document D that is being transported and generates image data. The multifunction device 100 can perform a print job or a transmission job based on the generated image data. However, the elements such as the configuration and arrangement described in this embodiment do not limit the scope of the invention and are merely illustrative examples.

[0015] (Overview of the multifunction printer 100) First, an overview of a multifunction peripheral 100 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing a multifunction peripheral 100 according to an embodiment.

[0016] As shown in FIG. 1, the multifunction device 100 includes a main control unit 1, a storage unit 2, an operation panel 3, a printer unit 4, a document transport unit 5, and a document reading unit 6.

[0017] The main control unit 1 controls the operation of the multifunction device 100. The main control unit 1 controls the operation of each unit of the multifunction device 100 for jobs such as copying and sending. The main control unit 1 includes a main control circuit 11, an image data generation circuit 12, an image processing circuit 13, and a communication circuit unit 14. For example, the main control unit 1 is a board (main control board). For example, the main control circuit 11 is a CPU. The main control circuit 11 performs processing and calculations related to jobs.

[0018] The image data generating circuit 12 includes a circuit for processing an analog image signal. For example, the image data generating circuit 12 includes an amplifier circuit, an offset circuit, and an A / D conversion circuit. The A / D conversion circuit converts the analog image signal adjusted by the amplifier circuit and offset circuit into digital data (image data). The image data generating circuit 12 generates read image data based on the analog image signal output by the document reading unit 6 after reading the document D. For example, the image data generating circuit 12 generates gray or color read image data.

[0019] The image processing circuit 13 performs image processing on the scanned image data. The image processing circuit 13 is an ASIC (an integrated circuit designed and developed for image processing). For example, in the case of a copy job, the image processing circuit 13 processes the scanned image data to generate image data for printing. The main control unit 1 causes the printer unit 4 to print based on the image data for printing. The communication circuit unit 14 includes a communication circuit and a communication memory. The communication memory stores communication software. The communication circuit unit 14 communicates with the computer 200. The computer 200 is, for example, a PC or a server. The communication circuit unit 14 can receive printing data from the computer 200. The main control unit 1 causes the printer unit 4 to print based on the received printing data (print job, fax reception printing).

[0020] The multifunction device 100 includes a RAM, a ROM, and a storage as a memory unit 2. The storage is either an HDD or an SSD, or both. The main control unit 1 controls each unit based on the programs and data stored in the memory unit 2.

[0021] The operation panel 3 includes a display panel 31, a touch panel 32, and hard keys 33. The main control unit 1 displays messages and a setting screen on the display panel 31. The main control unit 1 also displays operation images on the display panel 31. The operation images are, for example, buttons, keys, and tabs. Based on the output of the touch panel 32, the main control unit 1 recognizes the operated operation image. The hard keys 33 include a start key and a numeric keypad. The touch panel 32 and the hard keys 33 accept user setting operations (job-related operations). By operating the operation images and the hard keys 33, the user can perform job-related settings. The operation panel 3 accepts user settings. For example, the operation panel 3 accepts a setting of the resolution for reading a document. The operation panel 3 also accepts a setting of whether to read in color or monochrome.

[0022] The printer unit 4 includes a paper feed unit 4a, a paper transport unit 4b, an image forming unit 4c, and a fixing unit 4d. The paper feed unit 4a includes a paper feed cassette and a paper feed roller. The paper feed cassette stores paper. The paper feed roller sends out the paper. During a print job, the main control unit 1 causes paper to be supplied from the paper feed unit 4a to the paper transport unit 4b. The paper transport unit 4b includes a paper transport roller pair for transporting paper, and a paper transport motor. The paper transport motor rotates the paper transport roller pair. The paper transport roller pair transports the paper. The main control unit 1 causes the paper to be transported to the paper transport unit 4b.

[0023] The image forming unit 4c includes, for example, a photosensitive drum, a charging device, an exposure device, a developing device, and a transfer roller. The main control unit 1 causes the image forming unit 4c to form a toner image based on image data. The main control unit 1 causes the image forming unit 4c to transfer the toner image to the transported paper. The fixing unit 4d includes a heater and a fixing rotor. The heater heats the fixing rotor. The paper is transported while in contact with the fixing rotor. This causes the toner image to be fixed to the paper. The main control unit 1 causes the fixing unit 4d to fix the transferred toner image to the paper. The paper transport unit 4b ejects the printed paper outside the multifunction device 100.

[0024] (Document transport unit 5 and document reading unit 6) Next, an example of the document transport unit 5 and the document reading unit 6 according to the embodiment will be described with reference to Fig. 2 and Fig. 3. Fig. 2 and Fig. 3 are diagrams showing an example of the document transport unit 5 and the document reading unit 6 according to the embodiment.

[0025] The multifunction device 100 includes a document transport unit 5 and a document reading unit 6. The document transport unit 5 is sometimes called an automatic document feeder (ADF, DP). The document transport unit 5 is provided above the document reading unit 6. The combination of the document transport unit 5 and the document reading unit 6 is disposed, for example, at the top of the multifunction device 100.

[0026] As shown in FIG. 2, the document transport unit 5 includes a transport control unit 50 (corresponding to a control unit). The transport control unit 50 is communicably connected to the main control unit 1. The transport control unit 50 includes a transport control circuit 50a and a transport memory unit 50b. For example, the transport control circuit 50a is a CPU. The document transport unit 5 includes a ROM and a RAM as the transport memory unit 50b. For example, the transport control unit 50 is a control board provided inside the document transport unit 5. For a job involving document reading, the main control unit 1 issues an instruction to the transport control unit 50 to transport the document. For example, jobs involving document reading are a copy job and a transmission job. Based on the instruction from the main control unit 1, the transport control unit 50 controls the document transport operation of the document transport unit 5.

[0027] The document reading unit 6 includes a reading control unit 60. The reading control unit 60 is also connected to the main control unit 1 so as to be able to communicate with the main control unit 1. The reading control unit 60 includes a reading control circuit 60a and a reading storage unit 60b. For example, the reading control unit 60 is a CPU. The document reading unit 6 includes a ROM and a RAM as the reading storage unit 60b. For example, the reading control unit 60 is a control board provided inside the document reading unit 6. When a job involves reading a document, the main control unit 1 issues an instruction to read the document to the reading control unit 60. Based on the instruction from the main control unit 1, the reading control unit 60 controls the reading operation of the document D. Specifically, the reading control unit 60 controls the operation of the moving motor 6a, the lamp 6b, and the image sensor 6c (line sensor).

[0028] As shown in Fig. 3, a transport and reading contact glass 61 and a table reading contact glass 62 are provided on the upper surface of the document reading unit 6. The front side (nearby side) of the document transport unit 5 of the multifunction device 100 can be opened and closed in the vertical direction. When setting the document D on the table reading contact glass 62, the user lifts the document transport unit 5. The document transport unit 5 also functions as a cover that holds down each contact glass of the document reading unit 6 from above. On the other hand, when the document D is set in the document tray 51, the document transport unit 5 transports the document D toward the transport and reading contact glass 61.

[0029] 3, the document transport section 5 is provided with, in order from the upstream side in the document transport direction (from upstream to downstream), a document tray 51, a paper feed roller 52 (corresponding to a first rotating body), a separation and feeding section 53 (corresponding to a first rotating body), a paper feed sensor 7, a second rotating body 54, a first document transport roller pair 55a, a first timing sensor 71, a back side reading unit 512, a second timing sensor 72, a second document transport roller pair 55b, a third document transport roller pair 55c, a document discharge sensor 73, a document discharge roller pair 56, and a document discharge tray 57. A user places a document D (stack of documents) to be read in the document tray 51.

[0030] To rotate each rotating body of the document transport unit 5, the document transport unit 5 includes a first motor 8 (feed motor), a second motor 9 (secondary paper feed motor), a document transport motor 5a, and a document discharge motor 5b. The transport control unit 50 controls the ON / OFF and rotation speed of the first motor 8, the second motor 9, the document transport motor 5a, and the document discharge motor 5b.

[0031] The document tray 51 is provided with a set sensor 74. The set sensor 74 is a sensor for detecting whether or not a document D is set (placed) on the document tray 51. The output level of the set sensor 74 differs depending on whether or not a document D is set. The output of the set sensor 74 is input to the transport control unit 50. Based on the output of the set sensor 74, the transport control unit 50 recognizes whether or not a document D is present on the document tray 51. The transport control unit 50 notifies the main control unit 1 of the presence or absence of a document D. The main control unit 1 recognizes whether or not a document D is set on the document tray 51.

[0032] The document transport unit 5 feeds and transports the documents D in the document tray 51 one sheet at a time. The document transport unit 5 automatically and continuously sends out the documents D while leaving a gap between the documents. The documents D are finally discharged to the document discharge tray 57. A contact glass 61 for transport and reading is located midway along the document transport path (between the second document transport roller pair 55b and the third document transport roller pair 55c). The area above the contact glass 61 for transport and reading is the reading position for transport and reading. During transport and reading, the main control unit 1 causes the document reading unit 6 to read the image of the document D passing through the contact glass 61 for transport and reading.

[0033] The document transport unit 5 includes a first rotating body that sends out (feeds) the document D set in the document tray 51 one by one. The document transport unit 5 includes a paper feed roller 52 and a separation feed unit 53 as the first rotating body. The paper feed roller 52 is provided at a position where it contacts the downstream end of the document D set in the document tray 51 in the document transport direction. The first motor 8 rotates the paper feed roller 52. During transport and reading, the transport control unit 50 rotates the first motor 8. The paper feed roller 52 rotates and sends out the document D from the document tray 51. The separation feed unit 53 includes a paper feed belt 58, a drive roller 510, a driven roller 511, and a separation roller 59. The paper feed belt 58 is wound around the drive roller 510 and the driven roller 511. The paper feed belt 58 rotates in a direction that sends the document D downstream in the document transport direction.

[0034] The first motor 8 also rotates the drive roller 510. This causes the feed belt 58 to rotate in a direction that sends the document D downstream in the document transport direction. The separation roller 59 is provided at a position facing the feed belt 58. A plurality of documents D may be transported overlapping each other (multiple feed). In some cases, the documents D may be almost completely overlapped, and in other cases, a portion of a preceding document D may be transported overlapping a portion of a following document D. The separation roller 59 rotates in a direction that sends the document D back to the document tray 51. When multiple documents D are transported, the separation roller 59 separates the documents D. The lower document D is sent back toward the document tray 51. The first motor 8 also rotates the separation roller 59. A torque limiter is provided on the rotation shaft of the separation roller 59. When only one document D is transported, the torque limiter causes the separation roller 59 to rotate in a direction that sends the document D downstream in the document transport direction.

[0035] The paper feed sensor 7 is provided between the separation paper feed section 53 and the second rotating body 54. In other words, the paper feed sensor 7 is provided downstream in the document transport direction from the first rotating body (separation paper feed section 53) and upstream in the document transport direction from the second rotating body 54. For example, the paper feed sensor 7 is provided near the exit of the separation paper feed section 53. The paper feed sensor 7 is for detecting the arrival of the leading edge and the passing of the trailing edge of the document D. The paper feed sensor 7 is, for example, an optical sensor.

[0036] The paper feed sensor 7 has a different output level when it detects the presence of the original D and when it does not. The output of the paper feed sensor 7 is input to the transport control unit 50. Based on the output of the paper feed sensor 7, the transport control unit 50 can recognize that the leading edge of the original D (the end on the downstream side in the original transport direction) has reached the paper feed sensor 7. Also, based on the output of the paper feed sensor 7, the transport control unit 50 can recognize that the original D is passing through the paper feed sensor 7. Also, based on the output of the paper feed sensor 7, the transport control unit 50 can recognize that the trailing edge of the original D (the end on the upstream side in the original transport direction) has passed through (left) the paper feed sensor 7.

[0037] The second rotating body 54 and each document transport roller pair transport the document D toward the reading position and the document discharge tray 57. The second rotating body 54 is provided downstream of the first rotating body (separation feeding unit 53) in the document transport direction. The second rotating body 54 is a roller pair. The second motor 9 rotates the second rotating body 54. The document transport motor 5a rotates each document transport roller pair. A document discharge roller pair 56 is provided near the document discharge port (the end of the document transport path). The document discharge roller pair 56 discharges the document D after reading to the document discharge tray 57. The document discharge motor 5b rotates the document discharge roller pair 56. When transporting the document, the transport control unit 50 also rotates the second motor 9, the document transport motor 5a, and the document discharge motor 5b.

[0038] A first timing sensor 71 and a back-side reading unit 512 are provided between the first document transport roller pair 55a and the second document transport roller pair 55b. The first timing sensor 71 is provided upstream of the back-side reading unit 512 in the document transport direction. In a double-sided reading job, the back-side reading unit 512 reads the back side of the document D being transported. The setting of whether to read only one side (front side) of the document D or to read both sides can be performed on the operation panel 3.

[0039] The first timing sensor 71 is, for example, an optical sensor. The output level of the first timing sensor 71 differs depending on whether the presence of the document D is detected or not. The output of the first timing sensor 71 is input to the transport control unit 50. Based on the output of the first timing sensor 71, the transport control unit 50 can recognize that the leading edge of the document D has reached the first timing sensor 71. After recognizing that the leading edge of the document D has reached the first timing sensor 71, the transport control unit 50 causes the back surface reading unit 512 to start reading the document D when a predetermined back surface time has elapsed. The transport control unit 50 uses the first timing sensor 71 to measure the timing of starting back surface reading. By providing the back surface reading unit 512, the front and back surfaces of the document D can be read in one transport.

[0040] The back side reading unit 512 is a CIS type reading unit. The back side reading unit 512 includes a lamp, a lens, and an image sensor (line sensor). The image sensor of the back side reading unit 512 outputs an analog image signal. The analog image signal is input to the image data generating circuit 12. In the case of a job for reading both sides of the document D, the image data generating circuit 12 generates read image data of the back side of the document D.

[0041] 3, the document reading unit 6 includes a first moving frame 63, a second moving frame 64, a wire 65, a take-up drum 66, a lens 67, and an image sensor 6c within a housing. The first moving frame 63 includes a lamp 6b that irradiates light onto the document D and a first mirror 681. The second moving frame 64 includes a second mirror 682 and a third mirror 683. The lamp 6b is a light source that irradiates light in the main scanning direction. The lamp 6b includes one or more LEDs.

[0042] A number of wires 65 are attached to the first moving frame 63 and the second moving frame 64. For convenience, only one wire 65 is shown in FIG. 3. The other end of the wire 65 is connected to a winding drum 66. The moving motor 6a rotates the winding drum 66. The moving motor 6a can rotate in both forward and reverse directions. The first moving frame 63 and the second moving frame 64 can be freely moved in the horizontal direction (sub-scanning direction, left and right direction in FIG. 3). This movement allows the irradiation position of the lamp 6b, i.e., the position of the reading line, to be moved.

[0043] The operation panel 3 receives an instruction to start execution of a job. When an instruction to start execution of a job to read a document D is given, the main control unit 1 checks whether or not a document D is set in the document tray 51. When a document D is set, the main control unit 1 causes the document transport unit 5 and the document reading unit 6 to transport and read the document. Specifically, the main control unit 1 causes the document transport unit 5 to transport the document D. The main control unit 1 also causes the document reading unit 6 to read the document D that passes through the contact glass 61 for transport and reading. In this case, the reading control unit 60 positions the first moving frame 63 and the second moving frame 64 below the contact glass 61 for transport and reading.

[0044] When no document D is set on the document tray 51, the main control unit 1 causes the document reading unit 6 to read the document D set on the table reading contact glass 62 (table reading). In this case, the reading control unit 60 moves the first moving frame 63 and the second moving frame 64 in the sub-scanning direction. Note that the main control unit 1 does not cause the document transport unit 5 to transport the document D.

[0045] A second timing sensor 72 is provided downstream of the back side reading unit 512 in the document transport direction and upstream of the second document transport roller pair 55b in the document transport direction. For example, the second timing sensor 72 is an optical sensor. The second timing sensor 72 has a different output level when it detects the presence of the document D and when it does not detect it. The output of the second timing sensor 72 is input to the transport control unit 50 and the reading control unit 60. Based on the output of the second timing sensor 72, the transport control unit 50 and the reading control unit 60 recognize that the leading edge of the document D has reached the second timing sensor 72. After recognizing that the leading edge of the document D has reached the second timing sensor 72, the reading control unit 60 causes the image sensor to start reading the document D when a predetermined front surface time has elapsed. The front surface time is a time according to the transport speed of the document D. The reading control unit 60 uses the second timing sensor 72 to measure the timing of starting to read the front surface of the document D.

[0046] When reading the original D, the reading control unit 60 turns on the lamp 6b. The lamp 6b illuminates the original D. The light reflected by the original D is incident on the image sensor 6c via each mirror and the lens 67. The image sensor 6c is a line sensor. The image sensor 6c is capable of color reading. Each light receiving element of the image sensor 6c outputs an analog signal (analog image signal) according to the amount of received light. The analog image signal is input to the image data generation circuit 12. Based on the input analog image signal, the image data generation circuit 12 generates read image data.

[0047] (Registration mode) Next, an example of document transport in the registration-less mode according to the embodiment will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of document transport in the registration mode according to the embodiment.

[0048] In the multifunction device 100, either a registration mode or a registration-less mode can be selected as the feeding and reading mode. The operation panel 3 accepts the selection of whether to use the registration mode or the registration-less mode. The user selects the mode to be used in the feeding and reading.

[0049] In the registration mode, the document D is abutted against the second rotating body 54, causing the document D to bend and correct the skew of the document D. In other words, in this mode, the second rotating body 54 is used as a conventional registration roller pair. The document D being transported stops temporarily. Therefore, in the registration mode, the number of sheets read per unit time is smaller than in the registrationless mode. A user who wants to obtain image data with less image tilt even if the number of sheets read per unit time is small selects the registration mode. Conversely, a user who wants to read more sheets per unit time, even if the image may be tilted, selects the registrationless mode.

[0050] An example of the flow of document transport in the registration mode will be described below with reference to Fig. 4. The start of Fig. 4 is the point in time when transport and reading of document D starts in the registration mode. For example, this is the point in time when the user operates the start button on the operation panel 3 after document D is set on document tray 51.

[0051] First, the transport control unit 50 starts feeding one sheet of document D (Step #11). The transport control unit 50 rotates the first rotating body (first motor 8). At this time, the transport control unit 50 stops the rotation of the second rotating body 54 (second motor 9). Based on the output of the paper feed sensor 7, the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7 (Step #12). After recognizing that the leading edge of the document D has reached the paper feed sensor 7, the transport control unit 50 continues to rotate the first motor 8 for a predetermined time (Step #13).

[0052] The predetermined time is the time required to transport the original D the skew correction distance after the leading edge of the original D is detected by the feed sensor 7. The distance from the original detection position of the feed sensor 7 to the nip of the second rotating body 54 is denoted as α. The distance the original D is transported to bend the original D is denoted as β. The skew correction distance is α+β. After being transported for the predetermined time, the leading edge of the original D (the downstream end in the original transport direction) hits the second rotating body 54. Due to the elasticity of the original D that has been bent, the leading edge of the original D moves along the nip of the second rotating body 54. This corrects the skew of the original D.

[0053] After the first motor 8 has rotated for a predetermined time, the transport control unit 50 starts rotating the second rotating body 54 (Step #14). The transport control unit 50 also rotates each document transport roller pair and the document discharge roller pair 56 (Step #15). The transport control unit 50 rotates each motor so that the document D is transported at a predetermined transport speed. Note that when the transport of the first document D starts, the transport control unit 50 may immediately rotate the document transport motor 5a and the document discharge motor 5b. The transport control unit 50 continues to rotate the document transport motor 5a and the document discharge motor 5b until the last document D is discharged (except when a jam occurs).

[0054] On the other hand, as for the first motor 8, when a predetermined time has elapsed after the second motor 9 has started to rotate, the transport control unit 50 stops the first motor 8 and the first rotating body (the paper feed roller 52 and the separation feed unit 53) (Step #16). This is to prevent the next document D from being sent out immediately after the preceding document D. After the second rotating body 54 is in a state of pulling the document D, the transport control unit 50 stops the first motor 8. For example, after the second motor 9 has started to rotate, the transport control unit 50 stops the first motor 8 before the rear end of the document D passes the paper feed sensor 7.

[0055] After that, the transport control unit 50 also stops the second rotating body 54 and the second motor 9 (Step #17). This is to abut the next document D against the second rotating body 54. For example, the transport control unit 50 stops the second motor 9 after the transport distance after the second rotating body 54 starts to rotate exceeds the distance from the nip of the first document transport roller pair 55a to the nip of the second rotating body 54. In other words, the transport control unit 50 stops the second motor 9 after the first document transport roller pair 55a is in a state of pulling the document D.

[0056] Then, the transport control unit 50 determines whether the last document D of the document stack has been fed (step #18). For example, the transport control unit 50 checks the output level of the set sensor 74. When the output level is at a level indicating that no document D is present, the transport control unit 50 determines that the last document D has been fed. When the output level is at a level indicating that a document D is present, the transport control unit 50 determines that the last document D has not been fed (document D remains).

[0057] When it is determined that the last document D has not been fed (No in step #18), the transport control unit 50 executes step #11 (return to step #11). When it is determined that the last document D has been fed (Yes in step #18), the transport control unit 50 ends the transport of the document D (END). For example, when the last document D is discharged to the document discharge tray 57, the transport control unit 50 stops all motors.

[0058] (Registrationless Mode) Next, the registration-less mode according to the embodiment will be described with reference to Fig. 5 and Fig. 6. Fig. 5 is a diagram showing an example of the transport speed definition data D1 according to the embodiment. Fig. 6 is a diagram showing an example of document transport in the registration-less mode according to the embodiment.

[0059] First, the registration-less mode is a mode in which the document D does not abut against any of the rotating bodies (second rotating body 54, each document transport roller pair, document discharge roller pair 56) downstream of the first rotating body in the document transport direction. Except for the case in which the set document D protrudes significantly downstream in the document transport direction, the transport control unit 50 transports the document D, which has started to be fed, to the document discharge tray 57 without stopping it. The characteristics of the registration-less mode are listed below.

[0060] (Feature 1) The document D is not pressed against the pair of rollers. Since the document D is not butted against the paper, the registration-less mode can be said to be a mode in which skew of the document D is not corrected. In the registration-less mode, the time required for skew correction can be saved. In the registration-less mode, the number of sheets read per unit time during conveying and reading is greater than in the registration mode due to the specifications.

[0061] (Feature 2) The document D is not temporarily stopped at the rotating body downstream of the first rotating body in the document transport direction. Since there is no temporary stop, the transport control unit 50 may continue to rotate the second motor 9 (second rotating body 54), the document transport motor 5a (each document transport roller pair), and the document discharge motor 5b (document discharge roller pair 56) from the start of transport of the first document D to the completion of transport of the last document D. The start of transport of the first document D is the point at which the first motor 8 starts to rotate in order to feed the first document D. The completion of transport of the last document D is the point at which the document discharge sensor 73 recognizes the passage of the rear end of the last document D. The registration-less mode can be said to be a mode with higher productivity than the registration mode.

[0062] (Feature 3) The rotation speed of the first motor 8 (first rotating body) is controlled to keep the gap (paper gap) between the documents D constant. In the registration-less mode, the paper gap cannot be controlled using the registration roller pair. Therefore, the rotation speed of the first motor 8 (first rotating body) is controlled to prevent the gap between the document D to be fed and the preceding document D from becoming too narrow.

[0063] (Feature 4) During feeding of one document D, the transport speed of the first rotating body is changed from the first transport speed V1 to the second transport speed V2. Even though the second rotating body 54 has started conveying (even though the document D has entered the second rotating body 54), if there is a difference in conveying speed between the first rotating body 54 and the second rotating body 54, a problem such as a blockage may occur. Therefore, when the leading edge of the document D reaches the second rotating body 54, the conveying control unit 50 changes the rotation speed of the first motor 8 in accordance with the conveying of the second rotating body 54.

[0064] Specifically, in the registrationless mode, the transport control unit 50 changes the rotation speed of the first motor 8 during feeding of one sheet of the original D from a rotation speed at which the original D is transported at a first transport speed V1 to a rotation speed at which the original D is transported at a second transport speed V2. Hereinafter, the rotation speed of the first motor 8 at which the original D is transported at the first transport speed V1 is referred to as the "first rotation speed." Also, the rotation speed of the first motor 8 at which the original D is transported at the second transport speed V2 is referred to as the "second rotation speed."

[0065] (Feature 5) The second rotating body 54, each document transport roller pair, and document discharge roller pair 56 transport the document D at a second transport speed V2. In the registration-less mode, the rotating body downstream of the first rotating body in the document transport direction is rotated so that the document D is transported at the second transport speed V2. Specifically, the transport control unit 50 rotates the second motor 9 so that the peripheral speed of the roller of the second rotating body 54 becomes the second transport speed V2. The transport control unit 50 also rotates the document transport motor 5a so that the peripheral speed of the roller of each document transport roller pair becomes the second transport speed V2. The transport control unit 50 also rotates the document discharge motor 5b so that the peripheral speed of the roller of the document discharge roller pair 56 becomes the second transport speed V2.

[0066] In summary, when the documents D set on the document tray 51 are fed one by one, from the start of conveyance of the first document D to the end of conveyance of the last document D, the conveyance control unit 50 does not strike the document D against any of the rotating bodies downstream of the first rotating body in the document conveyance direction. Then, the conveyance control unit 50 continues to rotate the rotating body downstream of the first rotating body in the document conveyance direction, and causes the rotating body to convey the document D at the second conveyance speed V2.

[0067] The data size of the scanned image data varies depending on the set values ​​of the scanning resolution and color. In other words, the amount of data to be generated and processed varies depending on these set values. In the multifunction device 100, the second transport speed V2 varies depending on the combination of the set value of the scanning resolution and the set value of color / monochrome. Regardless of the combination, the first transport speed V1 is predetermined and is the same (constant). For example, the transport storage unit 50b (ROM) stores in a non-volatile manner the transport speed definition data D1 that defines the second transport speed V2 corresponding to the selected resolution and color setting. FIG. 5 is a diagram showing an example of the transport speed definition data D1.

[0068] The document reading unit 6 and the back side reading unit 512 have multiple reading resolutions. For example, the document reading unit 6 and the back side reading unit 512 can read at a resolution of either 300 dpi or 600 dpi. The operation panel 3 accepts the setting of the reading resolution. When the resolution is doubled in both the vertical and horizontal directions, the amount of data is quadrupled. Between 300 dpi and 600 dpi, it takes longer to read at 600 dpi.

[0069] Furthermore, when scanning color, image data for each of the color components R (Red), G (Green), and B (Blue) is generated. When scanning monochrome, gray image data is generated. Because there are more color components, processing color image data takes more time than processing monochrome image data.

[0070] 5, for example, in color / 300 dpi reading and monochrome / 300 dpi reading, the second conveying speed V2 is set to a first speed. In color / 600 dpi reading, the second conveying speed V2 is set to a second speed. In monochrome / 600 dpi reading, the second conveying speed V2 is set to a third speed.

[0071] The second conveying speed V2 is determined in consideration of the amount of image data processed and the time required for reading. In the document conveying unit 5 (multifunction device 100), the relationship is first speed>first conveying speed V1>third speed>second speed. For example, the first speed is about 750 to 800 mm / s. For example, the first conveying speed V1 is about 600 to 700 mm / s. For example, the second speed is about 250 to 350 mm / s. For example, the third speed is faster than the second speed by about 15 to 150 mm / s. At the second conveying speed V2, the document D enters the reading position (rear surface reading unit 512, contact glass 61 for conveying and reading). The faster the second conveying speed V2, the higher the productivity.

[0072] Next, an example of the flow of document transport in the registrationless mode according to the embodiment will be described with reference to Fig. 6. Fig. 6 describes an example of transporting and reading a plurality of documents D. The start of Fig. 6 is the point in time when an instruction is given to start a job to transport and read the document D. For example, it is the point in time when the start button is operated on the operation panel 3 for a job to transport and read the document D.

[0073] First, the transport control unit 50 sets the second transport speed V2 (step #21). For example, the main control unit 1 determines the second transport speed V2 based on the setting value of the job to be executed and the transport speed definition data D1. The main control unit 1 notifies the transport control unit 50 of the determined second transport speed V2. The transport control unit 50 sets the notified speed as the second transport speed V2. The second transport speed V2 may be faster or slower than the first transport speed V1.

[0074] Next, the transport control unit 50 starts rotating the first motor 8 to feed the first sheet of the document D (Step #22). When the document D is the first sheet of the document, there is no need to consider the distance between the first sheet of the document D and the preceding document D. Therefore, for the first sheet of the document D, the transport control unit 50 may continue to rotate the first motor 8 at the second rotation speed (the speed at which the document D is transported at the second transport speed V2).

[0075] Furthermore, the transport control unit 50 starts the rotation of each motor (the second motor 9, the document transport motor 5a, and the document discharge motor 5b) other than the first motor 8 (Step #23). Until the transport of the last document D is completed, the transport control unit 50 rotates each motor at a rotation speed at which the document D is transported at the second transport speed V2.

[0076] The sent original D passes through the transport and reading contact glass 61. When passing through, the original reading unit 6 reads the original D. The transport control unit 50 causes the original D that has passed through the transport and reading contact glass 61 to be discharged onto the original discharge tray 57.

[0077] In preparation for transporting the next document D, the transport control unit 50 stops the first motor 8 (Step #24). After it is recognized that the leading edge of the document D has reached the paper feed sensor 7, the transport control unit 50 stops the first motor 8 after the leading edge of the document D enters the second rotating body 54. The transport control unit 50 also stops the first motor 8 by the time it detects that the trailing edge of the document D has passed the paper feed sensor 7.

[0078] The time (feed time) until the first motor 8 starts to stop after the leading edge of the document D is detected to have reached the paper feed sensor 7 may be determined in advance. Furthermore, when the transport distance of the document D after the leading edge of the document D is detected to have reached the paper feed sensor 7 becomes the distance from the paper feed sensor 7 to the nip of the second rotating body 54 plus a margin, the transport control unit 50 may stop the first motor 8.

[0079] Based on the output of the set sensor 74, the transport control unit 50 checks whether or not the original D remains (Step #25). If the original D does not remain (No in Step #25), the transport control unit 50 ends the transport of the original D (Step #26 → End). For example, when the last original D is discharged, the transport control unit 50 stops the second motor 9, the original transport motor 5a, and the original discharge motor 5b.

[0080] If originals D remain (Yes in step #25), the transport control unit 50 starts the rotation of the first motor 8 to start feeding the next original D (step #27). For the second or subsequent originals D, when the transport control unit 50 recognizes that the rear end of the preceding original D has passed the feed sensor 7, it starts feeding the next original D. For the second or subsequent originals D, the transport control unit 50 finely controls the rotation speed of the first motor 8.

[0081] Furthermore, in order to control the rotation of the first motor 8, the transport control unit 50 measures the time (measurement time T0) from when the first motor 8 starts to rotate until it is recognized that the leading edge of the document D has reached the paper feed sensor 7 for each document D (step #28). The transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7 based on the output of the paper feed sensor 7.

[0082] Based on the length of the measured time T0, the transport control unit 50 controls the rotation speed of the first motor 8 (step #29). For the second and subsequent sheets of original D, the transport control unit 50 finely controls the rotation speed of the first motor 8 to adjust the distance between the original D that has started to be fed and the preceding original D (the original D one sheet before) (details will be described later). Then, the transport control unit 50 executes step #24 (return to step #24). The transport control unit 50 repeats feeding of original D until all originals D are fed.

[0083] While the measurement time T0 is being measured (the period from when the transport control unit 50 starts feeding until it detects that the leading edge of the document D has reached the transport control unit 50), the transport control unit 50 transports the document D at a speed equal to or lower than the first transport speed V1. The transport control unit 50 sets the rotation speed of the first motor 8 to be equal to or lower than the first rotation speed (first rotation speed=speed at which the document D is transported at the first transport speed V1).

[0084] For the second and subsequent sheets of document D, after it is recognized that the leading edge of document D has reached the paper feed sensor 7, the transport control unit 50 transports document D at a transport speed equal to or lower than the second transport speed V2 until it is stopped. The transport control unit 50 sets the rotation speed of the first motor 8 to be equal to or lower than the second rotation speed (second rotation speed=speed at which document D is transported at the second transport speed V2).

[0085] (Control of first motor 8) Next, an example of rotation control of the first motor 8 in the registration-less mode according to the embodiment will be described with reference to Figs. 7 to 14. Figs. 7 to 14 are diagrams showing an example of rotation control of the first motor 8 in the registration-less mode according to the embodiment. Figs. 7 to 10 show an example of control when the second conveying speed V2 is faster than the first conveying speed V1 (when the second conveying speed V2 = the first speed). Figs. 11 to 14 show an example of control when the second conveying speed V2 is slower than the first conveying speed V1 (when the second conveying speed V2 = the second speed or the third speed).

[0086] In the following, an example in which a stepping motor is used as the first motor 8 will be described. The transport control unit 50 can change the frequency of a pulse signal (clock signal) input to the stepping motor to change the rotation speed of the first motor 8. If the frequency changes too rapidly, the first motor 8 will step out. In the multifunction device 100, the rate of change of the frequency of the pulse signal, that is, the acceleration and deceleration (negative acceleration) of the rotation speed of the stepping motor, are predetermined. The transport control unit 50 changes the rotation speed of the first motor 8 at the predetermined acceleration and deceleration. Specifically, in the multifunction device 100, the absolute value of the acceleration and the absolute value of the deceleration are equal. When the first motor 8 accelerates and decelerates, the positive and negative slopes of the speed change are different, but the absolute value of the slope is equal.

[0087] First, an example of rotation control of the first motor 8 when starting feeding of the second or subsequent sheets of the document D in the registrationless mode and when the second conveying speed V2>the first conveying speed V1 (when the document is color or monochrome and has a resolution of 300 dpi) will be described with reference to Fig. 7 to Fig. 10. Four patterns will be described below.

[0088] (Pattern 1) (Condition 1) Required paper interval time - Measurement time T0 ≦ Required speed change time T1 When (Condition 1) is satisfied, the transport control unit 50 performs the control of Pattern 1. The required inter-page time is a time determined in advance to ensure that a certain interval is maintained between documents D. The required inter-page time is a time indicating the interval between documents D. For example, it is determined in advance in the specifications, such as 100 ms. The speed change time T1 is the time required to change from the first rotation speed to the second rotation speed. The speed change time T1 is, for example, any value within a range of several milliseconds to several tens of milliseconds. Since the first conveying speed V1 and the second conveying speed V2 are fixed, the speed change time T1 in patterns 1 to 4 can be treated as a constant.

[0089] FIG. 7 shows an example of the rotation speed control of the first motor 8 in pattern 1. The horizontal axis in FIG. 7 indicates time. The vertical axis in FIG. 7 indicates the transport speed. The intersection of the vertical and horizontal axes indicates the time when the first motor 8 starts to rotate (the time when feeding of each original D from the second sheet onwards begins). Specifically, the time when feeding of each original D from the second sheet onwards begins is the time when the transport control unit 50 recognizes, based on the output of the feed sensor 7, that the rear end of the preceding original D has passed the feed sensor 7.

[0090] If the document D being fed does not protrude downstream in the document transport direction, the measurement time T0 will be long. After the document D has been transported at the first transport speed V1 for a certain amount of time, the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. Transforming the equation of (Condition 1) gives: Required paper interval time-Time required for speed change T1≦Measurement time T0. If the measurement time T0 is long, (Condition 1) is satisfied. If the measurement time T0 is long, it can be considered that there is a sufficient gap between the document D being fed and the preceding document D (the document D one document before).

[0091] 7 is the point in time when the rotation speed of the first motor 8 reaches the first rotation speed after the first motor 8 starts to rotate (the point in time when the transport speed of the original D becomes the first transport speed V1). When the point in time P1 is reached, the transport control unit 50 rotates the first motor 8 at a constant speed at the first rotation speed. The point in time P2 is the point in time when the transport control unit 50 recognizes that the leading edge of the original D has reached the paper feed sensor 7. The measurement time T0 extends from the vertical axis in FIG. 7 to the point in time P2.

[0092] When it is recognized that the leading edge of the document D has reached the paper feed sensor 7, the transport control unit 50 changes the transport speed of the document D. Specifically, the transport control unit 50 changes (accelerates) the rotation speed of the first motor 8 from the first rotation speed to the second rotation speed. Time point P3 is the time point when the speed change (acceleration) from the first rotation speed to the second rotation speed is completed. Thereafter, the first rotating body transports the document D at the first speed. Until the first motor 8 stops, the transport control unit 50 rotates the first motor 8 at a constant speed at the second rotation speed (from time point P3 onwards). The interval between time point P2 and time point P3 is the speed change required time T1.

[0093] (Pattern 2) (Condition 2) Required paper interval time - Measurement time T0 > Required speed change time T1 (Condition 3) Required paper interval time - Measurement time T0 ≦ Required speed change time T1 + Required first stop time T2 + Required first acceleration time T3 When (Condition 2) is satisfied and (Condition 3) is satisfied, the transport control unit 50 performs the control of Pattern 2. The first required stop time T2 is the time required for the first motor 8 to stop from the first rotation speed (see FIG. 9). The first required acceleration time T3 is the time required from the start of rotation to reaching the first rotation speed (see FIG. 9). In the multifunction device 100, the absolute value of the slope of the speed change is the same during acceleration and deceleration. Therefore, the first required stop time T2 and the first required acceleration time T3 are equal and can be treated as constants. The first required stop time T2 and the first required acceleration time T3 are, for example, several tens of milliseconds.

[0094] When a document D that protrudes slightly downstream in the document transport direction is fed, the measurement time T0 is shorter than in the case of pattern 1. When the measurement time T0 is shorter than (required paper interval time-speed change required time T1), condition 2 is met. Then, the transport control unit 50 determines whether or not to stop the first motor 8 based on (condition 3). When (condition 3) is met, the transport control unit 50 determines to decelerate but not to stop the first motor 8.

[0095] An example of the rotation speed control of the first motor 8 in the case of pattern 2 will be described with reference to Fig. 8. Time point P4 is the time point at which the rotation speed of the first motor 8 reaches the first rotation speed after the first motor 8 starts to rotate. When time point P4 is reached, the conveyance control unit 50 rotates the first motor 8 at a constant speed, that is, the first rotation speed.

[0096] Time point P5 is the time point when the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. The period from the vertical axis of FIG. 8 to time point P5 is the measurement time T0. Upon recognizing that the leading edge of the document D has reached the paper feed sensor 7, the transport control unit 50 decelerates the rotation speed of the first motor 8 from the first rotation speed. After deceleration, the transport control unit 50 accelerates the rotation speed of the first motor 8 to the second rotation speed. Time point P5 indicates the start of the deceleration. Time point P6 indicates the end of the deceleration and the start of the acceleration of the rotation speed of the first motor 8.

[0097] Time point P7 indicates the time point when the rotation speed of the first motor 8 reaches the first rotation speed. Time point P8 indicates the time point when the rotation speed of the first motor 8 reaches the second rotation speed. The interval between time points P7 and P8 is the speed change required time T1. After that, the conveyance control unit 50 rotates the first motor 8 at a constant speed, at the second rotation speed, until the first motor 8 stops (from time point P8 onwards).

[0098] The transport control unit 50 determines the length of the period T4 during which the first motor 8 is decelerated based on the following (Equation 1). (Formula 1) Period T4 = (required paper interval time - measurement time T0 - speed change time T1) / 2 In other words, the transfer control unit 50 obtains ½ of the period from time P5 to time P7.

[0099] The transport control unit 50 continues to decelerate the rotation speed of the first motor 8 for the determined time. Then, when acceleration is resumed, the transport control unit 50 returns the rotation speed of the first motor 8 to the first rotation speed over the determined time (the same time as the deceleration).

[0100] When formula 1 is compared with FIG. 8, the period from when the first motor 8 starts to rotate until the rotation speed of the first motor 8 reaches the second rotation speed corresponds to the required paper interval time. In other words, the transport control unit 50 controls the first motor 8 so that the period from when the rotation starts to when the motor starts to rotate at a constant speed at the second rotation speed corresponds to the required paper interval time. For each document D, transport at the second transport speed V2 can be started after the required paper interval time has elapsed from the start of paper feeding. This makes it possible to prevent the paper interval from becoming too narrow.

[0101] (Pattern 3) (Condition 4) Required paper interval time - Measurement time T0 > Required time for shifting T1 + Required time for first stop T2 + Required time for first acceleration T3 (Condition 5) After the first motor 8 starts rotating, it is accelerated to the first rotation speed, and then the leading edge of the document D reaches the paper feed sensor 7. * Gear shift time T1 is the same as pattern 1 *The first stopping time T2 and the first acceleration time T3 are the same as in pattern 2.

[0102] When the original D protrudes significantly downstream in the original transport direction, the measurement time T0 becomes even shorter than in the case of pattern 2. For example, immediately after the first motor 8 has completed accelerating to the first rotation speed, the transport control unit 50 recognizes that the leading edge of the original D has reached the paper feed sensor 7. It can be considered that the gap between the original D being fed and the preceding original D is quite narrow. When (Condition 5) is met, the transport control unit 50 determines whether or not to stop the first motor 8 based on (Condition 4). When (Condition 4) is met, the transport control unit 50 determines to temporarily halt the first motor 8.

[0103] An example of the rotation speed control of the first motor 8 in the case of pattern 3 will be described with reference to Fig. 9. Time point P9 is the time point when the rotation speed of the first motor 8 reaches the first rotation speed after the first motor 8 starts rotating. The transport control unit 50 maintains the rotation speed of the first motor 8 at the first rotation speed. However, in the example of Fig. 9, the time for which the rotation speed is maintained is quite short (the period between time points P9 and P10).

[0104] Time point P10 is the time point when the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. The period from the vertical axis of Fig. 9 to P10 is the measurement time T0. In the case of measurement time T0 that satisfies (Condition 4), when it recognizes that the leading edge of the document D has reached the paper feed sensor 7, the transport control unit 50 decelerates the rotation speed of the first motor 8 from the first rotation speed. Time point P10 indicates the start time of deceleration.

[0105] The deceleration continues, and finally the transport control unit 50 stops the first motor 8. Time P11 indicates the time when the first motor 8 is stopped. After the motor is stopped, as time passes, the transport control unit 50 accelerates the rotation of the first motor 8 to the second rotation speed. Time P12 indicates the time when the acceleration starts. Time P13 indicates the time when the first motor 8 reaches the first rotation speed. When the acceleration is resumed, the transport control unit 50 returns the rotation speed of the first motor 8 to the first rotation speed over the determined time (the same time as the deceleration). In the multifunction device 100, the time length from time P10 to time P11 is equal to the time length from time P12 to time P13.

[0106] Time point P14 indicates the time point when the rotation speed of the first motor 8 becomes the second rotation speed. Until the first motor 8 stops, the transport control unit 50 rotates the first motor 8 at a constant speed at the second rotation speed (after time point P14). Between time points P11 and P12, the transport control unit 50 stops the first motor 8.

[0107] Based on the following (Equation 2), the transport control unit 50 determines the length of the first stop time T5. In the case of pattern 3, the first stop time T5 is the time during which the first motor 8 continues to be stopped. (Formula 2) First stop time T5 = (required paper interval time - measurement time T0 - required speed change time T1 - required first stop time T2 - required first acceleration time T3)

[0108] In Fig. 9, measured time T0 is the period from the vertical axis to time P10. Required gear shift time T1 is the period from time P13 to time P14. Required first stop time T2 is the period from time P10 to time P11. Required first acceleration time T3 is the period from time P12 to P13. As described above, required gear shift time T1, required first stop time T2, and required first acceleration time T3 can be treated as constants.

[0109] In pattern 3, the transport control unit 50 treats the period from the vertical axis in FIG. 9 to time point P14 as the required paper interval time. Based on (Equation 2), the transport control unit 50 calculates the first stop time T5 by subtracting the measurement time T0, the speed change required time T1, the first stop required time T2, and the first acceleration required time T3 from the required paper interval time. When the first motor 8 is decelerated and stopped, the transport control unit 50 keeps the first motor 8 stopped for the first stop time T5. This makes it possible to widen the paper interval. After the required paper interval time has elapsed from the start of paper feeding, transport at the second transport speed V2 can be started. This makes it possible to prevent the paper interval from becoming too narrow.

[0110] (Pattern 4) (Condition 6) After starting rotation, the leading edge of the document D is detected as reaching the paper feed sensor 7 before the rotation speed of the first motor 8 reaches the first rotation speed. In the case of paper with high friction or paper that easily sticks to itself, such as glossy paper, document D is likely to be dragged by the preceding document D. When document D that protrudes significantly downstream in the document transport direction is fed, measurement time T0 becomes even shorter than in the case of pattern 3. For example, immediately after the first motor 8 starts to rotate, the transport control unit 50 recognizes that the leading edge of document D has reached the paper feed sensor 7. This can be considered to mean that the gap between the document D being fed and the preceding document D is too narrow.

[0111] When (Condition 6) is satisfied, the conveyance control unit 50 stops the first motor 8. In other words, when (Condition 6) is satisfied, the conveyance control unit 50 determines that it is necessary to secure the paper gap by stopping the first motor 8.

[0112] An example of the rotation speed control of the first motor 8 in the case of pattern 4 will be described using FIG. 10. Time point P15 is the time point when the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. At time point P15, the first motor 8 has not reached the first rotation speed. In this case, the transport control unit 50 decelerates the rotation speed of the first motor 8. The transport control unit 50 starts decelerating at time point P15. The transport control unit 50 stops the first motor 8. Time point P16 in FIG. 10 indicates the time point when the first motor 8 stops.

[0113] After stopping, the transport control unit 50 accelerates the rotation speed of the first motor 8 to the second rotation speed. Time point P17 is the time point when the first motor 8 resumes rotation. Time point P18 indicates the time point when the rotation speed of the first motor 8 becomes the first rotation speed. The length of the period between time point P17 and time point P18 is the first acceleration required time T3. Time point P19 indicates the time point when the rotation speed of the first motor 8 becomes the second rotation speed. After that, until the first motor 8 stops, the transport control unit 50 rotates the first motor 8 at a constant speed at the second rotation speed (from time point P19 onwards).

[0114] Between time points P16 and P17 (first waiting time T6), the transport control unit 50 stops the first motor 8. Based on the following (Equation 3), the transport control unit 50 determines the length of the first waiting time T6 of the first motor 8. The first waiting time T6 is the time during which the first motor 8 continues to be stopped in pattern 4. (Formula 3) First waiting time T6 = (required paper interval time - measurement time T0 - time required from the start of deceleration of the accelerated first motor 8 to its stop (time T7) - time required for the rotation speed of the stopped first motor 8 to reach the second rotation speed)

[0115] In FIG. 10, the measured time T0 is the period from the vertical axis to time P15. Time T7 is the period from time P15 to time P16. The transport control unit 50 may measure the time T7 from time P15 to time P16. Also, since the absolute values ​​of the acceleration and deceleration are the same, the time T7 should be the same as the measured time T0. Therefore, the transport control unit 50 may substitute the measured time T0 for the time T7. The time until the rotation speed of the first motor 8 in the stopped state reaches the second rotation speed is the period from time P17 to time P19. The period from time P17 to time P19 is the sum of the first acceleration required time T3 and the speed change required time T1. The period from time P17 to time P19 can be treated as a constant.

[0116] That is, in pattern 4, the transport control unit 50 treats the period from the vertical axis in FIG. 10 to time point P19 as the necessary paper interval time. Based on (Equation 3), the transport control unit 50 calculates the first waiting time T6. When the transport control unit 50 decelerates and stops the first motor 8, it keeps the first motor 8 stopped for the first waiting time T6. This makes it possible to widen the paper interval. After the necessary paper interval time has elapsed from the start of paper feeding, transport at the second transport speed V2 can be started. This makes it possible to prevent the paper interval from becoming too narrow.

[0117] Next, an example of rotation control of the first motor 8 when starting feeding of the second or subsequent sheets of the document D in the registration-less mode and when the second conveying speed V2 is slower than the first conveying speed V1 will be described with reference to Figs. 11 to 14. Specifically, an example of rotation control of the first motor 8 when reading the document D in color or monochrome with a resolution of 600 dpi will be described. Four patterns of rotation control of the first motor 8 will be described below.

[0118] (Pattern 5) (Condition 7) Required paper interval time - Measurement time T0 ≦ Required speed change time T1 When (Condition 7) is satisfied, the transport control unit 50 performs the control of Pattern 5. The required inter-sheet time is the same as in patterns 1 to 4. The speed change required time T1 is the time required to change from the first rotation speed to the second rotation speed. Since the second conveying speed V2 is different, the speed change required time T1 in patterns 5 to 8 may be different from the speed change required time T1 in patterns 1 to 4. The speed change required time T1 in patterns 5 to 8 is, for example, any value within a range of several milliseconds to several tens of milliseconds. In the cases of patterns 5 to 8 as well, the first conveying speed V1 and the second conveying speed V2 are fixed, so the speed change required time T1 can be treated as a constant.

[0119] 11 shows an example of the rotation speed control of the first motor 8 in pattern 5. The intersection of the vertical axis and the horizontal axis indicates the time when the first motor 8 starts to rotate (the time when feeding of each document D from the second sheet onwards starts). Specifically, the transport control unit 50 starts to rotate the first motor 8 when it recognizes, based on the output of the paper feed sensor 7, that the rear end of the preceding document D has passed the paper feed sensor 7.

[0120] When the amount of protrusion of the document D downstream in the document transport direction during feeding is small, the measurement time T0 becomes long. After the document D has been transported at the first transport speed V1 for a certain period of time, the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. When the measurement time T0 is equal to or greater than (required paper interval time-time required for speed change T1), (Condition 7) is satisfied. When the measurement time T0 is long, it can be considered that there is a sufficient gap between the preceding document D and the document D being fed.

[0121] An example of the rotation speed control of the first motor 8 in the case of pattern 5 will be described with reference to FIG. 11. Time point P20 is the time point when the rotation speed of the first motor 8 reaches the first rotation speed after the start of rotation. When the time point P20 is reached, the transport control unit 50 rotates the first motor 8 at a constant speed at the first rotation speed. In FIG. 11, time point P21 is the time point when the transport control unit 50 recognizes the arrival of the leading edge of the document D at the paper feed sensor 7. In FIG. 11, the period from the vertical axis to P21 is the measurement time T0. When the transport control unit 50 recognizes the arrival of the leading edge of the document D at the paper feed sensor 7, the transport control unit 50 changes (decelerates) the rotation speed of the first motor 8 from the first rotation speed to the second rotation speed. The transport control unit 50 changes the transport speed of the document D. Time point P22 is the time point when the change (deceleration) to the second rotation speed is completed. The conveyance control unit 50 rotates the first motor 8 at a constant speed, the second rotation speed, until the first motor 8 stops (from time P22 onwards). The interval between time P21 and time P22 is the speed change required time T1 in pattern 5.

[0122] (Pattern 6) (Condition 8) Required paper interval time - Measurement time T0 > Required speed change time T1 (Condition 9) Required paper interval time - Measurement time T0 ≦ Required speed change time T1 + Required second stop time T8 + Required second acceleration time T9 When (Condition 8) is satisfied and (Condition 9) is satisfied, the transport control unit 50 performs the control of Pattern 6. The second required stop time T8 is the time required for the first motor 8 to stop from the second rotation speed. The second required acceleration time T9 is the time required from when the first motor 8 stops rotating to when it starts rotating and when the rotation speed reaches the second rotation speed (see FIG. 13).

[0123] In the multifunction device 100, the absolute value of the gradient of the speed change during acceleration is the same as during deceleration. Therefore, the second stop required time T8 and the second acceleration required time T9 are equal and can be treated as constants. Note that the second conveying speed V2 is different in patterns 5 to 8 from that in patterns 1 to 4. Therefore, the first stop required time T2 and the second stop required time T8 may be different, and the first acceleration required time T3 and the second acceleration required time T9 may be different. For example, the second stop required time T8 and the second acceleration required time T9 are several tens of milliseconds.

[0124] When the original D is fed so as to protrude slightly downstream in the original transport direction, the measurement time T0 is shorter than in the case of pattern 5. Based on (Condition 9), the transport control unit 50 determines whether or not to stop the first motor 8. When (Condition 8) and (Condition 9) are satisfied, the transport control unit 50 determines to decelerate but not to stop the first motor 8.

[0125] An example of the rotation speed control of the first motor 8 in the case of pattern 6 will be described with reference to FIG. 12. Time point P23 is the time point when the first motor 8 reaches the first rotation speed after the first motor 8 starts rotating. When time point P23 is reached, the transport control unit 50 rotates the first motor 8 at a constant speed at the first rotation speed. Time point P24 is the time point when the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. The period from the vertical axis to P24 is the measurement time T0. When it recognizes that the leading edge of the document D has reached the paper feed sensor 7, the transport control unit 50 decelerates the rotation speed of the first motor 8. After deceleration, the transport control unit 50 sets the rotation speed of the first motor 8 to the second rotation speed.

[0126] Time point P24 indicates the start of deceleration. Time point P25 indicates the time when the first motor 8 temporarily reaches the second rotation speed during the deceleration process. Time point P26 indicates the end of deceleration and the start of acceleration. Time point P27 indicates the time when the rotation speed of the first motor 8 reaches the second rotation speed. Thereafter, the conveyance control unit 50 rotates the first motor 8 at a constant speed, at the second rotation speed, until the first motor 8 stops (from time point P27 onwards). Here, in pattern 6, the time from time point P24 to time point P25 is the speed change required time T1.

[0127] The transport control unit 50 determines the length of the deceleration period T10 of the first motor 8 based on the following (Equation 4). (Formula 4) Deceleration period T10 = (required paper interval time - measurement time T0 - required speed change time T1) / 2 That is, the transport control unit 50 calculates half of the period from time P25 to time P27. The transport control unit 50 continues to decelerate the rotation speed of the first motor 8 throughout the speed change required time T1 and the calculated time. Then, when acceleration is resumed, the transport control unit 50 sets the rotation speed of the first motor 8 to the second rotation speed at the calculated time T10.

[0128] Comparing formula 4 with FIG. 12, in pattern 6, the transport control unit 50 treats the time from when the first motor 8 starts rotating until it reaches the second rotation speed as the required paper interval time. In other words, the transport control unit 50 controls the first motor 8 so that the time from when it starts rotating until it starts rotating at a constant speed at the second rotation speed is the required paper interval time. Transport at the second transport speed V2 can be started after the required paper interval time has elapsed from the start of paper feeding. This makes it possible to prevent the paper interval from becoming too narrow.

[0129] (Pattern 7) (Condition 10) Required paper interval time - Measurement time T0 > Required time for shifting T1 + Required time for second stop T8 + Required time for second acceleration T9 (Condition 11) After the first motor 8 starts rotating, it is accelerated to the first rotation speed, and then the leading edge of the document D reaches the paper feed sensor 7. * Gear shift time T1 is the same as pattern 5 * The second stop time T8 and the second acceleration time T9 are the same as in pattern 6.

[0130] When an original D is fed that protrudes considerably downstream in the original transport direction, the measurement time T0 becomes even shorter than in the case of pattern 6. For example, immediately after the acceleration to the first rotation speed is completed, the transport control unit 50 recognizes that the leading edge of the original D has reached the paper feed sensor 7. It can be considered that the gap between the original D being fed and the preceding original D is quite narrow. When (Condition 11) is satisfied, the transport control unit 50 judges whether or not to stop the first motor 8 based on (Condition 10). When (Condition 10) is satisfied, the transport control unit 50 judges to temporarily halt the first motor 8. When (Condition 10) and (Condition 11) are satisfied, the transport control unit 50 performs the processing of pattern 7.

[0131] An example of the rotation speed control of the first motor 8 in the case of pattern 7 will be described with reference to FIG. 13. Time point P28 is the time point when the rotation speed of the first motor 8 reaches the first rotation speed after the first motor 8 starts rotating. The conveyance control unit 50 maintains the rotation speed of the first motor 8 at the first rotation speed. However, in pattern 7, the time for which the rotation speed is maintained is shorter (the period between time point P28 and time point P29).

[0132] Time point P29 is the time point when the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. The period from the vertical axis to time point P29 is the measurement time T0. If the measurement time T0 satisfies (Condition 10), when the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7, the transport control unit 50 starts decelerating the first motor 8. Time point P29 indicates the start time of deceleration. The deceleration continues, and finally, the transport control unit 50 stops the first motor 8. Time point P30 indicates the time point when the rotation speed of the first motor 8 temporarily becomes the second rotation speed during the deceleration process. Time point P31 indicates the time point when the first motor 8 stops. After the stop, when time has passed, the transport control unit 50 accelerates the rotation speed of the first motor 8 to the second rotation speed.

[0133] Time point P32 indicates the start time of acceleration. Time point P33 indicates the time point when the rotation speed of the first motor 8 becomes the second rotation speed. Thereafter, the conveyance control unit 50 rotates the first motor 8 at a constant speed at the second rotation speed until the first motor 8 stops (from time point P33 onwards). When acceleration is resumed, the conveyance control unit 50 sets the rotation speed of the first motor 8 to the second rotation speed over the second acceleration required time T9. In the multifunction device 100, the length from time point P30 to time point P31 (second stop required time T8) is equal to the length from time point P32 to time point P33 (second acceleration required time T9).

[0134] Between time points P31 and P32, the transport control unit 50 stops the first motor 8. Based on the following (Equation 5), the transport control unit 50 determines the length of a second stop time T11 of the first motor 8. The second stop time T11 is the time during which the first motor 8 continues to be stopped. (Formula 5) Second stop time T11 = (required paper interval time - measurement time T0 - speed change required time T1 - second stop required time T8 - second acceleration required time T9)

[0135] In Fig. 13, measured time T0 is the period from the vertical axis to point P29. Required gear shift time T1 is the period from point P29 to point P30. Required second stop time T8 is the period from point P30 to point P31. Required second acceleration time T9 is the period from point P32 to P33. Because the acceleration and deceleration are fixed, required gear shift time T1, required second stop time T8, and required second acceleration time T9 can be treated as constants.

[0136] In pattern 7, the transport control unit 50 treats the period from the vertical axis in FIG. 13 to time point P33 as the required paper interval time. Based on (Equation 5), the transport control unit 50 calculates the second stop time T11 by subtracting the measurement time T0, the speed change required time T1, the second stop required time T8, and the second acceleration required time T9 from the required paper interval time. When the first motor 8 is decelerated and stopped, the transport control unit 50 keeps the first motor 8 stopped for the second stop time T11. This makes it possible to widen the paper interval. After the required paper interval time has elapsed from the start of paper feeding, transport at the second transport speed V2 can be started. This makes it possible to prevent the paper interval from becoming too narrow.

[0137] (Pattern 8) (Condition 12) After the start of rotation, the leading edge of the document D is detected as reaching the paper feed sensor 7 before the rotation speed of the first motor 8 reaches the first rotation speed.

[0138] When feeding an original D that protrudes significantly downstream in the original transport direction, the measurement time T0 becomes even shorter than in the case of pattern 7. For example, immediately after the first motor 8 starts to rotate, the transport control unit 50 recognizes that the leading edge of the original D has reached the feed sensor 7. This can be considered to be the result of the gap between the original being fed and the preceding original D being too close.

[0139] When (Condition 12) is satisfied, the transport control unit 50 determines that it is necessary to stop the first motor 8 and ensure the paper gap. An example of the rotational speed control of the first motor 8 in the case of pattern 8 will be described with reference to FIG. 14. Time point P34 is the time point when the transport control unit 50 recognizes that the leading edge of the document D has reached the paper feed sensor 7. At time point P34, the rotational speed of the first motor 8 has not reached the first rotational speed. In this case, the transport control unit 50 decelerates the first motor 8. At time point P34, the transport control unit 50 starts to decelerate. The transport control unit 50 stops the first motor 8. Time point P35 indicates the time point when the first motor 8 stops.

[0140] After the first motor 8 is stopped, the transport control unit 50 accelerates the rotation speed of the first motor 8 to the second rotation speed. Time point P36 is the time point when the first motor 8 resumes rotation. Time point P37 indicates the time point when the rotation speed of the first motor 8 becomes the second rotation speed. The interval between time point P36 and time point P37 is the second acceleration required time T9. After that, until the first motor 8 is stopped, the transport control unit 50 rotates the first motor 8 at a constant speed at the second rotation speed (from time point P37 onwards).

[0141] Between time points P35 and P36, the transport control unit 50 stops the first motor 8. Based on the following (Equation 6), the transport control unit 50 determines the length of the second waiting time T12. The second waiting time T12 is the time during which the first motor 8 continues to be stopped in pattern 8. (Formula 6) Second waiting time T12 = (required paper interval time - measurement time T0 - time T13 required from the start of deceleration of accelerated first motor 8 to its stop - second acceleration required time T9)

[0142] In FIG. 14, the measured time T0 is the period from the vertical axis to time P34. The time T13 required from the start of deceleration of the accelerated first motor 8 to stopping is the period from time P34 to time P35. For example, the transport control unit 50 may measure the time from time P34 to time P35. Also, since the absolute values ​​of the acceleration and deceleration are the same, the time T13 should be the same as the measured time T0. Therefore, the transport control unit 50 may substitute the measured time T0 for the time T13. The time required from the stopped state to reach the second rotation speed is the period from time P36 to time P37. The period from time P36 to time P37 is the second acceleration required time T9.

[0143] That is, in pattern 8, the transport control unit 50 treats the period from the vertical axis in FIG. 14 to time point P37 as the required paper interval time. Based on (Equation 6), the transport control unit 50 calculates the second waiting time T12. When the transport control unit 50 decelerates and stops the first motor 8, it keeps the first motor 8 stopped for the second waiting time T12. This makes it possible to widen the paper interval. After the required paper interval time has elapsed from the start of paper feeding, transport at the second transport speed V2 can be started. This makes it possible to prevent the paper interval from becoming too narrow.

[0144] In this manner, the document transport device (multifunction device 100) according to the embodiment includes a document tray 51, a first rotating body (feed roller 52, separation feed section 53), a first motor 8, a second rotating body 54, a second motor 9, a paper feed sensor 7, and a control section (transport control section 50). A plurality of documents D can be set in the document tray 51. The first rotating body sends out the documents D set in the document tray 51 one by one. The first motor 8 rotates the first rotating body. The second rotating body 54 is provided downstream of the first rotating body in the document transport direction, and sends the document D toward the reading position. The second motor 9 rotates the second rotating body 54 so as to transport the document D at a predetermined second transport speed V2. The paper feed sensor 7 is provided downstream of the first rotating body in the document transport direction and upstream of the second rotating body 54 in the document transport direction. The control unit recognizes the arrival of the leading edge of the document D at the paper feed sensor 7 and the passing of the trailing edge of the document D from the paper feed sensor 7 based on the output of the paper feed sensor 7. The control unit starts accelerating the first motor 8 when the transport of the document D starts. After the first motor 8 starts rotating, until the leading edge of the document D reaches the paper feed sensor 7, the control unit rotates the first motor 8 at a rotation speed equal to or lower than a first rotation speed for transporting the document D at a predetermined first transport speed V1. After the leading edge of the document D reaches the paper feed sensor 7, until the trailing edge of the document D passes the paper feed sensor 7, the control unit changes the rotation speed of the first motor 8 to a second rotation speed for transporting the document D at a second transport speed V2. After the rotation speed reaches the second rotation speed, the control unit stops the first motor 8 until the start of the feeding of the next document D. The control unit measures a measurement time T0, which is the time from the start of the rotation of the first motor 8 to the arrival of the leading edge of the document D at the paper feed sensor 7. When the time obtained by subtracting the measured time T0 from the predetermined required paper interval time is longer than the speed change required time T1, the control unit decelerates the first motor 8 and then accelerates it after the deceleration to adjust the paper interval between the document D being fed and the preceding document D. The speed change required time T1 is the time required to change the speed from the first rotation speed to the second rotation speed.

[0145] When a stack of documents is set on the document tray 51 and each document D is fed in succession, the next document D may be pulled (dragged) by the preceding document D. The likelihood of being pulled depends on various factors such as the paper quality, how the documents D are set, and humidity. The further the next document D protrudes downstream in the document transport direction, the shorter the measurement time T0 becomes when the next document D is fed. The measurement time T0 can be used to determine whether the gap between the documents is tight.

[0146] When the measurement time T0 is short, the first motor 8 is decelerated, and the transport of the document D can be intentionally delayed. The gap between the preceding document D and the next document D can be widened. Even if the rotating body downstream of the first rotating body in the document transport direction is not used as the registration roller pair, the gap between the documents D and the next document D can be sufficiently secured. Since the document D does not need to be abutted against the rotating body (roller pair), the operation noise of the document transport device can be suppressed (improved quietness). In addition, since the document D does not need to be temporarily stopped by the registration roller pair, the number of documents D transported (number of documents read) per unit time can be increased (improved productivity). In addition, even if the document D is not temporarily stopped by the registration roller pair, an appropriate gap can be maintained, so the number of documents D transported per unit time can be stabilized (stable productivity).

[0147] (Pattern 1, Pattern 5) In either case where the second conveying speed V2 is faster than the first conveying speed V1 or where the second conveying speed V2 is slower than the first conveying speed V1, when the time obtained by subtracting the measurement time T0 from the required paper interval time is equal to or shorter than the speed change required time T1, the control unit accelerates the first motor 8 to the first rotation speed, and then maintains the rotation speed of the first motor 8 at the first rotation speed. When the control unit recognizes that the leading edge of the document D has reached the paper feed sensor 7, the control unit changes the rotation speed of the first motor 8 to the second rotation speed. Based on the measurement time T0, it is possible to determine whether the document D that has started to be fed is protruding downstream in the document feed direction. When it is determined that the document D is not protruding downstream in the document feed direction, it is possible to prevent deceleration. It is possible to prevent the gap between the documents D from becoming too large.

[0148] (Pattern 2) When the second conveying speed V2 is faster than the first conveying speed V1, if the time obtained by subtracting the measured time T0 from the required paper interval is longer than the speed change required time T1 and the time obtained by subtracting the measured time T0 from the required paper interval is equal to or less than the sum of the speed change required time T1, the first stop required time T2, and the first acceleration required time T3, after the first motor 8 starts rotating, the control unit maintains the rotation speed of the first motor 8 that has reached the first rotation speed. When the control unit recognizes that the leading edge of the document D has reached the paper feed sensor 7, it decelerates the rotation speed of the first motor 8. After the deceleration, it accelerates the rotation speed of the first motor 8 to the second rotation speed. The first stop required time T2 is the time required for the first motor 8 to stop from the first rotation speed. The first acceleration required time T3 is the time required for the first motor 8 to start rotating after stopping its rotation and for the rotation speed to reach the first rotation speed. Based on the measured time T0, it can be determined whether or not the first motor 8 needs to be decelerated to obtain an appropriate paper gap. When the second conveying speed V2 is faster than the first conveying speed V1 and it is determined that feeding of the document D has started from a slightly protruding position, the speed can be decelerated to widen the gap between the document D being fed and the preceding document D. By controlling the rotation speed of the first motor 8, the gap between the document D being fed and the preceding document D can be adjusted to an appropriate gap.

[0149] (Pattern 6) When the second conveying speed V2 is slower than the first conveying speed V1, if the time obtained by subtracting the measured time T0 from the required paper interval is longer than the speed change required time T1 and the time obtained by subtracting the measured time T0 from the required paper interval is equal to or less than the sum of the speed change required time T1, the second stop required time T8, and the second acceleration required time T9, the control unit maintains the rotation speed of the first motor 8 that has reached the first rotation speed after the first motor 8 starts rotating. When the control unit recognizes that the leading edge of the document D has reached the paper feed sensor 7, the control unit decelerates the rotation speed of the first motor 8. After the deceleration, the control unit accelerates the rotation speed of the first motor 8 to the second rotation speed. The second stop required time T8 is the time required for the first motor 8 to stop from the second rotation speed. The second acceleration required time T9 is the time required for the first motor 8 to start rotating after stopping the rotation and for the rotation speed to reach the second rotation speed. Based on the measured time T0, it can be determined whether or not the first motor 8 needs to be decelerated to obtain an appropriate paper gap. When the second conveying speed V2 is slower than the first conveying speed V1, and it is recognized that feeding of the original D has started from a position that protrudes slightly downstream in the document conveying direction, the speed can be decelerated to widen the paper gap between the original D being fed and the preceding original D. By controlling the rotation speed of the first motor 8, it is possible to adjust the paper gap between the original D being fed and the preceding original D to an appropriate gap.

[0150] The control unit sets the absolute value of the acceleration of the rotation speed of the first motor 8 to the same value as the absolute value of the deceleration. The control unit sets the time for continuing the deceleration of the first motor 8 to 1 / 2 the time obtained by subtracting the measured time T0 and the time required for speed change T1 from the required paper interval time. When the second conveying speed V2 is faster than the first conveying speed V1, after the deceleration of the first motor 8, the control unit sets the rotation speed of the first motor 8 to the second rotation speed for 1 / 2 the time obtained by subtracting the measured time T0 and the time required for speed change T1 from the required paper interval time (Pattern 2). When the second conveying speed V2 is slower than the first conveying speed V1, after the deceleration of the first motor 8, the control unit sets the rotation speed of the first motor 8 to the second rotation speed for 1 / 2 the time obtained by subtracting the measured time T0 and the time required for speed change T1 from the required paper interval time (Pattern 6). The conveying speed at the point when the appropriate paper interval is reached (the point when the required paper interval time is reached) can be set to the second conveying speed V2. When the appropriate paper interval is reached, the transport speed of the document D being fed and the preceding document D can be made the same. The time to decelerate can be determined based on the required paper interval time. The document D being fed is transported at a speed that is neither too slow nor too fast relative to the preceding document D. The distance between the documents D can be kept appropriate.

[0151] (Pattern 3) When the second conveying speed V2 is faster than the first conveying speed V1, the control unit recognizes the arrival of the leading edge of the document D at the paper feed sensor 7 after accelerating the first motor 8 to the first rotation speed after the start of rotation, and when the time obtained by subtracting the measurement time T0 from the required paper interval is longer than the sum of the speed change required time T1, the first stop required time T2, and the first acceleration required time T3, the control unit maintains the rotation speed of the first motor 8 at the first rotation speed after accelerating to the first rotation speed after the start of rotation. When the control unit recognizes the arrival of the leading edge of the document D at the paper feed sensor 7, the control unit decelerates the rotation speed of the first motor 8 from the first rotation speed and stops the first motor 8. After stopping, the control unit accelerates the rotation speed of the first motor 8 to the second rotation speed. The first stop required time T2 is the time required for the first motor 8 to stop rotating from the first rotation speed. The first acceleration time T3 is the time required from when the first motor 8 stops rotating until it starts rotating and the rotation speed reaches the first rotation speed. Based on the measured time T0, it can be determined whether or not the first motor 8 needs to be temporarily stopped in order to obtain an appropriate paper gap. When the second conveying speed V2 is faster than the first conveying speed V1 and the feeding of the original D is started from a position protruding downstream in the document conveying direction, the motor can be decelerated and stopped to widen the gap between the document D being fed and the preceding document D. The gap between the document D being fed and the preceding document D can be adjusted to an appropriate gap simply by controlling the rotation speed of the first motor 8.

[0152] (Pattern 7) When the second conveying speed V2 is slower than the first conveying speed V1, the control unit recognizes the arrival of the leading edge of the document D at the paper feed sensor 7 after accelerating the first motor 8 to the first rotation speed after the start of rotation, and when the time obtained by subtracting the measurement time T0 from the required paper interval is longer than the sum of the speed change required time T1, the second stop required time T8, and the second acceleration required time T9, the control unit maintains the rotation speed of the first motor 8 at the first rotation speed after accelerating to the first rotation speed after the start of rotation. When the control unit recognizes the arrival of the leading edge of the document D at the paper feed sensor 7, the control unit decelerates the rotation speed of the first motor 8 from the first rotation speed and stops the first motor 8. After stopping, the control unit accelerates the rotation speed of the first motor 8 to the second rotation speed. The second stop required time T8 is the time required for the first motor 8 to stop rotating from the second rotation speed. The second acceleration time T9 is the time required from when the first motor 8 stops rotating until it starts rotating and the rotation speed reaches the second rotation speed. Based on the measured time T0, it can be determined whether or not the first motor 8 needs to be temporarily stopped in order to obtain an appropriate paper gap. When the second conveying speed V2 is slower than the first conveying speed V1 and when the feeding of the original D starts from a position protruding downstream in the document conveying direction, the motor can be decelerated and stopped to widen the gap between the original D being fed and the preceding original D. The gap between the original D being fed and the preceding original D can be adjusted to an appropriate gap simply by controlling the rotation speed of the first motor 8.

[0153] The control unit sets the absolute value of the acceleration of the rotation speed of the first motor 8 to the same value as the absolute value of the deceleration. When the second conveying speed V2 is faster than the first conveying speed V1, the control unit subtracts the measurement time T0, the speed change required time T1, the first stop required time T2, and the first acceleration required time T3 from the required paper interval time to obtain the first stop time T5, and keeps the first motor 8 stopped for the first stop time T5 (pattern 3). When the second conveying speed V2 is slower than the first conveying speed V1, the control unit subtracts the measurement time T0, the speed change required time T1, the second stop required time T8, and the second acceleration required time T9 from the required paper interval time to obtain the second stop time T11. The control unit keeps the first motor 8 stopped for the second stop time T11 (pattern 7). The conveying speed at the time when the appropriate paper interval is reached (the time when the required paper interval time is reached) can be set as the second conveying speed V2. It is possible to determine the time for which the first motor 8 is stopped in order to obtain an appropriate paper gap. When the appropriate paper gap is obtained, the transport speed of the document D being fed and the preceding document D can be made the same. The distance between the documents D can be adjusted to an appropriate distance.

[0154] (Pattern 4, Pattern 8) In either case where the second conveying speed V2 is faster than the first conveying speed V1 or where the second conveying speed V2 is slower than the first conveying speed V1, when the control unit recognizes the leading edge of the document D reaching the paper feed sensor 7 before accelerating the first motor 8 to the first rotation speed after the start of rotation of the first motor 8, the control unit decelerates the rotation speed of the first motor 8 and stops the first motor 8. After stopping, the control unit accelerates the rotation speed of the first motor 8 to the second rotation speed. Based on the measurement time T0, it is possible to determine whether the paper gap is narrow enough to recognize the leading edge of the document D reaching the paper feed sensor 7 before the first rotation speed is reached. When it is recognized that paper feeding has started in a considerably protruding state, the first motor 8 is quickly decelerated and stopped, so that the gap between the document D being fed and the preceding document D can be greatly widened. By simply controlling the rotation speed of the first motor 8, the distance between the document D being fed and the preceding document D can be adjusted to an appropriate distance.

[0155] When the second conveying speed V2 is faster than the first conveying speed V1, the control unit subtracts the measurement time T0, the time required from the start to the stop of the rotation of the first motor 8, and the time required from the stop of the rotation of the first motor 8 to the start of rotation and the time required for the rotation speed to reach the second rotation speed from the required paper interval time to obtain a first waiting time T6. When the first motor 8 is decelerated and stopped, the control unit keeps the first motor 8 stopped for the first waiting time T6 (pattern 4). When the second conveying speed V2 is slower than the first conveying speed V1, the control unit subtracts the measurement time T0, the time required from the start to the stop of the rotation of the first motor 8, and the time required from the stop of the rotation of the first motor 8 to the start of rotation and the time required for the rotation speed to reach the second rotation speed from the required paper interval time to obtain a second waiting time T12. When the first motor 8 is decelerated and stopped, the control unit keeps the first motor 8 stopped for the second waiting time T12 (pattern 8). The waiting time (the time for which the motor is stopped) of the first motor 8 can be determined so that the transport speed when the appropriate paper interval is reached is the second transport speed V2. When the appropriate paper interval is reached, the transport speed of the document D being fed and the preceding document D can be made the same. The document D being fed is transported at a speed that is neither too slow nor too fast relative to the preceding document D. The distance between the documents D can be kept appropriate.

[0156] In a job that involves reading an original document, the control unit determines a second conveying speed V2 based on the settings for reading the original document D. The second conveying speed V2 is faster or slower than the first conveying speed V1. Even if the original document D does not abut against the pair of registration rollers and the second conveying speed V2 is faster or slower than the first conveying speed V1, the paper gap between the original documents D can be adjusted to an appropriate paper gap.

[0157] When documents D set in document tray 51 are fed one by one, from the start of conveyance of the first document D to the end of conveyance of the last document D, the control unit does not abut the document D against any of the rotating bodies downstream of the first rotating body in the document conveyance direction, and continues to rotate the rotating body downstream of the first rotating body in the document conveyance direction at a rotation speed at which the document D is conveyed at the second conveyance speed V2. The document D can be conveyed without abutting against the roller pair and without being temporarily stopped. It is possible to provide a document conveying device that conveys documents D one by one with an appropriate paper spacing, even without providing a registration roller pair.

[0158] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than the description of the above embodiments, and further includes all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0159] 100 Multifunction device (original transport device) 50 Transport control unit (control unit) 51 Document tray 52 Paper feed roller (first rotor) 53 Separation feed unit (first rotating body) 54 Second rotating body 7 Paper feed sensor 8 First motor 9 Second motor T0 measurement time T1 Time required for shifting T2 Time required for first stop T3 First acceleration time T5 First stop time T6 1st waiting time T8 2nd stop time T9 Second acceleration time T11 Second stop time T12 Second waiting time V1 First conveying speed V2 Second conveying speed

Claims

1. A document tray that can hold multiple documents; a first rotating body that feeds the documents set on the document tray one by one; A first motor that rotates the first rotating body; a second rotating body provided downstream of the first rotating body in a document transport direction and configured to transport the document toward a reading position; a second motor that rotates the second rotating body so as to transport the document at a second transport speed that is determined in advance; a paper feed sensor provided downstream of the first rotating body in a document transport direction and upstream of the second rotating body in the document transport direction; a control unit that recognizes, based on an output of the paper feed sensor, the arrival of a leading edge of the document at the paper feed sensor and the passage of a trailing edge of the document from the paper feed sensor; The control unit is the first motor starts rotating when the transport of the document starts; After the first motor starts to rotate, until the leading edge of the document reaches the paper feed sensor, the first motor is rotated at a rotation speed equal to or lower than a first rotation speed for transporting the document at a predetermined first transport speed; changing a rotation speed of the first motor to a second rotation speed for transporting the document at a second transport speed after the leading edge of the document reaches the paper feed sensor and before the trailing edge of the document passes through the paper feed sensor; stopping the first motor after the second rotation speed is reached and before the next document feed start time; A measurement time is measured from the start of rotation of the first motor until the leading edge of the document reaches the paper feed sensor; when a time obtained by subtracting the measured time from a predetermined required paper interval time is longer than a time required for speed change, the first motor is decelerated and then accelerated after the deceleration, thereby adjusting the paper interval between the document being fed and the preceding document; The document transport device according to claim 1, wherein the speed change time is a time required for changing the rotation speed from the first rotation speed to the second rotation speed.

2. In either case where the second conveying speed is faster than the first conveying speed or where the second conveying speed is slower than the first conveying speed, When the time obtained by subtracting the measured time from the required paper interval is equal to or less than the required speed change time, The control unit is accelerating the first motor to the first rotational speed and then maintaining the rotational speed of the first motor at the first rotational speed; 2. The document transport device according to claim 1, wherein when the leading edge of the document reaches the paper feed sensor, the rotation speed of the first motor is changed to the second rotation speed.

3. When the second conveying speed is faster than the first conveying speed, when the time obtained by subtracting the measured time from the required paper interval time is longer than the required speed change time and the time obtained by subtracting the measured time from the required paper interval time is equal to or less than the sum of the required speed change time, the first stop required time, and the first acceleration required time, The control unit is After the first motor starts to rotate, the rotation speed of the first motor is maintained at the first rotation speed. When the sensor detects that the leading edge of the document has reached the document feed sensor, the sensor reduces the rotation speed of the first motor; After deceleration, accelerating the rotational speed of the first motor to the second rotational speed; the first required stop time is a time required for the first motor to stop from the first rotation speed, 3. The document transport device according to claim 1, wherein the first acceleration required time is a time required for the first motor to start rotating after stopping and for the rotation speed to reach the first rotation speed.

4. When the second conveying speed is slower than the first conveying speed, when the time obtained by subtracting the measured time from the required paper interval is longer than the required speed change time and the time obtained by subtracting the measured time from the required paper interval is equal to or less than the sum of the required speed change time, the second required stop time, and the second required acceleration time, The control unit is After the first motor starts to rotate, the rotation speed of the first motor is maintained at the first rotation speed. When the sensor detects that the leading edge of the document has reached the document feed sensor, the sensor reduces the rotation speed of the first motor; After deceleration, accelerating the rotational speed of the first motor to the second rotational speed; the second required stop time is a time required for the first motor to stop from the second rotation speed, 3. The document transport device according to claim 1, wherein the second acceleration required time is a time required for the first motor to start rotating after stopping rotation and for the rotation speed to reach the second rotation speed.

5. The control unit is The absolute value of the acceleration and the absolute value of the deceleration of the rotation speed of the first motor are set to be equal to each other, a time period during which the first motor continues to decelerate is half the time period obtained by subtracting the measured time and the speed change required time from the required paper interval time, When the second conveying speed is faster than the first conveying speed, after the first motor has finished decelerating, the rotation speed of the first motor is set to the first rotation speed for a time that is half the time obtained by subtracting the measured time and the speed change required time from the required paper interval time, A document transport device as described in claim 3 or 4, characterized in that when the second transport speed is slower than the first transport speed, after the first motor has finished decelerating, the rotational speed of the first motor is set to the second rotational speed for a time that is half the time obtained by subtracting the measured time and the speed change required time from the required paper interval time.

6. When the second conveying speed is faster than the first conveying speed, when the arrival of the leading edge of the document at the paper feed sensor is recognized after the first motor is accelerated to the first rotation speed after starting rotation, and the time obtained by subtracting the measured time from the required paper interval time is longer than the sum of the speed change required time, the first stop required time, and the first acceleration required time; The control unit is After starting rotation, the rotation speed of the first motor is accelerated to the first rotation speed, and then the rotation speed of the first motor is maintained at the first rotation speed; When the sensor detects that the leading edge of the document has reached the feed sensor, the sensor reduces the rotation speed of the first motor from the first rotation speed to stop the first motor; After stopping, accelerating the rotation speed of the first motor to the second rotation speed; the first required stop time is a time required for the first motor to stop rotating from the first rotation speed, 6. The document transport device according to claim 1, wherein the first acceleration required time is a time required for the first motor to start rotating after stopping and for the rotation speed to reach the first rotation speed.

7. When the second conveying speed is slower than the first conveying speed, when the arrival of the leading edge of the document at the paper feed sensor is recognized after the first motor is accelerated to the first rotation speed after starting rotation, and the time obtained by subtracting the measured time from the required paper interval time is longer than the sum of the speed change required time, the second stop required time, and the second acceleration required time; The control unit is After starting rotation, the rotation speed of the first motor is accelerated to the first rotation speed, and then the rotation speed of the first motor is maintained at the first rotation speed; When the sensor detects that the leading edge of the document has reached the feed sensor, the sensor reduces the rotation speed of the first motor from the first rotation speed to stop the first motor; After stopping, accelerating the rotation speed of the first motor to the second rotation speed; the second required stop time is a time required for the first motor to stop rotating from the second rotation speed, 7. The document transport device according to claim 1, wherein the second acceleration required time is a time required for the first motor to start rotating after stopping and for the rotation speed to reach the second rotation speed.

8. The control unit is The absolute value of the acceleration and the absolute value of the deceleration of the rotation speed of the first motor are set to be equal to each other, When the second conveying speed is faster than the first conveying speed, a first stop time is obtained by subtracting the measured time, the speed change required time, the first stop required time, and the first acceleration required time from the required paper interval time, and the first motor is kept stopped during the first stop time; When the second conveying speed is slower than the first conveying speed, a second stop time is obtained by subtracting the measured time, the speed change required time, the second stop required time, and the second acceleration required time from the required paper interval time, and the first motor is kept stopped during the second stop time. the first required stop time is a time required for the first motor to stop rotating from the first rotation speed, the first acceleration required time is a time required from when the first motor stops rotating to when the first motor starts rotating and when the rotation speed of the first motor reaches the first rotation speed, the second required stop time is a time required for the first motor to stop from the second rotation speed, 8. The document transport device according to claim 6, wherein the second acceleration required time is a time required for the first motor to start rotating after stopping rotation and for the rotation speed to reach the second rotation speed.

9. In either case where the second conveying speed is faster than the first conveying speed or where the second conveying speed is slower than the first conveying speed, when it is recognized that the leading edge of the document has reached the paper feed sensor before the first motor is accelerated to the first rotation speed after the rotation starts, The control unit is When the first motor starts to rotate and the sensor detects that the leading edge of the document has reached the feed sensor, the sensor reduces the rotation speed of the first motor and stops the first motor.

9. The document transport device according to claim 1, wherein after the first motor is stopped, the rotation speed of the first motor is accelerated to the second rotation speed.

10. When the second conveying speed is faster than the first conveying speed, The control unit is calculating a first waiting time from the required paper interval time by subtracting the measured time, a time required from the start to the stop of rotation of the first motor, and a time required from the stop of rotation of the first motor to the start of rotation and the time required for the rotation speed to reach the second rotation speed; when the first motor is decelerated and stopped, the first motor is kept stopped for the first waiting time; When the second conveying speed is slower than the first conveying speed, The control unit is calculating a second waiting time from the required paper interval time by subtracting the measured time, the time required from the start to the stop of rotation of the first motor, and the time required from the stop of rotation of the first motor to the start of rotation and the time required for the rotation speed to reach the second rotation speed; 10. The document transport device according to claim 9, wherein when the first motor is decelerated and stopped, the first motor is kept stopped for the second waiting time.

11. The control unit determines the second transport speed based on a setting for reading the original in a job in which an original is read, 9. The document transport device according to claim 1, wherein the second transport speed is faster or slower than the first transport speed.

12. When the originals set on the original tray are fed one by one, from the start of conveyance of the first original to the end of conveyance of the last original, The control unit is A document transport device as described in any one of claims 1 to 11, characterized in that the document is not abutted against any of the rotating bodies downstream of the first rotating body in the document transport direction, and the rotating bodies downstream of the first rotating body in the document transport direction continue to rotate at a rotational speed at which the document is transported at the second transport speed.

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