JP2019189433A - Medium conveyance device - Google Patents

Abstract

To provide a medium conveyance device capable of satisfactorily correcting skew of a medium such as a document without using a relatively expensive component such as an electromagnetic clutch or a one-way clutch.SOLUTION: When the size of a document is equal to or smaller than A6 size, after the document finishes to pass a detection position of an after-registration sensor 23, an ADF motor 35 is inversely driven. By the inverse driving, a register roller gear 51 rotates in a direction reverse to a normal rotation driving of the ADF motor 35, and a drive engagement part 54 provided while integral rotation with the register roller gear 51 is separated from a driven engagement part 55 provided while integral rotation with a drive roller 13 of a register roller 7. As a result, preparing for conveyance of a next document, an interval between the drive engagement part 54 and the driven engagement part 55, that is, a play angle between the register roller gear 51 and the register roller can be secured largely.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a medium conveying apparatus that conveys a medium such as a document.

  2. Description of the Related Art Conventionally, an image reading apparatus that reads an image of a document by an ADF (Auto Document Feeder) method has been provided. In the ADF method, for example, originals stacked on a tray are sandwiched between a separation roller and a pinch roller, and the originals are fed one by one into the housing by the rotation of the separation roller and the pinch roller. The image of the original is read by a CIS (Contact Image Sensor) unit.

  In the ADF type image reading apparatus, there is a case where the document is conveyed in a state where the edge in the document conveyance direction is inclined with respect to the conveyance direction, that is, the document is skewed. In order to correct this skew, a technique has been proposed in which the leading edge of an original is abutted against a resist roller that is stopped or reversed and the original is bent, and then the original is conveyed by rotating the resist roller forward ( For example, see Patent Document 1).

  In order to drive and stop the registration roller, an electromagnetic clutch or a one-way clutch is often used. However, in order to realize the same function as the electromagnetic clutch or the one-way clutch at a low cost, a so-called circular clutch mechanism can be employed. In this rotating clutch mechanism, a projection is provided on each of the shaft of the registration roller and the gear to which the driving force from the motor is transmitted. When the gear protrusion is away from the shaft protrusion, the registration roller stops without rotating. When the gear is rotated by forward rotation of the motor, the gear protrusion contacts the shaft protrusion from the upstream side in the rotation direction and presses the shaft protrusion, so that the registration roller rotates integrally with the shaft.

JP-A-8-319042

  A conveyance roller for conveying the document is provided on the downstream side in the conveyance direction with respect to the registration roller. Generally, after the leading edge of the document reaches the conveyance roller, the document conveyance speed by the conveyance roller is set to be higher than the document conveyance speed by the registration roller so that the document does not become slack. . For this reason, in the configuration in which the circling clutch mechanism is adopted, after the leading edge of the document reaches the conveyance roller, the document is pulled by the conveyance roller, and the registration roller is rotated by the document, thereby increasing the speed. As a result, the protrusion on the shaft of the registration roller separates from the protrusion on the gear before the original leaves the registration roller.

  At this time, the registration roller starts to rotate after the leading edge of the document reaches the registration roller due to an interval generated between the projection of the shaft and the projection of the gear, that is, a play angle generated between the shaft of the registration roller and the gear. The air transport time until it is determined. For example, when the length of the document in the transport direction is short, such as when an A6 size document is transported along the short direction along the transport direction, the trailing edge of the document after the leading edge of the document reaches the transport roller The amount of rotation of the registration roller until it leaves the registration roller is small, and the play angle generated between the shaft of the registration roller and the gear is small. Therefore, the registration roller stop time required to correct the skew of the next document, that is, the idle running time is insufficient, and the rotation of the registration roller starts before the leading edge of the document follows the registration roller. May not be corrected.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a medium conveying apparatus that can satisfactorily correct a skew of a medium such as a document without using relatively expensive parts such as an electromagnetic clutch or a one-way clutch.

  To achieve the above object, a medium conveying apparatus according to the present invention includes a driving source, a tray that supports the medium, a separation roller that separates and conveys the medium supported by the tray, and a driving source. Separation roller drive transmission mechanism for transmitting the driving force from the separation roller to the separation roller, a registration roller provided downstream of the separation roller in the medium transport direction, and a registration roller for transmitting the driving force from the drive source to the registration roller A drive transmission mechanism, a sensor provided on the downstream side in the conveyance direction with respect to the registration roller, and a control unit; and the registration roller drive transmission mechanism is rotated by a driving force from a drive source. 1 drive member, a first drive engagement portion provided so as to be integrally rotatable with the first drive member, and provided so as to be integrally rotatable with the registration roller, and when the drive direction of the drive source is switched, A first driven engagement portion having a predetermined play until it is engaged with the one drive engagement portion, and the control unit is configured to control the medium based on the time during which the sensor detects the medium during conveyance of the medium. Before determining whether the length in the transport direction is equal to or shorter than the predetermined length and determining that the length in the transport direction of the medium is equal to or shorter than the predetermined length, before the subsequent medium is transported from the tray. When the drive source is reversely driven by the first predetermined amount and it is determined that the length of the medium in the conveyance direction is larger than the predetermined length, the drive source is not reversely driven.

  According to this configuration, when the medium is transported, it is determined whether the length in the medium transport direction is equal to or less than a predetermined length. When the length of the medium in the conveyance direction is equal to or shorter than the predetermined length, the drive source is driven in reverse after the medium has passed the detection position of the sensor provided on the downstream side in the conveyance direction with respect to the registration roller. The By this reverse rotation drive, the first drive member rotates in the opposite direction to the forward drive of the drive source, and the first drive engagement portion provided so as to be integrally rotatable with the first drive member is provided so as to be integrally rotatable with the registration roller. The first driven engagement portion is separated from the first driven engagement portion. As a result, it is possible to ensure a large gap between the first drive engagement portion and the first driven engagement portion, that is, a play angle between the first drive member and the registration roller, in preparation for the next document conveyance. it can. As a result, when the next document is conveyed, the idle running from when the leading edge of the document reaches the registration roller until the first driving engagement portion engages with the first driven engagement portion and the registration roller starts rotating. Time can be secured and the skew of the original can be corrected satisfactorily.

  According to the present invention, it is possible to satisfactorily correct a skew of a medium such as a document without using relatively expensive parts such as an electromagnetic clutch or a one-way clutch.

1 is a cross-sectional view schematically showing a configuration of an image reading apparatus according to an embodiment of the present invention. 2 is a block diagram illustrating an electrical configuration of the image reading apparatus. FIG. 6 is a flowchart illustrating a flow of processing executed by a CPU when a job for reading an image of a document is executed. FIG. 3 is a diagram schematically showing a state of a drive system before starting document conveyance. FIG. 3 is a diagram schematically showing a state of a drive system at the start of document conveyance. FIG. 3 is a diagram schematically showing a state of a drive system after the start of document conveyance. FIG. 3 is a diagram schematically showing a state of a drive system when a conveyance force starts to be applied from a registration roller to a document. FIG. 3 is a diagram schematically showing a state of a drive system immediately after an original is separated from a registration roller. FIG. 3 is a diagram schematically showing a state of a drive system immediately after a document having a short length in a conveyance direction is separated from a registration roller. It is a figure which shows the state of the drive system at the time of the reverse drive of an ADF motor schematically. It is a figure which shows the state of the drive system at the time of reverse rotation drive of the ADF motor after completion | finish of a job.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

<Image reading device>
An image reading device 1 (an example of a medium transport device) illustrated in FIG. 1 is an electronic device that reads an image of a document by an ADF (Auto Document Feeder) method.

  The image reading apparatus 1 includes a supply tray 2 (an example of a tray). The supply tray 2 is provided, for example, outside the casing (not shown) of the image reading apparatus 1 and is configured to be able to support a plurality of documents stacked on the upper surface thereof. A conveyance path 3 is formed in the housing. The conveyance path 3 extends from one end of the supply tray 2 to the side opposite to the other end side, is folded back while being curved in a U shape, and passes over the contact glass 4 at a portion ahead of the folding. A reading device 5 is provided below the contact glass 4. The reading device 5 includes a light source and an image sensor. The image sensor includes, for example, a linear image sensor in which a plurality of light receiving elements are arranged in the main scanning direction.

  Between the supply tray 2 and the contact glass 4, a separation roller 6, a registration roller 7, and a conveyance roller 8 are provided in this order from the supply tray 2 side along the conveyance path 3. The separation roller 6 includes a pair of a driving roller 11 and a pinch roller 12, and the driving roller 11 and the pinch roller 12 are provided such that their peripheral surfaces are in contact with each other with the conveyance path 3 interposed therebetween. The registration roller 7 includes a pair of a driving roller 13 and a pinch roller 14, and the driving roller 13 and the pinch roller 14 are provided such that their peripheral surfaces are in contact with each other with the conveyance path 3 interposed therebetween. The transport roller 8 is composed of a pair of a drive roller 15 and a pinch roller 16, and the drive roller 15 and the pinch roller 16 are provided such that their peripheral surfaces are in contact with each other across the transport path 3. A torque limiter 17 is provided around the shaft of the registration roller 7 that supports the pinch roller 14 until a predetermined torque or more is input to the peripheral surface of the pinch roller 14 from the document conveyed on the conveyance path 3. The rotation of the pinch roller 14 is prevented so that the leading edge of the document is not conveyed downstream in the conveying direction. Even if the torque limiter 17 is not provided, there is no problem as long as the original is a thin paper such as a thin original. However, when transporting a thick original such as a thick original, the drive roller 15 and the pinch roller 14 may rotate against the torque applied from the original, so the torque limiter 17 is necessary. become. In addition, after the document reaches the conveying roller 8, the torque is transmitted to the shaft by the action of the torque limiter 17.

  The documents supported on the supply tray 2 are separated one by one by the separation roller 6, and are conveyed along the conveyance path 3 by the separation roller 6, the registration roller 7, and the conveyance roller 8. The separation roller 6, the registration roller 7, and the conveyance roller 8 are set such that the gear ratio and the roller diameter are set so that the roller on the downstream side in the conveyance direction of the original document has a higher peripheral speed. The peripheral speed increases in the order of the registration roller 7 and the conveyance roller 8. During the conveyance, when the document passes over the contact glass 4, the image on the contact surface of the document with the contact glass 4 is read by the reading device 5. That is, light from the light source of the reading device 5 is irradiated onto the reading target surface of the document that comes into contact with the contact glass 4, and reflected light on the reading target surface is received by the image sensor of the reading device 5. Reading of one line of the image in the main scanning direction is achieved. The image sensor outputs the read analog image signal for one line. Then, while the document is being conveyed, the image on the surface to be read is sequentially read line by line from the upstream end to the downstream end in the sub-scanning direction, which is the conveyance direction, thereby achieving reading of the image on the surface to be read.

  A tray sensor 21 is provided in the supply tray 2. The tray sensor 21 includes an actuator 22 that is displaced by contact of a document supported on the supply tray 2 and an optical sensor (not shown) that detects the displacement of the actuator 22. In a state where no document is supported on the supply tray 2, the actuator 22 is positioned at the non-detection position, and an off signal is output from the tray sensor 21. When the document is supported on the supply tray 2, the actuator 22 is displaced from the non-detection position to the detection position by the contact of the document, and an ON signal is output from the tray sensor 21.

  A post-registration sensor 23 (an example of a sensor) is provided at a position downstream of the registration roller 7 in the conveyance direction and upstream of the conveyance roller 8 in the conveyance direction. The post-registration sensor 23 includes an actuator 24 that is displaced by contact of a document conveyed along the conveyance path 3 and an optical sensor (not shown) that detects the displacement of the actuator 24. When the document is not in contact with the actuator 24, the actuator 24 is positioned at the non-detection position, and an off signal is output from the post-registration sensor 23. When the document comes into contact with the actuator 24, the actuator 24 is displaced from the non-detection position to the detection position, and an on signal is output from the post-registration sensor 23.

  A pre-reading sensor 25 is provided at a position downstream of the conveyance roller 8 in the conveyance direction and upstream of the contact glass 4 in the conveyance direction. The pre-reading sensor 25 includes an actuator 26 that is displaced by contact of a document conveyed along the conveyance path 3 and an optical sensor that detects the displacement of the actuator 26. When the document is not in contact with the actuator 26, the actuator 26 is positioned at the non-detection position, and an off signal is output from the sensor 25 before reading. When the document contacts the actuator 26, the actuator 26 is displaced from the non-detection position to the detection position, and an ON signal is output from the sensor 25 before reading.

  The tray sensor 21, the post-registration sensor 23, and the pre-reading sensor 25 may be configured to detect the presence of the document at the detection position, and may be configured by, for example, a reflection type or a transmission type ultrasonic sensor. .

<Electrical configuration>
As shown in FIG. 2, the image reading apparatus 1 includes an ASIC (Application Specific Integrated Circuit) 31, a ROM (Read Only Memory) 32, and a RAM (Random Access Memory) 33.

  The ASIC 31 includes a CPU 34 (an example of a control unit). The ROM 32 includes a rewritable nonvolatile memory such as a flash memory. The ROM 32 stores programs executed by the CPU 34 and various data. The RAM 33 is a volatile memory such as a DRAM (Dynamic Random Access Memory), and is used as a work area when the CPU 34 executes a program.

  An analog image signal output from the reading device 5 is converted into image data that is a digital signal by AFE (Analog Front End) or the like and input to the ASIC 31. The ASIC 31 receives ON / OFF signals output from the tray sensor 21, the post-registration sensor 23, and the pre-reading sensor 25.

  The CPU 34 executes programs for various processes based on information input to the ASIC 31, thereby ADF motor 35 (an example of a drive source) that is a drive source for the separation roller 6, the registration roller 7, and the transport roller 8. ) And the operation panel 36 that is a user interface. The operation panel 36 includes a touch panel, and is configured by superimposing an operation unit 38 such as a pressure-sensitive or capacitive transparent film switch on a display unit 37 such as a liquid crystal display. The display unit 37 displays various information and images such as operation keys. When the user performs a touch operation on the operation key displayed on the display unit 37, an instruction corresponding to the type of the operated operation key is received by the operation unit 38. When an instruction is received by the operation unit 38, a signal (data) corresponding to the content of the instruction is transmitted from the operation unit 38 toward the ASIC 31.

  The display unit 37 and the operation unit 38 may be provided separately and independently without constituting a touch panel.

<Document transport operation>
When executing a job for reading an image of one or a plurality of documents supported on the supply tray 2, the CPU 34 of the ASIC 31 executes the process shown in FIG. Before the job is started, a start key is displayed on the display unit 37 of the operation panel 36. When the user touches the start key, a signal instructing job start is input from the operation unit 38 to the ASIC 31.

  In response to the input of the signal (S11: YES), the CPU 34 controls a motor driver (not shown) provided corresponding to the ADF motor 35 to rotate the ADF motor 35 forward (S12).

  In order to transmit the driving force of the ADF motor 35 to the separation roller 6, the registration roller 7, and the conveyance roller 8, the image reading apparatus 1 includes a separation roller drive transmission mechanism 41, a registration roller drive transmission mechanism, as shown in FIG. 42 and a conveyance roller drive transmission mechanism 43 are provided.

  The separation roller drive transmission mechanism 41 includes a separation roller gear 45. The separation roller gear 45 is supported on the shaft 44 of the drive roller 11 of the separation roller 6 so as to be relatively rotatable. The separation roller gear 45 meshes with a motor gear 47 that is supported on the output shaft 46 of the ADF motor 35 so as not to be relatively rotatable. A drive engagement portion 48 (an example of a second drive engagement portion) is formed on one end face of the separation roller gear 45 as a protrusion extending along the radius of the separation roller gear 45. The shaft 44 has a columnar driven engagement portion 49 (an example of a second driven engagement portion) that extends in the radial direction from the peripheral surface at the same position in the axial direction as the drive engagement portion 48. Is formed.

  The registration roller drive transmission mechanism 42 includes a registration roller gear 51 and an intermediate gear 52. The registration roller gear 51 is supported on the shaft 53 of the driving roller 13 of the registration roller 7 so as to be relatively rotatable. The intermediate gear 52 meshes with both the separation roller gear 45 and the registration roller gear 51. On one end surface of the registration roller gear 51, a drive engagement portion 54 (an example of a first drive engagement portion) is formed as a protrusion extending along the radius of the registration roller gear 51. Further, the shaft 53 has a columnar driven engagement portion 55 (an example of a first driven engagement portion) that extends in the radial direction from the peripheral surface at the same position in the axial direction as the drive engagement portion 48. Is formed.

  The transport roller drive transmission mechanism 43 includes a transport roller gear 61, intermediate gears 62, 63, 64 and a pendulum gear 65. The transport roller gear 61 is supported on the shaft 66 of the drive roller 15 of the transport roller 8 so as not to be relatively rotatable. When the intermediate gear 63 meshes with both of the intermediate gears 62 and 64, the intermediate gears 62, 63, and 64 constitute a gear train. The intermediate gear 64 meshes with the transport roller gear 61. The pendulum gear 65 is rotatably supported at one end of the switch arm 67 and always meshes with the registration roller gear 51. The other end of the switch arm 67 is swingably supported by the shaft 53 of the drive roller 13 of the registration roller 7. As the switch arm 67 swings, the pendulum gear 65 is displaced to a position where it engages with the transport roller gear 61 and a position where it engages with the intermediate gear 62. The gear diameter of the transport roller gear 61 is smaller than the gear diameter of the registration roller gear 51.

  Before the start of normal rotation of the ADF motor 35, the drive engagement portion 48 of the separation roller drive transmission mechanism 41 rotates with respect to the driven engagement portion 49 in the rotation direction of the separation roller gear 45 during normal rotation of the ADF motor 35 (hereinafter, “ It is separated by a predetermined angle (for example, about 80 °) on the upstream side of “the normal rotation direction of the separation roller gear 45”. In addition, the drive engagement portion 54 of the registration roller drive transmission mechanism 42 rotates in the direction of rotation of the registration roller gear 51 when the ADF motor 35 rotates in the forward direction relative to the driven engagement portion 55 (hereinafter referred to as “normal rotation of the registration roller gear 51”). It is separated by a predetermined angle (for example, about 325 °) on the upstream side of “direction”.

  When the motor gear 47 is rotated by the normal rotation driving of the ADF motor 35 and the driving force is transmitted from the motor gear 47 to the separation roller gear 45 and the separation roller gear 45 rotates in the normal rotation direction, as shown in FIG. The part 48 approaches the driven engagement part 49. Further, the driving force is transmitted from the separation roller gear 45 to the registration roller gear 51 through the intermediate gear 52, and the registration roller gear 51 rotates in the forward rotation direction. Due to the rotation of the registration roller gear 51 in the forward rotation direction, the drive engagement portion 54 approaches the driven engagement portion 55. Then, as shown in FIG. 6, before the drive engagement portion 54 engages with the driven engagement portion 55, the drive engagement portion 48 engages with the driven engagement portion 49 by contact, When the drive engagement portion 48 presses the driven engagement portion 49, the drive roller 11 of the separation roller 6 starts to rotate in the normal rotation direction of the separation roller gear 45. As the driving roller 11 rotates, the pinch roller 12 of the separation roller 6 is driven to rotate, and the original is rolled into one sheet between the driving roller 11 and the pinch roller 12. It is conveyed by the conveying force received from the pinch roller 12.

  Since the drive engagement portion 54 of the registration roller drive transmission mechanism 42 is not engaged with the driven engagement portion 55, the drive roller 13 of the registration roller 7 is stopped without rotating. Therefore, when the leading edge of the document conveyed by the conveying force received from the separation roller 6 reaches the position of the registration roller 7, the leading edge enters between the driving roller 13 and the pinch roller 14 and stops. Thereafter, a conveying force is applied from the separation roller 6 to the document, so that the leading edge of the document is in a state along the nip between the driving roller 13 and the pinch roller 14, and the skew is corrected when the document is skewed. Is done.

  As shown in FIG. 7, when the drive engagement portion 54 of the registration roller drive transmission mechanism 42 is engaged with the driven engagement portion 55 by contact, the drive engagement portion 54 presses the driven engagement portion 55. As a result, the drive roller 13 of the registration roller 7 starts to rotate in the normal rotation direction of the registration roller gear 51. With the rotation of the driving roller 13, the pinch roller 14 is driven to rotate, and the original is conveyed toward the downstream side in the conveying direction by the conveying force received from the driving roller 13 and the pinch roller 14.

  When the registration roller gear 51 rotates in the forward rotation direction, the pendulum gear 65 meshes with the conveyance roller gear 61, and the conveyance roller gear 61 rotates in the same normal rotation direction as the registration roller gear 51. Since the gear diameter of the conveyance roller gear 61 is smaller than the gear diameter of the registration roller gear 51, when the roller diameter of the driving roller 13 of the registration roller 7 and the roller diameter of the driving roller 15 of the conveyance roller 8 are the same, the conveyance roller 8 The peripheral speed of the driving roller 15 is greater than the peripheral speed of the driving roller 13 of the registration roller 7. Therefore, after the leading edge of the document is sandwiched between the driving roller 15 and the pinch roller 16 of the conveying roller 8 and the conveying force is applied to the document from the driving roller 15 and the pinch roller 16, the document is pulled by the conveying roller 8. Thus, the speed is increased by the registration roller 7 being rotated around the original. As a result, as shown in FIG. 8, the driven engagement portion 55 of the registration roller drive transmission mechanism 42 moves forward from the drive engagement portion 54 to the normal rotation of the registration roller gear 51 until the document leaves the registration roller 7. Leave downstream in the direction.

  On the other hand, after starting the forward rotation of the ADF motor 35, the CPU 34 repeatedly determines whether or not the output signal of the post-registration sensor 23 is an ON signal (S13). When the leading edge of the document receiving the conveying force from the registration roller 7 reaches the position of the actuator 24 of the post-registration sensor 23 and the document contacts the actuator 24, the actuator 24 is displaced and an on signal is output from the post-registration sensor 23. Is done. When the CPU 34 determines that the output signal of the post-registration sensor 23 is an ON signal (S13: YES), the CPU 34 then repeatedly determines whether or not the output signal of the post-registration sensor 23 is an OFF signal (S14).

  When the trailing edge of the document leaves the actuator 24, the actuator 24 is displaced, and the signal output from the post-registration sensor 23 is switched from the on signal to the off signal. In response to this, when the CPU 34 determines that the output signal of the post-registration sensor 23 is an off signal, the CPU 34 determines whether or not the output signal of the tray sensor 21 is an off signal (S15). When the output signal of the tray sensor 21 is an ON signal (S15: NO), that is, when a document is supported on the supply tray 2, the CPU 34 outputs an ON signal from the post-registration sensor 23 during the conveyance of the previous document. Based on the set time, it is determined whether or not the size of the document is A6 or less (S16).

  When the length of the document in the transport direction is short, such as when the size of the document is A6 or less, as shown in FIG. 9, the document starts to receive the transport force from the transport roller 8, and then the document is a registration roller. 7 is short and the amount by which the registration roller 7 is rotated with the original is small, so that the driven engagement portion 55 is separated from the drive engagement portion 54 to the downstream side in the normal rotation direction of the registration roller gear 51. The distance is small. Therefore, when the CPU 34 determines that the size of the document is A6 or less (S16: YES), it controls the motor driver to reverse the ADF motor 35 by the first predetermined amount (S17). When the ADF motor 35 is driven in reverse rotation, the motor rotation speed is made larger than that during normal rotation driving. As shown in FIG. 10, the reverse rotation of the ADF motor 35 causes the separation roller gear 45 to rotate in the reverse rotation direction opposite to the normal rotation direction, so that the drive engagement portion 48 of the separation roller drive transmission mechanism 41 is driven driven portion. 49 away from the downstream side of the separation roller gear 45 in the reverse rotation direction, in other words, upstream of the forward rotation direction. Further, the registration roller gear 51 rotates in the reverse rotation direction opposite to the normal rotation direction, and the drive engagement portion 54 of the registration roller drive transmission mechanism 42 is downstream from the driven engagement portion 55 in the reverse rotation direction of the registration roller gear 51. In other words, it moves away to the upstream side in the forward rotation direction. As a result, the positional relationship between the drive engagement portion 54 and the driven engagement portion 55 is brought close to the state before the reading job is executed.

  When the ADF motor 35 rotates in the reverse direction, the rotation of the registration roller gear 51 in the reverse direction causes the pendulum gear 65 engaged with the registration roller gear 51 to move downstream in the reverse direction of the registration roller gear 51. The pendulum gear 65 meshes with the intermediate gear 62. Therefore, the driving force is transmitted from the registration roller gear 51 to the transport roller gear 61 through the pendulum gear 65 and the intermediate gears 62, 63, 64, and the transport roller gear 61 rotates in the forward direction without changing the rotation direction. As a result, the conveyance roller 8 continues to rotate in the direction in which the document is pushed downstream in the conveyance direction, that is, in the normal rotation direction. The first predetermined amount of reverse rotation driving is set so that the leading edge of the document pushed downstream in the conveying direction by the conveying roller ends before reaching the pre-reading sensor 25.

  After the first predetermined amount of reverse rotation of the ADF motor 35, the CPU 34 controls the motor driver to rotate the ADF motor 35 forward again (S12). Due to the normal rotation of the ADF motor 35, the next document supported on the supply tray 2 is turned into one sheet, and the one sheet is conveyed by the conveyance force received from the driving roller 11 and the pinch roller 12. Further, since the registration roller gear 51 rotates in the forward rotation direction, the pendulum gear 65 meshing with the registration roller gear 51 moves to the downstream side in the forward rotation direction of the registration roller gear 51, and the pendulum gear 65 moves to the transport roller gear. Mesh with 61 again. The subsequent operation of each unit is as described above.

  When there is no document supported on the supply tray 2 and the output signal of the tray sensor 21 is an off signal (S15: YES), the CPU 34 determines whether or not the output signal of the pre-reading sensor 25 is an off signal. Judgment is made (S18). When the trailing edge of the document moves away from the actuator 26 of the pre-reading sensor 25 and the output signal of the pre-reading sensor 25 switches from an on signal to an off signal, the CPU 34 determines that the output signal of the pre-reading sensor 25 is an off signal. (S18: YES). Then, the CPU 34 controls the motor driver to reverse the ADF motor 35 by the second predetermined amount (S19), and the series of processes shown in FIG. As shown in FIG. 11, the reverse rotation of the ADF motor 35 causes the separation roller gear 45 to rotate in the reverse rotation direction opposite to the normal rotation direction, and the drive engagement portion 48 of the separation roller drive transmission mechanism 41 becomes the driven engagement portion. 49 away from the downstream side of the separation roller gear 45 in the reverse rotation direction, in other words, upstream of the forward rotation direction. Further, the registration roller gear 51 rotates in the reverse rotation direction opposite to the normal rotation direction, and the drive engagement portion 54 of the registration roller drive transmission mechanism 42 is downstream from the driven engagement portion 55 in the reverse rotation direction of the registration roller gear 51. In other words, it moves away to the upstream side in the forward rotation direction. As a result, the positional relationship between the drive engagement portion 54 and the driven engagement portion 55 is returned to the state before execution of the reading job. The second predetermined amount is set larger than the first predetermined amount.

<Effect>
As described above, it is determined whether or not the size of the document is A6 size or less, in other words, whether or not the length of the document in the transport direction is equal to or less than the vertical size of A6. When the size of the original is A6 or less, the ADF motor 35 is driven in reverse after the original has passed the detection position of the post-registration sensor 23. By this reverse rotation driving, the registration roller gear 51 rotates in the opposite direction to that when the ADF motor 35 is driven forward, and the drive engagement portion 54 provided so as to be integrally rotatable with the registration roller gear 51 is connected to the driving roller 13 of the registration roller 7. It is separated from the driven engagement portion 55 provided so as to be integrally rotatable. As a result, it is possible to ensure a large gap between the drive engagement portion 54 and the driven engagement portion 55, that is, a play angle between the registration roller gear 51 and the registration roller, in preparation for the next document conveyance. As a result, when the next document is conveyed, the idle running from when the leading edge of the document reaches the registration roller 7 until the driving engagement portion 54 engages with the driven engagement portion 55 and the registration roller 7 starts rotating. Time can be secured and the skew of the original can be corrected satisfactorily.

  Further, when the document is not supported on the supply tray 2 and the tray sensor 21 does not detect the document, that is, when the output signal of the tray sensor 21 is an off signal, the post-registration sensor 23 detects the document. After the disappearance and after the pre-reading sensor 25 no longer detects the original, the ADF motor 35 is driven reversely by a second predetermined amount. As a result, when the document is conveyed by executing a new job, the driving engagement portion 54 engages with the driven engagement portion 55 after the leading edge of the document reaches the registration roller 7 and the registration roller 7 starts to rotate. It is possible to ensure a free running time until the document skew is corrected.

  The separation roller drive transmission mechanism 41 includes a separation roller gear 45, a drive engagement portion 48 that rotates integrally with the separation roller gear 45, and a driven engagement portion 49 that rotates integrally with the drive roller 11 of the separation roller 6. Thus, there is play until the drive engagement portion 48 engages with the driven engagement portion 49. Thereby, it is possible to provide an idle running time from the start of normal rotation of the ADF motor 35 to the start of rotation of the separation roller 6 during conveyance of the document.

  The conveyance roller drive transmission mechanism 43 is provided with a pendulum gear 65 that meshes with the registration roller gear 51. When the ADF motor 35 is driven to rotate forward, the pendulum gear 65 meshes with the transport roller gear 61, and the driving force is transmitted from the registration roller gear 51 to the transport roller gear 61 via the pendulum gear 65. On the other hand, when the ADF motor 35 is driven in reverse rotation, the pendulum gear 65 meshes with the intermediate gear 62, and the driving force is transmitted from the registration roller gear 51 to the transport roller gear 61 via the pendulum gear 65 and the intermediate gears 62, 63, 64. . As a result, even when the ADF motor 35 is driven in reverse rotation, the conveyance roller gear 61 rotates in the forward direction, so that the original is not pushed back upstream in the conveyance direction by the conveyance roller 8 and the conveyance of the original by the conveyance roller 8 is continued. Can do.

  When the ADF motor 35 is driven in reverse rotation, the motor rotation speed is made larger than that during normal rotation driving. Thereby, the time required for the movement of the pendulum gear 65 due to switching between the normal rotation driving and the reverse rotation driving of the ADF motor 35 can be shortened, and the loss due to the switching (a period during which no conveyance force is applied to the document) can be reduced.

  The pinch roller 14 of the registration roller 7 is provided with a torque limiter 17 that suppresses the rotation of the pinch roller 14 until the torque input from the document to the pinch roller 14 exceeds a predetermined value. As a result, the pinch roller 14 can be prevented from rotating when a stiff document abuts against the peripheral surface of the pinch roller 14 of the registration roller 7, and the conveyance force applied to the document due to the rotation can be suppressed. .

<Modification>
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

  In the above-described embodiment, the case where the CPU 34 executes each process has been described. However, the ASIC 31 may include a plurality of CPUs, and the plurality of CPUs may cooperate to execute each process.

  The medium conveying apparatus according to the present invention is not limited to the image reading apparatus 1, and can be widely applied to apparatuses that require a configuration for conveying a medium such as paper, such as a printer.

  In addition, various design changes can be made to the above-described configuration within the scope of the matters described in the claims.

1: Image reading device 2: Supply tray 6: Separating roller 7: Registration roller 8: Conveying roller 13: Driving roller 14: Pinch roller 17: Torque limiter 21: Tray sensor 23: Post-registration sensor 34: CPU
35: ADF motor 41: separation roller drive transmission mechanism 42: registration roller drive transmission mechanism 43: transport roller drive transmission mechanism 45: separation roller gear 48: drive engagement portion 49: driven engagement portion 51: registration roller gear 54: drive Engagement part 55: driven engagement part

Claims (6)

A driving source;
A tray for supporting the medium;
A separation roller for separating and conveying the medium supported by the tray one by one;
A separation roller drive transmission mechanism for transmitting a driving force from the drive source to the separation roller;
A registration roller provided downstream of the separation roller in the medium conveyance direction;
A registration roller drive transmission mechanism for transmitting a driving force from the drive source to the registration rollers;
A sensor that is provided downstream of the registration roller in the transport direction and detects a medium;
A control unit,
The registration roller drive transmission mechanism is
A first driving member that is rotated by a driving force from the driving source;
A first drive engagement portion provided so as to be integrally rotatable with the first drive member;
A first driven engagement portion which is provided so as to be integrally rotatable with the registration roller, and has a predetermined play before being engaged with the first drive engagement portion when the drive direction of the drive source is switched; Including
The controller is
Determining whether the length of the medium in the transport direction is equal to or less than a predetermined length based on the time during which the sensor detects the medium during transport of the medium;
If it is determined that the length of the medium in the transport direction is equal to or less than the predetermined length, before the subsequent medium is transported from the tray, the drive source is reversely driven by a first predetermined amount, and the medium A medium conveying apparatus that does not reversely drive the driving source when it is determined that the length in the conveying direction is larger than the predetermined length. It is a medium conveyance apparatus of Claim 1, Comprising:
A tray sensor for detecting a medium supported by the tray;
A medium conveying apparatus that, when the tray sensor detects no medium, reversely drives the drive source by a second predetermined amount after the sensor stops detecting the medium. The medium conveying apparatus according to claim 1 or 2,
The separation roller drive transmission mechanism is
A second driving member that is rotated by a driving force from the driving source;
A second drive engagement portion provided so as to be integrally rotatable with the second drive member;
A second driven engagement portion which is provided so as to be integrally rotatable with the separation roller, and has a predetermined play before being engaged with the second drive engagement portion when the drive direction of the drive source is switched; Including a medium conveying device. The medium conveying device according to any one of claims 1 to 3,
A conveyance roller that is provided downstream of the registration roller in the conveyance direction and conveys the medium;
Regardless of forward drive and reverse drive of the drive source, the drive force of the drive source is transmitted to the transport roller as a drive force that rotates the transport roller in the direction of transporting the medium downstream in the transport direction. A medium conveying apparatus further comprising a conveying roller drive transmission mechanism. It is a medium conveyance apparatus as described in any one of Claims 1-4, Comprising:
The control unit, when driving the drive source in the reverse direction, drives the drive source in the reverse direction at a faster speed than in the normal rotation drive. It is a medium conveyance device according to any one of claims 1 to 5,
The registration roller is provided with a driving roller to which a driving force from the driving source is transmitted via the registration roller drive transmission mechanism, and a peripheral surface abutting on a peripheral surface of the driving roller, and is driven by the driving roller. And a pinch roller that rotates,
The medium conveying device, wherein the pinch roller is provided with a torque limiter that suppresses rotation of the pinch roller until a torque input from the medium to the pinch roller exceeds a predetermined value.

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