JP2012176836A - Automatic document conveying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic document conveying device, where a roller driving structure for driving one of conveying rollers to rotate forward or holding one of the conveying rollers in a suspended state is constituted of a gear structure and a mechanical switching structure, thereby, reducing the whole cost for the structure for skew correction.SOLUTION: The first conveying roller 41 and the second conveying roller 42 are provided on a document conveyance path 26. A roller driving mechanism for transmitting a rotating power to a receiving gear 82 is provided between the output gear 81 and the receiving gear 82 provided on both rollers 41 and 42. The roller driving mechanism includes: a first intermediate gear 91; a second intermediate gear 92; a gear holder 93 for supporting both of the gears 91 and 92; and a switching mechanism including a solenoid 101. The second conveying roller 42 is switched with a switching operation of the gear holder 93 by the switching mechanism, such that the second conveying roller 42 is made in each state, that is, the roller 42 is driven to rotate forward, backward or suspended. The document skew correction is performed by the first conveying roller 41 being driven to rotate and the second conveying roller 42 being in the suspended state.

Description

  The present invention relates to an image reading apparatus applied to a copying machine, a scanner, a facsimile, and the like, and more particularly to an improvement in a driving structure of a conveying roller constituting an automatic document conveying device for a platen cover.

  In the automatic document feeder according to the present invention, the supply of rotational power to the conveyance roller provided in the document conveyance path is stopped to correct the skew of the recording paper. In this way, the conveyance roller is temporarily stopped. It is known in Patent Documents 1 to 3 to correct the skew of the recording paper. In the recording apparatus of Patent Document 1, a downstream transport roller is provided in a state where a lock device is provided between two pairs of transport rollers arranged at intervals along the transport path, and the upstream transport roller is stopped. Only the reverse rotation of the recording paper can be performed to correct the skew of the recording paper. The locking device is composed of a sun gear, two planetary gears, a clutch mechanism, etc., and utilizes the fact that the planetary gear revolves when the downstream transport roller is driven forward or reverse by a forward / reverse motor. Thus, the direction of the rotational power transmitted to the upstream conveying roller is switched.

  In the document reading apparatus of Patent Document 2, the document separation roller is rotationally driven by a stepping motor capable of normal rotation and reverse rotation, and at the same time, a contact sensor roller provided downstream of the document separation roller can be rotationally driven. A timer mechanism for temporarily stopping the transmission of power is disposed between these rollers and the stepping motor. By rotating the document separation roller while the contact sensor roller is stopped, the document is inclined. The line can be corrected.

  In the automatic document feeder according to the present invention, the rotational power of a normal motor is transmitted by a roller driving mechanism, and one of the two pairs of conveyance rollers is rotationally driven and the other is stopped to correct the skew of the document. This type of skew correction structure is known from Patent Document 3. There, the rotational power of the motor is transmitted to the passive gear of the transport roller via the first and second intermediate gears. Further, the feeding roller disposed on the upstream side of the conveying roller is rotationally driven via a missing gear that meshes with the first intermediate gear. The second intermediate gear is supported by a holder that can rotate around the first intermediate gear shaft, and a projection provided on the holder is operated by a cam provided on the side of the toothless gear, whereby the second intermediate gear and the passive gear are operated. The skew of the recording sheet is intermittently corrected.

JP 2009-29395 A (paragraph number 0065, FIG. 3) Japanese Unexamined Patent Publication No. 07-288852 (paragraph number 0039, FIG. 4) Japanese Unexamined Patent Publication No. 2007-112555 (paragraph number 0027, FIG. 5)

  The skew correction structure of Patent Document 1 requires a lock mechanism composed of a sun gear, two planetary gears, a clutch mechanism, and the like, and a forward / reverse motor that drives the sun gear in the forward or reverse direction. The overall structure is complicated and expensive. Similarly, the structure for skew correction of Patent Document 2 requires a stepping motor and a timer mechanism, so that the entire structure is complicated and the cost increases. There has also been proposed an automatic document conveying device that corrects skew of a recording sheet by intermittently driving power by an electromagnetic clutch to rotationally drive or stop a conveying roller. However, this type of skew correction structure is expensive because the electromagnetic clutch itself is expensive, and further, a control means for the electromagnetic clutch is required.

  In the skew correction structure of Patent Document 3, the rotational power of the motor is interrupted by a cam and a holder, and the conveyance roller is driven to rotate in the paper direction or held in a stopped state. Cost can be reduced compared to the correction structure. However, since the meshing state between the second intermediate gear and the passive gear of the transport roller is merely mechanically interrupted, it is sufficient to correct the skew using the transport roller. I am dissatisfied with the point that I cannot drive. For example, in an automatic document feeder, images on the first and second sides of a document may be readable. In that case, the conveyance roller is driven reversely to feed the document in a direction opposite to the paper feeding direction. In this case, the conveyance roller cannot be driven in reverse.

It is an object of the present invention to form a roller driving structure for driving one of the conveying rollers in a normal rotation state or holding it in a stopped state by a gear structure and a mechanical switching structure, and the entire structure for skew correction. An object of the present invention is to provide an automatic document feeder that can reduce costs.
SUMMARY OF THE INVENTION An object of the present invention is to provide a roller drive structure that can drive one of the conveyance rollers in the normal direction, drive in the reverse direction, or hold it in a stopped state, and can cope with image reading on both the front and back sides of the document in addition to the skew correction of the document. To provide an automatic document feeder provided.

  In the automatic document conveying apparatus according to the present invention, a first conveying roller 41 is disposed on the upstream side of the document conveying path 26, and a second conveying roller 42 is disposed on the downstream side of the first conveying roller 41. The automatic document feeder includes an output gear 81 that is rotated by receiving the power of a motor 80 that is driven and rotated in one direction, and a passive gear 82 that is provided on the second conveyance roller 42. Furthermore, a roller drive mechanism that transmits the rotational power of the output gear 81 to the passive gear 82 and a switching mechanism that switches the transmission state of the roller drive mechanism are provided. The roller driving mechanism is configured to be switchable by a switching mechanism between a state in which the second transport roller 42 is driven to rotate in the forward direction, a state in which it is driven in the reverse direction, and a state in which it is stopped. The skew feeding correction of the document is performed between the first transport roller 41 in a rotationally driven state and the second transport roller 42 in a stopped state.

  The roller driving mechanism supports the first intermediate gear 91 that is always meshed with the output gear 81, the second intermediate gear 92 that is always meshed with the first intermediate gear 91, the first intermediate gear 91, and the second intermediate gear 92, and outputs And a gear holder 93 that rotates around the gear shaft 83 of the gear 81. By switching the gear holder 93 with a switching mechanism, either the first intermediate gear 91 or the second intermediate gear 92 is engaged with the passive gear 82, and the second transport roller 42 can be driven to rotate forward or reversely. Further, the power transmission to the passive gear 82 can be interrupted by switching the gear holder 93 with the switching mechanism.

  The switching mechanism includes a driving member 101, a cam 102 that is intermittently rotated by the driving member 101 via a ratchet mechanism, a cam follower 95 that is provided on the gear holder 93 and that is switched by the cam 102, and cams the cam follower 95. And a spring 103 that is biased in a direction in close contact with 102.

  A contact glass 21 for reading an image of the document is disposed in the middle of the document transport path 26. The first surface of the document is respectively connected to the first transport path 31 that transports the first surface of the document toward the contact glass 21 and the fifth transport path 35 that transports the second surface of the document toward the contact glass 21. The first sensor 47 for detecting the reading timing of the second document 48 and the second sensor 48 for detecting the reading timing of the second side of the inverted document are arranged. Based on the output signals from the first sensor 47 and the second sensor 48, the roller driving mechanism is switched by the switching mechanism, and the second conveying roller 42 is held in a stopped state or driven in reverse.

  As shown in FIG. 9, the switching mechanism is composed of a solenoid 101 that can control the pull-in position of the plunger 109 in three stages. The gear holder 93 is directly switched by the solenoid 101 to switch between the state in which the second transport roller 42 is driven to rotate forward, the state in which the second transport roller 42 is driven in reverse rotation, and the state in which the second transport roller 42 is stopped. To be able to.

  In the present invention, the power of the motor 80 driven and rotated in one direction is transmitted to the passive gear 82 of the second conveying roller 42 through the output gear 81 and the roller driving mechanism. In addition, the driving state of the second conveying roller 42 can be switched to normal rotation, reverse rotation, or stop by switching the roller driving mechanism with the switching mechanism. As described above, if the motor 80 that rotates in one direction is used as a drive source and the driving state of the second transport roller 42 is mechanically switched by the roller driving mechanism to perform the skew correction, the skew correction is performed. The overall cost of the drive structure can be reduced. There is no need to use expensive parts such as stepping motors and electromagnetic clutches that have been frequently used in the conventional skew correction, and the second conveying roller 42 is driven using an inexpensive motor 80 that rotates in one direction as a drive source. This is because the state can be switched.

  Further, since the second conveyance roller 42 can be driven forwardly, reversely driven, or held in a stopped state, in addition to correcting the skew of the original, reading the images on the first and second sides of the original Can be carried out smoothly and continuously in the automatic document feeder 6. Furthermore, by holding the second conveying roller 42 in a stopped state, it is possible to reduce the load on the motor 80 and eliminate unnecessary power consumption. In addition, the first and second gears meshed with the passive gear 82 and the gear 82. The wear of the intermediate gears 91 and 92 can be reduced.

  According to the roller drive mechanism composed of the first intermediate gear 91, the second intermediate gear 92, and the gear holder 93 that supports both the gears 91 and 92, one of the intermediate gears 91 and 92 is engaged with the passive gear 82. By doing so, the second conveying roller 42 can be driven forwardly or reversely. Further, by separating the intermediate gears 91 and 92 from the passive gear 82, the second transport roller 42 can be held in a stopped state. Further, by operating the gear holder 93 with the switching mechanism and rotating the gear holder 93 around the gear shaft 83 of the output gear 81, the meshing state of the intermediate gears 91 and 92 and the passive gear 82 can be switched. As described above, according to the roller driving mechanism using the first and second intermediate gears 91 and 92 as the transmission element, the second conveying roller 42 is rotated forward, reverse, and stopped by using a gear that requires less cost. Since it can switch to each state, the manufacturing cost of a roller drive mechanism can be reduced.

  Since the switching mechanism is composed of basic mechanical elements such as the drive member 101, the cam 102, the ratchet mechanism, the cam follower 95, and the spring 103, the cost can be reduced. The overall cost of the structure for line correction can be reduced. In particular, the function of the automatic document feeder 6 can be improved while reducing the overall cost as compared with a conventional skew correction device using a forward / reverse motor or a stepping motor as a drive source or using an expensive electromagnetic clutch. .

  When the first and second sensors 47 and 48 for detecting the reading timing of the document are provided at predetermined positions on the document transport path 26 and the switching structure is operated using the output signals of both the sensors 47 and 48, A dedicated sensor for determining the operation timing of the roller drive mechanism can be omitted. Therefore, the power transmission state of the roller drive mechanism can be accurately switched while simplifying the structure of the automatic document feeder 6.

  By directly switching the gear holder 93 with the solenoid 101 that can control the pull-in position of the plunger 109 in three stages, the switching mechanism can be configured with a minimum number of components, and the overall cost of the roller drive mechanism can be further reduced. Further, since the gear holder 93 is directly switched by the solenoid 101, the gear holder 93 can be switched quickly and accurately without any time delay, and it is possible to cope with an increase in the document conveying speed.

It is a front view of the roller drive mechanism which concerns on this invention. 1 is a front view conceptually showing an image reading apparatus. FIG. 3 is a layout explanatory diagram conceptually showing a relationship between an automatic document feeder and a reading unit. FIG. 3 is a schematic front view showing the entire document conveyance path of the automatic document conveyance device. FIG. 3 is a schematic front view showing a document transport path when reading images on both sides of a document. It is the front view which fractured | ruptured a part which shows the switching mechanism of a roller drive mechanism. It is the front view which switched the roller drive mechanism to the normal rotation state. It is the front view which changed the roller drive mechanism into the reverse rotation state. It is a front view which shows another Example of a switching mechanism.

(Embodiment) FIGS. 1 to 8 show an embodiment in which the image reading apparatus according to the present invention is applied to a multifunction machine having a copy function and a facsimile function. In the present invention, “front / rear”, “left / right”, and “upper / lower” follow the cross arrows shown in FIG.

  In FIG. 2, the multifunction machine includes a recording unit 1 and an image reading unit 2 disposed on the upper side of the recording unit 1. The recording unit 1 includes an image recording device 3 and a fixing device 4. A platen cover 5 for opening and closing the document reading surface is provided on the upper surface of the image reading unit 2, and an automatic document feeder (hereinafter simply referred to as ADF) 6 is incorporated in the upper part of the platen cover 5. An operation panel 7 having various operation buttons is provided on the front surface of the image reading unit 2. A paper feed cassette 8 is disposed below the recording unit 1, and the recording paper conveyance path 10 between the paper feed cassette 8 and the paper discharge unit 9 below the image reading unit 2 is arranged along the recording paper conveyance path 10. An image recording device 3 and a fixing device 4 are arranged. The platen cover 5 swings up and down around a hinge (not shown) provided at the rear end thereof, thereby covering the top surface of the document placement table or opening the top surface of the document placement table.

  In FIG. 3, the upper surface of the document table is covered with a platen glass 13, and a reading unit 14 for reading the first surface of the document and a carriage for supporting the reading unit 14 are arranged therein. The reading unit 14 includes a light source 15, first to fourth mirrors 16 to 19, a CCD image sensor 20, and the like. By positioning the reading unit 14 directly below the contact glass 21, it is possible to read a sheet-like original image conveyed along the upper surface of the contact glass 21 by the ADF 6. Further, by scanning the reading unit 14 from the left side edge to the right side edge of the platen glass 13, it is possible to read a fixed document placed on the platen glass 13.

  As shown in FIG. 4, a document transport path 26 is provided inside the ADF 6 to connect a paper feed port 24 facing the upper document tray 22 and a paper discharge port 25 facing the lower paper discharge tray 23. . A pickup roller 28 and a paper feed roller 29 are disposed at the paper feed port 24, and a paper discharge roller 30 is provided at the paper discharge port 25. In FIG. 4, reference numeral 27 denotes a presser frame that presses the document against the paper feed roller 29. In order to continuously read the images on the first and second surfaces of the document by the reading unit 14, the document transport path 26 is configured as follows. The first surface of the document is a surface that is on the upper side when the document is placed on the document tray 22, and the second surface of the document is on the lower side when the document is placed on the document tray 22. It is a surface.

  The document conveyance path 26 includes a first conveyance path 31 that is continuous while curving in a counterclockwise direction starting from the paper feed port 24, a second conveyance path 32 that is continuous to the first conveyance path 31, and a second conveyance path. And a horizontal third conveyance path 33 extending from 32 to the sheet discharge outlet 25. The second conveyance path 32 includes a portion that is continuously inclined upward to the first conveyance path 31, a horizontal portion, and a portion that is inclined downward toward the third conveyance path 33. The document is conveyed through these first to third conveyance paths 31 to 33, and the image on the first surface of the document is read by the reading unit 14 during that time. The contact glass 21 is arranged facing a downward projecting curved portion where the first transport path 31 changes to the second transport path 32. The first conveyance path 31 is a conveyance path that conveys the first surface of the document toward the contact glass 21.

  The document conveyance path 26 includes fourth to sixth conveyance paths 34 to 36 in addition to the first to third conveyance paths 31 to 33 described above. The document on which the image on the first surface has been read is reversed in the fourth conveyance path 34 and further conveyed in the reverse direction to the contact glass 21 via the fifth conveyance path 35, so that the image on the second surface is read. Done. Further, the original on which the image on the second surface has been read is transported to the sixth transport path 36 via a part of the first transport path 31, so that a part of the second transport path 32 and the third The paper is discharged from the paper discharge outlet 25 via the conveyance path 33. The fifth conveyance path 35 is a conveyance path that conveys the second surface of the document toward the contact glass 21.

  The fourth conveyance path 34 connects between the middle part of the second conveyance path 32 and the end of the third conveyance path 33, and reverses the original on which the image reading on the first surface has been completed. The fifth conveyance path 35 bypasses between the adjacent portion of the second conveyance path 32 and the third conveyance path 33 and the start end portion of the second conveyance path 32, and the document is reversed by the fourth conveyance path 34. Is conveyed in the reverse direction toward the contact glass 21. The sixth conveyance path 36 bypasses the middle part of the first conveyance path 31 and the middle part of the second conveyance path 32, and the original on which the reading of the image on the second surface has been completed is transferred to the second conveyance path 32. Transport toward you.

  In order to circulate the document along each transport path as described above, first to fifth five sets of transport rollers 41 to 45 are arranged along the document transport path 26. The first transport roller 41 is disposed at a branch portion between the first transport path 31 and the sixth transport path 36, and includes a first roller 51 that is rotationally driven, a second roller 52 that circumscribes the first roller 51, and The third roller 53 is configured. The nip portion between the first roller 51 and the second roller 52 faces the first conveyance path 31, and conveys the document fed from the sheet feeding port 24 toward the second conveyance roller 42. Similarly, the nip portion between the first roller 51 and the third roller 53 faces the sixth conveyance path 36, and the document after reading the image on the second surface is transferred from the first conveyance path 31 to the sixth conveyance path. Transport to 36. A branch portion between the first conveyance path 31 and the sixth conveyance path 36 is provided with a first gate body 71 that blocks any one of these conveyance paths.

  The second transport roller 42 is disposed in the first transport path 31 upstream of the contact glass 21 and includes a fourth roller 54 that is rotationally driven and a fifth roller 55 that circumscribes the fourth roller 54. . The nip portion between the fourth roller 54 and the fifth roller 55 faces the first conveyance path 31, and the document is conveyed in the forward direction by driving the fourth roller 54 forward or reversely, or Can be transported in the reverse direction. Further, by driving the first transport roller 41 while the fourth roller 54 is stopped, it is possible to correct the skew of the document. Details thereof will be described later. A first sensor 47 that detects the reading timing of the first surface of the document is disposed on the upstream side of the second conveying roller 42. The first sensor 47 is constituted by an optical sensor, for example, and the reading unit 14 determines the reading timing of the image on the first surface of the document based on the output signal from the first sensor 47. Further, based on the output signal from the first sensor 47, the driving of the fourth roller 54 is stopped and the skew feeding correction is performed, details of which will be described later. The forward rotation direction of the fourth roller 54 refers to a state of rotating in the same direction (counterclockwise rotation direction) as the first roller 51, and the reverse rotation is defined as the reverse rotation direction.

  The third conveyance roller 43 is disposed at a branch portion between the second conveyance path 32 and the fifth conveyance path 35, and includes a sixth roller 56 that is rotationally driven, a seventh roller 57 that circumscribes the sixth roller 56, and An eighth roller 58 is used. The nip portion between the sixth roller 56 and the seventh roller 57 faces the second conveyance path 32, and conveys the document after reading the image on the first surface to the fourth conveyance roller 44. The nip portion between the sixth roller 56 and the eighth roller 58 faces the fifth conveyance path 35, and conveys the document that has been reversed in the fourth conveyance path 34 from the fifth conveyance path 35 toward the contact glass 21. To do. A branch portion between the second conveyance path 32 and the fifth conveyance path 35 is provided with a second gate body 72 that blocks any one of these conveyance paths. In the fifth conveyance path 35 facing the third conveyance roller 43, a second sensor 48 for detecting the reading timing of the document reversed in the fourth conveyance path 34 is disposed. The second sensor 48 is constituted by an optical sensor, for example, and the reading unit 14 determines the reading timing of the image on the second side of the inverted document based on the output signal from the second sensor 48. Further, based on the output signal from the second sensor 48, the fourth roller 54 is driven in reverse to convey the inverted document to the sixth conveying path 36, details of which will be described later.

  The fourth transport roller 44 is disposed on the upper side of the trapezoidal second transport path 32, and includes a ninth roller 59 that is rotationally driven and a tenth roller 60 that circumscribes the ninth roller 59. is there. The nip portion between the ninth roller 59 and the tenth roller 60 faces the second conveyance path 32. A third gate body 73 that blocks any one of these transport paths is provided at a branch portion of the second transport path 32 and the fourth transport path 34. A fourth gate body that blocks one of the second conveyance path 32 and the third conveyance path 33 at a branching portion of the second conveyance path 32, the third conveyance path 33, and the fifth conveyance path 35. 74 is provided.

  The fifth transport roller 45 is disposed at a branch portion between the third transport path 33 and the fourth transport path 34, and includes an eleventh roller 61 that is rotationally driven, a twelfth roller 62 that circumscribes the eleventh roller 61, and The 13th roller 63 is configured. The nip portion between the eleventh roller 61 and the twelfth roller 62 faces the fourth conveyance path 34, and conveys the document reversed in the fourth conveyance path 34 toward the fifth conveyance path 35. The nip portion between the eleventh roller 61 and the thirteenth roller 63 faces the third transport path 33, and these rollers 61 and 63 constitute the paper discharge roller 30 described above. A fifth gate body 75 that blocks any one of the transport paths is provided at a branch portion between the third transport path 33 and the fourth transport path 34.

  The first roller 51, the sixth roller 56, the ninth roller 59, and the eleventh roller 61 have a winding transmission structure or a gear transmission structure using a single motor 80 that is driven and rotated in one direction as a drive source. Simultaneously driven to rotate. Specifically, the first roller 51 and the eleventh roller 61 are rotationally driven in the counterclockwise direction in FIG. 4, and the sixth roller 56 and the ninth roller 59 are rotationally driven in the clockwise direction. The rotation direction of each roller 51-63 is as showing with the arrow in FIG.

  In order to perform skew correction of the original and to continuously read the images on the first and second sides of the original with the ADF 6, the output gear 81 provided on the first roller 51 and the fourth roller 54 are provided. A roller driving mechanism is provided between the passive gear 82 provided. The roller drive mechanism transmits the power of the output gear 81 to the passive gear 82, or transmits the reversed power to the passive gear 82, or stops the power transmission. The output gear 81 and the passive gear 82 are fixed to the gear shaft 83 of the first roller 51 and the gear shaft 84 of the fourth roller 54 that are rotatably supported, respectively.

  In FIG. 1, the roller driving mechanism includes a first intermediate gear 91 that always meshes with the output gear 81, a second intermediate gear 92 that always meshes with the first intermediate gear 91, a gear holder 93 that supports both gears 91 and 92, and a gear holder. 93 and a switching mechanism for switching operation. The gear holder 93 is made of a press-molded product integrally including front and rear arm portions 94 formed in an L shape and a cam follower 95 that connects upper ends of the arm portions 94.

  The output gear 81 and the first and second intermediate gears 91 and 92 are disposed between the front and rear arm portions 94, and the first and second intermediate gears 91 and 92 are respectively front and rear. Are supported by the gear shafts 96 and 97 supported by the arm portion 94. The entire gear holder 93 is supported by the gear shaft 83 of the output gear 81 and can be rotated around the gear shaft 83. By this rotation, one of the intermediate gears 91 and 92 is engaged with the passive gear 82, or The meshing state with the passive gear 82 can be eliminated. The output gear 81 and the passive gear 82 have the same number of teeth. The number of teeth of the first intermediate gear 91 is different from the number of teeth of the output gear 81, the passive gear 82 and the second intermediate gear 92, and the number of teeth of the second intermediate gear 92 is the number of teeth of the output gear 81 and the passive gear 82. It is different from. However, since both the first and second intermediate gears 91 and 92 only function as intermediate gears for transmitting rotational power, the drive rotational speed is increased between the output gear 81 and the passive gear 82, or There is no deceleration. However, the relationship of the number of teeth of each gear is not limited to the above, and other relationships can be taken.

  As shown in FIG. 6, the switching mechanism for the gear holder 93 uses the pull plunger type solenoid (driving member) 101 as a driving source, and intermittently rotates the egg-shaped cam 102 by the ratchet mechanism. Is swung around the gear shaft 83. The ratchet mechanism includes a ratchet gear 104 fixed to the rear side of the cam 102, a ratchet pawl 106 attached to the swing arm 105, and the like. The ratchet gear 104 is provided with four ratchet teeth, and the posture of the cam 102 can be switched by intermittently feeding each ratchet tooth 90 degrees clockwise in FIG.

  The swing arm 105 is rotatably supported by a cam shaft 107, and a projecting end of an operation rod 110 fixed to a plunger 109 is connected to a long hole 108 provided on the plate surface via a pin 111. . The ratchet pawl 106 is biased by a kick spring 112 in a direction in which it is pressed against the ratchet teeth. In addition, the plunger 109 is always biased in a direction of advancement by a spring (not shown) provided in the main body of the solenoid 101, and in a state where no drive current is supplied to the coil of the solenoid 101, As shown in FIG. 6, it protrudes out of the main body. In FIG. 1, reference numeral 103 denotes a compression coil spring that causes the cam follower 95 to be in close contact with the cam 102.

  The cam 102 includes a first cam surface 121 farthest from the center of the cam shaft 107, a second cam surface 122 closest to the center of the cam shaft 107, and a pair of smoothly connecting these cam surfaces 121 and 122. The third cam surface 123 is formed in an oval shape. When a drive current is supplied to the solenoid 101, the plunger 109 is drawn into the main body of the solenoid 101, and the swing arm 105 accompanies the plunger 109 and rotates downward. At the same time, the ratchet pawl 106 rotates the ratchet gear 104 by 90 degrees in the clockwise direction to change the posture of the cam 102. When the supply of the drive current to the solenoid 101 is stopped, the plunger 109 is pushed up to the standby position by a spring, and the ratchet pawl 106 moves over the ratchet teeth of the ratchet gear 104 and engages its passive surface. To do.

(Skewing Correction) The skew correction of the document is performed by rotationally driving the first conveyance roller 41 with the second conveyance roller 42 stopped. When the second conveying roller 42 is stopped, the first sensor 47 detects that the document has passed, and the switching mechanism is operated based on the output signal from the sensor 47 to show the posture of the cam 102 as shown in FIG. The state is switched, and the cam follower 95 is received by the third cam surface 123. In this state, since both the first intermediate gear 91 and the second intermediate gear 92 are separated from the passive gear 82, the second transport roller 42 is stopped. Therefore, the document conveyed by the first conveyance roller 41 is received at the nip portion between the fourth roller 54 and the fifth roller 55 at the conveyance start end, and further conveyed by the first conveyance roller 41. The posture of the original is corrected.

  After the second conveying roller 42 stops, the skew correction mode is canceled after a predetermined time has elapsed, and at the same time, the switching mechanism is operated to switch the posture of the cam 102 to the state shown in FIG. The roller 54 is driven in the forward direction to start conveying the document. When the solenoid 101 is operated from the state of FIG. 1, the cam 102 is rotated by 90 degrees by the plunger 109, and the first cam surface 121 pushes up the cam follower 95 against the biasing force of the spring 103. As a result, the gear holder 93 rotates counterclockwise around the gear shaft 83, so that the first intermediate gear 91 meshes with the passive gear 82 as shown in FIG. Drive to rotate in the direction. That is, the fourth roller 54 is driven to rotate forward in the same direction as the first roller 51, and conveys the document from the first conveyance path 31 to the second conveyance path 32, while the image on the first surface is read by the reading unit. 14 is read. Thereafter, as indicated by the continuous arrow line in FIG. 4, the sheet is discharged from the discharge port 25 via the second transfer path 32 and the third transfer path 33.

(Double-sided scanning of original) When reading images on the first and second sides of the original, the original is read from the second conveyance path 32 after reading the image on the first side of the original in the same manner as described above. It conveys to the 4th conveyance path 34, and reverses. Further, the inverted document is conveyed in the reverse direction toward the contact glass 21 via the fifth conveyance path 35, and the image on the second surface is read. In this conveyance process, the second sensor 48 detects that the original has passed, and based on the output signal from the sensor 47, the switching mechanism is operated to switch the posture of the cam 102 to the state shown in FIG. The cam follower 95 is received by the cam surface 122. As a result, the second transport roller 42 is rotationally driven in the reverse direction to transport the document to the sixth transport path 36 via a part of the first transport path 31, and the second transport path 32 and the third transport path. Then, the paper is discharged from the paper discharge outlet 25 through 33.

  In order to rotationally drive the second transport roller 42 in the reverse direction, the solenoid 101 is operated twice to switch the gear holder 93 from the state shown in FIG. 7 to the state shown in FIG. In the state where the solenoid 101 is operated once, the third cam surface 123 receives the cam follower 95 as shown in FIG. 1, but the posture of the cam 102 at this time is reversed 180 degrees from the posture shown in FIG.

  In the state where the solenoid 101 is operated for the second time, the second cam surface 122 of the cam 102 receives the cam follower 95 as shown in FIG. As a result, the gear holder 93 is pushed by the spring 103 and rotates clockwise around the gear shaft 83, the second intermediate gear 92 meshes with the passive gear 82, and the passive gear 82 faces away from the output gear 81. To rotate. That is, the fourth roller 54 is reversely driven in the reverse direction to the first roller 51 to convey the document from the first conveyance path 31 to the sixth conveyance path 36, while the image on the second surface is read by the reading unit 14. Read.

  The document conveyed in the reverse direction to the first conveyance roller 41 is guided by the first gate body 71 and passes through the nip portion between the first roller 51 and the third roller 53, and proceeds straight through the sixth conveyance path 36 to the second. 4 is conveyed to the conveying roller 44 (see FIG. 5). Further, the document that has passed through the fourth transport roller 44 is guided by the third gate body 73, transported from the second transport path 32 to the third transport path 33, and discharged from the discharge port 25. Each of the first to fifth gate bodies 71 to 75 is appropriately switched to the above-described direction for assisting the conveyance of the document, and blocks each conveyance path on the side where the document should not enter.

  As described above, according to the roller driving mechanism constituted by the first and second intermediate gears 91 and 92, the gear holder 93, the solenoid 101, the cam 102, and the like, the rotational power of the first roller 51 is supplied to the fourth roller 54. On the other hand, it can be transmitted intermittently or reversed. Accordingly, not only can the skew correction of the document be performed by the cooperative action of the first transport roller 41 and the second transport roller 42, but the second transport roller 42 is driven in the reverse direction so that the first surface and the second surface of the document are Image reading can be performed smoothly and continuously in the ADF 6.

  Further, since the solenoid 101 is used as a drive source and the posture of the gear holder 93 is switched to interrupt or drive the power to the fourth roller 54, the structure of the roller drive mechanism can be simplified and configured at a lower cost. . For example, in a conventional apparatus using a forward / reverse motor or a stepping motor as a drive source or using an electromagnetic clutch, the overall structure becomes complicated and the use of expensive parts is indispensable. The overall cost of the drive mechanism can be reduced. Further, in a state where it is not necessary to use the second transport roller 42, the load of the motor 80 can be reduced by stopping the second transport roller 42 by operating the solenoid 101 to change the posture of the cam 102. , Useless power consumption can be eliminated. Further, wear of the passive gear 82 and the gears 91 and 92 meshing with the gear 82 can be reduced.

  FIG. 9 shows another embodiment of the switching mechanism. Therefore, the cam 102 and the ratchet structure in the above embodiment are omitted, and the gear holder 93 is directly switched by the solenoid (driving member) 101. Specifically, the gear holder 93 can be switched using the solenoid 101 that can control the pull-in position of the plunger 109 in three stages. The gear holder 93 is provided with an operation arm 98, and a projecting end of an operation rod 110 fixed to the plunger 109 is connected via a pin 111 to a long hole 108 formed in the plate surface. Since others are the same as the previous embodiment, the same reference numerals are assigned to the same members, and descriptions thereof are omitted.

  According to the above switching mechanism, the first intermediate gear 91 meshes with the passive gear 82 in the state where the plunger 109 has advanced most from the main body portion of the solenoid 101, so that the fourth roller 54 can be driven forward. From this state, when the plunger 109 is pulled into the main body of the solenoid 101 by one step, the gear holder 93 rotates around the gear shaft 83 in the clockwise direction, and the first intermediate gear 91 is separated from the passive gear 82. . At this time, the second intermediate gear 92 approaches the passive gear 82, but does not mesh, so the fourth roller 54 stops. When the plunger 109 is further pulled into the main body of the solenoid 101 by one step, the gear holder 93 rotates in the clockwise direction around the gear shaft 83, so that the second intermediate gear 92 meshes with the passive gear 82. Accordingly, the fourth roller 54 is driven in reverse.

  As described above, when the gear holder 93 is directly switched by the solenoid 101, the cam 102 and the ratchet mechanism in the previous embodiment can be omitted, so that the structure of the switching mechanism can be simplified and the overall cost of the roller driving mechanism can be further reduced. . Further, since the gear holder 93 can be switched quickly and accurately without a time delay, there is an advantage that it is possible to cope with an increase in the document conveying speed.

  In the above-described embodiment, the document transport path 26 is configured by the first transport path 31 to the sixth transport path 36 so that the images of the first surface and the second surface of the document can be read. The structure does not need to be the structure described in the embodiment. Further, the roller driving mechanism may be provided anywhere as long as it is between the transport roller having the output gear and the transport roller having the passive gear to which the rotational power of the output gear is transmitted. The first transport roller 41 and the second transport roller 42 can be driven to rotate by dedicated motors. In this case, an output gear 81 is provided on the output shaft of the motor for the second transport roller 42. The drive member can be composed of an actuator other than a solenoid.

6 automatic document feeder 21 contact glass 26 document conveyance path 31 first conveyance path 32 second conveyance path 41 first conveyance roller 42 second conveyance roller 81 output gear 82 passive gear 83 gear shaft 91 first intermediate gear 92 second intermediate Gear 93 Gear holder 101 Drive member (solenoid)
102 Cam 104 Ratchet gear 106 Ratchet claw

Claims (5)

An automatic document conveying device in which a first conveying roller is disposed upstream of a document conveying path, and a second conveying roller is disposed downstream of the first conveying roller,
An output gear that is rotated and driven by the power of a motor that rotates in one direction, a passive gear that is provided on the second transport roller,
A roller drive mechanism for transmitting rotational power of the output gear to the passive gear;
A switching mechanism for switching the transmission state of the roller drive mechanism,
The roller driving mechanism is configured to be switchable by the switching mechanism between a state in which the second transport roller is driven to rotate forward, a state in which the second transport roller is driven in reverse rotation, and a state in which the roller is stopped.
An automatic document feeder, wherein skew feeding correction is performed between the first transport roller in a rotationally driven state and the second transport roller in a stopped state. A first intermediate gear in which the roller driving mechanism always meshes with the output gear;
A second intermediate gear that always meshes with the first intermediate gear;
A gear holder that supports the first intermediate gear and the second intermediate gear and rotates around a gear shaft of the output gear;
The gear holder is switched by the switching mechanism so that either the first intermediate gear or the second intermediate gear meshes with the passive gear, and the second transport roller can be driven to rotate forward or reversely. ,
The automatic document feeder according to claim 1, wherein the gear holder can be switched by the switching mechanism to interrupt power transmission to the passive gear.   The switching mechanism includes a driving member, a cam that is intermittently rotated by the driving member via a ratchet mechanism, a cam follower that is provided on the gear holder and that is switched by the cam, and the cam follower The automatic document feeder according to claim 1, further comprising a spring biased in a direction in close contact with the document. A contact glass for reading an image of the document is disposed in the middle of the document transport path,
Reading the first surface of the document on each of the first transport path for transporting the first surface of the document toward the contact glass and the fifth transport path for transporting the second surface of the document toward the contact glass. A first sensor for detecting the timing and a second sensor for detecting the reading timing of the second side of the inverted document;
2. The roller driving mechanism is switched by the switching mechanism based on output signals from the first sensor and the second sensor, and the second transport roller is held in a stopped state or driven in reverse. The automatic document feeder according to any one of 2 and 3. The switching mechanism is composed of a solenoid that can control the pull-in position of the plunger in three stages,
The gear holder is directly switched by the solenoid to switch between a state in which the second transport roller is driven to rotate forward, a state in which the second transport roller is driven in reverse rotation, and a state in which the second transport roller is stopped. The automatic document feeder according to claim 2, which is configured so that

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