JP2017024837A - Sheet conveyance device, image reading device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent second conveyance means from becoming a conveyance resistance of a sheet in comparison to a case of using freely-rotating means for freely rotating a second conveyance roller.SOLUTION: A sheet conveyance device comprises: conveyance means which conveys a document 6 to a reading position by a first conveyance roller 73, and conveys the document 6 having passed through the reading position to the first conveyance roller 73 by reversing the front and back sides of the document with switch back using a discharge roller 77; a single drive motor 321 whose rotation direction can be switched between the first and second directions; and movement means which moves a holding member holding a driven roller 77a in a freely-rotating manner out of a drive roller 77b arranged on the lower side in the vertical direction and the driven roller 77a arranged on the upper side in the vertical direction to the separation position in the direction of separating from the drive roller 77b.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a sheet conveying apparatus, an image reading apparatus, and an image forming apparatus.

  Conventionally, as a technique related to the sheet conveying apparatus, for example, a technique disclosed in Patent Document 1 has already been proposed.

  In Japanese Patent Laid-Open No. 2004-228867, when a document that has passed a reading position is switched back by a second transport roller and turned upside down and sent to the upstream side of the first transport roller, the first transport roller and the second transport Both the rollers rotate in reverse, the document is switched back and reaches the first transport roller, and then the first transport roller rotates forward and the second transport roller stops the document transport operation. Means are provided so that the document is not pulled between the first transport roller and the second transport roller.

  Further, Patent Document 1 includes a mode including a rotatable unit that allows the second conveying roller to rotate when the first conveying roller is rotated forward as the operation canceling unit.

JP 2007-217179 A

  According to the present invention, as compared with the case where a rotatable means that allows the second conveying roller to rotate is used, the second conveying means suppresses the sheet conveying resistance, and the sheet discharge property is ensured. The purpose is to do.

According to the first aspect of the present invention, the sheet is conveyed to the reading position by the first conveying roller, and the sheet that has passed through the reading position is switched back by the second conveying roller to reverse the front and back. Conveying means for conveying to the first conveying roller;
A single drive means capable of switching the rotation direction between the first and second directions;
Of the second conveying roller comprising a driving roller disposed below the vertical direction and a driven roller disposed above the vertical direction, a holding member that rotatably holds the driven roller is separated from the driving roller. Moving means for moving to a separated position in the direction of
Is a sheet conveying apparatus.
Here, the moving means rotates the first and second transport rollers when, for example, the sheet is switched back by the second transport roller and the front and back are reversed and transported to the first transport roller. When the direction is switched to the normal rotation direction, it can be configured as a conveyance force releasing means for releasing the conveyance force by the second conveyance roller.

  According to a second aspect of the present invention, the driven roller is rotatably supported by the holding member in a state in which the driven roller is allowed to move in a direction away from or in contact with the driving roller. It is a transport device.

  According to a third aspect of the present invention, the first conveying roller is connected to the driving unit via a rotating unit that rotates in a fixed direction regardless of the rotation direction of the driving unit. 2. The sheet conveying apparatus according to 2.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the driven roller of the second conveying roller is attached to an opening / closing unit provided to be openable and closable with respect to the main body of the sheet conveying apparatus. The sheet conveying apparatus according to claim 1.

  According to a fifth aspect of the present invention, the holding member is moved to the separation position via a tooth-missing gear that intermittently transmits the rotational driving force of the driving means. It is a sheet conveying apparatus of description.

According to a sixth aspect of the present invention, there is provided the sheet conveying apparatus according to any one of the first to fifth aspects,
Image reading means for reading an image from a sheet conveyed by the sheet conveying device;
An image reading apparatus.

The invention described in claim 7 is an image reading apparatus according to claim 6,
Image forming means for forming an image read by the image reading device on a recording medium;
An image forming apparatus.

  According to the first aspect of the present invention, it is possible to suppress the second conveyance unit from becoming a sheet conveyance resistance as compared with the case where a rotatable unit that rotates the second conveyance roller is used. In addition, sheet discharge performance can be ensured.

  According to the second aspect of the present invention, the second transport is compared with the case where the driven roller is not rotatably supported by the holding member in a state in which the driven roller is allowed to move away from or in contact with the driving roller. It is possible to reliably suppress the means from becoming a sheet conveyance resistance.

  According to the third aspect of the present invention, compared to the case where the first conveying roller is not provided with a rotating unit that rotationally drives the first conveying roller in a constant direction regardless of the rotating direction of the driving unit, the second original is conveyed. Can be started early.

  According to the fourth aspect of the present invention, the jammed document can be easily removed as compared with the case where a driving roller that is difficult to move is mounted on the opening / closing unit.

  According to the invention described in claim 5, compared to the case where the holding member is moved to the separation position without being synchronized with the operation of switching the rotation direction of the second transport roller from the reverse rotation direction to the normal rotation direction, It can suppress more reliably that the 2nd conveyance means serves as conveyance resistance of a sheet.

  According to the sixth aspect of the present invention, compared to the case where the sheet conveying device according to any one of the first to fifth aspects is not provided, the second conveying unit is suppressed from becoming a conveyance resistance of the document. can do.

  According to the seventh aspect of the present invention, as compared with the case where the image reading device according to the sixth aspect is not provided, the interruption of the image forming operation on the recording medium due to the poor conveyance of the document is suppressed. can do.

1 is an overall configuration diagram showing an image forming apparatus to which an image reading apparatus according to Embodiment 1 of the present invention is applied. 1 is a configuration diagram illustrating an image reading apparatus according to a first embodiment of the present invention. It is a block diagram which shows the sheet conveying apparatus which concerns on Embodiment 1 of this invention. 1 is a perspective configuration diagram illustrating a sheet conveying device according to a first embodiment of the present invention. It is a front block diagram which shows the sheet conveying apparatus which concerns on Embodiment 1 of this invention. It is a plane lineblock diagram showing the sheet conveyance device concerning Embodiment 1 of this invention. It is a perspective block diagram which shows the principal part of the sheet conveying apparatus which concerns on Embodiment 1 of this invention. It is a section lineblock diagram showing an electromagnetic clutch. It is a perspective block diagram which shows a discharge roller. It is a perspective block diagram which shows a discharge roller. It is a perspective block diagram which shows an opening / closing unit. FIG. 4A is a configuration diagram showing a state where the driven roller is in pressure contact with the driving roller, and FIG. 4B is a configuration diagram showing a state where the driven roller is separated from the driving roller. It is a block diagram which shows a discharge roller. It is a perspective lineblock diagram showing a tooth missing gear. 3 is a timing chart illustrating an operation of the sheet conveying apparatus according to the first embodiment of the present invention. It is explanatory drawing which shows operation | movement of the sheet conveying apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows operation | movement of the sheet conveying apparatus which concerns on Embodiment 1 of this invention. FIG. 4A is a configuration diagram showing a state in which one engagement portion of the tooth-missing gear is engaged with the tip portion of the solenoid, and FIG. 5B is a diagram showing one engagement portion of the tooth-missing gear and the tip portion of the solenoid. It is a block diagram which shows the state by which engagement with was released. FIG. 5A is a configuration diagram showing an intermediate state in which the cam portion of the tooth missing gear rotates, and FIG. 5B is a configuration diagram showing a state in which the cam portion of the tooth missing gear is stopped.

  Embodiments of the present invention will be described below with reference to the drawings.

[Embodiment 1]
FIG. 1 is a configuration diagram showing an overall outline of an image forming apparatus to which a sheet conveying apparatus and an image reading apparatus according to Embodiment 1 of the present invention are applied.

<Overall Configuration of Image Forming Apparatus>
The image forming apparatus 1 according to the first embodiment is configured as a color copying machine, for example. The image forming apparatus 1 is based on an image reading device 3 that reads an image of a document 6 as an example of a sheet, image data read by the image reading device 3, image data sent from an external personal computer, or the like. And an image forming unit 2 as an example of an image forming unit that forms an image on a recording medium. The image reading device 3 is arranged in a state of being supported by the support unit 4 above the apparatus main body 1 a that houses the image forming unit 2. A space for discharging a recording medium on which an image is formed is formed between the image reading apparatus 3 and the apparatus main body 1a.

  As shown in FIG. 1, the image reading device 3 has a control panel 66 as an operation unit for operating the image forming device 1 and the image reading device 3, on an upper portion of a front wall 311 positioned on the front surface of the casing 31. Is provided. The control panel 66 also has a touch panel 67 that serves as a display unit that displays an operation menu, warnings, messages, and the like to the user, and that receives various settings for the displayed operation menu, and a plurality of operation buttons 68.

  The image forming unit 2 holds a plurality of image forming apparatuses 10 that form toner images developed with toner constituting the developer, and the toner images formed by the respective image forming apparatuses 10, and finally records media As an example, an intermediate transfer device 20 that transports the recording paper 5 to a secondary transfer position for secondary transfer, and a feeding that accommodates and transports the required recording paper 5 to be supplied to the secondary transfer position of the intermediate transfer device 20. A paper device 50 and a fixing device 40 for fixing the toner image on the recording paper 5 secondarily transferred by the intermediate transfer device 20 are provided. The apparatus body 1a is formed of a support structure member, an exterior cover, and the like. Note that the image forming unit 2 is not limited to the electrophotographic method, and may employ other methods such as an ink jet method, a thermal head method, or a lithographic method as long as an image can be formed on a recording medium. There may be.

The paper feeding device 50 is disposed so as to exist at a position below the exposure device 13. The sheet feeding apparatus 50, the desired size, the paper container ₅₁ 1-51 ₄ a plurality of (or single) for housing in a state loaded with recording paper 5 such as the type, the recording from the paper container ₅₁ 1-51 ₄ It is mainly composed of delivery devices 52 and 53 that feed out the paper 5 one by one. The paper container 51 is attached so that it can be pulled out, for example, to the front side (side surface on which the user faces during operation) of the apparatus main body 1a.

  Between the sheet feeding device 50 and the intermediate transfer device 20, a plurality of sheet conveying rollers 54 and 55 for conveying the recording sheet 5 delivered from the sheet feeding device 50 to the secondary transfer position and a conveyance guide (not shown) are configured. A paper feed path 56 is provided. The paper transport roller 55 disposed at a position immediately before the secondary transfer position in the paper feed transport path 56 is configured as a roller (registration roller) that adjusts the transport timing of the recording paper 5, for example. Further, a transport roller 58 and a discharge roller 59 for discharging the recording paper 5 to a discharge storage portion 57 provided in the upper portion of the apparatus main body 1a are disposed on the downstream side of the fixing device 40 in the paper transport direction. .

  The plurality of image forming apparatuses 10 includes four image forming apparatuses 10Y, 10M, 10C, which respectively form toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K). It is composed of 10K. Each image forming apparatus 10 (Y, M, C, K) requires a rotating photosensitive drum 11 as an example of an image holding member and a peripheral surface (image holding surface) on which the image of the photosensitive drum 11 can be formed. And a charging device 12 for charging to the potential of the photosensitive drum 11 and the charged peripheral surface of the photosensitive drum 11 are irradiated with light LB based on image information (signals) to form an electrostatic latent image having a potential difference (for each color). An exposure device 13, a developing device 14 that develops the electrostatic latent image with toner of a corresponding color (Y, M, C, K) developer to form a toner image, and each toner image is an intermediate transfer device 20. And a drum cleaning device 16 that removes adhering matter such as toner remaining on the image holding surface of the photosensitive drum 11 after the primary transfer and cleans it.

  The intermediate transfer device 20 includes an intermediate transfer belt 21, a plurality of conveyance rollers 22 to 26 that convey the intermediate transfer belt 21 along the direction of the arrow, and an adherent such as toner remaining on the surface of the intermediate transfer belt 21. A belt cleaning device 27 that removes and cleans the belt. Further, a secondary transfer roller 28 as a secondary transfer device that performs secondary transfer of the toner images on the intermediate transfer belt 21 to the recording paper 5 at once is brought into contact with the transport roller 26 via the intermediate transfer belt 21. Is arranged.

  The fixing device 40 includes a heating rotator 41 and a pressing rotator 42. A contact portion between the heating rotator 41 and the pressing rotator 42 constitutes a fixing processing unit that fixes the toner image on the recording paper 5.

  Further, the image forming apparatus 1 includes a duplex unit 60 for forming images on both sides of the recording paper 5. When the recording sheet 5 having an image formed on one side is transported to the discharge accommodating portion 57 by the discharge roller 59, the duplex unit 60 holds the discharge roller while the discharge roller 59 holds the rear end of the recording sheet 5. The recording paper 5 is introduced through the switching gate 61 by rotating 59 in the reverse direction. The double-sided unit 60 has a double-sided conveyance path 65 composed of a plurality of conveyance rollers 62 to 64 for conveying the introduced recording sheet 5 with its front and back reversed and a conveyance guide (not shown).

  In FIG. 1, reference numerals 140 (Y, M, C, K) denote toner cartridges as developer storage containers that store a developer containing at least toner to be supplied to the corresponding developing device 14. In this embodiment, only the toner is stored in the toner cartridge 140 (Y, M, C, K).

  Reference numeral 100 denotes a control device that controls the image forming operation of the image forming apparatus 1 and the image reading operation of the image reading apparatus 3. The control device that controls the image reading operation of the image reading device 3 may be provided separately from the control device of the image forming device 1.

<Basic operation of image forming apparatus>
Hereinafter, a basic image forming operation by the image forming apparatus 1 will be described.

  Here, when the four image forming devices 10 (Y, M, C, K) are used to form a full-color image configured by combining toner images of four colors (Y, M, C, K). The image forming operation will be described.

  When the image forming apparatus 1 receives the command information of the request for the image forming operation (printing), the four image forming apparatuses 10 (Y, M, C, K), the intermediate transfer apparatus 20, the secondary transfer apparatus 28, and the fixing apparatus. 40 etc. starts.

  In each image forming device 10 (Y, M, C, K), for example, based on the image data of the surface (first surface) of the document 6 read by the image reading device 3, the corresponding color The toner images are visualized as toner images of four colors (Y, M, C, K) respectively developed with toner. When each color toner image formed by each image forming device 10 (Y, M, C, K) is conveyed to the primary transfer position, the primary transfer device 15 transfers the toner image of each color to the arrow of the intermediate transfer device 20. Primary transfer is performed in such a manner that the intermediate transfer belt 21 is rotated in the direction indicated by the arrow in order. Subsequently, the intermediate transfer device 20 holds the toner image primarily transferred by the rotation of the intermediate transfer belt 21 and conveys it to the secondary transfer position. On the other hand, the paper feeding device 50 sends out the required recording paper 5 to the paper feeding conveyance path 56 in accordance with the image forming operation. In the paper feed conveyance path 56, a paper conveyance roller 55 as a registration roller sends the recording paper 5 to the secondary transfer position in accordance with the transfer timing and supplies it.

  At the secondary transfer position, the secondary transfer roller 28 performs secondary transfer of the toner image on the intermediate transfer belt 21 onto the recording paper 5 at once. In addition, in the intermediate transfer device 20 after the secondary transfer is completed, the belt cleaning device 27 removes and removes adherents such as toner remaining on the surface of the intermediate transfer belt 21 after the secondary transfer.

  Subsequently, the recording sheet 5 on which the toner image is secondarily transferred is peeled off from the intermediate transfer belt 21 and the secondary transfer roller 28 and then conveyed to the fixing device 40. In the fixing device 40, necessary fixing processing (heating and pressing) is performed to fix the unfixed toner image on the recording paper 5. Finally, the recording paper 5 after the fixing is completed is discharged by a transport roller 58 and a discharge roller 59 to, for example, a discharge storage portion 57 disposed on the upper portion of the apparatus main body 1a.

  Further, when forming images on both sides of the recording paper 5, when the recording paper 5 having an image formed on one side is conveyed to the paper discharge unit 57 by the discharge roller 59, the discharge roller 59 moves the trailing edge of the recording paper 5. While being held, the rotation direction of the discharge roller 59 is switched to the reverse direction. The recording sheet 5 conveyed in the reverse direction by the discharge roller 59 is switched to the duplex unit 60 side by the switching gate 61. Thereafter, the recording paper 5 is conveyed to the conveyance roller 55 in a state where the front and back sides are reversed via a double-sided conveyance path 65 including conveyance rollers 62 to 64 and the like. The conveyance roller 55 feeds the recording paper 5 to the secondary transfer position in accordance with the transfer timing and supplies it. On the recording paper 5, the toner image is secondarily transferred from the intermediate transfer belt 21 to the back surface (second surface) of the document 6 based on the image data of the back surface (second surface) of the document 6 read by the image reading device 3. The The recording sheet 5 on which the toner image has been secondarily transferred is subjected to fixing processing by the fixing device 40 and is discharged by the discharge roller 59 to the discharge accommodating portion 57 installed at the upper portion of the apparatus main body 1a with the second side down. Is done.

  With the above operation, the recording paper 5 on which a full-color image formed by combining four color toner images is discharged. Note that the image forming apparatus 1 may naturally form a monochrome image on the recording paper 5 using only the black (K) image forming apparatus 10K.

<Configuration of image reading apparatus>
FIG. 2 is a schematic configuration diagram showing a configuration of an image reading apparatus to which the sheet conveying apparatus according to the first embodiment is applied.

  The image reading apparatus 3 is roughly divided into a casing 31 having a document reading surface formed on the upper end surface, a document pressing cover 32 attached to the casing 31 so as to be openable and closable, and one end of the document pressing cover 32 ( An automatic document feeder (DADF: Duplex Automatic Document Feeder) 33 provided at the left end portion in the illustrated example is provided.

  The image reading device 3 includes a first reading mode for reading images on the front and back surfaces of the document 6 while automatically conveying the document 6 one by one by the automatic document conveying device 33 according to a user operation, and will be described later. It is configured to be switchable to a second reading mode for reading an image of the document 6 placed on the document table 83. FIG. 2 shows the state of each member during document reading in the first reading mode.

  The automatic document feeder 33 includes a document storage unit 70 that can stack and store a plurality of documents 6 with the reading surface (first surface) facing upward, and a nudger roller 71 that feeds the document 6 from the document storage unit 70. A feed roller 72 that feeds and feeds the originals 6 fed by the nudger roller 71 one by one; a retard pad 72a that is pressed by the feed roller 72 and that feeds the originals 6 one by one; One transport roller 73, transport rollers 74 and 75 that transport the document 6 transported by the first transport roller 73 so as to pass the reading position, and a second transport that discharges the document 6 to the discharge container 76. A document conveying mechanism (conveying means) including a discharge roller 77 as an example of a roller is provided. These nudger roller 71, feed roller 72, transport rollers 73 to 75, and discharge roller 77 are driven by driving means described later when reading document 6. The first conveyance roller 73 is a registration roller that adjusts the conveyance timing of the document 6 to the reading position. In this embodiment, although not specifically described as a pair of rollers, the terms “conveying roller” and “discharging roller” include a pair of rollers.

  The first transport roller 73 mechanically corrects the inclination of the document 6 with respect to the transport direction (hereinafter referred to as “skew correction”) and corrects the edge of the document 6 in the same direction as the transport direction. Also works. As shown in FIG. 2, the conveying roller 73b as the driving roller among the first conveying rollers 73 is driven in the forward direction of the drawing at a predetermined timing from a stopped state using a driving motor or the like described later as a driving means. Driven to rotate to Ra. The conveyance roller 73a, which is a driven roller, rotates according to the conveyance roller 73b while being in pressure contact with the conveyance roller 73b.

  The first conveyance roller 73 is configured such that the front end of the document 6 conveyed by the feed roller 72 positioned upstream in the conveyance direction of the document 6 is conveyed while the conveyance roller 73b as a driving roller is stopped. It abuts against the pressure contact portion between the roller 73b and the transport roller 73a. Then, the first conveying roller 73 bends the leading end region of the document 6 so that the leading edge of the document 6 coincides with the axial direction of the first conveying roller 73 and then starts to convey the document 6. Make corrections.

  In addition, the automatic document feeder 33 is provided on the reading guide 78 above the reading window 79 and a curved reading guide 78 for guiding the document 6 to the reading position and guiding it from the reading position to the discharge direction. A back support member 80 that supports the back surface of the document, a first size detection sensor 81 that is provided in the document storage unit 70 and detects the size of the document 6 in the sub-scanning direction, and a document 6 that is also provided in the document storage unit 70. And a second size detection sensor 82 for detecting the size in the sub-scanning direction.

  The housing 31 of the image reading device 3 is formed as a rectangular parallelepiped box with a part of the upper end surface opened. The casing 31 includes an upper wall 312 that faces the document pressing cover 32, a bottom wall 313 that faces the upper wall 312, a side wall 314 that faces the sub-scanning direction (left and right direction in FIG. 2) across the bottom wall 313, and A side wall 315, the above-described front wall 311 (see FIG. 1), and a rear wall 316 facing the front wall 311 along the main scanning direction (a direction perpendicular to the paper surface of FIG. 2).

  The upper wall 312 of the housing 31 is formed with a large planar rectangular opening 317 at a portion corresponding to the document reading position of the document 6 read in the second reading mode. A transparent document table 83 (platen glass) that supports the document 6 is disposed in the opening 317. A transparent reading window 79 for reading the document 6 in the first reading mode is provided on the automatic document feeder 33 side of the document table 83. Between the reading window 79 and the document table 83, there is provided a guide member 84 having an inclined upper end surface that guides the document 6 that has passed the reading position to the transport roller 75 in the first reading mode.

  The image reading apparatus 3 emits light from a light source 85 as an example of illumination means including an illumination lamp or LED (Light Emitting Diode) that irradiates light for illuminating the document 6 inside the housing 31. The reflector 86 that reflects a part of the light directed toward the document 6, the first mirror 87 that receives the reflected light from the document 6, and the second mirror that receives the reflected light from the first mirror 87 88, a third mirror 89 that receives the reflected light from the second mirror 88, and an image made up of the reflected light from the third mirror 89, such as a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor). An image reading unit having an imaging lens 91 that forms an image on an image reading element 90 as an example of a reading unit. The light source 85 emits light toward the document 6 and the reflector 86. The first to third mirrors 87 to 89 and the imaging lens 91 constitute a reading optical system for reading the image of the document 6 by the image reading element 90.

  The light source 85, the reflector 86, and the first mirror 87 are attached to a first moving body 92 including a carriage that is arranged along the main scanning direction and is movable along the sub scanning direction by a driving unit. Yes. The first moving body 92 is guided by the first rail 93 and illuminates the reading target area of the document 6 while moving along the sub-scanning direction, and the reflected light of the document 6 is first reflected by the first mirror 87. Reflected toward the second mirror 88 of the second moving body 94. The first rail 93 is disposed on the rear wall 316 of the housing 31 along the sub-scanning direction.

  The second mirror 88 and the third mirror 89 are attached to a second moving body 94 including a carriage that is disposed along the main scanning direction and is movable along the sub-scanning direction by a driving unit. It has been. The second moving body 94 reflects the reflected light of the document 6 toward the imaging lens 91 of the image reading unit while being guided by the second rail 95 and moving in the sub-scanning direction. The second rail 95 is disposed on the bottom wall 313 of the housing 31 along the sub-scanning direction. The first rail 93 and the second rail 95 are arranged one by one so as to face both ends along the main scanning direction.

  The image reading unit includes an image reading substrate 97 on which the image reading element 90 is mounted. The imaging lens 91 and the image reading substrate 97 are attached to a base plate 96 supported by the bottom wall 313. In the image reading unit, the reflected light from the third mirror 89 passes through the imaging lens 91 and forms an image on the image reading element 90 made of CCD, CMOS, or the like, and the image reading element 90 reads the image of the document 6. Output image data. Image data read by the image reading element 90 is subjected to predetermined image processing such as shading correction as necessary by an image processing device (not shown), and is sent to the control device 100.

  In the first reading mode, as shown by the solid line in FIG. 2, the first and second moving bodies 92 and 94 are stopped at the reading position set at the left end of the casing 31, The document 6 is automatically conveyed by the automatic document feeder 33, the document 6 passing through the upper portion of the reading window 79 is illuminated by the light source 85, and the reflected light image from the document 6 is second and second by the first mirror 87. Reflected to the imaging lens 91 through the three mirrors 88 and 89. The image reading unit forms an image of the reflected light from the third mirror 89 on the image reading element 90 by the imaging lens 91, reads an image of the document 6 by the image reading element 90, and receives image data from the image reading element 90. Output.

  On the other hand, in the second reading mode, the first moving body 92 and the second moving body 94 are driven by a driving unit (not shown), and the original moves while the first moving body 92 moves along the sub-scanning direction. The moving amount of the second moving body 94 is ½ of the moving amount of the first moving body 92 so that the optical path length from the image reading position 6 to the image reading element 90 does not change. . In FIG. 2, the alternate long and two short dashes line indicates the positions of the first moving body 92 and the second moving body 94 when the first moving body 92 moves to the vicinity of the end of the document 6 in the sub-scanning direction.

<Configuration of main part of image reading apparatus>
As shown in FIG. 3, the image reading apparatus 3 according to the first embodiment is configured to roll the document 6 as an example of the sheet stored in the document storage unit 70 one by one and convey it to the reading position, and to read the document. A sheet conveying device 320 is provided for conveying the document 6 that has passed through the position back to the reading position in a state in which the document 6 is switched back and turned upside down. The sheet conveying device 320 is an example of a nudger roller 71, a feed roller 72, a retard pad 72a, a first conveying roller 73, conveying rollers 74 and 75, a discharge roller 77, and driving means for driving these rollers. A single driving source 321, a constant direction rotating mechanism 322 as an example of a rotating unit that rotates the first conveying roller 73 in a certain direction regardless of the rotating direction of the driving source 321, and the first conveying roller 73. The first drive transmission switching unit 323 as an example of a switching unit that switches between a state in which the driving force is transmitted and a state in which the driving force is not transmitted, and a state in which the driving force is transmitted to the feed roller 72 and the nudger roller 71 and a state in which it is not transmitted And a second drive transmission switching unit 324 as an example of the switching unit.

  As shown in FIG. 3, the sheet conveying device 320 conveys the document 6 conveyed by the nudger roller 71 so as to pass through the feed roller 72, the first conveying roller 73, the conveying rollers 74 and 75, and the discharge roller 77. By switching the rotation direction of the discharge roller 77 to the reverse direction, the front and back of the document 6 are reversed to the first transfer roller 73 by switching the rotation direction of the discharge roller 77 to the normal conveyance path 325 and the discharge roller 77. And a reverse conveying path 326 for conveying again. The normal transport path 325 includes guide members 325 a and 325 b that guide the front and back of the document 6, a reading guide 78, and a back support member 80. The guide members 325a and 325b are divided into a plurality along the normal conveyance path 325. The reverse conveyance path 326 includes guide members 326 a and 326 b that guide the front and back of the document 6.

  In addition, a switching gate 327 is provided at a branch position where the normal conveyance path 325 and the reverse conveyance path 326 branch to switch the conveyance path of the document 6 from the normal conveyance path 325 to the reverse conveyance path 326. The switching gate 327 is made of an elastically deformable synthetic resin film having a substantially Y-shaped cross section. As shown in FIG. 3, the switching gate 327 is usually arranged so that a part thereof crosses the normal conveyance path 325 obliquely. When the document 6 is transported to the discharge roller 77 along the normal transport path 325, the switching gate 327 is elastically deformed so as to open the normal transport path 325 by being pushed by the document 6, and the transport direction of the document 6 Is switched to the discharge roller 77. On the other hand, the switching gate 327 reverses the rotation direction of the discharge roller 77 while the discharge roller 77 holds the trailing edge of the document 6, and when the document 6 is conveyed to the reverse conveyance path 326, the discharge roller 77. Is switched from the normal conveyance path 325 to the reverse conveyance path 326.

  The sheet conveying device 320 includes a document sensor 328 that detects the leading edge of the document 6 at a position corresponding to the nudger roller 71. Further, a pre-registration sensor 329 for detecting the leading edge and the trailing edge of the document 6 is provided on the upstream side of the first transport roller 73 in the transport direction of the document 6. Further, the sheet conveying device 320 is arranged on the downstream side of the conveying roller 74 along the conveying direction of the document 6, and the registration sensor 329 a that detects the leading edge of the document 6 and the upstream of the discharging roller 77 along the conveying direction of the document 6. And an inverter sensor 329b that detects the rear end of the document 6.

  The configuration of the sheet conveying apparatus 320 will be described more specifically. As shown in FIGS. 4 and 5, the sheet conveying apparatus 320 includes a driving motor 321 as an example of a driving unit. The drive motor 321 is configured to be able to switch the rotation direction between a first direction (forward rotation direction) and a second direction (reverse rotation direction). An output gear 332 is attached to the output shaft 331 (see FIG. 5) of the drive motor 321. The output gear 332 rotates in the first and second directions R1 and R2 according to the rotation direction of the drive motor 321. The output gear 332 is meshed with the first idler gear 333a among the two idler gears 333 configured integrally. Of the two idler gears 333, the second idler gear 333b meshes with the first drive gear 334 for rotationally driving the first transport row 73 and the transport rollers 74 and 75. The first drive gear 334 is integrally provided with a sun gear 335 on one side along the axial direction and a drive pulley 336 on the other side.

  As shown in FIG. 6, the first drive gear 334, the sun gear 335, and the drive pulley 336 are supported by a support shaft 399 that spans between the first and second frames 397 and 398 of the sheet conveying device 320. It is attached to be freely rotatable. As shown in FIGS. 4 and 5, a drive belt 338 is stretched over the drive pulley 336. The drive belt 338 includes a tension pulley 339 that applies tension to the drive belt 338, a driven pulley 341 attached to one end of the rotation shaft 340 of the transport roller 74, and a driven pulley that changes the tension direction of the drive belt 338. (Not shown) and a driven pulley 343 (see FIG. 5) attached to one end of the rotation shaft 342 of the transport roller 75. In FIG. 6, symbol S indicates a coil spring that applies tension to the tension pulley 339.

  As shown in FIGS. 5 and 7, the first and second planetary gears 344 and 345 having a diameter smaller than that of the sun gear 335 are meshed with the outer periphery of the sun gear 335. The first and second planetary gears 344 and 345 are attached to the tip of the planet carrier 346, respectively. The planet carrier 346 is rotatably mounted on the support shaft 399 of the sun gear 335. The first and second planetary gears 344 and 345 are arranged such that a central angle on the one-way gear 348 side described later forms an angle smaller than 180 degrees. The planet carrier 346 is brought into pressure contact with the side surface of the sun gear 335 with a required pressure by an annular leaf spring 347 (see FIG. 4) formed in a curved shape. The planet carrier 346 rotates in the same direction as the sun gear 335 as the sun gear 335 rotates.

  As shown in FIG. 4, a one-way gear 348 as an example of a one-way gear that selectively meshes with the first or second planetary gears 344 and 345 is provided on the side of the sun gear 335. The one-way gear 348 is rotatably mounted on the rotation shaft 349 of the first transport roller 73. When the sun gear 335 rotates in the forward rotation direction (clockwise direction in the drawing), the one-way gear 348 rotates in the clockwise direction in the drawing by directly meshing with the first planetary gear 344 attached to the planet carrier 346. . Further, the one-way gear 348 rotates with the second planetary gear 345 attached to the planet carrier 346 when the sun gear 335 rotates in the reverse direction (counterclockwise direction in the figure), and the planet carrier 346 rotates in the reverse direction. By meshing with the intermediate gear 351, it rotates in the clockwise direction in the figure. Thus, the one-way gear 348 always rotates in a fixed direction (clockwise direction in FIG. 4) regardless of the rotation direction of the drive motor 321 that drives the sun gear 335 in the forward direction and the reverse direction. The sun gear 335, the first and second planetary gears 344, 345, the intermediate gear 351, and the one-way gear 348 constitute a constant direction rotating mechanism 322.

  As shown in FIGS. 5 and 7, the intermediate gear 351 is rotatably attached to the tip 352 a of the arm member 352. The intermediate gear 351 is always meshed with the one-way gear 348. The arm member 352 is mounted with its position fixed with respect to the support shaft 399. As shown in FIG. 6, the arm member 352 is disposed between the second frame 398 and the planet carrier 346. As described above, the planet carrier 346 is pressed against the side surface of the sun gear 335 by the annular leaf spring 347 interposed between the planet carrier 346 and the arm member 352. Further, the arm member 352 has columnar convex portions 346a and 346b provided on the planet carrier 346 on the side surfaces 352b and 352c of the support portion that rotatably supports the first and second planetary gears 344 and 345, respectively. The planet carrier 346 that abuts and rotates with the sun gear 335 is positioned. The intermediate gear 351 is coaxially provided with a driven pulley (not shown) that changes the tension direction of the drive belt 338. The intermediate gear 351 transmits the unidirectional gear 348 by reversing the rotation direction of the second planetary gear 345. The intermediate gear 351 is not limited to one, and may be composed of an odd number of intermediate gears meshed with each other.

  In this embodiment, the same gear is used as the first and second planetary gears 344 and 345 and the intermediate gear 351 in order to share the parts.

  As shown in FIG. 4, the one-way gear 348 is attached to a first electromagnetic clutch 323 as an example of first drive transmission switching means. As shown in FIG. 8, the first electromagnetic clutch 323 is attached to a rotor 323 a that is fixed to the rotary shaft 349 via a D-cut surface 349 a formed on the rotary shaft 349 of the first transport roller 73. A stator 323c arranged in a fixed state with respect to the rotor 323a via a bearing 323b, and an armature that is a movable piece that is rotatably attached to the rotary shaft 349 and is mounted with the one-way gear 348 fixed. 323d, an excitation coil 323e that is provided on the stator 323c and forms a magnetic circuit penetrating in the axial direction of the rotor 323a, and a cylindrical exterior 323f that doubles as a yoke and protects the excitation coil 323e. The exterior 323f is disposed adjacent to the one-way gear 348. The outer diameter of the exterior 323f is set larger than that of the one-way gear 348. The exterior 323f may be configured integrally with the stator 323c. Further, the stator 323c is fixed to the second frame 398 of the sheet conveying device 320 via a rotation preventing portion 323g. The armature 323d has a separation spring (not shown) that urges the armature 323d away from the rotor 323a, and forms a gap G between the vertical surface of the armature 323d and the side surface of the rotor 323a.

  The first electromagnetic clutch 323 couples the armature 323d and the rotor 323a against the separation spring by energizing the exciting coil 323e, and uses the rotational driving force of the armature 323d rotated by the one-way gear 348 as the rotor 323a. And the rotating shaft 349 to which the rotor 323a is fixed is rotated.

  On the other hand, in the first electromagnetic clutch 323, when the energization to the exciting coil 323e is cut off, the armature 323d is separated from the rotor 323a by the elastic force of the separation spring, and the rotational driving force of the armature 323d is not transmitted to the rotor 323a. Then, the rotating shaft 349 to which the rotor 323a is fixed is stopped. At that time, the armature 323d to which the one-way gear 348 is attached continues to rotate together with the one-way gear 348.

  Of the two idler gears 333, the second idler gear 333b meshes with the second drive gear 355 for rotationally driving the nudger roller 71, the feed roller 72, and the discharge roller 77, as shown in FIG. Has been. The second drive gear 355 is meshed with a driven gear 357 attached to the end of the rotation shaft 356 of the drive roller 77 b in the discharge roller 77. Further, as shown in FIG. 4, a transmission gear 358 that transmits a rotational driving force to the nudger roller 71 and the feed roller 72 is engaged with the driven gear 357. A second electromagnetic clutch 324 as an example of second drive transmission switching means is mounted on the rotation shaft 359 of the transmission gear 358. The second electromagnetic clutch 324 is configured in the same manner as the first electromagnetic clutch 323. In FIG. 4, reference numeral 324 g indicates a rotation stop portion of the second electromagnetic clutch 324.

  As shown in FIG. 4, a driven gear 360 made of a helical gear or a spur gear is fixedly attached to the rotating shaft 359 of the transmission gear 358. Further, the driven gear 360 is meshed with a transmission gear 361 that is a helical gear or a spur gear that transmits a rotational driving force to the feed roller 72.

  Furthermore, in this embodiment, as shown in FIG. 5, after the discharge roller 77 switches back the document 6 and transports it to the first transport roller 73, the rotation direction of the drive motor 321 is switched to the normal rotation direction. A release means (moving means) 362 for releasing the conveying force for the document 6 at a preset timing.

  As shown in FIG. 3, the release means 362 separates the driven roller 77 a positioned above in the vertical direction from the driving roller 77 b positioned below in the vertical direction among the discharge rollers 77 formed of a pair of rollers in pressure contact with each other. To the separated position. As shown in FIGS. 9 and 10, the driven roller 77 a of the discharge roller 77 is attached to an opening / closing unit 400 that is attached to the housing 31 of the image reading apparatus 3 so as to be freely opened and closed. As shown in FIG. 3, the opening / closing unit 400 constitutes an upstream end portion of a normal conveyance path 325 disposed below the nudger roller 17 and the feed roller 72 and an upper surface of the reverse conveyance path 326.

  As shown in FIG. 9, the main body 401 of the opening / closing unit 400 is provided with mounting portions 402 at both ends along the axial direction of the end portion located on the discharge roller 77 side in the upper portion. As shown in FIG. 11, the main body 401 of the opening / closing unit 400 is attached to the casing 31 of the image reading apparatus 3 so that the opening / closing unit 400 can be opened and closed with the attachment portion 402 as a fulcrum. The opening / closing unit 400 is configured to open and close the first conveying roller 73 side, which is an end portion on the downstream side in the conveying direction of the document 6, with a mounting portion 402 provided at the end portion on the discharge roller 77 side as a fulcrum. Has been. The opening / closing unit 400 is exposed to the outside by opening the cover 403 of the image reading device 3. The main body 401 of the opening / closing unit 400 is provided with an operation unit 404 for opening / closing the main body 401 on one side of the end portion located on the first conveying roller 73 side.

  As shown in FIGS. 9 and 10, a driven roller 77 a of the discharge roller 77 is rotatably attached to the main body 401 of the opening / closing unit 400. The main body 401 of the opening / closing unit 400 includes a support shaft 363 that is rotatably supported. An arm-shaped holding member 364 extending in a direction intersecting with the support shaft 363 is attached to the support shaft 363 in a fixed state. The holding members 364 are respectively disposed at both end portions along the axial direction of the driven roller 77a. As shown in FIG. 12A, a disc-shaped holding portion 405 that rotatably holds the driven roller 77a is provided at the distal end portion of the holding member 364. In the holding portion 405, a bearing hole 406 that rotatably supports the rotation shaft 77a 'of the driven roller 77a is formed in an elliptical shape along a substantially vertical direction. The length of the bearing hole 406 along the vertical direction is set longer than the diameter of the rotation shaft 77a 'of the driven roller 77a. Therefore, the driven roller 77a is allowed to move in a direction approaching the driving roller 77b by the gap ΔL in a state where the rotation shaft 77a 'is supported by the bearing hole 406 of the holding portion 405. In the illustrated embodiment, the lower end portion of the bearing hole 406 is opened, and the opening width is set smaller than the diameter of the rotating shaft 77a '.

  Further, as shown in FIG. 13, a coil spring 407 is stretched between the base end portion of the holding member 364 and the main body 401 of the opening / closing unit 400. The driven roller 77a that is rotatably attached to the holding member 364 is urged in a direction (in the clockwise direction in FIG. 13) that presses against the driving roller 77b around the support shaft 363 by the elastic force of the coil spring 407. . Further, the holding member 364 abuts against a stopper (not shown), so that the rotation position in the clockwise direction is restricted.

  As shown in FIGS. 9 and 10, an elevating arm 365 that raises and lowers the driven roller 77 a away from the driving roller 77 b is integrally formed in one end portion of the support shaft 363 in a direction intersecting the support shaft 363. Is provided. As shown in FIG. 5, the lifting arm 365 is driven up and down by intermittently transmitting a driving force from the driven gear 357 via the tooth-missing gear 367.

  On one side of the driven gear 357, as shown in FIGS. 4 and 5, a tooth missing gear 367 in which teeth are not provided in part along the circumferential direction is disposed. A solenoid 370 for intermittently driving the tooth missing gear 367 is provided on one side of the tooth missing gear 367.

  As shown in FIG. 14, the tooth missing gear 367 is configured by combining a first tooth missing gear 368 and a second tooth missing gear 369 coaxially. The first tooth missing gear 368 is integrally provided on one end side along the axial direction of the large diameter portion 371 and the large diameter portion 371 formed in a cylindrical shape having a relatively large outer diameter, and has a large diameter. And a small-diameter portion 372 formed in a hollow cylindrical shape having an outer diameter relatively smaller than that of the portion 371. On the outer periphery of the large diameter portion 371, a first gear portion 373 and a second gear portion 374 having a central angle smaller than 180 degrees are formed at positions symmetrical with respect to the center of the shaft. Yes. And between the 1st gear part 373 and the 2nd gear part 374, the 1st and 2nd tooth | gear part 375,376 with which the tooth | gear is not formed is provided. Further, on the outer periphery of the small diameter portion 372, two engaging portions 377 and 378 (see FIG. 5) are provided at positions different by 180 degrees. As shown in FIG. 5, the engaging portions 377 and 378 are inclined along one of the engaging surfaces 377 a and 378 a formed along the radial direction and the circumferential ends from the tips of the engaging surfaces 377 a and 378 a. The inclined surfaces 377b and 378b are formed as described above. As shown in FIG. 5, when the solenoid 370 is in the OFF state, the engagement portions 377 and 378 of the small diameter portion 372 are engaged with the tip 379a of the operating piece 379 biased by the spring 370a.

  On the other hand, as shown in FIG. 14, the second tooth missing gear 369 has a large diameter portion 380 formed in a cylindrical shape having a relatively large outer diameter, and one end along the axial direction of the large diameter portion 380. And a cam portion 381 provided integrally on the side. On the outer periphery of the large-diameter portion 380, similarly to the first toothless gear 368, a third gear portion 382 and a fourth gear portion 383 having an angle smaller than 180 degrees are the center of the shaft. It is formed at a position that is symmetrical with respect to. In addition, third and fourth tooth missing portions 384 and 385 are provided between the third gear portion 382 and the fourth gear portion 383. The third and fourth gear portions 382 and 383 and the third and fourth tooth missing portions 384 and 385 are the first and second gear portions 373 and 374 and the first and second tooth missing portions 375, respectively. , 376.

  The cam portion 381 is provided in a planar shape at a position closer to the rotation axis, in a first flat portion 381a provided in a planar shape parallel to the rotation axis, and in a position further away from the rotation axis than the first flat portion 381a. And a second flat portion 381b and curved portions 381c and 381d connecting the first and second flat portions 381a and 381b.

  Between the first tooth missing gear 368 and the second tooth missing gear 369, a rotational force that rotates the first tooth missing gear 368 in the clockwise direction in FIG. 5 with respect to the second tooth missing gear 369. A coil spring 386 is provided as an example of a rotational force applying means for applying the torque. One end of the coil spring 386 is inserted into the insertion hole 387 of the first toothless gear 368. The other end of the coil spring 386 is inserted into the insertion hole 388 (see FIG. 18) of the second toothless gear 369.

  The second tooth missing gear 369 is provided with a pin 389 as an example of a guided member on a side surface located on the first tooth missing gear 368 side. On the other hand, a guide groove 390 as an example of a guide portion is formed in the first tooth missing gear 368 corresponding to the pin 389. The guide groove 390 is formed in an arc shape so as to form a required center angle at a required position centered on the axis. In the state where the first tooth missing gear 368 and the second tooth missing gear 369 are combined, the first tooth missing gear 368 is rotated clockwise in FIG. 5 with respect to the second tooth missing gear 369 by the coil spring 386. A rotational force rotating in the direction is applied. Further, in the state shown in FIG. 5, the pin 389 is located on the one end 390 a side of the guide groove 390.

  As shown in FIG. 10, the tip portion 392 of the actuating member 391 is disposed so as to be always in pressure contact with the cam portion 381 of the second toothless gear 369 by an elastic force such as a coil spring (not shown). The actuating member 391 is rotatably attached to the first frame 397 via a support shaft 393 provided at the base end thereof. At the base end portion of the operation member 391, an operation portion 394 that raises and lowers the elevating arm 365 is provided on the side surface of the base end portion so as to protrude along the axial direction of the support shaft 393. In addition, a flat plate detection unit 395 for detecting the position of the operation member 391 by the position sensor 396 is provided at the tip of the operation member 391.

<Operation of Characteristic Part of Image Reading Apparatus>
In the image reading apparatus 3 according to this embodiment, images on the front and back sides of the document 6 are read as follows.

  That is, in the image reading device 3, as shown in FIG. 15, the control device 100 controls the drive motor 321 and the solenoid 370 of the sheet conveying device 320 based on detection signals from the pre-registration sensor 329 and the like. First, in the image reading apparatus 3, the drive motor 321 is activated, and the drive motor 321 drives the nudger roller 71, the feed roller 72, and the like. The documents 6 stored in the document storage unit 70 are conveyed one by one by a nudger roller 71 and a feed roller 72. At this time, the first conveying roller 73 is stopped because the first electromagnetic clutch 323 is off. The skew of the document 6 conveyed by the feed roller 72 is corrected by contacting the first conveyance roller 73 whose front end is stopped.

  At this time, as shown in FIGS. 4 and 5, when the drive motor 321 is rotationally driven in the normal rotation direction R <b> 1, the image reading device 3 is engaged with the sun gear 335 along with the rotational drive of the drive motor 321. The first planetary gear 344 moves to the one-way gear 348 side. The first planetary gear 344 is meshed with the one-way gear 348.

  Thereafter, as shown in “1” of FIG. 16, the first conveying roller 73 causes the rotational driving force of the one-way gear 348 to be applied to the rotating shaft 349 when the first electromagnetic clutch 323 is turned on. Then, the document 6 is conveyed to the discharge roller 77 via the conveyance rollers 73 and 74. As shown in FIG. 2, the image on the first surface of the document 6 is read by the image reading element 90 of the image reading unit stopped at the first reading position while passing through the upper portion of the reading window 79. Thereafter, in the case of single-sided reading, the document 6 is discharged to the discharge container 76 by the discharge roller 77.

  When the image reading device 3 reads images on both sides of the document 6, the drive motor 321 is temporarily stopped while the discharge roller 77 holds the trailing edge of the document 6, as shown in FIG. After that, it is rotated in the reverse rotation direction R2. When the drive motor 321 is rotated in the reverse direction, the transport rollers 73 and 74 driven by the drive motor 321 are also rotated in the reverse direction. On the other hand, the first transport roller 73 is rotationally driven in one direction by the constant direction rotating mechanism 322.

  The document 6 conveyed in the reverse direction by the discharge roller 77 is transferred to the reversal conveyance path 326 with the front and back being reversed via the switching gate 327 (see FIG. 3), as indicated by “2” in FIG. Be transported.

  The drive motor 321 is temporarily stopped after rotating in the reverse rotation direction for a preset time. At this time, as shown in FIG. 15, the solenoid 370 of the release means 362 is turned on for a preset time.

  As shown in FIG. 18A, the release means 362 normally has the solenoid 370 turned off, and the tip 379a of the operating lever 379 is engaged with one of the engaging portions 377 of the tooth missing gear 367. ing. At this time, the tooth missing gear 367 is stopped at a position where the second and fourth tooth missing portions 376 and 385 face the driven gear 357. Therefore, the rotational driving force of the driven gear 357 is not transmitted to the tooth missing gear 367. At this time, in the cam portion 381 of the tooth missing gear 367, the first cam portion 381a is in contact with the distal end portion 392 of the operating member 391. Therefore, the actuating member 391 is at a position rotated counterclockwise in FIG. Therefore, the actuating portion 394 of the actuating member 391 is rotated downward to push down the lifting arm 365, and the driven roller 77a of the discharge roller 77 is pressed against the driving roller 77b as shown in FIG. doing.

  Next, as shown in FIG. 15 and FIG. 18B, the release means 362 turns on the solenoid 370 for a preset time, so that the tip 379 a of the operating lever 379 and the toothless gear 367 are turned on. The engaged state with the engaging portion 377 is released. Then, of the tooth missing gear 367, the first tooth missing gear 368 is rotated by the elastic force of the coil spring 386, and the first gear portion 373 of the first tooth missing gear 368 is engaged with the driven gear 357. The Therefore, the first tooth missing gear 368 is driven to rotate counterclockwise in FIG. 18 by the driven gear 357. At that time, the second tooth missing gear 369 is stopped. When the first tooth missing gear 368 rotates more than a required angle in the counterclockwise direction in the drawing, the pin 389 of the second tooth missing gear 369 is guided in the first tooth missing gear 368 as shown in FIG. It abuts on the end portion 390b of 390. As a result, the second missing gear 369 is rotationally driven in the same direction with a required angle delayed from the first missing gear 368, and the third gear portion 382 is engaged with the driven gear 357.

  As shown in FIG. 19A, in the first tooth missing gear 368, the meshing between the first gear portion 373 and the driven gear 357 is completed, and the first tooth missing portion 375 is opposed to the driven gear 357. Rotation driving force is not transmitted from the driven gear 357. However, an elastic force in the clockwise direction in FIG. 5 is applied to the first tooth missing gear 368 by the coil spring 386. Therefore, as shown in FIG. 19A, the first toothless gear 368 continues to rotate in the clockwise direction in FIG. 5, and the other engagement portion 378 is the tip of the operating lever 379 of the solenoid 370. It stops in the state engaged with 379a.

  On the other hand, as described above, the second tooth missing gear 369 rotates in the same direction as the first tooth missing gear 368 with a predetermined angle behind the first tooth missing gear 368. Therefore, when the first tooth missing portion 375 of the first tooth missing gear 368 is rotated to a position facing the driven gear 357, the second tooth missing gear 369 is not yet driven by the third gear portion 382. 357 is engaged and continues to rotate.

  Thereafter, as shown in FIGS. 19 (a) and 19 (b), the second tooth missing gear 369 completes the engagement between the third gear portion 382 and the driven gear 357, and the third tooth missing portion 384 is moved. It rotates to a position facing the driven gear 357. Then, the rotational driving force is not transmitted from the driven gear 357 to the second tooth missing gear 369. At this time, the cam portion 381 of the second toothless gear 369 is positioned between the curved portion 381d and the second flat portion 382b so that the tip portion 392 of the actuating member 391 is in pressure contact with the cam portion 381. It is set to be a position that has already passed the dead center with the largest amount of eccentricity. Therefore, the second tooth missing gear 369 has the second flat portion 381b of the cam portion 381 and the distal end portion 392 of the actuating member 391 when the engagement of the third gear portion 382 and the driven gear 357 is completed. Rotational moment that rotates the second toothless gear 369 in the counterclockwise direction in FIG. 19A acts. As a result, as shown in FIG. 19B, the second tooth missing gear 369 rotates to a position where the entire surface of the second flat portion 381b of the cam portion 381 is in pressure contact with the distal end portion 392 of the operating member 391. And stop.

  At this time, the distal end portion 392 of the operating member 391 is pushed down by the cam portion 381 of the second tooth missing gear 369. The actuating member 391 is at a position rotated clockwise in FIG. Therefore, the operating portion 394 of the operating member 391 rotates upward to push up the lifting arm 365. The support shaft 363 provided with the lifting arm 365 rotates in the counterclockwise direction in FIG. Therefore, the driven roller 77a of the discharge roller 77 moves to a separated position separated from the drive roller 77b, as shown in FIG.

  The tooth missing gear 367 stops after the first tooth missing gear 368 stops first and then the second tooth missing gear 369 rotates in the same direction as the first tooth missing gear 368 with a delay. Meanwhile, the coil spring 386 is tightened by the second toothless gear 369 that rotates relative to the stopped first toothless gear 368.

  As described above, when the solenoid 370 is turned on, the driven roller 77a of the discharge roller 77 moves to a separated position away from the drive roller 77b, as shown in FIG. Thereafter, the drive motor 321 is rotationally driven in the forward rotation direction R1 as shown in FIG. 15, and the first transport roller 73 and the transport rollers 74 and 75 are as shown in “3” in FIG. Driven in the forward direction, the document 6 is conveyed. On the other hand, the drive roller 77b of the discharge roller 77 is driven in the discharge direction.

  Thereafter, as shown by “4” in FIG. 15, the drive motor 321 is once stopped and then driven again in the forward rotation direction. At this time, when the drive motor 321 is temporarily stopped, the solenoid 370 is turned on for a preset time to return from the state shown in FIG. 19B to the state shown in FIG. To do. Along with this, the driven roller 77a of the discharge roller 77 moves to a position in pressure contact with the drive roller 77b, as shown in FIG.

  After that, the drive motor 321 is temporarily stopped while the discharge roller 77 holds the trailing edge of the document 6, and then driven in the reverse direction to transport the document 6 to the reverse transport path 326. Then, after a preset time has elapsed after the pre-registration sensor 329 is turned on, the drive motor 321 is temporarily stopped, the solenoid 370 is turned on, and the driven roller 77a is separated from the drive roller 77b.

  Then, as indicated by “5” in FIG. 15, after the pre-registration sensor 329 is turned off, the solenoid 370 is turned on to return from the state shown in FIG. 19B to the state shown in FIG. . Along with this, the driven roller 77a of the discharge roller 77 moves to a position in pressure contact with the drive roller 77b, as shown in FIG. By doing so, the document 6 is discharged to the discharge storage portion 76 with the first surface facing down by the discharge roller 77.

  In this way, as indicated by “3” in FIG. 15, before the leading edge of the document 6 reaches the conveying roller 74, the rotation direction of the drive motor 321 is switched from the reverse rotation direction R2 to the normal rotation direction R1, and discharged. In the roller 77, as shown in FIG. 12B, the driven roller 77a is separated from the driving roller 77b. At this time, the holding member 364 that rotatably holds the driven roller 77a is provided with a gap ΔL that moves the driven roller 77a in a direction approaching the driving roller 77b. Therefore, there is a tolerance of parts constituting the release means 362 for moving the driven roller 77a to the separated position, an assembly tolerance of the parts, and the like, and the driven roller 77a temporarily hits the main body 401 of the opening / closing unit 400. Even so, the driven roller 77a is allowed to move to a position where no load is applied even when it is abutted against the main body 401 of the opening / closing unit 400. Accordingly, the movable amount of the holding member 364 can be set large even in a narrow range, and the drive motor 321 rotates in the normal rotation direction R1, and the drive roller of the discharge roller 77 as shown in FIG. 16 “3”. When 77b is rotationally driven in the discharge direction, it is avoided that the conveying force of the driving roller 77b acts on the document 6.

  Therefore, the release means 362 turns the solenoid 370 on / off to rotate the operation member 391 and separate the driven roller 77a of the discharge roller 77 from the drive roller 77b, so that the conveying force of the discharge roller 77 is applied to the document 6. Release the working state.

  At that time, as shown in FIG. 12B, the discharge roller 77 is further separated from the driving roller 77b even when the driven roller 77a is moved to a separated position away from the driving roller 77b. Therefore, it is possible to reliably avoid the conveying force of the discharge roller 77 from acting on the document 6.

  In this embodiment, as shown in FIG. 11, since the opening / closing unit 400 is attached to the casing 31 of the image reading apparatus 3 so as to be freely opened and closed, a normal conveyance path 325 and a reverse conveyance path 326 are provided. Thus, even when the document 6 is jammed, the document 6 can be easily removed. Further, the driven roller 77a of the discharge roller 77 is located on the drive roller 77 side. However, even when the driven roller 77a is separated from the drive roller 77b, the driven roller 77a is further movable in a direction away from the drive roller 77b. Therefore, even if the jam of the document 6 occurs in the vicinity of the discharge roller 77, the document 6 can be easily removed.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 1a ... Image forming apparatus main body 3 ... Image reading apparatus 31 ... Image reading apparatus housing | casing 62 ... Release means (moving means)
71 ... Nudger roller 72 ... Feed roller 72 ... First transport roller 77 ... Discharge roller 77a ... Driven roller 77b ... Drive discharge roller

Claims (7)

Conveying means for conveying the sheet to the reading position by the first conveying roller, and switching the sheet that has passed through the reading position by the second conveying roller to reverse the front and back to convey to the first conveying roller. When,
A single drive means capable of switching the rotation direction between the first and second directions;
Of the second conveying roller comprising a driving roller disposed below the vertical direction and a driven roller disposed above the vertical direction, a holding member that rotatably holds the driven roller is separated from the driving roller. Moving means for moving to a separated position in the direction of
A sheet conveying apparatus comprising:   The sheet conveying apparatus according to claim 1, wherein the driven roller is rotatably supported by the holding member in a state in which the driven roller is allowed to move in a direction away from or in contact with the driving roller.   3. The sheet conveying apparatus according to claim 1, wherein the first conveying roller is connected to the driving unit via a rotating unit that rotates in a fixed direction regardless of a rotation direction of the driving unit.   4. The sheet conveying apparatus according to claim 1, wherein the driven roller of the second conveying roller is attached to an opening / closing unit provided to be openable and closable with respect to a main body of the sheet conveying apparatus.   The sheet conveying apparatus according to any one of claims 1 to 4, wherein the holding member is moved to the separation position via a tooth-missing gear that intermittently transmits a rotational driving force of the driving unit. A sheet conveying device according to any one of claims 1 to 5,
Image reading means for reading an image from a sheet conveyed by the sheet conveying device;
An image reading apparatus comprising: An image reading apparatus according to claim 6;
Image forming means for forming an image read by the image reading device on a recording medium;
An image forming apparatus comprising:

Images