JP4168054B2 - Sheet conveying apparatus and image reading apparatus using the same - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus such as a copying machine, a facsimile machine, a scanner device, and the like, and a sheet conveying apparatus that feeds a document to a platen of these image reading apparatuses, and more specifically, guides a sheet to a platen position in a stable posture at all times. It relates to the improvement of the guide mechanism.

  In general, this type of sheet conveying apparatus is widely used as an apparatus that is disposed on a glass platen of an image reading apparatus, feeds an original sheet from a stacker to a reading position, and reads an image of an original that passes through the platen at a predetermined speed. Yes. The configuration is such that a sheet feed stacker and a sheet discharge stacker are arranged in parallel on the platen, and a U-shaped curved path from the sheet feed stacker to the sheet discharge stacker via the platen is provided. A structure is known in which sheets are fed one by one to a platen, and sheets read by the platen are stored in a paper discharge stacker.

  Such a sheet conveying apparatus is mounted on the platen of the image reading apparatus as a conveying unit, and is attached to the platen glass by a hinge device so as to be opened and closed. When reading a thick original such as a book original, the conveying unit is placed above the platen. To open up. For this reason, the transport unit attached to various image reading apparatuses must always be installed on the platen in a predetermined posture.

  On the other hand, in the above-described apparatus in which the paper feed stacker is arranged above the platen, the sheet fed from the paper feed stacker enters obliquely upward toward the platen, moves along the platen, and is then rolled up diagonally upward. It is stored in a paper discharge stacker above the platen. At this time, when the leading edge of the sheet enters the platen, the impact may cause the sheet to swing up and down, and when the leading edge of the sheet is lifted up from the platen, the sheet may swing up and down, which may cause blur in the read image. Therefore, the backup guide that is arranged above the platen and guides the sheet to the platen forms a gap that allows passage of the sheet between the platen and scoops up so as not to give an impact to the sheet unloaded from the platen. There must be.

  Therefore, as a backup guide, for example, Patent Document 1 discloses a transport unit having the above-described configuration in FIG. 1, and a plate-like curved backup guide is provided at a position facing the image reading unit of the platen. Is supported by a frame so as to be vertically movable or swingable with respect to the platen, and is always biased by a biasing spring on the platen side. In this guide, a mechanism is disclosed in which a protrusion is formed integrally with the platen surface to form a sheet passage gap between the guide plate and the gap between the platen surface and the backup guide is always kept constant.

Thus, when the plate-like guide member is mounted above and below the platen or swingably mounted, the guide member moves up and down or swings according to the size and shape of the platen facing (mainly dimensional error due to machine difference). The positions and postures of the end portions (both end portions or one end portion) of the guide member change due to the difference between the airframes or the backlash of the component parts each time it is opened and closed. As described above, when the position of the guide member is changed over the platen in the course of machine difference or aging, a step is generated or a space is generated, causing inadvertent stress to the sheet, resulting in deterioration of read image quality. Therefore, for example, Patent Document 2 discloses a configuration in which the backup guide is formed of a flexible film member. In Patent Document 2, a flexible film member such as a mylar is disposed between a carry-in guide arranged on the upstream side of the platen and a carry-out guide arranged on the downstream side, and the sheet is conveyed while pressing the sheet against the platen. Proposed.
JP 2002-171385 A (FIG. 2) JP 2001-309118 A (FIG. 2) JP-A-7-172618

  As described above, when a document sheet is fed from above to the platen image reading position and the document sheet after reading is carried out upward, as previously disclosed in Japanese Patent Application Laid-Open No. 2003-133620, the platen is positioned above the reading position of the platen. A plate-shaped guide member is arranged as a backup guide, and this guide member is moved up and down or swinging according to the platen position. Therefore, the influence on the original sheet differs depending on the position of the movable guide member. It can cause problems such as blurring. This is because the height position of the end portion of the plate-shaped guide member with respect to the platen differs depending on the difference in the machine body of the image reading apparatus to be mounted or the positional displacement of the component parts when opening and closing, so the friction load applied to the sheet, especially the sheet leading edge, is different. It is considered that the impact when entering the guide is transmitted as vibration to the sheet of the reading unit and causes image blurring. It is also known as a problem that a curled sheet or the like may cause a paper jam if a gap or a step is generated at the end of the swinging or vertically moving guide. Further, the sheet is loosened in a gap formed by the step and becomes a loop shape, and the image at the same position is read until the sheet at the rear end is removed from the roller and the loop is eliminated, and the image is distorted.

  In addition, as disclosed in Patent Document 2, when the backup guide is formed of a flexible member such as a plastic film, problems such as gaps and steps do not occur. Due to the pressing force of the member, the conveyance load becomes large, causing conveyance unevenness to deteriorate the image quality, and the film-shaped guide member is deteriorated with age, or the film-shaped guide member is discarded when the conveyance unit is opened and closed. Problems such as have occurred.

  Therefore, the present invention does not cause a step or a gap due to the difference in the machine body of the image reading apparatus, and the backup guide disposed above the platen stably guides the sheet from above the platen at substantially the same height position. The main problem is to provide a sheet conveying apparatus that does not exert stress such as impact on the sheet and can read high-quality images. Further, according to the present invention, when the sheet conveying device is installed on the platen of the image reading device so as to be freely opened and closed, the backup guide is lost due to the impact of the opening and closing, and the image that is guided does not change, and the image is stable for a long time. It is an object of the present invention to provide a sheet conveying apparatus that can be read and an image reading apparatus using the sheet conveying apparatus.

  The present invention adopts the following configuration in order to solve the above problems. First, according to the present invention, a backup guide disposed above a platen is a metal plate or other guide member that can withstand aging, and at least two guide members are coupled by shaft connection to form a curved conveyance path. The both ends of the connected guide member are supported at substantially the same height from the platen, and at least one of them is supported so as to be movable in the sheet conveying direction. Then, the guide member is provided with position restricting means for ensuring the height position of the platen. The back-up guide configured in this way has a difference in platen position, the curvature of the curved path to be formed changes even if a positional deviation occurs in a component such as a hinge device, a step or a gap may occur, In addition, image blurring is less likely to be caused by stress such as impact on the sheet.

  Further, by supporting the backup roller on the backup guide, a predetermined (sheet passing) gap is formed above the platen and the roller member backs up so that the sheet can be guided more smoothly. The backup roller may be a rotatable idling roller or may be connected to a driving unit that rotates in the sheet conveying direction. By arranging this backup roller at the connecting portion of the two (or three) guide members, no stress is exerted on the sheet even if the curved shape of the guide members is different.

  Further, the two guide members connected to each other support the end edge on the upstream side in the sheet conveying direction on the rotating shaft of the carry-in roller arranged on the upstream side of the platen, and the downstream end on the downstream side of the platen. The shaft is supported so as to be movable in the sheet conveying direction on the rotation shaft of the carry-out roller arranged in the sheet. As a result, in the process where the sheet leading edge reaches the platen from the carry-in roller, the positional relationship between the platen position and the backup guide is different from the machine body, and even if there is a deviation of the part position in the process of use, a guide having substantially the same shape from the same height position. In this case, there is no problem in image quality such as image blur. In the present invention, the support position of the guide member does not need to be supported by the rotation shafts of the carry-in roller and the carry-out roller. For example, the guide member is supported by a device frame (such as a side frame constituting the unit) in the vicinity of these rotation shafts. Of course, you may do.

  Further, at least one of the guide members connected to each other is provided with an urging means such as a spring between the apparatus frame in a bending direction. Alternatively, tension springs are provided at both ends of the connected guide members. As a result, the guide member that is pivotally connected does not move and deform. Further, as described above, when the one end of the guide member is supported on the rotating shaft and the backup roller is attached thereto, the position of the backup roller slightly moves in the sheet conveying direction. When this affects the image quality, the support shaft of the backup roller is restricted so as to move up and down only in the direction perpendicular to the reading position of the platen by a movement restricting means such as a long hole guide formed in the apparatus frame. And the both ends of a guide member are supported so that a movement in a sheet conveyance direction is possible. With such a configuration, the backup roller that backs up the sheet at the reading position moves up and down in a direction perpendicular to the platen, thereby enabling more stable sheet guidance.

  According to the present invention, a backup guide disposed above the platen is configured by connecting at least two guide members to each other by a shaft connection so as to be rotatable, and at least one end portion of the connected guide members can be moved in the sheet conveying direction. The guide member is provided with position restricting means for ensuring the height position of the platen and the relative position relationship between the backup guide and the platen depends on the sheet conveying device and the platen. Even if there is a difference in the machine body of the image reading apparatus to be attached or a positional deviation occurs in a component such as a hinge, the backup guide always guides the sheet entering the platen at a predetermined height position.

  Therefore, the back-up guide constructed in this way does not cause a step or a gap at the end of the guide member so that the curvature of the curved path to be formed changes to a large or small size. It is possible to prevent image blur due to stress such as impact when the leading edge of the sheet hits the guide member. Further, since the sheet loop formed by gaps such as steps is eliminated by connecting the guide members, speed fluctuations can be suppressed and image distortion can be prevented.

  The present invention will be described in detail below based on the preferred embodiments of the present invention shown in the drawings. FIG. 1 is an explanatory diagram of an overall layout configuration of an image reading device and a sheet conveying device installed therein, FIG. 2 is an enlarged explanatory diagram of a main part of the sheet conveying device, and FIG. 3 is a structural explanatory diagram of a backup guide. First, the image reading unit A will be described with reference to FIG. The illustrated image reading unit A is composed of a normal scanner device, and a second platen 7 on which an original that is difficult to convey a sheet such as a book original is placed on the upper surface of the casing 1, and the second platen 7 is adjacent to the second platen 7. A first platen 8 for reading a sheet document is disposed. The first and second platens 8 and 7 are formed of a transparent member such as glass, and are attached to the upper surface of the casing 1 by a fixing member 9. The fixing member 9 is a molding material such as resin, and the fixing portion 9 a on the right side of FIG. 2 forms a stepped portion lower than the platen surface so as to scoop up the sheet from the first platen 8. Further, the fixing portion 9b on the left side of FIG. 1 is designed so that a carry-in lower guide 23 described later is arranged upward.

  A carriage 2 supported by guide rails is provided below the first and second platens 8 and 7 so as to be movable along both platens. An imaging optical system 5 such as a light source lamp 3, a reflection mirror, and a condenser lens is mounted on the carriage 2, and a photoelectric conversion means including a photoelectric conversion element such as a CCD is mounted at the imaging position of the imaging optical system 5. ing. The carriage 2 is connected to a drive motor (not shown) so that the document set on the second platen 7 can be read in line order while moving along the platen. Therefore, the image pickup optical system is configured such that the carriage 2 is irradiated with light from the light source lamp 3 onto the original on the platen, and the reflected light is guided to the condensing lens by the reflecting mirror and imaged on the photoelectric conversion element 4 by this lens. 5 is configured. The carriage 2 is moved and controlled by a control means (not shown) so as to read a document moving on the first platen 8 while moving to the position of the first platen 8 and being stationary. The image reading unit A having the above configuration is well known as the configuration of various devices such as a scanner device, a copying machine, and a facsimile device.

  Next, the sheet conveying unit B will be described with reference to FIG. The illustrated sheet conveying unit B includes a “sheet feeding unit” that supplies a document sheet (hereinafter referred to as a sheet S) from the sheet feeding stacker 10 to the first platen 8 and a “platen backup unit” that guides the sheet S above the platen. And a “paper discharge unit” that picks up the read sheet from the platen and stores it in the upper paper discharge stacker 39. Each sheet conveying mechanism is incorporated as a unit into the exterior cover 18, and the exterior cover 18 shown in the figure has a monocoque structure and is formed of a resin molded product. A metal frame member is attached to a portion requiring strength or positional accuracy to be reinforced. is doing.

  Therefore, in the sheet feeding unit, the sheet feeding stacker 10 is attached to the exterior cover 18 with a resin tray member above the second platen 7. The sheet feed stacker 10 is inclined so that the sheet placed on the substantially horizontal platen is inclined. A kick roller 11 is disposed at the front end of the paper feed stacker 10 so as to swing up and down with respect to the tray. The kick roller 11 is attached to a distal end portion of a support arm 19, and a base end portion of the support arm 19 is supported by a rotating shaft 12 a of a paper feed roller 12 described later via a spring clutch (not shown). Drive is transmitted by the transmission belt so that the paper feed roller 12 rotates in the paper feed direction from the rotary shaft 12a. On the downstream side of the kick roller 11, a paper feed roller 12 is pivotally supported on a rotating shaft 12a via a one-way clutch (not shown). The paper feed roller 12 is made of a rubber material having a large friction coefficient, The sheets are separated one by one from the separation roller 13.

  A separation roller 13 is pressed against the paper feed roller 12, and the separation roller 13 is a stationary roller that is always stopped by a material having a smaller coefficient of friction than the paper feed roller 12 or in a direction opposite to the paper feed roller 12 (illustrated). It is composed of a reverse roller that rotates counterclockwise. Therefore, a paper feed section drive motor M1 that can be rotated forward and backward, which will be described later, is connected to the rotation shaft 12a of the paper feed roller 12. When the rotation shaft 12a is rotated clockwise in the figure, the spring clutch is loosened and the support arm 19 is turned clockwise. Rotating in the direction, the kick roller 11 descends from an upper position retracted from the paper feed stacker 10 to a position in contact with the sheet on the paper feed stacker 10. At the same time, the kick roller 11 receives the rotation of the rotary shaft 12a by the transmission belt and rotates in the paper feeding direction.

  Therefore, the sheet S on the paper feed stacker 10 is fed from the uppermost paper to the paper feed roller 12 and separated into a single sheet between the paper feed roller 12 and the separation roller 13. When the leading edge of the sheet reaches the registration roller 14 on the downstream side, the sheet feeding unit drive motor M1 is stopped by a signal from the registration sensor 15 and then reversely rotated. The reverse rotation of the paper feed unit drive motor M1 causes the spring clutch of the rotary shaft 12a to be tightly connected and the support arm 19 rotates counterclockwise, moving the kick roller 11 to the standby position above the paper feed stacker 10 and not shown. It stops against the stopper and is held in that position. At this time, the sheet feeding roller 12 and the kick roller 11 are configured not to rotate in the direction opposite to the sheet feeding direction by the one-way clutch of the rotating shaft 12a.

  On the other hand, the sheet S that has reached the registration roller 14 waits for a paper feed instruction signal in a state in which the sheet S is curved by a predetermined amount by a registration sensor 15 disposed in front of (upstream side) the registration roller 14. Therefore, a sheet carry-in path 16 for guiding the sheet to the first platen 8 of the image reading unit A is disposed on the downstream side of the paper feed roller 12, and the registration roller 14 is disposed in the sheet carry-in path 16. The registration roller 14 includes a driving roller and a driven roller that are in pressure contact with each other, and a registration driving motor M2 is connected to the driving roller. The sheet carry-in path 16 is formed in a curved path as shown in the figure, and is connected to a sheet discharge path, which will be described later, via a first platen 8 to form a substantially U-shaped sheet transport path as a whole.

  In the sheet carry-in path 16, a carry-in roller 20 and a roller 22 that follows the carry-in roller 20 are disposed in the vicinity of the first platen 8. The carry-in roller 20 is supported by a side frame (not shown) integrally formed with the exterior cover 18 by a rotation shaft 21 and is connected to a conveyance unit drive motor M3 described later. A lead sensor 17 for detecting the leading edge of the sheet is disposed on the upstream side of the carry-in roller 20, and when the leading edge of the sheet sent from the upstream registration roller 14 reaches the sensor position, the registration driving motor M2 is stopped. The sheet is kept waiting until the reading start instruction signal from the image reading unit A is reached. In addition, 16a in the figure is an idle roller attached to a guide constituting the carry-in route.

The carry-in roller 20 and the carry-in driven roller 22 pressed against the carry-in roller 20 are configured by supporting a plurality of rollers on the rotary shaft 21 at predetermined intervals in the sheet width direction. This is to prevent the sheet from skewing by arranging a plurality of rollers at intervals, since there is a possibility that the sheet will come into contact with the sheet if it is constituted by an integral roll member continuous in the sheet width direction.
Further, an unloading roller 30 is disposed on the downstream side of the first platen 8, and the unloading roller 30 is supported by a rotating shaft 31 supported by a side frame frame formed integrally with the exterior cover 18. Further, a carry-out driven roller 32 is arranged so as to come into pressure contact with the carry-out roller 30. As with the carry-in roller 20, the carry-out roller 30 is configured by supporting a plurality of roller members on the rotation shaft 31 at a predetermined interval.

  Next, the “platen backup unit” will be described. A backup guide 37 having the following configuration is arranged above the reading position P of the first platen 8 between the carry-in roller 20 and the carry-out roller 30 described above. The backup guide 37 includes a first guide member 24 that guides the sheet S sent from the carry-in roller 20 to the reading position P, a backup roller 38 that backs up the sheet S at the reading position P, and a sheet from the reading position P. The second guide member 27 guides toward the paper discharge path 40. A U-shaped curved path Q is formed above the first platen 8 by the first and second guide members 24 and 27. A guide roller 24 a shown in the drawing is disposed near the first platen 8 and is axially supported by the first guide member 24.

  Accordingly, each function will be described. At the reading position P of the first platen 8, the sheet S needs to be held at a predetermined height position from the first platen 8. If this height position exceeds the height position allowed from the depth of focus, the image will be blurred, and therefore, in the illustrated example, the height position of the sheet is regulated by the backup roller 38. When the leading edge of the sheet S reaching the reading position P abuts against the guide member and vibrates due to the impact, the sheet S vibrates up and down at the reading position P and causes image blurring. For this reason, the illustrated one smoothly guides the sheet S to the predetermined height position of the reading position P by the first guide member 24.

  Similarly, when the leading edge of the sheet that has passed the reading position P hits the second guide member 27, the impact is propagated to the sheet S at the reading position P, causing image blurring. It is necessary to consider such blurring or blurring of the image so as not to be affected by variations in the image forming apparatus, for example, variations in the mounting height position of the first platen 8 and parts accuracy of the backup guide 37. In particular, when the sheet conveying unit B is hinged to the image reading unit A and the platen is opened, it is necessary to consider that the height position of the backup guide 37 does not change every time the sheet conveying unit B is opened and closed.

  Therefore, in the present invention, the above-described backup guide 37 is configured as follows. First, the first guide member 24 and the second guide member 27 are constituted by separate plate members, and both are rotatably connected to form a curved path Q above the first platen 8. The first guide member 24 is integrally provided with first guide connecting members 25 on both sides in the sheet width direction. Similarly, the second guide member 27 is integrally provided with second guide connecting members 28. The first and second guide connecting members 25 and 28 are rotatably connected by a connecting support shaft 26. In the illustrated example, a backup roller 38 to be described later is provided on the connecting support shaft 26. The first guide connecting member 25 is loosely supported by one end portion 25a located on the upstream side in the sheet conveying direction on the rotating shaft 21 of the carry-in roller 20, and the second guide connecting member 28 is one end located on the downstream side in the sheet conveying direction. The portion 28a is supported on the rotary shaft 31 of the carry-out roller 30 so as to be movable in the sheet conveying direction.

  In the illustrated example, the end portion 28a of the second guide connecting member 28 is configured by a U-shaped bracket, and this bracket is fitted to the rotating shaft 31 of the carry-out roller 30 so that the end portion of the second guide member 27 is conveyed by the sheet. A predetermined amount of movement in the direction is supported. The first and second guide members 24 and 27 connected to each other are provided with position restricting means 29 for defining the height position with respect to the first platen 8. In the illustrated example, a position restricting means 29 is configured by a protrusion (see FIG. 3) that contacts the first platen 8 on the first guide connecting member 25. Accordingly, the first and second guide members 24 and 27 connected to each other are set at a predetermined height position by the position regulating means 29 abutting on the first platen 8 and swinging around the rotation shaft 21 of the carry-in roller 20. At this time, the second guide connecting member 28 is supported on the rotating shaft 31 of the carry-out roller 30 in a state where it is moved by a predetermined amount in the sheet conveying direction.

  The illustrated first and second guide members 24 and 27 are axially supported by the rotary shaft 21 of the carry-in roller 20 and the rotary shaft 31 of the carry-out roller 30 through the guide connecting members 25 and 28, respectively. Of course, this may be supported by a device frame different from the rotation shaft of each roller, for example, a side frame. In the illustrated example, the first guide member 24 is loosely supported by the rotation shaft 21 of the carry-in roller 20, and the second guide member 27 is supported by the rotation shaft 31 of the carry-out roller 30 so as to be movable in the sheet conveying direction. However, this is to reliably guide the sheet S entering the first platen 8 from the carry-in roller 20 without rattling, and depending on the specifications of the apparatus, the second guide connecting member 28 is axially supported on the rotating shaft 31, A structure in which the first guide member is axially supported on the rotation shaft 21 so as to be movable in the sheet conveyance direction may be employed.

  The first and second guide members 24 and 27 configured as described above may be provided with a backup roller above the reading position P of the first platen 8. In the illustrated example, a backup roller 38 is rotatably supported on a connecting support shaft 26 of both guide members 24 and 27. The backup roller 38 is formed of a roll member having a white surface and continuous in the sheet width direction, and is driven to rotate by a sheet passing on the first platen 8 or connected to a drive motor to rotate in the sheet conveying direction. And The illustrated one is connected to a conveyance unit drive motor M3 that drives the carry-in roller 20 and the carry-out roller 30 described above, and rotates in the sheet conveyance direction at the same peripheral speed as these rollers. In addition, the first and second guide members 24 and 27 having the above-described configuration are rotatably connected to each other to form a curved path Q above the first platen 8, but the direction in which the curvature is reduced, that is, the guide member. The urging means 36 is provided in the direction of urging the urging member downward.

  As shown in FIG. 3, a coil spring 36 is wound around a rotating shaft 21 that supports a first guide member 24 as shown in FIG. 3, and one end of the coil spring 36 is engaged with the connecting support shaft 26, thereby the coil spring. The other end of 36 is locked to a side frame frame (not shown). The coil spring 36 urges the guide members 24 and 27 toward the first platen 8 via the connecting support shaft 26 that connects the first and second guide members 24 and 27. This is a biasing force in a direction to reduce the curvature of the curved path Q formed by both guide members so that the first and second guide members 24 and 27 do not inadvertently float when the sheet conveying unit B is placed on the platen. Is acting. The biasing force causes the above-described position restricting means 29 to contact the first platen 8 with certainty, and the first and second guide members 24 and 27 form a curved path Q above the platen in a predetermined posture, and an impact from the outside. For example, the guide members 24 and 27 are not deformed.

  Next, a guide structure positioned on the carry-in side and the carry-out side of the first platen 8 facing the above-described backup guide 37 will be described with reference to FIG. A carry-in lower guide 23 is disposed upstream of the first platen 8 facing the first guide member 24 described above, and a scooping guide 33 is disposed at a position facing the second guide member 27. In particular, as shown in FIG. 7, the carry-in lower guide 23 is constituted by a guide plate that axially supports the carry-in driven roller 22, and the carry-in driven roller 22 is shifted from the carry-in roller 20 by the θ angle shown in the figure. It is in pressure contact.

  In this way, by shifting the carry-in driven roller 22 and the carry-in lower guide 23 arranged at the dotted line positions shown in the related art to a predetermined angle, the angle at which the sheet S enters the platen is reduced, and the impact of the sheet tip entering the platen is reduced, and at the same time The impact of the trailing edge of the sheet that has passed through the pressure contact portion falling on the carry-in lower guide 23 is suppressed. Similarly, the scooping guide 33 is constituted by a guide plate that is pivotally supported by a support shaft 34 that supports a transporting driven roller 32 that is in pressure contact with the transporting roller 30, and the transporting driven roller 32 and scooping guide 33 are also configured. It is shifted from the carry-out roller 30 by a predetermined angle θ.

  Further, the scooping guide 33 is pivotally supported by the support shaft 34 (the illustrated one is the rotating shaft 34 of the carry-out driven roller 32) supported on the side frame frame as described above, and is always counterclockwise illustrated by the spring 35. Is energized. The scooping guide 33 abuts on the platen fixing member 9 that fixes the first platen 8 and scoops up the sheet from the first platen 8. The illustrated spring 35 has one end fixed to a plate spring 34 a that presses the rotating shaft 34 of the driven roller 32 to the unloading (driving) roller 30 at all times, and the other end is scooped up by a scooping guide 33.

  In this way, the swingable scooping guide 33 abuts against the fixed portion 9a to restrict the position thereof, and the position restricting means 29 abuts against the first platen 8 to restrict the position thereof. At this time, the positional relationship between the abutting surface of the fixed portion 9a with which the scooping guide 33 abuts and the abutting surface of the first platen 8 with which the position restricting means 29 abuts is constant. The gap between 33 and the backup guide 37 is always kept constant. Further, with such a configuration, even when the sheet conveying unit B swings and adjusts so that the scanning line on the scanner side and the document are orthogonal to each other, the scooping guide 33 and the backup guide 37 are surely connected. The gap can be surely kept constant.

  Next, the paper discharge unit will be described. A paper discharge stacker 39 is disposed below the paper feed stacker 10 described above, and a sheet conveyed from the carry-out roller 30 is guided to the paper discharge stacker 39 through a paper discharge path 40. It is burned. A paper discharge sensor 46 is provided in the paper discharge path 40 to detect a paper jam occurring on the sheet or the leading and trailing edges of the sheet. A sheet discharge roller 45 capable of forward and reverse rotation is disposed at the exit end of the sheet discharge path 40, and the sheet sent from the carry-out roller 30 is stored in the sheet discharge stacker 39. A circulation path 41 is connected to the paper discharge path 40 so as to form a switchback path. The circulation path 41 is arranged so as to reverse the conveyance direction of the sheet fed by the paper discharge roller 45 and guide it to the registration roller 14 position of the carry-in path 16, and a path switching piece 43 is provided in the paper discharge path 40. is there. Accordingly, the sheet is carried out from the paper discharge path 40 to the paper discharge stacker 39 by the paper discharge roller 45, while the sheet is guided again from the circulation path 41 to the carry-in path 16 by reversing the paper discharge roller 45, and the registration rollers 14. After the posture is corrected, the first platen 8 is circulated so as to read the back side.

  Next, driving of each of the above roller members will be described. A paper feed drive motor M1 is connected to the kick roller 11 and the paper feed roller 12, a registration drive motor M2 is connected to the registration roller 14, and the carry-in roller 20, the backup roller 38, the carry-out roller 30, and the paper discharge. The roller 45 is connected to a transport unit drive motor M3. The paper feed unit drive motor M1 and the transport unit drive motor M3 are configured by motors that can be rotated forward and backward, and the registration drive motor M2 is configured by a motor that rotates in one direction. Therefore, the sheet feed unit drive motor M1 rotates and drives the kick roller 11 and the sheet feed roller 12 or the separation roller 13 by rotating in one direction as described above. The support arm 19 that supports the kick roller 11 is moved up and down to a position waiting on the stacker by the reverse rotation of the drive motor M1. The registration drive motor M2 is activated by a timing signal from the registration sensor 15 after a predetermined loop is formed on the sheet S sent by the paper feed roller 12, and feeds the sheet S to the position of the lead sensor 17 in the carry-in path 16. Then stop.

  The registration driving motor M <b> 2 receives the paper feed instruction signal from the image reading unit A and conveys the sheet to the carry-in roller 20. At this time, the conveyance unit drive motor M3 starts to rotate the carry-in roller 20 in the sheet conveyance direction in response to a paper feed instruction signal, and simultaneously drives the backup roller 38, the carry-out roller 30 and the paper discharge roller 45 to rotate. Further, when the sheet is conveyed from the sheet discharge path 40 to the circulation path 41, the conveyance unit drive motor M3 is driven in reverse. At this time, a one-way clutch is interposed between the carry-in roller 20, the backup roller 38, and the carry-out roller 30, so that these rollers do not rotate reversely.

  The backup guide 37 configured as described above forms a curved path Q above the first platen 8 by the first and second guide members 24 and 27 connected to each other, and the curved path Q is the first platen 8. A predetermined gap is formed by the position restricting means 29 between them and the sheet S is guided onto the first platen 8. The gap formed by the position restricting means 29 is set to an optimum position at which the sheet is not shaken up and down at the reading position P and the sheet S is backed up without causing uneven conveyance. In the illustrated example, a backup roller 38 is supported by the first and second guide members 24 and 27, and the gap with the backup roller 38 is set to an optimum value. Therefore, it is always caused by a dimensional error (machine difference) during the production of these guide members, or an installation position error due to rattling during use, and a dimensional error (machine difference) during production of the platen position of the image reading unit A as well. The positional dimensions between the backup roller 38 or the guide members 24 and 27 and the platen surface are not constant.

  Therefore, as shown in FIG. 3, when the platen position is low with respect to the backup roller 38, the position restricting means 29 contacts the platen position by the urging force of the urging means 36. At this time, the first guide member 24 swings around the rotation shaft 21 supporting the first guide member 24 in the direction indicated by the arrow, and similarly, the second guide member 27 swings around the rotation shaft 31. At this time, the first and second guide members 24 and 27 connected to each other are attached to the rotary shaft 31 so that the end portion 28a of the second guide connecting member 28 can move in the sheet conveying direction. As a result, the curved path Q is positioned above the first platen 8 at a predetermined distance from the backup roller 38, and at the same time, the first and second guide members 24 and 27 also greatly differ from each other in the distance from the first platen 8. Without being positioned at a predetermined position.

  Next, FIG. 4 shows a state when the platen position is high. In this case as well, the backup roller 38 and the first guide member 24 swing around the rotary shaft 21 in the direction of the arrow in the figure, and the second guide member 27 also rotates. Oscillates around 31. Accordingly, a curved path Q is formed above the first platen 8 without greatly changing the height position of the first platen 8 as in FIG. Although the case where the backup roller 38 is provided on the first and second guide members 24 and 27 has been described, the same applies to a structure without the backup roller 38.

  Therefore, the curved path Q formed above the first platen 8 changes depending on the variation of each component between the state shown in FIG. 3 and the state shown in FIG. 4, but both the first guide member 24 and the second guide member 27 There is no step or gap, and the curvature of the curved path Q is slightly changed. The sheet sent from the carry-in roller 20 is always guided to the carry-out roller 30 under substantially the same conditions, and the impact is applied to the leading end of the sheet. This causes no stress, and the frictional condition when contacting the guide member does not change greatly, so that the conveyance unevenness does not occur. In particular, for example, even a sheet with a leading end curled upward can be guided smoothly.

  Next, FIG. 5 shows a configuration of a backup guide different from that described above. The first and second guide members similar to those described above are composed of a first guide connecting member 50 and a second guide connecting member 51 as a connecting support shaft 52. A backup roller 38 is axially supported on the connection support shaft 52. The first guide connecting member 50 is supported at its end 50a by the illustrated bracket so as to be movable in the sheet conveying direction on the rotating shaft 21 of the carry-in roller 20. Similarly, the end portion 51a of the second guide connecting member 51 is supported on a rotating shaft 31 of the carry-out roller 30 by a bracket so as to be movable in the sheet conveying direction.

  The connecting support shaft 52 is restricted by a motion restricting means 53 formed by a long groove perpendicular to a platen formed on a side frame frame (not shown). Further, the first and second guide connecting members 50 and 51 are provided with position restricting means 29 that abuts the platen and restricts the position. Accordingly, the backup roller 38 shown in FIG. 3 swings around the rotation shaft 21 of the carry-in roller 20 and changes its position, whereas the backup roller 38 shown in FIG. 5 reads the platen along the movement restricting means 53. Since it moves in the vertical direction of the position P, image blurring is not caused. Other configurations are the same as those shown in FIG.

1 is an overall configuration diagram of an image reading device and a sheet conveying device built therein. FIG. FIG. 2 is an enlarged explanatory view of a main part of the sheet conveying apparatus in FIG. 1. FIG. 3 is a mechanism explanatory view of a backup guide in the apparatus of FIG. 2. The state explanatory view when the guide position of the backup guide of Drawing 2 changes. FIG. 4 is an explanatory diagram of a mechanism different from the backup guide mechanism of FIG. 3. FIG. 6 is a state explanatory diagram when the guide position in the backup guide mode of FIG. 5 changes. FIG. 3 is an explanatory diagram of a guide mechanism for guiding a sheet to a platen in the apparatus of FIG. 2.

Explanation of symbols

A Image reading unit B Sheet conveyance unit 7 Second platen 8 First platen 10 Paper feed stacker 11 Kick roller 12 Paper feed roller 16 Sheet carry-in path M1 Paper feed unit drive motor M2 Registration drive motor 20 Carry-in roller 21 Rotating shaft 23 Under carry-in Guide (platen side)
24 1st guide member 25 1st guide connection member 25a 1st guide shaft support part 26 Connection support shaft 27 2nd guide member 28 2nd guide connection member 28a 2nd guide shaft support part 29 Position control means 30 Unloading roller 31 Rotating shaft 33 Scoop Lifting guide 36 Biasing means (spring)
37 Backup guide 38 Backup roller 39 Paper discharge stacker P Image reading position Q Curved path

Claims (9)

An image reading platen;
A backup guide that is disposed above the platen and forms a curved conveyance path for guiding a sheet to the platen;
A conveying means for conveying the sheet to the platen along the backup guide,
The backup guide is configured such that at least two guide members separated in the sheet conveyance direction are connected to each other so as to be pivotable to form a curved conveyance path above the platen,
At least one end of the connected guide member is supported by an appropriate apparatus frame so as to be movable in the sheet conveying direction,
One of the guide members constituting the backup guide is provided with a position regulating means for contacting the platen and forming a sheet conveyance path between the backup guide and the platen. The conveying means is composed of a carry-in roller located on the upstream side of the platen and a carry-out roller located on the downstream side,
The upstream end of the backup guide in the sheet conveyance direction is supported on the rotation shaft of the carry-in roller, and the downstream end is supported on the rotation shaft of the carry-out roller, and the downstream end can be moved in the sheet conveyance direction. The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is supported. 3. The sheet conveying apparatus according to claim 1, wherein a backup roller unit facing the image reading position of the platen is axially supported by the backup guide. 4. A sheet conveying apparatus according to claim 3, wherein the backup roller means is connected to a driving means that rotates in the sheet conveying direction at substantially the same peripheral speed as the carry-in roller. The backup roller means supported on the shaft by the backup guide is provided with a movement restricting means that moves up and down substantially vertically to the image reading position of the platen.
The sheet conveying apparatus according to claim 3 or 4, wherein an upstream end and a downstream end of the backup guide are supported so as to be movable in the sheet conveying direction. The platen is provided with a sheet scooping guide on the downstream side of the image reading position,
6. The sheet scooping guide is disposed at a position facing the backup guide via a sheet transport path, and is constituted by a guide member that scoops up the sheet from the platen. The sheet conveying apparatus according to any one of the items. The urging means for urging the first and second guide members connected to each other so as to be pivotable in a direction to reduce the curvature of the curved conveyance path is provided. The sheet conveying apparatus according to any one of 1 to 6. An image reading platen;
Image reading means disposed on the platen;
A paper feed tray disposed above the platen;
A paper discharge tray disposed between the platen and the paper feed tray;
A curved sheet conveying path from the sheet feeding tray to the sheet discharge tray through the platen;
A backup guide disposed at a position facing the platen of the sheet conveying path;
Conveying means for conveying the sheet onto the platen along the backup guide,
The backup guide is configured such that at least two guide members separated in the sheet conveyance direction are connected to each other so as to be pivotable to form a curved conveyance path above the platen,
At least one end of the connected guide member is supported by an appropriate apparatus frame so as to be movable in the sheet conveying direction,
An image reading apparatus comprising: a position restricting unit that abuts the platen on one of the guide members constituting the backup guide and forms a sheet conveyance path between the backup guide and the platen. The backup guide is axially supported by backup roller means facing the image reading position of the platen,
The conveying means includes a carry-in roller located on the upstream side of the platen and a carry-out roller located on the downstream side,
9. The backup roller means, the carry-in roller, and the carry-out roller are connected to the same drive motor and are configured to rotate in the sheet conveyance direction at substantially the same peripheral speed. Image reading device.

Images