JP2009286516A - Document feeding device and image forming device mounted with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress upsizing and to reduce cost, in relation to a document feeding device for displacing an uppermost layer of a document bundle to a paper feeding position by elevating a lift plate. <P>SOLUTION: This document feeding device 20 is provided with the lift plate 22 for lifting a conveying direction downstream part of a document of a document mounting tray 21 up to the paper feeding position, an elevating mechanism 80 for elevating the lift plate 22 and a driving mechanism 70 for driving the elevating mechanism 80. The driving mechanism 70 includes the elevating mechanism 80 and is provided with a lower limit detection device 90 for detecting a lower limit of the lift plate 22 which are constituted as an integrated unit. The lower limit detection device 90 can be therefore arranged immediately near a driving source of the elevating mechanism 80. As a result, electric wires and the wiring processing members in relation to the lower limit device 90 are sufficed with amounts equivalent to those of the driving source, and arranging spaces for the electric wires and the wiring processing members can be secured together with the electric wires and the wiring processing members of the driving source. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a document feeding device applicable to an image forming apparatus represented by a copying machine or a printer. The present invention also relates to an image forming apparatus equipped with the document feeder.

  An image forming apparatus such as a copying machine or a facsimile normally includes a document feeding device that automatically feeds a plurality of documents to a document reading unit. The document feeder separates the documents one by one from the uppermost layer of the document stack stacked on the document loading tray, and sends the document toward the document reading unit. The original is read by the original reading unit, and then discharged onto a document discharge tray provided on the most downstream side of the original conveyance path.

  In the document feeder, there are a roller supply method and a suction supply method as a mechanism of a paper feed unit that feeds a document to the outside of the document placing tray. The roller supply method is generally widely used. In the roller supply method, the pickup roller contacts the uppermost layer of the document bundle and delivers the document to the sheet feeding roller on the downstream side in the transport direction, and the document is fed one by one to the outside of the document placing tray. .

  The pickup roller of the paper feed unit and the uppermost layer of the document bundle need to be in contact with each other during paper feeding. However, when paper feeding is not performed, a document may be placed on the document placement tray. It is necessary to evacuate at least one of them so that they do not touch. For this reason, the document feeder is provided with a mechanism that can swing between a feeding position where the pickup roller and the uppermost layer of the document bundle are in contact with each other, and a retreat position where one of them is separated from the other. There is something.

Among such document feeding devices, an example of a document feeding device that biases a downstream portion in a document transport direction of a bundle of documents stacked on a document placing tray toward a pickup roller can be seen in Patent Document 1. it can. The document feeder (document feeder) described in Patent Document 1 includes a sheet feed tray (lift plate) that raises and lowers a downstream portion in the document transport direction of a document bundle.
Japanese Patent Laying-Open No. 2005-8283 (page 6-9, FIGS. 4 and 7)

  The document feeding device (document feeding device) described in Patent Document 1 drives a lifting mechanism provided with a motor, a gear, and the like to raise and lower a paper feed tray (lift plate), and the uppermost layer of a document bundle. It is possible to displace the downstream portion in the document transport direction to the paper feed position. However, in this document feeder, the lower limit sensor of the lift plate is provided at a substantially central portion of the lift plate in the document width direction perpendicular to the document transport direction.

  Here, in general, a document feeder is provided with a control board on one end side in the document width direction of the apparatus, and functional members such as motors and sensors are supplied with power to the control board. Or send and receive signals. Therefore, when a lower limit sensor is provided at a substantially central portion in the document width direction as in the document feeding device described in Patent Document 1, an electric wire for supplying power and transmitting / receiving signals to the sensor is provided. It must be wired for a long time. As a result, many electric wires and wiring processing members thereof are necessary, and there is a concern that the cost increases due to an increase in materials used and parts used. In addition, taking into consideration the space for arranging these electric wires and wiring processing members, there is a risk of increasing the size of the document feeder.

  The present invention has been made in view of the above points, and is capable of suppressing an increase in size and cost of a document feeder that displaces the uppermost layer of a document bundle to a sheet feeding position by moving a lift plate up and down. It is an object of the present invention to provide an illustrated document feeder. It is another object of the present invention to provide an image forming apparatus equipped with such a document feeder.

  In order to solve the above-described problems, the present invention provides a document placing tray for stacking and storing documents, a paper feeding unit for separating and feeding documents one by one from the document placing tray, and a document on the document placing tray. In the document feeding apparatus including a lift plate that lifts the downstream portion in the transport direction to the paper feed position, a lift mechanism that lifts and lowers the lift plate, and a drive mechanism that drives the lift mechanism, the drive mechanism includes the lift In addition to including a mechanism, a lower limit detecting device for detecting the lower limit of the lift plate is provided, and these units are configured as a unit.

  In the document feeding device having the above-described configuration, the driving mechanism is disposed outside one end of the lift plate in the document width direction perpendicular to the document transport direction.

  Further, in the document feeding device having the above-described configuration, the elevating mechanism includes a cam that rotates by obtaining power from a driving source and swings the lift plate, and a rotating shaft thereof. An indicator piece provided on the rotating shaft of the cam and indicating the lower limit position of the lift plate, and a lower limit detection sensor for detecting the position of the indicator piece are provided.

  In the present invention, the document feeder is mounted on the image forming apparatus.

  According to the configuration of the present invention, the document placing tray that stores and stores the documents, the paper feeding unit that separates and feeds the documents one by one from the document placing tray, and the document placing tray downstream of the document transport direction In a document feeding apparatus including a lift plate that lifts a part to a paper feed position, a lift mechanism that lifts and lowers the lift plate, and a drive mechanism that drives the lift mechanism, the drive mechanism includes the lift mechanism In addition, since the lower limit detection device for detecting the lower limit of the lift plate is provided and is configured as a unit in which these are combined, the lower limit detection device is provided immediately on the drive source of the lifting mechanism such as a motor or a solenoid. Can be arranged. Thereby, the electric wire which concerns on a lower limit detection apparatus, and its wiring processing member need only be the quantity equivalent to a drive source. Therefore, it is possible to suppress materials used and parts used, and it is possible to prevent an increase in cost. Moreover, the arrangement space of the electric wires and the wiring processing members can be secured together with the electric wires of the driving source and the wiring processing members. As a result, it is possible to prevent an increase in the size of the document feeder. In this way, a document feeding device is provided that is suppressed in size and cost, compared to a document feeding device that moves the uppermost layer of the document bundle to the paper feeding position by moving the lift plate up and down. can do.

  In addition, since the drive mechanism is disposed outside one end of the lift plate in the document width direction perpendicular to the document conveyance direction, a control board is provided on one end side in the document width direction of the document feeder. If provided, this can be approached. Thereby, the electric wire which concerns on a lower limit detection apparatus, and its wiring process member can be further reduced, and the arrangement space concerning them can also be reduced. Accordingly, it is possible to further reduce the increase in size and cost of the document feeder.

  The elevating mechanism includes a cam for rotating the lift plate while obtaining power from a driving source and a rotating shaft thereof, and the lower limit detecting device is provided on the rotating shaft of the cam. Since the indicator piece indicating the lower limit position of the lift plate and the lower limit detection sensor for detecting the position of the indicator piece are provided, the elevating mechanism can be connected to the drive mechanism, and the rotary shaft It becomes possible to arrange a lower limit detection device at any of the locations. As a result, the elevating mechanism can be easily included in the drive mechanism, and the location of the lower limit detection device can be easily changed. In this way, it is possible to further improve the suppression of size increase and cost reduction in the document feeder.

  In the present invention, since the document feeder is mounted on the image forming apparatus, the image forming apparatus is mounted with the document feeder that moves the uppermost layer of the document bundle to the sheet feeding position by moving the lift plate up and down. It is possible to obtain an image forming apparatus in which an increase in size and a reduction in cost are achieved with respect to the apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  First, an image output operation of an image forming apparatus equipped with an original feeding apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic vertical sectional front view of an image forming apparatus. In the drawing, a solid line arrow indicates a sheet conveyance path and a conveyance direction, and a one-dot chain line arrow indicates a laser beam L.

  As shown in FIG. 1, a paper feed cassette 3 is disposed below the inside of the main body 2 of the image forming apparatus 1. The paper feed cassette 3 stores and accommodates paper P such as cut paper before printing. The sheets P are separated and sent one by one toward the upper left of the sheet cassette 3 in FIG. The paper feed cassette 3 can be pulled out horizontally from the front side of the main body 2.

  A first paper transport unit 4 is provided inside the main body 2 and to the left of the paper feed cassette 3. The first paper transport unit 4 is formed substantially vertically along the left side surface of the main body 2. The first paper transport unit 4 receives the paper P sent out from the paper feed cassette 3 and transports it to the transfer unit 10 vertically upward along the left side surface of the main body 2.

  A manual paper feed unit 5 is provided above the paper feed cassette 3 at a location on the right side which is the side opposite to the left side of the main body 2 where the first paper transport unit 4 is formed. Yes. In the manual sheet feeder 5, paper P of a size that is not contained in the paper cassette 3, thick paper, and OHP sheets that are to be fed one by one are placed.

  A second paper transport unit 6 is provided on the left side of the manual paper feed unit 5. The second paper transport unit 6 is located immediately above the paper feed cassette 3, extends substantially horizontally from the manual paper feed unit 5 to the first paper transport unit 4, and joins the first paper transport unit 4. Then, the second paper transport unit 6 receives the paper P or the like sent from the manual paper feed unit 5 and transports it to the first paper transport unit 4 substantially horizontally.

  On the other hand, a document feeding device 20 is provided on the upper surface of the main body 2 of the image forming apparatus 1, and an image reading device 7 is provided below the document feeding device 20. When the user copies an original, an original on which an image such as a character, a figure, or a pattern is drawn is loaded on the original feeding device 20. The document feeding device 20 separates the documents one by one and sends the document, and the image reading device 7 reads the image data.

  The reading of the document image, that is, the start of printing is executed using an operation panel (not shown) provided on the front side of the image reading device 7 at the upper part of the main body 2. The user can input and set printing conditions such as the paper size to be used, enlargement / reduction, and the presence / absence of double-sided printing from the operation panel.

  Information on the image data of the original is sent to the exposure device 8 disposed above the second paper transport unit 6 and in the center of the main body 2. The exposure device 8 irradiates the image forming unit 9 with laser light L controlled based on the image data.

  An image forming unit 9 and a transfer unit 10 are provided above the first paper transport unit 4 and to the left of the exposure device 8. In the image forming unit 9, an electrostatic latent image of the original image is formed by the laser light L irradiated by the exposure device 8, and a toner image is developed from the electrostatic latent image. The toner is supplied to the image forming unit 9 from a toner container 11 provided above the exposure device 8. The toner image formed by the image forming unit 9 is transferred by the transfer unit 10 to the pre-printing paper P sent in synchronization by the first paper transport unit 4.

  A fixing device 12 is provided above the transfer unit 10. The paper P carrying the unfixed toner image in the transfer unit 10 is sent to the fixing device 12, and the toner image is heated and pressed by a heat roller and a pressure roller to be fixed.

  A paper guide device 13 is provided above the fixing device 12. The paper P discharged from the fixing device 12 is discharged from the paper guide device 13 to the in-body paper discharge portion 14 provided in the cylinder of the image forming apparatus 1 when duplex printing is not performed.

  The discharge port portion from which the paper P is discharged from the paper guide device 13 toward the in-body paper discharge portion 14 functions as the switchback portion 15. When performing duplex printing, the switchback unit 15 changes the transport direction of the paper P discharged from the fixing device 12. Then, the paper P passes through the paper guide device 13 and is sent downward through the double-sided printing paper conveyance path 16 provided on the left side of the fixing device 12 and on the left side of the transfer unit 10, and again the first paper conveyance. It is sent to the transfer section 10 via the section 4.

  Next, the outline of the structure of the document feeder 20 mounted on the upper surface of the main body 2 will be described with reference to FIG. FIG. 2 is a schematic vertical sectional front view of the document feeder. A solid line arrow in FIG. 2 indicates a conveyance path and a conveyance direction of the document.

  As shown in FIG. 2, the document feeding device 20 includes a document placing tray 21, a lift plate 22, a document feeding unit 30, and a document discharge tray 23.

  The document placing tray 21 is provided on the upper part of the document feeding device 20. Documents can be stacked on the document placing tray 21 from above. The document placing tray 21 is configured to be inclined downward from upstream to downstream in the document conveying direction, that is, from right to left in FIG.

  The lift plate 22 is provided on the downstream side of the document tray 21 in the document transport direction. The lift plate 22 is composed of a plate-like member having a shape along the placement surface of the document placement tray 21. The lift plate 22 is provided so as to be rotatable in a vertical plane along the document conveying direction with a substantially horizontal support shaft 22a provided at the upstream portion as a center and a downstream end as a free end. The lift plate 22 is rotationally displaced about the support shaft 22a by the drive mechanism 70 (see FIG. 4) when supplying the document, and the downstream end of the document stacked on the document loading tray 21 is disposed above the lift plate 22. It is urged upward so as to come into contact with the paper feed unit 60. Details of the mechanism related to the operation of the lift plate 22 will be described later.

  The document feeding unit 30 includes a document supply port 31 and a sheet feeding unit 60 at the downstream end of the document loading tray 21 in the document transport direction. The paper feed unit 60 separates the originals stacked on the original placement tray 21 one by one from the uppermost layer, and supplies the originals toward the inside of the original feeding unit 30 through the original supply port 31. A first document conveyance path 32 extends toward the inside of the document feeding unit 30 on the downstream side of the document supply port 31.

  The tip of the first document transport path 32 reaches the bottom surface of the document feeder 20, and a document reading unit 33 is provided at this position. Further, following the first document conveyance path 32, a second document conveyance path 34 extends from the position of the document reading unit 33. The document sent to the document reading unit 33 moves further from the first document conveyance path 32 to the second document conveyance path 34, that is, from the left to the right in the position of the document reading unit 33 in FIG. During the process, the image data of the first surface, which is the lower surface, is read by the image reading device 7 (see FIG. 1) of the main body 2 provided below.

  A document switching unit 35 is provided downstream of the document reading unit 33 in the second document transport path 34. When it is necessary to read the image data of both the front and back sides of the document, the document that has reached the document switching unit 35 is distributed to the upper side of the second document transport path 34. Then, the conveyance direction is changed to the opposite direction by the document reversing unit 36 downstream of the document conveyance direction. The document whose transport direction has been changed passes through the upper side of the document switching unit 35 and is sent to the first document transport path 32 on the upstream side of the document reading unit 33, and the image data on the second surface is read again by the document reading unit 33. It is done.

  A document discharge port 37 is provided downstream of the document switching unit 35 and at the downstream end of the second document transport path 34. The document for which image data has been read is discharged from the document discharge port 37 to the document discharge tray 23.

  The document discharge tray 23 is provided below the document placement tray 21, and these trays are configured in two upper and lower stages. The document discharged to the document discharge tray 23 can be taken out from the front side of the document feeder 20.

  The document loading tray 21 and the document discharge tray 23 are opposite to each other in the document transport direction, that is, in FIG. 2, the document loading tray 21 sends the document to the left, and the document discharge tray 23 receives the document. It is configured to discharge toward the right. Thus, the document supply port 31 and the document discharge port 37 are provided on the same side of each tray, that is, on the left side in FIG. 2 with respect to the direction in which the document reading unit 33 exists. The first document transport path 32 and the second document transport path 34 extending from the document supply port 31 to the document discharge port 37 through the document reading unit 33 are formed in a U-shape in the vertical direction as shown in FIG. That is, it is provided in a shape curved in a U shape when viewed from the front.

  With the above configuration, the document feeding device 20 separates the documents stacked on the document placing tray 21 one by one and feeds them into the document feeding unit 30 and reads the image data by the document reading unit 33. The document is discharged onto the document discharge tray 23.

  Next, the detailed configuration of the document feeder 30 of the document feeder 20 will be described with reference to FIG. 3 in addition to FIG. FIG. 3 is a vertical sectional front view showing the document feeding portion of the document feeding device. In FIG. 3, the solid line arrows indicate the transport path and transport direction of the document.

  As described above, the document feeding unit 30 includes the document supply port 31 and the sheet feeding unit 60 at the downstream end of the document loading tray 21 in the document transport direction (see FIG. 3). As shown in FIG. 3, the first document conveyance path 32 extends downward on the downstream side of the document supply port 31.

  The paper feed unit 60 is provided above a substantially central portion in the document width direction that is perpendicular to the document conveyance direction, and includes a pickup roller 61, a paper feed belt 62, and a separation roller 63.

  The pickup roller 61 is provided immediately downstream of the document supply port 31. At the time of document supply, the downstream portion of the document stacked on the document placement tray 21 is lifted by the lift plate 22, and the uppermost layer at the downstream end of the document contacts the pickup roller 61 from below. The uppermost layer of the original is transferred to the paper feeding belt 62 by the pickup roller 61 and conveyed to the inside of the original feeding unit 30 by the paper feeding belt 62.

  The sheet feeding belt 62 is arranged on the downstream side of the pickup roller 61 so that the lower part of the surface projects into the first document conveyance path 32. Further, the paper feeding belt 62 is wound around two pulleys and rotates clockwise so that the original can be conveyed to the left from the original supply port 31 in FIG. The separation roller 63 is disposed below the paper feed belt 62 and is in contact with the paper feed belt 62. The document is inserted through a conveyance nip formed by the contact between the sheet feeding belt 62 and the separation roller 63.

  When a plurality of originals enter a conveyance nip formed by contact between the paper feed belt 62 and the separation roller 63, only the upper upper original that is overlapped is sent out by the paper feed belt 62. Due to the action of the separation roller 63, the overlapped lower document is not sent out, so that it is possible to prevent the problem of double feeding that the document is fed in a superimposed manner.

  On the first document conveyance path 32, a registration roller pair 38 and conveyance roller pairs 39 and 40 are provided downstream of the location of the paper feed unit 60. The registration roller pair 38 is composed of a registration roller 38a and a roller 38b that are in pressure contact with each other. The registration roller pair 38 corrects the oblique feed so that accurate reading can be performed on the document going to the document reading unit 33, and suitable timing. Measure and send out.

  A document reading unit 33 is provided downstream of the conveyance roller pair 40. Here, the first document conveyance path 32 extending from the document supply port 31 passes through the paper feeding unit 60, the registration roller pair 38, and the conveyance roller pairs 39 and 40 to the position of the document reading unit 33, and is counterclockwise when viewed from the front. Curved to rotate in the direction. Accordingly, the first document conveyance path 32 extends toward the left and below in FIG. 3 on the upstream side of the document reading unit 33, and the second document conveyance path 34 extending continuously from the first document conveyance path 32 is the document reading. On the downstream side of the portion 33, it extends obliquely upward to the right to the document discharge port 37 and the document discharge tray 23.

  The document reading unit 33 includes a reading guide member 41. The reading guide member 41 is disposed opposite to the contact glass 7 a of the image reading device 7 of the main body 2 provided below the document reading unit 33. The reading guide member 41 extends long in the document width direction, that is, in the front-rear direction of the document feeder 20, and has a shape in which a portion for guiding the document protrudes downward. When the document feeding device 20 is closed with respect to the image reading device 7, the reading guide member 41 is below the reading guide member 41 so that the document conveyed between the contact glass 7a and the contact glass 7a comes into contact with the contact glass 7a. To guide you.

  The document sent to the document reading unit 33 moves from the first document transport path 32 to the second document transport path 34, and moves from the left to the right in the lower part of the reading guide member 41 in FIG. In the middle, that is, when passing over the contact glass 7a, image data is read by a reading unit (not shown) arranged below the contact glass 7a.

  A document switching unit 35 is provided downstream of the document reading unit 33 in the second document transport path 34. The document switching unit 35 is provided with a switching guide 42 that can swing in a vertical plane around a support shaft (not shown) that extends substantially horizontally in the front-rear direction. The switching guide 42 extends long in the front-rear direction of the document feeder 20, that is, in the document width direction, and has a wedge-shaped vertical cross-sectional shape viewed from the front of the front end portion on the upstream side in the document conveyance direction so that the document can be easily distributed. ing. The switching guide 42 is driven by a solenoid (not shown) which is a driving device arranged on the back side thereof, and changes its posture so that the leading end on the upstream side in the document conveying direction is swung up and down.

  A document discharge port 37 and a document discharge roller pair 43 are provided on the downstream side of the document switching unit 35 and at the downstream end of the second document transport path 34. The document whose image data has been read is discharged from the document discharge port 37 to the document discharge tray 23 (see FIG. 2) by the document discharge roller pair 43.

  On the other hand, on the downstream side of the document switching unit 35, a third document conveyance path 44 extends obliquely upward and to the right with respect to the second document conveyance path 34 extending substantially rightward in FIG. When it is necessary to read the image data of both the front and back sides of the document, the posture of the switching guide 42 of the document switching unit 35 is changed downward, and the document on which the image data on the first surface is read by the document reading unit 33 is read. The document is fed from the middle of the second document conveyance path 34 to the document reversing unit 36 via the third document conveyance path 44.

  A first document branching section 45 is provided downstream of the document switching section 35 in the third document transport path 44. The first document branching section 45 is a branching point between the third document transport path 44 and the fifth document transport path 52, which will be described later, provided closer to the document discharge tray 23 than the third document transport path 44. A first branch guide 46 is provided between the five document transport paths 52.

  The first branch guide 46 extends long in the front-rear direction (document width direction) of the document feeder 20, and has a wedge-shaped vertical cross section when viewed from the front end of the downstream end of the third document transport path 44, that is, the upper end. I am doing. The lower portion of the first branch guide 46 is supported by being connected to the frame of the document feeder 20 by a spring material (not shown), and the upper end of the first branch guide 46 extends along the document conveyance direction with the support portion as a center. It can swing in a vertical plane.

  The first branch guide 46 is arranged so that the upper end side of the first branch guide 46 closes the third document conveyance path 44. Further, the spring material that supports the first branch guide 46 has a resilience enough to bend when the original comes into contact with the first branch guide 46. As a result, when the document passes through the third document transport path 44, the first branch guide 46 changes its posture so that the downstream end, that is, the upper end is swung to the right in FIG. When the document has passed through the location of the first branch guide 46, or when the document is not in contact, the first branch guide 46 swings the upper end portion to the left, and the posture shown in FIG. 3 Holds a posture to block the document transport path 44.

  A second document branching section 47 is provided at the downstream end of the third document transport path 44 and between the document reversing section 36. The second document branching portion 47 is provided with a second branching guide 48. The second branch guide 48 extends long in the front-rear direction (document width direction) of the document feeder 20, and has a vertical sectional shape as viewed from the front end of the downstream end of the third document conveyance path 44, that is, the right end portion in FIG. It has a wedge shape. In addition, the second branch guide 48 has a support shaft (not shown) extending in the front-rear direction substantially horizontally on the left side portion thereof, and swings in a vertical plane along the document transport direction with the support shaft as a center. It is possible to move.

  The second branch guide 48 is arranged so that the right end side in FIG. 3 closes the third document conveyance path 44. The second branch guide 48 is formed so as to be able to swing about the support shaft center by the contact of the document with the right end of the second branch guide 48. Thereby, when the document passes through the third document transport path 44, the second branch guide 48 changes the posture so that the downstream end, that is, the right end is swung upward in FIG. When the document has passed through the second branch guide 48 or when the document is not in contact, the second branch guide 48 swings the right end portion downward due to the action of gravity and a stopper (not shown). 3, that is, a posture that closes the third document conveyance path 44.

  The document reversing unit 36 is disposed downstream of the third document conveying path 44 and above the downstream portion of the second document conveying path 34, and includes a reversing roller pair 49 and a reversing tray 50.

  The reversing roller pair 49 is disposed at the most upstream portion of the document reversing unit 36 with respect to the third document conveying path 44, and a reversing roller 49 a that forms a conveying nip that abuts against each other and conveys the document, and a driven roller. 49b. The reverse roller 49a is rotated clockwise and counterclockwise in FIG. 3 by a motor (not shown). The driven roller 49b is in pressure contact with the reversing roller 49a from above. The reversing tray 50 is disposed immediately below the document placing tray 21 with a relatively narrow gap, and extends obliquely upward similarly to the document placing tray 21 (see FIG. 2).

  In the document reversing unit 36, the downstream portion of the document conveyed from the left to the right in FIG. 3 through the third document conveying path 44 is once sent to the reversing tray 50, and the upstream portion of the document is reversed. When the roller pair 49 is reached, the rotation of the reversing roller 49a is reversed while the document is held in the conveyance nip between the reversing roller 49a and the driven roller 49b, thereby moving the document conveyance direction from right to left. And change.

  In FIG. 3, a fourth document conveyance path 51 is provided on the left side of the document reversing unit 36 and the second document branching unit 47 and above the third document conveyance path 44 and the document reading unit 33. The fourth document transport path 51 extends leftward in FIG. 3 from the position of the document reversing unit 36 and the second document branching unit 47, and beyond that, upstream of the registration roller pair 38 in the first document transport path 32. It joins the part of. As a result, the document that has completely passed through the second document branching unit 47 and whose conveyance direction has been changed by the document reversing unit 36 passes through the fourth document conveyance path 51 and again reaches the first document on the upstream side of the document reading unit 33. The image data is sent to the conveyance path 32, reaches the document reading unit 33, and image data on the second surface, which is the lower surface, is read.

  Then, in the middle of the third document transport path 44, the first document branch section 45 upstream of the second document branch section 47, which is a branch section with the fourth document transport path 51, exits from the third document transport path 44. A fifth document conveyance path 52 is provided so as to be branched. The fifth document conveyance path 52 branches from the third document conveyance path 44 at the first document branching section 45 and extends downward, and the second document conveyance path 34 is downstream of the document switching section 35 having the switching guide 42. Have joined. A conveying roller pair 53 is provided in the middle of the fifth document conveying path 52. The fifth document transport path 52 is configured to switch the document that has been read on both the front and back image data back to the document reversing unit 36 and switch it back, so that the original document stacking tray 21 is stacked on the front and back. At the same time, the paper is transported in the direction of the document discharge tray 23 in the second document transport path 34 to be discharged to the document discharge tray 23.

  Next, a mechanism related to the operation of the lift plate 22 of the document feeder 20 will be described with reference to FIGS. 4 to 8 in addition to FIG. 4 is a partially enlarged perspective view of the periphery of the lift plate and the sheet feeding unit as seen from the front, FIG. 5 is a partially enlarged perspective view of the periphery of the drive mechanism of the lift plate as seen from the rear, and FIG. 6 is a perspective view showing the drive mechanism of the lift plate. FIGS. 7 and 7 are perspective views showing the drive mechanism of the lift plate similar to FIG. 6, with drawing of the lower limit detection sensor omitted, and FIG. 8 is a partially enlarged front view showing the location of the lift plate and the drive mechanism. is there.

  As shown in FIG. 4, the document feeder 20 includes a drive mechanism 70 for the lift plate 22. The drive mechanism 70 is disposed on the rear side of the lift plate 22 outside the one end in the document width direction, and downstream of the downstream end of the lift plate 22 in the document conveyance direction. The drive mechanism 70 includes a lift mechanism 80 for the lift plate 22, and includes a motor 71, a gear group 72, a housing 73, and a lower limit detection device 90 that are drive sources for driving the lift mechanism 80.

  As shown in FIGS. 5 to 8, the elevating mechanism 80 includes a driven gear 81, a cam 82, and an operating link 83.

  The driven gear 81 is fixed to a support shaft 81a that extends substantially horizontally in the document width direction, that is, the front-rear direction, and is rotatably provided about the axis of the support shaft 81a. The support shaft 81a extends forward from the location of the driven gear 81. The driven gear 81 is connected to the drive gear 71a of the motor 71 through the gear group 72, and rotates by obtaining power from the motor 71 as a drive source.

  The cam 82 is fixed to an end portion on the front side of a support shaft 81a that is a rotation shaft. As a result, the cam 82 rotates in a vertical plane along the document conveying direction according to the rotation of the driven gear 81.

  The operation link 83 is disposed below the cam 82 and extends laterally from the drive mechanism 70 toward the lift plate 22 on the upstream side in the document conveyance direction (see FIG. 8). The operation link 83 is supported by a support shaft 83a provided at an end portion on the downstream side in the document transport direction and extending substantially horizontally in the document width direction, that is, the front-rear direction, and is freely movable around the axis of the support shaft 83a. The upstream end, which is the end, is swingable in a vertical plane so as to swing up and down.

  In addition, the upper surface of the operation link 83 is disposed at a location corresponding to the peripheral surface of the cam 82. The circumferential surface of the cam 82 abuts on the upper surface of a substantially intermediate portion of the operation link 83 extending along the document conveyance direction. As shown in FIGS. 5 and 8, the lower end of the upstream end, which is the free end of the operating link 83, is a peripheral surface of the operating pin 22b that extends substantially horizontally from the back of the downstream portion of the lift plate 22 toward the rear. It is in contact with the upper side. In this way, the operation link 83 is disposed between the cam 82 and the lift plate 22, and transmits the movement associated with the shape of the cam 82 to the lift plate 22.

  On the other hand, a spring 22 c is provided below the lift plate 22. The spring 22c is disposed between the frame of the document feeder 20 (not shown) and the lift plate 22, and biases the downstream portion of the lift plate 22 upward. Thereby, the operation pin 22b of the lift plate 22 and the operation link 83, and the operation link 83 and the cam 82 are always in contact with each other. As a result, when the cam 82 obtains power from the motor 71 and rotates, the free end sides of the operating link 83 and the lift plate 22 swing up and down in conjunction with the shape of the cam 82.

  As shown in FIGS. 6 and 8, the lower limit detection device 90 includes a shielding plate 91 that is an instruction piece, and a lower limit detection sensor 92.

  As shown in FIG. 7, the shielding plate 91 extends toward the outer side in the radial direction of the support shaft 81a of the driven gear 81, and is fixed to the support shaft 81a so that the front and back planes are perpendicular to the axis of the support shaft 81a. ing. The shielding plate 91 is provided in the vicinity of the driven gear 81, and the shape seen from the front thereof is substantially trapezoidal. Further, the shielding plate 91 is formed on the support shaft 81a so as to protrude upward when the cam 82 fixed to the support shaft 81a pushes down the operating link 83 most, that is, when the lift plate 22 is pushed down most. (See FIG. 8).

  As shown in FIGS. 6 and 8, the lower limit detection sensor 92 is a location corresponding to the shielding plate 91 and is disposed above it. The lower limit detection sensor 92 includes a photo interrupter that is an optical sensor, and includes a light emitting unit and a light receiving unit that face each other, and a gap is provided between them. The lower limit detection sensor 92 identifies that the light emitted from the light emitting unit is incident on the light receiving unit, and other members exist between the light emitting unit and the light receiving unit by shielding this light. Is detected. That is, the lower limit detection sensor 92 detects the shielding plate 91 that appears and disappears between the light emitting unit and the light receiving unit. Since the shielding plate 91 protrudes upward in the state where the lift plate 22 is pushed down most, that is, toward the lower limit detection sensor 92, the lower limit detection sensor 92 detects the lower limit position of the lift plate 22 indicated by the shielding plate 91. It will be.

  The motor 71, the gear group 72, the elevating mechanism 80, and the lower limit detection device 90, which are the components as described above, are collectively provided in the housing 73 of the drive mechanism 70 as shown in FIGS. The drive mechanism 70 is configured as one unit.

  Next, the lifting / lowering operation of the lift plate 22 using the drive mechanism 70 will be described with reference to FIG. 9 in addition to FIG. FIG. 9 is a partially enlarged front view showing a lift plate similar to FIG. 8 and the location of its drive mechanism, and shows a state in which the posture of the lift plate is different from FIG.

  When the document is not sent out from the document placement tray 21 toward the document reading unit 33, the document may be placed again on the document placement tray 21, so that the lift plate 22 is used as shown in FIG. The downstream portion is held in the lowest position.

  In this regard, the lower limit detection sensor 92 of the lower limit detection device 90 of the drive mechanism 70 determines the lower limit position of the lift plate 22 pushed down by the cam 82 and the operation link 83 as described above, and the shielding plate 91 serving as an indicating piece thereof. Detect through When the document feeder 20 recognizes that the document on the document tray 21 has become empty, it controls the drive mechanism 70 to hold the lift plate 22 in the lower limit position and to rotate the pickup roller 61. Stop.

  On the other hand, when a document is placed on the document placement tray 21 and a document feed start command is received, the document feeder 20 activates a drive mechanism 70 that drives the lifting mechanism 80 of the lift plate 22.

  In the drive mechanism 70, as shown in FIG. 9, the motor 71 rotates counterclockwise when viewed from the front. Accordingly, the cam 82 of the lifting mechanism 80 and the shielding plate 91 of the lower limit detection device 90 are also rotated counterclockwise through the gear group 72 as viewed from the front.

  When the cam 82 rotates, the upstream side of the operating link 83 and the downstream portion of the lift plate 22 are gradually raised by the action of the shape of the cam 82 and the elastic force of the spring 22c. The lift of the downstream portion of the lift plate 22 following the rotation of the cam 82 continues until the uppermost layer of the document bundle reaches the paper feed position where it abuts against the pickup roller 61. When the uppermost detection sensor (not shown) detects the contact of the uppermost layer of the original bundle with the pickup roller 61, the pickup roller 61 and the paper feeding belt 62 are rotated in the original conveying direction, and the original is shown in FIG. In FIG. 9, the paper is fed out of the document placing tray 21 (see FIG. 3) toward the left.

  The presence of a document placed on the document placement tray 21 is constantly monitored using a document set sensor (not shown). While the document is present on the document placing tray 21, the posture of the lift plate 22 is controlled using the upper limit detection sensor so that the uppermost layer of the document bundle holds the sheet feeding position where it contacts the pickup roller 61. The document continues to be sent out from the document placing tray 21 by the paper feeding unit 60.

  Thereafter, when the document set sensor detects the last document in the document stack placed on the document placement tray 21, the document feeder 20 activates the drive mechanism 70 that drives the lifting mechanism 80 of the lift plate 22. . As a result, the drive mechanism 70 rotates the cam 82 counterclockwise when viewed from the front, and the cam 82 resists the elastic force of the spring 22c and moves the upstream side of the operating link 83 and the downstream portion of the lift plate 22 against each other. Press down. When the shielding plate 91 of the lower limit detection device 90 that rotates simultaneously with the cam 82 reaches the location of the lower limit detection sensor 92, the lower limit detection sensor 92 detects the presence of the shielding plate 91.

  When the lower limit detection sensor 92 detects the presence of the shielding plate 91, the document feeder 20 stops the motor 71 of the drive mechanism 70 and the rotation of the pickup roller 61 as described above. Thereby, as shown in FIG. 8, the lift board 22 can be hold | maintained with the attitude | position of a minimum position.

  As described above, the document placing tray 21 that stacks and stores the documents, the paper feed unit 60 that separates and feeds the documents one by one from the document placing tray 21, and the document transport direction of the document placing tray 21 In the document feeder 20 including the lift plate 22 that lifts the downstream portion to the paper feed position, the lift mechanism 80 that lifts and lowers the lift plate 22, and the drive mechanism 70 that drives the lift mechanism 80, the drive mechanism 70 is the drive mechanism 70. In addition to the lifting mechanism 80, the lower limit detecting device 90 for detecting the lower limit of the lift plate 22 is provided, and these are configured as a unit, so that the drive source of the lifting mechanism 80 such as a motor or a solenoid is immediately A lower limit detection device 90 can be arranged on the side. Thereby, the electric wire which concerns on the lower limit detection apparatus 90, and its wiring process member need only be the quantity equivalent to a drive source. Therefore, it is possible to suppress materials used and parts used, and it is possible to prevent an increase in cost. Moreover, the arrangement space of the electric wires and the wiring processing members can be secured together with the electric wires of the driving source and the wiring processing members. As a result, it is possible to prevent the document feeder 20 from becoming large. In this way, the document feeding device 20 can be reduced in size and reduced in cost with respect to the document feeding device 20 that moves the uppermost layer of the document bundle to the feeding position by moving the lift plate 22 up and down. 20 can be provided.

  Further, since the drive mechanism 70 is disposed on the back side of the lift plate 22 that is one end outside in the document width direction perpendicular to the document transport direction, the drive mechanism 70 is controlled to the back side in the document width direction of the document feeder 20. If a substrate is provided, it can be brought close to it. Thereby, the electric wire which concerns on the lower limit detection apparatus 90, and its wiring processing member can be further reduced, and the arrangement space concerning them can also be reduced. Accordingly, it is possible to further reduce the increase in size and cost of the document feeder 20.

  The elevating mechanism 80 is provided with a cam 82 for rotating the lift plate 22 and rotating with the power from the motor 71 that is a driving source, and a rotating shaft 81a. Since it is provided with a shielding plate 91 that is provided on the rotation shaft 81a and indicates a lower limit position of the lift plate 22, and a lower limit detection sensor 92 that detects the position of the shielding plate 91, the lifting mechanism 80 is driven by a drive mechanism. The lower limit detecting device 90 can be arranged at any location on the rotating shaft. As a result, the elevating mechanism 80 can be easily included in the drive mechanism 70, and the arrangement location of the lower limit detection device 90 can be easily changed. In this way, it is possible to further improve the reduction in size and cost of the document feeder 20.

  In the present invention, since the document feeder 20 is mounted on the image forming apparatus 1, the image is mounted with the document feeder 20 that moves the uppermost layer of the document bundle to the feeding position by moving the lift plate 22 up and down. As compared with the forming apparatus 1, it is possible to obtain the image forming apparatus 1 in which the enlargement is suppressed and the cost is reduced.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  For example, the image forming apparatus 1 equipped with the document feeder 20 is an image forming apparatus for monochrome printing using only black toner in the above embodiment, but is not limited to such a model, and is not An image forming apparatus for color printing of a tandem type or a rotary rack type that includes a transfer belt and can form an image by superimposing a plurality of colors may be used.

  The present invention can be used in a document feeding apparatus including a lift plate that lifts and displaces a downstream portion of a document placing tray in a document transport direction to a sheet feeding position.

1 is a schematic vertical sectional front view of an image forming apparatus equipped with an original feeding device according to an embodiment of the present invention. FIG. 2 is a schematic vertical sectional front view of the document feeder of FIG. 1. FIG. 3 is a vertical sectional front view showing a document feeding section of the document feeding device of FIG. 2. FIG. 3 is a partially enlarged perspective view of the periphery of a lift plate and a sheet feeding unit in FIG. 2 as viewed from the front. FIG. 3 is a partially enlarged perspective view of the periphery of the drive mechanism of the lift plate of FIG. 2 as viewed from the rear. It is a perspective view which shows the drive mechanism of the lift board of FIG. FIG. 9 is a perspective view showing a lift plate driving mechanism similar to that in FIG. 6, omitting the drawing of the lower limit detection sensor. FIG. 5 is a partially enlarged front view showing the lift plate of FIG. 4 and the location of its drive mechanism. FIG. 8 is a partially enlarged front view showing the same lift plate and drive mechanism as in FIG. 8, and shows a state where the posture of the lift plate is different from FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Main body 7 Image reading apparatus 20 Document feeding apparatus 21 Document placing tray 22 Lift plate 22a Support shaft 22b Actuation pin 22c Spring 23 Document discharge tray 30 Document feeding section 70 Drive mechanism 71 Motor (drive source)
72 Gear group 73 Housing 80 Elevating mechanism 81 Driven gear 81a Support shaft (rotating shaft)
82 Cam 83 Operating link 90 Lower limit detection device 91 Shield plate (indicator piece)
92 Lower limit detection sensor

Claims (4)

Document stacking tray for storing and stacking documents, a paper feed section for separating and feeding documents one by one from the document stacking tray, and a lift for lifting the downstream portion of the document stacking tray in the transport direction to the paper feed position In a document feeder provided with a plate, a lifting mechanism for lifting and lowering the lift plate, and a drive mechanism for driving the lifting mechanism,
The drive mechanism includes the elevating mechanism, and includes a lower limit detection device that detects a lower limit of the lift plate, and is configured as a unit in which these are combined.   The document feeder according to claim 1, wherein the driving mechanism is disposed outside one end of the lift plate in the document width direction perpendicular to the document conveyance direction.   The elevating mechanism includes a cam that rotates with the power from a drive source and swings the lift plate, and a rotation shaft thereof. The lower limit detection device is provided on the rotation shaft of the cam, and the lift plate The document feeding apparatus according to claim 1, further comprising: an indicating piece that indicates a lower limit position of the image forming apparatus; and a lower limit detecting sensor that detects a position of the indicating piece.   An image forming apparatus comprising the document feeding device according to claim 1.

Images