Patent Publication Number: US-2023164278-A1

Title: Document feeding apparatus, image reading apparatus, and image forming apparatus

Description:
FIELD OF THE INVENTION AND RELATED ART 
     The present invention relates to a document feeding apparatus which feeds documents into an image reading apparatus, an image reading apparatus, and an image forming apparatus having an image reading apparatus. 
     There have been known image forming apparatuses such as a copying machine, a facsimileing machine, etc., which are equipped with an image reading apparatus such as a scanner which obtains data of an image of a document by optically reading the image of the document. Some of these image reading apparatuses are equipped with an automatic document feeding apparatus (Automatic Document Feeder), which hereafter will be referred to as ADF) which can read multiple documents with a single operation. An ADF has a tray in which documents (each of which is in the form of a sheet of paper) are placed in layers. It feeds the documents one by one from the tray into an image reading apparatus with the use of its separating-conveying portion, and conveys each document to the reading portion of the image reading apparatus (Japanese Laid-open Patent Application No. 2005-247482: Patent Document 1). In the case of the ADF disclosed in Patent Document 1, a pair of sensors for detecting the presence of a document is positioned or disposed on the tray, and also, in the adjacencies of the separating-conveying portion, one for one, to detect the presence (or absence) of the document. Feeding of a document is started as the presence of a document in the tray is detected. 
     In recent years, it has been increasingly desired for an ADF to be able to feed a document of a small size, such as a name card (business card) and a bank check (which hereafter may be referred to as small document), into an image reading apparatus. Sheets of paper tend to adhere to each other due to the presence of static electricity. Further, as one of the stacked document (sheets of paper) is moved out of the stack, friction occurs between the document and the documents which are in contact with the document. Thus, in a case where multiple small documents (sheets of paper) are fed into an ADF, it sometimes occurs, because of the presence of static electricity and/or friction that the document (sheet of paper) which is to be fed next into the ADF remains stuck to the document (sheet of paper) which is to be fed first into the ADF. If the second document (sheet of paper) remains stuck to the first document (sheet of paper) to be fed, it sometimes occurs that the second document (sheet of paper), that is, the document (sheet of paper) which is not to be fed reaches the separating-conveying portion. As the second document (sheet of paper) reaches the separating-feeding portion, it is pinched by the separating-feeding portion. Therefore, the document (sheet of paper) is made to float from the tray. Consequently, whether or not a document (documents) is in the tray is erroneously detected. Therefore, the next document (documents) to be fed fails to be fed, and remains in the tray. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, there is provided a document feeding apparatus comprising: a document tray provided with a document placement surface placing documents; a feed roller, contactable to and separable from a top surface of the documents placed on the document tray, configured to feed the document in a feeding direction by rotating in contact with the top surface of the documents; a separation conveying unit, disposed downstream of said feed roller with respect to the feeding direction, configured to separate and convey the document fed from said feed roller, one by one; a first detecting unit, provided with a flag member movable so as to change a protrusion amount by which said flag member protrudes from the document placement surface at a first detecting position of the document surface overlapped with said feed roller in a widthwise direction perpendicular to the feeding direction, configured to detect that the document is at the first detecting position in a case in which the protrusion amount of said flag member is a first amount and detect that no document is at the first detecting position in a case in which the protrusion amount is a second amount greater than the first amount; and a control unit configured to execute an operation in a first mode in which a first detecting process is executed so as to detect the presence or absence of the document at the first detecting position before starting to lower said feed roller and the presence or absence of the document at the first detecting position is determined, and in a second mode in which a second detecting process is executed so as to detect the presence or absence of the document at the first detecting position after lowering said feed roller and the presence or absence of the document at the first detecting position is determined. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a perspective view of the image forming apparatus in the first embodiment of the present invention; it shows the general structure of the apparatus. 
         FIG.  2    is a sectional view of a combination of the reader and ADF in the first embodiment. 
         FIG.  3    is a combination of top and sectional views, respectively, of the essential portion of the ADF in the first embodiment. 
       Parts (a) and (b) of  FIG.  4    are a combination of top and sectional views, respectively, of the essential portion of the ADF in the first embodiment when a sheet of paper (document) is in the document tray. 
       Parts (a) and (b) of  FIG.  5    are a combination of a top and sectional views, respectively, of the essential portion of the ADF when a small document (sheet of paper) is in the document tray. 
         FIG.  6    is a block diagram of the control portion of the image forming apparatus in the first embodiment; it shows the structure of the control portion. 
       Parts (a) to (e) of  FIG.  7    are a combination of sectional views of the essential portion of the AFD in the first embodiment, when a small document (sheet of paper) is being fed into, and conveyed through, the ADF; it shows the movement and reaction of the document (sheet), which occur as the small (document) sheet of paper) is fed into, and conveyed through, the ADF. 
         FIG.  8    is a flowchart of the document (sheet) feeding-conveying sequence of the ADF in the first embodiment. 
         FIG.  9    is a top view of an example of referential ADF. 
       Parts (a) to (d) of  FIG.  10    are a combination of sectional views of the example of referential ADF; it shows how a document is detected. 
         FIG.  11    is a sectional view of the essential portion of the example of referential ADF when the second document is not in contact with the tray (second document is floating). 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Embodiment 1 
     &lt;Structure of Image Forming Apparatus&gt; 
     An automatic document reading apparatus  200  (which hereafter will be referred to as ADF  200 ), which is a document (sheet) feeding apparatus in this embodiment is described about its structure, with reference to appended drawings.  FIG.  1    is a schematic sectional view of the image forming apparatus  300  in this embodiment. The ADF  200  feeds a document, which is in the form of a sheet of paper, into the reading portion of the image forming apparatus  100 , conveys a document toward the image reading apparatus  100  (which hereafter will be referred to as reader  100 ), which reads a sheet, in the form of which a document is. Further, the ADF  200  is pivotally movable about a hinge, with which the top-rear edge of the reading unit  100  is provided, being enabled to be moved away from, or folded back upon, the reading unit  100 . Further, the ADF  200  and reading unit  100  are on the top side of the image forming apparatus  300  which is for forming an image on a sheet of recording medium with the use of its image forming means  300 B, which uses an electrophotographic or inkjet method. By the way, the structural design for the ADF  200  can be also applied to a manual document (sheet) feeding means, as a document (sheet) feeding apparatus, with which the image forming apparatus  300  is provided. 
     &lt;Structure of Image Reading Apparatus&gt; 
     Next, referring to  FIGS.  1  and  2   , the ADF  200  and reading unit  100  are described about their structure.  FIG.  2    is a sectional view of a combination of the ADF  200  and reading unit  100 . They show the structure of the combination. The reader  100  has: a document placement glass platen  101 , a top surface reading unit  104 , an optical system motor  225  ( FIG.  6   ), a document guide  109 , and a white color referential member  103 . The top surface reading unit  104  comprises a pair of top surface LEDs  105  and  106 , a top surface lens array  107 , and a top surface line sensor  108 . The top surface reading unit  104  reads the image of a document (sheet of recording medium) on the document placement glass platen  101 , line by line, while being moved along the pair of document guides  109 . Referring to  FIG.  2   , a glass  102 , through which the top surface of a document is read while the document is moved, is an integral part of the white color referential member  222 . The top surface reading unit  104  reads the image of the document (in the form of sheet of paper) conveyed onto the aforementioned glass  102  by the ADF  200 . 
     &lt;Structure of Automatic Document Feeding Apparatus&gt; 
     Next, referring to  FIG.  2   , the document (sheet) feeding operation of the ADF  200  is described. The ADF  200  has: a document tray  201  in which documents are placed in layers or on which documents are stacked; a separation roller pair  206 ; and a feed roller  204  contactable to and separable from the document tray  201 . Further, in terms of a plane which coincides with the document placement surface  201 A of the document tray  201 , on which documents are placed in layers, there is a document guiding surface  201 S, which guides a document toward the nip  206 N of the separation roller pair  206 , between the feed roller  204  and separation roller pair  206 . The nip  206 N of the separation roller pair  206  is positioned higher than the document placement surface  201 A as seen from the direction parallel to the axis of the feed roller  204 . Further, a cover portion  228  which is positioned in a manner to cover the top portion of the feed roller  204 , is provided with an arm  204 AM which supports the feed roller  204 . The arm portion  204 AM is positioned so that it does not come into contact with the document guiding surface  201 A as the feed roller  204  are lowered. 
     The documents in the document tray  201  in which the documents to be read are placed in layers are prevented by a combination of the separation roller pair  206  and feed roller  204  from being released downstream of the document tray  201  before the feeding of documents is started. The separation roller pair  206 , which is the separating-conveying means in this embodiment comprise a top separation roller  206   a , as the first roller, which forms the nip  206 N, as a separation nip, and a bottom separation roller  206   b  as the second roller. There are the first and second document sensors  205  and  206  for detecting the presence (or absence) of a document, between the separation roller pair  206  and feed roller  204 . In this embodiment, the second document detecting means is the first document sensor  205 , and the first document detecting means is the second document sensor  227 . Also in this embodiment, before the feed roller  204  begins to be rotated to feed a document into the reading unit  100 , the feed roller  204  is lowered to the top surface of the top one of the layered documents in the document tray  201 . Then, the rotation of the feed roller  204  is started with the feed roller  204  remaining in contact with the top surface of the top document. As a result, the top most document alone or the top most document and document(s) below are fed into the reading unit  100 . If the topmost document and documents below are fed together into the reading unit  100 , the topmost document is separated from the rest by the separation roller pair  206 , and then, is conveyed inward of the ADF  200 . 
     After being conveyed toward the interior of the ADF  200  by the separation roller pair  206 , the document reaches a puller roller pair  208 . Further in terms of the document feeding direction, there is a document conveyance detection sensor  207  for detecting a document as the document is conveyed toward the puller roller pair  208 , between the separation roller pair  206  and puller roller pair  208 . Also in terms of the document feeding direction, there is a document passage which has a read upstream roller pair  209  for conveying a document toward the glass  102 , through which a document is read as the document is conveyed across the glass  102 , on the downstream side of the puller roller pair  208 . As the document is conveyed to the document conveyance passage, the document is conveyed by the read upstream roller pair  209 , to a top surface reading position, and then, to a bottom surface reading position, which is on the downstream side of the top surface reading position. The top surface reading position is where the top surface of the document is read by the top surface reading unit  104 . The bottom surface reading position is where the bottom surface of the document is read by a bottom surface reading unit  212 . In an operation for reading the top surface of a document, the document is conveyed through the glass  102  for reading the top surface of the document while the document is being conveyed, and the glass  217  for reading the bottom surface of the document while the document is conveyed. While the document is conveyed between the glasses  102  and  217 , it is illuminated by a pair of top LEDs  105  and  106  while the document is moved on the underside of the top white color referential member  103  which is an integral part of the glass  102 . The light emitted by the top LEDs  105  and  106  are reflected by the top surface of the document, the document is read line by line by the top light sensor  108  through a top lens array  107 . That is, the image of the top surface of the document is read. 
     In an operation for reading both surfaces of a document, the top surface of the document is read by the top surface reading unit  104  as described above. As for the bottom surface of the document, it is read by the bottom surface reading unit  212  while the document is conveyed next to the bottom white color referential member  222  which is an integral part of the glass  102  for reading the top surface of a document while the document is conveyed. The bottom surface reading unit  212  comprises a pair of LEDs  213  and  214 , and a lens array  215 . It illuminates a document with the light from the LEDs  213  and  214 . As a document is conveyed along the bottom white color referential member  222 , the bottom reading unit  212  illuminates the document with the light from the bottom LEDs  213  and  214 . The light reflected by the bottom surface of the document is read by the bottom line sensor  216  through the bottom lens array  215 . That is, the bottom surface of the document is read by the bottom line sensor  216 . After the reading of a document, the document is conveyed by the downstream roller pair  218  to a discharge roller pair  219 , whereby it is discharged into a delivery tray  220 . In a case where two or more documents are in the document tray  201 , the above described sequence from the feeding of a document to discharging of the document is repeated until all documents are read and discharged into the delivery tray  220 . By the way, in addition to the CIS such as the one shown in Figure, a CCD or the like compact optical system which comprises a lens array  107  and mirrors may be employed as the bottom surface reading unit  212 . 
     At this time, an example of conventional ADF is described about it structural arrangement for detecting the presence (or absence) of a document (documents) in its document tray.  FIG.  9    is a top view of the referential (conventional) ADF  500 . As shown in  FIG.  9   , in the case of the ADF  500 , its sensor  504  for detecting the presence (or absence) of a document P in the document tray  501  is positioned at the center of the document tray  501  in terms of the widthwise direction of the document tray  501 , which is perpendicular to the direction in which a document is conveyed by a pickup roller  502 . Since the sensor  504  is positioned as described above, even if a document such as a name cart (business card) or a post card which is narrower than an ordinary sheet of recording medium needs to be read, whether or not the document is in the document tray  501  can be detected by the sensor  504 . In addition, in the case of the ADF  500 , its pickup roller  502  and separating-conveying means  503  are supported by the top cover of the document tray  501 . With the ADF  500  being structured as described above, the sensor  504  is likely to belong to the document tray  501 . 
     For example, referring to  FIGS.  10 ( a ) and  10 ( b ) , in a case where a sensor of a reflective type such as a photo-reflector is employed as the sensor  504 , the signal outputted by the sensor  504  will be ON or OFF depending on whether or not the sensor  504  received the light which was emitted by the sensor  504  and reflected by the document. Referring to  FIG.  10 ( a ) , in a case where the sensor  504  is a photo-reflector, if there is no document in the document tray  501 , the light emitted by the sensor  504  is reflected by the separating-conveying means  503 . The amount by which the light from the sensor  504  is reflected by the separating-conveying means  503  (dashed arrow mark F(a)) is smaller than the amount by which the light is reflected by a document. Thus, the sensor  504  outputs an OFF signal. On the other hand, referring to  FIG.  10 ( b ) , in a case where a document is in the document tray  501 , the light emitted by the sensor  504  is reflected by the document in the document tray  501 . The amount by which the light from the sensor  504  (arrow mark F(b) formed of broken line) is greater than the amount by which the light is reflected by the separating-conveying means  503 . Thus, the sensor  504  outputs an ON signal. Further, referring to  FIGS.  10 ( c ) and  10 ( d ) , it sometimes occurs, from the standpoint of cost, that a sensor which comprises a flag which moves toward or away from the document placement surface of the document tray  501 , is employed as the sensor  504 . In such a case, as the flag is made to move toward the document placement surface of the document tray  501 , by a document P as shown in  FIG.  10 ( c ) , the sensor  504  output an ON signal. On the other hand, as the flag moves away from the document placement surface of the document tray  501 , the sensor  504  outputs an OFF signal. 
     In a case where documents P and P+1 such as a name card (business card) and a post card, which are substantial in rigidity, and relatively short in terms of the direction in which they are conveyed, are consecutively fed into the ADF  500  structured as described above, it sometimes occurs that the document P+1 is lifted (made to float) away from the document placement surface of the document tray  501  as shown in  FIG.  11   . For example, if the document conveyance passage between the separating-conveying means  503  and pickup roller  502  is tilted, the document P+1 is lifted (made to float away) from the document placement surface of the document tray  501  by the document conveyance passage. Moreover, if the document P+1 happens to be in the form of a sheet of paper, as the document P+1 is lifted (made to float) away from the document placement surface of the document tray  501 , the flag of the sensor  504  is allowed to move upward. Consequently, the sensor  504  erroneously determines that there is no document in the document tray  501  in spite of the presence of the document P+1, which is the next on to be fed, in the document tray  501 . This is a problem. 
     Next, referring to  FIGS.  3  to  5   , the ADF  200  in this embodiment is described about its structural arrangement for detecting a document in the document tray  201 .  FIG.  3 ( a )  is a top view of the essential portion of the ADF  200  when there is no document in the document tray  201 . In terms of the document conveyance direction, there are the first document sensor  205  as the second detecting means in this embodiment, and the second document sensor  227  as the first detecting means, between the separation roller pair  206  and feed roller  204 . The detection position of the second document sensor  227 , that is, the first detecting position in this embodiment, is at the center of the ADF  200  in terms of the direction which is perpendicular to the document conveyance direction. Further, the detection position of the first document sensor  205 , which is the second detecting position in this embodiment, is offset in the widthwise direction of the document tray  201  (on the right side in terms of widthwise direction, as seen from upstream in terms of document conveyance direction). That is, in terms of the widthwise direction, the detecting position of the first document sensor  205  is on the outward side of the second document sensor  227 , with reference to the center of the document tray  201  in terms of the widthwise direction. By the way, the ADF  200  may be structured so that the detecting position of the first document sensor  205  is on the other side of the detecting position of the second document sensor  227  from the one in this embodiment, in terms of the widthwise direction. 
     There are a pair of regulating members  230   a  and  230   b , as document regulating means, on the document placement surface  201 A. The regulating members  230   a  and  230   b  have regulating surfaces  231   a  and  231   b , respectively, which regulate a document by the edges of the document in terms of the widthwise direction. The regulating members  230   a  and  230   b  are supported in such a manner that they are movable in the widthwise direction, on the document placement surface  201 A. In terms of the widthwise direction, the feed roller  204  is positioned so that its position coincides with the center of a document which is being regulated by the regulating members  230   a  and  230   b . The detecting position of the second document sensor  227  in the widthwise direction is disposed so as to overlap with the position of the feed roller  204  in the widthwise direction. That is, while a document is under the control of the regulating members  230   a  and  230   b , it is where it is detectable by the second document sensor  227 . 
       FIG.  3 ( b )  is a sectional view of the essential portion of the ADF  200  when there is no document in the document tray  201 . The first document sensor  205  is provided with a lever  205 A, which is supported by the cover portion  228  in such a manner that it is pivotally movable. The lever  205 A is positioned so that it hangs downward toward the document placement surface  201 A from the cover portion  228 . It pivotally moves in the document conveyance direction. A controller  200 A ( FIG.  2   ) can determine whether or not a document is at the detecting position of the first document sensor  205 , based on the amount of the pivotal movement of the lever  205 A. When a document is at the detecting position of the first document sensor  205 , the lever  205 A will have been moved by a preset amount, for example, 45 degrees, in the document conveyance direction, by the document, and therefore, will be blocking the light passage of an unshown photo-interrupter. The amount by which the lever  205 A will have been pivotally moved by a document when the document is in the detecting position of the first document sensor  205  is the third amount in this embodiment. As the lever  205 A is pivotally moved by 45 degrees into a position in which it blocks the light passage of the unshown interrupter, the first document sensor  205  outputs an ON signal. Thus, the controller  200 A can determine that a document is at the detecting position of the first document sensor  205 , based on the ON signal it received. On the other hand, when there is no document in the detecting position of the first document sensor  205 , the lever  205 A will have pivotally moved only 10 degrees, for example, in the document conveyance direction, and will have stopped without blocking the light passage of the photo-interrupter. The amount by which the lever  205 A will have been pivotally moved when no document is at the detecting position of the first document sensor  205  is the fourth amount in this embodiment, which is smaller than the third one. As the lever  205 A is pivotally moved by 10 degree, and therefore, the light passage of the unshown photo-interrupter is unblocked, the first document sensor  205  outputs an OFF signal. Thus, the controller  200 A can determine that no document is at the detecting position of the first document sensor  205 , based on the OFF signal it received. 
     The second document sensor  227  comprises a flag  227 A, which is allowed to move in such a manner that as the flag  227 A moves, it changes in the amount by which it protrudes from the document placement surface  201 A, and a photo-interrupter  229 , which is under the document placement surface  201 A. The flag  227 A is positioned so that it protrudes upward from the underside of the document placement surface  201 A through a slit with which the document placement surface  201 A is provided. It is vertically movable relative to the document placement surface  201 A. As the flag  227 A vertically moves relative to the document placement surface  201 A, the light passage from the light emitting portion of the photo-interrupter  229  to the light catching portion of the photo-interrupter  229  is blocked or unblocked by the flag  227 A. The controller  200 A can determine whether or not a document is at the detecting position of the second document sensor  227 , based on the amount by which the flag  227 A protrudes. When a document is at the detecting position of the second document sensor  227 , the flag  227 A will have been pushed down into the position (5 mm, for example, downward from document placement surface  201 A) in which it blocks the light passage. When the light passage of the photo-interrupter  229  is being blocked, the second document sensor  227  outputs an ON signal. Therefore, the controller  200 A determines that a document is at the detecting position of the second document sensor  227 , based on the ON signal it received. The amount by which the flag  227 A is protrusive from the document placement surface  201 A when the document is at the detecting position of the second document sensor  227  is the first amount in this embodiment. By the way, the first amount in this embodiment includes the amount by which the flag  227 A is protrusive from the document placement surface  201 A is zero, that is, when the flag  227 A is not protrusive from the document placement surface  201 A at all. 
     On the other hand, when no document is at the detecting position of the second document sensor  227  ( FIG.  3 ( b ) ), the flag  227 A is not being pushed downward by a document. Thus, the flag  227 A is in a position (5 mm upward from document placement surface  201 A, for example) in which it does not block the light passage of the photo-interrupter  229 . The second document sensor  227  outputs an OFF signal when the light passage of the photo-interrupter  229  is remaining unblocked. Therefore, the controller  200 A can determine, based on the OFF signal it received, that the no document is at the detecting position of the second document sensor  227 . The amount by which flag  227 A is protrusive from the document placement surface  201 A when no document is at the detecting position of the second document sensor  227  is the second amount in this embodiment, which is greater than the first amount. Further, when the feed roller  204  moves downward toward the document tray  201 , it moves in such a manner that its position relative to the flag  227 A becomes such a position that the light passage of the photo-interrupter  229  remains unblocked by the flag  227 A. 
     As described above, the ADF  200  can detect whether or not a document is at both the detecting positions of the first document sensor  205  and second document sensor  227  which are different in position in terms of the widthwise direction of a document. Thus, the controller  200 A can determine whether or not a document is on the document placement surface  201 A of the document tray  201 , and also, the size of the document, base on the detection signals outputted from the first and second document sensors  205  and  227 . 
     Next, the ADF  200  in this embodiment is described about its structural arrangement for determining the size of the document in the document tray  201 . By the way, referring to  FIGS.  4 ( a ) and  5 ( a ) , the length W in terms of the widthwise direction is the length of the feed roller  204  in terms of the width wise direction.  FIG.  4 ( a )  is a top view of the ADF  200  when a document S, which is wider than the length W, is in the document tray  201 . In this case, the presence of a document is detected at both the detecting positions of the first and second document sensors  205  and  227 , and both the first and second document sensors  205  and  227  output an ON signal. Thus, the controller  200 A determines that a document S, the width of which is greater than the length W is in the document tray  201 . 
       FIG.  4 ( b )  is a sectional view of the separation roller pair  206  and its adjacencies when a document S is in the document tray  201 . In this case, if the lever  205 A is in the position into which it moves by being pivotally moved by a preset amount by the document S, the first document sensor  205  outputs an ON signal, as described above. As the leading edge of the document S is moved into the area under the feed roller  204 , the position of each of the edge portions of the document S, in terms of the widthwise direction, overlaps with the detecting position of the first document sensor  205 . Thus, the lever  205 A of the first document sensor  205  is pivotally moved downstream (indicated by arrow mark F 1  in  FIG.  4 ( b ) ) in terms of the document conveyance direction, by the document S. Consequently, the light passage of the unshown photo-interrupter is blocked. Thus, the first document sensor  205  outputs an ON signal. As for the second document sensor  227 , its flag  227 A is pushed down by the document S as described above. Therefore, as the flag  227 A is moved into the position in which it blocks the light passage of the photo-interrupter  229 , the second document sensor  227  outputs an ON signal. As the leading edge of the document S is pushed into the area under the feed roller  204 , the flag  227 A of the second document sensor  227  is moved downward relative to the document placement surface  201 A. Consequently, the light passage of the photo-interrupter  229  is blocked by the flag  227 A. Thus, the second document sensor  227  outputs an ON signal. As described above, since both the first and second document sensors  205  and  207  output an ON signal, the controller  200 A determines that the width of the document S in the document tray  201  is greater than W. 
       FIG.  5 ( a )  is a top view of the ADF  200  when a document, which is less in width than W, is in the document tray  201 . In this embodiment, if a document K is no more than W in width, it will be referred to as a document of a “small size”. When the document K is in the document tray  201 , its position relative to the document tray  201  in terms of the widthwise direction remains regulated by the regulating members  230   a  and  230   b  in such a manner that in terms of the widthwise direction, the center of the document K coincides with the center of the feed roller  204 . In this case, it is detected that the document K is at the detecting position of the second document sensor  227 , but, the leading edge of the document K has not arrived at the detecting position of the first document sensor  205 . Therefore, it is determined that there is no document at the detecting position of the first document sensor  205 . That is, the first document sensor  205  outputs an OFF signal, and the second document sensor  227  outputs an ON signal. In a case where the first document sensor  205  outputs an OFF signal, and also the second document sensor  227  outputs an ON signal, the controller  200 A determines that the document in the document tray  201  is no greater than W in width in terms of the widthwise direction; it determines that the document in the document tray  201  is a document K, which is a small document. 
       FIG.  5 ( b )  is a sectional view of the separation roller pair  206  and its adjacencies when a document K is in the document tray  201 . As described above, the first document sensor  205  outputs an ON signal as its lever  205 A is pivotally moved by a preset amount by a document. More specifically, when the leading edge of the document K is in the area under the feed roller  204 , into which the document K was pushed, the edge portion of the document K has not reached the detecting position of the first document sensor  205 . That is, in terms of the widthwise direction, the edge portion of the document K is in such a position that does not overlaps with the detecting position of the first document sensor  205 . Therefore, the lever  205 A of the first document sensor  205  remains in such a state that it keeps the light passage of the unshown photo-interrupter open, and therefore, the first document sensor  205  outputs an OFF signal. On the other hand, as for the second document sensor  227 , its flag  227 A is pushed down by the document K as described above. Thus, as it is moved into a position in which it blocks the light passage of photo-interrupter  229 , it outputs an ON signal. As the leading edge of the document K is pushed into the area under the feed roller  204 , the flag  227 A of the second document sensor  227  is moved downward of the document placement surface  201 A by the document K. Therefore, the light passage of the photo-interrupter  229  is blocked by the flag  227 A. Consequently, the second document sensor  227  outputs an ON signal. That is, in this case, the first document sensor  205  outputs an OFF signal, whereas the second document sensor  227  outputs an ON signal. Therefore, the controller  200 A determines that a document K which is less in width than W is in the document tray  201 . By the way, the width of a document K, as the second width of a document, is equal to the width of a narrowest document which can be regulated by the regulating members  230   a  and  230   b , width of a document which is the same in width as a name card (business card), etc. Further, the width of a document which is W in width in terms of the widthwise direction, is greater than the width of the narrowest document which can be regulated by the regulating members  230   a  and  230   b , or the width of a document of the name card size. That is, in this embodiment, the second width is narrower than the first width. That is, it is the width of a document, the edge of the document, in terms of the widthwise direction, which does not overlap with the detecting position of the first document sensor  205 . Further, in this embodiment, the first width is equal to the width of a document, the edge of which in terms of the widthwise direction overlaps with the detecting position of the first document sensor  205 . 
     &lt;Control System&gt; 
     Next, referring to  FIG.  6   , the structural arrangement for controlling the operation of the ADF  200  is described.  FIG.  6    is a block diagram of a system for controlling the ADF  200  in operation. Referring to  FIG.  6   , the ADF  200  and image forming apparatus  300  are in electrical connection to each other by way of a pair of busses  401  and  402 . 
     &lt;Structure of Adf Controller&gt; 
     To begin with, the system for controlling the reading unit  100  and ADF  200  in operation is described about its structure. The controller  200 A, which is a means for controlling the reading unit  100  and ADF  200  in operation, has a CPU  301 , a ROM  302 , a RAM  303 , an image transferring portion  304 , an image memory  305 , and an image processing portion  306 . The CPU  301  is a computing means. It carries out the programs for controlling the reading unit  100  and ADF  200  in operation. The ROM  302  is a nonvolatile storage area, in which the programs for controlling the reading unit  100  and ADF  200  are stored. The RAM  303  is a storage area, which is used as the work area which the CPU  301  uses for computation. The CPU  301  downloads the programs in the ROM  302 , opens the programs in the RAM  303 , and carries out the programs to control the reading unit  100  and ADF  200  in operation. 
     The CPU  301  is in connection to a conveyance motor  224  for driving each of the rollers for conveying documents, in the ADF  200 . The conveyance motor  224  is in connection to the feed roller  204  and separation roller pair  206  by way of a separation clutch  223 . A document can be kept stationary in a position PS ( FIG.  2   ), in which the document is yet to reach the puller roller pair  208 , by the disconnection of the separation clutch  223 . Further, the CPU  301  is in connection to the first document sensor  205 , second document sensor  227 , conveyance sensor  207 , and read sensor  210 . The conveyance sensor  207  and read sensor  210  are such sensors that detect the edges of the document, at the detecting positions in the ADF  200 . The CPU  301  controls the conveyance motor  224  in driving pulse count. Driving pulse can be converted into the amount of distance by which a document is to be conveyed in the ADF  200 . That is the CPU  301  controls the ADF  200  in sheet conveyance, based on the amount of distance it calculates from the driving pulse count for the conveyance motor  224 . 
     Further, the CPU  301  is in connection to an optical system motor  225  for moving the top surface reading unit  104  in the secondary scan direction, an optical system HP sensor  226 , the image memory  305 , the image processing portion  306 , and the image transferring portion  304 . The top surface reading unit  104  and bottom surface reading unit  212  read the image of a document by scanning the document, line by line. The image memory  305  is a storage area for temporarily storing the data of the image of a document read by the top surface reading unit  104  and bottom surface reading unit  212 . The image processing portion  306  processes the image data in the image memory  305 . The image transferring portion  304  transfers the image data to the image transferring portion  314  of the controller  300 A by way of the bus  402 , after the processing of the image data by image processing portion  306 . 
     &lt;Structure of Controller on Main Assembly Side&gt; 
     Next, the controller  300 A of the image forming apparatus  300  is described about its structure. The controller  300 A controls the image forming apparatus  300  in overall operation. The image forming apparatus  300  is an image forming system which includes the image reading apparatus  100 . The controller  300 A controls the image forming apparatus  300  in overall operation. The controller  300 A is in connection to the controller  200 A in such a manner that communication is possible between the two controllers. It controls the image forming apparatus  300  in operation, based on the signals from the controller  200 A. Further, it outputs signals for controlling the reading unit  100  and ADF  200  in operation, to the controller  200 A. 
     The controller  300 A has the CPU  311 , a ROM  312 , a RAM  313 , an image transferring portion  314 , and an image memory  315 . The CPU  311  is a computing means of the main assembly of the image forming apparatus  300 . It carries out the programs for controlling the overall operation of the image forming apparatus  300 . The ROM  312  is a nonvolatile storage area, in which the control programs for the image forming apparatus  300  are stored. The RAM  313  is a storage area, which is used as a work area for the computation by the CPU  311 . As the CPU  311  reads the programs in the ROM  312 , opens them, and carries out the opened programs, the operation of the image forming apparatus  300  is controlled by the controller  300 A. An operation of the image forming apparatus  300  is the image forming operation by the image forming means  300 B, for example. The image transferring portion  314  receives image data from the image transferring portion  304 , and stores them in the image memory  315 . By the way, the image forming apparatus  300  is provided with an operating portion  316  which is for a user to give operational commands to the image forming apparatus  300 , reading unit  100 , and ADF  200 , and operational commands for displaying messages and images, to a user. The operating portion  316  is in communication with the CPU  311 . It displays images, and also, outputs information related to the operational commands for the image forming apparatus  300 , to the CPU  311 . 
     The CPU  311  is in communication with the CPU  301  by way of the bus  401 . It exchanges with the CPU  301 , the control commands related to the image reading operations of the reading unit  100  and ADF  200 , and controls data. For example, as the CPU  311  receives information related to a command to make the reading unit  100  and ADF  200  start an image reading operation, through the operating portion  316 , it outputs to the CPU  301 , information which demands the starting of an image reading operation. More concretely, as the CPU  311  receives from a user, information regarding the size of a document by way of the operating portion  316 , it transmits to the CPU  301 , information regarding the size of the document (dimension of document in terms of widthwise direction and document conveyance direction). Further, as the CPU  311  receives from the CPU  301 , information which indicates an occurrence of anomaly in the reading unit  100  and/or ADF  200 , it makes the operating portion  316  display to a user, such a message that is appropriate for the type of anomaly. 
     Next, what occur to a document K, that is, a document of a small size, if it is fed into the image reading apparatus  100  in this embodiment is described.  FIGS.  7 ( a )- 7 ( d )  are enlarged sectional views of the feed roller  204  and separation roller pair  206 , and their adjacencies. They show what occurs to the document K as the document K is fed into the ADF  200 . Referring to  FIG.  7 ( a ) , as the separation clutch  223  is engaged, the feed roller  204  is connected to the conveyance motor  224 , and therefore, rotates in the direction indicated by an arrow mark r by being driven by the conveyance motor  224 . Further, it moves downward into the document tray  201 , picks up the topmost document of the multiple layered documents in the document tray  201 , and conveys the document K in the direction indicated by an arrow mark D drawn with a dotted line. 
     Referring to  FIG.  7 ( b ) , as the leading edge of the document K is moved through the nip of the separation roller pair  206 , and reaches the puller roller pair  208 , the CPU  311  disengages the separation clutch  223  to stop the rotation of the feed roller  204 . This process is for preventing the problem that the document K+1, which is to be fed next, is fed into the ADF  200  immediately after the document K is moved through the nip of the feed roller  204 . However, in a case where multiple documents to be read are of a small size, the trailing edge of the document K is moved past the feed roller  204 , before the leading edge of the document K reaches the puller roller pair  208  and stops the rotation of the pickup roller. Thus, the feed roller  204  comes into contact with the document K+1 while remaining rotating. Consequently, the document K+1 is conveyed in the direction indicated by the dashed line arrow mark D, along with the document K, as shown in  FIG.  7 ( b ) . That is, the so-called “tagging” occurs. The occurrence of this phenomenon is not limited to a case where documents to be fed into an automatic document feeder are shorter than a certain value. For example, it possibly occurs in a case where the documents to be fed into an automatic document feeder are small in friction, and/or the preceding document and following document are remaining stuck to each other due to static electricity. 
     Referring to  FIG.  7 ( c ) , if the document K+1 is fed into the ADF  200  along with the document K, the document K+1 is made to upwardly separate (float) from the document tray  201 . Then, as the leading edge of the document K, which is to be fed into the document passage, reaches the puller roller pair  208 , the rotation of the front cover  20  stops. As the document K reaches the puller roller pair  208 , it is conveyed by the puller roller pair  208 , and the rollers which are on the downstream side of the document passage. Further, the rotation of the feed roller  204  and separation roller pair  206  is under the control of the separation clutch  223 . Moreover, there is a guiding surface  201 S between the feed roller  204  and separation roller pair  206 . The guiding surface  201 S is a part of the document placement surface  201 A of the document tray  201 . It guides a document toward the nip  206 N of the separation roller pair  206  by the leading edge of the document. Further, the nip  206 N of the separation roller pair  206  is higher in position than the document placement surface  201 A. Therefore, it is prevented that all the documents in the document tray  201  move downstream in terms of the document conveyance direction. Therefore, it is assured that only the topmost document is fed into the document conveyance passage. If the topmost document and the second document are fed into the ADF  200  in such a manner that the second one tags along the topmost one, it sometimes occurs that as the leading edge portion of the topmost one enters the nip  206 N of the separation roller pair  206 , the second one, or the one which is tagging along the topmost one, floats away from the document placement surface  201 A of the document tray  201 . In this embodiment, the phenomenon that as the leading edge of a document reaches the separation roller pair  206 , the trailing edge portion of the document floats away from the document placement surface  201 A of the document tray  201  is referred to as “document floatation”. During the “document floatation”, the separation clutch  223  remains disengaged, and therefore, neither the feed roller  204  nor separation roller pair  206  is rotating. Thus, the feed roller  204  does not have a power to move itself downward. That is, during the “document floatation”, the feed roller  204  remains separated from the document placement surface  201 A. 
       FIG.  7 ( d )  shows the state of the essential portion of the ADF  200 , in which the document K+2 has begun to be fed along (tag along) with the document K+1 while the document K+1 had begun to be fed along (tag along) with the document K. As the document K+ 2 , which is the last (bottommost document) in the document tray  201 , begins to be fed along with the document K+1, the leading edge of the document K+2 reaches the separation roller pair  206 . Then, as the trailing edge of the document K+1 passes by the feed roller  204 , the document K+2, that is, the next document begins to be fed. At this point in time, it is determined whether or not a document is on the document placement surface  201 A of the document tray  201 , based on the output of the second document sensor  227 , before the feed roller  204  is lowered to start feeding the next documents. The first detection in this embodiment is the process to detect the presence or absence of a document on the document placement surface  201 A of the document tray  201 . Further, the first mode in this embodiment is the operational mode in which whether or not a document is present at the detecting position of the second document sensor  227  on the document tray  201  before the lowering of the feed roller  204 . 
     In this case, however, the document K+2 is floating, and therefore, the flag  227 A of the second document sensor  227  will have moved in the direction indicated by the dashed line arrow mark f1 in  FIG.  7 ( d ) . Consequently, it is determined that no document is present at the detecting position of the second document sensor  227 . As described above, as the “tag-along” occurs, it is determined that no document is in the document tray  201  even though a document (documents) to be conveyed is in the document tray  201 . Therefore, it is possible that the document K+2 will remains unfed in the document tray  201 . 
     In comparison, in this embodiment, the feed roller  204  is lowered as shown in  FIG.  7 ( e ) . Then, it is determined, based on the result of the document detection by the second document sensor  227 , whether or not a document is on the document placement surface  201  A of the document tray  201 . More concretely, first, the separation clutch  223  is engaged to lower the feed roller  204  until the feed roller  204  presses on the document K+2. Therefore, the document K+2 is pushed down by the feed roller  204 , causing the flag  227 A of the second document sensor  227  to move downward (indicated by arrow mark f2) toward the document placement surface  201 A. Consequently, the document K+2 is placed on the document placement surface  201 A; the problem of “document floatation” is solved. Then, it is determined, based on the result of the document detection by the second document sensor  227 , whether or not the document K+2 is on the document placement surface  201 A of the document tray  201 . This process of detecting the presence (or absence) of a document on the document placement surface  201 A of the document tray  201  after the lowering of the feed roller  204  is the document detecting process in accordance with the present invention. Further, the second mode, in this embodiment, in which the presence (or absence) of a document at the detecting position of the second document sensor  227  on the document tray  201  is determined after the lowering of the feed roller  204  is the document conveyance mode for a small document, which is in accordance with the present invention. By the way, the ADF  200  may be structured so that in the small document conveyance mode, the second detection process is carried out after the first detection process. 
     As described above, in a case where a document is on the document placement surface  201 A of the document tray  201  in the small document conveyance mode, the second document sensor  227  is made to output an ON signal by the movement of the flag  227 A which is caused by the lowering of the feed roller  204 . On the other hand, in a case where the ADF  200  is in the small document conveyance mode, and no document is in the document tray  201 , the lowering of the feed roller  204  does not cause the flag  227 A to move. Therefore, the second document sensor  227  continues to output an OFF signal. As described above, in this embodiment, whether or not a document is on the document placement surface  201 A of the document tray  201  is detected after the placement of the “floating document” back on the document placement surface  201 A. Therefore, this embodiment can substantially reduce the ADF  200  in the probability with which the presence (or absence) of a document on the document placement surface  201 A of the document tray  201  is erroneously determined. 
     &lt;Document Feeding Sequence&gt; 
     Next, referring to  FIG.  8   , the operational sequence through which documents are fed into the ADF  200  in this embodiment, from its document tray  201 , is described.  FIG.  8    is a flowchart of the operational sequence through which the documents in the document tray  201  of the ADF  200  in this embodiment are fed into the main assembly of the document reading apparatus  200 . The document feeding operation diagramed in the form of the flowchart in  FIG.  8    is an operation which is carried out primarily by the controller  200 A; the programs stored in the ROM  302  are carried out by the CPU  301 . By the way, the flowchart in  FIG.  8    is applicable to both the operation for feeding a document to read only the image on one of the two surfaces of the document, and also, to read the images on both surfaces, one for one, of the document. 
     As a command to make the image reading apparatus  100  start reading the image of a document is inputted by a user with the use of the operating portion  316 , a signal to start the reading is outputted to the controller  300 A from the CPU  311  of the controller  300 A. As a result, the abovementioned sequence is started. As the signal to start the reading is inputted into the controller  200 A, the signal from the first document sensor  205  is confirmed (S 101 ). If the signal outputted from the first document sensor  205  is an ON signal (S 101 /Y), it is determined that the documents in the document tray  201  are not small, and the information for turning off the small document conveyance mode is stored in the RAM  303  (S 102 ). On the other hand, if the signal outputted by the first document sensor  205  is an OFF signal (S 101 /N), and the signal outputted by the second document sensor  227  is an ON signal (S 115 /Y), it is determined that the documents in the document tray  201  are documents of a small size. Then, the information for turning on the small document conveyance mode is stored in the RAM  303  (S 116 ). 
     Next, the conveyance motor  224  is driven to feed the documents from the document tray  201  (S 103 ), and the separation clutch  223  is engaged (S 104 ). Thus, the feed roller  204  moves down onto the topmost document in the document tray  201 , and rotates while remaining in contact with the top surface of the topmost document. Therefore, the topmost document is sent to the separation roller pair  206  by itself, or with the documents below the topmost one. Then, the document is conveyed toward the puller roller pair  208 . If two or more documents are sent to the separation roller pair  206 , the topmost one is separated from those under the topmost one, and sent to the puller roller pair  208 . If the conveyance sensor  207  outputs an ON signal (S 105 /Y), it is determined that a document has arrived at the puller roller pair  208  (S 106 ). As a document arrives at the puller roller pair  208 , the separation clutch  223  is disengaged (S 107 ) to stop the rotation of the feed roller  204  and separation roller pair  206 . As a document reaches the puller roller pair  208 , it is conveyed toward the top surface reading position, in which the image of the top surface of a document is read by the top surface reading unit  104 . By the way, in the case where both the image of the top surface of a document and the image of the bottom surface of the same document need to be read, the image of the bottom surface of the document is read by the bottom surface reading unit  212  after the reading of the image of the top surface of the document. As the signal outputted by the conveyance sensor  207  is made to change from an ON signal to an OFF signal by the conveyance of a document by the puller roller pair  208  (S 108 /Y), it is determined with reference to the RAM  303  whether or not the ADF  200  is in the small document conveyance mode (S 109 ). 
     It is known that in a case where the ADF  200  is in the small document conveyance mode (S 109 /Y), the documents in the document tray  201  are of a small size. Thus, the feed roller  204  is lowered (S 111 ) by the engagement of the separation clutch  223 , before the detection of the presence (or absence) of the documents in the document tray  201 . During this process, the documents in the document tray  201  are pushed down toward the document placement surface  201 A of the document tray  201  by the descending of the feed roller  204  toward the document placement surface  201 A of the document tray  201 . As described above, in a case where the small document conveyance mode is ON, the feed roller  204  is lowered to push the documents in the document tray  201  down toward the document placement surface  201 A of the document tray  201 , before the detection of the presence (or absence) of a document by the second document sensor  227 . Therefore, the problematic floating of a document will have been resolved before the detection of the presence (or absence) of a document in the document tray  201  by the second document sensor  227 . In other words, even if the flag  227 A of the second document sensor  227  is protruding upward beyond the document placement surface  201 A because of the floating of the document, the floating document is pushed down onto the document placement surface  201 A, and therefore, the flag  227 A of the second document sensor  227  is moved below the document placement surface  201 A by the document. Therefore, the output of the second document sensor  227  changes from an OFF signal to an ON signal. By the way, in S 111 , the feed roller  204  is lowered to the same position as the one for feeding a document. 
     After the completion of the lowering of the feed roller  204  (S 111 /Y), the output signal from the second document sensor  227  is confirmed (S 112 ). If the output signal from the second document sensor  227  is an ON signal (S 112 /N), there is a document in the document tray  201 . Therefore, the controller  200 A returns to S 105 , and repeats the steps S 105  to S 111  until there will be no document in the document tray  201 . As described above, in this embodiment, if it is detected that the documents in the document tray  201  are of a small size, whether or not a document is in the document tray  201  is determined after the lowering of the feed roller  204 . By the way, if the signal outputted from the second document sensor  227  is an OFF signal (S 112 /Y), there is no document in the document tray  201 . Thus, the conveyance motor  224  is stopped (S 114 ) by the disengagement of the separation clutch  223  (S 113 ) to end the document feeding operational sequence. 
     On the other hand, it is known that in a case where the small document conveyance mode is OFF (S 109 /N), the documents in the document tray  201  are not of a small size. In such a case, it is determined that the document in the document tray  201  is not floating. Then, the output signal of the first document sensor  205  is confirmed before the controller  200 A begins to lower the feed roller  204  (S 117 ). In a case where the output signal from the first document sensor  205  is not an ON signal (S 117 /N), at least one document is on the document placement surface  201 A of the document tray  201 . Therefore, the controller  200 A returns to S 104 , and repeats steps S 104  to S 109  until there will be no document in the document tray  201 . As described above, in this embodiment, if it is detected that the documents in the document tray  201  are not of a small size, whether or not at least one document is in the document tray  201  is determined after the feed roller  204  is lowered. On the other hand, in a case where the output signal from the first document sensor  205  is an OFF signal (S 11 /Y), there is no document in the document tray  201 . Therefore, the conveyance motor  224  is stopped (S 114 ) to end the document feeding operational sequence. By the way, after the starting of a document reading process, if both the output signal from the first document sensor  205  and that from the second document sensor  227  are OFF signals (S 101 /N and S 115 /N), the image of a document is read while the document is kept on the document placement glass platen  101 . Then, the image reading sequence is ended after the completion of the reading of this document ( FIG.  8   , A). 
     As described above, in this embodiment, in a case where the documents in the document tray  201  are likely to float, the feed roller  204  is lowered to press the document in the document tray  201  against the document placement surface  201 A of the document tray  201 , before whether or not there is a document in the document tray  201  is determined. Therefore, the ADF  200  in this embodiment is substantially lower in the probability with which whether or not a document is in the document tray  201  is erroneously determined due to the “document floatation”. 
     &lt;Miscellanies&gt; 
     In the first embodiment, the ADF  200  is structured so that the presence (or absence) of documents in the document tray  201  was detected based on whether or not the light passage of the photo-interrupter  229  is blocked by the flag  227 A of the second document sensor  227 . However, such a sensor as a photo-reflector, which detects the presence (or absence) of a document by projecting a beam of light toward the document passage, and measuring the amount by which the beam of light is reflected, may be employed in place of the second document sensor  227 . Even if a photo-reflector is employed in the place of the second document sensor  227 , it is possible to substantially reduce the ADF  200  in the probability with which the presence (or absence) of a document is erroneously detected due to the “document floatation”. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2020-004637 filed on Jan. 15, 2020, which is hereby incorporated by reference herein in its entirety.