JP2011102853A - Automatic document feeding apparatus, image reading apparatus, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To determine that a document is a loose-leaf document with economical constitution of a small parts count. <P>SOLUTION: When the document fed along a feeding path by a rotating first feeding roller is butted against a second feeding roller in a rotation stop state and subjected to skew correction, feeding torque F of the first feeding roller is detected (step S18). Also, based on thickness of the fed document, a threshold N of the feeding torque of the first feeding roller for discriminating whether the document is a loose-leaf document or an ordinary document is obtained (step S19). When the detected feeding torque F is equal to or under the obtained threshold N (step S20), the document is determined as the loose-leaf document (step S21). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an automatic document conveying device used for automatically conveying a document to an image reading device, an image reading device provided with the automatic document conveying device, and an image forming apparatus including such an image reading device. About.

  In an image forming apparatus such as a copying machine, operability when reading images of a plurality of documents is provided by providing an automatic document transport device (ADF unit) that automatically transports a document in a scanner device (scanner unit) that reads a document image. , Improving reading efficiency. Usually, the ADF unit automatically conveys the document so that the document placed on the document feed tray passes over the document image reading position provided in the scanner unit.

In the transport path of the ADF unit, a plurality of document sensors for detecting the transport position of the document is provided along the transport path. The document sensor normally optically detects the leading edge and the trailing edge of the document, and controls the switching timing of the conveyance path, the conveyance timing of the subsequent document, and the like based on the detection result of the document sensor. It is supposed to be.
The original transported in the transport path of the ADF unit is not limited to ordinary paper that is not provided with a through hole such as a binding hole, but on one side edge so that it can be bound to a dedicated binder. There may be a case of loose leaf paper (loose leaf original) in which a large number of spell holes (multiple holes: loose leaf holes) are arranged in a line.

  When a loose leaf document is transported along the transport path with the loose leaf hole positioned on the front side (leading side) or rear side (rear end side) in the transport direction, each document sensor provided in the transport path The side edge on the leading edge side or the side edge on the trailing edge side may be erroneously detected as the trailing edge or leading edge of the document. If such an erroneous detection is caused by the document sensor, the conveyance path switching timing, the document conveyance timing, and the like cannot be appropriately controlled, and a trouble such as a paper jam may occur in the conveyance path.

  In order to prevent such erroneous detection by the document sensor, it is proposed that the output of the document sensor is invalidated for a predetermined time when the leading edge or the trailing edge of the document is detected. Has been. However, in such a configuration, even in the case of a normal document in which no through hole is formed, the output of the document sensor is invalidated for a predetermined time. Etc. will be delayed, and the conveyance efficiency of the document may be reduced.

  In order to solve such a problem, it is detected whether a document conveyed on the conveyance path is a loose-leaf document or a normal document in which no through hole is formed. It is preferable to execute the subsequent document conveyance timing without waiting for the document to wait. As a result, it is possible to prevent a decrease in the conveyance efficiency of a normal document.

In Patent Document 1, when a through-hole is formed in a predetermined portion of the conveyed original paper by a reflection type optical sensor or the like and the formation of the through-hole is detected, the original paper is detected. A document feeding apparatus that performs control such as stopping the conveyance of the document is disclosed.
Further, in Patent Document 2, light is emitted from a light guide plate that guides light emitted from a light emitting element to a conveyed document, and light that has passed through a through hole (binding hole) provided in the document is transmitted by the light guide plate. A configuration is disclosed in which a phototransistor is guided to detect the presence of a through hole in a document sheet based on the output of the phototransistor.

Japanese Utility Model Publication No. 5-85740 JP 2005-204008 A

  In the configuration disclosed in Patent Document 1, when a through-hole exists at a predetermined position on a document placed on a document table, the through-hole is detected by a through-hole detection unit such as a reflective optical sensor. Can do. However, the document with through holes is not limited to punched paper with a small number of punch holes such as two holes, but may be a loose leaf document with many loose leaf holes. In order to detect, it is necessary to provide a detection means such as a reflective optical sensor at a position different from the punch hole. Therefore, in order to detect that the document is a loose-leaf document, there is a problem that the ADF unit becomes large and the economy is impaired.

Even in the configuration disclosed in Patent Document 2, since it is necessary to provide a pair of light guide plates with the document conveyance path interposed therebetween, the automatic document conveyance device may be increased in size. Moreover, since a light emitting element, a light guide plate, and a phototransistor are necessary, the number of parts increases, and the ADF unit may be enlarged and the economy may be impaired.
The present invention has been made in view of the above problems, and an object of the present invention is to detect a document in which a loose leaf hole is formed without increasing the size of the apparatus and without impairing the economy. The object is to provide an automatic document feeder. Another object of the present invention is to provide an image reading apparatus and an image forming apparatus provided with such an automatic document feeder.

  In order to achieve the above object, an automatic document conveying apparatus according to the present invention includes a first conveying roller that conveys a document in a conveying path, and a second conveying roller that is disposed downstream in the conveying direction of the first conveying roller. A rotation control means for controlling the rotation of the first transport roller and the second transport roller so that the document bends in a loop between the first transport roller and the second transport roller; and the first transport roller Torque detection means for detecting the torque of the roller during document conveyance; and document determination means for determining that the document is a loose-leaf document based on the magnitude of the torque detected by the torque detection means. It is characterized by.

An image reading apparatus according to the present invention is characterized in that the automatic document feeder is provided.
The image forming apparatus according to the present invention is characterized in that the image reading device is provided.

  In the automatic document feeder of the present invention, the loose-leaf document and the normal document are separated based on the document conveying torque by the first conveying roller when the conveyed document is bent in a loop shape by the first conveying roller and the second conveying roller. Since the determination is made, a special sensor or the like for detecting a loose-leaf document is not required. Therefore, it can suppress that an apparatus enlarges and that economical efficiency is impaired.

Preferably, the document determination unit determines that the document is a loose-leaf document when the torque detected by the torque detection unit is equal to or less than a preset threshold value.
Preferably, the apparatus further includes document thickness detection means for detecting the thickness of the document conveyed to the first conveyance roller, and the document determination means has a thickness of the document detected by the document thickness detection means. Accordingly, the document is discriminated based on the preset threshold value.

Preferably, the torque detection means detects the torque based on a motor current supplied to a motor that drives the first transport roller.
Preferably, the rotation control unit rotates the first conveyance roller in a state where the second conveyance roller is stopped, so that the leading end portion of the document conveyed by the first conveyance roller is moved to the second conveyance roller. It is characterized in that the front end portion of the document is bent in a loop shape against the roller.

Preferably, the torque detecting means detects the torque at a time when a predetermined time has elapsed after the leading edge of the document is abutted against the second transport roller, or the document is detected by the second transport roller. The torque is detected at a predetermined time interval after being abutted against.
Preferably, the rotation control unit rotates the first conveyance roller and the second conveyance roller to convey the document, and the rear end portion of the document passes through the first conveyance roller. The trailing edge of the document is bent in a loop shape by stopping the second conveying roller before.

  Preferably, the torque detecting means detects the torque at a time when a predetermined time has elapsed since the second conveying roller was stopped, or a predetermined time interval after the second conveying roller was stopped. And detecting the torque.

1 is a perspective view showing an MFP as an example of an image forming apparatus including an image reading apparatus provided with an ADF unit according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing a schematic configuration of the MFP viewed from the front side. It is a schematic diagram for demonstrating the original thickness sensor provided in the ADF unit. It is a schematic diagram for demonstrating the structure of the 1st conveyance roller and conveyance part motor which were provided in the ADF unit. FIG. 3 is a block diagram illustrating a configuration of a main part of a control system in the image reading apparatus. 6 is a graph showing a relationship between a document thickness t and a voltage (mV) output from a document thickness sensor. 6 is a graph showing a relationship between a motor current (mA) flowing through a transport motor provided in an ADF unit and a transport torque F (mNm) when a document is transported by a first transport roller. (A) is a schematic diagram for explaining a state in which the normal document is skew-corrected by the first conveyance roller and the second conveyance roller, and (b) is a diagram for explaining a state in which the loose-leaf document is similarly skew-corrected. FIG. 4C is a schematic diagram showing a state in which the rear end portion of the loose-leaf original having a loop formed at the rear end portion is bent between the first conveyance roller and the second conveyance roller. (A) is a graph showing a change in motor current (mA) of the conveyance unit motor when skew correction is performed on a normal document, and (b) is a motor current (mA) of the conveyance unit motor when skew correction is performed on a loose-leaf document. It is a graph which shows the change of. (A) is a table showing an example of the relationship between the document thickness t and the conveyance torque when the document thickness t is within a predetermined range, and (b) shows a threshold N for the document thickness t. A table showing the relationship between the thickness t and the threshold value N when set, (c) is a graph showing the relationship between the document thickness t and the conveyance torque F. It is a flowchart which shows the flow of the process in the discrimination control of the loose-leaf original document performed in ADF-CPU. 12 is a flowchart showing a flow of processing in loose leaf document discrimination control executed by the ADF-CPU of the image reading apparatus according to the second embodiment of the present invention. 10 is a graph showing a change in motor current (mA) when it is determined that a skew-corrected document is a loose-leaf document in the second embodiment. 10 is a flowchart showing a flow of processing in discrimination control of a loose-leaf document executed by an ADF-CPU in the third embodiment of the present invention.

[Embodiment 1]
<Configuration of image forming apparatus>
FIG. 1 is a perspective view showing an example of an image forming apparatus provided with an image reading apparatus according to an embodiment of the present invention. This image forming apparatus is a MFP (Multiple Function Peripheral) having functions such as a copying machine, a scanner, a printer, and a fax machine, and can transmit and receive data to and from a terminal device or the like via a network. . As shown in FIG. 1, the MFP includes an image forming apparatus main body A that forms a toner image on a recording sheet such as a recording sheet, and an image reading apparatus B provided on the image forming apparatus main body A. . The image reading apparatus B includes a scanner unit (scanner apparatus) 10 that reads a document image, and an ADF unit (automatic document feeder) 20 provided on the scanner unit 10.

  The ADF unit 20 constituting the image reading apparatus B is attached to the scanner unit 10 by a hinge mechanism so as to be freely opened and closed, and in a closed state covering the upper surface of the scanner unit 10, a document for reading an image is scanned. Automatically supplied to the unit 10. The scanner unit 10 optically reads an image of a document supplied by the ADF unit 20 or an image of a document manually placed on the platen glass 18 (see FIG. 2) in the scanner unit 10 by an operator. Generate data.

  The image forming apparatus main body A includes a printer unit 61 and a paper feeding unit 62 provided on the lower side of the printer unit 61, and a recording sheet in the paper feeding unit 62 is supplied to the printer unit 61. . The printer unit 61 generates a color toner image on a recording sheet by a known electrophotographic method based on image data generated by the scanner unit 10 or image data sent from a terminal device or the like via a network. Print. The recording sheet on which the toner image is printed by the printer unit 61 is discharged onto a discharge tray 63 of the image forming apparatus main body A provided on the lower side of the scanner unit 10.

<Configuration of ADF unit>
FIG. 2 is a schematic diagram illustrating a schematic configuration of the image reading apparatus B viewed from the front side. As shown in FIG. 2, the ADF unit 20 includes an ADF unit main body 21 that opens the upper surface of the scanner unit 10 by rotating upward from a closed state that covers the entire upper surface of the scanner unit 10, and a scanner. It has a document feed tray 22 attached to the ADF unit main body 21 so that a document transported to the unit 10 is placed thereon.

  The ADF unit 20 is placed on the document feed tray 22 on the left side (hereinafter simply referred to as “left side” and the opposite side as “right side”) facing the front of the ADF unit main body 21. A paper feed main body 21 </ b> A having a conveyance path for the original D inside is provided. A reversing path forming portion 21B having a reversing path 21p formed therein is provided in a lower portion of the paper feeding main body portion 21A so as to extend horizontally from the paper feeding main body portion 21A to the right side.

  The paper feed main body 21A and the reverse path forming portion 21B of the ADF unit main body 21 are integrally configured so as to cover the upper surface of the scanner unit 10 over almost the entire area. The document feed tray 22 is attached to the upper portion of the feed body portion 21A in a state where the right side portion is inclined above the reverse path forming portion 21B. A plurality of documents can be placed on the document feed tray 22 in a stacked state.

  The ADF unit 20 selectively selects a single-sided reading mode in which the scanner unit 10 reads only one side of the original, and a double-sided reading mode in which the scanner unit 10 sequentially reads both sides (front and back) of the original. In the single-sided reading mode, the document is placed on the document feed tray 22 with the document surface read by the scanner unit 10 facing upward.

  As shown in FIG. 1, the document feed tray 22 has a central portion in the direction orthogonal to the transport direction of the document D to be placed in the width direction in the transport path inside the feed body portion 21A (document A pair of positioning guides 22a for positioning the position in the width direction are provided so as to coincide with the center portion in the direction perpendicular to the conveyance direction of D). The pair of positioning guides 22a are linearly formed along both side edges in a direction orthogonal to the conveying direction of the placed document D, and are disposed on both sides in the width direction so as to sandwich the document D. Yes.

  As shown in FIG. 2, the document feed tray 22 in the ADF unit 20 includes three first document length sensors 23a and second document length sensors 23b that detect the length of the loaded document D in the conveyance direction. A third document length sensor 23c is provided. The first document length sensor 23a, the second document length sensor 23b, and the third document length sensor 23c are different in the order from the downstream side in the transport direction along the transport direction of the document D in the document feed tray 22. Each of the documents is arranged corresponding to the size of the document. When the document D is placed on the document feed tray 22, each of the documents D is detected by contacting the upstream edge of the document D in the transport direction. It becomes a state.

  A pickup roller 21 a that supplies the document D on the document feed tray 22 to the first transport path 21 d in the feed body 21 A is disposed on the side of the document feed tray 22 that is close to the feed body 21 A. Is provided. In the paper feed main body 21A, a separation roller 21c that separates the documents D supplied into the paper feed main body 21A one by one by the pickup roller 21a and transports them to the first transport path 21d is a document feed tray 22. It is provided close to. The separation roller 21c has a pair of roller portions that are in pressure contact with each other. The separation roller 21c is rotationally driven by a paper feed unit motor 25a, and a single document D conveyed by the pickup roller 21a passes between both roller units.

As shown in FIG. 3, on the downstream side in the document conveyance direction with respect to the separation roller 21c in the sheet feed main body 21A, the document for detecting the thickness of the document D conveyed on the first conveyance path 21d by the separation roller 21c. A thickness sensor 30 is provided close to the separation roller 21c.
The document thickness sensor 30 is constituted by a reflective optical distance measuring sensor, and is separated based on the reflected light from the document D when light is irradiated toward the document D conveyed from the separation roller 21c. A voltage corresponding to the thickness of one original D conveyed by the roller 21c is output as an electric signal. Note that a method of detecting the amount of light that is applied to the document and transmitted through the document may be used.

  As shown in FIG. 2, a first transport roller 21 i is provided on the left side in the paper feed main body 21 </ b> A, and a document separated and transported by the separation roller 21 c is documented by a document thickness sensor 30. Is detected and then conveyed to the first conveying roller 21i. A first document sensor 26a that detects the document D transported in the first transport path 21d is closer to the first transport roller 21i on the upstream side in the transport direction than the first transport roller 21i in the first transport path 21d. Is provided.

  The first transport roller 21i has a pair of roller portions that are in pressure contact with each other, and is rotationally driven by the transport motor 25b. FIG. 4 is a schematic diagram for explaining the configuration of the first conveyance roller 21i and the conveyance unit motor 25b. As shown in FIG. 4, the rotation of the conveyance unit motor 25 b is transmitted to the lower roller portion of the first conveyance roller 21 i by the transmission belt 29.

  Accordingly, the lower roller portion of the first transport roller 21i rotates by the rotational force of the transport motor 25b, and the upper roller portion rotates following the rotation of the lower roller portion. The document D supplied between both roller portions is conveyed to the second conveyance path 21e by the rotation of both roller portions. As will be described later, the rotational torque of the transport motor 25b is detected based on the motor current of the transport motor 25b when the first transport roller 21i is rotated.

The second transport path 21e is provided in a state of being curved downward in an arc shape on the left side of the paper feed main body 21A, and the document D transported by the first transport roller 21i is second transported. It is conveyed through the path 21e to a second conveyance roller 21j provided on the left side of the first conveyance roller 21i.
The second transport roller 21j also has a pair of roller portions that are in pressure contact with each other, and like the first transport roller 21i described above, the rotational force of the registration unit motor 25d is transmitted via the transmission belt. Are driven to rotate.

  The first transport roller 21i and the second transport roller 21j are used as skew correction rollers for the document D so that the transported document D is not inclined with respect to the transport direction. When skew correction is performed on the document D, the leading edge of the document D transported by the first transport roller 21i is abutted against both roller portions of the second transport roller 21j in a state where the rotation of the second transport roller 21j is stopped. . As a result, the document D is bent in a loop between the first transport roller 21i and the second transport roller 21j, and the leading edge of the document D is along the axial direction of the second transport roller 21j. That is, skew correction is performed so that the document D is not inclined with respect to the transport direction.

A first reading roller 21f is provided at a position near the lower scanner unit 10 in the ADF unit 20, and the document D that has passed through the second conveying roller 21j is conveyed to the first reading roller 21f. The first reading roller 21f also has a pair of roller portions that are in pressure contact with each other, and is rotationally driven by the reading unit motor 25c.
The document D transported from the second transport roller 21j to the first reading roller 21f is detected by the second document sensor 26b.

  The document that has passed through the first reading roller 21f passes above the slit glass (platen glass) 16 provided on the upper surface of the scanner unit 10, and an image on the document surface facing the slit glass 16 is passed during the passage. It is read by the scanner unit 10. The document on which the image has been read is conveyed to the first branch guide 21h via the second reading roller 21g having a pair of roller portions pressed against each other. The second reading roller 21g is rotationally driven by a reading unit motor 25c that rotationally drives the first reading roller 21f.

In the single-sided reading mode, the first branch guide 21h transports the document to the second branch guide 21m via a registration roller 21k having a pair of roller portions pressed against each other. 21m is discharged onto a document discharge portion provided on the reverse path forming portion 21B via a discharge roller 21q having a pair of roller portions pressed against each other.
The registration roller 21k is rotationally driven by a registration unit motor 25d that rotationally drives the second transport roller 21j. The paper discharge roller 21q is rotationally driven by a paper discharge motor 25e.

Above the second branch guide 21m, a third document sensor 26c for detecting the document D conveyed on the second branch guide 21m is provided.
In the double-sided reading mode, the first branch guide 21h conveys the document D to the second branch guide 21m via the registration roller 21k, and is placed on the lower surface of the document feed tray 22 by the second branch guide 21m. It conveys on the reversing guide arranged along. The registration roller 21k is reversely driven at a predetermined timing immediately before the trailing edge of the document passes, whereby the document is switched back and conveyed to the first conveyance roller 21i through the third conveyance path 21n. .

In the third transport path 21n, a fourth document sensor 26d that detects the document D transported in the third transport path 21n is provided.
The document D transported to the first transport roller 21i through the third transport path 21n passes again through the second transport path 21e with the front and back sides reversed, and the first reading roller 21f causes the slit glass 16 to move. It is conveyed upward.

  While the document D passes over the slit glass 16, an image on the document surface (second surface) facing the slit glass 16 is read by the scanner unit 10. The document D that has passed over the slit glass 16 is conveyed by the first branch guide 21h to the reverse roller 21z through the fourth conveyance path 21s. The document D transported to the reversing roller 21z is once transported to the reversing path 21p in the reversing path forming unit 21B, and then guided to the second branch guide 21m and turned upside down to the paper discharging roller 21q. And is discharged by the paper discharge roller 21q to the original discharge portion on the reverse path forming portion 21B.

<Configuration of scanner unit>
As shown in FIG. 2, the scanner unit 10 includes a housing 11 formed in a flat rectangular shape, and a first reading roller 21 f and a second reading roller of the ADF unit 20 are provided on the upper surface of the housing 11. A rectangular slit glass 16 is disposed along the roller axis direction so as to face the gap between the roller 21g and the roller axis direction. A rectangular platen glass 18 disposed on the right side of the slit glass 16 is provided on the upper surface of the housing 11. The platen glass 18 has a length approximately the same as the longitudinal direction (main scanning direction) length of the slit glass 16, and the horizontal direction (sub-scanning direction) extending from a position close to the slit glass 16 to the vicinity of the right end of the housing 11. ) Has a length.

  A first slider 12 configured to be slidable in the sub-scanning direction indicated by an arrow X in FIG. 2 is provided inside the housing 11, and the first slider 12 has a linear shape extending along the main scanning direction. A light source 12a is mounted. The first slider 12 is normally located at a home position between the slit glass 16 and the platen glass 18, and when the document is conveyed by the ADF unit 20, the scanner motor 43 causes the slit glass 16 to move. It is moved to the lower seat through position and stopped.

On the other hand, when reading the document D on the platen glass 18, the first slider 12 is reciprocated in the sub-scanning direction along the platen glass 18 by the scanner motor 43.
The first slider 12 reflects the reflected light from the document D passing on the slit glass 16 or the document D placed on the platen glass 18 at a substantially right angle in the direction opposite to the direction indicated by the arrow X. One mirror 12b is provided. A second slider 13 is provided on the left side of the first slider 12. The second slider 13 is mounted with a second mirror 13a and a third mirror 13b that are paired so as to invert the light reflected by the first mirror 12b in the direction of the arrow X.

  When reading the image of the document D placed on the platen glass 18, the second slider 13 is synchronized with the movement of the first slider 12 by the scanner motor 43 and 1 / speed of the first slider 12. It is moved in the same direction as the first slider 12 at a speed of 2. The light inverted in the direction of the arrow X by the second mirror 13a and the third mirror 13b is irradiated to the CCD 17 serving as an image reading means via a reduction lens (not shown).

<Configuration of control system in image reading apparatus>
FIG. 5 is a block diagram illustrating a configuration of a main part of a control system in the image reading apparatus B. The scanner unit 10 of the image reading apparatus B is provided with a scanner CPU 41 that controls the scanner motor 43 and the like, and the ADF unit 20 is provided with an ADF-CPU 51 that controls the conveyance of the document and the like. The scanner CPU 41 and the ADF-CPU 51 are configured so that data can be transmitted and received between them.

The ADF-CPU 51 is supplied with the output of the document thickness sensor 30 disposed in the vicinity of the separation roller 21c.
FIG. 6 is a graph showing the relationship between the thickness t (μm) of the document D and the voltage (mV) output from the document thickness sensor 30. The thickness t (μm) of the document D and the voltage (mV) output from the document thickness sensor 30 are approximately proportional to each other. The thickness of the document D increases as the thickness t (μm) of the document D increases. The voltage (mV) output from the sensor 30 increases. From such a relationship, the ADF-CPU 51 detects the thickness of the document D being conveyed based on the voltage (mV) output from the document thickness sensor 30.

  As shown in FIG. 5, the ADF-CPU 51 controls a motor drive IC 52 b for driving the transport unit motor 25 b provided in the ADF unit main body 21. The ADF-CPU 51 is provided with a conveyance torque conversion unit 51b for detecting the conveyance torque of the first conveyance roller 21i rotated by the conveyance unit motor 25b. The conveyance torque conversion unit 51b detects the conveyance torque of the first conveyance roller 21i based on the motor current supplied to the conveyance unit motor 25b via the motor drive IC 52b.

  When the document D is supplied between both roller portions in a state where both roller portions of the first transport roller 21i are rotated, the transport load on each roller portion increases and the rotation of the transport motor 25b decreases. In such a state, the motor current supplied to the transport motor 25b increases. As a result, the rotation of the transport motor 25b increases, and the transport torque of the first transport roller 21i increases.

  In addition, the leading edge of the document D is abutted between the roller portions of the second transport roller 21j, and the transport of the rear end portion of the document by the first transport roller 21i is continued in this state. Since the transport load of the first transport roller 21i increases sequentially, the rotation of the first transport roller 21i decreases. Also in this case, the motor current supplied to the transport motor 25b increases.

  FIG. 7 is a graph showing the relationship between the motor current (mA) supplied to the transport unit motor 25b and the transport torque F (mNm) of the first transport roller 21i. The conveyance torque F (mNm) of the first conveyance roller 21i and the motor current (mA) are in a substantially proportional relationship, and the motor current (mA) supplied to the conveyance unit motor 25b that drives the first conveyance roller 21i. When it increases, the conveyance torque F (mNm) of the first conveyance roller 21i also increases. Therefore, the transport torque F (mNm) of the first transport roller 21i can be detected based on the motor current (mA).

The conveyance torque conversion unit 51b of the ADF-CPU 51 calculates the conveyance torque F (mNm) of the first conveyance roller 21i based on the motor current (mA) supplied to the conveyance unit motor 25b.
As shown in FIG. 5, the ADF-CPU 51 drives each of the sheet feeding unit motor 25a, the reading unit motor 25c, the registration unit motor 25d, and the discharging unit motor 25e in the same manner as the conveyance unit motor 25b. The motor drive ICs 52a, 52c, 52d, and 52e are controlled.

  The ADF-CPU 51 is supplied with outputs of a first document length sensor 23a, a second document length sensor 23b, and a third document length sensor 23c provided on the document feed tray 22 in the ADF unit 20, respectively. ing. The ADF-CPU 51 determines the length of the document D placed on the document feed tray 22 based on the outputs of the first document length sensor 23a, the second document length sensor 23b, and the third document length sensor 23c. Is detected.

  The ADF-CPU 51 transmits the outputs of the first to third document length sensors 23a to 23c provided on the document feed tray to a system CPU (not shown) that controls the image forming apparatus main body A. . The system CPU selects a recording sheet corresponding to the detected length of the document D from the paper feeding unit 61 of the image forming apparatus main body A and conveys it to the printer unit 62.

  Further, the outputs of the first document sensor 26a, the second document sensor 26b, the third document sensor 26c, and the fourth document sensor 26d provided in the conveyance path of the ADF unit main body 21 are respectively provided. The ADF-CPU 51 controls the motor drive ICs 52a, 52c, 52d, and 52e based on the outputs of the first document sensor 26a, the second document sensor 26b, the third document sensor 26c, and the fourth document sensor 26d, respectively. , The rotation of the sheet feeding unit motor 25a, the conveyance unit motor 25b, the reading unit motor 25c, the registration unit motor 25d, and the discharging unit motor 25e are controlled.

The scanner CPU 41 drives the scanner motor 43 so that the first slider 12 and the second slider 13 move at a predetermined speed in a predetermined direction by controlling the motor drive IC 42 at the time of image reading. Further, the scanner CPU 41 controls an image processing unit 44 that processes image data read by the CCD 17.
The image processing unit 44 performs shading correction, sharpness adjustment, HVC adjustment, density correction, and the like on the image data obtained by the CCD 17 and prevents an image of a portion where a spell hole is formed in a loose-leaf original. Image processing is performed.

  When the ADF-CPU 51 performs control to bend the document D in a loop between the first transport roller 21i and the second transport roller 21j, the thickness t of the document D detected by the document thickness sensor 30 is detected. And the original D using a loose-leaf paper (hereinafter referred to as a loose-leaf original), and an original using a normal paper without a loose-leaf hole based on the transfer torque F of the first transfer roller 21i. And normal document) are determined.

  When executing the control of bending the document D in a loop shape, the rotation of the second transport roller 21j is stopped while the first transport roller 21i is rotationally driven. In this state, when the document D is transported to the first transport roller 21i, the leading edge of the document D that has passed through the first transport roller 21i is abutted against the second transport roller 21j. In this case, by further continuing the conveyance of the document D by the first conveyance roller 21i, the leading edge of the document D is abutted along the axial direction of the second conveyance roller 21j as a whole, and FIG. As shown to a), the front-end | tip part will be in the state bent in the loop shape. As a result, the document D is skew-corrected.

  FIG. 9A is a graph showing a change in motor current (mA) supplied to the transport motor 25b that rotationally drives the first transport roller 21i when skew correction is performed on a normal document. The transport unit motor 25b is in a peak state due to an inrush current when rotation driving is started. After that, since the normal document is not conveyed to the first conveyance roller 21i, a load (conveyance torque) for conveying the normal document is not applied, and the rotation speed is set to a predetermined rotational speed.

  In this case, when the normal document is transported to the first transport roller 21i, the transport load of the first transport roller 21i increases, so the rotation of the transport motor 25b decreases and is supplied to the transport motor 25b. The motor current also decreases (for example, time t1 in FIG. 9A). In such a state, the motor current supplied to the transport motor 25b increases. As a result, the conveyance torque of the first conveyance roller 21i increases, and the leading end portion of the normal document is conveyed to the second conveyance roller 21j.

  Thereafter, when the leading edge of the normal document in the conveyance direction is abutted against the second conveyance roller 21j (time t2 in FIG. 9A), the conveyance load of the first conveyance roller 21i that conveys the normal document increases sequentially. And the rotational speed decreases. Accordingly, the motor current supplied to the transport unit motor 25b is sequentially increased, and the transport torque of the first transport roller 21i is increased. Then, when the conveyance by the first conveyance roller 21i is continued in a state where the leading edge of the normal document is abutted against the second conveyance roller 21j, the normal document is bent in a loop shape, and the bending amount is also sequentially increased. To increase.

In such a state, the original document is corrected for skew and is in a state along the conveyance direction. In this case, since the normal document in which the loose leaf hole is not formed has a uniform bending strength throughout, it bends substantially evenly between the second conveyance roller 21j and the first conveyance roller 21i. There is no risk of bending.
If the state in which the leading edge of the normal document in the conveying direction is abutted against the second conveying roller 21j continues for a predetermined time (time t3 in FIG. 9A), the second conveying roller 21j is rotationally driven. As a result, since the leading edge of the normal document is conveyed, the conveyance load of the first conveyance roller 21i is sequentially reduced, and the rotation speed of the first conveyance roller 21i is increased. Accordingly, the motor current supplied to the transport unit motor 25b decreases sequentially, and the transport torque of the first transport roller 21i decreases.

In FIG. 9A, the time from the start of the transport unit motor 25b to the start of the rotation of the second transport roller 21j is indicated by T1 (ms). When the time T1 (ms) has elapsed, the amount of deflection of the normal document is maximized, so that the conveyance torque in the conveyance unit motor 25b is also maximized, and thus the motor current is also maximized.
On the other hand, a case will be described in which a loose-leaf document is transported with a loose-leaf hole positioned along the side edge on the leading end side in the transport direction. Since the loose-leaf original is lighter than the normal original having the same thickness as the loose-leaf hole is formed, the load on the loose-leaf original by the first conveying roller 21i is the same as when the normal original is being conveyed. And the rotational speed of the first transport roller 21i increases. Accordingly, as shown in FIG. 9B, the motor current supplied to the transport motor 25b is lower than that during normal document transport (indicated by a broken line in FIG. 9B).

  Further, since the bending strength (waist strength) of the side edge portion in which the loose leaf hole is formed is lower than that in the case where the loose leaf hole is not formed, the amount of deflection of the leading end portion of the loose leaf document is small. When it becomes larger, as shown in FIG. 8B, the loose-leaf document is bent at the portion where the loose-leaf hole is formed. Such a bent state of a loose-leaf original is normally caused by a loose-leaf original being conveyed over a length of about 6 mm from a linear state along the conveyance direction and bent into a loop shape regardless of the thickness of the loose-leaf original. appear. Even if the loose-leaf original is bent as described above, there is no risk of buckling during subsequent conveyance (note that the bent state of the loose-leaf original is exaggerated in FIG. 8B).

In such a bent state, as shown in FIG. 9 (b), the rotational load of the first transport roller 21i rapidly decreases, and the rotational speed of the first transport roller 21i increases rapidly. As a result, the motor current supplied to the transport unit motor 25b rapidly decreases.
As described above, since the normal document and the loose-leaf document having the same thickness have different document transport loads by the first transport roller 21i when bent in a loop shape, the transport unit that rotationally drives the first transport roller 21i. The magnitude of the motor current supplied to the motor 25b is also different. Also, the transport load of the first transport roller 21i is different and the motor current of the transport section motor 25b is different depending on the thickness of the document D being transported.

From this, it is a normal document based on the variation of the conveyance torque due to the variation of the conveyance load of the first conveyance roller 21i corresponding to the thickness of the document D being conveyed, that is, the variation of the motor current of the conveyance unit motor 25b. Or a loose-leaf original.
Note that the motor current of the transport unit motor 25b when transporting the document D increases sequentially while the document D is transported only by the first transport roller 21i, and immediately before the second transport roller 21j is rotationally driven ( It becomes the maximum immediately before the predetermined time (T1) elapses from the start of activation of the transport unit motor 25b. Therefore, since the difference between the motor current during normal document conveyance and the motor current during loose-leaf document conveyance is maximized at that time, discrimination between the normal document and the loose-leaf document is performed based on the motor current at that time. Preferably it is done.

  Further, when the rear end portion of the document D is transported by the first transport roller 21i, the transport of the front end side portion of the document D by the second transport roller 21j is also stopped, so that the document D is moved to the second transport roller. It will be in the state bent between 21j and the 1st conveyance roller 21i. In this case, in the case of a normal document, the document is bent almost uniformly between the second conveyance roller 21j and the first conveyance roller 21i (see FIG. 8A). When the loose leaf hole is formed along the edge, as shown in FIG. 8C, the loose leaf hole is bent at the portion.

In such a bent state, as in the case where a loose leaf hole is formed at the front end portion in the conveyance direction, a loose leaf original is usually about 6 mm longer than the interval between the first conveyance roller 21i and the second conveyance roller 21j. It is generated by being conveyed and bent in a loop shape.
Accordingly, a loop can be formed at the trailing edge of the document, and it can be determined that the document is a loose-leaf document based on the motor current supplied to the conveyance unit motor 25b.

  The discrimination between the normal document and the loose-leaf document is performed by, for example, setting a threshold N of the transport torque F (mN · m) of the first transport roller 21i in advance based on the thickness t of the transported document D, and performing skew correction. Is detected, the conveyance torque F (mN · m) of the first conveyance roller 21i at a preset time is detected, and the detected conveyance torque F (mN · m) of the first conveyance roller 21i is set. This is done by comparing the threshold value N.

FIG. 10A is a table showing an example of the threshold value N of the conveyance torque F (mN · m) of the first conveyance roller 21 i set based on the thickness t of the document D. In this table, the thickness t of the document D is 210 g / m ^{2 in} basis weight (223 μm in terms of μm, hereinafter this thickness 223 μm is referred to as “μ1”. In the following, the thickness indicated by the basis weight is also shown. When t is converted to μm and each value is less than “μ2”, “μ3”, and “μ4”) and is 128 g / m ² (= 148 μm = μ2) or more (210> t ≧ 128, that is, if μ1> t ≧ μ2) and the conveyance torque F (mNm) is larger than 105 mNm (assuming threshold = N1) (F> N1), it is determined as a normal document, and if it is equal to or less than threshold N1 ( N1 ≧ F), and it is determined as a loose-leaf original.

Further, when the thickness t of the document D is less than 128 g / m ² (= μ2) in basis weight and is 105 g / m ² (= 115 μm = μ3) or more (128> t ≧ 105, that is, μ2> If the conveyance torque F (mNm) is greater than 88 mNm (assumed to be the threshold value N2) at t ≧ μ3) (F> N2), it is determined as a normal document, and if it is less than the threshold value N2 (N2 ≧ F), the loose leaf Judged as a manuscript.

Further, when the thickness t of the document D is less than 105 g / m ² (= μ3) in basis weight and equal to or greater than 80 g / m ² (= 91 μm = μ4) (105> t ≧ 80, that is, μ3> If t ≧ μ4) and the conveyance torque F (mNm) is larger than 80 mNm (assumed to be the threshold value N3) (F> N3), it is determined as a normal document, and if it is equal to or less than the threshold value N3 (N3 ≧ F), loose leaf Judged as a manuscript. When the thickness t of the document D is less than 80 g / m ² (= μ4) in basis weight, if the conveyance torque F (mNm) is larger than 74 mNm (assumed to be the threshold value N4) (F> N4), If it is determined as a normal document and if it is equal to or less than the threshold value N4 (N4 ≧ F), it is determined as a loose leaf document.

FIG. 10B is a table showing the relationship between the thickness t (μm) of the document D and the threshold value N (mNm).
FIG. 10C is a graph showing the relationship between the thickness t (μm) of the document D and the threshold value N of the conveyance torque F (mNm). A broken line in FIG. 10C indicates that the thickness t and the conveyance torque F are in a proportional relationship, and a solid line indicates the four threshold values N set in FIG. As described above, by setting the four threshold values, it is possible to simplify the document discrimination control process. However, in order to improve the accuracy, it changes linearly according to the broken line in FIG. A threshold value that changes linearly with respect to the paper thickness to be set may be set.

FIG. 11 is a flowchart showing a flow of processing for discriminating between a loose-leaf original and a normal original executed by the ADF-CPU 51. In the following, the discrimination control process between the loose-leaf original and the normal original will be described based on this flowchart.
The discrimination control is started when the conveyance of the document D on the document feed tray 22 is started. Accordingly, at this time, the transport unit motor 25b is rotationally driven together with the paper feed unit motor 25a, the reading unit motor 25c, the registration unit motor 25d, and the paper discharge unit motor 25e.

  When the discrimination control is started, the document thickness sensor 30 is on standby until the conveyance of the document D is detected (see step S11 in FIG. 11), and the document D passes through the separation roller 21c and the document thickness. When the detection area of the sensor 30 is reached, the document conveyed by the document thickness sensor 30 is detected, and the output voltage changes (“Yes” in step S11). Thereby, the ADF-CPU 51 obtains the thickness of one document D conveyed from the separation roller 21c based on the electric signal output from the document thickness sensor 30 (step S12).

  Thereafter, it is determined whether skew correction needs to be performed on the conveyed document D (step S13). For example, when the user instructs that the skew correction need not be performed in order to immediately terminate the document image reading process by operating a selection switch provided on the operation panel of the image forming apparatus main body A, the skew is corrected. It is determined that the execution of correction is unnecessary. If it is not necessary to perform skew correction (“No” in step S13), the document discrimination control is terminated.

If skew correction is necessary (“Yes” in step S13), the rotation of the second conveyance roller 21j is stopped by stopping the rotation of the registration unit motor 25d that rotates the second conveyance roller 21j. (Step S14).
Thereafter, the process waits until the document D is detected by the first document sensor 26a (step S15). When the leading edge of the document D is detected by the first document sensor 26a (“Yes” in step S15), the count value of the timer count is set to a predetermined time TA and the count by the timer count (time measurement) is started. (Step S16). The predetermined time TA in this case is set in advance to be slightly shorter than the time until the second transport roller 21j is rotated after the leading edge of the transported document is detected by the first document sensor 26a. Yes.

  For example, the transport speed of the document D is 200 mm / s, the distance on the transport path from the first document sensor 26a to the first transport roller 21i is 100 mm, and the distance from the first transport roller 21i to the second transport roller 21j is 50 mm. If the loose-leaf original is bent over the length of 6 mm as described above to be bent at the loose-leaf hole, as described above, the time required for the original to be conveyed over 156 mm is set to 780 ms. .

When counting by the timer count is started, a standby state is entered until a predetermined time TA is reached (step S17).
In this case, the rotation of the first conveyance roller 21i is continued by continuing the rotation drive of the conveyance unit motor 25b. Accordingly, the conveyance of the document D is continued, and the leading edge of the document D is abutted against the second conveyance roller 21j. The document D starts to form a loop by being abutted against the second transport roller 21j. Then, when the count value of the timer count reaches the predetermined time TA (“Yes” in step S17), the transport torque conversion unit 51b of the ADF-CPU 51 counts based on the motor current (mA) supplied to the transport unit motor 25b. The conveyance torque F (mNm) of the one conveyance roller 21i is obtained (step S18). In this case, the threshold value N of the conveyance torque F (mNm) of the first conveyance roller 21i is determined based on the document thickness t obtained in step S12 (step S19), and the determined threshold value N and step S18 are determined. By comparing the transport torque F (mNm) of the first transport roller 21i obtained in step 1, it is determined whether the transported document is a normal document or a loose-leaf document (step S20).

  In step S20, if the conveyance torque F (mNm) is equal to or less than the threshold N as a result of the comparison between the conveyance torque F (mNm) and the threshold N (“Yes” in step S20), the conveyed original is regarded as a loose-leaf original. It determines and memorize | stores in the memory | storage part provided in ADF-CPU51 (step S21). When the conveyance torque F (mNm) is larger than the threshold value N (“No” in step S20), the conveyed document is determined as a normal document and stored in the internal storage unit (step S22). Thereafter, by rotating the registration unit motor 25c, the second transport roller 21j is rotated (step S23), and the process returns to the main routine. As a result, the document D bent in a loop shape is conveyed from the leading edge of the document D to the first reading roller 21f.

Thereafter, when the next document D is conveyed, the processing from S11 onward is similarly executed to determine whether the document is a normal document or a loose-leaf document.
When the transported document is determined to be a loose-leaf document, the ADF-CPU 51 detects when the leading edge of the determined document is detected by each of the first document sensor 26a to the fourth document sensor 26d. The output signals from the first document sensor 26a to the fourth document sensor 26d are invalidated for a predetermined time (the time required for the loose leaf hole forming region to pass through the detection position) from the point in time.

  As a result, even if the output of each of the first document sensor 26a to the fourth document sensor 26d is temporarily changed to a document non-detection state due to the loose leaf hole of the conveyed loose leaf document, the trailing edge of the conveyed document is detected. There is no risk of misjudging it as having been done. Accordingly, when each of the first document sensor 26a to the fourth document sensor 26d subsequently changes to a document non-detection state, it can be immediately determined that the trailing edge of the conveyed document has been detected.

  When the ADF-CPU 51 determines that the conveyed document is a normal document, the leading edge and the trailing edge of the determined document are detected by each of the first document sensor 26a to the fourth document sensor 26d. In such a case, control such as switching of the conveyance path and continuous conveyance of subsequent documents is immediately executed without waiting until a predetermined time elapses. Therefore, it is possible to prevent the timing of each control from being delayed.

Further, the ADF-CPU 51 outputs the stored document information to the scan-CPU 41.
The scan-CPU 41 confirms whether the original is a loose-leaf original or a normal original based on the original information from the ADF-CPU 51. At this time, when the document D is a loose-leaf document, the image data at the position of the loose-leaf hole (preset) is corrected to data without a loose-leaf hole when the image data of the document D is printed out. Thus, the loose leaf hole is prevented from being printed out as image data. Thereby, there is no possibility that a shadow of a loose leaf hole or the like is formed on the printed image, and a high-quality image can be obtained.

  As described above, in the present embodiment, a document is a normal document based on the thickness of the document to be conveyed and the motor current of the conveyance unit motor 25b that drives the first conveyance roller 21i that forms a loop in skew correction. Since it is determined whether the original is a loose-leaf original, it is not necessary to arrange a special sensor or the like for detecting a loose-leaf hole in the conveyance path. Therefore, there is no possibility that the ADF unit 20 is increased in size, and there is no possibility that the economy is impaired because the number of parts is small.

[Embodiment 2]
In the above embodiment, the ADF-CPU 51 is configured to obtain the conveyance torque of the first conveyance roller 21i when a predetermined time TA has elapsed after the document D to be conveyed is detected by the first document sensor 26a. However, in the present embodiment, the transport torque of the first transport roller 21i is sampled (detected) at a predetermined time interval after the transported document D is abutted against the second transport roller 21j, and the document D is a loose-leaf document. Or normal document. As described above, in the present embodiment, only the document discrimination control by the ADF-CPU 51 is different from the above embodiment.

  Hereinafter, the discrimination control of this embodiment executed by the ADF-CPU 51 will be described based on the flowchart of FIG. In the flowchart of FIG. 12, the processing from step S31 in which the document thickness sensor 30 detects the conveyance of the document D to step S35 in which the document D is detected by the first document sensor 26a is performed in steps S11 to S11 in the flowchart of FIG. Since it is the same as each step of S15, the description is abbreviate | omitted.

When the conveyance of the document D is detected by the first document sensor 26a (“Yes” in step S35), the count value of the timer count is set to a predetermined time TB, and the count by the timer count (time measurement) is started. (Step S36).
The predetermined time TB is set in advance to a time from when the leading edge of the document conveyed by the first document sensor 26a is detected until the leading edge reaches the first conveying roller 21i. For example, as in the above-described embodiment, when the conveyance speed of the document D is 200 mm / s and the distance from the first document sensor 26a to the first conveyance roller 21i is 100 mm, TB = 500 ms is set.

  After that, the system waits until the count value by the timer count reaches the set predetermined time TB (= 500 ms) (step S37). When the count value by the timer count reaches the set predetermined time TB (in step S37, “ Yes "), the count value of the timer count is set to a new set time TC, and counting by the timer count is started (step S38).

  The set time TC in this case is such that the leading edge of the document D that has passed through the first conveying roller 21i is abutted against the second conveying roller 21j, so that the conveying torque of the first conveying roller 21i is maximum (therefore, the first conveying roller 21i It is set in advance at a time immediately before the motor current supplied to the roller 21i becomes maximum. For example, when the distance from the first conveyance roller 21i to the second conveyance roller 21j is 150 mm, and the loose-leaf original is conveyed over a length of 6 mm while being abutted against the second conveyance roller 21j, it is bent. Assuming that, the time is set to be slightly shorter (for example, 760 ms) than 780 ms, which is the time during which the document is conveyed over 156 mm.

Next, the conveyance torque conversion unit 51b of the ADF-CPU 51 samples the motor current (mA) supplied to the conveyance unit motor 25b at predetermined time intervals (for example, 5 ms) (see FIG. 13), and the ADF-CPU 51 Based on the calculated motor current (mA), the transport torque F (mNm) of the first transport roller 21i is calculated (step S39).
Based on the calculated conveyance torque F (mNm) of the first conveyance roller 21i and the document thickness t calculated in step S32, whether the document to be conveyed is a normal document or a loose-leaf document. Is determined (step S40).

  The determination method in this case is to determine a threshold N of the conveyance torque F (mNm) of the first conveyance roller 21i based on the measured thickness t of the document, and for each sampling with respect to the determined threshold N. It is determined whether the determined transport torque F (mNm) of the first transport roller 21i is greater than the threshold value N. If the conveyance torque F (mNm) is larger than the threshold value N (“Yes” in step S41), the conveyed document D is determined as a normal document, and the conveyed document is set as a normal document. It memorize | stores in a memory | storage part (step S42).

  If the determination result in step S41 is not greater than the threshold value N (“No” in step S41), it is confirmed whether the count value of the timer count is a predetermined time TC (step S43), and the predetermined time If it is not TC (“No” in step S43), the process waits until a predetermined time interval ΔT (for example, 5 ms) elapses (step S44), and the predetermined time interval ΔT elapses. Then ("Yes" in step S44), the process returns to step S40, the transport torque F (mNm) is obtained based on the motor current supplied to the transport motor 25b, and the transport torque F (mNm) is less than the threshold value N. It is determined whether it is larger.

In this way, when the conveyance torque F (mNm) continues to be equal to or less than the threshold value N, the conveyed document D is not determined to be a normal document, and the timer count reaches a preset predetermined time TC. (“Yes” in step S43), the conveyed document is determined to be a loose-leaf document and stored in the storage unit (step S45).
In either case where it is determined that the original document is determined in step S42 or in the case where it is determined that the document is a loose-leaf document in step S45, the second conveying roller 21j is rotated by the registration unit motor 25c thereafter (step S46). . As a result, the document D which has been bent in a loop shape and whose skew has been corrected is conveyed to the first reading roller 21f.

  In the present embodiment, as described above, when the predetermined time TB elapses after the document D passes the first transport roller 21i, the transport torque F (mNm) of the first transport roller 21i measured at a predetermined time interval. Each is compared with a threshold value N set based on the thickness t of the document D to be conveyed, and when the conveying torque F (mNm) becomes larger than the threshold value N before the predetermined time TC elapses. Is determined to be a normal document, and if the transport torque F (mNm) does not become larger than the threshold value N even after the predetermined time TC has elapsed, the transported document is determined to be a loose-leaf document.

  Since the loose-leaf document has a large number of loose-leaf holes, the loose-leaf document is lighter in weight than a normal document in which no loose-leaf holes are formed, and the conveyance torque of the first conveyance roller 21i is smaller than that of a normal document. For this reason, as shown in FIG. 13, the motor current of the transport unit motor 25b is also smaller than the motor current during normal document transport. Therefore, in the case of a normal document having a large motor current, the set threshold value N is exceeded in a relatively short time, so that it is possible to shorten the time until the normal document is determined.

[Embodiment 3]
In the present embodiment, it is configured to detect whether a loose leaf hole is formed along the side edge at the rear end in the transport direction of the document D, and only the control executed by the ADF-CPU 51 is described above. It is different from each embodiment.
Hereinafter, the document discrimination control of the present embodiment executed by the ADF-CPU 51 will be described based on the flowchart of FIG.

The ADF-CPU 51 first determines the size of the document placed on the document feed tray 20 based on the detection results of the first document length sensor 23a, the second document length sensor 23b, and the third document length sensor 23c. (See step S51 in FIG. 14).
Next, the apparatus waits until the original thickness sensor 30 detects the original D (step S52). When the original thickness sensor 30 detects the conveyance of the original D ("Yes" in step S52), the original thickness sensor 30 is detected. On the basis of the electric signal output from, the thickness of one document D conveyed from the separation roller 21c is calculated (step S53).

Thereafter, as in the above embodiments, it is determined whether skew correction is necessary (step S54). If it is not necessary to perform skew correction (“No” in step S54), the document type discrimination control is terminated.
If skew correction is necessary (“Yes” in step S54), the process waits until the document D is detected by the first document sensor 26a (step S55). When the conveyance of the document D is detected by the first document sensor 26a (“Yes” in step S55), the ADF-CPU 51 determines that the trailing edge of the document D is based on the document size acquired in step S51. A time TD until a predetermined distance from the first conveying roller 21i is reached is obtained (step S56).

This time TD is set in advance to a time that is considered necessary until the bent end is bent into a loop when a loose leaf hole is formed at the rear end of the document D.
For example, the transport speed of the document D is 200 mm / s, the distance from the first document sensor 26a to the first transport roller 21i is 100 mm, and the loose-leaf document is 6 mm with the leading end portion stopped as described above. If the loose leaf hole portion is bent by being conveyed and bent over the length of the original document D, the time until the trailing edge of the document D reaches the front by a distance of 6 mm from the first conveying roller 21i, that is, The trailing edge of the document D is set to 470 ms required for being conveyed from the first document sensor 26a over 94 mm.

When the time TD is obtained, the time TD is set as the count value of the timer count, and counting (timekeeping) by the timer count is started (step S57).
Next, the system waits until the time TD when the count value by the timer count is set (step S58). In this case, the front end portion of the document D is skew-corrected after passing through the first transport roller 21i, and then the front end side portion passes through the second transport roller 21j, and the first transport roller 21i and the second transport roller 21j. It will be in the conveyance state by.

  Thereafter, when the time TD is counted by the timer count (“Yes” in step S58), the trailing edge of the document D reaches a position a predetermined distance (for example, 6 mm) from the first transport roller 21i. Thus, the rotation of the registration unit motor 25d that rotates the second transport roller 21j is stopped, and the rotation of the second transport roller 21j is stopped (step S59).

  As a result, the conveyance of the document D by the second conveyance roller 21j is stopped, and the ADF-CPU 51 resets the timer count and newly sets a predetermined time TE (step S60). This time TE is slightly shorter than the time required for the trailing edge of the document to pass through the first transport roller 21i after the second transport roller 21j is stopped. Accordingly, a time of about 27 ms, which is slightly shorter than 30 sm, which is a time required for the trailing edge of the document D having a length of 6 mm to pass through the first conveying roller 21i, is set.

In this case, the conveyance of the trailing end portion of the document D is continued by the first conveyance roller 21i by continuing the rotation drive of the conveyance unit motor 25b. Since the front end portion of the document D is stopped by the second transport roller 21j, the portion of the document D that has passed through the first transport roller 21i is bent in a loop shape.
Thereafter, when the count value of the timer count reaches a predetermined time TE (“Yes” in step S61), the transport torque conversion unit 51b of the ADF-CPU 51 counts based on the motor current (mA) supplied to the transport unit motor 25b. The conveyance torque F (mNm) of one conveyance roller 21i is obtained (step S62). Then, based on the obtained conveyance torque F (mNm) of the first conveyance roller 21i and the thickness t of the original obtained in step S53, the threshold N of the conveyance torque F (mNm) of the first conveyance roller 21i. (Step S63), and the determined threshold value N is compared with the transport torque F (mNm) of the first transport roller 21i obtained in step S62, so that the transported document is a normal document and a loose leaf. It is determined which of the originals (step S64).

The determination method in this case is the same as that in the first embodiment. When the determined transport torque F (mNm) of the first transport roller 21i is equal to or less than the threshold N with respect to the determined threshold N ( In step S64, “Yes”), the conveyed document D is determined to be a loose-leaf document, and the conveyed document is stored in the storage unit as a loose-leaf document (step S65).
In this case, the conveyance torque F (mNm) may be abruptly lowered due to the bent state in the loose leaf hole at the rear end portion of the loose leaf document. Therefore, it is determined as a loose-leaf original.

  If the conveyance torque F (mNm) is larger than the threshold value N (“No” in step S64), the conveyed document is determined as a normal document and stored in the internal storage unit (step S66). Next, the second conveyance roller 21j is rotated by rotating the registration unit motor 25c (step S67), and the process returns to the main routine. As a result, the rear end portion of the document D that is bent in a loop shape is eliminated from the loop shape and is sequentially conveyed to the first reading roller 21f.

Thereafter, when the next original D is conveyed, it is determined whether it is a normal original or a loose-leaf original by the processing after step S51.
The document discrimination control according to the present embodiment is normally executed after the document discrimination process according to the first or second embodiment is performed and the document is determined to be a normal document. This makes it possible to reliably determine that a loose-leaf original is a loose-leaf original regardless of whether the loose-leaf original is conveyed in a state where the loose-leaf hole is positioned at either the front end or the rear end in the conveyance direction. Therefore, it is possible to prevent the timing of performing various controls based on the detection states of the originals by the first original sensor 26a to the fourth original sensor 26d from being delayed during normal document conveyance.

  In addition, the processing for determining the loose-leaf document and the normal document in steps S61 to S66 in the present embodiment is replaced with steps S39 to S45 shown in FIG. 12 in the second embodiment until the predetermined time TE elapses. The conveyance torque F is sampled at a predetermined time interval ΔT and compared with a set threshold value N. When the conveyance torque F becomes larger than the threshold value N, it is determined as a normal document, and the predetermined time TE has elapsed. Even if the conveyance torque F does not become larger than the threshold value N, it may be determined that the document is a loose-leaf original.

The document discrimination process of the present embodiment is not limited to the configuration that is executed after the document discrimination process according to the first or second embodiment is performed as described above, and only the document discrimination process according to the present embodiment is executed alone. It is good also as a structure.
[Modification]
In each of the above embodiments, the thickness of the document is detected, and the conveyance torque threshold value determined as the loose-leaf document is set based on the thickness. Without detection, a threshold value of the conveyance torque at a highly versatile document thickness may be set in advance, and a loose-leaf document may be determined based on the threshold value.

  When only a specific type of document is used, a torque threshold value for the specific type of document may be set in advance. In addition, the transport torque is obtained from the motor current supplied to the transport motor 25b that rotationally drives the first transport roller 21i that transports the document. For example, the torque that directly detects the torque of the first transport roller 21i. It is good also as a structure which calculates | requires conveyance torque using a sensor.

  The present invention can detect that a document to be conveyed is a loose-leaf document in an automatic document feeder that automatically conveys a document without increasing the size of the device.

A Image forming apparatus main body B Image reading apparatus 10 Scanner unit 12 First slider 13 Second slider 20 ADF unit 21 ADF unit main body 21c Separating roller 21d First transport path 21i First transport roller 21j Second transport roller 22 Document feed tray 26a First document sensor 26b Second document sensor 26c Third document sensor 26d Fourth document sensor 30 Document thickness sensor 41 Scanner CPU
51 ADF-CPU
51b Conveying torque converter

Claims (10)

A first transport roller for transporting a document in the transport path;
A second transport roller disposed downstream in the transport direction of the first transport roller;
Rotation control means for controlling the rotation of the first conveyance roller and the second conveyance roller so that the document is bent in a loop between the first conveyance roller and the second conveyance roller;
Torque detection means for detecting torque during document conveyance of the first conveyance roller;
A document discriminating unit for discriminating that the document is a loose-leaf document based on the magnitude of the torque detected by the torque detecting unit;
An automatic document feeder characterized by comprising:   The automatic document feeder according to claim 1, wherein the document determination unit determines that the document is a loose-leaf document when the torque detected by the torque detection unit is equal to or less than a preset threshold value. A document thickness detecting means for detecting a thickness of the document conveyed to the first conveying roller;
3. The document discrimination unit according to claim 2, wherein the document discrimination unit discriminates the document based on the threshold set in advance according to the thickness of the document detected by the document thickness detection unit. Automatic document feeder.   The automatic document conveyance according to any one of claims 1 to 3, wherein the torque detection unit detects the torque based on a motor current supplied to a motor that drives the first conveyance roller. apparatus.   The rotation control unit rotates the first conveyance roller in a state where the second conveyance roller is stopped, thereby pushing the leading end portion of the document conveyed by the first conveyance roller to the second conveyance roller. 5. The automatic document feeder according to claim 1, wherein the leading end portion of the document is bent in a loop shape.   The torque detecting means detects the torque at a time when a predetermined time has elapsed after the leading edge of the document is abutted against the second conveying roller, or the document abuts against the second conveying roller. 6. The automatic document feeder according to claim 5, wherein the torque is detected at predetermined time intervals after being received.   The rotation control unit rotates the first conveyance roller and the second conveyance roller to convey the document, and before the trailing edge of the document passes through the first conveyance roller, the rotation control unit rotates the first conveyance roller and the second conveyance roller. 5. The automatic document feeder according to claim 1, wherein by stopping the second conveyance roller, the trailing edge of the document is bent in a loop shape. 6.   The torque detecting means detects the torque at a time when a predetermined time has elapsed since the second transport roller was stopped, or the torque detection means at a predetermined time interval after the second transport roller was stopped. The automatic document feeder according to claim 7, wherein the automatic document feeder is detected.   An image reading apparatus provided with the automatic document feeder according to claim 1.   An image forming apparatus comprising the image reading apparatus according to claim 9.

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