JP3849677B2 - Automatic document feeder - Google Patents

Description

  The present invention relates to an automatic document feeder in a so-called sheet-through type image reading apparatus that reads an image while conveying a document, and more specifically, can accurately detect the size of a document to be fed while being a short feeding path. The present invention relates to an automatic document apparatus provided with document size detection means.

  In general, an electrophotographic copying machine or a facsimile apparatus includes an automatic document feeder (ADF device) that separates documents set on a document tray one by one and continuously supplies them to a reading unit. As a reading method of document image information, a reading unit is arranged in the middle of the document conveyance path of the ADF apparatus to read the document while conveying the document, and a lower surface of the document on which the reading optical system is placed on the platen glass. A combination with a flatbed scanner (FBS) method that scans while moving the image has been widely adopted. In such an apparatus, when reading an automatically fed document, the reading optical system moves to a reading point in the middle of the document conveyance path and stops, and sequentially reads image information of the conveyed document.

In the ADF apparatus as described above, the size of the document being fed is detected by the sheet width detecting means disposed on the document feeding (conveying) path and the lead sensor, and based on this detection information. The reading device and other related devices are controlled. In an ADF apparatus equipped with such a document size detection means, a size sensor immediately after the document separation means, a sheet (document) width detection means, and a sheet at a predetermined time upstream of the reading position on the document transport path. A lead sensor for detecting the leading edge of the (original) is provided, and the sheet size being fed is estimated based on the on / off state of the size sensor when the lead sensor is on and the sheet width information by the sheet width detecting means. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 08-133551

  In the ADF apparatus as disclosed in Patent Document 1, the length of the document (sheet) along the conveyance path direction is substantially determined by the detection information at the leading edge of the document and the detection information at the trailing edge of the document. The detection of the leading edge and the trailing edge of the document by both the sensors needs to be performed on the downstream side of the document separation unit (separation unit) that ensures the page interval of the document. The distance along the conveyance path between the two sensors needs to be 1/2 or more of the maximum document length so that the size of all general-purpose rated sheets can be detected. In general, since the maximum document is A3 size, an interval of ½ of the length, that is, 210 mm or more must be ensured in the transport path from the document separating means to the reading unit. Securing the transport path has become an obstacle to downsizing the apparatus. In addition, it is necessary to arrange a plurality of types of sensors dedicated to document size detection along the conveyance path, leaving room for cost improvement.

  The present invention has been made in view of the above circumstances, and enables accurate document size detection even when the feeding path is shortened. Also, the number of sensors can be reduced to reduce the size and cost of the apparatus. The present invention provides an automatic document feeder capable of achieving the above.

The present invention relates to an automatic document feeder that feeds a document placed on a document placement unit, separates the documents one by one, and conveys them by a registration roller, and feeds them to a reading unit downstream of the feeding path. so,
A registration sensor for detecting a fed document in the vicinity of the upstream side of the registration roller;
Based on the detection signal of the registration sensor, on / off control of the registration roller is performed,
The distance between the registration sensor and the registration roller is the product of the elapsed time from the start of registration roller driving based on detection of the leading edge of the fed document by the registration sensor to the trailing edge detection of the feeding document by the registration sensor and the peripheral speed of the registration roller. Is provided with determination means for determining the document length by adding
In the vicinity of the upstream side of the reading unit, a lead sensor for controlling the reading start of the reading unit based on the detection of the leading edge of the fed document is disposed.
The distance along the feeding path between the registration sensor and the lead sensor is a length corresponding to at least half of the maximum document length,
A document shorter than a length corresponding to ½ of the maximum document length is determined by the determination means,
The length of a document longer than a length corresponding to ½ of the maximum document length is determined based on on / off information of the registration sensor and the lead sensor.

  According to the present invention, the on / off control of the registration roller is performed based on the detection signal of the fed document by the registration sensor, and the length of the fed document is determined. This eliminates the need for a dedicated size sensor, and it is not necessary to secure a space for disposing it, so that the feeding path can be shortened, and the cost of the apparatus is reduced and the size is reduced. Is planned. Since the registration roller on / off control and the document length determination are performed for each document to be fed, even when documents of different sizes are mixed-stacked on the document placement unit, Accurate size detection is performed for each document, and reading and the like are appropriately controlled according to each document.

  In the apparatus of the present invention, since the peripheral speed of the registration roller and the distance between the registration sensor and the registration roller are known, the length of the fed document can be easily calculated by these calculation processes. The document size can be determined by a combination with the document width detection information.

  When the fed document sent as described above reaches the read sensor, information indicating whether the trailing edge of the document has been detected by the registration sensor, its length data, and detection data of the document width. Since the document size is determined, the document size is determined before the reading is started, and reading control is accurately performed for each fed document based on the determined information.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a main part of an ADF 1 in a facsimile machine, a copying machine, or a so-called multifunction machine having both functions of a facsimile and copying.

  The ADF 1 shown in the figure is configured as a document feeding device for reading images on both sides of a sheet of document D conveyed one by one and outputting them as digital signals. A document tray 2b is detachably attached to the document supply port 2a of the ADF 1 so that the document tray 2b is inclined downward toward the document supply port 2a, and a document placement unit is formed by the document supply port 2a and the document tray 2b. 2 is configured. A pickup roller 3 for feeding out the original (paper) D deposited on the original placing portion 2 from the upper layer portion is disposed on the original supply port portion 2a. A document separating means 4 for separating and feeding the sheets one by one is provided. The document separating means 4 includes a separation roller 4a and a separation pad 4b urged so as to elastically contact the peripheral body of the separation roller 4a. The document fed out by the pickup roller 3 is introduced between the separation roller 4a and the separation pad 4b, and is separated one by one due to the difference in friction coefficient with respect to the two papers as the separation roller 4a rotates, and is fed downstream. Sent. 4c is a compression spring for elastically bringing the separation pad 4b into contact with the periphery of the separation roller 4a.

  The originals separated one by one by the original separating means 4 are registered rollers 6, first conveying rollers 7, and the like arranged sequentially along an original conveying path (original feeding path) 5 formed in a U-turn shape. The resist is conveyed by the second conveying roller 8 to the first reading point (reading unit) P1, and further fed to the second reading point P2 by the third conveying roller 9, and discharged to the discharge tray 11 by the discharge roller 10. Is done. A platen 12 is disposed at the first reading point P1, and when the document passes over the platen 12, the image information on the surface of the document is sequentially read by the reading and scanning device 13 waiting under the platen 12. As a digital signal.

  The reading scanning device 13 includes a light source 13a formed of a fluorescent lamp or a cold cathode tube, a plurality of mirrors 13b..., A condensing lens 13c, and a CCD (charge coupled device) 13d. It is mounted on 13e. Irradiation light from the light source 13a is reflected by the original passing through the reading point P1 on the platen 12, and then repeatedly reflected by the four mirrors 13b, is condensed by the condenser lens 13c, and enters the CCD 13d ( (Refer to the light path of the one-dot chain line). In the CCD 13d, image information drawn on the surface of the document is converted into an electric signal and output as a digital signal.

  The reading scanning device 13 in the figure is configured to be used also as a flat bed scanner (FBS). That is, although a part of the illustration is omitted, the FBS part 14 is coupled to the right side of the broken part in FIG. Although the carriage 13e is stationary at the reading position of the ADF document in the illustrated example, when the FBS document is read, the carriage 13e moves into the FBS unit 14 and reciprocates in the FBS unit 14 along the lower surface of the platen glass 15. The image information of the document placed on the platen glass 15 is read by the reading scanning device 13 in the same manner as described above. The ADF 1, the document tray 2b, and the discharge tray 11 are integrated to form a platen cover, and can be opened and closed up and down with the back side of the paper surface as a hinge portion (not shown). Accordingly, when the FBS unit 14 reads a document, the platen cover is opened and the document is placed on the exposed platen glass 15.

  As described above, the original whose surface image has been read at the first reading point P1 is further conveyed by the third conveying roller 9 to the second reading point P2, and this second reading point P2 is The contact point between the contact image sensor 16 disposed on the back side of the transported document and the platen roller 17 disposed in contact therewith. That is, the document introduced between the contact image sensor 16 and the platen roller 17 is fed while sliding the reading surface of the contact image sensor 16 by the rotation of the platen roller 17, and during this time the back image of the document is displayed. The image is read by the contact image sensor 16, converted into an electric signal, and output as a digital signal.

  The separation roller 4a, the registration roller 6, the first to third transport rollers 7 to 9, the platen roller 17 and the discharge roller 10 use a single motor (not shown) as a drive source and appropriately transmit gears or belts. Drive transmission is made through (same as above), and ON / OFF control is performed individually by an electromagnetic clutch (same as appropriate).

  The pickup roller 3 is configured to be driven and transmitted from the drive shaft 4d of the separation roller 4a. Briefly, a frame 3a is attached to the drive shaft 4d via a torque limiter (not shown) so as to be swingable up and down, and a support shaft 3b is supported on the front side of the frame 3a so as to be rotatable. ing. A belt 3d is stretched between a pulley 4e attached to the drive shaft 4d and a pulley 3c attached to the support shaft 3b, and the rotation of the drive shaft 4d passes through the pulley 4e, the belt 3d and the pulley 3c. The rotation of the support shaft 3b is transmitted to the pickup roller 3 via a one-way clutch (not shown).

  The pickup roller 3 configured as described above is positioned above the frame 3a in the standby state, and when the drive shaft 4d rotates in the forward direction (A direction), the frame 3a acts on the drive shaft 4d as a fulcrum by the action of the torque limiter. Swings downward. This swinging is stopped when the pickup roller 3 is pressed against the uppermost layer portion of the document D deposited on the document placing portion 2, but the transmission system (pulley 4e, belt) is driven by the continued rotation of the drive shaft 4d. The pickup roller 3 rotates via 3d and the pulley 3c). In this way, while the drive shaft 4d is rotating forward, the pickup roller 3 rotates while being pressed against the uppermost layer portion of the stacked originals D, so that the original document D is sequentially fed out from the uppermost layer portion. When the drive shaft 4d is temporarily stopped and reversely rotated (counter A direction), the frame 3a swings upward by the action of the torque limiter, and is held stationary in a standby state by the subsequent stop of the drive shaft 4d.

  The separation roller 4a is driven and transmitted from the drive shaft 4d via a not-shown one-way clutch. Accordingly, the document D is fed out from the pickup roller 3 as described above by the forward rotation of the drive shaft 4d, and the fed document is introduced between the separation roller 4a and the separation pad 4b, one by one as described above. Separated and fed downstream. The document D fed from the separation roller 4a is registered by the registration roller 6 and conveyed further downstream. The peripheral speeds of the rollers 7, 8, 9, 17, and 10 after the registration roller 6 are as follows. The peripheral speed of the separation roller 4 a and the pickup roller 3 is set to be larger than the peripheral speed of the separation roller 4 a and the registration roller 6. Accordingly, when the leading edge of the document D fed from the separation roller 4a reaches the registration roller 6, a transport load (tensile force) is applied to the document due to the difference in peripheral speed. However, the separation roller 4a and the pickup roller 3 are not described above. Thus, a one-way clutch (not shown) is incorporated, whereby both rollers 4a and 3 are idly rotated, and the conveying load is alleviated.

  Pressure rollers 6a, 7a, 8a, 9a and 10a are respectively provided on the registration roller 6, the first to third conveying rollers 7, 8, 9 and the discharge roller 10, and the original is nipped and conveyed by these rollers. The The separation roller 4a and the pickup roller 3 and pressure rollers 6a and 7a associated with the separation roller 4a are attached to the inside of a jam access cover 18 pivotally attached to the hinge pin 18a so as to be opened and closed vertically. Accordingly, when a document jam occurs in the document conveyance path 5 up to the second conveyance roller 8, the jam access cover 18 is opened to connect the separation pad 4b, the registration roller 6, and the first conveyance roller 7. Can be easily removed.

  The second conveying roller 8, the third conveying roller 9, the pressure rollers 8a, 9a, the platen roller 17 and the discharge roller 10 which are paired with the second conveying roller 8, the machine frame 19 forming the machine frame of the platen cover including the ADF 1, and the same. It is attached to a cylindrical intermediate inner guide frame 20 fixed to the frame. Further, the contact image sensor 16 and the pressure roller 10a are attached to an intermediate frame 21 pivotally attached to the drive shaft 6b of the registration roller 6 so that the drive shaft 6b can be opened and closed vertically. When the jam occurs at the third conveyance roller 9 or later, if the intermediate frame 21 is opened after the jam access cover 18 is opened, the contact between the contact image sensor 16 and the platen roller 17, and the discharge roller 10 and the pressure roller 10a Since the nip relationship is released, the jammed document can be easily taken out at this portion.

  A registration sensor 22 is provided between the separation roller 4 a and the registration roller 6, a document width detection sensor 23 is provided between the registration roller 6 and the first conveyance roller 7, and further, in the vicinity of the upstream side of the second conveyance roller 8. A lead sensor 24 is provided for each. The control means 25 (see FIG. 3) described later calculates and sets in advance based on the distance L1 between the registration sensor 22 and the registration roller 6 when the registration sensor 22 detects the leading edge of the document fed from the separation roller 4a. Control is performed so that the registration roller 6 is operated (the electromagnetic clutch is turned on) after elapse of the predetermined time (time until the leading edge of the document reaches the registration roller 6). Further, when the leading edge of the fed document is detected by the read sensor 24, the control means 25 controls the second conveying roller 8 to operate (same as above) so as to convey the resist to the reading point P, and also to read the scanning device. 13 is controlled in synchronism with the feeding of the original.

  The registration sensor 22 and the lead sensor 24 together with the document width detection sensor 23 constitute a feeding document size detecting means. The distance L along the document conveyance path (document feeding path) 5 between the document detection position of the registration sensor 22 and the document leading edge detection position by the lead sensor 24 is 1/2 or 1/2 of the maximum document length. Slightly larger. Accordingly, in this type of reading apparatus having the highest versatility, the maximum document size is A3, and thus L is set to 210 mm or slightly larger than 210 mm. The document size detecting means will be described below with reference to FIGS.

  In FIG. 2, the document width detection sensor 23 includes three filler sensors 23 a, 23 b, and 23 c provided side by side in a direction orthogonal to the document feeding direction B. In this embodiment, an example in which each document is aligned on the right side in the document feeding direction B is shown, but center alignment or left side alignment is not excluded. In the example of FIG. 2, the maximum document size is A3. In such a sensor arrangement, when the document sheet to be used is a rated sheet, the leading edge of the document fed from the registration roller 6 is the sensor 23a, By acting on 23b and 23c, the following document width information is obtained. In the following, (T) means vertical placement along the document feeding direction B, and (Y) means horizontal placement perpendicular to the document feeding direction B.

(1) When the sensors 23a, 23b, and 23c are all off, the document size is B5 (T) or smaller.
(2) When the sensor 23a is on and 23b and 23c are off, the document size is A4 (T).
(3) When the sensors 23a and 23b are on and 23c is off, the document size is B4 (T) or B5 (Y).
(4) When all the sensors 23a, 23b, and 23c are on, the document size is A3 (T) or A4 (Y).

  In the detection of the document width, the document fed by the pickup roller 3 and separated and fed by the separation roller 4a is resist-transferred by the registration roller 6 having a high peripheral speed as described above. On the downstream side, a page interval is ensured between the original document and the original document. Therefore, detection by the original document width detection sensor 23 is performed for each original document to be fed. In (3) and (4), the document size has not yet been determined, but the document trailing edge is turned off when the filler type registration roller 22 is turned off (when it is removed from the registration roller 22) or the document leading edge is filled with the filler. The document leading edge detection sensor 24 is reached, and when the sensor 24 is turned on, these uncertain document sizes are determined.

  In other words, after the leading edge of the document turns on the registration sensor 22, the operation of the registration roller 6 is turned on after the predetermined time has elapsed, and the timer 22a starts simultaneously. When the document transported by the registration roller 6 is registered and the sensors 23a and 23b are turned on and 23c is turned off as shown in (3), the fed document is either B4 (T) or B5 (Y). However, if the registration sensor 22 is turned off at the rear end before the tip reaches the lead sensor 24, the termer 22a is stopped and the elapsed time t is output to the CPU (control means) 25. Based on this input information, the CPU 25 calculates the length of the document by vt + L1 (v is the peripheral speed of the registration roller 6).

  Here, since the registration sensor 22 is turned off before the lead sensor 24 is turned on, the document length (vt + L1) is smaller than ½ of the maximum document length, that is, smaller than 210 mm. Therefore, it is determined that the document size is a B5 (Y) document. If the registration sensor 22 is not turned off when the lead sensor 24 is turned on, it is clear that the document length is 210 mm or more, and the size of the document is B4 (T). It is determined that In this case, when the read sensor 24 is turned on, the timer 22a is stopped and reset.

  Also, when the document transported by the registration roller 6 has the sensors 23a, 23b, and 23c turned on as shown in (4), the fed document is either A3 (T) or A4 (Y). However, when the leading end of the sensor 22 is turned off at the same time or immediately after the leading end reaches the lead sensor 24, the termer 22a is stopped and the elapsed time t is output to a CPU (control means) 25. . Based on this input information, the CPU 25 calculates the length of the document as vt + L1 as described above.

  Here, since the registration sensor 22 is turned off almost simultaneously or immediately after the lead sensor 24 is turned on, the document length (vt + L1) is smaller than ½ of the maximum document length, that is, smaller than 210 mm. Therefore, it is determined that the document size is an A4 (Y) document. If the registration sensor 22 is not turned off when the lead sensor 24 is turned on, it is clear that the document length is 210 mm or more, and the size of the document is A3 (T). It is determined that In this case as well, when the read sensor 24 is turned on, the timer 22a is stopped and reset.

  As described above, the sizes of all the fed documents are accurately determined based on the on / off information of the registration sensor 22, the detection information of the document width detection sensor 23, and the on / off information of the lead sensor 24. However, since the document size is determined before the leading edge of the document is introduced into the second transport roller 8, the CPU 25 accurately controls the operation of the second transport roller 8 and the reading scanning unit 13 based on the determined information. The That is, at the first reading point P1 or the second reading point P2, appropriate reading scanning control is performed based on the determined document size information, or appropriate output control of the reading image information is performed. In addition, since the document size is determined for each document, even when documents of different sizes are mixed and stacked on the document placement unit 2, the reading scanning control and the output control of the read image information are performed for each document. Done properly. Furthermore, since the registration sensor 22 is also used for document size detection, it is possible to reduce the number of sensors dedicated to document size detection, and it is not necessary to secure the installation space, thereby reducing the size of the apparatus. In particular, as shown in FIG. 1, a document feeding path is provided as in an ADF device in which a document is transported in a U-turn at one side of the FBS device and a discharge tray 11 is provided below the document tray 2b. If the length is limited, its effectiveness is extremely large. Further, since the length of the document is accurately calculated based on the above calculation formula, the legal size and letter size other than the rated size can be accurately determined based on the detection information from the document width detection sensor and the calculation result.

  In FIG. 1, reference numeral 26 denotes a document leading edge aligning shutter, which protrudes on the document placing portion 2 and can align the leading edge of the document D set on the document tray 2b in a standby state. The shutter 26 is provided in a link mechanism (not shown) 27 that swings up and down in conjunction with the rotation of the registration roller 6. It is configured to As described above, since the shutter 26 is moved in and out of the document placing portion 2 mechanically interlocking with the registration roller 6, it can be simply configured without using expensive electric parts such as a solenoid. it can.

  In the above-described embodiment, an example in which a filler-type sensor is used as the registration sensor 22, the document width detection sensor 23, or the lead sensor 24 has been described. However, the present invention is not limited to this, and sensors having other similar functions are also used. Is possible. Further, although an example for double-sided reading has been shown as an ADF apparatus, it goes without saying that the present invention can also be applied to an ADF apparatus for single-sided reading. Further, it goes without saying that the CPU 25 as the control means also controls operation of each mechanism unit of the apparatus in addition to the above.

It is a longitudinal cross-sectional view which shows the principal part of ADF and a scanning device. FIG. 5 is a schematic plan view for explaining an aspect of document width detection by a document width detection sensor. It is a control block diagram of this invention apparatus.

Explanation of symbols

1 ADF (Automatic Document Feeder)
2 Document placement section 5 Document transport path (feed path)
6 Registration Roller 22 Registration Sensor 24 Read Sensor 25 Control Unit P1 Reading Point (Reading Unit)
L Distance between the document leading edge detection sensor and the document contact position of the movement detection means L1 Distance between the registration sensor and the registration roller

Claims (1)

An automatic document feeder that feeds a document placed on a document placement unit, conveys the document by a registration roller while separating it one by one, and feeds it to a reading unit downstream of the feeding path,
A registration sensor for detecting a fed document in the vicinity of the upstream side of the registration roller;
Based on the detection signal of the registration sensor, on / off control of the registration roller is performed,
The distance between the registration sensor and the registration roller is the product of the elapsed time from the start of registration roller driving based on detection of the leading edge of the fed document by the registration sensor to the trailing edge detection of the feeding document by the registration sensor and the peripheral speed of the registration roller. Is provided with determination means for determining the document length by adding
In the vicinity of the upstream side of the reading unit, a lead sensor for controlling the reading start of the reading unit based on the detection of the leading edge of the fed document is disposed.
The distance along the feeding path between the registration sensor and the lead sensor is a length corresponding to at least half of the maximum document length,
A document shorter than a length corresponding to ½ of the maximum document length is determined by the determination means,
An automatic document feeder, wherein a document longer than a length corresponding to ½ of the maximum document length is determined based on on / off information of the registration sensor and the lead sensor.

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