JP2012124566A - Automatic document transport device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect spring-up at a rear end of a document bundle when a stapled original is fed by a plurality of sensors detecting a length of the original disposed on an original table so as to stop a paper feeding operation and to make a damage of the original to be minimum without installing an exclusive sensor for spring-up detection and other detecting means.SOLUTION: The automatic original transport device 100 sequentially separates a plurality of sheets of an original placed on the original table 2 to transport them from the original sheet positioned on an uppermost part. The transport device includes a plurality of sensors 30, 31, and 32 detecting the original length on the original table 2. A sensor detection state when the original is transported by a prescribed distance with the sensors 30, 31, and 32 is compared with a normal sensor detection state without spring-up of the original. When the sensor detection state differs from the normal sensor detection state, a transport operation of the original is interrupted.

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, a facsimile machine, and an automatic document feeder for supplying originals one by one to an image forming apparatus such as a digital multi-function machine having at least two of these functions, and an image forming apparatus having the same. It is.

  An automatic document feeder (hereinafter referred to as ADF as appropriate) mounted on an image reading device or the like separates and conveys a plurality of document bundles for each page when a plurality of document bundles are set in a document setting unit. Then, the image is read, and then the original is discharged. However, when the original bundle is subjected to stapling or clip processing, the original cannot be separated, and therefore these processes cannot be performed. For this reason, for example, a decal or the like indicating prohibition of a staple document or a clip document is pasted on the document setting unit, and the user is notified of that fact.

  However, if the user does not notice that the original bundle is stapled and sets the original bundle as usual and tries to convey it by ADF, the ADF feed roller tries to separate the original by force and feeds it by the feed roller. The uppermost document to be fed is rotated so that it is rolled up around the bound part, and it becomes a crease, it is torn, or the entire document bundle is rotated to become a distorted shape, resulting in damage to the document. There was a problem that. Further, when the stapled document bundle is to be conveyed, the trailing edge of the document bundle jumps up and floats from the document setting section, and the normal separation / conveyance / image reading process is stopped by detecting the jump of the document bundle. Although the technology is also known, there is a problem in that it is necessary to newly install document bounce-up detection means, leading to an increase in the number of parts and an increase in cost.

  In Japanese Patent Laid-Open No. 2004-260260, the bound original is placed on the original tray regardless of the binding position of the original and the material of the binding tool, and even when a part of the staple needle remains in the plurality of originals. In the document tray, a lifting detection sensor having a weight portion and an actuator mechanism is provided on the trailing edge guide that defines the trailing edge position of the document placed on the document tray. As a result, when the bound document is placed on the document tray, the lifted document moves the weight upward, so that the actuator operates and the lifted detection sensor can accurately detect the bound document.

  Japanese Patent Application Laid-Open No. 2004-228688 includes a plurality of detection sensors provided with a light emitting unit and a light receiving unit substantially coaxially with the axis of the paper feeding roller in order to detect abnormal paper feeding when a stapled document is fed. It discloses that abnormal paper feed is detected from a change in the amount of received light that is different from paper feed.

  However, in these conventional techniques, it is necessary to newly add means such as a lift detection sensor, and an increase in the number of parts and an increase in cost are inevitable.

  Therefore, the present invention provides a method for feeding a stapled document by a plurality of sensors that detect the length of the document provided on the document table without providing a dedicated sensor for detecting the jumping up or other detection means. An object of the present invention is to detect the jumping of the trailing edge of the original bundle, stop the paper feeding operation, and minimize the original damage.

  According to the present invention, there is provided an automatic document feeder in which one or a plurality of documents placed on a document table are separated one by one from the document located at the top and conveyed one by one on the document table. A plurality of sensors for detecting the length, and the sensor detection state at the time when the document is transported by a predetermined distance by the sensor is compared with a normal sensor detection state in which the document does not jump up; Is different from the normal sensor detection state, the problem can be solved by interrupting the document conveying operation.

Further, preferably, the sensor interrupts the document transport operation when the document is not detected when the document should be detected in the normal sensor detection state.
The sensor preferably detects the document size in addition to the document length.

The first sensor includes at least a first sensor, a second sensor, and a third sensor, and the first sensor is in a range of 210 mm to 257 mm from the end position on the downstream side in the transport direction when the original is placed on the original table. The second sensor is preferably arranged in a range of 257 mm to 297 mm, and the third sensor is preferably arranged in a range of 297 mm or more.
In addition, a fourth sensor and a fifth sensor are further provided, and the fourth sensor is arranged in front of the first sensor from an end position on the downstream side in the transport direction when the document is placed on the document table. The third sensor is preferably arranged in a range of 297 mm to 364 mm, and the fifth sensor is preferably arranged in a range of 364 mm or more.

  In addition, when the original is transported by a predetermined distance, the first sensor is disposed at a position capable of detecting at least a B5 vertical document, and the second sensor detects at least an A4 vertical document. The third sensor is arranged at a position capable of detecting at least a B4 vertical document, and the fourth sensor can detect at least an A4 horizontal document. It is preferable that the fifth sensor is arranged at a position where it can detect an A3 portrait document.

  Further, when the original is conveyed by a predetermined distance, the first sensor is disposed so as to be located within 10 mm from the upstream end of the B5 vertical size original in the conveying direction, and the second sensor Is arranged to be positioned within 10 mm from the upstream end of the A4 vertical size document in the conveyance direction, and the third sensor is 10 mm from the upstream end of the B4 vertical size document in the conveyance direction. The fourth sensor is disposed so as to be located within 10 mm from the end on the upstream side in the transport direction of the A4 horizontal size and A5 vertical size documents, The fifth sensor is preferably arranged so as to be located within 10 mm from the upstream end of the A3 vertical size original in the conveyance direction.

  The image forming apparatus of the present invention preferably includes the above-described automatic document feeder.

  According to the present invention, the plurality of sensors installed on the document table for detecting the document length not only detect the document length and document size when the document is set, but also when the document is conveyed by a predetermined distance. By comparing these sensor detection states with a normal sensor detection state in which there is no document bounce, it is possible to detect document bounce. When the document jump is detected, the document transport operation is interrupted, so that the document damage can be minimized. In addition, since it is not necessary to provide a dedicated sensor for detecting splashing and other detection means, an increase in the number of parts can be avoided and an increase in cost can be suppressed.

1 is a schematic cross-sectional view of an image forming apparatus including an automatic document feeder (ADF) 100 according to the present invention. 2 is a control block diagram illustrating a configuration of a control unit of the image forming apparatus. FIG. FIG. 4 is a block diagram illustrating a main part of an electric circuit of a second reading unit 25. FIG. 3 is a view showing a state in which a document bundle 1 whose leading end is stapled is set on a document table 2. It is a figure which shows the installation range of the document length detection sensors 30-32 of ADF. FIG. 6 is a diagram illustrating an arrangement of document length detection sensors when a sensor 33 and a sensor are further added to the sensor arrangement of FIG. 5.

  Next, FIG. 1 is a schematic cross-sectional view for explaining an image forming apparatus provided with the automatic document feeder (ADF) 100 of the present invention, and FIG. 2 is a control block diagram showing a configuration of a control unit of the image forming apparatus. The basic configuration, operation, and operation of the ADF 100 will be described. Note that the image formation in the image forming apparatus is the same as the conventional one, and the description is omitted.

  As shown in FIG. 1, the ADF 100 is fed with a document setting unit A for setting a bundle of documents to be read, a separation feeding unit B for separating and feeding documents one by one from the set document bundle. The resist portion C has a function of correcting the skew by temporarily abutting the original and a function of pulling out and transporting the skew-corrected original, and turns the conveyed original to convey the original surface toward the reading side (downward). Turn part D, first reading / conveying part E for reading the front surface image of the original document from below the platen glass, second reading / conveying part F for reading the back side image of the original document after reading, and the original on which the front and back side reading has been completed It has a paper discharge section G that discharges to the outside, and a stack section H that stacks and holds originals after reading.

  As shown in FIG. 2, the ADF 100 includes a pickup motor 101, a paper feed motor 102, a reading motor 103, a paper discharge motor 104, and a bottom plate raising motor 105 as drive units for driving these transport operations. And a controller 109 for controlling a series of operations.

  As shown in the figure, a controller 109 constituting the control unit of the image forming apparatus includes a registration sensor 17 for detecting the leading edge of the document and an original for detecting the set of the document via an interface and an internal bus (not shown). A set sensor 5, a paper discharge sensor 24 for detecting the leading edge of the discharged document, an abutment sensor 11, a document width sensor 13 for detecting the width of the document, a reading entrance sensor 15, and an appropriate paper feed position sensor 8 Input / output devices such as the bottom plate HP sensor 6 are connected. The controller 109 is connected to input / output devices such as the second reading unit 25, the pickup motor 101, the paper feed motor 102, the reading motor 103, the paper discharge motor 104, and the bottom plate raising motor 105. The controller 109 controls the second reading unit 25 and the motors 101 to 105 as desired according to the outputs from these sensors.

  The original bundle 1 to be read is set on the original table 2 including the movable original table 3 with the original surface facing upward. The document bundle 1 is positioned in the width direction perpendicular to the conveyance direction by a side guide (not shown). The document set is detected by the set filler 4 and the document set sensor 5, and this detection signal is transmitted to the controller 109, and is transmitted to the main body control unit 111 by the controller 109 via the I / F 107. Further, the length of the document in the conveyance direction is roughly determined by the document length detection sensors 30, 31, and 32 provided on the document table surface. The sensor is arranged so that at least whether it is vertical or horizontal of the same document size can be determined. As the document length detection sensors 30, 31, and 32, a known reflection type optical sensor or an actuator type sensor that can detect even one document is used.

  The movable document table 3 is configured to be movable up and down in the directions of arrows a and b shown in FIG. When the set filler 4 and the set sensor 5 detect that the document is set, the bottom plate raising motor 105 is rotated forward to raise the movable document table 3 so that the uppermost surface of the document bundle contacts the pickup roller 7.

  The appropriate paper feed position sensor 8 is a sensor that detects that the upper surface of the document bundle is maintained at an appropriate paper feed height so that the bottom plate does not rise too much. When the proper position sensor 8 is turned on, the bottom plate rise is stopped, and when the upper surface of the document is lowered while the paper feeding is repeated and the proper position sensor 8 is turned off, the bottom plate is raised and the proper position sensor 8 is turned on again. The upper surface position of the original bundle is always maintained at a height suitable for paper feeding. When all the set originals are fed, the bottom plate raising motor 105 is rotated forward to lower the movable original table 3 to the home position so that the next original bundle can be set.

  The pickup roller 7 is operated by the pickup motor 101 in the c and d directions shown in the figure by the cam mechanism, and is pushed by the upper surface of the document on the movable table 3 by the raising of the movable table 3 and rises in the c direction. 8, the upper limit can be detected. The main body operation unit 108 designates the duplex mode or the single side mode by pressing a key, and then the print key is pressed. The document control signal is transmitted from the main body control unit 111 to the ADF control unit 109 via the I / F 107. Then, the roller of the pickup roller 7 is rotationally driven by the forward rotation of the paper feed motor 102 to pick up several (ideally one) originals on the original table 2. The rotation direction is a direction in which the uppermost document in the clockwise direction in the drawing is conveyed to the sheet feeding port.

  Here, when setting the double-sided mode or the single-sided mode, the same setting may be made for all the originals set on the original table 2, and the first, second,... N Different settings may be made for each original document. For example, among all 10 originals, the first and tenth sheets can be set to the duplex mode, and the other can be set to the simplex mode.

  The paper feed belt 9 is driven in the clockwise paper feed direction in the drawing by the forward rotation of the paper feed motor 102, while the reverse roller 10 is driven to rotate in the reverse direction to the paper feed by the forward rotation of the paper feed motor 102. Thus, the top document and the document below it are separated, and only the top document can be fed. More specifically, the reverse roller 10 is in contact with the paper feed belt 9 at a predetermined pressure, and is rotated by the paper feed belt 9 when it is in direct contact with the paper feed belt 9 or in contact with a single original. If the document is rotated counterclockwise and the document enters between the sheet feeding belt 9 and the reverse roller 10 by two or more, the rotation force is set to be lower than the torque of the torque limiter. The roller 10 rotates in the clockwise direction, which is the original driving direction, and pushes back an excess original, thereby preventing double feeding.

  The document separated into one sheet by the action of the paper feed belt 9 and the reverse roller 10 is further fed by the paper feed belt 9, the leading edge is detected by the abutting sensor 11, and further advances to the pull-out roller 12 that stops. bump into. The document is then fed a predetermined amount from the detection of the abutting sensor 11 and is pressed against the pull-out roller 12 with a predetermined amount of deflection. In this state, the paper feed motor 102 is stopped. Then, the driving of the paper feed belt 9 is stopped. At this time, by rotating the pickup motor 101, the pickup roller is retracted from the upper surface of the document, and the document is fed only by the conveying force of the paper feed belt, whereby the leading edge of the document enters the nip of the pair of upper and lower rollers of the pull-out roller 12. Tip alignment, that is, skew correction is performed.

  The pull-out roller 12 has a skew correction function as described above, and also has a function of conveying the skew-corrected document to the intermediate roller 14 after separation, and is driven by a reverse drive of the paper feed motor 102. When the paper feed motor 102 is driven in reverse rotation, the pull-out roller 12 and the intermediate roller 14 are driven, but the pickup roller 7 and the paper feed belt 9 are not driven.

  When the document is transported from the registration unit C to the turn unit D by driving the pull-out roller 12 and the intermediate roller 14, the transport speed at the registration unit C is set higher than the transport speed at the reading transport unit E, The processing time for sending the document to the reading unit is shortened.

  When the leading edge of the document is detected by the reading entrance sensor 15, before the leading edge of the document enters the nip between the upper and lower roller pairs of the reading entrance roller 16, deceleration is started in order to make the document transportation speed the same as the scanning transportation speed. . At the same time, the reading motor 103 is driven in the normal direction to drive the reading inlet roller 16, the reading outlet roller 23, and the CIS outlet roller 27. When the registration sensor 17 detects the leading edge of the document, the registration sensor 17 decelerates over a predetermined conveyance distance, temporarily stops before the reading position 20, and transmits a registration stop signal to the main body control unit 111 via the I / F 107. Subsequently, when a reading start signal is received from the main body control unit 111, the document whose registration has been stopped is transported at an increased speed so as to rise to a predetermined transport speed before the leading end of the document reaches the scanning position. At the timing when the leading edge of the document detected by the pulse count of the reading motor reaches the reading unit, a gate signal indicating an effective image area in the sub-scanning direction on the first surface is sent to the main body control unit 111 after the first reading unit Sent until the edge is removed.

  In the case of single-sided document reading, the document that has passed through the reading conveyance unit E is conveyed to the paper discharge unit G through the second reading unit 25. At this time, when the leading edge of the original is detected by the paper discharge sensor 24, the paper discharge motor 104 is driven to rotate forward to rotate the paper discharge roller 28 counterclockwise. In addition, the discharge motor pulse count from the detection of the leading edge of the document by the discharge sensor 24 reduces the discharge motor drive speed immediately before the trailing edge of the document comes out of the nip of the pair of upper and lower rollers of the discharge roller 28 to discharge the document. Control is performed so that the document discharged onto the tray 29 does not jump out.

  In the case of double-sided document reading, DF control is performed on the second reading unit 25 at the timing when the document leading edge reaches the second reading unit 25 by the pulse count of the reading motor after the discharge sensor 24 detects the document leading end. A gate signal indicating an effective image area in the sub-scanning direction is transmitted from the unit 109 until the trailing edge of the original passes through the reading unit. The second reading roller 26 serves as a reference white portion for obtaining shading data in the second reading unit 25 as well as suppressing the floating of the document in the second reading unit 25.

  FIG. 3 is a block diagram illustrating a main part of the electric circuit of the second reading unit 25. As shown in the figure, the second reading unit 25 has a light source unit 200 including an LED array, a fluorescent lamp, a cold cathode tube, or the like. The second reading unit 25 includes a plurality of sensor chips 201 arranged in the main scanning direction (a direction corresponding to the document width direction), a plurality of OP amplifier circuits 202 individually connected to each sensor chip 201, and each OP. A plurality of A / D converters 203 individually connected to the amplifier circuit 202 are also provided. Further, the second reading unit 25 also includes an image processing unit 204, a frame memory 205, an output control circuit 206, an I / F circuit 207, and the like.

  The sensor chip 201 includes a photoelectric conversion element called a 1 × contact image sensor and a condenser lens. Prior to a document (not shown) entering the reading position by the second reading unit 25, a lighting ON signal is sent from the controller 109 to the light source unit 200. As a result, the light source unit 200 is turned on and irradiates the light toward the second surface of the document (not shown). The reflected light reflected by the second surface of the document is condensed on the photoelectric conversion element by the condensing lens and read as image information in the plurality of sensor chips 201. Image information read by each sensor chip 201 is amplified by an OP amplifier circuit 202 and then converted into digital image information by an A / D converter 203. The digital image information is input to the image processing unit 204 and subjected to shading correction and the like, and then temporarily stored in the frame memory 205. Thereafter, the data is converted into a data format that can be received by the main body control unit 111 by the output control circuit 206, and then output to the main body control unit 111 via the I / F circuit 107. Note that a timing signal for notifying the timing at which the leading edge of the document reaches the reading position by the second reading unit 25 (image data after that timing is treated as valid data), a light source lighting signal, a power source, etc. Is output.

Document size detection is performed as follows.
Normally, when a document is set on the document table 2, the document length detection sensors 30 to 32 provided on the document table 2 in a direction away from the movable document table 3 provide an outline of the document length (the sensor detects the document). How many mm to how many mm of the document length is detected). The document table 2 is provided with a plurality of width direction sensors (not shown) arranged in the front-rear direction. An outline of the width of the fed document (from what mm the document width depends on the number of documents detected by the sensor). How many mm). Based on the combination of the length in the length direction and the length in the width direction, the ADF 100 determines the size of the passed document and notifies the main body side.

Next, with reference to FIG. 4, a state in which the document bundle 1 whose front end is stapled is set on the document table 2 will be described.
For example, when a document that staples one corner on the downstream side in the conveyance direction or a document that staples two corners between the corner on the downstream side in the conveyance direction and the corner on the upstream side is set, As shown in FIG. 1, a document is detected by all of a document length detection sensor 30 as a first sensor, a document length detection sensor 31 as a second sensor, and a document length detection sensor 32 as a third sensor. The sensors 30 to 32 are all in an ON state. When the paper is fed by the pickup roller 7, the stapled document remains connected at the leading edge in the separation section of the ADF 100, and thus the uppermost document is normally subjected to a force in the sheet passing direction. Since a force acts on the document in the opposite direction, the trailing edge of the document jumps up. For this reason, normally, the sensor should be turned off from the upstream sensor in the transport direction after a certain time of transport, and sensor 30 is ON, sensor 31 is ON, sensor 32 is OFF, then sensor 30 is ON, sensor 31 is OFF, sensor 32 However, in this case, the document is as shown in FIG. 4 due to the jumping up. In this state, for example, all the sensors are turned off or only the sensor 30 is turned on. If the sheet feeding process is continued as it is, the stapled document bundle 1 may be forcibly conveyed and the document may be torn or folded. For this reason, it is necessary to configure the ADF so that the motor is stopped as soon as the normal sensors 30 to 32 detect the state as described above, and the damage to the document is minimized.

Here, whether the document bundle 1 is detected by the detection sensors 30 to 32 after the initial state where the document bundle 1 is set on the document table 2 and transported for a certain period of time and a certain distance depends on the document size and the document transport direction. These will be described below because they depend on whether they are in the portrait or landscape direction.
In particular, it is desirable to reliably detect A3, A4, and B4 documents that are frequently used. When the long side is vertical and the short side is horizontal, the A3 original is 420 mm long and 297 mm wide, the A4 original is 297 mm long and 210 mm wide, and the B4 original is 364 mm long and 257 mm wide.

  FIG. 5 is a diagram showing an installation range of the ADF document length detection sensors 30 to 32 in consideration of these document dimensions. As shown in the drawing, the sensor 30 is positioned at a position of 220 mm, and the sensor 31 is positioned at the downstream side in the transport direction when a document is set on the document table 2 such as the nip portion of the movable table 3 and the pickup roller 7. The position of 260 mm and the sensor 32 are respectively installed at a position of 325 mm. Here, the sensor 30 has a range of 210 mm to 257 mm, the sensor 31 has a range of 257 mm to 297 mm, and the sensor 32 has a range of 297 mm or more. A document is detected by a total of eight sensors including these sensors 30 to 32 and five width direction sensors (not shown).

  At this time, the initial state of ON / OFF of the sensors 30 to 32 at the time of setting each document size is as shown in Table 1 below. Here, A4T represents an A4 portrait size and represents that an A4 document is set to be fed in the portrait orientation with the short side at the top, and A4Y represents an A4 landscape size, and the A4 document is This indicates that the sheet is set so that the sheet is fed in the landscape direction with the long side at the top. As described above, since the A4 document is 297 mm long, the sensor 30 installed at the position of 220 mm is in the ON state (“1” in Table 1), and the sensor 31 installed at the position of 260 mm is in the ON state ( “1” in Table 1) The sensor 32 installed at a position of 325 mm is in an OFF state (“0” in Table 1). Therefore, it can be seen from the detection states “1, 1, 0” of the sensors 30 to 32 that this is A4T. As described above, the sensors 30 to 32 can also detect the document size. Table 1 also shows the ON / OFF states of the sensors 30 to 32 for other sizes of documents, based on the dimensions and the positional relationship between the sensors 30 to 32.

Tables 2 to 4 below show the length in the document transport direction and the distance (mm) from the upstream end of the document transport direction in the positional relationship of the sensors 30 to 32 to each sensor.
Table 2 shows an initial state in which a document is set. When the distance to the sensor 30 is obtained in the case of A4T, subtracting 297 mm, which is the length in the transport direction of A4T, from the distance of 220 mm to the sensor 30, it is −77 mm. Similarly, up to the sensor 31 is 260 mm−297 mm = −37 mm. Thus, the distance to the sensors 30 and 31 is a negative value. That is, A4T is detected by the sensors 30 and 31 and is in a state of “1” as shown in Table 1. Further, the distance to the sensor 32 is 325 mm−297 mm = 28 mm, and the distance to the sensor 32 is a positive value. In other words, A4T is not detected by the sensor 32 and is in a “0” state as shown in Table 1.

  On the other hand, Table 3 shows the distance (mm) to each sensor of the document when the document is conveyed by 35 mm. At this time, the same calculation is performed. In the case of A4T, the distances to the sensors 30 to 32 are −42 mm, −2 mm, and 63 mm. Therefore, in the case of A4T, the detection state of the sensors 30 to 32 does not change between the initial state and the 35 mm conveyance state. Similarly, in the case of other A3T, B4T, and B5T, the detection states of the sensors 30 to 32 do not change.

  However, in the case of a staple original, about 10 mm at the rear end jumps up, and this can be regarded as the original being shortened by about 10 mm. As shown in Table 4, when this is taken into account, in the case of A4T, the distance to the sensor 30 is −32 mm and is detected by the sensor 30, but the distance to the sensor 31 is 8 mm and is detected by the sensor 31. Not. Accordingly, the detection state of the sensor 31 changes from “1” to “0”. Similarly, in the case of B5T, the detection state of the sensor 30 changes from “1” to “0”.

  Table 5 shows the detection states of the sensors corresponding to Table 4. From the comparison between Table 5 and Table 1, it can be seen that the detection state is changed in the sensor 31 in the case of A4T, the sensor 32 in the case of B4T, and the sensor 30 in the case of B5T. As described above, the sensor detection state (Table 5) at the time when the document is conveyed by 35 mm by the plurality of sensors that detect the document length placed on the document table 2 is a normal sensor detection state in which the document does not jump up. When the sensor detection state is different from the normal sensor detection state as compared with (Table 1), the document transport operation is interrupted. More specifically, if these sensors are in a normal sensor detection state, the original conveying operation is interrupted when the original is not detected when the original is to be detected. Thus, for B4T, A4T, and B5T, the arrangement of the sensors 30 to 32 can detect a jump when the document advances by 35 mm from the change in the detection state of the sensor, and this jump is caused by a staple document or a clip document. I think that. Accordingly, at this time, the ADF interrupts the document feeding operation and displays an error on the operation panel of the image forming apparatus or generates an alarm sound to warn the user.

  FIG. 6 shows a case where a document length detection sensor 33 as a fourth sensor and a document length detection sensor 34 as a fifth sensor are further added in addition to the sensor arrangement of FIG. It is a figure which shows arrangement | positioning of a document length detection sensor. As shown in the drawing, the sensor 33 is at a position of 170 mm, and the sensor 34 is at the position of the end of the movable table 3 and the pickup roller 7 on the downstream side in the transport direction when the document is set on the document table 2. Each is installed at a position of 380 mm. Here, the sensor 30 is located in the range of 210 mm to 257 mm, the sensor 31 is located in the range of 257 mm to 297 mm, the sensor 32 is located in the range of 297 mm to 364 mm, and the sensor 34 is located in the range of 364 mm or more. The sensor 33 is positioned in the range of 210 mm or less.

  At this time, the initial state of ON / OFF of the sensors 30 to 32, 33, 34 at the time of setting each document size is as shown in Table 6. If the detection state of the sensors 33, 30 to 32, 34 is “1, 1, 1, 1, 1”, the document is A3T, and if “1, 1, 1, 1, 0”, the document is B4T. Yes, if “1, 1, 1, 0, 0”, the original is A4T, and if “1, 1, 0, 0, 0”, the original is B5T, and “1, 0, 0, 0” , 0 ”indicates that the document is A4Y, A5T, or B5Y. Also, it can be determined which of A4Y, A5T, and B5Y is by a width direction sensor (not shown).

In the following Tables 7 to 9, as in Tables 2 to 4, the length in the document transport direction and the upstream end of the document transport direction in the positional relationship of the sensors 30 to 32, 33, and 34 are shown. The distance (mm) to the sensor is shown.
As shown in Table 7 in the initial state, the sensor 33 detects A3T, B4T, A4T, B5T, A4Y, A5T, B5Y, and B6Y. As shown in Table 8, in the 35 mm conveyance state, A3T, B4T, A4T, B5T, A4Y, and A5T except B5Y and B6Y are detected by the sensor 33, and the detection states of the sensors at this time are B5Y and B6Y. In this case, only the sensor 33 changes. The other sensors 30 to 32 and 34 do not change from a negative value to a positive value in all document sizes.

  As can be seen from Table 8, when the document is conveyed by 35 mm, the sensor 30 is disposed at a position where at least a B5 portrait document can be detected. The sensor 31 is disposed at a position where at least an A4 portrait document can be detected. The sensor 32 is disposed at a position where at least a B4 vertical document can be detected. The sensor 33 is disposed at a position where at least an A4 landscape document can be detected. The sensor 34 is disposed at a position where an A3 vertical document can be detected.

  In addition, in consideration of the fact that about 10 mm of the trailing edge of the staple document jumps up, when the document is conveyed by 35 mm, the sensor 30 is within 10 mm from the upstream end in the conveyance direction of the B5 portrait document. It is arranged to be located in. The sensor 31 is disposed so as to be located within 10 mm from the upstream end in the transport direction of the A4 vertical document within 10 mm. The sensor 32 is disposed so as to be located within 10 mm from the upstream end of the B4 vertical document in the conveyance direction. The sensor 33 is disposed so as to be located within 10 mm to the upstream end of the A4 horizontal size and A5 vertical size in the conveyance direction of the original. The sensor 34 is disposed so as to be located within 10 mm from the upstream side in the conveyance direction of the A3 vertical document to the inside of the document.

  On the other hand, as shown in Table 9, in the case of a staple document, about 10 mm at the rear end jumps up, so it can be assumed that the document is further shortened by 10 mm. As can be seen from Table 9, from Table 8, the sensor 34 for A3T, the sensor 32 for B4T, the sensor 31 for A4T, the sensor 30 for B5T, the sensor 33 for A4Y, and the sensor A5T Even in the case of the sensor 33, the detection state changes from “1” to “0”.

  Table 10 shows the detection state of the sensor corresponding to Table 9. From the comparison between Table 10 and Table 6, the sensor 34 for A3T, the sensor 32 for B4T, the sensor 31 for A4T, the sensor 30 for B5T, the sensor 33 for A4Y, and the sensor 33 for A5T. It can be seen that the detection state (Table 10) has changed from the normal sensor detection state (Table 6) where there is no document jumping. As described above, the sensor detection state (Table 10) at the time when the document is conveyed by 35 mm by the plurality of sensors that detect the document length placed on the document table 2 is the normal sensor detection state in which the document does not jump up. When the sensor detection state is different from the normal sensor detection state as compared with (Table 6), the document conveying operation is interrupted. More specifically, if these sensors are in a normal sensor detection state, the original conveying operation is interrupted when the original is not detected when the original is to be detected. Thus, for A3T, B4T, A4T, B5T, A4Y, and A5T, the arrangement of the sensors 30 to 32, 33, and 34 can detect a jump when the document advances 35 mm from the change in the detection state of the sensor. This bounce is considered to be caused by a staple document or a clip document. Accordingly, at this time, the ADF interrupts the document feeding operation and displays an error on the operation panel of the image forming apparatus or generates an alarm sound to warn the user.

  By arranging the sensors 30 to 32, 33, and 34, it is possible to detect the jumping of the document in all cases of A3, B4, A4T, and A4Y that are frequently used. By adding a document size detection sensor in this way, it is possible to detect the jumping of the document in almost all document sizes. However, a dedicated sensor for this purpose is not provided, and the document size detection sensor jumps up. It also serves as a sensor for detection. Therefore, it is possible to avoid an increase in the number of parts and an increase in cost without the need to add a sensor for detecting splashing and other mechanisms.

  As described above, conventionally, a plurality of sensors arranged in the document transport direction on the document table are used only for detecting the size in the document length direction when the document is set. The jumping of the trailing edge of the document can also be detected based on the length of the document transported during feeding and the positional relationship between these sensors. At this time, the document damage can be minimized by stopping the paper feeding operation.

  Although the present invention has been described with reference to the illustrated examples, the present invention is not limited thereto. For example, the predetermined distance for transporting the document is not limited to 35 mm, and the arrangement positions of the sensors 30 to 32, 33, and 34 are not limited to the above example. Each sensor may be arranged at a position to detect each document size when the document is conveyed by a predetermined distance. At this time, each sensor may not be within 10 mm from the end on the upstream side in the conveyance direction of the document, and may be arranged so that the jumping can be appropriately detected.

1 Document Bundle 2 Document Table 3 Movable Document Table 25 Second Reading Unit 30 Document Length Detection Sensor (First Sensor)
31 Document length detection sensor (second sensor)
32 Document length detection sensor (third sensor)
33 Document length detection sensor (fourth sensor)
34 Document length detection sensor (fifth sensor)
100 Automatic document feeder (ADF)
109 controller

Japanese Patent No. 3467144 JP 2008-247540 A

Claims (8)

In an automatic document feeder that separates and conveys one or more documents placed on a document table one by one from the document located at the top,
A plurality of sensors for detecting a document length on the document table;
When the sensor detection state at the time when the document is transported by a predetermined distance by the sensor is compared with a normal sensor detection state in which the document does not jump up, and the sensor detection state is different from the normal sensor detection state, An automatic document feeder, wherein the document feeding operation is interrupted.   2. The conveying operation of the document is interrupted when the sensor is in the normal sensor detection state and the document is not detected when the document is to be detected. Automatic document feeder.   The automatic document feeder according to claim 1, wherein the sensor detects a document size in addition to a document length.   At least a first sensor, a second sensor, and a third sensor are provided, and the first sensor is in a range of 210 mm to 257 mm from the end position on the downstream side in the transport direction when the original is placed on the original table. The automatic document feeder according to claim 1, wherein the two sensors are arranged in a range of 257 mm to 297 mm, and the third sensor is arranged in a range of 297 mm or more.   A fourth sensor and a fifth sensor, wherein the fourth sensor is disposed in front of the first sensor from an end position downstream in the transport direction when the document is placed on the document table; 5. The automatic document feeder according to claim 4, wherein the third sensor is disposed in a range of 297 mm to 364 mm, and the fifth sensor is disposed in a range of 364 mm or more. When the document is conveyed by a predetermined distance,
The first sensor is disposed at a position capable of detecting at least a B5 vertical document.
The second sensor is disposed at a position capable of detecting at least an A4 vertical document.
The third sensor is arranged at a position capable of detecting at least a B4 vertical document.
The fourth sensor is disposed at a position capable of detecting at least an A4 landscape document,
The automatic document feeder according to claim 5, wherein the fifth sensor is disposed at a position where an A3 portrait document can be detected. When the document is conveyed by a predetermined distance,
The first sensor is disposed so as to be located inside the document within 10 mm from the upstream end in the conveyance direction of the B5 vertical document,
The second sensor is disposed so as to be located inside the document within 10 mm from the upstream end in the transport direction of the A4 portrait document,
The third sensor is disposed so as to be located inside the document within 10 mm from the upstream end in the transport direction of the B4 vertical document,
The fourth sensor is disposed so as to be located within 10 mm from the upstream end in the transport direction of the A4 horizontal size and A5 vertical size documents,
7. The automatic document conveyance according to claim 5, wherein the fifth sensor is disposed so as to be located within 10 mm from the upstream end in the conveyance direction of an A3 portrait document. apparatus.   An image forming apparatus comprising the automatic document feeder according to claim 1.

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