JP2012131637A - Sheet feeder, sheet reader, and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To start feed of a next document at optimum timing while balancing a merit of a leading end detection means with that of a rear end detection means.SOLUTION: This sheet feeder for transporting a separately-fed document to a reading position to read the document includes: a rear end detection means Sn3 to detect the rear end of a sheet having passed through a separating/feeding means 9; a first leading end detection means Sn1 arranged away from the separating/feeding means 9 on the downstream side in the transport direction by a predetermined distance; a second leading end detection means Sn2 arranged away from a document calling means on the downstream side in the transport direction by the predetermined distance; and a control means to determine the length in the transport direction of the document while being transported from the detection results of the rear end detection means Sn3 to detect the leading end of a document as well and the second leading end detection means Sn2. In the sheet feeder, when the transported document is determined to be smaller than a specific size by the control means, the feeding of the next document on a loading means is started at earlier one out of the time of the leading end detection of the preceding document by the first leading end detection means Sn1 and the time of the rear end detection of the preceding document by the rear end detection means.

Description

  The present invention relates to a sheet feeding device used in a mechanism for reading an image while conveying a document to a fixed reading device unit and conveying the document at a predetermined speed.

  In order to ensure a certain level of productivity in a so-called sheet-through type document feeder, a document is fed to a fixed reading unit, exposed while being conveyed at a predetermined speed, and read out. It is necessary to control the distance between the (preceding sheet) and the next original (following sheet) (hereinafter referred to as the sheet interval) as close as possible. For this reason, as a timing for feeding the next document, a technique is known in which it is detected that the trailing edge of the previous document has passed a predetermined location and the next document is fed using that as a trigger.

  For example, in Patent Document 1, for the purpose of increasing productivity, the start of the feeding operation of the next document is performed based on the detection of the trailing edge of the previous document by the document trailing edge detection sensor. Paper feeding is performed at a speed faster than the transport speed of the previous document. A means for detecting the trailing edge of the preceding document is provided at a position corresponding to the stack portion of the preceding document, and a means for controlling the feeding timing of the next document feeding means based on the passage detection signal at the trailing edge of the preceding document by the detecting means. The structure characterized by providing is disclosed.

  In addition to the above format, “specific sheet bundle size detecting means” for detecting whether or not the maximum length in the conveyance direction of the documents stacked on the document table is a predetermined value or more, and the document being conveyed A "document sheet leading edge detection means" for detecting whether or not the leading edge has reached a predetermined position, and a "document trailing edge detection means" for detecting that the trailing edge of the document being conveyed has passed the predetermined position, When it is detected by the “specific sheet bundle size detection means” that the maximum value in the conveyance direction length of the document bundle loaded on the document table is equal to or less than a predetermined value, the “sheet leading edge detection means” When it is detected that the leading edge of the document has reached a predetermined position, feeding of the next document is started, and the maximum value in the conveyance direction length of the document bundle loaded on the document table by the “specific sheet bundle size detecting means” Is a predetermined value If it is detected to be obtained, the document trailing edge by the "original trailing edge detection means" are also known means of the next document is started paper feed when it is detected that has passed through the predetermined position.

  However, with the conventional configuration that detects the trailing edge of the original and starts feeding the next original, the uppermost original of the original bundle can be reliably separated from other originals due to restrictions on the layout of the mechanical layout. It is difficult to arrange the sensor at a position where the fact can be directly detected (separation part nip position). Also, when dealing with documents with punched holes, the sensor can be temporarily undetected due to the punched holes, so even if the output of the sensor that detects the trailing edge of the document becomes undetected, It is necessary to confirm that the sensor output does not return from the non-detection state to the detection state by continuing the conveyance by a predetermined amount. This also has a disadvantageous effect on the request of “detecting the trailing edge of the document as soon as possible and starting sheet feeding control for the next document”.

  Further, switching between using the trailing edge detection unit or the sheet leading edge detection unit is performed depending on whether or not the maximum value of the conveyance direction length of the document bundle loaded on the document table exceeds a predetermined position. The conventional method has a problem that the cost is increased on the premise that a dedicated “specific document bundle size detecting means” is installed on the document table.

  SUMMARY OF THE INVENTION It is an object of the present invention to start feeding the next sheet at an optimum timing possible in the mechanical layout while satisfying the advantages of the sheet leading edge detecting means and the trailing edge detecting means regardless of the size of the sheet to be conveyed. .

  The above-described problems include sheet stacking means for stacking sheets, separation feeding means for separating and feeding the stacked sheets one by one, and sheet calling for sequentially feeding the stacked sheets to the separation feeding means. A sheet feeding apparatus comprising: a conveying unit that conveys the sheet to a reading position in order to read the image information of the separated and fed sheet; and a paper discharge unit that discharges the sheet from which the image information has been read. A trailing edge detecting means for detecting the trailing edge of the sheet that has passed through the separating and feeding means, and a downstream side of the trailing edge detecting means in the sheet conveying direction and a distance from the separating and feeding means by a predetermined distance. A first sheet leading edge detecting means, a second sheet leading edge detecting means disposed downstream of the trailing edge detecting means in the sheet conveying direction and at a distance from the sheet calling means by the predetermined distance; And a control unit for determining a length in the conveyance direction of the sheet being conveyed from the detection result of the second sheet leading edge detection unit. When it is determined that the sheet is smaller than the sheet size, the start of feeding the next sheet on the sheet stacking unit is detected when the front end of the front sheet is detected by the first sheet front end detecting unit, or the front sheet is detected by the rear end detecting unit. The problem is solved by setting the rear edge detection, whichever comes first. The predetermined distance is selected so that a specific sheet size can be recognized. For example, the predetermined distance is a value on the side of the letter in consideration of detection variation.

  When the trailing edge detection means detects the trailing edge of the front sheet, or when the control means determines that the size is less than the specific sheet size, the second sheet leading edge detection means detects the leading edge of the front sheet. It is preferable that the sheet calling means is brought into contact with the stacked sheets at any time earlier. When the trailing edge detection means detects the trailing edge of the front sheet, or when the control means determines that the size is less than the specific sheet size, the second sheet leading edge detection means detects the leading edge of the front sheet. It is envisaged that the sheet calling means is brought into contact with the stacked sheets, whichever comes first, and then the sheet calling means is driven to start feeding the next sheet on the sheet stacking means. The

  When the “sheet size mixed loading mode” indicating that a plurality of sheets of different sizes are stacked on the sheet bundle stacked on the sheet stacking unit is set, regardless of the determination by the control unit, When the trailing edge of the sheet is detected by the trailing edge detection means, the sheet calling means is brought into contact with the stacked sheet, and after completion of the contact, the sheet calling means is driven to feed the next sheet on the sheet stacking means. Is more preferable.

  When the control unit determines that the transport sheet is smaller than a specific sheet size, the front end of the transport sheet is moved to the first sheet earlier than the trailing end detection unit detects the rear end of the transport sheet. When the leading edge detection unit detects and the feeding of the next sheet on the sheet stacking unit is started, the driving amount of the sheet conveyance driving source is counted from the detection of the conveyance sheet leading edge by the first sheet leading edge detection unit. It is also convenient to provide an abnormality detection means for recognizing a conveyance abnormality when the trailing edge detection means does not detect the trailing edge of the conveyance sheet even if a predetermined value is exceeded, and to stop the sheet conveyance when a conveyance abnormality is recognized. is there. It is more preferable that the abnormality detection unit includes a notification unit that notifies the user when the conveyance abnormality is recognized and the sheet conveyance is stopped.

  According to the present invention, a sheet stacking unit that stacks sheets, a separation feeding unit that separates and feeds stacked sheets one by one, and a stacking sheet for sequentially feeding the stacked sheets to the separation feeding unit. A sheet feeding apparatus comprising: a sheet calling unit; a conveying unit that conveys a sheet to a reading position in order to read image information of a separately fed sheet; and a sheet discharging unit that discharges the sheet from which the image information has been read. A trailing edge detection unit that detects a trailing edge of the sheet that has passed through the separation feeding unit, and a position that is downstream of the trailing edge detection unit in the sheet conveyance direction and is separated from the separation feeding unit by a predetermined distance. First sheet leading edge detecting means disposed on the downstream side of the trailing edge detecting means in the sheet conveying direction and spaced apart from the sheet calling means by the predetermined distance; and The trailing edge detecting means for detecting the leading edge of the sheet, and a control means for determining the length in the conveying direction of the sheet being conveyed from the detection result of the second sheet leading edge detecting means. When it is determined that the sheet is smaller than the sheet size, the start of feeding the next sheet on the sheet stacking unit is detected when the front end of the front sheet is detected by the first sheet front end detecting unit, or the front sheet is detected by the rear end detecting unit. Since the trailing edge is detected, whichever comes first, the feeding of the next sheet can be started at the optimum timing possible in the mechanical layout regardless of the sheet size, and the productivity can be improved.

  When the trailing edge detection means detects the trailing edge of the front sheet, or when the control means determines that the size is less than the specific sheet size, the second sheet leading edge detection means detects the leading edge of the front sheet. If the sheet calling means is brought into contact with the stacked sheets at any time, the influence on the productivity due to the lowering of the calling means, which is a preparation operation necessary for the sheet feeding operation, can be reduced. .

  When the trailing edge detection means detects the trailing edge of the front sheet, or when the control means determines that the size is less than the specific sheet size, the second sheet leading edge detection means detects the leading edge of the front sheet. If the sheet calling means is brought into contact with the stacked sheets, and the sheet calling means is driven to start feeding the next sheet on the sheet stacking means, Suppressing the impact on productivity due to the lowering of the calling means, which is a preparatory operation necessary for operation, and starting the feeding of the next sheet at the optimum timing possible in the mechanical layout regardless of the sheet size, improving productivity Can be made.

  When the “sheet size mixed loading mode” indicating that a plurality of sheets of different sizes are stacked on the sheet bundle stacked on the sheet stacking unit is set, regardless of the determination by the control unit, When the trailing edge of the sheet is detected by the trailing edge detection means, the sheet calling means is brought into contact with the stacked sheet, and after completion of the contact, the sheet calling means is driven to feed the next sheet on the sheet stacking means. By starting the process, depending on the combination of the sizes of the stacked sheet bundles, it is possible to prevent the danger that the preceding sheet and the succeeding sheet collide and damage jam occurs.

  Further, when the control unit determines that the transport sheet is smaller than a specific sheet size, the front end of the transport sheet is moved to the first position earlier than the rear end detection unit detects the rear end of the transport sheet. When detection of one sheet leading edge detection means and feeding of the next sheet on the sheet stacking means starts, counting from detection of the leading edge of the conveyance sheet by the first sheet leading edge detection means and driving of the sheet conveyance driving source Even if the amount exceeds a predetermined value, the trailing edge detecting means includes an abnormality detecting means for recognizing a conveyance abnormality when the trailing edge of the conveyance sheet is not detected, and when the conveyance abnormality is recognized, the sheet conveyance is stopped, When an abnormality such as sensor misdetection occurs, it is possible to prevent jamming. If the abnormality detection unit includes a notification unit that notifies the user when the conveyance abnormality is recognized and stops the sheet conveyance, the problem can be solved quickly.

1 is a schematic configuration diagram of a sheet-through type automatic document feeder to which the present invention is applicable. 2 is a block diagram for hardware control in an automatic document feeder. FIG. It is a block diagram which shows the principal part of the electric circuit of CIS. It is the schematic which shows arrangement | positioning of each member of the conveyance path | route provided with the detection means. FIG. 10 is a diagram for explaining a pickup roller descending when a document smaller than a specific sheet size is conveyed. FIG. 10 is a diagram illustrating the start of pickup roller operation when a document having a certain length and less than a specific length is conveyed. FIG. 10 is a diagram illustrating the start of pickup roller operation when an original having a size less than a specific sheet size and less than a certain length is conveyed. FIG. 6 is a diagram illustrating a state when a document having a specific sheet size or larger is conveyed. FIG. 6 is a flowchart for explaining specific control in the sheet feeding apparatus according to the present invention, and shows a flow for obtaining fixed size information. FIG. 6 is a flowchart for explaining specific control in the sheet feeding apparatus according to the present invention, and shows a flow relating to timing for starting a sheet feeding operation for the third and subsequent sheets. It is a flowchart explaining the detailed control of an abnormality detection process.

  The sheet feeding apparatus according to the present invention is used in a sheet-through-type read original processing apparatus (hereinafter referred to as ADF) that reads an image by conveying the read original to a fixed reading unit. In FIG. 1, the ADF includes a document setting unit A for setting a bundle of originals to be read, a separation feeding unit B for separating and feeding the originals one by one from the set of originals, and a fed original. Resisting part C, which has a function of abutting alignment and a function of pulling out and conveying the original after alignment, a turn part D for turning the conveyed original and conveying the original surface toward the reading side (downward), the surface of the original A first reading / conveying unit E that reads an image from below the platen glass, a second reading / conveying unit F that reads a back side image of a document after reading a front image, and a paper discharge unit G that discharges a document whose front and back sides have been read out of the apparatus. , A stack unit H for stacking and holding documents after reading, driving units 101 to 105 for driving these conveying operations (not shown in FIG. 1, refer to FIG. 2), and a controller unit 100 for controlling a series of operations ( Not shown in FIG. It is constructed from Figure 2 reference) and.

  The original bundle 1 to be read is set on the original table 2 including the movable table 3, and the original face is set upward when setting. Further, the side surface of the document bundle 1 in the width direction is supported by a side guide (not shown), and positioning in a direction orthogonal to the document conveyance direction is performed. The document set is detected by the set filler 4 and the set sensor 5 and transmitted to the main body control unit 111 shown in FIG.

  The movable table 3 is configured to be movable up and down (directions a and b in FIG. 1) using a bottom plate raising motor 105. When the set filler 4 and the set sensor 5 detect that a document has been set, the bottom plate raising motor 105 is moved. The movable table 3 is raised so that the uppermost surface of the document bundle 1 comes into contact with the pickup roller 7 by rotating 105 forward.

  An appropriate paper feed position sensor 8 shown in the figure is a sensor that prevents the bottom plate of the movable original cable 3 from being raised too much and detects that the upper surface of the original bundle 1 is maintained at an appropriate paper feed height. is there. When the proper position sensor 8 is turned on, the bottom plate rise is stopped, and by repeatedly feeding paper, the upper surface position of the document is lowered, and when the proper position sensor 8 is turned off, the bottom plate is raised and the proper position sensor 8 is turned on again. By repeating the above, the top position of the original bundle is always maintained at a height suitable for paper feeding. When all the set originals are fed, the movable table 3 is lowered to the home position so that the bottom plate raising motor 105 can be rotated forward to set the next original bundle.

  The pickup roller 7 can be moved up and down (c and d directions in FIG. 1) by a pickup motor 101 via a cam mechanism (not shown), and the movable table 3 is lifted and pushed by the upper surface of the document on the movable table 3. The upper limit can be detected by the proper paper feed position sensor 8 which is raised in the direction c. In the main body operation unit 108 (FIG. 2), the duplex key mode or the single-side mode is designated by pressing a key, and then the print key is pressed, and a document feed signal is sent from the main body control unit 111 to the ADF controller unit 100 via the I / F 107. When transmitted, the pickup roller 7 is rotationally driven by the forward rotation of the paper feed motor 102 and picks up several (ideally one) originals on the original table 2. The rotation direction is a direction in which the uppermost document is conveyed to the sheet feeding port. Here, when setting the duplex mode or the simplex mode, the same setting may be made for all the documents set on the document table 2, or (first sheet, second sheet,... N). Different settings may be made for each original (for example, among all 10 originals, the first and tenth sheets are in the duplex mode, and the others are in the simplex mode).

  The paper feeding belt 9 is driven in the paper feeding direction by the normal rotation of the paper feeding motor 102, and the reverse roller 10 is driven to rotate in the reverse direction to the paper feeding by the normal rotation of the paper 102 to separate the uppermost original from the original under it. Thus, only the uppermost document is fed. More specifically, the reverse roller 10 is in contact with the paper feed belt 9 at a predetermined pressure, and when the paper feed belt 9 is in direct contact with the paper feed belt 9 or in contact with a single document, the reverse roller 10 is rotated. When the two or more originals enter between the paper feeding belt 9 and the reverse roller 10, the revolving force is set to be lower than the torque limiter torque. The roller 10 rotates in the clockwise direction, which is the original driving direction, and pushes back an excess original so as to prevent double feeding.

  The original separated 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. After that, it is sent by a predetermined distance from the detection of the abutting sensor 11, and as a result, it is pressed against the pull-out roller 12 with a predetermined amount, and the paper feeding motor 102 is stopped. As a result, the driving of the paper feed belt 9 is stopped. At this time, the pickup motor 101 is rotated to retract the pickup roller 7 from the upper surface of the document, and the document is fed only by the conveying force of the paper feed belt 9, so that the leading edge of the document is in the nip of the upper and lower rollers of the pull-out roller 12. Enter and align the tip (skew correction).

  The pull-out roller 12 has such a skew correction function, and is used for conveying the skew-corrected document after separation to the intermediate roller 14, and is driven by the reverse rotation of the paper feed motor 102. When the paper feed motor 102 rotates in reverse, 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.

  A plurality of document width sensors 13 are arranged in the depth direction, and detect the size in the width direction orthogonal to the transport direction of the document transported by the pull-out roller 12. Further, the length of the document in the conveying direction is detected from the motor pulse by reading the leading edge and the trailing edge of the document with the butting sensor 11.

  When the document is transported from the resist section C to the turn section D by driving the pull-out roller 12 and the intermediate roller 14, the transport speed at the resist section C is set to be higher than the transport speed at the reading transport section 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 of the turn portion D, the document transportation speed is reduced to the same speed as the scanning transportation speed before the leading edge of the document enters the nip between the upper and lower roller pairs of the scanning entrance roller 16. At the same time, the reading motor 103 is driven forward 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, it 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 accelerated and conveyed so as to rise to a predetermined conveying speed before the leading edge of the document reaches the reading position 20. At the timing when the leading edge of the document detected by the pulse count of the reading motor 103 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 from the first reading conveyance unit. Sent until the trailing edge of the document is removed.

  In the case of single-sided original reading, the original that has passed through the first reading conveyance unit E is conveyed to the paper discharge unit G via the second reading conveyance unit F. At this time, when the leading edge of the document is detected by the paper discharge sensor 24, the paper discharge motor 104 is driven to rotate forward, and the paper discharge roller 28 is rotated counterclockwise. In addition, the discharge motor pulse count from the detection of the leading edge of the document by the sheet discharge sensor 24 is reduced and discharged immediately before the trailing edge of the document comes out of the nip between the upper and lower roller pairs of the discharge roller 28. The document is controlled so as not to jump out of the paper discharge tray 29.

  In the case of double-sided document reading, the ADF controller unit with respect to the CIS 25 at the timing when the leading edge of the document reaches the contact image sensor (CIS) 25 by the pulse count of the reading motor 103 after the leading edge of the document is detected by the paper discharge sensor 24. A gate signal indicating an effective image area in the sub-scanning direction is transmitted from 100 until the trailing edge of the original is removed from the CIS. The second reading roller 26 serves as a reference white portion for acquiring shading data in the CIS while suppressing the floating of the document in the CIS 25.

  FIG. 3 is a block diagram showing a main part of an electric circuit of the CIS 25. As shown in FIG. As shown in the figure, the CIS 25 has a light source unit 200 composed of an LED array, a fluorescent lamp, a cold cathode tube, or the like. Also, a plurality of sensor chips 201 arranged in the main scanning direction (direction corresponding to the document width direction), a plurality of OP amplifier circuits 202 individually connected to each sensor chip 201, and individually connected to each OP amplifier circuit 202 are connected. A plurality of A / D converters 203 are also provided. Further, the image processing unit 204 includes 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. A lighting ON signal is sent from the controller unit 100 to the light source unit 200 before a document (not shown) enters the reading position by the CIS 25. 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. The controller unit 100 outputs a timing signal, a light source lighting signal, a power source, etc. for notifying the timing when the leading edge of the document reaches the reading position by the CIS 25 (image data after that timing is treated as valid data). It has become so.

  An example of the arrangement of the detecting means in the present invention is shown in FIG. Usually, a reflective sensor is often used for the Sn1 to Sn3 sensors, but a transmissive sensor or the like may be used. Sensors Sn1 and Sn2 vary in detection according to the length in the transport direction (216 mm for the letter side) for a specific sheet size (for example, the letter side or A4), which is frequently used by the user and therefore requires high productivity from the user. In consideration of the above, it is desirable to arrange at a position where a margin is expected (from the reference point to the sheet conveyance downstream side). However, the layout is not limited to the specific position as long as it is arranged in accordance with the document type meeting the user's request.

  Specifically, the sensor Sn1 is “first sheet leading edge detection means”. When this sensor Sn1 detects the leading edge of the document, the trailing edge of the document having the specific sheet size (216 mm in the horizontal direction in the above example) surely separates the separating portion (feed belt 9 and reverse roller 10). Is located at a downstream position along the sheet conveyance path by a value obtained by adding a necessary and sufficient margin to the threshold value (for example, 216 mm) from the nip portion of the reverse roller 10.

  The sensor Sn2 is “second sheet leading edge detecting means”. Similarly to Sn1, when this sensor Sn2 detects the leading edge of the document, the position where the trailing edge of the document having the length of the specific sheet size (216 mm in the above example of the letter side) has surely slipped out of the pickup roller 7 That is, it is arranged at a downstream position along the conveyance path by a value obtained by adding a necessary and sufficient margin to the threshold value (for example, 216 mm) from the pickup roller 7.

  The sensor Sn3 is a “sheet rear end detection means”. This sensor Sn3 is conventionally known, and is disposed at a position for detecting that the trailing edge of the document has left the separating portion on the conveyance path. However, due to mechanical layout restrictions, the sensor Sn3 is sufficiently close to the paper feed belt 9 such as the point where the trailing edge of the document completes separation (the point where the nip portion of the paper feed belt 9 and the reverse roller 10 passes). It is difficult to configure.

  A method of determining the size in the conveyance direction of the document to be conveyed by a size determination control unit (not shown) based on whether or not the size is a specific sheet size will be described. In the first place, a method for determining the size of the document in the conveyance direction is known, and in many cases, the document is conveyed at a constant conveyance speed, and is calculated from the detection time and the conveyance speed using the detection means in the conveyance path. In the present invention, since the timing for starting the feeding operation of the succeeding sheet is determined by “determined size information”, the fixed size information should be grasped early. In this example, skew correction is also performed at the initial stage of document conveyance, and the conveyance speed Is not constant, it is determined as follows. If skew correction is not performed in the middle of the determination area, it is possible to employ a length calculation method in the case of paper conveyance at a constant speed.

  First, the sensor Sn2, which is the second sheet leading edge detection means, is disposed at a position (threshold value + margin) that coincides with the length in the conveyance direction of the specific sheet from the position immediately after passing through the pickup roller 7. Since the conveyance speed fluctuates while the document advances from the sensor Sn3 which is the sheet trailing edge detection means to the sensor Sn2 past the pull-out roller 12, the length from the sensor Sn3 to the sensor Sn2 is the length at the layout distance (fixed value). The remaining sheet size is determined by calculating the pulse count of the conveyance drive source. That is, if the determination target document has a specific sheet size, this corresponds to the sum of the Sn3 to Sn2 layout distance and the distance from the pickup roller 7 to the sensor Sn3 (immediately after the pickup roller 7 to Sn3). The distance between immediately after the pickup roller 7 and Sn3 coincides with the value calculated by the pulse count of the driving source from the timing when the leading edge of the determination target document reaches the sensor Sn2 until the trailing edge passes Sn3 (number of pulses × Feed amount per pulse).

  A state of conveyance when it is determined that the “determined size information” determined by the “size determination control unit” using such a method is less than the specific sheet size will be described. Even in the case where “determined size information” is determined to be “less than a predetermined size”, the sensor Sn1, which is the first sheet leading edge detection means, is separated from the separation unit by a distance equal to the distance between the pickup roller 7 and Sn2. Since it is arranged at a position, different processing is required depending on the layout relationship between the sensors Sn1 to Sn3. That is, in one case, the length of the document determined to be less than the specific sheet size is longer than the layout distance between Sn1 to Sn3. In this case, the leading edge of the document reaches the sensor Sn1 (first sheet leading edge detection means) before the trailing edge of the document passes through the sensor Sn3 (back edge detection means). Therefore, the lowering operation of the pickup roller 7 is started when the leading edge of the document reaches the sensor Sn2 (second sheet leading edge detecting means) (FIG. 5). Then, after the leading edge of the document has reached the sensor Sn1 and after waiting for the completion of the lowering operation of the pickup roller 7, the driving of the pickup roller 7 and the paper feeding belt 9 is started for separation of the next document (FIG. 6). At this time, as described above, since the trailing edge of the document does not pass through the trailing edge detection means (sensor Sn3), control for starting the next document feeding start is performed only by the conventional trailing edge detection means (sensor Sn3). Compared to the above, it becomes possible to carry the document with a gap between the originals, and the productivity can be improved.

  However, even if it is determined by the confirmed size information that “less than a predetermined size”, if the document length is shorter than the layout distance between Sn1 to Sn3, before the leading edge of the document reaches the sensor Sn1, The rear end passes through the sensor Sn3 (FIG. 7). In this case, immediately after the completion of the lowering of the pickup roller 7 which started the lowering operation triggered by the arrival of the leading edge of the document at the sensor Sn2, the driving of the pickup roller 7 and the paper feeding belt 9 is immediately started to feed the next document. To do. Thereby, in the case where the leading edge detection by the first sheet leading edge detection means (sensor Sn1) is not required, that is, in the case where the sensor Sn3 detects the trailing edge of the document before the sensor Sn1 detects the leading edge of the document, productivity is increased. It is possible to maintain high productivity without incurring a situation of lowering.

  FIG. 8 shows a case where a document longer than the case where the leading edge of the document reaches the sensor Sn1 (FIG. 6) is conveyed before the trailing edge of the document passes through the sensor Sn3. In this case, the detection result (confirmed size information) of the size confirmation control means is “a predetermined size or more”. When such a document is being conveyed, even if the sensor Sn1 detects the leading edge of the document, the trailing edge of the document does not pass through the separation portion (the nip between the reverse roller 10 and the feed belt 9) (the sensor Sn3 is Therefore, if the feeding of the next document starts at this point, the previous document and the next document are double-fed (conveyed in a state where two sheets are overlapped with each other). It is inconvenient. Therefore, the feeding of the next document starts after the sensor Sn3 detects the trailing edge of the document.

  Details of the control in the present invention will be described with reference to FIG. 9 (9a, 9b). This control flow is a flow when the sheet size mixed mode is not set (released), and is the basis of the present invention. Incidentally, when the sheet size mixed loading mode is set, the pickup roller 7 starts to descend at the timing when the sensor Sn3 detects the trailing edge of the document, and the feeding process of the next document on the document table 2 is performed.

First, the sheet feeding control for the first and second sheets of the document bundle will be described in S1 to S9.
Waiting for the arrival of a paper feed start command requested from the main body control unit 111 of FIG. 2 through the I / F 107 (No in S1). When the command arrives (Yes in S1), the pickup roller 7 starts to descend to prepare for starting separation of the bundle of documents, and after the lowering process of the pickup roller 7 is completed, the first document feeding operation is started. (S2).

  After the trailing end of the first original is detected by the sensor Sn3 (Yes in S3), the pickup roller 7 starts to descend to prepare for starting separation of the second original (S4), and the lowering process of the pickup roller 7 is completed. After that, the feeding operation of the second original is started (S5).

  Further, when the trailing end of the document is detected by the sensor Sn3, fixed size information (length in the transport direction) of the first document is acquired (S6). The fixed size information acquisition means is known, and acquires fixed size information in the manner described above.

  If the confirmed size information acquired in S6 is equal to or larger than a predetermined value (threshold value + margin) set in advance (No in S7), the leading edge detection by the sensor Sn1 is invalid (starting the feeding operation for the third and subsequent sheets) Not used) (S9), and the process proceeds to S10. If the determination result in S7 is less than a predetermined value (Yes in S7), the leading edge detection by the sensor Sn1 is validated (used for starting the feeding operation for the third and subsequent sheets) in S8. That is, the timing for starting the feeding operation for the third and subsequent sheets is determined based on the determined size information of the first document.

  Usually, the determination using the fixed size information is performed only once (only the first original) at the start of continuous reading of the original bundle, and at this time during continuous feeding of the original bundle. However, the sheet feeding start timing may be determined for each fixed size information acquired in each sheet conveyance. In other words, the start timing of the (N + second) document feeding operation may be determined based on the determined size information of the Nth document.

  The above is the paper feed control for the first and second originals in the original bundle. As a conclusion, the timing for starting the feeding operation of the second original does not depend on the size of the first original. This is always performed at the timing when the sensor Sn3 detects the trailing edge of the first document.

The flow from S10 is a flow for controlling the start timing of feeding of the third and subsequent sheets according to the feature of the present invention for improving productivity.
In S10, it is confirmed whether the sensor Sn2, which is the second sheet leading edge detection means, detects the leading edge of the document and whether the leading edge detection is set to be valid in S8 / S9. If the result is Yes, the abnormality detection process is started in S18 (details will be described in the description of FIG. 10), and the pickup roller 7 starts to descend in S12. If the confirmation result in S10 is No, it is subsequently confirmed in S11 whether the sensor Sn3, which is the trailing edge detection means, has detected the trailing edge of the document. If the result is Yes, the process proceeds to S12, and the lowering control of the pickup roller 7 is started. If the confirmation result in S11 is also No, the process returns to S10, and this control is repeated until Yes in S10 or S11.

  Next, the process continues to S13. In S13, the sensor Sn1, which is the first sheet leading edge detection means, detects the leading edge of the document, and confirms whether the leading edge detection is enabled in S8 / Sn9. If the confirmation result is Yes, the abnormality detection process is started in S19, and the process proceeds to S15. If the answer is No in S13, it is checked in S14 whether the sensor Sn3 as the trailing edge detection means has detected the trailing edge of the document (if detected in S11, S14 is automatically detected). If the confirmation result is Yes, the process proceeds to S15. If the result of S14 is No, the process returns to S13, and the confirmation is repeated until either S13 or S14 becomes Yes. In S15, it is confirmed whether or not the lowering process of the pickup roller 7 started in S12 is completed. For the determination, known methods such as a method of determining whether or not a certain time has elapsed since the start of driving, a method based on sensor detection, and a combination thereof can be used. If No in S15, the process waits until completion. If Yes in S15, the process proceeds to S16, and the driving of the pickup roller 7 and the paper feed belt 9 is started to start the feeding operation of the next original.

  Thereafter, in S17, it is confirmed whether or not the next document still exists. If there is a next document (Yes in S17), the process proceeds to S20. Here, it is checked whether or not the leading edge of the document started feeding in S16 has reached the sensor Sn3 which is the trailing edge detection means, and waits until it reaches (while S20 is No). When the tip reaches the sensor Sn3 (Yes in S20), the process returns to S10 and the flow so far is repeated. If it is determined in S17 that there is no next original (No in S17), this process is terminated.

  Here, the control (S10 to S12) when using the sensor Sn2 as the second sheet leading edge detection means for the pickup lowering process and the control when using the sensor Sn1 as the first sheet leading edge detection means for the paper feed start process. Although the case where both are performed about (S13-S16) was described, only either one can also be performed according to a structure or other requirements. In that case, the control flow is such that S10 or S13 in the flow shown in FIG. 9 is omitted and the determination result is fixed at No.

  FIG. 10 shows the details of the abnormality detection process (S18, S19) in FIG. If the leading edge detection by the sensor Sn1 is not effective in S10 or S13, it is determined whether the trailing edge of the document is detected by the trailing edge detection means (sensor Sn3). Therefore, when the document bundle is not mixedly loaded, the fixed size information can be acquired correctly, and the sensor Sn3 detects the trailing edge of the document when a predetermined drive is performed as long as the detection by the sensors Sn1 and Sn2 is performed. It should be. If the trailing edge detection is not recognized even after the predetermined driving, there is a possibility that the sheet size of the original bundle is mixed or the detection means in the conveyance path is broken and the fixed size information is not correctly acquired. Suspected. If conveyance is continued as it is, the preceding document will collide with the subsequent document that starts feeding with the detection of the leading edge as a trigger, and it will interfere with document conveyance.Therefore, it is necessary to stop conveyance control immediately. The control flow is the flow shown in FIG.

  This control flow is called when the abnormality detection process is started in S18 or S19 of FIG. 9, and is processed in parallel with the flow of FIG. Depending on the document size and the time between documents, the controls shown in FIG. 9 to FIG. 10 may be called up, and the plurality of controls may be processed independently and in parallel.

  First, the drive pulse count of the drive motor when abnormality detection is started is acquired and recorded as a reference value (S31). That is, in FIG. 9, the state when the first sheet leading edge detecting means (sensor Sn1) or the second sheet leading edge detecting means (sensor Sn2) detects the leading edge of the document is recorded. Next, it is confirmed whether the sensor Sn3 has detected the trailing edge of the document (S32). If this result is Yes, it is determined that the conveyance is normal (S34), and this flow is ended. If the determination result in S32 is No (the trailing edge of the document has not yet reached the sensor Sn3), in S33, the current drive pulse number increases by a predetermined amount (Th) or more from the reference pulse count stored in S31. Check if you did. The determination threshold Th at this time is obtained by subtracting the distance from the position on the transport path of the sensor Sn1 to the sensor Sn3 from the distance from the position on the transport path of the sensor Sn1 to the separation unit (the paper feed belt 9 and the reverse roller 10). Or a distance obtained by subtracting the distance from the position on the Sn2 conveyance path to the sensor Sn3 from the distance from the position on the Sn2 conveyance path to the pickup roller 7 and using a margin added to it. .

  If the determination result in S33 is No, the process returns to S32 and continues. If the determination result in S33 is Yes, it is determined that the conveyance is abnormal (S35), and each drive source used for document conveyance is stopped (S36). As described above, since the failure of the detection means on the conveyance path is suspected, the fact is displayed on the operation unit 108 using means such as notifying the main body control unit 111 through the I / F 107. The user or the person in charge of machine maintenance is notified of the details of the suspected cause (S37), and this control is terminated. As the cause details, a plurality of different sizes may be mixed in the document bundle on the document table, or the detection unit may be broken.

  The overall mechanism of an image forming apparatus such as a copying machine or facsimile equipped with an ADF equipped with a sheet feeding apparatus according to the present invention is basically the same as that of the conventional one, and forms an image around a photosensitive member. For example, an image information reading device is disposed below the ADF, and a predetermined device necessary for the purpose, for example, a charging unit, an exposure unit, and a developing unit is provided.

7 Pickup roller 9 Paper feed belt 10 Reverse roller 11 Abutment sensor 12 Pullout roller 14 Intermediate roller Sn1 First sheet leading edge detection sensor Sn2 Second sheet leading edge detection sensor Sn3 Sheet trailing edge detection sensor

JP-A-9-301573

Claims (8)

  Sheet stacking means for stacking sheets, separation feeding means for separating and feeding the stacked sheets one by one, sheet calling means for sequentially feeding the stacked sheets to the separation feeding means, and separation A sheet feeding apparatus, comprising: a conveying unit that conveys a sheet to a reading position in order to read image information of a fed sheet; and a sheet discharging unit that discharges the sheet from which the image information has been read. A trailing edge detecting means for detecting the trailing edge of the sheet that has passed through the feeding means, and a first edge disposed downstream of the trailing edge detecting means in the sheet conveying direction and at a predetermined distance from the separation feeding means. A sheet leading edge detecting means; a second sheet leading edge detecting means disposed downstream of the trailing edge detecting means in the sheet conveying direction and at a predetermined distance from the sheet calling means; and a sheet leading edge. And a control means for determining the length in the conveyance direction of the sheet being conveyed from the detection result of the second sheet leading edge detection means, and the control means determines that the conveyance sheet is less than a specific sheet size. When it is determined that there is, the start of feeding of the next sheet on the sheet stacking unit is detected when the front end of the front sheet is detected by the first sheet front end detection unit or when the front end of the front sheet is detected by the rear end detection unit. A sheet feeding apparatus characterized by that one of which is earlier.   When the trailing edge detection means detects the trailing edge of the front sheet, or when the control means determines that the size is less than the specific sheet size, the second sheet leading edge detection means detects the leading edge of the front sheet. The sheet feeding device according to claim 1, wherein the sheet calling unit is brought into contact with the stacked sheets at any time earlier.   When the trailing edge detection means detects the trailing edge of the front sheet, or when the control means determines that the size is less than the specific sheet size, the second sheet leading edge detection means detects the leading edge of the front sheet. The sheet calling unit is brought into contact with the stacked sheets, whichever is earlier, and then the sheet calling unit is driven to start feeding the next sheet on the sheet stacking unit. The sheet feeding apparatus according to claim 1.   When the “sheet size mixed loading mode” indicating that a plurality of sheets of different sizes are stacked on the sheet bundle stacked on the sheet stacking unit is set, regardless of the determination by the control unit, When the trailing edge of the sheet is detected by the trailing edge detection means, the sheet calling means is brought into contact with the stacked sheet, and after completion of the contact, the sheet calling means is driven to feed the next sheet on the sheet stacking means. 2. The sheet feeding apparatus according to claim 1, wherein the sheet feeding device is started.   When the control unit determines that the transport sheet is smaller than a specific sheet size, the front end of the transport sheet is moved to the first sheet earlier than the trailing end detection unit detects the rear end of the transport sheet. When the leading edge detection unit detects and the feeding of the next sheet on the sheet stacking unit is started, the driving amount of the sheet conveyance driving source is counted from the detection of the conveyance sheet leading edge by the first sheet leading edge detection unit. An abnormality detection means for recognizing a conveyance abnormality when the trailing edge detection means does not detect the trailing edge of the conveyance sheet even if a predetermined value is exceeded, and the sheet conveyance is stopped when a conveyance abnormality is recognized. The sheet feeding apparatus according to any one of claims 1 to 3.   The sheet feeding apparatus according to claim 5, further comprising a notification unit that notifies a user when the abnormality detection unit recognizes a conveyance abnormality and stops sheet conveyance.   A sheet reading apparatus including the sheet feeding apparatus according to claim 1.   An image forming apparatus including the sheet feeding device according to claim 1.

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