JP2009035399A - Double feed detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly detect occurrence of double feed in a double feed detector capable of detecting double feed of paper sheets to be conveyed by using an optical sensor. <P>SOLUTION: In a paper feed device 10, an optical sensor 22 detects each transmitted light intensity in a plurality of sections of paper sheets to be conveyed by detecting the transmitted light intensity of a paper sheet in a plurality of times while the paper sheet is conveyed. An electronic control unit 28 selects three sections to be used for detecting double feed based on each transmitted light intensity La in a plurality of sections detected in a reference paper sheet to be conveyed in a preset mode. The electronic control unit 28 determines whether or not double feed occurs in the paper sheet to be conveyed by comparing the reference transmitted light intensity L<SB>THR</SB>calculated from the transmitted light intensity La in three sections with the transmitted light intensity Lb in three sections in the paper sheet to be conveyed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a double feed detection device, and more particularly, to a double feed detection device that detects double feed of a sheet conveyed using an optical sensor.

A multifeed detection device using an optical sensor is known. In such a double feed detection device, the occurrence of double feed is detected by utilizing the fact that the amount of light transmitted through the paper decreases when the paper is double fed. At this time, for example, a multifeed detection device that samples the amount of light received by the light receiving sensor in a plurality of sample ranges by a predetermined number of samples, and sets a plurality of sample ranges to an odd number, and the sample range in which double feed is detected is a majority. In this case, there has been proposed a double feed detection device that determines double feed. In addition, there has been proposed a double feed detection device that determines double feed when a double feed detection result is continuously obtained from a sample range on the leading end side of a sheet (see, for example, Patent Document 1).
JP 2001-63872 A

  For example, on a printed paper, a dark color may be printed depending on the location on the paper. In such a portion where a dark color is printed, the amount of transmitted light is low, and thus the amount of transmitted light is not significantly reduced by double feeding. Further, in a portion where a dark color is printed, the amount of transmitted light varies greatly due to variations in print density. For this reason, when the location where the dark color was printed in the technique described in the above-mentioned patent document becomes the sample range, it is difficult to determine the double feed.

  Therefore, the present invention has been made to solve the above-described problems, and an object thereof is to accurately detect the occurrence of double feed.

  In order to solve the above problems, a multifeed detection device according to an aspect of the present invention includes an optical sensor that detects light transmitted through a sheet by irradiating the conveyed sheet with light, and a multifeed on the sheet to be conveyed. A double feed determination unit for determining whether or not the occurrence of The optical sensor detects the amount of light transmitted through the paper a plurality of times while the paper is being conveyed, thereby detecting the amount of light transmitted at each of the plurality of detected locations on the paper being conveyed. Based on the transmitted light amount of each of the plurality of detected portions detected on the reference sheet, which is a sheet conveyed to obtain the reference transmitted light amount used for determining the occurrence of feeding, at least one of the plurality of detected portions. The selected transmitted light amount calculated based on the transmitted light amount of the reference sheet detected at the selected detected position of the reference sheet, and the selected detected detected object of the conveyed paper By comparing the amount of transmitted light detected at the location, it is determined whether or not double feeding has occurred in the conveyed paper.

  According to this aspect, it is possible to select a detection location suitable for double feed detection and perform a multifeed determination using the transmitted light amount detected at the detection location. For this reason, it is possible to accurately detect the occurrence of double feeding.

  The double feed determination unit may select a detected location where the detected transmitted light amount is within a predetermined range. According to this aspect, for example, it is possible to select a detection location where the detected transmitted light amount is within a predetermined range suitable for double feed detection, and it is possible to more accurately detect the occurrence of double feed.

  The double feed determination unit may select a predetermined number of detected locations closer to the leading end of the paper that is the leading portion of the paper when being conveyed. According to this aspect, since the double feed is detected based on the transmitted light amount at the detection portion close to the leading end of the sheet, it is possible to quickly detect the occurrence of the double feed.

  When there are a predetermined number or more of detected locations where the detected transmitted light amount is within the first predetermined range, the double feed determination unit is conveyed among the detected locations where the detected transmitted light amount is within the first predetermined range. When a predetermined number of detected locations closer to the front end of the paper, which is the leading portion of the paper, are selected, and the detected locations where the detected transmitted light amount is within the first predetermined range are less than the predetermined number, detection is performed. All the detected locations where the transmitted light amount is within the first predetermined range are selected, and the detected transmitted light amount is within the second predetermined range that defines a range of transmitted light amount lower than the first predetermined range. Of the detected locations, the number of detected locations closer to the front end of the sheet may be selected by a deficient number obtained by subtracting the number of detected locations already selected from a predetermined number. According to this aspect, it is possible to preferentially select a detected portion whose transmitted light amount is within an appropriate range by detecting double feeding. Therefore, it is possible to more accurately detect the occurrence of double feed.

  The double feed determination unit selects two or more detected locations from the plurality of detected locations based on the transmitted light amounts of the detected locations detected on the reference sheet, and the two or more detected locations on the reference sheet. The sum of the transmitted light amounts detected at the two or more detected locations in the conveyed paper is lower than the sum of the reference transmitted light amounts calculated based on the transmitted light amount of the reference sheet detected for each of the detected locations. It may be determined whether or not double feeding has occurred on the conveyed paper. Thus, by selecting a plurality of detected portions, it is possible to realize more accurate double feed detection.

  Further, the double feed determination unit selects two or more detected locations from among the detected locations based on the transmitted light amounts of the detected locations detected on the reference sheet, and The reference transmitted light amount is calculated based on the transmitted light amount of the reference sheet detected for each of the two or more detected locations, and the detected paper is detected from the calculated reference transmitted light amount for each of the two or more detected locations. By determining whether or not the amount of transmitted light is low, it may be determined whether or not double feeding has occurred on the conveyed paper. By selecting a plurality of detected portions in such a manner, it is possible to realize more accurate double feed detection.

  According to the present invention, it is possible to accurately detect the occurrence of double feeding.

  Hereinafter, embodiments of the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.

  FIG. 1 is an overall configuration diagram schematically illustrating a sheet feeding device 10 according to the present embodiment. The sheet feeding device 10 includes a sheet feeding mechanism 12, an optical sensor 22, an electronic control unit 28, and a control panel 30.

  The paper feed mechanism 12 is provided in the upper right part of the apparatus in a paper storage unit for storing stacked paper. The paper storage unit is provided with a paper feed table (not shown), on which papers stacked on the paper feed table are placed. The paper feed table is configured to be movable up and down. A paper height sensor (not shown) is provided at the upper part of the paper storage unit, and the elevation of the paper feed table is controlled so that the uppermost paper of the stacked paper is positioned at a predetermined height. . The paper feeding mechanism 12 is disposed slightly above the uppermost paper of the stacked paper.

  The paper feed mechanism 12 includes an air paper feed mechanism 14 and a pair of transport rollers 16. The air sheet feeding mechanism 14 has a plurality of sheet feeding belts and two rollers. Each of the plurality of paper feeding belts has the same width and the same circumferential length, and is mounted on the outer circumference of the two rollers so as to be arranged at equal intervals in the axial direction. The paper feed mechanism 12 is disposed so that the axial direction of the rollers is directed in the front-rear direction of the apparatus and the two rollers are horizontally aligned in the left-right direction. One of the rollers is driven by the transport motor 20.

  The air feeding mechanism 14 is also provided with an air suction mechanism. The air suction mechanism has a fan, and when the fan operates, an air flow for sucking air from the lower surface of the paper feeding belt is formed. The air flow passage is provided with a lid, and this lid closes and opens the opening provided in the air flow passage in response to the operation and stoppage of the sheet feeding solenoid 18.

  When the paper feed solenoid 18 is actuated, the opening provided in the air flow passage is closed to form a strong air flow that sucks air from the lower surface of the paper feed belt, and the uppermost paper of the stacked paper is fed. Adsorbed to the lower surface of the paper belt. The sheet adsorbed on the lower surface of the sheet feeding belt is sent out in the right direction of the apparatus as the sheet feeding belt is driven. The pair of transport rollers 16 are arranged in the vertical direction on the downstream side of the air feeding mechanism 14 in the paper transport direction (hereinafter referred to as “downstream side”). One of the pair of transport rollers 16 is also driven by the transport motor 20. The sheet sent out by the air feeding mechanism 14 is sandwiched by a pair of transport rollers 16 and further transported in the right direction of the apparatus.

  When the operation of the paper feed solenoid 18 is stopped, the opening provided in the air flow passage is opened so that the air flow for sucking air from the lower surface of the paper feed belt cannot adsorb the paper to the lower surface of the paper feed belt. Weakened. For this reason, when the operation of the paper feed solenoid 18 is stopped, the feeding of the uppermost paper of the stacked paper is stopped. Instead of the air feeding mechanism 14, a so-called friction type feeding mechanism that feeds the uppermost sheet of the stacked sheets by the frictional force of the roller surface may be employed.

  An optical sensor 22 is provided between the air feeding mechanism 14 and the transport roller 16. The optical sensor 22 includes a light emitting element 24 and a light receiving element 26. The light emitting element 24 is disposed above the paper conveyance path between the air feeding mechanism 14 and the conveyance roller 16 and irradiates light by infrared rays toward the paper conveyance path. The light receiving element 26 is disposed below the paper conveyance path between the air feeding mechanism 14 and the conveyance roller 16, receives light emitted by the light emitting element 24, and outputs a signal corresponding to the intensity of the received light. To do.

  The paper feed solenoid 18, the transport motor 20, and the optical sensor 22 are connected to the electronic control unit 28. The electronic control unit 28 includes a CPU that executes various arithmetic processes, a ROM that stores various control programs, a RAM that is used as a work area for data storage and program execution, and the like. The electronic control unit 28 controls the feeding of the uppermost sheet of the stacked sheets by switching the supply and stop of power supply to the sheet feeding solenoid 18 to turn the sheet feeding solenoid 18 on and off. The electronic control unit 28 also controls the operation of the transport motor 20 by supplying a drive signal to the paper feed mechanism 12 and controls the drive of the paper feed belt of the air paper feed mechanism 14 and the pair of transport rollers 16. . At this time, the electronic control unit 28 receives a pulse signal indicating the rotation speed from the transport motor 20. Further, the electronic control unit 28 controls on / off of the light emitting element 24, further receives a signal from the light receiving element 26, and is conveyed with the amount of light irradiated by the light emitting element 24 using the received signal. The amount of light transmitted through the paper to be detected is detected. A control panel 30 is also connected to the electronic control unit 28.

  FIG. 2 is a functional block diagram of the sheet feeding device 10 according to the present embodiment. In FIG. 2, the electronic control unit 28 depicts functional blocks realized by cooperation of hardware such as CPU, ROM, and RAM, and software. Therefore, these functional blocks can be realized in various forms by a combination of hardware and software.

The electronic control unit 28 includes a conveyance control unit 40, a double feed determination unit 44, a display control unit 46, and a storage unit 48. The conveyance control unit 40 controls the sheet feeding from the stacked sheets by controlling on / off of the sheet feeding solenoid 18 and the operation of the conveyance motor 20. Multifeed detection unit 44 calculates the reference transmitted light amount L _THR used for determining the double feed occurrence, by using the calculated reference transmitted light amount L _THR, the sheet conveyed, overlap a plurality of sheet transport It is determined whether or not a double feed to be performed has occurred. As described above, the optical sensor 22 and the electronic control unit 28 function as a double feed detection device that determines whether or not a double feed has occurred in the conveyed paper. The display control unit 46 displays information on the display 32 provided in the control panel 30. The storage unit 48 is configured by a storage device such as a hard disk or a flash memory that retains stored contents even when power supply is stopped.

FIG. 3 is a flowchart illustrating a procedure for setting the reference transmitted light amount in the sheet feeding device 10 according to the present embodiment. The display 32 of the control panel 30 is configured by an input touch panel. The user can select a preset mode by performing an input operation on the display 32. In the preset mode, detection of double feeding is not performed, and processing for acquiring the reference transmitted light amount L _THR is performed.

When the user presses the start button with the preset mode selected (S10), the paper feed mechanism 12 operates the air paper feed mechanism 14 and the transport roller 16 to remove the uppermost paper from the stacked paper. The paper feeding process for feeding is started (S12). Hereinafter, in the preset mode, a sheet transported to acquire the reference transmitted light amount L _THR is referred to as a reference sheet. The optical sensor 22 detects the transmitted light amount of the reference sheet being conveyed, and the double feed determination unit 44 uses the detection result of the optical sensor 22 to perform a transmitted light amount sampling process (S14).

  In the transmitted light amount sampling process, the double feed determination unit 44 first uses the detection result of the optical sensor 22 to determine whether, for example, the light amount received by the light receiving element 26 has decreased by a predetermined amount from the light amount irradiated by the light emitting element 24. By determining, it is determined whether or not the leading edge of the reference sheet has passed the detection location of the optical sensor 22. For this reason, the optical sensor 22 also functions as a paper transport sensor that detects the leading edge of the paper being transported.

  When it is determined that the leading edge of the reference sheet has passed the detection point of the optical sensor 22, the double feed determination unit 44 first outputs a pulse signal from the transport motor 20 after the leading edge of the reference sheet has passed the detection point of the optical sensor 22. Is set as the sampling reference time. Next, the double feed determination unit 44 receives the 21st pulse signal using the pulse signal at the sampling reference as the first pulse signal, and then receives the light 12 times at equal time intervals between two adjacent pulse signals. The amount of light transmitted through the reference sheet detected by the sensor 22 is acquired as a sample value. Hereinafter, the range of the reference sheet from which twelve sample values are acquired will be described as a “section” as a portion to be detected by the optical sensor 22. After receiving the 21st pulse signal, the optical sensor 22 detects the amount of light transmitted through the reference sheet a plurality of times while the reference sheet is being conveyed. Until the twelve sample values cannot be acquired during the interval, the amount of transmitted light in each of the plurality of intervals arranged in parallel with the sheet conveyance direction on the reference sheet is detected. In each section, the double feed determination unit 44 calculates a total of 10 of the acquired 12 sample values excluding the maximum value and the minimum value as the transmitted light amount La (S16).

When the transmitted light amount La is calculated, the multi-feed determining unit 44 is close to the leading end portion of the sheet being transported in a section where the transmitted light amount La is equal to or less than the first threshold value L1 and equal to or greater than the second threshold value L2. These are sequentially selected from the two (S18). Data indicating the first threshold value L1 and data indicating the second threshold value L2 are stored in the storage unit 48 in advance. When selecting a section where the transmitted light amount La is equal to or less than the first threshold value L1 and equal to or greater than the second threshold value L2, the double feed determination unit 44 determines whether or not the selection of a total of three sections has been completed by selecting the section. Determine (S20). When the selection of the three sections is completed (Y in S20), the storage unit 48 stores section identification information for identifying the selected three sections. Further, the double feed determination unit 44 calculates the reference transmitted light amount L _THR of each of the three sections by dividing each of the transmitted light quantities La of the three sections selected as locations used for the double feed determination by 1.5. To do. The storage unit 48 stores the calculated reference transmitted light amount L _THR for each of the three sections, and ends the processing in this flowchart. In this embodiment, three sections are selected. However, the number of sections to be selected as a section to be used for double feed detection is not limited to three. One, two, or four or more predetermined sections are selected. May be the number.

If the selection of the three sections is not completed even after determining whether or not the transmitted light amount La is equal to or less than the first threshold L1 and equal to or greater than the second threshold L2 for all the sections (N in S20), double feed determination The unit 44 sequentially selects sections in which the transmitted light amount La is less than the second threshold value L2 and equal to or greater than the third threshold value L3 from the side closer to the leading edge of the sheet (S22). Data indicating the third threshold value L3 is stored in the storage unit 48 in advance. When selecting a section in which the transmitted light amount La is less than the second threshold L2 and greater than or equal to the third threshold L3, the double feed determination unit 44 selects a section, thereby including a total of three sections including the section selected in S18. It is determined whether or not selection has been completed (S24). When the selection of the three sections is completed (Y in S24), the storage unit 48 uses the section identification information for identifying the selected three sections, and the reference transmission for each of the three sections calculated by the above-described calculation method. The light quantity L _THR is stored, and the processing in this flowchart is terminated. As described above, when the number of sections in the transmitted light amount range shown in S18 is less than 3, the double feed determination unit 44 has a calculated transmitted light amount La that is lower than the transmitted light amount range shown in S18. The number of sections within the range is selected by a shortage number obtained by subtracting the number of sections already selected from 3 which is the total number to be selected.

  If selection of the three sections is not completed even after determining whether or not the transmitted light amount La is less than the second threshold L2 and greater than or equal to the third threshold L3 for all sections (N in S24), double feed determination The unit 44 includes a section where the transmitted light intensity La is less than the third threshold L3 and equal to or more than the fourth threshold L4 until the selection of a total of three sections including the sections selected in S18 and S22 is completed. Are sequentially selected (S26). Data indicating the fourth threshold L4 is stored in the storage unit 48 in advance. Here, the fourth threshold value L4 is normally set to a value obtained experimentally so that the transmitted light amount La does not become a numerical value less than that. Further, the paper feeding device 10 may be configured such that the user can select the thin paper mode by performing an input operation on the control panel 30. When the thin paper mode is selected by the user, the double feed determination unit 44 may set a value smaller than that in the normal mode as the fourth threshold value L4.

When the selection of a total of three sections is completed, the storage unit 48 stores section identification information for identifying the selected three sections, and the reference transmitted light amount L _THR of each of the three sections calculated by the above-described calculation method. Then, the process in this flowchart is terminated. In this way, the double feed determination unit 44 may add up the number of sections within the transmitted light amount range indicated by S18 and the number of sections within the transmitted light amount range indicated by S22. If it is less than 3, the number of sections already selected from three, which is the total number for selecting the sections in which the calculated transmitted light quantity La is within the transmitted light quantity range lower than the transmitted light quantity range shown in S22. Select only the number of deficits you have drawn. The display control unit 46 determines whether the transmitted light amount La is less than the third threshold value L3 and equal to or greater than the fourth threshold value L4 for all the sections when the selection of the three sections is not completed. An error message may be displayed on the display 32.

  Here, the section selection method in the example shown in FIG. 4 will be described. As shown in FIG. 4, in this example, as a result of calculating the transmitted light amount La of each section of the reference sheet, the transmitted light amount La of the section 1 is 110 lumen seconds, the transmitted light amount La of the section 2 is 500 lumen seconds, and the section 3 The transmitted light amount La is 250 lumen seconds, the transmitted light amount La in the section 4 is 100 lumen seconds, the transmitted light amount La in the section 5 is 1000 lumen seconds, and the transmitted light amount La in the section 6 is 200 lumen seconds. Also. It is assumed that the first threshold L1 is 2200 lumen seconds, the second threshold L2 is 300 lumen seconds, the third threshold L3 is 150 lumen seconds, and the fourth threshold L4 is 90 lumen seconds.

  In S18, sections in which the transmitted light amount La satisfies 2200 lumen seconds ≧ transmitted light amount La ≧ 300 lumen seconds are sections 2 and 5. Therefore, the multifeed determination unit 44 first selects the section 2 and the section 5. However, even after determining whether or not the transmitted light amount La is 2200 lumen seconds ≧ transmitted light amount La ≧ 300 lumen seconds until the section 6, only two sections are selected, and the selection of the three sections is completed. do not do. For this reason, the double feed determination unit 44 then proceeds to S22. In S22, sections in which the transmitted light amount La satisfies 300 lumen seconds> transmitted light amount La ≧ 150 lumen seconds are sections 3 and 6. However, since two sections have already been selected, and it is only necessary to select one section that is insufficient in order to complete the selection of the three sections, the double feed determination unit 44 selects the section 3 and the section. 6, the section 3 closer to the front end of the sheet is selected as the section used for the double feed determination. Therefore, in the example illustrated in FIG. 4, the sections 2, 3, and 5 are selected as the sections used for the multifeed determination.

  FIG. 5 is a flowchart illustrating a sheet feeding procedure in the continuous sheet feeding mode in the sheet feeding device 10 according to the present embodiment. The user can select the continuous paper feed mode by performing an input operation on the display 32. When the user presses the start button with the continuous paper feed mode selected (S30), the paper feed mechanism 12 starts the paper feed process by operating the air paper feed mechanism 14 and the transport roller 16 (S32). . When sheet feeding is started, the optical sensor 22 detects the amount of transmitted light of the conveyed sheet. The double feed determination unit 44 uses the detection result of the optical sensor 22 to perform a transmitted light amount sampling process (S34), and calculates a transmitted light amount Lb. The procedure for calculating the transmitted light amount sampling process and the transmitted light amount Lb is the same as the procedure for calculating the transmitted light amount La in the preset mode.

When the transmitted light amount Lb is calculated, the double feed determination unit 44 stores the total of the transmitted light amounts Lb of the three sections selected as the sections used for the double feed determination in the conveyed paper in the storage unit 48. total reference transmitted light amount L _THR, that is, whether pre-calculated reference transmitted light amount L _THR sum more based on the respective amount of transmitted light La in the same three intervals of the reference paper in preset mode (S36) . If the total amount of transmitted light Lb in the three sections of the conveyed paper is greater than or equal to the total amount of reference transmitted light L _{THR in} the three sections of the reference sheet (Y in S36), the double feed determination unit 44 generates a double feed. The conveyance control unit 40 continues to convey the sheet as it is.

  At this time, the conveyance control unit 40 subtracts from the total conveyance number input by the user and determines whether or not the counter value indicating the number of remaining sheets to be conveyed is zero. It is determined whether the sheet determined not to be the last sheet to be transported (S38). If it is not the last sheet (N in S38), the conveyance control unit 40 decrements the counter value by 1, and returns to the process in S32 to send out the next sheet. In the case of the last sheet (Y in S38), the conveyance control unit 40 stops the operation of the sheet feeding mechanism 12 without sending out the next sheet, and ends the processing in this flowchart.

When the total amount of transmitted light Lb in the three sections of the conveyed paper is less than the total amount of reference transmitted light L _{THR in} the three sections of the reference sheet (N in S36), the double feed determination unit 44 determines that double feed has occurred Determination is made, and the conveyance control unit 40 stops the operation of the conveyance motor 20 and stops the feeding of the paper (S40). Further, the display control unit 46 displays a warning message on the display 32 to notify the user that double feed has occurred (S42). At this time, the display control unit 46 may display on the display 32 a guide screen illustrating the method of removing the double-fed paper. When the warning message is displayed on the display 32, the processing in this flowchart is temporarily terminated. When the double-fed paper is removed by the user and the start button is pressed again, the process is resumed from S30 for the remaining number of sheets to be transported.

  The present invention is not limited to the above-described embodiment. Various modifications such as design changes can be added to the above-described embodiments based on the knowledge of those skilled in the art, and embodiments to which such modifications are added can also be included in the scope of the present invention. . Here are some examples.

In a modification, for each reference sheet of a bundle of sheets composed of a plurality of reference sheets, three sections used for double _{feed detection} are selected and the reference transmitted light amount L _THR is calculated. Specifically, after the preset mode is selected and the number of sheets is input, when the user presses the start button, the paper feed mechanism 12 sets the input number of sheets from the stacked sheets as the reference sheet. Sequentially. The multi-feed determination unit 44 performs the processing of S14 to S24 for each of the plurality of sheets fed out, and the storage unit 48 identifies the order of feeding and the three selected sections for each of the plurality of sheets. And the calculated reference transmitted light amount L _THR are stored in association with each other.

Next, when the start button is pressed in the continuous paper feed mode, the double feed determination unit 44 corresponds to the total amount of transmitted light Lb in the selected three sections in the transported paper in the order in which the paper is sent out. It is determined whether or not double feeding has occurred by determining whether or not the total amount of the reference transmitted light amount L _THR of the three sections of the attached reference sheet is equal to or greater. When the conveyance of the number of sheets constituting the sheet bundle is completed, the double feed determination unit 44 resets the delivery order of the next paper to be sent out to 1 and repeats this process further. The double feed determination unit 44 repeats the above-described processing until the conveyance of the set number of sheet bundles input by the user is completed. Thereby, for example, it is possible to accurately detect double feeding even for a sheet bundle formed by overlapping sheets on which different images are recorded.

In another variation, in the preset mode, the multifeed determination unit 44 determines a predetermined number of sections (two or more of the plurality of sections) based on the transmitted light amount La of each of the plurality of sections detected on the reference sheet. For example, three sections) are selected, and the reference transmitted light amount L _THR is calculated based on the transmitted light amount La of the reference sheet detected for each of the selected predetermined number of sections in the reference sheet. The storage unit 48 stores the reference transmitted light amount L _THR calculated for each of a predetermined number of sections selected as sections used for double _{feed detection in association} with section identification information indicating the corresponding sections. Next, in the continuous paper feed mode, the multi-feed determination unit 44 calculates the transmitted light amount Lb of two or more sections selected in the preset mode on the transported paper, and transmits each of the selected predetermined number of sections. It is determined whether the light amount Lb is equal to or greater than the reference transmitted light amount L _THR . The multi-feed determining unit 44 determines that _multi- feed has occurred in the conveyed paper when the transmitted light amount Lb is less than the reference transmitted light amount L _THR in all selected sections.

The multi-feed determination unit 44 overlaps the conveyed paper when the transmitted light amount Lb is less than the reference transmitted light amount L _{THR in the} reference number of the selected predetermined number of sections. It may be determined that transmission has occurred. For example, when the multi-feed determination unit 44 selects three sections as sections to be used for multi-feed determination, and the transmitted light amount Lb is less than the reference transmitted light amount L _THR in two or more of the three sections. In addition, it may be determined that double feeding has occurred on the paper being conveyed. Thus, by comparing the amount of transmitted light Lb and the reference transmitted light amount L _THR at each of a plurality of sections, it is possible to detect accurately double feeding.

  In another modification, the multifeed determination unit 44 selects all sections in which the transmitted light amount La calculated for the reference sheet is within a predetermined light quantity range as sections to be used for multifeed detection regardless of the number of sections. May be. For example, when the multifeed determination unit 44 selects all sections in which the transmitted light amount La satisfies 2200 lumen seconds ≧ transmitted light amount La ≧ 150 lumenseconds as a section used for double feed detection, FIG. 4 illustrates. In the example, section 2, section 3, section 5, and section 6 are selected.

  In another variation, the double feed determination unit 44 determines that the number of detectable sections is equal to or greater than a predetermined number when the number of sections that can be detected by the optical sensor 22 in the reference sheet is less than a predetermined number due to a small paper size. A smaller number of sections than the case is selected as a section used for double feed detection. As a result, the possibility of selecting a section around the rear end of the sheet can be reduced, and rapid double feed detection can be realized.

1 is an overall configuration diagram schematically illustrating a sheet feeding device according to an embodiment. FIG. 3 is a functional block diagram of a sheet feeding device according to the present embodiment. 6 is a flowchart illustrating a procedure for setting a reference transmitted light amount in the sheet feeding device according to the present embodiment. It is a figure which shows the example of the transmitted light amount La in each area of a reference | standard paper. 6 is a flowchart illustrating a sheet feeding procedure in a continuous sheet feeding mode in the sheet feeding device according to the present embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Paper feeder, 12 Paper feed mechanism, 14 Air paper feed mechanism, 16 Conveyance roller, 18 Feed solenoid, 20 Conveyance motor, 22 Optical sensor, 24 Light emitting element, 26 Light receiving element, 28 Electronic control part, 30 Control panel, 32 display, 40 transport control unit, 44 double feed determination unit, 46 display control unit, 48 storage unit.

Claims (6)

An optical sensor that detects the amount of light transmitted through the paper by irradiating the paper to be conveyed;
A double feed determination unit that determines whether or not double feed has occurred in the conveyed paper;
With
The light sensor detects the transmitted light amount of each of the plurality of detected locations in the transported paper by detecting the transmitted light amount of the paper multiple times while the paper is transported,
The multi-feed determining unit is configured based on a transmitted light amount of each of a plurality of detected locations detected on a reference sheet that is a sheet conveyed to obtain a reference transmitted light amount used for determining the occurrence of multi-feed. At least one detected location is selected from the detected locations, and the reference transmitted light amount calculated based on the transmitted light amount of the reference sheet detected at the selected detected location of the reference sheet is conveyed. A double-feed detection device, characterized by determining whether or not a multi-feed has occurred on a conveyed paper by comparing the amount of transmitted light detected at the selected detected portion of the paper.   The multifeed detection device according to claim 1, wherein the multifeed determination unit selects a detected location where the detected transmitted light amount is within a predetermined range.   The multifeed detection device according to claim 2, wherein the multifeed determination unit selects a predetermined number of detected locations closer to the front end of the paper that is the leading portion of the paper when being conveyed. The multifeed determination unit
When there are a predetermined number or more of detected portions where the detected transmitted light amount is within the first predetermined range, the leading portion of the sheet when the detected transmitted light amount is conveyed among the detected portions where the detected transmitted light amount is within the first predetermined range Select a predetermined number of detected locations closer to the leading edge of the paper,
When the detected locations where the detected transmitted light amount is within the first predetermined range are less than the predetermined number, all detected locations where the detected transmitted light amount is within the first predetermined range are selected and detected. Among the detected locations where the transmitted light amount is within a second predetermined range that defines a transmitted light amount range lower than the first predetermined range, a detection location closer to the front end of the paper has already been selected from the predetermined number. 2. The multifeed detection device according to claim 1, wherein only a shortage number obtained by subtracting the number of detected portions is selected.   The multi-feed determination unit selects two or more detected locations from the plurality of detected locations based on the transmitted light amounts of the detected locations detected on the reference sheet, and the 2 in the reference sheet. From the sum of the reference transmitted light amounts calculated on the basis of the transmitted light amount of the reference sheet detected for each of the detected locations, the sum of the transmitted light amounts detected at the two or more detected locations on the conveyed sheet is calculated. The multifeed detection device according to claim 1, wherein it is determined whether or not a multifeed has occurred in the conveyed sheet by determining whether or not the sheet is low.   The multi-feed determination unit selects two or more detected locations from the plurality of detected locations based on the transmitted light amounts of the detected locations detected on the reference sheet, and the 2 in the reference sheet. A reference transmitted light amount is calculated on the basis of the transmitted light amount of the reference sheet detected for each of the above detected portions, and each of the two or more detected portions is detected on the conveyed sheet from the calculated reference transmitted light amount. 5. The multifeed detection apparatus according to claim 1, wherein it is determined whether or not a multifeed has occurred in the conveyed paper by determining whether or not the transmitted light amount is low. .

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