JP2015006951A - Conveyance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve accuracy of multi feeding determination in the case where printed paper is conveyed.SOLUTION: A stencil printer 1 includes: a paper feeding part 3 which conveys printed paper along a conveyance path; a paper sensor 4 which has a light emitting part 4a for emitting light to the conveyance path side and a light receiving part 4b arranged by facing the light emitting part 4a with the conveyance path being sandwiched in-between and receiving light from the light emitting part 4a; and a control unit 10 which generates a reference value for multi feeding determination at a plurality of sampling points preset with respect to the paper being conveyed on the basis of image data of a printed image of the paper being conveyed, which acquires a sample value corresponding to a light receiving amount of the light emitting part at the sampling points during the conveyance of the paper and which performs multi feeding determination of the paper by using the reference value and the sample value.

Description

  The present invention relates to a transport device that transports paper.

  2. Description of the Related Art Conventionally, there is known a technique for determining the presence or absence of so-called double feeding in which a plurality of sheets are conveyed in a superimposed manner.

  For example, in the paper transport device disclosed in Patent Document 1, the multi-feed determination unit includes the light transmittance set according to the paper type and the first sheet detected by the paper information detection unit which is a light transmission type sensor. The first sheet multi-feed determination is performed by comparing the light transmittance. For example, in the double feed of two sheets, the transmittance is about half that in the case of not double feed. For this reason, it is possible to determine multifeed based on the transmittance. When the first sheet is not a multi-feed, the multi-feed determining unit performs the subsequent multi-feed determination with reference to the detected transmittance of the first sheet. In this way, the paper transport device of Patent Document 1 improves the accuracy of double feed determination while enabling determination of double feed from the time of transport of the first sheet.

JP 2008-201512 A

  By the way, in a printing apparatus, printing may be performed on paper on which an image has been printed. For example, printing may be performed on the other side of a sheet on which the same image is printed on one side. In such a case, a plurality of printed sheets are conveyed from the paper feed table to the printing unit.

  Here, on the paper on which the image has been printed, the image portion is less likely to transmit light than the other portions. For this reason, in the image portion, the transmittance may decrease as in the case of double feeding. For this reason, in the technique of Patent Document 1, when a printed sheet is transported, there is a possibility that the accuracy of the multi-feed determination is lowered.

  The present invention has been made in view of the above, and an object of the present invention is to provide a transport device that can improve the accuracy of double feed determination when transporting printed paper.

  In order to achieve the above object, a first feature of a transport apparatus according to the present invention is a transport unit that transports printed paper along a transport path, a light emitting unit that emits light toward the transport path, and the transport Based on the image data of the printed image of the conveyed paper based on the detection unit having a light receiving unit that is disposed to face the light emitting unit across the path and receives light from the light emitting unit, Generating a reference value for determining multi-feed at a plurality of sampling points set for the sampling point, and obtaining a sample value corresponding to the amount of light received by the light receiving unit at the sampling point during conveyance of the paper; And a multi-feed determination unit that performs multi-feed determination of paper using the sample value.

  A second feature of the transport device according to the present invention is that the double feed determination unit calculates a difference value between the reference value and the sample value for each sampling point, and adds the difference value to calculate a difference integration. A value is calculated, and based on the difference integrated value, determination of double feeding of paper is performed.

  According to the first feature of the transport apparatus according to the present invention, the double feed determination unit obtains the reference value generated based on the image data of the printed image of the transported paper and the sample value acquired when transporting the paper. Used to make double feed judgment. Thereby, it is possible to determine the double feed with high accuracy from the first sheet. Therefore, the transport device can improve the accuracy of double feed determination when transporting printed paper.

  According to the second feature of the transport apparatus according to the present invention, the double feed determination unit calculates a difference integrated value by integrating the difference value between the reference value and the sample value for each sampling point, and based on the difference integrated value. Perform double feed judgment. Thereby, the influence of the temporary fluctuation of the sample value due to the flapping of the conveyed paper or the like can be suppressed, and the double feed determination accuracy can be further improved.

1 is a schematic configuration diagram of a stencil printing apparatus according to an embodiment. It is a control block diagram of the stencil printing apparatus according to the embodiment. It is a flowchart for demonstrating operation | movement of a stencil printing apparatus. It is a flowchart for demonstrating operation | movement of a stencil printing apparatus. FIG. 6 is a diagram illustrating a paper setting direction instruction screen. It is a flowchart of a printed paper double feed determination process. It is a figure which shows an example of the measured AD value in each sampling point in the case of the printed paper double feed determination process, a reference AD value, a difference value, and a difference integrated value. It is a figure which shows the other example of the measured AD value in each sampling point in the case of the printed paper double feed determination process, a reference AD value, a difference value, and a difference integrated value. FIG. 5 is a diagram illustrating printed paper that is double-fed.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals. However, it should be noted that the drawings are schematic and different from the actual ones. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

  Further, the embodiment described below exemplifies an apparatus or the like for embodying the technical idea of the present invention, and the technical idea of the present invention includes the material, shape, structure, The layout is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

  FIG. 1 is a schematic configuration diagram of a stencil printing apparatus provided with a transport device according to an embodiment of the present invention, and FIG. 2 is a control block diagram of the stencil printing apparatus shown in FIG. In the following description, the paper surface direction of FIG. Moreover, as shown in FIG. 1, when viewed from the user, the top, bottom, left, and right are defined as the top, bottom, left and right directions. In addition, a path indicated by a broken line in FIG. 1 is a conveyance path R along which a sheet as a print medium is conveyed, and a direction from left to right is a conveyance direction. In the following description, upstream and downstream mean upstream and downstream in the transport direction.

  As shown in FIGS. 1 and 2, the stencil printing apparatus 1 according to the present embodiment includes a plate making unit 2, a paper feeding unit 3, a paper sensor 4, a printing unit 5, a paper discharge unit 6, and a plate discharge unit. Unit 7, image reading unit 8, operation panel unit 9, and control unit 10. The claim conveying device includes a paper feed unit (corresponding to the claim conveying unit) 3, a paper sensor (corresponding to the detecting unit of claim) 4, and a control unit (corresponding to the double feed determining unit of the claim). ) 10.

  The plate making unit 2 makes a plate by punching a stencil sheet (not shown) with a thermal head (not shown).

  The paper feeding unit 3 feeds the paper P to the printing unit 5. The paper feed unit 3 includes a paper feed table 11, a primary paper feed roller 12, a secondary paper feed roller 13, and a paper feed clutch 14.

  The paper feed table 11 is used for loading paper P used for printing.

  The primary paper feed roller 12 transports the paper P stacked on the paper feed tray 11 to the secondary paper feed roller 13 while taking out the paper P one by one.

  The secondary paper supply roller 13 conveys the paper P conveyed from the primary paper supply roller 12 to the printing unit 5.

  The paper feed clutch 14 transmits a rotational driving force of a main motor 17 described later to the primary paper feed roller 12 and the secondary paper feed roller 13.

  The paper sensor 4 detects the paper P that is conveyed between the primary paper feed roller 12 and the secondary paper feed roller 13. The paper sensor 4 is used to detect double feeding of the paper P. The paper sensor 4 includes a light emitting unit 4a and a light receiving unit 4b.

  The light emitting unit 4 a is disposed below the transport path R at a predetermined position between the primary paper feed roller 12 and the secondary paper feed roller 13. The light emitting unit 4a emits light upward toward the transport path R. The light emitting unit 4a is composed of a light emitting diode, a laser diode, or the like.

  The light receiving unit 4b receives light from the light emitting unit 4a and outputs an electrical signal corresponding to the amount of light received. The light receiving unit 4b is disposed to face the light emitting unit 4a with the conveyance path R interposed therebetween. The light receiving unit 4b is made of, for example, a photodiode.

  The printing unit 5 performs printing on the paper P fed from the paper feeding unit 3. The printing unit 5 is disposed on the downstream side of the paper feeding unit 3. The printing unit 5 includes a printing drum 16, a main motor 17, an encoder 18, a press roller 19, and a press roller driving unit 20.

  The printing drum 16 performs printing by transferring ink to the paper P. The printing drum 16 is configured to be able to rotate counterclockwise in FIG. The printing drum 16 has a cylindrical shape, and a peripheral wall is formed of an ink-permeable member having a porous structure. On the outer peripheral surface of the printing drum 16, a stencil sheet that has been made is made. Ink is supplied to the inner peripheral surface of the printing drum 16 from an ink supply unit (not shown). Printing is performed by rotating the printing drum 16 and transporting the paper P to and from the press roller 19 while the ink passes through the peripheral wall of the printing drum 16 and the perforated portion of the stencil sheet and is transferred to the paper P. .

  The main motor 17 rotates the printing drum 16 in the counterclockwise direction in FIG.

  The encoder 18 outputs a pulse signal corresponding to the rotation angle of the printing drum 16.

  The press roller 19 presses the paper P fed from the secondary paper feed roller 13 against the outer peripheral surface of the printing drum 16. The press roller 19 is configured to be movable in the vertical direction. Specifically, the press roller 19 moves between a pressing position that presses the outer peripheral surface of the printing drum 16 during printing and a retracted position that retracts below the outer peripheral surface of the printing drum 16.

  The press roller driving unit 20 moves the press roller 19 in the vertical direction. The press roller driving unit 20 includes a solenoid (not shown) and the like.

  The paper discharge unit 6 discharges the paper P printed by the printing unit 5. The paper discharge unit 6 is disposed on the downstream side of the printing unit 5. The paper discharge unit 6 includes a belt conveyance unit 21, a paper discharge motor 22, and a paper discharge table 23.

  The belt transport unit 21 transports the paper P peeled from the printing drum 16 by a separation claw (not shown) to the paper discharge table 23.

  The paper discharge motor 22 drives the belt conveyance unit 21.

  The paper discharge table 23 is a stack on which the printed paper P conveyed by the belt conveyance unit 21 is stacked.

  The plate discharging unit 7 removes the used stencil sheet from the printing drum 16 and stores it.

  The image reading unit 8 optically reads an image of a document and generates image data.

  The operation panel unit 9 accepts user input operations and displays various screens. The operation panel unit 9 includes an input unit 26 and a display unit 27.

  The input unit 26 receives an input operation by a user and outputs an operation signal corresponding to the operation. The input unit 26 includes various operation keys, a touch panel, and the like.

  The display unit 27 displays various screens. The display unit 27 includes a liquid crystal display panel and the like.

  The control unit 10 controls the operation of each unit of the stencil printing apparatus 1. The control unit 10 includes a CPU, a RAM, a ROM, a hard disk, and the like.

  Specifically, the control unit 10 causes the stencil sheet made by the plate making unit 2 to plate on the printing drum 16, and then sequentially feeds the paper P from the paper feeding unit 3 to the printing unit 5. Control is performed so that printing is performed while the paper P is conveyed by the press roller 19. During the printing operation, the control unit 10 acquires the amount of light received by the light receiving unit 4b of the paper sensor 4 and determines whether or not the paper P is double-fed. Details of the double feed determination will be described later.

  Next, the operation of the stencil printing apparatus 1 will be described. 3 and 4 are flowcharts for explaining the operation of the stencil printing apparatus 1.

  First, in step S <b> 1 of FIG. 3, the control unit 10 determines whether an operation for selecting a print mode has been performed on the input unit 26.

  Here, there are a PC job mode and a plate-making printing mode as printing modes in the stencil printing apparatus 1. The PC job mode is a mode for performing printing based on a print job transmitted from an external PC (personal computer) (not shown). The plate-making printing mode is a mode for printing an image of a document read by the image reading unit 8. The user selects a PC job mode or a plate-making printing mode by operating the input unit 26.

  When it is determined that the operation for selecting the print mode is not performed (step S1: NO), the control unit 10 repeats step S1.

  When it is determined that an operation for selecting a print mode has been performed (step S1: YES), in step S2, the control unit 10 determines whether a PC job mode is selected as the print mode.

  If it is determined that the PC job mode has been selected (step S2: YES), in step S3, the control unit 10 determines whether a print job has been received from an external PC. A print job from the PC is transmitted to the stencil printing apparatus 1 by a user who has performed an operation for selecting a PC job mode on the input unit 26 and then operating the PC. When determining that the print job has not been received (step S3: NO), the control unit 10 repeats step S3.

  If it is determined that a print job has been received (step S3: YES), in step S4, the control unit 10 develops image data from the received print job. This image data is grayscale data representing black and white gradation for each pixel.

  Next, in step S5, the control unit 10 binarizes the image data to generate plate making data for stencil printing.

  Next, in step S <b> 6, the control unit 10 determines whether printing by the current print job is duplex printing.

  When it is determined that the printing is duplex printing (step S6: YES), in step S7, the control unit 10 determines whether or not the start of printing on the front surface is instructed by a user operation. When determining that the start of printing on the front side is not instructed (step S7: NO), the control unit 10 repeats step S7.

  If it is determined that the start of printing on the front side has been instructed (step S7: YES), in step S8, the control unit 10 executes printing on the front side.

  Specifically, first, the control unit 10 controls the stencil sheet used in the previous printing to be removed from the printing drum 16 by the plate discharging unit 7. Further, the control unit 10 controls the plate making unit 2 to perform plate making for surface printing based on the surface plate making data. Next, the control unit 10 clamps the front end of the stencil sheet made for surface printing to a clamping unit (not shown) of the printing drum 16. Thereafter, the control unit 10 rotates the printing drum 16 to make the stencil sheet arrive on the printing drum 16.

  Next, the control unit 10 moves the press roller 19 to the pressing position. Thereafter, the control unit 10 starts rotation of the printing drum 16 and driving of the belt conveyance unit 21. Then, the control unit 10 sequentially feeds the paper P for the designated number of print sheets from the paper feeding unit 3 to the printing unit 5. As a result, the paper P is sequentially conveyed from the paper supply unit 3 to the printing unit 5. Here, it is assumed that unprinted paper P is set in advance on the paper feed tray 11. The fed paper P is sequentially printed while being conveyed by the printing drum 16 and the press roller 19 in the printing unit 5. Thereafter, the printed paper P is transported by the belt transport unit 21 in the paper discharge unit 6 and sequentially discharged to the paper discharge tray 23.

  Here, during the above-described front surface printing operation, the control unit 10 performs double feed determination of the paper P using the amount of light received by the light receiving unit 4 b of the paper sensor 4. The double feed determination at this time can be performed using a known method. When the double feed is detected, the control unit 10 stops the printing operation and causes the display unit 27 to display a double feed error.

  When printing of the front side for the designated number of prints is completed, in step S9, the control unit 10 causes the display unit 27 to display a paper setting direction instruction screen 30 shown in FIG.

  The paper setting direction instruction screen 30 is a screen for instructing the user of the paper setting direction to the paper feed tray 11 at the time of reverse side printing. As shown in FIG. 5, the paper setting direction instruction screen 30 displays a message 31 for instructing the user the direction of the front-side printed paper to be set on the paper feed tray 11 at the time of back side printing. An illustration 32 for explaining the content of the message 31 is displayed on the paper setting direction instruction screen 30.

  Here, the paper setting direction on the paper feed tray 11 at the time of back side printing is in accordance with the orientation of the back side image with respect to the front side image after printing. The orientation of the back image with respect to the front image after printing is instructed by the user with the printer driver of the PC. Print direction information instructed by the user and indicating the orientation of the back image with respect to the front image after printing is included in the print job and transmitted to the stencil printing apparatus 1. In step S <b> 9 described above, the control unit 10 causes the display unit 27 to display the paper setting direction instruction screen 30 that indicates the paper setting direction in which the back image is printed in the direction indicated by the printing direction information.

  When the paper setting direction instruction screen 30 is displayed, the user performs an operation of setting the surface-printed paper P discharged onto the paper discharge tray 23 on the paper supply tray 11 according to the contents. When the setting of the front-side printed paper P on the paper feed tray 11 is completed, the user operates the input unit 26 to instruct to start printing on the back side.

  Note that a screen having the same content as the paper setting direction instruction screen 30 may be displayed on the display device (not shown) of the PC instead of the display unit 27 of the stencil printing apparatus 1. In addition, the paper setting direction instruction screen 30 may be displayed on the display unit 27 of the stencil printing apparatus 1, and a screen having the same contents may be displayed on the display device of the PC.

  Returning to FIG. 3, after step S <b> 9, in step S <b> 10, the control unit 10 determines whether or not an instruction to start printing on the back surface is given by a user operation. When determining that the start of printing on the back side is not instructed (step S10: NO), the control unit 10 repeats step S10.

  If it is determined that the start of printing on the back side has been instructed (step S10: YES), in step S11, the control unit 10 executes printing on the back side. The operation at the time of printing on the back surface is the same as the operation at the time of printing on the front surface described above. Here, at the time of the back side printing operation, the control unit 10 determines the double feed of the paper P by a printed paper double feed determination process described later.

  If it is determined in step S6 that printing by the current print job is single-sided printing (step S6: NO), in step S12, the control unit 10 determines whether printing start is instructed. When it is determined that the print start is not instructed (step S12: NO), the control unit 10 repeats step S12.

  If it is determined that the start of printing has been instructed (step S12: YES), in step S13, the control unit 10 executes single-sided printing. The single-sided printing operation is the same as the operation at the time of printing on the front surface in the above-described double-sided printing. Further, during the single-sided printing operation, similarly to the above-described surface printing operation in the double-sided printing, the double feed determination is performed using a known method. When the double feed is detected, the control unit 10 stops the printing operation and causes the display unit 27 to display a double feed error.

  If it is determined in step S2 that the prepress printing mode has been selected (step S2: NO), the control unit 10 displays a single-sided / double-sided printing setting screen (not shown) on the display unit 27 in step S14 of FIG. Let The single-sided / double-sided printing setting screen is a screen for the user to select single-sided printing or double-sided printing.

  Single-sided printing in the plate-making printing mode includes printing on one side of an unprinted sheet and printing on an unprinted side (back side) of a sheet that has been printed on one side in advance. One of these can be selected on the single-sided / double-sided printing setting screen. Here, when printing on a non-printed surface of a sheet that has been printed on one side in advance, when the number of printed sheets is plural, the same image is printed on these plural sheets.

  Next, in step S15, the control unit 10 determines whether or not double-sided printing is selected by a user operation.

  If it is determined that duplex printing has been selected (step S15: YES), in step S16, the control unit 10 reads images on both sides of the document.

  Specifically, the control unit 10 causes the display unit 27 to display an instruction for the user to set a document on the image reading unit 8. When a document is set on the image reading unit 8 by the user and the start of reading is instructed by a user operation, the control unit 10 causes the image reading unit 8 to read images on both sides of the document. The image reading unit 8 generates image data on both sides of the document. This image data is grayscale data representing black and white gradation for each pixel.

  Next, in step S <b> 17, the control unit 10 binarizes the image data on both sides of the document and generates plate making data for each side.

  After step S17, the control unit 10 proceeds to step S7 and performs subsequent processing. Thereby, double-sided printing is performed. Here, in the case of duplex printing in this prepress printing mode, the orientation of the back image with respect to the front image after printing is the same as that of the original read by the image reading unit 8 on the paper setting direction instruction screen 30 displayed in step S9. Such contents shall be displayed.

  If it is determined in step S15 that single-sided printing has been selected (step S15: NO), in step S18, the control unit 10 determines whether printing on a non-printed surface of a single-sided printed paper has been selected. .

  When it is determined that the printing on the unprinted side of the single-side printed paper is selected (step S18: YES), in step S19, the control unit 10 reads the printed image of the single-sided printed paper used for printing. Execute.

  Specifically, the control unit 10 causes the display unit 27 to display an instruction for causing the user to set a single-side printed sheet used for printing on the image reading unit 8. At this time, the control unit 10 displays an instruction to set the printed image so that the orientation of the printed image is a predetermined orientation. For example, the control unit 10 displays an instruction to set the printed image so that the top side of the printed image is behind the auto feeder of the image reading unit 8.

  When a user sets a single-side printed paper in the image reading unit 8 and instructs the user to start reading, the control unit 10 causes the image reading unit 8 to read a printed image on the single-side printed paper. The image reading unit 8 generates image data of a printed image on a single-side printed paper. This image data is grayscale data representing black and white gradation for each pixel. This image data is used to generate a reference AD value in a printed paper double feed determination process to be described later.

  Next, in step S <b> 20, the control unit 10 causes the display unit 27 to display a print image direction input screen (not shown). The print image direction input screen is a screen for allowing the user to instruct the orientation (print image direction) of the image printed on the unprinted surface (back surface) with respect to the printed image of the single-side printed paper. By operating the print image direction input screen, for example, the user instructs the top side of the printed image and the top side of the image printed on the unprinted surface (back surface) to be in the same direction.

  Next, in step S21, the control unit 10 determines whether or not the print image direction is instructed by a user operation on the print image direction input screen. When determining that the print image direction has not been instructed yet (step S21: NO), the control unit 10 repeats step S21.

  If it is determined that the print image direction has been instructed (step S21: YES), in step S22, the control unit 10 causes the display unit 27 to display a paper setting direction instruction screen 30. When the paper setting direction instruction screen 30 is displayed, the user performs an operation for setting the single-side printed paper used for printing on the paper feed tray 11 according to the content.

  Next, in step S <b> 23, the control unit 10 executes reading of an image of a document to be printed on an unprinted side of a single-side printed paper.

  Specifically, the control unit 10 causes the display unit 27 to display an instruction for the user to set a document on the image reading unit 8. At this time, the control unit 10 displays an instruction to set the image of the document so that the orientation of the document is a predetermined direction. For example, the control unit 10 displays an instruction to set the document image so that the top side of the image on the back side of the auto feeder of the image reading unit 8.

  When a document is set on the image reading unit 8 by the user and a start of reading is instructed by a user operation, the control unit 10 causes the image reading unit 8 to read an image of the document. The image reading unit 8 generates document image data.

  Next, in step S24, the control unit 10 binarizes the document image data to generate plate making data. Here, the control unit 10 generates plate-making data that can be printed in the print image direction designated by the user operation on the print image direction input screen displayed in step S20. For example, when an instruction is issued so that the top side of the printed image and the top side of the image printed on the non-printed surface (back side) are in the same orientation, the control unit 10 sets the paper set on the paper feed tray 11 The printing plate making data is generated so that the top side of the printed image and the top side of the original image read in step S23 are in the same direction.

  After step S24, the control unit 10 proceeds to step S12 and performs subsequent processing. Thereby, printing on an unprinted surface (back surface) is performed. Here, in the case of printing on a non-printed side (back side) of a sheet that has been printed on one side, during the printing operation on the non-printed side, the control unit 10 performs a print sheet double feed determination process, which will be described later. Perform double feed judgment.

  If it is determined in step S18 that printing on one side of the unprinted paper is selected instead of printing on the unprinted side of the single-sided printed paper (step S18: NO), the control unit 10 performs step S19. Steps S22 to S22 are omitted, and the process proceeds to step S23. Thereby, single-sided printing on unprinted paper is performed. Here, it is assumed that unprinted paper P is set in advance on the paper feed tray 11.

  Next, the printed paper double feed determination process will be described.

  As described above, during the printing operation on the back side in double-sided printing in the PC job mode and the plate-making printing mode, and the printing operation on the unprinted side (back side) of the single-side printed paper in the plate-making printing mode, The double feed determination of the paper P is performed by the feed determination processing. FIG. 6 is a flowchart of the printed paper double feed determination process.

  First, in step S31 of FIG. 6, the control unit 10 generates a reference AD value (corresponding to a reference value in claims) for each sampling point based on image data of a printed image on a sheet.

  Here, in the case of double-sided printing in the PC job mode, the image data of the printed image is the image data of the surface image obtained by developing the image in step S4 of FIG. In the case of duplex printing in the plate-making printing mode, the image data of the printed image is image data of the surface image obtained by reading the images on both sides of the document in step S16 of FIG. In the case of printing on a non-printed side (back side) of a single-side printed paper in the plate-making printing mode, the image data of the printed image is the one-sided printed used for printing in step S19 of FIG. 4 described above. This is image data obtained by reading a printed image on paper. As described above, these image data are gray scale data representing black and white gradations for each pixel.

  The sampling point is a point at which the amount of light received from the light emitting unit 4a that passes through the paper P conveyed by the paper feeding unit 3 and is received by the light receiving unit 4b is sampled. A plurality of sampling points are set at predetermined intervals in the sub-scanning direction (conveying direction) for the paper P conveyed by the paper supply unit 3. The position of the sampling point in the main scanning direction (front-rear direction) is the detection target position of the paper sensor 4 in the main scanning direction. The detection target position of the paper sensor 4 is a position on the transport path R of the optical axis of the paper sensor 4.

  The control unit 10 sets the pixel values of a plurality of pixels at positions corresponding to the respective sampling points when the paper P set in the direction designated on the paper setting direction instruction screen 30 is conveyed in the image data of the printed image. Based on this, a reference AD value for double feed determination is calculated. Specifically, the control unit 10 calculates an average value of pixel values of a plurality of pixels at positions corresponding to each sampling point as a reference AD value. Here, the control unit 10 calculates the reference AD value by converting the pixel value so that the pixel value of the white pixel in the image data of the printed image matches a white level value of an actual measurement AD value described later.

  Next, in step S <b> 32, the control unit 10 determines whether or not the leading edge of the paper P has reached the paper sensor 4. The control unit 10 determines that the leading edge of the paper P has reached the paper sensor 4 when the amount of light received by the light receiving unit 4b of the paper sensor 4 becomes a predetermined value or less. When it is determined that the leading edge of the paper P has not reached the paper sensor 4 (step S32: NO), the control unit 10 repeats step S32.

  When it is determined that the leading edge of the paper P has reached the paper sensor 4 (step S32: YES), in step S33, the control unit 10 determines whether or not the sampling timing has come. The sampling timing is the timing at which the sampling point is positioned at the detection target position of the paper sensor 4. The control unit 10 determines whether or not the sampling timing is reached based on the number of output pulses of the encoder 18 after the leading edge of the paper P reaches the paper sensor 4.

  Next, in step S34, the control unit 10 acquires an actual measurement AD value (corresponding to a sample value in the claims). Specifically, the control unit 10 acquires the measured AD value by sampling a digital signal obtained by A / D converting the output signal of the light receiving unit 4b. The measured AD value is a value converted so that the white level value becomes a predetermined AD value. The value of the white level is an AD value corresponding to the amount of light received by the light receiving unit 4b when there is no image portion of the printed image at the sampling point.

  Next, in step S35, the control unit 10 calculates a difference value at the current sampling point. The difference value is the magnitude of the difference between the reference AD value and the actually measured AD value.

  Next, in step S36, the control unit 10 calculates a difference integrated value up to the current sampling point. The difference integrated value is a value obtained by integrating the difference values of the respective sampling points from the first sampling point.

  Next, in step S37, the control unit 10 determines whether or not the difference integrated value has exceeded a threshold value.

  If it is determined that the difference integrated value has exceeded the threshold value (step S37: YES), in step S38, the control unit 10 determines that there is a double feed and stops the printing operation.

  Next, in step S39, the control unit 10 causes the display unit 27 to display a double feed error.

  If it is determined in step S37 that the difference integrated value is equal to or smaller than the threshold value (step S37: NO), in step S40, the control unit 10 determines whether or not the trailing edge of the paper P has passed through the paper sensor 4. . When the amount of light received by the light receiving unit 4b of the paper sensor 4 exceeds a predetermined value, the control unit 10 determines that the rear end of the paper P has passed through the paper sensor 4. If it is determined that the trailing edge of the paper P has not passed through the paper sensor 4 (step S40: NO), the control unit 10 returns to step S33.

  If it is determined that the trailing edge of the sheet P has passed through the sheet sensor 4 (step S40: YES), in step S41, the control unit 10 determines whether the sheet P whose trailing edge has passed the sheet sensor 4 is the last sheet. Judge whether or not.

  When determining that it is not the last sheet (step S41: NO), the control unit 10 returns to step S32. If it is determined that it is the last sheet (step S41: YES), the control unit 10 ends the printed sheet double feed determination process.

  Examples of the measured AD value, the reference AD value, the difference value, and the difference integrated value at each sampling point in the printed sheet double feed determination process are shown in FIGS. In the examples of FIGS. 7 and 8, the white level AD value = 500.

  FIG. 7 shows an example in which the paper P on which thick lines L1 and L2 parallel to the main scanning direction are printed is double-fed as shown in FIG. The thick lines L1 and L2 are printed at positions that pass the detection target position of the paper sensor 4. In the portion where the thick lines L1 and L2 are printed, the amount of transmitted light is smaller than in the other portions. Sampling points are set on a straight line 40 parallel to the transport direction passing through the detection target position of the paper sensor 4.

  On the other hand, FIG. 8 shows an example in which the printed paper P shown in FIG. 9 is normally conveyed without double feeding.

  In the case of normal conveyance without double feeding, as shown in FIG. 8, the measured AD value substantially matches the reference AD value, and the difference value at each sampling point is a small value close to zero. For this reason, the trailing edge of the paper P passes through the paper sensor 4 without the difference integrated value exceeding the threshold value. Here, in FIG. 7, FIG. 8, the threshold value of the difference integrated value is indicated by a two-point difference line.

  On the other hand, in the case of double feeding, as shown in FIG. 9, paper overlap and print image deviation occur. Therefore, in the case of double feeding, the measured AD value deviates from the reference AD value after the timing when the leading edge of the paper P overlapping on the lower side reaches the paper sensor 4. As a result, as shown in FIG. 7, the difference integrated value increases and exceeds the threshold value. Thereby, it is determined that there is a double feed. Note that FIG. 7 also shows the value after the difference integrated value exceeds the threshold value, but the printed sheet double feed determination process ends when the difference integrated value exceeds the threshold value.

  As described above, in the stencil printing apparatus 1, when the printed paper P is transported, the control unit 10 uses the reference AD value generated based on the image data of the printed image and the measured AD value to overlap. Judgment is made. As a result, the control unit 10 can determine the double feed with high accuracy from the first sheet. Therefore, according to the stencil printing apparatus 1, it is possible to improve the accuracy of double feed determination when transporting the printed paper P.

  Further, in the stencil printing apparatus 1, the control unit 10 calculates a difference integrated value, and performs multifeed determination based on the difference integrated value. Thereby, the influence of the temporary fluctuation of the measured AD value due to flapping of the conveyed paper P can be suppressed, and the accuracy of the double feed determination can be further improved.

  Note that the double feed determination may be performed by comparing the measured AD value at each sampling point with the reference AD value without using the difference integrated value. For example, it may be determined that there is a double feed when a predetermined number or more of sampling points whose difference value between the measured AD value and the reference AD value is a predetermined value or more are consecutive.

  Further, the position in the main scanning direction of the sheet P conveyed by the sheet feeding unit 3 is detected, a reference AD value is generated according to the detected position, and the multifeed determination is performed using the reference AD value. Also good. In this case, a position detection sensor for detecting the position of the conveyed paper P in the main scanning direction is arranged upstream of the paper sensor 4. The control unit 10 generates a reference AD value for each sampling point in accordance with the position in the main scanning direction of the paper P detected by the position detection sensor, and uses this for the double feed determination. Thereby, even when the positional deviation in the main scanning direction of the paper P conveyed by the paper feeding unit 3 occurs, it is possible to suppress a decrease in the accuracy of the double feed determination.

  Further, the threshold value of the difference integrated value may be changed according to the color of the paper used for printing. As a result, it is possible to cope with multi-feed determination of various color sheets.

  In the present embodiment, the printed paper double feed determination process has been described in the case where the printed paper P is transported on one side, but it can also be applied to the case of transporting the paper P having a printed image on both sides. .

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

DESCRIPTION OF SYMBOLS 1 Stencil printing apparatus 2 Plate making part 3 Paper feed part 4 Paper sensor 4a Light emission part 4b Light receiving part 5 Printing part 6 Paper discharge part 7 Discharge part 8 Image reading part 9 Operation panel part 10 Control part

Claims (2)

A transport unit that transports printed paper along a transport path;
A detection unit including a light emitting unit that emits light toward the conveyance path; and a light receiving unit that is disposed to face the light emission unit across the conveyance path and that receives light from the light emission unit;
Based on the image data of the printed image of the paper to be transported, a reference value for multi-feed determination at a plurality of sampling points set for the paper to be transported is generated, and at the time of paper transport, the sampling point A conveyance device comprising: a double feed determination unit that acquires a sample value corresponding to the amount of light received by the light receiving unit and determines a double feed of the paper using the reference value and the sample value.   The double feed determination unit calculates a difference value between the reference value and the sample value for each sampling point, calculates a difference integrated value by adding the difference values, and based on the difference integrated value, The transport apparatus according to claim 1, wherein multifeed determination is performed.