JP2024017239A - Media transport device and image forming device - Google Patents

Abstract

An object of the present invention is to improve the detection accuracy of a position detection mark. A sheet-like medium with a position detection mark is conveyed. A transport processing section Pr2, a detection section including a light emitting section 47 and a light receiving section 48, a conversion section that converts the amount of light received by the light receiving section 48 into a detected value, and a detection section based on the first and second detected values. and a calibration control unit Pr5 that determines the first threshold value. The calibration control unit Pr5 changes the first threshold according to the third detected value and determines the second threshold. The detection accuracy of the position detection mark can be increased. [Selection diagram] Figure 1

Description

The present invention relates to a medium transport device and an image forming device.

Conventionally, image forming apparatuses such as printers, copying machines, facsimile machines, and multifunction devices, such as electrophotographic color printers, are provided with an image forming unit, and in the image forming unit, a charging roller uniformly charges The surface of the charged photosensitive drum is exposed to light to form an electrostatic latent image, and the electrostatic latent image is developed with toner to form a toner image. Then, the toner image is transferred to paper as a medium and fixed in a fixing device, thereby forming an image on the paper and performing printing.

By the way, for example, in a printer that prints on a long sheet of paper such as die-cut label paper with a plurality of labels attached to a mount, a reflective sensor is disposed in the paper transport device as a medium transport device, The reflective sensor detects black marks as position detection marks formed on the paper at a constant pitch, and the position where the image is formed, that is, the printing position, is determined based on the position of the black mark. It has become.

The reflective sensor is disposed to face the paper, and includes a light emitting part that generates light, a light receiving part that receives light reflected by the paper, a reflector plate that reflects light when there is no paper on the reflective sensor, etc. Equipped with

In the printer, the amount of light reflected is small in the black mark area, which is the part where the black mark is formed, and the amount of light reflected is large in the blank area of the paper and the reflective plate. The amount of received light is converted into a reading value by an AD converter or the like, and it is determined whether a black mark has been detected depending on whether the reading value is less than a threshold value (see, for example, Patent Document 1).

Japanese Patent Application Publication No. 5-246414

However, in the conventional printer, when a sheet of paper is cut at a predetermined point, a shadow may be formed on the reflective plate at the edge of the cut sheet due to the light generated by the light emitting section. When the light receiving section receives the light reflected by the light receiving section, the shaded portion may be detected as a black mark. As a result, the detection accuracy of the reflective sensor becomes low, and the printing position may be determined incorrectly or the reflective sensor may generate an error.

SUMMARY OF THE INVENTION An object of the present invention is to provide a medium transport device and an image forming apparatus that can solve the problems of the conventional printer and improve the detection accuracy of position detection marks.

For this purpose, the medium conveyance device of the present invention is configured to convey a sheet-like medium on which position detection marks are attached.

and a medium conveyance unit that conveys the sheet-like medium, a detection unit that includes a light emission unit that generates light and a light reception unit that receives light, and a conversion unit that converts the amount of light received by the light reception unit into a detected value. and a detection value based on a first amount of received light reflected at the position detection mark, and a second amount of received light reflected at an area other than the position detection mark on the sheet-like medium. and a calibration control unit that determines the first threshold based on the detected value.

Further, after determining the first threshold, the calibration control unit changes the first threshold according to a detection value based on a third amount of light received by the light receiving unit, and determines a second threshold. do.

According to the present invention, the medium conveyance device conveys a sheet-like medium on which a position detection mark is attached.

and a medium conveyance unit that conveys the sheet-like medium, a detection unit that includes a light emission unit that generates light and a light reception unit that receives light, and a conversion unit that converts the amount of light received by the light reception unit into a detected value. and a detection value based on a first amount of received light reflected at the position detection mark, and a second amount of received light reflected at an area other than the position detection mark on the sheet-like medium. and a calibration control unit that determines the first threshold based on the detected value.

Further, after determining the first threshold, the calibration control unit changes the first threshold according to a detection value based on a third amount of light received by the light receiving unit, and determines a second threshold. do.

In this case, a detection value based on a first received amount of light reflected at the position detection mark, and a detection value based on a second received amount of light reflected in an area other than the position detection mark on the sheet-like medium. a first threshold value is determined based on the first threshold value, the first threshold value is changed according to a detection value based on a third amount of light received by the light receiving section after the first threshold value is determined, and a second threshold value is Since the threshold value is determined, the detection accuracy of the position detection mark can be increased.

1 is a control block diagram of a printer in an embodiment of the present invention. FIG. 1 is a conceptual diagram of a printer in an embodiment of the present invention. FIG. 3 is a diagram for explaining a state in which an edge of a black mark is detected by a reflective sensor according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a state in which a shadow is formed when the front end of a sheet passes over a reflection sensor in an embodiment of the present invention. FIG. 6 is a diagram showing a state in which a shadow is formed when the trailing edge of a sheet passes over a reflection sensor in an embodiment of the present invention. FIG. 7 is a diagram showing the transition of reading values when a sheet of paper passes over a reflective sensor in a reference example. FIG. 3 is a diagram for explaining a method of calibrating a reflection sensor in an embodiment of the present invention. It is a 1st flowchart which shows the operation|movement of a control part when performing calibration of the reflection sensor in embodiment of this invention. It is a 2nd flowchart which shows the operation|movement of a control part when performing calibration of the reflection sensor in embodiment of this invention. It is a 3rd flowchart which shows the operation|movement of a control part when performing calibration of the reflection sensor in embodiment of this invention. It is a 4th flowchart which shows the operation|movement of a control part when performing calibration of the reflection sensor in embodiment of this invention. It is a 5th flowchart which shows the operation|movement of a control part when performing calibration of the reflection sensor in embodiment of this invention. FIG. 3 is a diagram showing a subroutine of threshold value determination processing in an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a printer as an image forming apparatus will be described.

FIG. 2 is a conceptual diagram of a printer in an embodiment of the present invention.

In the figure, 10 is a printer that prints on a long paper P such as a label paper as a sheet-like medium, and the printer 10 conveys the paper P and is connected to a host computer (not shown) as a host device. For example, a printing unit 20 that forms an image on each label of die-cut label paper on which a plurality of labels are pasted at predetermined distances on a backing paper based on print data sent from the host computer; It includes a feeder unit Fd as a paper feeding unit that cuts the paper P along the length and supplies it to the printing unit 20, and a roll paper holder Rh that supplies the paper P to the feeder unit Fd.

Cs is the housing of the printing unit 20, Bd is the main body of the printing unit 20, that is, the main body of the apparatus, and Q1 is disposed on the upper part of the main body Bd of the apparatus, yellow, magenta, cyan, black, and white as a special color. An image forming section consisting of image forming units 12Y, 12M, 12C, 12Bk, and 12W as well as an LED head Hd as an exposure device, u is a transfer unit disposed below the image forming section Q1, and 31 is a fixing device. The fixing device M1 is a drum serving as a drive unit for image formation that rotates a photosensitive drum (toner drum) 13 as an image carrier disposed in each image forming unit 12Y, 12M, 12C, 12Bk, and 12W. It's a motor.

The transfer unit u transfers an image by a driving roller r1 as a first roller, a driven roller r2 as a second roller, a backup roller r3 as a third roller, the driving roller r1, the driven roller r2, and the backup roller r3. A transfer belt 21 as an intermediate transfer medium is stretched along the forming units 12Y, 12M, 12C, 12Bk, and 12W so that it can run freely, and the transfer belt 21 is disposed facing the photosensitive drum 13 via the transfer belt 21. A primary transfer roller 22 serving as a first transfer member and a first transfer roller, and a second transfer member disposed facing the backup roller r3 via the transfer belt 21, and A secondary transfer roller 23 and the like as a second transfer roller are provided. A primary transfer portion is formed between the photosensitive drum 13 and the primary transfer roller 22, and a secondary transfer portion is formed between the backup roller r3 and the secondary transfer roller 23. Further, M2 is a transfer motor serving as a transfer drive unit for causing the transfer belt 21 to run.

The fixing device 31 includes a heating belt 32 as a first fixing member, a pressure belt 33 as a second fixing member, and a heater 34 as a heat source. Further, M3 is a fixing motor serving as a fixing drive unit for driving the pressure belt 33 and the heating belt 32.

Hz is a housing of the feeder unit Fd, and Tn is arranged to be able to swing freely, protruding from the housing Hz toward the roll paper holder Rh side, and applies a predetermined tension to the paper P as it swings. A tension bar, Cu, is a cutter unit detachably arranged with respect to the housing Hz, and M4 is a feeding unit that feeds out the paper P from the roll paper holder Rh and supplies it to the printing unit 20. A feeder motor M5 serving as a paper motor is a winding motor serving as a winding drive unit for winding paper P onto a roll paper holder Rh.

The cutter unit Cu is composed of a rotary cutter, and includes a cutter mechanism Cm consisting of a rotary blade 41 as a first cutting member, a fixed blade 42 as a second cutting member, etc., and a cutting drive unit that rotates the rotary blade 41. It is equipped with a cut motor M6, etc., and cuts the paper P while conveying it.

The roll paper holder Rh includes a rotatably disposed feeding machine Sp, and a roll paper 14 as a roll medium formed by winding the paper P into a roll is loaded into the feeding machine Sp. . When the feeder motor M4 is driven, the paper P is fed out from the roll paper holder Rh, and after a predetermined tension is applied by the tension bar Tn, the paper P is fed from the paper feed port hin formed in the housing Hz to the feeder unit. Fd, and is conveyed through a paper conveyance path Rt1 as a medium conveyance path by a pair of conveyance rollers m1 and m2 as first and second conveyance members.

The paper transport path Rt1 extends between the paper feed port hin formed in the housing Hz at the most upstream side in the transport direction of the paper P and the discharge port hou formed in the housing Cs at the most downstream side. It is formed by letting A paper end is provided downstream of the paper feed port hin the paper transport path Rt1 as a medium detection unit for paper feed determination that detects the presence or absence of the roll paper 14 in the roll paper holder Rh, and as a paper feed sensor. A sensor s1 is disposed, the pair of conveyance rollers m1 is disposed downstream of the paper end sensor s1, and the front edge of the label of the paper P supplied to the cutter unit Cu is disposed downstream of the pair of conveyance rollers m1. a first cutter-in sensor s2 as a transmissive medium detection unit that detects (label edge), and a black mark, which will be described later, as an identification index and a position detection mark formed on the back side of the paper P. A second cutter-in sensor s3 as a reflective medium detection unit that detects the leading edge of the label (label edge) by detecting the edge of Bm (FIG. 3) is arranged adjacent to each other in the width direction of the paper P. will be placed.

In the cutter unit Cu, a cutter slit sensor s4 as a rotary blade detection section that detects the rotational position of the rotary blade 41 by detecting the slit is disposed facing the rotary blade 41, and is arranged to face the rotary blade 41. The conveyance roller pair m2 is arranged on the downstream side.

Further, a slack forming section Aru for forming slack in the paper P is set downstream of the cutter unit Cu in the feeder unit Fd, and the slack formed in the paper P is detected in the slack forming section Aru. A first slack sensor s5 as a medium detecting section for detecting slack is disposed downstream of the first slack sensor s5. A cutout sensor s6 as a part is provided.

Further, a pair of conveyance rollers m3 as a third conveyance member for conveying the cut paper P is disposed in the apparatus main body Bd, and the front edge of the paper P and A first paper edge sensor s7 as a medium detection unit for detecting a trailing edge is disposed, and a pair of conveyance rollers m4 as a fourth conveyance member is disposed downstream of the first paper edge sensor s7, A second paper edge sensor s8 as a medium detection unit that detects the leading edge and trailing edge of the paper P is disposed downstream of the pair of transport rollers m4, and downstream of the second paper edge sensor s8. , a lever sensor s9 as a medium detection unit that detects the presence or absence of paper P and the front end and rear end of paper P is disposed, and a pair of transport rollers m5 as a fifth transport member is disposed downstream of the lever sensor s9. A label sensor s10 as a transmission-type medium detection unit for detecting the leading edge of the label is provided downstream of the pair of transport rollers m5, and a black mark Bm is provided downstream of the label sensor s10. A reflective sensor s11 is provided as a reflective medium detection unit consisting of a black mark sensor that detects a black mark sensor, and the secondary transfer portion is formed downstream of the reflective sensor s11. , a second slack sensor s12 as a medium detection unit for slack detection that detects the slack of the paper P supplied to the fixing device 31 is provided, and the fixing device 31 is disposed downstream of the second slack sensor s12. A fuser outlet sensor s13 as a medium detection unit for detecting the paper P discharged from the fuser 31 is disposed downstream from the fuser outlet sensor s13. A pair of ejection rollers m6 as a sixth conveyance member for ejecting the paper P out of the apparatus main body Bd through the ejection port hou is disposed downstream of the pair of ejection rollers m6 and ejected outside the apparatus main body Bd. A discharge sensor s14 is provided as a medium detection unit for discharge that detects the paper P being discharged.

Further, the apparatus main body Bd includes a transport drive unit that is driven independently of the feeder motor M4, rotates the transport roller pairs m1 to m5 and the ejection roller pair m6, and transports the paper P within the printing unit 20. A transport motor M7 is provided.

When the transport motor M7 is driven, the paper P supplied from the feeder unit Fd to the printing unit 20 is transported along the paper transport path Rt1 by the transport roller pairs m3 to m5.

On the other hand, when the drum motor M1 is driven, the photoreceptor drum 13 in each image forming unit 12Y, 12M, 12C, 12Bk, and 12W is rotated, and the surface of the photoreceptor drum 13 is charged by a charging device (not shown). It is uniformly charged by a roller and exposed by the LED head Hd, so that an electrostatic latent image is formed on the surface of the photoreceptor drum 13. Then, toner as a developer in a toner cartridge (not shown) serving as a developer storage section is supplied to a developing roller (not shown) serving as a developer carrier, and is attached to the electrostatic latent image on the photoreceptor drum 13. Toner images of each color are formed on the surface.

Subsequently, when the transfer motor M2 is driven, the transfer belt 21 is caused to run, and in the primary transfer section, the toner images of each color on each photoreceptor drum 13 are sequentially superimposed on the transfer belt 21 by the primary transfer roller 22. A color toner image is formed by the transfer.

Then, the paper P sent to the printing unit 20 is transported by transport roller pairs m3 to m5 and sent to a secondary transfer section, where the color toner image on the transfer belt 21 is transferred to the paper P. is transferred to each label.

Therefore, the paper P on which the label edge is detected by the label sensor s10 or the paper P on which the edge of the black mark Bm is detected by the reflection sensor s11 and the color toner image on the transfer belt 21 are simultaneously transferred to secondary transfer. The conveyance speed of the paper P by the conveyance motor M7 is adjusted so that the sheet P reaches the same position.

Then, the paper P on which the toner images have been transferred to the labels is sent to the fixing device 31, where the color toner images on each label are heated by the heating belt 32 and pressed by the pressure belt 33. and fixed on the label. In this way, a color image is formed on the label.

The paper P on which the color image is formed on the label is conveyed along the paper conveyance path Rt1, and is discharged out of the apparatus main body Bd from the discharge port hou by a pair of discharge rollers m6.

Next, a state in which the edge of the black mark Bm is detected by the reflection sensor s11 will be described.

FIG. 3 is a diagram for explaining the state in which the edge of a black mark is detected by the reflective sensor in the embodiment of the present invention, and FIG. 4 is a diagram for explaining the state in which the front edge of the paper passes over the reflective sensor in the embodiment of the present invention. FIG. 5 is a diagram showing a state in which a shadow is formed when the trailing edge of a sheet passes over a reflection sensor in an embodiment of the present invention, and FIG. 6 is a diagram for reference. FIG. 7 is a diagram showing the transition of reading values when a sheet of paper passes over a reflective sensor in an example. In FIG. 6, the horizontal axis represents time, and the vertical axis represents reading value T.

In the figure, P is paper, Bm is a black mark, Ar1 is a black mark area where the black mark Bm is formed, Ar2 is a blank paper area that is an area other than the black mark Bm, s11 is a reflective sensor, and 47 is a light sensor. A light emitting section 48 generates light, a light receiving section 48 receives light reflected from the paper P, etc., and a reflecting plate 49. The reflective plate 49 is a white plate for reflecting light when the paper P is not on the reflective sensor s11 (on the paper transport path Rt1), and the paper P moves along the arrow A between the reflective plate 49 and the reflective sensor s11. conveyed in the direction.

In addition, in FIG. 6, Twh is a reading value T as a detected value of the amount of light that the light receiving section 48 receives from the blank section Ar2, and Tr is a reading value T of the amount of light that the light receiving section 48 receives from the reflecting plate 49. A certain reflector reading value Tbm is a black mark part reading value which is a reading value T of the amount of light that the light receiving section 48 receives from the black mark part Ar1.

The amount of light received by the light receiving section 48 is small at the black mark section Ar1, and large at the blank section Ar2 and the reflection plate 49, and can be processed into paper P by an AD converter 61 (FIG. 1) as a converting section, which will be described later. It is converted into a reading value T. The reading value T becomes smaller as the amount of light received by the light receiving section 48 is smaller, and becomes larger as the amount of light is larger.

Further, the processing circuit of the reflection sensor s11 is provided with a comparator 62 as a detection determination unit that determines whether or not the black mark Bm has been detected in conjunction with the reading value T. If it is larger than the threshold value α, an off signal indicating that the black mark Bm has not been detected is output, and if it is less than or equal to the threshold value α, an on signal indicating that the black mark Bm has been detected is output.

By the way, as shown in FIG. 4, when the light emitted by the light emitting section 47 hits the front end of the paper P when the paper P passes over the reflection sensor s11, or as shown in FIG. When the light emitted by the light emitting unit 47 hits the rear end of the paper P when the paper P passes over the reflection sensor s11, a shadow 50 may be formed on the reflection plate 49. , the threshold α is set at the midpoint between the blank section reading value Twh and the black mark section reading value Tbm,
α=(Twh+Tbm)/2
, the amount of light reflected by the shadow 50 decreases, and when the reading value T becomes less than the threshold value α, the portion of the shadow 50 is erroneously detected as the black mark portion Ar1.

As a result, the printing position is determined based on the shadow 50 detected on the front edge side of the paper P, and an image with a shifted printing position is formed.

Furthermore, in the printer 10 that performs printing while checking whether the intervals between the black marks Bm are correct in order to detect defects in the paper P, if the shadow 50 is erroneously detected as the black mark part Ar1, It is determined that the interval between the black marks Bm is incorrect, and it is determined that a defect in the paper P has been detected.

Therefore, in this embodiment, when the roll paper 14 is replaced in the roll paper holder Rh (FIG. 2), the paper P is used so that the reflective sensor s11 can correctly detect the black mark Bm on the paper P. Then, the reflection sensor s11 is calibrated.

Next, a method for calibrating the reflection sensor s11 will be explained.

FIG. 7 is a diagram for explaining a method for calibrating a reflection sensor according to an embodiment of the present invention. In the figure, time is plotted on the horizontal axis and reading value T is plotted on the vertical axis.

In the figure, P1 is the first sheet of paper cut to the length of two pages in order to calibrate the reflection sensor s11 (FIG. 3), and P2 is the second sheet of paper cut to the length of two pages. It is the paper of the eyes.

First, at the position ps1 of the first sheet P1, the amount of light emitted by the light emitting unit 47 is adjusted so that the reading value Twh of the blank section of the reflection sensor s11 becomes the reference value TW, which is the theoretical value when detecting the blank section Ar2. be adjusted. This adjustment of the amount of light emission is performed in order to obtain a stable reading T even if the reflection sensor s11 deteriorates over time. Note that the reference value TW is used as a second detected value for calibrating the reflection sensor s11.

Next, at the position ps2 of the first sheet P1, the reading value T from the leading edge to the trailing edge of the black mark portion Ar1 is measured, and the maximum reading value T among them is set as the black mark maximum reading value TBmax, and , is recorded in the RAM 54 (FIG. 1) as a second storage unit, which will be described later, as a first detected value based on the first amount of received light.

Further, at this time, a temporary threshold value β as a first threshold value is calculated based on the reference value TW and the black mark maximum reading value TBmax.

Subsequently, at position ps3 of the first sheet of paper P1, a reading value T from the leading edge to the trailing edge of the trailing edge, which is the first end of the first sheet of paper P1 including the shadow 50, is measured; The minimum reading value T among them is recorded in the RAM 54 as the trailing end minimum reading value TLmin and as the third detected value based on the third amount of received light for the trailing end.

Next, at position ps4 of the second sheet of paper P2, a reading value T from the front edge to the trailing edge of the front edge, which is the second end of the second sheet of paper P2 including the shadow 50, is measured. The minimum reading value T is recorded in the RAM 54 as the front end minimum reading value TPmin and as the fourth detected value based on the third amount of received light for the front end.

Also, at this time, the temporary threshold value β is changed (corrected) based on the reference value TW, the temporary threshold value β, the black mark maximum reading value TBmax, the trailing end minimum reading value TLmin, and the leading end minimum reading value TPmin, and the second threshold value A threshold value δ is calculated and set in the comparator 62 of the reflection sensor s11.

Subsequently, at position ps5 of the second sheet of paper P2, a test is performed to see if the reflective sensor s11 correctly detects the black mark Bm, and at position ps6 of the second sheet of paper P2, the reflective sensor s11 detects the black mark Bm. A test is performed to see if the shadow 50 at the rear end is erroneously detected as a black mark Bm.

Note that in this embodiment, a test is not performed to determine whether the reflective sensor s11 correctly detects the black mark Bm at a position immediately after the position ps4 of the second sheet P2. This ensures the time required for the reflection sensor s11 to stabilize after the front edge reading T is measured at the position ps4 of the second sheet P2, the threshold value δ is calculated, and it is set in the comparator 62. It's for a reason. If the time required for the reflective sensor s11 to stabilize after the threshold value δ is calculated and set in the comparator 62 is short, the reflective sensor s11 detects the black mark Bm at a position immediately after the position ps4 on the second sheet P2. You can test whether it is detected correctly. In that case, the length of the second sheet P2 can be shortened from two pages to one page.

Further, in the present embodiment, after the threshold value δ is set in the comparator 62, it is determined whether the comparator 62 of the reflection sensor s11 will not erroneously detect the shadow 50 at the front edge of the paper P2 as a black mark Bm. Although the test has not yet been conducted, this is a test to determine whether the shadow 50 is erroneously detected as a black mark Bm based on the front end minimum reading value of the shadow 50 at the front end of the third sheet P. It is also possible to arrange for the following to take place.

Next, a control device for the printer 10 will be explained.

FIG. 1 is a control block diagram of a printer in an embodiment of the present invention.

In the figure, 10 is a printer, 51 is a control unit that controls the entire printer 10, 53 is a flash ROM consisting of a flash memory as a first storage unit, 54 is a RAM consisting of a volatile memory, 56 is an operation panel, s9 is a lever sensor, s11 is a reflection sensor, Hd is an LED head, M4 is a feeder motor, M6 is a cut motor, M7 is a conveyance motor, and Cu is a cutter unit.

The control unit 51 includes a CPU (not shown) as an arithmetic unit, an input/output port, a timer, etc., and performs overall control of the printer 10, and also controls the printer 10 based on the program (software), control data, etc. recorded in the flash ROM 53. Performs various processing.

In addition to recording print data received from the host computer, the RAM 54 also records bitmap data generated by editing and expanding the print data. Further, various information generated as the program is executed is temporarily recorded in the RAM 54. Note that the RAM 54 functions as a work area when the CPU performs calculations.

The operation panel 56 includes an operation section 58 consisting of switches, keys, etc. for the operator to input instructions to the printer 10, and an LED (Light Emitting Diode) and an LCD (Liquid Crystal) for displaying the status of the printer 10. A display unit 59 is provided.

The reflection sensor s11 includes a sensor section 60 as a detection section including the light emitting section 47 and the light receiving section 48, the AD converter 61, a comparator 62, and the like.

The control section 51 includes a print processing section Pr1, a transport processing section Pr2, a panel control section Pr3, a paper position management section Pr4 as a medium position management section, a calibration control section Pr5, a cut control section Pr6, a lever sensor control section Pr7, It includes a reflection sensor control unit Pr8 and the like.

The print processing unit Pr1 performs print processing, generates image data based on the print data, sends the image data to the LED head Hd, and forms an image on each label of the paper P.

The transport processing unit Pr2 performs transport processing, drives the transport motor M7, and transports the paper P along the paper transport path Rt1.

The panel control unit Pr3 performs panel control processing, captures instructions input by the operator to the printer 10 by operating the operation unit 58, and forms various screens on the display unit 59 to display various items. I do things.

The paper position management unit Pr4 performs a paper position management process as a medium position management process, and manages the position of the paper P in the paper transport path Rt1.

The calibration control unit Pr5 performs a calibration control process and calibrates the reflection sensor s11.

The cut control unit Pr6 performs cut control processing and drives the cutter unit Cu to cut the paper P.

The lever sensor control unit Pr7 performs lever sensor control processing and monitors whether the lever sensor s9 detects the presence or absence of the paper P and the front and rear ends of the paper P.

The reflective sensor control unit Pr8 performs reflective sensor control processing, sets a threshold value δ for the reflective sensor s11, and monitors the comparator 62.

Next, the operation of the control unit 51 when calibrating the reflection sensor s11 in the printer 10 will be described.

FIG. 8 is a first flowchart showing the operation of the control unit when calibrating the reflective sensor according to the embodiment of the present invention, and FIG. 9 is a control when calibrating the reflective sensor according to the embodiment of the present invention. 10 is a third flowchart showing the operation of the control section when calibrating the reflection sensor in the embodiment of the present invention, and FIG. 11 is the third flowchart showing the operation of the control section in the embodiment of the present invention A fourth flowchart showing the operation of the control unit when calibrating the reflection sensor, and FIG. 12 is a fifth flowchart showing the operation of the control unit when calibrating the reflection sensor in the embodiment of the present invention. be.

First, when the operator operates the operation unit 58, inputs the interval between the black marks Bm on the setting screen formed on the display unit 59 (step S1), and presses the start button, the panel control unit Pr3 The interval is read and sent to the paper position management section Pr4.

Further, the calibration control unit Pr5 sets an initial value of 1 to an adjustment value col used when calculating the threshold value δ (step S2). The adjustment value col is changed when retrying the calibration when the calibration is not successful.

Subsequently, the transport processing unit Pr2 operates the feeder unit Fd in cooperation with the paper position management unit Pr4 and the cut control unit Pr6, drives the feeder motor M4, etc., starts transporting the paper P, and operates the cut motor M6 and the cut control unit Pr6. The cutter unit Cu is driven to cut the paper P into the length of two pages based on the interval between the black marks Bm, and the cut first sheet P1 is supplied to the printing unit 20 (step S3). Further, the conveyance processing unit Pr2 drives the conveyance motor M7 to convey the first sheet P1 supplied to the printing unit 20.

Next, the lever sensor control unit Pr7 waits for the lever sensor s9 to detect the front edge of the first sheet P1 (step S4), and the lever sensor s9 detects the front edge of the first sheet P1. Then, the paper position management unit Pr4 is notified that the front end of the paper P1 has been detected.

Then, the conveyance processing unit Pr2 conveys the first sheet of paper P1 until the position ps1 (FIG. 7) of the first sheet of paper P1 reaches above the reflective sensor s11 (step S5), and the position ps1 reaches the reflective sensor s11. When reaching the top, the conveyance of the first sheet P1 is temporarily stopped (step S6).

At this time, the conveyance processing unit Pr2 notifies the calibration control unit Pr5 that the conveyance of the first sheet P1 has been temporarily stopped at the position ps1. The calibration control unit Pr5 adjusts the amount of light emitted by the light emitting unit 47 until the reading value T of the reflection sensor s11 at the position ps1 becomes the reference value TW (step S7). Then, when the calibration control unit Pr5 completes the adjustment of the light emission amount at the position ps1 and notifies the transport processing unit Pr2 that the adjustment of the light emission amount has ended, the transport processing unit Pr2 Conveyance is restarted (step S8), and the first sheet P1 is conveyed until the position ps2 of the first sheet P1 reaches above the reflection sensor s11 (step S9).

When the position ps2 of the first sheet P1 reaches the reflection sensor s11, the sheet position management unit Pr4 notifies the calibration control unit Pr5 that the position ps2 has reached the reflection sensor s11. The calibration control unit Pr5 measures reading values T from the leading edge to the trailing edge of the black mark portion Ar1 while the position ps2 passes over the reflection sensor s11 (step S10), and calculates the maximum reading value T among them. is recorded in the RAM 54 as the maximum black mark reading value TBmax (step S11).

Next, the calibration control unit Pr5 reads the reference value TW and the black mark maximum reading value TBmax from the RAM 54, and sets the intermediate value between the reference value TW and the black mark maximum reading value TBmax to a temporary threshold value β.
β=(TW+TBmax)/2
(Step S12).

Subsequently, the lever sensor control unit Pr7 waits for the lever sensor s9 to detect the rear end of the first sheet P1 (step S13). When the lever sensor s9 detects the trailing edge of the first sheet of paper P1, the lever sensor control unit Pr7 notifies the paper position management unit Pr4 that the lever sensor s9 has detected the trailing edge of the first sheet of paper P1. Notice.

Further, the transport processing unit Pr2 transports the first sheet P1 until the position ps3 of the first sheet P1 reaches above the reflection sensor s11 (step S14).

When the position ps3 of the first sheet P1 reaches the reflection sensor s11, the sheet position management unit Pr4 notifies the calibration control unit Pr5 that the position ps3 has reached the reflection sensor s11. The calibration control unit Pr5 measures the reading value T from the leading edge to the trailing edge of the trailing edge of the first sheet P1 while the position ps3 passes over the reflection sensor s11 (step S15), and The minimum reading value T is recorded in the RAM 54 as the trailing end minimum reading value TLmin (step S16).

Next, the transport processing unit Pr2 operates the feeder unit Fd in cooperation with the paper position management unit Pr4 and the cut control unit Pr6, drives the feeder motor M4, etc. to transport the paper P, and operates the cut motor M6 and the cutter unit. The CPU is driven to supply the second sheet P2, which has been cut to a length of two pages based on the interval between the black marks Bm, to the printing unit 20 (step S17). Further, the conveyance processing unit Pr2 drives the conveyance motor M7 to convey the second sheet of paper P2.

Next, the lever sensor control unit Pr7 waits for the lever sensor s9 to detect the front edge of the second sheet P2 (step S18), and the lever sensor s9 detects the front edge of the second sheet P2. Then, the paper position management unit Pr4 is notified that the front end of the paper P2 has been detected.

Further, the transport processing unit Pr2 transports the second sheet P2 until the position ps4 of the second sheet P2 reaches above the reflection sensor s11 (step S19).

Then, when the position ps4 of the second sheet P2 reaches the reflection sensor s11, the sheet position management unit Pr4 notifies the calibration control unit Pr5 that the position ps4 has reached the reflection sensor s11. While the position ps4 passes over the reflective sensor s11, the calibration control unit Pr5 measures the reading value T from the leading edge to the trailing edge of the leading edge of the second sheet P2 (step S20), and The minimum reading value T is recorded in the RAM 54 as the front end minimum reading value TPmin (step S21).

Next, the calibration control unit Pr5 performs threshold value determination processing (step S22), calculates and determines the threshold value δ.

Then, in the threshold value determination process, the calibration control unit Pr5 determines whether or not the threshold value δ has been successfully determined (step S23), and if the threshold value δ has been successfully determined, the calibration control unit Pr5 sends the threshold value δ to the reflection sensor control unit Pr8. , the reflective sensor control unit Pr8 sets the threshold value δ to the comparator 62 of the reflective sensor s11 (step S24). If the determination of the threshold value δ fails (does not succeed), the reflection sensor control unit Pr8 records the threshold value determination error in the RAM 54 (step S25).

Next, the conveyance processing unit Pr2 and the paper position management unit Pr4 convey the paper P2 until the position ps5 of the second sheet P2 reaches and passes over the reflection sensor s11, and during this time, the reflection sensor control unit Pr8 The comparator 62 of the reflection sensor s11 is monitored (step S26).

Then, the reflective sensor control unit Pr8 determines whether the reflective sensor s11 has correctly detected the black mark Bm based on whether the ON signal is output from the comparator 62 (step S27).

If the ON signal is not output from the comparator 62 and the reflective sensor s11 does not correctly detect the black mark Bm, the reflective sensor control unit Pr8 records the black mark detection error in the RAM 54 (step S28), and The calibration control unit Pr5 is notified that the comparator 62 of the reflection sensor s11 was not turned on and off correctly at the position ps5 of the paper P2.

On the other hand, when the on signal is output from the comparator 62 and the reflective sensor s11 correctly detects the black mark Bm, the reflective sensor control unit Pr8 correctly turns on the comparator 62 of the reflective sensor s11 at the position ps5 of the second sheet P2. - Notify the calibration control unit Pr5 that it has been turned off.

Further, the transport processing unit Pr2 and the paper position management unit Pr4 transport the paper P2 until the position ps6 of the second paper P2 reaches and passes the reflection sensor s11, and during this time, the reflection sensor control unit Pr8 controls the reflection sensor s11. The comparator 62 of the sensor s11 is monitored (step S29).

Then, the reflective sensor control unit Pr8 determines whether the reflective sensor s11 has detected the shadow 50, depending on whether the ON signal is output from the comparator 62 (step S30).

When the on signal is output from the comparator 62 and the reflection sensor s11 detects the shadow 50, the reflection sensor control unit Pr8 records the shadow detection error in the RAM 54 (step S31), and also records the position ps6 of the second sheet P2. In this step, the calibration control unit Pr5 is notified that the comparator 62 of the reflection sensor s11 has not turned on and off correctly.

On the other hand, when the off signal is output from the comparator 62 and the reflection sensor s11 does not detect the shadow 50, the reflection sensor control unit Pr8 correctly turns on the comparator 62 of the reflection sensor s11 at the position ps6 of the second sheet P2. - Notify the calibration control unit Pr5 that it has been turned off.

Then, the calibration control unit Pr5 records in the RAM 54 that the calibration of the reflection sensor s11 has been successful (step S32).

Next, the transport processing unit Pr2 discharges the first sheet P1 and the second sheet P2 out of the apparatus main body Bd (step S33).

Then, the calibration control unit Pr5 refers to the RAM 54 and determines whether the calibration of the reflection sensor s11 has been successful (step S34). If the calibration of the reflective sensor s11 is successful, the panel control unit Pr3 displays on the display unit 59 that the calibration of the reflective sensor s11 has been successful (step S35), and ends the process.

On the other hand, if the calibration of the reflection sensor s11 fails (is not successful), the calibration control unit Pr5 determines whether two retries have been performed (step S36). If two retries have been performed, the panel control unit Pr3 displays on the display unit 59 that the calibration of the reflection sensor s11 has failed (step S37). If the calibration fails even after retrying twice, it is possible that there is an abnormality in the reflective sensor s11 or an abnormality in the paper P such as the black mark Bm being printed too thin. A message can be displayed on the display unit 59 to notify the operator of the occurrence of the error.

If two retries are not performed, the calibration control unit Pr5 refers to the RAM 54 and determines the type of error that has occurred (step S38).

To this end, the calibration control unit Pr5 determines whether the error that has occurred is a threshold determination error (step S39), and if the error that has occurred is a threshold determination error, retries the calibration (step S40). If the error that has occurred is not a threshold determination error, it is determined whether the error that has occurred is a black mark detection error (step S41).

If the error that has occurred is a black mark detection error, the calibration control unit Pr5 adds 0.2 as a control value to the adjustment value col for calculating the threshold value δ, and retries the calibration (step S42). ). Further, if the error that has occurred is not a black mark detection error, that is, if the error that has occurred is a shadow detection error, the calibration control unit Pr5 subtracts 0.2 as a control value from the adjustment value col and performs calibration. A retry is performed (step S43).

The adjustment value col is for adjusting the calculated threshold value δ in the threshold value determination process, and as described above, when a black mark detection error occurs, 0.2 is added to the adjustment value col. . For example, when the retry is the first time, the adjustment value col is 1.2 by adding 0.2 to the initial value 1. That is, since the threshold value δ is increased by 20%, even if the read value T of the black mark portion Ar1 by the reflective sensor s11 is large, if it is equal to or less than the threshold value δ, the black mark Bm is detected.

On the other hand, when a shadow detection error occurs, 0.2 is subtracted from the adjustment value col. For example, when the retry is the first time, the adjustment value col is 0.8 by subtracting 0.2 from the initial value 1. That is, since the threshold value δ is reduced by 20%, even if the reading value T of the front edge or the rear edge of the paper P by the reflection sensor s11 is large, if it is larger than the threshold value δ, the shadow 50 will not be detected. do not have.

Next, the flowchart will be explained.
Step S1: The operator inputs the interval between the black marks Bm.
Step S2: The calibration control unit Pr5 sets the adjustment value col to 1, which is an initial value.
Step S3: The conveyance processing unit Pr2 supplies the first sheet P1 cut to the length of two pages to the printing unit 20.
Step S4: The lever sensor control unit Pr7 waits for the lever sensor s9 to detect the front end of the first sheet P1. If the lever sensor s9 detects the front end of the first sheet P1, the process advances to step S5.
Step S5: The transport processing unit Pr2 transports the first sheet P1 until the position ps1 of the first sheet P1 reaches above the reflection sensor s11.
Step S6: The transport processing unit Pr2 temporarily stops transporting the first sheet P1.
Step S7: The calibration control unit Pr5 adjusts the amount of light emitted from the light emitting unit 47 until the reading value T of the reflection sensor s11 at the position ps1 of the first sheet P1 becomes the reference value TW.
Step S8: The conveyance processing unit Pr2 resumes conveyance of the first sheet P1.
Step S9: The transport processing unit Pr2 transports the first sheet P1 until the position ps2 of the first sheet P1 reaches above the reflection sensor s11.
Step S10: The calibration control unit Pr5 measures the read value T from the leading edge to the trailing edge of the black mark portion Ar1 while the position ps2 of the first sheet P1 passes over the reflective sensor s11.
Step S11: The calibration control unit Pr5 records the maximum black mark reading value TBmax in the RAM 54.
Step S12: The calibration control unit Pr5 determines the intermediate value between the reference value TW and the maximum black mark reading value TBmax as the temporary threshold value β.
Step S13: The paper position management unit Pr4 waits for the lever sensor s9 to detect the trailing edge of the first paper P1. If the lever sensor s9 detects the rear end of the first sheet P1, the process advances to step S14.
Step S14: The transport processing unit Pr2 transports the first sheet P1 until the position ps3 of the first sheet P1 reaches above the reflection sensor s11.
Step S15: The calibration control unit Pr5 measures the reading value T from the leading edge to the trailing edge of the trailing edge of the first sheet P1 while the position ps3 passes over the reflective sensor s11.
Step S16: The calibration control unit Pr5 records the trailing end minimum reading value TLmin in the RAM 54.
Step S17: The transport processing unit Pr2 supplies the cut second sheet P2 to the printing unit 20.
Step S18: The lever sensor control unit Pr7 waits for the lever sensor s9 to detect the front end of the second sheet P2. If the lever sensor s9 detects the front end of the second sheet P2, the process advances to step S19.
Step S19: The transport processing unit Pr2 transports the second sheet P2 until the position ps4 of the second sheet P2 reaches above the reflection sensor s11.
Step S20 The calibration control unit Pr5 measures the reading value T from the leading edge to the trailing edge of the front edge of the second sheet P2 while the position ps4 of the second sheet P2 passes over the reflection sensor s11. .
Step S21: The calibration control unit Pr5 records the front end minimum reading value TPmin in the RAM 54.
Step S22: The calibration control unit Pr5 performs threshold value determination processing.
Step S23: The calibration control unit Pr5 determines whether the threshold value δ has been successfully determined. If the determination of the threshold value δ is successful, the process proceeds to step S24, and if the determination of the threshold value δ fails, the process proceeds to step S25.
Step S24: The reflective sensor control unit Pr8 sets a threshold value δ in the comparator 62 of the reflective sensor s11, and proceeds to step S26.
Step S25: The reflection sensor control unit Pr8 records the threshold value determination error in the RAM 54, and proceeds to step S33.
Step S26: The transport processing unit Pr2 and the paper position management unit Pr4 transport the paper P2 until the position ps5 of the second paper P2 reaches and passes above the reflective sensor s11. During this time, the reflective sensor control unit Pr8 transports the paper P2 until the position ps5 of the second paper P2 reaches and passes the reflective sensor The comparator 62 of s11 is monitored.
Step S27: The reflective sensor control unit Pr8 determines whether the reflective sensor s11 has correctly detected the black mark Bm. If the reflective sensor s11 correctly detects the black mark Bm, the process advances to step S29; if the reflective sensor s11 does not correctly detect the black mark Bm, the process advances to step S28.
Step S28: The reflective sensor control unit Pr8 records the black mark detection error in the RAM 54, and proceeds to step S33.
Step S29 The conveyance processing unit Pr2 and the paper position management unit Pr4 convey the paper P2 until the position ps6 of the second sheet P2 reaches and passes above the reflection sensor s11, and during this time, the reflection sensor control unit Pr8 The comparator 62 of s11 is monitored.
Step S30: The reflective sensor control unit Pr8 determines whether the reflective sensor s11 has detected the shadow 50. If the reflection sensor s11 detects the shadow 50, the process proceeds to step S31, and if the reflection sensor s11 does not detect the shadow 50, the process proceeds to step S32.
Step S31: The reflection sensor control unit Pr8 records the shadow detection error in the RAM 54, and proceeds to step S33.
Step S32: The calibration control unit Pr5 records in the RAM 54 that the calibration of the reflection sensor s11 has been successful.
Step S33: The transport processing unit Pr2 discharges the first sheet P1 and the second sheet P2 to the outside of the apparatus main body Bd.
Step S34: The calibration control unit Pr5 determines whether the calibration of the reflection sensor s11 has been successful. If the calibration of the reflective sensor s11 is successful, the process proceeds to step S35, and if the calibration of the reflective sensor s11 fails, the process proceeds to step S36.
Step S35 The panel control unit Pr3 displays on the display unit 59 that the calibration of the reflection sensor s11 has been successful, and ends the process.
Step S36: The calibration control unit Pr5 determines whether two retries have been performed. If two retries have been performed, the process advances to step S37, and if two retries have not been performed, the process advances to step S38.
Step S37 The panel control unit Pr3 displays on the display unit 59 that the calibration of the reflection sensor s11 has failed, and ends the process.
Step S38: The calibration control unit Pr5 determines the type of error that has occurred.
Step S39: The calibration control unit Pr5 determines whether the error that has occurred is a threshold determination error. If the error that has occurred is a threshold determination error, the process proceeds to step S40, and if the error that has occurred is not a threshold value determination error, the process proceeds to step S41.
Step S40: The calibration control unit Pr5 retries the calibration, and returns to step S3.
Step S41: The calibration control unit Pr5 determines whether the error that has occurred is a black mark detection error. If the error that has occurred is a black mark detection error, the process proceeds to step S42, and if the error that has occurred is not a black mark detection error, the process proceeds to step S43.
Step S42: The calibration control unit Pr5 adds 0.2 to the adjustment value col, retries the calibration, and returns to step S3.
Step S43: The calibration control unit Pr5 subtracts 0.2 from the adjustment value col, retries the calibration, and returns to step S3.

Next, the operation of the threshold value determination process by the calibration control unit Pr5 will be explained.

FIG. 13 is a diagram showing a subroutine of threshold value determination processing in the embodiment of the present invention.

The calibration control unit Pr5 compares the trailing end minimum reading value TLmin and the leading end minimum reading value TPmin, and sets the smaller reading value T of the trailing end minimum reading value TLmin and the leading end minimum reading value TPmin as the end end minimum reading value. The value SHmin is set (step S22-1).

Next, the calibration control unit Pr5 compares the end minimum reading value SHmin and the black mark maximum reading value TBmax, and determines whether the end minimum reading value SHmin is less than or equal to the black mark maximum reading value TBmax ( Step S21-2).

When the edge minimum reading value SHmin is less than or equal to the black mark maximum reading value TBmax, the shadow 50 formed at the rear edge of the first sheet P1 or the shadow 50 formed at the front edge of the second sheet P2 Since the reading value T is less than the reading value T of the black mark portion Ar1, which is an abnormal state, the calibration control unit Pr5 determines that the determination of the threshold value δ has failed and returns.

On the other hand, when the edge minimum reading value SHmin is larger than the black mark maximum reading value TBmax, the calibration control unit Pr5 multiplies the edge minimum reading value SHmin by a predetermined coefficient, in this embodiment, 0.8. The value is compared with the temporary threshold value β, and it is determined whether the value obtained by multiplying the end minimum reading value SHmin by 0.8 is smaller than the temporary threshold value β (step S22-4).

If the value obtained by multiplying the end minimum reading value SHmin by 0.8 is smaller than the temporary threshold β, the calibration control unit Pr5 sets the threshold δ as shown in the following equation (1).
δ=((SHmin+TBmax)/2)×col...(1)
The intermediate value between the end minimum reading value SHmin and the black mark maximum reading value TBmax is calculated by multiplying the adjustment value colc (step S22-5), and it is determined that the threshold value δ has been successfully determined (step S22-6). .

Further, if the value obtained by multiplying the end minimum reading value SHmin by 0.8 is equal to or greater than the temporary threshold β, the calibration control unit Pr5 makes the threshold δ equal to the threshold β (step S22-7), and It is determined that the determination was successful (step S22-6).

Next, the flowchart will be explained.
Step S22-1 The calibration control unit Pr5 sets the smaller reading value T of the trailing end minimum reading value TLmin and the leading end minimum reading value TPmin as the end end minimum reading value SHmin.
Step S22-2 The calibration control unit Pr5 determines whether the end minimum reading value SHmin is less than or equal to the black mark maximum reading value TBmax. If the edge minimum reading value SHmin is less than or equal to the black mark maximum reading value TBmax, the process advances to step S22-3, and if the edge minimum reading value SHmin is greater than the black mark maximum reading value TBmax, the process advances to step S22-4.
Step S22-3: The calibration control unit Pr5 determines that the determination of the threshold value δ has failed, and returns.
Step S22-4 The calibration control unit Pr5 determines whether the value obtained by multiplying the end minimum reading value SHmin by 0.8 is smaller than the provisional threshold value β. If the value obtained by multiplying the end minimum reading value SHmin by 0.8 is smaller than the provisional threshold β, the process proceeds to step S22-5, and the value obtained by multiplying the end minimum reading value SHmin by 0.8 is greater than or equal to the provisional threshold β. If so, the process advances to step S22-7.
Step S22-5 The calibration control unit Pr5 calculates the threshold value β by multiplying the intermediate value between the end minimum reading value SHmin and the black mark maximum reading value TBmax by the adjustment value colc.
Step S22-6: The calibration control unit Pr5 determines that the threshold value δ has been successfully determined, and returns.
Step S22-7: The calibration control unit Pr5 makes the threshold value δ equal to the threshold value β, and proceeds to step S22-6.

In this embodiment, the value obtained by multiplying the edge minimum reading value SHmin by 0.8 and the temporary threshold value β are compared, and the value obtained by multiplying the edge portion minimum reading value SHmin by 0.8 is smaller than the temporary threshold value β. Since the threshold value δ is calculated when A margin of 20% of the minimum reading value SHmin can be provided. Therefore, it is possible to prevent the shadow 50 from being mistakenly detected as the black mark Bm.

Further, in this embodiment, the threshold value δ is not simply calculated based on the above formula (1), but the value obtained by multiplying the end minimum reading value SHmin by 0.8 is smaller than the temporary threshold value β. It is calculated based on the case. The temporary threshold value β is calculated based on the reference value TW and the maximum black mark reading value TBmax in the blank area Ar2.

Therefore, even if the reflection characteristics in the blank paper portion Ar2 vary depending on the type of paper P, the cause of the shadow 50, etc., the threshold value δ can be calculated with high accuracy.

Note that the black mark Bm, shadow 50, etc. can be detected based on the read value T of the amount of light received from the reflector 49, but in this case, it is possible to detect the black mark Bm, the shadow 50, etc. depending on the type of the reflector 49, the cause of the shadow 50, etc. If the reflection characteristics of the reflection plate 49 fluctuate, the threshold value δ cannot be calculated with high accuracy.

As described above, in the present embodiment, the maximum reading value TBmax of the black mark based on the first received amount of light reflected at the black mark Bm and the amount of light reflected at an area other than the black mark Bm on the paper P are calculated. A temporary threshold value β is determined based on a reference value TW based on the second amount of received light, and a rear end minimum reading value TLmin and a front end based on the third amount of received light received by the light receiving unit 48 after the provisional threshold value β is determined. Since the provisional threshold value β is changed according to the minimum reading value TPmin and the threshold value δ is determined, it is possible to improve the detection accuracy of the black mark Bm.

Further, when the shadow 50 is formed on the front end or the rear end of the paper P, it is possible to prevent the shadow 50 from being mistakenly detected as the black mark portion Ar1.

Therefore, an image can be formed at the printing position of the label on the paper P with high precision.

Furthermore, in the printer 10 that performs printing while checking whether the intervals between the black marks Bm are correct in order to detect a defect in the paper P, the portion of the shadow 50 is not mistakenly detected as the black mark portion Ar1. Therefore, the printer 10 does not judge that the interval between the black marks Bm is incorrect and that the paper P is missing.

As a result, wasteful consumption of toner and paper P can be prevented.

In this embodiment, an AD converter 61 is disposed in the reflective sensor s11, and the AD converter 61 converts the amount of light received by the light receiving section 48 into a reading value T. It is also possible for Pr8 to read the amount of light received from the reflection sensor s11 and convert it into a read value T.

In this embodiment, the printer 10 has been described, but the present invention can be applied to image forming apparatuses such as copying machines, facsimile machines, and multifunction devices.

Note that the present invention is not limited to the embodiments described above, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

47 Light emitting section 48 Light receiving section 60 Sensor section 61 AD converter Ar2 Blank paper section Bm Black mark P Paper Pr2 Conveyance processing section Pr5 Calibration control section T Reading value TBmax Black mark maximum reading value TLmin Trailing edge minimum reading value TPmin Front edge minimum reading value TW Reference value β Temporary threshold value δ Threshold value

Claims (8)

In a media conveyance device that conveys a sheet-like medium with a mark for position detection,
(a) a conveyance processing unit that conveys the sheet-like medium;
(b) a detection unit including a light emitting unit that generates light and a light receiving unit that receives light;
(c) a conversion unit that converts the amount of light received by the light receiving unit into a detected value;
(d) a detection value based on a first received amount of light reflected at the position detection mark, and a second received amount of light reflected from an area other than the position detection mark on the sheet-like medium; a calibration control unit that determines the first threshold based on the detected value,
(e) After determining the first threshold, the calibration control section changes the first threshold according to a detection value based on a third amount of light received by the light receiving section, and changes the second threshold. A medium transport device characterized in that: The medium transport device according to claim 1, wherein the converter is disposed in a reflection sensor. The medium conveying device according to claim 1, wherein the converting section is disposed in the control section, reads the first to third amounts of light received from the reflection sensor, and converts them into respective detected values. 2. The medium transport device according to claim 1, wherein the third amount of received light is the amount of received light reflected at an end of the sheet-like medium. The detection value based on the third amount of received light is based on the amount of light received reflected at the rear end of the sheet-like medium and the amount of light received reflected at the front end of the sheet-like medium. The medium transport device according to claim 4, wherein the detected value is the smaller of the detected values based on the detected value. The medium according to claim 1, wherein the calibration control unit increases the second threshold when the position detection mark cannot be detected correctly based on a detection value based on the first amount of received light. Conveyance device. The calibration control unit reduces the second threshold value when the end of the sheet-like medium cannot be correctly detected based on the detection value based on the third amount of received light. media transport device. An image forming apparatus comprising the medium transport device according to any one of claims 1 to 7.

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