JP2002127521A - Edge detector and printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an edge detector and a printer in which various sheets can be dealt with and the edge can be detected with high accuracy for various sheets. SOLUTION: The edge detector carries out a step for moving an edge sensor above a set sheet and measuring the sensor output on the sheet (Steps S1 and S2), a step for moving the edge sensor to a position deviated from the sheet and measuring the detection amount of sensor on the outside of the sheet (Steps S5 and S6), a step for determining a threshold value of the detection amount of sensor being used for detecting the sheet edge based on the detection amount of sensor on the sheet and the detection amount of sensor on the outside of the sheet (Step S9), and a step for detecting the sheet edge based on a fact that the detection amount of sensor has dropped below the threshold value or exceeded the threshold value when the edge sensor is moved in a range straddling the sheet edge (Step 10).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer for performing printing while scanning a print head in a direction perpendicular to a paper feeding direction, and an edge detecting device for detecting an edge of a paper in such a printer. .

[0002]

2. Description of the Related Art For example, large-sized paper such as A1 size or A0 size is intermittently fed in a vertical direction, and printing is performed while a print head is scanned in a horizontal direction. In inkjet printers,
In order to detect the lateral width of the paper or to detect the lateral deviation of the paper, an edge detecting device is provided for detecting the left and right edges of the paper set on the platen.

In a conventional edge detecting device, a sensor such as a photo sensor is scanned in a horizontal direction in a range straddling the edge of a sheet in a state where the sensor is opposed to the sheet set on a platen. The point at which the sensor output of the photosensor changes below a predetermined threshold value is detected as the edge of the sheet due to the difference from the reflected light amount of the platen at a position off the sheet.

The threshold value of the sensor output, which is used as a criterion for edge detection, is determined in advance by measuring sensor outputs on various types of paper or a platen using a tester or the like, and determining an optimum value from the measured values. It is generally done. Then, the threshold value thus obtained is set as it is in the control circuit of the mass production machine, and the edge detection is performed by the plurality of edge detection devices using the same threshold value.

[0005]

However, there is a problem that
In the above-described conventional edge detection device in which two thresholds are set, the sensor output is measured for all types of supported paper, and a threshold for appropriately detecting edges on all papers is not obtained. must not. In recent years, a wide variety of papers have been developed. However, if one threshold value is used for all papers, for example, the paper sheet whose reflectance deviates from the average is set. The threshold value is not optimal, and the edge detection point may deviate from the actual edge position, which may affect the accuracy of edge detection, making it difficult to support all paper types Problem arises.

Further, the sensitivity of the sensor, the reflectance of the paper surface and the platen surface, and the like have individual variations, and the sensitivity of the sensor and the surface condition of the platen change over time. Therefore, in edge detection using a threshold value obtained in advance using a testing machine or the like, since the optimum threshold value differs for each device and each paper, the detection accuracy cannot be improved. There were also issues.

An object of the present invention has been made in view of the above-mentioned circumstances, and provides an edge detecting device and a printer device capable of coping with various types of paper and performing high-accuracy edge detection even using various types of paper. It is in.

[0008]

In order to achieve the above object, an edge detecting device of the present invention is a sensor (for example, an edge sensor 40) for detecting a predetermined physical quantity (for example, an amount of reflected light) on the surface of an object to be measured. Transport means (for example, a carriage control motor 31 and a transport belt mechanism 71) capable of transporting the sensor over a set sheet over the edge of the sheet; control of the transport means and sensor output from the sensor On the paper, the sensor is moved on the set paper and the sensor detection amount on the paper is measured (for example, steps S1 and S1).
2) Out-of-paper sensor measurement processing for moving the sensor to a position off the paper and measuring the amount of sensor detection outside the paper (eg, step S5 and step S6); Threshold value determination processing (for example, step S9) for determining a threshold value of a sensor detection amount used for detecting a sheet edge based on the sensor detection amount in step S9, and moving the sensor in a range over the sheet edge. Control means (for example, CPU 10) for performing an edge detection process (for example, step S10) for detecting the edge of the sheet based on the fact that the sensor detection amount of the sensor has changed to be equal to or less than the threshold value during the operation. The configuration was adopted.

According to such a means, since the threshold value of the sensor detection amount used for detecting the paper edge can be obtained for each device, there is a variation in the portion related to the edge detection for each device. However, it is possible to obtain an optimum threshold value for each device and perform edge detection with high accuracy using the threshold value. Further, for example, if the threshold value is determined again each time the type of paper is changed or each time the paper is set, the optimum threshold value can be obtained without being influenced by the type of paper or the variation of each paper. And edge detection can be performed with high accuracy. Further, for example, if the threshold value is determined again every predetermined period, the edge detection can be always performed with high accuracy by finding the optimum threshold value without being affected by the aging of the sensor or the like.

Preferably, the out-of-paper sensor measurement process includes a provisional threshold value determination process (for example, step S3) for determining a provisional threshold value used for estimating a paper edge based on a sensor detection amount on the paper. A paper edge estimation process for estimating the position as a paper edge based on a change in the sensor detection amount of the sensor below or above the provisional threshold value while moving the sensor in a range across the edge of the paper (for example, Step S4) and an out-of-sheet position moving process of moving the sensor to a position estimated to be out of the sheet by moving the sensor in a direction away from the sheet from the estimated sheet edge (for example, step S5)
And a sensor detection amount measurement process (for example, step S6) for measuring the sensor detection amount at a position estimated to be out of the sheet, and the sensor detection amount measured in the sensor detection amount measurement process is determined to be outside the sheet. It is good to constitute so that it may be the amount of sensor detection.

In general, in an apparatus in which sheets are set and used, the area of the remaining portion outside the sheets is smaller than the area occupied by the set sheets. Therefore, it is easy to move the sensor on the paper and measure the sensor detection amount on the paper, but it is relatively difficult to move the sensor out of the paper and measure the sensor detection amount outside the paper.

Therefore, as described above, the edge of the sheet is estimated based on the provisional threshold value, and the sensor is further moved therefrom to perform the detection measurement, whereby the sensor detection amount outside the sheet can be obtained.

[0013] More preferably, the out-of-paper sensor measurement processing is performed so that the detection sensitivity is reduced when the sensor detection amount measured in the sensor detection amount measurement processing has not reached the provisional threshold value or less. Provisional threshold value correction processing for correcting the provisional threshold value (for example, step S8)
The paper edge estimation processing (for example, step S4), the out-of-paper position movement processing (for example, step S5), and the sensor detection amount measurement processing (for step S6) are performed again based on the corrected provisional threshold value. It is good to be configured to do so.

In the estimation of the paper edge based on the provisional threshold value, the paper edge cannot always be accurately grasped. For example, a portion having a low reflectance which rarely occurs on the paper is erroneously estimated as the paper edge. However, it can occur with a small probability that the position moved in the direction deviating from the sheet out of the sheet is also on the sheet.

Therefore, the sensor detection amount is measured at the position estimated to be outside the paper as described above, and it is checked whether there is any error.
Correcting the tentative threshold value when it is incorrect corrects the error, so that an optimal threshold value can be obtained more reliably.

According to another aspect of the present invention, a sensor for detecting a predetermined physical quantity on the surface of an object to be measured, and the sensor can be conveyed over a set sheet over a range across the edge of the sheet. On the paper sensor measurement processing for moving the sensor on the set paper and measuring the sensor detection amount on the paper by controlling the transport means and the sensor output from the sensor by controlling the transport means,
A threshold value determining process for determining a threshold value of a sensor detection amount used for detecting a sheet edge based on a sensor detection amount on the sheet and a sensor detection amount measured outside the sheet measured in advance; and Control means for performing edge detection processing for detecting the edge of the sheet based on the fact that the sensor detection amount of the sensor has changed below or above the threshold value while moving the sensor in the range across the edge of the sheet. Configuration.

In general, if the sensor detection amount outside the paper is measured in advance, it is considered that there will not be much change thereafter. Therefore, the optimum threshold value can be determined in a short time by the above-described means. It is possible to detect the paper edge with high accuracy and at high speed.

More specifically, it is desirable that the control means be configured to perform the process of determining the threshold value each time a sheet is set.

Further, the printer of the present invention intermittently feeds the paper (5) while holding it on the platen (53), and scans the print head (60) in a direction orthogonal to the paper feed direction. A printer device (1) for performing printing, the edge device being configured to detect an edge of a sheet (5) held on the platen (53) that intersects a scanning path of the print head (60). The configuration was such that a detection device was provided.

More specifically, the out-of-paper sensor measurement process includes moving the sensor (for example, the edge sensor 40) onto the platen (53) that has come off the paper (5), and detecting the sensor on the platen (53). This is a process for measuring the detection amount.
The sensor (for example, the edge sensor 40) is provided integrally with the print head (60), and is conveyed together with the print head (60).

According to such a printer device, it is possible to cope with various types of paper, and to detect the paper edge with high accuracy, thereby detecting the paper width and setting the printing position on the paper with high accuracy. Can do well.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing the main configuration of a printer according to an embodiment of the present invention.

The printer device 1 of this embodiment intermittently feeds large-size paper such as A1 size, A0 size, and large-size roll paper in the vertical direction, and moves the print head 60 that ejects ink dots in a horizontal direction. This is an ink jet printer for large-format paper that performs printing while scanning in the direction.

As shown in FIG. 1, the printer 1 has a CPU as control means for controlling the entire apparatus.
10, a paper feed motor 21 for feeding paper in the vertical direction, a servo driver 20 for controlling the driving of the motor 21, a print head 60, a head control unit 65 for ejecting ink from the print head 60 by dot printing, Head 60
Control motor 31 and its servo driver 30 as a transporting means for feeding the paper in the horizontal direction, an edge sensor 40 for detecting the edge of the sheet, and converting an analog output signal from the sensor 40 into a digital signal to convert the CPU 10 into a digital signal.
A sensor control circuit 45 having an A / D converter and the like for transmitting the information to the controller is provided. The edge sensor 40 includes:
For example, it is a photo sensor for detecting the reflected light of the sheet or the platen 53.

FIG. 2 shows the mechanism of the paper transport system of the printer 1, and is a view of the printer 1 as viewed from above.

The mechanism for feeding the paper is constituted by a grip roller 50 for feeding the paper 5 by rotating while pressing the paper 5, a paper presser 51 for pressing the paper 5 toward the grip roller 50, and a print head 60 for scanning. A platen 53 that sucks the paper 5 down by the vacuum fan 54 (FIG. 3) and stably fixes the paper 5, and a paper 5 after printing.
Driver 56 and winding motor 5 for winding
7. Tarumi sensor 5 for detecting the slack of paper 5 after printing
8, the above-described paper feed motor 21 and its servo driver 20
Etc. When the grip roller 50 is intermittently driven to rotate by the paper feed motor 21 in a state where the rotation amount can be controlled, the paper 5 set on the platen 53 is intermittently fed in the vertical direction. I have.

The platen 53 is formed of a black member having a small amount of light reflection, and is formed to be longer than the maximum sheet width supported by the printer 1. When the sheet 5 is set, the platen 53 The edge is exposed in a state where it protrudes to both sides of the sheet 5.

On the upstream side of the grip roller 50 in the paper transport direction, a paper feed sensor 59A for detecting the presence or absence of paper supply is provided.
However, on the downstream side of the platen 53, a paper discharge sensor 59B for detecting the presence or absence of paper discharge is provided.

FIG. 3 shows a mechanism of a transport system of the print head 60, and is a view of the printer apparatus viewed from the front side.

The print head 60 is mounted on a carriage 70 which is slidable in the horizontal direction, and the carriage 70 is slid in the horizontal direction, so that the platen 53 and the paper 5 set on the platen 53 are moved.
Is configured to scan and move in the horizontal direction above the. The edge sensor 40 is attached to a side end of the carriage 70 with its detection direction facing the platen 53, and is configured to scan and move with the print head 60.

The carriage 70 is fixed to a steel belt 72 of a transport belt mechanism 71 as a transport means, and slides laterally by rotating a pulley 73 of the transport belt mechanism 71 by a carriage control motor 31. It is configured.

The carriage 70 is provided with a linear sensor 75 for detecting the amount of movement, and the linear sensor 75 is provided with a detection groove of a linear scale 76 fixed along the moving direction of the carriage 70. Is detected, the amount of movement of the carriage 70 can be detected. The detection output from the linear sensor 75 is input to the servo driver 30 of the carriage control motor 31 and the control unit 65 of the print head 60, and is used to control the movement amount of the carriage 70, and to control the ink ejection timing of the print head 60. Used for

Further, a home position sensor 78 is attached to the frame of the apparatus. By detecting the projecting piece 78a of the carriage 70 by the sensor 78, it is possible to detect whether the carriage 70 is at the home position. Has become.

The printer 1 of this embodiment is configured as described above, and detects the edge of the sheet 5 set on the platen 53 by the following edge detection processing flow executed by the CPU 10. Thus, control is performed to check the width of the sheet 5 set, or to shift the printing start position in accordance with the deviation when the sheet 5 is set with a slight deviation. .

FIG. 4 is a flowchart showing a procedure of an edge detection processing flow executed by the CPU 10.
6 is an explanatory diagram showing an initial state of the edge detection processing flow, FIG. 7 is an explanatory diagram showing a state of the first stage, and FIG. 8 is an explanatory diagram showing an enlarged state of the first stage. FIG. 9 is an explanatory diagram showing a state of the second stage of the edge detection processing flow, and FIG. 10 is an explanatory diagram showing a state of the third stage.

This edge detection processing flow is, for example, 1
This process is performed before the start of the printing process for each printing process on a sheet of paper, and is started when a printing command is input from the host computer after the sheet is set. In the initial state of this edge detection processing flow,
As shown in FIG. 6, the carriage 70 is at the home position, and the edge sensor 40 is, for example, a sheet 5 or a platen 53.
It is located off the top.

When the edge detection processing flow is started in this initial state, first, in step S1, the carriage 70 is moved by a predetermined amount in the direction in which the sheet is set, thereby obtaining the edge as shown in FIGS. Sensor 40
Is placed on the paper. Paper 5 on platen 53
Is set to some extent, and there is a range in which the paper is reliably set no matter what width of paper is set. Therefore, by moving the edge sensor 40 to this range, the edge sensor 40 can be reliably arranged on the sheet.

Subsequently, in step S2, the sensor output voltage V1 of the edge sensor 40 is measured. The sensor output voltage measured here is proportional to the amount of light reflected from the paper surface. The processing in steps S1 and S2 is on-paper sensor measurement processing for measuring the sensor detection amount on paper.

Next, in step S3, a provisional threshold value for estimating the sheet edge is calculated based on the measured sensor output voltage V1 on the sheet. The provisional threshold value indicates a sensor output voltage when it is estimated that the edge sensor 40 has moved from the sheet 5 to the platen 53 while the edge sensor 40 is being scanned. 80 of the sensor output voltage
Calculate as% value. The process in step S3 is a provisional threshold value determination process.

Next, in step S4, an edge detection subroutine is executed using the above provisional threshold value as a set threshold value.

FIG. 5 shows a flowchart of the edge detection subroutine.

In the edge detection subroutine, first, the carriage 70 is moved to dispose the edge sensor 40 at a position where a sheet is always set (step S11).
Next, in the direction of the edge to be detected,
0 (step S12), the edge sensor 4
The sensor output from 0 is detected (step S13), and the detected value is compared with a set threshold value (step S13).
14). If the detected value is larger than the set threshold value, the process returns to step S12, and returns to steps S12 to S12.
The loop process of S14 is repeated. If the detected value is smaller than the set threshold value, the current position is determined to be the position of the paper edge, the edge detection subroutine ends, and the process returns to the main flow of FIG. That is, when the edge detection subroutine is executed, the carriage 70 stops at the position where the edge sensor 40 detects the paper edge.

Therefore, if the edge detection is not erroneously detected in the edge detection subroutine of step S4 in FIG. 4, the detection unit of the edge sensor 40 (for example, the photodiode 40a and the photo sensor 4
The carriage 70 is stopped in a state in which the edge of the sheet 5 overlaps with the vicinity of the range where 0b is arranged. That is,
The processing in step S4 is the paper edge estimation processing.

When the paper edge has been estimated, the process proceeds to step S5, and the carriage 70 is moved in a direction outside the paper by a predetermined distance (for example, 3 mm) from the detection point of the paper edge. Here, assuming that the edge detection in step S4 is not an erroneous detection, as shown in FIG.
Is disposed on a platen 53 outside the sheet. That is, the process of step S5 is an out-of-paper position moving process of moving the sensor to a position estimated to be out of the paper.

Subsequently, in step S6, the sensor output voltage V0 of the edge sensor 40 at the position estimated to be out of the sheet is measured, and the flow proceeds to step S7. That is, the process of step S6 is a sensor detection amount measurement process of measuring the sensor detection amount at a position estimated to be out of the sheet, and the sensor outside the sheet is obtained by a series of processes in steps S3 to S6 described above. An out-of-paper sensor measurement process for measuring the detection amount is configured.

When the sheet 5 is set on the platen 53, the area where the platen 53 is exposed outside the sheet may be smaller than the area occupied by the sheet 5, so that the edge sensor 40 is provided on the sheet. It is more difficult to move the edge sensor 40 onto the platen 53 outside the sheet than to move it. However, the sensor output voltage on the platen 53 can be reliably obtained by the out-of-paper sensor measurement processing in steps S3 to S6 described above.

In step S7, the measured sensor output voltage is compared with the provisional threshold value used in the edge detection subroutine in step S4, and if the sensor output voltage is smaller than the provisional threshold value, the edge sensor 40 is placed on the platen 53. If the sensor output voltage is equal to or higher than the provisional threshold value, the process proceeds to step S9.
Is determined to be erroneous detection, and the routine goes to step S8.

As a result, it is determined that an erroneous detection has occurred, and step S8
If the process has shifted to, a correction is made to further reduce the provisional threshold. For example, a value of 80% of the provisional threshold value before correction obtained in step S3 is calculated as the provisional threshold value after correction. Then, the processing from step S4 is repeated again.

These processes are performed for the following reasons. That is, in the edge detection subroutine of step S4, for example, a portion having a low reflectance that rarely occurs on the sheet is erroneously estimated as the sheet edge, and the position moved in the next step S5 is also on the sheet. Can occur with a small probability. Therefore, step S
Steps S4 and S5 after the correction processing of the provisional threshold value of No. 8
, The probability of erroneous detection of the paper edge in step S4 can be made as close to zero as possible.

On the other hand, as a result of the determination processing in step S7, when the edge sensor 40 determines that it is on the platen 53 and shifts to step S9, the sensor output voltage V1 on the paper measured in step S2 and the step S6 Based on the measured sensor output voltage V0 on the platen 53, an optimum fixed threshold value for determining the paper edge is determined. For example, the sensor output voltage V1 on paper
And an intermediate voltage value (V0 + V1) / 2 between the sensor output voltage V0 on the platen 53 and the sensor output voltage V0 is calculated as an optimal fixed threshold. That is, the process of step S9 is a threshold value determination process for determining the threshold value used for detecting the sheet edge.

Then, in the next step S10, the calculated fixed threshold value is set as a threshold value, and FIG.
Is executed. The content of the edge detection subroutine is the same as that of step S4,
Since the threshold value set here is an optimal value for detecting the paper edge, the detection unit of the edge sensor 40 (for example, the line in which the photodiode 40a and the photosensor 40b are arranged) The position just overlapping the edge of the paper 5 can be detected.

When the width of the sheet 5 is detected,
The edge detection subroutine of this step S10
Is performed twice on the left and right sides, and the width of the paper 5 is obtained by obtaining the distance between the two detection points.

When the edge of the sheet is detected by the edge detection subroutine of step S10, the flow of the edge detection processing is terminated.

As described above, according to the printer device 1 of this embodiment, the threshold value of the sensor output voltage used for detecting the paper edge can be obtained for each device. Even if there are variations in the parts related to edge detection such as sensitivity, mounting height, and surface condition of the platen 53, the optimum threshold value for each device is determined, and the threshold value is used to obtain high accuracy. Can be used to detect the edge of the sheet.

Since an optimum threshold value is determined each time printing is performed on a sheet, an optimum threshold value is determined in accordance with the type of sheet and individual differences of each sheet, thereby performing edge detection with high accuracy. I can do it. In addition, since the threshold value is determined every time printing is performed, the optimum threshold value is determined without being affected by the aging of the edge sensor 40 or the aging of the surface state of the platen 53. Detection can be performed.

Therefore, according to such a printer 1, it is possible to support various types of paper and to support various types of paper, and to detect the paper edge with high accuracy. The width can be detected and the print position on the paper can be set with high accuracy.

The present invention is not limited to the above embodiment, but can be variously modified. For example, in the embodiment, the sensor output voltage on the platen 53 is set to 1
Although it has been described that the measurement is performed for each printing process of the sheet, the sensor output on the platen 53 does not change so much for each printing process. Therefore, the sensor output on the platen 53 is measured and stored in advance. The optimum threshold value for detecting the sheet edge may be obtained using the value of the sensor output on the platen 53 and the value of the sensor output on the sheet to be measured each time.

Further, in the above-described embodiment, the optimum threshold value is determined again for each print processing of one sheet. However, for example, a change in the sheet type is confirmed by a user's key operation or the like. The process of re-determining the threshold may be performed only when the threshold value has been set, or the process of re-determining the threshold may be performed every predetermined period.

Further, the processing of confirming the position estimated to be out of the sheet performed in step S7 of the above embodiment and the correction processing of the provisional threshold value when it is determined that the sheet is not out of paper performed in step S8 are omitted. It is also possible.

The edge detecting apparatus of the present invention can be applied not only to the detection of the paper edge in the width direction of the ink jet printer, but also to other various apparatuses which need to specify the position of the paper. I can do it.

[0062]

As described above, according to the present invention,
The threshold value of the sensor detection amount used for detecting the paper edge is
Since the configuration is obtained for each device, even if there is a variation in the device related to edge detection such as sensor sensitivity for each device, an optimum threshold value for each device is obtained and the threshold value is determined. There is an effect that edge detection can be performed with high accuracy by using this method.

If the threshold value is determined again each time the type of paper is changed or each time the paper is set, for example, variations in the type of paper and the surface condition of each paper are affected. Instead, it is possible to determine an optimum threshold value and perform edge detection with high accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main configuration of a printer device according to an embodiment of the present invention.

FIG. 2 is a configuration diagram illustrating a mechanism of a paper transport system of the printer device.

FIG. 3 is a configuration diagram showing a mechanism of a carriage transport system of the printer device.

FIG. 4 is a flowchart illustrating a procedure of an edge detection process performed by the printer device according to the embodiment;

FIG. 5 is a flowchart showing a procedure of an edge detection subroutine process executed in steps S4 and S10 of the edge detection process.

FIG. 6 is an explanatory diagram showing an initial state of edge detection processing.

FIG. 7 is an explanatory diagram showing a state of a first stage of the edge detection processing.

FIG. 8 is an explanatory diagram showing an enlarged state of the first stage in FIG. 8;

FIG. 9 is an explanatory diagram showing a state of a second stage of the edge detection processing.

FIG. 10 is an explanatory diagram showing a state of a third stage of the edge detection processing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Printer apparatus 5 Paper 10 CPU 21 Paper feed motor 31 Carriage control motor 40 Edge sensor 53 Platen 60 Print head 70 Carriage 71 Transport belt mechanism

Claims (8)

[Claims] 1. A sensor for detecting a predetermined physical quantity on a surface of an object to be measured, a transport unit capable of transporting the sensor over a set sheet over an edge of the sheet, control of the transport unit, On-paper sensor measurement processing for moving the sensor over the set paper by the sensor output from the sensor to measure the amount of sensor detection on the paper, and moving the sensor to a position off the paper and out of the paper Out-of-paper sensor measurement processing to measure the sensor detection amount at
A threshold value determining process for determining a threshold value of a sensor detection amount used for detecting a sheet edge based on the sensor detection amount on the sheet and the sensor detection amount on the outside of the sheet; and Control means for performing edge detection processing for detecting an edge of a sheet based on a change in the sensor detection amount of the sensor below or above the threshold value while moving in a range across the edge. An edge detection device that is a feature. 2. The non-paper sensor measurement process includes: a provisional threshold value determination process for determining a provisional threshold value used for estimating a paper edge based on a sensor detection amount on the paper; A paper edge estimation process for estimating the position as a paper edge based on a change in the sensor detection amount of the sensor below or above the provisional threshold value while moving the sensor over the edge span; Out-of-paper position moving processing for moving the sensor to a position estimated to be out of the sheet by moving the sensor in a direction away from the sheet, and a sensor for measuring a sensor detection amount at the position estimated to be out of the sheet 2. A detection amount measurement process, wherein the sensor detection amount measured in the sensor detection amount measurement process is set as a sensor detection amount outside the paper. Of edge detection device. 3. The out-of-paper sensor measurement processing is provisionally performed so that the detection sensitivity is reduced when the sensor detection amount measured in the sensor detection amount measurement processing has not reached the provisional threshold or less. A provisional threshold value correction process for correcting a threshold value, wherein the paper edge estimation process, the out-of-paper position movement process, and the sensor detection amount measurement process are performed again based on the corrected provisional threshold value. The edge detecting device according to claim 2, wherein 4. A sensor for detecting a predetermined physical quantity on the surface of the object to be measured, a transport unit capable of transporting the sensor over a set sheet over the range of the edge of the sheet, control of the transport unit, On-paper sensor measurement processing for measuring the sensor detection amount on the paper by moving the sensor on the set paper based on the sensor output from the sensor, the sensor detection amount on the paper and the previously measured paper A threshold value determining process for determining a threshold value of a sensor detection amount used for detection of a sheet edge based on the sensor detection amount outside; and Control means for performing an edge detection process for detecting an edge of a sheet based on a change in the sensor detection amount of the sensor below or above the threshold value. An edge detecting device characterized by the above-mentioned. 5. The edge according to claim 1, wherein the control unit is configured to perform a process of determining the threshold value each time a sheet is set. Detection device. 6. A printer device for intermittently feeding a sheet while holding it on a platen and performing printing while scanning a print head in a direction orthogonal to the sheet feeding direction, wherein the printing apparatus holds the sheet on the platen. 6. A printer device, comprising: an edge detection device according to claim 1, wherein the edge detection device detects an edge of a sheet that intersects a scanning path of the print head. 7. The printer according to claim 6, wherein the out-of-paper sensor measurement process is a process of moving the sensor onto a platen off the paper and measuring a sensor detection amount on the platen. apparatus. 8. The printer device according to claim 6, wherein the sensor is provided integrally with the print head, and is configured to be conveyed together with the print head.