JP4577037B2 - Printing apparatus, medium detection method, and printing system - Google Patents

Description

  The present invention relates to a printing apparatus that prints on a medium, a medium detection method, a program, and a printing system.

  Inkjet printers are known as printing apparatuses that print dots by forming dots on various media such as paper, cloth, and film. This ink jet printer ejects ink of each color such as cyan (C), magenta (M), yellow (Y), and black (K) toward the medium, and forms dots on the medium by the ejected ink for printing. I do.

On the other hand, recently, such an ink jet printer can perform printing called “marginless printing” (see Patent Documents 1, 2, and 3). The “marginless printing” is a printing method in which ink is applied to the edge of the medium, and printing is performed so that no margin is generated on the medium. The ink ejected toward the edge of the medium may be detached from the medium. For this reason, such a printer is provided with an ink recovery unit for recovering ink that has been removed from the medium. The ink collecting unit is provided with an absorbing member such as a sponge, and the collected ink is absorbed and held by the absorbing member.
JP-A-8-213484 Japanese Patent Laid-Open No. 61-26385 JP-A-9-165328

However, in such a printing apparatus, a mist in which the ink is atomized is generated inside the printer due to the ink ejected from the nozzle, and the platen that supports the medium to be printed is stained by the mist. It has occurred. In particular, when “marginless printing” is performed, mist is likely to be generated by the ink that has been removed from the medium, and the platen stains are also noticeable.
If the platen becomes dirty, the medium on the platen cannot be accurately detected by a sensor or the like when printing is performed, so that the width and edges of the medium cannot be accurately detected. In some cases, the ink may be ejected to a position greatly deviated from the position or a size error may occur.
The present invention has been made in view of such circumstances, and an object of the present invention is to accurately detect a medium even when a platen is contaminated by mist or the like.

The main invention for achieving the object is as follows:
A printing section for printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
A value obtained by sampling the signal generated by the optical sensor at a predetermined period when the optical sensor is moved relative to the support portion during printing;
In a printing apparatus that detects the medium by comparing with a predetermined threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period shorter than the predetermined period. Then, the printing apparatus is characterized in that the predetermined threshold value is changed based on the value obtained by the sampling.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

=== Summary of disclosure ===
At least the following matters will become apparent from the description of the present specification and the accompanying drawings.

A printing section for printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
When printing, when the optical sensor moves relative to the support portion, a value obtained by sampling the signal generated by the optical sensor at a predetermined period, and a predetermined value In a printing apparatus that detects the medium by comparing with a threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period different from the predetermined period. The printing apparatus is characterized in that the predetermined threshold value is changed based on the value obtained by the sampling.

  In such a printing apparatus, when investigating the state of the support portion, when the optical sensor moves relative to the support portion, the signal generated by the optical sensor is sampled. Since the predetermined threshold value is changed based on the value obtained by sampling, erroneous detection of the medium can be prevented. Further, since the sampling cycle performed when investigating the state of the support portion is different from the sampling cycle performed when printing is performed, the support portion survey can be efficiently executed.

  In such a printing apparatus, the sampling cycle executed when investigating the state of the support portion may be shorter than the sampling cycle executed when the printing is performed. As described above, since the sampling cycle performed when investigating the state of the support portion is shorter than the sampling cycle performed when printing is performed, the support portion can be efficiently investigated.

  In such a printing apparatus, the sampling executed when investigating the state of the support portion and the sampling executed when performing the printing may be performed by the same controller. . As described above, when the two samplings are performed by the same controller, the support portion can be efficiently investigated.

  Further, in such a printing apparatus, when the printing is performed, the optical sensor is moved relative to the support part, and the optical sensor is used to investigate the state of the support part. The moving speed when moving relative to the support portion may be different. As described above, since the moving speeds are different from each other, the support portion can be efficiently investigated.

  Further, in such a printing apparatus, when the optical sensor moves relative to the support portion when investigating the state of the support portion, the optical sensor moves when the printing is performed. May be faster than the moving speed when moving relative to the support. As described above, since the movement speed of the optical sensor when investigating the state of the support section is faster than the movement speed of the optical sensor when printing, the investigation of the support section can be performed efficiently.

  In the printing apparatus, the range in which the optical sensor moves relative to the support portion when changing the predetermined threshold may extend over the entire support portion. As described above, since the movement range of the optical sensor extends over the entire support portion, a more appropriate investigation can be performed.

  Further, in such a printing apparatus, the range in which the optical sensor moves relative to the support portion when the predetermined threshold value is changed is such that the optical sensor detects the medium. It may be equal to the range of movement relative to the support part. Thus, if the movement range of the optical sensor is equal, a more appropriate investigation can be performed.

  In such a printing apparatus, the minimum value or the maximum value may be acquired from the signal output from the optical sensor, and the predetermined threshold value may be changed based on the minimum value or the maximum value. . If the minimum value or the maximum value is acquired in this way, the predetermined threshold value can be changed to a more appropriate value.

  In such a printing apparatus, when the minimum value or the maximum value does not reach a predetermined reference value, the predetermined threshold value need not be changed. As described above, when the minimum value or the maximum value does not reach the predetermined reference value, the threshold value can be appropriately changed by not changing the predetermined threshold value.

  Further, in such a printing apparatus, the state of the support unit may be investigated when the printing unit is not printing on the medium. If the survey is conducted at such timing, the survey can be carried out smoothly.

  In such a printing apparatus, the state of the support portion may be investigated when the power of the printing apparatus is turned on. If the survey is conducted at such timing, the survey can be carried out smoothly.

  In addition, such a printing apparatus includes a memory in which an execution history of borderless printing in which ink is ejected from the ink ejection unit toward the edge of the medium is stored, and the borderless printing is performed. When the execution history stored in the memory is checked and the marginless printing has never been executed, the support member emits light from the light emitting unit toward the support member. The predetermined threshold value may be changed based on the signal output from the optical sensor when the light reflected by the light receiving unit is received by the light receiving unit. If the borderless printing has not been executed in this way, the predetermined threshold value can be obtained by changing the predetermined threshold value.

  In the printing apparatus, the printing unit may perform printing by ejecting ink toward the medium. Thus, the present invention can be suitably applied to a printing apparatus that performs printing by discharging ink.

A printing section for printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
When printing, when the optical sensor moves relative to the support portion, a value obtained by sampling the signal generated by the optical sensor at a predetermined period, and a predetermined value In a printing apparatus that detects the medium by comparing with a threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period shorter than the predetermined period. Then, based on the value obtained by this sampling, the predetermined threshold value is changed,
The sampling executed when investigating the state of the support part and the sampling executed when performing the printing are performed by the same controller,
The movement speed when the optical sensor moves relative to the support portion when investigating the state of the support portion is such that the optical sensor is relative to the support portion when performing the printing. Faster than moving speed when moving,
The range in which the optical sensor moves relative to the support when changing the predetermined threshold is over the entire support.
The range in which the optical sensor moves relative to the support portion when changing the predetermined threshold is such that the optical sensor moves relative to the support portion when detecting the medium. Equal to the range to
Obtaining a minimum or maximum value from the signal output from the optical sensor, and changing the predetermined threshold based on the minimum or maximum value;
When the minimum value or the maximum value does not reach a predetermined reference value, the predetermined threshold value is not changed,
When the printing unit is not printing on the medium and when the printing apparatus is turned on, the state of the support unit is investigated,
A memory in which an execution history of borderless printing in which ink is ejected from the ink ejection unit toward the edge of the medium for printing is stored;
When the borderless printing is performed, if the execution history stored in the memory is checked and the borderless printing has not been performed, light is emitted from the light emitting unit toward the support member. Based on the signal output from the optical sensor when the light receiving unit receives the light reflected by the support member, the predetermined threshold is changed,
The printing apparatus, wherein the printing unit performs printing by ejecting ink toward the medium.

A printing section for printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. A printing apparatus including an optical sensor that generates a signal according to
When printing, when the optical sensor moves relative to the support portion, a value obtained by sampling the signal generated by the optical sensor at a predetermined period, and a predetermined value A medium detection method for detecting the medium by comparing with a threshold,
In order to investigate the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period different from the predetermined period. Then, the predetermined threshold value is changed based on the value obtained by the sampling.

A printing section for printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
When printing, when the optical sensor moves relative to the support portion, a value obtained by sampling the signal generated by the optical sensor at a predetermined period, and a predetermined value A program that is executed in a printing apparatus that detects the medium by comparing with a threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period different from the predetermined period. And steps to
And a step of changing the predetermined threshold based on the value obtained by the sampling.

In a printing system comprising a computer main body and a printing device connectable to the computer main body,
The printing apparatus includes a printing unit that performs printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
When printing, when the optical sensor moves relative to the support portion, a value obtained by sampling the signal generated by the optical sensor at a predetermined period, and a predetermined value A printing device that detects the medium by comparing with a threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period different from the predetermined period. The printing system is characterized in that the predetermined threshold value is changed based on the value obtained by the sampling.

=== Overview of Printing Apparatus ===
An embodiment of a printing apparatus according to the present invention will be described by taking an inkjet printer as an example.

  1 to 4 show the ink jet printer 1. FIG. 1 shows the appearance of the inkjet printer 1. FIG. 2 shows the internal configuration of the inkjet printer 1. FIG. 3 shows the transport section of the inkjet printer 1. FIG. 4 is a block diagram showing the system configuration of the inkjet printer 1.

  As shown in FIG. 1, the inkjet printer 1 has a structure for discharging a medium such as printing paper supplied from the back side from the front side, and an operation panel 2 and a paper discharge unit 3 are provided on the front side. The paper feeding unit 4 is provided on the back side. Various operation buttons 5 and display lamps 6 are provided on the operation panel 2. Further, the paper discharge unit 3 is provided with a paper discharge tray 7 that closes the paper discharge port when not in use. The paper feed unit 4 is provided with a paper feed tray 8 that holds cut paper (not shown). Note that the inkjet printer 1 may include a paper feed structure that can print not only on single-sheet-like printing paper such as cut paper but also on continuous media such as roll paper.

  Inside the ink jet printer 1, a carriage 41 is provided as shown in FIG. The carriage 41 is provided so as to be relatively movable along a predetermined direction (lateral direction in the figure). Around the carriage 41, a carriage motor (hereinafter also referred to as a CR motor) 42, a pulley 44, a timing belt 45, and a guide rail 46 are provided. The carriage motor 42 is constituted by a DC motor or the like, and functions as a drive source for relatively moving the carriage 41 along the predetermined direction. The timing belt 45 is connected to the carriage motor 42 via the pulley 44, and a part of the timing belt 45 is connected to the carriage 41. The carriage 41 is relatively driven along the predetermined direction by the rotation of the carriage motor 42. Move to. The guide rail 46 guides the carriage 41 along the predetermined direction.

  In addition, around the carriage 41, a linear encoder 51 that detects the position of the carriage 41, a conveyance roller 17 </ b> A for conveying the medium S along a direction that intersects the moving direction of the carriage 41, and this conveyance A paper conveyance motor 15 that rotates the roller 17A is provided.

  On the other hand, the carriage 41 is provided with an ink cartridge 48 that stores various inks, and a head 21 that performs printing on the medium S. The ink cartridge 48 contains, for example, each color ink such as yellow (Y), magenta (M), cyan (C), black (K), and is detachable from a cartridge mounting portion provided on the carriage 41. It is installed. In the present embodiment, the head 21 performs printing by ejecting ink onto the medium S. For this purpose, the head 21 is provided with a number of nozzles for ejecting ink. The ink ejection mechanism of the head 21 will be described in detail later.

  In addition, a cleaning unit 30 for eliminating clogging of the nozzles of the head 21 is provided inside the ink jet printer 1. The cleaning unit 30 includes a pump device 31 and a capping device 35. The pump device 31 is a device that sucks out ink from the nozzles in order to eliminate clogging of the nozzles of the head 21, and is operated by a pump motor (not shown). On the other hand, the capping device 35 seals the nozzles of the head 21 when printing is not performed (for example, during standby) in order to prevent clogging of the nozzles of the head 21.

  Next, the configuration of the transport unit of the inkjet printer 1 will be described. As shown in FIG. 3, the transport unit includes a paper insertion port 11A and a roll paper insertion port 11B, a paper feed motor (not shown), a paper feed roller 13, a platen 14, and a paper transport motor (hereinafter referred to as PF). (Also referred to as a motor) 15, a transport roller 17A, a paper discharge roller 17B, a free roller 18A, and a free roller 18B. In the present embodiment, the platen 14 corresponds to the support portion of the present invention.

  The paper insertion slot 11A is where the medium S, which is a medium, is inserted. The paper feed motor (not shown) is a motor that transports the medium S inserted into the paper insertion slot 11A into the ink jet printer 1, and is configured by a pulse motor or the like. The paper feed roller 13 is a roller that automatically conveys the medium S inserted into the paper insertion slot 11A into the ink jet printer 1 in the direction of arrow A in the figure (the direction of arrow B in the case of roll paper). It is driven by a motor. The paper feed roller 13 has a substantially D-shaped cross section. Since the circumferential length of the circumferential portion of the paper feed roller 13 is set longer than the conveyance distance to the conveyance roller 17A, the medium S can be conveyed to the conveyance roller 17A using this circumferential portion. The rotational driving force of the paper feed roller 13 and the frictional resistance of the separation pad (not shown) prevent a plurality of media S from being fed at a time.

  The platen 14 is a support unit that supports the medium S during printing. The paper transport motor 15 is a motor that feeds, for example, paper as the medium S in the paper transport direction, and is configured by a DC motor. The transport roller 17 </ b> A is a roller that feeds the medium S transported into the inkjet printer 1 by the paper feed roller 13 to a printable region, and is driven by the paper transport motor 15. The free roller 18A is provided at a position facing the transport roller 17A, and presses the medium S toward the transport roller 17A by sandwiching the medium S with the transport roller 17A.

  The paper discharge roller 17B is a roller that discharges the medium S on which printing has been completed to the outside of the inkjet printer 1. The paper discharge roller 17B is driven by the paper transport motor 15 by a gear (not shown). The free roller 18B is provided at a position facing the paper discharge roller 17B, and presses the medium S toward the paper discharge roller 17B by sandwiching the medium S between the paper discharge roller 17B.

<System configuration>
Next, the system configuration of the inkjet printer 1 will be described. As shown in FIG. 4, the inkjet printer 1 includes a buffer memory 122, an image buffer 124, a system controller 126, a main memory 127, and an EEPROM 129. The buffer memory 122 receives and temporarily stores various data such as print data transmitted from the host computer 140. The image buffer 124 acquires the received print data from the buffer memory 122 and stores it. The main memory 127 includes a ROM, a RAM, a flash memory, and the like. The system controller 126 corresponds to the controller of the present invention.

  On the other hand, the system controller 126 reads a control program from the main memory 127 and controls the entire inkjet printer 1 according to the control program. The system controller 126 of this embodiment includes a carriage motor control unit 128, a conveyance control unit 130, a head drive unit 132, a rotary encoder 134, and a linear encoder 51. The carriage motor control unit 128 drives and controls the rotation direction, rotation speed, torque, and the like of the carriage motor 42. Further, the head drive unit 132 performs drive control of the head 21. The conveyance control unit 130 controls various drive motors arranged in the conveyance system such as the paper conveyance motor 15 that rotationally drives the conveyance roller 17A.

  The print data sent from the host computer 140 is temporarily stored in the buffer memory 122. Necessary information is read from the print data stored here by the system controller 126. Based on the read information, the system controller 126 refers to the output from the linear encoder 51 and the rotary encoder 134 and controls the carriage motor control unit 128, the conveyance control unit 130, and the head drive unit 132 according to the control program. Control each one.

  The image buffer 124 stores print data of a plurality of color components received by the buffer memory 122. The head drive unit 132 acquires print data of each color component from the image buffer 124 according to a control signal from the system controller 126, and drives and controls the nozzles of each color provided in the head 21 based on this print data.

  In addition to the above, the inkjet printer 1 according to the present embodiment includes a reflective optical sensor 502 and a reflective optical sensor control unit 508. The reflective optical sensor 502 and the reflective optical sensor control unit 508 will be described in detail later.

<Head>
FIG. 5 is a diagram showing the arrangement of the ink nozzles provided on the lower surface of the head 21. On the lower surface of the head 21, as shown in the figure, nozzles comprising a plurality of nozzles # 1 to # 180 for each color of yellow (Y), magenta (M), cyan (C), and black (K). A column 211 is provided. The nozzles # 1 to # 180 of the nozzle row 211 of each color of yellow (Y), magenta (M), cyan (C), and black (K) correspond to the printing unit of the present invention.

  The nozzles # 1 to # 180 of each nozzle row 211 are arranged in a straight line along the transport direction of the medium S. Each nozzle row 211 is arranged in parallel with a space between each other along the moving direction (scanning direction) of the head 21. Each nozzle # 1 to # 180 is provided with a piezo element (not shown) as a drive element for ejecting ink droplets.

  When a voltage having a predetermined time width is applied between the electrodes provided at both ends of the piezoelectric element, the piezoelectric element expands according to the voltage application time and deforms the side wall of the ink flow path. As a result, the volume of the ink flow path contracts according to the expansion and contraction of the piezo element, and the ink corresponding to the contraction is ejected from the nozzles # 1 to # 180 of each color as ink droplets.

=== Linear encoder ===
Next, the linear encoder 51 will be described in detail. FIG. 6 schematically shows the configuration of the linear encoder 51 provided on the carriage 41.

  The linear encoder 51 includes a light emitting diode 452, a collimator lens 454, and a detection processing unit 456. The detection processing unit 456 includes a plurality of (for example, four) photodiodes 458, a signal processing circuit 460, and, for example, two comparators 462A and 462B.

  When the voltage Vcc is applied to both ends of the light emitting diode 452 via a resistor, light is emitted from the light emitting diode 452. This light is condensed into parallel light by the collimator lens 454 and passes through the linear encoder code plate 464. The linear encoder code plate 464 is provided with slits at predetermined intervals (for example, 1/180 inch (1 inch = 2.54 cm)).

  The parallel light that has passed through the linear encoder code plate 464 enters each photodiode 458 through a fixed slit (not shown) and is converted into an electrical signal. The electric signals output from the four photodiodes 458 are subjected to signal processing in the signal processing circuit 460, the signals output from the signal processing circuit 460 are compared in the comparators 462A and 462B, and the comparison result is output as a pulse. Pulses ENC-A and ENC-B output from the comparators 462A and 462B are output from the linear encoder 51.

  7A and 7B are timing charts showing waveforms of two output signals of the linear encoder 51 when the carriage motor 42 is rotating forward and when it is rotating backward. As shown in FIGS. 7A and 7B, the phase of the pulse ENC-A and the pulse ENC-B differ by 90 degrees in both cases of the forward rotation and the reverse rotation of the carriage motor 42. When the carriage motor 42 is rotating forward, that is, when the carriage 41 is moving along the guide rail 46, the pulse ENC-A is 90 degrees more than the pulse ENC-B, as shown in FIG. 7A. When the phase advances and the carriage motor 42 reverses, the phase of the pulse ENC-A is delayed by 90 degrees from the pulse ENC-B, as shown in FIG. 7B. One cycle T of the pulse ENC-A and the pulse ENC-B is equal to the time during which the carriage 41 moves through the slit interval of the linear encoder code plate 464.

  Then, the rising edge and rising edge of each of the output pulses ENC-A and ENC-B of the linear encoder 51 are detected, the number of detected edges is counted, and the rotational position of the carriage motor 42 is based on the counted value. Is calculated. This count is incremented by "+1" when one edge is detected when the carriage motor 42 is rotating forward, and is "-1" when one edge is detected when rotating reversely. Is added. The period of each of the pulses ENC-A and ENC-B is equal to the time from when one slit passes through the linear encoder 51 until the next slit passes through the linear encoder 51 of the linear encoder code plate 464. In addition, the pulse ENC-A and the pulse ENC-B are different in phase by 90 degrees. For this reason, the count value “1” of the count corresponds to ¼ of the slit interval of the linear encoder code plate 464. Thus, if the count value is multiplied by ¼ of the slit interval, the amount of movement of the carriage motor 42 from the rotational position corresponding to the count value “0” can be obtained based on the multiplication value. At this time, the resolution of the linear encoder 51 is ¼ of the slit interval of the linear encoder code plate 464.

=== Printing operation ===
Next, the printing operation of the above-described ink jet printer 1 will be described. Here, “bidirectional printing” will be described as an example. FIG. 8 is a flowchart showing an example of the processing procedure of the printing operation of the inkjet printer 1. Each process described below is executed by the system controller 126 reading a program stored in the main memory 127 or the EEPROM 129 and controlling each unit according to the program.

  Upon receiving print data from the host computer 140, the system controller 126 first performs a paper feed process to execute printing based on the print data (S102). The paper feed process is a process of supplying the medium S to be printed into the ink jet printer 1 and transporting it to a print start position (also referred to as a cue position). The system controller 126 rotates the paper feed roller 13 to send the medium S to be printed to the transport roller 17A. The system controller 126 rotates the transport roller 17A to position the medium S sent from the paper feed roller 13 at the print start position.

  Next, the system controller 126 executes a printing process for printing the medium S by moving the carriage 41 relative to the medium S. Here, first, forward printing is performed to eject ink from the head 21 while moving the carriage 41 in one direction along the guide rail 46 (S104). The system controller 126 drives the carriage motor 42 to move the carriage 41 and drives the head 21 based on the print data to eject ink. The ink ejected from the head 21 reaches the medium S and is formed as dots.

  After printing is performed in this way, next, a carrying process for carrying the medium S by a predetermined amount is executed (S106). In this transport process, the system controller 126 drives the paper transport motor 15 to rotate the transport roller 17A and transports the medium S by a predetermined amount relative to the head 21 in the transport direction. By this carrying process, the head 21 can print in an area different from the previously printed area.

  After carrying out the carrying process in this way, it is determined whether or not to discharge paper (S108). If there is no other data to be printed on the medium S being printed, a paper discharge process is executed (S116). On the other hand, if there is other data to be printed on the medium S being printed, the return pass printing is executed without performing the paper discharge process (S110). In this backward printing, printing is performed by moving the carriage 41 along the guide rail 46 in the direction opposite to the previous forward printing. Again, the system controller 126 drives the carriage motor 42 to rotate in the opposite direction to move the carriage 41 and drives the head 21 based on the print data to eject ink and perform printing.

  After performing the return pass printing, a carrying process is executed (S112), and then a paper discharge determination is made (S114). Here, if there is other data to be printed on the medium S being printed, the paper discharge process is not performed, the process returns to step S104, and the forward printing is executed again (S104). On the other hand, if there is no other data to be printed on the medium S being printed, a paper discharge process is executed (S116).

  After the paper discharge process is performed, next, a print end determination is performed to determine whether or not to end printing (S118). Here, based on the print data from the host computer 140, it is checked whether there is a medium S to be printed next. If there is a medium S to be printed next, the process returns to step S102, the paper feed process is executed again, and printing is started. On the other hand, if there is no medium S to be printed next, the printing process is terminated.

=== Borderless printing ===
In the inkjet printer 1 according to the present embodiment, “marginless printing” can be executed.

<Outline of borderless printing>
FIG. 9 and FIG. 10 explain the outline of “marginless printing” executed by the inkjet printer 1 according to the present embodiment. FIG. 9 illustrates the relationship between the print area P and the paper (medium) S when normal printing is performed, not “marginless printing”. FIG. 10 illustrates the relationship between the medium S and the printing area P when “marginless printing” is performed.

  In the case of normal printing, the print area P is set to a size smaller than the paper S so as to fit on the paper S as shown in FIG. A margin portion WH is formed along the left and right sides and the top and bottom sides of the periphery of the paper S. The process of storing the print area P on the paper S in this way is performed by a printer driver installed in the host computer 140. The printer driver generates print data such that the print area P fits on the paper S based on image data given from an application program executed by the host computer 140. Here, when processing image data that cannot fit the print area P in the paper S, the printer driver excludes a part of the image represented by the image data from the print target, or The image may be reduced so that it fits on the paper S. The print data thus created by the printer driver is transmitted from the host computer 140 to the inkjet printer 1. The inkjet printer 1 performs normal printing by executing print processing based on print data sent from the host computer 140.

  On the other hand, in the case of “borderless printing”, the print area P is set to be larger than the medium S so as to protrude from the medium S as shown in FIG. Unlike the case of the normal printing described with reference to FIG. 9, the margin portion WH is not formed on the peripheral edge of the medium S. Here, the entire medium S is covered with the printing region P, and no margin portion WH is formed at the peripheral edge of the medium S. As shown in FIG. 10, the margins of the medium S such as the left edge, the right edge, the upper edge, and the lower edge of the medium S are not limited to the case where no margin is formed at the periphery of the medium S. This includes the case where a margin is formed in part. That is, when the setting is made so that the print region P protrudes from the medium S even a little, it corresponds to “marginless printing”.

  The process for causing the print area P to protrude from the medium S in this way is performed by a printer driver or the like as in the case of normal printing. The printer driver generates print data such that the print area P protrudes from the medium S based on the image data given from the application program. Here, when processing image data such that the print area P is smaller than the medium S, the printer driver enlarges the print area P so that the print area P covers the entire medium S. The print data created in this way is transmitted from the host computer 140 toward the inkjet printer 1. The inkjet printer 1 executes “printing without borders” by executing a printing process based on the print data sent from the host computer 140. As a result, it is possible to realize printing that is excellent in appearance without borders.

  When such “marginless printing” is executed, the ink ejected from the nozzles # 1 to # 180 of each nozzle row 211 may be detached from the medium S. If the ink is detached from the medium S, there is a possibility of adverse effects such as staining the platen 14 or the like. Therefore, a printing apparatus that performs such “marginless printing” includes an ink collection unit that collects ink that has been removed from the medium S.

<Ink recovery unit>
11 and 12 show the state of the platen 14 provided with the ink recovery unit 352 according to the present embodiment. FIG. 11 is a plan view showing the entire state of the platen 14, and FIG. 12 is a perspective view partially showing the state of the platen 14.

  As shown in FIG. 11, the ink collection unit 352 includes a groove 354 formed in a horizontally long rectangular shape on the platen 14 along the movement direction of the carriage 41. The lateral width dimension (dimension in the moving direction of the carriage 41) L of the groove 354 is set corresponding to the maximum size of the medium S that can be printed by the inkjet printer 1. That is, if the maximum size of the printable medium S is “A4” size, the lateral width dimension L of the groove 354 is a dimension corresponding to the lateral width dimension of the “A4” size medium, that is, “A4” size medium. It is set to a dimension that is slightly longer than the horizontal width dimension. Further, the vertical dimension (dimension in the medium transport direction) M of the groove 354 is set to be slightly larger than the length dimension corresponding to the length dimension of the nozzle row 211 provided in the head 21. Is done. As a result, “borderless printing” can be executed for all printable sizes of media.

  The groove 354 is formed in a concave cross section as shown in FIG. An absorbent material 356 for absorbing the discarded ink is disposed inside the groove 354. The absorbent material 356 is formed of a material that can absorb ink, such as sponge, and can absorb and hold ink. As a result, the discarded ink can be prevented from scattering.

  Furthermore, a plurality of protrusions 362 and a plurality of rectangular protrusions 364 are provided inside the groove 354. The protrusions 362 and the rectangular protrusions 364 are provided side by side along the moving direction of the carriage 41, that is, along the length direction of the groove 354. In addition, a plurality of ribs 366 are integrally provided on the upper surface of the rectangular protrusion 364. The plurality of ribs 366 are formed side by side along the moving direction of the carriage 41 at intervals. The protrusions 362 and the protrusions 364 are provided to support the medium S to be printed, which is placed above the groove 354 from below. The upper end of the protrusion 362 and the rib 366 of the protrusion 364 come into contact with the lower surface of the medium S to support the medium S.

  In addition, ribs 368 for supporting the medium S from below are also formed at the peripheral edge of the groove 354. The ribs 368 at the peripheral edge of the groove portion 354 are arranged on the upper edge portion and the lower edge portion of the groove portion 354 so as to be spaced apart from each other along the movement direction of the carriage 41. As described above, the protrusions 362 and the ribs 366 and 368 are arranged at appropriate intervals, so that the medium S to be printed can be uniformly supported on the lower side. Thereby, it is possible to prevent the medium S from being bent during printing.

<Actual borderless printing>
FIG. 13 illustrates the state of printing when “marginless printing” is actually performed, and shows a cross-sectional view taken along the line AA ′ shown in FIG. 11. On the platen 14, as shown in the figure, as the groove portion 354, two groove portions 354 a and 354 b are provided facing the head 21 disposed above the platen 14. One groove portion 354 a is provided on the upstream side in the transport direction of the medium S, and is formed so as to face the nozzles # 178 to # 180 among the nozzles # 1 to # 180 of the nozzle row 211 of the head 21. Has been. The other groove portion 354b is provided on the downstream side in the transport direction of the medium S, and is formed so as to face the nozzles # 1 to # 3 among the nozzles # 1 to # 180 of the nozzle row 211 of the head 21. Has been. As a result, the ink ejected from the nozzles # 1 to # 3 and # 178 to # 180 of the head 21 is directly driven into the grooves 354a and 354b when the ink is removed from the medium S. The ink that has been driven into the grooves 354a and 354b is absorbed and collected by the absorbent material 356 in each of the grooves 354a and 354b.

  When printing is performed on the leading edge of the medium S in the transport direction, nozzles # 1 to # 3 provided on the downstream side in the transport direction are used to eject ink from these nozzles # 1 to # 3. In addition, printing is performed on the leading end of the medium S. In this case, the ink ejected from the nozzles # 1 to # 3 and removed from the medium S is collected in the groove portion 354b on the downstream side in the transport direction.

  Further, when printing is performed on the rear end portion of the medium S, ink is ejected from the nozzles # 178 to # 180 using the nozzles # 178 to # 180 provided on the upstream side in the transport direction. The rear end of the medium S is printed. In this case, the ink ejected from the nozzles # 178 to # 180 and removed from the medium S is collected in the groove portion 354a on the upstream side in the transport direction.

  During normal printing, the leading edge and the trailing edge of the medium S are formed as margins WH, so there is no need to print the leading edge and trailing edge, and the upstream side in the transport direction is not necessary. Since there is no need to discard ink in the groove 354a or the downstream groove 354b, there is no restriction on the use of nozzles as described above, and printing is performed on the medium S using all the nozzles # 1 to # 180. can do.

<Other examples of borderless printing>
In the embodiment described above, the print area P is set so as to protrude from the medium S. However, in the “marginless printing”, it is not always necessary to set the print area P to protrude from the medium S in this way. Absent. FIG. 14 illustrates an example of “marginless printing” when the print area P is not set so as to protrude from the medium S but is set so as to fit exactly on the medium S. As shown in the figure, even if the print area P does not protrude from the medium S, “marginless printing” without margins is performed by setting the print area P to fit the size of the medium S. be able to.

  Even in this case, as shown in FIG. 14, the margin is not necessarily formed at the periphery of the medium S, and the left edge, the right edge, the upper edge, and the lower edge of the medium S are not necessarily provided. For example, a case where a margin part is formed at a part of the peripheral edge of the medium S is also included. That is, if the print area P is set to fit the size of the medium S even a little, it corresponds to “marginless printing”.

  Even in such a case, the ink may be ejected from the medium S due to misalignment of the medium S or the like because the ink is driven to the edge of the medium S. For this reason, even when such a print region P is set so as to fit exactly on the medium S, it is necessary to collect ink that has been removed from the medium S. For this reason, the ink recovery unit 352 as described above is required.

=== Detection of medium ===
In the inkjet printer 1 according to the present embodiment, when printing is performed on the medium S, the position of the medium S is detected. The inkjet printer 1 according to the present embodiment includes a reflective optical sensor 502 in order to detect the position of the medium. The reflective optical sensor 502 corresponds to the optical sensor of the present invention.

<Reflective optical sensor>
FIG. 15 shows the reflective optical sensor 502. The reflection type optical sensor 502 is provided integrally with the carriage 41 as shown in the figure, and is arranged together with the nozzle row 211 on the lower surface of the head 21, as shown in FIG. The reflective optical sensor 502 includes a light emitting unit 504 and a light receiving unit 506, and is disposed with a space D between the medium S. The interval D is set to 5 mm, for example. The light emitting unit 504 and the light receiving unit 506 are disposed to face the medium S, respectively. The light emitting unit 504 is configured by a light emitting diode, for example, and emits light toward the medium S. The light receiving unit 506 is configured by, for example, a photodiode and receives light emitted from the light emitting unit 504 and reflected by the medium S.

The light component received by the light receiving unit 506 includes a regular reflection component of light emitted from the light emitting unit 504 and reflected by the medium S. The light receiving unit 506 is disposed at a position where such a regular reflection component can be received.
The light receiving unit 506 generates a signal corresponding to the intensity of the received light. The signal generated by the light receiving unit 506 is output to the outside as a detection result from the reflective optical sensor 502. The signal output from the reflective optical sensor 502 is input to the reflective optical sensor control unit 508 as shown in FIG.

<Reflective optical sensor controller>
The reflection type optical sensor control unit 508 has a function of controlling the reflection type optical sensor 502 in accordance with a command from the system controller 126. That is, the reflective optical sensor control unit 508 causes the light emitting unit 504 of the reflective optical sensor 502 to emit light, stops the light emission, or receives the light receiving unit 506 of the reflective optical sensor 502 according to a command from the system controller 126. It adjusts the light receiving sensitivity and so on.

  In addition, the reflection type optical sensor control unit 508 of this embodiment includes an A / D conversion unit 510, and the A / D conversion unit 510 outputs the light from the light receiving unit 506 of the reflection type optical sensor 502. It also has a function of converting the converted signal from an analog signal to a digital signal. Specifically, the reflection-type optical sensor control unit 508 performs A / D conversion on the signal output from the reflection-type optical sensor 502, converts the signal into a digital signal, and outputs the digital signal to the system controller 126. It has become.

<System controller>
The system controller 126 acquires the detection result of the light receiving unit 506 of the reflective optical sensor 502 as digital data from the reflective optical sensor control unit 508. The system controller 126 detects the position of the medium S to be printed based on the acquired digital data and the position information of the carriage 41 acquired from the linear encoder 51.

<Actual detection process>
Next, an actual processing example will be described. FIG. 16 illustrates the operation when the position of the medium S is detected. When detecting the position of the medium S, the carriage 41 moves toward the medium S along the direction of arrow A in FIG. 16A. At this time, light is emitted from the light emitting unit 504 of the reflective optical sensor 502 toward the platen 14, and the light reflected by the platen 14 is received by the light receiving unit 506 of the reflective optical sensor 502. Next, as shown in FIG. 16B, when the reflective optical sensor 502 provided on the carriage 41 reaches above one end of the medium S, the light is emitted from the light emitting unit 504 of the reflective optical sensor 502. The light is reflected by the medium S, and the reflected light is received by the light receiving unit 506 of the reflective optical sensor 502.

  When the light reflected by the medium S is received by the light receiving unit 506, the level of the signal output from the reflective optical sensor 502 changes greatly, so that the position of one end of the medium S can be detected. it can. Furthermore, as shown in FIG. 16C, when the carriage 41 moves along the direction of the arrow A and the reflective optical sensor 502 provided on the carriage 41 reaches above the other end of the medium S, The light emitted from the light emitting unit 504 of the reflective optical sensor 502 is reflected by the platen 14, and the reflected light is received by the light receiving unit 506 of the reflective optical sensor 502. At this time, since the level of the signal output from the reflective optical sensor 502 changes greatly again, the position of the other end of the medium S can be detected. Thereafter, as shown in FIG. 16D, when the carriage 41 further moves to a predetermined position, the medium S detection process ends.

  FIG. 17 briefly illustrates the relationship between the level of the signal output from the reflective optical sensor 502 and the medium S. When the carriage 41 moves and the reflective optical sensor 502 reaches one end of the medium S, the level of the signal output from the reflective optical sensor 502 is changed from a high level Va as shown in FIG. It greatly changes to a low level Vb. While the reflective optical sensor 502 is positioned above the medium S, a low level Vb signal is output from the reflective optical sensor 502. When the reflective optical sensor 502 reaches the other end of the medium S, the level of the signal output from the reflective optical sensor 502 is changed from a low level Vb to a high level Va again as shown in FIG. Change.

  The system controller 126 sequentially acquires digital data corresponding to the level of the signal output from the reflective optical sensor 502 through the reflective optical sensor control unit 508. Then, the system controller 126 sequentially compares the digital data acquired from the reflective optical sensor 502 with a predetermined threshold value V0 as shown in FIG. 17, and the level of the signal output from the reflective optical sensor 502 Is checked to see if it does not exceed its predetermined threshold value V0. Here, the predetermined threshold value V0 is set to an appropriate value between the high level Va and the low level Vb. When the level of the signal output from the reflective optical sensor 502 exceeds the predetermined threshold value V0, it is determined that one end of the medium S has been detected by the reflective optical sensor 502, and the linear type is detected. Based on the output information from the encoder 51, the position of the end of the medium S is specified and the position is stored in the main memory 127 or the like.

  Further, the system controller 126 sequentially compares the digital data acquired from the reflective optical sensor 502 with a predetermined threshold value V0, and the level of the signal from the reflective optical sensor 502 again reaches the predetermined threshold value V0. Check if it does not exceed. When the level of the signal output from the reflective optical sensor 502 again exceeds the predetermined threshold value V0, it is determined that the other end of the medium S has been detected by the reflective optical sensor 502. Based on the output information from the linear encoder 51, the position of the end of the medium S is specified, and the position is stored in the main memory 127 or the like. As a result, the positions of both ends of the medium S are specified, the position of the medium S can be detected, and the width dimension of the medium S can also be detected. The size of the medium S is also specified from the width dimension. be able to.

=== Survey of Platen 14 ===
In the inkjet printer 1 according to the present embodiment, the state of the platen 14 is investigated. The investigation process of the platen 14 executed here will be described in detail below.

<Reason for investigation>
The state of the platen 14 is investigated for the following reason. That is, in the case of a printing apparatus that performs printing by ejecting ink onto the medium S as in the ink jet printer 1 according to the present embodiment, the ejected ink is atomized to generate mist, and the platen 14 In addition, there is a problem that the peripheral portion becomes dirty. In particular, when “marginless printing” is performed, the ink ejected from the nozzles # 1 to # 180 does not reach the medium S and is detached from the medium S, so that mist is likely to occur. Dirt is also big.

  FIG. 18 illustrates a state when the platen 14 is soiled. FIG. 18B is a plan view showing an example of the degree of contamination of the platen 14 in FIG. 18A, and FIG. 18B is a cross-sectional view of the degree of contamination seen from the side. As shown in FIG. 18A, the atomized ink ejected from the nozzles # 1 to # 180 adheres to the periphery of the groove 354, the upper surface of the rectangular protrusion 364 in the groove 354, and the like. Dirt DT is formed. The ball-shaped stain DT is generated by the mist-like ink piled up and gradually growing like a crystal. As shown in FIG. 18B, the upper surface of the peripheral portion of the groove portion 354 and the inside of the groove portion 354 are formed. On the upper surface of the rectangular protrusion 364, it is piled up like a mountain.

  When the atomized ink reaches the inside of the groove portion 354, that is, on the absorbent material 356, it is absorbed by the absorbent material 356, and when adhering to the protruding portion 362 or the ribs 366, 368, It adheres to the medium S to be printed and is removed.

  When the platen 14 is dirty as described above, the stain DT on the platen 14 may be erroneously detected as the medium S when the medium S is detected by the reflective optical sensor 502. FIG. 19 shows an example of a signal output from the reflective optical sensor 502 when the platen 14 is dirty. When the platen 14 is dirty, as shown in the figure, the signal output from the reflective optical sensor 502 detects the dirt DT in addition to the rectangular pulse Wa indicating that the medium S has been detected. A steep pulse Wb generated by the above is included. This steep pulse Wb may exceed a predetermined threshold value V0 that serves as a reference in detecting the medium S. When the pulse Wb that exceeds the predetermined threshold value V0 is generated, the dirt DT on the platen 14 is determined to be a part of the medium S, and the position of the medium S may be erroneously detected. It was.

<Investigation method>
Therefore, in the inkjet printer 1 according to the present embodiment, in order to eliminate such erroneous detection of the medium S due to the dirt DT of the platen 14, the state of the platen 14 is investigated at an appropriate timing, and based on the investigation result. The predetermined threshold value V0 is changed as appropriate. Hereinafter, the process of changing the predetermined threshold value V0 will be described in detail.

  20 and 21 illustrate the state when the platen 14 is investigated. FIG. 20 is a plan view for explaining the investigation status of the platen 14. FIG. 21 is a side view for explaining the investigation status of the platen 14.

  The investigation of the platen 14 is performed when the medium S is not on the platen 14 by the reflective optical sensor 502. When examining the platen 14, as shown in FIG. 20, the carriage 41 provided with the reflective optical sensor 502 moves above the platen 14 along the direction of the arrow B in the figure. At this time, light is emitted from the light emitting unit 504 of the reflective optical sensor 502 toward the platen 14 as shown in FIG. Here, the emitted light is irradiated in a form straddling the groove 354 (absorbent material 356) on the platen 14 and its edge. The light emitted from the light emitting unit 504 is reflected by the groove 354 on the platen 14 or the edge thereof, and the reflected light is received by the light receiving unit 506 of the reflective optical sensor 502. Light emission from the light emitting unit 504 and light reception by the light receiving unit 506 are continuously performed while the carriage 41 moves on the platen 14.

  The reflective optical sensor 502 generates a signal corresponding to the intensity of light received by the light receiving unit 506 and outputs the signal to the reflective optical sensor control unit 508 (see FIG. 4). The reflection-type optical sensor control unit 508 converts the signal from the reflection-type optical sensor 502 from an analog signal to a digital signal by the A / D conversion unit 510 and outputs the converted signal to the system controller 126 as digital data. The system controller 126 acquires digital data from the reflective optical sensor 502, and acquires data corresponding to the effective range SA shown in FIG. Then, the system controller 126 determines whether or not it is necessary to change the predetermined threshold value V0 that is a reference for detecting the medium S based on the investigation result, and how to change the threshold value V0 when changing the threshold value. Judge whether to change to the correct value.

<Change threshold>
FIG. 22 shows an example of a signal output from the reflective optical sensor 502 when the platen 14 is examined by the reflective optical sensor 502. When there is dirt DT on the platen 14, a steep pulse Wb is generated in the signal output from the reflective optical sensor 502, as shown in FIG. Note that the pulse Wc included in the signal output from the reflective optical sensor shown in the figure is generated by receiving the light reflected from the rib 368 at the peripheral edge of the groove portion 354 of the platen 14 by the light receiving portion. It is.

  The system controller 126 obtains the minimum value Vc from the signal output from the reflection type optical sensor 502, and examines the magnitude of the steep pulse Wb generated when the platen 14 is contaminated DT. Then, the system controller 126 checks whether or not the acquired minimum value Vc exceeds a predetermined reference value Vk. When the acquired minimum value Vc exceeds the predetermined reference value Vk, the system controller 126 determines that it is necessary to change the threshold value V0 that has been the detection reference of the medium S so far, and acquires the acquired minimum value Vc. A new threshold value Vn is set between the value Vc and the signal level Vb obtained by detecting the medium S when the medium is detected. The new threshold value Vn set here may be set at the exact center between the acquired minimum value Vc and the signal level Vb obtained from the medium S when the medium is detected. It may be set so as to be biased to either one of the values Vc. Further, the new threshold value Vn set here is stored in the main memory 127 or the like by the system controller 126.

  Next, when the medium S detection process is executed, the medium S can be detected with the newly set threshold value Vn. For this reason, even if there is dirt DT or the like on the platen 14, it is possible to prevent the dirt DT or the like from being erroneously detected as the medium S. As a result, the medium S can be detected with higher accuracy than in the prior art in which the predetermined threshold value V0 is set as a fixed value.

  Here, the signal level Vb obtained by detecting the medium S at the time of detecting the medium S may be a signal level obtained from a specific type of medium such as “plain paper” or a plurality of types. Or a value obtained from the medium closest to the threshold value V0 (here, the maximum value).

<Investigation procedure>
FIG. 23 is a flowchart showing an example of a processing procedure for investigating the platen 14. When the platen 14 is investigated, the system controller 126 first drives the carriage motor 42 through the carriage motor control unit 128 to start moving the carriage 41 (S202). Thereby, the carriage 41 starts to move in the direction of the arrow B as shown in FIG. Light is emitted from the light emitting unit 504 of the reflective optical sensor 502 from the start of movement of the carriage 41.

  The system controller 126 acquires, from the linear encoder 51, whether or not the current position of the reflective optical sensor 502 provided on the carriage 41 is within the predetermined effective range SA when the carriage 41 starts moving. Sequential checking is performed based on the current position (S204). When the reflective optical sensor 502 falls within the predetermined effective range SA, the system controller 126 acquires the data of the signal output from the reflective optical sensor 502 from the reflective optical sensor control unit 508 ( In S206, it is checked whether or not the data is the minimum value (S208). If the data acquired from the reflective optical sensor control unit 508 is the minimum value, the system controller 126 stores the minimum value in the main memory 127 or the like.

  Next, based on the current position of the carriage 41 acquired from the linear encoder 51, the system controller 126 checks whether or not the current position of the reflective optical sensor 502 is out of the predetermined effective range SA (S210). If the current position of the reflective optical sensor 502 is still within the predetermined effective range SA, the system controller 126 returns to step S206 again, and again reflects the reflective optical sensor control unit 508. The data is acquired from, and it is checked whether or not the data is the minimum value (S208). The acquisition of these data (S206) and the check (S208) of whether or not it is the minimum value are continuously executed by the system controller 126 until the current position of the reflective optical sensor 502 is out of the predetermined effective range SA.

  Here, in step S210, when the current position of the reflective optical sensor 502 is out of the predetermined effective range SA, the system controller 126 stops the carriage 41 at the predetermined position. Thereby, the investigation process of the platen 14 is completed.

<Threshold change procedure>
Next, the procedure for changing the predetermined threshold value V0 based on the minimum value Vc obtained by examining the platen 14 in this manner will be described.

FIG. 24 is a flowchart showing a flow of processing performed when the predetermined threshold value V0 is changed. The system controller 126 acquires the minimum value Vc from the result of the investigation of the platen 14 (S302), and then compares the acquired minimum value Vc with a predetermined reference value Vk (S304). Then, it is checked whether or not the acquired minimum value Vc is below a predetermined reference value Vk (S306). If the acquired minimum value Vc does not fall below the predetermined reference value Vk, the system controller 126 determines that there is no need to change the threshold value V0, and immediately ends the process. On the other hand, if the acquired minimum value Vc is below the predetermined reference value Vk, the system controller 126 determines that the threshold value V0 needs to be changed, and acquires the acquired minimum value Vc and the medium detection. A new threshold value Vn that is sometimes set between the signal level Vb (see FIG. 22) obtained by detection of the medium S is calculated (S308).
Then, the system controller 126 replaces the calculated new threshold value Vn with the original threshold value V0 and stores it in the main memory 127 or the like so that the new threshold value Vn is used from the next medium detection time. (S310).

  In the embodiment described above, the predetermined threshold value V0 is changed based on the minimum value Vc. However, in the present invention, the level of the signal output from the reflective optical sensor is reversed in the plus and minus directions. Alternatively, the maximum value may be acquired from the signal and the predetermined threshold value V0 may be changed based on the maximum value.

=== Sampling period ===
In the inkjet printer 1 according to the present embodiment, the A / D conversion unit 510 performs the sampling cycle performed by the A / D conversion unit 510 when the medium S is detected during printing and the platen 14 is investigated. The sampling cycle is different. Specifically, the sampling cycle performed by the A / D conversion unit 510 when investigating the platen 14 is greater than the sampling cycle performed by the A / D conversion unit 510 when detecting the medium S during printing. It is set short.

  FIG. 25 shows the sampling periods performed by the A / D converter 510. FIG. 25A shows a sampling cycle performed by the A / D converter 510 when the medium S is detected during printing, and FIG. 25B shows sampling performed by the A / D converter 510 when examining the platen 14. It shows the period of.

  When detecting the medium S during printing, as shown in FIG. 25A, the A / D converter 510 samples the signal output from the reflective optical sensor 502 at the cycle Ts1. On the other hand, when investigating the platen 14, as shown in FIG. 25B, the A / D conversion unit 510 performs sampling of the signal output from the reflective optical sensor 502 at a cycle Ts2 shorter than the cycle Ts1. In FIG. 25A and FIG. 25B, a mark “▽” indicates a position where sampling is performed.

  In this way, the sampling cycle performed by the A / D conversion unit 510 when detecting the medium S during printing is different from the sampling cycle performed by the A / D conversion unit 510 when investigating the platen 14. The reason why this can be done is as follows. That is, when the medium S is detected when printing is performed, the print data sent from the host computer 140 needs to be sequentially processed by the system controller 126, so the processing load on the system controller 126 is greatly increased. Will do. For this reason, the system controller 126 cannot apply a great capability to the processing of signal data from the reflective optical sensor 502 sent through the reflective optical sensor control unit 508. Therefore, the signal data from the reflective optical sensor 502 sent through the reflective optical sensor control unit 508 must be processed with very limited capability. For this reason, it is very difficult to set the sampling cycle performed by the A / D conversion unit 510 short when the medium S is detected during printing.

  On the other hand, when the platen 14 is examined, the system controller 126 does not process the print data from the host computer 140, and therefore smoothly processes the data sent from the A / D conversion unit 510. be able to. For this reason, when investigating the platen 14, the sampling period performed by the A / D converter 510 can be shortened.

  Note that the sampling period performed by the A / D conversion unit 510 is changed by the reflective optical sensor control unit 508 according to a command from the system controller 126.

  Thus, the sampling cycle performed by the A / D conversion unit 510 when investigating the platen 14 is set to be shorter than the sampling cycle performed by the A / D conversion unit 510 when the medium S is detected during printing. By doing so, there are the following merits.

(A) The investigation time of the platen 14 can be shortened.
When investigating the platen 14, the sampling period performed by the A / D conversion unit 510 can be set short. Therefore, by increasing the moving speed of the carriage 41, that is, the moving speed of the reflective optical sensor 502, The time required for 14 surveys can be greatly reduced. That is, even when the number of samplings is the same as when the medium S is detected during printing, the processing time is shorter when the platen 14 is examined.

(B) The platen 14 can be investigated with high accuracy.
When the platen 14 is investigated, the sampling period performed by the A / D conversion unit 510 can be set short. Therefore, if the moving speed of the carriage 41, that is, the moving speed of the reflective optical sensor 502 does not change, the platen 14 is changed. Can be conducted with higher accuracy. That is, since the sampling interval on the platen 14 is narrowed, the state of the platen 14 can be examined in more detail. Thereby, it is possible to detect even a small dirt DT generated on the platen 14.

  FIG. 26A illustrates a sampling result obtained when the state of the platen 14 is examined in detail by setting the sampling period performed by the A / D conversion unit 510 short. When sampling is performed with a short period by the A / D conversion unit 510, as shown in the figure, even a small dirt DT generated on the platen 14 can be detected as a steep pulse Wd having a large amplitude. . Thereby, based on such a steep pulse Wd, it is possible to change the predetermined threshold value V0 which is a criterion for determining the presence or absence of the medium S as described above. For this reason, the small dirt DT and the like generated on the platen 14 can be found early, and the predetermined threshold value V0 can be dealt with early according to the dirt DT. Therefore, it is possible to prevent erroneous detection of the medium S in advance.

  On the other hand, when the medium S is detected during printing, sampling is performed by the A / D conversion unit 510 at a longer period than when the platen 14 is investigated, and therefore sampling is performed more than when the platen 14 is examined. The interval becomes wide and the state of the platen 14 is not detected in detail. For this reason, even the small dirt DT generated on the platen 14 is not detected as in the case where the platen 14 is investigated.

  FIG. 26B illustrates a sampling result when sampling is performed with a long period when a medium is detected during printing. When the medium S is detected during printing, if sampling is performed with a longer period than when the platen 14 is examined, as shown in the figure, small dirt DT on the platen 14 It is not detected as a pulse Wd having a large amplitude as in the investigation (see FIG. 26A), but as a pulse We having a smaller amplitude. Therefore, in determining whether or not the medium S, the pulse We having such a small amplitude is not determined as the medium S.

  For these reasons, when the platen 14 is investigated, the sampling is performed at a shorter cycle than when the medium S is detected when performing printing, and detection is performed when the medium S is detected when performing printing. Even small dirt DT that cannot be detected can be detected in advance when the platen 14 is investigated. Moreover, if the predetermined threshold value V0 is changed at an early stage corresponding to the small stain DT, the small stain DT is erroneously detected as the medium S when the medium S is detected during printing. Can be further prevented.

  As described above, in the inkjet printer 1 according to the present embodiment, the sampling cycle performed when the platen 14 is examined is set to be shorter than the sampling cycle performed when the medium S is detected during printing. As a result, it is possible to shorten the time required to investigate the platen 14. Further, the platen 14 is surveyed with high accuracy, and small stains DT and the like on the platen 14 are accurately detected in advance, and the predetermined threshold value V0 is changed early corresponding to the small stains DT. Accordingly, it is possible to sufficiently prevent erroneous detection of the medium S when the medium S is detected during printing.

=== Investigation timing ===
There are the following timings (A) to (E) as the timing at which the platen 14 is investigated.

(A) When the power is turned on When the power switch of the ink jet printer 1 is turned on, it is necessary to investigate the state of the platen 14 and reset the predetermined threshold value V0 as one of the initialization processes. To check.

(B) Before Print Job When print data transmitted from the host computer 140 is received by the inkjet printer 1, the state of the platen 14 is checked and a predetermined process is performed before executing print processing based on the print data. Check whether the threshold value V0 needs to be reset.

(C) Between print jobs After executing print processing based on the print data sent from the host computer 140, before the next print data is sent from the host computer 140 and executed based on the print data. Then, the state of the platen 14 is examined to check whether it is necessary to reset the predetermined threshold value V0.

(D) Every page When the medium S is fed from the paper feed unit 4, the state of the platen 14 is checked each time to check whether or not the predetermined threshold value V0 needs to be reset.

(E) First execution of borderless printing When “marginless printing” is executed for the first time in the inkjet printer 1, the state of the platen 14 is examined, and a predetermined threshold value V0 is appropriately set. The determination whether or not “marginless printing” is executed for the first time in the inkjet printer 1 is performed based on information stored in an appropriate storage unit mounted on the inkjet printer 1 such as the main memory 127, for example. . That is, for example, in an appropriate storage unit such as the main memory 127, execution history information regarding whether or not “marginless printing” has been executed so far in the inkjet printer 1 is stored. When the inkjet printer 1 is shipped as a product, information that “marginless printing” has not been executed is stored in the main memory 127 or the like as execution history information. When “marginless printing” is executed, the execution history information is changed by the system controller 126.

  The system controller 126 checks execution history information stored in the memory memory 127 or the like when “marginless printing” is executed. Then, the system controller 126 determines whether or not “marginless printing” is executed for the first time. When it is determined that “marginless printing” is executed for the first time, the system controller 126 emits light from the light emitting unit 504 of the reflective optical sensor 502 and examines the state of the platen 14. Then, based on the investigation result, a predetermined threshold value V0 is set as appropriate.

  In the present invention, the platen 14 need not be executed at the timings (A) to (E), and the platen 14 may be investigated at other timings other than the timings (A) to (E). .

=== Configuration of Printing System etc. ===
Next, as an example of a printing system according to the present invention, a printing system including an inkjet printer as a printing apparatus will be described as an example.

  FIG. 27 is an explanatory diagram showing an external configuration of the printing system. The printing system 1000 includes a computer main body 1102, a display device 1104, a printing device 1106 such as the inkjet printer 1, an input device 1108, and a reading device 1110. In this embodiment, the computer main body 1102 is housed in a mini-tower type housing, but is not limited thereto. The display device 1104 is generally a CRT (Cathode Ray Tube), a plasma display, a liquid crystal display device, or the like, but is not limited thereto. The printer described above is used as the printing apparatus 1106. In this embodiment, the input device 1108 is a keyboard 1108A and a mouse 1108B, but is not limited thereto. In this embodiment, the reading device 1110 uses a flexible disk drive device 1110A and a CD-ROM drive device 1110B. However, the reading device 1110 is not limited to this. For example, an MO (Magnet Optical) disk drive device or a DVD (Digital Versatile) is used. Disk) etc. may be used.

  FIG. 28 is a block diagram showing the configuration of the printing system shown in FIG. An internal memory 1202 such as a RAM and an external memory such as a hard disk drive unit 1204 are further provided in a housing in which the computer main body 1102 is housed.

  The computer program for controlling the operation of the inkjet printer 1 described above can be downloaded to a computer 1000 or the like connected to the printing apparatus 1106 via a communication line such as the Internet, for example, and can be read by a computer. It can be recorded in S and distributed. As the recording medium, for example, various recording media such as a flexible disk FD, a CD-ROM, a DVD-ROM, a magneto-optical disk MO, a hard disk, and a memory can be used. Note that information stored in such a storage medium can be read by various reading devices 1110.

  In the above description, an example in which the printing apparatus 1106 is connected to the computer main body 1102, the display apparatus 1104, the input apparatus 1108, and the reading apparatus 1110 to configure the printing system has been described, but the present invention is not limited thereto. is not. For example, the printing system may be configured by the computer main body 1102 and the printing device 1106, and the printing system may not include any of the display device 1104, the input device 1108, and the reading device 1110. For example, the printing apparatus 1106 may have a part of the functions or mechanisms of the computer main body 1102, the display apparatus 1104, the input apparatus 1108, and the reading apparatus 1110. As an example, the printing apparatus 1106 includes an image processing unit that performs image processing, a display unit that performs various displays, and a recording medium attachment / detachment unit for attaching / detaching a recording medium that records image data captured by a digital camera or the like. It is good also as a structure which has.

  The printing system realized in this way is a system superior to the conventional system as a whole system.

=== Other Embodiments ===
As described above, the printing apparatus such as a printer according to the present invention has been described based on one embodiment. However, the above-described embodiment is for facilitating the understanding of the present invention, and the present invention is limited and interpreted. Not meant to be The present invention can be changed or improved without departing from the gist thereof, and needless to say, the present invention includes equivalents thereof. In particular, even the embodiments described below are included in the printing apparatus according to the present invention.

  In the present embodiment, part or all of the configuration realized by hardware may be replaced by software, and conversely, part of the configuration realized by software may be replaced by hardware.

  In addition, a part of processing performed on the printing apparatus side may be performed on the host side, and a dedicated processing apparatus is provided between the printing apparatus and the host, and a part of processing is performed on this processing apparatus. May be performed.

<About the printing section>
In the embodiment described above, nozzles # 1 to # 180 for ejecting ink provided in the head 21 as shown in FIG. 5 have been described as examples of the printing unit of the present invention. The printing unit is not limited to the nozzles # 1 to # 180 for discharging such ink, and may be a printing unit having an ink discharging unit of another form. It may be a printing unit that performs printing. For example, a printing unit that prints on a medium by a dot impact method, prints on a medium by a laser beam method, or prints on a medium by any method such as a thermal transfer method or a sublimation method. If so, it corresponds to the printing section of the present invention.

<About support part>
In the above-described embodiment, the platen 14 as shown in FIGS. 11 to 13 has been described as an example of the support part of the present invention. However, the support part of the present invention is not limited to such a platen 14. First, any portion that supports the medium S on which printing is performed is included in the support portion of the present invention.

<About optical sensors>
In the embodiment described above, the reflection type optical sensor 502 as described above has been described as an example of the optical sensor of the present invention. However, in the optical sensor of the present invention, such a reflection type optical sensor is used. Any sensor that emits light toward the medium S and detects the light reflected by the medium S may be used.

  Further, in the above-described embodiment, as the optical sensor of the present invention, the reflection type optical sensor 502 installed on the carriage 41 and provided so as to be movable relative to the medium S or the platen (supporting portion) 14 is taken as an example. As described above, in the optical sensor of the present invention, it is not always necessary to be provided so as to be relatively movable with respect to the medium S or the platen (supporting portion) 14, and it is not necessarily provided on the carriage 41. Nor.

<Signal generated by optical sensor>
In the above-described embodiment, the signal generated by the reflective optical sensor 502 as the optical sensor of the present invention is an analog signal. However, in the present invention, the signal generated by the optical sensor is not an analog signal but a digital signal or the like. It does not matter.

<About media detection>
In the embodiment described above, the reflection type optical sensor 502 is provided on the carriage 41 as the optical sensor of the present invention, and the end position, width dimension, size, etc. of the medium S can be detected by the movement of the carriage 41. However, in the detection of the medium by the optical sensor of the present invention, it is not always necessary to be able to perform such detection. For example, if the medium can be detected, for example, by detecting the presence or absence of the medium, in any form. The medium may be detected.

<About sampling>
In the above-described embodiment, the sampling performed to detect the medium when performing printing and the sampling performed when examining the platen are performed by the same controller (system controller 126). The present invention is not limited to such a case, and sampling may be executed by different controllers.

<About moving range>
In the embodiment described above, the range in which the optical sensor (reflection optical sensor 502) of the present invention moves relative to the support portion (platen 14) of the present invention when the predetermined threshold value is changed is the support portion. However, in the present invention, the movement range of the optical sensor is not necessarily limited to the entire support portion, and may be only a part of the support portion.

<About printing devices>
In the above-described embodiment, the ink jet printer has been described as an example of the printing apparatus according to the present invention. However, the printing apparatus according to the present invention is not limited to such a printing apparatus. Any type of apparatus may be used as long as it is an apparatus that prints on a medium, such as a printer or a laser beam printer.

<About media>
For media, including plain paper, matte paper, cut paper, glossy paper, roll paper, paper, photo paper, roll-type photo paper, etc., in addition to these, film materials and cloth materials such as OHP film and gloss film, It may be a metal plate material or the like. That is, any medium can be used as long as it can be an ink ejection target.

<About the printing system>
In the above-described embodiment, the configuration in which the inkjet printer is connected to the computer main body has been described as the printing system according to the present invention. However, in the printing system according to the present invention, the printing apparatus connected to the computer main body includes: In addition to such an ink jet printer, other types of printing apparatuses may be used. For example, any type of apparatus may be used as long as it is an apparatus that performs printing on a medium, such as a dot impact printer or a laser beam printer.

  Further, in the above-described embodiment, the configuration including the display device 1104, the input device 1108, and the reading device 1110 in addition to the computer main body 1102 has been described as the printing system. In this case, it is not always necessary to provide such a configuration, and it is sufficient if the computer main body 1102 is provided in addition to the printing apparatus.

1 is a perspective view of an embodiment of a printing apparatus according to the present invention. FIG. 3 is a perspective view illustrating an internal configuration of the printing apparatus. Sectional drawing which shows the conveyance part of a printing apparatus. 1 is a block configuration diagram showing a system configuration of a printing apparatus. FIG. 3 is a plan view illustrating an example of an ink discharge unit of a printing apparatus. Explanatory drawing which showed the structure of the linear encoder typically. FIG. 7A is a timing chart showing the output waveform of the linear encoder during forward rotation, and FIG. 7B is a timing chart showing the output waveform of the linear encoder during reverse rotation. 6 is a flowchart for explaining an example of printing processing. FIG. 3 is an explanatory diagram illustrating a relationship between a printing area P and a medium S during normal printing. FIG. 5 is an explanatory diagram illustrating a relationship between a printing area P and a medium S during borderless printing. The top view which showed one Embodiment of the ink collection | recovery part of this invention. The perspective view which showed one Embodiment of the ink collection | recovery part of this invention. FIG. 3 is a cross-sectional view illustrating an embodiment of an ink recovery unit of the present invention. Explanatory drawing explaining the other example of borderless printing. Explanatory drawing explaining one Embodiment of the optical sensor of this invention. Explanatory drawing explaining an example of medium detection processing. Explanatory drawing explaining the signal output from the optical sensor of this invention. Explanatory drawing which shows an example when dirt arises in a platen. Explanatory drawing explaining the malfunction which arises by the stain | pollution | contamination of a platen. The top view for demonstrating the inspection method of a platen. The side view for demonstrating the inspection method of a platen. Explanatory drawing which showed an example of the signal output from a sensor at the time of investigation. The flowchart which showed an example of the investigation procedure of a platen. The flowchart which showed an example of the procedure in the case of resetting a threshold value. FIG. 25A is a diagram illustrating a sampling cycle when detecting a medium, and FIG. 25B is a diagram illustrating a sampling cycle when investigating a platen. FIG. 26A explains the sampling result when the platen is examined with a short sampling period, and FIG. 26B explains the sampling result when the medium is detected with a long sampling period. 1 is a perspective view for explaining an embodiment of a printing system according to the present invention. The block block diagram which shows the structure of the printing system of FIG.

Explanation of symbols

1 Inkjet printer, 2 operation panel, 3 paper discharge unit, 4 paper supply unit,
5 operation buttons, 6 indicator lamps, 7 paper discharge tray, 8 paper feed tray,
11A paper insertion slot, 11B roll paper insertion slot, 13 paper feed roller, 14 platen,
15 paper transport motor, 17A transport roller, 17B paper discharge roller,
18A free roller, 18B free roller, 21 heads,
30 cleaning unit, 31 pump device, 35 capping device,
41 Carriage, 42 Carriage motor, 44 Pulley, 45 Timing belt,
46 guide rail, 48 ink cartridge, 51 linear encoder,
122 buffer memory, 124 image buffer, 126 system controller,
127 main memory, 128 carriage motor control unit, 129 EEPROM,
130 transport control unit, 132 head drive unit, 134 rotary encoder,
140 host computer, 211 nozzle array,
352 Ink recovery part, 354 groove part, 354a groove part, 354b groove part,
356 Absorber, 362 Projection, 364 Projection, 366 Rib, 368 Rib,
452 Light emitting diode, 454 collimator lens, 456 detection processing unit,
458 photodiode, 460 signal processing circuit, 462A comparator,
462B comparator, 464 linear encoder code plate,
502 reflective optical sensor, 504 light emitting unit, 506 light receiving unit,
508 reflective optical sensor control unit, 510 A / D conversion unit,
1102 Computer main body 1104 Display device 1106 Printing device
1108 input device, 1108A keyboard, 1108B mouse,
1110 reading device, 1110A flexible disk drive device,
1110B CD-ROM drive device, 1204 hard disk drive unit,
S Medium

Claims (15)

A printing section for printing on the medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
A value obtained by sampling the signal generated by the optical sensor at a predetermined period when the optical sensor is moved relative to the support portion during printing;
In a printing apparatus that detects the medium by comparing with a predetermined threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period shorter than the predetermined period. Then, the printing apparatus is characterized in that the predetermined threshold value is changed based on the value obtained by the sampling.   The printing apparatus according to claim 1, wherein the sampling executed when investigating the state of the support portion and the sampling executed when performing the printing are performed by the same controller. .   When the printing is performed, the optical sensor moves relative to the support part, and the optical sensor moves relative to the support part when investigating the state of the support part. The printing apparatus according to claim 1, wherein the moving speed when moving is different.   The movement speed when the optical sensor moves relative to the support portion when investigating the state of the support portion is such that the optical sensor is relative to the support portion when performing the printing. The printing apparatus according to claim 3, wherein the printing apparatus is faster than a moving speed when moving.   The range in which the optical sensor moves relative to the support portion when changing the predetermined threshold value extends over the entire support portion. A printing apparatus according to 1.   The range in which the optical sensor moves relative to the support portion when changing the predetermined threshold is such that the optical sensor moves relative to the support portion when detecting the medium. The printing apparatus according to claim 1, wherein the printing apparatus is equal to a range to be printed.   The minimum value or the maximum value is obtained from the signal output from the optical sensor, and the predetermined threshold value is changed based on the minimum value or the maximum value. The printing apparatus according to item 1.   The printing apparatus according to claim 7, wherein the predetermined threshold value is not changed when the minimum value or the maximum value does not reach a predetermined reference value.   The printing apparatus according to claim 1, wherein the state of the support unit is examined when printing is not performed on the medium by the printing unit.   The printing apparatus according to claim 1, wherein when the power of the printing apparatus is turned on, the state of the support portion is investigated. A memory in which an execution history of borderless printing in which ink is ejected from the ink ejection unit toward the edge of the medium for printing is stored;
When executing the borderless printing, if the execution history stored in the memory is checked and the borderless printing has not been executed, light is emitted from the light emitting unit toward the support member. The predetermined threshold is changed based on the signal output from the optical sensor when the light reflected by the support member is received by the light receiving unit. The printing apparatus according to any one of 10.   The printing apparatus according to claim 1, wherein the printing unit performs printing by discharging ink toward the medium. A printing section for printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
A value obtained by sampling the signal generated by the optical sensor at a predetermined period when the optical sensor is moved relative to the support portion during printing;
In a printing apparatus that detects the medium by comparing with a predetermined threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period shorter than the predetermined period. Then, based on the value obtained by this sampling, the predetermined threshold value is changed,
The sampling executed when investigating the state of the support part and the sampling executed when performing the printing are performed by the same controller,
The movement speed when the optical sensor moves relative to the support portion when investigating the state of the support portion is such that the optical sensor is relative to the support portion when performing the printing. Faster than moving speed when moving,
The range in which the optical sensor moves relative to the support when changing the predetermined threshold is over the entire support.
The range in which the optical sensor moves relative to the support portion when changing the predetermined threshold is such that the optical sensor moves relative to the support portion when detecting the medium. Equal to the range to
Obtaining a minimum or maximum value from the signal output from the optical sensor, and changing the predetermined threshold based on the minimum or maximum value;
When the minimum value or the maximum value does not reach a predetermined reference value, the predetermined threshold value is not changed,
When the printing unit is not printing on the medium and when the printing apparatus is turned on, the state of the support unit is investigated,
A memory in which an execution history of borderless printing in which ink is ejected from the ink ejection unit toward the edge of the medium for printing is stored;
When executing the borderless printing, if the execution history stored in the memory is checked and the borderless printing has not been executed, light is emitted from the light emitting unit toward the support member. Based on the signal output from the optical sensor when the light receiving unit receives the light reflected by the support member, the predetermined threshold is changed,
The printing apparatus, wherein the printing unit performs printing by ejecting ink toward the medium. A printing section for printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. A printing apparatus including an optical sensor that generates a signal according to
A value obtained by sampling the signal generated by the optical sensor at a predetermined period when the optical sensor is moved relative to the support portion during printing;
A medium detection method for detecting the medium by comparing with a predetermined threshold,
In order to investigate the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period shorter than the predetermined period. Then, the predetermined threshold value is changed based on the value obtained by the sampling. In a printing system comprising a computer main body and a printing device connectable to the computer main body,
The printing apparatus includes a printing unit that performs printing on a medium;
A support unit for supporting a medium on which printing is performed by the printing unit;
An intensity of light received by the light receiving unit, the light receiving unit configured to be opposed to the support unit and movable relative to the support unit, and having a light emitting unit that emits light and a light receiving unit that receives light. And an optical sensor that generates a signal according to
A value obtained by sampling the signal generated by the optical sensor at a predetermined period when the optical sensor is moved relative to the support portion during printing;
A printing apparatus that detects the medium by comparing with a predetermined threshold value,
When investigating the state of the support part, when the optical sensor moves relative to the support part, the signal generated by the optical sensor is sampled at a period shorter than the predetermined period. The printing system is characterized in that the predetermined threshold value is changed based on the value obtained by the sampling.

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