JP4174764B2 - Paper feed error detecting device, printing apparatus, and paper feed error detecting method - Google Patents

Description

  The present invention relates to a paper feed error detecting device, a printing apparatus, and a paper feed error detecting method, and more particularly, a printing state detecting optical type for detecting a printing state on a surface of a printing medium using reflected light of light irradiated on the printing medium. The present invention relates to a paper feed error detecting device and a paper feed error detecting method using a sensor (hereinafter also referred to as “optical sensor”), and a printing apparatus equipped with such a paper feed error detecting device.

  An ink jet printer as a printing apparatus having a print head provided with a number of nozzles as ink discharge units discharges ink droplets from each nozzle of the print head and drops them on a printing medium such as printing paper. Print images and text.

  However, due to causes such as an increase in ink viscosity or air bubbles in the ink, any of a number of nozzles provided in the print head may become clogged and ink droplets may not be ejected.

  If the nozzles are clogged and ink droplets cannot be ejected, dot omission occurs in an image composed of a large number of dots formed by the ink droplets, leading to degradation of image quality.

  As an apparatus for inspecting and judging the ejection state of ink droplets from nozzles, a judgment pattern for forming one printing block for each nozzle is printed on a printing medium, and the reflected light of the light irradiated on the printing medium is used. A printing apparatus equipped with an ink discharge determination device that determines the presence or absence of ink discharge from each nozzle by detecting the intensity is known (for example, see Patent Document 1).

Such an ink discharge determination device includes an optical sensor having a light emitting unit and a light receiving unit, and irradiates light from the light emitting unit to the determination patterns formed on the print medium corresponding to the respective nozzles. The presence / absence of ink ejection from each nozzle is determined based on the output of the light receiving unit that receives the reflected light having the intensity corresponding to the printing state of the determination pattern.
JP-A-6-297728

  By the way, a printing medium, for example, printing paper in the printing apparatus is conveyed by a paper feed motor and a paper feed roller.

  The paper feed amount in the paper feed operation is controlled by a sub-scan driver that controls the drive operation in the paper feed direction based on a command from a system controller that controls the operation of the entire printing apparatus. It is transmitted to the print medium by a roller.

  However, the paper feed roller may be eccentric before the start of use due to manufacturing process variations. Moreover, it may become the state similar to eccentricity as a result by the uneven wear after a use start.

  Since the radius of the paper feed roller with eccentricity or uneven wear differs depending on the part, and the length of the arc with respect to a certain central angle also differs depending on the part, the circumference estimated from the radius in the design data or the radius when evenly worn There will be an error between the length of and the actual circumference.

  Therefore, when the paper feeding operation is performed using the paper feeding roller in which such eccentricity or uneven wear has occurred, an error occurs between the commanded paper feeding amount and the actual paper feeding amount.

  Since an error in the paper feed amount, that is, a paper feed error causes a decrease in print image quality, it is desirable that the paper feed control is adjusted so that the paper feed error is minimized in the printing apparatus.

  For this purpose, first, it is necessary to accurately detect how much paper feed error has occurred in each printing apparatus.

  Since the paper feed error is reflected in the print state of the print medium surface as a decrease in print image quality, there is a possibility that the paper feed error can be detected by printing a certain pattern and examining the print state.

  On the other hand, since the above-described ink discharge determination device detects the print state of the print medium surface reflected in the intensity of reflected light, the print state of the print medium surface is not limited to the determination of the ink discharge state from the nozzles. There is a possibility that it can be widely used as a printing operation state detection device that detects various operation states of the printing device reflected in the above.

  An object of the present invention is to detect a paper feed error in a printing apparatus using an optical sensor for detecting a printing state of a surface of a printing medium using reflected light of light irradiated to the printing medium, and To provide a paper feed error detecting device, a printing apparatus, and a paper feed error detecting method capable of adjusting paper feed operation control so that the paper feed error is minimized.

According to the first aspect of the printing apparatus according to the embodiment of the present invention,
A print medium transport mechanism for transporting the print medium;
A print head having a plurality of ink ejection portions arranged along the print medium conveyance direction;
A plurality of lines printed by an upstream nozzle row constituted by a part of the plurality of ink discharge portions of a print head having a plurality of ink discharge portions arranged along the print medium transport direction and intersecting the transport direction Printed on the reference pattern, and the downstream nozzle row formed by a part of the plurality of ink discharge portions located on the downstream side in the transport direction from the upstream nozzle row so as to overlap the reference pattern. A light emitting unit that emits irradiation light to a print medium on which a print pattern for paper feed error detection composed of a plurality of line-shaped adjustment patterns parallel to the reference pattern is printed;
A light receiving unit that receives and detects reflected light reflected on the surface of the print medium, and converts and generates a received light output signal having a value corresponding to the intensity of the reflected light that reflects the print density of the print pattern for detecting the paper feed error. When,
It is characterized by having.

According to the second aspect of the printing apparatus according to the embodiment of the present invention,
A print medium transport mechanism for transporting the print medium;
A print head having a plurality of ink ejection portions arranged along the print medium conveyance direction;
A plurality of line-shaped reference patterns that are printed by a plurality of lower end nozzle rows as the ink discharge units located upstream of the central direction of the print head and that cross the transport direction, and the print head Paper that is printed so as to overlap the reference pattern by a plurality of upper end nozzle rows as the ink discharge portions located downstream of the central portion in the transport direction, and includes a plurality of line-shaped adjustment patterns parallel to the reference pattern A light emitting unit that emits irradiation light to a print medium on which a print pattern for detecting a feed error is printed;
A light receiving unit that receives and detects reflected light reflected on the surface of the print medium, and converts and generates a received light output signal having a value corresponding to the intensity of the reflected light that reflects the print density of the print pattern for detecting the paper feed error. When,
It is characterized by having.

  In the configuration of the printing apparatus according to the embodiment of the present invention, the paper feed error detection print pattern is a paper of a paper feed operation executed between printing of the reference pattern and printing of the adjustment pattern. A plurality of prints may be printed while changing the feed amount stepwise.

  The adjustment pattern is a basic paper feed in which a print medium region located immediately below the lower end nozzle row or the upstream nozzle row is located immediately below the upper end nozzle row or the downstream nozzle row. It may be printed after an amount of paper feeding operation or a paper feeding operation of a paper feeding amount obtained by adding a correction value to the basic paper feeding amount. In this case, the correction value may be varied within a range of ± 1/2 with the arrangement interval of the ink ejection units as one unit.

  Further, it is preferable to further include a paper feed error determination unit that determines the correction value that minimizes the paper feed error by specifying the print pattern for detecting the paper feed error having the lowest print density.

According to the first aspect of the paper feed error detection method according to the embodiment of the present invention,
A plurality of lines intersecting the transport direction by an upstream nozzle row constituted by a part of the plurality of ink discharge portions of a print head having a plurality of ink discharge portions arranged along the print medium transport direction. A process of printing a reference pattern;
The print medium region located immediately below the upstream nozzle row is located immediately below the downstream nozzle row constituted by a part of the plurality of ink ejection units located downstream in the transport direction from the upstream nozzle row. Performing a paper feed operation of a basic paper feed amount to be performed or a paper feed operation of a paper feed amount obtained by adding a correction value to the basic paper feed amount;
A plurality of lines of adjustment patterns parallel to the reference pattern are printed by the downstream nozzle row so as to overlap the reference pattern, thereby forming a paper feed error detection print pattern including the reference pattern and the adjustment pattern. The process of
It is characterized by having.

According to the second aspect of the paper feed error detection method according to the embodiment of the present invention,
In the transport direction, a plurality of lower end nozzle rows as the plurality of ink discharge units located upstream of the central direction of the print head having a plurality of ink discharge units disposed along the print medium transport direction. A process of printing a plurality of intersecting reference patterns,
The print medium region located immediately below the lower end nozzle row is located immediately below the upper end nozzle row as the plurality of ink ejection portions located on the downstream side in the transport direction from the central portion of the print head. A process of performing a paper feed operation of a basic paper feed amount or a paper feed operation of a paper feed amount obtained by adding a correction value to the basic paper feed amount;
A plurality of line-shaped adjustment patterns parallel to the reference pattern are printed by the upper end nozzle row so as to overlap the reference pattern, and a paper feed error detection print pattern including the reference pattern and the adjustment pattern is formed. The process of
It is characterized by having.

  In the configuration of the paper feed error detection method according to the embodiment of the present invention, it is preferable to further include a process of repeating the series of processes while changing the correction value. In that case, the correction value may be varied in a range of ± 1/2 with the arrangement interval of the ink discharge portions as one unit. Further, in those cases, it is preferable to further include a step of determining the correction value that minimizes the paper feed error by specifying the print pattern for detecting the paper feed error having the lowest print density. .

Also, a process of irradiating the print medium printed with the paper feed error detection print pattern with irradiation light,
Receiving and detecting reflected light reflected from the surface of the print medium, and converting and generating a received light output signal having a value corresponding to the intensity of the reflected light reflecting the print density of the paper feed error detection print pattern; ,
It is good to have further provided.

  Even in that case, it is preferable to further include a step of determining the correction value that minimizes the paper feed error by specifying the print pattern for detecting the paper feed error having the lowest print density.

  According to the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention, the print state detecting optical sensor for detecting the print state on the surface of the print medium using the reflected light of the light irradiated on the print medium. Can be used to detect the paper feed error in the printing apparatus and adjust the paper feed operation control so that the paper feed error is minimized.

  Embodiments of a paper feed error detecting device, a printing apparatus, and a paper feed error detecting method according to the present invention will be described below with reference to the drawings.

  First, a schematic configuration of an ink jet printer that is a main application target of the configuration of the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention will be described.

  FIG. 1 is a perspective view showing a schematic configuration of a main part in an ink jet printer which is a main application target of the configuration of a paper feed error detecting device, a printing device, and a paper feed error detecting method according to the present invention.

  A printer 20 as an example of an ink jet printer is driven by a paper stacker 22, a motor (not shown), a conveyance roller 24 that conveys printing paper P as a printing medium, a platen plate 26, a carriage 28, and a carriage motor 30. A traction belt 32 driven by a carriage motor 30 and a guide rail 34 for guiding the carriage 28 are provided.

  The carriage 28 has a print head 36 having a plurality of nozzle rows each including a plurality of nozzles as ink ejection portions arranged along the transport direction (hereinafter also referred to as sub-scanning direction) of the printing paper P. , An optical sensor 41 as a determination device for determining whether or not ink is ejected from each nozzle, and a linear encoder 29 for reading the code plate 33 are mounted.

  A rotary encoder 25 is provided on the shaft of the transport roller 24, and the transport amount of the printing paper P is controlled based on the output of the rotary encoder 25. Accordingly, the position of the carriage 28 in the direction orthogonal to the printing paper conveyance direction (hereinafter also referred to as the main scanning direction) can be detected by the linear encoder 29, and the position of the printing paper P can be detected by the rotary encoder 25. is there. That is, the printer 20 is configured to be able to accurately recognize the relative position between the carriage 28 and the printing paper P based on the output signals of the encoders 25 and 29.

  The printing paper P is fed from the paper stacker 22 by a paper feeding roller (not shown), conveyed by the conveying roller 24, and sent on the surface of the platen plate 26 in the sub scanning direction SS.

  The carriage 28 is pulled by a pulling belt 32 driven by a carriage motor 30 and moves in the main scanning direction MS along the guide rail 34. The main scanning direction MS and the sub scanning direction SS are orthogonal to each other.

  FIG. 2 is a perspective view showing the arrangement of the nozzles and the optical sensor 41 when the print head 36 is viewed from above.

  The print head 36 includes a light black ink nozzle row KL for discharging light black ink, a light magenta ink nozzle row ML for discharging light magenta ink, and a light cyan ink nozzle for discharging light cyan ink. A line CL, a photo black ink nozzle line KP for discharging black ink mainly used for printing natural images, a dark black ink nozzle line KD for discharging dark black ink, and a dark cyan ink are discharged. There are provided a dark cyan ink nozzle row CD for discharging, a dark magenta ink nozzle row MD for discharging dark magenta ink, and a yellow ink nozzle row YD for discharging yellow ink. In this example, the first nozzle # 1 is arranged on the downstream side in the transport direction of the printing paper P.

  The optical sensor 41 mounted on the carriage 28 is disposed on the downstream side in the transport direction from the first nozzle # 1 of the yellow ink nozzle row YD located on the most anti-home position side of the print head 36, and further on the anti-home position side. Has been. In this example, for example, it is provided at a position of 8.58 mm downstream of the first nozzle in the yellow ink nozzle row YD in the transport direction and 51.75 mm on the non-home position side.

  A cleaning mechanism 200 is provided below the print head 36 mounted on the carriage 28 outside the print area within the movement range of the carriage 28 that moves along the guide rail 34. In FIG. 1, the cleaning mechanism 200 shows only the head cap 210, and other configurations are omitted.

  The head cap 210 is a confidential cap and covers the print head 36 when printing is not being performed to prevent the ink in the nozzles from drying. Therefore, the head cap 210 is provided at a standby position of the carriage 28, that is, a so-called home position side. Further, even when the nozzles are clogged, the print head 36 is covered with the head cap 210 and ink is sucked from the nozzles to perform cleaning.

  The optical sensor 41 that determines whether or not ink is ejected from each nozzle will be described in detail later.

  FIG. 3 is a block diagram showing an electrical configuration of the printer 20.

  The printer 20 includes a reception buffer memory 50 that receives a signal supplied from the host computer 100, an image buffer 52 that stores print data, a system controller 54 that controls the operation of the entire printer 20, and a main memory 56. ing.

  The system controller 54 includes a main scanning driver 61 that drives the carriage motor 30, a sub-scanning driver 62 that drives the conveyance motor 31, an optical sensor driver 63 that drives the optical sensor 41, and a head driver that drives the print head 36. 66 is connected.

  The optical sensor driver 63 includes a light amount control unit that can adjust the light emission amount of the light emitting unit 41 a provided in the optical sensor 41, and an output control unit that can adjust the output of the light receiving unit 41 b provided in the optical sensor 41. I have.

  Therefore, for example, it is possible to adjust the light emission amount of the light emitting unit 41a or the output of the light receiving unit 41b so that the output of the light receiving unit 41b that has received the light reflected by the predetermined printing paper becomes a predetermined value. The adjustment is performed by the system controller 54 controlling the optical sensor driver 63.

  A printer driver (not shown) of the host computer 100 determines various parameter values that define the printing operation based on the printing mode (high-speed printing mode, high-quality printing mode, etc.) designated by the user. The printer driver further generates print data for printing based on these parameter values, and transfers the print data to the printer 20.

  The transferred print data is temporarily stored in the reception buffer memory 50. In the printer 20, the system controller 54 reads necessary information from the print data stored in the reception buffer memory 50, and sends a control signal to each driver based on the read information.

  The image buffer 52 stores print data of a plurality of color components obtained by separating the print data received in the reception buffer memory 50 for each color component.

  The head driver 66 reads the print data of each color component from the image buffer 52 in accordance with a control signal from the system controller 54 and drives the nozzle row of each color provided in the print head 36 in accordance with this. The system controller 54 controls each part of the printer 20.

  Further, the print data transferred from the host computer 100 may be print data that has been separated for each color component before transfer from the host computer 100.

  FIG. 4 is an explanatory diagram schematically showing two types of configurations of the ink sensor for determining ink ejection.

  In the paper feed error detecting device, the printing device, and the paper feed error detecting method according to the present invention, a printing operation state detecting device for detecting various operation states of the printing device reflected in the printing state on the surface of the print medium, particularly a paper feed. Although an optical sensor is used as the error detection device, even when an optical sensor is used as the ink ejection determination device, the configuration of the optical sensor itself is exactly the same, so here the optical sensor is used as an optical device for ink ejection determination. This will be described as a sensor.

  As shown in FIG. 4A, the direction of the light emitting unit 41a is set so that the irradiation light La is irradiated perpendicularly to the surface of the printing paper as a printing medium, as an optical sensor for ink ejection determination. As shown in FIG. 4B, there is a configuration in which the direction of the light emitting portion 41a is set so that the irradiation light 41a is irradiated obliquely with respect to the surface of the printing paper as a printing medium. is there.

  As shown in FIGS. 4A and 4B, the optical sensor 41 for determining whether ink is ejected from the nozzle includes a light emitting unit 41a and a light receiving unit 41b. In the present embodiment, an example is shown in which one light receiving portion for mainly receiving the diffuse reflection component of the reflected light is provided as the light receiving portion 41b. It is good also as a structure which provided another light-receiving part for light-receiving a reflective component.

  The light emitting unit 41a is a light emitting device for irradiating light toward the printing paper. At the time of ink ejection determination, light is emitted toward an area of a printing paper on which a printing pattern including a printing block printed and formed corresponding to each nozzle by ink ejected from the nozzle is to be printed.

  In the normal configuration of the optical sensor 41, when the irradiation light from the light emitting unit is focused on the surface of the print medium, the area on which the printing paper is irradiated by the irradiation light (hereinafter referred to as “spot”). Spots are set so that one print block BL of the print pattern is included therein.

  Details of the print pattern will be described later.

  An arbitrary light emitting device such as a light emitting diode, a laser diode, or an incandescent bulb can be used for the light emitting unit 41a. The color of the irradiation light from the light emitting unit 41a is preferably a color that is complementary to the color of the determination target print image such as a print pattern. For example, red illumination light is used to detect a cyan print image, green illumination light is used to detect a magenta print image, and blue illumination light is used to detect a yellow print image. Good.

  When the color of the irradiation light and the color of the print image are in a complementary relationship, an output signal having a higher level can be obtained compared to the case where the color is not so.

  Therefore, in order to obtain a stable output for any color printed image, it is preferable to use a light emitting device whose irradiation light is white.

  The light receiving unit 41b is a photoelectric conversion device that detects reflected light reflected by the print pattern and converts it into an electrical signal. A photodiode, a phototransistor, or the like is preferably used as the light receiving element. Preferably, a light receiving element having good sensitivity characteristics with respect to visible light is used.

  It is desirable that the position of the light receiving portion 41b for mainly receiving the diffuse reflection component is not in the position of regular reflection with respect to the light emitting portion 41a.

  For example, as shown in FIG. 4A, the direction of the light emitting unit 41a is set so that the irradiation light from the light emitting unit 41a is irradiated perpendicularly to the surface of the printing paper as the printing medium, and from the surface of the printing paper. The direction of the light receiving portion 41b may be set so as to detect reflected light reflected obliquely. Alternatively, as shown in FIG. 4B, the direction of the light emitting unit 41a is set so that the irradiation light from the light emitting unit 41a is obliquely irradiated to the surface of the printing paper as the printing medium, and the surface of the printing paper is Alternatively, the direction of the light receiving unit 41b may be set so as to detect reflected light perpendicular to the light receiving unit 41b.

  In particular, in a print medium having a coating layer formed on the surface thereof, such as glossy printing paper, most of the incident light is regularly reflected by the coating layer on the surface, but the light receiving unit 41b is opposed to the light emitting unit 41a. If it is not attached at the regular reflection position, the color of the printing block under the coating layer can also be reliably determined.

  The irradiation light emitted from the light emitting unit 41a is reflected by the printing paper on which the printing block is printed, and the diffuse reflection component of the reflected light reaches the light receiving unit 41b. The light receiving unit 41b generates an electrical signal corresponding to the detected intensity of the reflected light and outputs it as an output signal.

  When the level of the output signal is smaller than a preset threshold value, it is determined that the ink is normally ejected from the nozzle that should form the print block irradiated with the irradiation light from the light emitting unit 41a, and the level of the output signal is determined. Is equal to or greater than the threshold value, it is determined that ink was not normally ejected from the nozzle.

  At this time, for example, the optical sensor 41 detects the level of the output signal from the light receiving unit 41b that detects the reflected light reflected by a predetermined unused printing paper, a printing pattern of each color printed on a predetermined printing medium, or the like. Is adjusted by the light amount control unit of the optical sensor driver 63 controlled by the system controller 54, or the light receiving unit 41b is adjusted by the output control unit of the optical sensor driver 63. The output of has been adjusted.

  When a plurality of light emitting devices are compared, there is an individual difference even if the same white light emitting device is used, and a difference occurs in the output value when a specific print pattern is irradiated.

  Accordingly, the light emitting device is configured by adjusting the light emission amount of the light emitting unit or the output of the light receiving unit by using the actually mounted optical sensor, the actual print medium, and the print pattern printed by the actual ink. It is possible to prevent misjudgment that may occur due to the individual difference between the two, the type of print medium, the type of ink color, and the like.

  FIG. 5 is an explanatory view schematically showing an example of an inspection pattern printed and formed with one color ink, and FIG. 6 is an explanatory view schematically showing an inspection print block BL constituting the inspection pattern. is there.

  In the ink ejection inspection, first, an inspection pattern is created. This test pattern is a test pattern that is printed and formed for each ink color by a nozzle row that ejects ink of each color. That is, when inspecting the ink ejection states of all the nozzles, inspection patterns corresponding to the number of colors of ink ejected from the nozzle rows of the print head 36 are formed.

  Therefore, in this embodiment, eight inspection patterns are created. Further, N print blocks BL are printed in an inspection pattern when N nozzles are arranged in a single color nozzle row and the N nozzles are inspected.

  The test pattern is composed of a plurality of test print blocks BL formed for each nozzle by the ink ejected from each nozzle, and one print block BL includes a plurality of ink dots PX as shown in FIG. It is formed by.

  Since one printing inspection block BL is formed by printing only with ink ejected from one nozzle, one printing inspection block BL is used for inspection of one nozzle corresponding thereto. FIG. 5 shows an inspection pattern formed by a nozzle row having 54 nozzles.

  This inspection pattern is configured by nine inspection print blocks BL arranged in the main scanning direction (left-right direction) and six in the sub-scanning direction. That is, six inspection print block arrays each including nine inspection print blocks arranged in the main scanning direction are formed in the sub-scanning direction.

  The first-stage inspection print block array located on the most downstream side in the transport direction is printed by the ninth nozzle # 9 to the first nozzle # 1, and the second-stage inspection print block array is the 18th nozzle. Printing is performed from # 18 to No. 10 nozzle # 10. Similarly, the sixth-stage inspection print block array is printed from No. 54 nozzle # 54 to No. 46 nozzle # 46.

  When printing each inspection printing block array constituting the inspection pattern, for example, the carriage 28 is scanned from the left side to the right side in FIG. No. 36, No. 27, No. 18, No. 9 nozzles # 54, # 45, # 36, # 27, # 18, # 9 are ejected to form a predetermined number of dots to form the main print block BL for inspection. Print only the width in the scanning direction. The carriage 28 continues to scan and ejects ink from nozzles # 53, # 44, # 35, # 26, # 17, and # 8, # 53, # 44, # 35, # 26, # 17, and # 8. A dot row or a line is formed by a predetermined number of dots for forming the inspection print block of the second row.

  As described above, each nozzle constituting the nozzle row is grouped into nozzles corresponding to the number of test print blocks arranged in the main scanning direction of the test pattern in order to form sub nozzle groups. Each inspection print block is formed by ejecting ink for each nozzle located in the same order in the sub-scanning direction.

  When the scanning by the carriage 28 from the left side to the right side in FIG. 5 is completed, the printing paper is conveyed by the nozzle pitch in the sub scanning direction. Thereafter, scanning by the carriage 28 is performed from the right side to the left side, and ink is ejected from a predetermined nozzle in the reverse order to the previous scanning to form a dot row or line.

  As described above, an operation for transporting printing paper by the nozzle pitch in the sub-scanning direction, and an operation for performing scanning in the main scanning direction while ejecting ink for each nozzle located in the same order in the sub-scanning direction of each sub-nozzle group. When nine dot rows or lines are formed, an inspection print block is formed. When ink is normally ejected from all the nozzles, an inspection pattern having 54 inspection print blocks is finally printed.

  As can be seen from FIG. 5, the inspection print blocks adjacent to each other in the main scanning direction (left-right direction), for example, the inspection print block formed by the 54th nozzle # 54 and the 53rd nozzle # 53 are used. The formed inspection print block is printed at a position shifted by the nozzle pitch in the sub-scanning direction.

  The dots forming each test print block are formed at equal intervals between the test print blocks adjacent to each other, and no blank portion is generated between the test print blocks.

  In the present embodiment, the conveyance amount in the conveyance of the printing paper executed during each scan of the carriage 28 is the nozzle pitch. However, the conveyance amount is arbitrary, and for example, the conveyance amount is half the nozzle pitch. The number of dots constituting each inspection print block increases, and the density of each inspection print block increases. At this time, the number of dot rows or lines constituting each inspection print block is 18.

  FIG. 7 is an explanatory diagram schematically showing the locus of spots on the inspection pattern during scanning by the optical sensor. As described above with reference to FIG. 5, the inspection print blocks adjacent to each other in the main scanning direction are printed at positions shifted by the nozzle pitch in the sub-scanning direction. In FIG. 7, for simplification, an inspection pattern 71 is shown in a state where the inspection print blocks are arranged and formed in a matrix without any deviation.

  When determining the presence or absence of ink ejection, the optical sensor 41 attached to the carriage 28 (FIG. 1) and the printing paper P are relatively moved, and the optical sensor 41 scans the inspection print block BL.

  At this time, the spot of the irradiation light La (FIG. 4) from the light emitting unit 41a of the optical sensor 41 is sequentially applied to each inspection print block BL as shown by the locus XY in FIG. The reflected light Lb is detected by the light receiving unit 41b, and the presence or absence of ink ejection is determined by comparing the level of the electrical signal output from the light receiving unit 41b with a predetermined threshold according to the detected intensity of the reflected light Lb. The comparison between the output signal level and a predetermined threshold is performed for each inspection print block BL.

  As shown in FIG. 2, in the present embodiment, the optical sensor 41 is arranged on the downstream side of all the nozzles of the print head 36, and therefore, for some printing blocks BL on the downstream side. Performs scanning by the optical sensor 41 in the moving operation of the carriage 28 when printing a part of the upstream printing block BL, and at the same time determines whether ink is ejected.

  The area irradiated with the printing paper by the light emitted from the light emitting unit 41a of the optical sensor 41 is a circular spot on the printing paper. In the present embodiment, the inspection printing block BL is included in the spot. Spots are set to include one.

  FIG. 8 is a graph showing the relationship between the output signal level and the determination threshold in determining whether or not ink is ejected.

  When there is a nozzle from which ink is not ejected due to clogging, the printing block corresponding to the nozzle among the inspection printing blocks BL formed on the printing paper is a blank printing block BLa in which ink is not dropped.

  When the printing block irradiated by the spot of the irradiation light emitted from the light emitting unit 41a of the optical sensor 41 is the blank printing block BLa, the intensity of the reflected light Lb detected by the light receiving unit 41b of the optical sensor 41 increases. The output signal level converted according to the detected intensity of the reflected light Lb increases.

  On the other hand, when the printing block irradiated by the spot is a normal printing block BLb printed normally, the intensity of the reflected light Lb detected by the light receiving unit 41b decreases, so that it depends on the detected intensity of the reflected light Lb. The output signal level to be converted is lowered.

  That is, the output signal level VL when the spot formed by the light emitting unit 41a scans the blank printing block BLa is a relatively high value, and the output signal level V0 when the spot scans the normal printing block BLb is relatively high. A low value.

  Therefore, as shown in FIG. 8, by setting the determination threshold Vth between the output signal level VL corresponding to the blank print block BLa and the output signal level V0 corresponding to the normal print block BLb, the output signal By comparing the level and the determination threshold value Vth, it is possible to accurately determine the presence or absence of ink ejection at each nozzle.

  The hardware operation when determining whether or not to discharge ink as described above is as follows.

  The determination unit 54 a of the system controller 54 (FIG. 3) compares the output signal level from the optical sensor 41 with a determination threshold value Vth that is set in advance and stored in the main memory 56 in order to determine the presence or absence of ink ejection. .

  When the output signal level is smaller than the threshold value Vth, the print block included in the spot is a normal print block printed normally, and ink is normally ejected from the nozzle used for printing the print block. Is determined. On the other hand, when the output signal level is larger than the threshold value Vth, the printing block included in the spot is a blank printing block in which ink has not been dropped, and ink is normally discharged from the nozzle used for printing the printing block. It is determined that the ink is not discharged.

  The printer 20 has a configuration in which one printing block is included in a region where the printing paper is irradiated by the irradiation light from the light emitting unit 41a, that is, the output of the linear encoder 29 and the output of the rotary encoder 25. The relative position between the carriage 28 and the printing paper can be recognized, and the relative position between the optical sensor 41 provided on the downstream side of all the nozzles in the transport direction and each nozzle is accurately adjusted and recognized in advance. It shall be.

  Therefore, when a blank print block in which ink has not been dropped is detected as a result of scanning the inspection print block by the optical sensor 41 by the scanning operation of the carriage 28 in order to determine the presence or absence of ink ejection. Based on the outputs of the linear encoder 29 and the rotary encoder 25, it is possible to identify the nozzle corresponding to the blank print block as an abnormal nozzle in which ink ejection is not normally performed.

  When an abnormal nozzle that does not eject ink normally is identified, flushing or the like is performed only on the abnormal nozzle to restore it to a good state, or other dots that should be originally formed by the abnormal nozzle It is also possible to form and print using this nozzle.

  By the way, as described in the description of the overall configuration of the printing apparatus with reference to FIGS. 1 and 3, the print medium in the printing apparatus, for example, printing paper, is supplied with a paper feed motor (carrying motor 31) and a paper feed roller (carrying roller 24 ).

  The paper feed amount in the paper feed operation is controlled by the sub-scan driver 62 that controls the drive operation in the paper feed direction (sub-scan direction) based on a command from the system controller 54 that controls the operation of the entire printing apparatus. .

  The paper feed motor and the paper feed roller operate accurately according to the control by the system controller 54 and the sub-scan driver 62, but the paper feed amount in the paper feed operation is finally transmitted to the print medium by the paper feed roller.

  Therefore, if eccentricity due to manufacturing process variation or uneven wear due to usage conditions occurs in the paper feed roller, an error may occur between the commanded paper feed amount and the actual paper feed amount. It becomes.

  Since the radius of the paper feed roller with eccentricity or partial wear differs depending on the part, and the length of the arc with respect to a certain central angle also differs depending on the part, the actual circumference length is worn according to the design data radius or evenly. This is because the length of the circumference assumed from the radius is different.

  An error in the paper feed amount, that is, a paper feed error causes a shift in the ink dropping position in the paper feed direction and causes a reduction in print image quality. Therefore, in the printing apparatus, the paper feed error is suppressed to a minimum. It is necessary to adjust the paper feed control.

  For this purpose, first, it is necessary to accurately detect how much paper feed error has occurred in each printing apparatus.

  Therefore, in the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention, the print medium surface is overlapped with a predetermined print pattern using the upper end nozzle row and the lower end nozzle row of the print head. The paper feed error is detected from the printing state on the surface of the print medium, and the optimum correction value for minimizing the paper feed error in the paper feed operation is determined.

  The above-described ink discharge determination device detects the print state of the print medium surface reflected in the intensity of reflected light, and thus is not limited to the determination of the ink discharge state from the nozzles, but the print state of the print medium surface. In the paper feeding error detecting device, the printing device, and the paper feeding error detecting method according to the present invention, the paper feeding error can be used as a printing operation state detecting device that detects various operating states of the printing device reflected in the paper. A paper feed error is detected by scanning a print pattern reflecting the above with an optical sensor.

  FIG. 9 is a plan view showing the formation region of the upper end nozzle row and the lower end nozzle row of the print head used in the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention. For simplification of the drawing, FIG. 9 shows only one nozzle row of the print head.

  Assuming that the length of the print head 36 in the paper feed direction (sub-scanning direction) is 1 inch, in the paper feed error detection device, the printing device, and the paper feed error detection method according to the present invention, the print head 36 is Divide into four equal nozzles in the sub-scanning direction and divide into four partial nozzle rows having a length of 1/4 inch. And the printing pattern mentioned later is printed using lower end nozzle row 36R and upper end nozzle row 36A among these four partial nozzle rows.

  In the present embodiment, it is assumed that the print head is arranged so that the upper end nozzle row 36A is located in the sub-scanning direction, that is, the downstream side in the paper feed direction, and the lower end nozzle row 36R is located on the upstream side.

  As is apparent from FIG. 9, when the print medium is fed by 3/4 inch in the sub-scanning direction, the print medium area located immediately below the lower end nozzle row 36R before the paper feed is exactly the upper end nozzle row. It will be located directly under 36A. If the area is not located directly below the upper end nozzle row 36A, an error has occurred in the paper feed amount.

  In this embodiment, the nozzle pitch of the print head 36, that is, the nozzle arrangement interval is 1/180 inch.

  FIG. 10 is a plan view schematically showing the configuration of a paper feed error detecting print pattern to be printed in the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention.

  In the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention, first, after the line-shaped reference pattern R (N) is printed by the lower end nozzle row 36R, immediately below the lower end nozzle row 36R. The paper feeding operation is executed while appropriately adding a correction value to the theoretical value of the paper feeding amount in which the print medium area located at is located just below the upper end nozzle row 36A.

  Here, the theoretical value of the paper feed amount is calculated from the image data to be printed when it is assumed that the paper feed roller has a dimension as designed data with no eccentricity or uneven wear. This is the value of the paper feed amount. In the following description of the embodiment, the theoretical value of the paper feed amount may be referred to as a basic paper feed amount.

  Then, a linear adjustment pattern A (N) similar to the reference pattern R (N) is printed over the reference pattern R (N) by the upper end nozzle row 36A.

  At this time, when the paper feed error is suppressed to the minimum, that is, when there is no error in the paper feed amount, adjustment with the reference pattern R (N) is performed as shown in FIG. The printing pattern A (N) is printed so as to overlap, and the printing density of the paper feed error detection printing pattern including the reference pattern R (N) and the adjustment pattern A (N) is minimized.

  On the other hand, when the maximum paper feed error occurs within the nozzle pitch range, that is, when the paper feed error is generated by ½ of the nozzle pitch, as shown in FIG. For detecting a paper feed error, a line constituting the reference pattern R (N) and a line constituting the adjustment pattern A (N) are alternately printed, and the reference pattern R (N) and the adjustment pattern A (N) are included. The print pattern has the maximum print density.

  A paper feed error detecting device, a printing apparatus, and a paper feed error detecting method according to the present invention are a paper feed error detecting print pattern comprising a line-shaped reference pattern R (N) and an adjustment pattern A (N) as described above. By detecting the print density, a paper feed error actually occurring is detected, and a correction value to be added to the theoretical value of the paper feed amount when the paper feed operation is executed is determined.

  Specifically, while changing the correction value to be added to the theoretical value of the paper feed amount within a range of ± 1/2 of the nozzle pitch, the reference pattern R (N) is changed after the paper feed operation. By respectively printing the adjustment pattern A (N), detecting the print density of the paper feed error detection print pattern corresponding to each correction value, and specifying the paper feed error detection print pattern with the lowest print density Then, the optimum value of the correction value to be added to the theoretical value of the paper feed amount is determined.

  The correction value is changed within the range of ± 1/2 nozzle pitch, that is, the range of 1 nozzle pitch. If the correction value is changed within the range, one of the correction values is always used. This is because the reference pattern R (N) and the adjustment pattern A (N) should be printed so as to overlap each other.

  FIG. 11 is an explanatory view schematically showing the operation of the paper feed error detecting apparatus and the printing apparatus and the process of the paper feed error detecting method according to the first embodiment of the present invention.

  In the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the first embodiment of the present invention, the basic paper feed amount, that is, the theoretical value of the paper feed amount is 3/4 = 540/720 inch. A series of “printing of reference pattern R (N) −paper feeding operation−adjustment pattern A (N)” while changing the correction value to be added to the basic paper feeding amount within a range of ± 1/2 nozzle pitch. By repeating the above operations and processes, a paper feed error detection print pattern corresponding to each correction value is printed.

  As described above, since the nozzle pitch of the print head 36 in the present embodiment is 1/180 inch, the correction value to be added to the theoretical value of the paper feed amount is in the range of ± 1/2 nozzle pitch, That is, it is varied within a range of ± 1/360 inch. If the fluctuation range of the correction value in one stage is as small as possible, the optimum value of the correction value can be determined more accurately. However, in this embodiment, 1/16 nozzle pitch, that is, 1/2880. The correction value will be changed in inches. Therefore, the correction value is changed within a range of ± 8/2880 inches.

  Specific contents of the operation of the paper feed error detecting device and the printing device and the process of the paper feed error detecting method according to the first embodiment of the present invention are as follows.

  As shown in FIG. 11, first, at the initial position P (−8) of the print head, the reference pattern R (−8) is printed on the print medium by the lower end nozzle row of the print head.

  After printing the reference pattern R (-8), the print medium is fed by a paper feed amount (540 / 720-8 / 2880) inches obtained by adding a correction value to the basic paper feed amount, and the print head position P (-7) ), The adjustment pattern A (-8) is printed by the upper end nozzle of the print head so as to overlap the reference pattern R (-8), and at the same time, the reference pattern R (-8) and the adjustment pattern A (-8). Accordingly, the reference pattern R (−7) is printed by the lower end nozzle row on the upstream side in the paper feed direction by 3/4 = 540/720 inch.

  Therefore, the adjustment pattern A (−8) is printed with a deviation of 8/2880 inches downstream of the reference pattern R (−8) in the paper feed direction.

  In FIG. 11, for easy understanding, the positions of the print head and the print pattern before and after the paper feeding operation are shifted to the left and right by the width of the print head. Are printed at the same position in the main scanning direction.

  After printing the adjustment pattern A (-8) and the reference pattern R (-7), the print medium is fed by the paper feed amount (540 / 720-7 / 2880) inch, which is obtained by adding the correction value to the basic paper feed amount. The adjustment pattern A (-7) is printed by the upper end nozzle of the print head so as to overlap the reference pattern R (-7) at the print head position P (-6), and at the same time, the reference pattern R (-7). The reference pattern R (−6) is printed by the lower end nozzle row on the upstream side in the paper feed direction by 3/4 = 540/720 inches from the adjustment pattern A (−7).

  Therefore, the adjustment pattern A (−7) is printed with a deviation of 7/2880 inches from the reference pattern R (−7) to the downstream side in the paper feeding direction.

  Thereafter, the same operations and processes as described above are repeated while changing the basic paper feed amount, that is, the correction value to be added to the theoretical value 540/720 inch of the paper feed amount by 1/2880 inches.

  Finally, after printing the adjustment pattern A (+7) and the reference pattern R (+8) at the print head position P (+8), the paper feed amount (540/720 + 8/2880) obtained by adding the correction value to the basic paper feed amount. When the print medium is fed by an inch and the adjustment pattern A (+8) is printed by the upper end nozzle of the print head so as to overlap the reference pattern R (+8) at the print head position P (+9), the reference pattern R A series of operations and processes relating to printing of the paper feed error detection print pattern comprising (N) and the adjustment pattern A (N) are completed.

  Note that the adjustment pattern A (+8) is printed by being shifted to the upstream side in the paper feed direction by 8/2880 inches with respect to the reference pattern R (+8).

  In parallel with the printing of the paper feed error detection print pattern, or after the printing of the paper feed error detection print pattern is finished, each paper feed error detection print pattern is scanned by the optical sensor to detect each paper feed error. The printing density of the printing pattern for printing is detected. That is, the spot 10 of the irradiation light from the light emitting portion of the optical sensor is sequentially applied to each paper feed error detection print pattern, and the reflected light from each paper feed error detection print pattern is detected by the light receiving portion, and the detected reflection is detected. A light reception output signal having a voltage level corresponding to the light intensity is converted and generated.

  In accordance with the principle described above, when the optical sensor scans a print pattern with a low print density, the light reception output signal level increases. When the optical sensor scans a print pattern with a high print density, the light reception output signal level decreases. .

  Here, since it is desired to specify a paper feed error detection print pattern printed with a paper feed error suppressed to a minimum, that is, a paper feed error detection print pattern having the lowest print density, scanning by an optical sensor is performed. As a result, the paper feed error detection print pattern from which the highest received light output signal level is obtained is specified by the determination unit 54a (see FIG. 3) as a paper feed error determination unit.

  The correction value added to the theoretical value of the paper feed amount in the paper feed operation immediately before printing the specified minimum density paper feed error detection print pattern suppresses the paper feed error in the printing apparatus to the minimum. This is the optimum correction value for this. The optimum correction value may be determined by the determination unit 54a serving as a paper feed error determination unit.

  Therefore, in the printing apparatus, when printing is performed thereafter, the optimum correction value is added to the theoretical value of the commanded paper feed amount to minimize the paper feed error and improve the print image quality. Can be achieved.

  Note that the paper feed error detection print pattern with the lowest print density may be identified visually without using an optical sensor.

  FIG. 12 is an explanatory view schematically showing the operation of the paper feed error detecting apparatus and the printing apparatus and the process of the paper feed error detecting method according to the second embodiment of the present invention.

  In the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the second embodiment of the present invention, the theoretical value of the paper feed amount, that is, the basic paper feed amount is set to 1 of the first embodiment. / 3 which is 1/4 = 180/720 inch, the frequency of adding the correction value to the basic paper feed amount is set once per three paper feed operations, and the correction value to be added to the basic paper feed amount is ± 1 By repeating the operation and process of “printing of reference pattern R (N) −paper feeding operation−adjustment pattern A (N)” while changing within the range of the / 2 nozzle pitch, paper feeding corresponding to each correction value is performed. Print error detection print pattern.

  Also in the second embodiment, the correction value to be added to the theoretical value of the paper feed amount is varied within a range of ± 1/2 nozzle pitch, that is, within a range of ± 1/360 inch. The variation width of the stage is 1/16 nozzle pitch, that is, 1/2880 inch. Therefore, the correction value is changed within a range of ± 8/2880 inches.

  Specific contents of the operation of the paper feed error detecting device and the printing device and the process of the paper feed error detecting method according to the second embodiment of the present invention are as follows.

  As shown in FIG. 12, first, at the initial position P (-8-2) of the print head, the reference pattern R (-8-2) is printed on the print medium by the lower end nozzle array of the print head.

  After printing the reference pattern R (−8-2), the print medium is fed by the basic paper feed amount 180/720 inches without adding the correction value, and the print head position P (−8-1) is set. The reference pattern R (-8-1) is printed by the lower end nozzle row.

  After printing the reference pattern R (-8-1), the print medium is fed by a basic paper feed amount of 180/720 inches without adding a correction value. At the print head position P (-8), the lower end of the print head The reference pattern R (-8) is printed by the nozzle row.

  Accordingly, the three reference patterns R (−8-2), R (−8-1), and R (−8) are set for each fixed basic paper feed amount to which no correction value is added. Will be printed.

  In FIG. 12, for easy understanding, the positions of the print head and the print pattern before and after the paper feeding operation are shifted to the left and right by the width of the print head. Are printed at the same position in the main scanning direction.

  After printing the reference pattern R (-8), the print medium is fed by a paper feed amount (180 / 720-8 / 2880) inches obtained by adding a correction value to the basic paper feed amount, and the print head position P (-7) is printed. -2), the adjustment pattern A (-8-2) is printed by the upper end nozzle of the print head so as to overlap the reference pattern R (-8-2), and at the same time, the reference pattern R (-8-2) and The reference pattern R (−7-2) is printed by the lower end nozzle row on the upstream side in the paper feed direction by 3/4 = 540/720 inches from the adjustment pattern A (−8-2).

  After printing the adjustment pattern A (-8-2) and the reference pattern R (-7-2), the print medium is fed by a basic paper feed amount of 180/720 inches without adding a correction value, and the print head position P In (−7-1), the adjustment pattern A (−8-1) is printed by the upper end nozzle of the print head so as to overlap the reference pattern R (−8-1), and at the same time, the reference pattern R (−8−) is printed. 1) and the adjustment pattern A (-8-1), the reference pattern R (-7-1) is printed by the lower end nozzle row on the upstream side in the paper feed direction by 3/4 = 540/720 inches.

  After printing the adjustment pattern A (-8-1) and the reference pattern R (-7-1), the print medium is fed by a basic paper feed amount of 180/720 inches without adding a correction value, and the print head position P In (-7), the adjustment pattern A (-8) is printed by the upper end nozzle of the print head so as to overlap the reference pattern R (-8), and at the same time, the reference pattern R (-8) and the adjustment pattern A ( From −8), the reference pattern R (−7) is printed by the lower end nozzle row on the upstream side in the paper feed direction by 3/4 = 540/720 inches.

  Accordingly, the three reference patterns R (−7−2), R (−7-1), and R (−7) are printed for every fixed basic paper feed amount to which no correction value is added. The paper feed amount between the reference pattern R (−8) and the reference pattern R (−7-2) is the paper feed amount (180 / 720-8 / 2880) inch obtained by adding the correction value to the basic paper feed amount. It has become. That is, a group of three reference patterns R (-8-2), R (-8-1), and R (-8) and three reference patterns R (-7-2) and R (-7- 1) The R (−7) group is printed with a deviation of (3 × 180 / 720−8 / 2880) = (540 / 720−8 / 2880) inches.

  On the other hand, a group of three adjustment patterns A (-8-2), A (-8-1), and A (-8) has three reference patterns R (-8-2) and R (-8). -1) and R (-8) groups are printed with a deviation of 8/2880 inches downstream in the paper feed direction.

  Hereinafter, the same operation and process as described above are performed while changing the correction value to be added to the theoretical value 180/720 inch of the basic paper feed amount by 1/2880 inch in one paper feed operation for every three paper feed operations. repeat.

  In the final stage of the series of operations and processes, the paper feed amount obtained by adding the correction value to the basic paper feed amount after printing the adjustment pattern A (+7) and the reference pattern R (+8) at the print head position P (+8). The print medium is fed by (180/720 + 8/2880) inches, and the adjustment pattern is formed by the upper end nozzle of the print head so as to overlap the reference pattern R (+ 8-2) at the print head position P (+ 9-2). A (+ 8-2) is printed.

  After printing the adjustment pattern A (+ 8-2), the print medium is fed by a basic paper feed amount of 180/720 inches without adding a correction value. At the print head position P (+ 9-1), the reference pattern R ( The adjustment pattern A (+ 8-1) is printed by the upper end nozzle of the print head so as to overlap + 8-1).

  After printing the adjustment pattern A (+ 8-1), the print medium is fed by a basic paper feed amount of 180/720 inches without adding a correction value. At the print head position P (+9), the reference pattern R (+8) is printed. When the adjustment pattern A (+8) is printed by the upper end nozzle of the print head so as to overlap with the print head, a series of print patterns for paper feed error detection printing composed of the reference pattern R (N) and the adjustment pattern A (N) are printed. The operation and process ends.

  In parallel with the printing of the paper feed error detection print pattern, or after the printing of the paper feed error detection print pattern is finished, each paper feed error detection print pattern is scanned by the optical sensor to detect each paper feed error. The printing density of the printing pattern for printing is detected. That is, the spot 10 of the irradiation light from the light emitting portion of the optical sensor is sequentially applied to each paper feed error detection print pattern, and the reflected light from each paper feed error detection print pattern is detected by the light receiving portion, and the detected reflection is detected. A light reception output signal having a voltage level corresponding to the light intensity is converted and generated.

  As described above, when the optical sensor scans a print pattern with a low print density, the light reception output signal level is high, and when the optical sensor scans a print pattern with a high print density, the light reception output signal level is low. .

  By the way, as described above, in the second embodiment, the three reference patterns R printed continuously immediately before or after the paper feed operation of the paper feed amount obtained by adding the correction value to the basic paper feed amount. Each of the reference patterns R (N) and the adjustment patterns A (N) is composed of three paper feed error detection print patterns including (N) and three adjustment patterns A (N) corresponding thereto. The amount of deviation is theoretically the same.

  Accordingly, the print densities of the three paper feed error detection print patterns printed immediately before or after the paper feed operation of the paper feed amount obtained by adding the correction value to the basic paper feed amount are theoretically the same. The received light output signal level obtained as a result of scanning these three paper feed error detection print patterns should be the same.

  However, if the paper feed roller is decentered or worn out, the print density and the light reception output signal level may slightly vary between the three paper feed error detection print patterns. .

  Therefore, in the second embodiment, from the three paper feed error detection print patterns continuously printed immediately before or after the paper feed operation of the paper feed amount obtained by adding the correction value to the basic paper feed amount. The average value of the received light output signal level, that is, the average received light output signal level is calculated for each print pattern group for paper feed error detection.

  Then, as a result of comparing the average light reception output signal level of each paper feed error detection print pattern group, by specifying the paper feed error detection print pattern group that obtained the highest average light reception output signal level, the average print density is The lowest print pattern group for paper feed error detection can be specified. In addition, the paper feed error detection print pattern group having the lowest average print density is a paper feed error detection print pattern group printed with the paper feed error suppressed to a minimum.

  That is, the correction value added to the theoretical value of the paper feed amount in the paper feed operation immediately before printing the specified minimum density paper feed error detection print pattern group minimizes the paper feed error in the printing apparatus. This is the optimum correction value for suppression.

  Therefore, when the printing apparatus executes printing thereafter, the optimum correction value is added to the commanded paper feed amount to minimize the paper feed error and improve the print image quality. Can do.

  In the second embodiment, the optimum correction value is determined using the average print density of the paper feed error detection print pattern group composed of a plurality of paper feed error detection print patterns, that is, the average received light output signal level. Therefore, the optimum correction value can be determined more accurately and reliably, and the print image quality can be improved while minimizing the paper feed error.

  FIG. 13 shows the formation region of the upper end nozzle row and the lower end nozzle row of the print head used in the paper feed error detecting device, the printing device, and the paper feed error detecting method when the print head is a multi-head. FIG. For simplification of the drawing, FIG. 13 shows only one nozzle row of the print head.

  Depending on the type of printing apparatus, there are those equipped with a plurality of print heads, that is, multi-heads. As shown in FIG. 13, for example, two print heads 136 and 236 are provided in the sub-scanning direction, that is, paper feed. Some are arranged in a column in the direction and are mounted on the carriage 28.

  The paper feed error detecting device, the printing device, and the paper feed error detecting method according to the present invention can also be applied to a printing device equipped with such a multi-head. When the print head is a multi-head, a plurality of print heads arranged in a column in the paper feed direction are regarded as one print head, and the lower end nozzle row 236R and the upper end nozzle row 136A are used. The aforementioned paper feed error detection print pattern is printed.

  Note that, regardless of whether the print head is a single head or a multi-head, the lower end nozzle row and the upper end nozzle row used for printing the paper feed error detection print pattern necessarily include the lowermost nozzle and the uppermost nozzle. Although it is not necessary, the larger the distance between the lower end nozzle row and the upper end nozzle row, the larger the paper feed amount during the paper feed operation for adding the correction value, and the accuracy of the optimum correction value can be improved. .

  Therefore, in the present embodiment of the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention, printing having a plurality of ink discharge portions (nozzles) arranged along the print medium transport direction. A nozzle row composed of a plurality of ink discharge portions located upstream in the transport direction from the center portion of the head is used as a lower end nozzle row, and the plurality of ink discharge portions located downstream in the transport direction from the center portion of the print head. This nozzle row is used as the upper end nozzle row.

  In the embodiment described above, in order to improve the accuracy of the optimum correction value, a nozzle row composed of a plurality of ink ejection portions located upstream of the central portion of the print head in the print medium conveyance direction is used as the lower end nozzle row. It is assumed that a nozzle row composed of a plurality of ink ejection portions located downstream from the central portion of the print head in the print medium conveyance direction is used as the upper end nozzle row.

  However, the lower end nozzle row is a nozzle row composed of a plurality of ink ejection portions located on the upstream side in the print medium transport direction from the central portion of the print head, and the upper end nozzle row is closer to the central portion of the print head It is an indispensable condition for implementing the paper feed error detecting device, the printing device, and the paper feed error detecting method according to the present invention that the nozzle row is composed of a plurality of ink ejection units located on the downstream side in the print medium conveying direction. Not that.

  In other words, the paper feed error detecting device, the printing apparatus, and the paper feed error detecting method according to the present invention include a plurality of ink ejecting portions of a print head having a plurality of ink ejecting portions arranged along the print medium conveying direction. An upstream nozzle row constituted by a part of a plurality of ink discharge portions positioned relatively upstream in the print medium transport direction is used instead of the lower end nozzle row, and the plurality of ink discharge portions of the print head Of these, even if a downstream nozzle row constituted by a part of a plurality of ink discharge portions positioned relatively downstream in the transport direction relative to the upstream nozzle row is used instead of the upper end nozzle row, the same operation is performed. The same effect can be obtained.

  The paper feed error detection device, the printing device, and the paper feed error detection method according to the present invention are not limited to inkjet printers, and various types of printing devices can be used by detecting the printing state of the print medium surface reflected in the intensity of reflected light. The present invention can be applied to a paper feeding error detection device, a printing device, and a paper feeding error detection method for all printing devices equipped with an optical sensor as a printing operation state determination device for determining an operation state.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing a schematic configuration of a main part in an ink jet printer that is a main application target of a configuration of a paper feed error detecting device, a printing device, and a paper feed error detecting method according to the present invention. 3 is a perspective view showing the arrangement of nozzles and optical sensors 41 when the print head is viewed from above. FIG. 2 is a block diagram illustrating an electrical configuration of a printer 20. FIG. It is explanatory drawing which shows typically the normal structure of the optical sensor for ink discharge determination which is an application object of this invention. It is explanatory drawing which shows typically an example of the pattern for a test | inspection printed and formed with the ink of one color. It is explanatory drawing which shows typically the printing block BL for a test | inspection which comprises the pattern for a test | inspection. It is explanatory drawing which shows typically the locus | trajectory of the spot on the pattern for a test | inspection at the time of the scanning by an optical sensor. It is a graph which shows the relationship between the output signal level and determination threshold value in determination of the presence or absence of ink discharge. It is a top view which shows the formation area of the upper end part nozzle row and lower end part nozzle row of the print head used in the paper feed error detection apparatus and printing apparatus which concern on this invention, and a paper feed error detection method. FIG. 3 is a plan view schematically showing a configuration of a paper feed error detection print pattern to be printed in the paper feed error detection device, the printing apparatus, and the paper feed error detection method according to the present invention. It is explanatory drawing which shows typically the process of the paper feed error detection apparatus and printing apparatus which concern on the 1st Embodiment of this invention, and the process of a paper feed error detection method. It is explanatory drawing which shows typically the process of the paper feed error detection apparatus and printing apparatus which concern on the 2nd Embodiment of this invention, and the process of a paper feed error detection method. The top view which shows the formation area of the upper end nozzle row and the lower end nozzle row of the print head used in the paper feed error detecting device, the printing device, and the paper feed error detecting method when the print head is a multi-head. It is.

Explanation of symbols

10 Irradiation area (spot)
20 Printer 22 Paper stacker 24 Carrying roller 25 Rotary encoder 26 Platen plate 28 Carriage 29 Linear encoder 30 Carriage motor 31 Carrying motor 32 Traction belt 33 Code plate 34 Guide rail 36 Print head 41 Optical sensor 41a Light emitting part 41b Light receiving part 50 Reception buffer memory 52 Image buffer 54 System controller 54a Determination unit 61 Main scanning driver 62 Sub scanning driver 63 Optical sensor driver 66 Head driver 71 Print pattern 100 Host computer 200 Cleaning mechanism 210 Head cap 36A, 136A Upper end nozzle row 36R, 236R Lower end nozzle row 136, 236 Print head BL constituting multi-head BL Print block BLa Blank print block BLb Normal print block CD Cyan ink nozzle row CL Light cyan ink nozzle row KD Black ink nozzle row KL Light black ink nozzle row KP Photo black ink nozzle row MD Dark magenta ink nozzle row ML Light magenta ink nozzle row YD Yellow ink nozzle row La Irradiation light Lb Reflected light MS Main scanning direction P Printing paper SS Sub scanning direction Vth Threshold value V0 Blank printing block output signal level VL Normal printing block output signal level R (N) Reference pattern A (N) Adjustment pattern P (N) Print head position

Claims (8)

A print medium transport mechanism for transporting the print medium;
A print head having a plurality of ink ejection portions arranged along the print medium conveyance direction;
A plurality of lines printed by an upstream nozzle row configured by a part of the plurality of ink ejection portions of a print head having a plurality of ink ejection portions arranged along the print medium conveyance direction and intersecting the conveyance direction Printed on the reference pattern by the downstream nozzle row constituted by a part of the plurality of ink discharge portions located downstream in the transport direction from the upstream nozzle row, A light emitting unit that emits irradiation light to a print medium on which a print pattern for paper feed error detection composed of a plurality of line-shaped adjustment patterns parallel to the reference pattern is printed;
A light receiving unit that receives and detects reflected light reflected on the surface of the print medium, and converts and generates a received light output signal having a value corresponding to the intensity of the reflected light that reflects the print density of the print pattern for detecting paper feed error When,
A printing apparatus comprising: A print medium transport mechanism for transporting the print medium;
A print head having a plurality of ink ejection portions arranged along the print medium conveyance direction;
A plurality of line-shaped reference patterns that are printed by a plurality of lower end nozzle rows as the ink discharge units located upstream of the central direction of the print head and that cross the transport direction, and the print head Paper that is printed so as to overlap with the reference pattern by a plurality of upper end nozzle rows as the ink ejection units located downstream of the central portion in the transport direction, and is made of a plurality of line-shaped adjustment patterns parallel to the reference pattern A light emitting unit that emits irradiation light to a print medium on which a print pattern for detecting a feed error is printed;
A light receiving unit that receives and detects reflected light reflected on the surface of the print medium, and converts and generates a received light output signal having a value corresponding to the intensity of the reflected light that reflects the print density of the print pattern for detecting paper feed error When,
A printing apparatus comprising:   The paper feed error detection print patterns are printed in plural while varying the paper feed amount of the paper feed operation executed between the printing of the reference pattern and the adjustment pattern. The printing apparatus according to claim 1, wherein:   The adjustment pattern has a basic paper feed amount at which the print medium region located immediately below the lower end nozzle row or the upstream nozzle row is located immediately below the upper end nozzle row or the downstream nozzle row. 4. The printing apparatus according to claim 1, wherein the printing apparatus is printed after a paper feed operation or a paper feed operation of a paper feed amount obtained by adding a correction value to the basic paper feed amount.   5. The printing apparatus according to claim 4, wherein the correction value is varied in a range of ± ½ with the arrangement interval of the ink ejection units as one unit. 6.   The paper feed error determination unit for determining the correction value that minimizes the paper feed error by specifying the print pattern for detecting the paper feed error having the lowest print density. The printing apparatus according to 4 or 5. A plurality of lines intersecting the transport direction by an upstream nozzle row constituted by a part of the plurality of ink discharge portions of a print head having a plurality of ink discharge portions arranged along the print medium transport direction. A process of printing a reference pattern;
The print medium region located immediately below the upstream nozzle row is located immediately below the downstream nozzle row constituted by a part of the plurality of ink ejection units located downstream in the transport direction from the upstream nozzle row. Performing a paper feed operation of a basic paper feed amount to be performed or a paper feed operation of a paper feed amount obtained by adding a correction value to the basic paper feed amount;
A plurality of lines of adjustment patterns parallel to the reference pattern are printed by the downstream nozzle row so as to overlap the reference pattern, thereby forming a paper feed error detection print pattern including the reference pattern and the adjustment pattern. The process of
A paper feed error detection method comprising: A plurality of lower end nozzle rows as the plurality of ink ejection units located upstream of the central direction of the print head having a plurality of ink ejection units arranged along the printing medium conveyance direction in the conveyance direction. A process of printing a plurality of intersecting reference patterns,
The print medium region located immediately below the lower end nozzle row is located immediately below the upper end nozzle row as the plurality of ink ejection portions located downstream of the central portion of the print head in the transport direction. A process of performing a paper feed operation of a basic paper feed amount or a paper feed operation of a paper feed amount obtained by adding a correction value to the basic paper feed amount;
A plurality of line-shaped adjustment patterns parallel to the reference pattern are printed by the upper end nozzle row so as to overlap the reference pattern, and a paper feed error detection print pattern including the reference pattern and the adjustment pattern is formed. The process of
A paper feed error detection method comprising:

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