JP4595298B2 - Optical sensor for printing operation state determination, printing apparatus, and printing operation state determination method - Google Patents

Description

  The present invention relates to a printing operation state determination optical sensor (hereinafter also referred to as an “optical sensor”), a printing apparatus, and a printing operation state determination method, and more particularly, to each ink discharge disposed in a print head of the printing apparatus. Printing operation state determination optical sensor and printing operation state determination method for determining various operation states of the printing apparatus reflected in the printing state of the surface of the printing medium, such as the presence or absence of ink ejection from the section, or the presence or absence of the printing medium, and The present invention also relates to a printing apparatus including such a printing operation state determination optical sensor.

  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.

  By the way, among the conventional printing apparatuses in which the conventional ink discharge determination device and other conventional ink discharge determination devices are mounted, the distance between the print head and the print medium surface in order to achieve high image quality in various print media, That is, there is a model that automatically adjusts and optimizes the paper gap according to the type of print medium.

  In such a printing apparatus, for example, in the case of flat and high-quality photographic paper with little waviness or cockling, the paper gap may be set to “small” and some cockling may occur. In the case of plain paper, the paper gap is set to “Large”, and in the case of board paper or CD-R or DVD-R, which is a very thick print medium compared to paper, the paper gap is set to that of plain paper. Improve image quality for each type of print media by automatically adjusting the paper gap according to the type of print media selected as the print media to be used, such as setting “Large +”, which is larger than the case. I am trying.

  Cockling is an “undulation” that may occur due to the influence of humidity, temperature, or the action of physical external force on a printing medium that is flat in an ideal state, particularly printing paper. "Means.

The above-described ink ejection determination device, that is, an ink ejection determination optical sensor is usually mounted on a carriage together with a print head, and the same applies to a printing device equipped with a paper gap automatic adjustment mechanism.
JP 2000-190587 A

  By the way, in the optical sensor for ink ejection determination composed of the reflection type sensor as described above, the detection characteristic of reflected light varies depending on the distance between the print medium surface and the light receiving unit, that is, the detection distance. There are characteristics.

  The detection distance has an optimum value that provides the best detection sensitivity in the light receiving unit of the optical sensor, and the detection sensitivity is lowered regardless of whether the detection distance is larger or smaller than the optimum value. If the detection distance is set to a value larger or smaller than the optimum value, the value of the received light output generated based on the detected reflected light even if the detection distance slightly changes during sensing by the optical sensor. Fluctuates greatly.

  If the light-receiving output value fluctuates greatly due to slight fluctuations in the detection distance, it may be confused with fluctuations in the light-receiving output based on changes in the printing state on the print medium, leading to erroneous determination in the ink ejection determination test. There's a problem.

  During the ink ejection determination test, the sensing operation is performed with the position of the optical sensor in the vertical direction, that is, the height being constant, so the main factor that fluctuates the detection distance after the start of the sensing operation is the cockling of the print medium It is.

  That is, when the ink ejection determining device scans the surface of the print medium on which cockling has occurred, the detection distance varies sequentially with the movement of the light irradiation position.

  Therefore, if the detection distance is set to the optimum value for sensing in advance, even if the detection distance varies somewhat, fluctuations in the received light output are suppressed to be relatively small and erroneous determination can be avoided. If it is set to a larger or smaller value, fluctuations in the received light output may cause erroneous determination due to fluctuations in the detection distance.

  Even in a printing apparatus equipped with the paper gap automatic adjustment mechanism and the optical sensor for ink discharge determination described above, an ink discharge determination test is performed as necessary. In the case of such a conventional printing apparatus, the ink discharge determination test is performed. Even when sensing with an optical sensor for this purpose, automatic paper gap adjustment is performed in accordance with the print medium used at that time.

  Since the print head and the optical sensor are mounted on the same carriage, the change in the paper gap due to the automatic adjustment also means the change in the detection distance of the optical sensor.

  The paper gap automatic adjustment mechanism automatically optimizes the paper gap according to the type of print medium in order to achieve high image quality on various print media, so the detection distance of the optical sensor is the optimum value. Often not set to.

  As a result, the conventional printing apparatus equipped with the paper gap automatic adjustment mechanism and the ink sensor for ink discharge determination has a problem that an erroneous determination in the ink discharge determination test is likely to occur.

  This problem is not limited to the determination of whether or not ink is ejected from each ink ejection unit, and various optical printer operating states that are reflected in the printing state of the printing medium surface or the presence or absence of the printing medium are detected using optical sensors. This is a problem that can occur in common when determining.

  An object of the present invention is to provide a printing apparatus that is reflected in the printing state of the surface of the printing medium or the presence or absence of the printing medium, such as the presence or absence of ink ejection from each ink ejection unit, even in a printing apparatus equipped with a paper gap automatic adjustment mechanism. It is an object to provide a printing operation state determination optical sensor, a printing apparatus, and a printing operation state determination method capable of accurately determining various operation states.

According to the printing operation state determination optical sensor according to the embodiment of the present invention,
A light emitting unit for emitting irradiation light to the print medium;
The reflected light reflected on the surface of the print medium is received and detected, and a received light output signal having a value corresponding to the intensity of the reflected light is converted and generated in order to determine the operation state of the printing apparatus based on the detection result. A light receiver;
A function of automatically adjusting a paper gap as a distance between a plurality of ink discharge portions formed on the print head and the surface of the print medium according to the type of the print medium, and a distance between the surface of the print medium and the light receiving portion A height adjusting mechanism having a function of setting a detection distance as a constant value regardless of the type of the print medium,
It is characterized by having.

A printing apparatus according to an embodiment of the present invention includes:
A print head on which a plurality of ink discharge portions for discharging ink are formed;
A light emitting unit that emits irradiation light to the print medium, and 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 An optical sensor having
A determination unit for determining an operation state of the printing apparatus based on a detection result by the optical sensor;
A carriage carrying the print head and the optical sensor;
A function of automatically adjusting a paper gap as an interval between the plurality of ink ejection units and the print medium surface according to the type of the print medium, and a detection distance as a distance between the print medium surface and the light receiving unit A carriage height adjusting mechanism having a function of setting a constant value regardless of the type of the print medium;
With
The detection distance is set by emitting the irradiation light from the light emitting unit to the print medium, and receiving the reflected light reflected on the surface of the print medium by the light receiving unit. It is performed during the sensing operation, which is an operation for converting and generating the received light output signal of a value according to the intensity,
The detection distance is set such that the distance between the print medium and the light receiving unit is an optimum value for detecting by detecting reflected light, and the optimum value is determined when the print medium is plain paper. Is the optimum value of the detection distance in the case of
In one pass in which the carriage is moved in the main scanning direction with the detection distance set to the optimum value, a printing operation for printing a printing pattern on the printing medium, and the printing printed by the printing operation The sensing operation for the pattern is performed,
It is characterized by that.

  In this case, the determination of the operation state may include determination of the position of the end portion of the print medium.

  The determination of the operation state includes determination of whether or not ink is ejected from each of a plurality of ink ejection units that eject ink, and a forward path when performing bi-directional (Bi-D) printing in the main scanning direction of the printing apparatus. Either the determination of the relative position adjustment state between the ink dropping position and the return ink dropping position, or the determination of the adjustment state of the paper feed amount in the sub-scanning direction of the printing apparatus may be included.

  The determination of the operation state may be performed by comparing the value of the light reception output signal with a predetermined threshold value.

  According to the printing operation state determination optical sensor, the printing apparatus, and the printing operation state determination method according to the present invention, in the printing apparatus equipped with the paper gap automatic adjustment mechanism, the print medium surface, the light receiving unit of the optical sensor, The detection distance is set to a constant value regardless of the type of print medium, so it is reflected in the print state of the print medium surface or the presence or absence of the print medium, such as the presence or absence of ink discharge from each ink discharge unit. It is possible to accurately determine various operating states of the printing apparatus.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of an optical sensor for printing operation state determination, a printing apparatus, and a printing operation state determination method according to the invention will be described with reference to the drawings. In this embodiment, as an example of the printing operation state determination optical sensor, the printing apparatus, and the printing operation state determination method according to the present invention, the ink ejection determination optical sensor, the printing apparatus, and the ink according to the present invention are described. A discharge determination method will be described.

  First, a schematic configuration of an ink jet printer which is a main application target of the configuration of the optical sensor for ink discharge determination, the printing apparatus, and the ink discharge determination method according to the present invention will be described.

  FIG. 1 is a perspective view showing a schematic configuration of a main part of an ink jet printer which is a main application target of the configuration of the optical sensor for ink discharge determination, the printing apparatus, and the ink discharge determination 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.

  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.

  FIG. 9 shows that when the detection distance is set to a value smaller than the optimum value in the optical sensor for ink ejection determination (a), when the detection distance is set to the optimum value (b), the value is detected to a value larger than the optimum value. It is explanatory drawing which shows typically the positional relationship of the light emission part 41a and the light-receiving part 41b of an optical sensor, the optical path of irradiation light and reflected light, and the surface of the printing medium P in each case (c) when distance is set.

  FIG. 10 is a graph showing the received light output characteristics with respect to the detection distance variation.

  The ink ejection determination optical sensor constituted by a reflection sensor has a characteristic that a detection characteristic of reflected light, that is, a light reception output characteristic fluctuates due to a change in detection distance.

  The detection distance, that is, the distance between the surface of the print medium P and the light receiving unit 41b has an optimum value that provides the best detection sensitivity and the maximum light reception output, and the detection distance is set to the optimum value Db. Is shown in FIG. 9 (b). Although the detection sensitivity is reduced regardless of whether the detection distance is larger or smaller than the optimum value Db, FIG. 9A shows a state where the detection distance is set to a value Da smaller than the optimum value. The state where the value Dc is set is shown in FIG. 9C. FIG. 9 shows the position of the surface of the printing paper P when the detection distances are Da, Db, and Dc.

  As shown in the graph of FIG. 10, when the detection distance is set to the optimum value Db, even if the detection distance fluctuates within the range of, for example, ΔDb with the optimum value Db as the center, the value of the light reception output hardly fluctuates. .

  On the other hand, when the detection distance is set to a value Da smaller than the optimum value, if the detection distance fluctuates in the range of, for example, ΔDa around the value Da, the fluctuation range of the light reception output value is ΔLDa, which is very large. Similarly, when the detection distance is set to a value Dc larger than the optimum value, if the detection distance fluctuates in the range of ΔDc, for example, with the value Dc as the center, the fluctuation range of the light reception output value is ΔLDc, which is very large.

  If the light-receiving output value fluctuates greatly due to slight fluctuations in the detection distance, it may be confused with fluctuations in the light-receiving output based on changes in the printing state on the print medium, which may lead to erroneous determination in the ink ejection determination test. is there.

  During the ink ejection determination test, the sensing operation is performed while the height of the optical sensor remains constant.However, if cockling occurs on the print medium, especially the print paper, the surface of the print paper is scanned by the optical sensor. As the light irradiation position moves, the detection distance varies sequentially.

  Therefore, when the detection distance is set to the optimum value Db in advance, even if the detection distance is slightly changed due to cockling of the printing paper P, the fluctuation of the received light output is suppressed to be very small, and erroneous determination hardly occurs. When the detection distance is set to a value Da smaller than the optimum value or a large value Dc, fluctuations in the received light output that cause erroneous determination may occur due to fluctuations in the detection distance.

  Even in a printing apparatus equipped with an automatic paper gap adjustment mechanism and an optical sensor for ink discharge determination, an ink discharge determination test is performed as necessary. Among such printing apparatuses, those having a conventional configuration are ink discharge. Print pattern printing for judgment test and sensing by optical sensor are executed in parallel, and at that time, paper gap automatic adjustment is performed according to the type of print medium selected as the print medium to be used. Done.

  Since the print head and the optical sensor are mounted on the same carriage, the detection distance of the optical sensor also varies as a result of the paper gap variation due to automatic adjustment.

  Also, the paper gap automatic adjustment mechanism automatically optimizes the paper gap according to the type of print medium for the purpose of improving image quality, so the detection distance of the optical sensor is not often set to the optimum value. As a result, in a conventional printing apparatus equipped with an automatic paper gap adjustment mechanism and an optical sensor for ink discharge determination, an erroneous determination can often occur in an ink discharge determination test.

  Therefore, in the first embodiment of the optical sensor for ink ejection determination, the printing apparatus, and the ink ejection determination method according to the present invention, on the assumption that the paper gap automatic adjustment mechanism is mounted on the printing apparatus, the ink Printing pattern printing for ejection determination test and sensing by optical sensor are not performed in parallel. First, the paper gap is automatically adjusted to the optimum value for the print medium used, and the ink ejection determination test After executing the printing of the printing pattern, the detection distance of the optical sensor, that is, the distance between the surface of the printing medium and the light receiving portion 41b is detected by receiving the reflected light regardless of the type of the printing medium to be used. The sensing operation is executed from the sensing operation start position by the optical sensor.

  Therefore, according to the first embodiment of the present invention, the print pattern for the ink ejection determination test can be printed with high image quality, and the sensing of the print pattern by the optical sensor is performed with very high accuracy. can do.

  As a result, in the printing apparatus equipped with the paper gap automatic adjustment mechanism, it is possible to determine the ejection state of the ink droplets from the nozzles very accurately.

  The adjustment of the paper gap and the detection distance of the optical sensor are both performed by a carriage height adjustment mechanism attached to the carriage.

  By the way, when considering the image quality of the print pattern printed on the print medium in the ink discharge determination test, the image quality of such a print pattern can determine the presence or absence of ink discharge from each ink discharge portion. If it is of the order, it is sufficient, and excessive high image quality is not necessary.

  Therefore, in the second embodiment of the optical sensor for ink discharge determination, the printing apparatus, and the ink discharge determination method according to the present invention on the assumption that the paper gap automatic adjustment mechanism is mounted on the printing apparatus, Printing pattern printing for ejection determination test and sensing by optical sensor are executed in parallel, and at that time, regardless of the type of printing medium used, optimization by automatic adjustment of paper gap is Instead, the detection distance of the optical sensor, that is, the distance between the print medium surface and the light receiving portion 41b is set to an optimum value for receiving and detecting the reflected light and fixed. Therefore, it is considered that the paper gap is often not set to the optimum value for executing printing on the print medium to be used. However, for the reason described above, the detection distance of the optical sensor is optimized in the second embodiment. Priority is given to setting a value.

  Therefore, according to the second embodiment of the present invention, the print pattern for the ink ejection determination test can be printed with an image quality sufficient for the purpose of use, and the print pattern sensing by the optical sensor is highly accurate. In addition, the efficiency of the ink ejection determination test can be improved.

  As a result, in the printing apparatus equipped with the paper gap automatic adjustment mechanism, it is possible to accurately determine the ejection state of the ink droplets from the nozzles.

  The optimum value of the detection distance set in the first and second embodiments of the ink ejection determination optical sensor, the printing apparatus, and the ink ejection determination method according to the present invention is constant regardless of the type of print medium used. Normally, the optimum value of the detection distance when plain paper is used as the print medium should be used.

  The reason for this is that plain paper is the print medium in which cockling is most likely to occur among the print media normally used in printing apparatuses. If the optimum detection distance for plain paper is adopted, cockling will not occur. This is because the influence can be minimized.

  Incidentally, the plain paper means a standard quality printing paper having a thickness of about 0.1 mm which is generally popular.

  The optical sensor for ink discharge determination, the printing apparatus, and the ink discharge determination method according to the present invention described above can detect the print state of the print medium surface and the presence or absence of the print medium reflected in the intensity of reflected light. Therefore, not only the determination of the ink discharge state from the nozzle, but also the printing operation state according to the present invention for determining various operation states of the printing apparatus reflected in the printing state on the surface of the printing medium or the presence or absence of the printing medium It can be widely used as a determination optical sensor, printing apparatus, and printing operation state determination method.

  For example, a printing pattern detection and printing apparatus for Bi-D adjustment that adjusts the relative position between the forward ink drop position and the backward ink drop position when bi-directional (Bi-D) printing in the main scanning direction of the printing apparatus is performed. The configuration of the present invention can also be applied to print pattern detection for adjusting the paper feed amount in the sub-scanning direction, print medium end (edge) detection by detecting the presence or absence of a print medium, and the like.

  When the configuration of the present invention is applied to the detection of the edge of the print medium, the operation and the process of printing the print pattern on the print medium are not necessary. However, in the present invention, the paper gap is set according to the type of the print medium. Therefore, the operation and process of automatically adjusting the paper gap according to the type of print medium is invalidated, and the detection distance depends on the type of print medium. The point which gives priority to the operation | movement and process which set to a fixed value first is the same.

  Also, when applying the configuration of the present invention to print pattern detection for Bi-D adjustment, high-precision pattern printing is required, and thus the configuration of the first embodiment is usually applied. However, in the case of a printing apparatus equipped with a paper gap automatic adjustment mechanism, adjustment values for Bi-D printing are set for each of a plurality of paper gap values.

  Therefore, when the optical sensor for ink discharge determination, the printing apparatus, and the ink discharge determination method according to the first embodiment of the present invention are applied to print pattern detection for Bi-D adjustment, a plurality of paper gaps are used. After the adjustment pattern is printed for each value, pattern detection may be performed.

  The printing operation state determination apparatus, the printing operation state determination system, the printing apparatus, and the printing operation state determination method according to the present invention are not limited to inkjet printers, and detect a printing state on the surface of a printing medium reflected in the intensity of reflected light. , A printing operation state determination device, a printing operation state determination system, a printing device, and a printing operation state determination for all printing devices equipped with an optical sensor as a printing operation state determination device for determining various operation states of the printing device It is possible to apply to the method.

1 is a perspective view illustrating a schematic configuration of a main part of an inkjet printer that is a main application target of a configuration of an optical sensor for determining a printing operation state, a printing apparatus, and a printing operation state determination 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 an inspection which comprises the pattern for an 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. When the detection distance is set to a value smaller than the optimum value in the optical sensor for ink ejection determination (a), when the detection distance is set to the optimum value (b), the detection distance is set to a value larger than the optimum value. 5C is an explanatory diagram schematically showing the positional relationship between the light emitting part and the light receiving part of the optical sensor, the optical paths of the irradiation light and the reflected light, and the surface of the print medium in each of the cases (c). It is a graph which shows the light reception output characteristic with respect to detection distance fluctuation | variation.

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 Unit 41b Light Receiving Unit 50 Reception Buffer Memory 52 Image Buffer 54 System Controller 54a Determination Unit 61 Main Scan Driver 62 Sub Scan Driver 63 Optical Sensor Driver 66 Head Driver 71 Print Pattern 100 Host Computer 200 Cleaning Mechanism 210 Head Cap BL Print Block BLa Blank Print Block BLb Normal Print Block CD Dark 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 V0 Output signal level of blank printing block VL Output signal level of normal printing block Da Detection distance Db with value smaller than optimum value Detection distance Dc with optimum value Detection distance ΔDa with value larger than optimum value Detection distance fluctuation ΔDb with detection distance Da Detection distance fluctuation ΔDc with detection distance Db Detection distance fluctuation ΔLDa at distance Dc Light reception output fluctuation ΔLDc at detection distance Da Light reception output fluctuation at detection distance Dc

Claims (4)

A print head on which a plurality of ink discharge portions for discharging ink are formed;
A light emitting unit that emits irradiation light to the print medium, and 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 An optical sensor having
A determination unit for determining an operation state of the printing apparatus based on a detection result by the optical sensor;
A carriage carrying the print head and the optical sensor;
A function of automatically adjusting a paper gap as an interval between the plurality of ink ejection units and the print medium surface according to the type of the print medium, and a detection distance as a distance between the print medium surface and the light receiving unit A carriage height adjusting mechanism having a function of setting a constant value regardless of the type of the print medium;
With
The detection distance is set by emitting the irradiation light from the light emitting unit to the print medium, and receiving the reflected light reflected on the surface of the print medium by the light receiving unit. It is performed during the sensing operation, which is an operation for converting and generating the received light output signal of a value according to the intensity ,
The detection distance is set such that the distance between the print medium and the light receiving unit is an optimum value for detecting by detecting reflected light, and the optimum value is determined when the print medium is plain paper. Ri optimum der of the detection distance in case where,
In one pass in which the carriage is moved in the main scanning direction with the detection distance set to the optimum value, a printing operation for printing a printing pattern on the printing medium, and the printing printed by the printing operation The sensing operation for the pattern is performed,
A printing apparatus characterized by that.   The printing apparatus according to claim 1, wherein the determination of the operation state includes determination of a position of an end portion of the print medium. Outward ink when the determination of the operating state, to perform ink determination of the presence of the ejection, bidirectional in the main scanning direction of the printing device (Bi-D) printing from each of the plurality of ink ejection portions for ejecting ink 2. The method according to claim 1, further comprising: determining a relative position adjustment state between the dropping position and the return ink dropping position, or determining a paper feed amount adjustment state in the sub-scanning direction of the printing apparatus. The printing apparatus according to 2.   The printing apparatus according to claim 1, wherein the determination of the operation state is performed by comparing a value of the light reception output signal with a predetermined threshold value.

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