JP2006334915A - Method for inspecting ink discharge for printing device and printing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a printing area of all inspection printing blocks for the number of ink discharge parts, and to make an inspection in a short period of time and with accuracy, in a printing device for inspecting whether there is an ink discharge failure from a plurality of ink discharge parts by printing a plurality of the inspection printing blocks. <P>SOLUTION: Twenty seven inspection printing blocks BL(A, B, C... ) are formed on a printing sheet by discharging ink from each two different nozzles (e.g. nozzles No. 54 and No. 53 for the block A) of 54 individual nozzles. Further, the individual printing blocks BL are irradiated with a illuminating spot light 10 from a luminescence part, and the reflected light from only the individual regions of the printing blocks BL, is received by a light receiving part. In addition, the output signal level complying with the light receiving level is compared with a specified threshold value and thereby, the presence of the discharge failure of at least one nozzle of the two nozzles used for forming the printing block BL, is judged. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a so-called inkjet printing apparatus that performs printing by ejecting ink onto a print medium from a plurality of ink ejection sections, and ejects ink from the printing apparatus that inspects whether or not there is ink ejection from the plurality of ink ejection sections. The present invention relates to an inspection method and its printing apparatus.

  An ink jet printer as a printing apparatus having a plurality of ink ejection units prints an image by ejecting ink droplets from nozzles as a plurality of ink ejection units. A print head of an inkjet printer is provided with a large number of nozzles. However, there are cases where some nozzles are clogged and ink droplets cannot be ejected due to an increase in the viscosity of ink or mixing of bubbles. When the nozzles are clogged, dots are lost in the image, causing deterioration in image quality.

  Therefore, as an apparatus for inspecting the ejection state (ejection / non-ejection) of ink droplets from each nozzle, for example, an inspection pattern that forms one inspection print block for each nozzle is printed on a print medium. A printing apparatus for inspecting the discharge state is known (see, for example, Patent Document 1). Such a printing apparatus has, for example, a reflective sensor having a light emitting unit and a light receiving unit, and irradiates the light emitted from the light emitting unit onto a print medium on which a test pattern is printed and receives the reflected light. By detecting the presence / absence of each printing block based on the output, the ejection state of the ink droplets from the nozzle used for the format of the printing block is determined.

  On the other hand, in recent years, with the increase in printing speed, the number of nozzles in the nozzle array along the sub-scanning direction provided in the print head has increased, and it is used to improve the quality of color printing of natural images. As the number of ink colors increases, the number of nozzle rows also increases, and the number of nozzles of the entire print head has increased. For this reason, in order to inspect the ink discharge state of all nozzles, printing a test pattern consisting of the same number of print blocks as the number of nozzles as in the conventional example described above increases the printing area, so a large amount of ink and printing paper are required. In addition to consumption, there is a problem that the printing time becomes longer. Further, since the ejection state of the ink droplet is inspected for each printing block, there is a problem that it takes time for the inspection. This problem becomes more prominent as the number of nozzles of the print head increases.

  Several proposals have been made in view of such problems. For example, Patent Documents 2 and 3 propose a method in which an inspection pattern as shown in FIG. 12 is printed on a print medium for each ink color and an ink discharge state is inspected as follows. In FIG. 12, reference numeral BL denotes a test print block printed by driving each of the nozzles each having a nozzle number indicated by a number with “#”. The printing blocks BL for each nozzle are printed adjacent to each other. Reference numeral 10 denotes a spot of light rays irradiated on the print medium from the light emitting portion of the reflective sensor. By making one printing block BL smaller than the spot 10 or making the spot 10 larger than one printing block BL, the spot 10 becomes a plurality of adjacent printing blocks BL, for example, nozzle numbers # 22, # as shown. Based on the output of the light receiving unit that simultaneously irradiates the four printing blocks BL formed by the nozzles 23, # 31, and # 32 and receives the reflected light, one or more of the four nozzles do not eject. It is determined whether or not.

According to such a method, for a plurality of (for example, four) nozzles at a time, although it is not possible to specify which one is non-ejection, it is possible to determine the presence or absence of non-ejection. Compared to the above, the inspection can be performed in a short time (for example, 1/4 time). In addition, the diameter of the spot 10 is the same as that of the prior art, and the printing area of the inspection pattern can be reduced to reduce the consumption of ink and printing paper, and the printing time can be shortened.
US Pat. No. 6,215,557 JP 2003-291318 A JP 2003-291319 A

  However, in the methods of Patent Documents 2 and 3, in the example of FIG. 12, when the four print blocks BL of nozzle numbers # 22, # 23, # 31, and # 32 are inspected, the spot 10 has four print blocks. Along with BL, each of the nozzles # 13, # 14, # 21, # 24, # 30, # 33, # 40, and # 41 around each of the print blocks BL is irradiated and corresponding nozzles Discharge / non-discharge affects the amount of light received by the light receiving unit. For example, when the nozzles # 40 and # 41 are not ejected, the amount of received light increases. For this reason, the presence or absence of non-ejection of the four nozzles corresponding to the four printing blocks BL cannot be accurately determined and may be erroneously determined.

  In addition, the accuracy is reduced when determining the four blocks at the end of the print block group. For example, when determining four blocks of # 37, # 38, # 46, and # 47, the upper end portion and the right end portion of the spot 10 protrude into an unprinted area, and reflected light there is also received. There is a case.

  On the other hand, it is conceivable to make the spot 10 small, but in that case, the ratio of the area that receives the light of each block differs greatly due to a slight error in the position of the spot 10 with respect to the four blocks, and an erroneous determination is made due to an error in the amount of received light There was a problem of inviting.

  The present invention has been made in view of such a problem, and the problem is to inspect whether or not ink is ejected from a plurality of ink ejection portions (nozzles) by printing a plurality of test printing blocks as described above. In the ink ejection inspection method of an ink jet type printing apparatus, the printing area of a plurality of inspection printing blocks can be small for the number of ink ejection portions, and the inspection can be performed in a short time and more accurately. It is in.

In order to solve the above problems, an ink discharge inspection method for a printing apparatus according to the present invention includes a plurality of ink discharge units that discharge ink to a print medium, a light emitting unit that irradiates light to the print medium, and printing. An ink discharge inspection method for a printing apparatus, comprising: a light receiving unit configured to receive reflected light of the light reflected by the medium; and inspecting presence or absence of ink discharge from the plurality of ink discharge units based on a light reception amount of the light receiving unit Because
A first step of forming a plurality of test print blocks on a print medium by individually discharging ink from a plurality of different ink discharge portions of the plurality of ink discharge portions;
Light is emitted from the light emitting unit to individual areas of the plurality of inspection print blocks formed on the print medium by the first step, and reflected light from only within the area is received by the light receiving unit, And a second step of determining whether at least one or more non-ejections among a plurality of ink ejection parts used for forming the inspection print block based on the amount of received light. .

  The printing apparatus according to the present invention includes a plurality of ink ejection units that eject ink onto a print medium, a light emitting unit that irradiates light to the print medium, and reflected light of the light reflected by the print medium. And a light receiving portion that receives light, and is configured to inspect the presence or absence of ink discharge from the plurality of ink discharge portions by the ink discharge inspection method of the printing apparatus according to the present invention.

  According to the present invention, since a plurality of test print blocks are individually formed by ejecting ink from a plurality of ink ejecting portions, each print block is formed by ejecting ink from one ink ejecting portion in the conventional example. Compared to the case, the number of printing blocks is reduced by a factor of one for the number of ink ejection sections, the overall printing area is remarkably reduced, the printing time is shortened, and the amount of ink and printing medium used for printing is reduced. Can be reduced. In addition, the number of inspections is reduced to a plurality according to the number of print blocks, and the time required for the inspection itself can be shortened. In addition, since the presence or absence of non-ejection is determined based on the amount of reflected light received from only the individual areas of the inspection print block, the influence of the formation state of the print blocks around the print block to be inspected and the amount of received light There is no problem such as error, and there is an excellent effect that the inspection can be performed accurately.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. Here, an embodiment in a serial type ink jet color printer (hereinafter abbreviated as a printer) is shown as an ink jet printing apparatus.

  FIG. 1 is a schematic perspective view illustrating a main mechanical configuration of the printer according to the first exemplary embodiment of the present invention. The printer 20 includes a paper stacker 22 that stores printing paper P as a printing medium, a paper feed roller 24 that is driven by a motor (not shown), and that transports the printing paper P, a platen plate 26, a carriage 28, and the like. A carriage motor 30 for movement, a traction belt 32 driven and driven by this, and a guide rail 34 for guiding the carriage 28 are provided. The carriage 28 includes a print head 36 having a large number of nozzles, and an ink discharge inspection unit 41 which is an optical sensor unit for inspecting the discharge state (discharge / non-discharge) of ink (droplets) from each of the nozzles. In addition, a linear encoder 29 for reading the code plate 33 is mounted. A rotary encoder 25 is provided on the shaft of the paper feed roller 24, and the transport amount of the printing paper P is controlled based on the output. Therefore, the position of the carriage 28 in the main scanning direction MS can be detected by the linear encoder 29, and the paper feed direction of the printing paper P, that is, the position in the sub-scanning direction SS can be detected by the rotary encoder 25. 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 output signals from the encoders 25 and 29.

  The printing paper P is fed from a paper stacker 22 by a paper feeding roller (not shown), conveyed by a paper feeding roller 24, and fed on the surface of the platen plate 26 in the sub scanning direction SS. The carriage 28 is pulled by the pulling belt 32 that travels by driving the carriage motor 30 and moves along the guide rail 34 in the main scanning direction MS and the opposite direction. The main scanning direction MS is perpendicular to the sub-scanning direction SS.

  FIG. 2 is a view of the print head 36 as viewed from the lower surface side. On the lower surface of the print head 36, a black ink nozzle group KD for discharging black ink, a dark cyan ink nozzle group CD for discharging dark cyan ink, and a light cyan ink nozzle for discharging light cyan ink. A group CL, a dark magenta ink nozzle group MD for discharging dark magenta ink, a light magenta ink nozzle group ML for discharging light magenta ink, and a yellow ink nozzle group YD for discharging yellow ink are provided. It has been. As indicated by the nozzle numbers of # 1, # 2,..., # 54, 54 nozzles are provided in each nozzle group, and the sub-scanning direction (printing paper conveyance direction) SS is provided for each nozzle group. The nozzle numbers # 1, # 2,... # 54 are assigned in order from the upstream side in the sub-scanning direction SS. At the time of printing, ink (for example, droplet-shaped ink) is ejected from each nozzle while the print head 36 moves in the main scanning direction MS together with the carriage 28 (FIG. 1).

  In the configuration of FIG. 1, a cleaning mechanism 200 is provided below the print head 36 mounted on the carriage 28 outside the print region in 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 an airtight cap, and covers the lower surface of the print head 36 when printing is not performed to prevent the ink in the nozzles from drying. For this reason, the head cap 210 is provided at a standby position of the carriage 28, a so-called home position side. Further, even when the nozzle is clogged, the print head 36 is covered with the head cap 210 and ink is sucked from the nozzle to perform cleaning. The ink ejection inspection unit 41, which is an optical sensor unit for inspecting the ink ejection state, will be described in detail later.

  FIG. 3 is a block diagram showing an electrical configuration of the printer 20. The printer 20 is a reception buffer memory 50 that receives and temporarily stores various data transmitted from the host computer 100, an image buffer 52 that stores print data, and a control unit that controls the overall operation of the printer 20. System controller (CPU) 54 and a main memory 56. As will be described later, the system controller 54 includes a determination unit 54a that determines the ink discharge state from the nozzles.

  The system controller 54 includes a main scanning driver 61 that drives the carriage motor 30, a sub-scanning driver 62 that drives the paper feed motor 31, an inspection unit driver 63 that drives the ink ejection inspection unit 41, and the print head 36. Is connected to a head driver 66 for driving the motor.

  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. Further, based on these parameter values, print data for printing is generated and transferred 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 by 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 group of each color of the print head 36 according to this. Note that the print data transferred from the host computer 100 may be separated for each color component by the host computer 100.

  Next, the configuration and operation of the ink ejection inspection unit 41 will be described with reference to FIG. As shown in (A) or (B) of FIG. 4, the inspection unit 41 includes a light emitting unit 41 a and a light receiving unit 41 b, and each is driven by an inspection unit driver 63. Here, the light receiving unit 41b is an example in which one light receiving unit for mainly receiving the diffuse reflection component of the reflected light is shown, but in addition to this, the regular reflection component of the reflected light is mainly received. It is good also as a structure which provided the other light-receiving part for doing.

  The light emitting unit 41 a is a light projecting unit for irradiating (projecting) light (spot light) La toward the printing paper P. That is, in the ink ejection inspection, the irradiation light La is emitted toward an area on the printing paper P where an image of an inspection print block to be described later is to be printed. As a light emitter of the light emitting unit 41a, a light emitting diode, a laser diode, an incandescent light bulb, or the like may be used. The color of the illuminant is preferably a color that is complementary to the color of the print image of the inspection print block to be inspected. For example, a red light emitter is used to detect a cyan print image, a green light emitter is used to detect a magenta print image, and a blue light emitter is used to detect a yellow print image. Good. If the color of the illuminant and the color of the printed image have a complementary relationship, the level of the output signal can be significantly increased as compared to the case where the color is not so. Therefore, in order to obtain a stable output for a printed image of any color, it is preferable to use a white light emitter as much as possible. The light emitting unit 41a is controlled by the system controller 54 so that the light emission amount can be adjusted as necessary.

  The light receiving unit 41b is a photoelectric conversion unit that receives the reflected light Lb of the irradiation light La reflected from the print image to be inspected on the printing paper P and converts it into an electrical signal. As the light receiving element of the light receiving unit 41b, a photodiode, a phototransistor, or the like is preferable. Preferably, a light receiving element having good sensitivity characteristics with respect to visible light is preferable.

  It is desirable that the position of the light receiving part 41b for mainly receiving the diffuse reflection component is not in the position of regular reflection with respect to the light emitting part 41a as shown in FIG. 4, and the light emitting part 41a as shown in FIG. The light-receiving unit 41b may be mounted obliquely with respect to the paper surface, and the light-emitting unit 41b may be inclined with respect to the paper surface as shown in FIG. 4B. The light receiving portion 41b may be attached perpendicular to the paper surface. In particular, in a print medium having a coating layer on the surface, such as a glossy print medium, most of the incident light is regularly reflected by the coating layer on the surface, but the positions of regular reflection between the light emitting part 41a and the light receiving part 41b are reflected. When not attached due to the relationship, the color of the inspection printing block under the coating layer can be reliably determined.

  At the time of inspection of the ink ejection state, first, an inspection pattern composed of a plurality of inspection print blocks described later is printed on the printing paper P prior to the inspection. Each inspection print block is formed (printed) by a plurality of nozzles, for example, two nozzles, as will be described later. Then, the light La is irradiated from the light emitting portion 41a onto each area of the inspection print block formed on the printing paper P, and the reflected light (diffuse reflection component) Lb is received only from the area. Based on the level of the output signal corresponding to the amount of light received by the light receiving portion 41b and received by the light receiving portion 41b, the ink (droplet) from all the nozzles is normally discharged from the plurality of nozzles used for forming the inspection print block. It is determined whether or not at least one nozzle is not ejected.

  FIG. 5 shows a part of an example of an inspection pattern formed with a certain ink color (for example, black), and FIG. 6 shows an inspection printing block (hereinafter simply referred to as a printing block) BL constituting the inspection pattern. FIG.

  The inspection pattern in FIG. 5 is an inspection pattern formed (printed) by each nozzle group that ejects ink of each color. That is, when inspecting the ink ejection state of all the nozzles of the print head 36, inspection patterns for the number of colors of ink ejected from all the nozzles of the print head 36 are formed. In this embodiment, six inspection patterns are formed. Will be formed. Each printing block BL is formed by a plurality of nozzles. In this embodiment, in order to simplify the description, one print block BL is formed by two nozzles, and the print head 36 has 54 nozzles per color. 27 printing blocks BL each formed by two nozzles are printed and configured.

  Each print block BL is formed as a matrix of a plurality of ink dots (here, 8 rows × 9 columns) by ink droplets ejected from two nozzles, as shown in FIG. And each printing block BL is used for the test | inspection of the discharge state of each two nozzles used for each formation. In FIG. 5, only 15 of the 27 print blocks BL are shown.

  This test pattern is formed by forming three print block arrays in which nine print blocks BL are arranged in the main scanning direction MS in the sub-scanning direction SS. A space having a predetermined width is formed between adjacent printing blocks BK. The first block A in the first-stage printing block array located on the most upstream side in the sub-scanning direction SS is printed as shown in FIG. 6 by the 54th nozzle # 54 and the 53rd nozzle # 53.

  Here, the dots by the nozzle # 54 and the dots by the nozzle # 53 are arranged in the main scanning direction MS and the sub-scanning direction SS at a predetermined dot pitch P for so-called solid printing that fills the printing paper with dots (ink dots) without gaps. They are formed alternately. That is, the dots formed by the nozzle # 54 and the dots formed by the nozzle # 53 are formed so as to be uniformly dispersed and mixed in both the main scanning direction MS and the sub-scanning direction SS.

  In this printing, the nozzle # 54 to nozzle # 53 are driven at intervals of 2P while moving the print head 36 in the main scanning direction MS, and then the print head 36 is returned and the printing paper is sub-scanned. This is performed by repeating the conveyance for 1P in the direction SS. In the first main scan, only nozzle # 54 is driven to form four dots in the uppermost row. In the second main scan, nozzles # 53 and # 54 are driven together to form five dots in the uppermost row by nozzle # 53 and five dots in the second row by nozzle # 54. To do. In the third main scan, both nozzles # 53 and # 54 are driven, and nozzle # 53 sets four dots in the second row, and nozzle # 54 sets four dots in the third row. Form. Subsequently, the main scanning similar to the second and third main scans is sequentially repeated to form half of two rows, and five dots are formed by the nozzle 54 in the lowermost eighth row in the eighth main scan. Are formed, four nozzles are formed in the eighth row by driving only nozzle # 53 in the ninth main scan, and the process is terminated.

  Similar to printing of block A, block B is printed by nozzles # 52 and # 51, block C is printed by nozzles # 50 and # 49, and block D is printed by nozzles # 48 and # 47. In this manner, each print block is sequentially printed with two different nozzles to form a test print pattern. Note that printing of such a test print pattern is performed under the control of the system controller 54 that is a control unit of the printer 20.

  Next, details of the ink ejection inspection method will be described. In the inspection, the printer 20 in FIG. 1 transports the printing paper P in the sub-scanning direction SS and prints the inspection printing pattern as described above, and then transports the printing paper P in the reverse direction of the sub-scanning direction SS. Then, the ink discharge inspection unit 41 is moved in the main scanning direction MS together with the carriage 28 while being conveyed again in the sub-scanning direction SS, and on each print block BL of the test print pattern printed on the print paper P. Scan. At this time, the irradiation light (spot light) La from the light emitting unit 41a of the inspection unit 41 shown in FIG. 4 is sequentially applied to each printing block BL, and the reflected light Lb from each printing block BL is sequentially received by the light receiving unit 41b. The ink discharge state is inspected by comparing the voltage of the electrical signal output from the light receiving unit 41b with a predetermined threshold value. The light of the irradiation light La emitted from the light emitting unit 41a becomes a circular spot on the printing paper P. At this time, the size of the spot 10 of the irradiation light La is set to one printing block as shown in FIG. By making the size smaller than the size of the BL area and applying the light to the individual areas of the print block, that is, by irradiating only the individual areas of the print block BL with the light from the light emitting unit 41a, Reflected light from only within the region is received by the light receiving unit 41b. Note that the size of the area on the printing paper P where the light receiving unit 41b can receive the reflected light Lb of the irradiation light La from the light emitting unit 41a using means such as a diaphragm (not shown) is larger than the individual areas of the printing block BL. By limiting it to be small, the reflected light from only the individual areas of the printing block BL may be received by the light receiving unit 41b.

  Here, when one or both of the two nozzles forming the printing block BL irradiated with the irradiation light La are non-ejection nozzles that do not eject ink droplets due to clogging or the like, the nozzles are printed on the printing paper P. Corresponding dots of the corresponding print block BL are not formed and are blank. For example, FIG. 7 shows a case where the 53rd nozzle # 53 of the 53rd nozzle # 53 and the 54th nozzle # 54 used for forming the printing block A in FIG. A print example is shown. In such a case, the amount of reflected light Lb received by the light receiving unit 41b of the inspection unit 41 is increased and the output signal level of the light receiving unit 41b is larger than when both of the two nozzles are normally ejected nozzles. descend. Therefore, the output signal level when there is a non-ejection nozzle is as shown in FIG. Compared to the output signal level (voltage value of the output signal) V0 when both of the two nozzles forming the print block BL are not non-ejection nozzles, one of the two nozzles is a non-ejection nozzle. The output signal level V1 is low, and the output signal level V2 when both of the two are non-ejection nozzles is further lower than the output signal level V1.

  Therefore, as shown in FIG. 7, a threshold value Vs is set between V0 and V1, and the output signal level is compared with the threshold value, thereby determining the ink droplet ejection state of the nozzle corresponding to the print block. Can be done accurately. Since the reflectance varies depending on the ink color of the print block and the values of the output signal levels V0 and V1 are also different, the threshold value Vs is set to a different value for each ink color accordingly.

  In order to make such a determination, the threshold value Vs data for each ink color is stored in the main memory 56 in the configuration of the control system of the printer 20 of FIG. Although not shown, in the inspection unit driver 63 (or outside thereof), an amplification circuit that amplifies the output signal of the light receiving unit 41b of the ink ejection inspection unit 41, and A / D conversion of the amplified output signal An A / D converter is provided, and the A / D converted digital data of the output signal level is input to the system controller 54. The system controller 54 is provided with a determination unit 54a that determines the ink discharge state. The determination unit 54a compares the input voltage value of the output signal level of the light receiving unit 41b with the threshold value Vs corresponding to the ink color of the print block BK to be inspected. The print block BL to which 10 is applied is solidly printed with no ink dots missing, and it is determined that the two nozzles used to form the print block BL are not non-ejection nozzles. If the threshold value is lower than the threshold value Vs, ink dots are missing from the print block BL, or the entire print block BL is blank, and one of the two nozzles used to form the print block BL or Both are determined to be non-ejection nozzles, and the nozzle numbers of the two nozzles are stored in the RAM portion of the main memory 56.

  Such a determination is sequentially performed on all the print blocks BL of the test pattern, and when all the determinations are completed, the system controller 54 refers to the main memory 56 to check the presence / absence of the non-ejection nozzles. If the nozzle is present, the cleaning mechanism 200 is driven to suck ink from the nozzle of the print head 36 to clean the nozzle, and the non-ejection nozzle is restored to a state where it can be ejected normally.

  According to the present embodiment as described above, one printing block BL is formed by two nozzles, so that one printing block is formed by one nozzle as in the conventional example of Patent Document 1. If the size of the printing block is the same, the number of printing blocks of the test pattern is halved for the number of nozzles, the printing area is halved, the printing time is shortened, and the ink used for printing and the printing paper The amount can be reduced. In addition, the number of inspections (number of determinations) is halved according to the number of print blocks, and the time required for the inspection itself can be shortened. Printing interruption time can be shortened. In the embodiment, one printing block BL is formed by two nozzles. However, it may be formed by three or more nozzles. In this case, the printing area of the inspection pattern is further increased. The time required for printing the inspection pattern and the time required for the inspection itself can be further shortened.

  Further, according to the present embodiment, as described above with reference to FIG. 5, the reflected light from only the individual areas of the print block BL is received by the light receiving unit 41b, and based on this, it is used for the format of each print block BL. Since the presence or absence of non-ejection of the nozzles determined is determined, there are no problems such as the influence of the formation state of the print blocks around the print block to be inspected and the error in the amount of received light as in the conventional examples of Patent Documents 2 and 3. Judgment can be performed accurately and inspection can be performed accurately.

In the first embodiment described above, the difference between the output signal levels V0 and V1 shown in FIG. 8 is small, and the difference between the levels V1 and V2 is large. This is because the printer is required to be able to perform solid printing on the recording paper with the same color, so that the printing block BK is formed by solid printing with the dot pattern shown in FIG. In solid printing, the relationship between the dot diameter L and the dot pitch P is
P ≤ L / √2
The dot pitch P is made smaller than the diameter L. For this reason, adjacent dots are printed partially overlapping as shown in FIG. When the printing block BL is printed with the dot pattern shown in FIG. 6 and one of the nozzles # 53 is not ejecting, the printing result is the dot pattern as shown in FIG. 7, and both are not ejecting. In comparison, the number of dots formed is ½, but the area occupied by all dots is considerably larger than ½ of the printing block BL. For this reason, the difference between the output signal levels V0 and V1 shown in FIG. 8 is reduced, and the difference between the levels V1 and V2 is increased.

  However, in order to accurately determine the presence or absence of non-ejection by comparing the output signal level and the threshold value Vs, the difference between the output signal levels V0 and V1 becomes larger, and the threshold value Vs is set to the output signal levels V0 and V1. It is preferable that the difference can be set with a margin.

  In order to improve this point, when printing the printing block BL, solid printing is performed in at least one of the main scanning direction and the sub-scanning direction so that dots formed by different nozzles do not overlap on the printing paper. Printing may be performed with a dot pitch larger than the dot pitch P and larger than the dot diameter.

  FIG. 9 shows an example of printing by the 53rd nozzle # 53 and the 54th nozzle # 54 in the printing example of the printing block BK according to the second embodiment. To print in this way, all the dots in the uppermost row are first formed with the nozzle # 53 at a dot pitch P of solid printing in the main scanning direction MS, and then half the dot pitch P in the sub-scanning direction SS. The printing paper is conveyed by 0.5P, and all dots in the second row are formed at a dot pitch P in the main scanning direction MS by nozzle # 54. Next, after 2.5P pitch printing paper is conveyed, all the dots in the third row are formed by nozzle # 53. This is sequentially repeated to form the printing block BK. Thereby, dots are formed at a pitch P in the main scanning direction MS but at a pitch of 1.5P in the sub-scanning direction SS.

  As shown in FIG. 9, a space is formed between the row of dots formed by nozzle # 53 and the row of dots formed by nozzle # 54, and the dots formed by nozzle # 53 and nozzle # 54 are formed. Dots formed do not overlap in the main scanning direction MS or the sub-scanning direction SS. There are a plurality of rows of dots formed by only one of the nozzles # 54 and # 53 in the main scanning direction MS, and dots formed by the nozzle # 54 and dots formed by the nozzle # 53 in the sub-scanning direction MS. Are alternately formed and are uniformly dispersed and mixed.

  If the printing block BL is formed with such a dot pattern, when one of the nozzles # 53 is not ejected, the formed printing block BL is as shown in FIG. 10, and both the nozzles # 53 and # 54 are formed. Compared to the case of FIG. 9 in which ejection is normally performed, the area occupied by all formed dots is ½, and is smaller than ½ of the area occupied by the entire printing block. When the spot 10 is applied to the printing block BL in FIG. 10 and the ejection state is inspected, the amount of reflected light Lb received by the light receiving unit 41b of the inspecting unit 41 is increased as compared with the case of FIG. As shown in FIG. 11, the output signal level V1 is lower than in the case of FIG. The output signal level V0 when both of the two nozzles are not ejecting is lower than that in the first embodiment, but the difference between the level V0 and the level V1 is larger than that in the first embodiment. Accordingly, the threshold value Vs can be set so that the difference between the threshold value Vs and the output signal levels V0 and V1 becomes large, the determination of the presence or absence of non-ejection can be performed accurately, and the inspection accuracy can be improved. It should be noted that the method of forming a printing block in such a manner that dots formed by different nozzles do not overlap as much as possible, particularly, each printing block is formed by a plurality of more than two nozzles to check whether there is any ejection failure. It is effective when judging.

  By the way, when ink is ejected from the nozzle, the ejection starts in a columnar shape from the ejection port of the nozzle, and eventually the ink leaves the ejection port. The flying columnar ink tends to be spherical due to surface tension, but when the columnar shape is long, it does not become one spherical droplet but separates into a plurality of droplets. Usually, the leading droplet is a large main droplet and the trailing droplet is a small satellite droplet that reaches the printing paper. During printing, since carriage scanning (main scanning) is in progress, satellite droplets land on the recording paper behind the main droplet landing position in the main scanning direction. On the other hand, in this embodiment, since dots formed by the same nozzle are arranged in the main scanning direction, the landing portion of the satellite droplets does not overlap with dots formed by different nozzles, which adversely affects non-ejection determination. Never give.

  In this embodiment, the dots in each row in the main scanning direction are formed at a pitch of 1.5 P in the sub-scanning direction. However, the present invention is not limited to this, and the pitch may be larger than the dot diameter. Of course. However, the range of 1.5P to 2P is desirable. Above that, the signal level V0 when there is no non-ejecting nozzle decreases, and the dynamic range of the signal used for non-ejecting determination decreases.

1 is a schematic perspective view illustrating a main mechanical configuration of a printer according to a first embodiment of the present invention. It is a bottom view of the print head of the printer. FIG. 2 is a block diagram illustrating an electrical configuration of the printer. 2 is an explanatory diagram illustrating a configuration and an operation of an ink discharge inspection unit of the printer. FIG. FIG. 4 is an explanatory diagram illustrating a part of an example of an inspection pattern printed for ink ejection inspection by the printer. It is explanatory drawing which shows the dot pattern of the printing block for a test | inspection which comprises the pattern for a test | inspection. It is explanatory drawing which shows the printing result in case one of the two nozzles which form the printing block for the same inspection does not discharge. It is a graph which shows the output signal level of the light-receiving part by the presence or absence of the non-ejection of the nozzle used for formation of the printing block for the inspection. FIG. 10 is an explanatory diagram showing a dot pattern of a test print block in Example 2. It is explanatory drawing which shows the printing result in case one of the two nozzles which form the printing block for the same inspection does not discharge. It is a graph which shows the output signal level of the light-receiving part by the presence or absence of the non-ejection of the nozzle used for formation of the printing block for the inspection. It is explanatory drawing explaining the test pattern which consists of the conventional test print block, and the discharge test method by it.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Spot of irradiated light 20 Printer 28 Carriage 30 Carriage motor 31 Paper feed motor 36 Print head 41 Ink discharge inspection part 41a Light emission part 41b Light reception part 54 System controller 54a Determination part 56 Main memory 100 Host computer 200 Cleaning mechanism # 1- # 54 Nozzle BL Inspection printing block La Irradiation light Lb Reflected light

Claims (8)

A plurality of ink ejection units that eject ink to the print medium, a light emitting unit that irradiates light to the print medium, and a light receiving unit that receives the reflected light of the light reflected by the print medium, An ink discharge inspection method for a printing apparatus for inspecting the presence or absence of ink discharge from the plurality of ink discharge portions based on the amount of light received by a light receiving portion,
A first step of forming a plurality of test print blocks on a print medium by individually discharging ink from a plurality of different ink discharge portions of the plurality of ink discharge portions;
Light is emitted from the light emitting unit to individual areas of the plurality of inspection print blocks formed on the print medium by the first step, and reflected light from only within the area is received by the light receiving unit, And a second step of determining whether at least one or more non-ejections among a plurality of ink ejection parts used for forming the inspection print block based on the amount of received light. Ink ejection inspection method for printing apparatus.   In the second step, the light from the light emitting unit is irradiated only in the individual regions of the inspection print block, so that the reflected light from only the individual regions of the inspection print block is reflected by the light receiving unit. 2. The ink ejection inspection method for a printing apparatus according to claim 1, wherein the ink is received.   In the second step, the size of the area on the print medium where the light receiving unit can receive the reflected light of the light from the light emitting unit is limited to be smaller than each area of the print block for inspection. The ink ejection inspection method for a printing apparatus according to claim 1, wherein reflected light from only an individual area of the printing block is received by the light receiving unit.   In the first step, the inspection print block is formed such that dots formed by a plurality of ink discharge portions are uniformly dispersed and mixed in at least one of the main scanning direction and the sub-scanning direction. An ink ejection inspection method for a printing apparatus according to claim 1.   In the first step, the inspection print block includes a plurality of dots formed by a single ink discharge portion in the main scanning direction, and is formed by a plurality of ink discharge portions in the sub-scanning direction. 2. The ink discharge inspection method for a printing apparatus according to claim 1, wherein the dots are uniformly dispersed and mixed.   In the first step, the inspection print block is formed with a dot pitch larger than the dot diameter so that dots formed by different ink ejection portions do not overlap at least one of the main scanning direction and the sub-scanning direction. The ink ejection inspection method for a printing apparatus according to claim 1, wherein:   In the second step, the voltage value of the output signal corresponding to the amount of light received by the light receiving unit that receives the reflected light of each of the plurality of test print blocks is compared with a predetermined threshold value. 2. The ink discharge of the printing apparatus according to claim 1, wherein at least one of the plurality of ink discharge portions used for forming the inspection print block is determined to be non-discharge. Inspection method.   A plurality of ink ejection units that eject ink to the print medium; a light emitting unit that irradiates light to the print medium; and a light receiving unit that receives the reflected light of the light reflected by the print medium. 8. A printing apparatus configured to inspect the presence or absence of ink ejection from the plurality of ink ejection sections by the ink ejection inspection method for a printing apparatus according to any one of items 1 to 7.

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