JP7424852B2 - Tablet printing device and tablet printing method - Google Patents

Description

Embodiments of the present invention relate to a tablet printing device and a tablet printing method.

In order to print identification information (an example of information) such as letters and marks on tablets, a printing technique is known that uses an inkjet head. A tablet printing device using this technology transports tablets using a transport device such as a conveyor, and discharges ink from each nozzle of an inkjet head placed above the transport device toward the tablets passing below the inkjet head. Print identification information on tablets.

Normally, tablets are arranged in rows in the transport direction, and the nozzle array is transported in a horizontal plane below the inkjet head, which is perpendicular to the transport direction. Printing is performed using the nozzle groups within the range. The length of the nozzle row of the inkjet head is longer than the diameter of the tablet, and the nozzle to be used for printing from among the plurality of nozzles included in the inkjet head is determined depending on the position to which the tablet has been conveyed. Although the tablets are not always conveyed in the same positional relationship with respect to the inkjet head, they are conveyed at approximately the same position (or a position in the vicinity thereof). Therefore, in the nozzle array of the inkjet head, there are nozzles that are used frequently and nozzles that are used less frequently.

Under these circumstances, if the tablets are transported in a state that is shifted from the row of tablets (shifted in the horizontal plane in a direction perpendicular to the conveyance direction), printing on the tablets in the misaligned state requires Not only frequently used nozzles but also infrequently used nozzles are used. For nozzles that are used less frequently, the ink at the tips of the nozzles is beginning to dry. For this reason, if a nozzle that is used infrequently is used, the ink ejected from the nozzle may become bent, or the amount of ink may be insufficient, resulting in blurred print or poorly printed tablets (hereinafter referred to as "defective tablets"). ) occurs, resulting in a decrease in productivity.

Japanese Unexamined Patent Publication No. 7-081050

The problem to be solved by the present invention is to provide a tablet printing device and a tablet printing method that can increase productivity.

The tablet printing device according to the embodiment of the present invention includes:
a transport section that transports the tablets;
a detection unit that detects the position of the tablet in a direction that intersects the conveyance direction of the tablet conveyed by the conveyance unit in a horizontal plane;
an inkjet head that prints by ejecting ink from a plurality of nozzles lined up in the intersecting direction on the tablets transported by the transport unit;
Of the range of nozzles used for printing on the tablet among the plurality of nozzles, which is determined based on the position of the tablet detected by the detection unit and the printing pattern to be printed on the tablet, a part thereof is If the tablets that are sequentially conveyed by the conveyance unit are out of a predetermined stable ejection range in which the ink can be stably ejected from among the plurality of nozzles, the ink is within the stable ejection range. Adjusting the nozzle range to be used so that the printing pattern after printing is reduced, and/or adjusting the range of nozzles to be used so as to shift the nozzle range to print on the tablet using only the nozzles of a control unit that causes the inkjet head to perform printing with nozzles within the used nozzle range;
Equipped with.

The tablet printing method according to the embodiment of the present invention includes:
a step of conveying the tablets by a conveying section;
a step of detecting, by a detection unit, a position of the tablet in a direction that intersects the conveyance direction of the tablet conveyed by the conveyance unit in a horizontal plane;
Based on the position of the tablet detected by the detection unit and the printing pattern to be printed on the tablet, print on the tablet among the plurality of nozzles arranged in the intersecting directions included in the inkjet head that prints on the tablet. A range of nozzles to be used is determined, and a part of the determined nozzle range to be used stably discharges ink from among the plurality of nozzles to the tablets that are sequentially transported by the transport unit. In order to print on the tablet using only the nozzles within the stable ejection range when the tablet exceeds a predetermined stable ejection range in which it is possible to adjusting the inkjet head to be reduced and/or shifting the used nozzle range, and causing the inkjet head to perform printing with nozzles within the adjusted used nozzle range;
has.

According to embodiments of the present invention, productivity can be increased.

FIG. 1 is a diagram showing a schematic configuration of a tablet printing device according to a first embodiment. FIG. 1 is a plan view showing a part of the tablet printing device according to the first embodiment. FIG. 3 is a diagram for explaining a stable ejection range according to the first embodiment. 7 is a flowchart showing the flow of adjustment processing for the nozzle range to be used according to the first embodiment. FIG. 3 is a first diagram for explaining reduction adjustment processing according to the first embodiment. FIG. 3 is a second diagram for explaining reduction adjustment processing according to the first embodiment. FIG. 7 is a first diagram for explaining shift adjustment processing according to a second embodiment. FIG. 7 is a second diagram for explaining shift adjustment processing according to the second embodiment. 12 is a flowchart showing the flow of adjustment processing for the nozzle range to be used according to the second embodiment. FIG. 7 is a diagram for explaining range expansion processing according to the third embodiment. FIG. 7 is a diagram for explaining reduction adjustment processing and shift adjustment processing according to another embodiment.

<First embodiment>
A first embodiment will be described with reference to FIGS. 1 to 6.

(Basic configuration)
As shown in FIG. 1, the tablet printing apparatus 1 according to the first embodiment includes a supply section 10, a conveyance section 20, a detection section 30, an imaging section 40, a printing section 50, an imaging section 60, It includes a collection section 70, an image processing section 80, and a control section 90. The detection section 30 is used to detect imaging timing, the imaging section 40 is used to detect a tablet position, and the imaging section 60 is used to inspect a printing state.

The supply section 10 has a hopper 11 and a chute 12. The supply section 10 is configured to be able to supply the tablets T to be printed to the conveyance section 20, and is positioned on one end side of the conveyance section 20. The hopper 11 accommodates a large number of tablets T, and sequentially supplies the accommodated tablets T to the shooter 12. The shooter 12 arranges the tablets T supplied from the hopper 11 in a line and supplies them to the transport section 20. The supply section 10 is electrically connected to the control section 90, and its driving is controlled by the control section 90.

The transport section 20 includes a transport belt 21, a drive pulley 22, a plurality of (three in the example of FIG. 1) driven pulleys 23, a motor (drive section) 24, a position detector 25, and a suction chamber (suction section) 26. are doing. The conveyor belt 21 is an endless belt, and is stretched around a drive pulley 22 and each driven pulley 23 . The drive pulley 22 and each driven pulley 23 are rotatably provided in the device body, and the drive pulley 22 is connected to a motor 24. The motor 24 is electrically connected to a control section 90, and its driving is controlled by the control section 90. The position detector 25 is a device such as an encoder, and is attached to the motor 24. This position detector 25 is electrically connected to the control section 90 and transmits a detection signal to the control section 90. The control unit 90 can obtain information such as the position, speed, and movement amount of the conveyor belt 21 based on the detection signal. The conveyor unit 20 rotates the conveyor belt 21 together with each driven pulley 23 by the rotation of the drive pulley 22 by the motor 24, and conveys the tablets T on the conveyor belt 21 in the direction of arrow A1 in FIG. 1 (transfer direction A1). .

As shown in FIG. 2, the conveyor belt 21 is provided with a plurality of circular suction holes 21a. These suction holes 21a are through holes that suck the tablets T, and are arranged in a line along the conveyance direction A1 so as to form one conveyance path. Each suction hole 21a is connected to the suction chamber 26 through a suction path (not shown) formed in the suction chamber 26 (see FIG. 1), and it is possible to obtain suction force from the suction chamber 26. It has become. A suction unit such as a pump is connected to the suction chamber 26 via a suction pipe (none of which is shown), and the pressure inside the suction chamber 26 is reduced by the operation of the suction unit. The suction tube is connected to approximately the center of the side surface of the suction chamber 26 (a surface parallel to the transport direction A1). Further, the intake section is electrically connected to the control section 90, and its driving is controlled by the control section 90. When the pressure inside the suction chamber 26 is reduced, the tablets T placed on each suction hole 21a of the conveyor belt 21 are suctioned by the suction chamber 26 and held on the conveyor belt 21.

The detection unit 30 is located downstream in the conveyance direction A1 from the position where the supply unit 10 is provided, and is provided above the conveyance belt 21. This detection unit 30 detects the position of the tablet T on the conveyance belt 21 in the X direction (conveyance direction A1) by emitting and receiving laser light, and functions as a trigger sensor for each device located downstream. As the detection unit 30, for example, various laser sensors such as a reflective laser sensor can be used. The detection unit 30 is electrically connected to the control unit 90 and transmits a detection signal to the control unit 90.

The imaging section 40 is positioned downstream in the conveyance direction A1 from the position where the detection section 30 is provided, and is provided above the conveyance belt 21. This imaging unit 40 performs imaging at the timing when the tablet T reaches directly below the imaging unit 40 based on the position information of the tablet T in the X direction detected by the detection unit 30 described above, and images the top surface of the tablet T ( (image for tablet position detection) is acquired, and the acquired image is transmitted to the image processing section 80. As the imaging unit 40, it is possible to use various cameras having an imaging element such as a CCD (charge coupled device) or a CMOS (complementary metal oxide semiconductor). The imaging section 40 is electrically connected to the control section 90 via the image processing section 80, and its driving is controlled by the control section 90. Note that lighting for imaging is also provided as necessary.

Here, the aforementioned detection unit 30 functions as a detection unit that detects the position of the tablet T on the conveyance belt 21 in the X direction (conveyance direction A1), and the imaging unit 40 acquires an image for detecting the tablet position. The image processing unit 80 determines the position of the tablet T on the conveyor belt 21 in the X direction as well as in the Y direction (in the horizontal plane, in the conveyance direction A1 (direction orthogonal to the direction) and the position in the θ direction (see FIG. 2). The imaging unit 40 and the image processing unit 80 function as a detection unit that detects at least the position of the tablet T on the conveyor belt 21 in a direction perpendicular to (an example of intersecting) the conveyance direction A1 in a horizontal plane.

The positions in the X direction and the Y direction detected from the above-described tablet position detection image are, for example, positions in the XY coordinate system with respect to the center of the imaging field of view of the imaging unit 40. Further, the position in the θ direction is, for example, a position indicating the degree of rotation of the tablet T with respect to the center line in the Y direction of the imaging field of view of the imaging unit 40. This position in the θ direction is detected when the tablet T has a directional shape, such as when the tablet T has a score line or when the tablet T is formed into an oval, oval, or square shape. be done.

The printing section 50 has an inkjet head 51. The inkjet head 51 is located downstream of the position where the imaging unit 40 is provided in the transport direction A1, and is provided above the transport belt 21. The inkjet head 51 has a plurality of nozzles 51a (see FIG. 2) and discharges ink individually from these nozzles 51a. This inkjet head 51 is provided so that the direction in which the nozzles 51a are lined up in a line (nozzle row) is perpendicular to the transport direction A1 (an example of crossing) in a horizontal plane. As the inkjet head 51, it is possible to use various inkjet print heads having drive elements such as piezoelectric elements, heating elements, or magnetostrictive elements. The inkjet head 51 is electrically connected to a control section 90, and its driving is controlled by the control section 90.

The imaging unit 60 is positioned downstream in the transport direction A1 from the position where the printing unit 50 is provided, and is provided above the transport belt 21. This imaging unit 60 performs imaging at the timing when the tablet T reaches directly below the imaging unit 60 based on the position information of the tablet T in the X direction detected by the detection unit 30 described above, and images the top surface of the tablet T ( (image for printing condition inspection) is acquired, and the acquired image is transmitted to the image processing section 80. As the imaging section 60, for example, similar to the above-described imaging section 40, it is possible to use various cameras having an imaging device such as a CCD or CMOS. The imaging section 60 is electrically connected to the control section 90 via the image processing section 80, and its driving is controlled by the control section 90. Note that lighting for imaging is also provided as necessary.

The recovery unit 70 is located downstream in the transport direction A1 from the position where the imaging unit 60 is provided, and is provided at the end of the transport unit 20 on the downstream side in the transport direction A1. The collecting section 70 is configured to separate and collect the tablets T that fall after being released from the holding by the conveying section 20 into good and defective tablets. Note that the conveyance section 20 releases the holding of the tablets T when each tablet T on the conveyance belt 21 reaches a predetermined position, for example, the downstream end of the conveyance section 20 in the conveyance direction A1.

The image processing unit 80 takes in the image for tablet position detection captured by the imaging unit 40 and the image for printing state inspection captured by the imaging unit 60, and processes the images using a known image processing technique. For example, the image processing unit 80 processes the image for tablet position detection obtained from the imaging unit 40 and obtains the positions of the tablet T in the X direction, Y direction, and θ direction (see FIG. 2). Further, the image processing unit 80 processes the image for printing condition inspection obtained from the imaging unit 60, and obtains the printing position, shape, and size of the printing pattern (for example, characters and marks) printed on the tablet T. .

In addition, the image processing unit 80 acquires position information in the X direction, Y direction, and θ direction of each tablet T acquired as described above, as well as print position information, shape information, and size information of the printing pattern on each tablet T. The information is transmitted to the control unit 90. When the image processing unit 80 transmits each piece of information, it adds the identification information of each imaging unit 40, 60 to the information and transmits it. Thereby, the control unit 90 can grasp which of the imaging units 40 and 60 the transmitted information corresponds to.

The control section 90 includes a microcomputer that centrally controls each section, and a storage section (none of which is shown) that stores processing information, various programs, and the like. The control section 90 controls the supply section 10, the transport section 20, the imaging section 40, the printing section 50, the imaging section 60, and the image processing section 80 based on various information and various programs. The control unit 90 also receives detection signals transmitted from the detection unit 30 and the position detector 25.

Based on the position information of the tablet T in the X direction, Y direction, and θ direction transmitted from the image processing unit 80, the control unit 90 sets printing conditions for the tablet T regarding the position information. The storage unit stores print data including print patterns such as characters and marks, print positions of the print patterns on the tablets T, and movement speed data of the conveyor belt 21.

For example, the control unit 90 determines the range of the nozzle 51a (used nozzle range) to be used for printing the target tablet T in the inkjet head 51 based on the positional information of the tablet T in the Y direction and the printing pattern, and Based on the positional information of the tablet T in the X direction, the timing to start printing on the tablet T is determined, and printing conditions are set. Further, when the tablet T has a directionality as described above, the control unit 90 sets printing conditions in accordance with the position of the tablet T in the θ direction based on the position information of the tablet T in the θ direction. do. As an example, the control unit registers in the storage unit of the control unit 90 180 types of print data in which the orientation of the print pattern is rotated by 1 degree in the range of 0 degrees to 179 degrees, and among these print data. From there, print data with an angle that matches the detected position in the θ direction is selected and printing conditions are set.

The control unit 90 also prints the print pattern in a predetermined shape and size at a predetermined position on the tablet T based on the print position information, shape information, and size information of the print pattern of the tablet T transmitted from the image processing unit 80. In other words, it is determined whether the printing pattern is correctly printed on the tablet T (printing condition inspection). For example, in determining the shape and size of the print pattern, the control unit 90 registers a print pattern for inspection in the storage unit of the control unit 90, and uses the print pattern for inspection and the actual printed tablet T. The printed pattern (printed pattern printed on the tablet T) is compared.

(How to determine the nozzle range to be used)
Next, the method (determination procedure) for determining the nozzle range to be used will be described. The control unit 90 basically determines the nozzle range to be used by the inkjet head 51 based on the positional information of the tablet T in the Y direction and the printing pattern, but the nozzle range to be used may be adjusted as follows. be.

In FIG. 3, the number of tablets is plotted on the vertical axis, and the nozzle number of the inkjet head 51 is plotted on the horizontal axis. A center position distribution graph) is shown. In FIG. 3, nozzle number 236 of the inkjet head 51 is the center position of the inkjet head 51. Note that the graph in FIG. 3 shows the results when 6000 tablets T were put into the tablet printing apparatus 1.

For example, when the tablet center position changes in the range of nozzle numbers 220 to 247, the number of tablets also changes, and in this graph, the number of tablets where the tablet center position passes directly under nozzle number 236 exceeds 800 tablets and reaches a maximum. It becomes. In other words, nearly 15% of the tablets are transported such that their centers are directly below nozzle number 236, which is the nozzle 51a located at the center of the inkjet head 51. Furthermore, if we include nozzle numbers 235 and 237 located next to nozzle number 236, and those that are transported so that the center of the tablet T is located at nozzle numbers 234 and 238 next to them, approximately 3,500 tablets T are It can be seen that the nozzle is transported so that its center is directly below these nozzles numbers 234 to 238. That is, more than 58% of the tablets T are conveyed so that their centers are directly under one of these five nozzle numbers 234 to 238. On the other hand, the number of tablets whose center position passes directly under nozzle numbers 220-223 is several tablets, and the number of tablets whose center position passes directly under nozzle numbers 246-247 is also several tablets.

In FIG. 3, the tablet center position is shifted to the left by 16 (=236-220) nozzles or to the right by 11 (=247-236) nozzles from nozzle number 236, where the number of tablets is maximum. , it fluctuates by a total of 27 (=247-220) nozzles. As an example, if the nozzle spacing is 0.04 mm (the same applies below), the tablet center position varies within a range of 27 x 0.04 = 1.08 mm, that is, about 1 mm.

In FIG. 3, the print pattern is "ABCDEFG" as an example, and if the width of the print pattern in the Y direction (see FIG. 2) is 4 mm, the number of nozzles used is 4/0.04+1=101 as described above. When the tablet center position is nozzle number 236, the nozzle range used is nozzle numbers 186 to 286. Further, when the tablet center position is nozzle number 247, the nozzle range used is nozzle numbers 197 to 297, and when the tablet center position is nozzle number 220, the nozzle range used is nozzle numbers 170 to 270. In this way, according to FIG. 3, the nozzle range used shifts within the range of nozzle numbers 170 to 297, so it changes within the range of (297-170) x 0.04 = 5.08 mm, that is, approximately 5 mm. It turns out.

Here, as an example, if the tablet center position is within the range of nozzle numbers 230 to 242, it is known in advance that the incidence of defective products is lower than a predetermined value (several percent such as 3%) and stable ejection is possible. This has been confirmed by experiment. When the tablet center position is nozzle number 230, the nozzle range used is nozzle numbers 180 to 280, and when the tablet center position is nozzle number 242, the nozzle range used is nozzle numbers 192 to 292. The stable ejection range H1 in which stable ejection is possible is the range of nozzle numbers 180 to 292, and is within the range of (292-180)×0.04=4.48 mm, that is, about 4.5 mm.

Note that the stable ejection range H1 is a range of the nozzles 51a that can stably eject ink among all the nozzles 51a while a large number of tablets T are being sequentially conveyed. The nozzle 51a located within this stable discharge range H1 becomes a "nozzle located within a predetermined range". Various information such as the stable ejection range H1 is set in advance in the storage section of the control section 90.

Next, the flow of adjustment processing for the range of nozzles to be used based on the above-mentioned stable ejection range H1 will be explained.

As shown in FIG. 4, in step S1, the imaging unit 40 performs imaging at the timing when the tablet T reaches directly below the imaging unit 40, and acquires an image including the top surface of the tablet T (an image for detecting the position of the tablet). The image processing unit 80 detects the positions of the tablet T in the X direction, Y direction, and θ direction.

In step S2, the control unit 90 grasps the position of the tablet T in the Y direction detected by the image processing unit 80, and detects the amount of deviation of the center position of the tablet T from the center position (reference position) of the inkjet head 51. do. Based on the position of the tablet T in the Y direction (positional shift amount) and the printing pattern to be printed on the tablet T, the nozzle range to be used for printing is determined from among all the nozzles 51a of the inkjet head 51.

In step S3, the control unit 90 determines whether the nozzle range in use is within the stable ejection range H1. This allows it to be determined whether or not the used nozzle range before adjustment is entirely within the stable ejection range H1.

In step S3, if the control unit 90 determines that the used nozzle range is within the stable ejection range H1 (YES), that is, if the used nozzle range before adjustment is within the stable ejection range H1, in step S4, Based on information such as the printing pattern, the inkjet head 51 is caused to print on the target tablet T using the nozzles 51a within the usable nozzle range (printing execution).

On the other hand, in step S3, if the control unit 90 determines that the used nozzle range is not within the stable discharge range H1 (NO), that is, if the used nozzle range before adjustment is not within the stable discharge range H1, then in step S5 , as shown in Figure 5, the amount by which the used nozzle range protrudes from the stable ejection range H1 before adjustment is detected as a percentage of the print pattern (used nozzle range), and the used nozzle range is stabilized according to this percentage. The reduction rate is determined so that it falls within the discharge range H1. For example, the reduction rate is determined by subtracting the above percentage multiplied by 2 from 100% (if the above percentage is 20%, the reduction rate is 100-(20×2)=60%).

In step S6, the control unit 90 determines whether the reduction ratio is less than or equal to a predetermined value (for example, 50%).

In step S6, if the control unit 90 determines that the reduction rate is larger than a predetermined percentage (NO), in step S7, it specifies the nozzle 51a to be used for printing based on the above-mentioned reduction rate, and as shown in FIG. Next, the nozzle range to be used is adjusted so that the print pattern after printing is reduced (reduction adjustment processing). Then, in step S4, the inkjet head 51 is caused to print on the target tablet T using the nozzles 51a within the adjusted nozzle range (printing execution). Note that the reduction in the transport direction A1 is controlled by the ejection timing.

On the other hand, in step S6, if the control unit 90 determines that the reduction rate is less than or equal to a predetermined percentage (YES), in step S8, printing is restricted, such as not printing with the inkjet head 51 on the target tablet T. (Printing restrictions). The predetermined percentage is set within a range in which, for example, even if the printed pattern is reduced and printed on the tablet T, the printed pattern printed on the tablet T will not become difficult to decipher or its appearance will not deteriorate. There is.

According to this method of adjusting the usable nozzle range, as shown in FIG. 6, when the usable nozzle range is within the stable ejection range H1, the control unit 90 executes printing with the nozzle 51a within the usable nozzle range, If the used nozzle range is not within the stable ejection range H1, the used nozzle range is adjusted so that the printed pattern after printing is reduced in order to keep the used nozzle range within the stable ejection range H1 (reduction adjustment process). According to this adjustment process, if a tablet T is misaligned in the Y direction from a row of tablets T and the nozzle range determined based on the amount of misalignment deviates from the stable ejection range H1, printing for that tablet T is performed. When this is executed, the used nozzle range is adjusted so that the print pattern after printing is reduced so that the used nozzle range is within the stable ejection range H1, and the nozzle range within the stable ejection range H1 is adjusted. 51a, that is, the frequently used nozzle 51a is used for printing, so it is possible to prevent the less frequently used nozzle 51a from being used for printing. This makes it possible to print using the frequently used nozzle 51a, so that the ink ejected from the nozzle 51a will not be bent or the amount of ink will be insufficient and the printing will be stable. This makes it possible to achieve high-quality printing, reduce defective tablets, and increase productivity.

(Printing process)
Next, the printing process (including the inspection process) performed by the above-mentioned tablet printing apparatus 1 will be explained. Note that various information such as print data required for printing is stored in advance in the storage section of the control section 90.

First, the conveyor belt 21 is driven, and as the drive pulley 22 and driven pulley 23 are rotated by the motor 24, the conveyor belt 21 rotates in the conveyance direction A1. Then, while the conveyor belt 21 is rotating, the tablets T are sequentially supplied from the hopper 11 to the shooter 12, arranged in a line by the shooter 12, and supplied onto the conveyor belt 21 at random rather than at regular intervals. The tablets T are lined up in a line on the conveyor belt 21 and conveyed at a predetermined moving speed.

The tablet T on the conveyor belt 21 is detected by the detection section 30. As a result, the positional information of the tablet T in the X direction is acquired and input to the control unit 90. This X-direction position information of the tablet T is stored in the storage section of the control section 90 and used in post-processing. Next, the tablet T on the conveyor belt 21 is imaged by the imaging section 40 at a timing based on the aforementioned positional information of the tablet T in the X direction, and the captured image is transmitted to the image processing section 80 . Based on the image transmitted from the imaging unit 40, position information of the tablet T (for example, position information in the X direction, Y direction, and θ direction) is generated by the image processing unit 80 and stored in the storage unit of the control unit 90. . Based on information such as the position information of the tablet T, the control unit 90 executes the above-mentioned adjustment process for the nozzle range in use, and print conditions including the nozzle range in use (for example, ink ejection position and ejection speed based on the nozzle in use). is set in the storage section of the control section 90.

In the adjustment process of the nozzle range to be used, the control unit 90 determines the nozzle range to be used based on the position information of the tablet T in the Y direction, and if the determined nozzle range to be used is within the stable ejection range H1, the control unit 90 adjusts the nozzle range to be used. Set printing conditions based on nozzle range, print pattern, etc. On the other hand, if the determined nozzle range to be used is not within the stable ejection range H1, it is selected whether to adjust the nozzle range to be used (reduction adjustment process) or to restrict printing by the inkjet head 51. When adjusting the used nozzle range, adjust the used nozzle range so that the printed pattern after printing is reduced so that the used nozzle range falls within the stable ejection range H1, and print based on the adjusted used nozzle range. Set conditions. Furthermore, when printing by the inkjet head 51 is restricted, printing on the target tablet T is prohibited, and the tablet T is transported without being printed.

The tablets T on the conveyor belt 21 are placed under the above-described printing conditions at a timing based on the X-direction position information of the tablets T generated by the image processing unit 80, that is, at a timing when the tablets T reach directly below the inkjet head 51. The inkjet head 51 prints based on the image. In the inkjet head 51, ink is suitably ejected from each nozzle 51a, and identification information such as characters (for example, alphabets, katakana, numbers) and marks (for example, symbols, figures) are printed on the printing surface that is the top surface of the tablet T. Ru. The ink applied to this tablet T dries quickly. Note that the ink may be dried using a drying section (not shown) that performs drying using gas or heat.

Thereafter, the tablet T with the identification information printed thereon is imaged by the imaging section 60 at a timing based on the aforementioned positional information of the tablet T in the X direction, and the captured image is transmitted to the image processing section 80 . Based on the individual images transmitted from the imaging section 60, print position information, shape information, and size information of the printing pattern for each tablet T are generated by the image processing section 80 and stored in the storage section of the control section 90. Based on the printing position information, shape information, and size information, the control unit 90 determines the quality of printing on the tablet T, and the printing quality result information indicating the quality of printing for each tablet T is stored in the storage unit of the control unit 90. Ru. For example, it is determined whether the print pattern is printed in a predetermined shape and size at a predetermined position on the tablet T, that is, whether the print pattern is normally printed on the tablet T, and the quality of printing is determined.

The control unit 90 registers reduction patterns for inspection (for example, printing patterns with several types of reduction ratios) in the storage unit in the print inspection of the tablet T printed based on the adjusted usage nozzle range described above. Then, the control unit 90 compares the reduced pattern for inspection with the printed pattern after actual printing to determine whether the printing is good or bad. Alternatively, a pre-stored inspection pattern may be reduced in accordance with the reduction ratio of the print pattern and used for inspection.

When the inspected tablet T is located at the downstream end of the conveyor belt 21 as the conveyor belt 21 moves, it is released from the state held by the conveyor belt 21 and falls from the conveyor belt 21 to the collecting section 70. recovered by. At this time, tablets T that passed the inspection fall as they are and are collected by the collection unit 70, while tablets T that failed the inspection are removed by air blowing while falling from the conveyor belt 21. be done. Note that the tablets T removed by the air blowing are collected, for example, by another collection container (not shown) provided next to the collection unit 70.

According to this printing process, the usable nozzle range is adjusted and determined by the above-described method of adjusting the usable nozzle range. If the used nozzle range is within the stable ejection range H1, the used nozzle range is used for printing as is without being changed, and if the used nozzle range is not within the stable ejection range H1, the used nozzle range is within the stable ejection range. In order to fit within H1, the nozzle range in use is adjusted so that the print pattern after printing is reduced (reduction adjustment process), and the nozzles 51a within the adjusted nozzle range in use are used for printing. This makes it possible to always print using the nozzle 51a within the stable ejection range H1, that is, the nozzle 51a that is frequently used, thereby reducing the number of defective tablets and increasing productivity.

In addition, the nozzle range used is adjusted so that the print pattern after printing (for example, the characters that were actually printed) is reduced, rather than the print pattern before printing (for example, the characters that are about to be printed). Therefore, the processing time can be reduced compared to printing pattern reduction processing.

In addition, if the amount of positional deviation of the tablet T is large, for example, if more than half of the nozzles used before the reduction adjustment process exceed the stable ejection range H1, the printed pattern will be reduced and the identification information will be difficult to decipher. It may also cause the appearance to deteriorate. Therefore, if the detected amount of positional deviation of the tablet T is not within a predetermined range, printing on the target tablet T may be restricted and the tablet T may be transported without being printed. . Alternatively, if a part of the usage nozzle range determined based on the amount of positional deviation of the tablet T protrudes from within the stable ejection range H1, and the amount of protrusion is greater than a predetermined value, for example, If the ratio (percentage) of the amount of protrusion to the nozzle range used exceeds a predetermined value, printing on the target tablet T may be prohibited.

Further, in the above embodiment, in order to obtain the amount of positional deviation of the tablet T, the amount of deviation of the center position of the tablet T with respect to the center position of the inkjet head 51 is calculated, but the present invention is not limited to this. For example, it is only necessary to detect the amount of displacement of the tablet T from a predetermined reference position, such as by determining the amount of displacement of the tablet T with respect to the center of the field of view of the imaging unit 40. Alternatively, the reduction adjustment process may be performed by determining in advance a threshold value for the positional deviation amount of the tablet T whose nozzle range is outside the stable ejection range H1, and comparing this threshold value with the actual positional deviation amount of the tablet T. It may be determined whether or not.

Here, when the tablet T is conveyed, the tablet T on the suction hole 21a is held on the conveyor belt 21 by suction from the suction hole 21a, but not all the suction holes 21a are completely blocked by the tablet T. do not have. In this case, since air is sucked through the suction hole 21a, an air current is generated above the suction hole 21a, and an air current flowing over the conveyance belt 21 along the conveyance direction A1 is also generated due to the movement of the conveyance belt 21. . Furthermore, since the inkjet head 51 and its surrounding members are located above the conveyor belt 21, the airflow flowing on the conveyor belt 21 collides with these members, further generating turbulence. Because these air currents are generated, the inkjet head 51 exists in an environment where the ink at the nozzle tip portion tends to dry. Under such circumstances, in order to suppress the occurrence of defective tablets and increase productivity, it is necessary to use the nozzle 51a within the stable ejection range H1 where ink drying at the nozzle tip is difficult to proceed, that is, the frequently used nozzle 51a. It is important to do so. Note that the above-mentioned drying section may be positioned downstream of the inkjet head 51 and provided above the conveyor belt 21. In this case, ink drying at the tip of the nozzle progresses more easily.

As explained above, according to the first embodiment, when it is determined that the used nozzle range is not within the stable ejection range H1, the printed pattern after printing is reduced in order to keep the used nozzle range within the stable ejection range H1. By adjusting the usable nozzle range so that the inkjet head 51 prints with the nozzle 51a within the adjusted usable nozzle range, it is possible to realize printing with the nozzle 51a within the stable ejection range H1. This makes it possible to use the nozzle 51a within the stable ejection range H1, that is, the nozzle 51a that is used frequently, and to suppress the use of the nozzle 51a that is outside the stable ejection range H1, that is, the nozzle 51a that is used less frequently. It is possible to suppress the occurrence of defective tablets and increase productivity.

<Second embodiment>
A second embodiment will be described with reference to FIGS. 7 to 9. In the second embodiment, differences from the first embodiment (shift adjustment processing) will be explained, and other explanations will be omitted.

In the second embodiment, the control unit 90 executes a shift adjustment process for shifting the nozzle range to be used, instead of the reduction adjustment process according to the first embodiment. For example, as shown in FIGS. 7 and 8, if the used nozzle range does not fall within the stable ejection range H1, the control unit 90 changes the used nozzle range to the center side of the inkjet head 51 (in FIG. 7, to the nozzle number 236 side). ) so that the nozzle range in use falls within the stable ejection range H1 (shift adjustment process). As shown in FIG. 8, when the nozzle range in use falls within the stable ejection range H1, printing is performed using the nozzle 51a within the nozzle range in use (see the topmost tablet T in FIG. 8).

Here, the tablet center position distribution graph shown in FIG. 7 is similar to the tablet center position distribution graph shown in FIG. 3 according to the first embodiment. Further, a shift tolerance range H2 shown in FIG. 7 is a range (shift tolerance range) in which printing with a shifted printing position is permitted, and is set in advance on both sides of the stable ejection range H1. Note that information such as the stable ejection range H1 and the deviation tolerance range H2 is set in advance in the storage unit of the control unit 90. For example, as shown in FIG. 7, the deviation tolerance range H2 is for 16 nozzles (16×0.04=0.64 mm), and exists on both sides of the stable ejection range H1. The allowable deviation range H2 on the left side of the stable ejection range H1 is nozzle numbers 164-180, and the allowable deviation range H2 on the right side of the stable ejection range H1 is nozzle numbers 292-308.

Next, the flow of adjustment processing for the nozzle range to be used based on the stable ejection range H1 and the deviation tolerance range H2 will be described.

As shown in FIG. 9, the process flow of steps S1 to S4 other than steps S11, S12, and S13 is the same as the process flow of steps S1 to S4 shown in FIG. 4 according to the first embodiment. Therefore, in the following, the processing flow regarding steps S11, S12, and S13, which have different processing flows, will be explained.

In step S3, if the control unit 90 determines that the used nozzle range is not within the stable ejection range H1 (NO), in step S11, the amount of deviation of the used nozzle range from the stable ejection range H1 is within the deviation tolerance range H2. Determine whether it exists or not.

In step S11, if the control unit 90 determines that the amount of deviation is within the deviation tolerance range H2 (YES), in step S12, the control unit 90 moves the nozzle toward the center of the inkjet head 51 so as to keep the used nozzle range within the stable ejection range H1. Adjust by shifting (the amount of shift is sometimes referred to as "shift amount") (shift adjustment process). Then, in step S4, the inkjet head 51 is caused to print on the target tablet T using the nozzles 51a within the adjusted nozzle range (printing execution).

On the other hand, in step S11, if the control unit 90 determines that the amount of deviation is not within the deviation tolerance range H2 (NO), in step S13, printing by the inkjet head 51 on the target tablet T is restricted (printing restriction).

According to this method of adjusting the usable nozzle range, as shown in FIG. 8, when the usable nozzle range is within the stable ejection range H1, the control unit 90 executes printing with the nozzle 51a within the usable nozzle range, If the used nozzle range is not within the stable ejection range H1 and the amount of deviation of the used nozzle range is within the deviation tolerance range H2, the nozzle range used is adjusted to be within the stable ejection range H1, that is, the print pattern is moved in the Y direction. Shift by a predetermined amount. According to this adjustment process, even if the nozzle range to be used, which is determined based on the amount of deviation, deviates from the stable ejection range H1 due to the deviation of the tablet T from the row of tablets T in the Y direction, printing for that tablet T can be performed. is executed, by adjusting the used nozzle range so that the print pattern after printing is within the stable ejection range H1, the nozzle 51a within the stable ejection range H1, that is, the nozzle 51a that is used frequently Since the nozzle 51a is used for printing, it is possible to prevent the nozzle 51a that is used less frequently from being used for printing. This makes it possible to print using the frequently used nozzle 51a, so that the ink ejected from the nozzle 51a will not be bent or the amount of ink will be insufficient and the printing will be stable. This makes it possible to achieve high-quality printing, reduce defective tablets, and increase productivity.

Note that the above-mentioned shift amount is, for example, the amount by which the used nozzle range deviates from the stable ejection range H1. However, this is just an example, and as long as the used nozzle range is within the stable discharge range H1, the used nozzle range may deviate from the stable discharge range H1 by more than the deviation amount. The shift amount may be changed and used based on.

As explained above, according to the second embodiment, when it is determined that the nozzle range in use is not within the stable ejection range H1, the nozzle range in use is shifted so as to fall within the stable ejection range H1. By making the adjustment and causing the inkjet head 51 to print using the nozzles 51a within the adjusted nozzle range, printing using the nozzles 51a within the stable ejection range H1 can be realized. This makes it possible to use the nozzle 51a within the stable ejection range H1, that is, the nozzle 51a that is used frequently, and to suppress the use of the nozzle 51a that is outside the stable ejection range H1, that is, the nozzle 51a that is used less frequently. It is possible to suppress the occurrence of defective tablets and increase productivity.

<Third embodiment>
A third embodiment will be described with reference to FIG. 10. In the third embodiment, differences from the second embodiment (range expansion processing) will be explained, and other explanations will be omitted.

FIG. 10 shows the farthest nozzle (leftmost nozzle) on the negative side in the Y direction among the ranges of individual nozzles used determined from the positional deviation amount of each tablet T when 6000 tablets T are input. It is a graph.

As shown in FIG. 10, the control unit 90 according to the third embodiment executes range expansion processing to expand the stable ejection range H1. In this range expansion process, if there are a plurality of left end nozzles in each use nozzle range determined based on the amount of positional deviation of the tablet T within the deviation tolerance range H2 shown in FIG. Among them, the stable ejection range H1 is expanded so that a predetermined number, for example, only one specific nozzle 51a, is at the end of the stable ejection range H1 (details will be described later).

First, by executing the shift adjustment process according to the second embodiment, nozzle number 180 becomes the leftmost nozzle in the used nozzle range, and the number of tablets used for printing is 96 (a total of 8 nozzles). =2+2+1+4+8+10+18+51). For example, in FIG. 10, if stable ejection is possible if the number of tablets corresponding to the nozzle number is 40 to 60 or more, the number of tablets for nozzle number 180 is 51, but if possible, this number can be reduced to 60. It is more desirable to set the amount above (approximately 1% or more of the number of inputs). Therefore, the left end of the stable ejection range H1 is set to nozzle number 180, and when nozzle numbers 173 to 179 are used for printing, nozzle number 180 is used for printing instead of the nozzle numbers 173 to 179. For example, when nozzle number 173 is used for printing, nozzle number 180 is used for printing instead of nozzle number 173, but the amount of deviation in the application position (the amount of dot deviation) at this time is 7 nozzles. For example, 7×0.04=0.28 mm.

Therefore, in order to suppress the above-mentioned amount of deviation in the application position, in the third embodiment, when there is a plurality of left end nozzles of each use nozzle range determined based on the amount of positional deviation of the tablet T within the deviation tolerance range H2. , the nozzle range to be used is shifted so that the left end of the nozzle range to be used is located at a predetermined specific nozzle 51a within the deviation tolerance range H2. If the number of tablets corresponding to the nozzle number is 40 to 60 or more, stable ejection is possible, and if the number of tablets corresponding to the nozzle number is at least 40 or more, stable ejection is possible. Therefore, when the left end nozzle of the determined usage nozzle range is located in the deviation tolerance range H2, the left end nozzle is located at a predetermined interval from nozzle number 180 at the left end of the stable discharge range H1, as shown in FIG. For example, shift the nozzle range to be used so that it becomes nozzle number 178. That is, the stable ejection range H1 is expanded, and the tablet T is printed using the nozzle 51a within the expanded stable ejection range H1. In the case shown in FIG. 10, if the left end nozzle of the determined used nozzle range is nozzle number 173 to 179, the used nozzle range is shifted so that nozzle number 178 becomes the left end nozzle of the used nozzle range. As a result, the number of tablets printed using the nozzle with nozzle number 178 as the left end nozzle is 45 (=2+2+1+4+8+10+18), which is a total of 7 nozzles. Since the number of tablets of nozzle number 180, which is within the stable ejection range H1, is 51, the stable ejection of nozzle number 180 is not impaired.

As described above, according to the second embodiment, when nozzle number 180 is used for printing instead of nozzle number 173, the amount of deviation in the application position is 7 nozzles (for example, 0.28 mm); According to the third embodiment, when a specific nozzle number 178 is forcibly used for printing instead of nozzle number 173, the amount of deviation in the application position is 5 nozzles (for example, 0.20 mm). Similarly for other nozzle numbers, in the third embodiment, the amount of deviation in the application position is smaller than in the second embodiment. In this way, the amount of deviation in the application position can be suppressed. However, depending on the size of the tablet T, the printing pattern, etc., the amount of deviation in the application position that becomes a problem (for example, the amount that makes the printing pattern printed on the tablet T difficult to decipher or makes it look bad) varies. Therefore, if the amount of deviation in the coating position is not a problem, it is not necessary to perform the above-mentioned range expansion process.

In addition, instead of shifting the used nozzle range so that the leftmost nozzle in the used nozzle range becomes nozzle number 178, it is changed so that the leftmost nozzle in the used nozzle range becomes only one of nozzle numbers 173 to 177 or 179. It is also possible to shift the nozzle range used. Also, instead of only one nozzle 51a, a predetermined number of nozzles 51a (nozzle numbers) are selected, and the usage nozzle range is changed so that the leftmost nozzle in the usage nozzle range is one of the selected multiple nozzle numbers. It is also possible to shift the . At this time, a predetermined number of nozzles 51a arranged at regular intervals may be selected, or a predetermined number of nozzles 51a arranged randomly may be selected.

As explained above, according to the third embodiment, the effects of the second embodiment can be obtained. Furthermore, according to the third embodiment, when adjusting the nozzle range to be used, the stable discharge range H1 explained in the second embodiment is expanded, and only the nozzles 51a within the expanded stable discharge range H1 are used. By adjusting the nozzle range used to print on the tablet T, it is possible to suppress the amount of deviation in the application position, and it is also possible to realize printing using the nozzle 51a within the stable ejection range H1. As a result, the occurrence of defective tablets can be suppressed and productivity can be increased. Note that, as the third embodiment, an example has been described in which the stable ejection range on the negative side of the Y direction is expanded, but the stable ejection range of the nozzle on the positive side of the Y direction (the right end nozzle) is similarly expanded.

<Other embodiments>
In the above description, an example was given in which either the reduction adjustment process or the shift adjustment process is executed, but the present invention is not limited to this, and both the reduction adjustment process and the shift adjustment process may be executed. . For example, in the process of adjusting the range of nozzles used, as shown in FIG. Shift adjustment processing is performed to adjust the nozzle range to be used so that it is shifted in the direction (see the arrow in FIG. 11). As an example, when the control unit 90 calculates a reduction rate based on the amount of positional deviation of the tablet T so that the nozzle range in use falls within the stable ejection range H1, the control unit 90 determines that the calculated reduction rate is a predetermined percentage (for example, 50 %), the obtained reduction rate is made larger than a predetermined percentage, and the nozzle range used is shifted to the center side of the inkjet head 51. As a result, even if the amount of misalignment of the tablet T is large, it is possible to print without making the identification information difficult to decipher or making it look bad. You can reduce it more reliably and increase productivity.

In addition, in the above explanation, execution of either the reduction adjustment process or the shift adjustment process or the execution of both the shift adjustment process and the reduction adjustment process was exemplified, but the amount of positional deviation of the tablet T Accordingly, select whether to execute only the reduction adjustment process, only the shift adjustment process, or both the reduction adjustment process and the shift adjustment process so that the nozzle range to be used is within the stable ejection range H1. You can do it like this. For example, if the amount by which part of the used nozzle range protrudes from within the stable ejection range H1 is greater than a predetermined value based on the amount of positional deviation of the tablet T, for example, the ratio of the protruded amount to the used nozzle range If (percentage) is equal to or greater than a predetermined percentage, only the shift adjustment process or both the shift adjustment process and the reduction adjustment process are executed. Note that if the ratio of the protrusion amount to the used nozzle range is smaller than a predetermined percentage, only the reduction adjustment process is executed. Also, depending on the character size of the print pattern, in order to keep the used nozzle range within the stable ejection range H1, it is possible to execute only the reduction adjustment process, only the shift adjustment process, or perform both the reduction adjustment process and the shift adjustment process. You may perform both or select one. For example, when the control unit 90 executes the reduction adjustment process according to the size of one character in the print pattern of the tablet T, if the control unit 90 determines that the reduction rate of the print pattern is less than a predetermined percentage that is difficult to decipher, the control unit 90 shifts Only the adjustment process is executed, or both the shift adjustment process and the reduction adjustment process are executed.

In addition, in the above description, the reduction adjustment process illustrated that the entire print pattern is reduced uniformly, but the invention is not limited to this. For example, the print pattern is It is also possible to reduce or transform only a part of the printed pattern. For example, if the print pattern is "ABCDEF", it is possible to reduce or transform only one or more of the characters. Furthermore, instead of reducing or transforming the entire character, it is also possible to reduce or transform only a part of the character. Note that when reducing one character, the entire character may be reduced equally, or one character may be reduced only in the Y direction.

In addition, in the above explanation, in the reduction adjustment process, the amount by which the used nozzle range protrudes from the stable ejection range H1 before adjustment is detected as a percentage of the print pattern (used nozzle range), and the used nozzle range is determined according to this percentage. Although the example shows that the reduction rate is determined so that the nozzle range falls within the stable ejection range H1, the reduction rate is not limited to this, and a stepwise reduction rate registered in advance (for example, 5% The selected pattern may be printed.

In addition, in the above explanation, when inspecting after printing, the reduced pattern for inspection is compared with the actual printed pattern after printing, but this is not limited to this, and the inspection hurdle itself is lowered. You can do it like this. In other words, settings are made in advance so that the reduced pattern is also recognized as "normal".

Furthermore, in the above explanation, the tablets T are conveyed in one row, but the number of rows is not limited to this, and may be two, three, or four or more, and is not particularly limited. The number of conveyor belts 21 may be two or more, and is not particularly limited. Further, the number of inkjet heads 51 may be two or more, and is not particularly limited.

Further, in the above description, a print head in which the nozzles 51a are arranged in one row is illustrated as the inkjet head 51, but the present invention is not limited to this. For example, a print head in which the nozzles 51a are arranged in a plurality of rows may be used. good. Alternatively, a plurality of inkjet heads 51 may be used in a horizontal plane in a direction perpendicular to the transport direction A1.

Further, in the above description, the inkjet head 51 is provided so that the direction in which the nozzles 51a are lined up is perpendicular to the conveying direction A1 in the horizontal plane, but the present invention is not limited to this. For example, the nozzles 51a They may be provided so that the direction in which they are lined up is a direction that intersects the conveyance direction A1 in a horizontal plane.

Further, in the above description, printing on one side of the tablet T was exemplified, but the invention is not limited to this. It is also possible to form one unit and arrange the units one above the other, so that the tablet T printed in the upper conveyance section 20 is reversed and delivered to the lower conveyance section 20, so that both sides of the tablet T can be printed. good.

Further, in the above description, the tablet T is held on the conveyor belt 21 by suction, but the invention is not limited to this. For example, the tablet T is held on the conveyor belt 21 by its own weight. Also good. Alternatively, the tablet T may be stored in a pocket and transported. Misalignment can occur even in pockets. Since the size of the pocket is always larger than the size of the tablet T, misalignment occurs within the pocket.

Here, the above-mentioned tablets can include tablets used for medicine, for eating and drinking, for cleaning, for industrial purposes, and for aromatic purposes. In addition, tablets include plain tablets, sugar-coated tablets, film-coated tablets, enteric-coated tablets, gelatin-encapsulated tablets, multilayer tablets, and dry-coated tablets, as well as various types of capsule tablets such as hard capsules and soft capsules. can be included in Furthermore, tablets can have various shapes such as a disc, a lens, a triangle, and an ellipse. Furthermore, when the tablet to be printed is for pharmaceutical use or food or drink use, edible ink is suitable as the ink to be used. As this edible ink, any of synthetic pigment ink, natural pigment ink, dye ink, and pigment ink may be used.

Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention, as well as within the scope of the invention described in the claims and its equivalents.

1 Tablet printing device 20 Conveyance section 40 Imaging section (part of detection section)
51 Inkjet head 51a Nozzle 80 Image processing section (part of detection section)
90 Control part H1 Stable discharge range T Tablet

Claims (10)

a transport section that transports the tablets;
a detection unit that detects the position of the tablet in a direction that intersects the conveyance direction of the tablet conveyed by the conveyance unit in a horizontal plane;
an inkjet head that prints by ejecting ink from a plurality of nozzles lined up in the intersecting direction on the tablets transported by the transport unit;
Of the range of nozzles used for printing on the tablet among the plurality of nozzles, which is determined based on the position of the tablet detected by the detection unit and the printing pattern to be printed on the tablet, a part thereof is If the tablets that are sequentially conveyed by the conveyance unit are out of a predetermined stable ejection range in which the ink can be stably ejected from among the plurality of nozzles, the ink is within the stable ejection range. Adjusting the nozzle range to be used so that the printing pattern after printing is reduced, and/or adjusting the range of nozzles to be used so as to shift the nozzle range to print on the tablet using only the nozzles of a control unit that causes the inkjet head to perform printing with nozzles within the used nozzle range;
A tablet printing device comprising: The control unit limits printing on the tablet by the inkjet head when the amount of positional deviation from a predetermined reference position based on the position of the tablet detected by the detection unit is not within a predetermined range. The tablet printing device according to claim 1. 3. The tablet printing apparatus according to claim 2, wherein the predetermined range is set based on a range in which the printed pattern is determined to be non-defective in an inspection. 2. The control unit restricts printing on the tablet by the inkjet head when the amount by which part of the used nozzle range protrudes from within the stable ejection range is equal to or greater than a predetermined value. Tablet printing device as described. When adjusting the usable nozzle range, the control unit expands the stable ejection range so that a predetermined nozzle among the nozzles outside the usable nozzle range is an end of the stable ejection range, and The tablet printing device according to any one of claims 1 to 4, wherein the range of nozzles used is adjusted so that printing is performed on the tablet using only nozzles within a discharge range. a step of conveying the tablets by a conveying section;
a step of detecting, by a detection unit, a position of the tablet in a direction that intersects the conveyance direction of the tablet conveyed by the conveyance unit in a horizontal plane;
Based on the position of the tablet detected by the detection unit and the printing pattern to be printed on the tablet, print on the tablet among the plurality of nozzles arranged in the intersecting directions included in the inkjet head that prints on the tablet. A range of nozzles to be used is determined, and a part of the determined nozzle range to be used stably discharges ink from among the plurality of nozzles to the tablets that are sequentially transported by the transport unit. In order to print on the tablet using only the nozzles within the stable ejection range when the tablet exceeds a predetermined stable ejection range in which it is possible to adjusting the inkjet head to be reduced and/or shifting the used nozzle range, and causing the inkjet head to perform printing with nozzles within the adjusted used nozzle range;
A tablet printing method having. A claim further comprising the step of restricting printing on the tablet by the inkjet head when the amount of positional deviation from a predetermined reference position based on the position of the tablet detected by the detection unit is not within a predetermined range. The tablet printing method according to item 6. 7. The method according to claim 6, further comprising the step of restricting printing on the tablet by the inkjet head when the amount by which part of the used nozzle range protrudes from within the stable ejection range is equal to or greater than a predetermined value. Tablet printing method. 8. The tablet printing method according to claim 7, wherein the predetermined range is set based on a range in which the printed pattern after printing is determined to be non-defective in an inspection. When adjusting the usage nozzle range, the stable discharge range is expanded so that a predetermined nozzle among the nozzles outside the usage nozzle range is the end of the stable discharge range, and the nozzle within the expanded stable discharge range is adjusted. The tablet printing method according to any one of claims 6 to 9, wherein the range of the nozzle used is adjusted so that the tablet is printed using only a nozzle.

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