Printing apparatus and control method therefor

Abstract

To provide a printing apparatus for performing printing on an outer peripheral surface of a printing medium having a truncated conical outer shape, capable of securing printing quality of the printing medium even when printing is performed on the outer peripheral surface of the printing medium while rotating the printing medium.SOLUTION: When a nozzle row 3b constituted by the nozzles that actually eject ink during printing of a printing medium 2 is defined as an ink ejection nozzle row 3e, a control unit of the printing apparatus moves and stops a carriage on which inkjet heads 3 are mounted such that the ink ejection nozzle row 3e is disposed at a position where a distances l in a main scanning direction between the ink ejection nozzle row 3e and an axial center of the printing medium 2 satisfies a predetermined relationship during printing of the printing medium 2.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a printing apparatus for printing on the outer peripheral surface of a printing medium having a truncated cone-shaped outer shape, and also to a printing apparatus control method for controlling the printing apparatus. [Background technology]

[0002] Conventionally, there has been known a printing device for printing using ultraviolet-curable ink on the outer peripheral surface of a printing medium having a cylindrical, truncated cone, or conical outer shape (see, for example, Patent Document 1). The printing device described in Patent Document 1 includes an inkjet head that ejects ink toward the outer peripheral surface of the printing medium, an ultraviolet irradiation device that cures the ink ejected onto the outer peripheral surface of the printing medium, a stage having a table on which the ultraviolet irradiation device is placed, a carriage on which the inkjet head is mounted, a carriage drive mechanism that moves the carriage in the main scanning direction, a stage drive mechanism that moves the stage in the sub-scanning direction, and a table lifting mechanism that raises and lowers the table.

[0003] In the printing device described in Patent Document 1, an inkjet head is formed with a large number of nozzles that eject ink. The lower surface of the inkjet head is an ink ejection surface on which a large number of nozzles are formed. On the ink ejection surface, a nozzle row is formed with a plurality of nozzles arranged in the sub-scanning direction. The ultraviolet irradiation device is equipped with a rotation mechanism that holds the print medium and rotates the print medium around its axis as the center of rotation. The rotation mechanism is equipped with a first rotating unit that holds one end of the print medium, a second rotating unit that holds the other end of the print medium, a motor for rotating the print medium, and a power transmission mechanism that connects the first rotating unit to the motor. The ultraviolet irradiation device is placed on a table so that the direction of the axis of the print medium coincides with the sub-scanning direction when viewed from above.

[0004] The printing device described in Patent Document 1 makes it possible to adjust the inclination of a substrate relative to the sub-scanning direction when viewed from the main scanning direction. When printing on a substrate having a truncated cone or conical outer shape, the inclination of the substrate is adjusted so that the axis of the substrate is inclined relative to the sub-scanning direction. Specifically, the inclination of the substrate is adjusted so that the top edge of the substrate is parallel to the sub-scanning direction. In this printing device, ink is ejected from an inkjet head stopped at a fixed position while the substrate is rotated by a rotation mechanism, to print on the outer surface of the substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2023-88834 Summary of the Invention [Problem to be solved by the invention]

[0006] In the printing device described in Patent Document 1, for example, when printing on the outer surface of a substrate having a truncated cone shape, the vertical distance between the larger outer diameter portion of the substrate and the ink ejection surface of the inkjet head is shorter at a position offset from the substrate's axis in the main scanning direction when viewed from the sub-scanning direction than the vertical distance between the smaller outer diameter portion of the substrate and the ink ejection surface. Therefore, when printing on the outer surface of the substrate while rotating it, the ink landing positions in the circumferential direction of the substrate shift between the larger outer diameter portion and the smaller outer diameter portion of the substrate. Furthermore, in the case of a substrate having a truncated cone shape, the generatrix of the substrate is tilted relative to the substrate's axis. This tilt also causes the ink landing positions in the circumferential direction of the substrate to shift between the larger outer diameter portion and the smaller outer diameter portion of the substrate. Furthermore, such misalignment of the ink landing positions can reduce the printing accuracy of the substrate.

[0007] Therefore, an object of the present invention is to provide a printing device for printing on the outer peripheral surface of a print substrate having a truncated cone-shaped outer shape, which can ensure print quality on the print substrate even when printing on the outer peripheral surface of the print substrate while rotating the print substrate.Another object of the present invention is to provide a printing device control method for printing on the outer peripheral surface of a print substrate having a truncated cone-shaped outer shape, which can ensure print quality on the print substrate even when printing on the outer peripheral surface of the print substrate while rotating the print substrate. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the printing device of the present invention is a printing device for printing on the outer peripheral surface of a print medium having an outer shape of a truncated cone, and includes a rotation mechanism that holds the print medium and rotates the print medium around the axis of the print medium as the center of rotation, an inkjet head that is arranged above the print medium and ejects ink toward the outer peripheral surface of the print medium, a carriage on which the inkjet head is mounted, a carriage drive mechanism that moves the carriage in a main scanning direction that is a direction perpendicular to the up-down direction and perpendicular to the axis of the print medium when viewed from the up-down direction, and a control unit that controls the printing device, and the inkjet head is formed with a plurality of nozzles that eject ink, and the ink jet The bottom surface of the jet head is an ink ejection surface on which a plurality of nozzles are formed, and on the ink ejection surface, a nozzle row is formed by a plurality of nozzles arranged in a sub-scanning direction perpendicular to the up-down direction and the main scanning direction, and the rotation mechanism rotates the print medium when printing on the print medium, and the nozzle row formed by the nozzles that actually eject ink when printing on the print medium is called the ink ejection nozzle row, and the distance in the main scanning direction between the ink ejection nozzle row and the axis of the print medium is called l (mm), the resolution of the image printed on the print medium is called R (dpi), the ejection frequency of ink ejected from the nozzles that make up the ink ejection nozzle row is called f (Hz), and the ejection speed of ink ejected from the nozzles that make up the ink ejection nozzle row is called V. f(mm / sec), the length of the substrate in the axial direction of the substrate is h (mm), the radius of the largest outer diameter part of the substrate is r1 (mm), the radius of the smallest outer diameter part of the substrate is r2 (mm), and the vertical distance between the part of the largest outer diameter part where ink ejected from the nozzles constituting the ink ejection nozzle row lands and the ink ejection surface is l g1 (mm), and the vertical distance between the part of the smallest outer diameter where ink ejected from the nozzles that make up the ink ejection nozzle row lands and the ink ejection surface is l g2 (mm), the direction of the generatrix of the printed material is the generatrix direction, and the width of the image printed on the printed material in the generatrix direction is d y (mm), and the distance in the generatrix direction between the part of the image printed on the substrate closest to the maximum outer diameter and the maximum outer diameter is l y (mm), the control unit is characterized in that, when printing on the printing medium, it moves and stops the carriage so that the ink ejection nozzle row is positioned at a position where the distance l satisfies the following relationship: TIFF2025150234000002.tif104170

[0009] In order to solve the above-mentioned problems, a method of controlling a printing device of the present invention provides a printing device for printing on an outer peripheral surface of a print medium having a truncated cone shape, the printing device comprising: a rotation mechanism for holding the print medium and rotating the print medium around an axial center of the print medium as a rotation center; an inkjet head disposed above the print medium and ejecting ink toward the outer peripheral surface of the print medium; a carriage on which the inkjet head is mounted; and a carriage drive mechanism for moving the carriage in a main scanning direction which is a direction perpendicular to the up-down direction and perpendicular to the axial center of the print medium when viewed from the up-down direction; a plurality of nozzles for ejecting ink formed in the inkjet head; The ink ejection surface has a nozzle array formed thereon, and the nozzle array is made up of a plurality of nozzles arranged in a sub-scanning direction perpendicular to the vertical direction and the main scanning direction, and the rotation mechanism is a control method for a printing device that rotates a print medium when printing on the print medium, and the nozzle array made up of nozzles that actually eject ink when printing on the print medium is called an ink ejection nozzle array, and the distance in the main scanning direction between the ink ejection nozzle array and the axis of the print medium is called l (mm), the resolution of the image printed on the print medium is called R (dpi), the ejection frequency of ink ejected from the nozzles that make up the ink ejection nozzle array is called f (Hz), and the ejection speed of ink ejected from the nozzles that make up the ink ejection nozzle array is called V f (mm / sec), the length of the substrate in the axial direction of the substrate is h (mm), the radius of the largest outer diameter part of the substrate is r1 (mm), the radius of the smallest outer diameter part of the substrate is r2 (mm), and the vertical distance between the part of the largest outer diameter part where ink ejected from the nozzles constituting the ink ejection nozzle row lands and the ink ejection surface is l g1 (mm), and the vertical distance between the part of the smallest outer diameter where ink ejected from the nozzles that make up the ink ejection nozzle row lands and the ink ejection surface is l g2 (mm), the direction of the generatrix of the printed material is the generatrix direction, and the width of the image printed on the printed material in the generatrix direction is d y(mm), and the distance in the generatrix direction between the part of the image printed on the substrate closest to the maximum outer diameter and the maximum outer diameter is l y (mm), the carriage is moved and stopped so that the ink ejection nozzle row is positioned at a position where the distance l satisfies the following relationship when printing on the printing medium. TIFF2025150234000003.tif104170

[0010] In this invention, if the nozzle array consisting of the nozzles that actually eject ink when printing on the print substrate is defined as the ink ejection nozzle array, the carriage is moved and stopped so that when printing on the print substrate, the ink ejection nozzle array is positioned at a position where the distance l in the main scanning direction between the ink ejection nozzle array and the axis of the print substrate satisfies the above relationship. Therefore, in this invention, it is possible to suppress the deviation in the circumferential direction of the print substrate between the ink landing position on the maximum outer diameter portion, which is the largest outer diameter part of the print substrate, and the ink landing position on the minimum outer diameter portion, which is the smallest outer diameter part of the print substrate, to less than half the dot pitch of the resolution of the image printed on the print substrate. Therefore, in this invention, it is possible to ensure the print quality of the print substrate even when printing on the outer surface of a print substrate having a truncated cone shape while rotating the print substrate.

[0011] In the present invention, for example, there are multiple ink ejection nozzle arrays. In this case, even if ink is ejected from the nozzles of the multiple ink ejection nozzle arrays together when printing on a substrate, it is possible to suppress the deviation in the circumferential direction of the substrate between the landing position of ink that lands on the maximum outer diameter portion and the landing position of ink that lands on the minimum outer diameter portion in each of the multiple ink ejection nozzle arrays to no more than half the dot pitch of the resolution of the image printed on the substrate.

[0012] In the present invention, it is preferable that the rotation mechanism includes a motor as a drive source, a power transmission mechanism for transmitting the power of the motor to the printing medium, and an encoder for detecting the rotational position and rotational speed of the motor or the printing medium, and the inkjet head includes a plurality of ejection energy generating elements for ejecting ink from each of the plurality of nozzles, and that the control unit, when printing on the printing medium, calculates the current rotational speed, which is the current rotational speed of the motor or the printing medium, based on the output signal of the encoder, compares the current rotational speed with a predetermined reference rotational speed, and, if the deviation of the current rotational speed from the reference rotational speed is less than a predetermined reference value, ejects ink from the nozzle at a normal ejection timing, which is the normal ejection timing based on the output signal of the encoder, if the deviation of the current rotational speed from the reference rotational speed is equal to or greater than the reference value and the current rotational speed is slower than the reference rotational speed, advances the ink ejection timing from the nozzle relative to the normal ejection timing, and if the deviation of the current rotational speed from the reference rotational speed is equal to or greater than the reference value and the current rotational speed is faster than the reference rotational speed, delays the ink ejection timing from the nozzle relative to the normal ejection timing. With this configuration, even if the current rotation speed deviates significantly from the reference rotation speed for some reason, it is possible to suppress deviation of the ink landing position in the circumferential direction of the printing medium, and therefore, even if the current rotation speed deviates significantly from the reference rotation speed for some reason, it is possible to suppress deterioration of the printing quality of the printing medium.

[0013] In the present invention, when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than a reference value, the control unit preferably increases the deviation of the ink ejection timing from the nozzles from the normal ejection timing as the size of one ink dot after landing on the print substrate decreases. As the size of one ink dot after landing on the print substrate decreases, print quality is more likely to deteriorate even if the deviation of the ink landing position in the circumferential direction of the print substrate remains the same. Therefore, with this configuration, even if the current rotation speed deviates significantly from the reference rotation speed for some reason, it is possible to suppress deterioration in the print quality of the print substrate, regardless of the size of one ink dot after landing on the print substrate. [Effects of the Invention]

[0014] As described above, in the present invention, in a printing device for printing on the outer peripheral surface of a substrate having a truncated cone shape, it is possible to ensure the printing quality of the substrate even when printing on the outer peripheral surface of the substrate while rotating the substrate. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a front view illustrating a configuration of a printing apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a block diagram illustrating the configuration of the printing apparatus shown in FIG. [Figure 3] FIG. 2A is a bottom view of the inkjet head and carriage shown in FIG. 1, and FIG. 2B is a bottom view for explaining the configuration of the inkjet head shown in FIG. [Figure 4] FIG. 2 is a front view for explaining the configuration of the ultraviolet irradiation device shown in FIG. [Figure 5] FIG. 5 is a side view for explaining the configuration of the rotation mechanism shown in FIG. [Figure 6] FIG. 5 is a side view for explaining the configuration of the rotation mechanism shown in FIG. [Figure 7]2 is a schematic diagram for explaining the arrangement position of nozzle rows when printing is performed on the outer peripheral surface of a frustum-shaped print medium by the printing device shown in FIG. 1. FIG. [Figure 8] 2 is a schematic diagram for explaining the arrangement position of nozzle rows when printing is performed on the outer peripheral surface of a frustum-shaped print medium by the printing device shown in FIG. 1. FIG. [Figure 9] 2 is a schematic diagram for explaining the arrangement position of nozzle rows when printing is performed on the outer peripheral surface of a frustum-shaped print medium by the printing device shown in FIG. 1. FIG. [Figure 10] 2 is a schematic diagram for explaining the arrangement position of nozzle rows when printing is performed on the outer peripheral surface of a frustum-shaped print medium by the printing device shown in FIG. 1. FIG. [Figure 11] 2 is a schematic diagram for explaining the arrangement position of nozzle rows when printing is performed on the outer peripheral surface of a frustum-shaped print medium by the printing device shown in FIG. 1. FIG. [Figure 12] 2 is a schematic diagram for explaining the arrangement position of nozzle rows when printing is performed on the outer peripheral surface of a frustum-shaped print medium by the printing device shown in FIG. 1. FIG. [Figure 13] 2 is a schematic diagram for explaining the arrangement position of nozzle rows when printing is performed on the outer peripheral surface of a frustum-shaped print medium by the printing device shown in FIG. 1. FIG. [Figure 14] 4 is a timing chart for explaining the timing of ejecting ink when printing on a print medium using the printing device shown in FIG. 1. [Figure 15] 4 is a timing chart for explaining a method of correcting ink ejection timing when printing on a print medium using the printing device shown in FIG. 1. [Figure 16] 3A to 3C are diagrams for explaining a method of correcting ink ejection timing when printing on a print medium using the printing device shown in FIG. 1. [Figure 17] 1. FIG. 4 is a diagram for explaining the allowable amount of deviation in the ink landing position according to the size of one ink dot when printing on a print medium using the printing device shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] (Overall configuration of the printing device) Fig. 1 is a front view illustrating the configuration of a printing device 1 according to an embodiment of the present invention. Fig. 2 is a block diagram illustrating the configuration of the printing device 1 shown in Fig. 1. Fig. 3(A) is a bottom view of the inkjet head 3 and carriage 7 shown in Fig. 1, and Fig. 3(B) is a bottom view illustrating the configuration of the inkjet head 3 shown in Fig. 3(A).

[0018] The printing device 1 of this embodiment is a device for printing on the outer peripheral surface of a printing substrate 2 having a cylindrical, truncated conical, or conical outer shape, and is, for example, a commercial inkjet printer. The printing device 1 prints on the outer peripheral surface of the printing substrate 2 using ultraviolet-curable ink. The printing substrate 2 is formed, for example, in a cylindrical shape. That is, the printing substrate 2 is formed in a cylindrical, truncated conical, or conical cylindrical shape. The printing substrate 2 is also formed, for example, from resin. The printing device 1 is capable of printing on multiple types of printing substrates 2 with different outer diameters and lengths.

[0019] The printing device 1 is equipped with an inkjet head 3 (hereinafter referred to as "head 3") that ejects ultraviolet-curable ink toward the outer peripheral surface of the print medium 2. The printing device 1 of this embodiment is equipped with multiple heads 3. Specifically, the printing device 1 is equipped with four heads 3. The printing device 1 also includes an ultraviolet irradiation device 4 for curing the ink ejected onto the outer peripheral surface of the print medium 2, a stage 6 having a table 5 on which the ultraviolet irradiation device 4 is placed, a carriage 7 on which the head 3 is mounted, a Y-bar 8 that holds the carriage 7 so as to enable movement in a main scanning direction perpendicular to the up-down direction (vertical direction), and a main body frame 9 that holds the stage 6 so as to enable movement in a sub-scanning direction perpendicular to the up-down direction and the main scanning direction.

[0020] The printing device 1 also includes a carriage drive mechanism 11 that moves the carriage 7 relative to the Y bar 8 in the main scanning direction, a stage drive mechanism 12 that moves the stage 6 relative to the main frame 9 in the sub-scanning direction, a table lifting mechanism 13 that raises and lowers the table 5, and a control unit 14 for controlling the printing device 1. The carriage drive mechanism 11 includes, for example, a motor 15 as a drive source and a power transmission mechanism such as a belt and pulleys that transmits the power of the motor 15 to the carriage 7. The stage drive mechanism 12 includes, for example, a motor as a drive source and a power transmission mechanism such as a belt and pulleys that transmits the power of the motor to the stage 6. The table lifting mechanism 13 includes, for example, a motor as a drive source and a power transmission mechanism such as a ball screw that transmits the power of the motor to the table 5.

[0021] In the following description, the sub-scanning direction (X direction in Fig. 1, etc.) is the front-to-rear direction, and the main scanning direction (Y direction in Fig. 1, etc.) is the left-to-right direction. In the following description, the X1 direction side in Fig. 5, etc., which is one side of the front-to-rear direction, is the "front" side, the X2 direction side in Fig. 5, etc., which is the opposite side, is the "rear" side, the Y1 direction side in Fig. 4, etc., which is one side of the left-to-right direction, is the "right" side, and the Y2 direction side in Fig. 2, etc., which is the opposite side, is the "left" side.

[0022] The upper surface of the table 5 is a plane perpendicular to the vertical direction. The ultraviolet irradiation device 4 placed on the table 5 is arranged below the head 3. The print medium 2 is held by the ultraviolet irradiation device 4 and arranged below the head 3. In other words, the head 3 is arranged above the print medium 2. The head 3 ejects ink downward. The ink ejected by the head 3 lands on the outer peripheral surface of the print medium 2 at the upper end of the print medium 2.

[0023] The head 3 is formed with a plurality of nozzles 3a that eject ink. Specifically, the large number of nozzles 3a are formed on the bottom surface of the head 3. The bottom surface of the head 3 is an ink ejection surface 3c on which the plurality of nozzles 3a (specifically, the large number of nozzles 3a) are formed. On the ink ejection surface 3c, a nozzle row 3b is formed from the plurality of nozzles 3a arranged in the sub-scanning direction (front-back direction). On the ink ejection surface 3c, a plurality of nozzle rows 3b are formed that are arranged in the main scanning direction (left-right direction). The head 3 is equipped with a plurality of piezoelectric elements (piezo elements) 16 for ejecting ink from each of the plurality of nozzles 3a. In this embodiment, the piezoelectric elements 16 are ejection energy generating elements.

[0024] As shown in Figure 3(A), for example, three of the four heads 3 mounted on the carriage 7 are arranged at the same position in the front-to-rear direction and are aligned in the left-to-right direction. The remaining head 3 is arranged at a position offset from the other three heads 3 in the front-to-rear direction. Three of the four heads 3 eject color inks, and the remaining head 3 ejects white ink. The viscosity of the white ink is higher than the viscosity of the color inks.

[0025] A motor 15 and a plurality of piezoelectric elements 16 are electrically connected to the control unit 14. A PC (personal computer) 18 is also electrically connected to the control unit 14. The PC 18 generates print data for printing on the print substrate 2. When printing on the print substrate 2, the print data generated by the PC 18 is sent from the PC 18 to the control unit 14. In other words, when printing on the print substrate 2, the print data sent from the PC 18 is input to the control unit 14.

[0026] (Configuration of ultraviolet irradiation device) Fig. 4 is a front view for explaining the configuration of the ultraviolet irradiation device 4 shown in Fig. 1. Figs. 5 and 6 are side views for explaining the configuration of the rotation mechanism 21 shown in Fig. 4.

[0027] The ultraviolet irradiation device 4 includes a rotation mechanism 21 that holds the substrate 2 and rotates it around its axis, an ultraviolet irradiator 22 that irradiates ultraviolet rays toward the outer peripheral surface of the substrate 2 to which ink is attached, and a cover 23 that covers the rotation mechanism 21 and the ultraviolet irradiator 22 from above. The cover 23 has an opening 23a through which the upper end of the substrate 2 is positioned. The ultraviolet irradiation device 4 is placed on the table 5 so that the axis of the substrate 2 coincides with the front-to-rear direction when viewed from above. In other words, the axis of the substrate 2 coincides with the front-to-rear direction when viewed from above. The carriage drive mechanism 11 moves the carriage 7 in a direction perpendicular to the axis of the substrate 2 when viewed from above.

[0028] The rotation mechanism 21 rotates the print substrate 2 when printing on the print substrate 2. In this embodiment, printing is performed on the print substrate 2 while the rotation mechanism 21 rotates the print substrate 2 with the carriage 7 stopped at a fixed position. When printing on the print substrate 2, the rotation mechanism 21 rotates the print substrate 2, for example, counterclockwise when viewed from the front. Also, in this embodiment, the length of the print substrate 2 (length in the axial direction) is longer than the width of the head 3 in the front-to-rear direction. Therefore, when printing on the print substrate 2, the table 5 is moved in stages in the front-to-rear direction (sub-scanning direction). The length of the print substrate 2 may be equal to the width of the head 3 in the front-to-rear direction, or may be shorter than the width of the head 3 in the front-to-rear direction.

[0029] The rotation mechanism 21 includes a motor 25 as a drive source and a power transmission mechanism 26 for transmitting the power of the motor 25 to the printing medium 2. The rotation mechanism 21 also includes a first rotating unit 27 that holds one end of the printing medium 2, a first holding unit 28 that rotatably holds the first rotating unit 27, a second rotating unit 29 that holds the other end of the printing medium 2, a second holding unit 30 that rotatably holds the second rotating unit 29, a rotating frame 31 to which the first holding unit 28 and the second holding unit 30 are attached, and an encoder 32 for detecting the rotational position and rotational speed of the printing medium 2. The motor 25 and the encoder 32 are electrically connected to the control unit 14. Note that the power transmission mechanism 26 and other components are not shown in FIG. 4.

[0030] The first rotating unit 27 and the second rotating unit 29 rotate together with the substrate 2. The first rotating unit 27 holds the rear end of the substrate 2, and the second rotating unit 29 holds the front end of the substrate 2. The power transmission mechanism 26 connects the first rotating unit 27 to the motor 25. The power transmission mechanism 26 includes a gear train 33. The gear train 33 includes a drive gear fixed to the output shaft of the motor 25 and a driven gear fixed to the first rotating unit 27. The encoder 32 is connected to the rear end of the first rotating unit 27. The second holding unit 30 is movable in the direction of the axis of the substrate 2. In this embodiment, the positions of the second rotating unit 29 and the second holding unit 30 in the direction of the axis of the substrate 2 are adjusted depending on the length of the substrate 2. The power transmission mechanism 26 may also be configured using pulleys, belts, etc.

[0031] The rotating frame 31 is rotatable relative to a lower frame 34 that constitutes the bottom surface of the ultraviolet irradiation device 4, with the left-right direction as the axis of rotation. The rotating frame 31 is also rotatable relative to the lower frame 34, with the rear end of the rotating frame 31 as the rotation center. In this embodiment, by rotating the rotating frame 31 relative to the lower frame 34, it is possible to adjust the inclination of the rotation mechanism 21 relative to the horizontal direction when viewed from the left-right direction. In other words, by rotating the rotating frame 31 relative to the lower frame 34, it is possible to adjust the inclination of the axis of the printing medium 2 relative to the horizontal direction.

[0032] In this embodiment, when printing on a printing substrate 2 having a cylindrical outer shape, the direction of the axis of the printing substrate 2 coincides with the front-to-rear direction (see FIG. 5). On the other hand, when printing on a printing substrate 2 having a truncated cone or conical outer shape, the direction of the axis of the printing substrate 2 is inclined with respect to the front-to-rear direction (see FIG. 6). In other words, the inclination of the rotation mechanism 21 is adjusted when printing on the outer peripheral surface of a printing substrate 2 having a truncated cone or conical outer shape. Specifically, the inclination of the rotation mechanism 21 is adjusted so that the top end of the printing substrate 2 is parallel to the front-to-rear direction.

[0033] The ultraviolet irradiator 22 includes an LED substrate on which numerous LED chips that emit ultraviolet light are mounted. The ultraviolet irradiator 22 is disposed to the left of the substrate 2. The ultraviolet irradiator 22 irradiates the substrate 2 with ultraviolet light from the left side immediately after ink has been ejected onto it. In this embodiment, the vertical position of the ultraviolet irradiator 22 is adjustable. The horizontal position of the ultraviolet irradiator 22 and the inclination of the ultraviolet irradiator 22 relative to the axis of the substrate 2 when viewed from the vertical direction are also adjustable. In this embodiment, when printing on a substrate 2 having a cylindrical outer shape, the ultraviolet irradiator 22 is installed so that the ultraviolet light emission surface of the ultraviolet irradiator 22 is parallel to the front-to-back direction. When printing on a substrate 2 having a truncated cone or conical outer shape, the inclination of the ultraviolet irradiator 22 is adjusted so that the ultraviolet light emission surface of the ultraviolet irradiator 22 is parallel to the left edge of the substrate 2.

[0034] (Nozzle array arrangement when printing on a truncated cone-shaped substrate) 7 to 13 are schematic diagrams for explaining the arrangement of the nozzle rows 3b when printing is performed on the outer peripheral surface of a truncated cone-shaped print medium 2 by the printing device 1 shown in Fig. 1. Fig. 9 is an enlarged view of part E in Fig. 8.

[0035] When printing on the outer peripheral surface of a substrate 2 having a truncated cone shape using the printing device 1, the tilt of the rotation mechanism 21 is adjusted so that the top edge of the substrate 2 is parallel to the front-to-rear direction, as described above. For example, as shown in FIG. 7, the axis of the substrate 2 is tilted by α (degrees) relative to the front-to-rear direction. The following describes the arrangement of the nozzle array 3b when printing on the outer peripheral surface of the substrate 2 having a truncated cone shape using the printing device 1. In the following description, the nozzle array 3b, which is composed of the nozzles 3a that actually eject ink when printing on the substrate 2, is referred to as the "ink ejection nozzle array 3e." In this embodiment, there are multiple ink ejection nozzle arrays 3e. For example, there are two ink ejection nozzle arrays 3e, and ink is ejected from both ink ejection nozzle arrays 3e toward the outer peripheral surface of the substrate 2. In the following description, the circumferential direction of the substrate 2 is referred to as the "circumferential direction."

[0036] When printing is performed on the outer peripheral surface of a substrate 2 having a truncated cone-shaped outer shape using the printing device 1, at positions offset from the axis of the substrate 2 in the left-right direction when viewed from the front-to-back direction, the vertical distance between the portion of the substrate 2 with a larger outer diameter and the ink ejection surface 3c of the head 3 is shorter than the vertical distance between the portion of the substrate 2 with a smaller outer diameter and the ink ejection surface 3c. Therefore, when printing is performed on the outer peripheral surface of the substrate 2 while rotating the substrate 2, the ink landing position in the circumferential direction shifts between the portion of the substrate 2 with a larger outer diameter and the portion of the substrate 2 with a smaller outer diameter. Furthermore, in the case of a substrate 2 having a truncated cone-shaped outer shape, the generatrix of the substrate 2 is tilted relative to the axis of the substrate 2, and this tilt also causes the ink landing position in the circumferential direction to shift between the portion of the substrate 2 with a larger outer diameter and the portion of the substrate 2 with a smaller outer diameter. If the ink landing positions are shifted, the printing accuracy on the printing medium 2 may be reduced.

[0037] If the part of the substrate 2 with the largest outer diameter is designated as the maximum outer diameter part 2a, the part of the substrate 2 with the smallest outer diameter is designated as the minimum outer diameter part 2b, and the resolution of the image P printed on the substrate 2 is designated as R (dpi (dots per inch)), in this embodiment, in order to ensure the print quality of the substrate 2 by suppressing the circumferential deviation between the landing position of ink landing on the maximum outer diameter part 2a and the landing position of ink landing on the minimum outer diameter part 2b to less than half the dot pitch of the resolution R, the ink discharge nozzle array 3e is positioned at a position where the distance l (mm) in the main scanning direction (left and right direction) between the ink discharge nozzle array 3e and the axial center of the substrate 2 satisfies the following relationship when printing on the substrate 2: TIFF2025150234000004.tif104170

[0038] where e t is a distance (mm) that is half the dot pitch of the resolution R of the image P printed on the substrate 2. e1 is the deviation (mm) of the ink landing position in the circumferential direction caused by the difference between the radius r1 of the maximum outer diameter portion 2a and the radius r2 of the minimum outer diameter portion 2b when ink ejected from the ink ejection nozzle array 3e positioned at a distance l from the axial center of the substrate 2 lands on the outer circumferential surface of the substrate 2. e2 is the deviation (mm) of the ink landing position in the circumferential direction caused by the inclination of the generatrix of the substrate 2 with respect to the axial center of the substrate 2 when ink ejected from the ink ejection nozzle array 3e positioned at a distance l from the axial center of the substrate 2 lands on the outer circumferential surface of the substrate 2.

[0039] Furthermore, when printing on the outer peripheral surface of the print medium 2, which has a truncated cone-shaped outer shape, the cause of the circumferential deviation of the ink landing position is that the outer diameter of the print medium 2 gradually changes in the axial direction of the print medium 2, and the direction of the generatrix of the print medium 2 is inclined with respect to the axial center of the print medium 2. Therefore, if the ink ejection nozzle row 3e is positioned at a position where the distance l satisfies the above relationship when printing on the print medium 2, the circumferential deviation between the landing position of the ink landing on the maximum outer diameter part 2a and the landing position of the ink landing on the minimum outer diameter part 2b can be suppressed to less than half the dot pitch of the resolution R.

[0040] Below, the methods for calculating the displacement amount e1 and displacement amount e2 will be explained in this order. In the following explanation, the center line in the left-right direction of the printing material 2 when viewed from the front-to-back direction is referred to as the center line CL. The center line CL intersects with the axial center of the printing material 2. Furthermore, the length of the printing material 2 in the axial direction of the printing material 2 is referred to as h (mm).

[0041] As shown in FIG. 9, the position where ink ejected from the ink ejection nozzle row 3e arranged at a distance l from the axis of the print medium 2 lands on the maximum outer diameter part 2a is defined as an impact position H1, the position where ink ejected from the ink ejection nozzle row 3e arranged at a distance l from the axis of the print medium 2 lands on the minimum outer diameter part 2b is defined as an impact position H2, and the vertical distance between the top end of the print medium 2 and the ink ejection surface 3c is defined as l. g0 (mm), and the vertical distance between the landing position H1 and the ink ejection surface 3c (i.e., the vertical distance between the portion of the maximum outer diameter part 2a where the ink ejected from the nozzles 3a constituting the ink ejection nozzle row 3e lands and the ink ejection surface 3c) is l g1 (mm), and the distance l g1 and distance l g0 The difference between these is the distance Δl g1 Then, the following relationship holds: TIFF2025150234000005.tif24170Therefore, The result is TIFF2025150234000006.tif12170.

[0042] The ejection speed of ink ejected from the ink ejection nozzle array 3e (i.e., the ejection speed of ink ejected from the nozzles 3a constituting the ink ejection nozzle array 3e) is V f (mm / sec), the time t1 (sec) until the ink ejected from the nozzle 3a constituting the ink ejection nozzle row 3e lands on the landing position H1 is TIFF2025150234000007.tif14170. If the ejection frequency of ink ejected from the ink ejection nozzle array 3e (i.e., the ejection frequency of ink ejected from the nozzles 3a constituting the ink ejection nozzle array 3e) is f (Hz), then the circumferential speed (speed in the circumferential direction) v1 (mm / sec) of the maximum outer diameter portion 2a is TIFF2025150234000008.tif14170. The rotation speed N (rev / sec) of the printing medium 2 is TIFF2025150234000009.tif13170. After ink is ejected from the nozzle 3a of the ink ejection nozzle row 3e, the movement distance x1 (mm) of the maximum outer diameter portion 2a in the circumferential direction until the ink lands at the landing position H1 is The file name will be TIFF2025150234000010.tif23170.

[0043] The peripheral speed (speed in the peripheral direction) v2 (mm / sec) of the minimum outer diameter portion 2b is TIFF2025150234000011.tif38170. The vertical distance between the landing position H2 and the ink ejection surface 3c (i.e., the vertical distance between the ink ejection surface 3c and the portion of the minimum outer diameter part 2b where ink ejected from the nozzles 3a constituting the ink ejection nozzle row 3e lands) is set to l. g2 (mm), the time t2 (sec) until the ink ejected from the nozzles 3a constituting the ink ejection nozzle row 3e lands at the landing position H2, and the moving distance x2 (mm) of the minimum outer diameter part 2b in the circumferential direction from the ink ejected from the nozzles 3a of the ink ejection nozzle row 3e until the ink lands at the landing position H2 are TIFF2025150234000012.tif15170TIFF2025150234000013.tif23170

[0044] From the above, the deviation e1 is The result is TIFF2025150234000014.tif40170.

[0045] Next, a method for calculating the displacement e2 will be described. In the following description, as shown in Figs. 10 and 11, the direction of the generatrix of the printing medium 2 is taken as the generatrix direction, and the width of the image P in the circumferential direction is taken as d x (mm), and the width of image P in the generatrix direction is d y The length of the printing medium 2 in the generatrix direction (i.e., the length of the generatrix of the printing medium 2) is b (mm). The distance in the generatrix direction between the part of the image P closest to the maximum outer diameter part 2a and the maximum outer diameter part 2a is l (mm). y (mm). That is, the distance l from the maximum outer diameter portion 2a y Image P is printed from a distance of (mm).

[0046] As shown in FIG. 10, the following relationship holds: TIFF2025150234000015.tif9170TIFF2025150234000016.tif11170Furthermore, if the distance a1 (mm) is specified as shown in Figure 10, Because it is TIFF2025150234000017.tif9170, TIFF2025150234000018.tif13170. The radius r3 (mm) of the printing medium 2 at the position where the part of the image P closest to the maximum outer diameter part 2a is placed is TIFF2025150234000019.tif10170, and from equations (2-1) to (2-3), The result is TIFF2025150234000020.tif58170.

[0047] As shown in FIG. 10, the distance in the generatrix direction between the part of the image P closest to the minimum outer diameter part 2b and the maximum outer diameter part 2a is l y1 (mm), The minimum radius r4 (mm) of the printing medium 2 at the position where the portion of the image P closest to the minimum outer diameter portion 2b is placed is The result is TIFF2025150234000022.tif33170.

[0048] As shown in Figure 12, if the axis (center) of the printing material 2 is taken as the origin, and point A is the point located at the same position in the main scanning direction as the ink ejection nozzle row 3e in the part of the image P closest to the maximum outer diameter portion 2a, and point B is the point located at the same position in the main scanning direction as the ink ejection nozzle row 3e in the part of the image P closest to the minimum outer diameter portion 2b, the coordinates of points A and B are expressed as follows: TIFF2025150234000023.tif22170

[0049] Angle θ based on the axis (origin) of the printing material 2 t (deg) and angle θ b (deg) is TIFF2025150234000024.tif34170. Angle θ t and angle θ b The difference between this and angle θ d teeth, The result is TIFF2025150234000025.tif84170.

[0050] As shown in FIG. 13, when the printing medium 2 formed in a truncated cone shape is symmetrically developed, the line passing through points A and B forms an angle θ d The amount of deviation caused by this tilt is the amount of deviation e2, which is expressed as follows: The result is TIFF2025150234000026.tif72170.

[0051] (Ink ejection timing correction control) FIG. 14 is a timing chart illustrating the ink ejection timing when printing on the print substrate 2 using the printing device 1 shown in FIG. 1. FIG. 15 is a timing chart illustrating a method for correcting the ink ejection timing when printing on the print substrate 2 using the printing device 1 shown in FIG. 1. FIG. 16 is a diagram illustrating a method for correcting the ink ejection timing when printing on the print substrate 2 using the printing device 1 shown in FIG. 1. FIG. 17 is a diagram illustrating the allowable amount ΔT of deviation in the ink landing position depending on the size of one dot of ink DI when printing on the print substrate 2 using the printing device 1 shown in FIG. 1.

[0052] As described above, when printing is performed on the print medium 2 by the printing device 1, print data transmitted from the PC 18 is input to the control unit 14. The control unit 14 prints on the print medium 2 based on the input print data. When printing on the print medium 2, the control unit 14 generates an ejection trigger signal for starting the ejection of ink from the nozzle 3a of the head 3 based on the output signal of the encoder 32 (see FIG. 14). Specifically, the control unit 14 generates the ejection trigger signal when the count number of the encoder pulses reaches a predetermined value (counts up). The control unit 14 also transmits a drive signal to the piezoelectric element 16 for ejecting ink from the nozzle 3a based on the ejection trigger signal. Specifically, the control unit 14 transmits a drive signal to the piezoelectric element 16 for ejecting one dot of ink from the nozzle 3a based on the ejection trigger signal, thereby ejecting ink from the nozzle 3a.

[0053] Here, if the rotational speed of the print medium 2 fluctuates significantly for some reason, the period of the encoder pulse fluctuates significantly, and the timing of generating the ejection trigger signal fluctuates significantly, which may cause the ink landing position in the circumferential direction to shift and reduce the printing accuracy of the print medium 2. In this embodiment, in order to ensure the print quality of the print medium 2, ejection timing correction control is performed to correct the timing of ink ejection from the nozzles 3a when the rotational speed of the print medium 2 fluctuates significantly. The control unit 14 has, as functional components for performing ejection timing correction control, an encoder measurement unit 43 to which an output signal of the encoder 32 is input, a comparison unit 44 to which an output signal of the encoder measurement unit 43 is input, and an ejection control unit 45 that controls the multiple piezoelectric elements 16 (see FIG. 2).

[0054] The encoder measurement unit 43 calculates the current rotation speed, which is the current rotation speed of the print substrate 2, based on the output signal of the encoder 32 when printing on the print substrate 2. Specifically, the encoder measurement unit 43 calculates the current rotation speed at regular intervals when printing on the print substrate 2. The encoder measurement unit 43 also calculates a reference rotation speed of the print substrate 2. Specifically, the encoder measurement unit 43 calculates the average value of a predetermined number of past current rotation speeds calculated before calculating the latest current rotation speed as the reference rotation speed of the print substrate 2.

[0055] The comparison unit 44 receives a current rotation speed signal and a reference rotation speed signal. The comparison unit 44 compares the current rotation speed with the reference rotation speed. Furthermore, the comparison unit 44 determines, as a result of comparing the current rotation speed with the reference rotation speed, whether or not correction control of the ejection timing is necessary. If the deviation of the current rotation speed from the reference rotation speed is less than a predetermined reference value, the comparison unit 44 determines that correction control of the ejection timing is unnecessary, and generates and outputs a no-correction signal. On the other hand, if the deviation of the current rotation speed from the reference rotation speed is equal to or greater than the reference value, the comparison unit 44 determines that correction control of the ejection timing is necessary, and generates and outputs a correction execution signal.

[0056] The output signal of the comparison unit 44 is input to the discharge control unit 45. When the no-correction-needed signal is input, the discharge control unit 45 causes ink to be discharged from the nozzles 3a at the normal discharge timing, which is the normal discharge timing based on the output signal of the encoder 32. That is, when the no-correction-needed signal is input to the discharge control unit 45, the control unit 14 generates a discharge trigger signal when the count number of encoder pulses reaches a predetermined value (see FIG. 14). In this way, when the deviation of the current rotation speed from the reference rotation speed is less than the reference value, the control unit 14 causes ink to be discharged from the nozzles 3a at the normal discharge timing.

[0057] On the other hand, when a correction execution signal is input and the current rotation speed is slower than the reference rotation speed, the ejection control unit 45 advances the timing of ejecting ink from the nozzle 3a relative to the normal ejection timing. In other words, when a correction execution signal is input to the ejection control unit 45 and the current rotation speed is slower than the reference rotation speed, the control unit 14 generates an ejection trigger signal before the count number of the encoder pulses reaches a predetermined value (before counting up) (see part F in FIG. 15(A)).

[0058] Furthermore, when a correction execution signal is input and the current rotation speed is faster than the reference rotation speed, the ejection control unit 45 delays the timing of ejecting ink from the nozzles 3a from the normal ejection timing. That is, when a correction execution signal is input to the ejection control unit 45 and the current rotation speed is faster than the reference rotation speed, the control unit 14 generates an ejection trigger signal after a predetermined time has elapsed after the count number of the encoder pulses reaches a predetermined value (after counting up) (see part G in FIG. 15(B)).

[0059] In this way, the control unit 14 advances the timing of ink ejection from the nozzle 3a relative to the normal ejection timing when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than the reference value and the current rotation speed is slower than the reference rotation speed, and delays the timing of ink ejection from the nozzle 3a relative to the normal ejection timing when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than the reference value and the current rotation speed is faster than the reference rotation speed.

[0060] The ejection control unit 45 is equipped with a digital filter, and when performing ejection timing correction control, it corrects the timing of ejecting ink from the nozzles 3 a so as to reduce the total absolute value of the deviation of the generation period of the ejection trigger signal from the average value. In other words, when performing ejection timing correction control, the ejection control unit 45 corrects the timing of ejecting ink from the nozzles 3 a so as to reduce the standard deviation of the generation period of the ejection trigger signal. Note that when performing ejection timing correction control, the ejection timing of ink from the nozzles 3 a is corrected so as to reduce the standard deviation of the generation period of the ejection trigger signal, so even if this ejection timing correction control is performed, it is not possible to completely eliminate deviations in the ink landing position in the circumferential direction.

[0061] The solid line of the "ejection trigger period" in Fig. 16 shows an example of the generation period of the ejection trigger signal when correction control of the ejection timing is performed. Also, the dashed line of the "ejection trigger period" in Fig. 16 shows an example of the generation period of the ejection trigger signal when correction control of the ejection timing is not performed despite a large fluctuation in the rotation speed of the print medium 2. In other words, the dashed line of the "ejection trigger period" in Fig. 16 shows an example of the generation period of the ejection trigger signal when ink is ejected from the nozzle 3a at the normal ejection timing despite a large fluctuation in the rotation speed of the print medium 2.

[0062] Depending on the conditions of the print substrate 2, such as the material of the print substrate 2, and the type of ink, the way the ink spreads on the print substrate 2 may change, which may change the size of one dot of ink DI (see FIG. 17) after it lands on the print substrate 2. For example, if the radial deviation of one dot of ink DI after it lands on the print substrate 2 is defined as the allowable deviation ΔT of the ink landing position in the circumferential direction, as shown in FIG. 17, the allowable deviation ΔT varies depending on the size of one dot of ink DI after it lands on the print substrate 2. Specifically, as the size of one dot of ink DI after it lands on the print substrate 2 decreases, the allowable deviation ΔT decreases. In this embodiment, when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than a reference value, the control unit 14 increases the deviation of the ink ejection timing from the nozzle 3 a from the normal ejection timing as the size of one dot of ink DI after it lands on the print substrate 2 decreases.

[0063] Specifically, when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than a reference value, the control unit 14 corrects the timing of ejecting ink from the nozzles 3a so that the standard deviation of the generation period of the ejection trigger signal becomes smaller as the size of one dot of ink DI after landing on the print substrate 2 becomes smaller. For example, when the size DI of one dot of ink after landing on the print substrate 2 is large, the generation period of the ejection trigger signal when the ejection timing correction control is performed becomes like the solid line of the "ejection trigger period" in Figure 16, and when the size of one dot of ink DI after landing on the print substrate 2 is small, the generation period of the ejection trigger signal when the ejection timing correction control is performed becomes like the two-dot chain line of the "ejection trigger period" in Figure 16.

[0064] (Main effect of this form) As described above, in this embodiment, the control unit 14 moves and stops the carriage 7 so that the ink ejection nozzle row 3e is positioned at a position where the distance l satisfies the above relationship during printing on the print substrate 2. Therefore, in this embodiment, it is possible to suppress the circumferential deviation between the landing position of ink on the maximum outer diameter portion 2a of the print substrate 2 and the landing position of ink on the minimum outer diameter portion 2b to less than half the dot pitch of the resolution R. Therefore, in this embodiment, it is possible to ensure the print quality of the print substrate 2 even when printing is performed on the outer peripheral surface of the print substrate 2 while rotating the print substrate 2, which has a truncated cone-shaped outer shape.

[0065] Furthermore, in this embodiment, ink is ejected from the nozzles 3a of the multiple ink ejection nozzle arrays 3e together when printing on the print medium 2, but the control unit 14 moves and stops the carriage 7 so that each of the multiple ink ejection nozzle arrays 3e is positioned at a position where the distance l satisfies the above relationship when printing on the print medium 2. Therefore, in this embodiment, even when ink is ejected from the nozzles 3a of the multiple ink ejection nozzle arrays 3e together when printing on the print medium 2, it is possible to suppress the circumferential deviation between the landing position of the ink that lands on the maximum outer diameter portion 2a and the landing position of the ink that lands on the minimum outer diameter portion 2b in each of the multiple ink ejection nozzle arrays 3e to less than half the dot pitch of the resolution R.

[0066] In this embodiment, when printing on the print medium 2, the control unit 14 advances the ink ejection timing from the nozzle 3 a relative to the normal ejection timing when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than a reference value and the current rotation speed is slower than the reference rotation speed, and delays the ink ejection timing from the nozzle 3 a relative to the normal ejection timing when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than a reference value and the current rotation speed is faster than the reference rotation speed. Therefore, in this embodiment, even if the current rotation speed significantly deviates from the reference rotation speed for some reason, it is possible to suppress deviations in the ink landing position in the circumferential direction. Therefore, in this embodiment, even if the current rotation speed significantly deviates from the reference rotation speed for some reason, it is possible to suppress deterioration in the print quality of the print medium 2.

[0067] In this embodiment, when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than a reference value, the control unit 14 increases the deviation of the ink ejection timing from the nozzle 3a from the normal ejection timing as the size of one dot of ink DI after landing on the print substrate 2 decreases. Therefore, in this embodiment, even if the current rotation speed deviates significantly from the reference rotation speed for some reason, it is possible to suppress a deterioration in the print quality of the print substrate 2, regardless of the size of one dot of ink DI after landing on the print substrate 2.

[0068] (Other embodiments) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this embodiment and various modifications can be made without departing from the spirit of the present invention.

[0069] In the above-described embodiment, the number of ink ejection nozzle rows 3e that actually ejects ink when printing on the print medium 2 may be one. Also, in the above-described embodiment, the rotation mechanism 21 may be provided with an encoder for detecting the rotational position and rotational speed of the motor 25, instead of the encoder 32. In this case, the control unit 14 calculates the current rotational speed of the motor 25 based on the output signal of this encoder when printing on the print medium 2. Also, the control unit 14 calculates, as the reference rotational speed of the motor 25, the average value of a predetermined number of past current rotational speeds calculated before the latest current rotational speed is calculated.

[0070] In the above-described embodiment, if the printing apparatus 1 only prints on a print medium 2 having a fixed outer diameter, the vertical position of the ultraviolet irradiator 22 does not need to be adjustable. Also, in the above-described embodiment, the printing apparatus 1 does not need to print on a print medium 2 having a cylindrical or conical outer shape. Furthermore, in the above-described embodiment, the ultraviolet irradiator 22 may be disposed below the print medium 2. Also, in the above-described embodiment, the printing apparatus 1 may be provided with a Y-bar drive mechanism that moves the Y-bar 8 in the sub-scanning direction instead of the stage drive mechanism 12. Also, in the above-described embodiment, the ejection energy generating element for ejecting ink from the nozzle 3a may be a heater (heat generating element). Also, in the above-described embodiment, the printing apparatus 1 may have only one head 3. [Explanation of symbols]

[0071] 1 Printing device 2 Printing material 2a Maximum outer diameter 2b Minimum outer diameter 3 heads (inkjet heads) 3a nozzle 3b Nozzle row 3c Ink ejection surface 3e Ink ejection nozzle row 7 Carriage 11 Carriage drive mechanism 14 Control Unit 16 Piezoelectric element (ejection energy generating element) 21 Rotation mechanism 25 motor 26 Power transmission mechanism 32 Encoder X sub-scanning direction Y main scanning direction

Claims

1. A printing device for printing on an outer peripheral surface of a printing medium having a truncated cone shape, a rotation mechanism that holds the medium to be printed and rotates the medium around the axis of the medium; an inkjet head that is disposed above the medium to be printed and that ejects ink toward the outer peripheral surface of the medium to be printed; a carriage on which the inkjet head is mounted; a carriage drive mechanism that moves the carriage in a main scanning direction that is a direction perpendicular to the up-down direction and perpendicular to the axis of the medium to be printed when viewed from the up-down direction; and a control unit that controls the printing device, The inkjet head is formed with a plurality of nozzles for ejecting ink, a lower surface of the inkjet head serving as an ink ejection surface on which a plurality of the nozzles are formed; On the ink ejection surface, a nozzle row is formed by a plurality of the nozzles arranged in a sub-scanning direction perpendicular to the vertical direction and the main scanning direction, the rotation mechanism rotates the printing medium when printing is performed on the printing medium; The nozzle row constituted by the nozzles that actually eject ink when printing on the print medium is defined as an ink ejection nozzle row, the distance in the main scanning direction between the ink ejection nozzle row and the axis of the print medium is defined as 1 (mm), the resolution of the image printed on the print medium is defined as R (dpi), the ejection frequency of ink ejected from the nozzles that constitute the ink ejection nozzle row is defined as f (Hz), and the ejection speed of ink ejected from the nozzles that constitute the ink ejection nozzle row is defined as V. ｆ (mm / sec), the length of the printing medium in the axial direction of the printing medium is h (mm), and the radius of the largest outer diameter part of the printing medium is r １ (mm), and the radius of the smallest outer diameter part of the printing medium is r ２ (mm), and the vertical distance between the portion of the maximum outer diameter where ink ejected from the nozzles constituting the ink ejection nozzle row lands and the ink ejection surface is l ｇ１ (mm), and the vertical distance between the portion of the minimum outer diameter part where ink ejected from the nozzles constituting the ink ejection nozzle row lands and the ink ejection surface is l ｇ２ (mm), the direction of the generatrix of the printing medium is the generatrix direction, and the width of the image printed on the printing medium in the generatrix direction is d ｙ (mm), and the distance in the generatrix direction between the part of the image printed on the printing medium closest to the maximum outer diameter and the maximum outer diameter is l ｙ (mm), a control unit that, when printing on the printing medium, moves and stops the carriage so that the ink ejection nozzle row is positioned at a position where the distance l satisfies the following relationship:

2. 2. The printing apparatus according to claim 1, wherein there are a plurality of ink ejection nozzle rows.

3. the rotation mechanism includes a motor as a drive source, a power transmission mechanism for transmitting the power of the motor to the printing medium, and an encoder for detecting the rotation position and rotation speed of the motor or the printing medium; the inkjet head includes a plurality of ejection energy generating elements for ejecting ink from each of the plurality of nozzles; 3. The printing device according to claim 1, wherein the control unit calculates a current rotational speed, which is a current rotational speed of the motor or the printing medium, based on the output signal of the encoder during printing on the printing medium, compares the current rotational speed with a predetermined reference rotational speed, and, if a deviation of the current rotational speed from the reference rotational speed is less than a predetermined reference value, ejects ink from the nozzles at a normal ejection timing, which is a normal ejection timing based on the output signal of the encoder; if a deviation of the current rotational speed from the reference rotational speed is equal to or greater than the reference value and the current rotational speed is slower than the reference rotational speed, advances the ink ejection timing from the nozzles relative to the normal ejection timing; and if a deviation of the current rotational speed from the reference rotational speed is equal to or greater than the reference value and the current rotational speed is faster than the reference rotational speed, delays the ink ejection timing from the nozzles relative to the normal ejection timing.

4. 4. The printing device according to claim 3, wherein, when the deviation of the current rotation speed from the reference rotation speed is equal to or greater than the reference value, the control unit increases the deviation of the ink ejection timing from the nozzle from the normal ejection timing as the size of one dot of ink after landing on the printing medium becomes smaller.

5. a control method for a printing device for printing on an outer peripheral surface of a substrate having a truncated cone shape, the control method comprising: a rotation mechanism for holding the substrate and rotating the substrate around an axial center of the substrate; an inkjet head disposed above the substrate and ejecting ink toward the outer peripheral surface of the substrate; a carriage on which the inkjet head is mounted; and a carriage drive mechanism for moving the carriage in a main scanning direction that is a direction perpendicular to a vertical direction and perpendicular to the axial center of the substrate when viewed from the vertical direction; the inkjet head is formed with a plurality of nozzles that eject ink, and the bottom surface of the inkjet head serves as an ink ejection surface on which the plurality of nozzles are formed, and on the ink ejection surface, a nozzle row is formed by the plurality of nozzles that are arranged in a sub-scanning direction that is perpendicular to the vertical direction and the main scanning direction; The nozzle row constituted by the nozzles that actually eject ink when printing on the print medium is defined as an ink ejection nozzle row, the distance in the main scanning direction between the ink ejection nozzle row and the axis of the print medium is defined as 1 (mm), the resolution of the image printed on the print medium is defined as R (dpi), the ejection frequency of ink ejected from the nozzles that constitute the ink ejection nozzle row is defined as f (Hz), and the ejection speed of ink ejected from the nozzles that constitute the ink ejection nozzle row is defined as V. ｆ (mm / sec), the length of the printing medium in the axial direction of the printing medium is h (mm), and the radius of the largest outer diameter part of the printing medium is r １ (mm), and the radius of the smallest outer diameter part of the printing medium is r ２ (mm), and the vertical distance between the portion of the maximum outer diameter where ink ejected from the nozzles constituting the ink ejection nozzle row lands and the ink ejection surface is l ｇ１ (mm), and the vertical distance between the portion of the minimum outer diameter part where ink ejected from the nozzles constituting the ink ejection nozzle row lands and the ink ejection surface is l ｇ２ (mm), the direction of the generatrix of the printing medium is the generatrix direction, and the width of the image printed on the printing medium in the generatrix direction is d ｙ (mm), and the distance in the generatrix direction between the part of the image printed on the printing medium closest to the maximum outer diameter and the maximum outer diameter is l ｙ (mm), a control method for a printing device, characterized in that, during printing on the printing medium, the carriage is moved and stopped so that the ink ejection nozzle row is positioned at a position where the distance l satisfies the following relationship:

Images