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 columnar, truncated conical, or conical outer shape, the printing apparatus being capable of shortening a printing time required for printing the printing medium while securing the printing quality of the printing medium.SOLUTION: A printing apparatus includes a rotating mechanism 21 for rotating a printing medium 2 with an axial center of the printing medium 2 as the center of rotation, and inkjet heads which are arranged above the printing medium 2 and eject ink toward an outer peripheral surface of the printing medium 2. The rotation mechanism 21 includes a motor 25 as a drive source, and rotates the printing medium 2 during printing on the printing medium 2. Print data for performing printing on the printing medium 2 is input to a control unit that controls the printing apparatus, and the control unit controls the rotation speed of the motor 25 on the basis of the print data during printing on the printing medium 2.SELECTED DRAWING: Figure 5

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 cylindrical, truncated conical or conical outer shape, and also to a 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 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, the ultraviolet irradiation device includes a rotation mechanism that holds the printing medium and rotates the printing medium around its axis. The rotation mechanism includes a first rotating unit that holds one end of the printing medium, a second rotating unit that holds the other end of the printing medium, a motor for rotating the printing medium, and a power transmission mechanism that connects the first rotating unit to the motor. The power transmission mechanism is composed of, for example, a pulley and a belt. In the printing device described in Patent Document 1, while the printing medium is rotated by the rotation mechanism, ink is ejected from an inkjet head that is stopped in a fixed position to print on the outer surface of the printing medium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-88834 Summary of the Invention [Problem to be solved by the invention]

[0005] In the printing device described in Patent Document 1, it is difficult to ensure print quality on the printed material unless the motor of the rotation mechanism is rotated at an appropriate rotation speed. For example, if the resolution of the image to be printed on the outer surface of the printed material is high, it is difficult to print accurately on the outer surface of the printed material unless the rotation speed of the motor is slowed down to slow down the rotation speed of the printed material. On the other hand, if the resolution of the image to be printed on the outer surface of the printed material is low, slowing down the rotation speed of the motor to slow down the rotation speed of the printed material will result in the printing time required to print on the printed material being longer than necessary.

[0006] Furthermore, for example, if the viscosity of the ink used to print on the substrate is high, the speed of the ink ejected from the inkjet head will slow down and it will take a long time for the ink to reach the substrate, so in this case, it will be difficult to print accurately on the outer circumferential surface of the substrate unless the rotation speed of the motor is slowed down to slow down the rotation speed of the substrate. On the other hand, if the viscosity of the ink used to print on the substrate is low, the speed of the ink ejected from the inkjet head will increase and the time for the ink to reach the substrate will be short, but even in this case, slowing down the rotation speed of the motor to slow down the rotation speed of the substrate will make the printing time longer than necessary.

[0007] Therefore, an object of the present invention is to provide a printing device for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which is capable of shortening the printing time required to print on the printing substrate while ensuring the print quality of the printing substrate.Another object of the present invention is to provide a printing device control method for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which is capable of shortening the printing time required to print on the printing substrate while ensuring the print quality of the printing substrate. [Means for solving the problem]

[0008] In order to solve the above problems, the printing device of the present invention is a printing device for printing on the outer surface of a printing substrate having a cylindrical, truncated cone or conical outer shape, and is equipped with a rotation mechanism that holds the printing substrate and rotates the printing substrate around its axis as the center of rotation, an inkjet head that is arranged above the printing substrate and ejects ink toward the outer surface of the printing substrate, and a control unit for controlling the printing device, wherein the rotation mechanism has a motor as a drive source and a power transmission mechanism for transmitting the power of the motor to the printing substrate, and rotates the printing substrate when printing on the printing substrate, and the control unit receives print data for printing on the printing substrate, and the control unit controls the rotation speed of the motor based on the print data when printing on the printing substrate.

[0009] In the present invention, the control unit calculates the optimum rotation speed of the motor based on the print data, and rotates the motor at the calculated rotation speed when printing on the printing medium.

[0010] In the printing device of the present invention, print data for printing on a substrate is input to the control unit. Therefore, in the present invention, if the print data includes data on the resolution of the image to be printed on the outer surface of the substrate and data on the viscosity of the ink used to print on the substrate, the control unit can determine the resolution of the image to be printed on the outer surface of the substrate and the viscosity of the ink used to print on the substrate based on the input print data. Also, in the present invention, the control unit controls the rotation speed of the motor based on the print data when printing on the substrate.

[0011] Therefore, in the present invention, for example, when the resolution of the image, etc. printed on the outer peripheral surface of the print medium is high or the viscosity of the ink used is high, it is possible to slow down the rotation speed of the motor to slow down the rotation speed of the print medium, and when the resolution of the image, etc. printed on the outer peripheral surface of the print medium is low or the viscosity of the ink used is low, it is possible to increase the rotation speed of the motor to increase the rotation speed of the print medium. Therefore, in the present invention, it is possible to shorten the printing time required to print on the print medium while ensuring the print quality of the print medium.

[0012] In the present invention, for example, a printing device includes multiple inkjet heads, a carriage on which the multiple inkjet heads are mounted, and a carriage drive mechanism that moves the carriage in a direction perpendicular to the axis of the print medium when viewed from above, where print data is set for each inkjet head, and where a control unit controls the rotation speed of a motor when printing on the print medium based on the print data set for the inkjet head located directly above the print medium. In this case, even when multiple inkjet heads are used to print on the print medium, the control unit controls the rotation speed of the motor based on the print data set for the inkjet head that actually ejects ink. Therefore, even when multiple inkjet heads are used to print on the print medium, it is possible to reduce the printing time required to print on the print medium while ensuring the print quality of the print medium.

[0013] In the present invention, the printing device includes a carriage on which one or more inkjet heads are mounted and a carriage drive mechanism that moves the carriage in a direction perpendicular to the axis of the print medium when viewed from above. The inkjet heads each have a plurality of nozzles formed on their undersides, each nozzle array being aligned in the direction of the axis of the print medium when viewed from above. The total number of nozzle arrays formed on all inkjet heads mounted on the carriage is two or more. Print data is set for each nozzle array. The control unit may control the rotation speed of the motor based on the print data set for the nozzle array positioned directly above the print medium when printing on the print medium. In this case, even when multiple nozzle arrays are used to print on the print medium, the control unit controls the rotation speed of the motor based on the print data set for the nozzle array that actually ejects ink. Therefore, even when multiple nozzle arrays are used to print on the print medium, it is possible to reduce the printing time required to print on the print medium while maintaining the print quality of the print medium.

[0014] In the present invention, the rotation mechanism preferably rotates the substrate only in a predetermined first direction when printing on the substrate, and also rotates the substrate in the first direction when setting a printing origin, which aligns the substrate's origin position relative to the inkjet head in the rotation direction of the substrate before printing on the substrate. In this case, for example, the printing device includes a pointer that irradiates light onto the outer surface of the substrate, and the power transmission mechanism includes a gear train or at least two toothed pulleys and a toothed belt stretched over the toothed pulleys. With this configuration, the rotation direction of the substrate during printing is the same as the rotation direction of the substrate when the printing origin was set. This reduces the effects of backlash in the gear train of the power transmission mechanism, making it possible to accurately start rotation of the substrate from the origin position when printing on the substrate. This improves the print quality of the substrate.

[0015] In the present invention, the rotation mechanism preferably includes an encoder for detecting the rotational position and rotational speed of the target object, an inkjet head formed with multiple nozzles for ejecting ink, and multiple ejection energy generating elements for ejecting ink from each of the multiple nozzles. When printing on the target object, the control unit generates an ejection trigger signal to start ejecting ink from the nozzles based on the output signal of the encoder, transmits a drive signal to the ejection energy generating elements to eject ink from the nozzles starting from the ejection trigger signal, and sets an ejection flag starting from the ejection trigger signal and clears the flag when transmission of the drive signal ends. If the motor rotation speed is normal, the next ejection trigger is generated after the ejection flag is cleared. If the next ejection trigger is generated while the ejection flag is cleared, the control unit preferably executes a predetermined error process. This configuration makes it possible to stop printing on the target object if the motor rotation speed increases for some reason, causing the ink to land incorrectly. This reduces the occurrence of printing defects on the target object.

[0016] In addition, in order to solve the above-mentioned problems, the control method for a printing device of the present invention is a printing device for printing on the outer surface of a printing substrate having a cylindrical, truncated cone-shaped or conical outer shape, and is equipped with a rotation mechanism that holds the printing substrate and rotates the printing substrate around the axis of the printing substrate as the center of rotation, and an inkjet head that is arranged above the printing substrate and ejects ink toward the outer surface of the printing substrate, the rotation mechanism is equipped with a motor as a drive source and a power transmission mechanism for transmitting the power of the motor to the printing substrate, and is a control method for a printing device that rotates the printing substrate when printing on the printing substrate, and is characterized in that the rotation speed of the motor is controlled based on print data for printing on the printing substrate when printing on the printing substrate.

[0017] In the control method for a printing device of the present invention, when printing on a substrate, the rotation speed of the motor is controlled based on print data for printing on the substrate. Therefore, in the present invention, if the print data includes data on the resolution of the image, etc. to be printed on the outer peripheral surface of the substrate and data on the viscosity of the ink used to print on the substrate, for example, if it is determined based on the print data that the resolution of the image, etc. to be printed on the outer peripheral surface of the substrate is high or if it is determined that the viscosity of the ink used to print on the substrate is high, it is possible to slow down the rotation speed of the motor and thereby slow down the rotation speed of the substrate.

[0018] Furthermore, with the present invention, for example, if it is determined based on the print data that the resolution of the image to be printed on the outer peripheral surface of the print medium is low, or if it is determined that the viscosity of the ink used is low, it is possible to increase the rotation speed of the motor and thereby increase the rotation speed of the print medium. Therefore, by controlling the printing device with the control method of the present invention, it is possible to shorten the printing time required to print on the print medium while ensuring the print quality of the print medium. [Effects of the Invention]

[0019] As described above, the present invention makes it possible to shorten the printing time required to print on a substrate having a cylindrical, truncated cone, or conical shape while ensuring the printing quality of the substrate in a printing device for printing on the outer surface of the substrate. [Brief explanation of the drawings]

[0020] [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] 1. FIG. 4 is a diagram for explaining a method for setting a printing origin for aligning the origin position of a printing medium in the rotation direction of the printing medium in the printing device shown in FIG. [Figure 8] 4 is a flowchart illustrating an example of a control method for the printing device shown in FIG. 1 when printing on a print medium. [Figure 9] 4 is a timing chart for explaining the timing of ink ejection when printing on a print medium using the printing device shown in FIG. 1; [Figure 10] 10A and 10B are diagrams for explaining the configuration of a power transmission mechanism according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0022] (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).

[0023] 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.

[0024] The printing device 1 is equipped with inkjet heads 3 (hereinafter referred to as "heads 3") that eject 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 multiple heads 3 are mounted, a Y-bar 8 that holds the carriage 7 so that it can move in the main scanning direction, and a main frame 9 that holds the stage 6 so that it can move up and down (vertical direction) and in a sub-scanning direction that is perpendicular to the main scanning direction.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The head 3 has a plurality of nozzles 3a formed therein for ejecting ink. Specifically, the large number of nozzles 3a are formed on the underside of the head 3. On the underside of the head 3, a nozzle row 3b is formed by the large number of nozzles 3a arranged in the sub-scanning direction (front-rear direction). On the underside of the head 3, a plurality of nozzle rows 3b are formed therein, arranged in the main scanning direction (left-right direction). The head 3 has 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.

[0029] As shown in FIG. 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-back direction and are also 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-back 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 that of the color inks. A pointer 17 is mounted on the carriage 7, which irradiates the outer peripheral surface of the print substrate 2 with light. That is, the printing device 1 is equipped with a pointer 17 that irradiates the outer peripheral surface of the print substrate 2 with light. The pointer 17 is, for example, an LED pointer. The pointer 17 is arranged above the print substrate 2.

[0030] 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. The print data in this embodiment is set for each head 3.

[0031] (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.

[0032] The ultraviolet irradiation device 4 includes a rotation mechanism 21 that holds the print medium 2 and rotates the print medium 2 around the axis of the print medium 2 as the rotation center, an ultraviolet irradiator 22 that irradiates ultraviolet rays toward the outer peripheral surface of the print medium 2 to which ink is attached, and a cover 23 that covers the rotation mechanism 21 and the ultraviolet irradiator 22 from above. An opening 23a is formed in the cover 23, through which the upper end of the print medium 2 is positioned.

[0033] The ultraviolet irradiation device 4 is placed on the table 5 so that the direction of the axis of the substrate 2 to be printed when viewed from above coincides with the front-to-back direction. In other words, the direction of the axis of the substrate 2 to be printed when viewed from above coincides with the front-to-back direction. The carriage drive mechanism 11 moves the carriage 7 in a direction perpendicular to the axis of the substrate 2 to be printed when viewed from above. The nozzle row 3b is arranged in the direction of the axis of the substrate 2 to be printed when viewed from above. The nozzle row 3b, which ejects ink toward the substrate 2 to be printed when printing on the substrate 2, is positioned directly above the substrate 2 to be printed.

[0034] The rotation mechanism 21 rotates the substrate 2 when printing on the substrate 2. In this embodiment, printing is performed on the substrate 2 while the rotation mechanism 21 rotates the substrate 2 with the carriage 7 stopped at a fixed position. When printing on the substrate 2, the rotation mechanism 21 rotates the substrate 2 in a counterclockwise direction when viewed from the front (hereinafter, this direction will be referred to as the "counterclockwise direction"). In other words, the rotation mechanism 21 rotates the substrate 2 only in the counterclockwise direction when printing on the substrate 2. The counterclockwise direction in this embodiment is a predetermined first direction.

[0035] In this embodiment, the length of the print medium 2 (length in the direction of the axis) is longer than the width of the head 3 in the front-to-rear direction. Therefore, when printing on the print medium 2, the table 5 is moved in stages in the front-to-rear direction (sub-scanning direction). The length of the print medium 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.

[0036] 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.

[0037] 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 according to the length of the substrate 2.

[0038] 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.

[0039] 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.

[0040] 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 and irradiates the substrate 2 with ultraviolet light from the left side. 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.

[0041] (How to set the origin position of the printing substrate) FIG. 7 is a diagram for explaining a method for setting a printing origin for aligning the origin position of the printing medium 2 in the rotation direction of the printing medium 2 in the printing apparatus 1 shown in FIG.

[0042] Before printing on the substrate 2 with the printer 1, a printing origin is set to align the origin position of the substrate 2 with respect to the head 3 in the direction of rotation of the substrate 2. An origin mark 2a, which is the target origin position, is marked on the outer circumferential surface of the substrate 2 (see Figure 7). When setting the printing origin, the operator manually operates the jog key provided on the operation panel of the printer 1 to gradually rotate the substrate 2 at a low speed (see Figure 7(B)).

[0043] Furthermore, when setting the printing origin, the operator rotates and stops the printing medium 2 while visually checking the position where the light emitted from the pointer 17 illuminates the origin mark 2a while irradiating the outer peripheral surface of the printing medium 2 with light emitted from the pointer 17 (see FIG. 7(C)). Once the printing medium 2 has been rotated and stopped to the position where the light emitted from the pointer 17 illuminates the origin mark 2a, the operator performs a predetermined operation to reset the encoder 32. Once the encoder 32 has been reset, setting of the printing origin is complete.

[0044] As described above, the rotation mechanism 21 rotates the substrate 2 only in the counterclockwise direction (counterclockwise when viewed from the front) when printing on the substrate 2 (see the arrow in FIG. 7(A)). Also, when setting the printing origin, if the operator operates the jog key, the rotation mechanism 21 rotates the substrate 2 in the counterclockwise direction (see the arrow in FIG. 7(B)). In other words, when setting the printing origin, the rotation mechanism 21 rotates the substrate 2 in the same direction as the rotation direction of the substrate 2 during printing.

[0045] (Printing device control method) Fig. 8 is a flowchart illustrating an example of a method for controlling the printing device 1 when printing on a substrate 2 using the printing device 1 shown in Fig. 1. Fig. 9 is a timing chart illustrating the ink ejection timing and the like when printing on a substrate 2 using the printing device 1 shown in Fig. 1.

[0046] As described above, when printing is performed on the print substrate 2 by the printing device 1, print data sent from the PC 18 is input to the control unit 14. Also, as described above, print data is set for each head 3, and when printing is performed on the print substrate 2, the print data set for each head 3 is input to the control unit 14. The print data in this embodiment includes, for example, data for one of the four heads 3 that will perform printing, data on the resolution of the image, etc., printed on the outer peripheral surface of the print substrate 2 by this head 3, and data on the viscosity of the ink ejected from this head 3. Below, an example of a method for controlling the printing device 1 when printing on the print substrate 2 using multiple heads 3 with the stage 6 stopped (i.e., with the print substrate 2 positioned at a predetermined position in the front-to-rear direction) will be described.

[0047] When printing on the substrate 2 using multiple heads 3 while the stage 6 is stopped, as shown in Fig. 8, the control unit 14 first receives print data (step S1). Then, the control unit 14 selects the head 3 that will immediately perform printing based on the received print data, moves the carriage 7 to a position where the selected head 3 is positioned directly above the substrate 2, and stops it (step S2). The control unit 14 also calculates, based on the print data, the optimal rotation speed of the motor 25 when printing with the selected head 3, and stores the calculated rotation speed (step S3). That is, in step S3, the control unit 14 calculates and stores the optimal rotation speed of the substrate 2 when printing with the selected head 3 based on the print data.

[0048] In step S3, the control unit 14 calculates the optimal rotation speed of the motor 25, for example, depending on the resolution of the image, etc. to be printed on the outer peripheral surface of the print medium 2 by the head 3 selected in step S2, the viscosity of the ink ejected from this head 3, etc. For example, as the resolution of the image, etc. to be printed on the outer peripheral surface of the print medium 2 by the selected head 3 increases, the optimal rotation speed of the motor 25 calculated in step S3 decreases. Also, for example, as the viscosity of the ink ejected from the selected head 3 increases, the optimal rotation speed of the motor 25 calculated in step S3 decreases.

[0049] Thereafter, the control unit 14 ejects ink from the head 3 selected in step S2 to print on the print substrate 2 while rotating the motor 25 at the rotation speed calculated in step S3 (step S4). Thereafter, the control unit 14 receives print data for printing with a head 3 different from the head 3 selected in step S2 (step S5). Thereafter, the control unit 14 selects a head 3 that will immediately perform printing based on the print data received in step S5, and moves the carriage 7 to a position where the selected head 3 is positioned directly above the print substrate 2 and stops it (step S6).

[0050] Furthermore, based on the print data received in step S5, control unit 14 calculates the optimum rotation speed of motor 25 when printing with the selected head 3 (step S7). In step S7, control unit 14 calculates the optimum rotation speed of motor 25, similar to step S3. Thereafter, control unit 14 compares the rotation speed of motor 25 calculated in step S7 with the rotation speed of motor 25 stored in step S3 (step S8), and determines whether the two compared rotation speeds are the same (step S9).

[0051] If the two rotation speeds compared in step S9 are different, the control unit 14 changes the rotation speed of the motor 25 stored in the control unit 14 to the rotation speed calculated in step S7 and stores it (step S10). On the other hand, if the two rotation speeds compared in step S9 are the same, the rotation speed of the motor 25 stored in the control unit 14 is maintained as is (step S11). Thereafter, the control unit 14 ejects ink from the head 3 selected in step S6 to print on the print medium 2 while rotating the motor 25 at the rotation speed stored in step S10 or the rotation speed maintained in step S11 (i.e., at the rotation speed calculated in step S7) (step S12).

[0052] Thereafter, the control unit 14 determines whether printing by all heads 3 used in printing the current print medium 2 (i.e., printing the print medium 2 while the stage 6 is stopped) has finished (step S13). If printing by all heads 3 has finished in step S13, printing of the print medium 2 using multiple heads 3 while the stage 6 is stopped is finished. On the other hand, if printing by all heads 3 has not finished in step S13, the process returns to step S5.

[0053] After printing on the print medium 2 using multiple heads 3 has started with the stage 6 stopped, at least in the first step S13, it is determined that printing by all heads 3 has not been completed, and the process returns to step S5. In step S8 after step S13, the rotation speed of the motor 25 stored in step S10 or the rotation speed maintained in step S11 is compared with the rotation speed of the motor 25 calculated in the immediately preceding step S7.

[0054] In this embodiment, as described above, the length of the print medium 2 (length in the axial direction) is longer than the front-rear width of the head 3. Therefore, if printing on the entire print medium 2 has not been completed, when printing on the print medium 2 according to the control flow shown in Fig. 8 is completed, the control unit 14 moves the stage 6 in the front-rear direction (i.e., moves the print medium 2 in the front-rear direction), and then prints on the print medium 2 according to the control flow shown in Fig. 8.

[0055] As described above, in this embodiment, the control unit 14 calculates the optimal rotation speed of the motor 25 based on the print data, and rotates the motor 25 at the calculated rotation speed when printing on the print substrate 2. Specifically, the control unit 14 calculates the optimal rotation speed of the motor 25 based on the print data set for the head 3 located directly above the print substrate 2, and rotates the motor 25 at the calculated rotation speed when printing on the print substrate 2. In other words, the control unit 14 controls the rotation speed of the motor 25 based on the input print data when printing on the print substrate 2. Specifically, the control unit 14 controls the rotation speed of the motor 25 based on the print data set for the head 3 located directly above the print substrate 2 when printing on the print substrate 2.

[0056] In steps S4 and S12, 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 selected head 3 based on the output signal of the encoder 32 (see FIG. 9). Specifically, the control unit 14 generates the ejection trigger signal when the count number of encoder pulses reaches a predetermined value. The control unit 14 also sends a drive signal to the piezoelectric element 16 for ejecting ink from the nozzle 3a, starting from the ejection trigger signal. Specifically, the control unit 14 sends a drive signal to the piezoelectric element 16 for ejecting one dot of ink from the nozzle 3a, starting from the ejection trigger signal, and ejects ink from the nozzle 3a.

[0057] 9, the control unit 14 sets a discharge flag starting from the discharge trigger signal, and clears the flag when transmission of the drive signal to the piezoelectric element 16 is completed. If the rotation speed of the motor 25 and the rotation speed of the printing medium 2 are normal, the discharge flag is cleared and the next discharge trigger is generated. On the other hand, if the rotation speed of the motor 25 increases for some reason (see part E in FIG. 9), the next discharge trigger is generated while the discharge flag is set. If the next discharge trigger is generated while the discharge flag is set, the control unit 14 sets an error flag and executes a predetermined error process.

[0058] (Main effect of this form) As described above, in this embodiment, print data for printing on the print substrate 2 is input to the control unit 14, and the print data includes data on the resolution of the image, etc., to be printed by the head 3, data on the viscosity of the ink ejected from the head 3, and the like. Therefore, in this embodiment, the control unit 14 can determine, based on the input print data, the resolution of the image, etc., to be printed on the outer peripheral surface of the print substrate 2 and the viscosity of the ink used to print on the print substrate 2. Also, in this embodiment, the control unit 14 calculates, based on the input print data, the optimal rotation speed of the motor 25 (the rotation speed of the print substrate 2) when printing with the head 3, and rotates the motor 25 and the print substrate 2 at the calculated rotation speed when printing on the print substrate 2. That is, in this embodiment, the control unit 14 controls the rotation speed of the motor 25 and the print substrate 2 based on the print data when printing on the print substrate 2.

[0059] Therefore, in this embodiment, when the resolution of the image, etc. printed on the outer peripheral surface of the print substrate 2 is high or when the viscosity of the ink used is high, it is possible to slow down the rotation speed of the motor 25 and slow down the rotation speed of the print substrate 2. Also, in this embodiment, when the resolution of the image, etc. printed on the outer peripheral surface of the print substrate 2 is low or when the viscosity of the ink used is low, it is possible to increase the rotation speed of the motor 25 and speed up the rotation speed of the print substrate 2. Therefore, in this embodiment, it is possible to shorten the printing time required to print on the print substrate 2 while ensuring the print quality of the print substrate 2.

[0060] In this embodiment, when printing on the print substrate 2, the control unit 14 controls the rotation speed of the motor 25 based on print data set for the head 3 placed directly above the print substrate 2. That is, in this embodiment, the control unit 14 controls the rotation speed of the motor 25 based on print data set for the head 3 that actually ejects ink. Therefore, in this embodiment, even when printing on the print substrate 2 using multiple heads 3, it is possible to shorten the printing time required to print on the print substrate 2 while ensuring the print quality of the print substrate 2.

[0061] In this embodiment, when the printing origin is set, the rotation mechanism 21 rotates the printing substrate 2 in the same direction as the rotation direction of the printing substrate 2 during printing. Therefore, in this embodiment, when printing on the printing substrate 2, the influence of backlash in the gear train 33 is suppressed, and it is possible to start rotation of the printing substrate 2 from the origin position with high accuracy. Therefore, in this embodiment, it is possible to improve the printing quality of the printing substrate 2.

[0062] In this embodiment, the control unit 14 executes error processing when the next ejection trigger is generated while the ejection in progress flag is set, as shown in Fig. 9. Therefore, in this embodiment, if the rotation speed of the motor 25 increases for some reason and the ink landing position is shifted, it is possible to stop printing on the print medium 2. Therefore, in this embodiment, it is possible to prevent printing defects from occurring on the print medium 2.

[0063] (Example 1 of a change in the printing device control method)

[0064] In the above-described embodiment, printing on the print substrate 2 may be performed using only one head 3 with the stage 6 stopped. In this case, when step S4 in the flowchart shown in FIG. 8 is completed, printing on the print substrate 2 with the stage 6 stopped is completed. Also, in this case, the control unit 14 does not need to store the calculated rotation speed of the motor 25 in step S3. Even in this case, since the control unit 14 controls the rotation speed of the motor 25 based on the print data when printing on the print substrate 2, it is possible to shorten the printing time required to print on the print substrate 2 while ensuring the print quality of the print substrate 2.

[0065] (Example 2 of a change in the printing device control method) As described above, the underside of the head 3 has multiple nozzle rows 3b arranged in the left-right direction. In the above-described embodiment, when printing on the substrate 2, the print data transmitted from the PC 18 to the control unit 14 and input may be set for each nozzle row 3b. That is, when printing on the substrate 2, print data set for each nozzle row 3b may be input to the control unit 14. In this case, the print data may include, for example, data for one of the multiple nozzle rows 3b that will perform printing, data on the resolution of the image printed on the outer peripheral surface of the substrate 2 by this nozzle row 3b, and data on the viscosity of the ink ejected from this nozzle row 3b. Hereinafter, with reference to the flowchart shown in FIG. 8 , a method for controlling the printing device 1 when printing on the substrate 2 using multiple nozzle rows 3b while the stage 6 is stopped will be described as a control method for the printing device 1 according to Modification 2.

[0066] In this modified example, when the control unit 14 receives print data in step S1 of the flowchart shown in Fig. 8, in step S2, the control unit 14 selects the nozzle row 3b that will immediately execute printing based on the received print data, and moves and stops the carriage 7 to a position where the selected nozzle row 3b is positioned directly above the print substrate 2. In addition, in step S3, the control unit 14 calculates the optimal rotation speed of the motor 25 when printing with the selected nozzle row 3b based on the print data, and stores the calculated rotation speed. In step S3, the control unit 14 calculates the optimal rotation speed of the motor 25 based on, for example, the resolution of an image to be printed on the outer peripheral surface of the print substrate 2 by the nozzle row 3b selected in step S2, the viscosity of the ink ejected from this nozzle row 3b, and the like.

[0067] Then, in step S4, the control unit 14 ejects ink from the nozzle row 3b selected in step S2 to print on the print substrate 2 while rotating the motor 25 at the rotation speed calculated in step S3. Then, in step S5, the control unit 14 receives print data for printing with a nozzle row 3b different from the nozzle row 3b selected in step S2. Then, in step S6, the control unit 14 selects the nozzle row 3b that will immediately perform printing based on the print data received in step S5, and moves and stops the carriage 7 to a position where the selected nozzle row 3b is positioned directly above the print substrate 2.

[0068] Furthermore, in step S7, the control unit 14 calculates the optimum rotation speed of the motor 25 when printing is performed with the selected nozzle row 3b, based on the print data received in step S5. Thereafter, the control unit 14 executes steps S8 to S11, as in the embodiment described above, and then in step S12, ejects ink from the nozzle row 3b selected in step S6 to print on the print medium 2 while rotating the motor 25 at the rotation speed stored in step S10 or the rotation speed maintained in step S11 (i.e., at the rotation speed calculated in step S7).

[0069] Thereafter, in step S13, the control unit 14 determines whether printing by all nozzle rows 3b used in the current printing of the print substrate 2 (i.e., printing of the print substrate 2 performed with the stage 6 stopped) has been completed. If printing by all nozzle rows 3b has been completed in step S13, printing of the print substrate 2 using the multiple nozzle rows 3b with the stage 6 stopped is completed. On the other hand, if printing by all nozzle rows 3b has not been completed in step S13, the process returns to step S5.

[0070] Thus, in this modified example, the control unit 14 calculates the optimum rotation speed of the motor 25 based on the print data set for the nozzle row 3b arranged directly above the print substrate 2, and rotates the motor 25 at the calculated rotation speed when printing on the print substrate 2. In other words, the control unit 14 controls the rotation speed of the motor 25 based on the print data set for the nozzle row 3b arranged directly above the print substrate 2 when printing on the print substrate 2.

[0071] In this modified example, even if printing on the substrate 2 is performed using multiple nozzle rows 3b, the control unit 14 controls the rotation speed of the motor 25 based on the printing data set for the nozzle row 3b that actually ejects ink, so even if printing on the substrate 2 is performed using multiple nozzle rows 3b, it is possible to shorten the printing time required to print the substrate 2 while ensuring the printing quality of the substrate 2.

[0072] In this modified example, the heads 3 mounted on the carriage 7 may include a head 3 having only one nozzle row 3b formed therein. Also, in this modified example, the number of heads 3 mounted on the carriage 7 may be one. In this case, multiple nozzle rows 3b are formed in the head 3. In other words, in this modified example, it is sufficient that the total number of nozzle rows 3b formed in all heads 3 mounted on the carriage 7 (i.e., one or multiple heads 3) is two or more.

[0073] (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 within the scope of the present invention.

[0074] 10, instead of the gear train 33, the power transmission mechanism 26 may include a toothed pulley 43 fixed to the output shaft of the motor 25, a toothed pulley 44 fixed to the first rotating part 27, and a toothed belt 45 stretched around the toothed pulleys 43 and 44. In the above-described embodiment, when the printing origin is set, the rotation mechanism 21 rotates the printing medium 2 in the same direction as the rotation direction of the printing medium 2 during printing. Therefore, even in this case, when printing on the printing medium 2, it is possible to suppress the effects of backlash of the toothed pulleys 43 and 44 and the toothed belt 45 and to start rotation of the printing medium 2 accurately from the origin position.

[0075] In the above-described embodiment, the rotation mechanism 21 may rotate the substrate 2 only in a clockwise direction when viewed from the front (hereinafter, this direction will be referred to as the "clockwise direction") when printing on the substrate 2. In this case, when setting the printing origin, it is preferable that the rotation mechanism 21 rotates the substrate 2 in the same clockwise direction as the rotation direction of the substrate 2 during printing. Also, as in the above-described embodiment, if the rotation mechanism 21 rotates the substrate 2 only in a counterclockwise direction when printing on the substrate 2, the rotation mechanism 21 may also rotate the substrate 2 in a clockwise direction when setting the printing origin. Furthermore, in the above-described embodiment, the rotation mechanism 21 may rotate the substrate 2 in both the counterclockwise and clockwise directions when printing on the substrate 2.

[0076] In the above-described embodiment, the printing data input to the control unit 14 does not have to include data on the resolution of the image, etc., printed on the outer peripheral surface of the substrate 2 by the head 3, or data on the viscosity of the ink ejected from the head 3. Also, in the above-described embodiment, if the printing device 1 only prints on substrates 2 having a fixed outer diameter, the vertical position of the ultraviolet irradiator 22 does not have to be adjustable. Furthermore, in the above-described embodiment, if the printing device 1 only prints on substrates 2 having a cylindrical outer shape, the tilt of the rotation mechanism 21 with respect to the horizontal when viewed from the left and right does not have to be adjustable, and the tilt of the ultraviolet irradiator 22 with respect to the axis of the substrate 2 when viewed from the top and bottom does not have to be adjustable.

[0077] In the above-described embodiment, the ultraviolet irradiation device 4 may be placed on the table 5 so that the direction of the axis of the print medium 2 when viewed from the top-bottom direction coincides with the left-right direction. Also, in the above-described embodiment, the ultraviolet irradiator 22 may be disposed below the print medium 2. Furthermore, 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]

[0078] 1 Printing device 2 Printing material 3 heads (inkjet heads) 3a nozzle 3b Nozzle row 7 Carriage 11 Carriage drive mechanism 14 Control Unit 16 Piezoelectric element (ejection energy generating element) 17 Pointer 21 Rotation mechanism 25 motor 26 Power transmission mechanism 32 Encoder 33 Gear train 43, 44 Toothed pulley 45 Toothed belt

Claims

1. A printing device for printing on the outer peripheral surface of a printing object having a cylindrical, truncated conical or conical outer shape, a rotation mechanism that holds the medium to be printed and rotates the medium around an axis of the medium, an inkjet head that is disposed above the medium to be printed and ejects ink toward the outer peripheral surface of the medium, and a control unit that controls the printing device; the rotation mechanism includes a motor as a drive source and a power transmission mechanism for transmitting power of the motor to the printing medium, and rotates the printing medium when printing is performed on the printing medium; The control unit receives print data for printing on the print medium, The printing device is characterized in that the control unit controls the rotation speed of the motor based on the print data when printing on the printing medium.

2. 2. The printing device according to claim 1, wherein the control unit calculates an optimal rotation speed of the motor based on the print data, and rotates the motor at the calculated rotation speed when printing on the printing medium.

3. a carriage on which the inkjet heads are mounted; and a carriage drive mechanism that moves the carriage in a direction perpendicular to an axis of the medium to be printed when viewed from above; the print data is set for each of the inkjet heads, 3. The printing device according to claim 1, wherein the control unit controls the rotation speed of the motor based on the print data set for the inkjet head positioned directly above the printing medium when printing on the printing medium.

4. a carriage on which one or more of the inkjet heads are mounted, and a carriage drive mechanism that moves the carriage in a direction perpendicular to the axis of the medium to be printed when viewed from above, A plurality of nozzles for ejecting ink are formed on the bottom surface of the inkjet head, a nozzle row is formed on the lower surface of the inkjet head by a plurality of the nozzles arranged in a direction of an axis of the printing medium when viewed from above and below; the total number of nozzle rows formed in all of the inkjet heads mounted on the carriage is two or more; the print data is set for each of the nozzle rows, 3. The printing device according to claim 1, wherein the control unit controls the rotation speed of the motor based on the print data set for the nozzle row positioned directly above the printing medium when printing on the printing medium.

5. 3. The printing device according to claim 1, wherein the rotation mechanism rotates the substrate only in a predetermined first direction when printing on the substrate, and rotates the substrate in the first direction when setting a printing origin to align the origin position of the substrate with the inkjet head in the rotation direction of the substrate before printing on the substrate.

6. a pointer that irradiates light onto the outer peripheral surface of the printing medium; 6. The printing apparatus according to claim 5, wherein the power transmission mechanism comprises a gear train or at least two toothed pulleys and a toothed belt wound around the toothed pulleys.

7. the rotation mechanism includes an encoder for detecting a rotational position and a rotational speed of the printing medium; The inkjet head is formed with a plurality of nozzles for ejecting ink, the inkjet head includes a plurality of ejection energy generating elements for ejecting ink from each of the plurality of nozzles; the control unit, when printing on the printing medium, generates an ejection trigger signal for starting the ejection of ink from the nozzle based on the output signal of the encoder, transmits a drive signal to the ejection energy generating element for ejecting ink from the nozzle starting from the ejection trigger signal, sets an ejection in progress flag starting from the ejection trigger signal, and clears the ejection in progress flag when the transmission of the drive signal is completed; If the rotation speed of the motor is normal, the ejection flag is cleared and the next ejection trigger is generated.

3. The printing apparatus according to claim 1, wherein the control unit executes a predetermined error process when the next ejection trigger is generated while the ejection flag is set.

8. A printing device for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated cone or conical outer shape, comprising: a rotation mechanism that holds the printing substrate and rotates the printing substrate around the axis of the printing substrate as the rotation center; and an inkjet head that is disposed above the printing substrate and ejects ink toward the outer peripheral surface of the printing substrate, the rotation mechanism comprising a motor as a drive source and a power transmission mechanism that transmits the power of the motor to the printing substrate; and a control method for a printing device that rotates the printing substrate when printing on the printing substrate, comprising: A control method for a printing device, comprising controlling the rotation speed of the motor based on print data for printing on the printing medium when printing on the printing medium.

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