Printing device, method for controlling printing device, ultraviolet irradiation device, and method for setting body to be printed

Abstract

Provided is a printing device for performing printing on the outer peripheral surface of a body to be printed having a truncated cone shape, wherein the print quality of a body to be printed can be ensured even when printing is performed on the outer peripheral surface of the body to be printed while the body to be printed is being rotated.　When a nozzle row 103b constituted of nozzles actually discharging ink during printing of a body 102 to be printed is an ink discharge nozzle row 103e, a control unit of the printing device moves and stops a carriage on which an inkjet head 103 is mounted so that the ink discharge nozzle row 103e is disposed at a position where a distance l in a main scanning direction between the ink discharge nozzle row 103e and an axial center of the body 102 to be printed satisfies a predetermined relation during printing of the body 102 to be printed.

Description

Printing device, printing device control method, ultraviolet irradiation device, and method for setting a material to be printed

[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.

[0002] The present invention also relates to an ultraviolet irradiation device used in a printing device for printing with ultraviolet-curable ink on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape.The present invention also relates to a printing device equipped with the ultraviolet irradiation device.The present invention further relates to a method for setting a printing substrate in the ultraviolet irradiation device.

[0003] Conventionally, there has been known a printing apparatus for printing using ultraviolet-curable ink on the outer peripheral surface of a printing medium having a cylindrical, truncated conical, or conical outer shape (see, for example, Patent Document 1). The printing apparatus 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.

[0004] In the printing device described in Patent Document 1, an inkjet head is formed with a large number of nozzles that eject ink. The underside of the inkjet head is an ink ejection surface on which a large number of nozzles are formed. A nozzle row is formed on the ink ejection surface by a plurality of nozzles arranged in the sub-scanning direction. The ultraviolet irradiation device includes a rotation mechanism that holds the print medium and rotates the print medium around its axis. The rotation mechanism includes 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 axis of the print medium coincides with the sub-scanning direction when viewed from above.

[0005] 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 peripheral surface of the substrate.

[0006] Also, conventionally, there is known an ultraviolet irradiation device used in a printing apparatus for printing with ultraviolet-curable ink on the outer peripheral surface of a printing medium having a cylindrical, truncated conical, or conical outer shape (see, for example, Patent Document 1). The ultraviolet irradiation device described in Patent Document 1 includes a rotation mechanism that holds the printing medium and rotates the printing medium around its axis, and an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the printing medium to which the ink is attached.

[0007] In the ultraviolet irradiation device described in Patent Document 1, the rotation mechanism includes a first rotating unit that holds one end of the printing medium and rotates together with the printing medium, a first holding unit that rotatably holds the first rotating unit, a motor for rotating the first rotating unit, a power transmission mechanism that connects the first rotating unit to the motor, a second rotating unit that holds the other end of the printing medium and rotates together with the printing medium, and a second holding unit that rotatably holds the second rotating unit. The second holding unit is movable together with the second rotating unit in the axial direction of the printing medium. In the ultraviolet irradiation device described in Patent Document 1, the positions of the second rotating unit and the second holding unit in the axial direction of the printing medium are adjusted depending on the length of the printing medium.

[0008] In a printing device using the ultraviolet irradiation device described in Patent Document 1, when printing on a substrate, ink is ejected from an inkjet head located above the substrate toward the outer surface of the substrate while the substrate is rotated by a rotation mechanism. In this printing device, when printing on the substrate, the timing of ejection of ink from the inkjet head is controlled based on, for example, the detection result of the rotation position of the first rotating part.

[0009] JP 2023-88834 A

[0010] 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 generatrix of the substrate is tilted relative to the substrate's axis. Therefore, when the substrate is viewed in the sub-scanning direction, if ink is ejected at a position offset left or right from the substrate's axis, the vertical distance between the larger outer diameter portion of the substrate and the ink ejection surface of the inkjet head is shorter than the vertical distance between the smaller outer diameter portion and the ink ejection surface. Therefore, when printing is performed on the outer surface of the substrate while rotating it, the ink landing positions in the circumferential direction of the substrate are offset between the larger outer diameter portion and the smaller outer diameter portion. 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 be offset between the larger outer diameter portion and the smaller outer diameter portion. Furthermore, if the ink impact positions are misaligned, there is a risk that the printing accuracy on the printing medium will decrease.

[0011] 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.

[0012] Furthermore, in a printing device that uses the ultraviolet irradiation device described in Patent Document 1, the timing of ink ejection from the inkjet head is controlled based on, for example, the detection results of the rotational position of the first rotating part when printing on a substrate. Therefore, in this printing device, if slippage occurs between the substrate and the first rotating part, which holds one end of the substrate and rotates together with the substrate, and the substrate no longer rotates in accordance with the rotation of the first rotating part, there is a risk that the printing accuracy of the substrate will decrease.

[0013] Therefore, an object of the present invention is to provide an ultraviolet irradiation device used in a printing device for printing with ultraviolet-curable ink on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which can hold the edge of the printing substrate and prevent slippage between the printing substrate and a rotating part that rotates together with the printing substrate. Another object of the present invention is to provide a printing device equipped with such an ultraviolet irradiation device. A further object of the present invention is to provide a method for setting a printing substrate in such an ultraviolet irradiation device.

[0014] 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 (Hz). 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 material is r ２ (mm), and the vertical distance between the part 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 ink ejection surface and the part of the smallest outer diameter where ink ejected from the nozzles that make up the ink ejection nozzle row lands is l ｇ２ (mm), the direction of the generatrix of the printing substrate is the generatrix direction, and the width of the image printed on the printing substrate 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:

[0015] 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 (dpi). 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 material is r ２ (mm), and the vertical distance between the part 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 ink ejection surface and the part of the smallest outer diameter where ink ejected from the nozzles that make up the ink ejection nozzle row lands is l ｇ２ (mm), the direction of the generatrix of the printing substrate is the generatrix direction, and the width of the image printed on the printing substrate 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.

[0016] In this invention, if the nozzle array consisting of nozzles that actually eject ink when printing on a 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 peripheral surface of a print substrate having a truncated cone shape while rotating the print substrate.

[0017] 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.

[0018] 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, causes the nozzle to eject ink 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, causes the ejection timing of ink from the nozzle to be earlier than 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, causes the ejection timing of ink from the nozzle to be later than 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.

[0019] 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 printing substrate decreases. As the size of one ink dot after landing on the printing substrate decreases, print quality is more likely to deteriorate even if the deviation of the ink landing position in the circumferential direction of the printing 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 printing substrate, regardless of the size of one ink dot after landing on the printing substrate.

[0020] In addition, in order to solve the above-mentioned problems, the ultraviolet irradiation device of the present invention is an ultraviolet irradiation device used in a printing device for printing with ultraviolet-curable ink on the outer peripheral surface of a printing medium having a cylindrical, truncated conical or conical outer shape, and is equipped with a rotation mechanism that holds the printing medium and rotates the printing medium around the axial center of the printing medium as the rotation center, and an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the printing medium to which the ink is attached, and the rotation mechanism is equipped with a rotating part that holds an end of the printing medium in the direction of the axial center of the printing medium and rotates together with the printing medium, and the end of the printing medium held in the rotating part is formed in a cylindrical shape, and the rotating part is equipped with a head and an axis the head, the retaining member, the contact member, and the nut are arranged in this order in the axial direction of the shaft; when the nut is turned in a direction that brings the head and the nut closer together, the retaining member elastically deforms and the outer diameter of the retaining member expands; and when the nut is turned in a direction that brings the head and the nut apart, the shape of the retaining member is restored and the outer diameter of the retaining member contracts.

[0021] In the ultraviolet irradiation device of the present invention, the rotating part that holds the end of the printing medium and rotates together with the printing medium includes a headed screw and nut, a holding member made of an annular elastic body whose outer surface contacts the inner surface of the printing medium, and an annular contact member that contacts the holding member. Also, in this invention, the screw head, holding member, contact member, and nut are arranged in this order in the axial direction of the screw shaft. Furthermore, in this invention, when the nut is turned in a direction that brings the head and nut closer together, the holding member elastically deforms, widening its outer diameter, and when the nut is turned in a direction that moves the head and nut apart, the holding member restores its original shape, narrowing its outer diameter.

[0022] Therefore, according to the present invention, by turning the nut in the direction that brings the head and the nut closer together to widen the outer diameter of the holding member, it is possible to increase the contact pressure between the outer surface of the holding member that contacts the inner surface of the substrate and the inner surface of the substrate. Therefore, according to the present invention, it is possible to suppress slippage between the substrate and the rotating part that holds the end of the substrate and rotates together with the substrate. Furthermore, according to the present invention, it is possible to change the outer diameter of the holding member depending on the position of the nut relative to the head, so it is possible to increase the contact pressure between the outer surface of the holding member and the inner surface of the substrate even if the inner diameter of the substrate changes. Therefore, according to the present invention, it is possible to suppress slippage between the rotating part and the substrate even if the inner diameter of the substrate changes.

[0023] In addition, in the present invention, when one axial side of the shaft portion is defined as the first direction side and the opposite side from the first direction side is defined as the second direction side, the head contacts the holding member from the first direction side, the contact member contacts the holding member from the second direction side, and the second direction side of the head preferably has a first tapered surface whose outer diameter tapers toward the second direction side, the first direction side of the contact member preferably has a second tapered surface whose outer diameter tapers toward the first direction side, and the holding member preferably has a third tapered surface that can contact the first tapered surface and a fourth tapered surface that can contact the second tapered surface. This configuration allows the outer diameter of the holding member to be uniformly widened or narrowed around the entire circumferential area of ​​the holding member when the nut is turned. This allows for precise alignment of the axis of the rotating part and the axis of the printing medium.

[0024] The holding member of the present invention may be made of rubber, for example.

[0025] Furthermore, the present invention may be configured such that, for example, when one side of the axis of the printed material is the third direction side, the rotation mechanism includes a rotating unit that holds the end of the printed material on the third direction side, a first holding unit that rotatably holds the rotating unit, a motor for rotating the rotating unit, and a power transmission mechanism that connects the rotating unit and the motor, and the rotating unit includes an annular ring member that contacts the end face of the printed material on the third direction side.

[0026] Furthermore, the present invention may be configured such that, for example, the side opposite the third direction side is the fourth direction side, the rotation mechanism includes a second rotating unit that holds the other end of the printed material on the fourth direction side and rotates together with the printed material, and a second holding unit that rotatably holds the second rotating unit, the second holding unit being movable together with the second rotating unit toward the axis of the printed material, and the positions of the second rotating unit and the second holding unit in the axis of the printed material are adjustable. In this case, the positions of the second rotating unit and the second holding unit in the axis of the printed material are adjusted according to the length of the printed material. Furthermore, in this case, it is possible to attach the end of the printed material to the rotating unit while moving the second rotating unit away from the rotating unit, and then move the second rotating unit and the second holding unit to attach the end of the printed material to the second rotating unit. This makes it easier to attach the printed material to the rotation mechanism.

[0027] Furthermore, in the present invention, when a direction perpendicular to the axis of the print medium when viewed from the top-bottom direction is defined as the left-right direction, the rotation mechanism includes a guide rail for guiding the second holding part in the direction of the axis of the print medium, a guide block that engages with the guide rail and to which the second holding part is fixed, a slide member that is held by a moving body including the second holding part and the guide block and is movable relative to the moving body in the direction of the axis of the print medium, an engaging member that is held by the slide member and is rotatable with respect to the slide member with the left-right direction as its axial direction, a restricting member for restricting movement of the slide member and the engaging member in the fourth direction, and ... engaging member in the fourth direction relative to the slide member in the rotational direction. a first biasing member that biases the engaging member toward one side of the movable body, a second biasing member that is compressed between the slide member and the movable body, and a slide member regulating portion that regulates the range of movement of the slide member relative to the movable body in the direction of the axis of the printed material, wherein the regulating member has a saw-tooth regulating portion on which a plurality of regulating surfaces are formed that are arranged at a constant pitch in the direction of the axis of the printed material, and the regulating surfaces are inclined surfaces that slope upward as they approach the fourth direction side, the engaging member has an engaging portion that engages with the regulating surface, the first biasing member biases the engaging member in the direction in which the engaging portion faces toward the regulating surface, and the second biasing member biases the movable body from the slide member toward the third direction side.

[0028] With this configuration, by rotating the engaging member in the direction opposite to the direction of biasing by the first biasing member, the engagement between the regulating surface of the regulating member and the engagement portion of the engaging member can be released, allowing the slide member and the engaging member to move in the fourth direction. Therefore, the slide member and the engaging member can be moved in the fourth direction with a simple operation. Furthermore, with this configuration, because the second biasing member biases the moving body in the third direction from the slide member, the biasing force of the second biasing member can press the second rotating portion against the end of the printing medium on the fourth direction side. Therefore, it is possible to increase the holding force of the printing medium held by the first holding portion and the second holding portion.

[0029] The ultraviolet irradiation device of the present invention can also be used in a printing device that includes a table on which the ultraviolet irradiation device is placed and an inkjet head that is disposed above a substrate and ejects ink toward the outer peripheral surface of the substrate. In this printing device, it becomes possible to hold the edge of the substrate and prevent slippage between the substrate and a rotating part that rotates together with the substrate.

[0030] In a method for setting a substrate to be printed on a rotation mechanism in an ultraviolet irradiation device according to the present invention, the sliding member is pushed in the third direction until the second rotating member contacts the fourth direction end of the substrate with the third direction end attached to the rotating member, and then the sliding member is further pushed in the third direction to set the substrate to the rotation mechanism. When the substrate is set on the rotation mechanism using this method, the biasing force of the second biasing member can increase the contact pressure between the fourth direction end of the substrate and the second rotating member and between the third direction end face of the substrate and the annular member of the rotating member. This increases the holding force of the substrate held by the rotating member and the second rotating member.

[0031] 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.

[0032] Furthermore, as described above, the present invention makes it possible, in an ultraviolet irradiation device used in a printing device for printing with ultraviolet-curable ink on the outer surface of a substrate having a cylindrical, truncated cone, or conical outer shape, to hold the edge of the substrate and suppress slippage between the substrate and a rotating part that rotates together with the substrate.

[0033] 1 is a front view illustrating the configuration of a printing device according to a first embodiment of the present invention. FIG. 1 is a block diagram illustrating the configuration of the printing device shown in FIG. 1. (A) is a bottom view of the inkjet head and carriage shown in FIG. 1, and (B) is a bottom view illustrating the configuration of the inkjet head shown in (A). FIG. 1 is a front view illustrating the configuration of the ultraviolet irradiation device shown in FIG. 1. FIG. 4 is a side view illustrating the configuration of the rotation mechanism shown in FIG. 4. FIG. 4 is a side view illustrating the configuration of the rotation mechanism shown in FIG. 4. FIG. 1 is a schematic diagram illustrating the arrangement of a nozzle array when printing on the outer peripheral surface of a truncated cone-shaped print medium using the printing device shown in FIG. 1. FIG. 1 is a schematic diagram illustrating the arrangement of a nozzle array when printing on the outer peripheral surface of a truncated cone-shaped print medium using the printing device shown in FIG. 1. FIG. 1 is a schematic diagram illustrating the arrangement of a nozzle array when printing on the outer peripheral surface of a truncated cone-shaped print medium using the printing device shown in FIG. 1. 19 is a schematic diagram for explaining the arrangement of nozzle rows when printing on the outer peripheral surface of a truncated cone-shaped print medium using the printing apparatus shown in FIG. 1 . 19 is a schematic diagram for explaining the arrangement of nozzle rows when printing on the outer peripheral surface of a truncated cone-shaped print medium using the printing apparatus shown in FIG. 1 . 19 is a timing chart for explaining ink ejection timing when printing on a print medium using the printing apparatus shown in FIG. 1 . 19 is a timing chart for explaining a method of correcting ink ejection timing when printing on a print medium using the printing apparatus shown in FIG. 1 . 19 is a diagram for explaining a method of correcting ink ejection timing when printing on a print medium using the printing apparatus shown in FIG. 1 . 19 is a diagram for explaining a tolerance for deviation of ink landing position according to the size of one dot of ink when printing on a print medium using the printing apparatus shown in FIG. 1 . 19 is a front view for explaining the configuration of a printing apparatus according to a second embodiment of the present invention. 19 is a front view for explaining the configuration of an ultraviolet irradiation device shown in FIG. 18 . 19 is a side view for explaining the configuration of a rotation mechanism shown in FIG. 19 . 19 is a side view for explaining the configuration of a rotation mechanism shown in FIG. 19 .20A is a side view of the second rotating unit shown in FIG. 20, (B) is a side view of the rotating unit shown in FIG. 20, and (C) and (D) are cross-sectional views of the rotating unit shown in (B). A plan view for explaining the configuration of the rotating mechanism shown in FIG. 19. A cross-sectional view of the E-E cross section of FIG. 23. An enlarged plan view for explaining the configuration of part F in FIG. 23. An enlarged plan view for explaining the configuration of part F in FIG. 23. A view for explaining a setting method when setting a printed material in the rotating mechanism shown in FIG. 20.

[0034] First Embodiment A first embodiment of the present invention will be described below with reference to the drawings.

[0035] (Overall Configuration of Printing Apparatus) Fig. 1 is a front view illustrating the configuration of a printing apparatus 101 according to a first embodiment of the present invention. Fig. 2 is a block diagram illustrating the configuration of the printing apparatus 101 shown in Fig. 1. Fig. 3(A) is a bottom view of the inkjet head 103 and carriage 107 shown in Fig. 1, and Fig. 3(B) is a bottom view illustrating the configuration of the inkjet head 103 shown in Fig. 3(A).

[0036] The printing device 101 of this embodiment is a device for printing on the outer peripheral surface of a printing substrate 102 having a cylindrical, truncated conical, or conical outer shape, and is, for example, a commercial inkjet printer. The printing device 101 prints on the outer peripheral surface of the printing substrate 102 using ultraviolet-curable ink. The printing substrate 102 is formed, for example, in a cylindrical shape. That is, the printing substrate 102 is formed in a cylindrical, truncated conical, or conical cylindrical shape. The printing substrate 102 is also formed, for example, from resin. The printing device 101 is capable of printing on multiple types of printing substrates 102 with different outer diameters and lengths.

[0037] The printing device 101 includes an inkjet head 103 (hereinafter referred to as the "head 103") that ejects ultraviolet-curable ink toward the outer peripheral surface of the print substrate 102. The printing device 101 of this embodiment includes multiple heads 103. Specifically, the printing device 101 includes four heads 103. The printing device 101 also includes an ultraviolet irradiation device 104 for curing the ink ejected onto the outer peripheral surface of the print substrate 102, a stage 106 having a table 105 on which the ultraviolet irradiation device 104 is placed, a carriage 107 on which the head 103 is mounted, a Y-bar 108 that holds the carriage 107 so as to enable movement in a main scanning direction perpendicular to the up-down direction (vertical direction), and a main body frame 109 that holds the stage 106 so as to enable movement in a sub-scanning direction perpendicular to the up-down direction and the main scanning direction.

[0038] The printing apparatus 101 also includes a carriage drive mechanism 111 that moves the carriage 107 in the main scanning direction relative to the Y bar 108, a stage drive mechanism 112 that moves the stage 106 in the sub-scanning direction relative to the main body frame 109, a table lifting mechanism 113 that raises and lowers the table 105, and a control unit 114 for controlling the printing apparatus 101. The carriage drive mechanism 111 includes, for example, a motor 115 as a drive source and a power transmission mechanism such as a belt and pulley that transmits the power of the motor 115 to the carriage 107. The stage drive mechanism 112 includes, for example, a motor as a drive source and a power transmission mechanism such as a belt and pulley that transmits the power of the motor to the stage 106. The table lifting mechanism 113 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 105.

[0039] 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 referred to as the "front" side, the X2 direction side in Fig. 5, etc., which is the opposite side, is referred to as the "rear" side, the Y1 direction side in Fig. 4, etc., which is one side of the left-to-right direction, is referred to as the "right" side, and the Y2 direction side in Fig. 4, etc., which is the opposite side, is referred to as the "left" side.

[0040] The upper surface of the table 105 is a plane perpendicular to the up-down direction. The ultraviolet irradiation device 104 placed on the table 105 is arranged below the head 103. The printing medium 102 is held by the ultraviolet irradiation device 104 and arranged below the head 103. In other words, the head 103 is arranged above the printing medium 102. The head 103 ejects ink downward. The ink ejected by the head 103 lands on the outer peripheral surface of the printing medium 102 at the upper end of the printing medium 102.

[0041] The head 103 is formed with a plurality of nozzles 103a that eject ink. Specifically, the large number of nozzles 103a are formed on the bottom surface of the head 103. The bottom surface of the head 103 is an ink ejection surface 103c on which the plurality of nozzles 103a (specifically, the large number of nozzles 103a) are formed. On the ink ejection surface 103c, a nozzle row 103b is formed by the plurality of nozzles 103a arranged in the sub-scanning direction (front-back direction). On the ink ejection surface 103c, a plurality of nozzle rows 103b are formed that are arranged in the main scanning direction (left-right direction). The head 103 is equipped with a plurality of piezoelectric elements (piezo elements) 116 for ejecting ink from each of the plurality of nozzles 103a. In this embodiment, the piezoelectric elements 116 are ejection energy generating elements.

[0042] 3A, for example, three of the four heads 103 mounted on the carriage 107 are disposed at the same position in the front-to-rear direction and are arranged in the left-to-right direction. The remaining head 103 is disposed at a position offset from the three heads 103 in the front-to-rear direction. Three of the four heads 103 eject color inks, and the remaining head 103 ejects white ink. The viscosity of the white ink is higher than the viscosity of the color inks.

[0043] The control unit 114 is electrically connected to a motor 115 and a plurality of piezoelectric elements 116. The control unit 114 is also electrically connected to a PC (personal computer) 118. The PC 118 generates print data for printing on the print substrate 102. When printing on the print substrate 102, the print data generated by the PC 118 is transmitted from the PC 118 to the control unit 114. In other words, when printing on the print substrate 102, the print data transmitted from the PC 118 is input to the control unit 114.

[0044] (Configuration of Ultraviolet Irradiation Device) Fig. 4 is a front view for explaining the configuration of the ultraviolet irradiation device 104 shown in Fig. 1. Figs. 5 and 6 are side views for explaining the configuration of the rotation mechanism 121 shown in Fig. 4.

[0045] The ultraviolet irradiation device 104 includes a rotation mechanism 121 that holds the substrate 102 and rotates it around its axis, an ultraviolet irradiator 122 that irradiates ultraviolet rays toward the outer peripheral surface of the substrate 102 to which ink is attached, and a cover 123 that covers the rotation mechanism 121 and the ultraviolet irradiator 122 from above. The cover 123 has an opening 123a through which the upper end of the substrate 102 is positioned. The ultraviolet irradiation device 104 is placed on the table 105 so that the axis of the substrate 102, as viewed from above, coincides with the front-to-back direction. In other words, the axis of the substrate 102, as viewed from above, coincides with the front-to-back direction. The carriage drive mechanism 111 moves the carriage 107 in a direction perpendicular to the axis of the substrate 102, as viewed from above.

[0046] The rotation mechanism 121 rotates the printing substrate 102 when printing on the printing substrate 102. In this embodiment, printing is performed on the printing substrate 102 while the rotation mechanism 121 rotates the printing substrate 102 with the carriage 107 stopped at a fixed position. When printing on the printing substrate 102, the rotation mechanism 121 rotates the printing substrate 102, for example, counterclockwise when viewed from the front. Also, in this embodiment, the length (length in the direction of the axis) of the printing substrate 102 is longer than the width of the head 103 in the front-to-rear direction. Therefore, when printing on the printing substrate 102, the table 105 is moved in stages in the front-to-rear direction (sub-scanning direction). Note that the length of the printing substrate 102 may be equal to the width of the head 103 in the front-to-rear direction, or may be shorter than the width of the head 103 in the front-to-rear direction.

[0047] The rotation mechanism 121 includes a motor 125 as a drive source and a power transmission mechanism 126 for transmitting the power of the motor 125 to the printing substrate 102. The rotation mechanism 121 also includes a first rotating unit 127 that holds one end of the printing substrate 102, a first holding unit 128 that rotatably holds the first rotating unit 127, a second rotating unit 129 that holds the other end of the printing substrate 102, a second holding unit 130 that rotatably holds the second rotating unit 129, a rotating frame 131 to which the first holding unit 128 and the second holding unit 130 are attached, and an encoder 132 for detecting the rotational position and rotational speed of the printing substrate 102. The motor 125 and the encoder 132 are electrically connected to the control unit 114. Note that the power transmission mechanism 126 and other components are not shown in FIG. 4.

[0048] The first rotating unit 127 and the second rotating unit 129 rotate together with the printing substrate 102. The first rotating unit 127 holds the rear end of the printing substrate 102, and the second rotating unit 129 holds the front end of the printing substrate 102. The power transmission mechanism 126 connects the first rotating unit 127 to the motor 125. The power transmission mechanism 126 includes a gear train 133. The gear train 133 includes a drive gear fixed to the output shaft of the motor 125 and a driven gear fixed to the first rotating unit 127. The encoder 132 is connected to the rear end of the first rotating unit 127. The second holding unit 130 is movable in the direction of the axis of the printing substrate 102. In this embodiment, the positions of the second rotating unit 129 and the second holding unit 130 in the direction of the axis of the printing substrate 102 are adjusted depending on the length of the printing substrate 102. The power transmission mechanism 126 may be configured by a pulley, a belt, or the like.

[0049] The rotating frame 131 is rotatable relative to a lower frame 134 that constitutes the bottom surface of the ultraviolet irradiation device 104, with the left-right direction as the rotation axis. The rotating frame 131 is also rotatable relative to the lower frame 134, with the rear end of the rotating frame 131 as the rotation center. In this embodiment, by rotating the rotating frame 131 relative to the lower frame 134, it is possible to adjust the inclination of the rotation mechanism 121 relative to the horizontal direction when viewed from the left-right direction. In other words, by rotating the rotating frame 131 relative to the lower frame 134, it is possible to adjust the inclination of the axis of the printing medium 102 relative to the horizontal direction.

[0050] In this embodiment, when printing on a printing substrate 102 having a cylindrical outer shape, the axis of the printing substrate 102 is aligned with the front-to-rear direction (see FIG. 5). On the other hand, when printing on a printing substrate 102 having a truncated cone or conical outer shape, the axis of the printing substrate 102 is tilted relative to the front-to-rear direction (see FIG. 6). In other words, the tilt of the rotation mechanism 121 is adjusted when printing on the outer peripheral surface of a printing substrate 102 having a truncated cone or conical outer shape. Specifically, the tilt of the rotation mechanism 121 is adjusted so that the top end of the printing substrate 102 is parallel to the front-to-rear direction.

[0051] The ultraviolet irradiator 122 is equipped with an LED substrate on which a large number of LED chips that emit ultraviolet light are mounted. The ultraviolet irradiator 122 is disposed on the left side of the substrate 102. The ultraviolet irradiator 122 irradiates the substrate 102 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 122 is adjustable. In addition, the horizontal position of the ultraviolet irradiator 122 and the inclination of the ultraviolet irradiator 122 with respect to the axis of the substrate 102 when viewed from the vertical direction are adjustable. In this embodiment, when printing on a substrate 102 that has a cylindrical outer shape, the ultraviolet irradiator 122 is installed so that the ultraviolet light emission surface of the ultraviolet irradiator 122 is parallel to the front-to-rear direction. In addition, when printing on a substrate 102 having a truncated cone or conical outer shape, the inclination of the ultraviolet irradiator 122 is adjusted so that the ultraviolet light emission surface of the ultraviolet irradiator 122 is parallel to the left edge of the substrate 102.

[0052] (Arrangement of nozzle rows when printing on a truncated cone-shaped print medium) Figures 7 to 13 are schematic diagrams for explaining the arrangement of nozzle rows 103b when printing on the outer peripheral surface of a truncated cone-shaped print medium 102 using the printing device 101 shown in Figure 1. Note that Figure 9 is an enlarged view of part E in Figure 8.

[0053] When printing on the outer peripheral surface of a print substrate 102 having a truncated cone-shaped outer surface using the printing device 101, the tilt of the rotation mechanism 121 is adjusted so that the top edge of the print substrate 102 is parallel to the front-to-rear direction, as described above. For example, as shown in FIG. 7 , the axis of the print substrate 102 is tilted by α (degrees) relative to the front-to-rear direction. The following describes the arrangement of the nozzle array 103b when printing on the outer peripheral surface of the truncated cone-shaped print substrate 102 using the printing device 101. In the following description, the nozzle array 103b composed of the nozzles 103a that actually eject ink when printing on the print substrate 102 is referred to as the "ink ejection nozzle array 103e." In this embodiment, there are multiple ink ejection nozzle arrays 103e. For example, there are two ink ejection nozzle arrays 103e, and ink is ejected from both ink ejection nozzle arrays 103e toward the outer peripheral surface of the print substrate 102. In the following description, the circumferential direction of the print substrate 102 is referred to as the "circumferential direction."

[0054] When printing is performed on the outer peripheral surface of a print medium 102 having a truncated cone-shaped outer shape using the printing device 101, the direction of the generatrix of the print medium 102 is inclined with respect to the axis of the print medium 102, so that at a position offset from the axis of the print medium 102 in the left-right direction when viewed from the front-to-back direction, the vertical distance between the portion of the print medium 102 with a larger outer diameter and the ink ejection surface 103c of the head 103 is shorter than the vertical distance between the portion of the print medium 102 with a smaller outer diameter and the ink ejection surface 103c. Therefore, if printing is performed on the outer peripheral surface of the print medium 102 while rotating the print medium 102 with the ink ejection nozzle row 103e offset from the axis, the landing position of the ink will be offset in the circumferential direction between the portion of the print medium 102 with a larger outer diameter and the portion of the print medium 102 with a smaller outer diameter. Furthermore, in the case of a printing medium 102 having an outer shape shaped like a truncated cone, the direction of the generatrix of the printing medium 102 is inclined with respect to the axis of the printing medium 102, and this inclination also causes the ink landing positions to deviate in the circumferential direction between the portions of the printing medium 102 with a large outer diameter and the portions of the printing medium 102 with a small outer diameter. If these deviations in the ink landing positions occur, there is a risk that the printing accuracy of the printing medium 102 will decrease.

[0055] The part of the printing medium 102 with the largest outer diameter is defined as a maximum outer diameter part 102a, the part of the printing medium 102 with the smallest outer diameter is defined as a minimum outer diameter part 102b, and the resolution of the image P printed on the printing medium 102 is defined as R (dpi (dots per In this embodiment, when the diameter of the ink droplets 103e is set to 1 / 2 the dot pitch of the resolution R, the deviation in the circumferential direction between the landing position of the ink droplets 103e on the maximum outer diameter portion 102a and the landing position of the ink droplets 103e on the minimum outer diameter portion 102b is suppressed to less than half the dot pitch of the resolution R. Specifically, in order to ensure the print quality of the print medium 102, the ink ejection nozzle row 103e is positioned so that the distance l (mm) in the main scanning direction (left-right direction) between the ink ejection nozzle row 103e and the axis of the print medium 102 satisfies the following relationship when printing on the print medium 102. In other words, the control unit 114 moves and stops the carriage 107 so that the ink ejection nozzle row 103e is positioned so that the distance l satisfies the following relationship when printing on the print medium 102:

[0056] Here, e ｔis the distance (mm) of half the dot pitch of the resolution R of the image P printed on the printing medium 102. １ is the radius r of the maximum outer diameter portion 102a when ink ejected from the ink ejection nozzle row 103e arranged at a position spaced a distance l from the axis of the print medium 102 lands on the outer circumferential surface of the print medium 102. １ and the radius r of the minimum outer diameter portion 102b ２ e is the deviation (mm) of the ink landing position in the circumferential direction due to the difference between ２ is the amount of deviation (mm) of the dot row tilted relative to the axis of the substrate 102 when ink ejected from the ink ejection nozzle row 103e, which is located at a position a distance 1 from the axis of the substrate 102, lands on the outer surface of the substrate 102.

[0057] Furthermore, when printing on the outer peripheral surface of the print medium 102, which has a truncated cone-shaped outer shape, the cause of the circumferential deviation of the ink landing position is that the generatrix of the print medium 102 is inclined relative to the axis of the print medium 102, causing the outer diameter of the print medium 102 to gradually change in the axial direction of the print medium 102, and the generatrix of the print medium 102 is inclined relative to the axis of the print medium 102. Therefore, if the ink ejection nozzle row 103e is positioned at a position where the distance 1 satisfies the above relationship when printing on the print medium 102, the circumferential deviation between the landing position of the ink landing on the maximum outer diameter portion 102a and the landing position of the ink landing on the minimum outer diameter portion 102b can be suppressed to less than half the dot pitch of the resolution R.

[0058] Hereinafter, the deviation amount e １ and the deviation amount e ２ The calculation methods for are explained in the following order. In the following explanation, the center line in the left-right direction of the printing substrate 102 when viewed from the front-to-back direction is defined as the center line CL. The center line CL intersects with the axial center of the printing substrate 102. The length of the printing substrate 102 in the axial direction of the printing substrate 102 is defined as h (mm).

[0059] As shown in FIG. 9, the position where ink ejected from the ink ejection nozzle row 103e arranged at a distance 1 from the axis of the print medium 102 lands on the maximum outer diameter portion 102a is defined as an impact position H1, the position where ink ejected from the ink ejection nozzle row 103e arranged at a distance 1 from the axis of the print medium 102 lands on the minimum outer diameter portion 102b is defined as an impact position H2, and the vertical distance between the top end of the print medium 102 and the ink ejection surface 103c is defined as l. ｇ０ (mm), and the vertical distance between the landing position H1 and the ink ejection surface 103c (i.e., the vertical distance between the portion of the maximum outer diameter part 102a where ink ejected from the nozzles 103a constituting the ink ejection nozzle row 103e lands and the ink ejection surface 103c) is l ｇ１ (mm), and the distance l ｇ１ and distance l ｇ０ The difference between ｇ１ Then, the following relationship holds: Therefore, This becomes:

[0060] The ejection speed of ink ejected from the ink ejection nozzle array 103e (i.e., the ejection speed of ink ejected from the nozzles 103a constituting the ink ejection nozzle array 103e) is V ｆ (mm / sec), the time t １ (sec) is In addition, if the ejection frequency of ink ejected from the ink ejection nozzle row 103e (i.e., the ejection frequency of ink ejected from the nozzles 103a constituting the ink ejection nozzle row 103e) is f (Hz), the circumferential speed (speed in the circumferential direction) of the maximum outer diameter portion 102a is v １ (mm / sec) is The rotation speed N (rev / sec) of the printing medium 102 is given by After ink is ejected from the nozzle 103a of the ink ejection nozzle row 103e, the movement distance x of the maximum outer diameter portion 102a in the circumferential direction until the ink lands at the landing position H1 is １ (mm) is This becomes:

[0061] The peripheral speed (speed in the peripheral direction) of the minimum outer diameter portion 102b is v ２ (mm / sec) is The vertical distance between the landing position H2 and the ink ejection surface 103c (i.e., the vertical distance between the ink ejection surface 103c and the portion of the minimum outer diameter portion 102b where ink ejected from the nozzles 103a constituting the ink ejection nozzle row 103e lands) is set to l ｇ２ (mm), the time t ２ (sec), and the movement distance x of the minimum outer diameter portion 102b in the circumferential direction from when ink is ejected from the nozzle 103a of the ink ejection nozzle row 103e until the ink lands at the landing position H2. ２ (mm) is This becomes:

[0062] From the above, the deviation amount e １ teeth, This becomes:

[0063] Next, the deviation amount e ２ In the following description, as shown in Figures 10 and 11, the direction of the generatrix of the printing medium 102 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 the image P in the generatrix direction is d ｙ The length of the printing medium 102 in the generatrix direction (i.e., the length of the generatrix of the printing medium 102) is b (mm). The distance in the generatrix direction between the part of the image P closest to the maximum outer diameter part 102a and the maximum outer diameter part 102a is l (mm). ｙ That is, the distance l from the maximum outer diameter portion 102a is ｙ Image P is printed at a distance of 1 mm.

[0064] As shown in FIG. 10, the following relationship holds: Also, as shown in FIG. １ When (mm) is specified, Therefore, The radius r of the printing medium 102 at the position where the part of the image P closest to the maximum outer diameter part 102a is placed is ３ (mm) is From equations (2-1) to (2-3), This becomes:

[0065] 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 102b and the maximum outer diameter part 102a is l ｙ１ (mm), The minimum radius r of the printing medium 102 at the position where the portion of the image P closest to the minimum outer diameter portion 102b is placed is ４ (mm) is This becomes:

[0066] As shown in Figure 12, if the axis (center) of the printing medium 102 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 103e in the part of the image P closest to the maximum outer diameter portion 102a, and point B is the point located at the same position in the main scanning direction as the ink ejection nozzle row 103e in the part of the image P closest to the minimum outer diameter portion 102b, the coordinates of points A and B are expressed as follows:

[0067] Angle θ based on the axis (origin) of the printing medium 102 ｔ (deg) and angle θ ｂ (deg) is Angle θ ｔ and angle θ ｂ The difference between this and angle θ ｄ teeth, This becomes:

[0068] As shown in FIG. 13, when a symmetrical development of the printing medium 102 formed in a truncated cone shape is considered, a line passing through points A and B forms an angle θ ｄ The amount of deviation caused by this inclination is the deviation amount e ２ The deviation amount e ２ teeth, This becomes:

[0069] (Correction control of ink ejection timing) Fig. 14 is a timing chart for explaining the ink ejection timing when printing on the print substrate 102 using the printing device 101 shown in Fig. 1. Fig. 15 is a timing chart for explaining a method for correcting the ink ejection timing when printing on the print substrate 102 using the printing device 101 shown in Fig. 1. Fig. 16 is a diagram for explaining a method for correcting the ink ejection timing when printing on the print substrate 102 using the printing device 101 shown in Fig. 1. Fig. 17 is a diagram for explaining the allowable amount ΔT of deviation in ink landing position depending on the size of one dot of ink DI when printing on the print substrate 102 using the printing device 101 shown in Fig. 1.

[0070] As described above, when printing is performed on the print substrate 102 by the printing device 101, print data transmitted from the PC 118 is input to the control unit 114. The control unit 114 prints on the print substrate 102 based on the input print data. When printing on the print substrate 102, the control unit 114 generates an ejection trigger signal for starting ink ejection from the nozzles 103a of the head 103 based on the output signal of the encoder 132 (see FIG. 14 ). Specifically, the control unit 114 generates the ejection trigger signal when the count number of encoder pulses reaches a predetermined value (counts up). The control unit 114 also transmits a drive signal to the piezoelectric element 116 for ejecting ink from the nozzles 103a based on the ejection trigger signal. Specifically, the control unit 114 starts transmitting a drive signal to the piezoelectric element 116 based on the ejection trigger signal, causing a predetermined amount of ink to be ejected from the nozzles 103a.

[0071] If the rotational speed of the print medium 102 fluctuates significantly for some reason, the period of the encoder pulse also fluctuates significantly, and the timing of generating the ejection trigger signal also fluctuates significantly. As a result, the ink landing position in the circumferential direction shifts, reducing the printing accuracy of the print medium 102. In this embodiment, in order to ensure the print quality of the print medium 102, ejection timing correction control is performed to correct the timing of ink ejection from the nozzles 103a when the rotational speed of the print medium 102 fluctuates significantly. The control unit 114 has functional components for performing ejection timing correction control, including an encoder measurement unit 143 to which an output signal from the encoder 132 is input, a comparison unit 144 to which an output signal from the encoder measurement unit 143 is input, and an ejection control unit 145 that controls the multiple piezoelectric elements 116 (see FIG. 2).

[0072] The encoder measurement unit 143 calculates the current rotation speed, which is the current rotation speed of the print substrate 102, based on the output signal of the encoder 132 during printing on the print substrate 102. Specifically, the encoder measurement unit 143 calculates the current rotation speed at regular intervals during printing on the print substrate 102. The encoder measurement unit 143 also calculates a reference rotation speed of the print substrate 102. Specifically, the encoder measurement unit 143 calculates the average value of a predetermined number of past current rotation speeds calculated before the latest current rotation speed is calculated, as the reference rotation speed of the print substrate 102.

[0073] The comparison unit 144 receives a current rotation speed signal and a reference rotation speed signal. The comparison unit 144 compares the current rotation speed with the reference rotation speed. Furthermore, the comparison unit 144 determines whether or not it is necessary to perform correction control of the ejection timing based on the comparison result between the current rotation speed and the reference rotation speed. If the deviation of the current rotation speed from the reference rotation speed is less than a predetermined reference value, the comparison unit 144 determines that it is not necessary to perform correction control of the ejection timing, 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 144 determines that it is necessary to perform correction control of the ejection timing, and generates and outputs a correction execution signal.

[0074] The output signal of the comparison unit 144 is input to the ejection control unit 145. When the no-correction-required signal is input, the ejection control unit 145 causes the nozzle 103a to eject ink at the normal ejection timing, which is the normal ejection timing based on the output signal of the encoder 132. That is, when the no-correction-required signal is input to the ejection control unit 145, the control unit 114 generates an ejection 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 114 causes the nozzle 103a to eject ink at the normal ejection timing.

[0075] 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 145 advances the timing of ejecting ink from the nozzle 103a relative to the normal ejection timing. In other words, when a correction execution signal is input to the ejection control unit 145 and the current rotation speed is slower than the reference rotation speed, the control unit 114 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. 15A).

[0076] Furthermore, when a correction execution signal is input and the current rotation speed is faster than the reference rotation speed, the ejection control unit 145 delays the timing of ejecting ink from the nozzle 103a from the normal ejection timing. In other words, when a correction execution signal is input to the ejection control unit 145 and the current rotation speed is faster than the reference rotation speed, the control unit 114 generates an ejection trigger signal after a predetermined time has elapsed after the count number of encoder pulses has reached a predetermined value (after counting up) (see part G in FIG. 15B).

[0077] In this way, the control unit 114 advances the timing of ink ejection from the nozzle 103a 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 103a 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.

[0078] The ejection control unit 145 is equipped with a digital filter, and when performing ejection timing correction control, it corrects the timing of ejecting ink from the nozzles 103 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 145 corrects the timing of ejecting ink from the nozzles 103 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 103 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.

[0079] 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. Furthermore, 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 printing medium 102. That is, 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 103a at the normal ejection timing despite a large fluctuation in the rotation speed of the printing medium 102.

[0080] Depending on the conditions of the print substrate 102, such as the material of the print substrate 102, and the type of ink, the way the ink spreads after landing on the print substrate 102 may change, which may change the size of one dot of ink DI (see FIG. 17) after landing on the print substrate 102. For example, if the radial deviation of one dot of ink DI after landing on the print substrate 102 is defined as the allowable amount ΔT for the deviation of the ink landing position in the circumferential direction of the print substrate 102, then as shown in FIG. 17, the allowable amount ΔT changes depending on the size of one dot of ink DI after landing on the print substrate 102. Specifically, the allowable amount ΔT decreases as the size of one dot of ink DI after landing on the print substrate 102 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 114 increases the deviation of the ink ejection timing from the nozzle 103a from the normal ejection timing as the size of one dot of ink DI after landing on the printing substrate 102 becomes smaller.

[0081] 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 114 corrects the timing of ejection of ink from the nozzle 103 a 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 102 becomes smaller. For example, when the size DI of one dot of ink after landing on the print substrate 102 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 102 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.

[0082] (Major Effects of the Present Embodiment) As described above, in the present embodiment, the control unit 114 moves and stops the carriage 107 so that the ink ejection nozzle row 103e is positioned at a position where the distance l satisfies the above relationship during printing on the print substrate 102. Therefore, in the present embodiment, it is possible to suppress the circumferential deviation between the landing position of ink on the maximum outer diameter portion 102a of the print substrate 102 and the landing position of ink on the minimum outer diameter portion 102b of the print substrate 102 to less than half the dot pitch of the resolution R. Therefore, in the present embodiment, it is possible to ensure the print quality of the print substrate 102 even when printing is performed on the outer peripheral surface of the print substrate 102 while rotating the print substrate 102, which has a truncated cone-shaped outer shape.

[0083] Furthermore, in this embodiment, ink is ejected from the nozzles 103a of the multiple ink ejection nozzle arrays 103e together when printing on the print substrate 102, but the control unit 114 moves and stops the carriage 107 so that each of the multiple ink ejection nozzle arrays 103e is positioned at a position where the distance 1 satisfies the above relationship when printing on the print substrate 102. Therefore, in this embodiment, even when ink is ejected from the nozzles 103a of the multiple ink ejection nozzle arrays 103e together when printing on the print substrate 102, it is possible to suppress the circumferential deviation between the landing position of the ink that lands on the maximum outer diameter portion 102a and the landing position of the ink that lands on the minimum outer diameter portion 102b in each of the multiple ink ejection nozzle arrays 103e to less than half the dot pitch of the resolution R.

[0084] In this embodiment, when printing on the print medium 102, the control unit 114 advances the ink ejection timing from the nozzle 103 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 103 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 the reference rotation speed and the current rotation speed is faster than the reference rotation speed. 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 deviations in the ink landing position in the circumferential direction. 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 deterioration in the print quality of the print medium 102.

[0085] 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 114 increases the deviation of the ink ejection timing from the nozzle 103 a from the normal ejection timing as the size of one dot of ink DI after landing on the print substrate 102 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 102, regardless of the size of one dot of ink DI after landing on the print substrate 102.

[0086] (Modifications) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this and various modifications can be made within the scope that does not change the gist of the present invention.

[0087] In the above-described embodiment, the number of ink ejection nozzle rows 103e that actually ejects ink when printing on the print substrate 102 may be one. Also, in the above-described embodiment, the rotation mechanism 121 may be provided with an encoder for detecting the rotational position and rotational speed of the motor 125, instead of the encoder 132. In this case, the control unit 114 calculates the current rotational speed of the motor 125 based on the output signal of this encoder when printing on the print substrate 102. Also, the control unit 114 calculates, as the reference rotational speed of the motor 125, the average value of a predetermined number of past current rotational speeds calculated before the latest current rotational speed is calculated.

[0088] In the above-described embodiment, if the printing device 101 only prints on a substrate 102 having a fixed outer diameter, the vertical position of the ultraviolet irradiator 122 does not need to be adjustable. Also, in the above-described embodiment, the printing device 101 does not need to print on a substrate 102 having a cylindrical or conical outer shape. Furthermore, in the above-described embodiment, the ultraviolet irradiator 122 may be disposed below the substrate 102. Also, in the above-described embodiment, the printing device 101 may be provided with a Y-bar drive mechanism that moves the Y-bar 108 in the sub-scanning direction instead of the stage drive mechanism 112. Also, in the above-described embodiment, the ejection energy generating element for ejecting ink from the nozzle 103 a may be a heater (heat generating element). Also, in the above-described embodiment, the printing device 101 may have only one head 103.

[0089] Second Embodiment A second embodiment of the present invention will be described below with reference to the drawings.

[0090] (Overall Configuration of Printing Apparatus) FIG. 18 is a front view for explaining the configuration of a printing apparatus 1 according to a second embodiment of the present invention.

[0091] 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 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.

[0092] The printing device 1 includes 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 includes multiple heads 3. For example, the printing device 1 includes 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 as to allow 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 allow movement in a sub-scanning direction perpendicular to the up-down direction and the main scanning direction.

[0093] 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, and a table lifting mechanism 13 that raises and lowers the table 5. The carriage drive mechanism 11 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 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 stage drive mechanism 12 moves the table 5 in the sub-scanning direction together with 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.

[0094] In the following description, the sub-scanning direction (X direction in FIG. 18, etc.) is the front-to-rear direction, and the main scanning direction (Y direction in FIG. 18, etc.) is the left-to-right direction. In the following description, the X1 direction side in FIG. 20, etc., which is one side of the front-to-rear direction, is referred to as the "front" side, the X2 direction side in FIG. 20, etc., which is the opposite side, is referred to as the "rear" side, the Y1 direction side in FIG. 19, etc., which is one side of the left-to-right direction, is referred to as the "right" side, and the Y2 direction side in FIG. 19, etc., which is the opposite side, is referred to as the "left" side.

[0095] 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. The lower surface of the head 3 is formed with a large number of nozzles that eject ink. The lower surface of the head 3 is formed with a nozzle row consisting of a large number of nozzles arranged in the front-to-rear direction. The lower surface of the head 3 is formed with a plurality of nozzle rows arranged in the left-to-right direction. The head 3 is equipped with a plurality of piezoelectric elements (piezo elements) for ejecting ink from each of the large number of nozzles.

[0096] (Overall Configuration of Ultraviolet Irradiation Device) Fig. 19 is a front view for explaining the configuration of the ultraviolet irradiation device 4 shown in Fig. 18. Figs. 20 and 21 are side views for explaining the configuration of the rotation mechanism 16 shown in Fig. 19.

[0097] The ultraviolet irradiation device 4 includes a rotation mechanism 16 that holds the substrate 2 and rotates the substrate 2 around its axis, an ultraviolet irradiator 17 that irradiates ultraviolet rays toward the outer peripheral surface of the substrate 2 to which ink is attached, and a cover 18 that covers the rotation mechanism 16 and the ultraviolet irradiator 17 from above. The cover 18 has an opening 18a through which the upper end of the substrate 2 is positioned.

[0098] 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, and the left-to-right direction (Y direction) is perpendicular to the direction of the axis of the substrate 2 to be printed when viewed from above. The nozzle row of the head 3 that 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. In the following description, the direction of the axis of the substrate 2 to be printed is referred to as the "axial direction of the substrate 2 to be printed."

[0099] The rotation mechanism 16 rotates the substrate 2 when printing on the substrate 2. In this embodiment, printing is performed on the substrate 2 while the rotation mechanism 16 rotates the substrate 2 with the stage 6 and carriage 7 stopped at a fixed position. When printing on the substrate 2, the rotation mechanism 16 rotates the substrate 2 counterclockwise when viewed from the front, for example. In this embodiment, the length (axial length) of the substrate 2 is longer than the front-to-rear width of the head 3. Therefore, when printing on the substrate 2, the substrate 2 is moved in a stepwise manner in the front-to-rear direction together with the table 5, the rotation mechanism 16, etc. Note that the length of the substrate 2 may be equal to the front-to-rear width of the head 3, or may be shorter than the front-to-rear width of the head 3.

[0100] The rotation mechanism 16 includes a motor 21 as a drive source and a power transmission mechanism 22 for transmitting the power of the motor 21 to the printing medium 2. The rotation mechanism 16 also includes a first rotating unit 23 as a rotating unit that holds the rear end of the printing medium 2, a first holding unit 24 that rotatably holds the first rotating unit 23, a second rotating unit 25 that holds the front end of the printing medium 2, a second holding unit 26 that rotatably holds the second rotating unit 25, a rotating frame 27 to which the first holding unit 24 and the second holding unit 26 are attached, and an encoder 28 for detecting the rotational position and rotational speed of the printing medium 2. Note that the power transmission mechanism 22 and other components are not shown in Figure 19.

[0101] As described above, the printing medium 2 is formed in a cylindrical shape. That is, the rear end of the printing medium 2 held by the first rotating unit 23 and the front end of the printing medium 2 held by the second rotating unit 25 are formed in a cylindrical shape. The first rotating unit 23 and the second rotating unit 25 rotate together with the printing medium 2. The motor 21 is disposed to the right of the printing medium 2. The power transmission mechanism 22 connects the first rotating unit 23 and the motor 21, and the motor 21 rotates the first rotating unit 23. The power transmission mechanism 22 includes a gear train 29. The gear train 29 includes a drive gear fixed to the output shaft of the motor 21 and a driven gear fixed to the first rotating unit 23, etc. The power transmission mechanism 22 may also be configured using a pulley, a belt, etc.

[0102] The second holding unit 26 is movable together with the second rotating unit 25 relative to the rotating frame 27 in the axial direction of the print medium 2. In this embodiment, the positions of the second rotating unit 25 and the second holding unit 26 in the axial direction of the print medium 2 can be adjusted, and the positions of the second rotating unit 25 and the second holding unit 26 in the axial direction of the print medium 2 are adjusted according to the length of the print medium 2. The encoder 28 is connected to the rear end of the first rotating unit 23. When printing on the print medium 2, the timing of ink ejection from the head 3 is controlled based on the output signal of the encoder 28.

[0103] The rotating frame 27 is rotatable relative to a lower frame 30 that constitutes the bottom surface of the ultraviolet irradiation device 4, with the left-right direction as the rotation axis. The rotating frame 27 is also rotatable relative to the lower frame 30, with the rear end of the rotating frame 27 as the rotation center. In this embodiment, by rotating the rotating frame 27 relative to the lower frame 30, it is possible to adjust the inclination of the rotation mechanism 16 with respect to the horizontal direction when viewed from the left-right direction. In other words, by rotating the rotating frame 27 relative to the lower frame 30, it is possible to adjust the inclination of the axis of the printing medium 2 with respect to the horizontal direction.

[0104] In this embodiment, when printing on a substrate 2 having a cylindrical outer shape, the axial direction of the substrate 2 coincides with the front-to-rear direction (see FIG. 20). On the other hand, when printing on a substrate 2 having a truncated cone or conical outer shape, the axial direction of the substrate 2 is inclined with respect to the front-to-rear direction (see FIG. 21). In other words, the inclination of the rotation mechanism 16 is adjusted when printing on the outer peripheral surface of a substrate 2 having a truncated cone or conical outer shape. Specifically, the inclination of the rotation mechanism 16 is adjusted so that the top end of the substrate 2 is parallel to the front-to-rear direction.

[0105] If one side of the axial direction of the print medium 2 is defined as the third direction side, and the other side of the axial direction of the print medium 2 opposite the third direction side is defined as the fourth direction side, in this embodiment, when printing on a print medium 2 having a cylindrical outer shape, the third direction side coincides with the rear side, and the fourth direction side coincides with the front side. On the other hand, when printing on the outer peripheral surface of a print medium 2 having a truncated cone or cone outer shape, the third direction side does not coincide with the rear side, and the fourth direction side does not coincide with the front side.

[0106] However, when printing on the outer peripheral surface of the substrate 2 having a truncated cone or conical outer shape, the inclination of the axis of the substrate 2 with respect to the front-to-rear direction is not so large, so even when printing on the outer peripheral surface of the substrate 2 having a truncated cone or conical outer shape, the third direction side generally coincides with the rear side, and the fourth direction side generally coincides with the front side. In this embodiment, the rear end of the substrate 2 is the end on the third direction side of the substrate 2, and the front end of the substrate 2 is the end on the fourth direction side of the substrate 2. A more specific configuration of the rotation mechanism 16 will be described later.

[0107] The ultraviolet irradiator 17 includes an LED substrate 31 on which a plurality of light-emitting elements (specifically, a large number of light-emitting elements) that emit ultraviolet rays (ultraviolet light) are mounted. The light-emitting elements are LED chips (UVLED chips). The LED substrate 31 is formed in the shape of a long, narrow rectangular plate. The LED substrate 31 is arranged so that the thickness direction of the LED substrate 31 coincides with the left-right direction. Furthermore, the LED substrate 31 is arranged so that the direction of the short side of the rectangular LED substrate 31 coincides with the up-down direction when viewed from the left-right direction, and the direction of the long side of the LED substrate 31 coincides with the front-to-back direction. The ultraviolet ray emission surface of the LED substrate 31 faces rightward.

[0108] The ultraviolet irradiator 17 is disposed on the left side of the substrate 2. The ultraviolet irradiator 17 irradiates the substrate 2 with ultraviolet light from the left side immediately after ink has landed thereon. In this embodiment, the vertical position of the ultraviolet irradiator 17 is adjustable. The left-right position of the ultraviolet irradiator 17 and the inclination of the ultraviolet irradiator 17 relative to the axis of the substrate 2 when viewed from the top-bottom direction are also adjustable. In this embodiment, when printing on a substrate 2 having a cylindrical outer shape, the ultraviolet irradiator 17 is installed so that the ultraviolet light emission surface of the ultraviolet irradiator 17 (i.e., the ultraviolet light emission surface of the LED substrate 31) 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 17 is adjusted so that the ultraviolet light emission surface of the ultraviolet irradiator 17 is parallel to the left edge of the substrate 2.

[0109] (Configuration of the first rotating part and the second rotating part) Figure 22 (A) is a side view of the second rotating part 25 shown in Figure 20, Figure 22 (B) is a side view of the first rotating part 23 shown in Figure 20, and Figures 22 (C) and (D) are cross-sectional views of the first rotating part 23 shown in Figure 22 (B).

[0110] As described above, the rotation mechanism 16 includes a first rotating unit 23 that holds the rear end of the substrate 2 (more specifically, the end of the substrate 2 on the third direction side), and a second rotating unit 25 that holds the front end of the substrate 2 (more specifically, the end of the substrate 2 on the fourth direction side). The first rotating unit 23 includes a headed screw 35 having a head 35a and a shaft 35b, a nut 36 that engages with the male thread formed on the shaft 35b, a holding member 37 made of an annular elastic body and whose outer surface contacts the inner circumferential surface of the substrate 2, a contact member 38 that contacts the holding member 37, and an annular member 39 that contacts the end surface of the substrate 2. The head 35a, holding member 37, contact member 38, annular member 39, and nut 36 are arranged in this order in the axial direction of the shaft 35b.

[0111] When the printing medium 2 is correctly attached to the rotation mechanism 16, the axial direction of the shaft portion 35b of the screw 35 coincides with the axial direction of the printing medium 2. If one axial side of the shaft portion 35b, that is, the V1 direction side in Fig. 22, is defined as the first direction side, and the other axial side of the shaft portion 35b opposite the first direction side (the V2 direction side in Fig. 22) is defined as the second direction side, when the printing medium 2 is correctly attached to the rotation mechanism 16, the first direction side coincides with the fourth direction side described above, and the second direction side coincides with the third direction side described above.

[0112] The holding member 37 is a chuck that contacts the print medium 2 and holds the end of the print medium 2 on the third direction side. The holding member 37 is arranged on the inner circumferential side of the print medium 2. As described above, the holding member 37 is made of an elastic material. Specifically, the holding member 37 is formed of a highly elastic material that adheres closely to the print medium 2. The holding member 37 in this embodiment is made of rubber. The holding member 37 is formed in an annular shape. Furthermore, the holding member 37 is formed in a cylindrical shape with a relatively short axial length of the shaft portion 35b. This makes it possible for the outer circumferential surface of the holding member 37 to come into surface contact with the inner circumferential surface of the print medium 2.

[0113] A portion of the shaft portion 35b is disposed on the inner circumferential side of the holding member 37. A portion of the head portion 35a may also be disposed on the inner circumferential side of the holding member 37. That is, at least a portion of the shaft portion 35b is disposed on the inner circumferential side of the holding member 37. The inner diameter of the holding member 37 is larger than the outer diameter of the shaft portion 35b. A substantially uniform gap is formed between the inner circumferential surface of the holding member 37 and the outer circumferential surface of the shaft portion 35b over the entire circumferential direction of the holding member 37.

[0114] The inner peripheral surface of the holding member 37 is formed with a tapered surface 37a in which the inner diameter decreases in a cone shape from the surface on the first direction side toward the second direction side, and a tapered surface 37b in which the inner diameter decreases in a cone shape from the surface on the second direction side toward the first direction side. The tapered surfaces 37a and 37b are formed from the middle portion of the wire diameter of the holding member 37 to the inner peripheral surface. In this embodiment, the tapered surfaces 37a and 37b have the same inclination angle, but these may be different.

[0115] The head 35a constitutes the end of the screw 35 on the first direction side. The outer diameter of the head 35a is smaller than the inner diameter of the material to be printed 2. The head 35a is arranged on the inner periphery of the material to be printed 2. The outer diameter of the head 35a is larger than the inner diameter of the holding member 37. The end of the shaft 35b on the second direction side is connected to a rotating shaft 40 (see Figures 20 and 21). The rotating shaft 40 is rotatably held by the first holding part 24. The axis of the screw 35 coincides with the axis of the rotating shaft 40.

[0116] The screw 35 is a flat head screw. The head 35a has a truncated conical seat. That is, the surface of the head 35a facing the second direction has a tapered surface 35c whose outer diameter tapers toward the second direction. The inclination angle of the tapered surface 35c is equal to the inclination angle of the tapered surface 37a. The tapered surface 35c of the head 35a contacts the tapered surface 37a of the holding member 37 from the first direction side. In this embodiment, the tapered surface 35c is a first tapered surface. The tapered surface 37a is a third tapered surface that can come into contact with the tapered surface 35c, which is the first tapered surface.

[0117] The annular member 39 is formed in a circular, flat plate shape. The annular member 39 is arranged so that the thickness direction of the annular member 39 coincides with the axial direction of the shaft portion 35b. The shaft portion 35b is inserted into the inner hole of the annular member 39. The outer diameter of the annular member 39 is larger than the inner diameter of the medium 2 to be printed and smaller than the outer diameter of the end of the medium 2 on the third direction side. The annular member 39 contacts the end surface of the medium 2 on the third direction side.

[0118] The contact member 38 is formed, for example, from resin. The contact member 38 is formed in an annular shape. The contact member 38 is also formed in a generally cylindrical shape with the axial length of the shaft portion 35b being relatively short. The outer diameter of the contact member 38 is smaller than the inner diameter of the medium to be printed 2. The shaft portion 35b is inserted into the inner hole of the contact member 38. The inner diameter of the contact member 38 is approximately equal to the outer diameter of the shaft portion 35b. The contact member 38 is movable relative to the shaft portion 35b in the axial direction of the shaft portion 35b. The contact member 38 is composed of a fixed portion 38a that fits into the inner circumferential surface of the annular member 39, and a tapered portion 38b that is arranged on the first direction side of the annular member 39. The tapered portion 38b is arranged on the inner circumferential side of the medium to be printed 2.

[0119] A tapered surface 38c is formed on the surface of the tapered portion 38b on the first direction side, with the outer diameter tapering down toward the first direction side. That is, the tapered surface 38c is formed on the surface on the first direction side of the contact member 38. The inclination angle of the tapered surface 38c is equal to the inclination angle of the tapered surface 37b. The tapered surface 38c of the contact member 38 contacts the tapered surface 37b of the holding member 37 from the second direction side. In this embodiment, the tapered surface 38c is a second tapered surface. Furthermore, the tapered surface 37b is a fourth tapered surface with which the tapered surface 38c, which is the second tapered surface, can come into contact.

[0120] In this embodiment, tapered surface 35c is formed on head 35a, tapered surface 38c is formed on contact member 38, and tapered surface 37a that contacts tapered surface 35c and tapered surface 37b that contacts tapered surface 38c are formed on retaining member 37. Therefore, even if the inner diameter of retaining member 37 is larger than the outer diameter of shank 35b, the axis of retaining member 37, which is formed in an annular shape, substantially coincides with the axis of screw 35. Nut 36 is disposed on the second direction side relative to contact member 38 and annular member 39. A washer 41 is disposed between nut 36 and annular member 39.

[0121] In this embodiment, when the nut 36 is turned in a direction that brings the head 35a and the nut 36 closer together (i.e., when the nut 36 is tightened relative to the screw 35), the contact member 38 and the annular member 39 move toward the head 35a. This causes the retaining member 37 to elastically deform, and its outer diameter expands (see FIG. 22C ). That is, the retaining member 37 sandwiched between the head 35a and the contact member 38 is pushed apart, increasing its outer diameter. At this time, the tapered surface 37a of the retaining member 37 contacts the tapered surface 35c of the head 35a, and the tapered surface 37b of the retaining member 37 contacts the tapered surface 38c of the contact member 38.

[0122] On the other hand, when the nut 36 is turned in a direction that separates the head 35a from the nut 36 (i.e., when the nut 36 is loosened from the screw 35), the contact member 38 and the annular member 39 move in a direction that separates the head 35a. As a result, the expanded shape of the holding member 37 is restored, and its outer diameter becomes smaller (see FIG. 22(D)).

[0123] The second rotating unit 25 includes a holding member 44 that contacts the end of the printing medium 2 on the fourth direction side, a fixed member 45 to which the holding member 44 is fixed, and a rotating shaft 46 to which the fixed member 45 is attached. The fixed member 45 is formed, for example, in the shape of a stepped cylinder. The end of the rotating shaft 46 on the second direction side is inserted into the inner periphery of the fixed member 45. The rotating shaft 46 is rotatably held by the second holding unit 26.

[0124] The holding member 44 is a chuck that contacts the end of the print medium 2 on the fourth direction side and holds the end of the print medium 2 on the fourth direction side. The holding member 44 is made of an elastic material similar to the holding member 37. That is, the holding member 44 is made of rubber. The holding member 44 is also formed in an annular shape. The holding member 44 is composed of a disk-shaped small-diameter portion 44a arranged on the inner periphery of the print medium 2 and a tapered portion 44c with a tapered surface 44b that contacts the end of the print medium 2 on the fourth direction side. The outer diameter of the small-diameter portion 44a is approximately equal to the inner diameter of the print medium 2. The tapered surface 44b is formed in a tapered shape such that the outer diameter gradually decreases toward the second direction side. The axis of the small-diameter portion 44a and the axis of the tapered portion 44c coincide with the axis of the rotation shaft 46.

[0125] (Configuration of the peripheral portions of the second rotating portion and the second holding portion) Fig. 23 is a plan view for explaining the configuration of the rotating mechanism 16 shown in Fig. 19. Fig. 24 is a cross-sectional view of the E-E cross section in Fig. 23. Figs. 25 and 26 are enlarged plan views for explaining the configuration of part F in Fig. 23. Note that Figs. 20 and 21 omit illustration of the configuration to be described below.

[0126] In addition to the above-described configuration, the rotation mechanism 16 includes a guide rail 50 for guiding the second holding portion 26 in the axial direction of the printing medium 2, and a guide block 51 (see FIG. 24 ) that engages with the guide rail 50 and to which the second holding portion 26 is fixed. The guide rail 50 is fixed to the rotating frame 27. The guide block 51 engages with the guide rail 50 from above. The guide block 51 is positioned below the second holding portion 26. The guide block 51 moves in the axial direction of the printing medium 2 together with the second rotating portion 25 and the second holding portion 26.

[0127] The rotation mechanism 16 also includes a fixed member 52 fixed to the guide block 51, a slide member 53 held by the fixed member 52 and movable relative to the fixed member 52 in the axial direction of the medium 2 to be printed, an engagement member 54 held by the slide member 53 and rotatable relative to the slide member 53 in the left-right direction as the axial direction of the rotation, a regulating member 55 for regulating movement of the slide member 53 and the engagement member 54 in the fourth direction, and a rotating member 56 held by the fixed member 52 and rotatable relative to the fixed member 52 in the up-down direction as the axial direction of the rotation. In this embodiment, the second rotating unit 25, the second holding unit 26, the guide block 51, the fixed member 52, the rotating member 56, etc. form a moving body 57. The slide member 53 is held by the moving body 57 and is movable relative to the moving body 57 in the axial direction of the medium 2 to be printed.

[0128] Furthermore, the rotation mechanism 16 includes a torsion coil spring 59 (see Figure 24) as a first biasing member that biases the engaging member 54 to one side in the rotation direction of the engaging member 54 relative to the slide member 53, a fixed shaft 60 fixed to the slide member 53, a compression coil spring 61 as a second biasing member that is compressed between the slide member 53 and the moving body 57, a tension coil spring 62 that biases the rotating member 56 to one side in the rotation direction of the rotating member 56 relative to the fixed member 52, and a detection mechanism 63 for detecting that the printing material 2 is correctly attached to the rotation mechanism 16.

[0129] The slide member 53 is formed with a guide hole 53a for guiding the slide member 53 relative to the fixed member 52 in the axial direction of the medium to be printed 2 and for restricting the range of movement of the slide member 53 relative to the fixed member 52 in the axial direction of the medium to be printed 2 (see FIG. 24 ). The guide hole 53a is an elongated hole that is long in the axial direction of the medium to be printed 2. A part of a guide screw 65 fixed to the fixed member 52 is disposed in the guide hole 53a. In this embodiment, the guide hole 53a and the guide screw 65 constitute a slide member restricting portion 66 for restricting the range of movement of the slide member 53 relative to the movable body 57 in the axial direction of the medium to be printed 2 (see FIG. 24 ). The slide member 53 is equipped with a rotation restricting portion 53b that restricts rotation of the rotating member 56 to one side in the rotation direction of the rotating member 56 relative to the fixed member 52, and a spring engaging portion 53c with which one end of the torsion coil spring 59 comes into contact.

[0130] The fixed shaft 60 is arranged so that its axial direction coincides with the axial direction of the printing medium 2. The fourth direction side end of the fixed shaft 60 is fixed to the slide member 53. A through hole is formed in the second holding portion 26, in which a part of the fixed shaft 60 is arranged. A part of the fixed shaft 60 is arranged on the inner circumferential side of the compression coil spring 61. The fourth direction side end of the compression coil spring 61 is in contact with the slide member 53. The third direction side end of the compression coil spring 61 is in contact with the second holding portion 26. The compression coil spring 61 biases the moving body 57 in the third direction from the slide member 53.

[0131] The regulating member 55 is formed in an elongated shape that is long and narrow in the axial direction of the print medium 2. The regulating member 55 is fixed to the rotating frame 27. The regulating member 55 has a sawtooth-shaped regulating portion 55b on which a plurality of regulating surfaces 55a (specifically, a large number of regulating surfaces 55a) are formed that are arranged at a constant pitch in the axial direction of the print medium 2 (see FIG. 24). The regulating portion 55b is formed on the upper surface of the regulating member 55. The regulating surface 55a is an inclined surface that slopes upward as it approaches the fourth direction side.

[0132] The engagement member 54 is rotatable relative to the slide member 53 around a rotation center shaft 67 (see FIG. 24 ) fixed to the end of the slide member 53 on the third direction side. The rotation center shaft 67 is arranged so that its axial direction coincides with the left-right direction. The rotation center shaft 67 is arranged below the spring engagement portion 53 c. An insertion hole through which the rotation center shaft 67 is inserted is formed in the end of the engagement member 54 on the third direction side. The engagement member 54 has an engagement portion 54 a that engages with the restriction surface 55 a (see FIG. 24 ). The engagement portion 54 a forms the lower end of the engagement member 54. When the printing medium 2 is correctly attached to the rotation mechanism 16, the end face on the fourth direction side of the engagement portion 54 a contacts the restriction surface 55 a with a predetermined contact pressure.

[0133] The engaging member 54 has a guide hole 54b formed therein for guiding the engaging member 54 in the direction of rotation of the engaging member 54 relative to the slide member 53 and for restricting the range of rotation of the engaging member 54 relative to the slide member 53 (see FIG. 24 ). The guide hole 54b is located on the fourth direction side of the rotation center shaft 67. The guide hole 54b is also located above the rotation center shaft 67. When viewed from the left-right direction, the shape of the guide hole 54b is formed in an arc shape with the axis of the rotation center shaft 67 as the center of curvature. A guide screw 68 that is fixed to the slide member 53 is inserted into the guide hole 54b.

[0134] A portion of the rotation center shaft 67 is disposed on the inner circumferential side of the torsion coil spring 59. One end of the torsion coil spring 59 contacts the spring engaging portion 53c of the slide member 53. The other end of the torsion coil spring 59 contacts the engaging member 54. When viewed from the right side, the torsion coil spring 59 biases the engaging member 54 in a counterclockwise direction (counterclockwise in FIG. 24 ) around the rotation center shaft 67. The engaging portion 54a constituting the lower end of the engaging member 54 is disposed above the restricting portion 55b. The torsion coil spring 59 biases the engaging member 54 in a direction in which the engaging portion 54a faces the restricting portion 55b.

[0135] When the engaging member 54 is rotated against the biasing force of the torsion coil spring 59 (i.e., when the engaging member 54 is rotated clockwise as viewed from the right side so that the engaging portion 54a moves away from the restricting portion 55b), the engaging portion 54a disengages from the restricting surface 55a as shown by the two-dot chain line in Figure 24. This makes it possible to move the slide member 53 and the engaging member 54 in the fourth direction. Note that a finger hook 54c is formed on the upper end of the engaging member 54 on the fourth direction side, for rotating the engaging member 54 against the biasing force of the torsion coil spring 59.

[0136] When the medium 2 is correctly attached to the rotation mechanism 16, the movement of the slide member 53 and the engaging member 54 in the fourth direction is restricted by the restricting surface 55a and the engaging portion 54a in contact with the restricting surface 55a. At this time, the compression coil spring 61 is compressed by a predetermined amount, and the biasing force of the compression coil spring 61 biases the moving body 57 in the third direction relative to the slide member 53. As a result, the tapered surface 44b of the holding member 44 is pressed against the end of the medium 2 on the fourth direction side with a predetermined contact pressure, and the end face of the medium 2 on the third direction side is pressed against the annular member 39 with a predetermined contact pressure.

[0137] The rotating member 56 is rotatable relative to the fixed member 52 around a rotation center axis fixed to the end of the fixed member 52 on the third direction side. This rotation center axis is arranged so that its axial direction and the up-down direction are approximately aligned. The rotating member 56 includes a regulated portion 56a arranged on the fourth direction side of the rotation regulating portion 53b, and a spring engaging portion 56b with which the end of the tension coil spring 62 on the fourth direction side engages. The regulated portion 56a is arranged at the left end of the rotating member 56 on the fourth direction side. The spring engaging portion 56b is arranged on the third direction side of the regulated portion 56a.

[0138] The detection mechanism 63 is an interlock switch having a contact member that forms a contact portion and a lever 63a that presses the contact member. The detection mechanism 63 is arranged on the third direction side of the rotating member 56. The detection mechanism 63 is attached to the fixed member 52 so that the lever 63a is arranged on the fourth direction side of the main body of the detection mechanism 63. The end of the rotating member 56 on the third direction side can come into contact with the lever 63a from the fourth direction side.

[0139] The end of the tension coil spring 62 on the third direction side is engaged with the second holding portion 26. The end of the tension coil spring 62 on the fourth direction side is engaged with the spring engaging portion 56b of the rotating member 56, as described above. When viewed from above, the tension coil spring 62 biases the rotating member 56 in a clockwise direction (clockwise direction in FIGS. 25 and 26 ) around the rotation center of the rotating member 56. Rotation of the rotating member 56 in the clockwise direction in FIGS. 25 and 26 is restricted by the rotation restricting portion 53b arranged on the third direction side of the restricted portion 56a.

[0140] When the printing medium 2 is correctly attached to the rotation mechanism 16, the compression coil spring 61 is compressed by a predetermined amount, the slide member 53 moves relatively in the third direction with respect to the movable body 57, and the rotation restriction portion 53b moves in the third direction. At this time, as shown in Fig. 26 , the rotating member 56 rotates in the clockwise direction in Fig. 26 , and the end portion of the rotating member 56 on the third direction side presses the lever 63a in the third direction. Specifically, the end portion of the rotating member 56 on the third direction side presses the lever 63a in the third direction to a position where the lever 63a presses the contact member of the detection mechanism 63.

[0141] This allows the detection mechanism 63 to detect that the medium 2 to be printed is correctly attached to the rotation mechanism 16. On the other hand, for example, when the medium 2 to be printed is not attached to the rotation mechanism 16, the compression coil spring 61 is not compressed, and the end of the rotating member 56 on the third direction side is separated from the lever 63a (see FIG. 25). At this time, the lever 63a is not in contact with the contact member of the detection mechanism 63. Therefore, the detection mechanism 63 is in the OFF state.

[0142] (Method of Setting the Printing Material) FIG. 27 is a diagram for explaining a method of setting the printing material 2 on the rotation mechanism 16 shown in FIG.

[0143] When setting the printed material 2 in the rotation mechanism 16, the operator first moves the movable body 57 together with the slide member 53 and the engaging member 54 in the fourth direction to a position where the printed material 2 can be placed between the first rotating part 23 and the second rotating part 25, and then attaches the end of the printed material 2 on the third direction side to the first rotating part 23.

[0144] In this case, for example, the outer diameter of the holding member 37 is narrowed to a position where the outer surface of the holding member 37 does not contact the inner surface of the print medium 2 (see FIG. 22(D)), and the holding member 37 etc. is then placed on the inner side of the print medium 2, and the nut 36 is then turned in the direction in which the head 35a and the nut 36 move closer to each other, thereby widening the outer diameter of the holding member 37 until the outer surface of the holding member 37 contacts the inner surface of the print medium 2 with a predetermined contact pressure (see FIG. 22(C)). Alternatively, the print medium 2 is press-fitted into the holding member 37 whose outer diameter has already been widened until the outer surface of the holding member 37 contacts the inner surface of the print medium 2 with a predetermined contact pressure.

[0145] The operator then pushes the slide member 53 in the third direction until the second rotating part 25 contacts the end of the fourth direction of the print medium 2, whose end on the third direction is attached to the first rotating part 23 (see FIG. 27A). That is, the operator pushes the slide member 53 in the third direction until the tapered surface 44b of the holding member 44 contacts the end on the fourth direction of the print medium 2. The operator then further pushes the slide member 53 in the third direction to set the print medium 2 in the rotation mechanism 16 (see FIG. 27B). That is, the slide member 53 and the engaging member 54 are moved in the third direction until the compression coil spring 61 is compressed by a predetermined amount, thereby setting the print medium 2 in the rotation mechanism 16. For example, the slide member 53 is pushed in the third direction by two to four restriction surfaces 55a.

[0146] When the slide member 53 and the engaging member 54 move in the third direction, the movable body 57 is also pushed by the compression coil spring 61 and moves in the third direction. Furthermore, when the slide member 53 and the engaging member 54 are moved in the third direction until the compression coil spring 61 is compressed by a predetermined amount, the end of the print medium 2 on the fourth direction side comes into contact with the tapered surface 44b of the holding member 44 at a predetermined contact pressure, and the end face of the print medium 2 on the third direction side comes into contact with the annular member 39 at a predetermined contact pressure. When the print medium 2 is to be removed from the rotation mechanism 16, the engaging member 54 is rotated against the biasing force of the torsion coil spring 59, and the slide member 53 and the engaging member 54 are moved in the fourth direction to a position where the print medium 2 can be removed from between the first rotating part 23 and the second rotating part 25.

[0147] (Major Effects of This Embodiment) As described above, in this embodiment, the first rotating part 23, which holds the end of the print medium 2 on the third direction side and rotates together with the print medium 2, is provided with a holding member 37 made of an annular elastic body and whose outer surface contacts the inner peripheral surface of the print medium 2. Also, in this embodiment, when the nut 36 is turned in a direction that brings the head 35a of the screw 35 and the nut 36 closer to each other, the holding member 37 elastically deforms and the outer diameter of the holding member 37 increases, and when the nut 36 is turned in a direction that moves the head 35a and the nut 36 away from each other, the shape of the holding member 37 is restored and the outer diameter of the holding member 37 decreases.

[0148] In this embodiment, the outer diameter of the holding member 37 is increased by turning the nut 36 in the direction in which the head 35a and the nut 36 approach each other, thereby increasing the contact pressure between the outer surface of the holding member 37 and the inner surface of the medium to be printed 2. This suppresses slippage of the first rotating part 23. Furthermore, in this embodiment, the size of the outer diameter of the holding member 37 can be changed depending on the position of the nut 36 relative to the head 35a, so that slippage of the first rotating part 23 can be suppressed even if the size of the inner diameter of the medium to be printed 2 changes.

[0149] In this embodiment, a tapered surface 35c is formed on the second direction side surface of the head 35a of the screw 35, and a second tapered surface 38c is formed on the first direction side surface of the contact member 38. Also, in this embodiment, the holding member 37 is formed with a tapered surface 37a with which the tapered surface 35c can come into contact and a tapered surface 37b with which the tapered surface 38c can come into contact. Therefore, in this embodiment, when the nut 36 is turned, it is possible to uniformly widen or narrow the outer diameter of the holding member 37 over the entire circumferential area of ​​the holding member 37. Therefore, in this embodiment, the axis of the first rotating part 23 and the axis of the printing medium 2 can be aligned with high precision.

[0150] In this embodiment, the position of the movable body 57 in the axial direction of the print medium 2 can be adjusted, and when setting the print medium 2 in the rotation mechanism 16, the movable body 57 is moved in the fourth direction together with the slide member 53 and the engaging member 54 to a position where the print medium 2 can be placed between the first rotating unit 23 and the second rotating unit 25, and the end of the print medium 2 in the third direction is attached to the first rotating unit 23. In this embodiment, the movable body 57 is then moved in the third direction together with the slide member 53 and the engaging member 54, and the end of the print medium 2 in the fourth direction is attached to the second rotating unit 25. In this way, in this embodiment, the work of attaching the print medium 2 to the rotation mechanism 16 can be easily performed.

[0151] In this embodiment, by rotating the engaging member 54 in the direction opposite to the direction of bias by the torsion coil spring 59, the engagement state between the restricting surface 55a of the restricting member 55 and the engaging portion 54a of the engaging member 54 is released, and the slide member 53 and the engaging member 54 can be moved in the fourth direction. Therefore, in this embodiment, the slide member 53 and the engaging member 54 can be moved in the fourth direction with a simple operation.

[0152] In this embodiment, the slide member 53 is pushed in the third direction until the second rotating part 25 contacts the end of the fourth direction of the print medium 2 with its end on the third direction attached to the first rotating part 23, and then the slide member 53 is further pushed in the third direction to set the print medium 2 in the rotation mechanism 16. That is, in this embodiment, the biasing force of the compression coil spring 61 increases the contact pressure between the end of the print medium 2 on the fourth direction side and the second rotating part 25 (specifically, the contact pressure between the end of the print medium 2 on the fourth direction side and the tapered surface 44b of the holding member 44) and the contact pressure between the end face of the print medium 2 on the third direction side and the annular member 39 of the first rotating part 23. As a result, in this embodiment, the holding force of the print medium 2 by the first rotating part 23 and the second rotating part 25 is increased.

[0153] (Modifications) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this and various modifications can be made within the scope that does not change the gist of the present invention.

[0154] In the above-described embodiment, the screw 35 does not have to be a flat head screw. That is, the tapered surface 35c may not be formed on the head 35a. In this case, the retaining member 37 also does not have the tapered surface 37a. Furthermore, in the above-described embodiment, the contact member 38 may not have the tapered surface 38c. In this case, the retaining member 37 also does not have the tapered surface 37b. If the tapered surfaces 35c, 37a, 37b, and 38c are not formed, it is preferable that the inner diameter of the retaining member 37 is approximately equal to the outer diameter of the shaft portion 35b. Even if the tapered surfaces 35c, 37a, 37b, and 38c are not formed, as long as the inner diameter of the retaining member 37 is approximately equal to the outer diameter of the shaft portion 35b, it is possible to uniformly widen or narrow the outer diameter of the retaining member 37 throughout the entire circumferential direction of the retaining member 37 by turning the nut 36.

[0155] In the above-described embodiment, the second rotating part 25 may have the same configuration as the first rotating part 23. In this case, the second rotating part 25 corresponds to the rotating part of the present invention. Also, in the above-described embodiment, for example, if the screw 35 is not a flat head screw, a contact member configured similarly to the contact member 38 may be disposed between the head 35a and the holding member 37. Furthermore, in the above-described embodiment, the axially intermediate portion of the printing medium 2, excluding the end on the third direction side of the printing medium 2 held by the first rotating part 23 and the end on the fourth direction side of the printing medium 2 held by the second rotating part 25, does not have to be formed in a cylindrical shape.

[0156] In the above-described embodiment, the contact member 38 and the annular member 39 may be integrally formed. The nut 36 and the annular member 39 may be integrally formed, or the nut 36, the contact member 38, and the annular member 39 may be integrally formed. In the above-described embodiment, the holding member 37 may be made of an elastic material other than rubber. Furthermore, in the above-described embodiment, the rotation mechanism 16 may be provided with a spring member other than the torsion coil spring 59 instead of the torsion coil spring 59, or a spring member other than the compression coil spring 61 instead of the compression coil spring 61.

[0157] In the above-described embodiment, if only printing on substrates 2 having a fixed outer diameter is performed by the printing device 1, the vertical position of the ultraviolet irradiator 17 does not have to be adjustable. Also, in the above-described embodiment, if only printing on substrates 2 having a cylindrical outer shape is performed by the printing device 1, the inclination of the rotation mechanism 16 with respect to the horizontal direction when viewed from the left and right does not have to be adjustable, and the inclination of the ultraviolet irradiator 17 with respect to the axis of the substrate 2 when viewed from the top and bottom does not have to be adjustable.

[0158] In the above-described embodiment, the ultraviolet irradiation device 4 may be placed on the table 5 so that the axial direction of the print medium 2 coincides with the left-right direction when viewed from the top-down direction. Also, in the above-described embodiment, the ultraviolet irradiator 17 may be disposed below the print medium 2 or to the right of the print medium 2. Furthermore, in the above-described embodiment, the printing apparatus 1 may be provided with a Y-bar drive mechanism, instead of the stage drive mechanism 12, that moves the Y-bar 8 in the sub-scanning direction together with the head 3 and carriage 7.

[0159] REFERENCE SIGNS LIST 1 Printing device 2 Printed material 3 Head (inkjet head) 4 Ultraviolet irradiation device 5 Table 16 Rotation mechanism 17 Ultraviolet irradiator 21 Motor 22 Power transmission mechanism 23 First rotating part (rotating part) 24 First holding part 25 Second rotating part 26 Second holding part 35 Screw 35a Head part 35b Shaft part 35c Tapered surface (first tapered surface) 36 Nut 37 Holding member 37a Tapered surface (third tapered surface) 37b Tapered surface (fourth tapered surface) 38 Contact member 38c Tapered surface (second tapered surface) 39 Annular member 50 Guide rail 51 Guide block 53 Slide member 54 Engaging member 54a Engaging part 55 Regulating member 55a Regulating surface 55b Regulating part 57 Moving body 59 Torsion coil spring (first biasing member) 61 Compression coil spring (second biasing member) 66 Slide member regulating portion V1 First direction side V2 Second direction side Y Main scanning direction, left-right direction 101 Printing device 102 Printing medium 102a Maximum outer diameter portion 102b Minimum outer diameter portion 103 Head (inkjet head) 103a Nozzle 103b Nozzle row 103c Ink ejection surface 103e Ink ejection nozzle row 107 Carriage 111 Carriage drive mechanism 114 Control unit 116 Piezoelectric element (ejection energy generating element) 121 Rotation mechanism 125 Motor 126 Power transmission mechanism 132 Encoder X Sub-scanning direction

Claims

1. A printing device for printing on the outer peripheral surface of a substrate having a truncated cone shape, comprising: a rotation mechanism that holds the substrate and rotates it around its axis as the center of rotation; an inkjet head that is disposed above the substrate and ejects ink toward the outer peripheral surface of the substrate; 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 substrate when viewed from the up-down direction; and a control unit for controlling the printing device; wherein the inkjet head has a plurality of nozzles that eject ink; the underside of the inkjet head is an ink ejection surface on which the plurality of nozzles are formed; and a nozzle row is formed on the ink ejection surface by the plurality of nozzles that are arranged in a sub-scanning direction that is perpendicular to the up-down direction and the main scanning direction; and the rotation mechanism rotates the substrate when printing on the substrate. 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), the control unit 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 when printing on the printing medium.

2. The printing device 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 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, 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, causes the nozzle to eject ink 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 ejection timing of ink from the nozzle 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 ejection timing of ink from the nozzle relative to the normal ejection timing.

4. A printing device as described in claim 3, characterized in that 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 printing device for printing on the outer peripheral surface of a substrate having a truncated cone shape, comprising: a rotation mechanism that holds the substrate and rotates it around its axis as the center of rotation; an inkjet head that is disposed above the substrate and ejects ink toward the outer peripheral surface of the substrate; a carriage on which the inkjet head is mounted; and a carriage drive mechanism that moves the carriage in a main scanning direction that is perpendicular to the vertical direction and perpendicular to the axis of the substrate when viewed from the vertical direction; a plurality of nozzles that eject ink are formed in the inkjet head, and the underside of the inkjet head serves as an ink ejection surface on which the plurality of nozzles are formed, and 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, and the rotation mechanism rotates the substrate when printing on it, 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), the method for controlling a printing device, characterized in that, when 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.

6. An ultraviolet irradiation device used in a printing device for printing with ultraviolet-curable ink on the outer peripheral surface of a substrate having a cylindrical, truncated cone, or conical outer shape, comprising: a rotation mechanism that holds the substrate and rotates it around its axis as the center of rotation; and an ultraviolet irradiator that irradiates ultraviolet light toward the outer peripheral surface of the substrate to which ink is attached; the rotation mechanism comprises a rotating part that holds the end of the substrate in the direction of its axis and rotates together with the substrate; the end of the substrate held in the rotating part is formed in a cylindrical shape; the rotating part comprises a headed screw having a head and a shaft, a nut that engages with a male thread formed on the shaft, a holding member made of an annular elastic body and whose outer peripheral surface contacts the inner peripheral surface of the substrate, and an annular contact member that contacts the holding member; at least a part of the shaft is arranged on the inner peripheral side of the holding member; and a part of the shaft is arranged on the inner peripheral side of the contact member. An ultraviolet irradiation device characterized in that the head, the retaining member, the contact member, and the nut are arranged in this order in the axial direction of the shaft portion, and when the nut is turned in a direction that brings the head and the nut closer together, the retaining member elastically deforms and the outer diameter of the retaining member increases, and when the nut is turned in a direction that moves the head and the nut apart, the shape of the retaining member is restored and the outer diameter of the retaining member decreases.

7. The ultraviolet irradiation device described in claim 6, characterized in that, when one axial side of the shaft portion is defined as a first direction side and the side opposite the first direction side is defined as a second direction side, the head contacts the holding member from the first direction side, the contact member contacts the holding member from the second direction side, a first tapered surface is formed on the surface of the head on the second direction side, the outer diameter of which tapers down toward the second direction side, the surface of the contact member on the first direction side is formed on the second direction side, the outer diameter of which tapers down toward the first direction side, and the holding member is formed with a third tapered surface with which the first tapered surface can come into contact and a fourth tapered surface with which the second tapered surface can come into contact.

8. The ultraviolet irradiation device according to claim 6 or 7, wherein the holding member is made of rubber.

9. The ultraviolet irradiation device of claim 6 or 7, characterized in that, when one side of the axis of the printed material is defined as a third direction side, the rotation mechanism comprises the rotating part that holds the end of the printed material on the third direction side, a first holding part that rotatably holds the rotating part, a motor for rotating the rotating part, and a power transmission mechanism that connects the rotating part and the motor, and the rotating part comprises an annular ring-shaped member that contacts the end face of the printed material on the third direction side.

10. The ultraviolet irradiation device described in claim 9, characterized in that, if the side opposite the third direction side is the fourth direction side, the rotation mechanism comprises a second rotating part that holds the other end of the printed material on the fourth direction side and rotates together with the printed material, and a second holding part that rotatably holds the second rotating part, the second holding part is movable together with the second rotating part in the direction of the axis of the printed material, and the positions of the second rotating part and the second holding part in the direction of the axis of the printed material are adjustable.

11. If the direction perpendicular to the axis of the printed material when viewed from above is defined as the left-right direction, the rotation mechanism comprises: a guide rail for guiding the second holding part in the direction of the axis of the printed material; a guide block that engages with the guide rail and to which the second holding part is fixed; a slide member that is held by a moving body including the second holding part and the guide block and is movable relative to the moving body in the direction of the axis of the printed material; an engaging member that is held by the slide member and is rotatable relative to the slide member with the left-right direction as its axial direction; a restricting member for restricting movement of the slide member and the engaging member in the fourth direction; a first biasing member that biases the engaging member to one side in the rotation direction of the engaging member relative to the slide member; a second biasing member that is compressed between the slide member and the moving body; and a slide member restricting part for restricting the movement range of the slide member relative to the moving body in the direction of the axis of the printed material; The ultraviolet irradiation device according to claim 10, characterized in that the regulating surface is an inclined surface that slopes upward as it approaches the fourth direction side, the engaging member has an engaging portion that engages with the regulating surface, the first biasing member biases the engaging member in a direction in which the engaging portion approaches the regulating surface, and the second biasing member biases the moving body from the slide member toward the third direction side.

12. A printing device comprising the ultraviolet irradiation device according to claim 6 or 7, a table on which the ultraviolet irradiation device is placed, and an inkjet head disposed above the substrate to be printed and which ejects the ink toward the outer peripheral surface of the substrate to be printed.

13. A method for setting a printed material in the rotation mechanism of the ultraviolet irradiation device described in claim 11, characterized in that the sliding member is pushed in the third direction until the second rotating part contacts the end of the printed material in the fourth direction with the end in the third direction attached to the rotating part, and then the sliding member is further pushed in the third direction to set the printed material in the rotation mechanism.

Images