JP6746459B2 - Inkjet printing machine - Google Patents

Description

The present invention relates to an inkjet printing machine.

A flexographic printing machine is generally used as a printing machine for printing an object to be printed (for example, a corrugated cardboard sheet). A flexographic printing machine uses a printing plate that has irregularities in the shape corresponding to the printed image on the surface, applies ink to the surface of the printing plate, and touches the printing plate with the printing object to print it. To print. The printing plate is manufactured according to the image to be printed and is detachably attached to the outer periphery of the plate cylinder. The image to be printed can be changed by replacing the printing plate on the outer periphery of the plate cylinder.

By the way, when printing with a flexographic printing machine, a different printing plate is required for each image to be printed. Therefore, even when printing on a relatively small number of print objects, it is necessary to manufacture a new printing plate as in the case of printing on a large number of print objects, which is high in cost. There was a problem.

Further, in the flexographic printing machine, it is necessary to replace the printing plate each time the image to be printed is changed. Therefore, particularly when printing on a relatively small number of corrugated board sheets, the printing cost is high because the time required to replace the printing plate is large compared to the time when the corrugated board sheets are actually printed. There was a problem that it was easy to rise.

Therefore, the inventor of the present application has studied the use of an inkjet printing machine as disclosed in Patent Document 1 as a printing machine capable of solving the above problems of the flexographic printing machine.

Since the inkjet printing machine of Patent Document 1 forms an image by the inkjet head ejecting ink particles at a timing corresponding to the image, it is necessary to manufacture a different printing plate for each image to be printed like a flexographic printing machine. There is no need to change the printing plate.

Then, the inventor of the present application actually has a rotary body that rotates while contacting a print object, a rotary encoder that detects the amount of movement of the surface of the rotary body, and a movement amount that is detected by the rotary encoder, in-house. An inkjet printer having an inkjet head that ejects ink particles at a timing according to the above was prototyped.

As a result, the inventor has found out the following problems.

That is, when printing is performed by ejecting ink particles from the inkjet head at a timing based on the detection signal of the rotary encoder, in order to obtain practical printing accuracy, the movement amount of the print target object with respect to the minimum detection angle of the rotary encoder is The ratio needs to be fine-tuned with extremely high precision. For example, when the length of the print target is 1 m, even if there is an error of 1% in the ratio of the movement amount of the print target to the minimum detection angle of the rotary encoder, the printed position is relative to the original position. There is a problem that the maximum fluctuation is about 10 mm. Then, in order to solve this problem, for example, the outer diameter dimension of the roller in the middle of the rotation transmission path for transmitting the rotation to the rotary encoder is processed and adjusted, and by adjusting the outer diameter dimension of the roller, the rotary encoder is adjusted. Although a method of finely adjusting the ratio of the movement amount of the printing object to the minimum detection angle of 1 can be considered, the work of adjusting the outer diameter of the roller by repeatedly processing is not easy. Even if the ratio of the amount of movement of the print object to the minimum detection angle of the rotary encoder is finely adjusted once, the movement of the print object to the minimum detection angle of the rotary encoder will then move due to abrasion of the surface of the rotating body. The ratio of the amounts may fluctuate, and in this case, it becomes necessary to readjust the ratio of the amount of movement of the print object to the minimum detection angle of the rotary encoder.

Further, when an inkjet head having a plurality of rows of ink ejection openings at intervals in the moving direction of the surface of the rotator is used, one image (for example, the rotator's A straight line continuous in the direction orthogonal to the moving direction of the surface may be formed. At this time, there is a distance of about several tens of millimeters between the ink ejection openings on the front row of the inkjet head and the ink ejection openings on the last row, and the ink ejection timing from the ink ejection openings on the front row The timing of ink ejection from the ink ejection ports of the row is controlled by using the detection signal of the rotary encoder. Here, for example, if there is a 3% error in the ratio of the movement amount of the printing object to the minimum detection angle of the rotary encoder, the ink ejected from the ink ejection ports in the front row and the ink ejection ports in the last row are ejected. It has been found that a deviation of 0.5 mm or more occurs between the ink and the ink that is formed, and as a result, there arises a problem that an image edge is blurred or a line of the image is bent. In order to solve this problem, it is necessary to finely adjust the ratio of the movement amount of the print object to the minimum detection angle of the rotary encoder with extremely high accuracy.

As a method of solving the above problem, for example, a method of correcting the ejection timing of ink from the inkjet head by data processing the detection signal of the rotary encoder is conceivable, but in order to secure a practical printing speed. Is required to be processed in a very short time (specifically, in μs unit), which is difficult to realize.

JP 2012-101371 A

The problem to be solved by the present invention is to provide an inkjet printing machine capable of printing with high accuracy.

In order to solve the above problems, the present invention provides an inkjet printing machine having the following configuration.
In particular,
A rotating body that rotates while contacting the print target,
A rotary encoder that detects the amount of movement of the surface of the rotating body,
A rotation transmission mechanism that transmits rotation from the rotating body to the rotary encoder,
An inkjet head for ejecting ink particles at a timing according to the amount of movement of the surface of the rotating body detected by the rotary encoder,
The rotation transmission mechanism includes a conical surface that rotates with the rotation of the rotating body, a circumferential surface that rotates in contact with the conical surface, and the conical surface and the circumferential surface in a generatrix direction of the conical surface. And a rotation transmission ratio adjusting section for relative displacement to
An inkjet printing machine is provided.

With this configuration, the rotation transfer ratio adjusting unit relatively displaces the conical surface and the circumferential surface in the generatrix direction of the conical surface, thereby finely adjusting the rotation transfer ratio of the rotation transmitted from the rotating body to the rotary encoder. it can. Therefore, it is possible to finely adjust the ratio of the movement amount of the print target to the minimum detection angle of the rotary encoder with extremely high accuracy.

As the inkjet head, an inkjet head having a plurality of rows of ink ejection openings arranged at intervals can be adopted.

With this configuration, when one image is formed by the inks ejected from the ink ejection ports of a plurality of columns, the ejection timing of the ink ejected from the ink ejection ports of each column can be controlled with high precision. , Sharp printing becomes possible.

The inclination angle of the conical surface with respect to the direction parallel to the axial direction is preferably set in the range of 2° to 5°.

By setting the inclination angle to 2° or more, it becomes possible to secure work efficiency when finely adjusting the rotary encoder. Further, by setting the inclination angle to 5° or less, it becomes easy to finely adjust the ratio of the movement amount of the print target object to the minimum detection angle of the rotary encoder with high accuracy.

The rotation transmission mechanism includes a first roller to which the rotation of the rotating body is input, and a second roller connected to the rotation shaft so as to rotate integrally with the rotation shaft of the rotary encoder, A configuration in which the conical surface is provided on the outer circumference of the first roller and the circumferential surface is provided on the outer circumference of the second roller can be adopted. In this case, the rotation transmission ratio adjusting unit is connected to a first roller support member that rotatably supports the first roller, and is movably connected to the first roller support member in the generatrix direction of the conical surface. An encoder support member may be used, and the rotary encoder may be fixed to the encoder support member.

In the ink jet printing machine of the present invention, the rotation transfer ratio adjusting unit relatively displaces the conical surface and the circumferential surface in the generatrix direction of the conical surface to finely adjust the rotation transfer ratio of the rotation transmitted from the rotating body to the rotary encoder. can do. Therefore, it is possible to finely adjust the ratio of the movement amount of the print target object to the minimum detection angle of the rotary encoder with extremely high accuracy, and it is possible to perform printing with high accuracy.

Schematic diagram showing an inkjet printer of an embodiment of the present invention Enlarged sectional view taken along line II-II of FIG. Enlarged view near the rotary encoder in Figure 1. A view of the vicinity of the rotary encoder shown in FIG. 3 as viewed from the downstream side in the moving direction of the belt. FIG. 1A is an enlarged view showing a part of a straight line when a straight line is printed after finely adjusting the ratio of the movement amount of the print object to the minimum detection angle of the rotary encoder shown in FIG. 1, and FIG. FIG. 2 is an enlarged view showing a part of a straight line when the straight line is printed before finely adjusting the ratio of the movement amount of the print object to the minimum detection angle of the rotary encoder shown in FIG.

FIG. 1 shows an inkjet printing machine according to an embodiment of the present invention. This inkjet printing machine includes a belt 1 that is rotationally driven by a drive source (not shown), a rotary encoder 2 that detects the amount of movement of the surface of the belt 1, and a rotation transmission mechanism 3 that transmits rotation from the belt 1 to the rotary encoder 2. The inkjet head 4 ejects ink particles at a timing corresponding to the amount of movement of the surface of the belt 1 detected by the rotary encoder 2.

The belt 1 is formed in an endless shape and is wound around a plurality of rollers 6. The belt 1 conveys the print target 5 placed on the upper surface of the belt 1 so that the print target 5 passes through a position facing the inkjet head 4. The inkjet head 4 is fixedly provided at a position facing the upper surface of the belt 1. The print target 5 is, for example, a corrugated cardboard sheet.

As shown in FIG. 2, the inkjet head 4 has a plurality of rows of ink ejection ports 13 arranged at intervals in the moving direction of the surface of the belt 1. The ink ejection openings 13 in each row are composed of a large number of ink ejection openings 13 arranged in a row in a direction (left-right direction in the drawing) orthogonal to the moving direction of the surface of the belt 1. In addition, the ink ejection ports 13 in each row are arranged in a direction (right and left in the figure) in which the ink ejection ports 13 in adjacent rows in the moving direction of the surface of the belt 1 (vertical direction in the figure) are orthogonal to the moving direction of the surface of the belt 1. Direction) and are arranged so as to be displaced from each other. Then, when the ink 14 is ejected from the ink ejection ports 13 of each row, the ejection timing is synchronized so that the ink 14 ejected from the ink ejection ports 13 of each row is moved in the moving direction of the surface of the belt 1. It is possible to form the image (for example, a straight line continuous in the direction orthogonal to the moving direction of the surface of the belt 1) on the surface of the print target 5 by adhering it to the positions aligned in the direction orthogonal to each other. The distance between the ink ejection openings 13 in the front row (the bottom row in the figure) and the ink ejection openings 13 in the last row (the top row in the figure) of the inkjet head 4 is in the range of 10 to 50 mm. Is set to.

As shown in FIGS. 3 and 4, the rotation transmission mechanism 3 is connected to the rotation shaft 21 so as to rotate integrally with the first roller 20 to which the rotation of the belt 1 is input and the rotation shaft 21 of the rotary encoder 2. The second roller 22 and the rotation transmission ratio adjusting unit 23 that adjusts the rotation transmission ratio of the rotation transmitted from the belt 1 to the rotary encoder 2.

A cylindrical surface 24 and a conical surface 25 are provided coaxially on the outer circumference of the first roller 20. The cylindrical surface 24 is in rolling contact with the belt 1. When the belt 1 rotates, the cylindrical surface 24 and the conical surface 25 rotate as the belt 1 rotates. The inclination angle of the conical surface 25 (the inclination angle of the conical surface 25 with respect to the direction parallel to the axial direction of the conical surface 25) is set in the range of 2° to 5°.

A circumferential surface 26 that contacts the conical surface 25 of the first roller 20 is provided on the outer circumference of the second roller 22. In the drawing, an example in which a cylindrical surface is used as the circumferential surface 26 is shown, but a conical surface having a vertex at the same position as the apex of the conical surface 25 or a position in the vicinity thereof is adopted as the circumferential surface 26. It is also possible.

The rotation transmission ratio adjusting unit 23 is configured to be relatively movable in the generatrix direction of the conical surface 25 via the first roller support member 27 that rotatably supports the first roller 20 and the first roller support member 27 via the slide mechanism 28. And an encoder support member 29 connected thereto. The rotary encoder 2 is fixed to the encoder support member 29. The rotation transmission ratio adjusting unit 23 is a mechanism that changes the rotation transmission ratio of the rotation transmitted from the belt 1 to the rotary encoder 2 by relatively displacing the conical surface 25 and the circumferential surface 26 in the generatrix direction of the conical surface 25. ..

The slide mechanism 28 adjusts the position of the base plate 30 fixed to the first roller support member 27, the slide plate 31 supported in parallel with the base plate 30, and the relative position of the slide plate 31 with respect to the base plate 30. And a part 32. The position adjusting section 32 includes a knob 33 for rotating operation, a feed screw section 34 that converts the rotation of the knob 33 into a parallel movement of the slide plate 31, and a clamp section 35 that holds the position of the slide plate 31 with respect to the base plate 30. Have. The first roller support member 27 has an inclined seat surface 36 for fixing the base plate 30. The inclined seat surface 36 is a flat surface that is inclined in the same direction as the contact portion of the conical surface 25 of the first roller 20 with the second roller 22. The clamp portion 35 is a mechanism that switches between a clamp state in which the position of the slide plate 31 is held with respect to the base plate 30 and a clamp release state in which the position of the slide plate 31 with respect to the base plate 30 is released by an external operation.

By the way, in order to obtain practical printing accuracy in the inkjet printing machine, it is necessary to finely adjust the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 with extremely high accuracy. For example, when the length of the print target 5 is 1 m, even if there is an error of 1% in the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2, the printed position is the original position. It varies about 10 mm at the maximum. Therefore, it is necessary to finely adjust the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 with extremely high accuracy. Further, even when the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 is finely adjusted once, thereafter, the rotary encoder 2 is damaged due to abrasion of the cylindrical surface 24 on the outer periphery of the first roller 20. The ratio of the movement amount of the print target 5 to the minimum detection angle may vary, and in this case, it becomes necessary to readjust the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2.

Further, in the above inkjet printer, since the inkjet head 4 has the ink ejection ports 13 in a plurality of rows, the ejection timing of the ink from the ink ejection openings 13 in each column of the inkjet head 4 is based on the detection signal of the rotary encoder 2. 2 to form one image (for example, a straight line continuous in the direction orthogonal to the moving direction of the surface of the belt 1) with the ink 14 ejected from each of the plurality of rows of ink ejection ports 13 as shown in FIG. can do. Here, for example, if there is an error in the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2, the ink 14 ejected from the ink ejection port 13 in the front row and the ink ejection port 13 in the last row. There is a gap between the ink and the ink 14 ejected from the ink, and as a result, the edges of the image are blurred or the lines of the image are bent. In order to solve this problem, it is necessary to finely adjust the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 with high accuracy.

Therefore, in the inkjet printer of the above-described embodiment, the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 can be finely adjusted as follows.

First, by operating the clamp portion 35 shown in FIG. 4, the holding of the position of the slide plate 31 with respect to the base plate 30 is released. Next, by rotating the knob 33 of the position adjusting unit 32, the slide plate 31 of the slide mechanism 28 is moved in parallel to the base plate 30. As a result, the conical surface 25 of the first roller 20 and the circumferential surface 26 of the second roller 22 are relatively displaced in the generatrix direction of the conical surface 25, and the rotation transmission ratio of the rotation transmitted from the belt 1 to the rotary encoder 2 is increased. Change. Specifically, the second roller 22 is relatively moved to the larger diameter side of the conical surface 25 of the first roller 20, so that the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 decreases. The rotation transmission ratio is changed to relatively move the second roller 22 toward the smaller diameter side of the conical surface 25 of the first roller 20, so that the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 is increased. The rotation transmission ratio changes in the following direction. Here, since the inclination angle of the conical surface 25 is 2° or more, the working efficiency when finely adjusting the rotary encoder 2 is secured, while the inclination angle of the conical surface 25 is 5° or less. Therefore, it becomes easy to finely adjust the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 with high accuracy. Then, the clamp portion 35 is operated again to hold the position of the slide plate 31 with respect to the base plate 30. In this way, the rotation transmission ratio of the rotation transmitted from the belt 1 to the rotary encoder 2 is finely adjusted, and the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 is finely adjusted with extremely high accuracy. You can

In this inkjet printing machine, as described above, the rotation transmission ratio adjusting unit 23 relatively displaces the conical surface 25 and the circumferential surface 26 in the generatrix direction of the conical surface 25, thereby transmitting the rotation from the belt 1 to the rotary encoder 2. The rotation transmission ratio of can be finely adjusted. Therefore, the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 can be finely adjusted with extremely high accuracy, and printing can be performed with high accuracy.

In addition, as shown in FIG. 2, this inkjet printing machine ejects the ink 14 ejected from each row of ink ejection ports 13 when forming one image with the ink 14 ejected from each row of ink ejection ports 13. It is possible to control the ejection timing of the ink jet printer with high precision, and sharp printing is possible.

In the inkjet printer of the above-described embodiment, a test is performed to confirm that sharp printing is possible when forming one image with the inks 14 ejected from the ink ejection ports 13 of the plurality of rows of the inkjet head 4. It was The test results are shown in FIGS. 5(a) and 5(b). In FIG. 5B, the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 has a 3% error, and the ink is ejected from each of the plural rows of ink ejection ports 13 of the inkjet head 4. An enlarged image of a part of a straight line when a continuous straight line is printed with the ink 14 in a direction orthogonal to the moving direction of the print target 5 is shown. On the other hand, in FIG. 5A, after performing the printing of FIG. 5B, a plurality of inkjet heads 4 are arranged in a state where the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2 is finely adjusted. An enlarged image of a part of a straight line when a continuous straight line is printed in the direction orthogonal to the moving direction of the print target 5 with the ink 14 discharged from each of the ink discharge ports 13 in the row is shown. In FIG. 5B, a straight edge is blurred due to a deviation in the ejection timing of the ink 14 from the ink ejection ports 13 of each row of the inkjet head 4, whereas in FIG. The ejection timings of the ink 14 from the ink ejection ports 13 of each row of the inkjet head 4 are synchronized with each other with high accuracy, and the straight edges are sharp. As described above, it is possible to confirm that sharp printing is possible by finely adjusting the ratio of the movement amount of the print target 5 to the minimum detection angle of the rotary encoder 2.

In the above-described embodiment, a sheet-fed inkjet printer that conveys the sheet-fed print target 5 by the belt 1 and ejects ink particles from the inkjet head 4 onto the surface of the sheet-fed print target 5 is taken as an example. As described above, according to the present invention, the print object 5 (for example, wrapping paper) that is continuous in the transport direction without interruption is moved while being bridged over a plurality of rollers, and the surface of the print object 5 is moved from the inkjet head 4 to It can also be applied to a rotary ink jet printing machine that ejects ink particles. In this case, the first roller 20 is provided so as to come into contact with the surface of the roller that rotates while being in contact with the print target 5 (the roller on which the print target 5 is bridged), and the first roller 20 is connected to the rotary encoder 2. The rotation transmission ratio adjusting unit 23 may be provided in the rotation transmission mechanism 3 that transmits rotation.

Further, in the above-described embodiment, the direct type inkjet printing machine that directly ejects the ink from the inkjet head 4 onto the surface of the printing target 5 has been described as an example. However, the present invention does not contact the printing target 5. While the inkjet head 4 is arranged so as to face the surface of the rotating intermediate transfer member (for example, a cylindrical plate cylinder), ink particles are ejected from the inkjet head 4 onto the surface of the intermediate transfer member, It is also possible to apply it to a transfer type inkjet printing machine that transfers ink from the surface to the print target 5. In this case, the first roller 20 is provided so as to come into contact with the surface of the intermediate transfer member, and the rotation transmission mechanism 3 that transmits the rotation from the first roller 20 to the rotary encoder 2 is preferably provided with the rotation transmission ratio adjusting unit 23. ..

1 Belt 2 Rotary Encoder 3 Rotation Transmission Mechanism 4 Inkjet Head 5 Printing Object 13 Ink Ejection Port 14 Ink 20 First Roller 21 Rotation Shaft 22 Second Roller 23 Rotation Transmission Ratio Adjusting Section 25 Conical Surface 26 Circular Surface 27 First Roller Support member 29 Encoder support member

Claims (4)

A rotating body (1) that rotates while contacting the print target (5);
A rotary encoder (2) for detecting the amount of movement of the surface of the rotating body (1),
A rotation transmission mechanism (3) for transmitting rotation from the rotating body (1) to the rotary encoder (2);
An inkjet head (4) for ejecting particles of the ink (14) at a timing according to the amount of movement of the surface of the rotating body (1) detected by the rotary encoder (2),
The rotation transmission mechanism (3) includes a conical surface (25) that rotates with the rotation of the rotating body (1), and a circumferential surface (26) that rotates while being in contact with the conical surface (25). A rotation transmission ratio adjusting part (23) for relatively displacing the conical surface (25) and the circumferential surface (26) in the generatrix direction of the conical surface (25),
Inkjet printing machine. The inkjet printing machine according to claim 1, wherein the inkjet head (4) has a plurality of rows of ink discharge ports (13) arranged at intervals. The inkjet printing machine according to claim 1 or 2, wherein an inclination angle of the conical surface (25) with respect to a direction parallel to the axial direction is set in a range of 2° to 5°. The rotation transmission mechanism (3) rotates the first roller (20) to which the rotation of the rotating body (1) is input and the rotation shaft (21) of the rotary encoder (2) so as to rotate together. A second roller (22) connected to a shaft (21), the conical surface (25) is provided on the outer periphery of the first roller (20), and the second roller (22) is provided on the outer periphery of the second roller (22). A circumferential surface (26) is provided,
The rotation transmission ratio adjusting unit (23) includes a first roller support member (27) that rotatably supports the first roller (20), and the conical surface (25) on the first roller support member (27). 4. An encoder support member (29) connected so as to be relatively movable in the generatrix direction of, and the rotary encoder (2) is fixed to the encoder support member (29). The described inkjet printing machine.