Printing apparatus

Abstract

To provide a printer that can early detect printing pitch misalignment that performs printing on a web.SOLUTION: The printer includes: a driving roll that has an encoder provided thereon and transports a web W that is plastic film; and a follower roll that has a rotational sensor, which is a non-contact type and magnetic detection type rotation sensor, provided thereon and guides the web W. Therefore, by assuming printing pitch misalignment based on the rotational condition of the follower roll measured by using the rotational sensor that is a non-contact type and magnetic detection type rotational sensor, the change in the rotational condition of the follower roll can be measured accurately, thereby allowing failure due to printing pitch misalignment to be accurately detected.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a printing device. [Background technology]

[0002] In printing devices such as gravure printing machines and inkjet printing machines that perform multicolor printing on a conveyed long print medium (web), it is important to understand the printing pitch deviation of the web in order to prevent printing defects such as misalignment. For this reason, various technologies for detecting printing pitch deviation have been developed (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-233746 Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, two print marks printed on a web are detected, and the detected marks are subjected to image analysis to calculate the detected positions of the two print marks, thereby calculating the print pitch.

[0005] However, the print pitch measurement method of Patent Document 1 uses multiple image sensors to measure the print pitch, so it cannot detect pitch misalignment unless there is actually a pitch misalignment that can be detected by the image sensors. Therefore, it is difficult to detect pitch misalignment before printing problems occur due to pitch misalignment.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a printing device that prints on a web and that is capable of detecting print pitch deviation at an early stage. [Means for solving the problem]

[0007] In order to achieve the above object, a printing device according to the present invention comprises: A drive roll is provided with an encoder and transports a web, which is a plastic film; a driven roll having a magnetic detection type rotation sensor installed thereon and guiding the transport of the web; Rotation information measured by the encoder and the magnetic detection type rotation sensor The difference in the transport speed between the driving roll and the driven roll is calculated from and a control unit that estimates the printing pitch deviation of the driven roll based on the above.

[0008] Also, a plurality of the driven rolls are provided, The plurality of driven rolls include a first driven roll; a second driven roll having a wrap angle of the web smaller than the wrap angle of the web of the first driven roll; This may also be the case.

[0009] Further, the wrap angle of the web of the second driven roll is 10 degrees or less. This may also be the case.

[0011] Further, the control unit Using a data set including setting values ​​that affect the print state and print pitch deviation as training data, the print state is determined using a prediction model generated by machine learning so as to predict the print pitch deviation from the setting values. This may also be the case.

[0012] The magnetic detection type rotation sensor is a detection target portion having a plurality of magnetic poles formed in a circumferential direction and disposed on a rotation shaft of the driven roll; a detection unit disposed on a fixed portion near the rotating shaft and configured to detect a magnetic flux density, The control unit an eccentricity state of the driven roll is estimated based on a variation in magnetic flux density detected by the magnetic detection type rotation sensor; This may also be the case. [Effects of the Invention]

[0013] The printing device of the present invention is a printing device that prints on a web of plastic film, and is equipped with a drive roll equipped with an encoder and a driven roll equipped with a non-contact magnetic detection rotation sensor, thereby reducing the rotational load on the driven roll and enabling early detection of printing pitch deviations caused by fluctuations in the tension of the driven roll. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a printing device according to a first embodiment of the present invention. [Figure 2] 1 is a front view showing the configuration of a printing unit according to a first embodiment. [Figure 3] FIG. 2 is a functional block diagram of a control unit according to the first embodiment. [Figure 4] 3 is a conceptual diagram showing the arrangement of magnetic poles of a detection target portion of a rotation sensor. FIG. [Figure 5] 10 is a graph showing an example of a waveform of magnetic flux density, which is an output of a rotation sensor. [Figure 6] 10A and 10B are diagrams illustrating an example of the movement of a rotation sensor when a roll has eccentricity. [Figure 7] FIG. 10 is a schematic diagram of a printing device according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] A printing apparatus according to an embodiment of the present invention will now be described with reference to the drawings.

[0016] (Embodiment 1) As shown in the schematic diagram of Figure 1, the printing apparatus 1 of this embodiment includes an unwinding device 11 that unwinds a rolled web W and sends it to a printing press, a gravure printing device 20 that performs multi-color printing on the web W sent out from the unwinding device 11, a winding device 12 that winds up the printed web W, and a control unit 40 (not shown).

[0017] The web W is a long printing medium made of plastic film. As a plastic film, the web W is prone to expansion and contraction due to the influence of factors such as environmental temperature and tension fluctuations, and is generally prone to problems such as printing misalignment. More specifically, if the web W is a non-breathable plastic film, air is likely to be trapped between the web W and the roll that transports the web W, which can easily cause problems such as the driven roll not keeping up with the transport speed of the web W. If the rotation of the driven roll does not keep up with the transport speed of the web W, the rotational resistance of the driven roll causes tension fluctuations in the web W. When tension fluctuations occur, the amount of expansion and contraction of the web W, which is a plastic film, changes, resulting in printing pitch deviations.

[0018] The unwinding device 11 is a device that delivers the web W set in a roll state to the gravure printing device 20.

[0019] The gravure printing apparatus 20 includes printing units 21 that print on the web W for each color. The gravure printing apparatus 20 according to this embodiment includes three printing units 21-1, 21-2, and 21-3. The gravure printing apparatus 20 also includes an in-feed roll 15 that feeds the web W into the printing unit 21-1, and an out-feed roll 16 that feeds the web W from the printing unit 21-3 to the winding device 12.

[0020] Fig. 2 is a diagram showing a detailed configuration of the printing unit 21. As shown in Fig. 2, the printing unit 21 includes guide rolls 211 and 217 that guide the web W, a plate cylinder 212, a furnishing roll 213, an impression cylinder 214, an ink pan 215, and a doctor blade 216. The printing unit 21 also includes a drying device D that dries the printed ink.

[0021] The web W sent out from the unwinding device 11 is guided by a guide roll 211, which is a non-driven driven roll, and transported to the printing section. In the printing section, ink from a plate cylinder 212 is transferred to the web W, thereby printing a pattern. The plate cylinder 212 is a roll on whose outer circumferential surface a pattern corresponding to the printing color of each printing unit is engraved, and is a drive roll that rotates by the driving force of a drive unit (motor) not shown. The plate cylinder 212 is a reference roll that serves as a reference for the transport speed of the web W in the printing unit 21 that includes the plate cylinder 212, and an encoder for measuring the rotation angle of the plate cylinder 212 is installed on the rotation shaft of the plate cylinder 212.

[0022] Furthermore, the web W printed in the printing section is guided by a plurality of guide rolls 217, which are driven rolls, passes through the drying device D, and is delivered from the printing unit 21. As shown in FIG. 2, the contact range between the web W and the guide roll 217, i.e., the wrap angle, varies depending on the arrangement position of the guide roll 217 within the printing unit 21. The guide rolls 217 are divided into a first driven roll 217a with a deep (large) wrap angle and a second driven roll 217b with a shallower (smaller) wrap angle than the guide roll 217a. Generally, when the wrap angle is deep, the force that the guide roll 217 receives from the web W due to tension becomes large, and when the wrap angle is shallow, the force that the guide roll 217 receives from the web W becomes small. The wrap angles of the guide rolls 217a and 217b may be set based on the detection sensitivity of tension fluctuations, which will be described later, taking into consideration the material of the web W, the set tension, etc. For example, the wrap angle of the guide roll 217a is set to be greater than 10 degrees, and the wrap angle of the guide roll 217b is set to be 10 degrees or less.

[0023] In this embodiment, a rotation sensor 60 is installed on at least one of the guide rolls 217a with a large wrap angle and at least one of the guide rolls 217b with a shallow wrap angle. The rotation sensor 60 is a non-contact magnetic detection rotation sensor that reads the rotation of a magnetic ring attached to the rotation shaft of the plate cylinder 212 with a magnetic sensor located near the magnetic ring on the frame of the printing unit 21. This makes it possible to measure the rotation states of driven rolls with different wrap angles.

[0024] The winding device 12 is a device that winds up the web W that has been fed from the unwinding device 11 and printed by the gravure printing device 20.

[0025] As shown in the block diagram of FIG. 3, the control unit 40 includes a control unit 41, a storage unit 42, a display unit 43, and an input unit 44.

[0026] The control unit 41 is composed of a CPU (Central Processing Unit), ROM (Read Only Memory), RAM (Random Access Memory), etc., and controls the operation of the entire printing device 1, including the operation of the drive roll. The control unit 41 also measures the rotation state of the rolls in each part of the printing device 1, and determines the state of print pitch deviation based on the measured rotation state.

[0027] The control unit 41 loads various operation programs and data stored in the ROM, storage unit 42, etc. of the control unit 41 into the RAM and operates the CPU, thereby realizing each function of the control unit 41 shown in Fig. 3. As a result, the control unit 41 operates as a rotation information acquisition unit 411, a print pitch estimation unit 412, and a determination unit 413.

[0028] The rotation information acquisition unit 411 acquires rotation information of each roll from the encoder of the connected drive roll and the rotation sensor 60 of the connected driven roll. The rotation information is data relating to the rotation angle of the roll measured by the encoder and each rotation sensor 60. The rotation information acquisition unit 411 also transmits the acquired rotation information to the printing pitch estimation unit 412.

[0029] The printing pitch estimation unit 412 calculates the transport speed of the web W for each roll based on the rotation information of each roll acquired by the rotation information acquisition unit 411 and the roll diameter stored in advance in a storage unit. The printing pitch estimation unit 412 also estimates the printing pitch deviation based on the difference between the transport speed of the web W calculated for each driven roll and the reference transport speed calculated for the drive roll, which is the reference roll.

[0030] The determination unit 413 determines whether the printing condition is normal or not based on the printing pitch deviation estimated above and the printing pitch deviation estimated using a learned model pre-stored in the memory unit 42.

[0031] The storage unit 42 is a non-volatile memory such as a hard disk or flash memory, and stores a program for estimating the print pitch deviation from the measured transport speed, a trained model used to determine the print state, and the like.

[0032] The display unit 43 is a display device, such as a liquid crystal monitor, provided in the control unit 40. The display unit 43 displays information such as the estimated print pitch deviation and the determination result of the print state.

[0033] The input unit 44 is an input device for inputting various setting values ​​of the printing apparatus 1, adjustment parameters related to detection of rotation information of each roll, roll diameter of each roll to be measured, etc. The input unit 44 is a keyboard, touch panel, mouse, etc. provided in the control unit 40.

[0034] Next, estimation of print pitch deviation and determination of print state in the printing device 1 according to this embodiment will be described.

[0035] When the operation of the gravure printing press, which is the printing device 1, starts, the web W is sent from the unwinding device 11 to the gravure printing device 20. In the gravure printing device 20, the guide rolls 211, 217, the plate cylinder 212, the furnishing roll 213, the impression cylinder 214, etc. rotate, and printing is performed on the web W being conveyed.

[0036] More specifically, in the printing section, a furnishing roll 213 immersed in ink stored in an ink pan 215 transfers ink to the outer peripheral surface of a plate cylinder 212. The ink transferred to the plate cylinder 212 is measured by being scraped off by a doctor blade 216. The plate cylinder 212 is rotated by the driving force of a drive motor M (not shown) so as to achieve a set printing speed (the conveying speed of the web W).

[0037] An encoder is also provided on the drive shaft 212 a that rotates the plate cylinder 212 , and transmits rotation information of the plate cylinder 212 to a rotation information acquisition unit 411 of the control unit 40 .

[0038] The web W is pressed against the plate cylinder 212 onto which the ink has been transferred by the impression cylinder 214. As a result, the ink is transferred to the web W, and printing is performed.

[0039] The web W onto which the ink has been transferred is guided by the guide roll 217 and dried in a drying device D provided in the printing unit 21. This allows the ink to be fixed to the web W, preventing problems such as bleeding.

[0040] 2, the web W sent out from the printing unit has its conveying direction changed upward by a guide roll 217a with a large wrap angle, and is sent out to the drying device D. This reduces the installation area of ​​the printing unit 21, and makes it possible to downsize the printing device 1. After the conveying direction is changed significantly, the web W is guided by a guide roll 217b with a shallow wrap angle from before it is inserted into the drying device D until it is discharged from the drying device D.

[0041] In this embodiment, a rotation sensor 60 is installed on both the guide roll 217a with a large wrap angle and the guide roll 217b with a shallow wrap angle, and the rotation state of each roll is measured. The number of guide rolls 217 on which the rotation sensor 60 is installed is not particularly limited, and the rotation sensor 60 can be installed on multiple guide rolls 217.

[0042] Then, the non-contact type rotation sensor 60 installed on the guide roll 217 transmits information on the rotation angle output based on the detected magnetic information to the rotation information acquisition unit 411 of the control unit 40.

[0043] In the gravure printing device 20, the printing units 21-1 to 21-3 sequentially print pictures in different colors. The web W on which printing of each color has been completed is wound up by the winding device 12.

[0044] The rotation information acquisition unit 411 of the control unit 40 acquires rotation information of the plate cylinder 212, which is the drive roll, and the guide roll 217, which is the driven roll, of each of the printing units 21. The rotation information acquisition unit 411 also transmits the acquired rotation information to the printing pitch estimation unit 412.

[0045] The printing pitch estimation unit 412 calculates the transport speed of the web W at each roll from the rotation information acquired by the rotation information acquisition unit 411, and estimates the printing pitch deviation at each driven roll based on the difference between the reference transport speed of the drive roll and the transport speed of the driven roll. For example, if the transport speed of any of the guide rolls 217 is lower than the reference transport speed of the plate cylinder 212, which is the reference roll, it is considered that the rotation of the guide roll 217 cannot keep up with the transport of the web W, and tension fluctuations occur in the web W. Tension fluctuations cause the web W, which is a plastic film, to stretch, resulting in printing pitch deviations.

[0046] The printing pitch estimation unit 412 estimates the magnitude of the printing pitch deviation for each driven roll based on the difference between the above-mentioned conveying speed of the driven roll and the reference conveying speed.

[0047] Furthermore, the determination unit 413 determines the printing state, i.e., whether printing is being performed normally, based on the printing pitch deviation estimated by the printing pitch estimation unit 412 based on measurements taken by the rotation sensor 60 and the printing pitch deviation estimated using a prediction model, which is a trained model pre-stored in the memory unit 42. More specifically, a prediction model that predicts the printing pitch deviation from the setting values ​​is created by machine learning using as training data a data set including the printing state, such as the conveyance speed, tension, etc. of the web W, and the type of web W, for example, the material, thickness, and width of the web W, in particular setting values ​​that affect the printing state based on the printing pitch deviation, and the printing pitch deviation measured when operating under those setting values. The machine learning algorithm for generating the prediction model is not particularly limited, and regression analysis, for example, can be used.

[0048] The determination unit 413 determines the printing condition based on a prediction model, setting values, estimated printing pitch deviation, and the like that have been created in advance and stored in the storage unit 42. Specifically, the determination unit 413 calculates the difference (difference in deviation amount) between the printing pitch deviation estimated by the printing pitch estimation unit 412 based on the acquired rotation information and the printing pitch deviation predicted using the prediction model from the setting values. If the calculated difference is equal to or greater than a predetermined threshold, the determination unit 413 determines that the printing pitch deviation for the roll in question exceeds an acceptable range and that an abnormality has occurred. If the determination unit 413 determines that an abnormality has occurred, it causes the display unit 43 to display information about the roll determined to have an abnormality. Furthermore, if the control unit 41 detects an abnormality, it may sound an alarm and stop operation of the printing device 1.

[0049] The control unit 40 continues to estimate the print pitch deviation and determine the print state as described above until the operation of the printing device 1 is completed.

[0050] As described above, in the printing apparatus 1 according to this embodiment, which prints on a plastic film web W, the plate cylinder 212, which is a driving roll, is equipped with an encoder, and the guide roll 217, which is a driven roll, is equipped with a magnetic detection rotation sensor 60. The printing apparatus 1 also estimates printing pitch deviation based on the difference between the reference conveyance speed of the driving roll and the conveyance speed of the driven roll, and determines whether the printing condition is appropriate. Therefore, since the printing apparatus 1 estimates printing pitch deviation based on the rotational state of the driven roll measured using the magnetic detection rotation sensor 60, which is a non-contact sensor, the rotational load on the driven roll is smaller than when a contact sensor is used, and changes in the rotational state of the driven roll can be measured with high accuracy. This makes it possible to accurately detect defects due to printing pitch deviation.

[0051] Furthermore, in this embodiment, a rotation sensor 60 is disposed on the guide roll 217b, which is one of the driven rolls of each printing unit 21 and has a shallow wrap angle with respect to the web W, to measure the rotation state and estimate the printing pitch deviation. In the guide roll 217b with a shallow wrap angle, the force acting on the roll due to the tension of the web W is small, but by using a magnetic detection type rotation sensor 60 with a small rotation load, it is possible to accurately detect changes in tension. Therefore, by measuring the rotation state of the guide roll 217b with the rotation sensor 60 with a small rotation load, it is possible to detect defects such as minute printing pitch deviations with high sensitivity.

[0052] In this embodiment, a rotation sensor 60 is disposed on the guide roll 217a, which is one of the driven rolls of each printing unit 21 and has a large wrap angle with respect to the web W, to estimate the printing pitch deviation. The force exerted on the guide roll 217a with a large wrap angle due to the tension of the web W is greater than that on the guide roll 217b with a shallow wrap angle. Therefore, by prioritizing detection of the printing pitch deviation estimated on the guide roll 217a with a large wrap angle over the printing pitch deviation estimated on the guide roll 217b with a shallow wrap angle, the detection sensitivity for the influence of the printing pitch deviation can be reduced. This allows for a small printing pitch deviation to be tolerated, making it possible to discover and identify serious defects, such as breaks in the web W, which occur infrequently.

[0053] Furthermore, the control unit 41 may be able to switch between the guide roll 217a with a large wrap angle and the guide roll 217b with a shallow wrap angle to give priority to detecting the print pitch deviation. This allows the detection sensitivity of defects to be switched appropriately to determine the printing state.

[0054] In addition, in this embodiment, the magnetic detection unit 61 is arranged on the fixed part of the printing unit 21, and the detected part 62 is arranged on the rotation shaft of the roll, but this is not limited to this. For example, the detected part 62 may be arranged on the fixed part of the printing unit 21, and the magnetic detection unit 61 may be arranged on the rotation shaft of the roll. This increases the degree of freedom in the arrangement of the rotation sensor 60.

[0055] (Variation) In the above-described embodiment, rotation sensor 60 is used, which detects the rotation angle by magnetic detection. However, rotation sensor 60', which can detect roll eccentricity by magnetic detection, may also be used. Rotation sensor 60' is fixed near drive shaft 212a of plate cylinder 212 of printing unit 21 and includes magnetic detection unit 61 that detects magnetic flux density. Rotation sensor 60' is also attached to drive shaft 212a of plate cylinder 212 and includes detection target 62 on which a magnetic pole pattern is formed so that the magnetic flux density detected by magnetic detection unit 61 changes as plate cylinder 212 rotates. In this way, rotation sensor 60' measures the rotation pitch of detection target 62 to estimate the eccentricity of the roll.

[0056] As shown in FIG. 4, the detectable portion 62 is formed with alternating north and south poles of equal width in the circumferential direction, with the width of the magnetic poles forming the reference pattern 62a being larger. This allows the reference position of the detectable portion 62 to be detected during rotation to be detected. The magnetic detection unit 61 detects changes in magnetic flux density caused by changes in nearby magnetic poles as the detectable portion 62 rotates, and outputs the detected changes as eccentricity information. While the number of magnetic poles magnetized in the detectable portion 62 is not particularly limited, for example, the width of one magnetic pole (angle viewed from the center of rotation) is set to approximately 10 degrees, and multiple magnetic poles are magnetized during one rotation. This allows for more detailed detection of fluctuations in rotation speed and roll eccentricity. If the roll is not eccentric, the change in magnetic flux density will have a regular waveform, as shown by the dashed line in the graph in FIG. 5.

[0057] If the roll is eccentric, changes occur in the magnitude of the magnetic flux density, the wave period, etc. The print pitch estimation unit 412 estimates the eccentric state of the roll from the difference between a reference waveform that indicates a state without eccentricity, which is stored in advance in the storage unit 42, and a waveform related to the acquired eccentricity information.

[0058] More specifically, the magnetic poles other than the reference pattern 62a of the detection target 62 are formed at equal intervals, so the waveform of the magnetic flux density fluctuates with the same period. However, if the roll is eccentric, as shown in Figures 6(A) and 6(B), the distance between the magnetic detection unit 61 and the detection target 62 varies depending on the rotation angle of the plate cylinder 212, so the period of the waveform of the magnetic flux density fluctuates. The printing pitch estimation unit 412 uses this period fluctuation to estimate the eccentricity state.

[0059] As described above, the method of estimating the eccentricity state based on the periodic fluctuations can also be performed using a general encoder. That is, the eccentricity state can be estimated from the fluctuations in the clock intervals of the encoder. However, these periodic fluctuations include not only the eccentricity of the roller, but also fluctuations due to the effects of expansion and contraction of the web W due to tension changes and the like, and slippage between the roll and the web W. In contrast, by using a magnetic detection type rotation sensor 60', the effects of the eccentricity of the roll can be separated from other effects such as expansion and contraction of the web W.

[0060] More specifically, as shown in FIGS. 6A and 6B, if the roll being measured is eccentric, the distance between the magnetic detection unit 61 and the detected portion 62 fluctuates. This causes the magnitude of the magnetic flux density detected by the rotation sensor 60′ to fluctuate, as shown in the graph in FIG. 5. Therefore, for example, if the periodic fluctuation is equal to or greater than a predetermined threshold and the fluctuation in the magnitude of the magnetic flux density is equal to or greater than a predetermined threshold, it can be determined that eccentricity has occurred. The printing pitch estimation unit 412 of this modified example estimates the eccentricity state based on the periodic fluctuation and the fluctuation in the magnitude of the magnetic flux density. This allows the printing device 1 to estimate the eccentricity state along with the rotation speed of each roll, thereby enabling early detection of the cause of defects such as print pitch deviation and reducing the occurrence of such defects.

[0061] (Embodiment 2) In the above-described first embodiment, an example has been described in which the printing apparatus 1 is equipped with a gravure printing apparatus 20 including a plurality of printing units 21, but other types of printing machines may also be used. In this embodiment, a printing apparatus 2 equipped with an inkjet printing apparatus will be described. The configurations of the unwinding device 11, winding device 12, control unit 40, etc. in this embodiment are the same as those in the first embodiment, so the same reference numerals are used and detailed description will be omitted.

[0062] 7, the printing apparatus 2 includes an unwinding device 11, a precoat unit 31, a precoat drying unit 32, a printing unit 33, a print drying unit 34, a winding device 12, and a plurality of transport rolls 36. The plurality of transport rolls 36 includes a feed roll 361 having a drive mechanism and a guide roll 362 having no drive mechanism.

[0063] The precoat unit 31 is a unit that is set in a roll state on the unwinding device 11 and applies a precoat liquid to the coating surface of the web W unwound from the unwinding device 11 to form a precoat layer on the coating surface. The web W in this embodiment is a plastic film similar to that in the first embodiment.

[0064] The precoat drying section 32 is disposed downstream of the precoat section 31 in the transport direction of the web W. The precoat drying section 32 is a unit that dries the precoat liquid applied to the coated surface of the web W in the precoat section 31.

[0065] The printing unit 33 is disposed downstream of the precoat drying unit 32 in the transport direction of the web W. The printing unit 33 is a unit that forms an image by applying ink ejected from a print head 33a to the coated surface of the web W (more specifically, the precoat layer formed on the coated surface).

[0066] The printed web W is transported to the print drying section 34. The ink on the surface of the web W is dried by passing through the interior of the print drying section 34. The dried web W is sent out from the print drying section 34 and taken up by the winding device 12.

[0067] In this embodiment, an encoder is installed on the feed roll 361 arranged upstream of the printing unit 33, and magnetic detection type rotation sensors 60 similar to those in the first embodiment are installed on multiple rolls of the guide rolls 362. The guide rolls 362 on which the rotation sensors 60 are installed include a guide roll 362a with a large wrap angle and a guide roll 362b with a shallow wrap angle. The wrap angles of the guide rolls 362a and 362b may be set taking into consideration the material of the web W, the set tension, and the like. For example, the wrap angle of the guide roll 362a is set to be greater than 10 degrees, and the wrap angle of the guide roll 362b is set to be 10 degrees or less.

[0068] In addition, the printing device 2 of this embodiment is equipped with a control unit 40 (not shown) similar to that of embodiment 1, and the control unit 40 acquires rotation information from the encoder and rotation sensor 60 of each roll to estimate the printing pitch deviation and determine the printing status.

[0069] Next, estimation of print pitch deviation and determination of print state in the printing device 2 according to this embodiment will be described.

[0070] When printing begins in the printing device 2, the web W sent out from the unwinding device 11 is transported sequentially through the precoat section 31, the precoat drying section 32, and the printing section 33, and a predetermined pattern is printed on the web W using ink ejected from the print head 33a of the printing section 33.

[0071] In the printing section 33, which is an inkjet printer, a plurality of print heads 33a print images of various colors in sequence. After the printing of each color is completed, the web W is dried in the print drying section 34 and then wound up by the winding device 12.

[0072] The control unit 40 also acquires rotation information from the encoder and rotation sensor 60 installed on each of the rolls, and estimates the printing pitch deviation as in the first embodiment. Specifically, the rotation information acquisition unit 411 acquires rotation information, which is data related to the rotation angle of the roll measured by the encoder and each rotation sensor 60. The printing pitch estimation unit 412 calculates the conveying speed of the web W on each roll based on the rotation information acquired by the rotation information acquisition unit 411 and the diameter of each roll stored in advance in the storage unit 42, etc. The printing pitch estimation unit 412 estimates the printing pitch deviation based on the difference between the reference conveying speed of the feed roll 361, which is the reference roll, and the conveying speed of each guide roll 362.

[0073] As in the first embodiment, the determination unit 413 determines the printing state, i.e., whether printing is occurring normally, based on the printing pitch deviation estimated by the printing pitch estimation unit 412 based on the acquired rotation information and the printing pitch deviation estimated using a prediction model, which is a trained model pre-stored in the storage unit 42. If the difference between the calculated printing pitch deviations is equal to or greater than a predetermined threshold, the determination unit 413 determines that the printing pitch deviation for the roll in question exceeds an acceptable range and that an abnormality has occurred. If the determination unit 413 determines that an abnormality has occurred, it causes the display unit 43 to display information about the roll determined to have an abnormality. Furthermore, if the control unit 41 detects an abnormality, it may sound an alarm and stop operation of the printing device 2.

[0074] As described above, in the printing device 2 according to this embodiment, an inkjet printing device that prints on a plastic film web W includes an encoder for the feed roll 361, which is a driving roll, and a magnetic detection rotation sensor 60 for the guide roll 362, which is a driven roll. The printing device 2 estimates the printing pitch deviation based on the difference between the reference conveyance speed of the driving roll and the conveyance speed of the driven roll, and determines whether the printing condition is appropriate. Therefore, since the printing device 2 estimates the printing pitch deviation based on the rotational state of the driven roll measured using the magnetic detection rotation sensor 60, which is a non-contact sensor, the rotational load on the driven roll is smaller than when a contact sensor is used, and changes in the rotational state of the driven roll can be measured with high accuracy. Therefore, defects due to printing pitch deviation can be accurately detected even in inkjet printing machines in which print heads of each color are installed close to each other.

[0075] Furthermore, in this embodiment, a rotation sensor 60 is disposed on the guide roll 362b, which is one of the driven rolls in the printing unit 33 and has a shallow wrap angle with respect to the web W, to estimate the printing pitch deviation. In the guide roll 362b with a shallow wrap angle, the force applied to the roll by the tension of the web W is small. Therefore, by measuring the rotation state of the guide roll 362b with the magnetic detection type rotation sensor 60, which has a small rotational load, it becomes possible to detect defects such as minute printing pitch deviations with high sensitivity.

[0076] In this embodiment, a rotation sensor 60 is disposed on the guide roll 362a, which is one of the driven rolls in the printing unit 33 and has a large wrap angle with respect to the web W, to estimate the printing pitch deviation. The force exerted on the guide roll 362a with a large wrap angle due to the tension of the web W is greater than that on the guide roll 362b with a shallow wrap angle. Therefore, by prioritizing detection of the printing pitch deviation estimated on the guide roll 362a with a large wrap angle over the printing pitch deviation estimated on the guide roll 362b with a shallow wrap angle, the detection sensitivity for the influence of the printing pitch deviation due to tension fluctuations can be reduced. This allows for a small printing pitch deviation to be tolerated, making it possible to detect and identify serious defects, such as breaks in the web W, which occur infrequently, and identify their location.

[0077] Furthermore, the control unit 41 may be able to switch between the guide roll 362a with a large wrap angle and the guide roll 362b with a shallow wrap angle to give priority to detecting the print pitch deviation. This allows the detection sensitivity of defects to be switched appropriately to determine the printing state.

[0078] In this embodiment, the rotation sensor 60 is a sensor that detects the rotation angle by magnetic detection, but a rotation sensor 60' that can detect the eccentricity of the roll by magnetic detection may be used, as in the modified example of embodiment 1. This makes it possible to detect the eccentricity of the roll in addition to the conveying speed of the web W on each roll, thereby making it possible to detect printing defects with greater accuracy.

[0079] Furthermore, in this embodiment, only the feed roll arranged upstream of the printing unit is used as the reference roll equipped with an encoder, but this is not limited to this. For example, rotation information from an encoder installed on an in-feed roll that feeds the web W from the unwinding device 11, an out-feed roll that transports the web W to the winding device 12, etc. may also be detected, and the difference in transport speed with other driving rolls and driven rolls may be calculated to estimate the printing pitch deviation. This makes it possible to detect the printing pitch deviation based on the transport speed of the web W throughout the printing device 2, thereby enabling more accurate multi-color printing. [Explanation of symbols]

[0080] 1, 2 printing device, 11 unwinding device, 12 winding device, 15 infeed roll, 16 outfeed roll, 20 gravure printing device, 21 printing unit, 211, 217 guide roll, 212 plate cylinder, 213 furnishing roll, 214 impression cylinder, 215 ink pan, 216 doctor blade, 31 precoat section, 32 precoat drying section, 33 printing section, 33a print head, 34 print drying section, 40 control unit, 41 control section, 411 rotation information acquisition section, 412 print pitch estimation section, 413 determination section, 42 memory section, 43 display section, 44 input section, 60, 60' rotation sensor, 61 magnetic detection section, 62 detected section, 62a reference pattern, D drying device, W web

Claims

1. A drive roll is provided with an encoder and transports a web, which is a plastic film; a driven roll having a magnetic detection type rotation sensor installed thereon and guiding the transport of the web; a control unit that estimates a printing pitch deviation of the driven roll based on a difference in transport speed between the drive roll and the driven roll calculated from rotation information measured by the encoder and the magnetic detection type rotation sensor, A printing device characterized by:

2. A plurality of the driven rolls are provided, The plurality of driven rolls include a first driven roll; a second driven roll having a wrap angle of the web smaller than the wrap angle of the web of the first driven roll, 2. The printing device according to claim 1.

3. The wrap angle of the web of the second driven roll is 10 degrees or less.

3. The printing device according to claim 2.

4. The control unit Using a data set including setting values ​​that affect the print state and print pitch deviation as training data, the print state is determined using a prediction model generated by machine learning so as to predict the print pitch deviation from the setting values.

2. The printing device according to claim 1.

5. The magnetic detection type rotation sensor includes: a detection target portion having a plurality of magnetic poles formed in a circumferential direction and disposed on a rotation shaft of the driven roll; a detection unit disposed on a fixed portion near the rotating shaft and configured to detect a magnetic flux density, The control unit an eccentricity state of the driven roll is estimated based on a variation in magnetic flux density detected by the magnetic detection type rotation sensor; 5. The printing device according to claim 1, wherein the printing device is a printer.

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