Ink jet printing apparatus

Abstract

To suppress occurrence of a drawing failure.SOLUTION: An inkjet printing device 1 includes: a nozzle for discharging ink toward an object to be drawn; a storage unit 42 for storing drawing data defining discharge timing corresponding to drawing information in the nozzle at each of a plurality of offset positions in a conveyance direction; an optical movement measuring sensor 30 for receiving light from the object to be drawn and generating a measured value relating to movement of the object to be drawn in a conveyance direction on the basis of the received light; and a drawing control unit 40c for controlling discharge of ink from the nozzle on the basis of reference position information indicating that the reference position of the object to be drawn is at a predetermined position, a current offset position with respect to the reference position based on the measured value generated by the optical movement measuring sensor 30, and the drawing data.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an inkjet printing apparatus that prints information by depositing ejected ink onto an object. [Background technology]

[0002] For example, on packaging materials such as cardboard, characters, symbols, images, etc. indicating various information such as dates, serial numbers, bar codes, etc. are drawn. Patent Document 1 discloses a drop-on-demand (DOD) type inkjet printing device that prints by ejecting ink onto packaging materials. In this inkjet printing device, ink supplied from an ink tank is ejected from an ejection port formed in a nozzle, and after flying to the surface of the packaging material as ink droplets, the ink droplets land on the surface to draw characters, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-144574 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, the drawing accuracy of an inkjet printing device is determined by the relative movement speed of the drawing target with respect to the nozzle and the distance between the drawing target and the nozzle. However, at the site where the drawing target is transported, there are variations in the transport line speed and the position of the drawing target in the line width direction transported by the transport line, and errors also occur in principle due to the drawing target slipping on the transport line. If the above-mentioned variations and errors exceed a preset landing accuracy tolerance, poor drawing results.

[0005] The present disclosure has been made in consideration of the above points, and an object of the present disclosure is to suppress the occurrence of poor drawing. [Means for solving the problem]

[0006] In order to achieve the above object, in one aspect of the present disclosure, an inkjet printing device that ejects ink for drawing information on an object transported by a transport device can be assumed. For example, the inkjet printing device can be configured to include an ink tank that contains the ink, a nozzle that ejects the ink supplied from the ink tank toward an object to be drawn, a storage unit that stores drawing data that specifies the ejection timing corresponding to the drawing information at the nozzle at each of a plurality of offset positions in the transport direction, an optical movement measurement sensor that receives light from the object to be drawn and generates a measurement value related to the movement of the object to be drawn in the transport direction based on the received light, and a drawing control unit that controls the ejection of ink from the nozzle based on reference position information indicating that the reference position of the object to be drawn is at a predetermined position, a current offset position relative to the reference position based on the measurement value generated by the optical movement measurement sensor, and the drawing data.

[0007] According to this configuration, information such as characters including numbers, symbols, bar codes, two-dimensional codes, images, etc. can be drawn on an object being conveyed by the conveying machine. At this time, a measurement value relating to the movement of the object to be drawn in the conveying direction is generated by the optical movement measurement sensor. Based on this measurement value and the reference position information of the object, it is possible to obtain a current offset position of the object relative to the reference position. By controlling the ejection of ink from the nozzles based on the obtained current offset position and the drawing data stored in the memory unit, the conveying line is adjusted. The effects of errors due to variations in scanning speed and slippage of the object being drawn are suppressed, and therefore the occurrence of drawing defects is suppressed. This drawing includes, for example, the printing of characters, codes, images, etc.

[0008] The reference position information may be a timing signal indicating that the object to be drawn, being conveyed by the conveyor, has reached a predetermined position. In this case, a timing signal output unit that outputs a timing signal may be further provided, and the drawing control unit may obtain the timing signal output from the timing signal output unit as the reference position information.

[0009] The optical movement measuring sensor can also generate the timing signal indicating that the object to be drawn has reached a predetermined position based on a change in the amount of received light. In this case, the drawing control unit can obtain the timing signal generated by the optical movement measuring sensor as the reference position information.

[0010] The optical movement measuring sensor may include a light projection unit that projects light onto the object to be drawn, and a light receiving unit that receives a speckle pattern that is generated according to the characteristics of the surface shape of the object to be drawn by the light projection unit and generates received light data including the speckle pattern. In this case, a measurement value regarding the movement of the object to be drawn in the transport direction can be generated with high accuracy based on the amount of movement of the speckle pattern generated by the light receiving unit.

[0011] The inkjet recording device may further include a movement amount acquisition unit that acquires a movement amount by the conveying device. In this case, when the accuracy of the measurement value generated by the optical movement measurement sensor is equal to or lower than a predetermined value, the drawing control unit can control the ejection of ink from the nozzles based on the movement amount acquired by the movement amount acquisition unit and the drawing data. In other words, when the accuracy of the measurement value is low, the drawing accuracy can be improved by controlling the ejection of ink from the nozzles based on the current offset position and the drawing data.

[0012] Furthermore, the drawing control unit can determine whether the measurement value generated by the optical movement measurement sensor exceeds a threshold value, and control the ejection of ink from the nozzle based on the movement amount acquired by the movement amount acquisition unit and the drawing data until the measurement value exceeds the threshold value. On the other hand, if the measurement value generated by the optical movement measurement sensor exceeds the threshold value, it can be assumed that the measurement value is inaccurate, and in this case, the ejection of ink from the nozzle can be controlled based on the current offset position and the drawing data, thereby improving drawing accuracy.

[0013] The optical movement measuring sensor can also measure the amount of movement of the object to be drawn in a direction perpendicular to the movement direction. In this case, the drawing control unit can correct vibration (bumping) in the vertical direction of the object to be drawn and improve drawing accuracy by controlling the ejection of ink from the nozzles based on the amount of movement in the direction perpendicular to the movement direction measured by the optical movement measuring sensor.

[0014] The inkjet printing device may further include a transport direction specification unit that specifies the transport direction. In this case, the drawing control unit can control the ejection of ink from the nozzles based on the transport direction specified by the transport direction specification unit. For example, an inkjet printing device configured so that the head pressure of the liquid surface of the ink contained in the ink tank is applied to the nozzles as negative pressure is installed such that the liquid surface is at a predetermined inclination range with respect to a horizontal plane. On the other hand, the transport direction of the transport device may be inclined, and the drawing control unit may control the ejection of ink from the nozzles based on the transport direction specified by the transport direction specification unit when the transport direction is inclined with respect to a horizontal plane. By controlling the ejection of ink from the nozzles so that the information is drawn parallel to the transport direction, the object to be drawn can be drawn in the same manner as if it were being transported horizontally. Effect of the Invention

[0015] As described above, the ejection of ink from the nozzles is controlled based on reference position information indicating that the reference position of the object to be drawn is at a specified position, the current offset position relative to the reference position based on the measurement value generated by the optical movement measurement sensor, and the drawing data stored in the memory unit, thereby making it possible to suppress the occurrence of drawing defects. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an inkjet printing apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram of an inkjet printing apparatus. [Diagram 3] FIG. 3 is a perspective view showing the inkjet printing apparatus during operation. [Figure 4] FIG. 4 is a diagram showing the ink path of the drawing machine. [Diagram 5] FIG. 5 is a diagram illustrating an example of the drawing data. [Figure 6] FIG. 6 is a perspective view of a drawing machine to which a sensor unit is fixed. [Figure 7] FIG. 7 is a view corresponding to FIG. 6 and showing another example of fixing the sensor unit. [Figure 8A] FIG. 8A is a flowchart showing an example of a drawing setting procedure. [Figure 8B] FIG. 8B is a flowchart illustrating an example of a processing procedure in the installation assistance mode. [Figure 8C] FIG. 8C is a diagram showing an example of a display screen when the installation assistance mode is executed. [Figure 8D] FIG. 8D is a diagram showing an example of a detailed display screen. [Figure 8E] FIG. 8E is a diagram for explaining drawing when the workpiece is transported at an angle. [Figure 8F] FIG. 8F is a diagram showing an example of the first correction image. [Figure 8G] FIG. 8G is a diagram showing an example of a correction value input screen. [Figure 8H]FIG. 8H is a diagram showing an example of the second correction image. [Figure 9] FIG. 9 is a flowchart showing an example of drawing control based only on the detected speed or distance. [Figure 10] FIG. 10 is a timing chart showing the time relationship of ink ejection when the constant speed drawing setting is used. [Figure 11] FIG. 11 is a timing chart showing the time relationship of ink ejection when the ink ejection speed is non-uniform. [Figure 12] FIG. 12 is a flowchart showing an example of control when the detection accuracy is deteriorated. [Figure 13] FIG. 13 is a flowchart showing an example of control when the detected speed exceeds the threshold value. [Figure 14] FIG. 14 is a flowchart showing an example of control of bumping correction. [Figure 15] FIG. 15 is a diagram for explaining a case where drawing data is offset by bumping correction. [Figure 16] FIG. 16 is a flowchart showing an example of control of bumping correction including the rotation direction. [Figure 17] FIG. 17 is a diagram showing a first example in which two optical movement measuring sensors are provided. [Figure 18] FIG. 18 is a diagram showing a second example in which two optical movement measuring sensors are provided. [Figure 19] FIG. 19 is a flowchart showing an example of the inclined line corresponding control. [Figure 20] FIG. 20 is a flowchart showing an example of a procedure for acquiring the inclination angle of the workpiece with respect to the drawing machine when the drawing machine is installed. [Figure 21] FIG. 21 is a flowchart showing an example of a procedure for processing when the tilt angle during transport of a workpiece exceeds the allowable value. [Figure 22] FIG. 22 is a diagram showing a third example in which two optical movement measuring sensors are provided. [Diagram 23] FIG. 23 is a diagram showing a fourth example in which two optical movement measuring sensors are provided. [Figure 24] FIG. 24 is a plan view showing the inkjet printing apparatus during operation. [Diagram 25] FIG. 25 is a diagram equivalent to FIG. 24, but in which two optical movement measuring sensors are provided. [Figure 26] FIG. 26 is a perspective view of a sensor unit having two optical displacement measuring sensors. [Figure 27] FIG. 27 is a diagram showing the internal structure of a sensor unit having two optical movement measuring sensors. [Figure 28] FIG. 28 is a front view of a sensor unit having two optical displacement measuring sensors. [Figure 29] FIG. 29 is a diagram showing the internal structure of a sensor unit having two optical movement measuring sensors when turned upside down. [Diagram 30] FIG. 30 is a perspective view of a sensor unit having two optical movement measuring sensors turned upside down. [Diagram 31] FIG. 31 is a diagram showing an example in which a sensor is housed in a main housing. [Diagram 32] FIG. 32 is a diagram showing an example in which the sensor housing is installed in a location separate from the main housing. [Diagram 33] FIG. 33 is a plan view showing an example equipped with a pressing mechanism for the print head. [Diagram 34] FIG. 34 is a flow chart showing an example of control when an optical movement measuring sensor is used as a timing sensor. [Diagram 35] FIG. 35 is a diagram showing the abnormality processing setting screen. [Diagram 36] FIG. 36 is a diagram showing the first warning screen. [Figure 37] FIG. 37 is a diagram showing the second warning screen. [Figure 38] FIG. 38 is a flowchart showing an example of the abnormality processing. [Figure 39] FIG. 39 is a flowchart showing an example of an abnormality process when distance measurement is performed. [Diagram 40]FIG. 40 is a flowchart showing an example of a process for evaluating the reliability of a sensor value. [Diagram 41] FIG. 41 is a flow chart showing an example of control including a drawing interruption process as an abnormality process. [Diagram 42] FIG. 42 is a flowchart showing an example of control for executing a drawing interruption process based on a result of distance measurement. [Diagram 43] FIG. 43 is a flowchart showing an example of control for notifying a distance abnormality based on the result of distance measurement. [Diagram 44] FIG. 44 is a flowchart showing an example of control for notifying an abnormality in distance and continuing drawing. [Diagram 45] FIG. 45 is a flowchart showing an example of control for invalidating the drawing start trigger when the distance is abnormal. [Diagram 46] FIG. 46 is a timing chart of input to the timing sensor and drawing execution. [Figure 47] FIG. 47 is a flowchart showing an example of a log file saving process during a drawing period. [Figure 48] FIG. 48 shows the drawing result confirmation screen. [Figure 49] FIG. 49 is a diagram showing a screen displaying time-series data. [Figure 50] FIG. 50 is a view equivalent to FIG. 3, showing an example in which an inspection device is used during operation. [Figure 51] FIG. 51 is a block diagram of the inspection device. [Figure 52] FIG. 52 shows the image display confirmation window. [Diagram 53] FIG. 53 shows an image display window for displaying an examination image. [Figure 54] FIG. 54 is a flow chart showing an example of processing for determining pass / fail using the measurement results of the workpiece transport speed and distance. [Figure 55] FIG. 55 is a flowchart showing an example of an inspection process after the drawing process is completed. [Figure 56]FIG. 56 is a flow chart showing an example of processing for determining pass / fail using the measurement results of the movement and distance perpendicular to the workpiece transport direction. [Figure 57] FIG. 57 is a flowchart showing an example of an inspection process using the measurement results of the movement and distance perpendicular to the workpiece transport direction. [Figure 58] FIG. 58 is a diagram showing an example of installation when a plurality of distance sensors are provided. [Figure 59] FIG. 59 is a flowchart showing an example of an inspection process in which a plurality of distance sensors are provided to determine pass / fail. [Figure 60] FIG. 60 is a flowchart showing an example of an inspection process when a plurality of distance sensors are provided. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, the embodiments of the present invention will be described in detail with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present invention, its applications, or its uses.

[0018] FIG. 1 is a diagram showing the overall configuration of an inkjet printing apparatus 1 according to an embodiment of the present invention, and FIG. 2 is a block diagram of the inkjet printing apparatus 1. The inkjet printing apparatus 1 includes, for example, a drawing machine 2, a sensor unit 3, a controller 4, and an operation terminal 5. The drawing machine 2 is a part that executes a drawing process on an object to be drawn, and is configured separately from the controller 4. The sensor unit 3 is a part that executes measurements necessary for the drawing machine 2 to execute a drawing process and measurements necessary for executing a drawing inspection, and is configured separately from the controller 4. The controller 4 is a part that controls the drawing machine 2 and the sensor unit 3, and can also be called a control device, a control unit, or the like. The operation terminal 5 is configured with a personal computer or the like, and is a part where a user inputs, for example, drawing information, performs various settings, selections, confirmations, and the like. The operation terminal 5 includes a terminal side display unit 5a, for example, a liquid crystal display, and a terminal side operation unit 5b, for example, a keyboard, a mouse, a pointing device, and the like.

[0019] The above-mentioned configuration example is merely an example, and the present invention is not limited to the above-mentioned configuration example. That is, the controller 4 may be incorporated in the operation terminal 5, or may be incorporated in the drawing machine 2. Also, the operation terminal 5 may function as the controller 4. Also, in Figs. 1 and 2, an external device 6 consisting of a programmable logic controller (PLC) or the like is shown, and this external device 6 is connected to the controller 4 so as to be able to communicate with it. A control signal output from the external device 6 is input to the controller 4. The external device 6 may be a device that constitutes a part of the inkjet printing device 1, or may be a device separate from the inkjet printing device 1.

[0020] 1 and 2 show an encoder 7 and a timing sensor 8. The encoder 7 is a movement amount acquisition unit that acquires information regarding the movement amount of the conveyor 10 shown in FIG. 3 described later. An example of the information regarding the movement amount is a pulse signal, and the movement amount can be calculated based on the number of these pulse signals. The timing sensor 8 is a sensor for detecting that an object to be drawn, which is conveyed by the conveyor 10, has reached a predetermined position, and can typically be constituted by a photoelectric sensor, a mark sensor, a distance sensor, or the like.

[0021] One or both of an encoder 7 and a timing sensor 8 are provided. The encoder 7 and the timing sensor 8 may be devices that constitute a part of the inkjet printing apparatus 1, or may be devices separate from the inkjet printing apparatus 1.

[0022] As shown in Fig. 3, the inkjet printing device 1 is a device for drawing various information on a workpiece W (an example of an object to be drawn) transported by a transport device 10, and is an in-line device that is incorporated into a manufacturing line (also called a production line). The transport device 10 is, for example, a belt conveyor, a roller conveyor, etc. The production line is made up of the transport device 10. The production line is installed in various factories, warehouses, etc.

[0023] The drawing machine 2 is fixed so that its relative position with respect to the conveyance machine 10 is in a predetermined positional relationship. There are no particular limitations on the members, devices, instruments, etc. for fixing the drawing machine 2, but examples thereof include a fixing member 11 such as a fixing stand or a bracket. The fixing member 11 may be fixed to the floor surface of a factory, a warehouse, etc., or may be fixed to the frame of the conveyance machine 10, etc.

[0024] When the inkjet printing device 1 is in operation, multiple workpieces W are placed on the conveying surface 10a of the conveyor 10 and conveyed in sequence in the direction of arrow A shown in FIG. 3. Therefore, the upstream side in the conveying direction is the right side in FIG. 3, and the downstream side in the conveying direction is the left side in FIG. 3. Multiple workpieces W are placed on the conveying surface 10a with intervals between them in the conveying direction, that is, the direction of arrow A. The direction perpendicular to the direction of arrow A and along the conveying surface 10a is defined as the width direction. The conveying surface 10a may be horizontal or inclined at a predetermined angle with respect to the horizontal plane, and therefore the direction of arrow A is not necessarily always horizontal.

[0025] All of the multiple workpieces W are not necessarily placed at the same position in the width direction of the transport surface 10a, and the positions of the workpieces W on the transport surface 10a may be shifted from one another in the width direction of the transport surface 10a. In addition, since the workpieces W are transported by the frictional force acting between the workpieces W and the transport surface 10a, the workpieces W may slip against the transport surface 10a for some reason. In this embodiment, as will be described later, the quality of drawing by the drawing machine 2 can be maintained good even if the workpieces W are shifted in the width direction or slip against the transport surface 10a.

[0026] The workpiece W is not particularly limited, but may be, for example, a packaging material for packaging various products. A typical example of a packaging material may be, for example, cardboard. The inkjet printing device 1 draws information such as characters including numbers, symbols, barcodes, two-dimensional codes, images, marks, illustrations, or combinations thereof on the workpiece W being transported by the transport device 10. When only characters are drawn, the inkjet printing device 1 may be called a printing device, and the drawing device 2 may be called a printing machine. Moreover, the drawing of information by the inkjet printing device 1 also includes the printing of images. In this case, the inkjet printing device 1 may be called a printing device. In the following description, the term drawing includes both printing and printing.

[0027] (Configuration of drawing machine 2) The drawing machine 2 is a DOD (Drop On Demand) type drawing machine that ejects ink only when required for drawing operation, but it may also be a CIJ (Continuous Ink Jet) type drawing machine that ejects ink even when no drawing operation is being performed other than the DOD type. Below, a case where a DOD type drawing machine is used as the drawing machine 2 of this embodiment will be described.

[0028] As shown in FIG. 2, the drawing machine 2 includes an ink supply unit 20, an ink path unit 21, an ink drainage unit 22, a print head drive unit 23, and a DOD print head (hereinafter, referred to as a print head). The drawing machine 2 also has a main housing 25 in which the print head 24 is provided. A member 25A (shown in Figs. 1 and 3) constituting the main housing 25 is a mounting portion for fixing the inkjet printing device 1 to an installation position. As shown in Fig. 3, by mounting the member 25A constituting the main housing 25 to a fixing member 11, the inkjet printing device 1 can be fixed so as not to move from a predetermined installation position. The mounting portion may be, for example, a bracket or a fastening member such as a bolt or a screw.

[0029] The print head 24 is fixed in a state housed inside the main housing 25, and the positional relationship between the main housing 25 and the print head 24 is fixed. The ink supply unit 20, the ink path unit 21, the ink drainage unit 22, and the print head drive unit 23 are also housed inside the main housing 25.

[0030] The print head 24 of the DOD type drawing machine 2 is a member equivalent to the nozzle of the present invention, and ejects ink for drawing information on the workpiece W. The print head 24 has a variety of structures, and may be any of the following types: thermal ink jet type, valve jet type, and piezoelectric type. In this embodiment, a piezoelectric type print head is used as the print head 24, which is capable of drawing from low resolution to high resolution, has a wide drawing width, and is highly durable.

[0031] As shown in Fig. 4, the print head 24 has a plurality of ejection ports 24a formed along the vertical direction (first direction). As shown in Fig. 3, an opening 25a that is long in the vertical direction is formed in the surface of the main housing 25 that faces the workpiece W. The surface on which the ejection ports 24a of the print head 24 are formed is disposed so as to face the outside through the opening 25a of the main housing 25. Therefore, ink ejected from the ejection ports 24a of the print head 24 flies from the opening 25a of the main housing 25 to the outside of the main housing 25 and adheres to the workpiece W.

[0032] Fig. 4 shows the ink path of the drawing machine 2. The ink supply unit 20 is a part that supplies ink to the ink path unit 21, and is equipped with an ink cartridge 20a. The ink cartridge 20a is detachably attached to the main body part of the ink supply unit 20, i.e., the main housing 25. When the ink in the ink cartridge 20a runs out, it can be replaced with a new ink cartridge 20a. Instead of the ink cartridge 20a, an ink reservoir that can be refilled with ink may be provided.

[0033] The ink path section 21 includes a subtank 21a that contains ink supplied from the ink cartridge 20a, an upstream path 21b, and a downstream path 21c. The ink cartridge 20a and the subtank 21a are ink tanks that contain ink. In this embodiment, the head pressure of the ink surface in the subtank 21a is applied as a negative pressure to the print head 24. Therefore, the ink discharged from the print head 24 is replenished by being sucked from the subtank 21a by the capillary phenomenon of a nozzle orifice (not shown) formed in the print head 24. The meniscus of the ink replenished to the print head 24 is located at a position according to the balance between the capillary phenomenon of the nozzle orifice and the head pressure of the ink surface in the subtank 21a. The ink is supplied from the ink cartridge 20a to the subtank 21a so that the head pressure of the ink surface in the subtank 21a is within a range that does not cause meniscus destruction.

[0034] In this embodiment, a structure is adopted in which the ink in the subtank 21a is supplied to the print head 24 by utilizing the head pressure of the ink level in the subtank 21a, so the drawing machine 2 is installed so that the ink level in the subtank 21a is within a predetermined range of inclination with respect to the horizontal plane. In other words, the ink level in the subtank 21a is allowed to be inclined with respect to the horizontal plane as long as it is within a range in which ink can be supplied to the print head 24 by utilizing the head pressure of the ink level in the subtank 21a during operation, and the drawing machine 2 is installed in such an installation position. Note that in this embodiment, the installation position is adjusted so that the ink level in the subtank 21a is approximately horizontal.

[0035] The upstream path 21b extends from the ink supply unit 20 to the subtank 21a and is a path for supplying the ink in the ink cartridge 20a to the subtank 21a. The upstream path 21b is provided with an upstream filter 21d for filtering the ink, an ink pump 21e for supplying the ink, and an upstream valve 21f for opening and closing the upstream path 21b, in that order from the upstream side. The subtank 21a is provided with a level gauge 21g for measuring the ink level in the subtank 21a. The level gauge 21g can be composed of, for example, a float sensor, a capacitance sensor, or an ultrasonic level sensor. The ink pump 21e and the upstream valve 21f are controlled by an ink path control unit 40a (shown in FIG. 2) described later, and adjust the ink level so that the ink level measured by the level gauge 21g falls within a predetermined range.

[0036] The downstream path 21c extends from the subtank 21a to the print head 24 and is a path for supplying the ink in the subtank 21a to the print head 24. The downstream path 21c is provided with a downstream valve 21h for opening and closing the downstream path 21c and a downstream filter 21i for filtering the ink, in that order from the upstream side. The downstream valve 21h is controlled by an ink path control unit 40a, which will be described later, and is in an open state when drawing is performed. By having such an ink path unit 21, it becomes possible to supply the ink supplied from the ink cartridge 20a to the subtank 21a from the subtank 21a to the print head 24 and to eject the ink supplied to the print head 24 from the ejection port 24a toward the workpiece W.

[0037] The ink path section 21 also includes a pressure adjustment path 26. One end of the pressure adjustment path 26 is connected to the upper part of the subtank 21a (where air is stored), and the other end of the pressure adjustment path 26 is open to the atmosphere. The pressure adjustment path 26 is provided with a first valve 26a, a second valve 26b, a pressure sensor 26c, an air pump 26d, and an air filter 26e. The pressure sensor 26c is for detecting the pressure in the part between the first valve 26a and the second valve 26b in the pressure adjustment path 26. The second valve 26b can also be kept open at all times except when the drawing machine 2 is being transported. In this case, the pressure sensor 26c measures the pressure in the subtank 21a, and by controlling the pressure in the subtank 21a, the ink discharge pressure and amount in the purge operation can be controlled.

[0038] The air pump 26d is for supplying air to a portion between the first valve 26a and the second valve 26b in the pressure adjustment path 26. For example, during maintenance of the drawing machine 2, the inside of the subtank 21a can be pressurized with air to a desired pressure by controlling the air pump 26d, the first valve 26a, and the second valve 26b. The air before being sucked into the air pump 26d is filtered by the air filter 26e.

[0039] The ink drainage section 22 includes a drainage path 22a for draining ink from the print head 24, a drainage tank 22b, and a drainage valve 22c. The upstream end of the drainage path 22a is connected to the print head 24, and the downstream end of the drainage path 22a is connected to the drainage tank 22b. The drainage valve 22c is provided in the middle of the drainage path 22a and is used to open and close the drainage path 22a. For example, during maintenance of the drawing machine 2 or before transporting the drawing machine 2, the ink in the downstream path 21c and the print head 24 is drained to the drainage tank 22b by pressurizing the subtank 21a with the air pump 26d of the pressure adjustment path 26. It is possible.

[0040] 2 is controlled by a drawing control unit 40c (described later) when performing a drawing operation. The print head driving unit 23 generates a driving electric waveform for driving the print head 24 and outputs it to the print head 24. The driving electric waveform is a waveform for individually driving the driving elements (piezo transducers) provided for each ejection port 24a of the print head 24 at a timing based on a drawing command output from the drawing control unit 40c.

[0041] (Detailed explanation of routing control) 1.Initial filling control The initial filling control is a control for replacing the air in the print head 24 with ink and filling the print head 24 with ink before starting operation of the inkjet printing device 1. First, ink is filled into the sub tank 21a. The ink path control unit 40a shown in FIG. 2 opens the downstream valve 21h, the second valve 26b, and the drain valve 22c shown in FIG. 4, and closes the first valve 26a and the upstream valve 21f. It also turns off the ink pump 21e and turns on the air pump 26d. This fills the ink in the sub tank 21a into the downstream path 21c, the print head 24, and the space between the print head 24 and the drain valve 22c, replacing the air.

[0042] 2. Control of ink supply to the subtank 21a The ink supply control to the subtank 21a is a control for keeping the ink level in the subtank 21a within a certain range. The ink path control unit 40a opens the first valve 26a, the second valve 26b, and the upstream valve 21f, and also opens the downstream valve 21h. In addition, the ink pump 21e is turned on, and the air pump 26d is turned off. In this way, ink can be supplied from the ink cartridge 20a to the subtank 21a so that the ink level measured by the level gauge 21g is always constant. For example, the amount of ink transported from the subtank 21a to the print head 24 side may be roughly estimated by software, and if the ink level measured by the level gauge 21g drops to a certain level, the ink supply operation may be continued until the level gauge 21g detects ON.

[0043] 3. Control of ink supply to print head 24 In this control, the ink path control unit 40a opens the downstream valve 21h, the first valve 26a, and the second valve 26b, and closes the upstream valve 21f and the drain valve 22c. Also, the ink pump 21e and the air pump 26d are turned off. As a result, when ink is discharged from the print head 24, the ink is drawn from the sub tank 21a by capillary action into the nozzle orifice in the print head 24. At this time, by making the ink level in the sub tank 21a lower in the direction of gravity than the discharge port 24a at the lowest end of the print head 24, the ink in the print head 24 is always under negative pressure, and this negative pressure is balanced with the capillary action of the nozzle orifice, so that an ink meniscus is formed at a specified position of the nozzle orifice. In other words, the positional relationship in the height direction between the print head 24 and the ink level in the sub tank 21a is set so that the negative pressure is such that an ink meniscus is formed at a specified position.

[0044] 4. Printhead purge control The print head purge control is a control for expelling foreign matter such as air that has entered the print head 24 due to destruction of the meniscus of the nozzle orifice, and paper powder that has adhered to the surface of the nozzle orifice or inside the nozzle orifice, from the print head 24. The ink path control unit 40a opens the second valve 26b and closes the first valve 26a, the downstream valve 21h, the upstream valve 21f, and the drain valve 22c. It also turns off the ink pump 21e. Then, the air pump 26d is turned ON. This control is performed, and the air pressure in the sub tank 21a is measured by a pressure gauge, and the air pump 26d is used to increase the air pressure until a constant pressure is reached.

[0045] After that, the ink path control unit 40a opens the downstream valve 21h and closes the upstream valve 21f, the first valve 26a, the second valve 26b, and the drainage valve 22c. It also turns off the ink pump 21e and the air pump 26d. As a result, the pressurized air pressure in the subtank 21a is used to pressurize and supply the ink in the subtank 21a to the print head 24, thereby removing foreign matter such as air that has entered the print head 24 and paper powder that has adhered to the surface of the nozzle orifice or inside the nozzle orifice from the print head 24.

[0046] 5. Drainage Control Drainage control is a control to empty all the ink in the ink path. Before performing this control, the ink cartridge 20a is removed. After that, the ink path control unit 40a opens the first valve 26a, the second valve 26b, and the upstream valve 21f, and also opens the downstream valve 21h. It also turns the ink pump 21e ON and the air pump 26d OFF. This moves all the ink in the upstream path 21b to the subtank 21a.

[0047] After that, the downstream valve 21h, the second valve 26b, and the drain valve 22c are opened, and the first valve 26a and the upstream valve 21f are closed. The ink pump 21e is turned OFF, and the air pump 26d is turned ON. As a result, the ink in the subtank 21a is pressurized by the air pump 26d, and the ink is discharged into the drain tank 22b through the downstream path 21c, the print head 24, and between the print head 24 and the drain valve 22c, and these parts are replaced with air. At this time, some ink is also discharged from the print head 24.

[0048] (Controller 4 configuration) As shown in FIG. 2, the controller 4 includes a control unit 40, a power supply unit 41, a storage unit 42, and an operation display unit 43. The control unit 40 is configured with a microcomputer including, for example, a central processing unit, various memories, etc., and is capable of executing software stored in advance. The control unit 40 includes an ink path control unit 40a, a drawing data generating unit 40b, a drawing control unit 40c, a workpiece movement amount acquiring unit 40d, a workpiece distance acquiring unit 40e, a drawing start timing acquiring unit 40f, a conveying direction identifying unit 40g, an evaluation unit 40h, and an abnormality processing unit 40i. Each of the units 40a to 40i of the control unit 40 is a part configured by hardware and software, and is described separately as each of the units 40a to 40i for convenience, but may be integrated in terms of hardware.

[0049] The power supply unit 41 converts AC power from the commercial power source 100 into DC power and supplies it to, for example, the control unit 40, the memory unit 42, the operation display unit 43, the drawing machine 2, etc., and is composed of, for example, a switching power supply.

[0050] The memory unit 42 is a part that stores drawing data that specifies the ejection timing corresponding to the drawing information at the ejection port 24a of the print head 24 at each of a plurality of offset positions in the transport direction. The memory unit 42 may be composed of, for example, a working memory. An example of the drawing data is shown in FIG. 5. The vertical direction in FIG. 5 is the arrangement direction of the ejection port 24a of the print head 24, which is the up-down direction during drawing in this embodiment. The horizontal direction in FIG. 5 is the transport direction of the work W, that is, the time axis direction, and the symbols L1, L2, L3, L4, L5, L6, and L7 respectively indicate the ejection timings. The timings indicated by the symbols L1 to L7 are the first to seventh ejection timings, respectively. The first ejection timing L1 is the timing for starting drawing, and the seventh ejection timing L7 is the timing for ending drawing. When the drawing process is executed based on the drawing data shown in FIG. 5, the first to seventh ejection timings L1 to L7 arrive in order, and the black dots in the figure are drawn. The print head 24 is controlled so that ink is ejected only from the ejection ports 24a corresponding to the squares indicated by .

[0051] 2, the operation display unit 43 includes a drawing machine side display unit 43a consisting of, for example, a liquid crystal display or the like, and a drawing machine side operation unit 43b consisting of operation keys or the like. The drawing machine side operation unit 43b is a section that accepts various operations by the user, such as drawing settings on the workpiece W, installation settings of the drawing machine 2, and maintenance execution instructions. A drawing setting screen, an installation screen, a maintenance execution instruction screen, etc. are displayed on the drawing machine side display unit 43a, and the user can operate the drawing machine side operation unit 43b while looking at the drawing machine side display unit 43a.

[0052] The ink path control unit 40a of the control unit 40 is a part that receives instructions from a user using the drawing machine side operation unit 43b, inputs from various sensors, etc., and outputs an execution command for the above-mentioned path controls 1 to 4 to the drawing machine 2. Each control after the ink path control unit 40a outputs the execution command to the drawing machine 2 is as described above.

[0053] The drawing data generating unit 40b is a part that generates drawing data as shown in Fig. 5 based on the input contents and setting contents inputted from the terminal side display unit 5a and the drawing device side operation unit 43b. The drawing data generated by the drawing data generating unit 40b is stored in the storage unit 42, for example.

[0054] The drawing control unit 40c reads out the drawing data stored in the memory unit 42, and receives information about the position and distance input from the sensor unit 3, the encoder 7, the timing sensor 8, etc., and a signal (timing signal) indicating that the workpiece W has reached a predetermined position. Then, based on the information about the position and distance, the timing signal, and the drawing data generated by the drawing data generation unit 40b, the drawing control unit 40c outputs a control signal to the print head drive unit 23 to control the ejection of ink from the ejection port 24a of the print head 24. The drawing control unit 40c will be described in detail later.

[0055] The workpiece movement amount acquisition unit 40d is a part that acquires the amount of movement of the workpiece W relative to the drawing machine 2 based on signals input from the sensor unit 3 and the encoder 7. The workpiece movement amount acquisition unit 40d detects the amount of movement of the workpiece W, thereby making it possible to acquire the position of the workpiece W relative to the drawing machine 2. The amount of movement and position of the workpiece W acquired by the workpiece movement amount acquisition unit 40d are input to the drawing control unit 40c.

[0056] The work distance acquisition unit 40e is a part that acquires the timing at which the drawing machine 2 starts drawing (drawing start timing) based on signals input from the sensor unit 3 and the timing sensor 8. The drawing start timing acquired by the work distance acquisition unit 40e is input to the drawing control unit 40c.

[0057] The drawing start timing acquisition unit 40f is a part that acquires the timing at which the workpiece W crosses a predetermined drawing start position based on signals input from the sensor unit 3 and the timing sensor 8. The signal acquired by the drawing start timing acquisition unit 40f is input to the drawing control unit 40c. The signal input from the sensor unit 3 and the timing sensor 8 functions as a trigger for starting drawing (drawing start trigger).

[0058] The transport direction specifying unit 40g is a part that specifies the transport direction of the workpiece W based on the output from the sensor unit 3. When the workpiece W is transported in the horizontal direction, the transport direction specifying unit 40g specifies that the workpiece W is transported in the horizontal direction and outputs this to the imaging control unit 40c. When the workpiece W is transported in an inclined direction, the transport direction specifying unit 40g specifies that the workpiece W is transported in an inclined direction, specifies the angle of inclination, and outputs this to the imaging control unit 40c. As will be described later, the imaging control unit 40c determines the direction specified by the transport direction specifying unit 40g. Based on the transport direction of the workpiece W, the ejection of ink from the ejection openings 24a of the print head 24 is controlled.

[0059] 6 is a perspective view specifically showing the drawing machine 2 to which the sensor unit 3 is fixed, as viewed from the ink ejection side. A bulging portion 25b is formed on the surface of the main housing 25 facing the workpiece W, the bulging portion 25b having a middle portion in the transport direction bulging in the ink ejection direction. The opening 25a is formed on the tip surface in the bulging direction of the bulging portion 25b.

[0060] The sensor unit 3 is fixed upstream in the transport direction of the bulging portion 25b on the surface of the main housing 25 that faces the workpiece W. Meanwhile, a liquid absorber 27 capable of absorbing ink is attached downstream in the transport direction of the bulging portion 25b on the surface of the main housing 25 that faces the workpiece W.

[0061] As shown in Fig. 7, the sensor unit 3 may be fixed downstream in the transport direction from the bulging portion 25b of the main housing 25 of the drawing machine 2. Also, the sensor unit 3 may be fixed above the bulging portion 25b of the main housing 25 of the drawing machine 2. The number of sensor units 3 fixed to one drawing machine 2 may be three as shown in Fig. 7, or any two of the three sensor units 3 shown in Fig. 7 may be used. In other words, the inkjet printing device 1 may have a plurality of sensor units 3.

[0062] (Configuration of sensor unit 3) 2, the sensor unit 3 includes an optical movement measurement sensor 30 that generates measurement values ​​related to the movement of the workpiece W relative to the print head 24, a distance sensor 31 that measures the distance in the ejection direction of the print head 24 to the workpiece W, and a sensor housing 32 that houses the optical movement measurement sensor 30 and the distance sensor 31. Both the optical movement measurement sensor 30 and the distance sensor 31 are optical measurement sensors, since they perform measurements using measurement light. In other words, the sensor unit 3 that constitutes the optical measurement sensor of this embodiment includes the optical movement measurement sensor 30 and the distance sensor 31.

[0063] The optical movement measuring sensor 30 and the distance sensor 31 are integrated into a sensor module by being housed in a common sensor housing 32. The sensor unit 3 can detect the drawing start timing, the transport speed (movement distance) of the work W, the distance to the work W, and the like. The distance in the ejection direction of the print head 24 to the work W is also referred to as the distance to the work W. In addition, in this embodiment, the expression "distance in the ejection direction of the print head 24 to the work W" is used, but this is defined only for the convenience of specifying the distance between the work W and the drawing machine 2, and may be defined as the distance between the ejection port 24a of the print head 24 and the drawing surface of the work W, for example, or may be defined as the distance between any part of the print head 24 and any part of the work W.

[0064] The optical movement measuring sensor 30 irradiates light in the ejection direction of the print head 24, receives the light reflected from the workpiece W, and generates a measurement value related to the movement of the workpiece W in the conveying direction based on the received light. In this embodiment, an OTS (Optical Tracking Sensor) is used as such an optical movement measuring sensor 30, which can continuously capture images of the workpiece W at high speed and obtain the amount of movement of the workpiece W by image processing the obtained images. The OTS that can be used as the optical movement measuring sensor 30 may be either a type that uses a light-emitting diode as a light source and measures the amount of movement of the captured image, or a type that uses a laser as a light source and measures the amount of movement of a speckle pattern. In this embodiment, a type that uses a laser with a deeper depth as a light source is adopted compared to a type that uses a light-emitting diode as a light source. The reason for this is that the distance between the print head 24 and the workpiece W may vary, for example, by about 10 mm. In addition to the OTS, a laser Doppler velocimeter or the like may be used as the optical movement measuring sensor 30. It can also be used.

[0065] The OTS using a laser as a light source includes a light projection unit 30a that projects light (laser light) onto the workpiece W, and a light receiving unit 30b that receives a speckle pattern that is generated according to the characteristics of the surface shape of the workpiece W by the light projection unit 30a and generates received light data including the speckle pattern. The light receiving unit 30b is configured with an imaging device having an image sensor such as a CMOS (complementary metal oxide semiconductor). The field of view of the imaging device may overlap with the diameter of the spot light projected from a distance sensor 31 consisting of a laser distance sensor described later.

[0066] This OTS generates a measurement value related to the movement of the workpiece W in the conveying direction based on the movement amount of the speckle pattern included in the light receiving data generated by the light receiving unit 30b. That is, the optical movement measuring sensor 30 can generate a measurement value related to the movement of the workpiece W based on a measurement image generated by capturing an image of the workpiece W with an imaging device.

[0067] The optical movement measuring sensor 30 measures not only the amount of movement of the workpiece W in the transport direction, but also the amount of movement in a direction perpendicular to the transport direction. When the optical movement measuring sensor 30 measures the amount of movement in a direction perpendicular to the transport direction, it also generates a measurement value related to the movement in the direction perpendicular to the transport direction. Since the transport direction of the workpiece W and the direction perpendicular to the transport direction are mutually orthogonal, the optical movement measuring sensor 30 can generate measurement values ​​of two axes that are mutually orthogonal. In this case, the optical movement measuring sensor 30 determines the measurement value related to the movement of the workpiece W in the transport direction from the generated measurement values ​​of the two axes.

[0068] The optical system of the light receiving unit 30b does not have a lens. By making the optical system without a lens in this way, the depth of field of the light receiving unit 30b can be secured larger than that of an optical system with a lens. As a result of securing a large depth of field of the light receiving unit 30b, the measurable range of the optical movement measurement sensor 30 can be widened. This makes it possible to measure the work W passing at a distance from the print head 24, increasing the degree of freedom of the transport position of the work W, reducing the cost of manufacturing the production line, and reducing the need to check the transport position of the work W. Furthermore, since the usable distance range is widened, the degree of freedom of the installation method of the drawing machine 2 is improved. The optical system of the light receiving unit 30b may have a lens.

[0069] As the distance sensor 31, it is possible to use conventionally known devices such as a triangulation distance sensor, a TOF (Time Of Flight) distance sensor, an ultrasonic sensor, etc. The distance sensor 31 of this embodiment is a laser distance sensor capable of projecting a spot light generated by a laser light onto a measurement object.

[0070] The distance sensor 31 and the optical movement measurement sensor 30 are disposed at approximately the same height. Specifically, when the distance sensor 31 and the optical movement measurement sensor 30 are fixed to the sensor housing 32, the height of the measurement light projected from the distance sensor 31 and the height of the measurement light projected from the optical movement measurement sensor 30 match. This allows the distance sensor 31 and the optical movement measurement sensor 30 to measure the same height portion of the workpiece W.

[0071] The mounting positions of the distance sensor 31 and the optical movement measurement sensor 30 can be adjusted in the height direction. For example, when adjusting the height position of the distance sensor 31 and the optical movement measurement sensor 30, the adjustment can be made by moving the housing 32 itself in the vertical direction relative to the main housing 25. Also, for example, the sensor housing 32 is provided with a mounting mechanism for mounting the distance sensor 31 to the sensor housing 32, and a mounting mechanism for mounting the optical movement measurement sensor 30 to the sensor housing 32. The mounting mechanism for the distance sensor 31 is configured so that the height of the distance sensor 31 can be changed within a predetermined range. Also, the mounting mechanism for the optical movement measurement sensor 30 is configured so that the height of the distance sensor 31 can be changed within a predetermined range. The height of the optical movement measurement sensor 30 can be changed within a predetermined range. This allows the distance sensor 31 and the optical movement measurement sensor 30 to be placed at the same height. Note that the distance sensor 31 and the optical movement measurement sensor 30 may be placed at different heights. The distance sensor 31 and the optical movement measurement sensor 30 may be directly attached to the drawing machine 2, or may be indirectly attached while maintaining a certain relationship with the drawing machine 2. Either of these attachment forms is included in the form of attachment corresponding to the drawing machine 2.

[0072] Since the distance sensor 31 can generate a timing signal based on the distance data measured by the distance sensor 31, the distance sensor 31 can also be called an optical timing sensor. Specifically, based on the change in the distance to the workpiece W in the ejection direction of the print head 24 measured by the distance sensor 31, a timing signal indicating that the reference position of the workpiece W is at a predetermined position can be generated. This distance sensor 31 is disposed downstream of the optical movement measurement sensor 30 in the conveying direction of the workpiece W, and it is possible to specify the drawing start timing at this position. Since the distance sensor 31 is disposed downstream of the optical movement measurement sensor 30 in the conveying direction of the workpiece W, the optical movement measurement sensor 30 can generate a measurement value related to the movement of the workpiece W before the distance sensor 31 generates a timing signal. Note that the generation of the timing signal by the distance sensor 31 and the generation of the measurement value by the optical movement measurement sensor 30 may be at the same timing.

[0073] The sensor housing 32 that houses the optical movement measuring sensor 30 and the distance sensor 31 is detachably fixed to the main housing 25. As shown in FIG. 6, the front portion 32a of the sensor housing 32 has a window portion 32b made of a light-transmitting cover that transmits light. The light receiving portion 30b (shown in FIG. 2) of the optical movement measuring sensor 30 captures an image of the workpiece W through the window portion 32b. The distance sensor 31 also irradiates measurement light onto the workpiece W through the window portion 32b, and receives the measurement light reflected by the workpiece W through the window portion 32b. In other words, the optical movement measuring sensor 30 and the distance sensor 31 are provided so as to be able to measure the workpiece W through the window portion 32b.

[0074] Since the print head 24 is provided in the main housing 25, the optical movement measuring sensor 30 and the distance sensor 31 are fixed to the main housing 25 so that their relative positional relationship with the print head 24 is a predetermined positional relationship. Examples of the detachable fixing structure include, but are not limited to, a fastening structure using screws or bolts, and a structure in which a first engagement portion provided in the sensor housing 32 is engaged with a second engagement portion provided in the main housing 25.

[0075] The optical movement measuring sensor 30 and the distance sensor 31 are attached to fixed positions relative to the print head 24 so that the positional relationship between the optical movement measuring sensor 30 and the distance sensor 31 and the print head 24 is a known value in the transport direction of the workpiece W. Since the optical movement measuring sensor 30 and the distance sensor 31 are housed in a common sensor housing 32, the distance sensor 31 is disposed at a position offset in the same direction as the optical movement measuring sensor 30 along the transport direction relative to the print head 24.

[0076] The user may input the respective positions where the optical movement measuring sensor 30 and the distance sensor 31 are attached as setting values ​​to the control unit 40. This makes it possible to improve the drawing accuracy while increasing the degree of freedom in installing the optical movement measuring sensor 30 and the distance sensor 31.

[0077] 3, the optical movement measuring sensor 30 of the sensor unit 3 is disposed at a position offset in the transport direction with respect to the print head 24, specifically at a position offset upstream in the transport direction. The vertical position (first direction) of the region to be drawn, to which the ejection port 24a of the print head 24 is directed, and the vertical position of the region whose current offset position is measured by the optical movement measuring sensor 30 at least partially overlap each other. The drawing machine 2 is positioned so that accurate measurements of the movement of the area to be drawn can be obtained.

[0078] The optical movement measuring sensor 30, the distance sensor (which also functions as a timing sensor) 31, and the print head 24 are arranged in this order from upstream in the conveying direction of the workpiece W. By arranging them in this manner, it is possible to start measuring the movement amount of the workpiece W in a state where the optical movement measuring sensor 30 is outputting a valid measurement value.

[0079] The optical movement measuring sensor 30 and the distance sensor 31 are disposed at a position offset upstream of the print head 24 along the transport direction for the following reason. That is, ink mist that does not land on the work W, called satellites, generated when ink is discharged from the print head 24, and ink splashes that bounce off the work W flow downstream of the print head 24 due to the wind flow caused by the transport of the work W relative to the print head 24. For this reason, if the optical movement measuring sensor 30 and the distance sensor 31 are disposed downstream of the print head 24, the window portion 32b that serves as the detection surface of the optical movement measuring sensor 30 and the distance sensor 31 is likely to be soiled with ink and induce detection failure. However, in this case, a dead space that cannot be measured by the optical movement measuring sensor 30 is theoretically generated at the final end (downstream end) of the transport direction of the work W. When drawing is performed in the dead space, a supplementary process may be performed, such as constant speed control using the final measurement value of the optical movement measuring sensor 30, or acceleration control using the final acceleration measured by the optical movement measuring sensor 30.

[0080] When the workpiece W is transported to a predetermined position opposite the print head 24, the print head 24 is directed toward the region of the workpiece W to be imaged. The distance sensor 31 can also irradiate the workpiece W with measurement light to measure the current offset position, and the region of the workpiece W to which the distance sensor 31 irradiates the measurement light is the region of the workpiece W measured by the distance sensor 31. In this embodiment, the distance sensor 13 is installed so that the vertical position of the region to be imaged to which the print head 24 is directed and the vertical position of the region to which the distance sensor 31 measures the current offset position overlap at least partially. In other words, since the region to be imaged and the region measured by the distance sensor 31 overlap at least partially, the distance from the print head 24 to the region to be imaged can be accurately measured.

[0081] (Drawing Settings) Based on the flowchart shown in Fig. 8A, the drawing setting performed before operation of the inkjet printing apparatus 1 will be described. When performing drawing setting, the user uses, for example, the terminal display unit 5a and terminal operation unit 5b of the operation terminal 5, or the operation display unit 43 of the controller 4. A setting screen (GUI) is displayed on the terminal display unit 5a or the drawing machine display unit 43a. Setting operations by the user are accepted by the terminal operation unit 5b or the drawing machine operation unit 43b.

[0082] In step SA1 of Fig. 8A, the user performs initial settings. In the initial settings, the user selects a GUI language, inputs the equipment configuration such as the number of drawing machines 2, and inputs equipment installation information. The equipment installation information includes arrangement information of the drawing machines 2 (such as the inclination of the drawing machines 2), line flow direction information relative to the drawing machines 2, transport speed information, and the like. The contents of the selection operations and input operations performed by the user are acquired by the control unit 40.

[0083] In step SA2, the user executes drawing common settings, which include setting the manufacturing serial number counter and replacement settings (such as obfuscating the manufacturing date and lot number).

[0084] In step SA3, the process waits for the user to start drawing settings. Specifically, it is determined whether drawing settings have been started by the user. When drawing settings have been started, the process proceeds to step SA4. In step SA4, it is determined whether a logo (image) is to be drawn. If an image is to be drawn, the process proceeds to step SA5, where the image data is converted to a resolution and size that can be drawn by the drawing device 2 using a dedicated terminal such as a personal computer, to create a dedicated logo file, and the file is saved in the memory unit 42 of the drawing device 2.

[0085] If step SA4 returns NO and an image is not drawn, the process proceeds to step SA6. In step SA6, the user sets the drawing contents. Specifically, the user selects the job number to be set as the drawing contents, or selects the drawing contents to be edited by the job number. A job is a drawing data set to be drawn on one work W, and this job contains drawing data such as that shown in FIG. 5.

[0086] In step SA7, the user sets the delay from when the drawing start trigger is received to when drawing starts, which is used in common within the jobs selected in step SA6. The delay from when the drawing start trigger is received to when drawing starts may be set, for example, by time or by position (mm).

[0087] In step SA8, a drawing element (block) is added to the job. Then, the process proceeds to step SA9, where drawing elements such as character strings, barcodes, two-dimensional codes, and logos are set to the added drawing elements. At this time, the user sets the thickness of the characters to be drawn, the character size, the barcode size, the two-dimensional code size, the logo size, and their position information. The drawing data also includes the print pitch, etc.

[0088] In step SA10, it is determined whether the addition of drawing elements is complete. Steps SA8, SA9, and SA10 are repeated until the addition of all drawing elements is complete. When the addition of all drawing elements is complete, the process proceeds to step SA11. In step SA11, the job is stored in the storage unit 42 of the drawing machine 2.

[0089] (Installation Assist Mode) In the inkjet printing device 1 of this embodiment, the ink is supplied to the print head 24 by the head pressure of the ink level in the subtank 21a, so when the drawing machine 2 is installed, it is necessary to install the drawing machine 2 so that it is within a predetermined inclination range. As a means for this adjustment, for example, it is possible to adjust the attitude of the drawing machine 2 using a level. However, when adjusting the attitude using a level, there is a problem that it is difficult for the user to notice changes over time after the drawing machine 2 is installed. In addition, the conveying speed of the work W is either secondarily grasped from the setting of the conveying machine 10, or a speed measuring device such as an encoder 7 is required. In addition, depending on the relative position of the drawing machine 2 with respect to the work W, in order to confirm that the drawing machine 2 is installed within the specifications, it is necessary to stop the work W once and measure the distance between the work W and the print head 24. Furthermore, the inclination and drawing quality of the drawing cannot be known until drawing is actually performed on the work W, and it was necessary to repeatedly draw, install the drawing machine 2, and correct various settings.

[0090] In response to this, the inkjet printing apparatus 1 of this embodiment is capable of executing an installation assist mode for assisting the user in installing the drawing device 2 and reducing the burden of the installation work on the user. The installation assist mode will be described in detail below with reference to the flowchart shown in FIG. 8B.

[0091] For example, after the drawing setting shown in FIG. 8A, the inkjet printing apparatus 1 automatically or in response to a user's instruction proceeds to step SA100 in FIG. 8B. In step SA100, the control unit 40 executes a process of transitioning to the installation assistance mode. In step SA101, the light Monitoring is started by the optical movement measuring sensor 30 and the distance sensor 31. In step SA102, when the workpiece W is transported, the workpiece W is measured by the optical movement measuring sensor 30 and the distance sensor 31. In this step SA102, the drawing process is not executed.

[0092] In step SA103, the measurement results of the optical movement measuring sensor 30 and the distance sensor 31 are displayed. Specifically, as shown in Fig. 2, the controller 4 has an output unit 44, which is a part that outputs information about the installation state based on the measurement values ​​generated by the optical movement measuring sensor 30 and the distance sensor 31. For example, the output unit 44 generates a measurement result display screen 50 shown in Fig. 8C and displays it on the drawing machine side display unit 43a or the terminal side operation unit 5b. At least one of the drawing machine side display unit 43a and the terminal side operation unit 5b is a display unit that displays information about the installation state output from the output unit 44. The output by the output unit 44 includes external output and internal output.

[0093] The measurement result display screen 50 is provided with a work size display area 51 which displays the work size, which is the dimension of the work W in the transport direction, a work transport speed display area 52 which displays the average transport speed of the work W, a distance display area 53 which displays the maximum distance between the print head 24 and the work W, a vertical movement amount display area 54 which displays the amount of movement in the direction perpendicular to the transport direction of the work W, and an inclination display area 55 which displays the inclination of the drawing machine 2.

[0094] The work size, the transport speed of the work W, the distance between the print head 24 and the work W, the amount of movement in the direction perpendicular to the transport direction of the work W, and the inclination of the drawing machine 2 are generated based on the measurements of the optical movement measuring sensor 30 and the distance sensor 31 included in the sensor unit 3, and are examples of information related to the installation state. Other information related to the installation state may be displayed on the measurement result display screen 50.

[0095] The output unit 44 can also output, as information relating to the installation state, a diagram (an example of information) showing the relationship between the distance measured by the distance sensor 31 (the distance between the print head 24 and the workpiece W) and a specified distance range (also called the drawing distance range) defined in the specifications of the drawing machine 2. For example, the distance measured by the distance sensor 31 is displayed as shown in FIG. 8C, and the output unit 44 generates and outputs a diagram showing whether the distance is within the specified distance range or outside the specified distance range, thereby allowing the user to check the installation state relating to the distance on the measurement result display screen 50.

[0096] The output unit 44 can also output, as information on the installation state, a diagram showing the relationship between the conveying speed of the work W measured by the optical movement measuring sensor 30 (which becomes the movement speed of the work W) and the specified speed range defined in the specifications. For example, the conveying speed measured by the optical movement measuring sensor 30 is displayed as shown in FIG. 8C, and the output unit 44 generates and outputs a diagram showing whether the speed is within the specified speed range or outside the specified speed range, so that the user can check the installation state regarding the speed on the measurement result display screen 50.

[0097] The output unit 44 can also output, as information on the installation state, a diagram showing the inclination of the conveying direction determined from the two-axis measurement values ​​measured by the optical movement measurement sensor 30. For example, as shown in Fig. 8C, the drawing machine 2 is shown in a schematic diagram, and the inclination of the conveying direction can be shown by tilting this schematic diagram.

[0098] When the user operates the details button 56 on the measurement result display screen 50 shown in Fig. 8C, the output unit 44 generates a details display screen 60 as shown in Fig. 8D and displays it on the drawing machine side display unit 43a or the terminal side operation unit 5b. The details display screen 60 is provided with a graph display area 61 for displaying the time series changes in the measurement data in a graph format. For example, by looking at the graph in Fig. 8D, it is possible to see that the workpiece W is gradually moving in a direction (diagonal direction) away from the drawing machine 2. You can see that.

[0099] In step SA104 in Fig. 8, it is determined whether or not there is a problem with the installation state based on the measurement result displayed in step SA103. For example, it is determined whether or not the maximum value of the distance between the workpiece W and the print head 24 is within the specifications of the drawing machine 2, and if it exceeds the specifications, it is determined that there is a problem with the installation position of the drawing machine 2. The determination in step SA104 may be made by the user or the controller 4. In the example shown on the detail display screen 60 in Fig. 8D, it is necessary to adjust the relative positional relationship between the drawing machine 2 and the workpiece W so that they approach each other.

[0100] If it is measured that the distance between the workpiece W and the print head 24 is gradually changing, it is determined that the workpiece is moving at an angle and there is a problem with the installation. In this case, it is necessary to adjust the angle.

[0101] If there is a large variation in the distance between the workpiece W and the print head 24, it is determined that there is a problem with the installation because the drawing machine 2 is not fixed or the guide for the workpiece W is unstable. In this case, it is necessary to fix the drawing machine 2 and adjust the guide.

[0102] The size of the work W can be ascertained based on the movement distance of the work W in the transport direction, and it can be determined whether or not the relationship between the movement distance of the work W in the transport direction and the drawing size is satisfied. If the relationship between the movement distance of the work W in the transport direction and the drawing size is not satisfied, it is determined that there is a problem with the installation state.

[0103] If there is a large variation in the transport speed of the workpiece W when the constant speed drawing setting is used, printing using the constant speed drawing setting is not possible, and it is determined that there is a problem with the installation conditions.

[0104] If the amount of movement of the workpiece W in the direction perpendicular to the transport direction is monotonically increasing or decreasing, it means that the workpiece W is moving diagonally relative to the drawing machine 2, and it is determined that there is a problem with the installation state.

[0105] If the vibration in the direction perpendicular to the conveying direction of the workpiece W is large, it means that the workpiece W is bumping (described later) or the installation of the drawing machine 2 is incomplete, and it is determined that there is a problem with the installation state. In this case, it is necessary to adjust the conveying machine 10 or reconsider the installation of the drawing machine 2.

[0106] If it is determined that there is a problem with the installation position of the drawing machine 2, the process proceeds from step S104 to step SA101. If it is determined that there is no problem with the installation position of the drawing machine 2, the process proceeds from step S104 to step SA105, and the measurement result is reflected in the drawing settings.

[0107] There are cases where the workpiece W is transported at an angle to the horizontal direction. In this case, there is no problem with drawing if the drawing machine 2 is also tilted to match the transport direction of the workpiece W, but as described above, there are cases where the drawing machine 2 cannot be tilted to match the transport direction of the workpiece W. In that case, as shown in the upper part of FIG. 8E, a process is executed to tilt the image to be drawn by an angle α corresponding to the transport direction of the workpiece W, and the drawing control unit 40c controls the ejection of ink based on the image that has been subjected to this process, thereby making it possible to obtain a correct final drawing result as shown in the lower part of FIG. 8E. A specific flow will be described later.

[0108] The optical movement measuring sensor 30 that measures the amount of movement of the workpiece W may need to be corrected depending on the state of the workpiece W. The installation assistance mode has the advantage that installation adjustments can be made without actually drawing on the workpiece W, but if necessary, a correction image may be drawn in the installation assistance mode to correct the optical movement measuring sensor 30. The correction image is For example, it is assumed that a reference image including a plurality of print patterns at predetermined intervals is drawn from the print head 24 onto the workpiece W. The correction image is drawn by the drawing control unit 40c.

[0109] FIG. 8F shows an example of a first correction image. After drawing this first correction image, the dimensions are measured, and the deviation between the measured dimensions and the first correction image is used as a correction coefficient, thereby correcting the optical movement measurement sensor 30. FIG. 8G shows a correction value input screen 70, which has an input area 71 for inputting the measurement result of the first correction image after drawing. The correction coefficient can be calculated based on the value input in the input area 71 and the dimensions of the first correction image on the drawing data.

[0110] 8H shows an example of the first correction image. By drawing such a grid pattern at regular intervals, the optical movement measuring sensor 30 can be corrected, and the amount of movement of the workpiece W in the direction perpendicular to the conveying direction and in the diagonal direction can be visually grasped.

[0111] As described above, the drawing control unit 40c draws, on a workpiece, a correction image that is assumed to be drawn on the workpiece W at a predetermined interval from the print head 24, and accepts input of the drawing result of the correction image drawn on the workpiece W. Then, the drawing control unit 40c performs calibration based on a comparison between the drawing result of the correction image and the predetermined interval.

[0112] (Controlled by drawing control unit) 2 acquires reference position information indicating that the reference position of the workpiece W is at a predetermined position, and measurement values ​​generated by the optical movement measurement sensor 30. After acquiring the reference position information and the measurement values ​​output from the optical movement measurement sensor 30, the drawing control unit 40c controls the ejection of ink from the ejection port 24a of the print head 24 based on the drawing data and a current offset position with respect to the reference position based on the reference position information and the measurement values ​​output from the optical movement measurement sensor 30.

[0113] The reference position information acquired by the imaging control unit 40c is a timing signal indicating that the workpiece W being transported by the transport device 10 has reached a predetermined position. The timing sensor 8 is a sensor that detects that the workpiece W being transported by the transport device 10 has reached a predetermined position, and therefore the imaging control unit 40c acquires a signal output from the timing sensor 8 as a timing signal. In addition, the external device 6 can indirectly acquire that the workpiece W being transported by the transport device 10 has reached a predetermined position by a detector (not shown), and therefore the imaging control unit 40c may acquire a signal output from the external device 6 as a timing signal. The timing sensor 8 and the external device 6 are examples of timing signal output units that output timing signals.

[0114] When the distance sensor 31 is made to function as an optical timing sensor, the drawing control unit 40c receives a timing signal generated by the distance sensor 31. In this case, the drawing control unit 40c controls the ejection of ink from the ejection port 24a based on the drawing data stored in the storage unit 42 and the current relative positions from the ejection port 24a of the print head 24 to each of a plurality of offset positions of the drawing data, the current relative positions being based on measurement values ​​generated by the optical movement measurement sensor 30 with reference to the timing signal generated by the distance sensor 31.

[0115] Since the sensor housing 32 is fixed to the main housing 25, the optical movement measuring sensor 30, the distance sensor 31, and the print head 24 are positioned and fixed. The relative positional relationship between the optical movement measuring sensor 30, the distance sensor 31, and the print head 24 is determined based on the timing signal generated by the distance sensor 31, and the time when drawing information is drawn on the workpiece W. The optical movement measuring sensor 30 is set to satisfy a relationship that allows it to receive light from the workpiece W until the completion of the measurement. The light from the workpiece W includes light that is irradiated onto the workpiece W and reflected on the surface of the workpiece W.

[0116] Also, the optical movement measuring sensor 30 of the sensor unit 3 may generate a timing signal indicating that the workpiece W has reached a predetermined position based on a change in the amount of received light. That is, when the workpiece W being transported enters the light projection range of the optical movement measuring sensor 30 from outside the light projection range, the amount of light received by the optical movement measuring sensor 30 changes. The timing at which the amount of light changes can be regarded as the timing at which the workpiece W has reached a predetermined position, so that the optical movement measuring sensor 30 can generate a timing signal without using the timing sensor 8 or the external device 6. That is, the optical movement measuring sensor 30 is a part that receives light from the workpiece W, generates a measurement value regarding the movement of the workpiece W in the transport direction based on the received light, and generates a timing signal indicating that the reference position of the workpiece W has been detected.

[0117] The drawing control unit 40c can acquire the timing signal generated by the optical movement measuring sensor 30 as reference position information. In this case, the drawing control unit 40c acquires the current relative position from the ejection port 24a of the print head 24 to each of the multiple offset positions of the drawing data based on the measurement value generated by the optical movement measuring sensor 30 with reference to the timing signal generated by the optical movement measuring sensor 30, and controls the ejection of ink from the ejection port 24a based on the acquired current relative position and the drawing data stored in the storage unit 42. The drawing control unit 40c can also generate a timing signal at the timing when the amount of light received by the optical movement measuring sensor 30 changes, and acquire the timing signal.

[0118] An offset amount from a reference position on the workpiece W to a position where the drawing information is drawn can be defined as a first offset amount, and an offset amount from the reference position on the workpiece W to the discharge port 24a of the print head 24 can be defined as a second offset amount. The sensor housing 32 is positioned and fixed with respect to the discharge port 24a of the print head 24 in accordance with the second offset amount. In this case, the drawing control unit 40c can determine the current relative position from the discharge port 24a of the print head 24 to each of the multiple offset positions of the drawing data based on the first offset amount and the second offset amount.

[0119] (Drawing control based only on detection speed or distance) FIG. 9 is a flowchart showing an example of a procedure of drawing control according to only the detection speed or distance detected by the sensor unit 3. This control is executed when the transport speed (movement amount) of the work W cannot be accurately obtained without the sensor unit 3. That is, when the drawing data shown in FIG. 5 is drawn in a constant speed drawing setting in which the transport speed of the work W is assumed to be constant, all of the time intervals of the first to seventh timings L1 to L7 are equal, as shown in FIG. 10. On the other hand, when the transport speed of the work W is non-uniform due to control using the encoder 7, the time intervals of the first to seventh timings L1 to L7 are unequal, as shown in FIG. 11. In this way, the drawing control unit 40c controls the ejection of ink from the ejection port 24a based on the current relative positions from the ejection port 24a of the print head 24 to each of the multiple offset positions of the drawing data and the drawing data.

[0120] Here, it is assumed that the conveying speed of the conveying machine 10 is unstable or the conveying speed detected by the encoder 7 is unstable. It is also assumed that the workpiece W gets caught on a member such as a guide (not shown) while being conveyed by the conveying machine 10, causing the speed of the workpiece W to drop below the conveying speed of the conveying machine 10. Furthermore, when the conveying machine 10 starts or stops, there will be an acceleration / deceleration region, and the speed of the workpiece W will become unstable in the acceleration / deceleration region.

[0121] In response to these issues, in the present embodiment, drawing control is performed based on the speed or distance obtained by the sensor unit 3, which can directly detect the conveying speed of the workpiece W, so that constant speed drawing and non-constant speed drawing can be performed by reflecting the actual conveying speed of the workpiece W without relying on the unstable conveying speed of the conveying machine 10.

[0122] The following is an explanation based on the flowchart shown in Fig. 9. After the drawing operation starts, in step SB1, the drawing control unit 40c acquires the drawing data set included in the job saved in step SA11 of the flowchart shown in Fig. 8A. In step SB2, the drawing device 2 waits for drawing to start, and proceeds to step SB3 after waiting a predetermined time. In step SB3, the drawing device 2 determines whether or not a timing signal has been input. If no timing signal has been input, the process proceeds to step SB2, where the drawing device 2 continues to wait for drawing to start.

[0123] If a timing signal is input, it means that the workpiece W has reached a predetermined position, and the process proceeds to step SB4. In step SB4, the workpiece movement amount acquisition unit 40d acquires the movement amount of the workpiece W based on the measurement value output from the optical movement measurement sensor 30 of the sensor unit 3. The drawing control unit 40c calculates the current offset position of the workpiece W relative to the reference position based on the timing signal and the movement amount of the workpiece W. The movement amount of the workpiece W is constantly acquired.

[0124] In step SB5, the position of the ejection port 24a of the print head 24 relative to the current position of the workpiece W is determined based on the current offset position relative to the reference position of the workpiece W calculated in step SB4 and the drawing data stored in the memory unit 42. If the position of the ejection port 24a is not a position from which ink should be ejected, the process proceeds to step SB4, where the current offset position relative to the reference position of the workpiece W is calculated. On the other hand, if the position of the ejection port 24a is a position from which ink should be ejected, the process proceeds to step SB6, where the drawing control unit 40c controls the print head drive unit 23 to eject ink from the ejection port 24a.

[0125] Then, the process proceeds to step SB7, where it is determined whether or not all of the drawing data has been drawn. If there is drawing data that has not been drawn, the process proceeds to step SB4. On the other hand, if all of the drawing data has been drawn, the drawing operation is terminated and the process waits for the next workpiece W to be transported.

[0126] (Control when detection accuracy decreases) There may be cases where the detection accuracy of the optical movement measuring sensor 30 of the sensor unit 3 is low due to some cause. For example, if dirt adheres to the light receiving surface of the optical movement measuring sensor 30, the amount of received light may decrease and a measurement value may not be generated. Also, there may be cases where the amount of movement of the speckle pattern cannot be measured and a measurement value may not be generated. The flowchart shown in Fig. 12 shows control including processing assuming a case where the detection accuracy of the optical movement measuring sensor 30 is low.

[0127] Steps SC1 to SC4 shown in Fig. 12 are the same as steps SB1 to SB4 shown in Fig. 9. In step SC5, the detection accuracy of the optical movement measuring sensor 30 is judged. For example, if the amount of light received by the optical movement measuring sensor 30 is below a threshold and the amount of movement of the speckle pattern cannot be measured, it is judged that the accuracy of the measurement value generated by the optical movement measuring sensor 30 is below a predetermined level and that the situation is prone to drawing defects, and the program proceeds to step SC6. In other cases, it is judged that the detection accuracy of the optical movement measuring sensor 30 is high and that the situation is unlikely to cause drawing defects, and the program proceeds to step SC7.

[0128] In step SC6, the workpiece movement amount acquisition unit 40d acquires the movement amount based on the constant speed drawing setting or the encoder 7. The movement amount can also be acquired without using the encoder 7. That is, the user operates the terminal side operation unit 5b or the operation display unit 43 to obtain the movement amount shown in FIG. The conveying speed of the conveyor 10 can be set by the flowchart, and the movement amount of the workpiece W by the conveyor 10 can be calculated based on the set conveying speed. In this case, the terminal side operation unit 5b or the operation display unit 43 is a movement amount acquisition unit that acquires the movement amount by the conveyor 10. After the workpiece movement amount acquisition unit 40d acquires the movement amount based on the constant speed drawing setting or the encoder 7, the drawing control unit 40c calculates the current offset position of the workpiece W relative to the reference position based on the timing signal and the movement amount of the workpiece W.

[0129] In step SC6, a process of notifying the user of the error can also be performed. The error notification may include a message urging the user to perform maintenance, such as removing foreign matter adhering to the sensor unit 3.

[0130] On the other hand, if the detection accuracy of the optical movement measuring sensor 30 is high and the process proceeds to step SC7, the work movement amount acquisition unit 40d acquires the movement amount of the work W based on the measurement value output from the optical movement measuring sensor 30 of the sensor unit 3. The drawing control unit 40c calculates the current offset position of the work W relative to the reference position based on the timing signal and the movement amount of the work W.

[0131] After step SC6 or step SC7, in step SC8, the position of the ejection port 24a of the print head 24 relative to the current position of the workpiece W is determined based on the current offset position of the workpiece W relative to the reference position calculated in step SC6 or step SC7 and the drawing data stored in the memory unit 42. If the position of the ejection port 24a is not a position where ink should be ejected, the process proceeds to step SC4. On the other hand, if the position of the ejection port 24a is a position where ink should be ejected, the process proceeds to step SC9. Steps SC9 and SC10 are the same as steps SB6 and SB7 in FIG. 9, respectively.

[0132] In this way, when the accuracy of the measurement value generated by the optical movement measurement sensor 30 is below a predetermined level, the drawing control unit 40c can control the ejection of ink from the ejection port 24a based on the constant speed drawing setting or the movement amount based on the encoder 7 and the drawing data, so that drawing can be performed based on the actual transport speed (movement amount) of the workpiece W.

[0133] In this control, the processes of steps SC5 to SC7 are performed, and thus switching occurs between the measurement value generated by the optical movement measuring sensor 30 and the value based on the constant speed drawing setting or the encoder 7. At the time of this switching, a discontinuous change in the work speed occurs due to a processing delay, so that a supplementary process such as linear interpolation may be performed before and after the switching to smoothly connect the control speed before and after the switching so that the drawing result does not look strange.

[0134] (Control when the detected speed exceeds the threshold) Fig. 13 shows a control including a process assuming a case where the detection speed detected by the sensor unit 3 exceeds a threshold value. When the conveying speed of the conveyor 10 is set in advance according to the flowchart shown in Fig. 8A, a normal drawing process is executed based on the constant speed drawing setting or the output from the encoder 7. For example, the conveying speed set by the constant speed drawing setting has higher accuracy than the speed detected by the optical movement measurement sensor 30, so that under normal circumstances, a good drawing state is obtained by executing the drawing process based on the constant speed drawing setting or the output from the encoder 7.

[0135] However, there may be a case where the workpiece W gets caught on some member on the conveying surface 10a, making it impossible to detect the speed of the workpiece W. In such a case, the speed detected by the optical movement measuring sensor 30 exceeds a preset speed threshold, and drawing is performed according to the speed detected by the optical movement measuring sensor 30, regardless of the constant speed drawing setting or the output from the encoder 7. Hereinafter, the optical The control when the speed detected by the movement measurement sensor 30 exceeds the threshold value will be described.

[0136] Steps SD1 to SD4 shown in Fig. 13 are the same as steps SB1 to SB4 shown in Fig. 9. In step SD5, the movement amount based on the constant speed drawing setting or the encoder 7 is acquired, and a movement determination is performed based on the acquired movement amount. That is, the movement amount acquired in step SD4 is compared with the movement amount acquired in step SD5, and it is determined whether or not the measurement value generated by the optical movement measuring sensor 30 exceeds a preset speed threshold. This threshold can be set, for example, to about ±10% of the transport speed of the constant speed drawing setting.

[0137] If it is determined in step SD5 that the measurement value generated by the optical movement measuring sensor 30 does not exceed the threshold, it is presumed that the workpiece W is not stuck or the like, and in this case, it is within the specified error range and the process proceeds to step SD6. On the other hand, if it is determined in step SD5 that the measurement value generated by the optical movement measuring sensor 30 exceeds the threshold, it is presumed that the workpiece W is stuck or the like, and in this case, it is outside the specified error range and the process proceeds to step SD7.

[0138] In step SD6, the workpiece movement amount acquisition unit 40d acquires the movement amount based on the constant speed drawing setting or the output from the encoder 7. After the workpiece movement amount acquisition unit 40d acquires the movement amount based on the constant speed drawing setting or the output from the encoder 7, the drawing control unit 40c calculates the current offset position of the workpiece W relative to the reference position based on the timing signal and the movement amount of the workpiece W.

[0139] In step SD7, the work movement amount acquisition unit 40d acquires the movement amount of the work W based on the measurement value output from the optical movement measurement sensor 30 of the sensor unit 3. The drawing control unit 40c calculates the current offset position of the work W relative to the reference position based on the timing signal and the movement amount of the work W. Steps SD8 to SD10 are the same as steps SC8 to SC10 in FIG.

[0140] Therefore, the drawing control unit 40c determines in step SD5 whether the measurement value generated by the optical movement measuring sensor 30 exceeds the threshold value, and controls the ejection of ink from the ejection port 24a based on the drawing data and the movement amount based on the constant speed drawing setting or the output from the encoder 7 until the measurement value exceeds the threshold value. On the other hand, if the measurement value generated by the optical movement measuring sensor 30 exceeds the threshold value as a result of the determination in step SD5, the drawing control unit 40c can control the ejection of ink from the ejection port 24a based on the current offset position acquired based on the measurement value generated by the optical movement measuring sensor 30 and the drawing data.

[0141] In this control, the processes of steps SD5 to SD7 are performed, and switching occurs between the measurement value generated by the optical movement measuring sensor 30 and the value based on the constant speed drawing setting or the output from the encoder 7. At the time of this switching, a step change occurs from the setting value to the control value, so that a control may be performed to smoothly connect the control speed before and after the switching by performing a complementation process such as linear interpolation before and after the switching so as not to cause discomfort in the drawing result.

[0142] Furthermore, if the measurement value generated by the optical movement measuring sensor 30 chatters with respect to the threshold value, which is the criterion for switching between the measurement value generated by the optical movement measuring sensor 30 and the value based on the uniform speed drawing setting or the output from the encoder 7, an unnatural drawing result will occur. In order to suppress the occurrence of such unnaturalness, a hysteresis may be provided for the threshold value, and control may be performed so that switching due to chattering does not occur frequently.

[0143] Also, if it is determined in step SD5 that the measurement value generated by the optical movement measuring sensor 30 exceeds the threshold, the process does not proceed to step SC7, but the measurement value generated by the optical movement measuring sensor 30 is It is also possible to perform control such that a user is notified by a warning or the like that the value exceeds the threshold value.

[0144] (Bumping correction) For example, a conveyor that generates a large amount of vibration, such as a roller conveyor, may be used as the conveyor 10. The workpiece W conveyed by such a conveyor 10 has a vibration component perpendicular to the conveying direction of the workpiece W. Assuming that the workpiece W is conveyed horizontally, the workpiece W will vibrate irregularly in the vertical direction relative to the drawing machine 2. If the workpiece W has a vibration component perpendicular to the conveying direction, there is a risk that the drawing quality will be significantly reduced. In this embodiment, the vibration of the workpiece W in a direction perpendicular to the conveying direction is called "bumping." Pumping includes both regular and irregular vibrations.

[0145] The inkjet printing apparatus 1 according to this embodiment is configured to be able to perform bumping correction in order to suppress deterioration of the drawing quality caused by bumping of the workpiece W. In the bumping correction, the drawing control unit 40c controls the ejection of ink from the ejection port 24a of the print head 24 based on the amount of movement of the workpiece W in a direction perpendicular to the transport direction measured by the optical movement measuring sensor 30. Details of the bumping correction will be described below based on the flowchart shown in FIG.

[0146] Steps SE1 to SE3 shown in Fig. 14 are the same as steps SB1 to SB3 shown in Fig. 9. In step SE4, the work movement amount acquisition unit 40d acquires the movement amount of the work W in the transport direction (defined as the X direction) and the movement amount in the direction perpendicular to the transport direction (defined as the Y direction) based on the measurement value output from the optical movement measurement sensor 30 of the sensor unit 3. When the measurement value output from the optical movement measurement sensor 30 contains an X direction component and a Y direction component, the movement amount in the X direction and the movement amount in the Y direction can be acquired by executing a process to separate the measurement value into the X direction component and the Y direction component.

[0147] The drawing control unit 40c calculates the current offset position of the workpiece W relative to the reference position in the X direction based on the timing signal and the movement amount of the workpiece W in the X direction. At this time, the current offset position of the workpiece W relative to the reference position in the Y direction is also calculated. Note that the X direction is the arrangement direction of the multiple discharge ports 24a, and is the vertical direction when the workpiece W is transported horizontally. Also, the Y direction can be said to be a direction perpendicular to the arrangement direction of the multiple discharge ports 24a.

[0148] In step SE5, the position of the ejection port 24a of the print head 24 relative to the current position of the workpiece W in the X direction is determined based on the current offset position of the workpiece W relative to the reference position in the X direction calculated in step SE4 and the drawing data stored in the memory unit 42. If the position of the ejection port 24a in the X direction is not a position from which ink should be ejected, the process proceeds to step SE4, where the current offset position of the workpiece W relative to the reference position in the X direction is calculated. On the other hand, if the position of the ejection port 24a in the X direction is a position from which ink should be ejected, the process proceeds to step SE6.

[0149] In step SE6, the drawing data is offset by the amount of movement in the Y direction from the reference position. For example, the original data of the drawing data shown in FIG. 15 is the drawing data shown in FIG. 5. In FIG. 15, ejection timing t3 and ejection timing t5 show a case where it is detected that the workpiece W has moved one pixel upward from the reference position. In this case, the drawing data at ejection timing t3 and ejection timing t5 are offset by one pixel downward in a direction that cancels out the upward movement of the workpiece W. Also, ejection timing t4 shows a case where it is detected that the workpiece W has moved two pixels upward from the reference position. In this case, the drawing data at ejection timing t4 is offset by two pixels downward in a direction that cancels out the upward movement of the workpiece W.

[0150] The offset amount and offset direction of the drawing data can be accurately obtained based on the measurement value output from the optical movement measurement sensor 30. Also, although not shown, when it is detected that the workpiece W has moved downward from the reference position at a certain discharge timing, the drawing data is offset upward to cancel out the downward movement of the workpiece W. The offset of data can also be called a shift of data. Steps SE7 and SE8 in FIG. 14 are the same as steps SB6 and SB7 in FIG. 9, respectively.

[0151] (Bumping correction including rotation direction) When the workpiece W being transported by the transport device 10 is viewed from the print head 24 side, it is assumed that the workpiece W is displaced in the rotation direction around the horizontal axis. In such a case, the inkjet printing device 1 according to this embodiment can perform bumping correction including the rotation direction of the workpiece W to improve the drawing quality. The control content of the bumping correction including the rotation direction will be described based on the flowchart shown in FIG. 16. When performing bumping correction including the rotation direction, a first optical movement measuring sensor 30A and a second optical movement measuring sensor 30B are provided as in the first example shown in FIG. 17. The first optical movement measuring sensor 30A and the second optical movement measuring sensor 30B are the same.

[0152] 17, a first sensor unit 3A having a first optical movement measuring sensor 30A, a first sensor housing 32A, and a distance sensor 31, and a second sensor unit 3B having a second optical movement measuring sensor 30B and a second sensor housing 32B are detachably attached to a main housing 25. The first sensor housing 32A is disposed upstream of the print head 24 in the transport direction. On the other hand, the second sensor housing 32B is disposed downstream of the print head 24 in the transport direction. This allows the first optical movement measuring sensor 30A and the second optical movement measuring sensor 30B to be installed apart from each other in the transport direction.

[0153] 18, a first optical movement measurement sensor 30A and a second optical movement measurement sensor 30B are housed in one sensor housing 32. The first optical movement measurement sensor 30A is disposed upstream of the second optical movement measurement sensor 30B in the conveying direction. In this second example, similar to the first example, the first optical movement measurement sensor 30A and the second optical movement measurement sensor 30B can be installed apart from each other in the conveying direction.

[0154] Steps SF1 to SF3 in Fig. 16 are the same as steps SB1 to SB3 shown in Fig. 9. In step SF4, the work movement amount acquisition unit 40d acquires the movement amount of the work W in the X direction and the Y direction based on the measurement value output from the first optical movement measurement sensor 30A, and also acquires the movement amount of the work W in the X direction and the Y direction based on the measurement value output from the second optical movement measurement sensor 30B. The drawing control unit 40c calculates the current offset position of the work W with respect to the reference position in the X direction based on the timing signal and the movement amount of the work W in the X direction.

[0155] In step SF5, a position calculation of the workpiece W relative to the discharge port 24a of the print head 24 is performed in the X direction of the workpiece W based on the current offset position of the workpiece W relative to the reference position in the X direction calculated in step SF4 and the drawing data. At this time, a position calculation of the workpiece W relative to the discharge port 24a of the print head 24 is also performed in the Y direction. Furthermore, a rotation direction and a rotation amount (θ) of the workpiece W around the horizontal axis are calculated based on the measurement values ​​output from the first optical movement measuring sensor 30A and the measurement values ​​output from the second optical movement measuring sensor 30B.

[0156] In step SF6, the position of the discharge port 24a of the print head 24 relative to the current position of the workpiece W in the X direction is calculated based on the current offset position of the workpiece W relative to the reference position in the X direction calculated in step SF5 and the drawing data stored in the memory unit 42. If the position of the ejection port 24a in the X direction is not a position from which ink should be ejected, the process proceeds to step SF4. On the other hand, if the position of the ejection port 24a in the X direction is a position from which ink should be ejected, the process proceeds to step SF7.

[0157] In step SF7, the drawing data is offset by the amount of movement in the Y direction and the amount of rotation from the reference position. The offset in the Y direction is as described above. The offset in the rotation direction can be performed in a similar manner to the offset in the Y direction, and the drawing data is offset in a direction that cancels the rotation of the workpiece W. In step SF7, control is executed so that drawing data that has already been drawn is not drawn again. Steps SF8 and SF9 in FIG. 16 are the same as steps SB6 and SB7 in FIG. 9, respectively.

[0158] When the amount of movement in the X direction and the amount of movement in the Y direction (vibration speed) exceed the limit speed at which correction can be performed, processing may be performed in which bumping correction is not performed, or processing may be performed in which an error is notified to the user.

[0159] For example, among the multiple discharge ports 24a arranged in the vertical direction of the print head 24, a predetermined number of discharge ports 24a on the upper side and a predetermined number of discharge ports 24a on the lower side can be set as discharge ports 24a for correction margins. In this case, when bumping correction is not performed, the drawing process is performed only with the discharge ports 24a other than the discharge ports 24a for correction margins, i.e., the discharge ports 24a in the vertical middle part. On the other hand, when bumping correction is required, drawing can be performed so as to cancel the vibration of the workpiece W by using a predetermined number of discharge ports 24a on the upper side including the upper end (upper correction margin) and a predetermined number of discharge ports 24a on the lower side including the lower end (lower correction margin). In this case, when a large vibration that exceeds the upper and lower correction margins occurs in the workpiece W, a process of not performing bumping correction or a process of notifying the user of an error is performed.

[0160] Also, the user may be able to set the vibration amount to be subjected to bumping correction. Since there is a response delay due to bumping correction, it is assumed that when the measured vibration amount is small, the vibration amount will be increased by bumping correction. Therefore, when the measured vibration amount is equal to or less than a predetermined amount, a cancellation process for canceling the bumping correction may be executed.

[0161] (Inclined line compatible) The inkjet printing device 1 of this embodiment uses head pressure to supply ink to the print head 24. While this allows for a simple structure, it also requires that the ink level in the subtank 21a be within a specified range of inclination with respect to the horizontal plane (several degrees of inclination with respect to the horizontal plane), which places restrictions on the installation of the drawing machine 2. Also, with regard to the attitude of the subtank 21a that supplies ink to the print head 24, there is a tolerance for inclination depending on the positional relationship with the supply port on the print head 24 side.

[0162] On the other hand, there are cases where the conveying direction of the conveyor 10 is inclined. For example, the inclination is such that the line is lower toward the downstream side in the conveying direction, or the line is higher toward the downstream side in the conveying direction. When installing the drawing machine 2 on such an inclined line, if the inclination of the inclined line exceeds the specified inclination of the drawing machine 2, it becomes impossible to install the drawing machine 2, and the range of application of the drawing machine 2 is limited.

[0163] In response to this, in the inkjet printing apparatus 1 according to this embodiment, the drawing unit 2 is set within a specified inclination while being able to handle inclined lines, so that it is possible to execute inclined line correspondence control. Details of the inclined line correspondence control will be described with reference to the flowchart shown in FIG.

[0164] Steps SG1 to SG4 are the same as steps SE1 to SE4 shown in FIG. In step SG5, the conveying direction specification unit 40g determines the inclination direction and inclination angle θ of the conveying surface 10a of the conveying machine 10 based on the movement amount in the X direction and the movement amount in the Y direction of the workpiece W acquired in step SG4. The inclination direction and inclination angle θ of the conveying surface 10a of the conveying machine 10 coincide with the conveying direction of the workpiece W. The inclination direction and inclination angle θ can be calculated by atan(Y / X), and the calculated inclination direction and inclination angle θ are temporarily stored. The measured value at the time of the previous drawing may be used as this inclination angle θ. The calculated inclination angle θ may also be corrected later.

[0165] In step SG6, the drawing data is affine transformed based on the transport direction identified by the transport direction identification unit 40g, so that drawing in a direction parallel to the inclination, i.e., the desired drawing is performed on the workpiece W, is configured.

[0166] In step SG7, similarly to step SG4, the workpiece movement amount acquiring unit 40d acquires the movement amount of the workpiece W in the X direction and the Y direction based on the measurement value output from the optical movement measuring sensor 30.

[0167] In step SG8, ​​the position of the ejection port 24a of the print head 24 relative to the current position of the workpiece W is determined based on the current offset position relative to the reference position of the workpiece W calculated in step SG7 and the drawing data. If the position of the ejection port 24a is not a position where ink should be ejected, proceed to step SG7. On the other hand, if the position of the ejection port 24a is a position where ink should be ejected, proceed to step SG9. In step SG9, when the conveying direction specified by the conveying direction specifying unit 40g is inclined with respect to the horizontal plane, the drawing control unit 40c controls the ejection of ink from the ejection port 24a so that information such as character strings and images is drawn parallel to the conveying direction. Step SG10 is the same as step SB7 in FIG. 9. This example is suitable for a case where the installation reliability of the drawing machine 2 with respect to the conveying machine 10 is low.

[0168] (Obtaining the inclination angle of the workpiece when installed) The inclination angle of the workpiece W during transportation by the transport device 10 can also be acquired when the drawing machine 2 is installed. This example is suitable when it is desired to avoid measurement errors of the sensor unit 3 or when the installation reliability of the drawing machine 2 relative to the transport device 10 is high. Below, with reference to Fig. 20, a procedure for acquiring the inclination angle of the workpiece W relative to the drawing machine 2 when the drawing machine 2 is installed will be described.

[0169] In step SH1, the control unit 40 waits for the workpiece W to pass in front of the sensor unit 3. The passage of the workpiece W can be detected by the optical movement measurement sensor 30 of the sensor unit 3 or by the encoder 7. In step SH2, it is determined whether or not a drawing start trigger has been input. If the drawing start trigger has not been input, the process returns to step SH1, and if the drawing start trigger has been input, the process proceeds to step SH3.

[0170] In step SH3, the work movement amount acquisition unit 40d acquires the movement amount of the work W in the X direction and the Y direction based on the measurement value output from the optical movement measurement sensor 30. In step SH4, the transport direction specification unit 40g determines the tilt direction and tilt angle θ of the transport surface 10a of the transport device 10 based on the movement amount of the work W in the X direction and the Y direction acquired in step SH3. This makes it possible to acquire the tilt direction of the work W during transport as an installation correction value and store it in the memory unit 42 or the like. The tilt angle acquired in this flow is used when performing affine transformation on the drawing data.

[0171] (When the tilt angle during transport of the workpiece exceeds the allowable value) FIG. 21 shows a procedure for processing when a tilt angle θ of a workpiece W that exceeds a preset allowable value of the tilt angle is detected. Steps SI1 to SI6 correspond to steps in FIG. This is the same as SG1 to SG6.

[0172] In step SI7, the tilt angle θ determined in step SI5 is obtained, and it is determined whether the obtained tilt angle θ exceeds a threshold value (tolerance value). If it is determined in step SI7 that the tilt angle θ exceeds the threshold value, the process proceeds to step SI8, where the tilt angle error is notified to the user. When notifying the user of the tilt angle error, drawing may be continued or may be stopped. On the other hand, if it is determined in step SI7 that the tilt angle θ does not exceed the threshold value, the process proceeds to step SI4. Steps SI9 to SI12 are the same as steps SG7 to SG10 in FIG. 19, respectively.

[0173] (Installation example) In the first example shown in Fig. 17, the print head 24 is disposed between the first optical movement measuring sensor 30A and the second optical movement measuring sensor 30B as described above. That is, by additionally providing the second optical movement measuring sensor 30B downstream of the print head 24 in the transport direction of the work W, it is possible to eliminate the dead space at the final end in the transport direction of the work W. However, since there is a possibility that detection failure of the second optical movement measuring sensor 30B is likely to occur due to the influence of ink mist and ink rebound splashes on the downstream side of the transport direction of the work W, for example, a positive pressure generating device such as an air purge can be used to keep the detection surface of the second optical movement measuring sensor 30B at positive pressure to reduce the influence of the ink mist and ink rebound splashes.

[0174] 18, the first optical movement measuring sensor 30A, the distance sensor 31, the second optical movement measuring sensor 30B, and the print head 24 are arranged in this order from upstream in the transport direction of the workpiece W. By arranging in this manner, it is possible to start measuring the amount of movement of the workpiece W while the first optical movement measuring sensor 30A is outputting a valid measurement value, and it is possible to minimize the dead space (portion that cannot be measured by the optical movement measuring sensor) at the final end in the transport direction of the workpiece W.

[0175] 22 is a diagram showing a third example in which the first optical movement measurement sensor 30A and the second optical movement measurement sensor 30B are provided. In this third example, the first optical movement measurement sensor 30A and the second optical movement measurement sensor 30B are accommodated in one sensor housing 32. The first optical movement measurement sensor 30A is disposed upstream of the second optical movement measurement sensor 30B in the transport direction. The sensor housing 32 is attached to the downstream side of the main housing 25 in the transport direction of the workpiece W. Therefore, the first optical movement measurement sensor 30A and the second optical movement measurement sensor 30B are disposed downstream of the print head 24 in the transport direction of the workpiece W.

[0176] As in the third example, by arranging the first optical movement measuring sensor 30A, the second optical movement measuring sensor 30B, and the distance sensor 31 downstream of the print head 24, drawing can be performed without generating dead space up to the final end in the transport direction of the workpiece W. However, in order to suppress detection failures due to ink splashes, etc., it is preferable to use the positive pressure generating device to keep the detection surfaces of the first optical movement measuring sensor 30A, the second optical movement measuring sensor 30B, and the distance sensor 31 at positive pressure.

[0177] In the case shown in FIG. 22, the sensor housing 32 is detachably attached to the main housing 25 at a position offset to the downstream side (one side) along the transport direction of the workpiece W. On the other hand, in the cases shown in FIGS. 3 and 18, the sensor housing 32 is detachably attached to the main housing 25 at a position offset to the upstream side (the other side) along the transport direction of the workpiece W. In this way, the sensor housing 32 according to this embodiment can be positioned at a first position offset to one side along the transport direction of the workpiece W and at a second position offset to the other side relative to the main housing 25. The user can select whether to attach the sensor housing 32 to the first position or the second position depending on the workpiece W, the image drawing content, the structure of the conveyor 10, the line configuration, etc. The height of the sensor housing 32 in the first position and the second position can be adjusted.

[0178] 23 is a diagram showing a fourth example in which a first optical movement measuring sensor 30A and a second optical movement measuring sensor 30B are provided. In this fourth example, the first optical movement measuring sensor 30A, the second optical movement measuring sensor 30B, and the distance sensor 31 are attached above the print head 24. This makes it possible to minimize the dead space at both downstream and upstream ends in the transport direction of the workpiece W.

[0179] Although not shown, the first optical movement measuring sensor 30A, the second optical movement measuring sensor 30B and the distance sensor 31 may be attached below the print head 24. In this case, the dead space at both ends, downstream and upstream, in the conveying direction of the work W, can be minimized. The optical movement measuring sensor and the distance sensor may be attached to all of the upstream, downstream, upper and lower sides of the print head 24, or may be attached to any two or three locations among the upstream, downstream, upper and lower sides of the print head 24. Both or one of the optical movement measuring sensor and the distance sensor may be embedded in the print head 24. One of the measurement sensor and the distance sensor may be embedded in the print head 24, and the other may be provided outside the print head 24.

[0180] 3 etc. shows an example of drawing on the side surface of the workpiece W, but the present invention is not limited to this and can also be applied to drawing on the top surface or bottom surface of the workpiece W. When drawing on the top or bottom surface of the workpiece W, the drawing machine 2 can be installed so that the discharge port 24a of the print head 24 faces the surface to be drawn.

[0181] Fig. 24 is a plan view showing the inkjet printing device 1 during operation. As shown in this figure, the sensor housing 32 is positioned and fixed to the print head 24 so that the front part 32a and the window part 32b of the sensor housing 32 are positioned further back than the print head 24 (positions farther away from the workpiece W) in the distance direction from the print head 24 (the vertical direction in Fig. 24). That is, the optical movement measuring sensor 30 is positioned and fixed to the print head 24 so that the window part 32b is positioned further back than the print head 24, and the optical movement measuring sensor 30 is positioned and fixed to the print head 24 by the sensor housing 32. The window part 32b may be located on the same plane as the tip part of the main housing 25.

[0182] Here, let us consider a case where drawing is performed on the side surface of the workpiece W. When drawing on the side surface of the workpiece W, the front surface 32a and the window portion 32b of the sensor housing 32 are set back from the print head 24, so that the distance D2 between the side surface of the workpiece W and the front surface 32a (window portion 32b) of the sensor housing 32 is set longer than the distance D1 between the side surface of the workpiece W and the tip of the print head 24. This allows the front surface 32a of the sensor housing 32 to be separated from the landing surface of the ink particles on the workpiece W, so that splashes of ink bouncing off the workpiece W and splashes of satellites are less likely to adhere to the front surface 32a of the sensor housing 32. In addition, the workpiece W is less likely to collide with the sensor housing 32, and the distance between the print head 24 and the workpiece W is not affected by the installation position of the sensor housing 32, so that the throw distance (drawing distance range) of the drawing machine 2 can be maximized.

[0183] The sensor housing 32 may be positioned and fixed relative to the print head 24 so that the front portion 32a and the window portion 32b of the sensor housing 32 are in a position forward of the print head 24 (a position approaching the workpiece W). In this case, the front portion 32a and the window portion 32b of the sensor housing 32 and the print head 24 may be located at the same position.

[0184] 25 is a plan view showing the inkjet printing device 1 in operation, in which the first optical movement measurement sensor 30A and the second optical movement measurement sensor 30B are provided. The first optical movement measurement sensor 30A and the second optical movement measurement sensor 30B are the same. The measurement range of the first optical movement measurement sensor 30A is shown as a first measurement range 110, and the measurement range of the second optical movement measurement sensor 30B is shown as a second measurement range 120. In addition, the measurement light projected from the distance sensor 31 is shown as reference numeral 130.

[0185] The depth of field of the light receiving unit 30b of the first optical movement measuring sensor 30A and the second optical movement measuring sensor 30B is indicated by the symbol D3. The lower limit (the side closer to the sensor) of the movement amount measurable range of the first optical movement measuring sensor 30A is determined by the measurable distance for a white workpiece with high reflectivity, and the upper limit (the side farther from the sensor) is determined by the measurable distance for a black workpiece with low reflectivity. At a distance below the lower limit of the movement amount measurable range of the first optical movement measuring sensor 30A, the amount of light on the light receiving unit 30b is saturated for the white workpiece, and sufficient speckle contrast cannot be obtained, making it impossible to measure the movement amount. In addition, above the upper limit of the movement amount measurable range of the first optical movement measuring sensor 30A, the amount of light on the light receiving unit 30b is insufficient due to the low amount of received light, and the speckle contrast is buried in noise components, making it impossible to measure the movement amount. Here, the white workpiece and the black workpiece are based on JCS M001:2000, with code number D250 (color name: white) being the white workpiece and code number D260 (color name: black) being the black workpiece.

[0186] 25, the drawing distance range of the print head 24 is indicated by the symbol D4. The depth of field D3 of the light receiving unit 30b is wider than the drawing distance range D4 of the print head 24, and the drawing distance range D4 of the print head 24 is included in the depth of field D3 of the light receiving unit 30b.

[0187] That is, since the light receiving unit 30b is fixed to the sensor housing 32, the position of the light receiving unit 30b is determined by attaching the sensor housing 32 to the main housing 25. In this example, the optical movement measuring sensor 30 is fixed to the print head 24 by the sensor housing 32 so that the depth of field of the light receiving unit 30b in the distance direction from the print head 24 includes the drawing distance range of the print head 24, and the sensor housing 32 serves as a fixing part for positioning and fixing the optical movement measuring sensor 30 to the print head 24. The fixing part may be a bracket or the like configured separately from the sensor housing 32, or may include a fastening member such as a bolt or a screw.

[0188] Furthermore, in the distance direction from the discharge port 24a of the print head 24, the distance sensor 31 is positioned and fixed relative to the print head 24 so that the measurement range of the distance sensor 31 (for convenience, indicated by the same reference symbol D3 as the light receiving unit 30b) includes the drawing distance range of the print head 24. By setting the distance between the print head 24 and the workpiece W within the drawing distance range, good drawing can be performed without any disturbance in the drawing. In other words, the drawing distance range is the distance between the print head 24 and the workpiece W that does not exceed the allowable value for drawing quality. The measurement range of the distance sensor 31 and the depth of field of the light receiving unit 30b may be different.

[0189] As shown in this figure, the first optical movement measuring sensor 30A and the second optical movement measuring sensor 30B are arranged at an interval in the conveying direction of the workpiece W, and a distance sensor 31 is further arranged between the first optical movement measuring sensor 30A and the second optical movement measuring sensor 30B, thereby preventing measurement errors at the end of the workpiece W in the conveying direction. That is, as shown in FIG. 25, the first optical movement measuring sensor 30A measures the workpiece W, and the second optical movement measuring sensor 30B measures the workpiece W. When W is not measured, it can be determined that the upstream end of the workpiece W in the transport direction is measured by the distance sensor 31. On the other hand, when the first optical movement measuring sensor 30A is not measuring the workpiece W and the second optical movement measuring sensor 30B is measuring the workpiece W, it can be determined that the downstream end of the workpiece W in the transport direction is measured by the distance sensor 31.

[0190] 25, as shown by virtual lines, the sensor housing 32 housing the first optical movement measuring sensor 30A and the second optical movement measuring sensor 30B can also be attached to the downstream side of the main housing 25. The sensor housing 32 is configured to be detachable on both the upstream side and downstream side of the transport direction of the workpiece W with respect to the print head 24. The sensor housing 32 is positioned and fixed on both the upstream side and downstream side of the transport direction of the workpiece W with respect to the print head 24. However, this is not limited to this, and the sensor housing 32 may be positioned and fixed only on the upstream side or only on the downstream side of the transport direction of the workpiece W with respect to the print head 24.

[0191] 26 to 28 show a specific example of a sensor unit 3 having a first optical movement measuring sensor 30A and a second optical movement measuring sensor 30B. This sensor unit 3 is attached to the upstream side of the main housing 25 in the position shown in Figs. 26 to 28, i.e., in the position where the top of Figs. 26 to 28 is the top when attached. The sensor housing 32 of this sensor unit 3 is detachable from the print head 24 in an upside-down position as shown in Figs. 29 and 30.

[0192] 31, the optical movement measuring sensor 30 and the distance sensor 31 may be housed in the main housing 25 without providing the sensor housing 32 for housing the optical movement measuring sensor 30 and the distance sensor 31 outside the main housing 25. For example, an area for housing the optical movement measuring sensor 30 and the distance sensor 31 may be provided inside the main housing 25, and the optical movement measuring sensor 30 and the distance sensor 31 may be housed in this area, or the sensor housing 32 may be housed therein. Furthermore, by providing a light-transmitting section 25B that transmits the measurement light of the optical movement measuring sensor 30 and the distance sensor 31 in a portion of the main housing 25 facing the workpiece W being transported, it becomes possible for the optical movement measuring sensor 30 and the distance sensor 31 to perform measurements.

[0193] As shown in Fig. 32, the sensor housing 32 can be installed in a location separate from the main housing 25. In the example shown in Fig. 32, the sensor housing 32 is installed above the workpiece W, making it possible to measure the workpiece W from above. In a line where tall and short workpieces W are mixed, by installing the sensor housing 32 above the workpiece W, both the tall and short workpieces W can be measured with high accuracy using the optical movement measurement sensor 30 with a large depth of field. In the case of this mounting pattern, since the distance sensor 31 cannot measure the distance between the workpiece W and the print head 24, a separate distance sensor 31 is attached to the print head 24 side.

[0194] 33 is a plan view showing an example equipped with a pressing mechanism 130 for the print head 24. Although the sensor housing 32 is shown by a virtual line, the position of the sensor housing 32 is not limited to the position shown in the figure, and may be, for example, on the upstream side of the main housing 25 or on the upper side.

[0195] The upstream side of the main housing 25 has a mounting portion 25A. The pressing mechanism 130 includes a positioning member 131 that is positioned and fixed to the conveyor 10, and a coil spring 132 as an elastic body. The positioning member 131 is provided with a rod 131a that extends in a horizontal direction perpendicular to the conveying direction. The mounting portion 25A of the main housing 25 is supported so as to be slidable in the horizontal direction perpendicular to the conveying direction relative to the rod 131a.

[0196] The rod 131a is inserted through the coil spring 132, and the direction of contraction of the coil spring 132 coincides with the axial direction of the rod 131a. It is disposed closer to the workpiece W than the coil spring 132, so that the coil spring 132 constantly presses the attachment portion 25A of the main housing 25 in the direction in which ink is ejected.

[0197] A work guide 133 is provided on the upstream side of the main housing 25. If the work W is transported toward the upper side in Fig. 33, it comes into contact with the work guide 133, and an upward force in Fig. 33 acts on the work guide 133. If the coil spring 132 is compressed by this force, the print head 24 moves upward in Fig. 33, but the distance between the print head 24 and the work W is maintained at a predetermined distance. Therefore, even if the work W is transported toward the upper side in Fig. 33, drawing can be performed without any disturbance.

[0198] (Multiple nozzle configuration) The inkjet printing device 1 is configured with one print head 24, but the number of print heads 24 is not limited to one, and inkjet printing devices 1 with multiple print heads 24 are also included in embodiments of the present invention.

[0199] That is, although not shown, the inkjet printing device 1 includes, for example, a first print head (first nozzles) and a second print head (second nozzles). The first print head has a plurality of ejection ports aligned in a predetermined direction. The second print head also has a plurality of ejection ports aligned in a predetermined direction. The number of ejection ports of the first print head and the number of ejection ports of the second print head may be the same or different.

[0200] The first print head is provided in a first housing. The second print head is provided in a second housing that can be arranged apart from the first housing. In other words, since the first housing and the second housing are separate, they can be arranged in different locations, and therefore can draw on different parts of the workpiece W.

[0201] The drawing data stored in the memory unit 42 includes drawing data for the first nozzle and drawing data for the second nozzle. The drawing data for the first nozzle and the drawing data for the second nozzle may be different or the same. The drawing control unit 40c controls the ejection of ink from the multiple ejection ports formed in the first nozzle based on the current offset position and the drawing data for the first nozzle, and also controls the ejection of ink from the multiple ejection ports formed in the second nozzle based on the current offset position and the drawing data for the second nozzle. This allows drawing at multiple locations on the workpiece W using one inkjet printing device 1.

[0202] (Control when using optical movement measurement sensor as timing sensor) The optical movement measuring sensor 30 can be used as a timing sensor to detect when the workpiece W transported by the transport machine 10 has reached a predetermined position. Hereinafter, the control when the optical movement measuring sensor 30 is used as a timing sensor will be described in detail with reference to the flowchart shown in FIG.

[0203] Steps SJ1 and SJ2 shown in Fig. 34 are the same as steps SB1 and SB2 shown in Fig. 9. In step SJ3, the drawing start timing acquisition unit 40f judges whether the amount of light received by the optical movement measurement sensor 30 is sufficient. A situation in which the amount of light received is "sufficient" is a situation in which the optical movement measurement sensor 30 can generate a measurement value (normal measurement value) with a high degree of accuracy that allows it to be used as a timing sensor. If it is judged in step SJ3 that the amount of light received by the optical movement measurement sensor 30 is sufficient, the process proceeds to step SJ4, whereas if the amount of light received by the optical movement measurement sensor 30 is insufficient and it cannot be used as a timing sensor, the process proceeds to step SJ2.

[0204] In step SJ4, the drawing start timing acquisition unit 40f judges whether or not the amount of speckle patterns generated by the optical movement measurement sensor 30 is sufficient. A situation in which the "amount of speckle patterns is sufficient" is a situation in which the optical movement measurement sensor 30 can generate measurement values ​​with a high degree of accuracy that allows it to be used as a timing sensor. If it is judged in step SJ4 that the amount of speckle patterns generated by the optical movement measurement sensor 30 is sufficient, the process proceeds to step SJ5, whereas if the amount of speckle patterns generated by the optical movement measurement sensor 30 is insufficient and it cannot be used as a timing sensor, the process proceeds to step SJ2.

[0205] In step SJ5, since the amount of light received by the optical movement measuring sensor 30 is sufficient and the amount of speckle patterns is also sufficient, the drawing start timing acquisition unit 40f judges the measurement value output from the optical movement measuring sensor 30 as a timing sensor ON signal. Then, the process proceeds to step SJ6. Steps SJ6 to SJ9 are the same as steps SB4 to SB7 shown in FIG.

[0206] In other words, the timing when the optical movement measuring sensor 30 detects the workpiece W and starts to generate normal measurement values ​​is set as the pseudo timing sensor ON timing, and the drawing operation is started. Note that, since detection noise occurs when the optical movement measuring sensor 30 detects both end edges of the workpiece W in the transport direction, if the noise becomes a problem, a noise removal process can be applied.

[0207] (Abnormal processing) As described above, the drawing machine 2 performs drawing on the workpiece W being transported in front of the drawing machine 2 in accordance with the transport speed of the workpiece W. When the transport speed of the workpiece W is constant, constant speed drawing is performed, and when the transport speed is not constant, the transport speed is acquired using the encoder 7, and the workpiece speed is calculated from the encoder signal to perform drawing (encoder drawing). In either of these methods, the drawing start timing can be determined by the timing sensor 8, the optical movement measurement sensor 30, etc.

[0208] However, since there is no way to know whether the conveying speed of the workpiece W was really constant when performing constant-speed drawing, even if the drawing was disturbed as a result of performing constant-speed drawing, the cause was not known. In addition, in the case of encoder drawing, even if the drawing was disturbed due to slippage of the encoder 7 or the workpiece W getting caught, it was difficult to detect the disturbance in the drawing. In addition, when the detection surface of the timing sensor 8 was dirty with dust or ink particles, it was difficult to judge the reliability of the timing sensor 8, and periodic maintenance of the timing sensor 8 was necessary. In addition, when the workpiece W bumps, there is no problem if bumping correction is performed, but if bumping correction is not performed, there is no way to evaluate whether the bumping of the workpiece W affects the drawing quality. In addition, when an angle deviation occurs between the drawing machine 2 and the conveying machine 10, there is no problem if tilt correction is performed, but if tilt correction is not performed, there is no way to know the angle deviation. Furthermore, if the workpiece W is cardboard, when the flapper of the cardboard comes off, the timing sensor 8 may malfunction, detecting the flapper and thinking that the workpiece W has arrived, resulting in an error in the drawing start position. As described above, there are various causes of drawing defects, but since it is difficult to prevent drawing defects in advance with conventional constant speed drawing and encoder drawing, it is necessary to check the drawing quality with a camera or by a person, which is time-consuming.

[0209] In the inkjet printing device 1 of this embodiment, the reliability of the measurement by the optical movement measurement sensor 30 is evaluated, and based on the evaluation results, abnormality processing is executed if the reliability of the measurement by the optical movement measurement sensor 30 is low, thereby making it possible to suppress the occurrence of drawing defects due to the various causes described above.

[0210] The control unit 40 of the controller 4 is configured as hardware and software. The evaluation unit 40h and the abnormality processing unit 40i are configured as follows: The evaluation unit 40h and the abnormality processing unit 40i are separated for convenience, but may be integrated in terms of hardware.

[0211] The evaluation unit 40h is a part that evaluates the reliability of the measurement by the optical movement measurement sensor 30. Specifically, the evaluation unit 40h can evaluate the reliability based on the amount of light received by the optical movement measurement sensor 30. If the amount of light received by the optical movement measurement sensor 30 is sufficient, a highly accurate measurement value can be generated, so in this case, the evaluation unit 40h evaluates that the reliability of the measurement by the optical movement measurement sensor 30 is high. On the other hand, if the amount of light received by the optical movement measurement sensor 30 is insufficient, the accuracy of the measurement value decreases or a measurement value cannot be generated, so in this case, the evaluation unit 40h evaluates that the reliability of the measurement by the optical movement measurement sensor 30 is low. If the amount of light received by the optical movement measurement sensor 30 is outside a predetermined range (for example, less than a predetermined amount), the abnormality processing unit 40i executes abnormality processing, assuming that the reliability does not meet a predetermined standard. The cause of insufficient amount of light received by the optical movement measurement sensor 30 can be when the detection surface of the optical movement measurement sensor 30 is dirty with dust or ink particles.

[0212] In addition, the evaluation unit 40h can evaluate the reliability based on whether the optical movement measurement sensor 30 can perform measurement. When the optical movement measurement sensor 30 can perform measurement, the evaluation unit 40h evaluates that the reliability of the measurement by the optical movement measurement sensor 30 is high. On the other hand, when the optical movement measurement sensor 30 cannot perform measurement, the evaluation unit 40h evaluates that the reliability of the measurement by the optical movement measurement sensor 30 is low. When the optical movement measurement sensor 30 cannot perform measurement, the abnormality processing unit 40i executes abnormality processing since the reliability does not meet a predetermined standard. In this way, the abnormality processing unit 40i is a part that executes abnormality processing when the reliability evaluated by the evaluation unit 40h does not meet a predetermined standard.

[0213] The evaluation elements of the evaluation unit 40h are not limited to the amount of light received by the optical movement measurement sensor 30 and whether the amount of light received by the optical movement measurement sensor 30 can be measured, but can include, for example, the distance of the print head 24 to the workpiece W in the ejection direction, the movement of the workpiece W in the transport direction, the amount of movement of the workpiece W in a direction perpendicular to the transport direction, the amount of movement of the workpiece W in a direction inclined to the transport direction, the amount of light received by the distance sensor 31, the recognition rate of the speckle pattern of the optical movement measurement sensor 30, the contrast of the drawing object that is generated according to the amount of light received from the workpiece W that is the drawing object, the quality of the speckle pattern that is generated according to the characteristics of the surface shape of the workpiece W, the distance the workpiece W is transported from when the drawing start timing signal turns ON to when it turns OFF, and the difference from the input of the encoder 7, etc.

[0214] When evaluating reliability based on the distance to the workpiece W in the ejection direction of the print head 24, if it can be determined that the workpiece W is located farther away than the drawing distance, the printing reliability is evaluated as low, and if it can be determined that the workpiece W is located within the drawing distance, the reliability is evaluated as high. By evaluating reliability based on the movement of the workpiece W in the transport direction, it can be determined whether the workpiece W is accelerating or decelerating, or is stopped, and for example, if it can be determined that the workpiece W is accelerating or decelerating, or if it can be determined that the workpiece W is stopped, the reliability is evaluated as low.

[0215] When evaluating reliability based on the amount of movement of the workpiece W in the direction perpendicular to the transport direction, if the amount of movement of the workpiece W in the direction perpendicular to the transport direction is greater than a predetermined amount, it can be inferred that bumping has occurred, in which case the reliability is evaluated as low, and if the amount of movement of the workpiece W in the direction perpendicular to the transport direction is less than a predetermined amount, the reliability is evaluated as high.

[0216] When evaluating the reliability based on the amount of movement in a direction inclined to the conveying direction of the workpiece W, it is possible to determine whether or not an angle misalignment occurs between the drawing machine 2 and the conveying machine 10. When the angular misalignment occurring between the drawing machine 2 and the conveyor 10 is a predetermined value or more, the reliability is evaluated as low, and when the angular misalignment occurring between the drawing machine 2 and the conveyor 10 is less than a predetermined value, the reliability is evaluated as high. Furthermore, when evaluating the reliability based on the amount of light received by the distance sensor 31, the reliability can be evaluated in the same way as in the case of the optical movement measurement sensor 30.

[0217] When reliability is evaluated based on the recognition rate or contrast distribution of the speckle pattern of the optical movement measuring sensor 30, it is possible to evaluate reliability based on the reliability of the measured value and the presence or absence of the influence of disturbance. For example, when the influence of disturbance light is large and the recognition rate of the speckle pattern is low, the reliability is evaluated as low. In this case, when the recognition rate of the speckle pattern is less than a predetermined value, the abnormality processing unit 40i performs abnormality processing since the reliability does not meet a predetermined standard.

[0218] When reliability is evaluated based on the distance the workpiece W is transported from when the drawing start timing signal turns ON to when it turns OFF, this can correspond to the peeling off of the flapper of the cardboard of the workpiece W, and if this distance is greater than a specified value, the reliability is evaluated as low.

[0219] When reliability is evaluated based on the difference with the input from the encoder 7, it becomes possible to detect slippage or sticking of the workpiece W, and if this difference is a predetermined value or more, the reliability is evaluated as low.

[0220] Examples of the abnormality processing executed by the abnormality processing unit 40i include a notification processing for notifying the user that an abnormality has occurred, an interruption processing for interrupting drawing, and a reset processing for resetting a drawing start trigger. The abnormality processing unit 40i may execute only one of the notification processing and the interruption processing, or may execute both the notification processing and the interruption processing. When executing both the notification processing and the interruption processing, the notification processing and the interruption processing may be executed simultaneously, or one may be executed first and then the other.

[0221] The notification process includes both a warning that notifies when an abnormality may have occurred, and a notification when an abnormality has actually occurred. Only one of these may be executed as the notification process, or both may be executed.

[0222] Furthermore, as the abnormality processing executed by the abnormality processing unit 40i, a log of the drawing processing may be stored. The stored log includes the drawing time, the drawing contents, the drawing result, the measurement result by the optical movement measuring sensor 30, etc. The log can be stored in the storage unit 42, for example.

[0223] When drawing is performed based on the optical movement measuring sensor 30, if it is determined that the reliability evaluated by the evaluation unit 40h does not meet a predetermined standard, the abnormality processing unit 40i may execute a switching process to switch to drawing based on the output of the encoder 7 as the abnormality processing. Also, when drawing is performed based on the optical movement measuring sensor 30, if it is determined that the reliability evaluated by the evaluation unit 40h does not meet a predetermined standard, the abnormality processing unit 40i may execute a switching process to switch to constant speed drawing as the abnormality processing. In other words, when the reliability evaluated by the evaluation unit 40h does not meet a predetermined standard, the drawing control unit 40c controls the ejection of ink from the ejection port 24a based on the movement amount acquired by the encoder 7 and the drawing data.

[0224] In addition, when drawing is being performed without bumping correction, if the amount of movement of the workpiece W in a direction perpendicular to the transport direction becomes greater than a predetermined amount, the abnormality processing unit 40i may perform bumping correction as abnormality processing.

[0225] In this embodiment, the user can set the abnormality processing. 35, and displays it on the drawing machine display unit 43a or the terminal display unit 5a, etc. The user can configure the abnormality processing settings by operating the drawing machine operation unit 43b or the terminal operation unit 5b while viewing the abnormality processing settings screen 200.

[0226] The abnormality processing setting screen 200 is provided with a first selection area 201 for selecting whether or not to interrupt drawing when a warning is issued, a second selection area 202 for selecting whether or not to interrupt drawing when an abnormality occurs, a third selection area 203 for selecting whether or not to save a log when a warning is issued, a fourth selection area 204 for selecting whether or not to execute switching processing when an abnormality occurs, a fifth selection area 205 for selecting whether or not to execute switching processing when a warning is issued, and a sixth selection area 206 for selecting whether or not to save the time when the abnormality occurred.

[0227] When the user operates the first selection area 201 to turn it ON, drawing can be interrupted when a warning occurs, and when the user operates the first selection area 201 to turn it OFF, drawing can be continued when a warning occurs. That is, the drawing machine side operation unit 43b or the terminal side operation unit 5b is an example of a reception unit that receives a selection of whether to execute or not execute the interruption process. The abnormality processing unit 40i is configured to execute the interruption process when it receives a selection to execute the interruption process, and not to execute the interruption process when it receives a selection not to execute the interruption process.

[0228] When the user operates the second selection area 202 to turn it ON, drawing can be interrupted at the stage where an abnormality occurs, and when the user operates the second selection area 202 to turn it OFF, drawing can be continued even if an abnormality occurs. When the user operates the third selection area 203 to turn it ON, a log can be saved when a warning occurs, and when the user operates the third selection area 203 to turn it OFF, a log will not be saved when a warning occurs. When the user operates the fourth selection area 204 to turn it ON, a switching process can be executed at the stage where an abnormality occurs, and when the user operates the fourth selection area 204 to turn it OFF, a switching process will not be executed even if an abnormality occurs. When the user operates the fifth selection area 205 to turn it ON, a switching process can be executed at the stage where an abnormality occurs, and when the user operates the fifth selection area 205 to turn it OFF, a switching process will not be executed when a warning occurs. When the user operates the sixth selection area 206 to turn it ON, a time when an abnormality occurs can be saved, and when the user operates the sixth selection area 206 to turn it OFF, a time when an abnormality occurs will not be saved.

[0229] In this way, when multiple abnormality processes can be executed, the user can select whether to execute or not execute each abnormality process, and the selection can be accepted by the drawing machine operation unit 43b or the terminal operation unit 5b. Note that only one abnormality process can be executed.

[0230] FIG. 36 shows a first warning screen 210 displayed on the drawing machine display unit 43a or the terminal display unit 5a by executing the notification process. The first warning screen 210 displays the cause of the decrease in reliability, as well as a method for eliminating the cause. In this example, the cause of the decrease in the amount of light received by the optical movement measuring sensor 30 and a method for eliminating the decrease in the amount of light received are displayed. When displaying the first warning screen 210 by executing the notification process, the abnormality processing unit 40i displays it on top of an already displayed screen. This improves the user's visibility.

[0231] 37 shows a second warning screen 211 displayed on the drawing machine display unit 43a or the terminal display unit 5a by execution of the notification process. The second warning screen 211 displays the cause of the decrease in reliability, the time when the cause occurred, and a preview of the drawing result. In this example, an abnormality in the transport speed of the workpiece W is displayed as the cause of the decrease in reliability.

[0232] Fig. 38 is a flow chart showing a series of operations for abnormality processing. Steps SK1 and SK2 are the same as steps SB1 and SB2 shown in Fig. 9, respectively. In step SK3, a drawing start trigger is input. In step SK4, the drawing start trigger input in step SK3 is evaluated, and if there is no problem, the process proceeds to step SK5, whereas if there is a problem, the process returns to step SK2.

[0233] In step SK5, the drawing process is started. In step SK6, the optical movement measurement sensor 30 measures the movement of the work W. In step SK7, the evaluation unit 40h evaluates the reliability of the measurement value generated by the optical movement measurement sensor 30 in step SK6. If the reliability evaluated by the evaluation unit 40h meets a predetermined standard, the process proceeds to step SK8, where the drawing control unit 40c controls the ejection of ink from the ejection port 24a to execute the drawing process. On the other hand, if the reliability evaluated by the evaluation unit 40h does not meet the predetermined standard, the process proceeds to step SK9, where the abnormality processing unit 40i executes abnormality processing. Step SK10 is the same as step SB7 shown in FIG. 9. If all drawing is completed, the process proceeds to step SK11, where the input of the next drawing start trigger is awaited.

[0234] FIG. 39 is a flow chart showing an example of abnormality processing when distance measurement is performed. In step SL1, the distance sensor 31 starts measuring the distance to the workpiece W in the ejection direction of the print head 24. In step SL2, the workpiece W transported by the transport device 10 is detected. In step SL3, the distance to the workpiece W in the ejection direction of the print head 24 is measured by the distance sensor 31, and the evaluation unit 40h acquires the measured value. In step SL4, it is determined whether the measured value acquired in step SL3 is within the drawing distance. If the workpiece W is within the drawing distance, the process proceeds to step SL5. If the workpiece W is farther away than the drawing distance, the process proceeds to step SL6, where the abnormality processing unit 40i executes abnormality processing.

[0235] In step SL5, it is determined whether the workpiece W has abnormally approached or moved away from the print head 24 based on the measurement values ​​acquired in step SL3. If the workpiece W has abnormally approached or moved away from the print head 24, it is assumed that some abnormality has occurred, and the process proceeds to step SL6, where the abnormality processing unit 40i executes abnormality processing. If there has been no abnormal approach or movement, the process proceeds to step SL7. In step SL7, it is determined whether all drawing has been completed, and if not, the process proceeds to step SL3, and if completed, the process proceeds to step SL1 to wait for the arrival of the next workpiece W.

[0236] Fig. 40 is a flow chart showing an example of a reliability evaluation process of the sensor value. Steps SM1 and SM2 are the same as steps SK2 and SK3 in Fig. 38, respectively. In step SM3, measurement by the optical movement measuring sensor 30 is started. In step SM4, it is determined whether or not a workpiece W is present within the measurable range of the optical movement measuring sensor 30. If a workpiece W is not present, the process proceeds to step SM3, and if a workpiece W is present, the process proceeds to step SM5.

[0237] In step SM5, it is determined whether or not there is a sufficient amount of light received by the optical movement measuring sensor 30. If it is determined in step SM5 that the amount of light received by the optical movement measuring sensor 30 is sufficient, the process proceeds to step SM6, and if it is determined that the amount of light received by the optical movement measuring sensor 30 is insufficient, the process proceeds to step SM7.

[0238] In step SM6, it is determined whether or not the amount of speckle patterns generated by the optical movement measuring sensor 30 is sufficient. If it is determined in step SM6 that the amount of speckle patterns generated by the optical movement measuring sensor 30 is sufficient, the process proceeds to step SM8. On the other hand, if it is determined that the amount of speckle patterns generated by the optical movement measuring sensor 30 is insufficient, If so, proceed to step SM9.

[0239] In step SM8, the drawing control unit 40c executes drawing control based on the measurement value of the optical movement measurement sensor 30. Then, the process proceeds to step SM10, where it is determined whether the movement distance of the workpiece W in the conveying direction is sufficient. If the movement distance of the workpiece W in the conveying direction is insufficient, the process proceeds to step SM3, and if the movement distance is sufficient, the process proceeds to step SM1.

[0240] In step SM9, which is reached when it is determined in step SM6 that the amount of speckle patterns is insufficient, the abnormality processing unit 40i notifies the user that the workpiece W cannot be measured due to scratches or disturbance light.

[0241] Meanwhile, in step SM7, it is determined whether or not the amount of speckle patterns generated by the optical movement measuring sensor 30 is sufficient. If it is determined in step SM7 that the amount of speckle patterns generated by the optical movement measuring sensor 30 is sufficient, the process proceeds to step SM11, whereas if it is determined that the amount of speckle patterns generated by the optical movement measuring sensor 30 is insufficient, the process proceeds to step SM12.

[0242] In step SM11, the abnormality processor 40i notifies the user that disturbance noise has occurred. In step SM12, the abnormality processor 40i notifies the user that there is no measurement target, that the working distance (WD) is incorrect, that there is a hole, etc.

[0243] After steps SM9, SM11, and SM12, the process proceeds to step SM13, where the error processor 40i switches between drawing based on the output of the encoder 7, drawing based on the previous conveying speed of the work W, and drawing based on a preset value. In step SM14, the error processor 40i executes error output or warning output to notify the user. Then, the process proceeds to step SM10.

[0244] FIG. 41 is a flow chart showing an example of control including interruption processing of drawing. Steps SN1 to SN4 are the same as SK1 to SK4 in FIG. 38, respectively. In step SN5, measurement by the optical movement measuring sensor 30 is started. In step SN6, the movement of the workpiece W is measured by the optical movement measuring sensor 30. In step SN7, it is determined whether there is a problem with the measurement value generated by the optical movement measuring sensor 30 due to an insufficient amount of light received by the optical movement measuring sensor 30 or an insufficient amount of speckle patterns. If there is no problem with the measurement value generated by the optical movement measuring sensor 30, the process proceeds to step SN8, where the drawing control unit 40c executes drawing control based on the measurement value of the optical movement measuring sensor 30.

[0245] If there is a problem with the measurements generated by the optical movement measuring sensor 30, the process proceeds to step SN9 to determine whether or not the drawing interruption process has been selected. If the drawing interruption process has not been selected, the process proceeds to step SN10, and if the drawing interruption process has been selected, the process proceeds to step SN12 to interrupt the drawing process.

[0246] In step SN10, it is determined whether or not a switching process for switching to drawing based on the output of the encoder 7 or a preset value has been selected. If the switching process has not been selected, the process proceeds to step SN8, whereas if the switching process has been selected, the process proceeds to step SN11, where the abnormality processing unit 40i switches to drawing based on the output of the encoder 7.

[0247] In step SN13, it is determined whether drawing has been completed or not. If drawing has not been completed, the process proceeds to step SN14, where the reliability of the measured value is evaluated. If the reliability of the measured value does not meet the criteria, If not, the process proceeds to step SN15, where a warning is issued to the user. In step SN16, it is determined whether or not the setting to suspend drawing when a warning is issued is made, and if the setting to suspend drawing is made, the process proceeds to step SN17, where drawing is suspended and an error is output. When an abnormality is detected, printing may be performed based on the last movement amount that satisfied a predetermined standard.

[0248] (Control based on the distance between the print head and the workpiece) The drawing accuracy of the drawing machine 2 is determined by whether or not the distance (also called TD=Throw Distance, PG=Paper Gap, etc.) between the print head 24 and the work W meets a predetermined standard. In other words, if the distance between the print head 24 and the work W becomes too large to meet the predetermined standard, the landing position of the ink particles on the work W will deviate from the ideal position defined by the drawing data, causing greater disturbance in the drawing.

[0249] If this distortion of the drawing exceeds the tolerance of the drawing quality, a drawing defect will occur, resulting in a defective product during manufacturing. For example, if the drawing of characters is disturbed to the extent that it cannot be distinguished by visual inspection or by OCR inspection with a print inspection machine in a later process, and if the drawing of a barcode or two-dimensional code is disturbed to the extent that it cannot be read by a code reader or does not meet the specified grade of the code quality standard.

[0250] In the inkjet printing device 1 of this embodiment, the cause of the disturbance in the drawing can be inferred by directly measuring the distance between the print head 24 and the workpiece W. That is, the distance (TD) in the ejection direction of the print head 24 to the workpiece W is measured by the distance sensor 31 of the sensor unit 3, and the drawing control unit 40c is configured to control the ejection of ink based on the determination result of whether or not the distance in the ejection direction of the print head 24 to the workpiece W measured by the distance sensor 31 satisfies a predetermined standard. In controlling the ejection of ink, the drawing control unit 40c acquires a timing signal generated based on the change in the distance in the ejection direction of the print head 24 to the workpiece W measured by the distance sensor 31.

[0251] For example, FIG. 42 is a flow chart of control for executing interruption processing of drawing based on the result of distance measurement by the distance sensor 31. Steps SP1 to SP3 are the same as steps SB1 to SB3 in FIG. 9. In step SP4, the distance in the ejection direction of the print head 24 to the workpiece W is measured by the distance sensor 31, and a measurement value is generated. In step SP5, it is determined whether the measurement value generated in step SP4 is abnormal or not. Abnormality occurs when the distance in the ejection direction of the print head 24 to the workpiece W measured by the distance sensor 31 does not meet a predetermined standard. Here, the predetermined standard is the distance at which the ink droplets ejected from the ejection port 24a can land at an ideal position on the workpiece W. There is a range for the ideal position, and if the distance in the ejection direction of the print head 24 to the workpiece W meets the predetermined standard, it can be identified by an OCR inspection of a print inspection machine in a later process, and if a barcode or two-dimensional code is drawn, it can be read by a code reader. On the other hand, if drawing is performed when the distance in the ejection direction of the print head 24 to the workpiece W does not meet a specified standard, it may be impossible to distinguish it during OCR inspection, and the barcode or two-dimensional code may not be readable by a code reader.

[0252] If it is determined in step SP5 that the distance is normal, the process proceeds to step SP6, where the workpiece movement amount acquisition unit 40d acquires the movement amount of the workpiece W based on the measurement value output from the optical movement measuring sensor 30. Steps SP7 to SP9 are the same as steps SB5 to SB7 in FIG.

[0253] If it is determined in step SP5 that the distance is abnormal, the distance in the discharge direction of the print head 24 to the workpiece W measured by the distance sensor 31 does not meet the predetermined standard, so the drawing process is not executed, and the drawing interruption process is executed, and this flow is ended. The timing of executing the drawing interruption process may be any timing between the start of drawing and just before the end. In particular, by executing the drawing interruption process before the start of drawing, it becomes possible to avoid waste due to poor drawing of the workpiece W.

[0254] FIG. 43 is a flow chart showing an example of control for notifying a distance abnormality based on the result of distance measurement. Steps SQ1 to SQ9 are the same as steps SP1 to SP99 shown in FIG. 42, respectively. If it is determined in step SQ5 that the distance is abnormal, the process proceeds to step SQ10, where, for example, the abnormality processing unit 40i executes a distance abnormality notification. The distance abnormality notification is a process for notifying the user that the distance to the workpiece W measured by the distance sensor 31 in the ejection direction of the print head 24 is abnormal, and the abnormality processing unit 40i generates a notification screen and displays it on the drawing machine side display unit 43a or the terminal side display unit 5a, etc. In the example shown in FIG. 43, the distance abnormality notification is executed and drawing interruption processing is executed. For example, when the distance to the workpiece W measured by the distance sensor 31 in the ejection direction of the print head 24 is the same as the drawing possible distance, the distance abnormality is notified and drawing is continued, and the drawing quality is judged visually or by an inspection machine in a post-process.

[0255] Fig. 44 is a flow chart showing an example of control for notifying a distance abnormality based on the result of distance measurement and continuing drawing. Steps SR1 to SR9 are the same as steps SQ1 to SQ9 shown in Fig. 43. In step SR10, after executing a distance abnormality notification similar to step SQ10 shown in Fig. 43, the process proceeds to step SR6 and drawing continues.

[0256] For example, when the distance to the workpiece W measured by the distance sensor 31 in the ejection direction of the print head 24 is the same as the drawing possible distance, a distance abnormality is notified and drawing is interrupted, and the user is made to carry out processing for the drawing abnormality. For example, the workpiece W for which a distance abnormality has been notified is rejected by a rejection device in a subsequent process, or the conveyor 10 is stopped and the operator manually rejects it.

[0257] The notification of the distance abnormality shown in FIG. 43 may have a different notification name depending on whether the distance abnormality is determined before the drawing start position or after the drawing start position. If the distance abnormality is determined before the drawing start position, the user can be notified that there is no defective drawing on the workpiece W and that the workpiece W can be reused. On the other hand, if the distance abnormality is determined after the drawing start position, the user can be notified that there is a possibility of a defective drawing on the workpiece W. Therefore, different processes can be performed at a later stage.

[0258] The distance that is the threshold for determining whether or not the distance is abnormal may be a fixed value for the device at the time of shipment from the factory, or may be a user-settable value taking into consideration dependency on the user's installation environment. The distance that is the threshold for determining whether or not the distance is abnormal may not be a single value, but may be divided into a case where the abnormality is determined using multiple distance thresholds and drawing is interrupted and a case where drawing is continued. That is, the abnormality may be determined using a distance threshold for interrupting drawing and a distance threshold for continuing drawing. After determining that the distance is abnormal, the user may be able to set whether to continue or interrupt drawing. When determining that the distance is abnormal, some kind of notification may be given to the user to optimize the working distance.

[0259] FIG. 45 is a flowchart showing an example of control for disabling the drawing start trigger when the distance is abnormal, and for enabling the next input drawing start trigger. Steps SU1 to SU6 are the same as steps SR1 to SR6 in FIG. 44, respectively. If the distance to the workpiece W in the ejection direction of the print head 24 measured by the distance sensor 31 is abnormal, the process proceeds to step SU7, where it is determined whether drawing has not yet started. If drawing has not yet started, the process proceeds to step SU8, where the drawing start process is cancelled, i.e., the drawing start trigger is disabled. If drawing has already started, the process proceeds to step SU6. Steps SU9 to SU11 are the same as steps SR7 to SR9 in FIG. 44, respectively.

[0260] For example, if the workpiece W is cardboard, on a line where defects such as cardboard flaps being half-open due to faulty box-making occur frequently, the drawing start point of the timing sensor 8 may become incorrect, or if an optical movement measurement sensor 30 is used, the movement amount may not be measured correctly due to deviation from the measurable distance or a drop in measurement accuracy. In such a case, by temporarily disabling the drawing start trigger and then using the point where the distance measurement has stabilized as the trigger, drawing on the workpiece W can be performed based on the correct end face.

[0261] (Event detection and log file storage processing) At the site where the workpiece W is being transported, there is variation in the transport speed of the transport machine 10, and variation in the widthwise position of the workpiece W on the transport surface 10a, and in principle there is also error due to the workpiece W slipping on the transport surface 10a. If the above-mentioned variations and errors exceed the preset tolerance for ink droplet landing accuracy, poor drawing results.

[0262] There are various types of drawing defects, such as missing or missing characters, smudged or dirty characters, etc. When a drawing defect occurs on the conveyor 10, it is necessary to collect information such as the drawing execution time and drawing interval, identify the cause of the drawing defect, and take measures, but identifying the cause can be difficult.

[0263] Fig. 46 is a timing chart of the input of the drawing start trigger output from the timing sensor 8 and drawing execution. As shown in this figure, the drawing machine 2 performs drawing in accordance with the transport speed of the workpiece W when the workpiece W passes in front of it, but in the case of such a drawing method, conventionally, the only information that could be left during drawing execution was the drawing time and the drawing interval. It was extremely difficult to guess the cause of the above-mentioned drawing failure based on only the information of the drawing time and the drawing interval.

[0264] The inkjet printing apparatus 1 of this embodiment has a recorder function that allows the cause of an event to be easily analyzed after the event has occurred during operation, such as a drawing failure, thereby solving the conventional problem of identifying the cause of a drawing failure.

[0265] As shown in FIG. 2, the inkjet printing device 1 includes an event detection unit 45 and a storage processing unit 46 as a unit for realizing the recorder function. The event detection unit 45 is a unit that detects an event related to the drawing state based on the optical movement measurement sensor 30 and the distance sensor 31 of the sensor unit 3. The storage processing unit 46 is a unit that links information about the measurement values ​​generated by the optical movement measurement sensor 30 and the distance sensor 31 and information about the event with at least a part of the drawing data in response to the event detection unit 45 detecting the event, and stores the information as a log file in the storage unit 42 or the like. For example, the conveying speed of the work W generated by the optical movement measurement sensor 30, the amount of movement in a direction perpendicular to the conveying direction of the work W, the moving speed in a direction perpendicular to the conveying direction of the work W, etc. can be stored as a log file. In addition, the distance between the print head 24 and the work W generated by the distance sensor 31 can also be stored as a log file. For example, various other information such as the temperature of the print head 24 and the remaining amount of ink may be stored as a log file. The storage destination of the log file is not limited to the storage unit 42, and may be another storage device, etc.

[0266] Fig. 49 is a flow chart showing the process of saving a log file during the drawing period. In step SV1, the drawing machine 2 waits for drawing to start, and proceeds to step SV2 after waiting a predetermined time. In step SV2, a timing signal is input, and the process proceeds to step SV3. If no timing signal is input, the process remains in step SV1.

[0267] In step SV3, the drawing process is executed, and the distance sensor 31 measures the distance between the print head 24 and the workpiece W to generate a measurement value, and further the optical movement measurement sensor 30 measures the amount of movement of the workpiece W to generate a measurement value. When the drawing process is completed in step SV4, the process proceeds to step SV5, where the measurement values ​​during the drawing period are saved in the memory unit 42 as a log file.

[0268] The event detection unit 45 detects, as an event related to the drawing state, the measurement value measured by the distance sensor 31 being outside a predetermined range. In other words, when the distance between the print head 24 and the workpiece W becomes negative, it can be assumed that the workpiece W has collided with the print head 24, and the event detection unit 45 detects this as an event related to the drawing state.

[0269] When the distance between the print head 24 and the workpiece W exceeds the drawing distance range of the drawing machine 2 and the print head 24 and the workpiece W are separated significantly, the measurement value measured by the distance sensor 31 is deemed to be outside the specified range. When the distance between the print head 24 and the workpiece W exceeds the drawing distance range of the drawing machine 2, drawing becomes distorted, and so the event detection unit 45 detects this as an event related to the drawing state.

[0270] If the distance between the print head 24 and the workpiece W changes significantly during drawing, it can be assumed that, for example, the guide of the conveyor 10 has come off and the workpiece W is meandering. In this case, the drawing is disturbed, so the event detection unit 45 detects this as an event related to the drawing state.

[0271] The event detection unit 45 detects, as an event related to the drawing state, that the measurement value generated by the optical movement measurement sensor 30 is outside a predetermined range. The predetermined range is a range in which good drawing quality can be maintained. If the conveying speed of the workpiece W generated by the optical movement measurement sensor 30 is not constant, it can be estimated that, for example, the workpiece W has come into contact with a guide of the conveyor 10 and become clogged. If the conveying speed of the workpiece W is not constant, the drawing will be disturbed, and the event detection unit 45 detects this as an event related to the drawing state.

[0272] If there is a period during which the conveying speed of the workpiece W generated by the optical movement measuring sensor 30 is zero, it can be estimated that, for example, the conveying machine 10 has suddenly stopped. If there is a period during which the conveying speed of the workpiece W is zero, this is not a normal state and can cause disturbance in the drawing, so the event detection unit 45 detects this as an event related to the drawing state.

[0273] When the optical movement measuring sensor 30 intermittently measures the movement of the workpiece W in a direction perpendicular to the conveying direction, it can be estimated that the workpiece W is bumping. When the workpiece W is bumping, unless a bumping correction process is performed, the drawing will be disturbed, so the event detection unit 45 detects this as an event related to the drawing state.

[0274] The event detection unit 45 detects, as an event related to the drawing state, that a measurement value related to the movement of the work W in a direction perpendicular to the conveying direction measured by the optical movement measurement sensor 30 is outside a predetermined range. In addition, since the optical movement measurement sensor 30 can generate measurement values ​​related to the movement of two mutually perpendicular axes, the event detection unit 45 detects, as an event related to the drawing state, that a measurement value related to the movement in the conveying direction determined from the measurement values ​​of the two axes measured by the optical movement measurement sensor 30 is outside a predetermined range.

[0275] For example, if the optical movement measuring sensor 30 measures that the workpiece W is moving at a substantially constant speed in a direction perpendicular to the conveying direction, it can be estimated that the line of the conveying machine 10 is inclined or that the drawing machine 2 is inclined with respect to the conveying direction of the workpiece W. If the workpiece W is moving at a constant speed in a direction perpendicular to the conveying direction, the drawing will be disturbed, so it is necessary to estimate the drawing state. The event detection unit 45 detects this as an event that occurs.

[0276] Fig. 48 shows a drawing result confirmation screen 140 for the user to confirm the contents of the log file saved by the saving processing unit 46. As shown in Fig. 2, the inkjet printing device 1 includes a presentation unit 47 that presents information about the measurement values ​​generated by the optical movement measuring sensor 30 and the distance sensor 31. The presentation unit 47 generates the drawing result confirmation screen 140 shown in Fig. 48 and displays it on the drawing machine side display unit 43a or the terminal side display unit 5a, or displays it on an external device by outputting data necessary for this drawing.

[0277] The drawing result confirmation screen 140 is provided with a number display area 141 in which a number (drawing number) is displayed as an example of information for identifying a drawing process, a distance display area 142 in which the distance between the print head 24 and the workpiece W is displayed, a speed display area 143 in which the transport speed of the workpiece W is displayed, and a vertical direction display area 144 in which the movement amount in a direction perpendicular to the transport direction of the workpiece W and the movement speed in a direction perpendicular to the transport direction of the workpiece W are displayed. The drawing number, distance, speed, and movement amount are displayed in a horizontal line so that the distance, speed, movement amount, etc. in the drawing process identified by the drawing number are associated with the drawing number. The line-up direction of these may be vertical. Any one or two of the distance, speed, and movement amount may be displayed.

[0278] The distance, speed, and amount of movement are each compared with a predetermined range (also called a threshold), and values ​​that exceed the predetermined range are displayed in a manner that makes them distinguishable from other values. Values ​​that exceed the predetermined range can be easily identified by, for example, highlighting them, displaying them in bold, or using a different color from other values. In this way, the storage processing unit 46 can store the comparison results between the measurement values ​​generated by the distance sensor 31 and the thresholds. The presentation unit 47 can present the comparison results between the measurement values ​​generated by the distance sensor 31 and the thresholds to the user in various ways.

[0279] Also, a real-time clock may be built into the drawing device 2 or the controller 4. By having a real-time clock built into the drawing device 2 or the controller 4, the save processing unit 46 can associate the drawing number with the time and save it. This makes it possible to associate the time when an event occurred with the log. Also, it is possible to select and display only the log file in which an event occurred.

[0280] The save processing unit 46 collects log files, and the presentation unit 47 generates statistical information, which can be presented to the user by the rendering device display unit 43a or the terminal display unit 5a.

[0281] Here, the concept of a job generally exists in the industrial drawing machine 2. For example, a job exists for each type of workpiece W, and in this case, a job is what determines drawing data for each type.

[0282] When the presentation unit 47 generates statistical information, it reads the log files collected by the storage processing unit 46 and sorts them by a predetermined period. The predetermined period is, for example, "day," "shift," "week," "job," etc. For example, one collection can be formed by only the log files of a certain job.

[0283] The statistical information includes the maximum, minimum, and average value of the distance between the print head 24 and the workpiece W during a specified period, the maximum, minimum, and average value of the transport speed of the workpiece W, the maximum, minimum, and average value of the movement amount of the workpiece W in a direction perpendicular to the transport direction, the number of times that the distance between the print head 24 and the workpiece W falls outside a specified range, the number of times that the transport speed of the workpiece W falls outside a specified range, and the transport speed of the workpiece W. The statistical information includes the number of times the amount of movement in the direction perpendicular to the direction falls outside a predetermined range, etc. An arbitrary part or all of the statistical information is presented by the presentation unit 47 in a table format as shown in FIG.

[0284] The presentation unit 47 can present not only statistical information but also time-series data to the user. The time-series data can include a plurality of data, such as the distance between the print head 24 and the workpiece W before and after the detection of an event, the transport speed of the workpiece W, and the amount of movement in a direction perpendicular to the transport direction of the workpiece W. In this case, the storage processing unit 46 stores the distance between the print head 24 and the workpiece W before and after the detection of an event, the transport speed of the workpiece W, and the amount of movement in a direction perpendicular to the transport direction of the workpiece W, in association with at least a portion of the drawing data. The storage period of the time-series data by the storage processing unit 46 can be set arbitrarily. For example, the storage processing unit 46 stores information about the measurement value and information about the event as time-series data from the time when the timing sensor 8 outputs a timing signal until drawing on the workpiece W is completed.

[0285] The inkjet printing device 1 includes a temporary storage unit 46a that temporarily stores information related to the measurement values ​​generated by the optical movement measuring sensor 30. The temporary storage unit 46a stores the measurement values ​​of the optical movement measuring sensor 30 regardless of the presence or absence of an event. When the event detection unit 45 detects an event, the storage processing unit 46 reads out information corresponding to the event from the information stored in the temporary storage unit 46a, and stores the read information in association with at least a portion of the drawing data.

[0286] When presenting the time-series data, the presentation unit 47 generates a graph display screen 150 as shown in Fig. 49 and displays it on the drawing machine display unit 43a or the terminal operation unit 5b. The horizontal axis of this graph is time, and the vertical axis is the distance between the print head 24 and the workpiece W.

[0287] Time series data based on the log file may be displayed on the graph display screen 150, not just before and after the detection of an event. From the graph shown in Fig. 49, it can be seen that the distance between the print head 24 and the workpiece W tends to increase over time, which makes it possible to infer misalignment of the rails that guide the workpiece W on the production line, changes in the position of the drawing machine 2, etc. This makes it possible to take measures before a printing defect occurs. When displaying time series data before and after the detection of an event, it is possible to set the event to occur in the center of the time axis direction.

[0288] The controller 4 may be provided with a communication module capable of communicating with the outside. In this case, for example, at least one of the log file, statistical information, and time-series data may be transmitted to a device desired by the user and used in that device.

[0289] In addition, the user can extract and use the data contained in the log file. After extracting the desired data from the data contained in the log file, the user can edit and process the extracted data using another tool, etc., and use it in a production report, etc.

[0290] Examples of information related to the measured values ​​stored by the storage processing unit 46 may include data on the amount of light received by the optical movement measurement sensor 30, or may include time-series data on the amount of light received by the optical movement measurement sensor 30 before and after the detection of an event. In this case, the event detection unit 45 detects an event based on a decrease in the amount of light received by the optical movement measurement sensor 30. That is, when ink splashes from the work W adhere to the window portion 32b of the sensor housing 32, the amount of light received by the optical movement measurement sensor 30 decreases, which may result in a decrease in measurement accuracy or an inability to measure. Since this is an event that induces disturbance in the drawing, the event detection unit 45 detects it as an event related to the drawing state.

[0291] In the inkjet printing device 1, the event detection unit 45 detects the reception of the optical movement measuring sensor 30. The sensor includes a cleaning unit 49 (shown in FIG. 2) that cleans the window 32b of the sensor housing 32 when an event is detected based on a decrease in the amount of light. The cleaning unit 49 is made up of a blower (an example of a positive pressure generating device) that blows compressed air onto the window 32b, and a wiper-like device that wipes the window 32b, and is a part that automatically cleans the window 32b. Note that the user may be prompted to clean the window 32b, and the user may clean it.

[0292] (Inspection equipment) FIG. 50 shows an example in which the inspection device 500 is used during operation of the drawing machine 2. The inspection device 500 is a device for inspecting information drawn by the drawing machine 2 on the workpiece W transported by the transport machine 10. The installation position of the inspection device 500 is downstream of the drawing machine 2 in the transport direction of the workpiece W. At this installation position, the inspection device 500 captures an image of the information drawn on the workpiece W to generate an inspection image, and judges whether the drawing state is good or bad based on the generated inspection image. In other words, the inspection device 500 is an image inspection machine. The inspection device 500 may be a part of the inkjet printing device 1, or may be a device separate from the inkjet printing device 1.

[0293] As shown in FIG. 51, the inspection device 500 includes a main body 510, a sensor unit 3, a controller 4, and an operation terminal 5. The sensor unit 3, the controller 4, and the operation terminal 5 are the same as those described above. The main body 510 may be incorporated in the sensor unit 3. The external device 6, the power source 100, the encoder 7, and the timing sensor 8 are also the same as those described above. The external device 6, the power source 100, the encoder 7, and the timing sensor 8 may be devices that constitute a part of the inspection device 500, or may be devices separate from the inspection device 500. The inkjet printing device 1 may include the inspection device 500 and the drawing machine 2, or may exclude the inspection device 500.

[0294] The main body 510 includes an imaging unit 511, an illumination unit 512, a storage unit 513, and an arithmetic processing unit 514. The imaging unit 511, the illumination unit 512, the storage unit 513, and the arithmetic processing unit 514 may be integrated together, or only some of them may be separate units.

[0295] The illumination unit 512 is a part that illuminates the inspection target area, and is equipped with a light-emitting element such as an LED. The imaging unit 511 is a part that images the inspection target area and generates an inspection image, and is equipped with an optical system 511a and an imaging board 511b. The optical system 511a is composed of a lens that receives light irradiated from the illumination unit 512 and reflected by the inspection target area. The inspection target area in the inspection device 500 is a drawn area on the workpiece W.

[0296] The imaging board 511b is provided with a CMOS (complementary metal oxide semiconductor) image sensor 511c, an FPGA 511d, and a DSP 511e. The image sensor 511c receives light incident from an optical system and generates an inspection image. The FPGA 511d and the DSP 511e are for performing filter processing and the like on the inspection image inside the imaging unit 511, and a signal output from the CMOS sensor 511c is input to the FPGA 511d and the DSP 511e.

[0297] The storage unit 513 also stores inspection parameters for judging the quality of the drawing state of the information drawn on the workpiece W. For example, the storage unit 513 can store a plurality of types of inspection parameters, and the plurality of types of inspection parameters may include a first inspection parameter for judging the quality of the drawing state of the information drawn on the workpiece W, and a second inspection parameter having a narrower tolerance for judging the state as good than the first inspection parameter. The storage unit 513 may be configured as a part of the storage unit 42 of the controller 4 of the inkjet printing device 1.

[0298] The calculation processing unit 514 includes a quality determination unit 514a and a determination unit 514b. The quality determination unit 514a is a part that determines the quality of a drawing state regarding information drawn on the workpiece W based on the inspection image generated by the imaging unit 511 and the inspection parameters stored in the storage unit 513. The quality determination unit 514a and the determination unit 514b may be provided inside the drawing machine 2 or inside the operation terminal 5. The determination unit 514b may be provided in the controller 4.

[0299] The inspection device 500 can be switched between a setting mode for setting various parameters such as imaging settings, registering a master image that serves as a standard for determining pass / fail, generating (learning) a classifier that enables internal discrimination between pass / fail images, and an operation mode for determining pass / fail of the drawing state based on an inspection image obtained by capturing an image of an area to be inspected at the site where the drawing process is actually performed. In the setting mode, a user performs preliminary operations to enable discrimination between pass / fail products by a desired inspection.

[0300] The inspection device 500 can be switched between a rule-based inspection mode (standard inspection mode) in which the quality of the drawing state is judged based on various feature amounts (e.g., color, edge, position, etc.) in the inspection image, and a learning-based inspection mode (learning inspection mode) in which a classifier is generated and the quality of the drawing state is judged by the generated classifier. In the standard inspection mode, the user sets which feature amount contained in the image is to be used for the inspection, as well as a threshold value (part of the inspection parameters), and the like, and the quality is judged according to the settings.

[0301] When important characters as a product, such as the date and time of manufacture or the expiration date, are drawn, the inspection device 500 judges whether the drawn state is good or bad based on the result of image recognition, whether the character string is the one set in advance by the user in the drawing common setting (step SA2 in FIG. 8A). There are various methods for judging the good or bad state based on the result of image recognition. For example, whether there are blobs (a mass of black pixels) that look like characters in the inspection image, and if there are blobs, whether there are a predetermined number of them. In addition, when judging the good or bad state of the drawn state, it may be judged based on whether it is readable by OCR recognition. Generally, a good or bad judgment using OCR recognition can obtain a more accurate result, but it is inevitable that the OCR result by the inspection device 500 will misread the character string (judging the drawn result that should be judged as normal as abnormal) with a certain probability. The reason for the misjudgment when OCR recognition is used is that the good or bad standard that is readable by the human eye does not match the good or bad standard judgment of the OCR recognition by the inspection device 500. Products that are determined to be non-defective are rejected from the production line and become defective products, which necessitates the disposal of the erroneously determined non-defective products or the need to visually check them again, resulting in reduced production efficiency.

[0302] For example, if the user cannot accept the above-mentioned disposal, an inspection will be adopted to check whether the character string is the one set in advance by the user in the drawing common settings as described above. However, this inspection only checks whether characters are present and the number of characters is correct, so it cannot detect errors in the character string or drawing quality. In contrast to inspections using OCR recognition, defective products may be sent to the subsequent process as non-defective products, which has the disadvantage of incurring extra costs, such as rework in the subsequent process or the need to recall the product as a defective product if it is released onto the market.

[0303] Therefore, in this embodiment, if the position or movement of the workpiece W is outside the scope of inspection, it is determined that the drawing state is poor. For example, if the position or movement of the workpiece W is outside the scope of inspection, it is also possible to determine that the drawing state is poor regardless of the inspection image generated by the imaging unit 511. This makes it possible to perform a pass / fail judgment close to visual perception. A specific description will be given below.

[0304] First, the determination unit 514b will be described. The determination unit 514b determines whether the optical movement measuring sensor 30 or the distance sensor 31. The determination unit 514b can use various methods to determine whether the position or movement of the workpiece W is outside the inspection range, some of which will be described below.

[0305] For example, the determination unit 514b determines that the position or movement of the workpiece W is not to be inspected when the measurement value generated by the distance sensor 31 is outside a predetermined range. Also, the determination unit 514b determines that the position or movement of the workpiece W is not to be inspected when the measurement value measured by the optical movement measurement sensor 30 is outside a predetermined range. Also, when the optical movement measurement sensor 30 generates a measurement value related to the movement of the workpiece W in a direction perpendicular to the conveying direction by the conveyor 10, the determination unit 514b determines that the position or movement of the workpiece W is not to be inspected when the measurement value related to the movement in the direction perpendicular to the conveying direction measured by the optical movement measurement sensor 30 is outside a predetermined range. Also, when the optical movement measurement sensor 30 generates measurement values ​​of two axes perpendicular to each other, the determination unit 514b determines that the position or movement of the workpiece W is not to be inspected when the measurement value related to the movement in the conveying direction determined from the measurement values ​​of the two axes measured by the optical movement measurement sensor 30 is outside a predetermined range.

[0306] When the optical movement measuring sensor 30 acquires a current offset position relative to the reference position of the work W, the determining unit 514b determines that the position or movement of the work W is not subject to inspection when the current offset position acquired by the optical movement measuring sensor 30 is outside a predetermined range. In addition, when the accuracy of the measurement value generated by the optical movement measuring sensor 30 is equal to or less than a predetermined value, the determining unit 514b determines whether the position or movement of the work W is not subject to inspection based on the movement amount of the work W by the conveyor 10 acquired by the work movement amount acquiring unit 40d of the controller 40. Furthermore, the determining unit 514b determines whether the measurement value generated by the optical movement measuring sensor 30 exceeds a threshold value, and determines whether the position or movement of the work W is not subject to inspection based on the movement amount of the work W by the conveyor 10 acquired by the work movement amount acquiring unit 40d until the measurement value generated by the optical movement measuring sensor 30 exceeds the threshold value, while determining whether the position or movement of the work W is not subject to inspection based on the measurement value generated by the optical movement measuring sensor 30 when the measurement value generated by the optical movement measuring sensor 30 exceeds the threshold value.

[0307] When the determining unit 514b determines that the position or movement of the work W is outside the inspection target, the pass / fail determining unit 514a determines that the drawing state is poor regardless of the inspection image generated by the imaging unit 511. By adding the measurement value related to the position or movement of the work W to the pass / fail determination by the pass / fail determining unit 514b, a pass / fail determination close to a visual sense can be made. On the other hand, when the determining unit 514b determines that the position or movement of the work W is within the inspection target, the pass / fail determining unit 514a makes a pass / fail determination based on the inspection image generated by the imaging unit 511.

[0308] When the first inspection parameter and the second inspection parameter are stored in the storage unit 513, the pass / fail judgment unit 514a judges the pass / fail of the drawing state based on the inspection image generated by the imaging unit 511 and the first inspection parameters when making the pass / fail judgment. However, when the determination unit 514b determines that the position or movement of the work W is outside the inspection target, the pass / fail judgment unit 514a judges the pass / fail of the drawing state based on the second inspection parameters and the inspection image generated by the imaging unit 511.

[0309] When the inspection device 500 is used, the inspection device 500 and the controller 4 of the inkjet printing device 1 are communicatively connected, so that the pass / fail judgment results of the inspection device 500, the inspection images, etc. can be output to the controller 4. In this case, the event detection unit 45 shown in FIG. 2 can detect an event related to the drawing state based on the judgment results of the inspection device 500. The storage processing unit 46 associates information about the inspection image captured by the imaging unit 511 of the inspection device 500 with at least a part of the drawing data and stores it. Note that the inspection device 500 and the operation terminal 5 are communicatively connected, so that the pass / fail judgment results of the inspection device 500, the inspection images, etc. can be output to the operation terminal 4. The data may be output to the user terminal 5.

[0310] The presentation unit 47 can present information on the measurement value generated by the optical movement measurement sensor 30 or the measurement value generated by the distance sensor 31, and information on the inspection image captured by the imaging unit 511 of the inspection device 500, in association with at least a part of the drawing data. For example, as shown in FIG. 52, when the user checks the log file by viewing the drawing result confirmation screen 140 and finds a value (abnormal value) that exceeds a predetermined range among the values ​​indicating the distance, speed, and movement amount, when the user selects the drawing number to which the abnormal value belongs, the presentation unit 47 displays an image display confirmation window 160 superimposed on the drawing result confirmation screen 140. The image display confirmation window 160 is provided with a display button 160a and a non-display button 160b. When the display button 160a is operated, the presentation unit 47 displays an image display window 161 for displaying the inspection image corresponding to the drawing number superimposed on the drawing result confirmation screen 140 as shown in FIG. 53. The drawing result confirmation screen 140 may include at least one of the drawing data extracted from the inspection image, the drawing state, and the margin of error when the drawing state is determined to be good.

[0311] FIG. 54 is a flow chart showing an example of a process for determining pass / fail using the measurement results of the conveying speed and distance of the work W. Steps S101 to S103 are the same as SB1 to SB3 shown in FIG. 9. In step S104, the determination unit 514b of the inspection device 500 executes distance measurement based on the measurement value generated by the distance sensor 31. In step S105, the determination unit 514b determines whether the distance detected in step S104 is abnormal, that is, whether the measurement value generated by the distance sensor 31 is outside a predetermined range. If it is determined that the distance is normal (the measurement value generated by the distance sensor 31 is within a predetermined range), the process proceeds to step S106, where the determination unit 514b acquires the movement amount of the work W based on the measurement value generated by the optical movement measurement sensor 30. If it is determined that the distance is abnormal in step S105 (the measurement value generated by the distance sensor 31 is outside a predetermined range), the process proceeds to step S107, where the determination unit 514b records that the distance is abnormal in the storage unit 513 or the like, and proceeds to step S106.

[0312] In step S108, the determining unit 514b determines whether the conveying speed detected in step S106 is abnormal, i.e., whether the measurement value generated by the optical movement measuring sensor 30 is outside a predetermined range. If it is determined that the conveying speed is normal (the measurement value generated by the optical movement measuring sensor 30 is within a predetermined range), the process proceeds to step S110. If it is determined in step S108 that the conveying speed is abnormal (the measurement value generated by the optical movement measuring sensor 30 is outside a predetermined range), the process proceeds to step S109, where the determining unit 514b records in the memory unit 513 or the like that the conveying speed is abnormal, and the process proceeds to step S110. Steps S110 and S111 are the same as steps SB6 and SB7 in FIG. 9, respectively.

[0313] In step S112, the inspection device 500 transmits the distance abnormality record of step S107 and the transport speed abnormality record of step S109 to the drawing machine 2. As shown in Fig. 54, it may be determined that there is an abnormality if there is only one abnormality, or it may be determined that there is an abnormality if the abnormality occurs consecutively more than a specified number of times. Also, it may be determined that there is an abnormality according to an algorithm.

[0314] In addition, if the number of characters to be printed on the work W is set to, for example, four, and the inspection device 500 determines that the number of characters to be printed is five, it can also determine that the product is good if the distance and amount of movement are normal.

[0315] FIG. 55 is a flowchart showing an example of an inspection process after drawing processing is completed. In step S201, the inspection device 500 waits for the drawing inspection to start. In step S202, the distance abnormality record and the transport speed abnormality record recorded in the flowchart shown in FIG. 54 are acquired. In step S203, it is determined whether or not a trigger for starting the drawing inspection has been input. When the input is received, the process proceeds to step S204, where drawing inspection processing is started. In step S205, the pass / fail judgment unit 514a judges based on the inspection image and the inspection parameters that the result is defective, and if the result is good, the process proceeds to step S206, and if the result is good, the process proceeds to step S207. In step S207, the pass / fail judgment unit 514a judges whether the distance is abnormal, and if the distance is abnormal, the process judges the result as defective and proceeds to step S208, and if the result is good, the process proceeds to step S209. In step S209, the pass / fail judgment unit 514a judges whether the conveying speed is abnormal, and if the conveying speed is abnormal, the process judges the result as defective and proceeds to step S210, and if the result is good, the process proceeds to step S211.

[0316] In step S211, it is determined that the drawing state is good. In step S212, the user is notified of whether the drawing state is good or bad, and also of the cause and reason if the drawing state is bad. For example, the presentation unit 47 can present the reason why the inspection device 500 has determined that the drawing state is bad, by linking it to at least a part of the drawing data. Examples of the reason include a distance abnormality (the workpiece W is too far away from the print head 24) or a transport speed abnormality (the transport speed of the workpiece W is too slow, too fast, or fluctuating), etc.

[0317] The presentation unit 47 can also present a method of correcting the drawing state corresponding to the reason why the drawing state is judged to be negative by the inspection device 500. For example, if the reason why the drawing state is judged to be negative is an abnormal distance, a method of adjusting a guide so that the workpiece W does not move away from the print head 24 is presented to the user as a method of correcting the drawing state. Also, if the reason why the drawing state is judged to be negative is an abnormal transport speed, a method of adjusting the speed of the workpiece W within a predetermined speed range is presented to the user as a method of correcting the drawing state. The drawing machine 2 may obtain the reason why the drawing state is judged to be negative, and automatically perform a correction of the drawing state corresponding to that reason.

[0318] Fig. 56 is a flowchart showing an example of processing for determining pass / fail using the measurement results of the movement and distance perpendicular to the transport direction of the workpiece W. Steps S301 to S305 and S307 are the same as steps S101 to S105 and S107, respectively, in Fig. 54. In step S306, not only the movement amount (movement speed) of the workpiece W in the transport direction but also the movement amount (movement speed) in the direction perpendicular to the transport direction is measured.

[0319] Steps S308 and S309 are the same as steps S108 and S109 in FIG. 54. In step S310, the determination unit 514b determines whether the vibration of the workpiece W is abnormal based on the amount of movement of the workpiece W in the direction perpendicular to the conveying direction. If it is determined that the vibration of the workpiece W is abnormal, the process proceeds to step S311, where the determination unit 514b records in the memory unit 513 or the like that the vibration of the workpiece W is abnormal, and proceeds to step S312. In step S312, the inclination of the conveying direction of the workpiece W is calculated based on the amount of movement of the workpiece W in the conveying direction and the amount of movement in the direction perpendicular to the conveying direction, and it is determined whether the calculated inclination is abnormal. If it is determined that the inclination of the workpiece W in the conveying direction is abnormal, the process proceeds to step S313, where the determination unit 514b records in the memory unit 513 or the like that the inclination of the workpiece W in the conveying direction is abnormal, and proceeds to step S314. Steps S314 and S315 are the same as steps S110 and S111 in FIG. 54, respectively.

[0320] In step S316, the inspection device 500 transmits to the drawing machine 2 the transfer speed abnormality record of step S309, the vibration abnormality record of the workpiece W of step S311, and the tilt abnormality record of the transfer direction of the workpiece W of step S313.

[0321] FIG. 57 is a flow chart showing an example of an inspection process using the measurement results of the movement and distance perpendicular to the conveying direction of the workpiece W. Steps S401 to S410 correspond to steps in FIG. In step S411, the quality determining unit 514a determines whether the workpiece W has a vibration abnormality, and if the workpiece W has a vibration abnormality, the workpiece W is determined to be defective and the process proceeds to step S412, and if the workpiece W is good, the process proceeds to step S413.

[0322] In step S413, the quality determining unit 514a determines whether the workpiece W is inclined in the transport direction. If the workpiece W is inclined, the process determines the workpiece W is defective and proceeds to step S414. If the workpiece W is inclined, the process proceeds to step S415.

[0323] In step S415, it is determined that the drawing state is good. In step S416, the user is notified of the quality of the drawing state, and if the drawing state is poor, the user is also notified of the cause and reason. For example, the user can be notified that the conveying direction of the workpiece W is tilted, that the workpiece W is bumping, etc.

[0324] The inclination of the workpiece W in the transport direction can be obtained using a first distance sensor 31A and a second distance sensor 31B arranged vertically as shown in Fig. 58. By measuring two different points in the height direction of the workpiece W using the first distance sensor 31A and the second distance sensor 31B, it becomes possible to measure abnormal inclination of the workpiece W relative to the drawing machine 2, and it becomes possible for the inspection device 500 to judge abnormalities based on the abnormal values.

[0325] FIG. 59 is a flow chart showing an example of an inspection process in which the first distance sensor 31A and the second distance sensor 31B are provided to perform pass / fail judgment. Steps S501 to S503 are the same as steps S301 to S303 shown in FIG. 56. In step S504, the measurement value Y1 generated by the first distance sensor 31A is acquired. In step S505, the determination unit 514b determines whether or not Y1 is abnormal, that is, whether or not the measurement value Y1 generated by the first distance sensor 31A is outside a predetermined range. If it is determined that Y1 is normal (the measurement value generated by the first distance sensor 31A is within a predetermined range), the process proceeds to step S507. If it is determined that Y1 is abnormal (the measurement value generated by the first distance sensor 31A is outside a predetermined range) in step S505, the process proceeds to step S506, where the determination unit 514b records that Y1 is abnormal in the storage unit 513 or the like, and the process proceeds to step S507.

[0326] In step S507, the measurement value Y2 generated by the second distance sensor 31B is acquired. In step S508, the determination unit 514b determines whether or not Y2 is abnormal, that is, whether or not the measurement value Y2 generated by the second distance sensor 31B is outside a predetermined range. If it is determined that Y2 is normal (the measurement value generated by the second distance sensor 31B is within a predetermined range), the process proceeds to step S510. If it is determined in step S508 that Y2 is abnormal (the measurement value generated by the second distance sensor 31B is outside a predetermined range), the process proceeds to step S509, where the determination unit 514b records in the storage unit 513 or the like that Y2 is abnormal, and the process proceeds to step S510.

[0327] In step S510, the determination unit 514b calculates the inclination of the workpiece W. In step S511, the determination unit 514b determines whether the inclination of the workpiece W calculated in step S510 is outside a predetermined range. If it is determined that the inclination of the workpiece W is normal (within a predetermined range), the process proceeds to step S513. If it is determined in step S511 that the inclination of the workpiece W is abnormal (outside a predetermined range), the process proceeds to step S512, where the determination unit 514b records in the memory unit 513 or the like that the inclination of the workpiece W is abnormal, and the process proceeds to step S513. Steps S513 to S517 are the same as steps S106, S108, S109, S110, and S111 shown in FIG. 54, respectively.

[0328] In step S518, the inspection device 500 transmits to the drawing machine 2 the distance Y1 abnormality record of step S506, the distance Y2 abnormality record of step S509, the tilt abnormality record of step S512, and the conveying speed abnormality record of step S515.

[0329] Fig. 60 is a flow chart showing an example of an inspection process when a first distance sensor 31A and a second distance sensor 31B are provided. Steps S601 to S606 are the same as steps S401 to S406 in Fig. 59, respectively. In step S607, the pass / fail determination unit 514a executes a determination of inclination abnormality of the workpiece W, and if there is an inclination abnormality, it is determined to be defective and the process proceeds to step S608, and if it is pass, the process proceeds to step S609.

[0330] In step S609, the quality determination unit 514a performs a quality determination for the distance Y1, and if Y1 is abnormal, the quality determination unit 514a determines that the distance is defective and proceeds to step S610, and if Y1 is good, the quality determination unit 514a performs a quality determination for the distance Y2, and if Y2 is abnormal, the quality determination unit 514a determines that the distance is defective and proceeds to step S612, and if Y2 is good, the quality determination unit 514a performs a quality determination for the distance Y2, and if Y2 is abnormal, the quality determination unit 514a proceeds to step S613.

[0331] In step S613, the quality determination unit 514a determines whether the conveying speed is abnormal, and if the conveying speed is abnormal, it determines that the sheet is defective and proceeds to step S614, and if the conveying speed is good, it proceeds to step S615. Steps S615 and S616 are the same as steps S211 and S212 in FIG. 55, respectively.

[0332] In addition, when the quality judgment unit 514a judges the quality of the drawing state, the user can select whether to use both the measurement results of the conveying speed and distance of the work W or to use only one of them. For example, a selection screen can be displayed to accept the selection of the conveying speed and distance. In addition, the threshold value for judging that an abnormality exists may be set in advance or may be set by the user. In other words, the user can arbitrarily select whether the threshold value for judging that the conveying speed and distance of the work W are abnormal should be an initial setting value determined from the capacity of the drawing machine 2 or a user setting value that takes into account the installation noise (effects of wind, etc.) in the user's environment.

[0333] (Action and effect) According to this embodiment, when the inkjet printing apparatus 1 is installed, the optical movement measuring sensor 30 or the distance sensor 31 can generate measurement values ​​related to the position or movement of the workpiece W transported by the transport device 10. The measurement values ​​generated by the optical movement measuring sensor 30 or the distance sensor 31 include the positional relationship between the print head 24 and the workpiece W, the movement speed and movement amount of the workpiece W, etc., so that it is possible to obtain information related to the installation state of the inkjet printing apparatus 1 based on the measurement values ​​generated by the optical movement measuring sensor 30 or the distance sensor 31. This eliminates the need for the user to perform test drawing and adjustments many times, improving usability during installation.

[0334] Furthermore, when various information is drawn on the workpiece W being conveyed by the conveyor 10, the optical movement measuring sensor 30 generates measurement values ​​relating to the movement of the workpiece W in the conveying direction. Based on these measurement values ​​and reference position information of the workpiece W, it becomes possible to acquire the current offset position of the workpiece W relative to the reference position. By controlling the ejection of ink from the print head 24 based on the acquired current offset position and drawing data, the effects of variations in the conveying line speed, variations in the position of the workpiece W in the width direction, and errors due to slippage of the workpiece W are suppressed, thereby suppressing the occurrence of drawing defects.

[0335] When performing the drawing process, the evaluation unit 40h evaluates the reliability of the measurement by the optical movement measurement sensor 30. For example, if the amount of light received by the optical movement measurement sensor 30 is less than a predetermined amount, it is determined that the reliability does not meet a predetermined standard, and abnormality processing can be executed. In other words, when the reliability of the measurement by the optical movement measurement sensor 30 does not meet the predetermined standard, abnormality processing can be executed at an appropriate timing, thereby suppressing the occurrence of a large number of drawing defects.

[0336] In addition, the distance sensor 31 measures the distance to the workpiece W, and the ejection of ink can be controlled based on the result of determining whether the distance to the workpiece W satisfies a predetermined standard. This makes it possible to deal with cases where poor drawing may occur due to the distance to the workpiece W being too far, for example, and thus suppresses the occurrence of poor drawing.

[0337] Furthermore, if an event related to the drawing state occurs during operation of the drawing machine 2, the event may cause drawing defects. In response to this, a measurement value related to the position or movement of the workpiece W transported by the transport machine 10 is acquired, and an event related to the drawing state that occurs during operation of the drawing machine 2 is detected by the event detection unit 45 based on the acquired measurement value. In response to detection of this event, information related to the measurement value generated by the optical movement measurement sensor 30 or the distance sensor 31 and information related to the event are stored in a state linked to at least a part of the drawing data, so that by checking the stored contents after the event occurs, it becomes possible to analyze the cause of the event, including whether the event is caused by the position or movement of the workpiece W and what the drawing state is.

[0338] The above-described embodiment is merely illustrative in all respects and should not be construed as limiting. Furthermore, all modifications and variations within the scope of the claims are within the scope of the present invention. [Industrial Applicability]

[0339] As described above, the present disclosure can be used when drawing various types of information on packaging materials such as cardboard. [Explanation of symbols]

[0340] 1 Inkjet printing device 2 drawing machine 3 Sensor unit 10. Conveyor 20a ink cartridge 21a Subtank 24 Print head (nozzle) 30 Optical movement measurement sensor 31 Distance Sensor 32 Sensor housing 40c Drawing control unit 40g Conveying direction specification part 42 Storage section 44 Output section 45 Event detection section 46 Storage Processing Unit 46a Temporary storage section 47 Presentation section 49 Cleaning Department 500 Inspection Equipment 514a Good / bad judgement section 514b Decision section

Claims

1. An inkjet printing apparatus that ejects ink for drawing information on an object conveyed by a conveying device, an ink tank for storing the ink; a nozzle for ejecting the ink supplied from the ink tank toward an object to be drawn; a storage unit configured to store drawing data that defines ejection timing corresponding to drawing information for the nozzles at each of a plurality of offset positions in the transport direction; an optical movement measurement sensor that receives light from the object to be imaged and generates a measurement value related to the movement of the object to be imaged in the conveying direction based on the received light; a drawing control unit that controls the ejection of ink from the nozzles based on reference position information indicating that a reference position of the object to be drawn is at a predetermined position, a current offset position with respect to the reference position based on the measurement value generated by the optical movement measuring sensor, and the drawing data; An inkjet printing apparatus comprising:

2. 2. The inkjet printing apparatus according to claim 1, An inkjet printing apparatus, wherein the reference position information is a timing signal indicating that the object to be imaged, being transported by the transport device, has reached a predetermined position.

3. 3. The inkjet printing apparatus according to claim 2, A timing signal output unit that outputs the timing signal is further provided. The drawing control unit obtains the timing signal output from the timing signal output unit as the reference position information.

4. 3. The inkjet printing apparatus according to claim 2, the optical movement measuring sensor generates the timing signal indicating that the object to be imaged has reached a predetermined position based on a change in the amount of received light; The inkjet printing apparatus, wherein the drawing control unit acquires the timing signal generated by the optical movement measuring sensor as the reference position information.

5. 2. The inkjet printing apparatus according to claim 1, The optical movement measurement sensor includes a light projection unit that projects light onto the object to be drawn, and a light receiving unit that receives a speckle pattern that is generated according to the characteristics of the surface shape of the object to be drawn by the light projected from the light projection unit and generates light reception data including the speckle pattern, and generates the measurement value based on the amount of movement of the speckle pattern included in the light reception data generated by the light receiving unit.

6. 2. The inkjet printing apparatus according to claim 1, A movement amount acquisition unit that acquires a movement amount of the conveyor, An inkjet printing device, wherein the drawing control unit controls the ejection of ink from the nozzles based on the movement amount acquired by the movement amount acquisition unit and the drawing data when the accuracy of the measurement value generated by the optical movement measurement sensor is below a predetermined level.

7. 2. The inkjet printing apparatus according to claim 1, A movement amount acquisition unit that acquires a movement amount of the conveyor, The drawing control unit determines whether the measurement value generated by the optical movement measuring sensor exceeds a threshold value, and controls the ejection of ink from the nozzle based on the movement amount acquired by the movement amount acquisition unit and the drawing data until the measurement value exceeds the threshold value. When the measured value exceeds a threshold value, the ink ejection from the nozzle is controlled based on the current offset position and the drawing data.

8. 2. The inkjet printing apparatus according to claim 1, the optical movement measuring sensor measures the amount of movement of the object to be drawn in a direction perpendicular to the conveying direction; The drawing control unit controls the ejection of ink from the nozzles based on the amount of movement measured by the optical movement measuring sensor in a direction perpendicular to the transport direction.

9. 2. The inkjet printing apparatus according to claim 1, The optical movement measuring sensor generates measurements in two mutually orthogonal axes, and determines a measurement relating to the movement in the transport direction from the generated measurements in the two axes.

10. 2. The inkjet printing apparatus according to claim 1, A conveying direction specifying unit that specifies the conveying direction is further provided, The drawing control unit controls the ejection of ink from the nozzles based on the transport direction specified by the transport direction specifying unit.

11. 11. The inkjet printing apparatus according to claim 10, a head pressure of the liquid surface of the ink contained in the ink tank is applied to the nozzle as a negative pressure; An inkjet printing apparatus, wherein the liquid surface is set within a predetermined range of inclination with respect to a horizontal plane.

12. 12. The inkjet printing apparatus according to claim 11, The drawing control unit controls the ejection of ink from the nozzles so that the information is drawn parallel to the transport direction when the transport direction specified by the transport direction specifying unit is inclined with respect to a horizontal plane.

13. 2. The inkjet printing apparatus according to claim 1, The nozzle further includes a housing in which the nozzle is provided, The optical movement measuring sensor is fixed to the housing so that a positional relationship between the optical movement measuring sensor and the nozzles is set to a predetermined positional relationship.

14. 2. The inkjet printing apparatus according to claim 1, The nozzle has a plurality of ejection ports formed along a first direction, An inkjet printing device, wherein the optical movement measuring sensor is positioned at an offset position along the transport direction relative to the nozzle, and the position in the first direction of the area to be drawn to which the nozzle is directed and the position in the first direction of the area where the current offset position is measured by the optical movement measuring sensor are installed so as to at least partially overlap each other.

15. 2. The inkjet printing apparatus according to claim 1, the nozzle includes a first nozzle provided in a first housing and having a plurality of discharge ports, and a second nozzle provided in a second housing that can be arranged apart from the first housing and having a plurality of discharge ports; the storage unit includes drawing data for the first nozzles and drawing data for the second nozzles as the drawing data; The drawing control unit determines, based on the current offset position and the drawing data for the first nozzle, and controls the ejection of ink from the plurality of ejection ports formed in the first nozzle based on the current offset position and drawing data for the second nozzle, and also controls the ejection of ink from the plurality of ejection ports formed in the second nozzle based on the current offset position and drawing data for the second nozzle.

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