Discharge device, discharge method, and program

Abstract

To provide a discharge device, a discharge method, and a program capable of reducing errors in height information when irregularities, grooves, or holes exist on a printing target surface.SOLUTION: A discharge device comprises: a head that discharges liquid onto a printing target surface of a printing target; an actuator that moves the head at least in a Z-axis direction; a height information detection unit that emits an energy body having a larger area than a shape variation of a surface present on the printing target surface, and detects height information indicating a distance between the head and the printing target surface; a control unit that controls the head so that the distance between the printing target surface and the head falls within a set range on the basis of the height information detected by the height information detection unit; a determination unit that determines a state of the printing target surface; and a correction unit that corrects errors in the height information according to characteristics of absorbing the energy body of the printing target including the determined state.SELECTED DRAWING: Figure 1C

Description

[Technical Field]

[0001] The present invention relates to a discharge device, a discharge method, and a program. [Background technology]

[0002] When printing on an uneven surface, simply scanning an inkjet head (an example of a head) horizontally will result in variations in the gap between the inkjet head and the surface, resulting in misalignment of the ink (an example of a liquid) landing position and poor image quality. To prevent this, a technology has been developed that controls the inkjet head based on height information detected by a height information detection unit to keep the distance between the surface and the inkjet head within a set range, thereby printing on the print medium (see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0003] However, with the above technology, when there are irregularities, grooves, holes, etc. on the surface to be printed, the energy emitted from the height information detection unit is reflected, scattered, or absorbed by the irregularities, grooves, holes, etc., resulting in large errors in the height information.

[0004] The present invention has been made in consideration of the above, and aims to provide an ejection device, an ejection method, and a program that can reduce errors in height information when unevenness, grooves, holes, etc. are present on the surface to be printed. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems and achieve the object, the present invention comprises a head that ejects liquid onto the printing surface of a printing object, an actuator that can move the head in at least the Z-axis direction, a height information detection unit that fires an energy body with an area larger than the shape change of the surface present on the printing surface to detect height information that indicates the distance between the head and the printing surface, a control unit that controls the head based on the height information detected by the height information detection unit so that the distance between the printing surface and the head is within a set range, a discrimination unit that discriminates the state of the printing surface, and a correction unit that corrects errors in the height information according to the characteristics of the printing object to absorb the energy body, including the discriminated state. [Effects of the Invention]

[0006] According to the present invention, when unevenness, grooves, holes, etc. exist on the surface to be printed, it is possible to reduce errors in height information. [Brief explanation of the drawings]

[0007] [Figure 1A] FIG. 1A is a diagram showing an example of the overall configuration of a discharge device according to this embodiment. [Figure 1B] FIG. 1B is a diagram showing an example of the external features of the discharge device according to this embodiment. [Figure 1C] FIG. 1C is a diagram showing an example of a functional block of the discharge device according to the present embodiment. [Figure 2] FIG. 2 is a diagram illustrating an example of the configuration of the discharge device according to this embodiment as viewed from the Y-axis direction. [Figure 3A] FIG. 3A is a diagram for explaining an example of a problem that may occur when using the height information detection unit in the discharge device according to this embodiment and a solution thereto. [Figure 3B] FIG. 3B is a diagram for explaining an example of a problem that may occur when using the height information detection unit in the discharge device according to this embodiment and a solution thereto. [Figure 3C]FIG. 3C is a diagram for explaining an example of a problem that may occur when using the height information detection unit in the discharge device according to this embodiment and a solution thereto. [Figure 4A] FIG. 4A is a diagram illustrating an example of an energy body emitted by a height information detection unit of the discharge device according to this embodiment. [Figure 4B] FIG. 4B is a diagram illustrating an example of an energy body emitted by the height information detection unit of the discharge device according to this embodiment. [Figure 4C] FIG. 4C is a diagram illustrating an example of an energy body emitted by the height information detection unit of the discharge device according to this embodiment. [Figure 5A] FIG. 5A is a diagram for explaining an example of a method for correcting height information in accordance with the absorption characteristics of the energy body of the printing target in the discharge device according to the present embodiment. [Figure 5B] FIG. 5B is a diagram for explaining an example of a method for correcting height information in accordance with the absorption characteristics of the energy body of the printing target in the discharge device according to the present embodiment. [Figure 5C] FIG. 5C is a diagram for explaining an example of a method for correcting height information in accordance with the absorption characteristics of the energy body of the printing target in the discharge device according to the present embodiment. [Figure 5D] FIG. 5D is a diagram for explaining an example of a method for correcting height information in accordance with the absorption characteristics of the energy body of the printing target in the discharge device according to the present embodiment. [Figure 5E] FIG. 5E is a diagram for explaining an example of a method for correcting height information in accordance with the absorption characteristics of the energy body of the printing target in the discharge device according to the present embodiment. [Figure 5F] FIG. 5F is a diagram for explaining an example of a method for correcting height information in accordance with the absorption characteristics of the energy body of the printing target in the discharge device according to the present embodiment. [Figure 6] FIG. 6 is a diagram for explaining an example of the relationship between the correction constant a of the absorption characteristics of the energy body and the structural value of the printing object in the ejection device according to this embodiment. [Figure 7] FIG. 7 is a diagram for explaining an example of the flow of printing processing in the X-axis direction in the ejection device according to this embodiment. [Figure 8] FIG. 8 is a diagram for explaining an example of the timing of the printing operation in the ejection device according to the present embodiment. [Figure 9] FIG. 9 is a diagram for explaining an example of a preferable positional relationship between the inkjet head and the height information detection unit in the ejection device according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a discharge device, a discharge method, and a program will be described in detail with reference to the accompanying drawings.

[0009] Fig. 1A is a diagram showing an example of the overall configuration of a discharge device according to the present embodiment, which will be described with reference to Fig. 1A.

[0010] The discharge device 1 shown in FIG. 1A is a device that divides a wide liquid application area (an example of a printing target), such as a road surface, into multiple print areas, moves sequentially to each print area, and divides print data to be printed on the liquid application area into multiple print images and prints them. In other words, the print images will be described below as image data obtained by dividing the print data. FIG. 1A(a) is a side view of the discharge device 1, and FIG. 1A(b) is a plan view of the discharge device 1 viewed from above. Note that "printing" refers to applying or spraying ink onto roads, walls, car bodies (sides), roofs, etc.

[0011] 1A, the discharge device 1 includes a printing unit 21 and a control unit 22. Note that the discharge device 1 may have a system configuration in which the printing unit 21 and the control unit 22 are separate entities.

[0012] The printing unit 21 is a unit that ejects ink while moving to print on a surface below the ejection device 1, such as the surface of a road (hereinafter, may be simply referred to as the "road surface"). Note that "ink" is an example of a liquid that is applied or sprayed onto a road surface. Furthermore, the target onto which the ink is ejected is not limited to the road surface, but may also be the surface of a predetermined printing medium, which is the surface below the ejection device 1. As shown in FIG. 1A , the printing unit 21 includes a carriage 2, a main scanning guide 3, a two-dimensional camera 8, a GNSS receiver 9, a tire 10, a sub-scanning guide 11, a structure 12, and a holding stay 14.

[0013] The carriage 2 is a member that holds an inkjet head 2a (see FIG. 1B), which will be described later, and moves in the main scanning direction (arrow A shown in FIG. 1A(b)) along a main scanning guide 3, and moves in the sub-scanning direction as the main scanning guide 3 moves in the sub-scanning direction (arrow B shown in FIG. 1A(b)). The carriage 2 moves back and forth in the main scanning direction along the main scanning guide 3 by a head moving mechanism comprised of a belt, pulleys, a motor, etc. As shown in FIG. 1A, the carriage 2 is installed on the side of the front side of the main scanning guide 3 (opposite the holding stay 14, on the open end side of the pair of sub-scanning guides 11).

[0014] The main scanning guide 3 is a rail member that supports the carriage 2 to move in the main scanning direction and is supported horizontally on the sub-scanning guide 11 so that it can move in the sub-scanning direction. The main scanning guide 3 moves back and forth on the sub-scanning guide 11 in the sub-scanning direction, which is perpendicular to the main scanning direction, by a rail movement mechanism made up of a belt, pulleys, motor, etc. Note that the main scanning guide 3 does not necessarily have to be perpendicular to the sub-scanning guide 11, and may at least intersect with it.

[0015] In other words, the carriage 2 carrying the inkjet head 2a can move freely in the forward / backward direction (sub-scanning direction) and left / right direction (main scanning direction) on a horizontal plane surrounded by a pair of sub-scanning guides 11 and holding stays 14 of the ejection device 1.

[0016] The two-dimensional camera 8 is an imaging device that captures images of the road surface and the vicinity of the printed image printed on the road surface. Therefore, the imaging direction of the two-dimensional camera 8 is downward. The two-dimensional camera 8 transmits the captured images to the controller unit 6. The two-dimensional camera 8 may be powered by a battery installed in itself, or may be powered by the power supply system 5 assuming continuous operation.

[0017] The GNSS receiver 9 is a receiving device that receives positioning signals from positioning satellites based on a GNSS (Global Navigation Satellite System) such as a GPS (Global Positioning System) to measure the current position on Earth. The GNSS receiver 9 transmits the received positioning signals to the controller unit 6.

[0018] A plurality of tires 10 are attached to the lower part of the sub-scanning guide 11 and are wheel members for moving the printing unit 21 by being manually pushed by an operator, etc. This allows the discharge device 1 to move in four directions: forward, backward, left, and right. Furthermore, when printing by discharging ink from the inkjet head 2a, the tires 10 are locked, thereby preventing the discharge device 1 from moving during printing. Note that the tires 10 are not limited to being attached to the lower part of the sub-scanning guide 11, and may be attached, for example, by a shaft extending outward from the outer side surface of the sub-scanning guide 11.

[0019] The sub-scanning guides 11 are a pair of guide members extending in the sub-scanning direction that form the base of the printing unit 21. The sub-scanning guides 11 support the main scanning guide 3, the structure 12, etc. from below. A GNSS receiver 9 is attached to the side of the sub-scanning guide 11.

[0020] The structure 12 is a quadrangular pyramid-shaped structure made up of pipes, etc. The structure 12 has a two-dimensional camera 8 mounted at its apex.

[0021] The holding stay 14 is a holding member that connects the rear end vicinity of a pair of sub-scanning guides 11 that extend in the sub-scanning direction, and maintains the relative positions of the pair of sub-scanning guides 11. Therefore, the front end of the sub-scanning guide 11 has an open configuration that is not connected by a stay member such as the holding stay 14. In other words, the configuration in which one member of the holding stay 14 is connected to two members of the sub-scanning guide 11 forms a U-shape when viewed from above (in a plan view).

[0022] As shown in FIG. 1A, the control unit 22 includes an ink supply system 4, a power supply system 5, and a controller unit 6.

[0023] The ink supply system 4 is a unit that supplies ink used for printing to the inkjet head 2a of the carriage 2 via a pipe 4a, which is an ink flow path. In this embodiment, the ink supply system 4 moves in accordance with the printing unit 21, but this is not limited to this and the ink supply system 4 may also be self-propelled, independent of the printing unit 21.

[0024] The power supply system 5 is a unit that supplies power to drive the control unit 22, the head moving mechanism, the rail moving mechanism, the inkjet head 2a, and the like.

[0025] The controller unit 6 is a control unit for controlling the operation of the discharge device 1. For example, the controller unit 6 controls the operations of the head moving mechanism, the rail moving mechanism, and the inkjet head 2a, and estimates the position of the discharge device 1 from the positioning signal received by the GNSS receiver 9. The controller unit 6 also stores the positioning signal received by the GNSS receiver 9 as odometry information such as the accumulated movement amount of the discharge device 1. Note that the discharge device 1 may include multiple GNSS receivers 9, and the controller unit 6 may correct the position information from the positioning signals received by the multiple GNSS receivers 9.

[0026] In addition, the discharge device 1 shown in FIG. 1A has been described as being moved by being pushed by an operator in principle, but is not limited to this, and the discharge device 1 may also be a self-propelled device equipped with a motor or the like that can control the rotation of the tire 10.

[0027] FIG. 1B is a diagram showing an example of the external features of a discharge device according to this embodiment. FIG. 1C is a diagram showing an example of functional blocks of a discharge device according to this embodiment. In this embodiment, the discharge device includes an X-axis actuator 111, a Y-axis actuator 112, and a Z-axis actuator 113. The discharge device 1 discharges ink while moving an inkjet head 2a in the X, Y, and Z-axis directions. Here, the inkjet head 2a is an example of a head (liquid discharge unit) that discharges ink (an example of liquid) onto a printing surface 500 of a printing object. The inkjet head 2a also includes height information detection units 121 and 131 that detect height information, which is the distance between the inkjet head 2a and the printing surface 500 in the Z-axis direction.

[0028] In this embodiment, the X-axis actuator 111, the Y-axis actuator 112, and the Z-axis actuator 113 are examples of actuators that move the inkjet head 2a at least in the Z-axis direction. The actuators may also move the inkjet head 2a in either or both the X-axis direction (main scanning direction) and the Y-axis direction (sub-scanning direction) in addition to the Z-axis direction. In this embodiment, the height information detection units 121 and 131 are examples of height information detection units that detect height information indicating the distance between the inkjet head 2a and the printing target surface 500 by emitting energy bodies with an area larger than the surface shape (state) variations of the printing target surface 500, such as irregularities, grooves, and holes. This allows the energy bodies emitted from the height information detection units 121 and 131 to be irradiated onto a detection area larger than the irregularities, grooves, holes, and the like present on the printing target surface 500 to obtain height information, thereby reducing the occurrence of height information detection errors due to irregularities, grooves, holes, and the like.

[0029] The control unit 22 of the ejection device 1 also includes a central control unit 200. The central control unit 200 controls the ejection of ink from the inkjet head 2a, the operation of the X-, Y-, and Z-axis actuators 111-113, and the detection of height information by the height information detection units 121 and 131. Here, height information refers to the distance (gap) in the Z-axis direction between the inkjet head 2a and the printing surface 500 of the printing object. The central control unit 200 is provided in a position that does not interfere with the printing operation. The central control unit 200 and each of the controlled objects (X-, Y-, and Z-axis actuator drivers 211-213, height information detection units 121 and 131, ink supply maintenance unit 221, and ink ejection control unit 222) can communicate with each other via wire or wirelessly.

[0030] The discharge device 1 is fixed to the printing surface 500 by a fixed part such as a tire 10. The shape of the fixed part may be other than legs and wheels. The printing surface 500 may extend infinitely. Also, in FIG. 1B, the Z-axis direction is defined as the vertical direction, but the coordinate system may be defined so that the Z-axis direction is the horizontal direction. Since the area that can be printed with the discharge device 1 is limited, when printing a large image, after printing is completed at a certain position, the discharge device is moved and printing is repeated so that the image is connected.

[0031] A user operates the discharge device 1 using a user operation unit 201 such as a PC (Personal Computer) or a touch panel. The user operation unit 201 exchanges various commands and data with a central control unit 200. The central control unit 200 can control the X-axis actuator 111, the Y-axis actuator 112, and the Z-axis actuator 113 via an X-axis actuator driver 211, a Y-axis actuator driver 212, and a Z-axis actuator driver 213.

[0032] The central control unit 200 also acquires height information from the height information detection units 121 and 131, exchanges various commands and data with the ink supply maintenance unit 221, and sends a discharge control signal to the ink discharge control unit 222 to discharge ink from the inkjet head 2a at the appropriate timing. The memory 202 stores discrimination information for discriminating the type of three-dimensional object, which is an example of the printing target. The central control unit 200 reads this discrimination information as needed and uses it to correct the height information. The discharge device shown in FIGS. 1A and 1B is merely one embodiment, and while the Z-axis actuator 113 is necessary to adjust the gap between the inkjet head 2a and the printing target surface 500, the X- and Y-axis actuators 111 and 112 are not essential.

[0033] Next, a description will be given of an example of a specific configuration of the central control unit 200. In this embodiment, the central control unit 200 has a control unit 200a, a discrimination unit 200b, and a correction unit 200c.

[0034] The control unit 200a is an example of a control unit that controls the inkjet head 2a based on the height information detected by the height information detection units 121, 131 so that the distance between the printing surface 500 and the inkjet head 2a is within a set range.

[0035] The discrimination unit 200b is an example of a discrimination unit that discriminates the state of the printing surface 500. In this embodiment, the discrimination unit 200b discriminates the state of the printing surface 500 based on discrimination information stored in the memory 202.

[0036] The correction unit 200c is an example of a correction unit that corrects errors in height information detected by the height information detection units 121, 131 in accordance with the energy body absorption characteristics of the printing object, including the determined state of the printing object surface 500. As a result, the printing object is identified and corrections are made to the obtained height information in accordance with the energy body absorption characteristics of that object, so that errors in the height information can be reduced when unevenness, grooves, holes, etc. exist on the printing object surface 500.

[0037] 2 is a diagram illustrating an example of the configuration of the discharge device according to this embodiment as viewed from the Y-axis direction. Since the positional relationship between the inkjet head 2a and the height information detection units 121 and 131 is known in advance, the height information detected by the height information detection units 121 and 131 can be converted into the gap between the inkjet head 2a and the printing target surface 5a.

[0038] In this embodiment, it is mainly assumed that the printing surface 500 is not flat in the horizontal direction, but has unevenness, as shown in Fig. 2. In such a case, simply scanning the inkjet head 2a in the horizontal direction using the X-axis actuator 111 will result in deviations in the ink landing position, resulting in poor image quality, due to variations in the gap between the inkjet head 2a and the printing surface 500 depending on the location on the printing surface 500.

[0039] Therefore, in order to eliminate deviations in the ink landing positions, the central control unit 200 performs printing while controlling the inkjet head 2a in the Z-axis direction using the Z-axis actuator 113 so that the distance between the printing target surface 500 and the inkjet head 2a is within a set range, based on height information detected by the height information detection units 121, 131. Roughly speaking, it is sufficient if the trajectory of the movement of the lower surface of the inkjet head 2a traces the surface of the printing target 500.

[0040] Since height information must be obtained before ink is ejected, the height information detectors 121, 131 must be located ahead of the inkjet head 2a in the direction of travel. In this embodiment, it is assumed that the inkjet head 2a prints while reciprocating in the X-axis direction, and therefore the height information detectors 121, 131 are provided at both ends of the inkjet head 2a in the X-axis direction. If printing is performed only in either the positive or negative direction in the X-axis direction, it is sufficient to provide the height information detectors 121, 131 only on the side in the direction of travel. Furthermore, since the inkjet head 2a repeatedly moves back and forth in the X-axis direction and in the Y-axis direction during printing, if adjustments are also made to the inkjet head 2a when moving in the Y-axis direction, a height information detector may also be provided in the direction of travel in the Y-axis direction.

[0041] 3A to 3C are diagrams illustrating an example of a problem and solution that may occur when using the height information detection unit in the discharge device according to this embodiment. While the explanation in FIGS. 3A to 3C focuses on the height information detection unit 131 and the printing target surface 500, the same applies to the height information detection unit 121 and the printing target surface 500. As shown in FIG. 3A, when the printing target surface 500 is not flat and has a hole 700, and the height information detection unit 131 emits energy bodies 101 toward the printing target surface 500 and detects gaps at successive times, it is preferable that the printing target surface 500 be recognized as an ideal printing target surface 600 (dotted line area).

[0042] 3B, if the area of ​​the energy body 101 is smaller than that of the hole 700, the energy body 101 may reach deep into the hole 700, and the height information detection unit 131 may detect a value greater than the gap to the ideal printing surface 600. Furthermore, if the hole 700 is connected to an internal cavity or the like, it may not be possible to detect the gap at all.

[0043] To solve this problem, as shown in Figure 3C, an energy body 102 with an area larger than the hole 700 is used. This prevents the energy body 102 from penetrating deep into the hole 700, and because height information is determined from a wide area, it becomes possible to recognize the surface 600 as an ideal printing target when gaps are detected over a continuous period of time.

[0044] 4A to 4C are diagrams illustrating an example of an energy body emitted by a height information detection unit of a discharge device according to this embodiment. In FIG. 4A, the vertical axis represents the detection sensitivity of the height information detection units 121 and 131, and the horizontal axis represents the position coordinates of the detection range of the height information detection units 121 and 131. In FIGS. 4B and 4C, the vertical axis represents the detection result of height information, and the horizontal axis represents the position coordinates of the detection range of the height information detection units 121 and 131. FIG. 4A shows an example of an energy body 101 emitted by the height information detection units 121 and 131. The shape of the detection range 110 of the energy body 101 is not limited to a perfect circle. However, here, if the detection range 110 is a circle with a radius R, the gap detection sensitivity of the height information detection units 121 and 131 has the characteristic of being highest at the center O of the detection range 110 (position coordinate: 0) and lowest at the ends of the detection range 110 (position coordinate: ±R). When such height information detection units 121, 131 are used, the correction unit 200c can determine one piece of height information for the circular detection range 110 of radius R. Furthermore, since the detection range 110 of diameter 2R is sufficiently larger than the diameter of the hole 700 shown in FIG. 3A, even if the hole 700 is present on the printing surface 500, the detection of the height information is less affected. If the detection sensitivity shown in FIG. 4A has constant characteristics independent of position, the correction unit 200c may obtain the average value of the height information within the detection range 110.

[0045] 4B, if the detection range 110 of the energy body 101 is a circle with a radius R and height information detection units 121, 131 capable of acquiring the distribution of height information within the detection range 110 are used, height information obtained by dividing the circle with radius R into multiple points can be obtained. The correction unit 200c may simply average these pieces of height information, or may perform processing such as weighting with a normal distribution as shown in FIG. 4A, or excluding values ​​above a certain threshold as abnormal values. In other words, it is sufficient to determine one piece of height information for the detection range 110 regardless of the means.

[0046] FIG. 4C is a diagram illustrating an application example when using the means of FIG. 4B. By obtaining height information divided into multiple locations, a representative value such as an average value can be determined. The amount of movement of inkjet head 2a in the Z-axis direction is determined by the representative value, but there is variation in the height information within detection range 110. For example, compared to the representative value, the nozzle at position (a) (nozzle of inkjet head 2a) is taller, and the nozzle at position (b) is shorter.

[0047] As a result, the distance from inkjet head 2a to the printing surface 500 is close at the position indicated by symbol (a) and far away at the position indicated by symbol (b), so if ink is ejected at the same timing, the ink will land on the printing surface 500 earlier at the position indicated by symbol (a) and later at the position indicated by symbol (b). To align this landing timing, correction unit 200c corrects the ejection timing to be later than the representative value at the position indicated by symbol (a) and earlier than the representative value at the position indicated by symbol (b). The correction value may be determined by comparing it with the representative value of the height information.

[0048] That is, the correction unit 200c may determine a single representative value for the height information detected within the detection range of the energy body. This allows height information to be obtained from a detection range wider than the irregularities, grooves, and holes on the printing target surface 500, making it less likely for detection errors to occur due to the irregularities, grooves, and holes. Furthermore, if the correction unit 200c can obtain a distribution of height information within the detection range of the height information detection units 121 and 131, it may determine a correction value for the ejection (landing) timing based on the error in the height information compared to the representative value. This makes it possible to reduce the deviation in the landing position within the detection range when the distribution of height information within the detection range of the height information detection units 121 and 131 can be obtained.

[0049] 5A to 5F are diagrams illustrating an example of a method for correcting height information to match the absorption characteristics of the energy body of the printing target in the ejection device according to this embodiment. In FIGS. 5B to 5F, the vertical axis represents height information (measured distance) detected by the height information detection units 121 and 131. FIG. 5A shows an example in which height information needs to be corrected to match the absorption characteristics of the energy body 102 of the printing target. The printing target shown in FIG. 5A represents a porous body, for example, and includes irregularities, grooves, holes 700, and voids 800 connected to them. In such a structure, even if an energy body 102 with an area larger than the hole 700 is emitted from the height information detection unit 131, it is absorbed, and a value greater than the ideal distance to the printing target surface 600 may be detected. Therefore, it is necessary to acquire the absorption characteristics of the energy body 102 of the printing target and determine a correction value for the height information.

[0050] 5B shows an example in which the error in the height information monotonically increases with the measurement distance. In this case, the correction unit 200c simply sets the correction value for the height information (height information correction value) in accordance with the absorption characteristics of the energy body 102 so as to eliminate the error in the height information. Also, as shown in FIG. 5C, there may be cases in which the error in the height information does not change depending on the measurement distance and the height information correction value remains constant. That is, the error in the height information may be calculated using a function that uses a correction constant that is constant or that uses the measurement distance as a variable, regardless of the measurement distance of the height information by the height information detection units 121 and 131.

[0051] 5D shows an example in which the absorption characteristics of the energy body 102 are linear with respect to the measured distance. For example, if the absorption characteristics of the energy body 102 are a straight line of y = 0.01·x, and the distance (height information) detected by the height information detection unit 131 is 100 mm, the height information correction value is 1 mm, so the correction unit 200c subtracts 1 mm from the height information to obtain an actual gap of 99 mm. The value of a in FIG. 5D is a correction constant that determines how strong the correction is when the measured distance is a variable.

[0052] 5E shows an example in which the absorption characteristics of the energy body 102 are nonlinear with respect to the measured distance. For example, if the absorption characteristics of the energy body 102 are a quadratic function of y = 0.0001·x^2, when the distance (height information) detected by the height information detection unit 131 is 100 mm, the height information correction value is 1 mm, so the correction unit 200c subtracts 1 mm from the height information to obtain the actual distance of 99 mm. The value a in FIG. 5E is also a correction constant that determines how strongly to correct when the measured distance is a variable.

[0053] 5F shows an example in which the absorption characteristics of the energy body 102 increase monotonically but do not pass through the origin. Some height information detection units 131 cannot measure height information up to a certain measurement distance d (>0), but even in such cases, the absorption characteristics of the energy body 102 can be applied to measurement distances d and above. When the height information correction value is a function that uses the measurement distance as a variable, the function does not need to pass through the origin.

[0054] To obtain a height information correction value for a measured distance, for example, the height information measured by the height information detection unit 131 that emits an energy body 102 having a wide area of ​​the detection range 110 can be compared with the true height information to measure the error. To obtain the true height information, the following methods (1) to (4) can be used. (1) An energy body 102 that is not absorbed by the printing object is used. (2) A small-area energy body 101 is used to trace the surface of the printing object, and abnormal measurement values ​​that appear to be holes are excluded, and the remaining measurement points are smoothed and converted into data. (3) Take a photo with a camera and process the image. (4) A height information detection unit is used that comes into contact with the printing object to obtain height information.

[0055] FIG. 6 is a diagram illustrating an example of the relationship between the correction constant a of the absorption characteristics of the energy body in the discharge device according to this embodiment and the structural value of the printing object. In FIG. 6, the vertical axis represents the correction constant, and the horizontal axis represents the structural value of the printing object. In FIGS. 5A to 5F, when the height information correction value is a function with the measurement distance as a variable, the correction constant a is used as the correction strength. This correction constant a may have a monotonically increasing relationship with the structural value of the printing object as a variable. Specifically, when the printing object is a porous body, physical values ​​such as the hole area ratio and the grain size of the material can be called the structural value of the printing object. The higher this structural value, the stronger the absorption characteristics of the energy body 102 and the higher the correction strength must be. Therefore, as shown in FIG. 6, the correction constant a may monotonically increase with the structural value of the printing object as a variable. This allows the correction constant and height information correction value to be calculated from the structural value of the printing object.

[0056] 7 is a diagram for explaining an example of the flow of printing processing in the X-axis direction in the discharge device according to this embodiment. For simplicity, a case where printing operation is performed in the X-axis direction will be considered here.

[0057] First, the user selects whether or not to adjust the gap (Step S1). If gap adjustment is not required (Step S1: No), the gap adjustment mode is turned OFF (Step S2). The inkjet head 2a moves to its initial position in the Z-axis direction (Step S3). This initial position in the Z-axis direction remains fixed until the end of the printing operation.

[0058] When the printing operation starts (step S4), the inkjet head 2a prints while moving in the X-axis direction by an amount Δx (step S5). The inkjet head 2a repeats step S5 until it reaches the end of the printing range in the X-axis direction (step S6).

[0059] If gap adjustment is to be performed (step S1: Yes), the gap adjustment mode is turned ON (step S7). Next, the central control unit 200 determines the printing object (step S8). Next, the central control unit 200 sets the target gap r and a correction function for height information before the printing operation (step S9). The inkjet head 2a moves to an initial position in the Z-axis direction that corresponds to the target gap r (step S10). When the printing operation starts (step S11), the inkjet head 2a prints while moving in the X-axis direction by a movement amount Δx (step S12).

[0060] When the inkjet head 2a moves by the amount Δx in the X-axis direction, the height information changes. Therefore, the height information detection units 121, 131 detect the height information z at this time, and the central control unit 200 calculates the height information correction value c using a height information correction function to obtain the true height information z' = zc (step S13). The central control unit 200 then obtains the gap error e = r - z' and calculates the amount of movement Δz in the z-axis direction. This calculation is preferably performed using feedback control such as PI control or PID control. Once the amount of movement Δz in the z-axis direction is determined, the inkjet head 2a moves by Δz in the Z-axis direction (step S14). The ejection device then repeats steps S12 to S14 until it reaches the end of the printing range in the X-axis direction (step S15).

[0061] FIG. 8 is a diagram illustrating an example of the timing of the printing operation in the ejection device according to this embodiment. In this embodiment, immediately after ejecting ink and detecting height information, the central control unit 200 starts moving the inkjet head 2a in the X-axis direction by an amount Δx and calculating the amount of movement Δz in the Z-axis direction. After calculating the amount of movement Δz, the central control unit 200 moves the inkjet head 2a in the Z-axis direction by an amount Δz, ejecting ink, and detecting height information. The central control unit 200 repeats this sequence. In other words, while the ejection device moves by an amount Δx in the X-axis direction, it must complete the following: ejecting ink, detecting height information, calculating the amount of movement Δz in the Z-axis direction, and moving by the amount Δz in the Z-axis direction.

[0062] FIG. 9 is a diagram illustrating an example of a preferable positional relationship between the inkjet head and the height information detection unit in the ejection device according to this embodiment. In FIG. 9, the movement distance between point P at a certain time and point P' at the next time is assumed to be Δx. The width of the print area 900 printed by the head array provided on the inkjet head 2a is assumed to be W, and the distance between the center positions of the inkjet head 2a and the height information detection units 121 and 131 is assumed to be L. The central control unit 200 detects the height information at point P at a certain time and simultaneously ejects ink. When printing a large-area image, it is desirable to arrange the print area 900 so that there are no seams, and therefore it is desirable that the edge of the print area 900 at a certain time P and the edge of the print area 900 at the next time P' coincide with each other.

[0063] Furthermore, it is desirable that the central control unit 200 adjusts the gap based on the height information at point P, and ejects ink when the center of the inkjet head 2a coincides with the next point P'. An example of the simplest positional relationship that satisfies these conditions is W=L=Δx. Note that the height information detection units 121, 131 may acquire height information not in the vicinity of the inkjet head 2a but at a sufficient distance from the inkjet head 2a. In this case, it is desirable that L be an integer multiple of W. Therefore, L=N·W=N·Δx (N is an integer).

[0064] That is, the center-to-center distance between the inkjet head 2a and the height information detection units 121, 131 may be an integer multiple of the width of the printing area of ​​the inkjet head 2a. This allows ink to be ejected when the center of the inkjet head 2a coincides with the position where the height information was measured in advance, and allows the printing area to be arranged seamlessly to print on a large area.

[0065] As described above, according to the ejection device of this embodiment, the energy body 102 emitted from the height information detection units 121, 131 is irradiated onto a detection area larger than the irregularities, grooves, holes, etc. present on the printing surface 500 to obtain height information, so detection errors in the height information due to irregularities, grooves, holes, etc. are less likely to occur, and the printing object is identified and corrections made to the obtained height information in accordance with the absorption characteristics of the energy body 102, so that when irregularities, grooves, holes, etc. are present on the printing surface 500, errors in the height information can be reduced.

[0066] The program executed by the discharge device of this embodiment is provided by being pre-installed in a ROM (Read Only Memory) etc. The program executed by the discharge device of this embodiment may be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk).

[0067] Furthermore, the program executed by the discharge device of this embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Also, the program executed by the discharge device of this embodiment may be provided or distributed via a network such as the Internet.

[0068] The program executed by the discharge device of this embodiment has a modular structure including the above-mentioned units (control unit 200a, discrimination unit 200b, correction unit 200c), and in actual hardware, an example of a processor such as a CPU (Central Processing Unit) reads and executes the program from the ROM, thereby loading the above-mentioned units onto the main memory, and the control unit 200a, discrimination unit 200b, and correction unit 200c are generated on the main memory.

[0069] For example, aspects of the present invention are as follows. <1> a head that ejects liquid onto a printing surface of a printing object; an actuator that can move the head in at least the Z-axis direction; a height information detection unit that detects height information indicating the distance between the head and the printing surface by emitting an energy body having an area larger than the shape change of the surface present on the printing surface; a control unit that controls the head based on the height information detected by the height information detection unit so that the distance between the printing surface and the head falls within a set range; a determination unit that determines the state of the printing surface; a correction unit that corrects an error in the height information according to the characteristics of the printing object that absorbs the energy body, including the determined state; A discharge device comprising: <2> The actuator moves in either or both of an X-axis direction and a Y-axis direction. <1> The discharge device according to claim 1. <3> The height information is determined to be one representative value within the detection range of the energy body. <1> or <2> The discharge device according to claim 1. <4> The error in the height information is calculated by a function using a correction constant when the measurement distance is a variable or is constant, regardless of the height information detected by the height information detection unit. <1> from <3> 10. The discharge device according to claim 9, wherein <5> the correction constant monotonically increases with the structural value of the printing object as a variable; <4> The discharge device according to claim 1. <6> When the distribution of the height information can be acquired within the detection range of the height information detection unit, a correction value for the ejection timing is determined based on an error of the height information compared with the representative value. <3> The discharge device according to claim 1. <7> the center-to-center distance between the head and the height information detection unit is an integer multiple of the width of the printing area of ​​the head; <1> from <6> 10. The discharge device according to claim 9, wherein <8> A discharge method performed by a discharge device including a head that discharges a liquid onto a printing surface of a printing object, an actuator that can move the head in at least the Z-axis direction, and a height information detection unit that detects height information indicating a distance between the head and the printing surface by firing an energy body having an area larger than a shape change of a surface existing on the printing surface, controlling the head based on the height information detected by the height information detection unit so that the distance between the printing surface and the head is within a set range; determining the condition of the printing surface; correcting an error in the height information according to the energy absorption characteristics of the printing object, including the determined state; A discharge method comprising: <9> a computer that controls a discharge device that includes a head that discharges a liquid onto a printing surface of a printing object, an actuator that can move the head in at least the Z-axis direction, and a height information detection unit that detects height information that indicates the distance between the head and the printing surface by firing an energy body that has an area larger than the shape change of the surface that exists on the printing surface; a control unit that controls the head based on the height information detected by the height information detection unit so that the distance between the printing surface and the head falls within a set range; a determination unit that determines the state of the printing surface; a correction unit that corrects an error in the height information according to the characteristics of the printing object that absorbs the energy body, including the determined state; A program to make it function as such. [Explanation of symbols]

[0070] 1 Discharge device 2a inkjet head 113 Z-axis actuator 121,131 Height information detection unit 200 Central Control Unit 200a control unit 200b Discrimination part 200c correction section 202 memory [Prior art documents] [Patent documents]

[0071] [Patent Document 1] Japanese Patent Application Publication No. 2019-171856

Claims

1. a head that ejects liquid onto a printing surface of a printing object; an actuator capable of moving the head in at least the Z-axis direction; a height information detection unit that detects height information indicating the distance between the head and the printing surface by emitting an energy body having an area larger than the shape change of the surface present on the printing surface; a control unit that controls the head based on the height information detected by the height information detection unit so that the distance between the printing surface and the head falls within a set range; a determination unit that determines the state of the printing surface; a correction unit that corrects an error in the height information according to the energy absorption characteristics of the printing object, including the determined state; A discharge device comprising:

2. The discharge device according to claim 1 , wherein the actuator moves in either or both of an X-axis direction and a Y-axis direction.

3. The discharge device according to claim 1 or 2, wherein the height information is determined to have one representative value within the detection range of the energy body.

4. The discharge device according to claim 1 or 2, wherein the error in the height information is calculated by a function using a correction constant that is constant or that uses a measurement distance as a variable, regardless of the height information detected by the height information detection unit.

5. The ejection device according to claim 4 , wherein the correction constant monotonically increases with a structural value of the printing object as a variable.

6. The ejection device according to claim 3 , wherein when a distribution of the height information can be obtained within the detection range of the height information detection unit, a correction value for the ejection timing is determined from an error of the height information compared with the representative value.

7. The ejection device according to claim 1 or 2, wherein the center-to-center distance between the head and the height information detection unit is an integral multiple of the width of the printing area of ​​the head.

8. A discharge method carried out by a discharge device including a head that discharges a liquid onto a print target surface of a print target, an actuator that can move the head in at least the Z-axis direction, and a height information detection unit that detects height information indicating a distance between the head and the print target surface by firing an energy body having an area larger than a shape change of a surface existing on the print target surface, controlling the head based on the height information detected by the height information detection unit so that the distance between the printing surface and the head is within a set range; determining the condition of the printing surface; correcting an error in the height information according to the energy absorption characteristics of the printing object, including the determined state; A discharge method comprising:

9. a computer that controls a discharge device that includes a head that discharges a liquid onto a printing surface of a printing object, an actuator that can move the head in at least the Z-axis direction, and a height information detection unit that detects height information that indicates the distance between the head and the printing surface by firing an energy body that has an area larger than the shape change of a surface that exists on the printing surface; a control unit that controls the head based on the height information detected by the height information detection unit so that the distance between the printing surface and the head falls within a set range; a determination unit that determines the state of the printing surface; a correction unit that corrects an error in the height information according to the energy absorption characteristics of the printing object, including the determined state; A program to make it function as such.

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