JP2017132075A - Inkjet printing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inkjet printing device that can reduce deterioration in printing image quality.SOLUTION: A control part controls a lifting drive part 7 to lift up/down a rotation shaft while controlling a head position adjusting mechanism 9 to extend and shorten a gap distance, and controls a rotation drive part 8 to rotate an inkjet head 41 depending on irregularity of a surface of a printing medium 15 detected by a distance sensor 25 during movement of the inkjet head 41 in a primary scanning direction.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an inkjet printing apparatus that prints by ejecting ink from an inkjet head.

  2. Related Art Inkjet printing apparatuses that perform printing by ejecting ink from nozzles onto a print medium while moving an inkjet head having a plurality of nozzles are known. In such an ink jet printing apparatus, printing may be performed on a print medium having unevenness on the surface. Conventionally, a technique has been proposed in which the height of an inkjet head is adjusted according to the thickness of a print medium to reduce fluctuations in the head gap (for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 7-117306

  However, while the unevenness on the surface of the printing medium has a three-dimensional change, in the technique disclosed in Patent Document 1 described above, the relative position between the inkjet head and the surface of the printing medium is variable only in the vertical direction. It was difficult to make it completely follow. That is, for the three-dimensional unevenness, the distance from the nozzle to the printing medium (gap distance) varies for each individual nozzle, so that a nozzle with an inappropriate gap distance may be generated only by vertical position control. there were. If the head gap is partially inappropriate, bleeding or rubbing occurs, which may cause deterioration in print image quality.

  The present invention has been made in view of the above. The nozzle surface of the inkjet head is made to follow the unevenness of the surface of the printing medium, and the head gap is partially improperly avoided to reduce the deterioration of the print image quality. An object of the present invention is to provide an ink jet printing apparatus that can be used.

  In order to achieve the above object, a first feature of an ink jet printing apparatus according to the present invention is that an ink jet head having a plurality of nozzles arranged along the sub-scanning direction and the ink jet head orthogonal to the sub-scanning direction. A main scanning drive unit that moves in a scanning direction; a detection unit that detects irregularities on the surface of the print medium; a rotation driving unit that rotates the inkjet head around a rotation axis parallel to the sub-scanning direction; A control unit that controls the ink jet head to eject the ink from the nozzle to the print medium and print an image on the print medium while moving the ink jet head in the main scan direction by the main scan driving unit, and the control unit includes the ink jet The rotation drive unit according to the unevenness of the surface of the print medium detected by the detection unit during movement of the head in the main scanning direction Thus in possible to eject ink at a predetermined timing while rotating the ink jet head.

  A second feature of the ink jet printing apparatus according to the present invention is further provided with an adjustment unit that adjusts a distance between the ink jet head and the surface of the print medium, and the control unit adjusts the angle of the ink jet head with respect to the surface of the print medium. Accordingly, the adjustment control of the distance is performed by the adjustment unit.

  A third feature of the ink jet printing apparatus according to the present invention is that the adjusting unit moves the rotating shaft up and down to adjust the distance from the print medium surface to the rotating shaft, the ink jet head, It is provided with at least one of a head position adjusting mechanism that expands and contracts a gap distance with the print medium surface.

  A fourth feature of the ink jet printing apparatus according to the present invention is that the control unit controls the ejection timing of the ink by the ink jet head in accordance with the distance, angle, and relative speed of the ink jet head with respect to the print medium surface. There is to do.

  According to the first feature of the inkjet printing apparatus according to the present invention, the control unit rotates the inkjet head by the rotation drive unit at a predetermined timing according to the unevenness of the surface of the print medium detected by the detection unit. Ink is ejected. Accordingly, the nozzle surface can be made parallel to the unevenness of the print medium by rotating and tilting the inkjet head while maintaining the gap distance, and for all nozzles on the nozzle surface, from the nozzle to the print medium. The distance (gap distance) can be made constant, the occurrence of a portion where the gap distance is not appropriate is reduced, and the deterioration of the print image quality due to bleeding or rubbing can be avoided.

  According to the second feature of the ink jet printing apparatus according to the present invention, the adjustment unit adjusts the distance between the ink jet head and the surface of the print medium, so that the ink jet head follows the unevenness of the surface of the print medium. As a result, it is possible to avoid the end portion of the ink jet head from coming into contact with the print medium, and it is possible to avoid damage to the ink jet head and contamination of the print medium. The adjustment unit adjusts the distance between the inkjet head and the surface of the print medium, for example, based on a reference plane calculated by leveling the surface of the print medium having irregularities or an average height position of the entire print medium. It moves up and down in the vertical direction with respect to the obtained virtual plane.

  According to the third feature of the ink jet printing apparatus according to the present invention, the control unit rotates the ink jet head when the shaft is moved up and down by the lift drive unit according to the angle of the ink jet head with respect to the print medium surface. In this state, the entire rotary shaft can be moved up and down, the configuration from the rotary shaft to the inkjet head can be simplified, and when the gap distance is expanded and contracted by the head position adjusting mechanism, the surface closer to the print medium surface. Adjustment in position is possible. In addition, when both the elevation drive unit and the head position adjustment mechanism are provided, the apparatus configuration and operation control can be diversified.

  According to the fourth feature of the ink jet printing apparatus according to the present invention, the control unit controls the ink discharge timing of the ink jet head according to the distance, angle and relative speed of the ink jet head with respect to the print medium surface. The deviation in the landing position caused by tilting the head can be corrected by controlling the ejection timing. If the discharge timing is corrected and the discharge frequency limit of the inkjet head is exceeded, for example, it becomes impossible to discharge, and the distance between the head rotation axis and the media is further adjusted to enable discharge. Can do.

1 is a perspective view illustrating a schematic configuration of an inkjet printing apparatus according to an embodiment. It is a principal part perspective view of the shuttle unit in the inkjet printing apparatus shown in FIG. It is a control block diagram of the inkjet printing apparatus shown in FIG. It is the schematic of the nozzle surface of the inkjet head in the inkjet printing apparatus shown in FIG. It is explanatory drawing which shows a rotation drive part, a raising / lowering drive part, and a head position adjustment mechanism from a side surface. It is explanatory drawing which shows the state of the head gap before control from a side surface. It is explanatory drawing which shows the state of the head gap after control from the side. It is a side view which shows the rotation angle of an inkjet head, and the distance from a medium to a rotating shaft. It is explanatory drawing which shows the change of the discharge timing at the time of rotating the inkjet head which concerns on embodiment. 2 is a flowchart for explaining the operation of the inkjet printing apparatus shown in FIG. 1.

  Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same or equivalent parts and components are denoted by the same or equivalent reference numerals.

  The following embodiments exemplify devices for embodying the technical idea of the present invention, and the technical idea of the present invention is the material, shape, structure, arrangement, etc. of each component. Is not specified as follows. The technical idea of the present invention can be variously modified within the scope of the claims.

(Configuration of inkjet printer)
FIG. 1 is a perspective view showing a schematic configuration of an ink jet printing apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view of main parts of the shuttle unit in the ink jet printing apparatus shown in FIG. FIG. 3 is a control block diagram of the inkjet printing apparatus shown in FIG. FIG. 4 is a schematic view of the nozzle surface of the ink jet head in the ink jet printing apparatus shown in FIG. In the following description, the vertical and horizontal directions indicated by the arrows in FIG.

  As shown in FIGS. 1 and 3, the inkjet printing apparatus 1 according to the present embodiment includes a shuttle base unit 2, a flat bed unit 3, a shuttle unit 4, a storage unit 5, and a control unit 6. .

  The shuttle base unit 2 supports the shuttle unit 4 and moves the shuttle unit 4 in the front-rear direction (sub-scanning direction). The shuttle base unit 2 includes a gantry 11 and a sub-scanning drive motor 12.

The gantry 11 supports the shuttle unit 4. The gantry 11 is formed in a rectangular frame shape. Sub-scanning drive guides 13A and 13B extending in the front-rear direction are formed on the left and right frames of the gantry unit 11, respectively. The sub-scanning drive guides 13A and 13B guide the shuttle unit 4 that moves in the front-rear direction.
The sub-scanning drive motor 12 moves the shuttle unit 4 in the front-rear direction.

  The flat bed unit 3 holds a print medium 15 made of a building material or the like. The flat bed unit 3 is disposed inside the gantry 11 of the shuttle base unit 2. The flat bed unit 3 has a medium placement surface 3a that is a horizontal surface on which the print medium 15 is placed. The flat bed unit 3 can adjust the height of the medium placement surface 3a by an elevating mechanism such as a hydraulic drive mechanism.

  The shuttle unit 4 prints an image on the print medium 15. As shown in FIGS. 1 to 3, the shuttle unit 4 includes a housing 21, a main scanning drive unit 22, a head unit 24, a distance sensor 25, a rotation drive unit 8, a lift drive unit 7, and a head. And a position adjusting mechanism 9.

  The casing 21 holds each part such as the head unit 24. The casing 21 is formed in a gate shape straddling the flat bed unit 3 in the left-right direction. The left and right legs 26A and 26B of the housing 21 are supported by the gantry 11 of the shuttle base unit 2 and are movable along the sub-scanning drive guides 13A and 13B. The horizontal portion 27 between the leg portions 26A and 26B of the housing 21 is opened at the lower side in order to eject ink from the head unit 24 to the print medium 15.

  The main scanning drive unit 22 moves the main scanning movement table 71 in the left-right direction when moving the head unit 24 in the main scanning direction orthogonal to the sub-scanning direction. The main scanning driving unit 22 includes a driving belt 31, a pair of pulleys 32 </ b> A and 32 </ b> B, a main scanning driving motor 33, and a main scanning driving guide 34.

The drive belt 31 moves the main scanning movement table 71 by rotating around. The drive belt 31 is stretched between the pulleys 32A and 32B.
The pulleys 32A and 32B support the drive belt 31 and move the drive belt 31 around. The pulleys 32A and 32B are rotatably supported on the rear wall of the housing 21. The pulleys 32A and 32B are spaced apart from each other in the left-right direction and are arranged at the same height. The pulley 32 </ b> B is connected to the output shaft of the main scanning drive motor 33, and transmits the rotational driving force of the main scanning drive motor 33 to the drive belt 31.
The main scanning drive motor 33 rotates the pulley 32B to move the drive belt 31 around.

  The main scanning drive guide 34 guides the main scanning movement table 71 to move along the left-right direction. The main scanning drive guide 34 is formed in a long shape extending in the left-right direction. The main scanning drive guide 34 is installed on the rear wall of the casing 21.

  The head unit 24 prints an image by ejecting ink onto the print medium 15 while moving in the left-right direction. The head unit 24 is mounted on the main scanning movement table 71 and moves in the left-right direction together with the main scanning movement table 71. The head unit 24 includes four inkjet heads 41.

  The four inkjet heads 41 are arranged in parallel in the left-right direction. As shown in FIG. 4, the inkjet head 41 has a plurality of nozzles 43 arranged at a predetermined pitch along the sub-scanning direction that open to a nozzle surface 41 a that is the lower surface thereof, and print ink from the nozzles 43. 15 is discharged. The four inkjet heads 41 eject inks of different colors (for example, cyan, black, magenta, and yellow).

  The head position adjusting mechanism 9 adjusts the distance r from the rotary shaft 82 to the print medium surface in order to expand and contract the gap distance d in order to secure the gap distance d between the inkjet head 41 and the print medium 15 surface. This is a mechanism as a unit, and includes a base 91, a driving force transmission unit 92, and a vertical movement driving motor 93.

  The base 91 is a table on which the head unit 24 is mounted. The base 91 is connected to the rotation drive unit 8 as shown in FIG. The vertical drive motor 93 is a motor connected to the driving force transmission unit 92 and generates a driving force. The vertical movement drive motor 93 is composed of, for example, an ultrasonic motor. The driving force transmission unit 92 is a rack and pinion member that converts the rotational driving force of the vertical movement drive motor 93 into vertical movement. When the driving force transmitting unit 92 transmits the driving force, the head position adjusting mechanism 9 moves the head unit 24 up and down with respect to the rotational driving unit 8 to expand and contract the distance r from the rotating shaft 82 to the surface of the printing medium, and thereby the inkjet. The gap distance d between the head 41 and the surface of the print medium 15 is expanded or contracted.

  The rotation drive unit 8 is a drive unit that rotates the inkjet head 41, and includes a base 81, a rotation shaft 82, and a rotation drive motor 83. The base 81 has a disk shape, is connected to the base 91 of the head position adjusting mechanism 9, and can move up and down. The rotation shaft 82 is an axis parallel to the sub-scanning direction, is fixed to the center of the base 81, and rotates the base 81 about the rotation shaft 82. The rotational drive motor 83 is a motor that generates a rotational force, and transmits the rotational force to the base 91 via the rotational shaft 82. The rotation drive motor 83 is composed of, for example, an ultrasonic motor.

  The elevation drive unit 7 is a drive mechanism that raises and lowers the rotation shaft 82 of the rotation drive unit 8, and acts as an adjustment unit that adjusts the distance between the surface of the print medium 15 and the inkjet head 41 by the operation of raising and lowering the rotation shaft 82. . The elevation drive unit 7 includes a main scanning movement table 71, a vertical movement drive motor 73, and a drive force transmission unit 72. The main scanning movement table 71 is fixed to the driving belt 31 and moves in the left-right direction along the main scanning driving guide 34 by the circumferential movement of the driving belt 31. The vertical drive motor 73 is a motor connected to the driving force transmission unit 72 and generates a driving force. The vertical movement drive motor 73 is composed of, for example, an ultrasonic motor. The driving force transmission unit 72 is a rack and pinion member that converts the rotational driving force of the vertical movement driving motor 73 into vertical movement, and is connected to the rotational driving unit 8.

  When the driving force of the vertical drive motor 73 is transmitted to the driving force transmission unit 72, the driving force transmission unit 72 raises and lowers the base 81 of the rotation driving unit 8 in the vertical direction. As a result, the rotary shaft 82 is raised and lowered along the vertical direction R, and the distance r from the surface of the print medium 15 to the rotary shaft 82 is corrected. In addition, the raising / lowering of the rotating shaft 82 by this raising / lowering drive part 7 is the virtual surface obtained on the basis of the reference plane AL calculated by leveling the unevenness | corrugation of the printing medium surface, ie, the average height position of the whole printing medium, for example. Up and down along a vertical direction R perpendicular to a flat surface.

  The distance sensor 25 is a detection unit that detects irregularities on the surface of the print medium 15. The distance sensor 25 is mounted in the head unit 24, is formed in a long shape extending in the left-right direction, and is longer than the entire width in the left-right direction of the print medium 15. Thereby, the distance sensor 25 can measure the surface height of the entire print medium 15. The distance sensor 25 is installed on the rear wall of the housing 21. The distance sensor 25 is composed of, for example, a laser displacement sensor. The distance sensor 25 may be configured to be fixed on the front side in the moving direction (main scanning direction) of the head unit 24 and move in the left-right direction together with the head unit 24. Further, when the head unit 24 can eject both in the forward path and in the backward path, the distance sensor 25 is installed one at each end in the direction in which the head unit 24 moves (main scanning direction), and main scanning is performed together with the head unit 24. The structure which can be moved to a direction may be sufficient. Thereby, the distance sensor 25 can measure the surface height of the printing medium 15 in the upstream side of the inkjet unit, that is, the printing area to be printed next.

  The storage unit 5 stores a control profile. The control profile is used in print processing described later. The control profile includes the degree of expansion / contraction of the gap distance d by the head position adjusting mechanism 9 according to the unevenness of the surface of the print medium 15, the elevation distance of the rotary shaft 82 by the elevation drive unit 7, and the rotation of the inkjet head 41 by the rotation drive unit 8. This is data indicating the moving angle, the ejection timing of the inkjet head 41, and the like. Here, the ink ejection speed of each nozzle 43 has manufacturing variations even in the same inkjet head 41. The ink ejection speed of each nozzle 43 in the control profile is measured in advance. The storage unit 5 includes an HDD (Hard Disk Drive) or the like.

  The control unit 6 is an arithmetic processing unit that controls the operation of each unit of the inkjet printing apparatus 1, and is built in the inkjet printing apparatus 1 or connected to an external personal computer or programmable logic controller (PLC: programmable logic controller). It can be realized by a dedicated control device such as a CPU, a RAM, a ROM, and the like, and is provided with a communication function as required.

  The control unit 6 performs printing for one pass by ejecting ink from the inkjet head 41 to the printing medium 15 while moving the inkjet head 41 in the main scanning direction, and then moves the shuttle unit 4 in the sub-scanning direction. The controller 6 prints an image on the print medium 15 by alternately repeating the printing operation for one pass and the movement of the shuttle unit 4.

  The controller 6 is driven to move up and down while expanding and contracting the gap distance d by the head position adjusting mechanism 9 according to the unevenness of the surface of the print medium 15 detected by the distance sensor 25 during the movement of the inkjet head 41 in the main scanning direction. The rotating shaft 82 is moved up and down by the unit 7, and the inkjet head 41 is rotated by the rotation driving unit 8. Here, the gap distance d is a distance between the inkjet head 41 (nozzle surface 41a) and the surface of the print medium 15 (head gap).

  The printing control by the control unit 6 will be described in detail. FIG. 6 is an explanatory view showing the state of the head gap before the control from the side, and FIG. 7 is an explanatory view showing the state of the head gap after the control from the side. FIG. 8 is a side view showing the rotation angle θ of the head and the distance r from the medium to the rotation axis according to the present embodiment. FIG. 9 is an explanatory diagram showing a change in ejection timing when the inkjet head according to the present embodiment is rotated.

  As shown in FIG. 6, the inkjet printing apparatus 1 may print a print medium 15 having a surface with irregularities. In the area A1 in FIG. 6, K is an appropriate gap distance, but the head gap is widened at positions such as Y and M. When such a print medium 15 is printed, ink landing deviation occurs due to the head gap being different from the surroundings, and print quality degradation due to streaks or unevenness is conspicuous with respect to a printed image when there is no ink landing deviation. Cheap. Therefore, for such a type of print medium 15, a print process that can reduce the landing deviation of the ink is performed as compared with the normal print process.

  In this printing process, first, as shown in FIG. 7, during the movement in the main scanning direction of the inkjet head 41 in the printing operation for one pass, the rotation drive unit 8 performs inkjet according to the unevenness of the surface of the print medium 15. The head 41 is rotated. By rotating and tilting the inkjet head 41, the surface of the nozzle 43 can be made parallel to the unevenness of the print medium 15, and the gap distance d can be maintained. The rotation angle θ of the rotation drive unit 8 is calculated from the average height of the print medium detected by the distance sensor 25.

  At this time, as a result of the control unit 6 following the ejection surface of the inkjet head 41 so as to be parallel to the unevenness of the surface of the print medium 15, the end of the inkjet head 41 is in a position where it contacts the print medium 15. In this case, according to the angle of the inkjet head 41 with respect to the surface of the print medium 15, the inkjet head 41 is moved up and down in a predetermined direction by at least one of the head position adjusting mechanism 9 and the lift drive unit 7, and the print medium 15 and the inkjet medium. Control to adjust the distance from the head 41 is performed.

By the way, if the inkjet head 41 is rotated to be parallel to the unevenness of the print medium 15, there is a problem that the landing position is shifted. Therefore, the control unit 6 controls the ejection timing of ink by the inkjet head 41 according to the distance, angle, and relative speed of the inkjet head 41 with respect to the surface of the print medium 15. Specifically, as shown in FIG. 8, the control unit 6 sets the distance from the rotation shaft 82 to the printing medium as r, the head angle as θ, the ink ejection timing correction value as t, and the moving speed of the head unit 24 as V. As shown in FIG.
t = r · sin θ / V
It is assumed that the moving speed of the head unit 24 is constant. In this way, it is possible to correct the deviation in the landing position by tilting the head by controlling the ejection timing.

  Here, the rotation angle θ of the head depends on the condition of the uneven surface of the print medium 15, and therefore has a different value for each ejection position. For this reason, depending on the unevenness of the print medium 15, the ejection timing of adjacent dots may be too close or the ejection timing may be reversed. FIG. 9 is an explanatory diagram showing the actual discharge time when the discharge timing according to the present embodiment is corrected. The horizontal axis shows the time, and the vertical axis shows the change in the discharge timing before and after the correction. Numbers 1 to 15 in the figure indicate the discharge order. In the example shown in FIG. 9, the discharge time of No. 9 is earlier than the discharge time of No. 8, and the discharge time of No. 13 is later than the discharge time of No. 14. In addition, the discharge intervals of No. 5, No. 6, and No. 7 may be shortened. In such a case, the discharge cannot be performed because the discharge frequency limit of the inkjet head 41 is exceeded.

  In the present embodiment, when the ejection timing is corrected by the control unit 6 and ejection becomes impossible due to exceeding the ejection frequency limit of the inkjet head 41, the height position of the rotary shaft 82 is further moved along the vertical direction R. The distance r is changed so that ejection can be performed so that an appropriate gap distance d can be secured for all nozzles. Specifically, the control unit 6 is rotated by the lift drive unit 7 along the vertical direction R perpendicular to the reference plane AL while the head position adjusting mechanism 9 expands and contracts the distance r from the rotation shaft 82 to the print medium. The shaft 82 is moved up and down to ensure a gap distance d.

(Operation of Inkjet Printing Apparatus 1)
Next, the operation of the inkjet printing apparatus 1 will be described.
FIG. 5 is a flowchart for explaining the operation of the inkjet printing apparatus 1. The process of the flowchart of FIG. 5 starts when a print job is input to the inkjet printing apparatus 1 from an external personal computer. Prior to the start of the process in the flowchart shown in FIG. 5, the print medium 15 is placed on the medium placement surface 3 a of the flat bed unit 3.

  First, before starting printing, the control unit 6 controls the sub-scanning drive motor 12 to move the ink-jet head 41 in the sub-scanning direction to move to the printing start position, and to move the ink-jet head 41 in the main scanning direction. .

  The control unit 6 expands and contracts the gap distance d by the head position adjusting mechanism 9 according to the unevenness of the surface of the print medium 15 detected by the distance sensor 25 while the inkjet head 41 is moving in the main scanning direction. The rotary shaft 82 is moved up and down by the lift drive unit 7, and the inkjet head 41 is rotated by the rotary drive unit 8.

  Specifically, first, the control unit 6 detects the height of the print medium 15 by the distance sensor 25 to detect irregularities on the surface of the print medium 15 (step S1). Then, the control unit 6 acquires the height information of the print medium 15 detected by the distance sensor 25. Then, the control unit 6 determines the angle at which the inkjet head 41 is rotated from the unevenness of the surface of the print medium 15, and controls the rotation drive unit 8 to rotate a predetermined rotation angle θ about the rotation shaft 82. (Step S2). At this time, the control unit 6 controls the lifting / lowering by the lifting / lowering driving unit 7 according to the angle of the inkjet head 41 with respect to the surface of the print medium 15.

  Thereafter, the control unit 6 corrects the ejection timing based on the rotation angle θ (step S3). Specifically, the control unit 6 controls the ejection timing of the ink by the inkjet head 41 according to the distance, the rotation angle θ, and the relative speed of the inkjet head 41 with respect to the surface of the print medium 15 (Step S3). In the present embodiment, the correction value of the ejection timing is calculated from the distance r from the rotation shaft 82 to the print medium 15, the rotation angle θ, and the moving speed V of the head unit 24.

  Next, the control unit 6 determines whether or not the ejection timing correction value is within a certain range (step S4). If the correction value is within the certain range (step S4: YES), printing is performed at the corrected timing. Is executed (step S6). On the other hand, if the correction value is out of a certain range (step S4: NO), the distance between the rotary shaft 82 and the print medium 15 is adjusted so as to enable discharge (step S5), and printing is executed. (Step S6). In this adjustment, the distance r is adjusted by the head position adjusting mechanism 9, and the rotary shaft 82 is moved up and down by the lift drive unit 7, so that the gap distance d between the inkjet head 41 and the surface of the print medium 15 is expanded and contracted. . This adjustment may be performed by driving the elevation drive unit 7 and the head position adjusting mechanism 9 or may be adjusted by driving only one, but the inkjet head 41 is provided with both. It is more preferable because the degree of freedom of the inclination angle and the discharge frequency can be expanded.

(Action / Effect)
As described above, in the inkjet printing apparatus 1, the control unit 6 is driven to move up and down while expanding and contracting the gap distance d by the head position adjusting mechanism 9 according to the unevenness of the surface of the print medium 15 detected by the distance sensor 25. The rotating shaft 82 is moved up and down by the unit 7, and the inkjet head 41 is rotated by the rotation driving unit 8. Thereby, the nozzle 43 surface can be made parallel to the unevenness of the printing medium 15 by rotating and tilting the inkjet head 41 while maintaining the gap distance d. As a result, the distance (gap distance d) from the nozzle 43 to the print medium 15 can be made constant for all the nozzles 43 on the surface of the nozzle 43, and the occurrence of a part where the gap distance d is not appropriate is reduced. In addition, it is possible to avoid deterioration in print image quality due to bleeding or rubbing.

  Further, according to the present embodiment, the control unit 6 causes the inkjet head 41 to move the rotary shaft 82 perpendicular to the reference plane AL by the elevation drive unit 7 according to the rotation angle θ of the inkjet head 41 with respect to the surface of the print medium 15. Since it is moved up and down along the vertical direction R, it is possible to avoid the end of the inkjet head 41 from coming into contact with the print medium 15 as a result of following the surface so as to be parallel to the unevenness of the print medium 15 surface. It is possible to avoid damage to the inkjet head 41 and contamination of the print medium 15. As described above, according to the present embodiment, both the lifting drive unit 7 and the head position adjusting mechanism 9 are provided according to the rotation angle θ, so that the apparatus configuration and operation control around the inkjet head 41 are diversified. be able to.

  In addition, according to the present embodiment, the control unit 6 controls the ink discharge timing by the ink jet head 41 according to the distance, angle, and relative speed of the ink jet head 41 with respect to the surface of the print medium 15, so that the head is tilted. Thus, the deviation of the landing position can be corrected by controlling the discharge timing. If the discharge timing is corrected and the discharge frequency limit of the inkjet head 41 is exceeded, for example, it becomes impossible to discharge, the distance between the rotary shaft 82 and the medium is further changed so that the discharge can be performed. be able to.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiments. For example, some components may be deleted from all the components shown in the embodiment.

θ ... Rotation angle AL ... Reference plane d ... Gap distance R ... Vertical direction r ... Distance from rotating shaft to printing medium 1 ... Inkjet printing apparatus 2 ... Shuttle base unit 3 ... Flat bed unit 3a ... Medium placement surface 4 ... Shutter unit 5 ... Storage unit 6 ... Control unit 7 ... Elevating drive unit 8 ... Rotation drive unit 9 ... Head position adjusting mechanism 11 ... Base unit 12 ... Sub-scanning drive motor 13A, 13B ... Sub-scanning drive guide 15 ... Printing medium 21 ... Housing 22 ... Main scanning drive unit 24 ... Head unit 25 ... Distance sensor 26A, 26B ... Leg portion 27 ... Horizontal portion 31 ... Drive belt 32A, 32B ... Pulley 33 ... Main scanning drive motor 34 ... Main scanning drive guide 41 ... Inkjet Head 41a ... Nozzle surface 43 ... Nozzle 71 ... Main scanning movement table 72 ... Driving force transmission unit 73 ... Vertical drive motor DESCRIPTION OF SYMBOLS 81 ... Base 82 ... Rotary shaft 83 ... Rotation drive motor 91 ... Base 92 ... Driving force transmission part 93 ... Vertical motion drive motor

Claims (4)

An inkjet head having a plurality of nozzles arranged along the sub-scanning direction;
A main scanning drive unit that moves the inkjet head in a main scanning direction orthogonal to the sub-scanning direction;
A detection unit for detecting irregularities on the surface of the print medium;
A rotation drive unit that rotates the inkjet head around a rotation axis parallel to the sub-scanning direction;
A control unit that controls to print an image on the print medium by ejecting ink from the nozzle to the print medium while moving the inkjet head in the main scanning direction by the main scanning drive unit;
The control unit performs a predetermined timing while rotating the inkjet head by the rotation driving unit according to the unevenness of the surface of the print medium detected by the detection unit during the movement of the inkjet head in the main scanning direction. An ink jet printing apparatus, wherein ink is ejected in An adjustment unit for adjusting a distance between the inkjet head and the print medium surface;
2. The inkjet printing apparatus according to claim 1, wherein the control unit performs adjustment control of the distance by the adjustment unit according to an angle of the inkjet head with respect to the print medium surface.   The adjustment unit raises and lowers the rotation shaft to adjust a distance from the print medium surface to the rotation shaft, and a head position adjustment to expand and contract a gap distance between the inkjet head and the print medium surface. The inkjet printing apparatus according to claim 2, further comprising at least one of a mechanism.   The said control part controls the discharge timing of the said ink by the said inkjet head according to the distance, angle, and relative speed with respect to the said printing medium surface of the said inkjet head. An ink jet printing apparatus as described in 1.

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