JP2018001688A - Ink jet printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet printer which can reduce deterioration of a printing image quality while suppressing contact between an ink jet head and a printing medium.SOLUTION: An ink jet printer 1 comprises: curve surface pedestal 17 having a medium loading surface 17a which is formed into a curve surface shape so that a center thereof becomes higher than both sides in a main scanning direction, and a stationary part 26 which fixes a printing medium 21 along the medium loading surface 17a and on the medium loading surface 17a; and an ink jet head 37 which discharges an ink onto the printing medium 21 on the medium loading surface 17a while moving in the main scanning direction, and prints an image.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an ink jet printing apparatus that prints by discharging ink from an ink jet head onto a print medium.

  An inkjet printing apparatus that prints by ejecting ink from an inkjet head to a print medium while moving the inkjet head is known (see, for example, Patent Document 1).

  In such an ink jet printing apparatus, the print medium is fixed on a flat table by an air suction method or the like in order to fix the print medium while ensuring flatness.

JP 2008-279727 A

  By the way, in the above-described inkjet printing apparatus, for example, printing may be performed on a print medium in which protrusions such as a construction magnet are provided on the end of the surface.

  When printing with such a print medium fixed on a flat table, it is necessary to increase the head gap in order to prevent contact between the inkjet head and the protrusions of the print medium. As the head gap is larger, the ink landing position is more likely to be displaced, so that the print image quality may be deteriorated due to the ink landing position being displaced.

  The present invention has been made in view of the above, and an object of the present invention is to provide an ink jet printing apparatus that can reduce a decrease in print image quality while suppressing contact between an ink jet head and a print medium.

  In order to achieve the above object, a first feature of the ink jet printing apparatus according to the present invention is that a medium mounting surface formed in a curved shape so that the center is higher than both sides in the main scanning direction, and a printing medium are provided. Ink is discharged to the print medium on the medium mounting surface while moving in the main scanning direction while moving in the main scanning direction along with the medium mounting surface and fixed on the medium mounting surface. And an inkjet head for printing an image.

  A second feature of the ink jet printing apparatus according to the present invention is that image data to be printed according to a length in a main scanning direction in a plan view of a print target region of the print medium curved along the medium placement surface. The image processing unit further includes an image processing unit that reduces the image in the main scanning direction, and the inkjet head performs printing based on the image data reduced in the main scanning direction by the image processing unit.

  A third feature of the ink jet printing apparatus according to the present invention is a discharge control that adjusts at least one of the ink discharge timing and the discharge speed in accordance with a change in the head gap during movement of the ink jet head in the main scanning direction. It is in providing a part further.

  A fourth feature of the ink jet printing apparatus according to the present invention is that the fixing unit sandwiches an end portion of the print medium in the main scanning direction between the medium placement surface and the print medium. It is to be fixed on the surface.

  According to the first feature of the ink jet printing apparatus according to the present invention, the print medium is placed along the medium placement surface formed in a curved shape curved so that the center is higher than both sides in the main scanning direction. Secure on the surface. Accordingly, when printing on a print medium having a protrusion at the end in the main scanning direction, the protrusion is lowered from the inkjet head by lowering the protrusion to a lower position than the center of the print medium in the main scanning direction. Be kept away. At the same time, the head gap becomes smaller toward the center in the main scanning direction, so that the degree of enlargement of the head gap can be suppressed. As a result, it is possible to reduce a decrease in print image quality while suppressing contact between the inkjet head and the print medium.

  According to the second feature of the ink jet printing apparatus according to the present invention, the image to be printed according to the length in the main scanning direction in plan view of the print target area of the print medium curved along the medium placement surface. The image in the data is reduced in the main scanning direction. As a result, it is possible to prevent the print image from stretching (elongation of the print image when the print medium is returned from the curved state to the flat state after printing) and the print image from protruding from the print target area of the print medium. Therefore, it is possible to suppress the quality deterioration of the printed matter.

  According to the third feature of the ink jet printing apparatus of the present invention, at least one of the ink ejection timing and the ejection speed is adjusted according to the change in the head gap during the movement of the ink jet head in the main scanning direction. As a result, the ink landing position shift due to the change in the head gap can be suppressed, so that the deterioration of the print image quality can be further reduced.

  According to the fourth feature of the ink jet printing apparatus according to the present invention, the fixed part sandwiches the end of the print medium in the main scanning direction between the medium placement surface and the print medium is placed on the medium placement surface. It is fixed on the top. For this reason, since the print medium can be fixed on the medium placement surface without using the air suction method, even a print medium made of a member that is difficult to suck, such as a porous material, is placed along the medium placement surface. Can be fixed on the surface. In addition, since the fixed portion sandwiches an end portion of the print medium that is lower than the central portion in the main scanning direction between the medium mounting surface, in order to avoid contact between the inkjet head and the fixed portion. An increase in the head gap can be suppressed.

1 is an overall perspective view of an inkjet printing apparatus according to an embodiment. It is a front view which shows typically schematic structure of the inkjet printing apparatus shown in FIG. It is sectional drawing along the main scanning direction of the curved surface base of the inkjet printing apparatus shown in FIG. It is a control block diagram of the inkjet printing apparatus shown in FIG. It is a flowchart for demonstrating the operation | movement at the time of printing using a curved surface base with the inkjet printing apparatus shown in FIG. It is explanatory drawing of the method of calculating head gap expansion amount.

  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.

  FIG. 1 is an overall perspective view of an ink jet printing apparatus according to an embodiment of the present invention. FIG. 2 is a front view schematically showing a schematic configuration of the ink jet printing apparatus shown in FIG. 3 is a cross-sectional view along the main scanning direction of the curved pedestal of the ink jet printing apparatus shown in FIG. FIG. 4 is a control block diagram of the inkjet 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, 2, and 4, 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, and a control unit 5.

  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 to move 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 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 includes a mounting table 16, a curved base (corresponding to a medium support unit in claims) 17, a plurality of legs 18, a suction pump 19, and a mounting table lifting / lowering driving unit 20.

  The mounting table 16 is a table on which the print medium and the curved base 17 are selectively mounted. The mounting table 16 is formed in a hollow rectangular parallelepiped shape. The upper surface of the mounting table 16 is a horizontal plane. On the upper surface of the mounting table 16, a plurality of suction holes (not shown) that communicate the internal space of the mounting table 16 with the outside are formed. When the print medium is placed on the top surface of the mounting table 16, the print medium is fixedly held by the suction force generated in the suction hole by driving the suction pump 19. The mounting table 16 is configured such that a curved surface base 17 can be attached to and detached from the upper surface thereof.

  The curved pedestal 17 is a pedestal that supports and fixes a print medium when the inkjet printing apparatus 1 performs printing on a predetermined type of print medium. The print medium supported by the curved pedestal 17 has protrusions at both ends in the left-right direction (main scanning direction), for example. That is, the curved pedestal 17 supports, for example, the print medium 21 shown in FIGS. The print medium 21 includes a plate-like base material portion 22 and two protrusions 23 that protrude from the surface of the base material portion 22. The protrusion 23 is formed in a long shape extending in the front-rear direction. The two protrusions 23 are respectively arranged on the left end and the right end of the base material portion 22.

  As shown in FIGS. 1 to 3, the medium placement surface 17 a that is the upper surface of the curved pedestal 17 is formed in a curved surface that is curved so that the center is higher than both sides in the main scanning direction (left-right direction). Specifically, the medium placement surface 17a is formed to have an upwardly convex arc shape in a cross section along the main scanning direction.

  On the medium placement surface 17a, the print medium 21 is placed along the medium placement surface 17a with the center of the print medium 21 aligned with the center of the medium placement surface 17a in the main scanning direction. The medium placement surface 17 a is formed so that the highest point of the protrusion 23 of the print medium 21 does not become higher than the highest point of the base material portion 22 when the print medium 21 is placed in this way. The medium placement surface 17a is formed such that the height difference h in the print target area of the print medium 21 is equal to or less than a predetermined reference value when the print medium 21 is placed as described above. Here, the print target area of the print medium 21 is an area between the two protrusions 23. The height difference h is a difference in height between the highest point and the lowest point of the print target area of the print medium 21 on the medium placement surface 17a. Specifically, the height difference h is a difference in height between the center position in the main scanning direction of the print target area of the print medium 21 on the medium placement surface 17a, and the left end and the right end.

  The curved pedestal 17 is provided with a fixing portion 26 that fixes the print medium 21 along the medium placement surface 17a on the medium placement surface 17a. Four fixing portions 26 are arranged on each of the left end portion and the right end portion of the medium placement surface 17a. The left fixing portion 26 sandwiches the left end of the print medium 21 between the medium placement surface 17a, and the right fixing portion 26 places the right end of the print medium 21 between the medium placement surface 17a. The print medium 21 is fixed on the medium placement surface 17a. The fixed portion 26 is configured so that the highest point of the fixed portion 26 does not become higher than the highest point of the base material portion 22 of the print medium 21 when the end portion of the print medium 21 is sandwiched between the medium placement surface 17a. It is configured. The fixing part 26 is made of, for example, a leaf spring.

  The curved pedestal 17 includes a plurality of types in which the radius of the arc formed by the medium placement surface 17a, the width of the medium placement surface 17a, the position of the fixing portion 26, and the like are designed according to the type of the print medium 21. And they are interchangeable.

  The leg 18 supports the mounting table 16. The leg part 18 is comprised so that expansion-contraction is possible. Thereby, the mounting table 16 can be moved up and down.

  The suction pump 19 exhausts air from the internal space of the mounting table 16 when the curved base 17 is not used and a printing medium is mounted on the upper surface of the mounting table 16. As a result, the suction pump 19 generates a suction force in the suction hole of the mounting table 16 and fixes the print medium to the upper surface of the mounting table 16 by the suction force.

  The mounting table lifting / lowering drive unit 20 moves the mounting table 16 up and down. The mounting table raising / lowering drive unit 20 includes a hydraulic raising / lowering mechanism or the like.

  The shuttle unit 4 prints an image on a print medium. As shown in FIGS. 1, 2, and 4, the shuttle unit 4 includes a housing 31, a main scanning drive guide 32, a main scanning drive motor 33, a head lifting guide 34, a head lifting motor 35, and a head. A unit 36.

  The housing 31 houses each part such as the head unit 36. The housing 31 is formed in a gate shape straddling the flat bed unit 3 in the left-right direction. The casing 31 is supported by the gantry 11 of the shuttle base unit 2 and is movable along the sub-scanning drive guides 13A and 13B.

  The main scanning drive guide 32 guides the head unit 36 to move in the left-right direction (main scanning direction). The main scanning drive guide 32 is formed in a long shape extending in the left-right direction.

  The main scanning drive motor 33 moves the head unit 36 in the left-right direction.

  The head lifting guide 34 guides the head unit 36 to move in the vertical direction. The head lifting guide 34 is formed in an elongated shape in the vertical direction. The head lifting guide 34 is configured to be movable in the left-right direction along the main scanning drive guide 32 together with the head unit 36.

  The head lifting motor 35 moves the head unit 36 up and down.

  The head unit 36 prints an image by ejecting ink onto a print medium while moving in the left-right direction along the main scanning drive guide 32. The head unit 36 includes four inkjet heads 37.

  The ink-jet head 37 has a plurality of nozzles (not shown) arranged in the front-rear direction and opened in a nozzle surface 37a that is the lower surface thereof, and ejects ink from the nozzles. The four inkjet heads 37 are arranged in parallel in the left-right direction. The four inkjet heads 37 eject cyan (C), magenta (M), yellow (Y), and black (K) inks, respectively.

  The control unit 5 controls the operation of the entire inkjet printing apparatus 1. The control unit 5 includes a CPU, a RAM, a ROM, a hard disk, and the like. The control unit 5 includes a mechanical control unit 41, an image processing unit 42, and a discharge control unit 43. Each unit of the control unit 5 is configured by the CPU operating according to a program stored in a hard disk or the like.

  The mechanical control unit 41 controls the movement of the shuttle unit 4 by the sub-scanning drive motor 12, the movement of the head unit 36 by the main scanning drive motor 33, and the lifting / lowering of the head unit 36 by the head lifting / lowering motor 35. The mechanical control unit 41 controls the driving of the suction pump 19 and the lifting / lowering of the mounting table 16 by the mounting table lifting / lowering driving unit 20.

  The image processing unit 42 performs RIP (Raster Image Processor) processing on print job data in PDL (Page Description Language) format to generate image data to be printed, and generates drop data based on the image data. . The drop data is data indicating the number of ink drops (number of droplets) ejected from the nozzles of the inkjet head 37 to each pixel. When printing using the curved pedestal 17, the image processing unit 42 reduces the image in the image data to be printed in the main scanning direction according to the print width d for the print medium 21 curved along the medium placement surface 17 a. . Here, as shown in FIG. 3, the printing width d is a length in the main scanning direction in a plan view of the printing target area of the printing medium 21 curved along the medium placement surface 17 a. In other words, the printing width d is the length in the main scanning direction of an area in which the printing target area of the printing medium 21 curved along the medium placement surface 17a is projected onto the horizontal plane.

  The ejection control unit 43 controls the inkjet head 37 based on the drop data generated by the image processing unit 42 to eject ink. When printing using the curved base 17, the discharge controller 43 adjusts the ink discharge timing according to the change in the head gap G during movement of the inkjet head 37 in the main scanning direction. The head gap G is the distance between the nozzle surface 37a of the inkjet head 37 and the print medium 21, as shown in FIG. Since the print medium 21 on the curved pedestal 17 is curved in the main scanning direction, the head gap G changes while the inkjet head 37 is moving in the main scanning direction.

  Next, an operation when printing is performed using the curved base 17 in the inkjet printing apparatus 1 will be described.

  FIG. 5 is a flowchart for explaining an operation when printing is performed using the curved base 17 in the inkjet printing apparatus 1. The process of the flowchart of FIG. 5 starts when print job data in PDL format is input to the inkjet printing apparatus 1.

  In step S1 of FIG. 5, the image processing unit 42 of the control unit 5 performs RIP processing on the print job data to generate image data to be printed in RGB format.

  Next, in step S2, the image processing unit 42 reduces the image in the image data to be printed in the main scanning direction according to the print width d. Specifically, the image processing unit 42 assumes that the length in the main scanning direction of the print target area of the print medium 21 in a flat state is L, and has a reduction ratio of d / L in the main scanning direction. Reduce the image in the image data. While the image data to be printed is for printing on the print medium 21 in a flat state, the print medium 21 on the curved surface base 17 is reduced in the main scanning direction in plan view, so that the print image is printed. The image processing unit 42 performs image reduction in the main scanning direction so as to fit in the region.

  Here, the length L in the main scanning direction of the print target area of the print medium 21 in the flat state is the print target of the surface (upper surface) of the print medium 21 on the medium placement surface 17a as shown in FIG. Corresponds to the arc length of the arc formed by the range. The arrow height of the arc corresponds to the above-described height difference h, and the chord length of the arc corresponds to the above-described printing width d. When the radius of this arc is r and the central angle is θ (rad), the following equations (1) to (3) are established.

L = r × θ (1)
d = r × sin (θ / 2) (2)
h = r × (1-cos (θ / 2)) (3)
The arc length L is a value determined in the print medium 21. As described above, the arrow height (height difference) h is a design value determined to be equal to or less than a predetermined reference value. The chord length (printing width) d can be calculated using the value of the arc length L, the value of the arrow height (height difference) h, and equations (1) to (3).

  Next, in step S <b> 3 of FIG. 5, the image processing unit 42 converts the image data in the RGB format after image reduction in the main scanning direction into image data in the CMYK format corresponding to the ink color of each inkjet head 37. This color conversion can be performed using a table in which the correspondence between RGB values and CMYK values is recorded in advance.

  Next, in step S4, the image processing unit 42 performs halftone processing on the image data of each color after color conversion to generate drop data for each ink color. As halftone processing, error diffusion processing or dither mask processing can be applied.

  Next, in step S5, the ejection control unit 43 of the control unit 5 calculates the ejection timing correction amount Δt corresponding to the head gap enlargement amount ΔG at the position of each pixel in the main scanning direction. The head gap expansion amount ΔG is an expansion amount of the head gap G with respect to the standard value Gs. The ejection timing correction amount Δt is a timing correction amount with respect to the reference ejection timing when the head gap G is the standard value Gs.

  Here, at the time of printing using the curved pedestal 17, the height of the head unit 36 is adjusted so that the head gap G becomes the standard value Gs at the highest point of the print medium 21. For this reason, the head gap G is larger than the standard value Gs at a position other than the highest point of the print medium 21. In the position where the head gap G is larger than the standard value Gs, in order to land the ink on the target position on the print medium 21, the ink is ejected at a timing earlier than the case where the head gap G is the standard value Gs. There is a need to. Therefore, in order to correct the ink ejection timing according to the change in the head gap G, the ejection control unit 43 calculates the ejection timing correction amount Δt according to the head gap expansion amount ΔG.

  Specifically, the ejection control unit 43 linearizes between the ejection timing correction amount Δt0 when the head gap G is the standard value Gs and the ejection timing correction amount Δtmax when the head gap expansion amount ΔG is the maximum value. A discharge timing correction amount Δt corresponding to the head gap expansion amount ΔG is calculated by interpolation.

  Here, when the head gap G is the standard value Gs, it is not necessary to correct the ejection timing, and therefore Δt0 = 0. The maximum value of the head gap expansion amount ΔG is the height difference h. The ejection timing correction amount Δtmax when the head gap expansion amount ΔG is the maximum value is obtained by experiments in advance.

  The head gap enlargement amount ΔG at the position of each pixel in the main scanning direction is calculated as follows.

  The equation of the circle of radius r centered on the point (0, −r) shown in FIG. 6 is the following equation (4).

x ² + (y + r) ² = r ² (4)
The arc in the range of −d / 2 ≦ x ≦ d / 2 and −h ≦ y ≦ 0 in FIG. 6 corresponds to the arc formed by the print target range of the surface (upper surface) of the print medium 21 on the medium placement surface 17a. To do. The radius r can be calculated using the value of the arc length L, the value of the arrow height (height difference) h, and equations (1) to (3).

  The following formula (5) is obtained by modifying the formula (4).

y ² + 2 × r × y + x ² = 0 (5)
By substituting the value of x corresponding to the position of each pixel in the main scanning direction into Equation (5) and solving for y, the value of y corresponding to the head gap expansion amount ΔG at the position of the pixel is obtained. Of the solutions obtained by solving Equation (5) for y, the absolute value of the larger value (the smaller absolute value) is the value of the head gap expansion amount ΔG.

  The ejection timing correction amount Δt corresponding to the head gap expansion amount ΔG at the position (coordinates) of each pixel in the main scanning direction for each combination of the types of the curved surface base 17 and the print medium 21 used is controlled as a table in advance. It may be held in the part 5. In this case, the discharge control unit 43 can acquire the discharge timing correction amount Δt from this table.

  Returning to FIG. 5, in step S <b> 6, the control unit 5 executes printing. Specifically, first, the mechanical control unit 41 of the control unit 5 controls the sub-scanning drive motor 12 to move the shuttle unit 4 from the standby position to the print processing start position. The standby position of the shuttle unit 4 is the position of the shuttle unit 4 indicated by a solid line in FIG. The printing process start position of the shuttle unit 4 is the position of the shuttle unit 4 indicated by a two-dot chain line in FIG. Prior to the input of print job data, the print medium 21 is placed on the medium placement surface 17 a of the curved pedestal 17 and fixed by the fixing unit 26. Further, the height of the mounting table 16 is adjusted by the mounting table lifting / lowering drive unit 20.

  Next, the mechanical control unit 41 controls the head lifting motor 35 to adjust the height of the head unit 36 so that the head gap G at the highest point of the print medium 21 becomes the standard value Gs.

  Next, the mechanical control unit 41 controls the main scanning drive motor 33 to move the head unit 36 in the main scanning direction, while the ejection control unit 43 controls the ink jet head 37 based on the drop data to eject ink. Print for one pass. Here, the ejection control unit 43 adjusts the ink ejection timing based on the ejection timing correction amount Δt corresponding to the head gap enlargement amount ΔG at the position of each pixel in the main scanning direction. Specifically, the ejection controller 43 causes each pixel to eject ink at a timing earlier than the reference ejection timing by the ejection timing correction amount Δt.

  When printing for one pass is completed, the mechanical control unit 41 controls the sub-scanning drive motor 12 to move the shuttle unit 4 backward to the printing position for the next pass. The control unit 5 forms an image on the print medium 21 by alternately repeating the printing for one pass and the movement of the shuttle unit 4 described above. When printing for one sheet is completed, the mechanical control unit 41 controls the sub-scanning drive motor 12 to place the shuttle unit 4 at the standby position. Thereby, the printing operation is completed.

  As described above, in the inkjet printing apparatus 1, when printing is performed using the curved surface base 17, the print medium 21 is fixed on the medium placement surface 17a by the fixing unit 26 along the medium placement surface 17a. Accordingly, the protrusion 23 is moved away from the inkjet head 37 by lowering the end portion to a lower position with respect to the central portion of the print medium 21 in the main scanning direction. At the same time, since the head gap G becomes smaller toward the center in the main scanning direction, the degree of expansion of the head gap G can be suppressed. As a result, according to the inkjet printing apparatus 1, it is possible to reduce the deterioration of the print image quality while suppressing the contact between the inkjet head 37 and the print medium 21.

  In the inkjet printing apparatus 1, when printing is performed using the curved pedestal 17, the image processing unit 42 prints an image to be printed according to the print width d for the print medium 21 curved along the medium placement surface 17 a. The image in the data is reduced in the main scanning direction. The ink jet head 37 performs printing based on the reduced image data. As a result, the print image expands (elongation of the print image when the print medium 21 is returned from the curved state to the flat state after printing), or the print image protrudes from the print target area of the print medium 21. Since it can prevent, the quality deterioration of printed matter can be suppressed.

  Further, in the inkjet printing apparatus 1, when printing is performed using the curved pedestal 17, the ejection control unit 43 sets the ink ejection timing according to the change in the head gap G during movement of the inkjet head 37 in the main scanning direction. adjust. Thereby, the landing position deviation of the ink due to the change of the head gap G is suppressed. As a result, it is possible to further reduce the decrease in print image quality.

  Further, in the inkjet printing apparatus 1, the fixing unit 26 fixes the print medium 21 on the medium placement surface 17a by sandwiching the end of the print medium 21 in the main scanning direction between the medium placement surface 17a. To do. As a result, the print medium can be fixed on the medium placement surface 17a without using the air suction method. Therefore, even a print medium made of a member that is difficult to suck, such as a porous material, is placed along the medium placement surface 17a. It can be fixed on the medium placement surface 17a. In addition, the fixed portion 26 is configured to sandwich an end portion of the print medium 21 that is lower than the central portion in the main scanning direction between the medium placement surface 17a, and therefore, between the inkjet head 37 and the fixed portion 26. In order to avoid contact, it is possible to prevent the head gap G from expanding.

  In addition, when printing on a print medium made of a member that is difficult to suck, such as a porous material, it is preferable to perform printing using the curved pedestal 17 even if there are no protrusions on the print medium. In the case of a print medium made of a porous material, even if it is placed on the top surface of the mounting table 16 and is fixed by air suction by the suction pump 19, there is a possibility that the suction cannot be sufficiently performed and the flatness cannot be secured. On the other hand, when the curved pedestal 17 is used, the fixing unit 26 can fix the print medium along the medium placement surface 17a. As a result, it is possible to reduce the deterioration of the print image quality as compared with the case where the air suction method cannot ensure the flatness of the print medium and the print medium is printed with unevenness.

  In the above-described embodiment, the ejection control unit 43 adjusts the ink ejection timing according to the change in the head gap G during the movement of the inkjet head 37 in the main scanning direction. However, even if the ink ejection speed is adjusted. Good. In this case, the ink ejection speed is made faster than the standard ejection speed by an amount corresponding to the head gap expansion amount ΔG. The ink ejection speed can be adjusted by, for example, the driving voltage of the inkjet head 37. The adjustment of the ink ejection timing and the adjustment of the ejection speed may be combined.

  In the embodiment described above, the print medium 21 is fixed on the medium placement surface 17a by the fixing unit 26 that sandwiches the print medium 21 with the medium placement surface 17a, but the print medium 21 is placed on the medium placement surface 17a. The means for fixing to is not limited to this. For example, a configuration in which the print medium 21 is fixed on the medium placement surface 17a by an air suction method may be used. Specifically, the curved surface base 17 is provided with a plurality of suction holes that open on the medium placement surface 17 a and communicate with the plurality of suction holes of the placement table 16. Accordingly, by driving the suction pump 19, a suction force is generated in the suction hole opened in the medium placement surface 17a, and the print medium 21 can be fixed on the medium placement surface 17a by the suction force. That is, in this case, the suction pump 19 functions as a fixed portion. Although this configuration is not suitable for fixing a print medium made of a member that is difficult to suck, such as a porous material, any print medium made of a suckable member can be fixed on the medium placement surface 17a.

  In the above-described embodiment, the medium placement surface 17a is a curved surface having an upwardly convex arc shape in a cross section along the main scanning direction. However, the shape of the medium placement surface is not limited to this. The medium placement surface only needs to be formed in a curved shape so that the center is higher than both sides in the main scanning direction.

  In the embodiment described above, the curved pedestal 17 having the medium placement surface 17a is detachable from the placement table 16, but the curved pedestal 17 is omitted and the upper surface of the placement table 16 is the same as the medium placement surface 17a. The curved surface may be used. In this configuration, the printing medium may be fixed to the upper surface of the mounting table 16 by a fixing unit similar to the fixing unit 26 instead of the air suction method.

  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.

DESCRIPTION OF SYMBOLS 1 Inkjet printing apparatus 2 Shuttle base unit 3 Flat bed unit 4 Shuttle unit 5 Control part 16 Mounting base 17 Curved surface base 17a Medium mounting surface 19 Suction pump 26 Fixing part 36 Head unit 37 Inkjet head 42 Image processing part 43 Discharge control part

Claims (4)

A medium mounting surface formed in a curved shape that is curved so that the center is higher than both sides in the main scanning direction; and a fixing unit that fixes the print medium on the medium mounting surface along the medium mounting surface. A medium support having
An inkjet printing apparatus comprising: an inkjet head that prints an image by ejecting ink onto a printing medium on the medium placement surface while moving in a main scanning direction. An image processing unit for reducing an image in the image data to be printed in the main scanning direction according to a length in the main scanning direction in a plan view of the print target region of the print medium curved along the medium placement surface; Prepared,
The inkjet printing apparatus according to claim 1, wherein the inkjet head performs printing based on image data reduced in the main scanning direction by the image processing unit.   The apparatus further comprises a discharge controller that adjusts at least one of ink discharge timing and discharge speed in accordance with a change in head gap during movement of the inkjet head in the main scanning direction. An ink jet printing apparatus as described in 1.   The fixing unit is configured to fix the print medium on the medium placement surface by sandwiching an end portion of the print medium in the main scanning direction with the medium placement surface. Item 4. The inkjet printing apparatus according to any one of Items 1 to 3.