Printing apparatus

Abstract

To provide a printing device that can prevent ink from being discharged to the outside of a printing surface of a printing medium without troubling a user.SOLUTION: A printing device is provided with: a conveying unit 2 which conveys a three-dimensional printing medium P having a side surface erected in a direction perpendicular to a conveyance surface, in a predetermined conveying direction; a head unit 10 that discharges liquid droplets to the side surface of the printing medium P conveyed by the conveying unit 2; a distance detecting part 5, provided closer to an upstream side in the conveying direction than the head unit 10, which detects a distance between the printing medium P conveyed by the conveying unit 2 and the distance detecting part; and a control part 60 that determines a printing condition on the basis of the distance detected by the distance detecting part 5 and performs printing control on the basis of the determined printing condition.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a printing device that prints on a three-dimensional print medium. [Background technology]

[0002] 2. Description of the Related Art Conventionally, inkjet printing devices have been proposed that perform printing by ejecting ink onto a print medium.

[0003] Inkjet printing devices that eject ink from above in a vertical direction onto a printing medium that is positioned so that the printing surface is horizontal, as well as inkjet printing devices that print onto a printing medium that is positioned so that the printing surface is in a direction other than horizontal, for example by ejecting ink from a direction perpendicular to the printing surface, have been proposed.

[0004] For example, Patent Document 1 proposes a device that transports products or packaging containers horizontally using a belt conveyor and prints on the sides of the transported products or packaging containers using an inkjet head. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-175574 Summary of the Invention [Problem to be solved by the invention]

[0006] When printing on a print medium transported by a belt conveyor as described above, various settings must be configured to print at a desired position on the side of the print medium. For example, Patent Document 1 proposes taking images of the print medium being transported with a camera on a mobile device, calculating the transport speed using the multiple captured images, and determining the print position, etc. based on the transport speed.

[0007] However, in Patent Document 1, it is necessary to take multiple images using the camera of a mobile device, which is time-consuming. Furthermore, depending on the photographer's shooting technique, it may be difficult to capture an appropriate image, requiring multiple shots, or the accuracy of the calculation of the transport speed may decrease, resulting in a decrease in the accuracy of the printing position. If the printing position is outside the printing surface of the printing medium, ink will be ejected into an area where there is no printing surface, which may result in the surrounding area being contaminated with ink.

[0008] SUMMARY OF THE INVENTION An object of the present invention is to provide a printing device that can prevent ink from being ejected outside the printing surface of a print medium without requiring the user to do any effort. [Means for solving the problem]

[0009] The printing device of the present invention comprises a transport unit that transports a three-dimensional printing medium having sides that are erected perpendicular to the transport surface in a predetermined transport direction, a head unit that ejects droplets onto the sides of the printing medium transported by the transport unit, a distance detection unit that is located upstream of the head unit in the transport direction and detects the distance to the printing medium transported by the transport unit, and a control unit that determines printing conditions based on the distance detected by the distance detection unit and performs printing control based on the determined printing conditions. [Effects of the Invention]

[0010] According to the printing device of the present invention, a distance detection unit is provided that detects the distance to the transported printing medium, printing conditions are determined based on the distance detected by the distance detection unit, and printing control is performed based on the determined printing conditions, thereby preventing ink from being ejected outside the printing surface of the printing medium without any effort on the part of the user. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an external perspective view showing a basic configuration of an inkjet printing apparatus using an embodiment of the printing apparatus of the present invention; [Figure 2] Diagram showing the detailed configuration of the line head [Figure 3] FIG. 1 is a block diagram showing the configuration of a control system of an inkjet printing apparatus using an embodiment of the printing apparatus of the present invention. [Figure 4] FIG. 1 is an explanatory diagram illustrating the process of an inkjet printing apparatus using an embodiment of the printing apparatus of the present invention. [Figure 5] 10 is a flowchart illustrating the process of an inkjet printing apparatus using an embodiment of the printing apparatus of the present invention. [Figure 6] FIG. 10 is a diagram showing an example of distance information detected by a distance detection unit; [Figure 7] FIG. 10 is a diagram showing an example of image data to be printed. [Figure 8] FIG. 10 is an explanatory diagram illustrating an example of applying mask processing to image data. [Figure 9] FIG. 10 is an explanatory diagram illustrating an example of applying mask processing to image data. [Figure 10] FIG. 10 is an explanatory diagram illustrating an example of performing a reduction process on image data. [Figure 11] FIG. 10 is an explanatory diagram illustrating an example of performing a reduction process on image data. [Figure 12] FIG. 10 is a diagram showing an example in which a character region is not subjected to reduction processing. [Figure 13] A diagram showing an example of a print medium being placed on the joint of a belt conveyor. DETAILED DESCRIPTION OF THE INVENTION

[0012] An inkjet printing apparatus using one embodiment of the printing apparatus of the present invention will be described in detail below with reference to the drawings. Figure 1 is an external perspective view showing the schematic configuration of the inkjet printing apparatus 1. In the description of the embodiment shown below, the up, down, left, right, front, and rear directions indicated by arrows in Figure 1 are defined as the up, down, left, right, front, and rear directions of the inkjet printing apparatus 1. The up and down directions of the inkjet printing apparatus 1 are also defined as the vertical direction.

[0013] As shown in FIG. 1, the inkjet printing device 1 includes a head unit 10, a transport unit 2, and a distance detection unit 5.

[0014] The transport unit 2 transports the print medium P in the direction of the arrow shown in Fig. 1. The print medium P may be, for example, a three-dimensional print medium (for example, a box such as a cardboard box) having a printing surface Ps that stands upright in the vertical direction as shown in Fig. 1. However, the print medium P is not limited to a box, and may be any object that has a printing surface that stands upright in the vertical direction, such as a cylindrical can. In this embodiment, the transport unit 2 corresponds to the transport section of the present invention.

[0015] The transport unit 2 includes a support table 3 and a transport belt unit 4. The support table 3 is a table that supports the transport belt unit 4.

[0016] The conveyor belt section 4 includes two platen rollers 2a (see FIG. 4) and a conveyor belt 2b (see FIG. 4) that extend in a direction perpendicular to the conveyance direction of the print medium P. The two platen rollers 2a are arranged parallel to and spaced apart in the conveyance direction of the print medium P. A circular conveyor belt 2b is stretched between the two parallel platen rollers 2a. Note that the conveyor unit 2 shown in FIG. 1 shows only a portion of it, and in reality, it is assumed to extend further in the front-to-rear direction.

[0017] The drive motor 21 is driven under the control of the control unit 60, which will be described later, causing the platen roller 2a to rotate and the conveyor belt 2b to move, thereby conveying the printing medium P. The conveying unit 2 also has an encoder 20 (see FIG. 3), and a pulse signal from the encoder 20 is output to the control unit 60. The control unit 60 measures the width of the printing medium P in the conveying direction based on the input pulse signal; measurement of the width of the printing medium P will be described in detail later.

[0018] The head unit 10 performs printing by ejecting ink onto the printing surface Ps of the print medium P transported by the transport unit 2.

[0019] 1, the head unit 10 has four line heads 11, 12, 13, and 14. The four line heads 11 to 14 are provided to extend in the vertical direction and are arranged parallel to the transport direction of the printing medium P. In this embodiment, each of the line heads 11 to 14 corresponds to a head portion of the present invention.

[0020] The four line heads 11 to 14 eject ink of C (cyan), M (magenta), Y (yellow), and K (black), respectively.

[0021] 2 is a diagram showing the detailed configuration of the line heads 11 to 14. Here, the configuration of the line head 11 out of the four line heads 11 to 14 will be described, but the remaining line heads 12 to 14 have the same configuration.

[0022] The line head 11 includes six inkjet heads 11a, 11b, 11c, 11d, 11e, and 11f.

[0023] Each of the inkjet heads 11a to 11f has a plurality of nozzles that eject ink, and the nozzles are arranged in a vertical direction. Note that the nozzle arrangement direction refers to the direction in which the nozzle row is longest, for example, when the nozzles are arranged two-dimensionally.

[0024] The line head 11 also has a first head row consisting of three inkjet heads 11a, 11c, and 11e, and a second head row consisting of three inkjet heads 11b, 11d, and 11f. The first head row and the second head row are arranged adjacent to each other at different positions in the transport direction of the printing medium P.

[0025] The three inkjet heads 11a, 11c, and 11e of the first head row are arranged at a predetermined interval in the vertical direction, and the three inkjet heads 11b, 11d, and 11f of the second head row are arranged at a predetermined interval in the vertical direction.

[0026] As shown in FIG. 2, the inkjet heads 11a, 11c, and 11e of the first head row and the inkjet heads 11b, 11d, and 11f of the second head row are arranged in a staggered manner so as to be at different positions in the vertical direction.

[0027] For example, when printing a straight line extending in the vertical direction using the line head 11, the straight line is printed by ejecting ink from the first head row and the second head row at different timings.

[0028] The distance detection unit 5 is provided upstream of the head unit 10 in the transport direction, and detects the distance to the printing medium P transported by the transport unit 2 from above the printing medium P. The distance detection unit 5 has a distance measurement sensor such as a laser displacement sensor or an ultrasonic sensor.

[0029] The distance D (see FIG. 4A) between the head unit 10 and the distance detection unit 5 in the transport direction is preferably equal to or greater than the maximum width in the transport direction of the print medium P on which printing is expected. For example, it is set to a distance about 1.5 times the maximum width.

[0030] FIG. 3 is a block diagram showing the configuration of a control system of the inkjet printing apparatus 1 of this embodiment.

[0031] The inkjet printing apparatus 1 includes a control unit 60. The control unit 60 includes a CPU (Central Processing Unit) and storage media such as semiconductor memory and a hard disk, and controls the entire inkjet printing apparatus 1. The control unit 60 executes a print control program stored in advance in a storage medium such as semiconductor memory or a hard disk, and controls the operation of each part of the inkjet printing apparatus by operating electrical circuits.

[0032] In particular, the control unit 60 of this embodiment determines printing conditions based on the distance detected by the distance detection unit 5, and performs printing control based on the determined printing conditions. Specifically, in this embodiment, height information (vertical width) and width information in the transport direction of the printing surface Ps of the printing medium P are calculated based on the distance detected by the distance detection unit 5, and masking is performed on the image data based on the calculated height information and width information and the size of the image data to be printed. The masking process of this embodiment is a process of masking a portion of the image data, thereby controlling printing so that ink is not ejected from the nozzles of the inkjet head that correspond to the masked portion.

[0033] Next, print control including mask processing in the inkjet printing apparatus 1 of this embodiment will be described with reference to the flowcharts shown in FIGS.

[0034] First, the distance L between the conveying surface of the conveyor belt unit 4 and the distance detection unit 5 is set in the control unit 60 (S10). The distance L may be set by a user using a predetermined input device (not shown) to input a value measured in advance, or may be measured and set by the distance detection unit 5 at the start of printing.

[0035] Then, a print medium P to be printed is placed upstream of the conveyor belt unit 4 (S12), and in response to a print request from a user, the print medium P is conveyed by the conveyor belt unit 4 toward the distance detection unit 5 (S14), as shown in FIG. 4A.

[0036] Then, as shown in FIG. 4B, when the printing medium P reaches the distance detection unit 5, distance measurement by the distance detection unit 5 begins (S16). The distance detection unit 5 continues measuring the distance until the printing medium P passes under the distance detection unit 5. Then, distance information detected by the distance detection unit 5 is output to the control unit 60. FIG. 6 is a diagram showing an example of distance information detected by the distance detection unit 5.

[0037] The control unit 60 determines the printing range of the image data based on the distance information shown in Fig. 6. Specifically, the control unit 60 calculates height information H of the printing medium P and width information W in the transport direction from the distance information shown in Fig. 6 (S18). The control unit 60 calculates the height information H of the printing medium P by subtracting the distance A (see Fig. 4B) detected by the distance detection unit 5 from the distance L set and input in S10. The control unit 60 also obtains the width information W of the printing medium P by calculating the transport distance from the count number of pulse signals of the encoder 20 from the rising edge to the falling edge of the distance information signal shown in Fig. 6.

[0038] Then, when the image data to be printed is image data as shown in FIG. 7, the control unit 60 compares the height information H of the printing medium P with the height information Hg of the image data, and also compares the width information W of the printing medium P with the width information Wg of the image data (S20).

[0039] It should be noted that, instead of using the height information Hg and width information Wg of the entire image data including the margins as in this embodiment, it is also possible to use the height information and width information of the image data that will actually be printed excluding the margins, as shown by the dotted rectangle in Fig. 7. The dotted rectangle in Fig. 7 is used to explain the height information and width information of the image data, and is not what will be printed.

[0040] Then, the control unit 60 determines the printing range of the image data based on the comparison results between the height information H of the printing medium P and the height information Hg of the image data, and the comparison results between the width information W of the printing medium P and the width information Wg of the image data (S22).

[0041] When H < Hg as shown in, for example, FIG. 8A, the control unit 60 masks the image data by deleting the upper part (the part of Hg - H) of the image data as shown in FIG. 8B, etc., so that the printing range of the image data fits within the printing surface Ps of the printing medium P. Further, when W < Wg as shown in, for example, FIG. 9A, the control unit 60 masks the image data by deleting the horizontal part (the part of Wg - W) of the image data as shown in FIG. 9B, etc., so that the printing range of the image data fits within the printing surface Ps of the printing medium P.

[0042] Further, the control unit 60 acquires the rising time of the distance information signal shown in FIG. 6, and counts the pulse signal of the encoder 20 from that rising time.

[0043] Then, the control unit 60 starts ink ejection from the head unit 10 (S24) when the count number of the pulse signal from the rising time of the distance information signal reaches the count number corresponding to the preset printing start timing. The count number corresponding to the printing start timing is calculated in advance based on the distance D shown in FIG. 4A and the printing start position in the conveyance direction on the printing surface Ps.

[0044] Then, the control unit 60 ejects ink from the line heads 11 to 14 of the head unit 10 based on the printing range of the image data determined as described above, and performs a printing process on the printing surface Ps (S26).

[0045] Then, as shown in FIG. 4C, when there is a printing medium P to be printed next (S28, YES), the processes from S16 to S26 are repeated. When there is no printing medium P to be printed next (S28, NO), the process ends.

[0046] According to the inkjet printing apparatus 1 of the present embodiment, a distance detection unit 5 is provided that detects the distance from above the printed medium P to the conveyed printed medium P. Based on the distance detected by the distance detection unit 5, the conditions for mask processing are determined, and printing control is performed based on the determined conditions. Therefore, it is possible to prevent ink ejection outside the printing surface of the printed medium without the user's effort.

[0047] In addition, since the mask processing is performed as described above, it is possible to prevent ink ejection outside the printing surface by simple processing.

[0048] In the inkjet printing apparatus 1 of the above embodiment, when the image data to be printed does not fit within the printing surface Ps of the printed medium P, mask processing is performed on the image data. However, the present invention is not limited to this, and reduction processing may be performed on the image data so that it fits within the printing surface Ps of the printed medium P.

[0049] For example, when the relationship between the height information H of the printed medium P and the height information Hg of the image data is H < Hg as shown in FIG. 10A, for example, the control unit 60 performs reduction processing on the image data so that it fits within the printing surface Ps of the printed medium P as shown in FIG. 10B.

[0050] Also, for example, when W < Wg as shown in FIG. 11A, reduction processing is performed on the image data so that it fits within the printing surface Ps of the printed medium P as shown in FIG. 11B. In this way, when reduction processing is performed, it is possible to prevent ink ejection outside the printing surface without missing the printed image.

[0051] In addition, when the control unit 60 performs reduction processing on the image data as described above, the character information included in the image data may be recognized, and the reduction processing conditions may be changed between the region of the character information and the region other than the region of the character information.

[0052] For example, if the image data to be printed is as shown in Fig. 7, it is possible to perform a reduction process on the image data of the illustration region R other than the text region so that it fits within the printing surface Ps of the printing medium P, while not performing a reduction process on the image data of the text region, as shown in Fig. 12. By not performing a reduction process on the text region in this way, it is possible to ensure the clarity of the text.

[0053] Regarding the recognition of the character area, information on the character area and information on other areas may be added to the image data, or the character data included in the image data may be automatically recognized. A known method for automatically recognizing the character data may be used, but for example, a convolutional neural network may be used.

[0054] Furthermore, when the printing medium P is transported using a circular transport belt 2b, as in the inkjet printing device 1 of the above embodiment, there may be a seam in the transport belt. When the printing medium P is transported using a transport belt with a seam, the printing medium P may be placed on the seam. When the printing medium P is placed on the seam in this way, the position of the printing medium P becomes higher, as shown in FIG. 13, and a misalignment of the printing position of the image data occurs.

[0055] Therefore, for example, if the height information H of the printing medium P is equal to or greater than a predetermined threshold, the control unit 60 may perform a shift process on the image data to move the image data to be printed upward based on the difference between the height information H of the printing medium P and the threshold.

[0056] The shift process may involve, for example, moving the image data upward by the amount corresponding to the difference between the height information H and the threshold value. By performing shift process on the image data based on the difference between the height information H of the printing medium P and the threshold value in this way, it is possible to prevent misalignment of the printing position of the image data even when the printing medium P is placed on a joint in the conveyor belt.

[0057] Furthermore, for the height information H of the printing medium P to be compared with the above threshold value, the average value of multiple height detection signals detected continuously while a specific printing medium P is transported under the distance detection unit 5 may be used, or the highest height detection signal among the multiple height detection signals may be used as the height information H.

[0058] Furthermore, the height information of the printing medium P set and input by the user may be used as the preset threshold value, or when performing printing processing on multiple printing media P, the threshold value may be the cumulative average of the height information H of multiple printing media P calculated sequentially as the multiple printing media P are transported sequentially. The cumulative average means that a new average value is calculated using the previous average value, the new value, and the number of elements.

[0059] Furthermore, when calculating the cumulative average of the height information H of the printing medium P as described above, the height information H of each printing medium may be the average value of multiple height detection signals detected continuously while being transported under the distance detection unit 5, or the highest height detection signal among the multiple height detection signals may be used.

[0060] Furthermore, in the inkjet printing apparatus 1 of the above embodiment, a masking process or a reduction process is performed as a method for preventing ink from being ejected outside the printing surface Ps, but this is not limiting. For example, in the case of image data that has a margin below the range of the image data that will actually be printed (the range indicated by the dotted square in FIG. 7), as in the image data shown in FIG. 7, if the height information H of the printing medium P is smaller than the height information Hg of the image data, the control unit 60 may perform a shift process that moves the range of the image data that will actually be printed, excluding the margin, downward. In this case, the shift process may be performed by a length of (Hg-H), for example.

[0061] In addition, the control unit 60 may compare the vertical length BL of the bottom margin of the range of image data to be actually printed (the range indicated by the dotted square in Figure 7) with the length (Hg-H), and if BL > (Hg-H), perform the above-mentioned shift processing, and if BL ≦ (Hg-H), perform the above-mentioned mask processing or reduction processing.

[0062] Furthermore, in the inkjet printing device 1 of the above embodiment, the distance detection unit 5 is provided above the print medium P, but the position of the distance detection unit 5 is not particularly limited as long as it is configured to detect the top surface of the print medium P. For example, a reflector is provided above the print medium P, and light is emitted toward the reflector and the light reflected by the reflector is directed downward (toward the print medium P). The distance may be measured by receiving the light that is reflected by the print medium P and then reflected by the reflector. The positions of the light emitting unit that emits light and the light receiving unit that receives the reflected light are not particularly limited. For example, the light emitting unit and light receiving unit may be provided below the conveyor belt by providing a thin hole in the conveyor belt that always transmits the emitted light and reflected light.

[0063] The present invention is not limited to the above-described embodiments, and the components can be modified and embodied in practice without departing from the spirit of the invention. Furthermore, various inventions can be formed by appropriately combining the multiple components disclosed in the above-described embodiments. For example, all of the components shown in the embodiments can be appropriately combined. Naturally, various modifications and applications are possible without departing from the spirit of the invention.

[0064] The present invention further discloses the following supplementary notes. (Addendum)

[0065] In the printing device of the present invention, if the height information of the printing medium calculated based on the distance detected by the distance detection unit is equal to or greater than a predetermined threshold, the control unit can determine the printing conditions based on the difference between the height information and the threshold.

[0066] In the printing device of the present invention, the control unit can determine, as the printing conditions, the conditions for reduction processing of image data to be printed on a printing medium.

[0067] In the printing device of the present invention, the control unit recognizes the character information contained in the image data, and can change the conditions for the reduction process between the area containing the character information and the area other than the area containing the character information.

[0068] In the printing device of the present invention, the control unit can determine, as the printing conditions, the conditions for masking the image data to be printed on the printing medium. [Explanation of symbols]

[0069] 1. Inkjet printing device 2 Transport unit 3 Support stand 4 Conveyor belt section 5. Distance detection unit 10 Head Unit 10~14 line head 11a~11f inkjet head 20 Encoder 60 Control Unit A. Distance H Height information of the printing medium Hg Height information of image data P Print media Ps printing side W Printing media width information Wg Image data width information

Claims

1. a conveying unit that conveys a three-dimensional print medium having a side surface that stands perpendicular to a conveying surface in a predetermined conveying direction; a head unit that ejects droplets onto a side surface of the print medium transported by the transport unit; a detection unit that is provided upstream of the head unit in the transport direction and above the top surface of the print medium, and that detects the height distance of the top surface of the print medium transported by the transport unit and the length of the top surface in the transport direction; a control unit that determines the range of the side of the printing medium based on the height distance of the top surface of the printing medium detected by the detection unit and the length of the top surface in the transport direction, compares the range of the side with the size of the image data to be printed, and based on the comparison result, performs image processing on the image data so that the printing range falls within the side, and controls printing based on the processed image data.

2. A printing device as described in claim 1, wherein when the height information of the printing medium calculated based on the distance of the height of the top surface detected by the detection unit is equal to or greater than a predetermined threshold, the control unit determines the conditions of the image processing based on the difference between the height information and the threshold.

3. 3. The printing device according to claim 1, wherein the control unit determines, as the image processing conditions, conditions for reduction processing of the image data to be printed on the printing medium.

4. 4. The printing device according to claim 3, wherein the control unit recognizes character information contained in the image data, and changes the conditions of the reduction process between an area containing the character information and an area other than the area containing the character information.

5. A printing device as described in Claim 4, wherein the control unit does not perform the reduction process on the area of ​​the character information, but performs the reduction process on an area other than the area of ​​the character information.

6. 3. The printing apparatus according to claim 1, wherein the control unit determines, as the image processing conditions, conditions for masking the image data to be printed on the printing medium.

7. A printing device as described in claim 1, wherein the control unit calculates a cumulative average of the height distance of the top surfaces of multiple printing media transported sequentially by the transport unit as a threshold value, and performs a shift process on the image data to be printed on the printing medium to be printed based on the difference between the calculated threshold value and the height distance of the top surfaces of the printing medium to be printed at this time, and performs printing control based on the image data after the shift process.

Images