Printing apparatus and method for adjusting the transport amount thereof

Abstract

This configuration provides a set of test patterns that can be printed to help obtain adjustment values ​​for reducing transport errors that occur in the edge regions in the transport direction of the printed area on the medium. [Solution] The printing apparatus comprises a recording head, a main scanning unit, a transport unit, and a control unit. The transport unit comprises an upstream drive roller including a first gear, a downstream drive roller including a second gear, and a rotating element meshed with the first gear and the second gear. The control unit performs control to form a first test pattern by ejecting droplets from the recording head, which is moving along the main scanning direction, into a cantilevered printing area when the phase of the rotating element is in the first phase, and to form a second test pattern by ejecting droplets from the recording head, which is moving along the main scanning direction, into the cantilevered printing area when the phase of the rotating element is in the second phase, which is shifted by k (n / m) periods from the first phase by 1 or more.

Description

Technical Field

[0001] The present invention relates to a printing apparatus that conveys a medium between main scans, and a method for adjusting the conveyance amount thereof.

Background Art

[0002] As a printing apparatus, an inkjet printer that alternately repeats main scanning in which droplets are ejected from a recording head moving along the main scanning direction onto a medium, and sub-scanning in which the medium is conveyed in a conveyance direction intersecting the main scanning direction between the main scans is known. The conveyance unit that conveys the medium includes an upstream-side conveyance roller pair positioned upstream from the recording head in the conveyance direction, and a downstream-side conveyance roller pair positioned downstream from the recording head. The upstream-side conveyance roller pair includes an upstream-side drive roller, and the downstream-side conveyance roller pair includes a downstream-side drive roller. The medium is conveyed in the conveyance direction by rotating the drive roller while at least one of the upstream-side conveyance roller pair and the downstream-side conveyance roller pair nips the medium.

[0003] Regarding the conveyance amount of the medium during each sub-scan, errors may occur due to eccentricity of the drive roller or a non-circular cross-sectional shape of the drive roller. Due to this error, density unevenness occurs, such as faint streaks like white streaks or dark streaks like black streaks. The recording apparatus disclosed in Patent Document 1 can record a test pattern group on the medium that helps to correctly obtain adjustment values for suppressing density unevenness by eliminating the influence of the conveyance roller error, which is the aforementioned error, as much as possible.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, even when adjustment values ​​were set in the printing device to suppress transport roller errors, it was found that density unevenness occurred in the edges of the printed area on the media in the transport direction. [Means for solving the problem]

[0006] The printing apparatus of the present invention is a printing apparatus capable of printing a group of test patterns for obtaining adjustment values ​​for the amount of media transported, A recording head capable of ejecting droplets onto the aforementioned medium, A main scanning unit that moves the recording head along the main scanning direction, A transport unit that transports the medium in a transport direction intersecting the main scanning direction, The system comprises a recording head, a main scanning unit, and a control unit that controls the operation of the transport unit, The aforementioned transport unit is An upstream drive roller, which includes a first gear and is located upstream of the recording head in the transport direction, A second gear is included, along with a downstream drive roller located downstream of the recording head in the transport direction, The system comprises a rotating element that meshes with the first gear and the second gear, At least one of the upstream drive roller and the downstream drive roller rotates in contact with the medium, thereby conveying the medium in the conveying direction. The printing area for the medium includes a cantilevered printing area in which the medium is transported with one of the upstream drive roller and the downstream drive roller separated. The aforementioned test pattern group includes a first test pattern and one or more second test patterns. The control unit, A first control that forms the first test pattern in the cantilever printing region when the rotating element is in a phase relative to the first phase, The present invention includes a second control, in which the second test pattern is formed in the cantilever printing area when the rotating element is in a phase relative to a second phase of 1 or more that is shifted by k(n / m) periods from the first phase, with m being an integer of 2 or more, n being an integer of 1 or more that is less than m, and k being all integers from 1 to m-1.

[0007] Furthermore, the present invention relates to a method for adjusting the transport amount of a printing apparatus, comprising a recording head capable of ejecting droplets onto a medium, a main scanning unit that moves the recording head along the main scanning direction, and a transport unit that transports the medium in a transport direction intersecting the main scanning direction, wherein the method for adjusting the transport amount of the medium is capable of printing a group of test patterns for obtaining an adjustment value for the transport amount of the medium. The aforementioned transport unit is An upstream drive roller, which includes a first gear and is located upstream of the recording head in the transport direction, A second gear is included, along with a downstream drive roller located downstream of the recording head in the transport direction, The system comprises a rotating element that meshes with the first gear and the second gear, At least one of the upstream drive roller and the downstream drive roller rotates in contact with the medium, thereby conveying the medium in the conveying direction. The printing area for the medium includes a cantilevered printing area in which the medium is transported with one of the upstream drive roller and the downstream drive roller separated. The aforementioned test pattern group includes a first test pattern and one or more second test patterns. The aforementioned method for adjusting the conveying amount is: A first step is to form the first test pattern in the cantilever printing region while the rotating element is in a phase relative to the first phase, A second step is to form the second test pattern in the cantilever printing area, where m is an integer of 2 or more, n is an integer of 1 or more and less than m, and k is all integers from 1 to m-1, and the rotation element is in a phase relative to a second phase of 1 or more that is shifted by k(n / m) periods from the first phase. A third step of adjusting the conveyance amount based on the first test pattern and one or more of the second test patterns, which has an aspect.

Brief Description of Drawings

[0008] [Figure 1] A diagram schematically showing an example of a printing apparatus. [Figure 2] A diagram schematically showing an example of a recording head and a printed image. [Figure 3] A diagram schematically showing examples of top printing, double-sided printing, and bottom printing. [Figure 4] A diagram schematically showing an example of the structure of a conveyance unit. [Figure 5] A diagram schematically showing an example of calculating an adjustment value from a first test pattern and a second test pattern. [Figure 6] A flowchart schematically showing an example of a conveyance amount adjustment process. [Figure 7] A diagram schematically showing an example of printing a test pattern group. [Figure 8] FIGS. 8A and 8B are diagrams schematically showing an example of adjusting the conveyance amount of a medium. [Figure 9] [[ID=三十二]]A diagram schematically showing another example of a test pattern group.

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described. Of course, the following embodiments are merely illustrative of the present invention, and not all of the features shown in the embodiments are necessarily essential to the solution means of the invention.

[0010] (1) Outline of the aspect included in the present invention: First, an outline of the aspect included in the present invention will be described with reference to the examples shown in FIGS. 1 to 9. Note that the drawings of the present application are diagrams schematically showing examples, and the magnification ratios in each direction shown in these drawings may be different, and the drawings may not be consistent. Of course, each element of this aspect is not limited to the specific examples indicated by the reference numerals. In the "outline of the aspect included in the present invention", the content in parentheses means a supplementary explanation of the immediately preceding word. Furthermore, in this application, the numerical range "Min~Max" means a value greater than or equal to the minimum value Min and less than or equal to the maximum value Max.

[0011] [Aspect 1] A printing apparatus 1 according to one embodiment, as illustrated in Figures 1 to 4, is a printing apparatus 1 capable of printing a test pattern group TP0 for obtaining an adjustment value V for the transport amount of a medium ME1 (for example, the transport amount L shown in Figure 8A), and comprises a recording head 30, a main scanning unit 40, a transport unit 50, and a control unit U1. The recording head 30 is capable of ejecting droplets 37 onto the medium ME1. The main scanning unit 40 moves the recording head 30 along the main scanning direction D1. The transport unit 50 transports the medium ME1 in a transport direction D3 that intersects the main scanning direction D1. The control unit U1 controls the operation of the recording head 30, the main scanning unit 40, and the transport unit 50. The conveying unit 50 comprises an upstream drive roller 51, a downstream drive roller 52, and a rotating element (e.g., a spur gear 53). The upstream drive roller 51 includes a first gear 51a and is located upstream of the recording head 30 in the conveying direction D3. The downstream drive roller 52 includes a second gear 52a and is located downstream of the recording head 30 in the conveying direction D3. The rotating element (53) meshes with the first gear 51a and the second gear 52a. The conveying unit 50 conveys the medium ME1 in the conveying direction D3 by rotating with at least one of the upstream drive roller 51 and the downstream drive roller 52 in contact with the medium ME1.

[0012] Here, the printing area AR0 for the medium ME1 includes a cantilevered printing area AR2 in which the medium ME1 is transported with one of the upstream drive roller 51 and the downstream drive roller 52 separated. The test pattern group TP0 includes a first test pattern TP1 and one or more second test patterns TP2. The control unit U1 performs the following processing, as illustrated in Figure 6. (a1) A first control (e.g., steps S102 to S106) in which the rotating element (53) is in a phase (e.g., rotation angle) with respect to a first phase (e.g., first angle θ1) (e.g., initial angle). (a2) A second control (e.g., steps S108 to S112) in which the second test pattern TP2 is formed in the cantilever printing area AR2, with m being an integer of 2 or more, n being an integer of 1 or more and less than m, and k being all integers from 1 to m-1, and the rotation element (53) being in a phase relative to (e.g., initial angle) a second phase (e.g., second angle θ2) which is shifted by k (n / m) periods from the first phase (θ1).

[0013] Tests revealed that in the cantilevered printing region AR2, where the medium ME1 is transported with one of the upstream drive rollers 51 and the downstream drive roller 52 separated, density unevenness occurs, which is thought to depend on the phase of the rotating element (53) rather than the drive rollers. In the double-sided printing region AR1, where the medium ME1 is transported with both the upstream drive roller 51 and the downstream drive roller 52 in contact, the aforementioned density unevenness was not observed. In the above embodiment, the first test pattern TP1 is printed on the cantilevered printing area AR2 when the rotating element (53) is in a phase relative to the first phase (θ1), and the second test pattern TP2 is printed on the cantilevered printing area AR2 when the rotating element (53) is in a phase relative to one or more second phases (θ2) that are shifted by k (n / m) periods from the first phase (θ1). Therefore, based on the printing position of the first test pattern TP1 and the printing positions of one or more second test patterns TP2, an adjustment value V can be determined so as to cancel out the transport error that depends on the phase of the rotating element (53), and the amount of transported medium ME1 can be adjusted to reduce the aforementioned transport error. Accordingly, the above embodiment can provide a printing apparatus capable of printing a group of test patterns that are useful for obtaining an adjustment value to reduce the transport error that occurs in the edge region in the transport direction of the printing area on the medium.

[0014] Various examples can be given to the embodiments described above. The term "medium" refers to an object transported by the transport unit, and is not limited to printed media. It may also refer to a laminate consisting of two or more layers, such as a laminate of a first printed medium and a second medium supporting the first medium. Examples of rotating elements include gears, toothed belts, chains, etc. The rotating element may also be a combination of multiple elements selected from the aforementioned elements, such as a combination of multiple gears. Examples of gears include spur gears, bevel gears, helical gears, etc. The phase of a rotating element can also be described as its rotational position. When a rotating element undergoes circular motion, such as in a spur gear, the rotation angle of the rotating element corresponds to its phase. When a rotating element is a combination of multiple elements, the phase of the rotating element is defined as the phase where the circumference of the rotating element is the least common multiple of the circumferences of the individual elements. The conveying unit may transmit the driving force from the rotating element to both drive rollers, or it may transmit the driving force from the upstream drive roller to the downstream drive roller via the rotating element, or it may transmit the driving force from the downstream drive roller to the upstream drive roller via the rotating element. The cantilevered printing area may be the upper printing area located on the upper end side in the transport direction of the printing area on the medium, or the lower printing area located on the lower end side in the transport direction of the printing area on the medium. In this application, "first," "second," ... are terms used to identify each component included in a group of similar components, and do not imply any order. Of course, the above-mentioned supplementary statement also applies in the following embodiments.

[0015] [Aspect 2] As illustrated in Figure 5, m=2 and n=1 is also acceptable. That is, the control unit U1 may perform the second control (S108~S112) to form the second test pattern TP2 in the cantilever printing area AR2 when the rotation element (53) is in a phase relative to the second phase (θ2), which is shifted by 1 / 2 period from the first phase (θ1). In the above case, since fewer test patterns need to be printed, the number of times the medium ME1 needs to be resupplied to the transport path or back-fed is reduced, and the test pattern set can be printed in a short time.

[0016] [Aspect 3] As illustrated in Figure 4, the downstream drive roller 52 may have a smaller diameter than the upstream drive roller 51. The cantilever printing area AR2 may include a lower end printing area AR4 in which the medium ME1 is conveyed by the rotation of the downstream drive roller 52 while the upstream drive roller 51 is separated, as illustrated in Figures 2, 3, etc. The control unit U1 may perform the first control (S102-S106) to form the first test pattern TP1 in the lower end printing area AR4, and the second control (S108-S112) to form the second test pattern TP2 in the lower end printing area AR4. The upstream drive roller 51 requires higher transport accuracy than the downstream drive roller 52 in order to accurately position the medium ME1 during medium transport between main scans. Since a larger roller diameter increases the contact area between the roller and the medium ME1, improving transport stability, the upstream drive roller 51 is generally larger in diameter than the downstream drive roller 52. If the medium ME1 is transported only by the smaller-diameter downstream drive roller 52, the transport error will be large, so a significant effect can be obtained in adjusting the transport amount by determining the adjustment value V based on the printing position of each test pattern printed in the lower end printing area AR4. Therefore, the above embodiment can provide a preferred example for printing a group of test patterns.

[0017] [Aspect 4] As illustrated in Figure 5, the first test pattern TP1 and the second test pattern TP2 may be a group of pitch lines in which multiple lines LN0 along the main scanning direction D1 are arranged at intervals in the transport direction D3. In the above case, since the adjustment value V can be calculated from multiple lines LN0, it is possible to provide a printing device that can print a set of test patterns that are useful for obtaining more accurate adjustment values.

[0018] [Aspect 5] As illustrated in Figure 5, the range RG of the pitch line group in the transport direction D3 may be less than or equal to the design circumference PM of the rotating element (53). Even if the range RG of the pitch line group in the transport direction D3 is less than or equal to the design circumference PM of the rotating element (53), a first test pattern TP1 based on the first phase (θ1) and a second test pattern TP2 based on the second phase (θ2) are formed in the cantilever printing area AR2. Therefore, regardless of the relationship between the design circumference PM of the rotating element (53) and the diameters of the downstream drive roller 52 and the upstream drive roller 51, the adjustment value V can be calculated. For example, if the design circumference PM of the rotating element (53) is larger than the downstream drive roller 52, it is not possible to form a test pattern for one rotation of the rotating element (53) in the area where the medium is transported cantilevered by the downstream drive roller alone. However, by making the range RG of the pitch line group smaller than the circumference of the rotating element (53) and dividing it into a first test pattern TP1 and a second test pattern TP2, a printing apparatus can be provided that can print a group of test patterns for which the adjustment value V can be calculated regardless of the size of each component of the transport section.

[0019] [Aspect 6] By the way, a method for adjusting the transport amount of a printing apparatus 1 according to one embodiment includes the following steps, as illustrated in Figure 6. (b1) A first step ST1 in which the first test pattern TP1 is formed in the cantilever printing region AR2 while the rotating element (53) is in a phase with respect to the first phase (θ1). (b2) A second step ST2 in which the second test pattern TP2 is formed in the cantilever printing area AR2, where m is an integer of 2 or more, n is an integer of 1 or more but less than m, and k is all integers from 1 to m-1, and the phase of the rotating element (53) is a phase based on a second phase (θ2) of 1 or more which is shifted by k (n / m) periods from the first phase (θ1). (b3) A third step ST3 in which the transport amount is adjusted based on the first test pattern TP1 and one or more second test patterns TP2.

[0020] In the above embodiment, the first test pattern TP1 is printed on the cantilever printing area AR2 when the rotating element (53) is in a phase relative to the first phase (θ1), and the second test pattern TP2 is printed on the cantilever printing area AR2 when the rotating element (53) is in a phase relative to one or more second phases (θ2) that are shifted by k (n / m) periods from the first phase (θ1). By adjusting the transport amount of the medium ME1 based on the first test pattern TP1 and one or more second test patterns TP2, the transport error that depends on the phase of the rotating element (53) is reduced. Therefore, the above embodiment can provide a transport amount adjustment method that reduces the transport error that occurs in the area at the edge in the transport direction of the printing area on the medium.

[0021] Furthermore, the above-described embodiments are applicable to a printing system including the above-described printing apparatus, a control method for the above-described printing apparatus, a control program for the above-described printing apparatus, a computer-readable non-temporary medium on which the control program is recorded, and so on. The above-described printing apparatus may consist of a plurality of distributed parts.

[0022] (2) Specific examples of printing devices: Figure 1 schematically illustrates a printing device 1. In this specific example, printing device 1 is assumed to be the printer 2 itself, but printing device 1 may also be a combination of printer 2 and host device HO1. Printer 2 may have an internal reading unit 19 for reading the print image IM3, and may include additional elements not shown in Figure 1. The reading unit 19 may be connected to printer 2 as an external device. Figure 2 schematically illustrates the recording head 30 and the print image IM3. Figure 3 schematically illustrates top-edge printing, double-sided printing, and bottom-edge printing. The printer 2 shown in Figure 1 is an inkjet printer that ejects liquid 36 containing ink as droplets 37, and is a serial printer that repeats main scanning and sub-scanning. The concept of liquid 36 includes ink containing colorants, processing liquids that react with the colorants in the ink, solutions that improve image quality, etc. Ink in a broad sense includes the aforementioned processing liquids and solutions. The droplets of ink are called ink droplets. The printer 2 includes a controller 10, a semiconductor memory RAM (Random Access Memory) 21, a communication I / F (interface) 22, a storage unit 23, an operation panel 24, a recording head 30, a main scanning unit 40, a transport unit 50, a reading unit 19, etc. The controller 10 is an example of a control unit U1. The control unit U1 may also be a combination of the controller 10 and a host device HO1. The controller 10, RAM 21, communication I / F 22, storage unit 23, and operation panel 24 are connected to a bus and are able to input and output information to each other.

[0023] The controller 10 includes a processor, a CPU (Central Processing Unit) 11, a color conversion unit 12, a halftone processing unit 13, a rasterization processing unit 14, a drive signal transmission unit 15, and the like. Based on an image IM1 acquired from either a host device HO1, a memory card (not shown), or the like, the controller 10 controls the ejection of droplets 37 by the recording head 30, the main scanning by the main scanning unit 40, and the transport of the medium ME1 by the transport unit 50. It can be said that the controller 10 controls the operation of the recording head 30, the main scanning unit 40, and the transport unit 50 so that a printed image IM3 corresponding to the image IM1 is formed on the medium ME1. The image IM1 may have, for example, two pixels each containing R (red), G (green), and B (blue). 8 Tone (or 2 16 An RGB image, represented by RGB data with integer values ​​for gradation, etc., can be applied. The controller 10 can be configured using an SoC (System on a Chip) or the like.

[0024] The CPU 11 is the device that primarily handles information processing and control in the printer 2. The color conversion unit 12 refers to a color conversion LUT (lookup table) which defines the correspondence between the gradation values ​​of R, G, and B and the gradation values ​​of C (cyan), M (magenta), Y (yellow), and K (black), and converts the RGB data representing the image IM1 into ink amount data DA1. The ink amount data DA1 is, for example, a 2-bit color of C, M, Y, and K for each pixel. 8 Tone (or 2 16 It has integer values ​​for gradation, etc. The ink amount data DA1 represents the amount of liquid 36 of C, M, Y, and K used per pixel. Also, if the resolution of the RGB data is different from the print resolution, the color conversion unit 12 first converts the resolution of the RGB data to the print resolution, or converts the resolution of the ink amount data DA1 to the print resolution.

[0025] The halftone processing unit 13 reduces the number of gradations in the gradation values ​​of each pixel constituting the ink amount data DA1 by performing halftone processing using one of the following methods: dithering, error diffusion, etc., thereby generating dot data DA2. The dot data DA2 represents the formation state of the dots 38 of the droplets 37 on a pixel-by-pixel basis. The dot data DA2 may be binary data indicating the presence or absence of dot formation, or it may be multi-level data with three or more gradations that can accommodate dots of different sizes, such as small, medium, and large. The rasterization processing unit 14 generates raster data DA3 by performing a rasterization process that rearranges the dot data DA2 in the order in which the dots 38 are formed during printing.

[0026] The drive signal transmission unit 15 generates a drive signal SG1 from the raster data DA3 and outputs it to the drive circuit 31 of the recording head 30. The drive signal SG1 corresponds to the voltage signal applied to the drive element 32 of the recording head 30. For example, if the raster data DA3 is "dot formation", the drive signal transmission unit 15 outputs a drive signal SG1 that ejects droplets for dot formation. Also, if the raster data DA3 is data with three or more values, the drive signal transmission unit 15 outputs a drive signal SG1 that ejects droplets for large dots if the raster data DA3 is "large dot formation", and outputs a drive signal SG1 that ejects droplets for small dots if the raster data DA3 is "small dot formation". The printed image IM3 is formed on the medium ME1 according to the drive signal SG1. The elements described above (11-15) may be configured as an ASIC (Application Specific Integrated Circuit), and the data to be processed may be read directly from RAM21 or the processed data may be written directly to RAM21.

[0027] The main scanning unit 40, controlled by the controller 10, includes a carriage drive unit 41 including a servo motor, a carriage 42 on which the recording head 30 is mounted, and a long guide 43 whose longitudinal direction is oriented in the main scanning direction D1. The main scanning unit 40 moves the carriage 42 back and forth along the main scanning direction D1 by driving the carriage drive unit 41 according to the control of the controller 10. In other words, the main scanning unit 40 moves the recording head 30 along the main scanning direction D1. The transport unit 50, controlled by the controller 10, includes an upstream roller pair (51, 61), a downstream roller pair (52, 62), a spur gear 53 as an example of a rotating element, and a drive source 54 such as a servo motor. The upstream roller pair includes an upstream drive roller 51 and an upstream driven roller 61, and is located upstream of the recording head 30 in the transport direction D3. Note that being located upstream of the recording head 30 means being located toward the recording head 30 in the transport path 49. The downstream roller pair includes a downstream drive roller 52 and a downstream driven roller 62, and is located downstream of the recording head 30 in the transport direction D3. Being located downstream of the recording head 30 means being located away from the recording head 30 in the transport path 49. The transport unit 50 transports the medium ME1 along the transport path 49 in the transport direction D3 by rotating the drive rollers (51, 52) according to the control of the controller 10. Although the transport path 49 shown in Figure 1 is curved, the transport path 49 may also be a straight path. The platen 48 in the transport path 49 supports the medium ME1 by contacting it.

[0028] As shown in Figure 2, the main scanning direction D1 is the direction that intersects with the nozzle alignment direction D4 of the nozzles 34 in the nozzle row 33, for example, the direction perpendicular to the nozzle alignment direction D4. Figure 2 shows that the right direction is the forward direction D11 of the main scanning, and the left direction is the return direction D12 of the main scanning. The carriage 42 is fixed to an endless belt (not shown) and is movable along the guide 43 in the forward direction D11 and the return direction D12. The transport direction D3 is the direction that intersects with the main scanning direction D1, for example, the direction perpendicular to the main scanning direction D1. When the transport unit 50 intermittently feeds the medium ME1 in the transport direction D3, the transport direction D3 can also be called the feeding direction. The sub-scanning direction D2 is the direction opposite to the transport direction D3. During the main scan, the controller 10 controls the main scanning unit 40 to move the recording head 30 along the main scanning direction D1 and to eject droplets 37 from the nozzle row 33. During the sub-scan between main scans, the controller 10 controls the transport unit 50 to send the medium ME1 a predetermined distance in the transport direction D3. The printer 2 forms a print image IM3, including the test pattern group TP0, on the medium ME1 by repeating the main scan and sub-scan. The medium ME1 is the printing medium that holds the print image. The material of the medium ME1 is not particularly limited, and various materials such as paper, resin, and metal are possible. The shape of the medium ME1 is also not particularly limited, and various shapes such as rectangles and rolls are possible, and it may also be a three-dimensional shape.

[0029] The recording head 30 shown in Figure 2 has multiple nozzle rows 33 on its nozzle surface 30a, each row having multiple nozzles 34 capable of ejecting droplets 37 onto the medium ME1, arranged in the nozzle alignment direction D4 at a predetermined nozzle pitch interval. Here, a nozzle means a small hole from which a droplet is ejected, and a nozzle row means an arrangement of multiple nozzles. The nozzle surface 30a is the ejection surface for the droplets 37. The multiple nozzles 34 in each nozzle row 33 may be arranged in a staggered pattern in the nozzle alignment direction D4, or in other words, in two rows in the nozzle alignment direction D4. The multiple nozzle rows 33 include a C nozzle row 33C capable of ejecting C ink as liquid 36, an M nozzle row 33M capable of ejecting M ink as liquid 36, a Y nozzle row 33Y capable of ejecting Y ink as liquid 36, and a K nozzle row 33K capable of ejecting K ink as liquid 36. Each droplet 37 is ejected from the nozzle 34 onto the medium ME1, targeting a pixel. Of course, a C droplet 37 forms a C dot 38 on the medium ME1, an M droplet 37 forms an M dot 38 on the medium ME1, a Y droplet 37 forms a Y dot 38 on the medium ME1, and a K droplet 37 forms a K dot 38 on the medium ME1. The printer 2 may have multiple recording heads 30.

[0030] The drive circuit 31 of the recording head 30 applies a voltage signal to the drive element 32 according to the drive signal SG1 input from the drive signal transmission unit 15. The drive element 32 may be a piezoelectric element that applies pressure to the liquid 36 in a pressure chamber communicating with the nozzle 34, or it may be a drive element that generates bubbles in the pressure chamber by heat to eject droplets 37 from the nozzle 34. Liquid 36 is supplied to the pressure chamber of the recording head 30 from a liquid supply unit 35 such as an ink cartridge or ink tank. The liquid 36 in the pressure chamber is ejected as droplets 37 from the nozzle 34 toward the medium ME1 by the drive element 32. As a result, dots 38 of droplets 37 are formed on the medium ME1, and a printed image IM3 represented by a pattern of dots 38 is formed on the medium ME1. The printer 2 may perform bidirectional printing, forming the print image IM3 in both the forward direction D11 and the return direction D12, or it may perform unidirectional printing, forming the print image IM3 in only one of the forward direction D11 or the return direction D12.

[0031] RAM21 stores images IM1 and the like received from the host device HO1 or memory (not shown). The communication I / F22 is connected to the host device HO1 by wire or wireless and inputs and outputs information to the host device HO1. The host device HO1 includes computers such as personal computers and tablet terminals, mobile phones such as smartphones, digital cameras, digital video cameras, etc. The storage unit 23 may be a non-volatile semiconductor memory such as flash memory, or a magnetic storage device such as a hard disk. The operation panel 24 includes an output unit 25 such as a liquid crystal panel for displaying information, an input unit 26 such as a touch panel for receiving operations on the display screen, etc.

[0032] The reading unit 19 may be a solid-state image sensor such as a line sensor or area sensor composed of CCD (Charge Coupled Devices), or it may be a CMOS (Complementary Metal-Oxide Semiconductor) image sensor, a CIS (Contact Image Sensor) type or CCD type image sensor, etc. In this specific example, the reading unit 19 is equipped with an analog / digital conversion circuit that converts the analog amount of the detection voltage of each pixel into a digital value, and the analog density amount corresponding to each detection voltage is converted into a digital density value by the analog / digital conversion circuit and output to the controller 10.

[0033] As shown in Figure 3, the transport unit 50 transports the medium ME1 in the transport direction D3 by rotating with at least one of the upstream drive roller 51 and the downstream drive roller 52 in contact with the medium ME1. As a result, upper edge printing PT1 is performed with the downstream drive roller 52 away from the medium ME1, then double-sided printing PT2 is performed with both drive rollers (51, 52) in contact with the medium, and finally lower edge printing PT3 is performed with the upstream drive roller 51 away from the medium ME1. The printing area AR0 for the medium ME1 is divided into the upper edge printing area AR3 where upper edge printing PT1 is performed, the double-sided printing area AR1 where double-sided printing PT2 is performed, and the lower edge printing area AR4 where lower edge printing PT3 is performed. Of course, the double-sided printing area AR1 is located between the upper edge printing area AR3 and the lower edge printing area AR4 in the transport direction D3. The upper edge printing area AR3 is the area where the medium ME1 is transported by the rotation of the upstream drive roller 51 with the downstream drive roller 52 away. The lower printing area AR4 is the area in which the medium ME1 is transported by the rotation of the downstream drive roller 52 while the upstream drive roller 51 is separated. The upper printing area AR3 and the lower printing area AR4 are a cantilevered printing area AR2 in which the medium ME1 is transported while either the upstream drive roller 51 or the downstream drive roller 52 is separated.

[0034] Figure 4 schematically illustrates the structure of the transport unit 50. The upstream drive roller 51 includes a coaxial first gear 51a that contacts the medium ME1 with its body 51b, and is located upstream of the recording head 30 in the transport direction D3. The downstream drive roller 52 includes a coaxial second gear 52a that contacts the medium ME1 with its body 52b, and is located downstream of the recording head 30 in the transport direction D3. The gears (51a, 52a) shown in Figure 4 are spur gears, but the gears (51a, 52a) may also be bevel gears, helical gears, etc. The diameter d1 of the body 51b of the upstream drive roller 51 is larger than the diameter d2 of the body 52b of the downstream drive roller 52. This is because the upstream drive roller 51 is required to have higher transport accuracy than the downstream drive roller 52 in order to accurately position the medium ME1 being transported during sub-scanning. The first gear 51a has a larger diameter than the second gear 52a in order to make the speed of the parts that contact the medium ME1 on the upstream drive roller 51 and the downstream drive roller 52 nearly the same. The spur gear 53 meshes with the first gear 51a and the second gear 52a. The diameter d3 of the spur gear 53 shown in Figure 4 is larger than the diameter of the gears (51a, 52a). The drive source 54 shown in Figure 4 directly rotates the spur gear 53, and as a result indirectly rotating the upstream drive roller 51, which includes the first gear 51a, and the downstream drive roller 52, which includes the second gear 52a. That is, the rotational driving force from the drive source 54 is transmitted to the upstream drive roller 51 and the downstream drive roller 52 via the spur gear 53. Figure 4 shows that the drive source 54 rotates the spur gear 53 counterclockwise, and as a result rotates the upstream drive roller 51 and the downstream drive roller 52 clockwise. A servo motor that operates according to the control of the controller 10 can be used as the drive source 54.

[0035] The drive source 54 may also directly rotate the upstream drive roller 51 or the downstream drive roller 52. When the drive source 54 directly rotates the upstream drive roller 51, the rotational driving force from the drive source 54 is transmitted to the downstream drive roller 52 via the first gear 51a and the spur gear 53. When the drive source 54 directly rotates the downstream drive roller 52, the rotational driving force from the drive source 54 is transmitted to the upstream drive roller 51 via the second gear 52a and the spur gear 53.

[0036] It is conceivable that "transport roller errors" may occur in the amount of media ME1 transported during each sub-scan, due to factors such as the drive rollers (51, 52) in contact with the media ME1 being eccentric or the cross-sectional shape of the drive rollers not being perfectly circular. Therefore, as disclosed in Japanese Patent Application Publication No. 2024-51459, the amount of media ME1 transported is adjusted by printing a group of test patterns designed to eliminate the effects of "transport roller errors" as much as possible. However, even when adjustment values ​​to suppress "transport roller errors" are set in the printer 2, it has been found that density unevenness occurs in the edge region of the print area AR0 in the transport direction D3, such as faint white streaks or dark black streaks. These streaks are also called banding. Tests revealed that density unevenness occurred in the upper printing area AR3 and the lower printing area AR4, i.e., the cantilevered printing area AR2, which is thought to depend on the rotation angle of the spur gear 53 rather than the drive rollers (51, 52). In the double-sided printing area AR1, where the medium ME1 is transported with both the upstream drive roller 51 and the downstream drive roller 52 in contact, the aforementioned density unevenness was not observed.

[0037] The reason why the aforementioned density unevenness occurs only in the cantilevered printing area AR2 is, although this is speculative, likely due to the following: The spur gear 53 may have manufacturing errors such as eccentricity or a non-circular cross-sectional shape. The dashed-dotted line in Figure 4 shows a spur gear 53A with an offset center CE. Due to such manufacturing errors, it is thought that density unevenness dependent on the rotation angle of the spur gear 53 occurs in the cantilever printing region AR2, where the peripheral speed of the spur gear 53 is directly transmitted to the drive rollers (51, 52). Here, the position where the spur gear 53 meshes with the first gear 51a is different from the position where it meshes with the second gear 52a. From this, it is thought that in the double-sided printing region AR1, the error in the amount of material transported, which appears via the upstream drive roller 51 due to the eccentricity of the spur gear 53, and the error in the amount of material transported, which appears via the downstream drive roller 52, cancel each other out to some extent. It is presumed that the above-mentioned density unevenness is not observed because the error dependent on the rotation angle of the spur gear 53 is canceled out to some extent in this way.

[0038] In this specific example, in order to suppress the density unevenness mentioned above, a test pattern group TP0, including the first test pattern TP1 and the second test pattern TP2, is printed in the cantilevered printing area AR2, as shown in Figure 2. The first test pattern TP1 and the second test pattern TP2 are printed with the rotation angles of the spur gear 53 differing by a predetermined angle. The details are explained below.

[0039] Figure 5 schematically illustrates how the adjustment value V is calculated from the test patterns (TP1, TP2). For clarity, Figure 5 exaggerates the transport error by assuming that, for every 30° rotation of the spur gear 53 (for example, every 30° rotation), a single line LN0 along the main scanning direction D1 is printed in the cantilever printing area AR2 by droplets 37 ejected from a predetermined nozzle 34. The controller 10 controls the rotation angle θ of the spur gear 53 and then controls the printing of lines LN0 by ejecting droplets 37 from a predetermined nozzle 34 of the recording head 30, which moves along the main scanning direction D1, into the cantilevered printing area AR2. The test patterns (TP1, TP2) can be described as a group of pitch lines in which multiple lines LN0 are arranged at intervals in the transport direction D3 along the main scanning direction D1. Here, the six lines LN0 in each pitch line group will be called lines LN1 to LN6. The same "predetermined nozzle 34" is used to form lines LN1 to LN6.

[0040] With respect to the first test pattern TP1 shown in Figure 5, the controller 10 performs a first control to form the first test pattern TP1 in the cantilever printing area AR2 when the spur gear 53 is at a rotation angle with respect to the first angle θ1. The first angle θ1 is an example of the first phase. The controller 10 sets the initial angle of the spur gear 53 to the first angle θ1 and prints a line LN1 in the cantilever printing area AR2 by ejecting droplets 37 from a predetermined nozzle 34 of the recording head 30 that moves along the main scanning direction D1. Next, the controller 10 rotates the spur gear 53 by 30° and prints a line LN2 in the cantilever printing area AR2 by ejecting droplets 37 from a predetermined nozzle 34 of the recording head 30 that moves along the main scanning direction D1. The amount LA1 of the media ME1 transported by the rotation of the spur gear 53 at this time is the distance between the line LN1 and the line LN2 in the transport direction D3. Next, the controller 10 rotates the spur gear 53 by 30° and prints line LN3 in the cantilever printing area AR2 by similar droplet ejection. The transport amount LA2 at this time is the distance between lines LN2 and LN3. Next, the controller 10 rotates the spur gear 53 by 30° and prints line LN4 in the cantilever printing area AR2 by similar droplet ejection. The transport amount LA3 at this time is the distance between lines LN3 and LN4. Next, the controller 10 rotates the spur gear 53 by 30° and prints line LN5 in the cantilever printing area AR2 by similar droplet ejection. The transport amount LA4 at this time is the distance between lines LN4 and LN5. At this point, if there is no transport error, the sum of transport amounts LA1 to LA4 is assumed to be a predetermined reference value RV. The reference value RV can be set according to, for example, the ideal value (let's call it α) when there is no error in the spacing between a predetermined pitch line and adjacent pitch lines, and in the example shown in Figure 5, it is 4α. Finally, the controller 10 rotates the spur gear 53 by 30° to print the line LN6 onto the cantilevered printing area AR2 by similar droplet ejection. The transport amount LA5 at this time is the distance between lines LN5 and LN6. The range RG of the pitch line group (LN1~LN6) in the transport direction D3 is less than or equal to the design circumference PM of the spur gear 53.

[0041] Regarding the second test pattern TP2 shown in Figure 5, the controller 10 performs a second control to form the second test pattern TP2 in the cantilever printing area AR2 when the rotation angle of the spur gear 53 is based on the second angle θ2, which is shifted by 1 / 2 period, or 180°, from the first angle θ1. The second angle θ2 is an example of the second phase. The controller 10 sets the initial angle of the spur gear 53 to the second angle θ2 and prints the line LN1 in the cantilever printing area AR2 by ejecting droplets 37 from a predetermined nozzle 34 of the recording head 30 that moves along the main scanning direction D1. Next, the controller 10 rotates the spur gear 53 by 30° and prints the line LN2 in the cantilever printing area AR2 by ejecting droplets 37 from a predetermined nozzle 34 of the recording head 30 that moves along the main scanning direction D1. The amount of media ME1 transported LB1 by the rotation of the spur gear 53 at this time is the distance between the line LN1 and the line LN2 in the transport direction D3. Subsequently, the controller 10 rotates the spur gear 53 by 30° increments, printing lines LN3, LN4, LN5, and LN6 onto the cantilever printing area AR2 by similar droplet ejection. Figure 5 also shows the transport amounts LB2 between lines LN2 and LN3, LB3 between lines LN3 and LN4, LB4 between lines LN4 and LN5, and LB5 between lines LN5 and LN6. The range RG of the pitch line group (LN1~LN6) in the transport direction D3 is less than or equal to the design circumference PM of the spur gear 53.

[0042] Assuming that the eccentricity of the spur gear 53 reduces the overall conveyance amounts LA1 to LA5 for the first test pattern TP1, as shown in Figure 5, then for the second test pattern TP2, the reference rotation angle θ differs by 180° from that of the first test pattern TP1, resulting in a tendency for the variation in conveyance amounts to be shifted by 180° compared to the first test pattern TP1. Figure 5 shows that the overall conveyance amounts LB1 to LB5 are larger for the second test pattern TP2. Therefore, in this specific example, both the transport amounts LA1-LA5 in the first test pattern TP1 and the transport amounts LB1-LB5 in the second test pattern TP2 are reflected in the adjustment value V. As a result, an adjustment value V is obtained in which the transport error caused by the rotation angle θ of the spur gear 53, in particular the transport error caused by the eccentricity of the spur gear 53, is canceled out, and the transport error occurring in the cantilevered printing area AR2 at the end of the printing area AR0 in the transport direction D3 can be reduced.

[0043] Figure 5 shows an example of calculating the adjustment value V, where the difference between the reference value RV and the corresponding transport amount is the individual error EA1, EA2, EB1, and EB2. As mentioned above, the reference value RV is a value determined based on the interval α of each pitch line group, and in the example shown in Figure 5, it is 4α. For the first test pattern TP1, the first individual error EA1 is 4α-(LA1+LA2+LA3+LA4), and the second individual error EA2 is 4α-(LA2+LA3+LA4+LA5). The average error EA0 is (EA1+EA2) / 2. For the second test pattern TP2, the first individual error EB1 is 4α-(LB1+LB2+LB3+LB4), and the second individual error EB2 is 4α-(LB2+LB3+LB4+LB5). The average error EB0 is (EB1+EB2) / 2. By setting the average value of these errors EA0 and EB0 (EA0 + EB0) / 2 to the adjustment value V, the transport error caused by the rotation angle θ of the spur gear 53 is canceled out, and the transport error occurring in the cantilever printing area AR2 is reduced.

[0044] Here, to explain the second control in general terms, let m be an integer greater than or equal to 2, n be an integer greater than or equal to 1 and less than or equal to m, and k be all integers from 1 to m-1. Here, for the sake of generalization, we will also describe the case where the period of the spur gear is greater than one period. By doing so, we can increase the number of pitch line groups formed by creating a group of pitch lines that is shifted so that the period of the spur gear is greater than one period, and thereby obtain a more accurate adjustment value V. The controller 10 performs the second control to form the second test pattern TP2 in the cantilever printing area AR2 when the spur gear 53 is at a rotation angle based on a second angle θ2 of 1 or more, which is shifted by k(n / m) periods from the first angle θ1. In the example shown in Figure 5, since m=2 and n=1, k can only be 1, and the k(n / m) period is 1 / 2 period, or 180°. As will be explained in more detail later, if m=3 and n=1 as shown in Figure 9, k will be 1 and 2, and the k(n / m) periods will be 1 / 3 period and 2 / 3 period, or 120° and 240°. In this case, as the second test pattern TP2, a group of pitch lines based on θ2=θ1+120° and a group of pitch lines based on θ2=θ1+240° will be printed in the cantilevered printing area AR2. If m=5 and n=2, k will be 1, 2, 3, and 4, and the k(n / m) period will be 2 / 5 period, 4 / 5 period, 6 / 5 period, and 8 / 5 period. In this case, as the second test pattern TP2, a group of pitch lines based on θ2=θ1+144°, a group of pitch lines based on θ2=θ1+288°, a group of pitch lines based on θ2=θ1+432°, and a group of pitch lines based on θ2=θ1+576° will be printed in the cantilevered printing area AR2.

[0045] Furthermore, the number of lines LN0 included in the test patterns (TP1, TP2) is not limited to 6; it may be 2 to 5, or even 7 or more. The rotation angle of the spur gear 53 between lines LN0 is not limited to 90°; it may be less than 90° or greater than 90°. By reducing the rotation angle of the spur gear 53 between lines LN0 and increasing the number of lines LN0 included in the test patterns (TP1, TP2), the adjustment value V can be calculated from more lines LN0, and a more accurate adjustment value V can be obtained. For example, suppose the rotation angle of the spur gear 53 between lines LN0 is 5°, and TP1 and TP2 are formed to have 25 pitch lines each. In this case, TP1 is formed while the spur gear 53 rotates in the range of θ1 to θ1+120°, and TP2 is formed while it rotates in the range of θ1+180° to θ1+180°+120°, that is, in the range of θ1+180° to θ1+300°. Furthermore, the reference value RV is not limited to 4α, which is the interval between 5 pitch lines; it can be α to 3α, or even 5α or more. For example, as mentioned above, if TP1 and TP2 each have 25 pitch lines, and the reference value RV is set to 14α, which is the average of 15 pitch lines, then EA1 = RV - (LA1 + LA2 + ... + LA14). The same applies to EB. In this case, EA and EB can be calculated from EA1 to EA11 and from EB1 to EB11, respectively, so the average error can be obtained from 11 individual errors, resulting in a more accurate adjustment value V. Furthermore, as long as the transport volume can be obtained, two or more of the multiple lines LN0 included in the test patterns (TP1, TP2) may be formed in the cantilever printing area AR2 in a single main scan.

[0046] (3) Specific examples of conveyance volume adjustment processes: Figure 6 schematically illustrates the transport amount adjustment process performed by the control unit U1 shown in Figure 1. Here, steps S102 to S106 correspond to the first process ST1 and the first control, steps S108 to S112 correspond to the second process ST2 and the second control, and steps S114 to S116 correspond to the third process ST3. Hereafter, the term "step" may be omitted, and the step number may be indicated in parentheses. Figure 7 schematically illustrates the printing of the test pattern group TP0 for obtaining the adjustment value V of the transport amount of the medium ME1 according to the flow in Figure 6.

[0047] The controller 10, acting as the control unit U1, performs at least the processes S102 to S112, and may also perform the processes S114 and S116. The processes S114 and S116 may be performed by the host device HO1, also acting as the control unit U1. The transport amount adjustment process starts when the controller 10 receives a print instruction for the test pattern group TP0. The print instruction may be an instruction resulting from a print request from the host device HO1 to the printer 2, or an instruction resulting from a print start operation to the input unit 26 of the printer 2, etc. As a prerequisite, the controller 10 prints a group of test patterns TP0 in the lower end printing area AR4, in which the rotation angle θ of the spur gear 53 is shifted by 180° between the first test pattern TP1 and the second test pattern TP2. The first test pattern TP1 and the second test pattern TP2 are printed so as to be aligned in the main scanning direction D1.

[0048] When the transport amount adjustment process starts, the controller 10 controls the rotation angle θ of the spur gear 53 so that the first angle θ1 is at the printing start position of the first test pattern TP1 in the lower end printing area AR4, for example, at the position of line LN1 shown in Figure 5 (S102). When the medium ME1 is supplied to the transport path 49 shown in Figure 1, it is nipped by the upstream roller pair (51, 61) and transported in the transport direction D3, and then nipped by the downstream roller pair (52, 62) and transported in the transport direction D3. Therefore, the controller 10 should control the drive rollers (51, 52) to idle so that the rotation angle θ of the spur gear 53 at the time the medium ME1 is nipped by the upstream roller pair (51, 61) is the first angle θ1 at the aforementioned printing start position.

[0049] After processing in S102, the controller 10 controls the transport of the medium ME1 in the transport direction D3 to the aforementioned printing start position, and controls the rotation angle θ of the spur gear 53 to the first angle θ1 as shown in Figure 7 (S104). Referring to the example shown in Figure 5, the medium ME1 is transported so that the droplets 37 ejected from a predetermined nozzle 34 of the recording head 30 land at the position of line LN1 in the lower end printing area AR4, and the rotation angle θ of the spur gear 53 becomes the first angle θ1.

[0050] After processing in S104, the controller 10 controls the recording head 30 to move along the main scanning direction D1 and print the first test pattern TP1 in the lower end printing area AR4 by ejecting droplets 37 from a predetermined nozzle 34 (S106). Referring to the example shown in Figure 5, the controller 10 prints line LN1 in the lower end printing area AR4 by droplets 37 from the predetermined nozzle 34 when the initial angle of the spur gear 53 is the first angle θ1, and thereafter controls the spur gear 53 to rotate by predetermined angles and print lines LN2, LN3, ... by droplets 37 from the predetermined nozzle 34. As a result of processing in S106, the first test pattern TP1, such as the pitch line group shown in Figure 6, is printed in the lower end printing area AR4 as a cantilevered printing area AR2. As described above, the controller 10 performs a first control to form the first test pattern TP1 in the cantilever printing area AR2 when the spur gear 53 is rotating at an angle relative to the first angle θ1.

[0051] After processing in S106, the controller 10 controls the rotation angle θ of the spur gear 53 so that the second angle θ2 occurs at the printing start position of the second test pattern TP2 in the lower end printing area AR4, for example, at the position of line LN1 shown in Figure 5 (S108). The second angle θ2 is shifted by 180° from the first angle θ1. For example, the controller 10 discharges the medium ME1 on which the first test pattern TP1 has been formed from the transport path 49, and controls the rotation angle θ of the medium ME1 that has been supplied back to the transport path 49 so that the second angle θ2 occurs at the aforementioned printing start position. The controller 10 only needs to control the drive rollers (51, 52) to idle so that the rotation angle θ of the spur gear 53 at the time the medium ME1 is nipped by the upstream roller pair (51, 61) is the second angle θ2 at the aforementioned printing start position. Furthermore, the transport unit 50 is capable of performing a backfeed, which returns the medium ME1 in the backfeed direction opposite to the transport direction D3, and is capable of disengaging the spur gear 53 from the gears (51a, 52a) of the drive rollers (51, 52). In this case, the controller 10 may perform control to backfeed the medium ME1 on which the first test pattern TP1 has been formed to the aforementioned printing start position, disengage the spur gear 53 from the gears (51a, 52a), rotate the spur gear 53 by 180°, and then re-engage the spur gear 53 from the gears (51a, 52a).

[0052] After processing in S108, the controller 10 controls the transport of the medium ME1 in the transport direction D3 to the aforementioned printing start position, and controls the rotation angle θ of the spur gear 53 to the second angle θ2 as shown in Figure 7 (S110). Referring to the example shown in Figure 5, the medium ME1 is transported so that the droplets 37 ejected from a predetermined nozzle 34 of the recording head 30 land at the position of line LN1 in the lower end printing area AR4, and the rotation angle θ of the spur gear 53 becomes the second angle θ2.

[0053] After processing in S110, the controller 10 controls the recording head 30 to move along the main scanning direction D1 and eject droplets 37 from a predetermined nozzle 34 to print the second test pattern TP2 next to the first test pattern TP1 in the lower end printing area AR4 (S112). Referring to the example shown in Figure 5, the controller 10 prints line LN1 in the lower end printing area AR4 by droplets 37 from the predetermined nozzle 34 when the initial angle of the spur gear 53 is the second angle θ2, and thereafter controls the spur gear 53 to rotate by predetermined angles to print lines LN2, LN3, ... by droplets 37 from the predetermined nozzle 34. As a result of processing in S112, the second test pattern TP2, such as the pitch line group shown in Figure 6, is printed in the lower end printing area AR4. That is, the test pattern group TP0, including the first test pattern TP1 and the second test pattern TP2, is formed in the lower end printing area AR4 as a cantilevered printing area AR2. As described above, the controller 10 performs a second control to form the second test pattern TP2 in the cantilever printing area AR2 when the rotation angle of the spur gear 53 is based on a second angle θ2 which is 180° shifted from the first angle θ1.

[0054] After processing in S112, the control unit U1, i.e., the controller 10 or host device HO1, causes the reading unit 19 to read the test pattern group TP0 on the medium ME1 and acquires the read data of the test pattern group TP0 (S114). Finally, the control unit U1 detects each line LN0 of the test patterns (TP1, TP2) from the read data, acquires the transport amount from the pitch line group, for example, the transport amounts LA1~LA5, LB1~LB5 shown in Figure 5, calculates an adjustment value V from the transport amount, and applies the adjustment value V to the printer 2 (S116). For example, the control unit U1 calculates the average error EA0 based on the transport amount obtained from the first test pattern TP1, calculates the average error EB0 based on the transport amount obtained from the second test pattern TP2, and calculates the adjustment value V = (EA0 + EB0) / 2. As described above, the control unit U1 obtains an adjustment amount V for adjusting the transport amount L of the medium ME1 (see Figure 8A).

[0055] Figure 8A schematically illustrates how the transport amount L of the medium ME1 is adjusted when it is greater than the value before adjustment, for example, the reference value RV. Figure 8B schematically illustrates how the transport amount L of the medium ME1 is adjusted when it is less than the value before adjustment, for example, the reference value RV. The memory unit 23 of the printer 2 shown in Figure 1 is capable of storing the adjustment value V, and the transport unit 50 transports the medium ME1 so that the transport amount is adjusted according to the adjustment value V. In Figures 8A and 8B, "RV" indicates that the stored value is the reference value RV, and "RV+V" indicates that the transport amount L is adjusted according to the adjustment value V.

[0056] In the example shown in Figure 8A, when the transport amount L is not adjusted ("RV"), a transport error Ei = RV - L occurs. In this case, the transport error Ei is a negative value and can vary depending on the rotation angle θ of the spur gear 53. An adjustment value V is obtained from the transport error Ei, taking the rotation angle θ into consideration, and this adjustment value V is stored in the storage unit 23. Then, the transport unit 50 adjusts the transport amount L according to the adjustment value V so that the absolute value of the transport error Ei decreases. In the example shown in Figure 8B, when the transport amount L is not adjusted ("RV"), the transport error Ei = RV - L is a positive value and can vary depending on the rotation angle θ of the spur gear 53. When an adjustment value V is obtained from the transport error Ei, taking the rotation angle θ into consideration, and this adjustment value V is stored in the storage unit 23, the transport unit 50 adjusts the transport amount L according to the adjustment value V so that the absolute value of the transport error Ei decreases.

[0057] As described above, the control unit U1 adjusts the transport amount L based on the first test pattern TP1 and the second test pattern TP2. As shown in the example above, the rotation angle θ of the spur gear 53 is shifted by 180° between the first test pattern TP1 and the second test pattern TP2. Therefore, by obtaining an adjustment value V based on the first test pattern TP1 and the second test pattern TP2, the transport error caused by the rotation angle θ of the spur gear 53 is canceled out. Accordingly, this example makes it possible to print a test pattern group TP0 that is useful for obtaining an adjustment value V to reduce the transport error that occurs in the cantilevered printing area AR2 at the end of the printing area AR0 on the medium ME1 in the transport direction D3. As a result, the transport error that occurs in the cantilevered printing area AR2 can be reduced. In addition, because the rotation angle θ is shifted by 180° between the first test pattern TP1 and the second test pattern TP2, fewer test patterns need to be printed. This reduces the number of times the medium ME1 needs to be resupplied to the transport path 49 or back-fed, and the test pattern group TP0 can be printed in a short time.

[0058] Furthermore, by forming the test pattern group TP0 in the lower printing area AR4, transport errors caused by the downstream drive roller 52 having a smaller diameter than the upstream drive roller 51 can be effectively reduced. Moreover, since the test patterns (TP1, TP2) are pitch line groups, the adjustment value V can be calculated from multiple lines LN0, making it possible to print a test pattern group TP0 that helps in obtaining a more accurate adjustment value V. Furthermore, even if the range RG of the pitch line group in the transport direction D3 is less than or equal to the design circumference PM of the spur gear 53, in particular less than the circumference PM, and even less than or equal to PM / 2, since the first test pattern TP1 based on the first angle θ1 and the second test pattern TP2 based on the second angle θ2 are formed in the cantilever printing area AR2, the adjustment value V can be calculated regardless of the relationship between the circumference PM and the diameters of the drive rollers (51, 52). Therefore, it is possible to print a test pattern group TP0 that can calculate the adjustment value V regardless of the size of each component of the transport unit 50.

[0059] (4) Variations: Various modifications of this invention are conceivable. For example, the color combination of liquid 36 is not limited to C, M, Y, and K, but may also include orange, green, light cyan at a lower concentration than C, light magenta at a lower concentration than M, dark yellow at a higher concentration than Y, light black at a lower concentration than K, colorless for image quality improvement, etc. Also, some of the colors in the color combination of liquid 36 C, M, Y, and K may be omitted. The entity performing the above-described processing is not limited to the CPU; it may also be an electronic component other than the CPU, such as an ASIC. Of course, multiple CPUs may cooperate to perform the above-described processing, or a CPU and another electronic component (such as an ASIC) may cooperate to perform the above-described processing. The drive rollers (51, 52) may not only transport the medium in contact with the medium to be printed on, but may also transport a laminate of the first medium to be printed on and one or more second mediums in contact with the second medium. The second medium may include a support medium such as a sheet or film that supports the first medium, a protective medium such as a sheet or film that protects the first medium, and so on.

[0060] The rotating element described above was a spur gear 53, but the rotating element may be a gear other than a spur gear, or a toothed belt, chain, etc. Also, the rotating element may be a combination of multiple elements. For example, if the rotating element is a combination of multiple spur gears, the number of teeth of each spur gear can be taken as the circumference, and the least common multiple of these tooth counts can be treated as the number of teeth of the rotating element. Of course, the multiple elements included in the rotating element may be a combination of multiple gears other than spur gears, or may include a toothed belt, chain, etc.

[0061] As illustrated in Figure 9, a group of test patterns TP0 in which the rotation angle θ of the spur gear 53 is shifted by less than 180° between the first test pattern TP1 and the second test pattern TP2 may be printed on the cantilever printing area AR2. Figure 9 shows a medium ME1 in which the second test pattern TP2 is formed on the cantilever printing area AR2 when m=3 and n=1, and the rotation angle of the spur gear 53 is based on multiple second angles θ2 which are shifted by k (n / m) periods from the first angle θ1. Each test pattern (TP1, TP2) is a group of pitch lines including multiple lines LN0. In the example shown in Figure 9, the controller 10 performs a first control to form a first test pattern TP1 in the upper printing area AR3 and the lower printing area AR4 when the spur gear 53 is rotating at an angle relative to a first angle θ1. The controller 10 also performs a second control to form a second test pattern TP2 with k=1 in the upper printing area AR3 and the lower printing area AR4 when the spur gear 53 is rotating at an angle relative to a second angle θ2 = θ1 + 120°, which is 120° from the first angle θ1, and a second control to form a second test pattern TP2 with k=2 in the upper printing area AR3 and the lower printing area AR4 when the spur gear 53 is rotating at an angle relative to a second angle θ2 = θ1 + 240°, which is 240° from the first angle θ1. As a result, the first test pattern TP1 based on the first angle θ1, the second test pattern TP2 based on the second angle θ2 = θ1 + 120° when k=1, and the second test pattern TP2 based on the second angle θ2 = θ1 + 240° when k=2 are printed in the upper printing area AR3 and the lower printing area AR4.

[0062] The control unit U1 can obtain multiple first individual errors from the first test pattern TP1, multiple second individual errors from the second test pattern TP2 with k=1, and multiple third individual errors from the second test pattern TP2 with k=2, from the test pattern group TP0 shown in Figure 9. Next, the control unit U1 can calculate the first average error from the multiple first individual errors, the second average error from the multiple second individual errors, and the third average error from the multiple third individual errors. Then, the control unit U1 can calculate an adjustment value V by averaging the first average error, the second average error, and the third average error. By storing the adjustment value V in the storage unit 23, the transport unit 50 adjusts the transport amount according to the adjustment value V so that the transport error is reduced. Of course, there are various possible combinations of m and n, such as m=4 and n=1, m=5 and n=1, m=5 and n=2, and so on.

[0063] (5) Conclusion: As described above, according to the present invention, in various embodiments, it is possible to provide a printing apparatus capable of printing a group of test patterns useful for obtaining adjustment values ​​to reduce transport errors occurring in the edge region of the printing area on a medium in the transport direction, a transport amount adjustment method for reducing transport errors occurring in the edge region of the printing area on a medium in the transport direction, and other configurations. Of course, even in embodiments consisting only of the constituent elements of the independent claims, the basic functions and effects described above can be obtained. Furthermore, configurations obtained by substituting or changing the combinations of each configuration disclosed in the above-mentioned examples, configurations obtained by substituting or changing the combinations of each configuration disclosed in the prior art and the above-mentioned examples, etc., are also possible. The present invention also includes these configurations, etc. [Explanation of Symbols]

[0064] 1…Printing device, 2…Printer, 10…Controller, 19…Reading unit, 30…Recording head, 33…Nozzle row, 34…Nozzle, 36…Liquid, 37…Droplet, 38…Dot, 40…Main scanning unit, 41…Carriage drive unit, 42…Carriage, 50…Conveying unit, 51…Upstream drive roller, 51a…First gear, 51b…Main body, 52…Downstream drive roller, 52a…Second gear, 52b…Main body, 53…Spur gear, 54…Drive source, 61…Upstream driven roller, 62…Downstream driven roller, AR0…Printing area, AR1…Double-sided printing area, AR2…Single-sided printing area, AR3…Upper Edge printing area, AR4...Bottom edge printing area, D1...Main scanning direction, D2...Sub scanning direction, D3...Transport direction, D4...Nozzle alignment direction, HO1...Host device, IM1...Image, IM3...Printed image, L...Transport amount, LN0...Line, ME1...Media, PM...Perimeter, PT1...Top edge printing, PT2...Double-sided printing, PT3...Bottom edge printing, RG...Range, ST1...First process, ST2...Second process, ST3...Third process, TP0...Test pattern group, TP1...First test pattern, TP2...Second test pattern, U1...Control unit, V...Adjustment value, d1, d2, d3...Diameter, θ1...First angle, θ2...Second angle.

Claims

1. A printing apparatus capable of printing a set of test patterns for obtaining adjustment values ​​for the amount of media transported, A recording head capable of ejecting droplets onto the aforementioned medium, A main scanning unit that moves the recording head along the main scanning direction, A transport unit that transports the medium in a transport direction intersecting the main scanning direction, The system comprises a recording head, a main scanning unit, and a control unit that controls the operation of the transport unit, The aforementioned transport unit is An upstream drive roller, which includes a first gear and is located upstream of the recording head in the transport direction, A second gear is included, along with a downstream drive roller located downstream of the recording head in the transport direction, The system comprises a rotating element that meshes with the first gear and the second gear, At least one of the upstream drive roller and the downstream drive roller rotates in contact with the medium, thereby conveying the medium in the conveying direction. The printing area for the medium includes a cantilevered printing area in which the medium is transported with one of the upstream drive roller and the downstream drive roller separated. The aforementioned test pattern group includes a first test pattern and one or more second test patterns. The control unit, A first control that forms the first test pattern in the cantilever printing region when the rotating element is in a phase relative to the first phase, A printing apparatus that performs a second control, in which the rotating element is in a state in which the second test pattern is formed in the cantilever printing area when m is an integer of 2 or more, n is an integer of 1 or more and less than m, and k is all integers from 1 to m-1, and the rotation element is in a state in which the rotation element is in a state based on a second phase of 1 or more which is shifted by k (n / m) periods from the first phase.

2. The printing apparatus according to claim 1, wherein the control unit performs the second control to form the second test pattern in the cantilever printing area when the rotating element is in a phase relative to the second phase which is shifted by 1 / 2 period from the first phase.

3. The downstream drive roller has a smaller diameter than the upstream drive roller. The cantilever printing area includes a lower end printing area in which the medium is transported by the rotation of the downstream drive roller while the upstream drive roller is separated, The printing apparatus according to claim 1 or 2, wherein the control unit performs the first control to form the first test pattern in the lower end printing area, and the second control to form the second test pattern in the lower end printing area.

4. The printing apparatus according to claim 1 or claim 2, wherein the first test pattern and the second test pattern are a group of pitch lines in which multiple lines are arranged at intervals in the transport direction along the main scanning direction.

5. The printing apparatus according to claim 4, wherein the range of the pitch line group in the transport direction is less than or equal to the design circumference of the rotating element.

6. A method for adjusting the transport amount of a printing apparatus, comprising a recording head capable of ejecting droplets onto a medium, a main scanning unit that moves the recording head along the main scanning direction, and a transport unit that transports the medium in a transport direction intersecting the main scanning direction, wherein the apparatus is capable of printing a group of test patterns for obtaining an adjustment value for the transport amount of the medium, The aforementioned transport unit is An upstream drive roller, which includes a first gear and is located upstream of the recording head in the transport direction, A second gear is included, along with a downstream drive roller located downstream of the recording head in the transport direction, The system comprises a rotating element that meshes with the first gear and the second gear, At least one of the upstream drive roller and the downstream drive roller rotates in contact with the medium, thereby conveying the medium in the conveying direction. The printing area for the medium includes a cantilevered printing area in which the medium is transported with one of the upstream drive roller and the downstream drive roller separated. The aforementioned test pattern group includes a first test pattern and one or more second test patterns. The aforementioned method for adjusting the conveying amount is: A first step of forming the first test pattern in the cantilever printing region while the rotating element is in a phase relative to the first phase, A second step is to form the second test pattern in the cantilever printing area, where m is an integer of 2 or more, n is an integer of 1 or more and less than m, and k is all integers from 1 to m-1, and the rotation element is in a phase relative to a second phase of 1 or more that is shifted by k (n / m) periods from the first phase. A method for adjusting the amount of material being transported, comprising a third step of adjusting the amount of material being transported based on the first test pattern and one or more second test patterns.

Images