JP5577920B2 - Printer - Google Patents

Description

  The present invention relates to a technique for suppressing the occurrence of color misregistration.

  A conventionally known line printer includes a long ink nozzle unit provided with nozzles, and performs a printing operation for each line. In the case of a color printer, an ink nozzle unit is provided for each color.

  FIG. 10A is a diagram of a plurality of ink nozzle units 100 of a conventional color line printer as viewed from the ink ejection surface side. Each ink nozzle unit 100 includes a plurality of nozzle forming portions 101 arranged in the longitudinal direction, and nozzles for ejecting ink are densely provided in each nozzle forming portion 101. FIG. In FIG.

  As shown in FIG. 10A, four ink nozzle units 100 are provided at predetermined intervals HD, and each ink nozzle unit 100 ejects ink of different colors from the nozzles. In the printing operation, by ejecting ink from each of the four ink nozzle units 100, for example, four lines having different colors are printed on a sheet. Then, the paper is transported in the transport direction A, and four lines are printed again.

  In the example shown in FIG. 10A, ink nozzle units 100Y and 100C that discharge Y (yellow), C (cyan), M (magenta), and K (black) ink from the upstream side in the sheet conveyance direction. , 100M, 100K in this order.

  Therefore, as the printing and the conveyance of the paper are repeated, the Y line first printed on the paper by the ink nozzle unit 100Y is positioned immediately below the ink nozzle unit 100C. The C line is printed so that it overlaps with. That is, after the Y line is printed, when the paper is conveyed by a predetermined interval HD, the C line is printed on the same line, and when the paper is further conveyed by the predetermined interval HD, the same line is printed. Are printed with M lines overlaid, and when the paper is further conveyed by a predetermined interval HD, K lines are printed over the same lines. Thereby, a color image is printed on the paper.

JP 2008-168497 A JP-A-8-281983 JP-A-11-147328 JP-A-11-198460

  However, line printers are prone to print quality degradation due to mechanical variations, and there is a problem in that even if an attempt is made to land ink at the same position on a sheet, the landing position is shifted and color misregistration occurs. That is, the conveyance of the sheet is performed by a plurality of rollers and a gear that transmits driving. Variations occur in the rollers and gears constituting the transport system due to manufacturing errors, temporal variations, environmental variations, and the like. If the roller deviates from a perfect circle or if vibration occurs due to the meshing of the gears, meandering of the paper will occur. As a result, even if inks of different colors are to be landed at the same position, the positions are shifted.

  FIG. 10B is a diagram schematically showing a mechanism that causes variations in the landing positions of ink. On the left side of the drawing, the arrangement of the nozzle forming portions 101 of the respective colors is illustrated, and on the right side of the drawing, the state of meandering of the paper is shown as a graph. The graph on the right side of the drawing shows the relationship between the amplitude of the meandering of the paper on the horizontal axis and the conveyance distance of the paper on the vertical axis. Further, the circles shown in the graph on the right side of the drawing indicate the ink landing positions 102 at the respective transport distances.

  As described above, in the case of printing with Y, C, M, and K being overlapped in this order, Y ink is landed on the paper first, and then when the paper is conveyed by a predetermined distance HD, the C ink is placed at the same position. When ink is landed and then the paper is transported HD by a predetermined interval, M ink is landed at the same position, and when the paper is transported HD by a predetermined distance, K ink is landed at the same position. That is, in the graph on the right side of FIG. 10B, ideally, the Y ink landing positions 102Y, the C ink landing positions 102C, the M ink landing positions 102M, and the K ink landing positions 102K are vertically aligned. It is desirable to line up.

  However, in practice, the paper is conveyed while meandering. Therefore, even if each color ink is made to land on the same point on the paper, in actuality, as shown in FIG. 10B, the landing positions of the respective inks vary, causing color misregistration.

  SUMMARY An advantage of some aspects of the invention is that it provides a printer that can suppress variations in the landing positions of ink and suppress the occurrence of color misregistration.

  In order to achieve this object, a printer of the present invention includes a driving roller for transporting a recording medium in a first direction and a dot for forming dots on the recording medium transported in the first direction. A plurality of ink nozzle units, each ink nozzle unit being arranged such that a longitudinal direction of each ink nozzle unit is along a second direction orthogonal to the first direction, and the plurality of ink nozzle units Two adjacent ink nozzle units of the units include the plurality of ink nozzle units arranged at positions separated by a predetermined interval, and the length of the outer periphery of the driving roller is the driving roller Is set so that the distance that the recording medium is transported in the first direction becomes approximately HD / a when the recording medium rotates once, and the HD indicates the predetermined interval. Wherein a represents an integer of 1 or more.

  According to the printer described above, the driving roller takes substantially the same phase every time the recording medium is conveyed by a predetermined interval HD. Therefore, the dots formed by a certain ink nozzle unit and the dots formed by the next ink nozzle unit when the recording medium is conveyed by a predetermined distance HD in the first direction are accompanied by the rotation of the drive roller. Even if the recording medium meanders, it is formed at substantially the same position on the recording medium. Therefore, variation in the ink landing position can be suppressed, and occurrence of color misregistration can be suppressed.

  The printer further includes a driven roller that is driven by the drive roller. The length of the outer periphery of the driven roller is such that the recording medium is conveyed in the first direction when the driven roller makes one rotation. The distance is set to be approximately HD / b, and b preferably represents an integer of 1 or more. In this way, even if the recording medium meanders with the rotation of the driven roller, the plurality of ink nozzle units can form dots at substantially the same position on the recording medium. And the occurrence of color misregistration can be suppressed.

  The printer further includes a pinch roller that comes into contact with the recording medium conveyed in the first direction, and the outer circumference of the pinch roller has a length when the pinch roller rotates once. Is set so that the distance conveyed in the first direction is approximately HD / c, and c preferably represents an integer of 1 or more. In this way, even if the recording medium meanders with the rotation of the pinch roller, the plurality of ink nozzle units can form dots at substantially the same position on the recording medium. And the occurrence of color misregistration can be suppressed.

  In the above-described printer, the recording medium further driven by the driving roller to convey the recording medium in the first direction, and the recording medium that contacts the endless belt and is conveyed in the first direction. Is provided with a non-contact roller that does not come into contact with the outer circumference of the non-contact roller so that the recording medium is transported in the first direction when the non-contact roller makes one rotation. The d is preferably an integer of 1 or more. In this way, even if the recording medium meanders as the non-contact roller rotates, the plurality of ink nozzle units can form dots at substantially the same position on the recording medium. Variations can be suppressed and the occurrence of color misregistration can be suppressed.

  In the above printer, further comprising an endless belt that is driven by the drive roller to convey the recording medium in the first direction, and the length of the outer periphery of the roller existing on the inner peripheral side of the endless belt is: It is preferable that the thickness is set in consideration of the thickness of the endless belt, and the outer peripheral length of the roller existing on the outer peripheral side of the endless belt is set to a value irrelevant to the thickness of the endless belt.

  In the printer described above, the a is preferably an integer of 1 to 3. In this way, a more robust design can be achieved as compared to the case where a is a larger integer.

  In the above-described printer, the ink nozzle unit further includes a plurality of nozzle rows each including a plurality of nozzles arranged along the longitudinal direction of the ink nozzle unit, and is orthogonal to the longitudinal direction of the ink nozzle unit. When the distance between the nozzles located at both ends of the ink nozzle unit in the direction of movement is ND, the distance that the recording medium is conveyed in the first direction when the drive roller makes one rotation is approximately ND / f. It is preferable that the length of the outer periphery of the drive roller is set so that f represents an integer of 1 or more.

  According to the above-described printer, it is possible to suppress the variation in the ink landing position between the nozzles located at both ends in the direction orthogonal to the longitudinal direction of the ink nozzle unit from being affected by the meandering of the recording medium. .

  In the printer, the ink nozzle unit that forms M color dots and the ink nozzle unit that forms C color dots among the plurality of ink nozzle units are preferably arranged adjacent to each other. .

  According to the above-described printer, it is possible to suppress the variation in the ink landing position, particularly for the color in which the variation in the ink landing position is more conspicuous.

(A) is a fragmentary sectional view of the printer which is 1st Embodiment of this invention, (b) is a bottom view of an ink nozzle unit. It is a figure explaining arrangement | positioning of the nozzle formed in a nozzle formation part, It is a figure which takes the position in the longitudinal direction of an ink nozzle unit on a horizontal axis, and takes the position in a conveyance direction on a vertical axis | shaft. It is a figure explaining the operation | movement of dot row formation for 1 line by an ink nozzle unit. 5 is a table showing the relationship between the conveyance amount of paper per rotation of each roller and the outer circumference and diameter of each roller derived from the conveyance amount of paper per rotation. (A) is a figure which shows typically the structure of a conveyance mechanism, (b) is arrange | positioned at the conveyance amount of the sheet | seat per rotation of the roller arrange | positioned at the inner peripheral side of an endless belt, and an outer peripheral side. FIG. 6 is a diagram showing a comparison of a sheet conveyance amount per rotation of a roller. It is a figure explaining the mechanism by which the variation of an ink landing position is suppressed by the printer of this embodiment. 6 is a graph showing a result of simulating a relationship between a meandering cycle of paper and variations in ink landing positions. (A) is a figure explaining the dot row | line for 1 line formed by the ink nozzle unit attached with the ideal attachment angle, (b) was inclined and attached from the ideal attachment angle. It is a figure explaining the dot row for 1 line formed of an ink nozzle unit. It is a figure which shows typically the conveyance mechanism of the printer of a modification. (A) is the figure which looked at the ink nozzle unit of the conventional color line printer from the ink discharge surface side, (b) is the figure which showed typically the mechanism in which the dispersion | variation in the landing position of an ink generate | occur | produces. is there.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1A is a partial cross-sectional view of the printer 1 according to the first embodiment of the present invention. The printer 1 is an inkjet line printer.

  The printer 1 is provided with a paper feed mechanism 20, a transport mechanism 30, a recording mechanism 40, and a paper discharge mechanism 60. The paper feed mechanism 20 is provided with a paper feed tray 21 capable of storing a plurality of sheets P (an example of a recording medium) and a paper feed roller 22. The paper feed roller 22 sends out the uppermost paper P among the plurality of papers P stacked and stored in the paper feed tray 21 one by one to the transport mechanism 30 described later.

  A pair of feed rollers 23a and 23b and a pair of feed rollers 24a and 24b are arranged between the paper feed mechanism 20 and the transport mechanism 30 along the transport path of the paper P. The paper P sent out from the paper feed mechanism 20 is sent out to the transport mechanism 30 while being guided by the feed roller pair 23a, 23b and the feed roller pair 24a, 24b.

  The transport mechanism 30 includes an endless belt 31, a driving roller 32, a driven roller 33, a platen 34, an upstream pinch roller 35, a downstream pinch roller 36, a cleaning roller 37, and a cleaning pinch roller 38. Provided. The endless belt 31 is wound around a driving roller 32 and a driven roller 33. The drive roller 32 is a roller for transporting the paper P in the transport direction A, and is connected to a transport motor (not shown). The drive roller 32 is rotated in the direction of arrow B in FIG. To do. The endless belt 31 is driven by the drive roller 32 to travel so as to transport the paper P in the transport direction A, and the driven roller 33 is also driven by the drive roller 32 to rotate. The outer peripheral surface 31a of the endless belt 31 is subjected to silicone treatment and has adhesiveness.

  The platen 34 has a portion of the endless belt 31 that faces the ink nozzle units 41Y, 41C, 41M, and 41K (hereinafter referred to as the ink nozzle unit 41 when there is no need to distinguish between them) on the inner peripheral surface of the endless belt 31. It supports from the 31b side.

  The upstream pinch roller 35 is rotatably installed above the driven roller 33, and the downstream pinch roller 36 is rotatably installed above the drive roller 32. The upstream pinch roller 35 and the downstream pinch roller 36 are urged downward by a spring (not shown), come into contact with the outer peripheral surface 31 a of the endless belt 31, and rotate as the endless belt 31 travels. When the paper P has been transported, the upstream pinch roller 35 and the downstream pinch roller 36 come into contact with the paper P, so that the paper P transported in the transport direction A is placed between the endless belt 31. Rotate with pinching.

  The cleaning roller 37 rotates in contact with the outer peripheral surface 31 a of the endless belt 31 to remove dust attached to the outer peripheral surface 31 a of the endless belt 31. The cleaning pinch roller 38 is disposed so as to contact the inner peripheral surface 31 b of the endless belt 31 and sandwich the endless belt 31 with the cleaning roller 37. The cleaning roller 37 and the cleaning pinch roller 38 are disposed at a position where they contact the endless belt 31 but do not contact the paper P conveyed in the conveyance direction A by the endless belt 31.

  In this configuration, the paper P sent out from the paper feed mechanism 20 to the transport mechanism 30 is adhesively held on the outer peripheral surface 31 a of the endless belt 31, and the ink nozzle unit 41 of the recording mechanism 40 as the endless belt 31 travels. And is conveyed to the area opposite to.

  The recording mechanism 40 will be described. The recording mechanism 40 is provided with an ink nozzle unit 41 for forming dots on the paper P transported in the transport direction A, and a frame 43. As shown in FIG. 1A, the ink nozzle unit 41 is transported in the order of ink nozzle units 41Y, 41C, 41M, and 41K that discharge Y, C, M, and K inks from the upstream side in the transport direction A. Arranged at predetermined intervals along the direction A and supported by the frame 43. Each ink nozzle unit 41 ejects ink supplied from four ink cartridges 44, respectively. Each ink nozzle unit 41 is disposed with a slight gap between the ejection surface 41 a and the outer peripheral surface 31 a of the endless belt 31.

  The paper P conveyed by the endless belt 31 passes through the gap between the ink nozzle unit 41 and the endless belt 31. At that time, ink is ejected from a plurality of nozzles formed on the ejection surface 41 a toward the printing surface, which is the upper surface of the paper P, and a desired color image is formed on the paper P.

  The paper discharge mechanism 60 includes a pair of curved guides 61a and 61b through which the paper P is transported from the transport mechanism 30, and a pair of paper discharge rollers 62a and 62b disposed downstream in the transport direction from the pair of guides 61a and 61b. , And a pair of paper discharge rollers 63a and 63b disposed in the vicinity of the paper discharge port 64 on the downstream side in the transport direction from the pair of feed rollers 62a and 62b.

  The paper P that has been transported in the transport direction A by the transport mechanism 30 is peeled off from the outer peripheral surface 31 a by a peeling member (not shown) and then transported to the paper discharge mechanism 60. Then, the paper P conveyed between the pair of guides 61a and 61b is conveyed upward by the feed roller pair 62a and 62b and the feed roller pair 63a and 63b, and is discharged through the paper discharge port 64.

  FIG. 1B is a bottom view of the ink nozzle unit 41. In the following description, the direction orthogonal to the transport direction A on the printing surface of the paper P is defined as the C direction. As shown in FIG. 1B, each ink nozzle unit 41 is arranged such that its longitudinal direction is along the C direction. The longitudinal direction of the ink nozzle unit 41 and the C direction are preferably parallel, but the longitudinal direction of the ink nozzle unit 41 and the C direction have an angle within a predetermined range (for example, within a range of ± 1 °). It may be. However, in the first embodiment, it is assumed that each ink nozzle unit 41 has a longitudinal direction arranged in parallel with the C direction.

  In each of the ink nozzle units 41, eight nozzle forming portions 42 are formed on the ejection surface 41a. The upper and lower bases of the trapezoidal nozzle forming portions 42 are parallel to the longitudinal direction of the ink nozzle unit 41, and the oblique sides 42 b of the adjacent nozzle forming portions 42 are orthogonal to the longitudinal direction of the ink nozzle unit 41. Overlap each other in the direction of

  FIG. 2 is a diagram for explaining the arrangement of the nozzles 42n formed in the nozzle forming unit 42. The horizontal axis indicates the position in the longitudinal direction of the ink nozzle unit 41, and the vertical axis indicates the position in the transport direction A. Take. As shown in FIG. 2, the plurality of nozzles 42n are arranged along the longitudinal direction (left and right direction in FIG. 2) of the ink nozzle unit 41 to form a nozzle row 42a. Each nozzle forming portion 42 is formed with a plurality of nozzle rows 42a. In the ink nozzle unit 41, the plurality of nozzles 42n formed in one ink nozzle unit 41 are arranged so that their longitudinal positions are different from each other. For example, only one nozzle 42 n is formed for each ink nozzle unit 41 at the longitudinal position “100 mm” of the ink nozzle unit 41.

  As shown in FIG. 2, in the printer 1, the plurality of ink nozzle units 41 are arranged for each inter-unit distance HD. The printer 1 of the first embodiment determines the length of the outer periphery of each roller constituting the transport mechanism 30 based on the inter-unit distance HD, and details will be described later with reference to FIG. FIG. 2 shows the end nozzle distance ND. As shown in FIG. 2, the end-nozzle distance ND is a distance between nozzles located at both ends in a direction orthogonal to the longitudinal direction of the ink nozzle unit 41 in one ink nozzle unit 41. The end nozzle distance ND will be described in detail when the printer 1 of the second embodiment is described.

  FIG. 3 is a diagram for explaining an operation of forming a dot row for one line by the ink nozzle unit 41. However, in FIG. 3, the size and relative positional relationship of each nozzle 42 n are not accurately illustrated for easy understanding of the drawing.

  During the printing operation in the printer 1, the ink nozzle unit 41 first ejects ink from the nozzle row 42 a 1 on the most upstream side in the transport direction A among the many nozzle rows 42 a to form dots on the paper P. Thereafter, the paper P is transported slightly, and then ink is ejected from the nozzles 42n of the nozzle array 42a2 arranged next to the nozzle array 42a1 in the transport direction A, so that the dots previously formed on the paper P are discharged. In the meantime, after further forming dots, the paper P is further conveyed slightly. Then, by repeating the operation of ejecting ink from the nozzle row 42a3 next to the nozzle row 42a2 and transporting the paper P, one ink nozzle unit 41 performs a dot row for one line with the C direction as the longitudinal direction. 70 is formed.

  Then, when the dot row 70 formed on the paper P is transported to the lower side of the next ink nozzle unit 41 by transporting the paper P, the next ink nozzle unit 41 is already on the paper P. A new dot row 70 is formed so as to overlap the formed dot row 70. Therefore, in the printer 1, when the ink ejected from each ink nozzle unit 41 lands on the same position of the paper P (that is, when dots overlap), the occurrence of color misregistration is suppressed. On the other hand, when the landing positions of the ink ejected from the ink nozzle units 41 vary, color misregistration occurs.

  In the printer 1 according to the first embodiment, the length of the outer circumference of the roller of the transport mechanism 30 is set to a value based on the inter-unit distance HD, thereby suppressing variations in ink landing positions due to meandering of the paper P and color misregistration. It is comprised so that generation | occurrence | production of can be suppressed.

FIG. 4 shows the amount of paper transport per rotation of each roller 32, 33, 35-38 provided in the transport mechanism 30 and the rollers 32, 33, 35-35 derived from the paper transport amount per rotation. It is a table | surface which shows the relationship between the outer periphery of 38, and a diameter. In the table shown in FIG. 4, HD indicates the inter-unit distance HD. A, b, c ₁ , c ₂ , d ₁ , and d ₂ each represent an integer of 1 or more. Δ represents the thickness of the endless belt 31 (FIG. 1A).

The “sheet transport amount per rotation” shown in FIG. 4 is the distance that the outer peripheral surface 31a of the endless belt 31 moves while each roller 32, 33, 35 to 38 rotates once, in other words, each roller. This means the distance that the paper P is transported in the transport direction A while 32, 33, 35 to 38 are rotated once. That is, the drive roller 32 is set so that the distance that the paper P is conveyed in the conveyance direction A when the drive roller 32 makes one rotation is substantially HD / a. The driven roller 33 is set so that the distance that the paper P is transported in the transport direction A when the driven roller 33 makes one rotation is substantially HD / b. The upstream pinch roller 35 is set so that the distance that the paper P is transported in the transport direction A when the upstream pinch roller 35 makes one rotation is approximately HD / c ₁ . The downstream pinch roller 36 is set so that the distance that the paper P is transported in the transport direction A is approximately HD / c ₂ when the downstream pinch roller 36 rotates once. The cleaning roller 37 is set so that the distance that the paper P is transported in the transport direction A when the cleaning roller 37 makes one rotation is approximately HD / d ₁ . The cleaning pinch roller 38 is set so that the distance that the paper P is conveyed in the conveyance direction A when the cleaning pinch roller 38 makes one rotation is substantially HD / d ₂ .

In other words, in the printer 1, the driving roller 32, the driven roller 33, the upstream pinch roller 35, the downstream pinch roller 36, the cleaning roller 37, and the cleaning pinch roller 38 are respectively a, b, c ₁ , c ₂ , When d ₁ and d _{2 are} rotated, the paper P is conveyed by HD.

  In the printer 1, by setting the transport amount of the paper per rotation of each of the rollers 32, 33, 35 to 38 in this way, it is possible to suppress variations in the ink landing positions caused by the meandering of the paper P. The mechanism will be described later with reference to FIG.

  Further, “roller outer circumference (length of roller outer circumference)” and “roller diameter” shown in FIG. 4 are values derived from “paper conveyance amount per rotation” of each of the rollers 32, 33, 35 to 38. . In the present embodiment, the length and diameter of the outer circumference of the roller existing on the outer circumferential side of the endless belt 31 are set to values irrelevant to the thickness Δ of the endless belt 31. Details will be described with reference to FIG. On the other hand, for the rollers present on the inner peripheral side of the endless belt 31, the length and diameter of the outer periphery thereof are set to values that consider the thickness Δ of the endless belt 31. The error range of the roller outer circumference and the roller diameter is preferably within a range of ± 0.1%, and more preferably within a range of ± 0.05%.

  FIG. 5A is a diagram schematically illustrating the configuration of the transport mechanism 30. As shown in FIG. 5A, in the transport mechanism 30 of the printer 1, the upstream side pinch roller 35, the downstream side pinch roller 36, and the cleaning roller 37 exist on the outer peripheral side of the endless belt 31. On the other hand, the driving roller 32, the driven roller 33, and the cleaning pinch roller 38 exist on the inner peripheral side of the endless belt 31.

FIG. 5B shows the amount of paper transport per rotation (2πr) for the rollers existing on the outer peripheral side of the endless belt 31 and the amount of paper per rotation of the rollers existing on the inner peripheral side of the endless belt 31. It is a figure which compares and shows conveyance amount (2 (pi) (r + (DELTA))). The conveyance amount of the sheet per one rotation is equal to the distance that the outer peripheral surface 31a of the endless belt 31 moves while the roller makes one rotation. For this reason, in the case of a roller that rotates in contact with the outer peripheral surface 31 a of the endless belt 31, the outer periphery (2πr) of the roller is equal to the conveyance amount of the sheet per rotation. Therefore, the conveyance amount of the sheet per rotation and the radius r of the roller satisfy the relationship of the following expression (1).
Paper transport amount per rotation = 2πr (1)
On the other hand, in the case of a roller that rotates in contact with the inner peripheral surface 31 b of the endless belt 31, the conveyance amount of paper per rotation is larger than the length of the outer periphery of the roller because of the thickness Δ of the endless belt 31. That is, the conveyance amount of the sheet per rotation and the radius r of the roller satisfy the relationship of the following equation (2).
Paper transport amount per rotation = 2π (r + Δ) (2)
In the present embodiment, for each of the rollers existing on the outer peripheral side of the endless belt 31 and the rollers existing on the inner peripheral side, the above formulas (1) and (2) are used properly, so that each roller The length and diameter of the outer periphery can be set.

  Returning to FIG. For the rollers (rollers 35, 36, and 37) existing on the outer peripheral side of the endless belt 31, the roller radius r is calculated from the “sheet transport amount per rotation” and the above equation (1). Then, the length of the outer circumference of the roller based on the radius r of the roller thus calculated and the roller diameter are shown in the table of FIG. On the other hand, for the rollers (rollers 32, 33, and 38) existing on the inner peripheral side of the endless belt 31, the radius r of the roller is calculated from the “sheet transport amount per rotation” and the above equation (2). Then, the length of the outer circumference of the roller based on the radius r of the roller thus calculated and the roller diameter are shown in the table of FIG. Each of the rollers 32, 33, 35 to 38 of the printer 1 is manufactured with the outer circumference length and the roller diameter shown in FIG. 4 as target dimensions.

With reference to FIG. 6, a mechanism for suppressing variations in ink landing positions in the printer 1 will be described. The arrangement of the nozzle forming portions 42 for each color is illustrated on the left side of the drawing in FIG. 6, and the state of meandering of the paper P is graphed on the right side of the drawing. The graph on the right side of the drawing shows the meandering position of the paper P in the longitudinal direction (C direction) of the ink nozzle unit 41 and the vertical axis shows the transport distance of the paper P in the transport direction A. The graph on the right side of the drawing shows HD = 82 [mm], a = 2, b = 2, c ₁ = 5, c ₂ = 5, d ₁ = 1, d ₂ = 4, Δ = 0.1 [mm] ], When the rollers 32, 33, 35 to 38 are designed, a locus drawn by a certain point on the paper P while the paper P is conveyed on the endless belt 31 is shown. In addition, a circle on the graph on the right side of the drawing indicates an ink landing position 76.

  As shown in the graph of FIG. 6, in the printer 1, the paper P conveyed by the endless belt 31 meanders. Here, in the printer 1, the inter-unit distance HD is an integral multiple of the sheet conveyance amount per rotation of each of the rollers 32, 33, 35 to 38. That is, it is an integral multiple of the period of each of the rollers 32, 33, 35 to 38 that contact the endless belt 31. Therefore, the inter-unit distance HD is an integral multiple of the meandering cycle of the paper P caused by the rotation of the rollers 32, 33, 35 to 38.

That is, according to the printer 1, while the paper P is conveyed through the inter-unit distance HD, the driving roller 32 rotates approximately a, the driven roller 33 rotates approximately b, and the upstream pinch roller 35 rotates approximately c ₁ times. and, downstream pinch roller 36 is substantially _{c 2} rotates, the cleaning roller 37 is approximately _{d 1} rotating, cleaning the pinch roller 38 is substantially _{d 2} rotates. That is, each time the paper P is conveyed by the inter-unit distance HD, the rollers 32, 33, 35 to 38 have substantially the same phase. In other words, the meandering of the paper P shows a waveform in which the phases are aligned for each inter-unit distance HD. Therefore, the dots formed by a certain ink nozzle unit 41 and the dots formed by the next ink nozzle unit 41 when the paper P is transported by the inter-unit distance HD in the transport direction A are assumed to meander. Are formed at substantially the same position on the paper P. Therefore, variation in the ink landing position can be suppressed, and occurrence of color misregistration can be suppressed.

Here, as the values of a, b, c ₁ , c ₂ , d ₁ , and d ₂ are increased, the diameter of each of the rollers 32, 33, 35 to 38 can be designed to be smaller, and the printer 1 can be downsized. be able to. On the other hand, the smaller the values of a, b, c ₁ , c ₂ , d ₁ , and d ₂ , the more robust the design can be made. The relationship between the values of a, b, c ₁ , c ₂ , d ₁ , and d ₂ and the robustness will be described with reference to FIG.

  FIG. 7 is a graph showing the result of simulating the relationship between the meandering cycle of the paper P and the variation in the ink landing position. In the graph of FIG. 7, the horizontal axis represents the meandering period of the paper P, and the vertical axis represents the average value of variations in the ink landing positions. Further, in order to create the graph of FIG. 7, the inter-unit distance HD was assumed to be 82 mm, and the simulation was carried out by changing the meandering cycle of the paper P.

  For example, when the conveyance amount of the sheet per rotation of the rollers 32, 33, 35 to 38 of the conveyance system is 41 mm (82 mm / 2), the meandering period of the sheet P can be set to 41 mm (FIG. 7). As point D). In the simulation result in this case, as shown in FIG. 7, the average value of variations in the ink landing positions is zero. Similarly, when the transport amount of the paper per rotation of each of the rollers 32, 33, 35 to 38 is about 27.3 mm (82 mm / 3), the meandering cycle of the paper P can be set to 27.3 mm. (Indicated as point E in FIG. 7). Also in the simulation result in this case, as shown in FIG. 7, the average value of the variation in the ink landing position is zero. That is, as described with reference to FIG. 6, the value obtained by dividing the inter-unit distance HD by an integer is used as the sheet conveyance amount per rotation of each of the rollers 32, 33, 35 to 38. Variations in landing positions can be suppressed.

  Here, each roller 32, 33, 35-38 usually has a manufacturing error. For this reason, the meandering cycle of the paper P may deviate from the target value due to manufacturing errors. Although not shown, there is a possibility that the meandering cycle of the paper P may deviate from the target value due to the influence of meshing of the gear for transmitting the driving force to the roller.

  A point F in FIG. 7 shows a case where the meandering cycle of the paper P is 41 mm + α. Further, a point G in FIG. 7 shows a case where the meandering cycle of the paper P is 27.3 mm + α. As is apparent from FIG. 7, the variation in the ink landing position is greater when the meandering period of the paper P is 41 mm + α (in the case of the point F) than in the case of 27.3 mm + α (in the case of the point G). The average value of is small. That is, both are examples in which the meandering period of the paper P is deviated by α from the target value. However, at the point F where the meandering period of the paper P is larger, variations in ink landing positions are suppressed, and robustness is improved. I know it ’s good.

Thus, in order to obtain robustness, it is advantageous that the meandering period of the paper P is larger. That is, it is advantageous that a, b, c ₁ , c ₂ , d ₁ and d ₂ are small. On the other hand, in order to reduce the size of the device, it is advantageous that a, b, c ₁ , c ₂ , d ₁ , and d ₂ are large. Here, it is preferable that a, b, c ₁ , c ₂ , d ₁ , and d ₂ are any integers from 1 to 3. If it does in this way, it can be set as a robust design, suppressing the enlargement of an apparatus. In addition, since the design tolerance of the rollers and gears related to the conveyance of the paper P can be made relatively large, the manufacturing cost of the printer 1 can be reduced.

  As shown at points F and G in FIG. 7, when the meandering period of the paper P deviates from the ideal period, the meandering deviation increases cumulatively as the distance in the transport direction A increases. . As a result, as the distance between the two ink nozzle units 41 in the transport direction A increases, color misregistration due to variations in ink landing positions is more likely to occur. Therefore, in the printer 1 of this embodiment, as described with reference to FIG. 1, the ink nozzle unit 41M that forms M color dots and the ink nozzle unit 41M that forms C color dots are adjacent to each other. Are arranged as follows. In this way, it is possible to suppress the variation in the ink landing position and the color shift, particularly for the two colors (that is, the M color and the C color) in which the variation in the ink landing position is more conspicuous.

  Next, a second embodiment will be described. Note that, in the printer 1 of the second embodiment, the same components as those of the printer 1 of the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  In the printer 1 of the first embodiment, the sheet conveyance amount per rotation of each of the rollers 32, 33, 35 to 38 is a value that correlates with the inter-unit distance HD. On the other hand, in the printer 1 of the second embodiment, the transport amount of paper per rotation of each of the rollers 32, 33, 35 to 38 is a value that correlates not only with the inter-unit distance HD but also with the end-nozzle distance ND. It is.

In the printer 1 of the second embodiment, the inter-unit distance HD and the end-nozzle distance ND (see FIG. 2) satisfy the relationship HD / m = ND / n (where m> n, m Is an integer of 2 or more, and n is an integer of 1 or more. And in the printer 1 of 2nd Embodiment, the conveyance amount of the sheet | seat per rotation of each roller 32, 33, 35-38 is each determined as follows.
Paper transport amount per rotation of the driving roller 32 = HD / a = ND / f
Paper transport amount per rotation of the driven roller 33 = HD / b = ND / g
Conveyance amount of paper per one rotation of the upstream side pinch roller 35 = HD / c ₁ = ND / h ₁
Paper transport amount per rotation of the downstream pinch roller 36 = HD / c ₂ = ND / h ₂
Paper transport amount per rotation of the cleaning roller 37 = HD / d ₁ = ND / i ₁
Transport amount of paper per rotation of the cleaning pinch roller 38 = HD / d ₂ = ND / i _{2
However, a, b, c 1,} c 2, d 1, d 2 is an integer of 2 or _{more, f, g, h 1,} h 2, i 1, i 2 is an integer of 1 or more.
_{Further, a> f, b> g} , c 1> h 1, c 2> h 2, satisfying the _{d 1> i 1, d 2} > i 2 relationship.

That is, for the drive roller 32, (a, f) = (2, 1), (3, 1), (3, 2), (4, 1). However, when the inter-unit distance HD and the end-nozzle distance ND are set to HD: ND = 3: 1 (that is, when m = 3 and n = 1), (a, f) = (3,1), (6,2)... Similarly, for example, when HD: ND = 3: 2 is set (that is, when m = 3 and n = 2), (a, f) = (3, 2), (6, 4) ... and so on. Similarly for (b, g), (c ₁ , h ₁ ), (c ₂ , h ₂ ), (d ₁ , i ₁ ), (d ₂ , i ₂ ), the inter-unit distance HD and the end An integer set corresponding to the ratio with the inter-nozzle distance ND can be taken.

  In the printer 1 of the second embodiment, the outer lengths and diameters of the rollers 32, 33, 35 to 38 are set so as to obtain the above-mentioned “sheet transport amount per rotation”. In addition, since the calculation method of the length and diameter of the outer periphery is the same as the calculation method described in the first embodiment, description thereof is omitted. In addition, according to the printer 1 of the second embodiment, it is possible to further suppress variations in ink landing positions caused by errors when the ink nozzle unit 41 is attached. The mechanism will be described with reference to FIG.

  FIG. 8A is a diagram for explaining a dot line 70 for one line formed when the ink nozzle unit 41 is attached at an ideal attachment angle. In the case of “attached at an ideal attachment angle”, the longitudinal direction X of the ink nozzle unit 41 is completely parallel to the C direction, that is, on the surface parallel to the printing surface of the paper P. It means that the attachment is performed at an attachment angle at which an angle θ formed by the direction X with respect to the transport direction A is 90 °.

  In the following description, the direction perpendicular to the longitudinal direction X of the ink nozzle unit 41 is defined as the Y direction. In addition, in the ink nozzle unit 41, a large number of nozzle rows 42a are actually formed. However, in order to make the drawing easy to understand, in FIG. 8, one ink nozzle unit 41 has one end in the Y direction. Only the nozzle row 42a1 located, the nozzle row 42a3 located at the other end in the Y direction, and the nozzle row 42a2 located between the nozzle row 42a1 and the nozzle row 42a3 are illustrated.

  As shown in FIG. 8A, when the ink nozzle unit 41 is mounted at an ideal mounting angle, the ink lands at a predetermined interval x. That is, when the position of the dot formed by the nozzle row 42a1 at one end in the Y direction is set to the reference position (0), the dot formed by the nozzle row 42a2 is formed at a position separated by x from the reference position. The dots formed by the nozzle row 42a3 at the other end are formed at a position 2x away from the reference position.

  However, the ink nozzle unit 41 may be attached to the frame 43 with an inclination from an ideal attachment angle due to an error during the attachment work. That is, the angle θ formed by the longitudinal direction X of the ink nozzle unit 41 with respect to the transport direction A on the surface parallel to the printing surface of the paper P may not be 90 °.

  FIG. 8B is a diagram for explaining a dot row 70 for one line formed by the ink nozzle unit 41 attached at an inclination from an ideal attachment angle. As shown in FIG. 8B, when the ink nozzle unit 41 is mounted inclined from an ideal mounting angle, variations in ink landing positions are most likely to be a problem between the nozzles at both ends in the Y direction. In FIG. 8B, for convenience of explanation, the ink nozzle unit 41 is shown in a considerably inclined state.

  That is, when the position of the dot formed by the nozzle row 42a1 at one end in the Y direction is the reference position (0), the dot formed by the nozzle row 42a2 is ideally formed at a position separated by x from the reference position. In spite of what should be done, they are formed at positions separated by x ′. In addition, the dots formed by the nozzle row 42a3 are ideally formed at a position 2x 'away from the reference position, although they should be formed at a position 2x away from the reference position.

  Therefore, when the position of the dot formed by the nozzle row 42a1 at one end in the Y direction is set to the reference position (0), the deviation amount of the dot formed by the nozzle row 42a2 from the ideal position is (x′−x). is there. Similarly, the amount of deviation of the dots formed by the nozzle row 42a3 at the other end in the Y direction from the ideal position is 2 (x′−x). That is, when the amount of deviation of the position of the dot formed by each nozzle row 42a is obtained using the position of the dot formed by the nozzle row 42a1 at one end in the Y direction as a reference position, it is formed by the nozzle row 42a3 at the other end in the Y direction. In the dot, the amount of deviation becomes the largest.

  As described above, in the printer 1 of the second embodiment, the amount of paper transport per rotation of each of the rollers 32, 33, 35 to 38 is set as a value that also correlates with the end-nozzle distance ND.

For example, the length of the outer periphery of the drive roller 32 is set so that the distance that the paper P is transported in the transport direction A when the drive roller 32 rotates once is approximately ND / f. That is, while the paper P is transported in the transport direction A by the end nozzle distance ND, the drive roller 32 rotates approximately f. Similarly, while the sheet P is conveyed by the distance ND between the end nozzle in the conveying direction A, the driven roller 33 is almost g rotated, the upstream pinch roller 35 is substantially h ₁ rotation, the downstream pinch roller 36 is substantially h ₂ rotations, the cleaning roller 37 rotates approximately i ₁ and the cleaning pinch roller 38 rotates approximately i ₂ .

  As a result, in the printer 1 of the second embodiment, the meandering phase of the paper P when dots are formed by the nozzle row 42a1 at one end in the Y direction is when dots are formed by the nozzle row 42a3 at the other end in the Y direction. Is substantially equal to the meandering phase of the paper P. Therefore, it is possible to suppress the variation in the ink landing positions between the nozzles located at both ends in the Y direction of the ink nozzle unit 41 from being affected by the meandering of the paper P.

  In the above embodiment, the transport direction A corresponds to an example of the first direction, and the C direction corresponds to an example of the second direction. The cleaning roller 37 and the cleaning pinch roller 38 correspond to examples of non-contact rollers, respectively.

  Although the present invention has been described based on the embodiments, the present invention is not limited to the above-described embodiments, and various improvements and modifications can be easily made without departing from the spirit of the present invention. Can be inferred.

  For example, in the above embodiment, the paper P is transported by the endless belt 31, but the present invention can be applied to a printer that does not have the endless belt 31.

  FIG. 9 is a diagram schematically illustrating a conveyance mechanism 90 of a printer according to a modification. As shown in FIG. 9, the transport mechanism 90 of the modified printer is provided with a plurality of drive rollers 94 that transport the paper P below the ink nozzle unit 92. Also in this case, the length of the outer periphery of the driving roller 94 is set so that the distance that the sheet P is conveyed in the conveying direction A when the driving roller 94 makes one rotation is substantially HD / a. The same effects as those of the first embodiment can be obtained.

  In the above embodiment, the main rollers 32, 33, 35 to 38 constituting the transport mechanism 30 have been described as setting the outer circumference length based on the inter-unit distance HD or the end-nozzle distance ND. However, other rollers (for example, a charging roller for electrostatically adsorbing the paper P to the endless belt 31 or a tension roller for applying tension to the endless belt 31) that affect the meandering cycle of the paper P are transport mechanisms 30. In this case, the length of the outer periphery based on the inter-unit distance HD or the end-nozzle distance ND may also be set for the roller.

  In the above embodiment, the main rollers 32, 33, 35 to 38 constituting the transport mechanism 30 have been described as setting the outer circumference length based on the inter-unit distance HD or the end-nozzle distance ND. However, the outer circumference length based on the inter-unit distance HD or the end-nozzle distance ND may be set only for a roller (for example, the driving roller 32) that greatly affects the meandering cycle of the paper P.

  In the above-described embodiment, the printer 1 has been described as including the four-color ink nozzle units 41. However, ink nozzle units of two, three, five, or more colors may be prepared.

  In the printer 1 of the above embodiment, the ink nozzle unit 41 is provided with a plurality of nozzle rows 42a. However, the present invention is also applicable to a printer in which each ink nozzle unit is provided with one nozzle row. The invention can be applied.

  In the printer 1 of the above embodiment, the ink nozzle unit 41 is provided with the nozzles 42n for each trapezoidal nozzle forming portion 42. However, the ink nozzle unit 41 is not provided with the trapezoidal nozzle forming portion 42, and simply includes ink. The present invention can also be applied to a printer having a configuration in which a plurality of nozzle rows along the longitudinal direction of the nozzle unit are provided in each ink nozzle unit. For example, for a printer in which each ink nozzle unit has one rectangular nozzle forming portion whose longitudinal direction is the longitudinal direction of the ink nozzle unit, and a plurality of nozzle rows are provided in the nozzle forming portion. The present invention can be applied.

1 Printer 31 Endless Belt 32 Drive Roller 33 Driven Roller 35 Upstream Pinch Roller 36 Downstream Pinch Roller 37 Cleaning Roller 38 Cleaning Pinch Roller 41 Ink Nozzle Unit 42a Nozzle Row 42n Nozzle P Paper

Claims (7)

A printer,
A drive roller for conveying the recording medium in the first direction;
A plurality of ink nozzle units for forming dots on the recording medium transported in the first direction, wherein each ink nozzle unit has a longitudinal direction of each ink nozzle unit different from the first direction; The plurality of inks that are arranged along a second direction orthogonal to each other, and two adjacent ink nozzle units of the plurality of ink nozzle units are arranged at positions separated by a predetermined interval. A nozzle unit;
With
The plurality of ink nozzle units eject inks of different colors,
Each of the ink nozzle units is provided with a plurality of nozzle rows composed of a plurality of nozzles arranged along the longitudinal direction of the ink nozzle unit.
The length of the outer periphery of the drive roller is such that when the drive roller makes one revolution, the distance that the recording medium is conveyed in the first direction becomes approximately HD / a and approximately ND / f. , Is set,
The HD, the indicates the predetermined distance, said a is indicates an integer of 2 or more,
The ND represents a distance between nozzles located at both ends of each ink nozzle unit in a direction orthogonal to the longitudinal direction of each ink nozzle unit, and f represents an integer of 1 or more . The printer of claim 1, further comprising:
A driven roller that follows the drive roller;
The length of the outer periphery of the driven roller is set so that the distance that the recording medium is conveyed in the first direction when the driven roller makes one rotation is approximately HD / b,
The printer “b” represents an integer of 1 or more. The printer according to claim 1 or 2, further comprising:
A pinch roller that contacts the recording medium conveyed in the first direction;
The length of the outer periphery of the pinch roller is set so that the distance that the recording medium is conveyed in the first direction when the pinch roller makes one rotation is approximately HD / c,
The printer c represents an integer of 1 or more. The printer according to any one of claims 1 to 3, further comprising:
An endless belt driven by the drive roller to convey the recording medium in the first direction;
A non-contact roller that contacts the endless belt and does not contact the recording medium conveyed in the first direction;
The length of the outer periphery of the non-contact roller is set such that the distance that the recording medium is conveyed in the first direction when the non-contact roller makes one rotation is approximately HD / d,
The d is a printer indicating an integer of 1 or more. The printer according to any one of claims 1 to 4, further comprising:
An endless belt driven by the drive roller to convey the recording medium in the first direction;
The length of the outer periphery of the roller existing on the inner peripheral side of the endless belt is set to a value considering the thickness of the endless belt, and the outer peripheral length of the roller existing on the outer peripheral side of the endless belt is: A printer set to a value irrelevant to the thickness of the endless belt. The printer according to claim 1, wherein a is an integer of 2 or 3. Among the plurality of ink nozzle unit, and an ink nozzle unit to form dots of M color, and the ink nozzle unit to form a C color dots are arranged so as to be adjacent to each other, any of claims 1 to 6 Printer.