JP2013067031A - Inkjet recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration in image quality due to mechanical distortion without performing a discharge control of ink.SOLUTION: An inkjet recording device includes: a head unit having at least one recording head for discharging ink; and a carriage in which a plurality of head units for individually discharging ink in multiple colors are aligned in a scanning direction, which reciprocates in the scanning direction with a guide rail. The ink in multiple colors is ranked in order of becoming thinner as the darkest ink among the ink in multiple colors comes first. On one side of a reference head unit, less than half of the head units among the head units other than the reference unit are arranged so that the rank of the discharged ink becomes larger as separating from the reference unit. On the other side of the reference unit, the remaining head units are arranged so that the rank of the discharged ink becomes larger as separating from the reference unit.

Description

  The present invention relates to an ink jet recording apparatus.

  Conventionally, in an ink jet recording apparatus, a recording head corresponding to each color is mounted on a carriage, and the carriage reciprocates along a guide rail so that the recording head scans on a recording medium. (See Patent Document 1).

JP 2005-343909 A

By the way, in recent years, in order to make it possible to form an image even on a large-sized cloth, the size of an inkjet recording apparatus for textile printing has been increased. When the apparatus itself becomes large, the influence of the mechanical distortion of the guide rail also becomes large, and the ink landing position is displaced for each color. In particular, when inks of different colors are overprinted at the same position, this influence greatly reduces the image quality.
To prevent this, the mechanical distortion of the guide rail can be completely eliminated, but it is not practical to remove it completely. In addition, although it is conceivable to shift the ink ejection timing for each location where distortion occurs and to suppress positional deviation, the location of distortion differs from device to device, so it is technical to perform discharge control suitable for each device. The reality is that this is accompanied by a lot of difficulties.
An object of the present invention is to suppress image quality degradation caused by mechanical distortion without performing ink ejection control.

An ink jet recording apparatus according to the invention of claim 1
A head unit having at least one recording head for ejecting ink;
A guide rail extending along a scanning direction orthogonal to the conveyance direction of the recording medium;
A plurality of the head units that individually eject a plurality of colors of ink are mounted in a state of being arranged along the scanning direction, and a carriage that reciprocates in the scanning direction by the guide rail,
The ink with the highest density among the inks of the plurality of colors is ranked first, and is ranked in the order of decreasing density,
When the head unit that discharges the darkest ink among the plurality of head units is a reference head unit,
On one side of the reference head unit, less than half of the head units other than the reference head unit are arranged so that the order of ink to be ejected increases as the head unit moves away from the reference head unit. ,
On the other side of the reference head unit, among the head units other than the reference head unit, the remaining head units are arranged so that the order of ink to be ejected increases as the distance from the reference head unit increases. It is characterized by being.

  According to the present invention, image quality degradation caused by mechanical distortion is suppressed without performing ink ejection control.

1 is a perspective view illustrating a schematic configuration of an inkjet head according to an embodiment. It is the schematic explanatory drawing which looked at the carriage concerning this embodiment from the lower part. FIG. 3 is a schematic explanatory view of the carriage of FIG. 2 as viewed from the front. It is explanatory drawing which shows the landing position of the ink when the guide rail of this embodiment is an ideal state without mechanical distortion. It is explanatory drawing which shows the landing position of the ink in case the guide rail of this embodiment has mechanical distortion. It is the table | surface which put together the determination result of image quality degradation for every condition. A case where a head unit that discharges the first ink having a high density, a head unit that discharges the second ink, and a head unit that discharges the third ink are arranged from the downstream side to the upstream side in the scanning direction is shown. It is explanatory drawing. The head unit that discharges the first ink having a high density is arranged in the center, the head unit that discharges the second ink is on the downstream side in the scanning direction, and the head unit that discharges the third ink is on the upstream side in the scanning direction. It is explanatory drawing which shows the case where it has arranged.

  The best mode for carrying out the present invention will be described below with reference to the drawings. However, although various technically preferable limitations for implementing the present invention are given to the embodiments described below, the scope of the invention is not limited to the following embodiments and illustrated examples.

FIG. 1 is a perspective view showing the entire inkjet recording apparatus 1 of the present embodiment. As shown in FIG. 1, the ink jet recording apparatus 1 includes a transport device 2 that transports the recording medium along the horizontal direction, and a head unit 3 (see FIG. 2) that ejects ink from above onto the transported recording medium. Mounted on the carriage 4, a scanning device 5 that transports the carriage 4 along a horizontal direction orthogonal to the transport direction of the recording medium, a maintenance unit 6 that performs maintenance of each head unit 3 mounted on the carriage 4. The nozzle moisturizing unit 7 for moisturizing each head unit 3, a control device (not shown) for controlling these components, and a frame 100 for supporting the whole are provided.
In the following description, the horizontal direction along the recording medium conveyance direction is referred to as the Y-axis direction, and the horizontal direction along the carriage 4 conveyance direction is referred to as the X-axis direction or the scanning direction. To do.

The transport device 2 includes a drive roller 21 and a driven roller (not shown), a drive motor 22, and a transport belt 23.
The drive roller 21 and the driven roller are rotatably supported by the shaft, and the drive roller 21 is disposed so as to extend in the scanning direction X. The drive motor 22 is a drive source for rotationally driving the drive roller 21, and is attached to one end side of the drive roller 21.
The conveyor belt 23 is formed in an endless shape, and is stretched between the driving roller 21 and the driven roller. When the driving roller 21 rotates, the conveying belt 23 circulates between the driving roller 21 and the driven roller and conveys the recording medium placed on the upper surface thereof in the conveying direction F along the Y-axis direction. When the rotation of the roller 21 is stopped, the circulation between both rollers is stopped, and the conveyance of the recording medium is stopped.
When the head unit 3 completes one-way scanning along the X-axis direction according to the control of the control device, the drive motor 22 rotates the drive roller 21 by a predetermined amount to convey the recording medium by a predetermined distance in the conveyance direction. When the head unit 3 starts scanning in the direction opposite to the scanning direction X and ends, the driving roller 21 is rotated again by a predetermined amount, and the recording medium is transported by a predetermined distance in the transport direction F and stopped. The recording medium is so-called intermittently conveyed.
As the recording medium, it is possible to use resin films, metals, etc. in addition to paper and fabric.

As shown in FIG. 1, the frame 100 includes a rectangular main body portion 101 extending along the X-axis direction, a first base portion 102 that supports one end portion in the X-axis direction of the main body portion 101, and the main body portion 101. And the second base portion 103 that supports the other end portion in the X-axis direction.
The first base portion 102 supports the one end portion of the main body portion 101 from below while storing and holding the nozzle moisturizing portion 7 therein. Further, the second base portion 103 supports the other end portion of the main body portion 101 from below while storing and holding the maintenance portion 6 therein.
The main body 101 stores and holds a pair of guide rails 51, 51 of the scanning device 5, which will be described later, in the X-axis direction, and the carriage 4 extends along the X-axis inside the main body 101. Be transported.
Further, the first base portion 102 and the second base portion 103 are disposed on both sides in the X-axis direction with the above-described transport device 2 interposed therebetween, and the main body portion 101 is installed above the transport device 2. Thus, it is possible to form an image by ejecting ink from each head unit 3 mounted on the carriage 4 while transporting the carriage 4 in a direction orthogonal to the transport direction of the recording medium by the transport device 2.

  The scanning device 5 includes a pair of bar-shaped guide rails 51 and 51 that are supported so as to extend along the X-axis direction inside the main body 101 of the frame 100. The pair of guide rails 51 and 51 are provided so as to straddle the upper portion of the transport belt 23 of the transport device 2. A box-shaped carriage 4 is supported on the guide rails 51 and 51 so as to be reciprocally movable along the X-axis direction.

The carriage 4 is a substantially rectangular housing having an open top, and a plurality of head units 3 are mounted on the bottom plate. As shown in FIG. 1, the carriage 4 has arm portions 41 and 41 extending toward both sides in the Y-axis direction at the upper part of both side surfaces in the Y-axis direction, and the arm portions 41 and 41 are respectively linear guides. Is placed on the upper portion of the guide rails 51, 51, and can slide on the guide rails 51, 51 along the X-axis direction.
A linear motor (not shown) is provided between the guide rails 51 and 51 and the arm portions 41 and 41 of the carriage 4. That is, each guide rail 51, 51 is equipped with a linear motor stator, each arm 41, 41 of the carriage 4 is equipped with a mover, and the carriage 4 is controlled by current control of the stator side coil. A transport operation along the X-axis direction is given.

FIG. 2 is a schematic explanatory view of the carriage 4 as viewed from below. FIG. 3 is a schematic explanatory view of the carriage 4 as viewed from the front. As shown in FIGS. 2 and 3, in the inkjet recording apparatus 1, Y (yellow), Lm (light magenta), Or (orange), M (magenta), Bk (black), Bl (blue), Lk ( Nine head units 3 are mounted so as to correspond to nine colors of light black), C (cyan), and Lc (light cyan), respectively.
As shown in FIG. 3, in each head unit 3, nine recording heads 31 are arranged in a staggered manner along the Y-axis direction. As a result, a total of 81 recording heads 31 are mounted on the carriage 4. Each recording head 31 is configured to eject ink both when the carriage 4 is reciprocally scanned and when the carriage 4 is reciprocated based on ejection control from the control device.

FIG. 4 is an explanatory diagram showing ink landing positions when the guide rails 51 and 51 are in an ideal state without mechanical distortion. FIG. 4A is an explanatory diagram showing the landing position of the ink A that first lands on the recording medium P when the carriage 4 is scanned once in the scanning direction X1. FIG. 4B is an explanatory diagram showing the landing position of the ink B that finally lands on the recording medium P when the carriage 4 is scanned once in the scanning direction X1.
Even if the ejection control of the recording head 31 of each head unit 3 is performed so that the landing position of the ink B is the same as the landing position of the ink B, if the guide rails 51 and 51 are not distorted, Thus, no positional deviation occurs between ink A and ink B.

FIG. 5 is an explanatory diagram showing ink landing positions when the guide rails 51 and 51 are mechanically distorted. FIG. 5A is an explanatory diagram showing the landing position of the ink A that first lands on the recording medium P when the carriage 4 is scanned once in the scanning direction X1. FIG. 5B is an explanatory diagram showing the landing position of the ink B that finally lands on the recording medium P when the carriage 4 is scanned once in the scanning direction X1.
As shown in FIG. 5, the guide rails 51 and 51 are partially distorted at the time of manufacture or due to environmental temperature or deterioration with time. For this reason, even if the recording head 31 of each head unit 3 is controlled to eject the ink A and the ink B at the same position, the ink A and the ink on the recording medium P as shown in FIG. A misalignment with B occurs. If there is a positional deviation between the inks A and B that are intended to land at the same position, the edge of the image becomes blurred and the image quality deteriorates.

Therefore, the present inventors can determine the deterioration in image quality visually even if there is a positional deviation by making the interval H between the recording heads 31 that eject inks of different colors different from the density difference of the ink. I examined whether. Here, the interval H between the recording heads 31 is the length between the nozzles of the pair of recording heads 31. As the ink density, for example, L * that is the coordinates of the CIELAB color space is used. The dark ink has L * <40, the medium ink has 40 ≦ L * <60, and the light ink has 60 ≦ L *.
The ink A and the ink B are ejected at the same position by the distorted guide rails 51 and 51 using the dark ink B, the medium density ink B, and the light ink B for each density ink A. The image quality deterioration due to the positional deviation is determined visually. This is executed at different intervals H.

  FIG. 6 is a table that summarizes the determination results of image quality degradation for each condition. When the interval H is large, the influence of the distortion of the guide rails 51 and 51 becomes large, so that the positional deviation of the landing position increases. However, if either ink A or ink B is a low-density ink, the interval H is large. It can be seen that there is not much influence on the visual judgment. In addition, the condition where the determination result is NG is that the interval H is 400 mm or more, and at least one of the ink A and the ink B has a high density. That is, it can be seen that even if inks having a high density are ejected as close as possible and inks having a low density are ejected at positions away from the ink having a high density, the visual image quality degradation is small.

For example, among the inks of a plurality of colors used in the present embodiment, the ink of Bk having the highest density is ranked first, and the ink is ranked in order of decreasing density, the second is the ink of Bl, the third is the ink of M, 4 The third is Lk ink, the fifth is C ink, the sixth is Or ink, the seventh is Lm ink, the eighth is Lc ink, and the ninth is Y ink.
Here, in order to eject inks having a high density from close to each other and inks having a low density at positions away from the ink having a high density, the head unit 3 that simply ejects each ink is scanned in the order of density. It is also possible to arrange them along X1. However, in this case, when a plurality of colors of ink are ejected to the same position, the position of the first ink differs in the depth direction of the recording medium P when the carriage 4 moves forward and backward. For example, a case where three colors of ink are ejected for convenience is illustrated. FIG. 7 shows a head unit 3 that ejects the first ink having a high density, a head unit 3 that ejects the second ink, and a head that ejects the third ink from the downstream side to the upstream side in the scanning direction X1. It is explanatory drawing which shows the case where the unit 3 is arranged. In this case, when all the ink is ejected to the same position during the reciprocating scanning of the carriage 4, the carriage 4 moves in the scanning direction X1, and therefore, on the recording medium P as shown in FIG. The first ink I1, the second ink I2, and the third ink I3 are arranged in order from the bottom. On the other hand, when all the ink is ejected to the same position when the carriage 4 reciprocates, the carriage 4 moves in the scanning direction X2, so as shown in FIG. The third ink I3, the second ink I2, and the first ink I1 are arranged in order from the bottom.
As described above, if the position of the darkest first ink greatly differs in the depth direction of the recording medium P during forward movement and backward movement, the image quality is affected, which is not preferable.
For this reason, in order to prevent the position of the darkest first ink from being greatly different due to different scanning directions, the head unit 3 that discharges the first ink may be arranged in the center. For example, FIG. 8 shows that the head unit 3 that discharges the first ink having a high density is disposed in the center, and the head unit 3 that discharges the second ink discharges the third ink on the downstream side in the scanning direction X1. It is explanatory drawing which shows the case where the head unit 3 is arranged in the upstream of the scanning direction X1. In this case, the first ink I1 is arranged at substantially the same position in the depth direction of the recording medium P regardless of which of the scanning directions X1 and X2 the carriage 4 is scanned.

That is, if the head unit 3 that discharges the ink with the highest density among the plurality of head units 3 is a reference head unit, one side of the reference head unit has a head unit 3 other than the reference head unit, Less than half of the head units 3 are arranged so that the order of ink to be ejected increases as they move away from the reference head unit, and the other side of the head units other than the reference head unit remains on the other side of the reference head unit. The head units 3 need only be arranged so that the order of ink to be ejected increases as they move away from the reference head unit.
When this is applied to the ink jet recording apparatus 1 of the present embodiment, as shown in FIG. 3, the head unit 3 that discharges the first ink (Bk) becomes the reference head unit. In FIG. 3, the numbers shown in the head unit 3 indicate the rank. Further, on one side of the reference head unit, a head unit 3 that discharges the second ink (Bl) in order from the side closest to the reference head unit, a head unit 3 that discharges the fourth ink (Lk), A head unit 3 that ejects the fifth ink (C) and a head unit 3 that ejects the eighth ink (Lc) are arranged. Further, on the other side of the reference head unit, a head unit 3 that discharges the third ink (M), a head unit 3 that discharges the sixth ink (Or), in order from the side closer to the reference head unit, A head unit 3 for ejecting the seventh ink (Lm) and a head unit 3 for ejecting the ninth ink (Y) are arranged. In this arrangement order, the head unit 3 that ejects the C ink and the head unit 3 that ejects the Lc ink are arranged adjacent to each other, so that these head units 3 are arranged apart from each other. The image quality can be improved.

  As described above, according to the present embodiment, when the head unit 3 that discharges the ink with the highest density among the plurality of head units 3 is set as a reference head unit, the reference head unit is arranged on one side of the reference head unit. Of the head units 3 other than the head unit, less than half of the head units 3 are arranged so that the order of ink to be ejected increases as they move away from the reference head unit. Among the head units 3 other than the head unit, the remaining head units are arranged so that the order of the inks to be ejected increases as they move away from the reference head unit. Ink with low density can be ejected at a position away from ink with high density. As a result, even if the guide rails 51 and 51 are mechanically distorted, it is difficult to visually determine deterioration in image quality by simply adjusting the arrangement of the head units 3 without performing ink ejection control. it can.

Note that the present invention is not limited to the above embodiment, and can be modified as appropriate.
For example, in the above embodiment, the case where the head unit 3 has nine recording heads 31 has been described as an example. However, the total number of recording heads 31 included in the head unit 3 is not limited as long as it is one or more. Good.
Further, the total number of head units 3 is not limited to nine. It is also possible to change the total number of head units 3 according to the type of ink. For example, if the ink types are eight colors, the total number of head units 3 is eight.
Further, on the side of the reference head unit, less than half of the head units 3 other than the reference head unit are arranged so that the order of ink to be ejected increases as the head unit 3 moves away from the reference head unit. If the remaining head units 3 are arranged on the other side of the reference head unit so that the order of the ink to be ejected increases as they move away from the reference head unit, the arrangement order of the head units 3 is not limited. It may be. As an arrangement order other than the above, for example, the head units 3 that eject odd-numbered inks are arranged on one side of the reference head unit so that the rank increases as the distance from the reference head unit increases. For example, the head units 3 that eject even-numbered inks are arranged on the other side of the reference head unit so that the rank increases as the distance from the reference head unit increases.

DESCRIPTION OF SYMBOLS 1 Inkjet recording apparatus 2 Conveyance apparatus 3 Head unit 4 Carriage 5 Scanning apparatus 6 Maintenance part 7 Nozzle moisture retention part 10 Inkjet recording apparatus 21 Drive roller 22 Drive motor 23 Conveyance belt 31 Recording head 41 Arm part 51 Guide rail 100 Frame 101 Main body part 102 Base part 103 Base part H Interval P Recording medium

Claims (1)

A head unit having at least one recording head for ejecting ink;
A guide rail extending along a scanning direction orthogonal to the conveyance direction of the recording medium;
A plurality of the head units that individually eject a plurality of colors of ink are mounted in a state of being arranged along the scanning direction, and a carriage that reciprocates in the scanning direction by the guide rail,
The ink with the highest density among the inks of the plurality of colors is ranked first, and is ranked in the order of decreasing density,
When the head unit that discharges the darkest ink among the plurality of head units is a reference head unit,
On one side of the reference head unit, less than half of the head units other than the reference head unit are arranged so that the order of ink to be ejected increases as the head unit moves away from the reference head unit. ,
On the other side of the reference head unit, among the head units other than the reference head unit, the remaining head units are arranged so that the order of ink to be ejected increases as the distance from the reference head unit increases. An ink jet recording apparatus.

Images