JP2004314434A - Liquid discharging device and its discharging timing adjustment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve a forming position precision of dot arrays of a return travel as a whole by reducing reference dot arrays to be an adjustment reference of a discharging timing in the return travel for a plurality of liquid discharging heads. <P>SOLUTION: An adjustment method for the discharging timing of a liquid discharging device is equipped with the liquid discharging heads having a plurality of nozzle arrays for discharging a liquid towards a medium thereby forming the dot arrays, a mobile body which moves back and forth holding a plurality of the liquid discharging heads, and an adjusting means for adjusting the discharging timing of the liquid in the return travel. The reference dot array is formed on the medium by discharging the liquid in the forward travel from nozzle arrays of one liquid discharging head of the plurality of liquid discharging heads. Moreover, the dot arrays are formed by discharging the liquid in the return travel from nozzle arrays of the other liquid discharging heads. The discharging timing in the return travel of the nozzle arrays of the other liquid discharging heads is adjusted on the basis of a deviation amount of a formation position of the dot arrays and a formation position of the reference dot array. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention is directed to a liquid ejection head having a plurality of nozzle rows that form a dot row by ejecting liquid toward a medium, a moving body that holds a plurality of the liquid ejection heads and reciprocates, The present invention relates to a method for adjusting the ejection timing of a liquid ejection apparatus including an adjustment unit for adjusting the ejection timing.
[0002]
[Prior art]
Among liquid ejecting apparatuses that eject liquid from a nozzle row (in which a number of nozzles are aligned in a straight line) toward a medium, an ink jet printer that ejects ink as the liquid is particularly widespread. This ink jet printer includes a print head as a liquid ejection head having a plurality of the nozzle rows, and a carriage as a moving body that reciprocates in the main scanning direction while holding the print head. Then, the printing paper as the medium is intermittently fed in a sub-scanning direction orthogonal to the main scanning direction, and the carriage is moved in the main scanning direction while the paper feeding is stopped, and is directed toward the printing paper. Ink droplets are ejected from the nozzle rows to form a large number of dot rows on the printing paper (a large number of dots, which are landing marks of ink drops, are aligned on a straight line in the nozzle row direction). . Then, such a paper feed and the movement of the carriage are alternately repeated to form a predetermined print image on the print paper.
[0003]
Some of these ink jet printers have a function of so-called "bidirectional printing" for the purpose of improving the printing speed, i.e., those capable of forming the dot row in bidirectional scanning of the carriage in the forward and backward directions. is there. However, in this bidirectional printing, due to the landing time difference between the forward path and the return path in the main scanning direction, the backlash of the driving mechanism, etc., the dot row formation positions on the forward path and the return path are mutually different. Since there is a possibility that the image quality of the printed image is degraded due to the deviation in the scanning direction, in order to prevent this, the deviation amount of the formation position is measured in advance, and the adjustment of shifting the ejection timing of the return path by the deviation amount is performed. Then, the dot rows on the outward path and the return path are made to substantially match. In other words, ink is ejected from the nozzle array on the printing paper on the outward path to form a dot array serving as a reference for the adjustment (hereinafter referred to as a reference dot array), and liquid is ejected from the same nozzle array on the return path to form a dot. Form a column. Then, the amount of deviation of the dot line on the return path from the reference dot line is measured, and the shift amount of the ejection timing is set so as to reduce the amount of deviation (for example, see Patent Document 1). Usually, the minimum unit that can independently adjust the ejection timing is the print head unit.For example, in the case of a single head, the setting of the shift amount is performed only once, and the reference dot row is also set. One.
[0004]
By the way, recently, the kind of such an ink jet printer has also increased, and for example, by providing a plurality of print heads in parallel on the carriage, a large ink jet printer capable of performing large format printing such as row A No. 0 has been provided. I have. Also in the case of a printer having a plurality of print heads, the adjustment of the bidirectional printing is performed for each print head as described above. That is, each of the print heads forms a reference dot row on the outward pass of a predetermined nozzle row in the print head, and the dot row formed on the return pass of the same nozzle row substantially matches this reference dot row. The return timing is set.
[0005]
[Patent Document 1]
JP-A-11-334055
[0006]
[Problems to be solved by the invention]
However, when there are a plurality of print heads, the reference dot row exists for each print head, and therefore, there is a reference for adjusting the ejection timing in the return path by the number of print heads. If there are a plurality of references, there is a risk that variations in the formation positions of the references may get on the errors in the formation positions of the dot rows on the return path, and as a result, the accuracy of the formation positions of the dot rows on the return path deteriorates as a whole. .
The present invention has been made in view of such a problem, and an object of the present invention is to reduce a reference dot row that is a reference for adjusting the discharge timing of the return path for a plurality of liquid discharge heads, and to reduce the dot row of the return path. An object of the present invention is to realize a liquid ejection apparatus capable of improving the formation position accuracy as a whole and a method of adjusting the ejection timing thereof.
[0007]
[Means for Solving the Problems]
A main aspect of the present invention is a liquid ejection head having a plurality of nozzle arrays for ejecting liquid toward a medium to form a dot array, a moving body that holds a plurality of the liquid ejection heads and reciprocates, and the liquid in a return path. Adjusting means for adjusting the ejection timing of the liquid ejection device, comprising: a nozzle array of any one of the plurality of liquid ejection heads; To form a reference dot row on the medium, and form a dot row by discharging liquid in the return path from a nozzle row of another liquid discharge head, forming the dot row and the reference dot row. A discharge timing of the other liquid discharge head in a return path of a nozzle row based on a deviation amount of the liquid discharge head. It is an adjustment method.
Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
The description of the detailed description of the invention in this specification makes it clear at least the following.
A liquid ejection head having a plurality of nozzle rows for ejecting liquid toward a medium to form a dot row, a moving body holding a plurality of the liquid ejection heads and reciprocating, and adjusting the ejection timing of the liquid in a return path Adjusting means for adjusting the ejection timing of a liquid ejection apparatus, comprising: ejecting a liquid in a forward path from a nozzle row of any one of the plurality of liquid ejection heads to a medium. In addition to forming a reference dot row, the liquid is discharged from the nozzle row of another liquid discharge head in the return path to form a dot row, and the deviation amount between the dot row formation position and the reference dot row formation position is determined. And adjusting the ejection timing of the nozzle array of the other liquid ejection head in the return path based on the ejection timing.
[0009]
According to such a method of adjusting the ejection timing, the reference dot array is formed on the medium by ejecting the liquid in the outward path from the nozzle array of any one of the plurality of liquid ejection heads. In addition, the ejection timing of the other liquid ejection heads other than the liquid ejection head having formed the reference dot row in the return pass is also different from the dot row formed in the return pass by the nozzle row of the other liquid ejection head and the reference dot row. Adjustment is made based on the amount of deviation from the formation position. In other words, the reference dot row is also used as the adjustment reference for the ejection timing of the other liquid ejection head in the return path. Therefore, it is possible to prevent an increase in the number of adjustment standards due to the presence of different adjustment standards for each liquid ejection head, thereby causing a variation in the formation position of the standards that occurs when there are a plurality of adjustment standards. Can be reduced to a small extent. As a result, the accuracy of the dot row formation position on the return path can be improved as a whole.
[0010]
In this method of adjusting the ejection timing, it is preferable that the moving body moves by receiving a moving force, and the nozzle line forming the reference dot line be a nozzle line closest to the line of action of the moving force.
According to such an ejection timing adjustment method, the reference dot row is formed using the nozzle row closest to the line of action of the moving force. This is because, as the moving force is directly transmitted to the portion of the moving body closer to the action line, the vibration during the movement is small, that is, the nozzle row closest to the action line moves toward the medium during the movement. This is because the landing position deviation of the discharged liquid due to vibration is small, and can be a more accurate adjustment reference.
Since the general definition of the above-mentioned term "action line" is "a straight line passing through the point where the force acts and facing the direction of the force", the action line of the movement force is defined as "the point at which the movement force acts". , And a straight line directed in the direction of the moving force. "
[0011]
In this method of adjusting the ejection timing, a pair of action points on the action line receive moving forces in opposite directions to each other, and the moving force reciprocates the moving body, and the nozzle row that forms the reference dot row is It is preferable that the nozzle row closest to the middle point between the pair of action points is a nozzle row among a plurality of nozzle rows closest to the action line.
According to such a method of adjusting the ejection timing, in the moving body that reciprocates upon receiving the moving force, the portion where the vibration is the smallest on average is the middle point between the pair of action points of the moving force. Therefore, if the reference dot row is formed using the nozzle row closest to the middle point, the most accurate adjustment reference can be obtained. Then, by adjusting the ejection timing of another liquid ejection head based on this, it is possible to further improve the formation position accuracy of the dot rows formed by the plurality of liquid ejection heads on the return path.
[0012]
In such a method of adjusting the ejection timing, it is preferable that the medium is intermittently conveyed in a direction intersecting with the moving direction of the moving body, and the moving body moves and discharges the liquid toward the medium while the medium is stopped. desirable.
According to such a method of adjusting the ejection timing, the medium is intermittently transported in a direction intersecting with the moving direction of the moving body, and the liquid is ejected while the medium is stopped. For this reason, the liquid can be ejected to the medium in the intermittent transport direction, and a wide plane of the medium including the moving direction and the intermittent transport direction can be a target of the liquid ejection.
[0013]
In this method of adjusting the ejection timing, it is preferable that the amount of liquid droplets per nozzle for forming the dot row for calculating the amount of deviation be less than the maximum amount of liquid droplets ejected by the nozzle.
According to such a method of adjusting the ejection timing, the amount of liquid droplets per nozzle for forming the dot row for calculating the amount of deviation is set to be less than the maximum amount of liquid droplets ejected by the nozzles. The reason for this is that the discharge speed or the like changes depending on the amount of liquid droplets, and the landing position may change, and it is closer to the actual use that the discharge frequency in actual use is high and less than the maximum liquid appropriate amount. This is because adjustment can be performed in a state.
In other words, according to this method, since the adjustment is performed using a dot row that is less than the maximum liquid droplet amount, which is a dot row close to the dot row in actual use, the amount of deviation of the dot row formation position can be more accurately evaluated. It becomes.
[0014]
In such an ejection timing adjustment method, the liquid is ink for printing a print image on the medium, and the nozzles can form large, medium, and small dots by adjusting the amount of the liquid droplet, It is desirable that the dot row for calculating the shift amount is composed of small dots.
In general, in the halftone area of a printed image, a dot row forming position in which a dot row forming position shift is particularly noticeable is a dot row composed of small dots. Here, in the adjustment method, a dot row of small dots is formed to calculate the shift amount. Therefore, it is possible to minimize the variation of the dot row with respect to the dot row of the small dots, thereby improving the image quality in the halftone area.
[0015]
In this method of adjusting the ejection timing, the liquid is a plurality of types of ink for printing a print image on the medium, and each nozzle row of the liquid ejection head includes one of the plurality of types of ink. It is desirable that the adjustment value of the ejection timing be shared for each of the liquid ejection heads.
According to such a method of adjusting the ejection timing, the adjustment value of the ejection timing is shared for each of the liquid ejection heads over a plurality of nozzle rows provided in the liquid ejection head. Therefore, the device configuration can be simplified.
[0016]
In this method of adjusting the ejection timing, the plurality of types of inks include at least one set of dark inks and light inks having substantially the same hue and different densities, and the misalignment is determined by the nozzle row associated with the light inks. It is desirable to form a dot row for calculating the quantity.
According to such a method of adjusting the ejection timing, the adjustment value of the ejection timing is set by the dot row of the light ink that is frequently used in the halftone area when at least the dark and light ink is included. Therefore, the image quality in the halftone area can be improved.
[0017]
In the method of adjusting the ejection timing, it is preferable that the plurality of types of ink include at least magenta ink, and the dot row for calculating the shift amount is formed by a nozzle row associated with the magenta ink.
According to such a method of adjusting the ejection timing, the ejection timing is set based on the magenta ink dot row that is frequently used in the halftone area. Therefore, the image quality in the halftone area can be improved.
[0018]
In this method of adjusting the ejection timing, the ejection of the liquid from the nozzle array is performed based on a reference ejection signal for driving the nozzle array, and a plurality of types of reference ejection signals having different waveforms are provided so as to be selectable. It is desirable to set an adjustment value of the ejection timing for each type of signal.
In general, if the type of the waveform of the reference ejection signal is different, the ejection speed of the liquid is also different, and accordingly, the shift amount of the dot row formation position is also changed. Therefore, in the above adjustment method, an adjustment value of the ejection timing is set for each type of the reference ejection signal. Therefore, it is possible to reliably improve the dot row formation position accuracy in the return path.
[0019]
In this method of adjusting the ejection timing, the liquid is ink for printing a print image on the medium, and the liquid ejection apparatus sets a print mode of the print image when printing the print image on the medium. It is desirable to have a print mode setting means, and to drive the nozzle array based on a reference discharge signal of a type corresponding to the set print mode.
According to such a method of adjusting the ejection timing, by setting the print mode, a reference ejection signal suitable for a printed image can be selected, which is excellent in convenience.
[0020]
Further, a moving body that reciprocates by receiving moving forces in opposite directions at a pair of points of action on the line of action of the moving force, and is intermittently conveyed in a direction intersecting with the moving direction of the moving body while being held by the moving body. A plurality of liquid ejection heads having a plurality of nozzle arrays for ejecting liquid toward a medium to form a dot array, and adjusting means for adjusting the ejection timing of the liquid in the return path, wherein the medium is stopped. A method for adjusting the ejection timing of a liquid ejection device that ejects liquid toward the medium by moving the moving body, wherein the liquid is a plurality of types of ink for printing a print image on the medium. Each of the nozzle rows of the liquid ejection head is associated with one type of ink among a plurality of types, and the plurality of types of inks have substantially the same hue and have different densities. The liquid ejecting head includes a pair of dark ink and light ink, and ejects the liquid in the outward path from the nozzle row closest to the middle point between the pair of action points among the liquid ejection heads closest to the action line. A reference dot row is formed on the medium, and a liquid is ejected in the return path from a nozzle row of another liquid ejection head to form a dot row. The amount of deviation between the dot row formation position and the reference dot row formation position Adjusting the ejection timing in the return path of the nozzle row of the other liquid ejection head, the nozzles of the nozzle row can form large, medium, and small dots by adjusting the amount of ejected liquid droplets, The dot row for calculating the shift amount is composed of small dots, and the adjustment value of the ejection timing is shared for each of the liquid ejection heads, and the dot row is associated with the light ink. Forming a dot row for calculating the deviation amount, and discharging the liquid from the nozzle row is performed based on a reference discharge signal for driving the nozzle row, so that a reference discharge signal having a different waveform can be selected. A print mode setting unit that sets an adjustment value of the ejection timing for each type of the reference ejection signal, and sets a print mode of the print image when printing a print image on a medium; A method for adjusting the ejection timing of a liquid ejection apparatus, wherein the nozzle array is driven based on a reference ejection signal associated with a set print mode.
According to such a method of adjusting the ejection timing, all the effects described above are exhibited, and thus the object of the present invention is most effectively achieved.
[0021]
A liquid ejecting head having a plurality of nozzle arrays for ejecting liquid toward a medium to form a dot array; a moving body holding the plurality of liquid ejecting heads and reciprocating; and a timing of ejecting the liquid in a return path. A liquid ejecting apparatus comprising: a nozzle array of any one of the plurality of liquid ejecting heads, which ejects liquid in a forward path and outputs a reference dot array to a medium. And forming a dot row by discharging liquid from the nozzle row of the other liquid discharge head in the return path, based on the amount of deviation between the dot row forming position and the reference dot row forming position. It is also possible to realize a liquid discharge apparatus in which the discharge timing in the return path of the nozzle row of another liquid discharge head is adjusted.
[0022]
=== Schematic Configuration Example of Liquid Discharge Apparatus ===
FIG. 1 is a perspective view illustrating an outline of a color inkjet printer (hereinafter, referred to as a color printer) 20 as a first embodiment of a liquid ejection apparatus.
The color printer 20 is an ink jet printer capable of outputting a color image, for example, cyan (C), light cyan (light cyan, LC), magenta (M), light magenta (light magenta, LM), yellow (Y This is an inkjet printer that prints a print image by discharging liquids such as six color inks of black (K) onto various media such as printing paper to form dots. The color inks are not limited to the above six colors, and for example, dark yellow (dark yellow, DY) may be used. Further, the color printer 20 is compatible with relatively large single-sheet print paper such as roll paper in which print paper is wound in a roll shape as shown in FIG. .
Such a color printer 20 is roughly divided into a printing unit 3 that discharges ink and prints on the roll paper P, and a print paper transport unit 5 that transports the roll paper P. Hereinafter, each part will be described.
[0023]
――― (1) Printing department ―――
The printing unit 3 includes a carriage 28 as a moving body that holds a plurality of print heads 36, and moves the carriage 28 in a direction (hereinafter, referred to as a sub-scanning direction) substantially orthogonal to a transport direction of the roll paper P (hereinafter, also referred to as a sub-scanning direction). A pair of upper and lower guide rails 34 for guiding the carriage 28 to reciprocate in the main scanning direction or the left and right direction, a carriage motor 30 for reciprocating the carriage 28, and a moving force of the carriage motor 30. And a position detecting sensor 18 for detecting the current position of the carriage 28 in the main scanning direction.
[0024]
(1-A) Carriage
The carriage 28 is a substantially rectangular flat plate, and is supported by the guide rail 34 in such a manner that its lower edge protrudes forward from the upper edge. At the center in the sub-scanning direction at each of the left edge and the right edge of the carriage 28, engagement portions 28a and 28b for fixing the traction belt 32 are provided. Then, a leftward moving force F is applied by the traction belt 32 from the left engaging portion 28a, and the carriage 28 moves to the left in the main scanning direction, which is the outward path, and conversely, from the right engaging portion 28b. Moves to the right, which is the return path, with the rightward moving force F applied.
[0025]
The moving force F is oriented in the main scanning direction, and therefore, the line of action of the moving force F (a straight line passing through the point at which the moving force works and oriented in the direction of the moving force) is defined by the left and right engaging portions 28a. , 28b. The portion near the line of action is a portion where vibration during movement of the carriage 28 is small because the moving force F is directly transmitted. This relates to the adjustment of the ejection timing of each print head 36 described later.
[0026]
Eight print heads 36 are arranged on the entire surface of the carriage 28. FIG. 2 shows the print head 36 in an enlarged manner. The print head 36 has a number of nozzles n for discharging ink. The nozzles n form a nozzle row N by being arranged in a row at a predetermined pitch k · D along the sub-scanning direction. Six nozzle rows N are provided for each print head 36, and these nozzle rows N are juxtaposed at a design pitch Wn in the main scanning direction. The arrangement of the print head 36 and the nozzles n will be described later.
[0027]
FIG. 3 shows a plan layout of the print head 36 on the carriage 28. In this figure, the carriage 28 is seen from the back side, that is, from the platen 26 side described later, and the right and left sides of FIG. As shown in the figure, four print heads 36 are arranged in a left area and a four print head 36 are also arranged in a right area with respect to a center of the plane of the carriage 28 in the left-right direction. Reference numerals 36 are aligned in a straight line at a design pitch 2L0 (= 2 (H + kD)) along the sub-scanning direction. In other words, in each area, the print heads 36 adjacent to each other in the sub-scanning direction are arranged at an interval corresponding to one print head 36 therebetween. Here, H indicates the total length of the nozzle row N as shown in FIG. 2, and is also referred to as head height below.
[0028]
On the other hand, as shown in FIG. 3, the print heads 36 adjacent to each other on the left and right are arranged at the design pitch Wh in the main scanning direction, and in the sub-scanning direction, only half of the design pitch 2L0. The print heads 36 are thus shifted, so that the print heads 36 are arranged in a zigzag pattern on the left and right sides of the plane of the carriage 28. More specifically, the print heads 36 in one area (for example, the right area) are arranged corresponding to the intervals where the print head 36 does not exist in one area (for example, the left area). The space portions where the print heads 36 do not exist in the respective regions complement each other. Therefore, for example, when the eight print heads 36 on the carriage 28 are combined, it becomes equivalent to having a nozzle row of about eight times the total length of the nozzle row N, thereby printing a large print image in a very short time. It can be executed by
[0029]
The plane arrangement center C2 of these eight print heads 36 coincides with the plane center C1 of the carriage 28. Therefore, a line segment connecting the left and right engagement portions 28a and 28b of the traction belt 32 divides the plane arrangement of the print head 36 into upper and lower portions in the sub-scanning direction. , 28b coincides with the plane arrangement center C2.
[0030]
(1-B) Guide rail
As shown in FIG. 1, two guide rails 34 are provided along the main scanning direction. These guide rails 34 are vertically arranged at an interval in the sub-scanning direction, and are supported at both left and right end portions by a frame (not shown) serving as a base. The two guide rails 34 are arranged such that the lower guide rail 341 is disposed before the upper guide rail 342, and thus the carriage 28 bridged between them has the lower edge thereof as described above. Are reciprocated in the main scanning direction while maintaining an inclined state protruding forward.
[0031]
The guide rail 342 is provided with a linear encoder code plate 19, which is a component of the position detection sensor 18 of the carriage 28, along the guide rail 342. A linear encoder 17 which is another component of the position detection sensor 18 is fixed to the carriage 28. Thus, the current position of the carriage 28 in the main scanning direction can be recognized. The position detection sensor 18 will be described later.
[0032]
(1-C) Traction belt
The traction belt 32 is a metal band, one end of which is fixed to the left engagement portion 28a of the carriage 28, and the other end of which is fixed to the right engagement portion 28b through the back side of the carriage 28. ing. The traction belt 32 is wrapped around a pair of pulleys 44a and 44b provided at left and right movement stroke ends of the carriage 28. The carriage motor 30 is connected to one of the pulleys 44a, and the carriage motor 30 applies a moving force F in the main scanning direction to the carriage 28 via the traction belt 32. As a result, the carriage 28 reciprocates in the left and right directions.
[0033]
(1-D) Position detection sensor
FIG. 4 schematically shows a configuration of the position detection sensor 18 attached to the carriage 28. The position detection sensor 18 includes a linear encoder code plate 19 fixed to the guide rail 342 and the linear encoder 17 fixed to the carriage 28.
[0034]
In the linear encoder code plate 19, slits are formed at predetermined intervals along the main scanning direction.
The linear encoder 17 includes a light emitting diode 17a, a collimator lens 17b, and a detection processing unit 17c. The detection processing unit 17c has a plurality (for example, four) of photodiodes 17d, a signal processing circuit 17e, and, for example, two comparators 17fA and 17fB.
[0035]
When the voltage VCC is applied to both ends of the light emitting diode 17a via a resistor, light is emitted from the light emitting diode 17a. This light is converged into parallel light by the collimator lens 17b and passes through the linear encoder code plate 19. The linear encoder code plate 19 is provided with slits at predetermined intervals (for example, 1/180 inch (1 inch = 2.54 cm)).
[0036]
The parallel light that has passed through the linear encoder code plate 19 enters each photodiode 17d through a fixed slit (not shown) and is converted into an electric signal. The electric signals output from the four photodiodes 17d are subjected to signal processing in a signal processing circuit 17e, and the signals output from the signal processing circuit 17e are compared in comparators 17fA and 17fB, and the comparison result is output as a pulse. The pulses ENC-A and ENC-B output from the comparators 17fA and 17fB are output from the encoder 17.
[0037]
FIGS. 5A and 5B are timing charts showing waveforms of two output signals of the linear encoder 17 at the time of forward rotation and reverse rotation of the carriage motor.
[0038]
As shown in FIGS. 5A and 5B, the phases of the pulse ENC-A and the pulse ENC-B differ by 90 degrees both in the forward rotation and in the reverse rotation of the carriage motor. When the carriage motor 30 is rotating forward, that is, when the carriage 28 is moving in the forward direction, as shown in FIG. 5A, the phase of the pulse ENC-A leads the phase of the pulse ENC-B by 90 degrees. When the carriage motor 30 is rotating in the reverse direction, that is, when moving in the backward direction, the phase of the pulse ENC-A is delayed by 90 degrees from the pulse ENC-B, as shown in FIG. 5B. One cycle T of the pulse ENC-A and the pulse ENC-B is equal to the time during which the carriage 28 moves through the slit interval of the linear encoder code plate 19.
[0039]
In the present embodiment, the width of the slit (white portion) of the linear encoder code plate 19 is twice the resolution of the color printer 20, for example, 360 dpi here. That is, when the carriage 28 scans in the main scanning direction, it is detected that the carriage 28 has moved a distance corresponding to 360 dpi every time a pulse is output from the encoder 17. Therefore, for example, in the initial operation when the color printer 20 is started, the home position set in advance to be the standby position of the carriage 28 is recognized, and the pulses output from the linear encoder 17 are counted. Can be detected in the main scanning direction.
[0040]
Further, by equally dividing the pulse output from the linear encoder 17, the position of the carriage 28 can be detected with a higher resolution than the slit of the linear encoder code plate 19. For example, when the pulse output from the linear encoder 17 is divided into four, the position of the carriage 28 can be detected and controlled with an accuracy of 1440 dpi.
[0041]
――― (2) Printing paper transport section ―――
As shown in FIG. 1, a printing paper transport unit 5 for transporting the roll paper P is provided on the back side of the two guide rails 34. The print paper transport unit 5 transports the roll paper P above the upper guide rail 342, and a roll paper holding unit 35 that rotatably holds the roll paper P below the lower guide rail 341. And a platen 26 along which the roll paper P transported between the roll paper holding unit 35 and the roll paper transport unit 37 is arranged.
[0042]
(2-A) Platen
The platen 26 has a plane extending over the entire width of the roll paper P to be conveyed, and is provided so as to be inclined so as to be parallel to the plane of the carriage 28 that scans in the inclined state. The print heads 36 are attached to the carriage 28 at equal intervals.
[0043]
(2-B) Roll paper holding unit
The roll paper holding unit 35 includes a holder 27 that rotatably holds the roll paper P. The holder 27 has a shaft 27a serving as a rotation axis while holding the roll paper P. Both ends of the shaft 27a are provided to prevent meandering and skew of the supplied roll paper P. Guide disks 27b are provided respectively.
[0044]
(2-C) Roll paper transport unit
The roll paper transport unit 37 rotates the smap roller 24 for transporting the roll paper P, the nipping roller 24 a that is disposed to face the smap roller 24, and holds the roll paper P between the smap roller 24 and the smap roller 24. And a transport motor 31 for movement. A drive gear 40 is provided on the axis of the transport motor 31, and a relay gear 41 meshing with the drive gear 40 is provided on the axis of the smap roller 24. The power of the transport motor 31 is transmitted via the drive gear 40 and the relay gear 41. The light is transmitted to the smap roller 24. That is, the roll paper P held by the holder 27 is sandwiched between the smap roller 24 and the sandwiching roller 24 a, and the transport motor 31 conveys the roll paper P along the platen 26.
[0045]
=== Print Head Configuration ===
As shown in FIG. 2, the print head 36 has six nozzle rows N in which a large number of nozzles n are aligned in a straight line along the sub-scanning direction. At the design pitch Wn. In the present embodiment, as the nozzle row N, a black nozzle row Nk, a cyan nozzle row Nc, a light cyan nozzle row Nlc, a magenta nozzle row Nm, a light magenta nozzle row Nlm, and a yellow nozzle row Ny are provided for each ink color to be ejected. In a row.
Each nozzle row N has 180 nozzles n1 to n180, and each nozzle n is provided with a piezo element (not shown) as a driving element for driving the nozzle n to eject ink droplets. Have been. The nozzles n1, n2,... N180 of the nozzle row N are arranged at a constant nozzle pitch kD along the sub-scanning direction. Here, D is a dot pitch in the sub-scanning direction, and k is an integer of 1 or more. Note that the dot pitch D in the sub-scanning direction is also equal to the pitch of the main scanning line (raster line).
Then, at the time of printing, the roll paper P is intermittently conveyed by a predetermined conveyance amount by the printing paper conveyance unit 5, and the carriage 28 alternately moves at least one of the outward path and the homeward path in the main scanning direction while the intermittent conveyance is stopped. During this movement, ink droplets are ejected from each nozzle n. However, depending on the printing method, not all nozzles n are always used, and only some nozzles n may be used.
[0046]
=== Print head drive ===
Next, driving of the print head 36 will be described with reference to FIG.
FIG. 6 is a block diagram showing the configuration of the drive signal generator provided in the head control unit 63 (FIG. 9). FIG. 7 shows the original drive signal ODRV and the print signal showing the operation of the drive signal generator 200. 6 is a timing chart of PRT (i) and a drive signal DRV (i).
[0047]
The drive signal generation unit 200 shown in FIG. 6 is provided independently for each print head 36, and the ejection timing of ink droplets can be adjusted for each print head 36.
The drive signal generator 200 includes a plurality of mask circuits 204, an original drive signal generator 206, and an original drive signal shift corrector 207 as means for adjusting the ejection timing of ink droplets. The mask circuit 204 is provided corresponding to a plurality of piezo elements for driving the nozzles n1 to n180 of the print head 36, respectively. In FIG. 6, the number in parentheses at the end of each signal name indicates the number of the nozzle to which the signal is supplied.
The original drive signal generation unit 206 generates an original drive signal ODRV commonly used for the nozzles n1 to n180. The original drive signal ODRV is a signal including two pulses of the first pulse W1 and the second pulse W2 within the main scanning period for one pixel, and is a reference ejection signal for ejecting ink droplets from each nozzle. is there. That is, all the nozzles n of the print head 36 eject ink droplets for each print head 36 based on the same original drive signal ODRV.
The output of the original drive signal ODRV is started when the carriage 28 reaches the output start positions 281f and 281b set for each of the forward scan and the backward scan, and is set corresponding to the output start positions 281f and 281b. The motor stops when it reaches the output stop positions 282f and 282b (see FIG. 1).
[0048]
That is, in the forward scan scanning from right to left in FIG. 1, when the position detection sensor 18 detects that the output start position 281f on the right side has been reached, output is simultaneously started over all the print heads 36, Ink droplets are ejected at the same ejection timing. However, in the case where the print head 36 itself has an individual difference that the ejection speed is slightly different for each print head 36, even if the ink droplets are ejected at the same ejection timing, the arrival time to the roll paper P Are different from each other, it is not possible to form a dot row at the same target position on the roll paper P. Accordingly, in order to cope with such a case where there is an individual difference, the output start position 281f of the forward path can be shifted and adjusted left and right in the main scanning direction by the original drive signal shift correction unit 207 for each print head 36. ing.
[0049]
On the other hand, in the output start position 281b of the backward scanning that scans from left to right in FIG. 1, a dot row formed on the backward path based on the output start position 281b is formed based on the output start position 281f of the forward path. The dot row is set in advance so as to coincide with the position in the main scanning direction. However, this return path is also set on the assumption that there is no individual difference for each print head 36. Therefore, in order to cope with the case where there is an individual difference or the like, the output start position 281b of the return path can be shifted right and left in the main scanning direction by the original drive signal shift correction unit 207 for each print head 36.
[0050]
The shift amounts in the forward scan and the backward scan are calculated by a shift amount calculation method described later, and are stored in a shift amount setting table 581 (see FIG. 8) in the ROM 58 described later. Then, each time printing is performed, the original drive signal shift correction unit 207 of each print head 36 reads the corresponding shift amount with reference to the table 581 and shifts the output start position for each print head 36. I have.
[0051]
As shown in FIG. 6, the input serial print signal PRT (i) is input to the mask circuit 204 together with the original drive signal ODRV output from the original drive signal generator 206. The serial print signal PRT (i) is a 2-bit serial signal per pixel, and each bit corresponds to the first pulse W1 and the second pulse W2, respectively. The mask circuit 204 is a gate for masking the original drive signal ODRV according to the level of the serial print signal PRT (i). That is, when the serial print signal PRT (i) is at the 1 level, the mask circuit 204 passes the corresponding pulse of the original drive signal ODRV as it is and supplies it to the piezo element as the drive signal DRV, while the serial print signal PRT (i) ) Is at the 0 level, the corresponding pulse of the original drive signal ODRV is cut off.
[0052]
As shown in FIG. 7, the original drive signal ODRV sequentially generates a first pulse W1 and a second pulse W2 in each pixel section T1, T2, T3, T4. The pixel section has the same meaning as the main scanning period for one pixel. When the print signal PRT (i) corresponds to the 2-bit pixel data "1, 0" as shown in the figure, only the first pulse W1 is output in the first half of one pixel section. Thus, small ink droplets are ejected from the nozzles, and small dots (small dots) are formed on the printing paper. When the print signal PRT (i) corresponds to 2-bit pixel data “0, 1”, only the second pulse W2 is output in the latter half of one pixel section. Thus, a medium-sized ink droplet is ejected from the nozzle, and a medium-sized dot (medium dot) is formed on the printing paper. When the print signal PRT (i) corresponds to the 2-bit pixel data “1, 1”, the first pulse W1 and the second pulse W2 are output in one pixel section. As a result, large ink droplets are ejected from the nozzles, and large dots (large dots) are formed on the printing paper. When the print signal PRT (i) corresponds to 2-bit pixel data “0, 0”, neither the first pulse W1 nor the second pulse W2 is output in one pixel section. In this case, no ink droplet is ejected from the nozzle, and no dot is formed on the printing paper.
[0053]
As described above, the drive signal DRV (i) in one pixel section is shaped so as to have four different waveforms according to the four different values of the print signal PRT (i), and based on these signals, The print head 36 can form dots of three different sizes or can be made not to form dots.
[0054]
=== Control Configuration Example of Liquid Discharge Apparatus ===
Next, an example of a control configuration of the color printer 20 as a liquid ejection device will be described with reference to FIGS. FIG. 9 is a block diagram illustrating a control configuration of the color printer 20, and FIG. 10 is a block diagram illustrating a configuration of the image processing unit 38.
The color printer 20 is used by being connected to a computer 90 such as a personal computer, and prints a print image on roll paper P based on image data transmitted from the computer 90. Note that the above-described configuration in which the computer 90 is added to the color printer 20 can also be called a “liquid ejection device” in a broad sense.
[0055]
The computer 90 includes a CRT 21, a display device such as a liquid crystal display device (not shown), an input device such as a keyboard and a mouse, and a drive device such as a flexible drive device and a CD-ROM drive device. In the computer 90, an application program 95 operates under a predetermined operating system. A video driver 91 is incorporated in the operating system, and an application program 95 for performing image retouching and the like performs desired processing on an image to be processed, and outputs an image to the CRT 21 via the video driver 91. indicate.
[0056]
The color printer 20 includes an image processing unit 38 as information generating means to which image data and the like from an application program 95 are input, a system controller 54 for controlling the operation of the entire color printer 20, a RAM 56, and a ROM 58. I have. Note that the RAM 56 and the ROM 58 referred to here are both memories from which data can be read / written. The difference between the two is that the RAM 56 requires electricity supply to hold the stored contents, whereas the ROM 58 does not require it. Is a point. The ROM 58 stores the shift amount setting table 581 related to the output start position of the original drive signal ODRV described above. The system controller 54 further includes a main scanning drive circuit 61 for driving the carriage motor 30, a sub-scanning drive circuit 62 for driving the transport motor 31, and a print head 36. Eight head control units 63 as control means for controlling the control unit 36 and the position detection sensor 18 for detecting the position of the carriage 28 are connected.
[0057]
Then, when the application program 95 issues a print command, the image processing unit 38 provided in the color printer 20 receives image data from the application program 95 and converts it into print data PD. As shown in FIG. 10, inside the image processing unit 38, a resolution conversion module 97, a color conversion module 98, a halftone module 99, a rasterizer 100, a UI printer interface module 102, a raster data storage unit 103, a color conversion lookup table LUT, a buffer memory 50, and an image buffer 52 are provided.
[0058]
The resolution conversion module 97 serves to convert the resolution of the color image data formed by the application program 95 into a corresponding print resolution based on information such as a print mode received together with the image data. The image data whose resolution has been converted in this way is still image information composed of three color components of RGB. The color conversion module 98 converts the RGB image data for each pixel into multi-tone data of a plurality of ink colors that can be used by the color printer 20 with reference to the color conversion lookup table LUT.
[0059]
The color-converted multi-tone data has, for example, 256 tone values. The halftone module 99 generates a halftone image data by executing a so-called halftone process. Here, the halftone divides an image into, for example, a predetermined region including a plurality of portions where pixels can be formed, and sets the density in each region to a plurality of portions forming the region, such as a large dot, a medium dot, and a large dot. It is assumed that the density of each area is represented by whether or not to form a dot or a small dot. Therefore, in the halftone image data, the data of each pixel is generated as binary data indicating the gradation of each pixel.
[0060]
The halftone image data is rearranged in a desired data order by the rasterizer 100 and output to the raster data storage unit 103 as final print data PD. The print data PD includes raster data indicating a dot formation state in each main scan and data indicating a sub-scan feed amount.
[0061]
On the other hand, the user interface display module 101 provided in the computer 90 has a function of displaying various user interface windows related to printing, and a function of receiving a user's input in those windows. For example, the user can instruct the user interface display module 101 on the type, size, print mode, and the like of the printing paper.
[0062]
The UI printer interface module 102 has a function as an interface between the user interface display module 101 and the color printer 20. The command interpreted by the user through the user interface is interpreted and various commands COM are transmitted to the system controller 54 and the like. Conversely, the command COM received from the system controller 54 and the like is interpreted and various displays are performed on the user interface. Or For example, the instruction regarding the type, size, print mode, and the like of the printing paper received by the user interface display module 101 is sent to the UI printer interface module 102, and the UI printer interface module 102 interprets the instructed instruction. To send the command COM to the system controller 54. Then, based on the print mode, print information (resolution of the image to be printed, information on nozzles used for printing, information on data indicating the sub-scan feed amount), the print data PD is converted to the halftone module 99 or the rasterizer. 100, and output to the raster data storage unit 103.
[0063]
The print data PD output to the raster data storage unit 103 is temporarily stored in the buffer memory 50, converted into data corresponding to the nozzle, and stored in the image buffer 52. The system controller 54 of the color printer 20 controls the main scanning drive circuit 61, the sub-scanning drive circuit 62, the head control unit 63, and the like based on the information of the command COM output by the UI printer interface module 102, The printing is performed by driving the nozzles of each color provided on the print head 36 based on the data.
[0064]
The print mode mainly includes a color definition mode for defining the color of the print image and an image quality definition mode for defining the image quality of the print image, and is defined by a combination of these as shown in FIG. . As the color defining mode, any one of a full-color mode in which printing is performed using all six inks and a monochrome mode in which printing is performed using single-color ink such as black ink alone can be selected and set. On the other hand, the image quality defining mode is a so-called interlace method (a method in which a raster line (a line in the main scanning direction in a print image) is formed at a dot pitch D in the sub-scanning direction smaller than the nozzle pitch k · D). A high image quality mode in which dots are recorded by using raster lines that are adjacent to each other in the scanning direction with different nozzles, or a so-called band method (a raster line in an area corresponding to the head height H by one scan is used for nozzles). One of the high-speed modes in which dots are printed at high speed using a method of forming dots at a pitch kD can be selected and set. The ink used in the monochrome mode is not limited to black ink, and other inks such as cyan ink may be used. The high-quality mode is not limited to the interlace mode, but may be a so-called overlap mode in which one raster line (one line in the main scanning direction in a print image) is printed by scanning a plurality of times, or a combination thereof. The method may be used.
[0065]
=== Bidirectional printing operation of liquid ejection device ===
FIG. 12 is an explanatory diagram for explaining the bidirectional printing operation of the color printer 20 as the above-described liquid ejection device. Here, as an example of this bidirectional printing operation, a case where one print image “A” 12 is printed on roll paper P using four print heads 36 a, 36 c, 36 e, and 36 g located in the left area of the carriage 28. Will be described. It is assumed that the size of the print image “A” 12 in the sub-scanning direction is approximately eight times the head height H of the print head 36 as shown in FIG. It is assumed that “monochrome, high speed”, which is the print mode 4 in FIG. 11, is selected and set as the print mode. Thus, when scanning is performed once each in the forward path and the backward path, the print image "A" 12 is formed by performing printing in a band manner by the four print heads 36a, 36c, 36e, and 36g in each scan.
[0066]
That is, the print image “A” 12 is divided into eight band images 12a, 12b,... 12h in the sub-scanning direction. The odd-numbered band-shaped images 12a, 12c, 12e, and 12g are printed on the four print heads 36a, 36c, 36e, and 36g from the top in the sub-scanning direction on the outward path, and the remaining even-numbered band-shaped images are printed on the return path. The user instructs to print the images 12b, 12d, 12f, and 12h.
[0067]
These instructions received from the user interface display module 101 are sent to the UI printer interface modules 102 provided in the four image processing units 38a, 38c, 38e, and 38g described above, and the UI printer interface module 102 receives the instructions. The command COM is interpreted and the command COM is transmitted to the system controller 54.
[0068]
Next, the user gives an instruction to perform printing in the application program 95 or the like. When the application program 95 that has received this instruction issues a print command, the above-described four image processing units 38a, 38c, 38e, and 38g cause the respective band-shaped images 12a, 12c, and 12e to be data for the forward scan. , 12g are received from the application program 95, are converted into print data PD, and are transmitted to the buffer memory 50. Each of the image processing units 38a, 38c, 38e, and 38g transmits the print data PD corresponding to each of the print heads 36a, 36c, 36e, and 36g to the image buffer 52 after being received by the buffer memory 50.
[0069]
Further, each of the image processing units 38a, 38c, 38e, 38g transmits the above-mentioned command COM to the system controller 54. The system controller 54, based on the information received from each of the image processing units 38a, 38c, 38e, 38g, includes a main scanning drive circuit 61, a sub-scanning drive circuit 62, and the four head control units 63a, 63c, A control signal is sent to 63e and 63g.
[0070]
Further, each of the head control units 63a, 63c, 63e, and 63g transmits a signal from the image buffer 52 in the image processing unit 38a, 38c, 38e, or 38g corresponding to each head control unit 63 according to a control signal from the system controller 54. Read the print data of each color component. Then, each head control unit 63a, 63c, 63e, 63g controls the corresponding print head 36a, 36c, 36e, 36g based on the read data.
[0071]
Then, the carriage motor 30 is controlled by the main scanning drive circuit 61 to move the carriage 28 in the forward direction of the main scanning, and the respective print heads 36a controlled by the respective print head control units 63a, 63c, 63e, 63g. , 36c, 36e, and 36g, the odd-numbered band-shaped images 12a, 12c, 12e, and 12g are printed on the roll paper P. At this time, the output of the original drive signal ODRV that controls the ejection of the ink is started when the carriage 28 reaches the output start position 281f on the outward path. However, in detail, the original drive signal shift correction unit 207 associated with each print head 36 reads the corresponding forward shift amount setting value from the shift amount setting table 581 and starts the output start by the set value. The output starts after shifting from the position 281f. Thus, when each print head 36 ejects ink droplets to form a dot row at the same target position in the main scanning direction, the dot row actually formed by the nozzle row of each print head 36 Are formed so as to coincide with each other in the main scanning direction. Thereafter, when the carriage 28 moves to the left side in the figure and reaches the output stop position 282f, the output of the original drive signal ODRV is stopped.
[0072]
When the forward scan is performed as described above, the even-numbered band image 12b is formed by the next backward scan in a blank portion corresponding to the head height H existing between the odd-numbered band images 12a, 12c, 12e, and 12g. , 12d, 12f, and 12h, the transport motor 31 feeds the roll paper P by the head height H. Then, the image processing units 38a, 38c, 38e, and 38g receive the image data corresponding to the respective band-shaped images 12b, 12d, 12f, and 12h from the application program 95 as the data for the backward scanning, respectively. The same processing as that in the forward scan is performed, and in the backward scan, ink is ejected from each of the print heads 36a, 36c, 36e, and 36g, and even-numbered strip images 12a, 12c, 12e, and 12g are printed. Also in this return path, the output of the original drive signal ODRV that controls the ejection of the ink is started when the carriage 28 reaches the output start position 281b of the return path. The drive signal shift correction unit 207 reads out the corresponding shift amount setting value of the return path from the shift amount setting table 581, shifts the output start position 281b by the set value, and starts the output. Thus, when each print head 36 ejects ink droplets to form a dot row at the same target position in the main scanning direction, the dot row actually formed by the nozzle row of each print head 36 Are formed so as to coincide with each other in the main scanning direction. Thereafter, when it moves to the right side in the figure and reaches the output stop position 282b, the output of the original drive signal ODRV is stopped, and the backward scanning is completed, and at the same time, the bidirectional printing operation is completed.
[0073]
The shift amount setting value is calculated by a shift amount calculation method described below, and is stored in the shift amount setting table 581 in advance.
[0074]
=== Method of Calculating Shift Amount Related to Output Start Position of Original Drive Signal ===
(A) Outline of calculation method
The shift amount for each print head 36 is calculated as follows.
First, any one of the plurality of print heads 36 shown in FIG. 3 is used as a reference print head 36s, and ink droplets are ejected from the nozzle array N of the reference print head 36s in the outward path, as shown in FIG. A reference dot row Rs is formed on the roll paper P. In the forward pass, ink droplets are also ejected from the nozzle row N of the print head 36 to be shifted, which is the print head 36 other than the reference print head 36s, to form a dot row Rf for calculating the forward shift amount. Form. Then, based on the shift amount Sf between the formation position of the dot row Rf and the formation position of the reference dot row Rs, the shift amount of the print head 36 to be shifted in the forward path is calculated, and is calculated as a shift amount setting value. In the forward path column of the shift amount setting table 581 in the ROM 58.
[0075]
In addition, ink droplets are ejected from the same nozzle array N that ejected the ink droplets in the forward pass in the return pass to form a dot row Rb for calculating the shift amount in the return pass as shown in FIG. 14, and this dot row Rb is formed. The shift amount in the return path of the print head 36 to be shifted is calculated based on the shift amount Sb between the position and the formation position of the reference dot row Rs. Then, this is stored in the return path column of the table 581 as a shift amount setting value. Regarding the return path, the reference print head 36s is also included in the print heads 36 to be shifted.
[0076]
When the shift amount is calculated in this way, the dot rows Rb for all the print heads 36 on the return path as well as the forward path are aligned with one reference dot row Rs as a reference. That is, one reference dot row Rs is shared as the adjustment reference for the return path of all the print heads 36. Therefore, it is possible to prevent the number of reference dot rows from being increased by using different reference dot rows for each print head 36, thereby making it possible to reduce the number of adjustment criteria that are likely to occur when there are a plurality of adjustment criteria. Can be reduced to a small extent. As a result, the formation position accuracy of the dot rows formed on the outward path and the return path during bidirectional printing can be improved as a whole.
[0077]
As shown in FIG. 3, a nozzle row N closest to the line of action of the pulling force F of the pulling belt 32, which is the moving force of the carriage 28, is used as the nozzle row Ns forming the reference dot row Rs. Is desirable. That is, in the illustrated example, the reference dot row Rs may be formed using any one of the nozzle rows N included in the print head 36d or the print head 36e. The reason for this is that, in the portion of the carriage 28 that is closer to the line of action, the traction force F is more directly transmitted, so that the vibration during the movement of the carriage 28 is small. This is because an ink droplet ejected toward the roll paper P during the movement has a small dot formation position shift as a landing position shift due to vibration and can be an accurate adjustment index.
[0078]
Further, as shown in this example, when there are a plurality of nozzle rows N closest to this line of action, such as six rows, the pair of engaging portions which are the points of action of the pair of traction forces F are provided. The reference dot row Rs is preferably formed by the nozzle row Ns closest to the middle point M between 28a and 28b. The reason for this is that, in the carriage 28 during the reciprocating movement, the portion where the vibration is the smallest on average is the middle point M between the pair of action points 28a and 28b. In the case of the present embodiment, since this midpoint M corresponds to the plane center C1 of the carriage 28, the reference dot row Rs is formed by the nozzle row Ns closest to the plane center C1.
[0079]
In the illustrated example, there is one nozzle row Ns that satisfies the above condition for each of the print heads 36d and 36e, but any of these nozzle rows Ns may be used. In the description, it is assumed that the nozzle row Ns (black nozzle row Nk) of the print head 36e is selected as the nozzle row forming the reference dot row.
[0080]
(B) Explanation of the specific procedure of the calculation method
First, the calculation of the shift amount in the outward path is performed as follows.
While the forward scan of the carriage 28 is performed at the steady speed V used for printing, ink droplets are directed toward the roll paper P from all the nozzles of each black nozzle row Nk, Nk,. Rfh is ejected only once to the same target position in the main scanning direction to form a reference dot row Rs and dot rows Rfa, Rfb,... Rfh for calculating the shift amount, as shown in FIG. In FIG. 13 (the same applies to FIG. 14), the alphabets suffixed to the dot rows Rfa, Rfb,... Rfh and the shift amounts Sfa, Sfb,. The head 36 is shown.
[0081]
Here, these eight dot rows Rfa, Rfb,... Rfh should be on the same straight line (indicated by a dashed line in the figure) as the reference dot row Rs, and thus each dot row Rfa, Rfa, The shift amounts Sfa, Sfb,... Sfh of Rfb,... Rfh in the main scanning direction are the shift amounts. Therefore, these shift amounts Sfa, Sfb,... Sfh are read and input to the forward path column of the shift amount setting value in the shift amount setting table 581 shown in FIG.
As a method of reading and inputting the shift amounts Sfa, Sfb,... Sfh from the dot rows Rs, Rf, the visually read out shift amounts Sf may be manually input by an input device of the computer 90. The image pickup device picks up the dot rows Rs and Rf, performs appropriate image processing on the picked-up image to calculate shift amounts Sfa, Sfb,... Sfh, and transmits the calculated values to the ROM 58 as shift amount data. Then, it may be stored in the shift amount setting table 581.
[0082]
Next, the calculation of the shift amount on the return path is performed as follows. While performing the forward scan of the carriage 28 at the steady speed V, the ink droplets are directed toward the roll paper P from only the black nozzle row Nk of the print head 36e having formed the reference dot row Rs at a predetermined target position in the main scanning direction. The target is ejected only once to form a reference dot row Rs as shown in FIG. The ejection of the ink droplets is performed by all the nozzles constituting the nozzle row Nk. Thereafter, ink droplets are directed toward the roll paper P from all the nozzles of each black nozzle row Nk, Nk,... Nk of all the print heads 36 shown in FIG. Rbh is ejected only once to the target position, and dot rows Rba, Rbb,... Rbh for calculating the shift amount are formed as shown in FIG. In this case, the reference print head 36s (36e) that formed the reference dot row Rs on the forward pass also forms the dot row Rbe on the return pass, but this also applies to the reference print head 36s (36e). This is because it is necessary to perform a shift adjustment of the output start position.
[0083]
Here, similarly to the case of the above-mentioned forward path, these eight dot rows Rb should originally be on the same straight line (indicated by a dashed line in the drawing) as the reference dot row Rs, The shift amounts Sba, Sbb,... Sbh of the dot rows Rba, Rbb,... Rbh with respect to Rs in the main scanning direction are the shift amounts. Therefore, these shift amounts Sba, Sbb,... Sbh are input in the return path column of the shift amount setting value in the shift amount setting table 581.
As for the reference print head 36 s (36 e), as shown in FIG. 14, the dot row Rbe on the return path is formed at the same position as the reference dot row Rs in the sub-scanning direction. In such a case, it is preferable to form a dot row as follows.
[0084]
FIG. 15 shows an example of the formation of the dot row. When the reference dot row Rs is formed on the outward path, the nozzles n1 to n90 in the upper half area of the black nozzle row Nk of the reference print head 36s (36e) are used. By discharging ink droplets, only the upper half portion Rsu in the above-described reference dot row Rs is formed. That is, the lower half dots are not formed without ejecting ink droplets from the nozzles n91 to n180.
On the other hand, when the dot row Rbe for calculating the shift amount is formed on the return path, ink droplets are ejected from the nozzles n91 to n180 in the lower half area of the black nozzle row Nk of the print head 36e, and the above-described dot row Only the lower half Rbed of Rbe is formed. That is, upper half dots are not formed without ejecting ink droplets from nozzles n1 to n90.
In this manner, the reference dot row Rsu and the dot row Rbed for calculating the shift amount can be formed with their positions shifted in the sub-scanning direction, and the shift amount of the reference print head 36s (36e) on the return path can be formed. It becomes easy to visually recognize the sag amount Sbe.
[0085]
It is preferable that the size of the dots forming the reference dot row Rs and the dot rows Rf and Rb for calculating the shift amount be in a state closer to actual use, that is, a size that is frequently used. This is because the ink droplet amount changes depending on the dot size, but the discharge speed and the like change in accordance with the ink droplet amount, and the dot formation position as the landing position changes. For example, as described above, the dot size of this embodiment has three levels of large, medium, and small, but it is preferable to use medium dots and small dots that are actually used more frequently than large dots. Further, in the printed image at the time of actual use, the deviation of the dot row formation position is conspicuous in the halftone region of the color image, and in this halftone region, small dots are frequently used. It is preferable to form dot rows Rs, Rf, Rb using dots.
[0086]
In the present embodiment, since the shift amounts are calculated by forming the dot lines Rs, Rf, and Rb using the black nozzle lines Nk, the shift amount setting value has the smallest deviation in the formation position of the black ink dot lines. It becomes the numerical value which becomes. Therefore, when the output start position is shifted using this set value, the ejection speed of the dot row of the other color ink in the print head 36 becomes lower due to the viscosity difference from the black ink and the like. Therefore, there is a possibility that the formation position of the dot row slightly shifts.
Accordingly, when there is a color ink whose formation position deviation is desired to be suppressed to be smaller than the black ink, it is preferable to calculate the shift amount by forming the dot rows Rs, Rf, Rb using the color ink. .
[0087]
For example, if it is desired to reduce the formation position deviation of the halftone area and improve the image quality, the shift amount may be calculated using the color ink used in the halftone area. More specifically, when six color inks having light cyan and light magenta in addition to cyan, magenta, yellow, and black are used as in the present embodiment, the color frequently used in the halftone area is light cyan. And light magenta. Accordingly, the dot rows Rs, Rf, Rb may be formed by either light cyan or light magenta, and the shift amount may be calculated based on the rows. When four color inks of cyan, magenta, yellow, and black are used, cyan and magenta are frequently used in the halftone area. Therefore, in the case of these four colors, dot rows Rs, Rf, and Rb may be formed of either cyan or magenta, and the shift amount may be calculated based on the rows. Incidentally, when it is desired to reduce both the formation position deviations of the two colors constituting the halftone area, the average value of the shift amount of one of these two colors and the shift amount of the other color is used. May be used as the shift amount.
[0088]
In the present embodiment, the waveform of the original drive signal ODRV has only one type of waveform shown in FIGS. However, a plurality of types of waveforms of the original drive signal ODRV may be provided corresponding to the print mode, and the original drive signal ODRV may be selectively used according to the print mode.
In the case of this configuration, it is desirable that the shift amount setting table 581 be further provided for each type in association with the type of waveform. The reason for this is that if the type of the waveform of the reference ejection signal ODRV is different, the ejection speed of the ink droplet is also different, and the displacement of the dot row formation position is also changed accordingly.
[0089]
=== Modified example ===
FIG. 16 is a block diagram illustrating a configuration of the drive signal generator 200 of the print head 36 according to a modification of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description of the same components will be omitted.
As shown in FIG. 6, the print head 36 according to the first embodiment has a configuration in which a drive signal generating unit 200 is provided for each print head 36, that is, six nozzle rows N in the print head 36 are common. Of the original drive signal ODRV. Therefore, the ejection timing cannot be independently adjusted for each nozzle row N in the print head 36.
On the other hand, in the present modified example shown in FIG. 16, the drive signal generating section 200 is provided for each nozzle row N, whereby the ejection timing can be independently adjusted for each nozzle row N in the print head 36. ing.
According to this configuration, it is possible to cope with a case where the ejection speed is different for each nozzle row N, for example, a case where the ejection speed of the ink droplet is changed for each color ink due to a difference in viscosity of each color ink. Therefore, the dot row forming position accuracy can be further improved. In this configuration, it goes without saying that the shift amount in the shift amount setting table 581 is set not for each print head 36 but for each nozzle row N.
[0090]
=== Other Embodiments ===
As described above, the liquid ejection device and the like according to the present invention have been described based on one embodiment. However, the above-described embodiment of the present invention is for facilitating understanding of the present invention, and limits the present invention. is not. The present invention can be changed and improved without departing from the gist thereof, and the present invention naturally includes equivalents thereof.
[0091]
For example, the embodiments described below are also included in the liquid ejection device according to the present invention. That is, a color filter manufacturing apparatus, a dyeing apparatus, a fine processing apparatus, a semiconductor manufacturing apparatus, a surface processing apparatus, a three-dimensional modeling machine, a liquid vaporizing apparatus, an organic EL manufacturing apparatus (especially a polymer EL manufacturing apparatus), a display manufacturing apparatus, and a film forming apparatus The same technology as in the present embodiment may be applied to an apparatus, a DNA chip manufacturing apparatus, and the like. These methods and manufacturing methods are also within the scope of application.
[0092]
In the above-described embodiment, the ink such as the dye ink or the pigment ink is ejected from the nozzle n. However, the liquid ejected from the nozzle n is not limited to such ink. For example, a liquid (including water) containing a metal material, an organic material (especially a polymer material), a magnetic material, a conductive material, a wiring material, a film forming material, an electronic ink, a processing liquid, a gene solution, etc. is discharged from the nozzle. May be. If such a liquid is directly discharged toward an object, material saving, process saving, and cost reduction can be achieved.
[0093]
In the above-described embodiment, the pair of engaging portions 28a and 28b for receiving the moving force F in the main scanning direction is provided at the center of the carriage 28 in the sub-scanning direction, but the positions of the engaging portions 28a and 28b are However, the present invention is not limited to this. For example, as shown in FIG. 17A and FIG. 17B, it may be provided at the end in the sub-scanning direction. 17A shows the case where the engaging portions 28a and 28b are provided at the upper end of the carriage 28, and FIG. 17B shows the case where the engaging portions 28a and 28b are provided at the lower end. In any case, it is needless to say that the nozzle row Ns closest to the middle point M of the engaging portions 28a and 28b is preferable as the nozzle row Ns forming the reference dot row Rs.
[0094]
In the above-described embodiment, the reference dot row Rs, the dot rows Rfa, Rfb,... Rfh for calculating the shift amount, and the dot rows Rba, Rbb,. However, the dot row forming method is not limited to this.
[0095]
For example, one dot row may be divided into a plurality of portions, and dots of each portion may be sequentially formed by a plurality of scans to complete the one dot row. This will be described in detail with reference to the reference dot row Rs as an example. In the first forward scan as shown in FIG. 18, ink is supplied only from the odd-numbered nozzles n1, n3, n5,. By ejecting droplets, dots Do (indicated by black circles) of the dot row Rs are formed by thinning out every other dot, and in the second forward scan, the even-numbered nozzles not ejected in the first forward scan Ink droplets may be ejected only from n2, n4, n6,... n180, and the thinned portion may be filled with a dot De (shown by a white circle). By forming the dot row Rs in this way, it is possible to reproduce an ejection state close to the actual printing, and to improve the accuracy of the shift adjustment. It should be noted that the distribution of the dot portion formed in the first forward scan and the dot portion formed in the second forward scan are not limited to the above-described one-by-one nozzle unit. You may make it sort by each. That is, in the first forward scan, ink droplets are ejected from the nozzles # 1, # 2, # 5, # 6,..., And in the second forward scan, the remaining nozzles # 3, # 4, # 7 , # 8,... May be ejected.
[0096]
Further, blank portions between the dots forming the dot rows Rs, Rfa,... Rbh are filled by a plurality of scans to increase the printing resolution of each dot row Rs, Rfa,. Is also good. That is, the dot pitch (interval between dots) of the dot rows Rs, Rfa,... Rbh may be made smaller than the nozzle pitch k · D by repeating scanning and paper feeding. Then, the dot rows Rs, Rfa,... Rbh are made clear, and the visibility is improved.
[0097]
In the above-described embodiment, the ink is ejected using the piezo element. However, the method of discharging the liquid is not limited to this. For example, another method such as a method of generating bubbles in a nozzle by heat may be used.
In the above-described embodiment, the roll paper P has been described as an example of the printing paper.
[0098]
【The invention's effect】
According to the present invention, there is provided a liquid ejecting apparatus capable of reducing a reference dot array serving as a reference for adjusting the ejection timing of the return path for a plurality of liquid ejection heads and improving the formation position accuracy of the dot row of the return path as a whole. It is possible to realize a method of adjusting the ejection timing.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an outline of a first embodiment of a color printer according to the present invention.
FIG. 2 is an enlarged view showing a print head.
FIG. 3 is a plan view of a print head on a carriage.
FIG. 4 is an explanatory diagram schematically showing a configuration of a linear encoder.
FIG. 5A is a timing chart showing waveforms of two output signals of a linear encoder. FIG. 5B is a timing chart showing waveforms of two output signals of the linear encoder.
FIG. 6 is a diagram illustrating a configuration of a drive signal generation unit provided in the head control unit.
FIG. 7 is a timing chart showing the operation of the drive signal generator.
FIG. 8 is a shift amount setting table.
FIG. 9 is a block diagram illustrating a control configuration of the color printer.
FIG. 10 is a block diagram illustrating a configuration of an image processing unit.
FIG. 11 is a diagram for explaining a print mode.
FIG. 12 is an explanatory diagram illustrating a bidirectional printing operation of the color printer.
FIG. 13 is an explanatory diagram for explaining a method of calculating a shift amount related to an output start position of an original drive signal.
FIG. 14 is an explanatory diagram for describing a method of calculating a shift amount related to an output start position of an original drive signal.
FIG. 15 is an example of forming a dot row.
FIG. 16 is a diagram illustrating a configuration of a drive signal generation unit provided in a head control unit according to a modification of the first embodiment.
FIG. 17A is an explanatory diagram for describing another embodiment according to the present invention. FIG. 17B is an explanatory diagram for describing another embodiment according to the present invention.
FIG. 18 is an explanatory diagram for explaining another embodiment according to the present invention.
[Explanation of symbols]
3 printing section 5 printing paper transport section
12 Print image 12a to 12h Band image
17 Linear encoder 17a Light emitting diode
17b Collimator lens 17c Detection processing unit
17d photodiode 17e signal processing circuit
17fA, 17fB comparator
18 Position detection sensor 19 Code plate for linear encoder
20 color printer 21 CRT
24 Smap roller 24a Nipping roller
26 Platen 27 Holder
27a Shaft 27b Guide disk
28 Carriage 28a, 28b Engagement part
30 Carriage motor 31 Transport motor
32 Towing belt 34 Guide rail
341 Lower guide rail 342 Upper guide rail
35 Roll paper holder
36, 36a-36h Print head 36s Reference print head
37 Roll paper transport section
38, 38a-38h Image processing unit
40 Drive gear 41 Relay gear
44a, 44b Pulley 50 Buffer memory
52 Image buffer 54 System controller
56 RAM 58 ROM
61 main scanning drive circuit 62 sub-scanning drive circuit
63, 63a to 63h Head control unit
90 Computer 91 Video Driver
95 Application program 97 Resolution conversion module
98 Color conversion module 99 Halftone module
100 rasterizer
101 User interface display module
102 UI printer interface module
103 Raster data storage
200 drive signal generator 204 mask circuit
206 Original drive signal generation unit 207 Original drive signal shift correction unit
281f, 281b Output start position 282f, 282b Output stop position
581 Shift amount setting table
C1 Center of plane of carriage C2 Center of plane arrangement of print head
M Middle point COM command
F Moving force, Traction force LUT Color conversion lookup table
n, n1 to n180 nozzle
N, Nk, Nc, Nlc, Nm, Nlm, Ny nozzle row
P roll paper PD print data
Rs reference dot row
Rb, Rba-Rbh Dot sequence for calculating shift amount on return route
Rf, Rfa to Rfh Dot row for calculating the shift amount in the forward path
Sb, Sba-Sbh Deviation amount of return trip
Sf, Sfa-Sfh Outward deviation

Claims (13)

A liquid ejection head having a plurality of nozzle rows for ejecting liquid toward a medium to form a dot row, a moving body that holds a plurality of the liquid ejection heads and reciprocates, and adjusts the ejection timing of the liquid in a return path Adjusting means, and a method of adjusting the ejection timing of a liquid ejection apparatus comprising:
From one of the plurality of liquid ejection heads, the nozzle array of one of the liquid ejection heads ejects the liquid on the outward path to form a reference dot array on the medium, and the liquid is ejected from the nozzle array of the other liquid ejection head on the return path. To form a dot row, and based on the amount of deviation between the dot row formation position and the reference dot row formation position, adjust the ejection timing in the return path of the nozzle row of the other liquid ejection head. A method for adjusting a discharge timing of a liquid discharge device, characterized by comprising: The method for adjusting the ejection timing of the liquid ejection device according to claim 1,
The moving body receives a moving force and moves,
A nozzle row forming the reference dot row is a nozzle row closest to the line of action of the moving force, wherein the ejection timing of the liquid ejection apparatus is adjusted. The method for adjusting the ejection timing of the liquid ejection device according to claim 2,
At a pair of action points on the action line, receiving a moving force in opposite directions, the moving body reciprocates by the moving force,
A nozzle row forming the reference dot row is a nozzle row closest to a middle point between the pair of action points among a plurality of nozzle rows closest to the action line; Method of adjusting the ejection timing of the ink. The method for adjusting the ejection timing of the liquid ejection device according to claim 1,
The medium is intermittently conveyed in a direction intersecting with the moving direction of the moving body, and the moving body moves while the medium is stopped and discharges the liquid toward the medium. How to adjust the timing. The method for adjusting the ejection timing of the liquid ejection device according to claim 1,
A method for adjusting the ejection timing of a liquid ejection apparatus, wherein the amount of liquid droplets per nozzle for forming the dot row for calculating the amount of deviation is smaller than the maximum amount of liquid droplets ejected by the nozzles. The method for adjusting the ejection timing of the liquid ejection device according to claim 5,
The liquid is ink for printing a print image on the medium,
The nozzle can form large, medium, and small dots by adjusting the amount of the liquid droplet,
A method of adjusting the ejection timing of a liquid ejection apparatus, wherein the dot row for calculating the shift amount is composed of small dots. A method for adjusting the ejection timing of a liquid ejection device according to claim 1,
The liquid is a plurality of types of ink for printing a print image on the medium, and each nozzle row of the liquid ejection head is associated with one type of ink among a plurality of types. A method for adjusting the ejection timing of a liquid ejection device, wherein the adjustment value of the ejection timing is shared for each liquid ejection head. The method for adjusting a discharge timing of a liquid discharge device according to claim 7,
The plurality of types of inks include at least one set of dark inks and light inks having substantially equal hues and different densities,
A method for adjusting the ejection timing of a liquid ejection apparatus, wherein a dot array for calculating the shift amount is formed by a nozzle array associated with the light ink. The method for adjusting a discharge timing of a liquid discharge device according to claim 7,
The plurality of types of inks include at least a magenta ink,
A method for adjusting the ejection timing of a liquid ejection apparatus, wherein a dot array for calculating the shift amount is formed by a nozzle array associated with the magenta ink. The method for adjusting the ejection timing of a liquid ejection device according to claim 1,
The ejection of the liquid from the nozzle array is performed based on a reference ejection signal that drives the nozzle array,
Multiple types of reference discharge signals with different waveforms are selectable,
A method for adjusting the ejection timing of a liquid ejection apparatus, wherein an adjustment value of the ejection timing is set for each type of the reference ejection signal. The method for adjusting the ejection timing of a liquid ejection device according to claim 10,
The liquid is ink for printing a print image on the medium,
The liquid ejecting apparatus has a print mode setting means for setting a print mode of the print image when printing a print image on a medium,
A method for adjusting the ejection timing, wherein the nozzle array is driven based on a reference ejection signal of a type corresponding to the set print mode. A moving body that reciprocates by receiving moving forces in opposite directions at a pair of points of action on a line of action of the moving force, and a medium that is intermittently conveyed in a direction intersecting the moving direction of the moving body while being held by the moving body A plurality of liquid ejection heads having a plurality of nozzle rows for ejecting liquid toward to form a dot row, and adjusting means for adjusting the ejection timing of the liquid in the return path, wherein the medium is stopped while the medium is stopped. A method for adjusting a discharge timing of a liquid discharge device in which a moving body moves to discharge a liquid toward the medium,
The liquid is a plurality of types of ink for printing a print image on the medium, and each nozzle row of the liquid ejection head is associated with one type of ink among a plurality of types, and The plurality of types of inks include at least one set of dark inks and light inks having substantially equal hues and different densities,
Of the liquid ejection heads closest to the action line, from the nozzle row closest to the midpoint between the pair of action points, the liquid is ejected on the outward path to form a reference dot row on the medium, and the other liquid The liquid is ejected from the nozzle row of the ejection head in the return path to form a dot row, and the nozzle row of the other liquid ejection head is determined based on the amount of deviation between the dot row formation position and the reference dot row formation position. Adjust the discharge timing in the return path of
The nozzles of the nozzle row can form large, medium, and small dots by adjusting the amount of liquid droplets to be ejected, and the dot row for calculating the shift amount is composed of small dots.
While the adjustment value of the ejection timing is shared for each liquid ejection head, a dot row for calculating the shift amount is formed by a nozzle row associated with the light ink,
The ejection of the liquid from the nozzle array is performed based on a reference ejection signal for driving the nozzle array, and a plurality of types of reference ejection signals having different waveforms are selectably provided, and the ejection is performed for each type of the reference ejection signal. Set the timing adjustment value,
A print mode setting unit configured to set a print mode of the print image when printing the print image on a medium; and driving the nozzle array based on a reference ejection signal associated with the set print mode. A method for adjusting the ejection timing. A liquid ejection head having a plurality of nozzle rows for ejecting liquid toward a medium to form a dot row, a moving body that holds a plurality of the liquid ejection heads and reciprocates, and adjusts the ejection timing of the liquid in a return path Adjusting means, and a liquid ejecting apparatus comprising:
From one of the plurality of liquid ejection heads, the nozzle array of one of the liquid ejection heads ejects the liquid on the outward path to form a reference dot array on the medium, and the liquid is ejected from the nozzle array of the other liquid ejection head on the return path. To form a dot row, and based on the amount of deviation between the dot row forming position and the reference dot row forming position, the discharge timing in the return path of the nozzle row of the other liquid discharge head is adjusted. A liquid ejecting apparatus characterized in that:

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