Patent Application
20060012631
1. Field of the Invention
The present invention relates to an ink jet recording apparatus, a recording head and an ink jet recording method, and more particularly to an ink jet recording apparatus that employs a recording head for multi-phase drive and an ink jet recording method using this apparatus.
2. Description of the Related Art
There has been known an ink jet recording apparatus as a recording apparatus capable of printing on various kinds of recording mediums, such as standard paper and the like. The ink jet recording apparatus jets ink, serving as a coloring agent, directly on a recording medium from nozzles mounted on the surface of a recording head opposing to the recording medium, the ink landing, being absorbed or fixed on the medium, to thus form an image on the recording medium. The ink jet recording apparatus has several superior advantages, such as simple processing, quietness at the time of printing, and high print-quality of characters and images.
Some ink jet recording apparatuses have high density of nozzles on a recording head for obtaining high quality images. However, as the recording head has higher density of nozzles, the number of nozzles simultaneously driven becomes larger, which increases the current flowing at the leading edge of drive, to thereby increase the load in drive circuits for the recording head.
In order to reduce the load in drive circuits of the recording head, there has been known some ink jet recording apparatuses in which aligned nozzles on a recording head are driven at different timings from each other for printing (refer to JP-Tokukai-2002-137388 and JP-Tokukai-2003-326687). JP-Tokukai-2002-137388 discloses a recording head in which two columns of nozzles are arranged in parallel in a main scanning direction, and three nozzles arranged in a sub scanning direction on a column are driven with three phases, that is, phase 1, phase 2 and phase 3, respectively. A printer head disclosed in JP-Tokukai-2003-326687 also uses 3-phase drive in which nozzles are driven in order of A, B, and C.
In an ink jet recording apparatus having such a recording head for 3-phase drive, nozzles on the recording head are generally arranged with displacement in the main scanning direction for respective phases. This is what is called staggered arrangement, and jetting of ink from the nozzles has been controlled so as to record at periods as shown in
The nozzles 100a, 100b and 100c for respective phases are controlled to switch the phase at either timing of the strobe pulse width. Switching of phases corresponds to a frequency, and the strobe pulse width corresponds to a period of each phase. In a conventional recording method, the strobe pulse has switched the drive phases three times within one pixel time so that the nozzles 10a, 100b and 100c driven in phase 1, phase 2 and phase 3, respectively, can record the pixels in a straight line in the sub scanning direction.
According to such phase switching, when the nozzles 100a, 100b and 100c jet ink in this order from the upstream in the main scanning direction, the nozzle 100b in phase 2 jets ink later than the nozzle 100a in phase 1, but because of reverse displacement of nozzle 100b by a staggered pitch in the main scanning direction, its movement needs longer time by the staggered pitch, so that a recorded pixel by nozzle 100b has been resultantly recorded adjacent to the pixel jetted by nozzle 100a in the sub scanning direction. Similarly, although the nozzle 100c in phase 3 jets ink later than the nozzle 100b in phase 2 because of reverse displacement of nozzle 100c by a staggered pitch in the main scanning direction, its movement needs longer time by the staggered pitch, so that a recorded pixel by nozzle 100c has been recorded adjacent to the pixel jetted by nozzle 100b in the sub scanning direction. Thus, the conventional ink jet recording apparatus has recorded pixels in a straight line utilizing the staggered pitch between nozzles.
Such an ink jet recording apparatus has recorded pixels with such a method as shown in
Thus, when the staggered nozzles on a recording head are driven with a time difference at every phase, even if nozzles in phase 2 are driven later than those in phase 1, and nozzles in phase 3 later than those of phase 2, the time to be recorded is adjusted by each additional time for nozzles in phase 2 and phase 3 to move by the staggered pitch width, so that every phase of nozzles could record pixels on a straight line in the sub scanning direction.
In the present application, the upstream in the main scanning direction in a serial-type recording head having staggered nozzles means the front side thereof, and the downstream the rear side thereof. In
However, when pixels are recorded in a straight line using staggered nozzles on a recording head with multi-phase drive as in the conventional printer, each phase has to be switched within one pixel time, so that the carriage speed in the main scanning direction has been limited by nozzle-drive frequency of the recording head. In other words, the fewer number of drive phases make the less number of switching of strobe pulses, which causes strobe pulse width to the one pixel time (pixel clock) to be relatively wider, allowing relatively higher carriage speed. On the other hand, the larger number of drive phases need the larger number of switching of strobe pulses, which causes strobe pulse width to be relatively narrower, resulting in relatively lower carriage speed.
The carriage speed in the main scanning direction has been also limited by the staggered pitch between nozzles on a recording head. That is, one pixel has to be recorded while a nozzle on the head moves by the staggered pitch, so that the nozzle moves at the most by the staggered pitch in the time necessary for jetting ink for one pixel. Accordingly, the upper limit of carriage speed has been the value of a staggered pitch divided by the time necessary for jetting ink for one pixel.
However, the larger staggered pitch makes the size of recording head larger, and also causes a problem in that it needs a new manufacturing technology for producing recording heads having a larger staggered pitch.
As described above, an ink jet recording apparatus, having staggered nozzles on the head with multi-phase drive, is limited in achieving higher carriage speed, because the carriage speed limitation depends on the nozzle-drive frequency and the staggered pitch.
In conventional serial type ink jet recording apparatuses, a multi-pass recording method has been widely used. In this recording method, a column of nozzles are divided into a few blocks of nozzles, and image data to be recorded are allotted and distributed into these blocks of nozzles with intermittent feeding of paper for each block to complete this image recording. According to this multi-pass recording method, pixels on one same line, which are naturally recorded by one same nozzle, are divided into plural blocks, and each block is recorded by mutually different nozzles. Therefore, even if there exist misalignment of nozzles, or ink jet failure in some nozzles, these irregularities could be made averaged, and perceived as unnoticeable misalignment of recorded pixels. Thus, serial type ink jet recording apparatuses have been supposed to apply multi-pass scanning of a carriage.
To the contrary, line-type ink jet recording apparatuses, which employ recording heads for multi-phase drive, also have the same problems as in the serial-type ink jet recording apparatuses. That is, when the multi-phase drive recording head having staggered nozzles thereon records pixels in a straight line, each phase of the nozzles has to be switched within one pixel time, whereby the feeding speed of a print medium in a feeding direction is limited by nozzle-drive frequency of the recording head. The fewer number of drive phases allow the feeding speed to be higher, and the larger number of drive phases make the feeding speed relatively lower.
The feeding speed is also limited by a staggered pitch, and the upper limit of feeding speed is the value of a staggered pitch divided by the time necessary for jetting ink for one pixel. However, the larger staggered pitch makes the size of recording head larger.
As described above, if pixels were recorded in a line using the multi-phase drive recording head having staggered nozzles thereon, the recording speed has been inevitably limited in both line type and serial type ink jet recording apparatuses, because the feeding speed or carriage speed, i.e., recording speed depends on the nozzle-drive frequency and the staggered pitch.
In accordance with the first aspect of the present invention, the ink jet recording apparatus comprises:
According to the first aspect of the present invention, in the case that the recording head is driven with multi-phase drive, recording is performed with the recorded pixel locations shifted in the main scanning direction in the serial type and with the recorded pixel locations shifted in the feeding direction of the recording medium in the line type. Thus, as in a conventional recording apparatus, it is not necessary to switch each phase within one-pixel time, so that the strobe pulse width of each phase can be made wider relative to a pixel clock, allowing each phase of period for driving the nozzles to be longer. Even in the case of increasing the number of the drive phase, by increasing the shifted number of pixels and the number of scanning of the recording head, the strobe pulse width of each phase can be made wider relative to a pixel clock, allowing each phase of period for driving the nozzles to be longer.
Therefore, since it is not necessary to switch each phase within one-pixel time, carriage speed in the serial type or feeding speed of the recording medium in the line type, that is, the recording speed does not depend on a staggered pitch as in the conventional apparatus. Thus, the recording speed can be increased. For recording images with high quality, nozzles on the recording head need to be arranged in high density, however, even in this case, high quality images can be obtained with improved productivity, by applying multi-phase drive with the recorded pixel locations shifted at every drive-phase switching.
In accordance with the second aspect of the present invention, the ink jet recording apparatus comprises:
According to the second aspect of the present invention, it is not necessary to switch each phase within one-pixel time even when the recording head is driven with multi-phase drive, so that carriage speed does not depend on a staggered pitch.
Moreover, since the strobe pulse width can be made wider relative to a pixel clock, carriage speed can be increased when the strobe pulse is constant.
Therefore, even when the recording head has nozzles with high density, high quality images can be obtained by applying multi-phase drive and plural times of scanning of the head with the recorded pixel locations shifted at every drive-phase switching in the main scanning direction.
Preferably, the control unit controls the ink jetting such that, a recorded pixel location X which indicates where a recorded pixel is located from a reference position in the main scanning direction when an arbitrary pixel as the reference position is set to one is given by
X={(i−1)×f+P−1}×D+1,
Accordingly, by expressing the recorded pixel locations and the number of scanning of the recording head by the above expressions, the same effects as in the second aspect of the present invention can be achieved.
In accordance with the third aspect of the present invention, the ink jet recording apparatus comprises:
According to the third aspect of the present invention, the recording head comprises nozzle columns of multiples of the number of drive phases, which comprise the nozzles jetting the same kind of ink, nozzle positions of each of the nozzle columns corresponding to each other in the main scanning direction, and recording is performed such that the nozzles on different nozzle columns of the recording head jet ink onto different recorded pixel locations. Thus, all pixels, covered with the recording width of the head in the sub scanning direction, can be recorded by one time scanning of the recording head.
Moreover, the same effects as in the second aspect of the present invention can be achieved. At the same time, when one image is recorded by multiple scanning, there are sometimes found displacement in the main scanning direction due to reciprocating scanning of the recording head, slanting movement of the recording medium, misalignment of head assembling, or the like, which is possible to cause fluctuation in a vertical direction (sub scanning direction) in the image recorded on the medium, that is, distortion in right-and-left direction on inherently straight lines. However, it is possible, in the invention, to record all pixels covered with the recording width of the head in the sub scanning direction by one time scanning of the head in the main scanning direction. This recording by one time scanning can effectively suppress fluctuation in the image, thereby obtaining high quality images with improved productivity.
Preferably, the control unit controls to record all pixels covered with a recording width by one time scanning of the recording head in the main scanning direction.
Accordingly, it is possible that the recording head comprises nozzle columns of multiples of the number of drive phases, which comprise the nozzles jetting the same kind of ink, nozzle positions of each of the nozzle columns correspond to each other in the main scanning direction, recording is performed such that the nozzles on different nozzle columns of the recording head jet ink onto different recorded pixel locations, allowing all pixels, covered with the recording width of the head in the sub scanning direction, recorded by one time scanning of the recording head. Therefore, the fluctuation in the image can effectively suppress, so that the same effects as in the third aspect of the present invention can be achieved more efficiently.
Preferably, a distance between the nozzle columns of the recording head is set to (a pixel pitch in the main scanning direction) times (n times the number of drive phases plus one), where n is a natural number.
Accordingly, in the recording head, for example, when the number of drive phases is three, a distance between the nozzle columns is four times, seven times of the pixel pitch or the like, and when the number of drive phases is four, a distance between the nozzle columns is five times, nine times of the pixel pitch or the like. Thus, even when the same STB signal is applied to each nozzle column, ink jetted from the nozzles on different nozzle columns does not placed on the same recorded pixel locations. Moreover, it is possible to record the pixel locations next to the pixel locations which was recorded by the nozzles on the adjacent nozzle column, so that the effects in the third aspect of the present invention can be certainly achieved.
In accordance with the fourth aspect of the present invention, the ink jet recording apparatus comprises:
According to the fourth aspect of the present invention, even in the case of the ink jet recording apparatus comprising line type heads, it is not necessary to switch each phase within one-pixel time when the recording heads are driven with multi-phase drive, so that feeding speed of the recording medium does not depend on a staggered pitch.
Moreover, since the strobe pulse width can be made wider relative to a pixel clock, feeding speed can be increased when the strobe pulse is constant.
Therefore, even when each recording head has nozzles with high density, high quality images can be obtained by applying multi-phase drive and recording with the recorded pixel locations shifted at every drive-phase switching in the feeding direction.
In accordance with the fifth aspect of the present invention, the ink jet recording apparatus comprises:
According to the fifth aspect of the present invention, although ink jet recording is performed in the same manner as in the fourth aspect of the present invention, the recording head comprises nozzle rows of multiples of the number of drive phases, which comprise the nozzles jetting the same kind of ink, nozzle positions of each of the nozzle rows corresponding to each other in the feeding direction, and recording is performed such that the nozzles on different nozzle rows of the recording head jet ink onto different recorded pixel locations. Thus, even in the case of the line type ink jet recording apparatus, all pixels are recorded on the medium fed under the facing surface of the recording head, enabling to certainly achieve the effects in the fourth aspect of the present invention.
Preferably, a distance between the nozzle rows of the recording head is set to (a pixel pitch in the feeding direction) times (n times the number of drive phases plus one), where n is a natural number.
Accordingly, in the recording head, for example, when the number of drive phases is three, a distance between the nozzle rows is four times, seven times of the pixel pitch or the like, and when the number of drive phases is four, a distance between the nozzle rows is five times, nine times of the pixel pitch or the like. Thus, even when the same STB signal is applied to each nozzle row, ink jetted from the nozzles on different nozzle rows does not placed on the same recorded pixel locations. Moreover, it is possible to record the pixel locations next to the pixel locations which was recorded by the nozzles on the adjacent nozzle row, so that the effects in the fifth aspect of the present invention can be certainly achieved.
Preferably, the nozzles of the recording head are aligned.
Accordingly, carriage speed or feeding speed of the recording medium does not depend on a staggered pitch, but depend on a pixel pitch. That is, the staggered pitch is usually about ten micron, and given by (pixel pitch in the main scanning direction or the feeding direction/the number of drive phases). Accordingly, if the pixel pitch in the main scanning direction or the feeding direction is one inch (25400 μm)/720 dpi, and the number of phases is three, then the staggered pitch is 11.759 μm. Also, a pixel pitch is one inch (25400 μm)/720 dpi=35.278 μm. Thus, the pixel pitch is three times of the staggered pitch, and therefore the upper limit of carriage speed or feeding speed of the recording medium is permitted three times higher than conventional one.
Preferably, the nozzles of the recording head are staggered so that the nozzles are displaced in the main scanning direction for every drive phase.
Accordingly, the same effects as in each of the above aspect of the present invention can be achieved. Moreover, since the recording head in which the nozzles are staggered is used, the recording mode in the conventional ink jet recording apparatus can be easily used only by a mode switching.
In the case of the nozzles in the 3-phase drive, an actual pitch is given by a difference between the above described pixel pitch and the staggered pitch, that is, 35.278-11.759=23.519 μm. This is two times the staggered pitch, and therefore the recording method according to the invention can achieve two times higher upper limit of carriage speed than conventional one.
Similarly, if the drive phase is four or five, the actual pitch becomes three or four times the staggered pitch, respectively, that is, the upper limit of carriage speed can be attained by (the number of drive phases minus one) times the conventional one.
Preferably, the control unit drives the nozzles of the recording head from a nozzle arranged at downstream in the main scanning direction sequentially with the drive phase switching.
Accordingly, abrupt switching for each phase is not needed to be in time for recording. Therefore each phase of period can take longer time, resulting in higher carriage speed of the recording medium.
Preferably, the nozzles of each of the recording heads are staggered so that the nozzles are displaced in the feeding direction for every drive phase.
Accordingly, the same effects as in the fourth and fifth aspects of the present invention can be achieved. Moreover, since the recording head in which the nozzles are staggered is used, the recording mode in the conventional ink jet recording apparatus can be easily used only by a mode switching.
In the case of the nozzles in the 3-phase drive, an actual pitch is given by a difference between the above described pixel pitch and the staggered pitch, that is, 35.278-11.759=23.519 μm. This is two times the staggered pitch, and therefore the recording method according to the invention can achieve two times higher upper limit of feeding speed than conventional one.
Similarly, if the drive phase is four or five, the actual pitch becomes three or four times the staggered pitch, respectively, that is, the upper limit of feeding speed can be attained by (the number of drive phases minus one) times the conventional one.
Preferably, the control unit drives the nozzles of each of the recording heads from a nozzle arranged at downstream in the feeding direction sequentially with the drive phase switching.
Accordingly, abrupt switching for each phase is not needed to be in time for recording. Therefore each phase of period can take longer time, resulting in higher feeding speed of the recording medium.
Preferably, the control unit switches the drive phases such that, when a period to switch each drive phase is given by T, a clock period to record a pixel by T′, and the number of drive phases by f, then
T=T′×{(D−1)+(f−1)/f}.
Accordingly, it has found out that the drive phase switching period can be expressed by the above expression.
Preferably, the control unit drives the recording head with three-phase drive.
Accordingly, by using the recording head of the 3-phase drive, the same effects as in each of the above aspect of the present invention can be achieved.
In accordance with the sixth aspect of the present invention, the recording head drivable with multi-phase drive, comprises: nozzle columns of multiples of the number of drive phases, which comprise the nozzles jetting the same kind of ink,
In accordance with the seventh aspect of the present invention, the recording head drivable with multi-phase drive, comprises: nozzle rows of multiples of the number of drive phases, which comprise the nozzles jetting the same kind of ink,
Preferably, the nozzles are aligned on each of the nozzle columns or the nozzle rows.
Preferably, the nozzles of each of the nozzle columns are staggered so that the nozzles are displaced in the main scanning direction for every drive phase.
Preferably, the nozzles of each of the nozzle rows are staggered so that the nozzles are displaced in the feeding direction for every drive phase.
Preferably, a distance between the nozzle columns is set to (a pixel pitch in the main scanning direction) times (n times the number of drive phases plus one), where n is a natural number.
Preferably, a distance between the nozzle rows is set to (a pixel pitch in the feeding direction) times (n times the number of drive phases plus one), where n is a natural number.
In accordance with the eighth aspect of the present invention, the ink jet recording method comprises:
In accordance with the ninth aspect of the present invention, the ink jet recording method comprises:
Preferably, the determining recorded pixel locations is such that, a recorded pixel location X which indicates where a recorded pixel is located from a reference position in the main scanning direction when an arbitrary pixel as the reference position is set to one is given by
X={(i−1)×f+P−1}×D+1,
In accordance with the tenth aspect of the present invention, An ink jet recording method comprises:
Preferably, the jetting ink is performed so that all pixels covered with a recording width by one time scanning of the recording head in the main scanning direction is recorded.
Preferably, the switching drive phases is performed in the recording head so that a distance between the nozzle columns of the recording head is set to (a pixel pitch in the main scanning direction) times (n times the number of drive phases plus one), where n is a natural number.
In accordance with the eleventh aspect of the present invention, the ink jet recording method comprises:
In accordance with the twelfth aspect of the present invention, the ink jet recording method comprises:
Preferably, the switching drive phases is performed in the recording head so that a distance between the nozzle rows of the recording head is set to (a pixel pitch in the feeding direction) times (n times the number of drive phases plus one), where n is a natural number.
Preferably, the jetting ink is performed so that the ink is jetted from aligned nozzles arranged on the recording head.
Preferably, the jetting ink is performed so that the ink is jetted from staggered nozzles arranged on the recording head with the nozzles displaced in the main scanning direction for every drive phase.
Preferably, the switching drive phases is performed so that drive phases of the nozzles on the recording head are sequentially switched from a nozzle arranged at downstream side in the main scanning direction.
Preferably, the jetting ink is performed so that the ink is jetted from staggered nozzles arranged on the recording head with the nozzles displaced in the feeding direction for every drive phase.
Preferably, the switching drive phases is performed so that drive phases of the nozzles on the recording head are sequentially switched from a nozzle arranged at downstream side in the feeding direction.
Preferably, the switching drive phases is performed to switch the drive phases such that, when a period to switch each drive phase is given by T, a clock period to record a pixel by T′, and the number of drive phases by f, then
T=T′×{(D−1)+(f−1)/f}.
Preferably, the switching drive phases is performed by driving the recording head with three-phase drive.
The present invention will become more fully understood from the detailed description and accompanying drawings given below, but these are not intended to limit the present invention, and wherein;
A first embodiment of the invention will now be explained with reference to FIGS. 1 to 7.
The ink jet recording apparatus 1 is a serial type ink jet recording apparatus in which recording heads 6 scan in a direction (main scanning direction) perpendicular to a feeding direction of a recording medium P with the jetting of ink droplets during head movement to form images. This ink jet recording apparatus 1 has a platen 2 supporting the medium P from its underside as shown in
Mounted on the carriage 5 are a plurality of serial type recording heads 6 for jetting respective colored inks (the colors of yellow (Y), magenta (M), cyan (C), and black (K)) so that the ink jetting surface of each head 6 faces the medium P supported on the platen 2.
The ink jet recording apparatus of the invention preferably uses photo curable ink, including radical polymerized type ink, cationic polymerized type ink or hybrid type ink, which is cured by ultraviolet irradiation. It is particularly preferable in the embodiment to use energy accumulating type cationic polymerized type ink, which is little affected by oxygen in the polymerization reaction and curable by longer irradiation time even if low illuminance of ultraviolet rays are used.
The carriage 5 also has irradiating devices 7 at both sides of the recording heads 6 for curing the ink deposited on the recording medium P by irradiation of light. As a light source provided within the irradiating device 7, there may be used a fluorescent lamp, mercury lamp, metal halide lamp or the like for irradiating ultraviolet rays, electron beam, x-rays, visible light, infrared rays or the like, and in the embodiment ultraviolet rays are employed as the light source.
As shown in
The image processing unit 9 receives encoded input image data sent from a host system 12 through an interface (I/F) 13, and sends the image data converted to a data format to be processed by the printer 1 to the head drive unit 10. The host system 12 is connected to external apparatuses (not shown) through a network, and the host system 12 or the external apparatus sends to the ink jet recording apparatus 1 image data to be recorded and also executes input process to control overall operation of the printer 1. The host system 12 or the external apparatus can also execute input process for setting a drive frequency to drive the recording heads 6.
Each recording head 6 is what is called a serial type head, and has a plurality of nozzles on the ink-jetting surface thereof, being aligned in the sub scanning direction to jet ink onto the recording medium (see
The head drive unit 10 is controlled to jet inks from the nozzles of the recording heads 6 by applying to piezoelectric elements of the recording heads 6 pulse voltage to record the data relating to the recorded image obtained from the image processing unit 9 based on the signals sent from the control unit 8.
The main scanning mechanism 11 has a drive motor (not shown) for driving the carriage 5, and activation of the drive motor by the control unit 8 causes the carriage 5 to scan along the guide rails in the scanning direction.
The feeding devices 3 comprises feed motors and feed rollers (both not shown) for being periodically and rotatably driven to feed the recording medium P by a unit of predetermined feed amount, and actuation of the feed motors by the control unit 8 allows the medium P to be intermittently fed during image recording.
The irradiating devices 7 cure the ink deposited on the recording medium P by irradiation of ultraviolet rays given from the light sources.
The control unit 8 comprises CPU, ROM and RAM (none of them shown), and processing programs stored in the ROM are developed and stored into the RAM to be executed by the CPU. The control unit 8 controls the main scanning mechanism 11 for reciprocally moving the carriage in the main scanning direction during image recording, and also controls the feeding devices 3 for feeding the medium P in the sub scanning direction. The control unit 8 further sends to the head drive unit 10 command signals, such as the driving frequency set by the host system 12 or the external apparatus, and causes the head drive unit 10 to apply pulse voltages to the respective piezoelectric elements of the recording heads 6 based on given image recording information for jetting ink from the nozzles on the recording heads 6 by a predetermined period.
In the ink jet recording apparatus 1 of the embodiment, the recording heads 6 are controlled with a multi-phase drive by the control unit 8. In a case of 3-phase drive, for example, assuming that three nozzles constitute one group among the nozzles aligned in the sub scanning direction on each head 6, a first nozzle and every third nozzle (spaced by two nozzles between them) aligned in the sub scanning direction, simultaneously jet ink by phase 1 drive, similarly, a second nozzle adjacent to the first nozzle in the sub scanning direction and every third nozzle jet ink by phase 2 drive, and a third nozzle adjacent to the second nozzle in the sub scanning direction and every third nozzle jet ink by phase 3 drive.
The control unit 8 in the embodiment controls ink jetting from the nozzles such that, every time a drive phase is switched, recording starts with recorded pixel locations shifted in the main scanning direction by integer times the pixel width of recording resolution.
In
STB 1 indicates a strobe pulse for switching the phase at the nozzle 21a, STB 2 at the nozzle 21b, and STB 3 at the nozzle 21c, and respective phases of the nozzles 21a, 21b and 21c are changed at either timing in the strobe pulse width. This phase switching corresponds to a frequency, and the strobe pulse width corresponds to a period of each phase.
By switching phases of the nozzles 21a, 21b and 21c in this order from the upside of the sub scanning direction for recording a contiguous pixel in the main scanning direction for each phase, time for one pixel can be fully used as the strobe pulse width for each phase. In other words, by controlling ink jetting from nozzles on the head 6 so as to record contiguous pixels in the main scanning direction, each phase period can be made wider relative to a pixel clock.
Further, the control unit 8 controls ink jetting from the nozzles so as to perform three times of interleaving. Here, the interleaving means that a plurality of contiguous pixels in a scanning direction are recorded with plural times of scanning. For example, three times of interleaving means that a plurality of contiguous pixels in the scanning direction are formed with three times of scanning by jetting ink every three pixels (spaced by two pixels) in the scanning direction.
Thus, the nozzles 21a, 21b and 21c in the 3-phase drive are controlled to start recording while moving by one pixel in the main scanning direction, and to perform three times of interleaving. Resultantly, the first scanning records pixels on a slant as shown in
Regarding recorded pixels thus recorded with ink jetting from the nozzles under the control of the control unit 8, a recorded pixel location X, which indicates where a specific recorded pixel is located from a reference position in the main scanning direction when an arbitrary pixel as the reference position is set to 1, and the number of carriage scanning S necessary for completing record, are given by following expressions, respectively:
X={(i−1)×f+P−1}×D+1 (1)
and
S=f×D×Rp/Rn (2)
or
S=f×D×Pn/Pp (3)
where i is the number of a pixel when counted from the reference position out of pixels recorded by one same nozzle in the main scanning direction,
Referring to
As shown in
With regard to the number of scanning S, applying the expression (2) with substitution by f=3, D=1, Rp=360 dpi and Rn=360 dpi, S=3 is obtained, therefore it is understood that all pixels can be recorded by three times of scanning. In
In this embodiment, the recorded pixel location X from the reference position can be also obtained by using the expression (1). Assuming that a recorded pixel at left and uppermost end is defined as the reference position, the pixel location X, for example, recorded at a second position (i=2) out of pixels recorded in a first scanning, is obtained by substituting in the expression (1) by i=2, f=3, P=1 and D=1, resulting in X=4. That is, the pixel recorded at the second position in the first scanning is a 4th pixel counted from the pixel of reference position in the main scanning direction.
As to the number of scanning S, since the recording resolution in the sub scanning direction in
Further, the control unit 8 controls ink jetting from the nozzles so as to perform six times of interleaving. Here, six times of interleaving means that a plurality of contiguous pixels in the scanning direction are formed with six times of scanning by jetting ink every six pixels (spaced by five pixels) in the scanning direction.
In
Further, the control unit 8 controls ink jetting from the nozzles so as to perform four times of interleaving. Here, four times of interleaving means that a plurality of contiguous pixels in the scanning direction are formed with four times of scanning by jetting ink every four pixels (spaced by three pixels) in the scanning direction.
In
A description will now be given of an ink jet recording method according to the invention using the ink jet recording apparatus 1 described above. The description below assumes for convenience that entire pixels are recorded on the recording medium P.
Initially, when the control unit 8 receives predetermined image recording information from the host system 12 or the external apparatus, the control unit 8 moves the recording heads 6 up to a record starting position on the recording medium P.
Upon starting record, in the first scanning of the head 6, a nozzle 24a driven in phase 1 records pixels on a first row in the main scanning direction every three pixels (spaced by two pixels), a nozzle 24b driven in phase 2 on a second row, and a nozzle 24c driven in phase 3 on a third row. That is, recording starts from the position shifted by one pixel in the main scanning direction for each phase. Repetition of such process causes respective phase of nozzles to record pixels on the slant. Then, the feeding devices 3 feed the recording medium P in the sub scanning direction by 85-pixel length. Thereafter, by a second scanning, pixels are recorded on respective phase of rows, each pixel being contiguous to the recorded pixel of the first scanning in the main scanning direction. Next, the feeding devices 3 again feed the recording medium P in the sub scanning direction by 85-pixel length, and the heads 6 records residual pixels in a third scanning. With these three times of scanning, entire pixels are recorded.
During the image recording on the recording medium, the irradiating devices 7 irradiate ultraviolet rays on the ink deposited on the medium P to cure the ink.
Meanwhile, if the medium P is fed by 85-pixel length after head scanning, while the number of pixels in the sub scanning direction is 256, one nozzle for one pixel line remains unused in case of three times of scanning. Therefore, the nozzle at the upper end or lower end in the sub scanning direction is inhibited from jetting ink in one scanning of the three times of scanning.
Referring to
In the embodiment, if the medium P is fed by 85-pixel length after head scanning, while the number of pixels in the sub scanning direction is 512, one nozzle for one pixel row remains unused in case of three times of scanning. Therefore, the nozzle at the upper end and/or lower end in the sub scanning direction is inhibited from jetting ink in one or plural times of scanning of the six times of scanning.
According to the ink jet recording apparatus 1 and the ink jet recording method in the embodiment described above, nozzles, aligned in the sub scanning direction on the recording head 6 to be driven with multi-phase drive, record pixels by jetting of ink with the recorded pixel locations shifted by integer times recording-resolution in the main scanning direction at every drive-phase switching. With this structure, it is not necessary to switch each phase within one-pixel time, and therefore carriage speed does not depend on a staggered pitch, allowing each phase of period for driving the recording head 6 to be longer. Further, even if nozzles on the head 6 are arranged in high density, high quality images can be obtained with improved productivity, by applying multi-phase drive and plural times of scanning of the head with the recorded pixel locations shifted in the main scanning direction at every drive-phase switching.
In other words, according to the ink jet recording apparatus 1 and the ink jet recording method in the embodiment, since the one-pixel time can be fully used for switching a phase, carriage speed does not depend on a staggered pitch, which differs from a conventional method, but on a pixel pitch. The staggered pitch is usually about ten micron, and given by (pixel pitch in a main scanning direction/the number of drive phases). Accordingly, if the pixel pitch in the scanning direction is one inch (25400 μm)/720 dpi, and the number of phases is three, then the staggered pitch is 11.759 μm. In a conventional ink jet recording apparatus, carriage speed has depended on this staggered pitch. To the contrary, a pixel pitch is one inch (25400 μm)/720 dpi=35.278 μm. Thus, the pixel pitch is three times longer than the staggered pitch, and therefore the upper limit of carriage speed is permitted three times higher than conventional one, if the ink jet recording apparatus according to the embodiment is used with its recording method.
In the ink jet recording apparatus 1 and the ink jet recording method according to the embodiment, recorded pixel location X is represented by the expression (1), and the number of carriage scanning S by the expressions (2) or (3).
A second embodiment of the invention will now be explained with reference to FIGS. 8 to 12.
An ink jet recording apparatus 1 in the embodiment is a serial type ink jet recording apparatus, and similar to the first embodiment comprises a platen 2, feeding devices 3, guide rails 4, and a carriage 5 having recording heads 6 and irradiating devices 7 mounted thereon.
However, each recording head 6 of the embodiment has staggered nozzles arranged thereon. A staggered pitch is the value of a recorded pixel pitch divided by the number of drive phases. In the embodiment, the recorded pixel pitch is one inch (25400 μm)/720 dpi, and the number of drive phases is three, therefore the staggered pitch is 11.759 μm.
As shown in
Further, as in the first embodiment, the recording heads 6 of the embodiment is controlled with multi-phase drive, and the control unit 8 controls ink jetting from the nozzles such that, every time drive phases are switched, recording starts with a recorded pixel location shifted in the main scanning direction by integer times the pixel width of recording resolution.
Further, the nozzles 26a, 26b and 26c are controlled to start recording with 3-phase drive while shifted by one time pixel-width (by one pixel) in the main scanning direction at every phase switching, and to perform three times of interleaving. As a result, the first scanning records pixels on a slant as shown in
Since the embodiment is the same as the first embodiment except that the nozzles on the head 6 are staggered, recorded pixel location X and the number of carriage scanning S are also calculated by the expressions (1) to (3).
In
In
Accordingly, if the strobe pulse width, i.e., switching period for each phase is given by T, clock period for recorded pixels (the time for the head to move by a recorded pixel pitch) by T′, and the number of drive phases by f, then
T=T′×{(D−1)+(f−1)/f} (4)
In
According to such a recording method, because three times of switching is performed within 2-pixel time, a strobe pulse width can be made wider relative to the pixel clock, compared with a conventional recording method in which three times of switching is performed within 1-pixel time as shown in
In
In this example, the expression (4) is also applicable for calculating the phase switching period for each phase T. For
According to this recording method, because three times of switching is performed within 5-pixel time, a strobe pulse width can be made relatively wider with respect to the pixel clock, compared with a conventional recording method in which three times of switching is performed within 1-pixel time as shown in
In
In this example, the expression (4) is also applicable for calculating the phase switching period T. For
According to this recording method, because four times of switching is performed within 3-pixel time, a strobe pulse width can be made relatively wider with respect to the pixel clock, compared with a conventional recording method in which three times of switching is performed within 1-pixel time as shown in
In the case that nozzles are staggered on the recording head 6, if ink jetting would be performed sequentially from the upstream side nozzle in the main scanning direction as shown in
A description will now be given of an ink jet recording method according to the invention in the points different from the first embodiment, using the ink jet recording apparatus 1 described above. The description below assumes for convenience that entire pixels are recorded on the recording medium P.
Referring to
In the embodiment, three times of scanning also make one nozzle for one pixel line left unused. Therefore, the nozzle at the upper end or lower end in the sub scanning direction is inhibited from jetting ink in one scanning of the three times of scanning.
According to the ink jet recording apparatus 1 and the ink jet recording method in the embodiment described above, carriage speed does not depend on a staggered pitch, as in the first embodiment, allowing each phase of period for driving the recording head 6 to be longer.
A recorded pixel location X is also represented by the expression (1), and the number of carriage scanning S by the expressions (2) or (3).
Further, the phase switching period for each phase T is given by the expression (4), because the head 6 has staggered nozzles mounted thereon in the embodiment.
Additionally, since the staggered nozzles in the embodiment are driven from the nozzle at the downstream side in the main scanning direction, abrupt switching for each phase is not needed to be in time for recording. Therefore each phase of period can take longer time, resulting in higher carriage speed.
An actual pitch in the case of staggered arrangement is given by a difference between the pixel pitch and the staggered pitch, that is, 35.278-11.759=23.519 μm. This is two times the staggered pitch, and therefore the recording method according to the invention can achieve two times higher upper limit of carriage speed than conventional one. Similarly, if the drive phase is four or five, the actual pitch becomes three or four times the staggered pitch, respectively, that is, the upper limit of carriage speed can be attained by (the number of drive phases minus one) times the conventional one.
In the embodiment described above, recording is performed by one way carriage scanning in the main scanning direction, but when the carriage scans to a reverse direction in bidirectional recording, the same effect as those described above can be achieved by switching the drive phases in a reverse order.
A third embodiment of the invention will now be explained with reference to FIGS. 13 to 20.
An ink jet recording apparatus 1 in the embodiment is a serial type ink jet recording apparatus, and similar to the first embodiment in that the printer 1 comprises a platen 2, feeding devices 3, guide rails 4, and a carriage 5 having recording heads 6 and irradiating devices 7 mounted thereon.
However, in the embodiment, each recording head 6 comprises nozzle columns of multiples of the number of drive phases, which comprises nozzles jetting the same kind of ink. The nozzles are arranged in a straight line for each column. A description will be given below of a case in which three columns of the aligned nozzles are used with 3-phase drive.
In order to provide three nozzle columns, each nozzle jetting the same kind of ink, as shown in
As shown in
Each nozzle of the nozzle columns 14a, 14b and 14c is positioned on a straight line extending in the main scanning direction. A distance L between the nozzle columns in the embodiment is set to (a pixel pitch in the main scanning direction) multiplied by (n multiplied by the number of drive phases plus 1), where n is a natural number.
In the embodiment, the pixel pitch in the main scanning direction is one inch (25400 μm)/720 dpi, and the number of drive phases is three, and n=1, therefore (n multiplied by the number of drive phases plus 1)=4, and resultantly the distance L=141.11 μm. If n=3, then (n multiplied by the number of drive phases plus 1)=10, and the distance L=352.78 μm.
As shown in
Further, as in the first embodiment, the recording head 6 of the embodiment is controlled with multi-phase drive, and the control unit 8 controls ink jetting from the nozzles such that, every time drive phases are switched, recording starts with a recorded pixel location shifted in the main scanning direction by integer times the pixel width of recording resolution.
However, in the embodiment, ink droplets jetted from nozzles on different nozzle columns do not strike the same recorded pixel location on the recording medium, but strike different recording positions on the recording medium. Especially, nozzles on different nozzle columns and on a same position line in the main scanning direction record on different recorded pixel locations in the main scanning direction from each other in respective drive phases.
The ink jetting from the nozzles on one nozzle column is controlled by the control unit 8 in the same manner as shown in
In this embodiment, as the control of the ink jetting from the nozzles by the control unit 8 shown in
That is, in this embodiment, STB 1 shown in
A description will now be given of an ink jet recording method according to the invention, using the ink jet recording apparatus 1 of the embodiment. The description below assumes for convenience that entire pixels are recorded on the recording medium P as in the first embodiment.
Initially, when the control unit 8 receives predetermined image recording information from the host system 12 or the external apparatus, the control unit 8 determines a recorded pixel location at each drive phase switching so that the recorded pixel location can be shifted by integer times the pixel width of recording resolution in the main scanning direction (every one time the pixel width in the embodiment as described above), and moves the recording head 6 up to a record starting position on the recording medium P.
Subsequently, the control unit 8 makes the recording head 6 scan in the main scanning direction with the drive phase of the recording head 6 switched as shown in
Regarding to the nozzle 31a of the nozzle column 14a, the nozzle 32a of the nozzle column 14b, and the nozzle 33a of the nozzle column 14c, as the distance L between the nozzle columns, in the case that n=1, that is, the distance between the nozzle columns has three times the pixel pitch in the main scanning direction, when the drive phase is switched by the strobe pulse STB 1, the three nozzles jet ink on three recorded pixel locations as indicated by arrows in
Subsequent phase switching causes the three nozzles to record additional three pixel locations as indicated by arrows in
With such recording, all recorded pixel locations succeeding to a pixel location A shown in
According to the ink jet recording apparatus 1 and its recording method in the embodiment, all pixels, covered with the recording width of the head 6 in the sub scanning direction, can be recorded by one time scanning of the head 6 in the main scanning direction, which differs from the first and second embodiments. This will be understood from
In the embodiment, instead of the recording method that all pixels are recorded by one time scanning of the head 6 as shown in
As described above, according to the printer 1 and its recording method of the embodiment, control method by the control unit 8 is the same as in the first embodiment, and therefore the same effects as in the first embodiment can be achieved. That is, carriage speed does not depend on a staggered pitch, and therefore each phase of period for driving the recording head 6 can be made longer. Further, high quality images can be obtained with improved productivity, by applying multi-phase drive and the recording with recorded pixel locations shifted in the main scanning direction at every drive phase switching, even if nozzles on the head 6 are arranged in high density.
When one image is recorded by multiple scanning as in the first embodiment, there are sometimes found displacement in the main scanning direction due to reciprocating scanning of the head 6, slanting movement of the medium P, misalignment of head assembling, or the like, which is possible to cause fluctuation in a vertical direction (sub scanning direction) in the image recorded on the medium P, that is, distortion in right-and-left direction on inherently straight lines. To the contrary, it is possible, in the embodiment, to record all pixels covered with the recording width of the head 6 in the sub scanning direction by one time scanning of the head 6 in the main scanning direction. This recording by one time scanning can effectively suppress fluctuation in the image, thereby obtaining high quality images with improved productivity.
Referring to
The third embodiment may be arranged by using staggered nozzles as in the second embodiment. As shown in
Each nozzle on the nozzle columns 16a, 16b and 16c, and 17a, 17b and 17c is positioned on a straight line extending in the main scanning direction. Each distance L between the nozzle columns is set to (a pixel pitch in the main scanning direction) times (n times the number of drive phases plus 1), where n is a natural number.
When the head 6 or the heads 6d, 6e and 6f are, respectively, controlled as shown in
In the embodiments shown in
A fourth embodiment of the invention will now be explained with reference to
The “upstream” and “downstream” in the line-type ink jet recording apparatus are defined with a feeding direction of a recording medium as a standard. That is, the upstream in the feeding direction is the upper side in
As shown in
The recording heads 43, 44, 45 and 46 are so-called line-type heads, and jet inks of yellow, magenta, cyan and black, respectively, in the embodiment. Since the number of drive phases in the embodiment is three, each color of head, for example, the head 43 for yellow ink, as shown in
Each line head forming the recording head has one row of nozzles, and each nozzle on the three line heads is positioned on a line in the feeding direction. The distance L between the nozzle rows is set to (a pixel pitch in the feeding direction) times (n times the number of drive phases plus 1), where n is a natural number.
In the embodiment, the pixel pitch in the feeding direction is one inch (25400 μm)/720 dpi, for example, the number of drive phases is three and n=1, then (n times the number of drive phases plus 1)=4, and the distance L=141.11 μm. In this embodiment, if n=100 and (n times the number of drive phases plus 1)=301, then the distance L=10619 μm=10.619 mm.
At the downstream side of the recording heads 43, 44, 45 and 46 in the feeding direction of the medium P, provided are irradiating devices 47, 48, 49 and 50, each device extending on substantially entire width of the medium P for curing inks deposited on the medium P by irradiation of light. As a light source provided inside the irradiating device 47 or the like, there may be used a fluorescent lamp, mercury lamp, metal halide lamp or the like for irradiating ultraviolet rays, electron beam, x-rays, visible light, infrared rays or the like, and in the embodiment ultraviolet rays are employed as the light source.
The ink jet recording apparatus 40 of the embodiment, as in the first to third embodiments, preferably uses photo curable ink, including radical polymerized type ink, cationic polymerized type ink and hybrid type ink, which is cured by ultraviolet irradiation. It is particularly preferable in the embodiment to use energy accumulating type cationic polymerized type ink, which is little affected by oxygen in the polymerization reaction and curable by longer irradiation time even if low illuminance of ultraviolet rays are used.
As shown in
The image processing unit 52 functions as in the first to third embodiments, receiving encoded input image data sent from a host system 54 through an interface (I/F) 55, and sends to the head drive unit 53 the image data converted to a data format to be processed by the ink jet recording apparatus 40.
The head drive unit 53 is controlled to jet inks from the nozzles of the recording heads 43 to 46 by applying to piezoelectric elements of the recording heads 43 to 46 pulse voltage to record the data relating to the recorded image obtained from the image processing unit 52 based on the signals sent from the control unit 51.
The feeding devices 42 comprise feed motors and feed rollers (both not shown) for being rotatably driven to feed the recording medium P by a unit of predetermined feed amount, and actuation of the feed motors by the control unit 51 allows the medium P to be fed during image recording.
The control unit 51 comprises CPU, ROM and RAM (none of them shown), and processing programs stored in the ROM are developed and stored into the RAM to be executed by the CPU. The control unit 51 controls the feeding devices 42 for feeding the medium P in the feeding direction during image recording. The control unit 51 further sends to the head drive unit 53 command signals, such as the driving frequency set by the host system 54 or the external apparatus, and causes the head drive unit 53 to apply pulse voltages to the respective piezoelectric elements of the recording heads 43-46 based on given image recording information for jetting ink from the nozzles on the recording heads 43-46 by a predetermined period.
The ink jetting from nozzles on one nozzle row is controlled by the control unit 51 in the same manner as in the third embodiment described above (see
In this embodiment, as the control of the ink jetting from nozzles shown in
That is, in the embodiment, STB 1 shown in
A description will now be given of an ink jet recording method according to the invention, using the ink jet recording apparatus 40 in the embodiment.
Initially, when the control unit 51 receives predetermined image recording information from the host system 54 or the external apparatus, the control unit 51 determines recorded pixel locations at each phase switching of the heads 43-46 so that the recorded pixel locations for the nozzles can be shifted by integer times the pixel width of recording resolution in the feeding direction (every one time the pixel width, or one pixel width in the embodiment), and moves the recording medium P up to a record starting position.
Subsequently, the control unit 51 makes the recording medium P carried in the feeding direction with the drive phase switched by a pixel width as shown in
At this time, inks are jetted on respective recorded pixel locations as shown in
According to the ink jet recording apparatus 40 in the embodiment and its recording method, recorded result shown in
Thus, the fourth embodiment achieves the same actions and effects as in the third embodiment.
However, in the case that line-type recording heads are used as in the embodiment, the heads do not scan over the medium P, and therefore the ink jet recording apparatus has to be so constructed that all pixels are recorded when the medium P passes under the recording heads 43-46. That is, as described in the third embodiment, such a recording method can not be employed that a first scanning records half of the entire pixels and next scanning records the rest of the pixels.
As alternatives in the embodiment, the ink jet recording apparatus may have appropriate structures. For example, one head may have three rows of aligned nozzles formed thereon, instead of one set of three line heads, the head may have staggered nozzles, or the head may have double the nozzle rows, six rows, with 3-phase drive.
These alternative structures can also attain the same effects as in the present embodiment and the third embodiment. That is, if one set of three line heads shown in
Let it be assumed that each nozzle line formed on three line heads 43a, 43b and 43c shown in
Nozzles 37a through 39c on the nozzle rows 19a, 19b and 19c are driven with 3-phase drive, and with the phase sequentially switched from the nozzles at the downstream side in the feeding direction (37a, 38a and 39a, and the like in this case).
For example, when nozzles 37a, 37b and 37c fixed in position jet inks in this order on the recording medium fed under the nozzles, pixels are recorded as shown in
Nozzles 38a, 38b and 38c on the nozzle row 19b record pixels contiguous to the pixels recorded by the nozzles 37a, 37b and 37c in the feeding direction, because the nozzles 38a, 38b and 38c and corresponding nozzles on the row 19a are, respectively, spaced by the pixel pitch times (n times the number of drive phases plus 1). Nozzles 39a, 39b and 39c further record pixels next to the recorded pixels. Thus, all pixels are recorded on the medium fed under the facing surface of the recording head 43 as shown in
As described above, the ink jet recording apparatus comprising line-type recording heads can also attain the same effects as in the second embodiment, as well as the effects in the third and the present embodiments.
The entire disclosure of Japanese Patent Application Nos. 2004-207594 which was filed on Jul. 14, 2004 and 2004-354221 which was filed on Dec. 7, 2004 is incorporated into the present invention in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| PATENT2004-207594 | Jul 2004 | JP | national |
| PATENT2004-354221 | Dec 2004 | JP | national |
