Patent Publication Number: US-2009237444-A1

Title: Liquid ejecting apparatus and method of cleaning liquid ejecting head

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a liquid ejecting apparatus having a liquid ejecting head that ejects liquid from nozzle openings and a method of cleaning the liquid ejecting head. 
     2. Related Art 
     An ink jet printing apparatus such as an ink jet printer or a plotter includes an ink jet printhead which is able to discharge ink stored in an ink storage unit such as an ink cartridge and an ink tank as ink drops. 
     The ink jet printhead here includes pressure generating chambers which are in communication with nozzle openings and a pressure generating unit that causes a pressure change in the pressure generating chambers to cause liquid drops to be discharged from the nozzle openings. As the pressure generating unit to be mounted on the ink jet printhead includes, for example, a vertically vibrating piezoelectric element, a flexibly vibrating piezoelectric element, and the one using electrostatic force. 
     In the ink jet printheads as described above, air bubbles entered when replacing the ink cartridge or those contained in the ink may stay in the pressure generating chambers, so that a print failure such as “dot missing” might occur. Therefore, the ink jet printing apparatus includes a suction cap which is connected to a suction pump that sucks ink in the vicinity of the nozzle openings. 
     The suction cap prevents the print failure such as the dot missing by filling the pressure generating chambers with ink by being capped on an end surface of the ink jet printhead and performing a sucking action which sucks the ink in the vicinity of the nozzle openings. 
     However, when the sucking action that sucks the ink from all the nozzle openings is carried out, the ink is also sucked out from the pressure generating chambers in an normal state which are filled the ink, the amount of ink consumption is disadvantageously increased. 
     Therefore, an ink jet printing apparatus configured to specify a nozzle block such as a nozzle row which includes a plurality of nozzle openings having the pressure generating chambers in which an ink filling failure occurs, and performing the sucking action only for such the nozzle block is proposed (for example, see JP-A-2005-53047 and JP-A-2005-262821). 
     Alternatively, there is proposed a configuration in which the piezoelectric elements are brought into micro-vibrations during the sucking action, so that the air bubble dischargeability property is improved (for example, see JP-A-11-78067). 
     However, according to JP-A-2005-53047 and JP-A-2005-262821, since the sucking action is performed for the nozzle block, even when the pressure generating chambers filled normally with ink exist in the nozzle block, the ink is sucked from the normal pressure generating chamber. Therefore, there remains the problem of increase in amount of ink consumption. 
     Also, in order to perform the sucking action for the nozzle blocks selectively as in JP-A-2005-53047 and JP-A-2005-262821, there arise problems such that the apparatus is upsized, and the cost is increased. 
     Also, in JP-A-2005-262821, a method of performing the sucking action for the nozzle block and a flushing action by driving the piezoelectric element to cause the ink to be discharged selectively according to the number of the nozzle openings at which the dot missing occurs in the nozzle block, to cause only the nozzle openings at which the dot missing occurs to perform the flushing action when performing the flushing action, and to bring the nozzle openings at which the dot missing does not occur into micro vibrations is disclosed. However, the method in JP-A-2005-262821 simply performs the sucking action and the flushing action step by step according to the number of the nozzle openings having the dot missing, and brings the nozzle openings at which the dot missing does not occur into micro vibrations simultaneously with the flushing action in order to prevent increase in viscosity. In other words, the method in JP-A-2005-262821 simply causes the sucking action, the flushing action, and the micro vibration to be performed step by step, and when the flushing action is performed only for the nozzle openings at which the dot missing occurs and the micro vibrations are generated at the nozzle openings at which the dot missing does not occur, vibrations occurs in the respective pressure generating chambers, a flow of the ink from the pressure generating chambers filled normally filled with ink to the pressure generating chambers insufficiently filled with ink does not occur, so that the amount of ink consumption in the sucking action cannot be reduced. 
     In JP-A-11-78067, the air bubble dischargeability is improved by bringing the piezoelectric elements into micro vibrations during the sucking action, but the amount of ink consumption cannot be reduced. 
     Such problems exist not only in the ink jet printing apparatus, but also in the liquid ejecting apparatus which ejects liquid other than ink. 
     SUMMARY OF THE INVENTION 
     An advantage of some aspects of the invention is to provide a liquid ejecting apparatus in which the amount of liquid consumption is reduced and hence the cost is reduced without upsizing the apparatus, and a method of cleaning the liquid ejecting head. 
     According to a first aspect of the invention, there is provided a liquid ejecting apparatus including: a plurality of nozzle openings that eject liquid; pressure generating chambers in communication with the respective nozzle openings; a liquid ejecting head including a pressure generating unit that causes the pressure generating chambers to generate a pressure change; a sucking unit that covers the nozzle openings and sucks the liquid from the nozzle openings; a suction control unit that causes the sucking unit to suck the liquid from the nozzle openings; and a liquid flow control unit that brings the pressure generating units into vibrations selectively corresponding to the pressure generating chambers to vibrate when sucking the liquid by the sucking unit and controls a flow of fluid in the pressure generating chambers by not driving the pressure generating units corresponding to the non-selected pressure generating chambers. 
     In this configuration, the flowability of the liquid on the side of the non-selected desired pressure generating chambers is enhanced by restraining the flowability of the liquid in the selected pressure generating chambers, so that efficient suction of the liquid in the non-selected pressure generating chambers is achieved by the sucking unit. Accordingly, the liquid dischargeability from the nozzle openings which communicate with the desired pressure generating chambers is improved, so that a sucking action is achieved in a short time by a small number of times, whereby the amount of liquid consumption is reduced. In addition, since the amount of liquid consumption is reduced without upsizing the apparatus, the cost is decreased. 
     Preferably, the vibrations that the liquid flow control unit causes the selected pressure generating unit to perform is micro vibrations. In this configuration, since the action to press the liquid out from the nozzle openings by driving pulses is prevented by supplying micro vibration pulses to bring the selected pressure generating unit into micro vibrations, unnecessary exhaust of the liquid by the driving pulses is minimized. 
     Preferably, a detecting unit that detects a liquid filling state in the pressure generating chambers is further provided, and the liquid flow control unit brings the pressure generating unit corresponding to the pressure generating chambers normally filled with the liquid into vibrations on the basis of the result of detection of the detecting unit. Accordingly, air bubbles are efficiently discharged together with the liquid from the pressure generating chambers having a filling failure and including the air bubbles staying therein. 
     Preferably, the sucking unit includes a cap member that covers the nozzle openings and a sucking device that is connected to the cap member and sucks the interior of the cap member. Accordingly, the interior of the flow channel of the pressure generating chamber or the like is cleaned by sucking the liquid from the nozzle openings by the cap member. 
     Preferably, the liquid flow control unit applies vibration pulses having high frequencies in comparison with discharge driving pulses for discharging liquid to the pressure generating unit to cause vibrations. Accordingly, the possibility that the liquid is supplied to the selected pressure generating chambers by the vibrations by the vibration pulses having the high frequencies in comparison with the discharge driving pulses is reduced, so that enhancement of the liquid flowability on the side of the non-selected desired pressure generating chambers is ensured. 
     According to a second aspect of the invention, there is provided a method of cleaning a liquid ejecting head that performs a sucking action for sucking liquid from a plurality of nozzle openings of the liquid ejecting head having the plurality of nozzle openings that ejects the liquid, pressure generating chambers in communication with the respective nozzle openings; and a pressure generating unit that causes a pressure change in the pressure generating chambers, including: controlling a flow of the liquid in the pressure generating chambers by selectively bringing the pressure generating units corresponding to the pressure generating chambers into vibrations and sucking the liquid from the nozzle openings without bringing the pressure generating units corresponding to the non-selected pressure generating chambers into vibrations. 
     In this configuration, the flowability of the liquid on the side of the non-selected desired pressure generating chambers is enhanced by restraining the flowability of the liquid in the selected pressure generating chambers, so that efficient suction of the liquid in the non-selected pressure generating chambers is achieved. Accordingly, the liquid dischargeability from the nozzle openings which communicate with the desired pressure generating chambers is improved, so that the sucking action is achieved in a short time by a small number of times, whereby the amount of liquid consumption is reduced. In addition, since the amount of liquid consumption is reduced without upsizing the apparatus, the cost is decreased. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings where like numbers reference like elements. 
         FIG. 1  is a schematic perspective view of a printing apparatus according to a first embodiment of the invention. 
         FIG. 2  is a cross-sectional view of a printhead according to the first embodiment of the invention. 
         FIG. 3  is a schematic perspective view showing the printhead and a sucking unit according to the first embodiment of the invention. 
         FIG. 4  is a cross-sectional view of the printhead and the sucking unit according to the first embodiment of the invention. 
         FIG. 5  is a block diagram showing a control configuration of the printing apparatus according to the first embodiment of the invention. 
         FIG. 6  is a schematic cross-sectional view showing a sucking action according to the first embodiment of the invention, 
         FIG. 7  is a schematic plan view showing the sucking action according to the first embodiment of the invention. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     The invention will be described in detail on the basis of embodiments. 
     First Embodiment 
       FIG. 1  is a schematic perspective view of an ink jet printing apparatus as an example of a liquid ejecting apparatus according to a first embodiment of the invention. 
     A liquid ejecting apparatus according to the first embodiment is, for example, an ink jet printing apparatus and, as shown in  FIG. 1 , printhead units  1 A and  1 B having the ink jet printhead, descried later in detail, each include ink cartridges  2 A and  2 B which constitute ink supply units demountably mounted thereon, and a carriage  3  having the printhead units  1 A and  1 B mounted thereon are provided on a carriage shaft  5  attached to an apparatus body  4  so as to be capable of moving in the axial direction. The printhead units  1 A and  1 B are configured to discharge black ink composition and color ink compositions, respectively. 
     A drive motor  6  is provided near one end of the carriage shaft  5 , and a first pulley  6   a  having a groove on the outer periphery thereof is provided at the distal end of the shaft of the drive motor  6 . A second pulley  6   b  corresponding to the first pulley  6   a  of the drive motor  6  is rotatably provided near the other end of the carriage shaft  5 , and a timing belt  7  formed of an annular resilient member such as rubber is provided between the first pulley  6   a  and the second pulley  6   b.    
     Then, by a drive force from the drive motor  6  transmitted to the carriage  3  via the timing belt  7 , the carriage  3  having the printhead units  1 A and  1 B mounted thereon is moved along the carriage shaft  5 . On the other hand, a platen  8  is provided on the apparatus body  4  along the carriage  3 . This platen  8  is configured to be able to rotate by a drive force of a paper feed motor, not shown, and a printing sheet S as a printing medium such as paper supplied by a paper feed roller or the like, not shown, is wound around the platen  8  and is transported. 
     Provided in a non-printing area on the side of the platen  8 , which is the end in the direction of movement of the carriage  3  is a sucking unit  40  which performs a sucking action by sucking ink from nozzle openings of the ink jet printhead described later. 
     The ink jet printhead to be mounted on the ink jet printing apparatus as described above will be described.  FIG. 2  is a cross-sectional view showing an example of the ink jet printhead according to the first embodiment of the invention. 
     An ink jet printhead  10  shown in  FIG. 2  is of a type having a vertically vibrating piezoelectric element, and a spacer  11  includes a plurality of pressure generating chambers  12  arranged in parallel with each other, and both ends of the spacer  11  are sealed by a nozzle plate  14  having nozzle openings  13  corresponding to the respective pressure generating chambers  12  and a diaphragm  15 . The spacer  11  is formed with a reservoir  17  as a common ink chamber of the plurality of pressure generating chambers  12  by being communicated with the respective pressure generating chambers  12  via ink supply ports  16  respectively, and an ink cartridge, not shown, is connected to the reservoir  17 . 
     In contrast, distal ends of piezoelectric elements  18  are in contact with the diaphragm  15  on the opposite side from the pressure generating chambers  12  in areas corresponding to the respective pressure generating chambers  12 . The piezoelectric elements  18  is formed by laminating a piezoelectric material  19 , and electrode forming materials  20  and  21  alternately in a vertical sandwich-like pattern, and an inactive area which does not contribute to vibrations is secured to a fixed substrate  22 . The fixed substrate  22 , the diaphragm  15 , the spacer  11 , and the nozzle plate  14  are integrally fixed via the base  23 . 
     In the ink jet printhead  10  configured as descried above, ink is supplied to the reservoir  17  via an ink flow channel communicated to the ink cartridge, and is distributed to the respective pressure generating chambers  12  via the ink supply ports  16 . Actually, the piezoelectric elements  18  are contracted by applying a voltage to the piezoelectric elements  18 . Accordingly, the diaphragm  15  is deformed (pulled upward in the drawing) together with the piezoelectric elements  18  and hence the capacities of the pressure generating chambers  12  are increased, whereby ink is drawn into the pressure generating chambers  12 . Then, by releasing a voltage applied to the electrode forming materials  20  and  21  of the piezoelectric elements  18  according to record signals from a drive circuit after having filled the interior with ink up to the nozzle openings  13 , the piezoelectric elements  18  is elongated, and is restored to the original state. Accordingly, since the diaphragm  15  is displaced as well and is restored to the original state, the pressure generating chambers  12  is compressed, and the interior pressure is increased, so that ink drops are discharged from the nozzle openings  13 . In other words, in the first embodiment, vertically vibrating piezoelectric elements  18  are provided as pressure generating units for causing the pressure change in the pressure generating chambers  12 . 
     In the ink jet printhead  10  as described above, air bubbles entering when the cartridges  2 A and  2 B are mounted initially or replaced or air bubbles contained in the ink during a printing operation stays in the pressure generating chambers  12  and the air bubbles absorb the pressure variations in the pressure generating chambers  12 , so that the discharge of the ink drops cannot be performed normally, and a print failure such as the dot missing might occur. Therefore, in the non-printing area of the ink jet printing apparatus, there is provided the sucking unit  40  that sucks the air bubbles together with ink from the flow channels of the pressure generating chambers  12  or the like via the nozzle openings  13 . 
     The sucking unit  40  will be described in detail now.  FIG. 3  is a schematic perspective view showing the ink jet printhead and the sucking unit, and  FIG. 4  is a cross-sectional view of the ink jet printhead and the sucking unit. 
     As shown in  FIG. 3 , the sucking unit  40  includes a cap member  41  that covers the nozzle openings of the ink jet printhead  10  and a sucking device  43  such as a vacuum pump connected to the cap member  41  via a tube  42 . 
     The cap member  41  is provided so as to oppose the nozzle plate  14  of the ink jet printhead  10 , and is provided so as to cover all the plurality of nozzle openings  13 . 
     The cap member  41  includes a suction port  41   a  that opposes the nozzle plate  14  and opens over the entire nozzle openings  13  as shown in  FIG. 4 . The cap member  41  covers all the nozzle openings  13  by the edge portion of the suction port  41   a  coming into contact with a surface of the nozzle plate  14 . The cap member  41  includes a communication port  41   b  on the surface thereof opposite from the suction port  41   a  so as to communicate with the suction port  41   a,  and the sucking device  43  is connected to the communication port  41   b  via the tube  42 . 
     The sucking unit  40  configured as described above brings the edge portion of the suction port  41   a  of the cap member  41  into contact with the surface of the nozzle plate  14  and causes the sucking device  43  to perform the sucking action to bring the interior of the cap member  41  into a negative pressure and suck the ink in the flow channels such as the pressure generating chambers  12  from the nozzle openings  13  together with the air bubbles. The cap member  41  has a role to cover the nozzle openings  13  at a timing other than the sucking action, such as when the power is turned off, at the waiting time, at regular timings, or the like and prevent ink near the nozzle openings  13  from increase in viscosity due to drying of the ink. 
     A control configuration for controlling the ink jet printhead as described above will be described now. FIG.  5  is a block diagram showing the control configuration of the ink jet printhead. 
     As shown in  FIG. 5 , an ink jet printing apparatus I includes the ink jet printhead  10  which corresponds to a mechanism portion which actually performs a printing job, the sucking unit  40  that sucks the ink from the nozzle openings  13  of the ink jet printhead  10 , and a controller  50  that controls actions of the ink jet printhead  10  and the sucking unit  40 . 
     The controller  50  includes a print control unit  51 , a printhead driving circuit  52 , a printing position control unit  53 , a suction control unit  54 , and a liquid flow control unit  55 . 
     The print control unit  51  controls the printing operation of the ink jet printhead  10  and, for example, applies driving pulses to the piezoelectric elements  18  via the printhead driving circuit  52  in association with the input of a print signal, and causes the ink jet printhead  10  to discharge ink. 
     The printing position control unit  53  determines the position of the ink jet printhead  10  at the time of printing and at the time of being capped in a primary scanning direction and a secondary scanning direction. More specifically, the printing position control unit  53  drives the drive motor  6  and moves the carriage  3  in the primary scanning direction to position the ink jet printhead  10  in the primary scanning direction, then drives the paper feed motor, not shown, to rotate the platen  8  and move the printing sheet S in the secondary scanning direction, thereby positioning the ink jet printhead  10  in the secondary direction with respect to the printing sheet S. Then, the printing position control unit  53  moves the carriage  3  on which the ink jet printhead  10  is mounted in the primary scanning direction when printing, and moves the printing sheet S in the secondary scanning direction. At the time of the sucking action, the printing position control unit  53  moves the carriage  3  on which the ink jet printhead  10  is mounted toward the sucking unit  40  provided in the non-printing area. 
     In the first embodiment, the ink jet printing apparatus I further includes a detector  56 . The detector  56  detects an ink filling state in the respective pressure generating chambers  12  of the ink jet printhead  10 . In the first embodiment, the detector  56  is configured to detect the ink filling state in the pressure generating chambers  12  by detecting the dot missing. More specifically, the detector  56  is, for example, an optical sensor or the like such as a scanner which causes the ink jet printing apparatus I to print a test pattern reads the printed pattern as an image, and detects the dot missing. The detector  56  is not specifically limited to this type, and may be configured to detect directly the ink filling state in the pressure generating chambers  12 , and those known in the related art may be employed. 
     The suction control unit  54  controls the sucking action of the sucking unit  40 . In other words, the suction control unit  54  activates the sucking device  43  of the sucking unit  40  at a predetermined timing, and causes the sucking unit  40  to perform the sucking action for sucking the ink in the vicinity of the nozzle openings  13  of the ink jet printhead  10 . Specifically, the suction control unit  54  moves the ink jet printhead  10  to a position opposing the cap member  41  via the printing position control unit  53 , caps the ink jet printhead  10  with the cap member  41 , and drives the sucking device  43 , thereby causing the sucking action. 
     The liquid flow control unit  55  controls the suction control unit  54  at a predetermined timing, causes the sucking unit  40  to perform the sucking action for sucking the ink in the vicinity of the nozzle openings  13  of the ink jet printhead  10 , and controls the print control unit  51  on the basis of the ink filing state in the pressure generating chambers  12  detected by the detector  56 , thereby bringing selectively the piezoelectric elements  18  corresponding to the pressure generating chambers  12  which is normally filled with ink into micro vibrations 
     In other words, the liquid flow control unit  55  controls the suction control unit  54  to cause the sucking unit  40  to perform the sucking action while bringing the piezoelectric elements  18  corresponding to the nozzle openings  13  other than the nozzle openings  13  having the dot missing detected by the detector  56 , that is, the nozzle openings  13  from which the ink drops are normally discharged into micro vibrations. In this manner, in the first embodiment, the liquid flow control unit  55  selects the nozzle openings  13  from which the ink drops are normally discharged, that is, the pressure generating chambers  12  filled with ink normally, and brings the piezoelectric elements  18  corresponding to the selected pressure generating chambers  12  into micro vibrations as the vibrations. Then, the liquid flow control unit  55  determines the piezoelectric elements  18  corresponding to the pressure generating chambers  12  which are in communication with the nozzle openings  13  where the dot missing occurs (the pressure generating chambers  12  having the ink filling failure) as unselect elements, and does not drive the corresponding piezoelectric elements  18 . 
     When pressure waves are generated in the pressure generating chambers  12  filled with ink normally by the micro vibrations, as shown in  FIG. 6 , the pressure wave of pressure generating chambers  12 A filled with ink normally and flows of ink from the reservoir  17  to the pressure generating chambers  12 A by suction cancel each other, so that the flow of ink sucked from the nozzle openings  13  in communication with the pressure generating chambers  12 A filled with ink normally is weakened. In contrast, on the side of pressure generating chambers  12 B having the ink filling failure, that is, having air bubbles staying therein, the flow of ink from the reservoir  17  to the pressure generating chambers  12 B is increased by an amount corresponding to the amount of weakening of the flow of the ink on the side of the pressure generating chambers  12 A which is filled with ink normally, so that the flows of the ink sucked from the nozzle openings  13  are amplified. 
     Therefore, the sucking action achieves improvement of the air bubble dischargeability from the pressure generating chambers  12  having the air bubbles staying therein and having the filling failure from the nozzle openings  13 . Since the air bubble dischargeability is improved, the sucking action is achieved in a short time (smaller number of times of sucking) in comparison with a case in which the micro vibrations are not generated, so that reduction of the amount of ink consumption is achieved. In particular, as shown in  FIG. 7 , when the number of the nozzle openings  13  where the dot missing occurs, that is, the number of the pressure generating chambers  12 B having the ink filling failure due to the air bubbles staying therein is small, the amount of ink discharged from many of the pressure generating chambers  12 A filled normally with ink is reduced and, correspondingly, the efficient ink discharge from the side of the pressure generating chambers  12 B having the ink filling failure is achieved. In other words, the liquid flow control unit  55  restrains the flowability of liquid in the selected pressure generating chambers  12 , and enhances the flowability of ink in the non-selected desired pressure generating chambers  12  and, consequently, efficient suction of ink in the pressure generating chambers  12  which are not selected by the sucking unit  40  is achieved. 
     The micro vibrations that the liquid flow control unit  55  causes the piezoelectric elements  18  to generate is the driving pulses to an extent which does not cause ink to be discharged, and the cycle may be selected adequately according to the viscosity of the ink or the structure of the ink jet printhead  10  or the like. In the first embodiment, micro vibration driving pulses having square waves at relatively high frequencies are applied to the piezoelectric elements  18 . Such the micro vibration driving pulses are set to have high-frequency waves in comparison with discharge driving pulses for causing the piezoelectric elements  18  to discharge ink, so that the supply of the ink from the reservoir  17  to the pressure generating chambers  12  corresponding to the piezoelectric elements  18  which are brought into micro vibrations is weakened and the flow of ink toward the pressure generating chambers  12  having the ink filling failure is amplified. In the first embodiment, the piezoelectric elements  18  is selectively brought into micro vibrations during the sucking action, so that an action of ink to be pushed out from the nozzle openings  13  which are in communication with the pressure generating chambers  12  filled with ink normally is minimized, and the discharge of ink from the normal nozzle openings  13  is restrained. In other words, it is because the probability that liquid is pushed out also from the nozzle openings  13  from which the ink drops are discharged normally as well is high if the piezoelectric elements  18  corresponding to the normal pressure generating chambers  12  are driven during the sucking action using the normal discharge driving pulses. As a matter of course, driving the piezoelectric elements  18  during the sucking action is not limited to the micro vibrations (micro vibration driving pulses), and other driving pulses (including the discharge driving pulses) may be used. 
     When the liquid flow control unit  55  controls the suction control unit  54  to cause the sucking device  43  to perform the sucking action, the sucking action may be performed at a predetermined pulses, or continuously for a certain time period. The micro vibrations of the piezoelectric elements  18  may be generated so as to match the pulses of the sucking action, or may be performed constantly during the sucking action irrespective of the pulses of the sucking action. 
     The sucking action that the liquid flow control unit  55  causes to perform by controlling the suction control unit  54  is performed at a predetermined timing such as the time of replacement of the ink cartridges  2 A and  2 B, at the time of waiting, before the printing job, or during the printing job as described above. Therefore, although not shown specifically, by providing a timer unit or the like for measuring time, the sucking action may be performed adequately according to the result of measurement of the timer unit. 
     Another Embodiment 
     Although the embodiment of the invention has been descried thus far, the basic configuration of the invention is not limited to the configuration described above. For example, in the first embodiment described above, the detecting unit  56  that detects the ink filling state in the pressure generating chambers  12  is provided, and the liquid flow control unit brings the piezoelectric elements  18  corresponding to the pressure generating chambers  12  normally filled with ink into micro vibrations on the basis of the result of detection of the detecting unit  56 . However, the invention is not specifically limited thereto and, for example, it is also possible, for example, not to provide the detecting unit  56  and to provide a plurality of nozzle opening groups including a plurality of nozzle openings  13  to achieve the sucking action while bringing the pressure generating chambers  12  corresponding to the respective nozzle opening groups into micro vibrations in sequence. 
     Although the liquid flow control unit  55  is provided separately from the print control unit  51  in the first embodiment described above, since the liquid flow control unit  55  simply brings the selected piezoelectric elements  18  into vibrations, the print control unit  51  may be adapted to also serve as the liquid flow control unit  55 . It is also possible to cause the liquid flow control unit  55  to control the sucking unit  40 , that is, to cause the liquid flow control unit  55  to also serve as the suction control unit  54 . 
     Also, the vertically vibrating piezoelectric elements  18  which is formed by laminating the piezoelectric material  19  and the electrode forming materials  20  and  21  alternately for the expansion and contraction in the vertical direction is exemplified as the pressure generating unit which causes the pressure change in the pressure generating chambers  12  in the first embodiment described above. However, the invention is not specifically limited thereto and, for example, a thin-film type piezoelectric element formed by laminating the respective layers by film formation and lithography method or a thick-film type piezoelectric element formed by bonding green sheets or the like may be employed as the flexibly vibrating piezoelectric element formed by sandwiching a piezoelectric element layer formed of crystallized piezoelectric material by two electrodes of a lower electrode and an upper electrode. Also, as the pressure generating unit, so-called an electrostatic actuator or the like which generates a static electricity between the diaphragm and the electrode and causes the liquid drops to be discharged from the nozzle openings by deforming the diaphragm by the static electricity may also be used. 
     As the ink jet printing apparatus I descried above, the one in which the ink jet printhead  10  (the printhead units  1 A and  1 B) is mounted on the carriage  3  and moves in the primary scanning direction is exemplified. However, the invention is not limited thereto and, for example, the invention may also be applied to a so-called line type printing apparatus in which the ink jet printhead  10  is fixed and performs the printing job only by moving the printing sheet S such as paper in the secondary scanning direction. 
     The invention is intended to be applied widely to general liquid ejecting heads and, for example, the invention may be applied to printhead such as various ink jet printheads used in an image printing apparatus such as printers, a color material ejecting head used for manufacturing color filters of liquid crystal displays or the like, electrode material ejecting heads used for forming electrodes such as organic ED displays, FEDs (field emission displays) or the like, or biological organic substances ejecting heads used for manufacturing bio chips. The liquid ejecting apparatus having such the liquid ejecting head mounted thereon is not specifically limited as a matter of course.