JP2010167683A - Liquid delivering apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid delivering apparatus for performing a flushing operation, which can ensure delivering stability while improving discharging effect of fine air bubbles in a liquid delivering head. <P>SOLUTION: A drive signal for flushing generated by a drive signal generating circuit is constituted by including a drive pulse Pf for flushing and a vibration-damping drive pulse Pd which is generated after this drive pulse Pf for flushing to suppress residual vibration at the time of flushing. An interval between the drive pulse for flushing and the vibration-damping drive pulse, is adjusted to a value by which a vibration-damping expansion element p21 is loaded to a piezoelectric element at the timing of negating the residual vibration generated in a pressure generating room by accompanying a delivering operation of ink by a contracting element p13. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid ejecting apparatus such as an ink jet printer, and more particularly to a liquid ejecting apparatus that performs a flushing operation for discharging bubbles in the vicinity of a nozzle by forcibly ejecting a liquid from the nozzle.

  For example, a liquid ejection apparatus is an apparatus that includes a liquid ejection head capable of ejecting liquid from a nozzle and ejects various liquids from the liquid ejection head. As a representative example of this liquid ejection apparatus, for example, an ink jet recording head (hereinafter simply referred to as a recording head) as a liquid ejection head is provided, and liquid ink is ejected from the nozzle of this recording head to a recording medium such as recording paper. An image recording apparatus such as an ink jet printer (hereinafter simply referred to as a printer) that records an image or the like by discharging and landing on a (landing target) can be given. In recent years, liquid ejecting apparatuses have been applied not only to the image recording apparatus but also to various manufacturing apparatuses such as a manufacturing apparatus for a color filter such as a liquid crystal display.

  Here, taking the above ink jet printer (hereinafter simply abbreviated as a printer) as an example, this printer is a series of ink flow paths from a common ink chamber (reservoir) to a nozzle through a pressure generating chamber, and pressure generation. Mounted with a recording head having a pressure generating element (for example, a piezoelectric element) for changing the volume of the chamber, and a driving signal generating circuit (driving signal generating means) for generating a driving signal to be supplied to the pressure generating element I have. Then, an ejection drive pulse included in the drive signal is applied to the piezoelectric element to cause a pressure fluctuation in the ink in the pressure generating chamber, and the ink is ejected from the nozzle using the pressure fluctuation. In such printers, the ink surface exposed to the nozzles (meniscus) is exposed to the atmosphere, causing the solvent to evaporate and the ink to thicken, or bubbles to enter the pressure generation chamber, etc. to generate pressure. Ink discharge failure may occur due to the absorption of the pressure change in the room.

  For this reason, in order to maintain good ink ejection, various techniques related to maintenance processing have been proposed (see, for example, Patent Document 1). In the configuration disclosed in Patent Document 1, the nozzle is temporarily sealed with a cap, and in this sealed state, the inside of the cap is set to a negative pressure, and an ejection driving pulse is applied to the piezoelectric element to apply pressure to the pressure generating chamber. A maintenance process (cleaning process) is performed in which a pressure fluctuation is caused in the ink of the ink to cause the ink to be ejected idle, and the thickened ink and bubbles are forcibly discharged. However, even if the above maintenance process is performed, pressure fluctuations during maintenance cannot be sufficiently applied to very small bubbles (for example, bubbles having a diameter of several tens of μm), and are completely removed. It is difficult.

  Therefore, in this type of printer, a flushing operation for forcibly ejecting ink is performed separately from the above-described cleaning process. Specifically, after performing the above-described cleaning process, after performing initial filling when the ink cartridge is replaced, or during a printing operation (recording operation), every predetermined time (for example, every 9 seconds) In addition, the recording head is moved to an ink receiving member located at a position away from the recording medium, and ink is repeatedly ejected at that position. In this flushing operation, an attempt has been made to increase the pressure difference per unit time by increasing the drive voltage (potential difference from the highest potential to the lowest potential) of the flushing drive pulse applied to the piezoelectric element to the maximum.

JP 2007-136989 A

  However, when the pressure difference per unit time is increased in the flushing operation, the residual vibration is increased accordingly. If the flushing operation is repeated in a state where the residual vibration is not attenuated, the ejection becomes unstable, and there is a possibility that, for example, a mist may be generated and adhered to the nozzle surface. Further, when the next operation (recording operation, etc.) is performed after the flushing operation, a standby time is required until the residual vibration is attenuated to the extent that the next operation is not affected, and the operation speed is reduced accordingly. There was also a fear.

  The present invention has been made in view of such circumstances, and an object of the present invention is to perform a flushing operation capable of ensuring ejection stability while improving the discharge effect of minute bubbles in the liquid ejection head. An object of the present invention is to provide a liquid ejecting apparatus for performing the operation.

The present invention has been proposed to achieve the above object, and a liquid discharge head capable of discharging liquid from the nozzle by driving a pressure generating element that varies the volume of a pressure generating chamber communicating with the nozzle. A liquid discharge apparatus comprising: a drive signal generator that generates a drive signal including a drive pulse for driving the pressure generating element at a constant cycle;
The drive signal generator is
An expansion element that expands the pressure generation chamber by changing from a contraction potential corresponding to a state in which the pressure generation chamber is contracted to an expansion potential corresponding to a state in which the pressure generation chamber is expanded, and from the expansion potential to the contraction potential And a contraction element that contracts the pressure generation chamber to generate a flushing drive pulse whose drive voltage voltage change is larger than that of a discharge drive pulse used for controlling liquid ejection onto a recording medium. Configured,
After the flushing drive pulse, a vibration suppression drive pulse that suppresses residual vibration generated by driving the pressure generating element by the flushing drive pulse is generated.

  In the above-described embodiment, it is desirable to adopt a configuration in which the interval between the flushing drive pulse and the vibration suppression drive pulse is determined based on the natural vibration period Tc of the liquid in the pressure generation chamber.

  Further, in the above-described embodiment, the vibration suppression drive pulse expands the pressure generation chamber to such an extent that liquid is not discharged from the nozzle, and the vibration suppression to contract the pressure generation chamber to the extent that liquid is not discharged from the nozzle. A configuration including at least a contraction element may be employed.

  Furthermore, in the above embodiment, the vibration suppression drive pulse includes at least a vibration suppression expansion element that expands the pressure generation chamber and a vibration suppression discharge element that contracts the pressure generation chamber and discharges liquid from the nozzle. It can also be adopted.

  According to the present invention, since the vibration suppression drive pulse is generated after the flushing drive pulse, the residual vibration after the flushing operation is suppressed, so that the ejection during the subsequent flushing operation can be stabilized. Thereby, generation | occurrence | production of mist etc. can be suppressed. In addition, since the standby time for converging the residual vibration can be shortened, the flushing operation can be performed at a higher frequency. As a result, the time required for maintenance can be shortened. Further, when other processing such as a normal recording operation is performed after the flushing operation, it is possible to shift to the next processing in a shorter time.

FIG. 3 is a perspective view illustrating a configuration of a printer. It is a schematic diagram explaining the structure of a carriage, a capping mechanism, and a pump mechanism. FIG. 3 is a partial cross-sectional view of a recording head. It is a perspective view explaining a cap member. It is a schematic diagram explaining the sealing state of a capping mechanism. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a flowchart explaining the flow of maintenance control. It is a figure explaining the structure of the drive signal used by flushing operation | movement. It is a figure explaining the structure of the drive signal in 2nd Embodiment. It is a figure explaining the structure of the drive signal in 3rd Embodiment.

  The best mode for carrying out the present invention will be described below with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet recording apparatus (hereinafter referred to as a printer) will be described as an example of the liquid ejection apparatus of the present invention.

  FIG. 1 is a perspective view illustrating the basic configuration of the printer 1. As shown in FIG. 1, a printer 1 has a carriage 3 attached to a guide shaft 2, and a recording head 4 (a kind of liquid ejection head of the present invention) is attached to the lower surface thereof. Further, inside the carriage 3 is provided a cartridge holder portion (not shown) for detachably holding the ink cartridge. The carriage 3 is connected to a timing belt 8 that is stretched between a drive pulley 6 and an idler pulley 7 that are joined to a rotation shaft of a carriage motor (pulse motor) 5. By driving, the recording paper 9 moves in the width direction (main scanning direction).

  The ink cartridge is a storage member that stores ink (a kind of liquid of the present invention). This ink is obtained by dissolving or dispersing a color material in an ink solvent. For example, a pigment or a dye is used as the color material, and water is used as the ink solvent. When the ink cartridge is mounted on the cartridge holder portion, an ink supply needle (not shown) provided on the cartridge holder portion is inserted into the ink cartridge. Since the ink supply needle communicates with the ink flow path of the recording head 4, the ink in the ink cartridge can be supplied into the recording head 4 when the ink supply needle is inserted. Then, in order to fill the ink in the ink cartridge into the flow path in the recording head 4, initial filling described later is performed. As the ink cartridge, a type arranged on the printer main body (housing) side and supplied to the recording head 4 through an ink supply tube can be adopted.

  A platen 11 is provided below the guide shaft 2. The platen 11 is a plate-like member that supports the recording paper 9 from below. The platen 11 is provided with a liquid absorbing member 12 such as a sponge. In addition, a paper feed roller 13 is disposed in parallel with the guide shaft 2 on the upstream side of the liquid suction member 12. The paper feed roller 13 is rotated by a driving force from a paper feed motor 14 (stepping motor or DC motor) when the recording paper 9 is conveyed.

  A home position is set at a position within the movement range of the carriage 3 and outside the platen 11. The recording head 4 is positioned at the home position in the standby state. At this home position, a wiper mechanism 15 for wiping the nozzle forming surface of the recording head 4 and a capping mechanism 16 capable of sealing the nozzle forming surface in a non-recording state are arranged side by side along the guide shaft 2. Has been.

  As shown in FIG. 3, the recording head 4 is composed of a pressure generating unit 18 and a flow path unit 19, and these are integrated in an overlapped state. The pressure generating unit 18 includes a pressure generating chamber plate 22 for partitioning the pressure generating chamber 21, a communication port plate 23 having a supply side communication port 26 and a first communication port 28a, and a diaphragm on which the piezoelectric element 24 is mounted. 25 and laminated and integrated by firing or the like. The flow path unit 19 includes a supply port plate 29 having a supply port 27 and a second communication port 28b, a reservoir plate 31 having a reservoir 30 and a third communication port 28c, and a nozzle plate having a nozzle 32 formed therein. It is comprised by adhere | attaching the plate member which consists of 33 in a lamination | stacking state.

  A plurality of piezoelectric elements 24 are arranged on the outer surface of the diaphragm 25 on the side opposite to the pressure generating chambers 21 in a state corresponding to each pressure generating chamber 21. The illustrated piezoelectric element 24 is a vibrator in a flexural vibration mode, and is configured with a piezoelectric body 24c sandwiched between a drive electrode 24a and a common electrode 24b. When a drive signal (drive pulse) is applied to the drive electrode of the piezoelectric element 24, an electric field corresponding to the potential difference is generated between the drive electrode 24a and the common electrode 24b. This electric field is applied to the piezoelectric body 24c, and deforms according to the strength of the electric field applied with the piezoelectric body 24c. That is, as the potential of the drive electrode 24a is increased, the piezoelectric layer 20c contracts in a direction orthogonal to the electric field, and the diaphragm 25 is deformed so that the volume of the pressure generating chamber 21 is reduced.

  2, 4, and 5, the capping mechanism 16 moves the cap member 37 in a direction in which the cap member 37 is moved closer to or away from the nozzle forming surface of the recording head 4. A mechanism (not shown), a flexible drain tube 39 communicating between the sealing empty portion 36 and the drain tank 38, and a pump 40 disposed in the middle of the drain tube 39 Composed.

  The cap member 37 is a tray-like member having an open top surface having a bottom portion 41 and a side wall portion 42 standing up from the periphery of the bottom portion 41, and a space surrounded by the bottom portion 41 and the side wall portion 42 is sealed. Part 36. The cap member 37 is made of an elastic member such as rubber and is attached to a support member 43 made of synthetic resin or metal. In addition, a liquid absorbing member 44 is laid in the sealing empty portion 36. The liquid absorbing member 44 is made of a liquid absorbing material such as felt or sponge that can absorb ink. A through hole is formed in the bottom of the cap member 37, and a drain tube 39 is connected to the through hole in a liquid-tight state. In addition, another through-opening is opened at the bottom of the cap member 37, and an air release tube 47 constituting an air release path is connected to the through-opening. An air release valve 48 is provided in the middle of the air release tube 47. That is, by opening and closing the atmosphere release valve 48, the sealed state of the sealing empty portion 36 in a state where the nozzle forming surface is sealed and the atmosphere open state can be switched. The cap member 37 also functions as an ink receiving portion that receives ink ejected from the nozzles 32 in the flushing operation.

  The drainage tube 39 is a member constituting an ink discharge path. In the present embodiment, the drainage tube 39 is constituted by a silicon tube having high chemical resistance and elasticity. The pump 40 (negative pressure generation source) provided in the middle of the drainage tube 39 constitutes a pump mechanism together with the drive motor. The pump mechanism in the present embodiment uses the paper feed motor 14 as a drive motor for driving the pump 40.

  In the sealed state in which the nozzle forming surface of the recording head 4 is sealed by the cap member 37, the nozzle 32 on the nozzle forming surface faces into the sealing void 36, and the tip of the cap member 37 and the nozzle forming surface are in contact with each other. It adheres in a liquid-tight state (see FIG. 5). Then, when the pump 40 is operated in this sealed state and the atmosphere release valve 48 is closed, the inside of the sealed empty portion 36 is depressurized, so that the ink in the recording head 4 is sucked through the nozzles 32, It can be discharged outside the head. Using this, when the ink cartridge is mounted, the initial filling for filling the ink flow path of the recording head 4 with the ink in the ink cartridge and the cleaning for removing the thickened ink and bubbles in the ink flow path are performed. This suction control is performed in the processing.

  Next, the electrical configuration of the printer 1 will be described. As shown in FIG. 6, the printer 1 includes a printer controller 51 and a print engine 52. The printer controller 51 stores an interface 53 (external I / F 53) that receives print data from a host computer (not shown), a RAM 54 that stores various data, a control routine for various data processing, and the like. ROM 55, control unit 57 including CPU, drive signal generation circuit 58 capable of generating a drive signal to be supplied to recording head 4, oscillation circuit 59 generating a clock signal, drive signal for recording operation and maintenance operation An interface 60 (internal I / F 60) for transmitting a control signal or the like to the print engine 52 side is provided. These units are electrically connected to each other via an internal bus. The print engine 52 includes a carriage motor (pulse motor) 5 that moves the carriage 3, a paper feed motor 14 that rotates the paper feed roller 13, a recording head 4 (electric drive system), and the like.

  The control unit 57 is a part that performs various controls in the printer 1, and controls each unit of the print engine 52. For example, in controlling the recording operation, dot pattern data is generated based on print data from a host computer (not shown), and the generated dot pattern data is transferred to the recording head 4. Further, the carriage motor 5 is operated to move the carriage 3 (that is, the recording head 4), and the paper feed motor 14 is operated to transport the recording paper 9 (recording medium). When recording an image or text on the recording paper 9 based on the print data, the drive signal generation circuit 58 generates a drive signal including a drive signal pulse to be used when printing on the recording medium. For example, as shown in FIG. 8 of Japanese Patent Application Laid-Open No. 2003-11352, the drive pulse has a voltage that changes with a predetermined potential difference along the time axis. Further, when ejecting ink droplets of various sizes, a plurality of types of drive pulses that change voltage with different potential differences may be generated. Further, the controller 57 controls the suction by the pump (tube pump) 40 by operating the paper feed motor 14 at the time of initial filling and cleaning.

  Next, a description will be given of a series of maintenance controls including a suction operation at the time of initial filling and cleaning and a flushing operation performed thereafter in the above configuration.

FIG. 7 is a flowchart showing the flow of maintenance control.
First, the control unit 57 controls the carriage motor 5 to move the carriage 3 to the home position, and capping the nozzle formation surface of the recording head 4 by the capping mechanism 16 (S1). At this time, by closing the air release valve 48, the inside of the sealing empty portion 36 in the capped state is switched to a sealed state (liquid tight / air tight state).

  Subsequently, the control unit 57 applies a driving pulse to the paper feed motor 14 to start driving the pump 40 and starts a suction operation (S2). In this suction operation, at the time of initial filling, the ink flow path in the recording head 4 is decompressed to fill the ink in the ink cartridge into the ink flow path of the recording head 4. Further, at the time of cleaning, the thickened ink and bubbles are forcibly discharged from the nozzle 32. If the suction operation is performed for a predetermined time, the control unit 57 stops the suction operation by stopping the operation of the pump 40 (S3). In this suction operation, relatively large bubbles existing in the ink flow path can be discharged from the nozzle 32. For example, a very small bubble having a diameter of about several tens of μm is formed in the pressure generating chamber 21 and the nozzle 32. May remain.

  For this reason, in the printer 1 according to the present invention, the flushing drive pulse is continuously applied to the piezoelectric element 24 following the above suction operation, so that the ink in the pressure generating chamber 21 is stronger than the recording operation. A flushing operation for forcibly ejecting ink from the nozzle 32 by applying a pressure fluctuation is performed (S4), thereby discharging the minute bubbles. In this flushing operation, the air release valve 48 is opened, the capping state is released, and the cap member 37 is slightly separated from the nozzle forming surface.

  FIG. 8 is a diagram for explaining the flushing drive signal used in the flushing operation. This drive signal includes a flushing drive pulse Pf and a vibration suppression drive pulse Pd that is generated after the flushing drive pulse Pf and suppresses residual vibration caused by ink ejection by the flushing drive pulse Pf. Configured to repeatedly generate a set of these pulses at a constant period. The reference potential of this drive signal (the potential that becomes the reference for the change in the potential of the drive pulse) is the potential corresponding to the state in which the piezoelectric element 24 is maximally displaced toward the pressure generating chamber 21 and contracts the pressure generating chamber 21 ( The contraction potential is adjusted to Vx. The potential Vm is a potential (expansion potential) corresponding to a state in which the piezoelectric element 24 is displaced to the maximum side opposite to the pressure generation chamber 21 to expand the pressure generation chamber 21, and in the present embodiment. , The ground potential (GND).

The flushing drive pulse Pf has a pressure difference per unit time by setting the drive voltage Vd to be sufficiently higher than the drive voltage of the ejection drive pulse used during the recording operation on the recording medium to increase the voltage change. An expansion element p11 that is a drive pulse that is increased and changes from the contraction potential Vx to the expansion potential Vm to rapidly expand the pressure generating chamber 21, an expansion maintaining element p12 that maintains the expansion potential Vm for a certain period of time, and expansion A contraction element p13 that changes from the potential Vm to the contraction potential Vx and rapidly contracts the pressure generation chamber 21 is formed. When the flushing drive pulse Pf is applied to the piezoelectric element 24, first, the piezoelectric element 24 is bent in a direction away from the pressure generating chamber 21 by the expansion element p11, whereby the pressure generating chamber 21 corresponds to the contraction potential Vx. It expands from the contraction volume to the expansion volume corresponding to the expansion potential Vm. By this expansion, the meniscus of the nozzle 32 is largely drawn toward the pressure generating chamber 21 side. And the expansion state of this pressure generation chamber 21 is maintained over the supply period of the expansion maintenance element p12. Thereafter, the piezoelectric element 24 is bent toward the pressure generating chamber 21 by applying the contraction element p13. Due to the displacement of the piezoelectric element 24, the pressure generating chamber 21 is rapidly contracted from the expansion volume to the contraction volume. The ink in the pressure generation chamber 21 is pressurized by the rapid contraction of the pressure generation chamber 21, and the ink is ejected from the nozzle 32.
The flushing drive pulse Pf can obtain elements p11 and p13 of larger voltage change by increasing the drive voltage Vd. Therefore, it is sufficient that the voltage change of the pulse element included in the flushing drive pulse Pf is larger than the change of the voltage of the pulse element included in the ejection drive pulse used during the recording operation, and in particular, included in the drive pulse. As for the pulse element having the maximum voltage change among the pulse elements to be generated, it is sufficient that the voltage change included in the ejection drive pulse used during the recording operation is larger than the voltage change of the maximum pulse element. In particular, when there are a plurality of types of ejection drive pulses used during the recording operation, the drive pulse that changes the maximum voltage is the comparison target.

On the other hand, the vibration suppression drive pulse Pd is a drive pulse in which the drive voltage is set sufficiently smaller than the flushing drive pulse Pf (for example, about 30% of Vd), from the contraction potential Vx to the vibration suppression expansion potential Vc. A damping / expansion element p21 that expands and expands the pressure generating chamber 21, an expansion maintaining element p22 that maintains the damping / expansion potential Vc for a certain period of time, and a pressure generating chamber 21 that changes from the damping / expansion potential Vc to the contraction potential Vx. And a damping / shrinking element p23 for contracting The interval between the flushing drive pulse Pf and the damping drive pulse Pd, for example, the time Δt from the beginning of the contraction element p13 of the flushing drive pulse Pf to the start of the damping expansion element p21 of the damping drive pulse Pd is contracted. The damping / expansion element p21 is adjusted to a value to be applied to the piezoelectric element 24 at a timing at which the residual vibration generated in the pressure generation chamber 21 due to the ink ejection operation by the element p13 is canceled. Specifically, the interval Δt is set to n · Tc / 2 (n: integer). However, Tc is a natural vibration period (Helmholtz resonance period) generated in the ink in the pressure generation chamber 21. The natural vibration period Tc is individually determined by the recording head according to the size of the ink flow path in the head including the pressure generating chamber 21. For this reason, the natural vibration periods Tc are different among the same type of recording heads, and the interval Δt is individually set to a value based on Tc for each recording head.
In addition, the said natural vibration period Tc can be represented by following Formula (1), for example, as shown by patent document 2003-11352.
Tc = 2π√ [[(Mn × Ms) / (Mn + Ms)] × Cc] (1)
In the formula (1), Mn represents inertance in the nozzle 32, Ms represents inertance of the supply side communication port 26 and the supply port 27, and Cc represents compliance of the pressure generating chamber 21 (volume change per unit pressure, degree of softness). ).
In the above equation (1), inertance M indicates the ease of ink movement in the ink flow path, and is the mass of ink per unit cross-sectional area. Then, assuming that the density of the ink is ρ, the cross-sectional area of the surface orthogonal to the ink flow direction of the flow path is S, and the length of the flow path is L, the inertance M can be expressed by the following equation (2). it can.
Inertance M = (density ρ × length L) / cross-sectional area S (2)
In addition to the equation (1), any vibration cycle may be used as long as the pressure generating chamber 21 has.

  When the damping drive pulse Pd is applied to the piezoelectric element 24, first, the piezoelectric element 24 is bent in a direction away from the pressure generating chamber 21 by the damping expansion element p21, thereby causing the pressure generating chamber 21 to reach the contraction potential Vx. Slowly expands from the corresponding contraction volume to the intermediate expansion volume corresponding to the damping expansion potential Vc. By this expansion, the meniscus of the nozzle 32 is drawn into the pressure generating chamber 21 side. And the expansion state of this pressure generation chamber 21 is maintained over the supply period of the expansion maintenance element p22. After that, the piezoelectric element 24 is bent toward the pressure generation chamber 21 by applying the vibration damping contraction element p23. Due to the displacement of the piezoelectric element 24, the pressure generating chamber 21 is contracted to such an extent that ink is not discharged from the intermediate expansion volume to the contraction volume. As a result, a pressure vibration (counter vibration) having a phase different from that of the residual vibration due to the vibration suppression drive pulse Pd (preferably opposite in phase) is generated, and the residual vibration is reduced by the counter vibration.

  In this flushing operation, the control unit 57 repeatedly applies the flushing drive signal generated from the drive signal generation circuit 58 to the piezoelectric element 24, thereby continuously ejecting a predetermined number of inks to each nozzle 32. Is executed. This continuous idle discharge process is called a continuous flushing set. The pressure change due to the flushing operation acts on bubbles staying in the ink flow path. By repeating such a strong pressure change many times, minute bubbles dissolve in the ink. Thereby, minute bubbles that could not be discharged by the above-described suction operation or normal flushing operation can be discharged together with the ink.

  Here, when the pressure difference per unit time is increased in the flushing operation, the residual vibration is increased accordingly. If the flushing operation is repeated in a state where the residual vibration is not attenuated, the ejection becomes unstable, and there is a possibility that, for example, a mist may be generated and adhered to the nozzle surface. Further, when the next operation (recording operation, etc.) is performed after the flushing operation, a standby time is required until the residual vibration is attenuated to the extent that the next operation is not affected, and the operation speed is reduced accordingly. There was also a fear. In this respect, in the printer according to the present invention, the residual vibration is suppressed by generating the vibration suppression drive pulse Pd after the flushing drive pulse Pf, so that the ejection at the time of flushing can be stabilized and the above problems can be prevented. can do. Moreover, since the standby time for converging the residual vibration can be shortened by suppressing the residual vibration, the flushing operation can be performed at a higher frequency. As a result, the time required for maintenance can be shortened. Further, when other processing such as a normal recording operation is performed after the flushing operation, it is possible to shift to the next processing in a shorter time.

  If the flushing operation is executed for a predetermined cycle as described above, the control unit 57 stops the flushing operation (S5). After that, the nozzle forming surface is wiped by the wiper mechanism 15 (S6), and the ink adhering to the nozzle forming surface is wiped off. When the wiping is finished, a series of maintenance control is finished.

In addition, regarding the vibration suppression drive pulse Pd, in the first embodiment, an example in which the drive pulse does not eject ink is shown, but the present invention is not limited thereto. For example, as in the vibration suppression drive pulse Pd ′ in the second embodiment shown in FIG. 9, it is possible to employ a configuration in which residual vibration is suppressed while ejecting ink.
FIG. 9 is a diagram illustrating the configuration of the drive signal in the second embodiment. In the present embodiment, the reference potential Vx ′ is adjusted to a value lower than the contraction potential Vx in the above embodiment, for example, about 90% of Vx. Therefore, the drive voltage Vd ′ of the flushing drive pulse Pf ′ is lower than the drive voltage Vd of the flushing drive pulse Pf of the first embodiment. Further, the waveform of the damping drive pulse Pd ′ is different from the waveform of the damping drive pulse Pd in the first embodiment. Specifically, this vibration suppression drive pulse Pd ′ includes a vibration suppression expansion element p31, a vibration suppression expansion hold element p32, a vibration suppression discharge element p33, a vibration suppression contraction hold element p34, and a vibration suppression return element p35. Consists of. The damping expansion element p31 is a waveform element that changes from the reference potential Vx ′ to the damping expansion potential Vc ′ to expand the pressure generating chamber 21, and the damping expansion hold element p32 is constant at the damping expansion potential Vc ′. Waveform element. The damping discharge element p33 is a waveform element that changes steeply from the damping expansion potential Vc ′ to the contraction potential Vx and thereby discharges ink from the nozzle 32, and the damping contraction hold element p34 sets the contraction potential Vx. It is a waveform element that is maintained for a predetermined period. The vibration damping return element p35 is a waveform element that restores the electric potential with a constant gradient that does not cause ink to be ejected from the contraction potential Vx to the reference potential Vx ′ and converges the residual vibration after ejection by the vibration damping ejection element p33. .

  In the second embodiment, ink is ejected by the vibration suppression drive pulse Pd ′ at a timing (or a timing close to it) that is in an opposite phase to the residual vibration generated during the flushing by the flushing drive pulse Pf ′. Further, an interval between the flushing drive pulse Pf ′ and the vibration suppression drive pulse Pd ′ is determined. Thereby, the residual vibration can be suppressed while discharging the ink and discharging the bubbles.

  FIG. 10 is a diagram illustrating the configuration of the drive signal in the third embodiment. In the present embodiment, the flushing drive pulse has the same configuration as the flushing drive pulse Pf in the first embodiment, and the damping drive pulse has the same configuration as the damping drive pulse Pd ′ in the second embodiment. It is. On the other hand, the present embodiment is characterized in that an element for adjusting the potential is generated before and after the damping drive pulse Pd ′. Specifically, a potential adjustment element p41 that gently lowers the potential from the contraction potential Vx to the damping reference potential Vc "between the flushing driving pulse Pf and the damping driving pulse Pd ', and the damping reference potential Vc. And a first reference potential hold element p42 for maintaining “a” for a certain period of time. In addition, after the vibration suppression drive pulse Pd ′, a second reference potential hold element p43 that maintains the vibration suppression reference potential Vc ″ for a certain period of time, and a potential for gently returning the potential from the vibration suppression reference potential Vc ″ to the contraction potential Vx. A return element p44 is generated. In the third embodiment, the driving voltage Vd of the flushing driving pulse Pf can be set to a value higher than the driving voltage Vd ′ of the flushing driving pulse Pf ′ in the second embodiment, so that the bubble discharging effect is achieved. Residual vibration can be reduced while further improving.

  In each of the above-described embodiments, the interval between the flushing drive pulse Pf and the vibration suppression drive pulse Pd is exemplified by the configuration determined according to the natural vibration period Tc for each head, but is not limited to this. It can also be determined based on information indicating ejection characteristics given to each head (for example, information on ejection amount for each nozzle array).

  In each of the above embodiments, the so-called flexural vibration type piezoelectric element 24 is exemplified as the pressure generating element. However, the present invention is not limited to this, and for example, a so-called longitudinal vibration type piezoelectric element can be employed. In this case, the illustrated drive signal has a waveform in which the potential change direction, that is, the top and bottom are inverted.

  Furthermore, in the above description, the ink jet printer 1 which is a kind of liquid ejecting apparatus has been described as an example, but the present invention can also be applied to other liquid ejecting apparatuses in which residual bubbles are a problem. For example, a display manufacturing apparatus that manufactures color filters such as liquid crystal displays, an electrode manufacturing apparatus that forms electrodes such as organic EL (Electro Luminescence) displays and FEDs (surface emitting displays), and chips that manufacture biochips (biochemical elements) The present invention can also be applied to a manufacturing apparatus and a micropipette that supplies an accurate amount of a very small amount of sample solution.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 4 ... Recording head, 16 ... Capping mechanism, 21 ... Pressure generating chamber, 24 ... Piezoelectric element, 32 ... Nozzle, 37 ... Cap member, 51 ... Printer controller, 52 ... Print engine, 57 ... Control part, 58 ... Drive signal generation circuit

Claims (4)

A liquid discharge head capable of discharging a liquid from the nozzle by driving a pressure generating element that fluctuates the volume of the pressure generating chamber communicating with the nozzle, and a drive signal including a drive pulse for driving the pressure generating element at a constant cycle. A liquid ejection device including a drive signal generation unit for generating,
The drive signal generator is
An expansion element that expands the pressure generation chamber by changing from a contraction potential corresponding to a state in which the pressure generation chamber is contracted to an expansion potential corresponding to a state in which the pressure generation chamber is expanded, and from the expansion potential to the contraction potential And a contraction element that contracts the pressure generation chamber to generate a flushing drive pulse whose drive voltage voltage change is larger than that of a discharge drive pulse used for controlling liquid ejection onto a recording medium. Configured,
A liquid ejection apparatus, wherein after the flushing drive pulse, a vibration suppression drive pulse that suppresses residual vibration caused by driving the pressure generating element with the flushing drive pulse is generated.   The liquid ejection apparatus according to claim 1, wherein an interval between the flushing drive pulse and the vibration suppression drive pulse is determined based on a natural vibration period Tc of the liquid in the pressure generation chamber.   The vibration suppression drive pulse includes at least a vibration suppression expansion element that expands the pressure generation chamber to such an extent that liquid is not discharged from the nozzle and a vibration suppression contraction element that contracts the pressure generation chamber to an extent that liquid is not discharged from the nozzle. The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is configured as follows.   The vibration suppression drive pulse includes at least a vibration suppression expansion element that expands the pressure generation chamber and a vibration suppression discharge element that contracts the pressure generation chamber and discharges liquid from the nozzle. The liquid ejection apparatus according to claim 1 or 2.

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