JP2011207078A - Liquid ejecting apparatus and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid ejecting apparatus that suppresses an ejection failure caused by liquid thickening, and a control method for the same.SOLUTION: The liquid ejecting apparatus includes: a recording head that imparts pressure variations into each pressure chamber due to operation of each piezoelectric vibrator to eject ink, charged in each pressure chamber, from each nozzle; a drive-signal generating circuit that drives each piezoelectric vibrator to generate a micro-vibration pulse which micro-vibrates the ink in each nozzle to an extent that the ink is not ejected from the nozzle; and a control part that causes micro-vibration of a meniscus by applying a micro-vibration pulse to the piezoelectric vibrator, which corresponds to the nozzle that is not allowed to eject the ink, during the execution of recording processing to recording paper. The control part is configured to execute flushing for recovering an ejection capability by ejecting ink at start of the recording or while directing the nozzles toward a capping member. The control part raises a voltage value Vh2 of a micro-vibration pulse for a return path when a prescribed period of time elapses from the end of the flushing higher than a voltage value Vh1 of a micro-vibration pulse for a forward path.

Description

  The present invention relates to a liquid ejecting apparatus including a liquid ejecting head such as an ink jet recording head, and a control method for the liquid ejecting apparatus.

  The liquid ejecting apparatus is an apparatus that includes a liquid ejecting head capable of ejecting (discharging) liquid and ejects various liquids from the liquid ejecting head. As a representative example of this liquid ejecting apparatus, for example, an ink jet recording head (hereinafter simply referred to as a recording head) as a liquid ejecting head is provided, and droplet-like ink is recorded on recording paper or the like from the nozzles of the recording head. 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 ejecting or landing on a medium (a target to be ejected) can be given. In recent years, liquid ejecting apparatuses are 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.

  The printer generates a drive signal including an ejection pulse, which is a kind of drive pulse, and applies (supplies) the generated ejection pulse to a pressure generating element (for example, a piezoelectric vibrator or a heating element). There is one configured to apply a pressure change to the liquid in the pressure chamber (pressure generation chamber) by driving, and to eject the liquid from a nozzle communicating with the pressure chamber using the pressure change.

  By the way, in a general printer, when the power is off or in a standby state where printing is not performed with the power on, the non-printing area where the nozzle forming surface of the recording head is out of the printing (recording) area It is sealed (capped) by a capping member provided on the surface. As a result, evaporation of the ink solvent from the nozzles is suppressed. However, during the printing operation (recording operation), the nozzle forming surface is released from the capping state, so that the meniscus in the nozzle is exposed to the atmosphere. For this reason, during the period when the capping member is released, the ink solvent gradually evaporates from the nozzle as time passes, so that the viscosity of the ink near the nozzle increases. When the viscosity of the ink becomes remarkable, there is a possibility that a problem (ejection failure) such as a decrease in the weight or flying speed of the ejected ink or an ejection of the ink may occur.

  In order to prevent such ink ejection failure, various maintenance processes are performed. For example, during a recording operation on a recording medium, the recording operation is interrupted every predetermined interval or every time a specified number of pages are printed, and provided on a capping member or a platen provided in a non-printing area. By moving the recording head to the ink receiving portion and causing the nozzles to face these capping members and the like, the droplets are ejected from the nozzles (discarding) (hereinafter referred to as flushing), thereby increasing the viscosity of the ink. Forced removal is done.

  In addition, during the recording operation on the recording medium, a fine vibration pulse that vibrates the meniscus in the nozzle so as not to eject the ink from the nozzle is applied to the pressure generating element, and the thickened ink near the meniscus and the ink on the pressure chamber side The fine vibration operation that suppresses the ejection failure by agitating the nozzles is performed on the nozzles that do not eject ink. In the printer configured to repeatedly apply the fine vibration pulse to the pressure generating element, for example, by gradually shortening the interval between the fine vibration pulses, the residual vibration of the meniscus caused by the fine vibration pulse generated previously. Is applied to the pressure generating element at the timing of canceling out, to thereby suppress the residual vibration of the meniscus as much as possible before the start of the recording operation executed after the application of the fine vibration pulse. A printer capable of ensuring ejection stability has been proposed (see, for example, Patent Document 1).

JP 2003-80702 A

  However, in recent years, so-called large format printers have been developed that can handle recording media of a size larger than the recording media compatible with printers used in general households. Since the moving distance becomes long, the above-mentioned flushing interval tends to become long during the recording operation. For this reason, even if fine vibration is performed on a nozzle with a low ejection frequency among the nozzles, it is difficult to reliably suppress the ink thickening even though the progress of the ink thickening can be delayed. there were.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid ejecting apparatus and a control method for the liquid ejecting apparatus that can suppress ejection failure due to liquid thickening. It is to provide.

In order to achieve the above object, a liquid ejecting apparatus according to an aspect of the present invention provides a liquid ejecting head that applies pressure fluctuation to a pressure chamber by the operation of a pressure generating unit, and ejects liquid filled in the pressure chamber from a nozzle;
A drive signal generator for driving the pressure generating means to generate a micro-vibration pulse that causes the liquid in the nozzle to vibrate to such an extent that the liquid is not ejected from the nozzle;
A control unit that applies the fine vibration pulse to the pressure generating unit corresponding to the nozzle that does not eject the liquid during the injection process on the landing target, and performs fine vibration of the meniscus,
The controller controls the micro-vibration pulse at the time when the ejection process is started or at the end of the ejection capacity recovery process aimed at recovering the ejection capacity by ejecting the liquid toward a region other than the landing target. The voltage value of the micro-vibration pulse is higher than the voltage value at a time when the injection process is started or when a predetermined time has elapsed from the end of the injection capacity recovery process.
Note that the recovery of the jetting ability is close to the state before liquid viscosity is thickened (ideally the state at the time of manufacturing) by jetting the liquid thickened by evaporation of the liquid solvent from the nozzle. This means that the liquid ejection capability, that is, the amount of liquid to be ejected and the flying speed are brought close to an ideal state in terms of design and specifications.
In addition, the “end point of the injection capacity recovery process” refers to the injection capacity recovery process executed last time of the injection capacity recovery processes executed intermittently between the start and end of the injection process. It means the end point.

  According to this configuration, the pressure generating means causes the pressure variation in the pressure chamber, the liquid ejecting head that ejects the liquid filled in the pressure chamber from the nozzle, and the pressure generating means is driven to remove the liquid in the nozzle. During the ejection process for the landing target, the fine vibration pulse is applied to the pressure generating means corresponding to the nozzle that does not eject the liquid. A control unit that performs fine vibrations of the meniscus, and the control unit is configured to perform fine control at the end of the injection capacity recovery process for injecting liquid toward the area other than the landing target and recovering the injection capacity. Since the voltage value of the micro-vibration pulse is higher than the voltage value of the vibration pulse when the predetermined time has elapsed since the end of the jetting capacity recovery process, the liquid can be more reliably It is possible to win. As a result, it is possible to suppress ejection failure due to liquid thickening. In particular, even in a configuration in which the interval between the jetting capacity recovery process and the next jetting capacity recovery process tends to be long, such as a printer called a so-called large format, it is possible to suppress thickening at the nozzle.

In the above configuration, a scanning mechanism for reciprocating the liquid ejecting head with respect to the landing target is provided,
The controller preferably increases the voltage value of the micro-vibration pulse at the time of the return path from the voltage value of the micro-vibration pulse at the time of the forward path at a timing at which the moving direction of the liquid ejecting head is switched from the forward path to the return path.

  According to this configuration, the scanning mechanism that reciprocates the liquid ejecting head with respect to the landing target is provided, and the control unit switches the moving direction of the recording head from the forward path to the backward path, and the voltage value of the minute vibration pulse during the forward path Further, since the voltage value of the fine vibration pulse at the time of the return path is increased, the voltage of the fine vibration pulse can be changed without extending the injection processing time and without increasing the load on the circuit. That is, since the liquid is not ejected during the period in which the forward path and the backward path are switched, the voltage change process of the fine vibration pulse is not interrupted during the ejection process by changing the voltage of the fine vibration pulse during this period. . Accordingly, it is possible to prevent the time for the injection process from becoming long. Further, at this timing, since the liquid ejection is not performed, the processing of the control unit can be assigned to the voltage change of the fine vibration pulse, so that an increase in circuit load can be suppressed.

Further, the control method of the liquid ejecting apparatus of the present invention includes a liquid ejecting head that gives a pressure fluctuation to the pressure chamber by the operation of the pressure generating means, and ejects the liquid filled in the pressure chamber from the nozzle,
During the ejection process for the landing target, the generated fine vibration pulse is applied to the pressure generating unit corresponding to the nozzle that does not eject the liquid, thereby driving the pressure generating unit to discharge the liquid in the nozzle from the nozzle. A control method of a liquid ejecting apparatus that finely vibrates a meniscus to the extent that liquid is not ejected,
End of the jetting ability recovery process is more than the voltage value of the micro-vibration pulse at the end of the jetting ability recovery process aiming to recover the jetting capacity by jetting the liquid toward the region other than the landing target. The voltage value of the micro-vibration pulse is increased at a time when a predetermined time has elapsed from the time.
According to this control method, pressure fluctuation caused by applying a fine vibration pulse to the pressure generating means can be applied to the meniscus that thickens in each nozzle without excess or deficiency, and injection defects can be efficiently suppressed. Can do. In particular, during the execution of the injection process, it is possible to suppress thickening at a nozzle with a low injection frequency, and thus it is possible to prevent an injection failure at the nozzle.

FIG. 2 is a perspective view illustrating a schematic configuration of a printer. FIG. 3 is a perspective view of the recording head as viewed from the pressure generating unit side. FIG. 3 is a cross-sectional view of a main part for explaining the configuration of a recording head. 2 is a block diagram illustrating an electrical configuration of a printer. FIG. It is a figure explaining the relationship between the viscosity of an ink, and the fine vibration drive voltage in printing. It is a wave form diagram explaining the structure of a minute vibration pulse, Comprising: (a) is a forward vibration pulse, (b) is a backward vibration pulse. It is a figure explaining the switching timing of a drive voltage. It is a table | surface explaining the experimental result which measured the ejection failure occurrence rate with respect to the drive voltage at the time of a dot missing test | inspection, and the width of printed matter. It is a figure explaining the relationship between the viscosity of the ink in 2nd Embodiment, and the fine vibration drive voltage in printing.

  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, a case where the liquid ejecting apparatus of the present invention is applied to the ink jet recording apparatus shown in FIG.

  The printer 1 has a recording head 2 which is a kind of liquid ejecting head, a carriage 4 to which an ink cartridge 3 for storing ink (a kind of liquid in the present invention) is detachably attached, and a lower part of the recording head 2. A carriage movement mechanism 7 (corresponding to the scanning mechanism in the present invention) for reciprocating the arranged platen 5 and the carriage 4 on which the recording head 2 is mounted in the paper width direction of the recording paper 6 (a kind of landing target); A paper feed mechanism 8 that conveys the recording paper 6 in a paper feed direction that is a direction orthogonal to the direction is roughly configured. Here, the paper width direction is the main scanning direction (head scanning direction indicated by symbol X in FIG. 1), and the paper feed direction is orthogonal to the sub-scanning direction (head scanning direction indicated by symbol Y in FIG. 1). Direction).

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction X, and is moved along the guide rod 9 in the main scanning direction X by the operation of the carriage moving mechanism 7. It is configured. The position of the carriage 4 in the main scanning direction X is detected by the linear encoder 10, and a detection signal is transmitted to the control unit 46 (see FIG. 4) as position information. Thereby, the control unit 46 can control the recording operation (jetting operation) and the like by the recording head 2 while recognizing the scanning position of the carriage 4 (recording head 2) based on the position information from the linear encoder 10. .

  A home position serving as a scanning base point is set in an end area outside the recording area within the moving range of the carriage 4 (right side in FIG. 1). The home position in this embodiment includes a capping member 12 (corresponding to a region other than the landing target in the present invention) that seals the nozzle formation surface (nozzle plate 36: see FIG. 3) of the recording head 2, and the nozzle formation surface. A wiper member 13 for wiping is disposed. The printer 1 is moved forward (indicated by reference numeral X1 in FIG. 1 and corresponding to the forward path in the present invention) when the carriage 4 (recording head 2) moves from the home position toward the opposite end. Characters, images, and the like are recorded on the recording paper 6 in both directions when the carriage 4 returns from the opposite end to the home position side (indicated by reference numeral X2 in FIG. 1 and corresponds to the return path in the present invention). In other words, so-called bidirectional recording is possible. The capping member 12 is a tray-like member having an open top surface, and is made of an elastic member such as rubber or elastomer, and has a liquid-absorbing member made of a liquid-absorbing material such as felt or sponge that can absorb ink therein. (Not shown) is laid. The capping member 12 configured in this manner will be described later for eliminating (removing) thickened ink and bubbles remaining in the ink by ejecting (discarding) ink droplets (a kind of ink). Used as an ink receiving portion for receiving ink droplets in flushing (a type of ejection capability recovery process). In addition to the capping member 12, there is a configuration in which an ink receiving portion that receives ink droplets at the time of flushing is provided at the end of the platen 5 opposite to the home position side.

  Next, the configuration of the recording head 2 will be described. Here, FIG. 2 is a perspective view of the recording head 2 as viewed from the pressure generating unit side, and FIG. 3 is a cross-sectional view of the main part of the recording head 2. The illustrated recording head 2 is composed of a pressure generating unit (or actuator unit) 19 and a flow path unit 20, and these are integrated in an overlapped state. The pressure generating unit 19 includes a piezoelectric vibrator 26 (corresponding to pressure generating means in the present invention), a diaphragm 27, and a pressure generating chamber plate 22 for partitioning a pressure chamber (pressure generating chamber) 21, It is comprised by integrating by baking etc.

  Further, the flow path unit 20 is configured by stacking a supply port forming plate 32 in which the supply port 30 and the second communication port 31 are formed, and a reservoir plate 35 in which the reservoir 33 and the first communication port 34 are formed. Yes. A nozzle plate 36 having nozzles 28 is provided on the surface of the reservoir plate 35 opposite to the supply port forming plate 32.

  The diaphragm 27 is made of an elastic plate material. A plurality of piezoelectric vibrators 26 are disposed on the outer surface of the vibration plate 27 opposite to the pressure chambers 21 in a state corresponding to the pressure chambers 21. The illustrated piezoelectric vibrator 26 is a vibrator in a flexural vibration mode, and is configured with a piezoelectric body 26c sandwiched between a drive electrode 26a and a common electrode 26b. When a drive signal is applied to the drive electrode of the piezoelectric vibrator 26, an electric field corresponding to the potential difference is generated between the drive electrode 26a and the common electrode 26b. This electric field is applied to the piezoelectric body 26c, and is deformed according to the strength of the electric field applied with the piezoelectric body 26c.

  The pressure generating chamber plate 22 is formed of a thin ceramic material plate having a thickness suitable for forming the pressure chamber 21, for example, alumina, zirconia, or the like, and an empty portion for partitioning the pressure chamber 21 is in the thickness direction of the plate. It is formed in a state of penetrating through. The pressure chambers 21 are elongated holes that are formed in a row at a constant pitch that is the same as the pitch of the nozzles 28 of the nozzle plate 36 and that are elongated in the left-right direction orthogonal to the row direction.

  The supply port forming plate 32 is a thin plate-like member made of a metal material such as stainless steel. As shown in FIG. 3, the supply port forming plate 32 has a plurality of supply ports 30 penetrating in the thickness direction. A second communication port 31 penetrating in the plate thickness direction is formed so as to correspond to the first communication port 34 of the reservoir plate 35. The supply port 30 is a portion that provides fluid resistance (flow resistance) to ink in the ink flow path (liquid flow path). Regarding the supply port 30, the diameter on the reservoir 33 side is wider than the diameter on the pressure chamber 21 side. The supply port 30 is formed by press working. The supply port forming plate 32 is formed with a compliance portion 38 whose thickness is sufficiently thinner than other portions. The compliance portion 38 is manufactured by recessing the region corresponding to the reservoir 33 of the reservoir plate 35 by etching or the like from the surface opposite to the reservoir 33 in the plate thickness direction to form a recess 39.

  The reservoir plate 35 is a plate-like member made of a metal material such as stainless steel. The reservoir plate 35 is formed with an empty portion for partitioning the reservoir 33 in a state of penetrating the plate thickness direction. This empty portion defines the reservoir 33. The reservoir 33 is a part that functions as a liquid chamber common to the plurality of pressure chambers 21, and is provided for each ink type (color), and stores the ink supplied from the ink cartridge 3. The reservoir plate 35 is formed with a plurality of first communication ports 34 penetrating in the plate thickness direction so as to correspond to the second communication ports 31.

  The nozzle plate 36 is a plate-like member made of a metal material such as stainless steel. In this nozzle plate 36, a plurality of nozzles 28 are arranged in a row to form nozzle rows (nozzle groups). In this embodiment, the nozzle rows are opened at a constant pitch (for example, 180 dpi). It is composed of 180 nozzles 28. The nozzle plate 36 may be made of an organic plastic film or the like in addition to the metal material.

  Each plate member is integrally joined between the pressure generating unit 19 and the supply port forming plate 32, between the supply port forming plate 32 and the reservoir plate 35, and between the reservoir plate 35 and the nozzle plate 36. It becomes. Thereby, as shown in FIG. 3, the reservoir 33 and the other end of the pressure chamber 21 communicate with each other through the supply port 30. In addition, one end of the pressure chamber 21 and the nozzle 28 communicate with each other through the first communication port 34 of the reservoir plate 35 and the second communication port 31 of the supply port forming plate 32. A series of ink flow paths (liquid flow paths) that connect the pressure generating unit 19 and the nozzles 28 from the reservoir 33 through the pressure chambers 21 is formed for each nozzle 28.

  In the recording head 2 configured as described above, the corresponding pressure chamber 21 contracts or expands by deforming the piezoelectric vibrator 26, and pressure fluctuations occur in the ink in the pressure chamber 21. By controlling the ink pressure, the ink can be ejected (discharged) from the nozzle 28. When the pressure chamber 21 having a constant volume is preliminarily expanded before ink is ejected, ink is supplied into the pressure chamber 21 from the reservoir 33 through the supply port 30. Further, when the pressure chamber 21 is rapidly contracted after the preliminary expansion, ink is ejected from the nozzle 28.

Next, the electrical configuration of the printer 1 will be described.
FIG. 4 is a block diagram illustrating an electrical configuration of the printer 1. The printer 1 in this embodiment is schematically configured by a printer controller 40 and a print engine 41. The printer controller 40 stores an external interface (external I / F) 42 to which print data from an external device such as a host computer is input, a RAM 43 that stores various data, a control program for various controls, and the like. ROM 44, nonvolatile storage element 45 such as EEPROM or flash ROM, control unit 46 that performs overall control of each unit according to a control program stored in ROM 44, oscillation circuit 47 that generates a clock signal, A drive signal generation circuit 48 (corresponding to a drive signal generation unit in the present invention) that generates a drive signal COM to be supplied to the recording head 2, and dot pattern data and drive signals obtained by developing print data for each dot An internal interface (internal I / F) 4 for outputting to the recording head 2 It is equipped with a door. The print engine 41 includes the recording head 2, a carriage moving mechanism 7, and a paper feeding mechanism 8.

  The control unit 46 controls ink droplet ejection by the recording head 2 and other components of the printer 1 according to an operation program stored in the ROM 44. The control unit 46 converts print data input from an external device via the external I / F 42 into ejection data used for ejecting ink droplets in the recording head 2. The converted ejection data is transferred to the recording head 2 through the internal I / F 49, and the recording head 2 controls the supply of the drive signal COM to the piezoelectric vibrator 26 based on the ejection data, thereby ejecting ink droplets. That is, a recording operation (jetting operation) is performed.

  Here, the viscosity increase of the ink in the ink flow path of the recording head 2 will be described. In the printer 1, the meniscus (free surface) exposed from the nozzles 28 is exposed to air as time passes, and the ink solvent is evaporated to increase the viscosity of the ink. That is, the viscosity of the ink in the vicinity of the meniscus is particularly high at the time of manufacture. May rise more. Then, when the viscosity of the ink is increased in this way, there is a possibility that the ink is not ejected from the nozzle 28, and there is a possibility that ejection failure such as so-called dot omission or flight bending occurs. For this reason, the printer 1 is performing a recording process (printing process, corresponding to the ejecting process in the present invention) in which ink is ejected onto the recording paper 6 by using a recording drive pulse to print a text or an image. At regular intervals, the recording head 2 is moved to a position for receiving ink called a flushing point provided on the capping member 12 or the platen at the home position and is made to be opposed to the ink receiving portion. Execute. In this flushing, the thickened ink is forcibly removed by repeatedly applying a flushing drive pulse to the piezoelectric vibrator 26.

  The recording drive pulse is generated from the drive signal generation circuit 48 when the normal print mode for printing text, images, etc. on the recording paper 6 is set. For example, the recording drive pulse drops (changes) the potential with a constant gradient. ) To expand (expand) the pressure chamber 21, an expansion maintaining element that maintains the terminal potential of the expansion element for a certain period of time, and a potential that increases (changes) at a constant gradient to contract (compress) the pressure chamber 21. And at least a contraction element. Then, each element of the recording drive pulse is applied to the piezoelectric vibrator 26, whereby the piezoelectric vibrator 26 is driven and ink is ejected from the nozzle 28. Note that the recording drive pulse in the present invention may include other elements. For example, it is possible to adopt a configuration in which a damping element for damping residual vibration is inserted after the contraction element.

FIG. 5 is a diagram for explaining the relationship between the viscosity of the ink and the in-print micro-vibration driving voltage, in which the change in the viscosity of the ink is shown on the upper side and the change in the drive voltage is shown on the lower side in the figure.
The printer 1 according to the present invention is configured to perform flushing (indicated by reference numeral FL in FIG. 5) each time the recording head 2 is moved to the capping member 12 at the home position while the recording process is being executed. ing. That is, the printer 1 executes the flushing FL every time the recording head 2 executes the forward path and backward path recording processes. In FIG. 5, the illustration of the processing time of the flushing FL is omitted. The flushing driving pulse used for the flushing FL drives the piezoelectric vibrator 26 for the purpose of restoring the jetting ability and seals the area other than the recording paper 6 from the nozzle 28, that is, the nozzle forming surface in this embodiment. This is a drive pulse for ejecting ink toward the capping member 12 in the state. In the flushing FL using the flushing drive pulse of the present invention, the injection for one shot in the flushing FL is used as the flushing unit [seg] (flushing segment). In the flushing FL, the flushing drive pulse is repeatedly applied (supplied) to the piezoelectric vibrator 26 by a predetermined number of flushing segments (for example, the total number to several hundred segments), so that the ink in the ink flow path 28 is discharged.

  Incidentally, as shown in the upper side of FIG. 5, the ink thickens in the vicinity of the nozzles 28 with the passage of time from the start of execution of the recording process or the end of the previous flushing FL. Then, by performing the above flushing FL every time the recording head 2 reciprocates, the thickened ink (Vis2) in the vicinity of the meniscus is ejected from the nozzle 28, whereby the ink on the pressure chamber 21 side is ejected into the nozzle 28. The ink that is newly supplied and thickened in the nozzle 28 is replaced with ink having a viscosity (Vis1) before thickening. However, as shown in the upper graph of FIG. 5, it is ideal that the viscosity of the ink decreases to the original viscosity every time flushing is performed, but during the recording process, the ink in the nozzles 28 increases in viscosity. It is difficult to reliably prevent ink thickening only by flushing.

  Therefore, in the printer 1 of the present invention, the drive signal generation circuit 48 generates the micro-vibration pulse P that causes the meniscus to vibrate so that the ink in the nozzle 28 is not ejected from the nozzle 28 by driving the piezoelectric vibrator 26. The control unit 46 is configured to apply the fine vibration pulse P to the piezoelectric vibrator 26 corresponding to the nozzle 28 that does not eject ink during the execution of the forward path recording process and the backward path recording process. ing. In addition, even in this type of conventional printer, there is a printer in which so-called fine vibration in printing is performed in which fine vibration is performed using a fine vibration pulse to a nozzle to which ink is not ejected during execution of a recording process.

  However, for example, in a so-called large format printer, since the moving distance of the recording head becomes long, the interval for performing the flushing during the recording operation tends to become long. For this reason, it is difficult to reliably prevent the ink from thickening even if the fine vibration in printing is performed. In particular, in a nozzle that has a low ejection frequency (or that never ejects ink) among the nozzles, even if fine vibration is performed, the thickening of the ink proceeds more significantly than a nozzle that has a high frequency of ink ejection. Even if the progress of the thickening of the ink can be delayed, it has been more difficult to reliably suppress the thickening of the ink. For this reason, during the recording process, the ink viscosity is different for each nozzle 28.

  Therefore, the printer 1 of the present invention is characterized in that the control unit 46 changes (increases) the drive voltage Vh of the fine vibration pulse P according to the viscosity of the ink. Specifically, the drive voltage of the micro-vibration pulse P at a time when a predetermined time has passed from the value of the drive voltage Vh of the micro-vibration pulse P at the time when the recording process is started or at the end of the flushing FL. It is configured to increase the value of Vh. More specifically, the driving voltage of the micro-vibration pulse P2 for performing micro-vibration during the execution of the backward recording process is higher than the driving voltage Vh of the micro-vibration pulse P1 for performing micro-vibration during the execution of the outward recording process. It is comprised so that Vh may become high. For this reason, the drive signal generation circuit 48 in the present embodiment is configured so that the drive voltage Vh is higher than the forward vibration pulse P1 generated during the forward path X1 for executing the forward recording process and the forward vibration pulse P1. (Twice in the present embodiment) are set, and two types of micro vibration pulses P are generated, including the micro vibration pulse P2 for the return path generated at the time of the return path X2 for executing the return path recording process. The control unit 46 is configured to switch the slight vibration pulse P from the forward fine vibration pulse P1 to the backward fine vibration pulse P2 when switching from the forward recording process to the backward recording process.

  The forward micro-vibration pulse P1 is a trapezoidal pulse signal, and the potential difference (drive voltage) between the reference potential VB and the lowest potential VL1 is set to Vh1 (eg, 5.0 V). This forward vibration pulse P1 has a reference potential VB at the start potential and a minimum potential VL1 at the end potential, and drops the potential with a constant gradient from the reference potential VB to the minimum potential VL1 during a time width t1 (for example, 5 μs). The first pulse element p11 to be generated, the second pulse element p12 that maintains the lowest potential VL1 that is the rear end potential of the first pulse element p11 for a certain period of time (for example, 2 μs), and the start potential is the lowest potential VL1, the terminal potential is the reference potential VB, and is composed of a third pulse element p13 that increases the potential with a constant potential difference Vh1 during a time width t3 (for example, 5 μs). Since this waveform is a slight vibration within printing, the reference potential VB is the intermediate potential VC of the printing waveform.

  On the other hand, the backward vibration pulse P2 is a trapezoidal pulse signal, and the forward vibration pulse P2 is set such that the lowest potential VL2 is lower than the lowest potential VL1 of the forward vibration pulse P1. Different from P1. In other words, the return path vibration pulse P2 is set so that the drive voltage Vh2 is higher than the drive voltage Vh1 of the forward path vibration pulse P1 (for example, 10 V which is twice Vh1). The return vibration pulse P2 has a reference potential VB at the start potential and a minimum potential VL2 at the end potential, and drops the potential with a constant gradient from the reference potential VB to the minimum potential VL2 during a time width t1 (for example, 5 μs). The first pulse element p21 to be generated, the second pulse element p22 that maintains the lowest potential VL2 that is the rear end potential of the first pulse element p21 for a certain period of time (for example, 2 μs), and the start potential is the lowest potential VL2, the terminal potential is the reference potential VB, and is composed of a third pulse element p23 that increases the potential with a constant potential difference Vh2 during a time width t3 (for example, 5 μs). Since this waveform is a slight vibration within printing, the reference potential VB is the intermediate potential VC of the printing waveform.

  Then, the control unit 46 in the present embodiment switches the forward path fine vibration pulse P1 to the backward path fine vibration pulse P2 at the timing of switching the moving direction of the recording head 2 from the forward path X1 to the return path X2. On the other hand, the control unit 46 switches the return path fine vibration pulse P2 to the forward path fine vibration pulse P1 at the timing of switching the moving direction of the recording head 2 from the return path X2 to the forward path X1. That is, the control unit 46 increases the drive voltage Vh of the fine vibration pulse P from Vh1 at the time of the forward path X1 to Vh2 at the time of the return path X2 at the timing of switching the moving direction of the recording head 2 from the forward path X1 to the return path X2. That is, since the recording process is performed on the forward path X1 immediately after the recording process start time or the flushing end time point, the drive voltage of the micro vibration pulse P (forward micro vibration pulse P1) is set to Vh1 at this time. When a predetermined time has elapsed from the start of processing or the end of flushing and the recording process is switched to the return path X2, the driving voltage of the micro vibration pulse P (return micro vibration pulse P) is higher than Vh2. Set to

FIG. 7 is a diagram for explaining the switching timing of the drive voltage Vh.
Next, the timing for switching the forward vibration pulse P1 to the return vibration pulse P2 will be described more specifically. In the recording process of the present embodiment, the meniscus in the nozzle 28 is slightly vibrated during the period outside the recording process between the forward recording process period in which the outward recording process is performed and the backward recording process period in which the backward recording process is performed. There are provided a fine vibration period outside the recording process executed for the purpose and a fine vibration period before the backward recording process executed before the backward recording process is executed. Then, the control unit 46 uses the forward path within the period from the end of the forward recording process period during which the forward path recording process is performed to before the fine vibration period before the backward recording process, that is, within the fine vibration period outside the recording process (for example, 0.8 ms). The fine vibration pulse P1 is switched to the backward vibration pulse P2.

  By switching the fine vibration pulse P during the fine vibration period outside the recording process, the voltage of the fine vibration pulse P can be changed without extending the recording processing time and without increasing the load on the circuit. In other words, since ink is not ejected during the period when the forward path and the return path are switched, the voltage change process of the fine vibration pulse is not interrupted during the recording process by changing the voltage of the fine vibration pulse during this period. . Accordingly, it is possible to prevent the time for the injection process from becoming long. Further, at this timing, the processing of the control unit 46 can be assigned to the voltage change of the minute vibration pulse because the processing such as the development of the print data is not performed because the ink is not ejected. Thereby, an increase in circuit load can be suppressed.

  In the present embodiment, the forward fine vibration pulse P1 is changed to the backward fine vibration pulse at the timing before and after the recording head 2 decelerating after the forward recording process on the recording paper 6 is stopped (that is, the moving direction is switched). You may employ | adopt the structure which switches to P2. According to this configuration, the fine vibration pulse P can be switched while avoiding the timing at which the meniscus vibrates due to the deceleration of the recording head 2. As a result, it is possible to suppress the inconvenience that the meniscus vibration due to the deceleration of the recording head 2 is excited by the fine vibration outside the recording process and the ink is erroneously ejected from the nozzle 28.

  FIG. 8 shows the ejection failure occurrence rate with respect to the drive voltage Vh of the micro-vibration pulse P and the width [inch] of the printed matter (the actual printed area, not the dimension of the recording medium) during the ejection inspection (Bi-d). It is a figure explaining the experimental result which was done. In addition, “xx” in FIG. 8 indicates that an ejection failure has occurred in 11 or more nozzles, and “×” indicates that an ejection failure has occurred in 4 or more and 10 or less nozzles, “△” indicates that ejection failure has occurred in nozzles of 1 nozzle or more and 3 nozzles or less, and “◯” indicates that ejection of all nozzles 28 is good (no ejection failure occurs). Yes.

  As shown in FIG. 8, when neither the forward fine pulse P1 nor the fine return pulse P2 is applied to the piezoelectric vibrator 26 (first stage in FIG. 8), ink is ejected from the nozzle 28 at 17 inches or more. A so-called dot dropout that was not jetted occurred. Then, when the drive voltage Vh2 of the backward vibration pulse P2 is changed in a state where the drive voltage Vh1 of the forward vibration pulse P1 is set to 5.0 V (from the second stage to the fourth stage in FIG. 8). First, when the drive voltage Vh2 of the return path vibration pulse P2 is set to 5.0 V (the same value as Vh1), a dot dropout occurs when a printed matter of 44 inches or more is printed, and the return path vibration pulse P2 When the driving voltage Vh2 of P2 was set to 7.5V (1.5 times Vh1), dot missing occurred when printing a printed product of 100 inches or more. On the other hand, when the driving voltage Vh2 of the return path fine vibration pulse P2 was set to 10.0 V (twice Vh1), no dot omission occurred in the case where a printed matter of 100 inches or less was printed. In other words, it can be seen that the occurrence of injection failure can be suppressed by increasing the drive voltage Vh2 of the backward micro-vibration pulse P2 with respect to the drive voltage Vh1 of the forward micro-vibration pulse P1.

  As described above, the printer 1 according to the present embodiment includes the recording head 2 that applies pressure fluctuation in the pressure chamber 21 by the operation of the piezoelectric vibrator 26 and ejects ink filled in the pressure chamber 21 from the nozzles 28, and the piezoelectric vibration. A drive signal generation circuit 48 that generates a micro-vibration pulse P that drives the child 26 to slightly vibrate the ink in the nozzles 28 to the extent that the ink is not ejected from the nozzles 28, and ejects ink toward the recording paper 6. A control unit 46 that applies a micro-vibration pulse P to the piezoelectric vibrator 26 corresponding to the nozzle 28 that does not eject ink during the recording process, and performs micro-vibration of the meniscus. When the predetermined time has elapsed from the end of the flushing, the recovery voltage is less than the drive voltage Vh1 of the forward micro-vibration pulse P1 at the end of the forward path X1. Since it is set for high driving voltage Vh2 of the backward vibrating pulse P2 at time X2, it is possible to more reliably suppress the thickening of the ink. As a result, ejection failure due to ink thickening can be suppressed. In particular, even in a configuration in which the interval between the jetting capacity recovery process and the next jetting capacity recovery process tends to be long, such as a printer called a so-called large format, it is possible to suppress thickening at the nozzle.

  By the way, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the description of the scope of claims.

FIG. 9 is a diagram for explaining the relationship between the viscosity of the ink and the in-print fine vibration driving voltage in the second embodiment, showing the change in the viscosity of the ink on the upper side in the figure, and the driving voltage on the lower side in the figure. Shows changes.
In the first embodiment described above, the forward vibration pulse P1 set to the drive voltage Vh1 generated during the forward path X1 that is the end time of the flushing FL during the recording process, and the predetermined time from the end time of the flushing FL. In the second embodiment, the printer 1 according to the second embodiment is configured to be able to generate the return path micro-vibration pulse P2 set to the drive voltage Vh2 (Vh2> Vh1) generated during the return path X2. Is configured to generate a fine vibration pulse P that gradually increases the drive voltage Vh from the forward path X1 to the return path X2 at the end of the flushing FL during the recording process. According to this configuration, since the fine vibration pulse P having a voltage corresponding to the change in the viscosity of the ink can be applied to the piezoelectric vibrator 26, the forward fine vibration pulse P1 and the backward fine vibration pulse P2 are piezoelectrically vibrated. Pressure fluctuation due to application to the child 26 can be applied to the meniscus that thickens in each nozzle 28 without excess or deficiency, and injection failure can be efficiently suppressed.

  In each of the above embodiments, the so-called flexural vibration type piezoelectric vibrator 26 is exemplified as the pressure generating means. However, the present invention is not limited to this, and for example, a so-called longitudinal vibration type piezoelectric vibrator can be employed. is there. In this case, with respect to the exemplified drive signal, the waveform changes in the direction of potential change, that is, upside down.

  The above has been described by taking the printer 1 which is a type of liquid ejecting apparatus as an example, but the present invention can also be applied to other liquid ejecting apparatuses. 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 or the like.

DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording head, 6 ... Recording paper, 7 ... Carriage moving mechanism, 12 ... Capping member, 21 ... Pressure chamber, 26 ... Piezoelectric vibrator, 28 ... Nozzle, 46 ... Control part, 48 ... Generation of drive signal Circuit, P1: Outward vibration pulse, P2: Return vibration pulse, X: Main scanning direction, X1: Outward path, X2: Return path

Claims (3)

A liquid ejecting head that applies pressure fluctuation to the pressure chamber by the operation of the pressure generating means, and ejects the liquid filled in the pressure chamber from the nozzle;
A drive signal generator for driving the pressure generating means to generate a micro-vibration pulse that causes the liquid in the nozzle to vibrate to such an extent that the liquid is not ejected from the nozzle;
A control unit that applies the fine vibration pulse to the pressure generating unit corresponding to the nozzle that does not eject the liquid during the injection process on the landing target, and performs fine vibration of the meniscus,
The control unit performs the fine vibration at the time when the ejection process is started or when the liquid is ejected toward a region other than the landing target to end the ejection capacity recovery process for the purpose of restoring the ejection capacity. The liquid ejecting apparatus, wherein the voltage value of the micro-vibration driving pulse is higher than the voltage value of the pulse at a time when the ejection process is started or when a predetermined time has elapsed from the end of the ejection capacity recovery process. . A scanning mechanism for reciprocating the liquid ejecting head with respect to the landing target;
The control unit increases the voltage value of the micro-vibration pulse during the return path from the voltage value of the micro-oscillation pulse during the forward path at a timing when the moving direction of the liquid ejecting head is switched from the forward path to the return path. The liquid ejecting apparatus according to 1. A pressure ejecting means that gives a pressure variation in the pressure chamber, and includes a liquid ejecting head that ejects liquid filled in the pressure chamber from a nozzle;
During the ejection process for the landing target, the generated fine vibration pulse is applied to the pressure generating unit corresponding to the nozzle that does not eject the liquid, thereby driving the pressure generating unit to discharge the liquid in the nozzle from the nozzle. A control method of a liquid ejecting apparatus that finely vibrates a meniscus to the extent that liquid is not ejected,
From the voltage value of the micro-vibration pulse at the time when the ejection process is started or when the liquid is ejected toward a region other than the landing target to end the ejection capacity recovery process for the purpose of restoring the ejection capacity. And a method of controlling the liquid ejecting apparatus, wherein the voltage value of the micro-vibration pulse is increased at the time when the ejection process is started or when a predetermined time has elapsed from the end of the ejection capacity recovery process.

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