JP2008229890A - Liquid droplet ejection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent ink from drying by finely vibrating droplets near a nozzle in such a range that consumption energy and heat generation are not excessive. <P>SOLUTION: The ink in the nozzle is prevented from drying by applying waveforms 52 for fine vibration for finely vibrating meniscuses to actuators applying pressure to the ink in the pressure chamber. The waveforms 52 for fine vibration are applied to a plurality of actuators within one printing cycle while displacing application timings by predetermined delay times t5 to t8. The delay times is set such that pressure fluctuation becomes large by crosstalk. The pressure fluctuation becomes large by the crosstalk, thereby the drying preventing effect can be secured even though the number of the pulses of the waveform 52 for the fine vibration applied to the actuator is reduces. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a droplet ejecting apparatus having a nozzle for ejecting droplets.

  In a liquid droplet ejecting apparatus having a nozzle for ejecting liquid droplets and an actuator for applying pressure to the liquid to eject liquid droplets from the nozzle, the liquid in the vicinity of the nozzle is thickened or dried (hereinafter, both are summarized) And drying), the liquid in the nozzle may not be ejected normally as droplets. In order to prevent the liquid from drying in the vicinity of the nozzle, it is conceivable to drive the actuator to such an extent that droplets are not ejected from the nozzle to stir the liquid near the nozzle. Patent Document 1 has a pressure chamber and a nozzle communicating with the pressure chamber, and changes the volume of the pressure chamber in a predetermined cycle so that droplets are not ejected from the nozzle.

JP 2006-123452 A (Claim 1)

  However, the liquid in the vicinity of the nozzle is vibrated minutely so that the liquid droplets are not ejected from the nozzle. Therefore, in order to prevent drying, it is necessary to vibrate the liquid many times to generate sufficient convection in the liquid in the vicinity of the nozzle. is there. Therefore, the actuator must be driven many times. In this case, the heat generated by the actuator or the electric circuit for driving the actuator may be excessive. In addition, energy consumption for driving the actuator is increased.

  An object of the present invention is to provide a droplet ejecting apparatus capable of preventing drying by minutely vibrating a liquid in the vicinity of a nozzle within a range where consumption energy and heat generation do not become excessive.

  The droplet ejecting apparatus of the present invention includes a flow path unit having a plurality of nozzles and a plurality of pressure chambers communicating with the plurality of nozzles, respectively, and changing the volumes of the plurality of pressure chambers, thereby A plurality of actuators for applying pressure to the liquid in the pressure chamber; a drive means for applying an ejection drive pulse for ejecting droplets from the nozzles to each of the plurality of actuators; and a control for controlling the drive means Means. The control means causes the drive means to apply a fine vibration drive pulse for finely vibrating the meniscus of the liquid in the nozzle to the extent that the liquid droplets are not ejected from the nozzle to the actuator. The fine vibration drive pulse is applied to each of the plurality of actuators that have control means and are located apart from each other at a timing at which the pressure fluctuation generated in the meniscus becomes larger than when the single pulse is applied alone.

  When a plurality of actuators are driven almost simultaneously or sequentially, the volume, velocity, and the like of droplets ejected from a certain nozzle may be different from those when driven independently. Such a phenomenon is called crosstalk. It is considered that crosstalk is generated when vibration generated in one pressure chamber propagates to another pressure chamber. It has been confirmed by the present inventor that the influence of crosstalk varies depending on the timing of applying drive pulses to a plurality of actuators. Therefore, in the present invention, the micro-vibration driving pulse is applied to each actuator at such a timing that the pressure fluctuation generated in the meniscus becomes larger than when it is applied alone. That is, since the meniscus is vibrated greatly due to the influence of crosstalk, the effect of preventing drying can be ensured with a smaller number of pulses than in the case where the influence of crosstalk is small. On the other hand, the smaller the number of pulses applied to the actuator, the smaller the heat generated from the actuator and driving means, and the lower the energy consumption. Therefore, according to the present invention, it is possible to realize a configuration capable of preventing drying by minutely vibrating the liquid in the vicinity of the nozzle within a range where energy consumption and heat generation are not excessive.

  Further, in the present invention, the fine vibration control means causes the drive means to apply a plurality of fine vibration drive pulses less than all of the plurality of actuators, thereby causing the meniscus to be affected by crosstalk as described above. Can be vibrated greatly, and the effect of preventing drying can be secured. Further, at this time, due to the increase in crosstalk, pressure fluctuations caused by crosstalk may occur in pressure chambers corresponding to other actuators. In this case, it is possible to give a fine vibration to the nozzle meniscus without driving the actuator corresponding to the pressure chamber. Therefore, the number of actuators to which the fine vibration driving pulse is applied can be further reduced. According to this configuration, since the number of actuators to be driven is reduced, energy consumption and heat generation are suppressed as a whole.

  Further, in the present invention, the plurality of pressure chambers constitute a pressure chamber row extending along a predetermined direction, and the fine vibration control means is arranged at predetermined intervals with respect to the predetermined direction in the driving means. The effect of the invention according to claim 2 can be realized by applying the fine vibration driving pulse to the actuator corresponding to the pressure chamber. In addition, when pressure chambers are arranged in a row, if pressure is applied to a predetermined number of pressure chambers, pressure fluctuations due to crosstalk occur in the pressure chambers between them. There is no need to apply pressure (apply a micro-vibration drive pulse to the corresponding actuator). According to this configuration, since the number of actuators to be driven is reduced, energy consumption and heat generation are suppressed as a whole.

  Further, in the present invention, the plurality of pressure chambers constitute a plurality of pressure chamber rows extending in parallel with each other along a predetermined direction, and the fine vibration control means supplies the whole pressure to the driving means. The fine vibration driving pulse may be applied to the actuators corresponding to a plurality of the pressure chamber rows smaller than the number of chamber rows. Accordingly, as described above, the meniscus can be vibrated greatly due to the influence of crosstalk, and the effect of preventing drying can be ensured. Furthermore, when the pressure chambers are arranged in a plurality of rows, by applying pressure to the pressure chamber rows every predetermined number of rows, it is possible to cause pressure fluctuations due to crosstalk in the pressure chamber rows in between, There is no need to apply pressure for microvibration. According to this configuration, since the number of actuators to be driven is reduced, energy consumption and heat generation are suppressed as a whole.

  In the present invention, the plurality of pressure chambers are divided into a plurality of pressure chamber groups in a row direction of the pressure chambers, and the fine vibration control means corresponds to the drive means and the partial pressure chamber groups. The fine vibration driving pulse may be applied to each actuator. Accordingly, as described above, the meniscus can be vibrated greatly due to the influence of crosstalk, and the effect of preventing drying can be ensured. Furthermore, when the pressure chambers are divided into a plurality of pressure chamber groups and a part of the pressure chamber groups is arranged so as to sandwich the remaining pressure chamber group, by applying pressure to the part of the pressure chamber groups, Pressure fluctuations caused by crosstalk can be generated in the remaining pressure chamber groups sandwiched between them. According to this configuration, since the number of actuators to be driven is reduced, energy consumption and heat generation are suppressed as a whole.

  In the present invention, the fine vibration control means may cause the pressure fluctuation generated in the meniscus of the first actuator to be larger than when the fine vibration drive pulse is applied alone to the first actuator. The driving means applies the fine vibration driving pulse to the second actuator, and a predetermined time shorter than one printing cycle after the fine vibration driving pulse is applied to the second actuator. It is preferable that the fine vibration driving pulse is applied to the first actuator after elapse of time. According to this configuration, by applying a micro-vibration driving pulse to the two actuators with a predetermined time in between, the actuator can be driven so that the pressure fluctuation increases due to crosstalk.

  In the present invention, the ejection drive pulse is applied to the first actuator, and the second time after a predetermined time shorter than one print cycle has elapsed since the ejection drive pulse was applied to the first actuator. The absolute difference between the pressure fluctuations generated in the meniscus of the second actuator between when the injection drive pulse is applied to the actuator and when the injection drive pulse is applied alone to the second actuator When the value is smaller when the predetermined time is not zero than when the predetermined time is zero, the control means causes the driving means to move the first actuator relative to the first actuator. The ejection drive pulse is applied, and the time t has elapsed since the ejection drive pulse was applied to the first actuator. It is preferable to apply the ejection driving pulse to the second actuator after. According to this configuration, the actuator is driven so that the influence of the crosstalk is reduced when the ejection driving pulse is applied, and the actuator is so affected that the influence of the crosstalk is increased when the fine vibration driving pulse is applied. Is driven. Therefore, a configuration using the influence of crosstalk is realized when the droplets are jetted and the adverse effect of the crosstalk is suppressed and the droplets near the nozzle are vibrated minutely.

  In the present invention, a micro-vibration driving pulse is applied to each actuator corresponding to each pressure chamber at a timing at which the pressure fluctuation generated in the meniscus increases, and the meniscus is vibrated greatly due to the influence of crosstalk. The effect of preventing drying can be ensured. In addition, since the number of pulses is reduced, heat generation from the actuator and driving means is reduced, and energy consumption can be reduced.

  Hereinafter, a preferred embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a schematic configuration of an ink jet printer 1 which is an embodiment of a droplet ejecting apparatus according to the present invention. In the following description, the direction from the front toward the back toward FIG. 1 is defined as the downward direction, and the opposite direction is defined as the upward direction.

  A control unit 100 is installed in the inkjet printer 1 (hereinafter referred to as “printer 1”). The control unit 100 controls the operation of each unit in the printer 1. A carriage 9 and guide shafts 6 and 7 are installed inside the printer 1. The guide shafts 6 and 7 extend along the left-right direction in FIG. The carriage 9 is supported on the guide shafts 6 and 7 so as to be slidable along these.

  The carriage 9 supports a recording head 30 (droplet ejection head) and an ink tank 9b. In the recording head 30, a plurality of nozzles 15 are formed on the lower surface, and an ink tank 9a is connected thereto. Inside the printer 1 is stored an ink cartridge 5 that stores ink of each color, for example, black Bk, cyan C, magenta M, and yellow Y. The ink tank 9 a is connected to each ink cartridge 5 through a flexible ink supply tube 8. In the recording head 30, an ink flow path for introducing ink from the ink tank 9a to the nozzle 15 is formed as will be described later. As a result, the ink of each color supplied from the ink cartridge 5 to the ink tank 9a is supplied to each nozzle 15 via the ink flow path, and downward from the nozzle 15 as ink droplets (hereinafter referred to as ink droplets). Be injected.

  The carriage 9 is connected to an endless belt 11 spanned between a pulley of the carriage motor 10 and the pulley 11a, as is well known, and the right and left of FIG. Move back and forth in the direction. The printing paper P is transported by a known transport mechanism (not shown) in a direction perpendicular to the moving direction of the carriage 9 at a position below the recording head 30.

  Print pattern data corresponding to an image is transmitted to the control unit 100 from an external device such as a PC (personal computer). The control unit 100 drives the recording head 30 while controlling the transport mechanism and the carriage motor 10 based on print pattern data transmitted from a PC or the like, as will be described later, thereby printing an image corresponding to the print pattern data on the printing paper. Form on P.

  Further, the printer 1 has a flushing receiving member 4. The flushing receiving member 4 is disposed below the guide shafts 6 and 7 on the left outer side of the sheet conveyance area. The flushing receiving member 4 accommodates therein a porous ink absorbing material such as urethane foam. When the carriage 9 moves to a position (flushing area) where the recording head 30 outside the paper conveyance area faces the flushing receiving member 4 and ink droplets are ejected from the recording head 30, ink absorption in the flushing receiving member 4 is absorbed. Ink drops are absorbed by the material.

  The printer 1 also has a recovery device 2. The recovery device 2 is disposed below the guide shafts 6 and 7 on the right side of the sheet conveyance area. The recovery device 2 includes a suction cap (not shown) that can be attached to and detached from the nozzle surface of the recording head 30 and a suction pump (not shown) connected to the suction cap, as is well known. When the carriage 9 moves to a position (recovery area) where the recording head 30 outside the sheet conveyance area faces the suction cap and the nozzle surface of the recording head 30 is covered by the suction cap, recording is performed by driving the suction pump. Ink in the nozzles of the head 30 is sucked.

  The printer 1 has a wiper device 3. After the above suction operation, when the carriage 9 moves into the paper transport area, the wiper device 3 wipes the nozzle surface of the recording head 30 as is well known.

  FIG. 2 is a lower surface (nozzle surface) view of the recording head 30. The recording head 30 has a plurality of nozzles 15, and each nozzle 15 is opened on the lower surface. The nozzles 15 are arranged along the longitudinal direction of the recording head 30, and five nozzle rows 35M, 35C, 35Y and 35Bk are formed at intervals in a direction perpendicular to the row direction. Ink droplets of the same color are ejected from the nozzles 15 belonging to each nozzle row. From the nozzle rows 35M, 35C, 35Y and 35Bk, ink droplets of four colors of magenta M, cyan C, yellow Y and black Bk are ejected, respectively. In the present embodiment, two rows of nozzle rows 35Bk are provided.

  A plurality of pressure chambers 16 in which ink is stored are formed inside the recording head 30. The pressure chamber 16 has a long shape in a direction orthogonal to the row direction of the nozzles. There is a one-to-one correspondence between the pressure chamber 16 and the nozzle 15. Each pressure chamber 16 is arranged in a row corresponding to and parallel to the nozzle rows 35M, 35C, 35Y and 35Bk. Thereby, the pressure chamber rows 36M, 36C, 36Y and 36Bk are formed. The pressure chambers 16 belonging to the pressure chamber rows 36M, 36C, 36Y and 36Bk correspond to the nozzles 15 belonging to the nozzle rows 35M, 35C, 35Y and 35Bk, respectively. In the present embodiment, two pressure chamber rows 36Bk corresponding to the two nozzle rows 35Bk are provided.

  Hereinafter, the internal configuration of the recording head 30 will be described in more detail with reference to FIG. FIG. 3 is a longitudinal sectional view of the recording head 30 taken along line III-III in FIG. The recording head 30 has a flow path unit 20 and an actuator unit 31 bonded to the upper surface of the flow path unit 20 with an adhesive. A flexible flexible wiring board 40 is electrically joined to the upper surface of the actuator unit 31.

  The channel unit 20 is configured by stacking a plurality of plates 20a to 20f. Each of the plates 20a to 20f is formed with a plurality of through holes that form ink flow paths. The through holes formed in the plates 20c and 20d constitute a manifold channel 14 for each row of pressure chambers. These manifold channels 14 are connected to the ink tank 9a in a region not shown.

  Each through-hole formed in the uppermost plate 20 a in the flow path unit 20 constitutes each pressure chamber 16. Each through hole formed in the lowermost plate 20 f constitutes each nozzle 15. By laminating the plates 20a to 20f, these through holes communicate with each other to form an ink flow path from the manifold flow path 14 to the nozzles 15 via the plurality of pressure chambers 16 in each row.

  The actuator unit 31 has a structure in which a plurality of piezoelectric ceramic layers 31a such as PZT (lead zirconate titanate), common electrodes 32, and individual electrodes 33 are alternately stacked. The individual electrode 33 is installed at a position overlapping the lower pressure chamber 16 formed in the flow path unit 20 on a one-to-one basis in a plan view. The common electrode 32 extends over a range including a plurality of regions where the individual electrodes 33 extend in plan view. The common electrode 32 and the individual electrode 33 are electrically connected to the wiring formed on the flexible wiring board 40 in a region not shown.

  The actuator unit 31 is driven as follows by a drive pulse supplied via the flexible wiring board 40. All the common electrodes 32 are held at the ground potential. A drive waveform signal including a drive pulse is supplied to the individual electrode 33 via the flexible wiring board 40. As a result, when a potential difference is generated between the individual electrode 33 and the common electrode 32, the ceramic layer 31a is deformed, pressure is applied to the ink in the pressure chamber 16, and the ink is ejected from the nozzle 15 as ink droplets. Can do.

  Hereinafter, the electrical configuration of the printer 1 will be described with reference to FIGS. 4 and 5.

  FIG. 4 is a block diagram showing the electrical configuration of the printer 1. The control unit 100 of the printer 1 includes a CPU (Central Processing Unit) 41, a control circuit 22, a ROM (Read Only Memory) 12, a RAM (Random Access Memory) 13, an interface 27, motor drivers 45 and 46, an image memory 25, and And a drive circuit 49. The ROM 12 stores a control program and various drive waveform data for ejecting ink droplets, and the RAM 13 temporarily stores various work data and the like. The CPU 41, ROM 12, RAM 13, and control circuit 22 are connected to each other via an address bus 23 and a data bus 24. The CPU 41 operates in accordance with a program stored in advance in the ROM 12 and executes various control processes.

  An operation panel 44, a motor driver 45, and a motor driver 46 are connected to the CPU 41. The transport motor 48 is a motor that drives the transport mechanism of the printing paper. Motor drivers 45 and 46 control driving of the carriage motor 10 and the transport motor 48, respectively. The printer 1 also detects a paper sensor 17 that detects the presence or absence of the printing paper P, an origin sensor 18 that detects that the recording head 30 is at the origin position, and that the ink cartridge 5 is in a normal mounting state. An ink cartridge sensor 19 is installed. Detection results of the paper sensor 17, the origin sensor 18, and the ink cartridge sensor 19 are input to the CPU 41. The control unit 100 can acquire the position in the direction along the guide shafts 6 and 7 of the recording head 30 based on the detection result of the origin sensor 18 and the control amount of the motor driver 45.

  The control circuit 22 is a gate array circuit and is connected to the interface 27 and the image memory 25. Further, it is connected to the recording head 30 via the flexible wiring board 40. A drive circuit 49 is mounted on the flexible wiring board 40, and a signal from the control circuit 22 is transmitted to the recording head 30 via the drive circuit 49.

  The control circuit 22 stores print pattern data transmitted from an external device such as a PC via the interface 27 in the image memory 25. Then, a reception interrupt signal WS is generated based on data transmitted from the PC or the like via the interface 27, and the signal WS is transmitted to the CPU 41. When receiving the signal WS, the CPU 41 generates a recording timing signal TS and a control signal RS, and transmits the signals TS and RS to the control circuit 22. When receiving the recording timing signal TS and the control signal RS, the control circuit 22 generates the print data signal DATA based on the print pattern data stored in the image memory 25. The signal DATA is a serial data signal for causing the recording head 30 to eject ink droplets so as to form an image corresponding to the print pattern data. Further, the control circuit 22 generates a transfer clock TCK and a strobe signal STB that are synchronized with the signal DATA. Further, the drive waveform signal ICK is generated based on the drive waveform data stored in the ROM 12. The drive waveform signal ICK includes various printing waveform signals 51 and minute vibration waveform signals 52 described later. Signals DATA, TCK, STB and ICK are transmitted to the drive circuit 49.

  The signal STB includes a signal indicating the length of a period during which the data latch circuit 36 described later latches the signal DATA. The control circuit 22 holds data indicating the application timing of applying the signal ICK in association with each of the five columns of the pressure chamber columns 36M to 36Bk. Table 1 below shows an example of data held by the control circuit 22. The second line of Table 1 corresponds to data when a printing waveform signal described later is applied, and the third line of Table 1 corresponds to data when a waveform signal for minute vibration described later is applied. .

  Table 1 includes each of the pressure chamber rows 36M, 36C, 36Y and 36Bk and time values t1 to t8 indicating application timing. These time values indicate the time from the tip of one printing cycle. For example, the time value t2 of cyan C indicates that the application timing of the waveform signal for printing to the individual electrode 33 corresponding to the pressure chamber row 36C is a time t2 after the leading end of one printing cycle. The control circuit 22 outputs the signal ICK to the individual electrode 33 corresponding to each pressure chamber row 36 at the application timing corresponding to Table 1. Note that t1 to t8 are set according to an application timing determination method described later.

  FIG. 5 is a block diagram showing a configuration of the drive circuit 49. The drive circuit 49 includes a serial-parallel converter 64, a data latch circuit 63, a selection circuit 62, and a driver circuit 61. The selection circuit 62 and the driver circuit 61 correspond to the nozzles 15 formed in the recording head 30 on a one-to-one basis. The signal DATA from the control circuit 22 is input to the serial-parallel converter 64 together with the signal TCK. The signal STB is input to the data latch circuit 63, and the signal ICK is input to the selection circuit 62.

  The serial-parallel converter 64 converts the signal DATA serially transferred from the control circuit 22 in synchronization with the signal TCK into parallel data, and outputs the parallel data to the data latch circuit 63. The data latch circuit 63 latches the parallel data from the serial-parallel converter 64 based on the signal STB and outputs it to the selection circuit 62.

  The selection circuit 62 selects the signal ICK corresponding to the waveform indicated by the parallel data from the data latch circuit 63 and outputs it to the driver circuit 61. The driver circuit 61 converts the signal ICK from the selection circuit 62 into a voltage suitable for the actuator unit 31 and outputs the voltage to the individual electrodes 33 of the recording head 30 as drive pulses.

  Hereinafter, the drive waveform signal applied to the individual electrode 33 will be described in more detail with reference to FIG. The drive waveform signal mainly corresponds to a signal having two types of waveforms. The first is a printing waveform signal 51 (FIG. 6A) for forming an image on the printing paper P by ejecting ink droplets from the recording head 30. The second is a minute vibration waveform signal 52 (FIG. 6B) for minutely vibrating the ink (meniscus) in the vicinity of the nozzle 15.

  In the waveform signal for printing, a plurality of types of waveforms corresponding to the size and number of ink droplets to be ejected are prepared, and FIG. 6A is one of them. The printing waveform 51 has three ejection drive pulses 51a and one non-ejection drive pulse 51b for one printing cycle Ta.

  When one drive pulse 51 a is supplied to the individual electrode 33, the potential of the individual electrode 33 changes to the pulse height of the drive pulse 51 a, and one ink droplet corresponds to one drive pulse 51 a. It is ejected from the nozzle 15 corresponding to. Accordingly, by supplying the three drive pulses 51a, a total of three ink droplets are ejected. On the other hand, the non-ejection drive pulse 51b is applied at a timing that substantially cancels the residual pressure wave of the ink generated by the ejection drive pulse. The drive pulse 51b has a smaller pulse width than the ejection drive pulse 51a, and no ink droplets are ejected from the nozzles 15 even when supplied to the individual electrode 33 as in the later-described drive pulse 52a.

  The minute vibration waveform 52 has two non-ejection drive pulses 52a (fine vibration drive pulses) for one printing cycle Ta. The pulse width W2 of the drive pulse 52a is smaller than the pulse width W1 of the drive pulse 51a. In the piezoelectric actuator, like the capacitor, the potential of the individual electrode 33 gradually increases, so that the supply of one pulse is completed before the potential of the individual electrode 33 reaches the magnitude corresponding to the pulse height. By setting the width, the deformation of the piezoelectric ceramic layer is reduced. That is, the pulse width W <b> 2 is adjusted to a size that prevents ink droplets from being ejected from the nozzle 15.

  In the above configuration, the control unit 100 controls the drive of the recording head 30 and the motor drivers 45 and 46 as follows. The first is print control. The control unit 100 moves the carriage 9 based on print pattern data transmitted from a PC or the like, and supplies a print waveform signal to the recording head 30. As a result, an image based on the print pattern data is formed on the print paper P. For example, when the recording head 30 is moved once from right to left in FIG. 1 along the image printing area, the control unit 100 forms an image for one line and prints each time the one line is formed. The paper P is transported by the transport device.

  The second is fine vibration control. The control unit 100 supplies a predetermined number of minute vibration waveform signals to the recording head 30 to minutely vibrate ink in the vicinity of the nozzles 15 without ejecting ink droplets from the nozzles 15 (fine vibration control means). . Such fine vibration control is executed at a predetermined timing between printing controls. For example, it is executed when the carriage 9 is decelerated and accelerated so as to reverse the moving direction when printing of one line is completed and printing of the next line is started. As a result, the ink in the vicinity of the nozzle 15 is agitated and dried, and the ink droplet ejection performance from the nozzle 15 is suppressed from deteriorating.

  FIG. 7 is a diagram illustrating a delay mode of the waveform 51 for printing, and FIG. 8 is a diagram illustrating a delay mode of the waveform 52 for minute vibration. SIG1 to SIG4 and SIG5 to SIG8 are a waveform 51 for printing and a waveform 52 for minute vibration respectively supplied from the control circuit 22 corresponding to different pressure chamber 36 rows, and for the two rows of pressure chambers 36Bk, A common printing waveform 51 and micro-vibration waveform 52 are supplied. SIG1 to SIG4 delay the printing waveform 51 by t1 to t4 from the leading end of the printing cycle, respectively. SIG5 to SIG8 delay the micro-vibration waveform 52 by t5 to t8 from the tip of the printing cycle, respectively. Note that t1 to t4 and t5 to t8 are different values, and both are zero (t1 and t5 include zero) or more and less than Ta.

  Hereinafter, an example of a method for determining conditions such as the application timing of the drive waveform signal in each of the printing control and the fine vibration control will be described with reference to FIGS. 9 and 10. FIG. 9 shows a series of steps S1 to S4 executed to determine the application timing.

  First, ink droplets are ejected independently from the nozzles 15 belonging to the nozzle array 35 formed on the recording head 30, and the ejection speed of ink from each nozzle array 35 is measured (S1). In the present embodiment, “independently” ejecting ink droplets means ejecting ink droplets from only one nozzle 15 belonging to any one nozzle row 35 within one printing cycle. The ejection speed of the ink droplet is derived, for example, by capturing a track of the ink droplet from the horizontal direction as a moving image and analyzing the captured image.

  Next, the ink droplets are ejected from the plurality of nozzle rows 35 including the nozzle row 35 to which the nozzle 15 measured in S1 belongs, while sandwiching a predetermined delay time within one printing cycle, and the ink droplet ejection speed is measured. . Then, the injection speed is measured a plurality of times while variously changing the delay time (S2). When ejecting ink droplets from a plurality of nozzle rows 35, ink droplets may be ejected from all nozzles 15 included in each nozzle row 35, or some of the nozzles 15 included in each nozzle row 35. Ink droplets may be ejected from only.

  For example, FIG. 10 shows the result of measuring the ejection speed of ink droplets by ejecting ink droplets from one nozzle row 35Bk and 35C of the plurality of nozzle rows 35 at a predetermined application timing within one printing cycle. It is a graph of one Example. Note that the delay time on the horizontal axis in FIG. 10 indicates the time from the ejection of ink droplets from the nozzle row 35Bk to the ejection of ink droplets from the nozzle row 35C. v1 indicates an ejection speed when ink droplets are ejected independently from the nozzles 15 belonging to the nozzle array 35Bk, and v2 indicates an ejection speed when ink droplets are ejected from both the nozzle arrays 35Bk and 35C. When measuring v2, ink droplets are ejected from all the nozzles 15 belonging to the same nozzle row 35Bk and 35C.

  As shown in FIG. 10, when ink droplets are ejected from the two nozzle rows 35Bk and 35C within one printing cycle, the ejection speed v2 is higher than in the case of v1 in which the ink droplets are ejected alone. May be different. For example, the delay time is zero, that is, the speed v2 when the drive waveform signal is simultaneously applied to the two nozzle rows 35 is smaller than v1 when the drive waveform signal is applied alone. In the region where the delay time is about 3 microseconds, the speed v2 is larger than v1. The difference in the injection speed is considered to be due to so-called crosstalk. That is, vibration generated in one pressure chamber 16 propagates to the ink in another pressure chamber 16 through the cavity unit, and affects the pressure fluctuation of the ink meniscus in the nozzle corresponding to the other pressure chamber 16. Yes. From the graph of FIG. 10, it is derived that the influence of crosstalk varies depending on the amount of time (delay time) when the application timing of the two nozzle arrays 35 is shifted.

  Next, in S3 of FIG. 9, the injection speed measured in S1 is compared with the injection speed measured in S2. Thus, it is evaluated how the influence of the crosstalk appears in what delay time (S3).

  For example, according to the graph of FIG. 10, in the region between two alternate long and short dash lines (region where the delay time is about 0.80 to about 1.8 microseconds), the magnitudes of v1 and v2 are close and the delay time is The change in v2 with respect to the change is small, and the injection speed is fairly stable. That is, in this region, the influence of crosstalk is small and the meniscus pressure fluctuation is small. On the other hand, v2 has a maximum value when the delay time is around 3.2 microseconds. That is, in this region, it is considered that the meniscus pressure fluctuation is large due to the influence of the crosstalk, and the injection speed is increased in superposition thereto.

  Therefore, the printing control application timing is determined so that the influence of the crosstalk is relatively small, and the fine vibration is generated so that the delay time is such that the influence of the crosstalk is relatively large and the ejection speed becomes large. The application timing of control is determined (S4 in FIG. 9). That is, in FIG. 10, the printing control is applied to the pressure chamber rows 36 </ b> Bk and 36 </ b> C so as to take a delay time of 0.8 μs to 1.8 μs, for example, 1.2 μs, where the influence of crosstalk is relatively small. Determine timing. Then, in FIG. 10, the application timing of the fine vibration control for the pressure chamber rows 36Bk and 36C is determined so as to take a delay time in the vicinity of 3.2 microseconds at which the influence of crosstalk is maximized. In this case, even if there is an influence of crosstalk, the ink droplets are set so as not to be ejected from the nozzles by the fine vibration control. Specifically, in Table 1, each numerical value is determined so that t4-t2 is 1.2 microseconds, and each numerical value is determined so that t8-t6 is 3.2 microseconds.

  These steps S1 to S4 are repeated for other combinations of nozzle rows 35 such as a combination of nozzle rows 35M and nozzle rows 35Bk. Then, t1 to t8 in Table 1 are all determined. Thereby, the timing for applying the drive waveform signal is determined in both the print control and the fine vibration control.

  Finally, the number of micro-vibration waveform signals necessary for preventing drying in the micro-vibration control is determined (S5). That is, the number of times that the fine vibration control is performed before the carriage movement is obtained so that even if the ejection operation is not performed while the carriage 9 moves along the printing paper, the ejection can be normally performed immediately after that. is there. For example, a minute vibration waveform signal corresponding to 100 printing cycles or 200 printing cycles of the printing cycle Ta is applied to one fine vibration control, and thereafter, a time during which the ejection operation is not performed (hereinafter referred to as “drying time”) is described as follows. Keep it. Then, when the printing control is executed to form a solid image or the like, it is observed whether or not the edge of the image is disturbed.

  In the above example, the fine vibration control is performed for each nozzle row. For example, the meniscus can also be applied by applying a minute vibration waveform signal at a predetermined timing to a plurality of nozzles positioned apart from each other in the nozzle row. The pressure fluctuation that occurs in can be increased. By executing S1 to S5, it is possible to set the timing for applying the minute vibration waveform signal, the number of times of driving, and the like. The various aspects will be described below.

  In the first mode, the minute vibration waveform signal is applied only to each individual electrode 33 corresponding to every other pressure chamber 16 in each of the pressure chamber rows 36. The deviation in the application timing of the waveform signal for minute vibration between every other pressure chamber 16 is set by S1 to S4. Accordingly, a large pressure fluctuation can be generated in the ink meniscus in the nozzle, and a large pressure fluctuation can be generated for the adjacent nozzle to which the waveform signal for minute vibration is not applied. The pressure fluctuation generated in every other pressure chamber 16 not only propagates through the cavity unit, but also propagates to the adjacent pressure chamber via the manifold channel 14 and vibrates the ink in the corresponding nozzle. I will let you.

  For the above control, the control circuit 22 outputs a plurality of types of micro-vibration waveform signals 52 that are shifted by the application timing from the start of the printing cycle Ta to each selection circuit 62 as a signal ICK. The control circuit 22 outputs a signal designating any one of a plurality of types of waveform signals 52 for micro vibrations as the signal DATA corresponding to every other pressure chamber 16. Thereby, the minute vibration waveform signal 52 is applied to each individual electrode 33 of every other pressure chamber 16 with a difference in application timing.

  In the second mode, the minute vibration waveform signal is applied only to each individual electrode 33 corresponding to the plurality of pressure chamber rows 36 among all the pressure chamber rows. As described above for the nozzle arrays 35Bk and 35C, the application timing of the waveform signal for micro vibration is set. The control circuit 22 outputs a plurality of types of micro-vibration waveform signals 52 that are shifted by the application timing from the start of the printing cycle Ta to each selection circuit 62. Further, the control circuit 22 outputs a signal designating any one of a plurality of types of minute vibration waveform signals 52 as the signal DATA corresponding to the nozzle rows 35Bk and 35C. As a result, the minute vibration waveform signal 52 is applied to the individual electrodes 33 corresponding to the nozzle rows 35Bk and 35C with a difference in application timing.

  In the above case, the vibration generated by driving the actuator for the pressure chamber rows 36Bk and 36C propagates to the remaining pressure chamber rows 36Y and 36M without applying the waveform signal for minute vibration, and the corresponding nozzle 35Y And vibration can be applied to the ink meniscus in 35M.

In the third mode, a waveform signal for minute vibration is applied to each of the pressure chamber groups E, F, and G (see FIG. 2) divided into a plurality in the column direction of the pressure chambers. Then, among the pressure chamber groups, a waveform signal for minute vibration is applied to a plurality of pressure chamber groups smaller than the total number of groups at the timing at which crosstalk is generated as described above. The control for this is similar to the control in the first mode, except that every other pressure chamber is replaced with a pressure chamber group.
In this case, in the pressure chamber groups E, F, and G divided into three or more, only the pressure chamber groups E and G at both ends are applied with the waveform signal for minute vibration, so that the pressure chamber groups sandwiched between them. Even if the waveform signal for minute vibration is not applied to F, vibration generated by driving the actuator with respect to the pressure chamber groups E and G propagates, and vibration can be given to the meniscus of ink in the corresponding nozzle. .

  Tables 2 and 3 are evaluations of results of printing an image in order to determine S5 in the first to third modes. Table 2 shows a case where a minute vibration waveform signal for 100 cycles is applied in one fine vibration control, and Table 3 shows a case where a minute vibration waveform signal for 200 cycles is applied. In each table, “first”, “second”, and “third” indicate cases where the fine vibration control is executed in each of the first to third modes. “◯” indicates that the image is not disturbed, “△” indicates that the image is disturbed but within the practical range, and “×” indicates that the image is not suitable for practical use. Indicates that there is a disturbance.

  The following effects are exhibited by the present embodiment having the above-described configuration. As described above, the application timing of the drive waveform signal in the fine vibration control is determined so as to have a delay time that has a large influence of crosstalk and a large meniscus amplitude. Accordingly, it is possible to prevent the droplets near the nozzles from drying even with a drive waveform signal having a small number of pulses as a whole. Further, even if no drive waveform signal is applied to the pressure chambers sandwiched between the plurality of pressure chambers to which the drive waveform signal is applied, the ink in the nozzles is vibrated to obtain a drying prevention effect. As a result, the number of pulses can be further reduced. As a result, since the number of pulses is reduced, the heat generation of the actuator unit 31 and the drive circuit 49 is reduced, and the consumed energy is also suppressed.

  In the present embodiment, the application timing of the drive waveform signal in the print control is set so that the influence of crosstalk is relatively small. For example, in FIG. 10, it is set in the region of 0.80 to 1.8 microseconds where the influence of crosstalk is relatively small. Accordingly, it is possible to suppress a drop in the ejection speed of ink droplets due to the influence of crosstalk or a variation in ejection speed between the nozzles 15 due to the influence of crosstalk during printing control. Therefore, it is possible to suppress a drop in print quality due to a change in ink droplet ejection speed due to crosstalk during print control.

  The above is a description of a preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and various modifications are possible within the scope described in the means for solving the problems. Is.

<Modification>
In the first mode, the same fine vibration control may be alternately performed on every other pressure chamber and every other pressure chamber. In the second mode, the same fine vibration control may be alternately performed on the pressure chamber rows 36Bk and 36C and the remaining pressure chamber rows 36Y and 36M. In this case, t5 and t7 in Table 1 are also used. In the third mode, the pressure chambers may be divided into four or more groups, and the same fine vibration control may be alternately performed on two or more groups. In this way, two fine vibration control vibrations are alternately applied to one meniscus, and drying prevention can be achieved efficiently.
Further, the first mode is for a predetermined number of pressure chambers such as every second or every third, and the second mode is further provided with a plurality of pressure chamber rows, which is smaller than the total number of rows. In the third mode, the third mode can further divide the pressure chambers into a plurality of groups and perform fine vibration control on each of a plurality of groups smaller than the total number of groups.

  In the above-described embodiment, a method in which the recording head 30 moves together with the carriage 9 is employed. However, a fixed ink jet head may be employed. Moreover, although the piezoelectric method is employed in the above-described embodiment, an inkjet head employing another method such as a thermal method may be used. Further, unlike an ink jet printer, the present invention may be applied to an apparatus that ejects various liquids such as a liquid other than ink, for example, an apparatus that applies a colored liquid to produce a color filter of a liquid crystal display device.

  Note that the method for determining the application timing of the drive waveform signal in the above embodiment is merely an example. When printing control or fine vibration control is executed, the distribution status of the individual electrode 33 to which the drive waveform signal is applied and the individual electrode 33 to which the drive waveform signal is not applied varies in various ways. Therefore, in determining the application timing, it is preferable that the injection speed is measured in various measurement situations corresponding to various distribution situations.

  In the above-described embodiment, one micro-vibration waveform 52 includes two drive pulses 52a. However, one or three or more drive pulses 52a may be included in one minute vibration waveform 52.

It is a top view which shows the internal structure of the inkjet printer which is one Embodiment of this invention. FIG. 2 is a bottom view of the recording head in FIG. 1. FIG. 3 is a longitudinal sectional view of the recording head taken along line III-III in FIG. 2. FIG. 2 is a block diagram showing an electrical configuration of the ink jet printer of FIG. 1. FIG. 5 is a block diagram illustrating a configuration of a drive circuit in FIG. 4. FIG. 5 is a diagram illustrating an example of a waveform of a drive waveform signal supplied to the drive circuit of FIG. 4. It is a figure which shows an example of the waveform for printing applied to the individual electrode of FIG. 3 over 2 printing cycles. It is a figure which shows an example of the waveform for fine vibrations applied to the individual electrode of FIG. 3 over 2 printing cycles. It is a flowchart which shows a series of steps of the application timing determination method which determines the application timing in which a drive waveform signal is applied to an individual electrode in fine vibration control. 10 is a graph showing the relationship between the ink ejection speed measured in one embodiment of the application timing determination method of FIG. 9 and the delay time of the application timing.

Explanation of symbols

1 Inkjet printer (printer)
15 Nozzle 16 Pressure chamber 30 Recording head 31 Actuator unit 35 (35C, 35M, 35Y, 35Bk) Nozzle array 36 (36C, 36M, 36Y, 36Bk) Pressure chamber array 49 Drive circuit 51 Printing waveform 52 Micro vibration waveform 51a, 51b, 52a Drive pulse 100 controller

Claims (7)

A flow path unit having a plurality of nozzles and a plurality of pressure chambers respectively communicating with the plurality of nozzles;
A plurality of actuators for applying pressure to the liquid in the plurality of pressure chambers by changing the volumes of the plurality of pressure chambers;
Driving means for applying an ejection driving pulse for ejecting droplets from the nozzle to each of the plurality of actuators;
Control means for controlling the drive means;
With
The control means includes
The drive means has fine vibration control means for applying a fine vibration drive pulse for finely vibrating the meniscus of the liquid in the nozzle to the extent that liquid droplets are not ejected from the nozzle to the actuator,
A liquid droplet ejecting apparatus, wherein the fine vibration driving pulse is applied to a plurality of actuators positioned apart from each other at a timing at which a pressure fluctuation generated in the meniscus becomes larger than when applied alone.   2. The droplet ejecting apparatus according to claim 1, wherein the fine vibration control unit causes the drive unit to apply a plurality of fine vibration drive pulses less than all of the plurality of actuators. The plurality of pressure chambers constitute one pressure chamber row extending along a predetermined direction,
The fine vibration control means causes the drive means to apply the fine vibration drive pulse to the actuators corresponding to the pressure chambers arranged at predetermined intervals in the predetermined direction. Droplet ejector. The plurality of pressure chambers constitute a plurality of pressure chamber rows extending parallel to each other along a predetermined direction;
3. The fine vibration control means causes the driving means to apply the fine vibration driving pulse to the actuators corresponding to a plurality of pressure chamber rows smaller than the total number of pressure chamber rows. The droplet ejecting apparatus according to 1. The plurality of pressure chambers are divided into a plurality of pressure chamber groups in a row direction of the pressure chambers,
The droplet ejecting apparatus according to claim 2, wherein the micro vibration control unit causes the driving unit to apply the micro vibration driving pulse for each of the actuators corresponding to the partial pressure chamber group. The fine vibration control means includes
The driving means is applied to the second actuator so that the pressure fluctuation generated in the meniscus of the first actuator is larger than that when the fine vibration driving pulse is applied to the first actuator alone. The fine vibration drive pulse is applied to the first actuator after a predetermined time shorter than one print cycle has elapsed since the fine vibration drive pulse was applied to the second actuator. The liquid droplet ejecting apparatus according to claim 1, wherein a minute vibration driving pulse is applied. The ejection drive pulse is applied to the first actuator, and the ejection is applied to the second actuator after a predetermined time shorter than one printing cycle has elapsed since the ejection drive pulse was applied to the first actuator. An absolute value of a difference in pressure fluctuation generated in the meniscus of the second actuator between when the drive pulse is applied and when the injection drive pulse is applied alone to the second actuator is the predetermined value. If the predetermined time is t which is not zero than when the time is zero,
The control means includes
The drive means applies the ejection drive pulse to the first actuator, and after the time t has elapsed since the ejection drive pulse was applied to the first actuator, The droplet ejecting apparatus according to claim 1, wherein the ejection driving pulse is applied to an actuator.

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