JP7184670B2 - LIQUID EJECTOR AND INKJET PRINTER INCLUDING THE SAME - Google Patents

Description

The present invention relates to a liquid ejection device and an inkjet printer having the same.

Conventionally, a pressure chamber in which liquid is stored, a partition plate that partitions a part of the pressure chamber, an actuator connected to the partition plate, a nozzle that communicates with the pressure chamber, and a drive signal are supplied to the actuator. and a control device for driving an actuator. Such a liquid ejecting apparatus is provided, for example, in an inkjet printer (hereinafter sometimes simply referred to as a printer) that ejects ink as a liquid.

In a printer equipped with the above-described liquid ejection device, when a control device supplies a drive pulse signal (hereinafter referred to as a drive pulse) to an actuator, the actuator deforms, and the partition plate deforms accordingly. As a result, the volume of the pressure chamber increases or decreases, and the pressure of the ink in the pressure chamber changes. Ink is ejected from the nozzles in accordance with this pressure change. The ejected ink flies as droplets (ink droplets) and lands on a recording medium such as recording paper. As a result, one dot is formed on the recording paper. An image or the like is formed by forming a large number of such dots on the recording paper. In the liquid ejecting apparatus described above, dot size adjustment is performed by a so-called multi-dot method in which a drive signal having a plurality of drive pulses is generated within a drive cycle for forming one dot.

By the way, in the liquid ejecting apparatus as described above, the viscosity of the ink changes as the environmental temperature changes. For example, when the temperature of the ink increases, the fluidity of the ink increases, making it easier to eject the ink. As a result, the flight speed of the droplets may change and the landing position may shift, or the size of the dots may change to change the density of the image. Further, for example, when the temperature of the ink becomes low, the fluidity of the ink is lowered, making it difficult to eject the ink. As a result, the dot size may become smaller and the image quality may deteriorate.

For example, Patent Document 1 discloses a liquid ejecting apparatus that can stably eject liquid droplets over a wide temperature range. In Japanese Patent Application Laid-Open No. 2004-200000, the method of correcting the drive signal is different depending on whether the ink temperature is lower than the reference temperature or higher than the reference temperature.

JP 2017-189899 A

However, according to studies by the present inventors, when a plurality of droplets are ejected by a plurality of driving pulses to form one large dot, the ejection stability may be degraded. Specifically, the vibration of the pressure chamber and the meniscus increases due to the residual vibration of the drive pulse of the previously ejected droplet, and the ink adheres to the vicinity of the nozzle opening, resulting in an uneven wettability distribution. In some cases, the droplets ejected next tend to be curved in flight, and ink mist tends to occur. Such a problem cannot be ignored in a business-use large-format printer that forms dots of a larger size at a higher speed than in a home-use printer.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid ejecting apparatus capable of stably ejecting droplets over a wide temperature range. Another object of the present invention is to provide an inkjet printer equipped with the above liquid ejecting device.

A liquid ejection apparatus according to the present invention includes a liquid ejection head that ejects liquid, a temperature sensor that detects the temperature of the liquid, and a control device that controls the liquid ejection head. The liquid ejection head includes a case in which a pressure chamber in which the liquid is stored is formed, a partition plate provided in the case and partitioning a part of the pressure chamber, and an electric discharge head connected to the partition plate. An actuator that deforms when a signal is supplied, and a nozzle formed in the case and communicating with the pressure chamber are provided. The control device expands and contracts the pressure chamber for each drive cycle to eject a (N-2)th droplet (where N is an integer of 3 or more). -2) a drive pulse, and a (N-2)th drive pulse, which is located after the (N-2)th drive pulse, for ejecting the (N-1)th droplet by expanding and contracting the pressure chamber. 1) having at least a drive pulse and an Nth drive pulse positioned behind the (N−1)th drive pulse and for ejecting the Nth droplet by expanding and contracting the pressure chamber; and a drive signal generation circuit for generating a reference drive signal, and at least the (N-1)th drive pulse of the reference drive signal when the temperature detected by the temperature sensor is lower than a predetermined reference temperature. A drive voltage and a first temperature correction coefficient for increasing the drive voltage of the Nth drive pulse are calculated, and if the temperature detected by the temperature sensor is higher than the reference temperature, at least the reference drive signal a correction coefficient calculation circuit for calculating a second temperature correction coefficient that lowers the drive voltage of the (N-1)th drive pulse and the drive voltage of the Nth drive pulse, and the temperature detected by the temperature sensor is higher than the reference temperature. If the temperature detected by the temperature sensor is higher than the reference temperature, the reference drive signal is corrected by the second temperature correction factor. A drive signal correction circuit that corrects with a coefficient, and a drive signal supply circuit that supplies part or all of the corrected reference drive signal to the actuator. When the Helmholtz natural vibration period of the liquid ejection head is Tc, the Nth drive pulse is p×Tc (where p is an integer of 2 or more) from the start of the (N−1)th drive pulse. ) is started at a later time. Let ΔV _min (N−1) be a change amount of the drive voltage at the minimum potential of the (N−1)th drive pulse corrected by the first temperature correction coefficient or the second temperature correction coefficient, and the Nth drive pulse where ΔV _min (N) is the amount of change in the driving voltage at the minimum potential of the temperature sensor, ΔV _min (N−1)<ΔV _min (N) when the temperature detected by the temperature sensor is lower than the reference temperature Moreover, when the temperature detected by the temperature sensor is higher than the reference temperature, ΔV _min (N−1)>ΔV _min (N) is established.

According to the liquid ejecting apparatus of the present invention, ΔV _min (N−1)<ΔV _min (N) is established when the temperature detected by the temperature sensor is lower than the reference temperature. When the ink temperature is lower than the reference temperature, the ink viscosity increases. Therefore, when the (N-1)th droplet is ejected by the (N-1)th drive pulse, the residual vibration of the (N-2)th drive pulse is attenuated to some extent. However, by increasing the drive voltage of the (N-1)th drive pulse above the drive voltage at the reference temperature, the residual vibration of the (N-2)th drive pulse can be further damped. Although it is necessary to eject the same amount of liquid from the nozzles at the low temperature as at the reference temperature, since ΔV _min (N−1)<ΔV _min (N) is established, ejection is not performed by the Nth driving pulse. It is possible to increase the amount of the Nth droplet to be drawn. As a result, droplets can be stably ejected from the nozzle in the temperature range from room temperature to low temperature.

Further, when the temperature detected by the temperature sensor is higher than the reference temperature, ΔV _min (N−1)>ΔV _min (N) is established. When the temperature of the ink is higher than the reference temperature, the viscosity of the ink decreases. Therefore, when the (N-1)th droplet is ejected by the (N-1)th drive pulse, the residual vibration of the (N-2)th drive pulse is not attenuated so much. Therefore, by lowering the drive voltage of the (N-1)th drive pulse below the drive voltage at the reference temperature, the residual vibration of the (N-2)th drive pulse can be damped. Although it is necessary to eject the same amount of liquid from the nozzle at the high temperature as at the reference temperature, since ΔV _min (N−1)>ΔV _min (N) is established, ejection is not performed by the Nth drive pulse. It is possible to increase the amount of the Nth droplet to be drawn. As a result, droplets can be stably ejected from the nozzle in the temperature range from room temperature to high temperature.

Another aspect of the present invention provides an inkjet printer including the above liquid ejection device. This inkjet printer can stably form large-sized dots by the multi-dot method. Therefore, for example, variation in dot size can be reduced, and image quality can be improved. In addition, it is possible to reduce contamination of the recording medium and the main body of the printer caused by ink mist and the like.

According to the present invention, it is possible to provide a liquid ejecting apparatus capable of stably ejecting a desired amount of liquid droplets in a wide temperature range from low temperature to high temperature using the multi-dot method.

1 is a perspective view of a printer according to one embodiment; FIG. 1 is a front view of main parts of a printer according to one embodiment; FIG. 1 is a cross-sectional view of part of a liquid ejection head according to an embodiment; FIG. 1 is a block diagram showing the configuration of a liquid ejection device according to one embodiment; FIG. FIG. 4 is a waveform diagram of a reference drive signal according to one embodiment; FIG. 4 is a waveform diagram of a drive signal after correction when the temperature is lower than the reference temperature; FIG. 4 is a waveform diagram of a drive signal after correction when the temperature is higher than the reference temperature;

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a liquid ejection device and an inkjet printer (hereinafter referred to as a printer) having the liquid ejection device according to the present invention will be described below with reference to the drawings. The embodiments described herein are of course not intended to specifically limit the invention. Further, members and parts having the same action are denoted by the same reference numerals, and redundant explanations are omitted or simplified.

FIG. 1 is a perspective view of a printer 10 according to one embodiment. FIG. 2 is a front view showing the main parts of the printer 10. As shown in FIG. In the following description, when the user views the printer 10 from the front, the side where the user moves away from the printer 10 is the front, and the side where the user approaches the printer 10 is the rear. Left, right, top, and bottom mean left, right, top, and bottom, respectively, when the printer 10 is viewed from the front. References F, Rr, L, R, U, and D in the drawings mean front, rear, left, right, up, and down, respectively. Reference Y in the drawings indicates the main scanning direction. Here, the main scanning direction Y is the horizontal direction. Symbol X indicates the sub-scanning direction. Here, the sub-scanning direction X is the front-rear direction, and is orthogonal to the main scanning direction Y in plan view. However, the above directions are merely directions for convenience of explanation, and do not limit the installation mode of the printer 10 in any way, and do not limit the present invention in any way.

As shown in FIG. 1, the printer 10 is an inkjet printer. The printer 10 is a so-called large-sized printer that is longer in the main scanning direction Y than a printer for home use. For example, the printer 10 is a business printer. In this embodiment, printer 10 prints an image on recording medium 5 .

The recording medium 5 is, for example, recording paper. However, the recording medium 5 is not limited to recording paper. For example, the recording medium 5 includes a sheet made of a resin material such as polyvinyl chloride (PVC) or polyester, a metal plate made of aluminum or iron, a glass plate, a wood plate, or the like.

As shown in FIG. 2, the printer 10 includes a casing 12 (see also FIG. 1), a guide rail 13, a platen 14, a carriage 11, an ink head 25, and a carriage movement mechanism . The ink head 25 is an example of a liquid ejection head. The guide rail 13 is arranged inside the casing 12 . The guide rail 13 extends in the main scanning direction Y. As shown in FIG. The carriage 11 is engaged with the guide rail 13 . A plurality of ink heads 25 are mounted on the carriage 11 . The carriage 11 is reciprocated in the main scanning direction Y along the guide rail 13 by the carriage movement mechanism 18 . The carriage moving mechanism 18 has pulleys 29 b and 29 a arranged on the left end side and right end side of the guide rail 13 . A carriage motor 18a is connected to the pulley 29a. The carriage motor 18a may be connected to the pulley 29b. The pulley 29a is driven by the carriage motor 18a. An endless belt 16 is wound around each of the pulleys 29a and 29b. Carriage 11 is fixed to belt 16 . When the pulleys 29a and 29b rotate and the belt 16 runs, the carriage 11 moves laterally.

Although there is a balance with resolution, the scanning speed of the carriage 11 may be set faster from the viewpoint of improving throughput. For example, during normal printing, the scanning speed can be set to approximately 600 to 900 mm/s at a drive frequency of approximately 14 kHz. Further, the scanning speed can be set to approximately 1000 to 1200 mm/s at a drive frequency of approximately 20 kHz during high-speed printing, for example.

As shown in FIG. 1, platen 14 is provided within casing 12 . The platen 14 extends in the main scanning direction Y. As shown in FIG. A recording medium 5 is placed on the platen 14 .

Printer 10 includes a media transport mechanism (not shown). The medium transport mechanism transports the recording medium 5 in the sub-scanning direction X. As shown in FIG. The media transport mechanism includes a plurality of grit rollers (not shown), a plurality of pinch rollers (not shown), and a feed motor (not shown). A grit roller is provided on the platen 14 . A pinch roller is positioned above the grit roller. The pinch roller is arranged at a position facing the grit roller. The grit roller is connected to a feed motor (not shown). The grit roller is driven and rotated by the feed motor. When the grit roller rotates while the recording medium 5 is sandwiched between the grit roller and the pinch roller, the recording medium 5 is conveyed in the sub-scanning direction X. As shown in FIG.

As shown in FIG. 2, the printer 10 has multiple ink cartridges 21 . Inks of different colors are stored in the plurality of ink cartridges 21 . Ink is an example of a liquid. For example, the printer 10 includes five ink cartridges 21 each storing cyan ink, magenta ink, yellow ink, black ink, and white ink. The properties of each ink are adjusted so that they can be stably ejected from the ink head 25 . The viscosity of the ink is adjusted to approximately 1 mPa·s to 50 mPa·s, for example, approximately 3 mPa·s to 10 mPa·s. Let the said viscosity be the value measured according to JISZ8803 (2001). For viscosity measurement, for example, a cone-plate rotary viscometer (TVE-25L manufactured by Toki Sangyo Co., Ltd.) can be used.

As shown in FIG. 3, the printer 10 includes a liquid ejection device 20. As shown in FIG. The liquid ejection device 20 includes an ink head 25 , a control device 28 that controls the operation of the ink head 25 , and a thermistor 27 .

As shown in FIG. 2, an ink head 25 is provided for each color ink. The ink head 25 ejects ink. The ink head 25 ejects ink toward the recording medium 5 to form ink dots on the recording medium 5 . An image or the like is formed on the recording medium 5 by arranging a large number of dots. The ink head 25 has a plurality of nozzles 35 (see FIG. 3) for ejecting ink on the surface facing the recording medium 5 (the lower surface of the ink head 25 in this embodiment).

As shown in FIG. 2, the ink head 25 and the ink cartridge 21 for each color are connected by an ink supply path 22 . The ink supply path 22 is an ink flow path that supplies ink from the ink cartridge 21 to the ink head 25 . The ink supply path 22 is composed of, for example, a flexible tube. A liquid feed pump 23 is provided in the ink supply path 22 . However, the liquid-sending pump 23 is not necessarily required and can be omitted. A part of the ink supply path 22 is covered with a cable protection guide device 17 .

As shown in FIG. 3, the ink head 25 includes a hollow case 31 having an opening 31a and a partition plate 32 attached to the case 31 so as to block the opening 31a. A pressure chamber 33 in which ink is stored is formed in the case 31 . The partition plate 32 partitions a part of the pressure chamber 33 . The partition plate 32 is elastically deformable inside and outside the pressure chamber 33 . The partition plate 32 is configured to be deformable so as to increase and decrease the volume of the pressure chamber 33 . The partition plate 32 is typically a resin film.

As shown in FIG. 3, the side wall of the case 31 is formed with an ink inlet 34 through which ink flows. In addition, the ink inlet 34 only needs to communicate with the pressure chamber 33, and the position of the ink inlet 34 is not limited at all. Ink is supplied from the ink cartridge 21 to the pressure chamber 33 through the ink inlet 34, and a predetermined amount of ink is temporarily stored. The nozzle 35 is formed on the bottom surface 31 b of the case 31 . The nozzle 35 communicates with the pressure chamber 33 . The nozzles 35 eject ink (droplets) toward the recording medium 5 . The liquid surface (free surface) of the ink inside the nozzle 35 forms a meniscus 35a.

The pressure chamber 33 has a Helmholtz natural vibration period Tc. The Helmholtz natural vibration period Tc depends on the material, size, and shape of each component constituting the pressure chamber 33, such as the case 31 and the partition plate 32, the arrangement position of the component, the opening area of the nozzle 35, the physical properties of the ink (for example, viscosity ) and so on. The Helmholtz natural vibration period Tc is a vibration period unique to the ink head 25 during ink ejection. The Helmholtz natural vibration period Tc is, for example, a vibration period of several microseconds to several tens of microseconds. A residual vibration having this vibration period is generated in the pressure chamber 33 after the droplet is discharged.

As shown in FIG. 3, the ink head 25 has piezoelectric elements 36 . The piezoelectric element 36 is an example of an actuator. The piezoelectric element 36 is connected to the partition plate 32 . More specifically, the piezoelectric element 36 is connected to the surface of the partition plate 32 opposite to the surface on the pressure chamber 33 side. A portion of the piezoelectric element 36 is fixed to a fixing member 39 provided on the case 31 . The piezoelectric element 36 is connected to the controller 28 via a flexible cable 37 . An electric signal is supplied to the piezoelectric element 36 via a flexible cable 37 . In this embodiment, the piezoelectric element 36 is a laminate in which piezoelectric materials and conductive layers are alternately laminated. The piezoelectric element 36 expands or contracts upon receiving an electrical signal from the control device 28 and functions to elastically deform the partition plate 32 to the outside or inside the pressure chamber 33 . Here, a longitudinal vibration mode piezo element (PZT) is employed. PZT in the longitudinal vibration mode is flexible in the stacking direction, and contracts when discharged, for example, and expands when charged. However, the form of the piezoelectric element 36 is not particularly limited.

As shown in FIG. 3, the thermistor 27 is provided on the inner wall surface of the case 31 (the right inner wall surface in FIG. 3). The thermistor 27 is an example of a temperature sensor that detects the temperature of liquid (here, ink) ejected from the ink head 25 . Here, the temperature of the inner wall surface of the case 31 is detected and approximated to the temperature of the ink. The thermistor 27 is, for example, a diode sensor, a metal thin film sensor, or the like. Note that the thermistor 27 may be provided, for example, on the outer wall surface of the case 31, the ink supply path 22, or the like. Also, the temperature sensor may be a thermocouple that can directly detect the temperature of the ink. Also, the temperature sensor may be provided in the carriage 11 or the casing 12, for example, to detect the environmental temperature of the printer 10 or the ink head 25. FIG. In this case, the ink temperature can be extrapolated from the sensed ambient temperature.

In the ink head 25, for example, the piezoelectric element 36 contracts by lowering the potential of the piezoelectric element 36 from an intermediate potential (reference potential). Then, following this, the partition plate 32 is elastically deformed from the initial position to the outside of the pressure chamber 33, and the pressure chamber 33 expands. The expansion of the pressure chamber 33 means that the volume of the pressure chamber 33 increases due to the deformation of the partition plate 32 . Next, by raising the potential of the piezoelectric element 36, the piezoelectric element 36 expands in the stacking direction. As a result, the partition plate 32 elastically deforms toward the inside of the pressure chamber 33, and the pressure chamber 33 contracts. Note that the contraction of the pressure chamber 33 means that the volume of the pressure chamber 33 is reduced due to the deformation of the partition plate 32 . Due to such expansion and contraction of the pressure chamber 33, the pressure inside the pressure chamber 33 fluctuates. Due to this pressure fluctuation in the pressure chamber 33 , the ink in the pressure chamber 33 is pressurized and ejected from the nozzle 35 in the form of droplets. After that, by returning the potential of the piezoelectric element 36 to the intermediate potential, the partition plate 32 returns to the initial position and the pressure chamber 33 expands. At this time, ink flows into the pressure chamber 33 from the ink inlet 34 .

The controller 28 is communicably connected to the carriage motor 18 a of the carriage moving mechanism 18 , the feed motor of the medium transport mechanism, the liquid feed pump 23 , and the ink head 25 . A controller 28 controls these operations. Controller 28 is typically a computer. The control device 28 includes, for example, an interface (I/F) for receiving print data from an external device such as a host computer, a central processing unit (CPU) for executing control program instructions, and programs executed by the CPU. , a RAM used as a working area for developing programs, and a storage device such as a memory for storing the programs and various data.

As shown in FIG. 4, the control device 28 includes a drive signal generation circuit 40, a correction coefficient calculation circuit 50, a drive signal correction circuit 60, and a drive signal supply circuit . In the following description, the signal that the drive signal supply circuit 70 supplies to the piezoelectric element 36 is referred to as the supply signal. Although details will be described later, the supplied signal is a signal consisting of part or all of the reference drive signal generated by the drive signal generation circuit 40, or part or all of the reference drive signal corrected by the drive signal correction circuit 60. be. The hardware configuration of the drive signal generation circuit 40, the correction coefficient calculation circuit 50, the drive signal correction circuit 60, and the drive signal supply circuit 70 is not limited at all, and may be the same as the conventional one.

A drive signal generation circuit 40 generates a reference drive signal for driving the ink head 25 . The reference drive signal has a plurality of drive pulses. The driving pulse typically includes a waveform element that causes the pressure chamber 33 to expand by dropping the potential, a waveform element that maintains the dropped potential to keep the pressure chamber 33 expanded, and a waveform element that keeps the pressure chamber 33 expanded. and a waveform element that raises the potential and causes the pressure chamber 33 to contract. The reference drive signal has N (where N is an integer equal to or greater than 3) drive pulses. The reference drive signal has at least the (N-2)th drive pulse, the (N-1)th drive pulse, and the Nth drive pulse for each drive cycle.

FIG. 5 is a waveform diagram of the reference drive signal S according to one embodiment. The horizontal axis t represents time, and the vertical axis V represents potential. tx represents one driving cycle. The drive signal generation circuit 40 is configured to repeatedly generate the reference drive signal S as shown in FIG. 5 for each drive cycle. The reference drive signal S in FIG. 5 has four drive pulses P1, P2, P3, and P4 in one drive cycle, and is an example in which the number of N is four. A reference drive signal S in FIG. 5 is, for example, a drive signal at a reference temperature (eg, 28° C.). In the present embodiment, as will be described later, the reference drive signal S sequentially generates four drive pulses P1, P2, P3, and P4 to continuously eject the first to fourth droplets from the nozzle 35. to spit out. Thereby, one large dot can be formed on the recording medium 5 .

As shown in FIG. 5, the reference drive signal S has a first drive pulse P1, a second drive pulse P2, a third drive pulse P3, and a fourth drive pulse P4. The second drive pulse P2 is an example of the (N-2)th drive pulse. The third drive pulse P3 is an example of the (N-1)th drive pulse. The fourth drive pulse P4 is an example of the Nth drive pulse. The second drive pulse P2 is positioned (generated) after the first drive pulse P1. The third drive pulse P3 is positioned (generated) after the second drive pulse P2. The fourth drive pulse P4 is positioned (generated) after the third drive pulse P3.

As shown in FIG. 5, the first drive pulse P1 has a first falling waveform T11 that descends from an intermediate potential _V0 to a first minimum potential _Vmin1 , and a first minimum potential maintenance waveform T11 that maintains the first minimum potential _Vmin1 . T12 and a first rising waveform T13 rising from the first minimum potential _Vmin1 to the intermediate potential _V0 . The first drive pulse P1 has a so-called trapezoidal waveform. A first droplet (ink droplet) is ejected from the nozzle 35 at a predetermined ejection speed by the first drive pulse P1.

As shown in FIG. 5, the second drive pulse P2 has a second forward falling waveform T21 falling from the intermediate potential _V0 to the second minimum potential _Vmin2 and a second minimum potential maintaining waveform _T21 maintaining the second minimum potential Vmin2. a waveform T22, a second pre-rising waveform T23 that rises from the second minimum potential _Vmin2 to the second potential _V2 , a second sustaining waveform T24 that maintains the second potential _V2 , and a second potential _V2 to the second potential V2 A second post-rising waveform T25 rising to the maximum potential _Vmax2 , a second maximum potential maintaining waveform T26 maintaining the second maximum potential _Vmax2 , and a second post-rising waveform T26 falling from the second maximum potential _Vmax2 to the intermediate potential _V0 . and a falling waveform T27. The second drive pulse P2 has a so-called pull-push-pull waveform. A second droplet (ink droplet) is ejected from the nozzle 35 at a predetermined ejection speed by the second drive pulse P2. The second droplet is an example of the (N-2)th droplet. Further, after the second droplet is ejected, the pressure chamber 33 is given an expansion/contraction vibration having a phase opposite to that when the droplet is ejected. Thereby, the kinetic energy of the meniscus 35a can be reduced and the pressure chamber 33 can be stabilized.

As shown in FIG. 5, the third driving pulse P3 has a third falling waveform T31 that descends from the intermediate potential _V0 to the third minimum potential _Vmin3 , and a third minimum potential maintenance waveform T31 that maintains the third minimum potential _Vmin3 . T32, and a third rising waveform T33 rising from the third minimum potential _Vmin3 to the intermediate potential _V0 . The third drive pulse P3 has a so-called trapezoidal waveform. A third droplet (ink droplet) is ejected from the nozzle 35 at a predetermined ejection speed by the third driving pulse P3. The third droplet is an example of the (N−1)th droplet.

As shown in FIG. 5, the fourth driving pulse P4 has a fourth forward falling waveform T41 falling from the intermediate potential _V0 to the fourth minimum potential _Vmin4 , and a fourth minimum potential maintaining waveform _T41 maintaining the fourth minimum potential Vmin4. a waveform T42, a fourth pre-rising waveform T43 rising from the fourth minimum potential _Vmin4 to the fourth potential _V4 , a fourth sustaining waveform T44 maintaining the fourth potential _V4 , and a fourth potential _V4 to the fourth potential V4 A fourth post-rising waveform T45 rising to the maximum potential _Vmax4 , a fourth maximum potential maintaining waveform T46 maintaining the fourth maximum potential _Vmax4 , and a fourth post-rising waveform T46 falling from the fourth maximum potential _Vmax4 to the intermediate potential _V0 . and a falling waveform T47. The fourth drive pulse P4 has a so-called pull-push-pull waveform. A fourth droplet (ink droplet) is ejected from the nozzle 35 at a predetermined ejection speed by the fourth drive pulse P4. A fourth droplet is ejected at a speed greater than or equal to that of the third droplet. A fourth droplet is an example of an Nth droplet. Further, after the fourth droplet is ejected, the pressure chamber 33 is given an expansion/contraction vibration having a phase opposite to that during ejection of the droplet. Thereby, the kinetic energy of the meniscus 35a can be reduced and the pressure chamber 33 can be stabilized.

The first drive pulse P1, the second drive pulse P2, the third drive pulse P3, and the fourth drive pulse P4 once increase and then decrease the volume of the pressure chamber 33 (the pressure chamber 33 is once expanded and then contracted). ) is the drive pulse. In other words, the first driving pulse P1 to the fourth driving pulse P4 are driving pulses for once decompressing the pressure chamber 33 and then increasing it. The first driving pulse P1 to the fourth driving pulse P4 are driving pulses for ejecting the first droplet to the fourth droplet, respectively.

In this embodiment, V _max4 >V _max2 >V ₄ >V ₀ >V ₂ >V _min1 >V _min3 >V _min4 >V _min2 . However, the relative magnitudes of V _max4 , V _max2 , V _{4 ,} V ₀ , V _{2 ,} V _min1 , V _min3 , V _min4 and V _min2 are not limited to those described above.

As shown in FIG. 5, the reference drive signal S has a first connection waveform C1, a second connection waveform C2, and a third connection waveform C3. The first connection waveform C1 is a waveform that connects the first drive pulse P1 and the second drive pulse P2. The first connection waveform C<b>1 is supplied to the piezoelectric element 36 when at least the first drive pulse P<b>1 and the second drive pulse P<b>2 are supplied to the piezoelectric element 36 . The second connection waveform C2 is a waveform that connects the second drive pulse P2 and the third drive pulse P3. The second connection waveform C2 is supplied to the piezoelectric element 36 when at least the second drive pulse P2 and the third drive pulse P3 are supplied to the piezoelectric element 36 . The third connection waveform C3 is a waveform that connects the third drive pulse P3 and the fourth drive pulse P4. The third connection waveform C3 is supplied to the piezoelectric element 36 when at least the third drive pulse P3 and the fourth drive pulse P4 are supplied to the piezoelectric element 36 .

As shown in FIG. 5, in the present embodiment, the fourth drive pulse P4 is started at a timing p×Tc (where p is an integer equal to or greater than 2) after the start of the third drive pulse P3. is set. Said p is 2, for example. As a result, the operation of the fourth drive pulse P4 can be synchronized with the Helmholtz natural oscillation period Tc, and ejection of the fourth droplet can be stabilized. Moreover, since the entire waveform length of the reference drive signal S can be shortened, the drive frequency can be increased, and high-speed printing can be achieved. In this specification, "p×Tc" is not limited to the case of strictly matching theoretical p×Tc, but allows fluctuations and errors of Tc. For example, "p × Tc" may be a value within the range of theoretical px Tc - (1/8) × Tc to px Tc + (1/8) × Tc, preferably the theoretical p It is a value within the range of ×Tc−(1/10)×Tc to p×Tc+(1/10)×Tc.

As shown in FIG. 5, in the present embodiment, the discharge time of the third drive pulse P3 and the fourth drive pulse P4 (that is, the total time of discharge and discharge maintenance) is the Helmholtz natural vibration period Tc of the ink head 25. It is set to 1/2. That is, when the start time of the third falling waveform T31 is t1 and the end time of the third minimum potential maintaining waveform T32 is t2, t1 and t2 are expressed by the following equation (1): t2-t1=(1/ 2) ×Tc; is set to satisfy. When the start time of the fourth pre-falling waveform T41 is t3 and the end time of the fourth minimum potential maintaining waveform T42 is t4, t3 and t4 are expressed by the following equation (1): t4−t3=(1/2 )×Tc; In this manner, the third drive pulse P3 and the fourth drive pulse P4 are configured so that the expanded state of the pressure chamber 33 is maintained for (1/2)×Tc. Thereby, the amplitude of the Helmholtz natural vibration period Tc of the pressure chamber 33 can be increased. By synchronizing the expansion and contraction of the pressure chamber 33 with the Helmholtz natural oscillation period Tc in this way, it is possible to stabilize the droplet ejection and to eject relatively large droplets with a lower drive voltage.

A correction coefficient calculation circuit 50 calculates a first temperature correction coefficient and a second temperature correction coefficient for correcting the reference drive signal S. FIG. As shown in FIG. 4, the correction coefficient calculation circuit 50 includes a determination circuit 51 and a calculation circuit 52, for example. The temperature detected by the thermistor 27 is input to the determination circuit 51 . Determination circuit 51 compares the temperature sensed by thermistor 27 with a reference temperature and determines whether the temperature sensed by thermistor 27 is lower than, equal to, or higher than the reference temperature. The reference temperature is predetermined according to, for example, the temperature environment in which the printer 10 is installed, the installation position of the thermistor 27, the viscosity of the ink contained in the ink cartridge 21, and the like. The reference temperature is, for example, normal temperature (eg, 28° C.). The arithmetic circuit 52 calculates a first temperature correction coefficient and a second temperature correction coefficient from the temperature of the ink detected by the thermistor 27, taking into consideration the viscosity and fluidity of the ink. The arithmetic circuit 52 calculates the first temperature correction coefficient when the temperature detected by the thermistor 27 is lower than a predetermined reference temperature (eg, 28° C.) (eg, 15° C. to 27° C.). The arithmetic circuit 52 calculates the second temperature correction coefficient when the temperature detected by the thermistor 27 is higher than the reference temperature (for example, 29° C. to 45° C.). The first temperature correction coefficient and the second temperature correction coefficient are set so that the size of the dots formed on the recording medium 5 is not affected by the temperature change of the ink (that is, the ink liquid contained in the dots in a wide temperature range). This is a coefficient for correcting the reference drive signal S so that the amount (volume) is constant. The first temperature correction coefficient is a coefficient that raises (increases) the driving voltages of at least the third driving pulse P3 and the fourth driving pulse P4 in the reference driving signal S. That is, the first temperature correction coefficient becomes a value that increases expansion and contraction of the pressure chamber 33 . The second temperature correction coefficient is a coefficient that lowers (reduces) the drive voltages of at least the third drive pulse P3 and the fourth drive pulse P4 in the reference drive signal S. That is, the second temperature correction coefficient becomes a value that reduces expansion and contraction of the pressure chamber 33 . Note that a well-known calculation method can be used to calculate the first temperature correction coefficient and the second temperature correction coefficient, so the description thereof will be omitted here. Further, the arithmetic circuit 52 does not calculate the first temperature correction coefficient and the second temperature correction coefficient when the temperature detected by the thermistor 27 is the same as the reference temperature.

The drive signal correction circuit 60 corrects the reference drive signal S. FIG. The drive signal correction circuit 60 corrects the reference drive signal S with the first temperature correction coefficient when the temperature detected by the thermistor 27 is lower than the reference temperature. The reference drive signal S corrected by the first temperature correction coefficient is supplied to the drive signal supply circuit 70 as the corrected drive signal SA. The drive signal correction circuit 60 corrects the reference drive signal S with the second temperature correction coefficient when the temperature detected by the thermistor 27 is higher than the reference temperature. The reference drive signal S corrected by the second temperature correction coefficient is supplied to the drive signal supply circuit 70 as the corrected drive signal SB. Note that the drive signal correction circuit 60 does not correct the reference drive signal S when the temperature detected by the thermistor 27 is the same as the reference temperature. That is, the reference drive signal S is supplied to the drive signal supply circuit 70 .

FIG. 6 is an example of the drive signal SA after correction. In the example shown in FIG. 6, the corrected drive signal SA is indicated by a solid line, and the reference drive signal S is indicated by a two-dot chain line. As shown in FIG. 6, the drive voltages of the first drive pulse P1 to the fourth drive pulse P4 of the corrected drive signal SA are higher than the drive voltages of the first drive pulse P1 to the fourth drive pulse P4 of the reference drive signal S. each high. Here, high means that the absolute value of the difference with respect to the intermediate potential _V0 is large. In other words, for example, the third minimum potential _Vmin3A of the third drive pulse P3 of the corrected drive signal SA is lower than the third minimum potential _Vmin3 of the third drive pulse P3 of the reference drive signal S, and the corrected drive signal SA is lower than the fourth minimum potential _Vmin4 of the fourth drive pulse P4 of the reference drive signal S, and is lower than the fourth minimum potential _Vmin4 of the fourth drive pulse P4 of the corrected drive signal SA. The potential _Vmax4A is higher than the fourth maximum potential _Vmax4 of the fourth drive pulse P4 of the reference drive signal S. When the amount of change in drive voltage at the minimum potential of the third drive pulse P3 corrected by the first temperature correction coefficient is ΔV _min 3 and the amount of change in drive voltage at the minimum potential of the fourth drive pulse P4 is ΔV _min 4 , ΔV _min 3<ΔV _min 4. Preferably, ΔV _min 3≦0.63ΔV _min 4 holds. Here, ΔV _min 3=V _min3A −V _min3 is established. ΔV _min 3 is an example of ΔV _min (N−1). ΔV _min 4=V _min4A −V _min4 is established. ΔV _min 4 is an example of ΔV _min (N). Further, when the amount of change in the drive voltage at the maximum potential of the fourth drive pulse corrected by the first temperature correction coefficient is ΔV _max 4, ΔV _min 3<ΔV _max 4 is established. Further, ΔV _min 4>ΔV _max 4 holds between ΔV _min 4 and ΔV _max 4. The amount of change in the drive voltage at the minimum potential of the first drive pulse P1 and the amount of change in the drive voltage at the minimum potential of the second drive pulse P2 corrected by the first temperature correction coefficient are greater than ΔV _min 3 and ΔV _min . less than 4

FIG. 7 is an example of the corrected drive signal SB. In the example shown in FIG. 7, the corrected drive signal SB is indicated by a solid line, and the reference drive signal S is indicated by a chain double-dashed line. As shown in FIG. 7, the drive voltages of the first drive pulse P1 to the fourth drive pulse P4 of the corrected drive signal SB are higher than the drive voltages of the first drive pulse P1 to the fourth drive pulse P4 of the reference drive signal S. respectively low. Here, "low" means that the absolute value of the difference with respect to the intermediate potential _V0 is small. In other words, for example, the third minimum potential _Vmin3B of the third drive pulse P3 of the corrected drive signal SB is higher than the third minimum potential _Vmin3 of the third drive pulse P3 of the reference drive signal S, and the corrected drive signal SB is higher than the fourth minimum potential _Vmin4 of the fourth drive pulse P4 of the reference drive signal S, and is higher than the fourth maximum potential _Vmin4 of the fourth drive pulse P4 of the corrected drive signal SB. The potential _Vmax4B is lower than the fourth maximum potential _Vmax4 of the fourth drive pulse P4 of the reference drive signal S. When the amount of change in drive voltage at the minimum potential of the third drive pulse P3 corrected by the second temperature correction coefficient is ΔV _min 3 and the amount of change in drive voltage at the minimum potential of the fourth drive pulse P4 is ΔV _min 4 , ΔV _min 3>ΔV _min 4. Preferably, ΔV _min 3≧2ΔV _min 4 holds. Here, ΔV _min 3=V _min3 −V _min3B is established. ΔV _min 4=V _min4 −V _min4B is established. Further, when the amount of change in the drive voltage at the maximum potential of the fourth drive pulse corrected by the second temperature correction coefficient is ΔV _max 4, ΔV _min 3>ΔV _max 4 is established. Further, ΔV _min 4>ΔV _max 4 holds between ΔV _min 4 and ΔV _max 4. The amount of change in the drive voltage at the minimum potential of the first drive pulse P1 and the amount of change in the drive voltage at the minimum potential of the second drive pulse P2 corrected by the second temperature correction coefficient are greater than ΔV _min 4 and ΔV _min less than 3

The drive signal supply circuit 70 supplies a part or all of the reference drive signal S, the corrected drive signal SA, and the corrected drive signal SB to the piezoelectric elements 36 of the ink head 25 . By appropriately selecting the drive pulse to be supplied to the piezoelectric element 36, the liquid amount (volume) of the ink ejected from the nozzles 35 of the ink head 25 in one drive cycle can be changed. Thereby, the size of the ink dots formed on the recording medium 5 can be changed. The printer 10 according to this embodiment can form dots of three different sizes. That is, as shown in FIG. 4, the drive signal supply circuit 70 has a small dot forming portion 71, a medium dot forming portion 72 and a large dot forming portion 73. FIG. The small dot forming portion 71 is an example of a first dot forming portion. The medium dot forming portion 72 is an example of a second dot forming portion. The large dot forming portion 73 is an example of a third dot forming portion. When forming a small dot, the small dot forming section 71 supplies the piezoelectric element 36 with a second drive pulse P2 which is part of the drive signal and a first drive pulse which is another part of the drive signal. The pulse P1, the third drive pulse P3 and the fourth drive pulse P4 are not supplied. The small dot formation unit 71 ejects small dot liquid droplets from the nozzles 35 . Here, the small dot droplet corresponds to the second droplet. When forming a medium dot, the medium dot forming section 72 supplies the piezoelectric element 36 with the third drive pulse P3 and the fourth drive pulse P4, but does not supply the first drive pulse P1 and the second drive pulse P2. . The medium dot formation unit 72 ejects medium dot liquid droplets from the nozzles 35 . Here, the medium-dot droplet corresponds to the merged third and fourth droplets. The large dot forming section 73 supplies the piezoelectric element 36 with a first driving pulse P1, a second driving pulse P2, a third driving pulse P3 and a fourth driving pulse P4 when forming a large dot. The large dot formation unit 73 ejects large dot liquid droplets from the nozzles 35 . Here, the large-dot droplet corresponds to a merged droplet of the first, second, third, and fourth droplets. For example, a small dot has an ink mass of approximately 8 ng to approximately 10 ng, a medium dot has an ink mass of approximately 12 ng to approximately 16 ng, and a large dot has an ink mass of approximately 20 ng to approximately 24 ng.

Next, operation of the printer 10 will be described. When the printer 10 is activated by the user, the controller 28 prepares to start printing. Specifically, print data and various data representing the characteristics of the ink head 25 (for example, the Helmholtz natural vibration period Tc) are read from the control device 28 . The control device 28 also lowers the potential of the piezoelectric element 36 to the intermediate potential _V0 to slightly expand the pressure chamber 33 . In this state, the ink head 25 waits until any one of the reference drive signal S, corrected drive signal SA, and corrected drive signal SB is sent from the control device 28 .

When the user instructs the printer 10 to print, the controller 28 drives the feed motor of the media transport mechanism. As a result, the recording medium 5 is conveyed in the sub-scanning direction X and arranged at a predetermined print position. The control device 28 drives the carriage motor 18 a of the carriage moving mechanism 18 . The control device 28 drives the ink head 25 while moving the carriage 11 in the main scanning direction Y. As shown in FIG. More specifically, part or all of the drive signal is supplied to the piezoelectric element 36 of the ink head 25 as an electrical signal. As a result, the piezoelectric element 36 expands and contracts according to the drive signal, and the pressure in the pressure chamber 33 changes. As a result, droplets having a predetermined mass are ejected from the nozzle 35 at a predetermined ejection speed. The ejected droplets land on the recording medium 5 to form one dot. When one line (one pass) is printed by repeating such operations, the feed motor of the medium transport mechanism is driven, and the recording medium 5 is placed at the print position for the next line (pass). The printer 10 repeats this to perform predetermined printing.

As described above, according to the liquid ejecting apparatus 20 of the present embodiment, when the temperature detected by the thermistor 27 is lower than the reference temperature (for example, 28° C.), ΔV _min (N−1)<ΔV _min (N) is established. do. Here, ΔV _min 3<ΔV _min 4 holds. When the ink temperature is lower than the reference temperature, the ink viscosity increases. Therefore, when the third droplet is ejected by the third drive pulse P3, the residual vibration of the second drive pulse P2 is attenuated to some extent. However, by raising the drive voltage of the third drive pulse P3 above the drive voltage at the reference temperature, the residual vibration of the second drive pulse P2 can be further damped. Although it is necessary to eject the same amount of liquid from the nozzle 35 as at the reference temperature even at a low temperature (for example, 20° C. to 27° C.), since ΔV _min 3<ΔV _min 4 holds, the fourth driving pulse The volume of the fourth drop ejected by P4 can be increased. Accordingly, droplets can be stably ejected from the nozzle 35 in a temperature range from room temperature to low temperature (for example, 15° C. to 28° C.).

Also, when the temperature detected by the thermistor 27 is higher than the reference temperature, ΔV _min (N−1)>ΔV _min (N) is established. Here, ΔV _min 3>ΔV _min 4 holds. When the temperature of the ink is higher than the reference temperature, the viscosity of the ink decreases. Therefore, when the third droplet is ejected by the third drive pulse P3, the residual vibration of the second drive pulse P2 is not attenuated so much. Therefore, by lowering the drive voltage of the third drive pulse P3 below the drive voltage at the reference temperature, the residual vibration of the second drive pulse P2 can be damped. Although it is necessary to eject the same amount of liquid from the nozzle 35 at a high temperature (for example, 29° C. to 45° C.) as at the reference temperature, since ΔV _min 3>ΔV _min 4 holds, the fourth driving pulse The volume of the fourth drop ejected by P4 can be increased. Accordingly, droplets can be stably ejected from the nozzle 35 in a temperature range from room temperature to high temperature (for example, 28° C. to 45° C.).

In the liquid ejecting apparatus 20 of this embodiment, ΔV _min 3<ΔV _max 4 is established when the temperature detected by the thermistor 27 is lower than the reference temperature. Thereby, the residual vibration of the fourth drive pulse P4 can be further damped in the temperature range from room temperature to low temperature.

In the liquid ejecting apparatus 20 of this embodiment, ΔV _min 3>ΔV _max 4 is established when the temperature detected by the thermistor 27 is higher than the reference temperature. Thereby, the residual vibration of the fourth driving pulse P4 can be further damped in the temperature range from room temperature to high temperature.

In the liquid ejecting apparatus 20 of the present embodiment, ΔV _min 4>ΔV _max 4 is established between ΔV _min 4 and ΔV _max 4 . This makes it possible to attenuate the residual vibration of the fourth driving pulse while increasing the droplet volume of the fourth droplet ejected by the fourth driving pulse.

In the liquid ejecting apparatus 20 of this embodiment, ΔV _min 3≦0.63ΔV _min 4 is established when the temperature detected by the thermistor 27 is lower than the reference temperature. As a result, droplets can be stably ejected in a temperature range from room temperature to low temperature.

In the liquid ejecting apparatus 20 of this embodiment, ΔV _min 3≧2ΔV _min 4 is established when the temperature detected by the thermistor 27 is higher than the reference temperature. As a result, droplets can be stably ejected in a temperature range from room temperature to high temperature.

In the liquid ejecting apparatus 20 of the present embodiment, the third driving pulse P3 and the fourth driving pulse P4 are configured so that the expanded state of the pressure chamber 33 is maintained for (1/2)×Tc. there is That is, in the third drive pulse P3 and the fourth drive pulse P4, the pressure chamber 33 is switched from the expanded state to the contracted state at the timing of (1/2)×Tc. As a result, the third drive pulse P3 and the fourth drive pulse P4 act to amplify the Helmholtz natural vibration period Tc of the pressure chamber 33 . As a result, the ejection stability of droplets is improved, and the amount of expansion and contraction of the pressure chamber 33 is increased, so that larger droplets can be ejected.

In the liquid ejection device 20 of this embodiment, the driving signal supply circuit 70 includes a small dot forming section 71 , a medium dot forming section 72 and a large dot forming section 73 . For example, when droplets are ejected by the large dot forming section 73, the residual vibration of the second driving pulse P2 may affect the third driving pulse P3. Residual vibration can be attenuated to stably eject large droplets.

The printer 10 of this embodiment includes a liquid ejection device 20, and the liquid is ink. The printer 10 having the liquid ejection device 20 can stably form large dots by the multi-dot method. Therefore, for example, variation in dot size can be reduced, and image quality can be improved. In addition, it is possible to reduce contamination of the recording medium 5 and the main body of the printer caused by ink mist and the like.

The preferred embodiments of the present invention have been described above. However, the above-described embodiments are merely examples, and the present invention can be implemented in various other forms.

In the above-described embodiment, ΔV _max 4 is a value greater than 0, but is not limited to this. That is, the fourth maximum potential V _max4A of the fourth drive pulse P4 of the corrected drive signal SA and the corrected drive signal SB is the same as the fourth maximum potential V _max4 of the fourth drive pulse P4 of the reference drive signal S (ΔV _max ( N)=0).

In each of the embodiments described above, the piezoelectric element 36 in the longitudinal vibration mode is used as the actuator, but the present invention is not limited to this. The actuator may be a transverse mode piezoelectric element. Further, the actuator is not limited to the piezoelectric element, and may be, for example, a magnetostrictive element.

In the above-described embodiment, the ejection head is the ink head 25 mounted on the printer 10, but it is not limited to this. The ink head 25 can be mounted on, for example, various manufacturing apparatuses employing an inkjet method, measuring instruments such as a micropipette, and the like, and can be used for various purposes.

10 Printer (inkjet printer)
20 liquid ejection device 25 ink head (liquid ejection head)
28 control device 32 partition plate 33 pressure chamber 35 nozzle 36 piezoelectric element (actuator)
40 drive signal generation circuit 50 correction coefficient calculation circuit 60 drive signal correction circuit 70 drive signal supply circuit

Claims (9)

a liquid ejection head for ejecting liquid;
a temperature sensor that detects the temperature of the liquid;
a control device that controls the liquid ejection head,
The liquid ejection head is
a case in which a pressure chamber in which the liquid is stored is formed;
a partition plate provided in the case and partitioning a part of the pressure chamber;
an actuator connected to the partition plate and deformed when an electric signal is supplied;
a nozzle formed in the case and communicating with the pressure chamber;
The control device is
(N-2)th drive pulse for ejecting the (N-2)th droplet (where N is an integer equal to or greater than 3) by expanding and contracting the pressure chamber in each drive cycle; and an (N−1)th driving pulse positioned behind the (N−2)th driving pulse and for ejecting the (N−1)th droplet by expanding and contracting the pressure chamber. , and an Nth drive pulse positioned behind the (N−1)th drive pulse and for ejecting the Nth droplet by expanding and contracting the pressure chamber. a drive signal generation circuit for
when the temperature detected by the temperature sensor is lower than a predetermined reference temperature, at least the drive voltage of the (N−1)th drive pulse and the drive voltage of the Nth drive pulse of the reference drive signal calculating a first temperature correction coefficient to be increased, and when the temperature detected by the temperature sensor is higher than the reference temperature, the drive voltage of at least the (N-1)th drive pulse of the reference drive signal and a correction coefficient calculation circuit for calculating a second temperature correction coefficient for decreasing the drive voltage of the Nth drive pulse;
When the temperature detected by the temperature sensor is lower than the reference temperature, the reference drive signal is corrected with the first temperature correction coefficient, and the temperature detected by the temperature sensor is higher than the reference temperature. a drive signal correction circuit for correcting the reference drive signal with the second temperature correction coefficient,
a drive signal supply circuit that supplies part or all of the corrected reference drive signal to the actuator;
When the Helmholtz natural vibration period of the liquid ejection head is Tc, the Nth drive pulse is p×Tc (where p is an integer of 2 or more) from the start of the (N−1)th drive pulse. ) is started at a later time, and
Let ΔV _min (N−1) be a change amount of the drive voltage at the minimum potential of the (N−1)th drive pulse corrected by the first temperature correction coefficient or the second temperature correction coefficient, and the Nth drive pulse where ΔV _min (N) is the amount of change in the driving voltage at the minimum potential of the temperature sensor, ΔV _min (N−1)<ΔV _min (N) when the temperature detected by the temperature sensor is lower than the reference temperature and ΔV _min (N−1)>ΔV _min (N) when the temperature detected by the temperature sensor is higher than the reference temperature. The temperature detected by the temperature sensor is ΔV _max (N), where ΔV max (N) is the amount of change in the drive voltage at the maximum potential of the N-th drive pulse corrected by the first temperature correction coefficient or the second temperature correction coefficient. 2. The liquid ejecting apparatus according to claim 1, wherein ΔV _min (N−1)<ΔV _max (N) is established when the temperature is lower than the reference temperature. 3. The liquid ejecting apparatus according to claim 2, wherein ΔV _min (N−1)>ΔV _max (N) is established when the temperature detected by the temperature sensor is higher than the reference temperature. 4. The liquid ejecting apparatus according to claim 2, wherein ΔV _min (N)>ΔV _max (N) is established between ΔV _min (N) and ΔV _max (N). 5. The liquid ejection according to claim 1, wherein ΔV _min (N−1)≦0.63ΔV _min (N) holds when the temperature detected by the temperature sensor is lower than the reference temperature. Device. 6. The liquid ejecting apparatus according to claim 1, wherein ΔV _min (N−1)≧2ΔV _min (N) holds when the temperature detected by the temperature sensor is higher than the reference temperature. 2. From claim 1, wherein the (N-1)th drive pulse and the Nth drive pulse are configured such that the expanded state of the pressure chamber is maintained for a time of (1/2)×Tc. 7. The liquid ejection device according to any one of 6. The drive signal supply circuit is
a first dot formation unit that does not supply the (N−1)th drive pulse and the Nth drive pulse but supplies the (N−2)th drive pulse to the actuator;
a second dot formation unit that does not supply the (N−2)th drive pulse to the actuator and supplies the (N−1)th drive pulse and the Nth drive pulse to the actuator;
and a third dot forming section that supplies the (N-2)th driving pulse, the (N-1)th driving pulse and the Nth driving pulse to the actuator. The liquid ejection device according to any one of 1. An inkjet printer comprising the liquid ejection device according to any one of claims 1 to 8, wherein the liquid is ink.

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