JP2011020280A - Liquid delivering apparatus and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid delivering apparatus and the like preventing dots from being separated while suppressing occurrence of mist or the like when a highly viscous liquid is delivered. <P>SOLUTION: The liquid delivering apparatus includes: a liquid delivering head which includes a pressure generating chamber that communicates with a nozzle opening, and a pressure generating element that causes pressure fluctuation of a liquid in the pressure generating chamber, and delivers the liquid from the nozzle opening by operation of the pressure generating element; and a driving signal generating part which generates a driving pulse for driving the pressure generating element. The nozzle opening has a first portion whose opening area is smaller on a liquid delivering side than a pressure generating chamber side, and a second portion communicating with the delivering side end of the first portion. The driving pulse includes a plurality of expansion elements for drawing in a meniscus, and a delivering element for delivering a liquid droplet by changing voltage so as to contract the pressure generating chamber. The expansion element includes a first expansion element, and a second expansion element for drawing in the meniscus at a different voltage change rate from the first expansion element. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid ejection apparatus such as an ink jet printer and a control method thereof, and in particular, discharges liquid from the nozzle opening by applying pressure fluctuation to the pressure generation chamber communicating with the nozzle opening. The present invention relates to a liquid discharge apparatus including a liquid discharge head to be controlled and a control method thereof.

The liquid ejection apparatus is an apparatus that includes a liquid ejection head capable of ejecting liquid and ejects various liquids from the liquid ejection head. As a representative example of this liquid ejection apparatus, for example, an ink jet recording head (hereinafter simply referred to as a recording head) as a liquid ejection head is provided, and liquid ink is ejected from the nozzle of this recording head to a recording medium such as recording paper. An image recording apparatus such as an ink jet printer (hereinafter simply referred to as a printer) that records an image or the like by discharging and landing on a (landing target) can be given. In recent years, liquid ejecting apparatuses have been applied not only to the image recording apparatus but also to various manufacturing apparatuses such as a manufacturing apparatus for a color filter such as a liquid crystal display.
In the liquid ejection device, a pressure change is applied to the liquid in the pressure generation chamber by applying a discharge drive pulse to a pressure generation element (for example, a piezoelectric vibrator or a heating element) and driving the pressure generation element. Some are configured to eject liquid from a nozzle communicating with the pressure generating chamber. In such a liquid ejecting apparatus, the amount of ejected liquid can be increased by increasing the amplitude of pressure vibration applied to the liquid in the pressure generating chamber. In other words, it is possible to increase the amount of liquid ejected by increasing the drive voltage of the ejection drive pulse (see, for example, Patent Document 1).

JP 2003-94656 A

In recent years, attempts have been made to discharge a liquid (hereinafter also referred to as a high-viscosity liquid) having a higher viscosity than a conventionally treated liquid such as UV ink (ultraviolet curable ink), for example. That is, in the past, liquids having a low viscosity such as water were targeted, but in recent years, attempts have been made to eject high viscosity liquids of 6 millipascal seconds or more. In order to obtain a sufficient discharge amount when discharging the high-viscosity liquid, it is necessary to give the liquid in the pressure generation chamber a pressure change having a magnitude corresponding to the discharge amount. However, when the pressure change is increased, the flying speed of the liquid also increases, and a phenomenon in which the rear end portion of the liquid extends like a tail tends to occur. Then, there is a possibility that the tail portion separates from the droplet main body and flies and does not land on the regular position (desired position) on the landing target. For example, an ink jet printer has a problem in that the tail part becomes a mist and is displaced from a normal position and landed to separate dots, thereby causing deterioration in image quality. In particular, in a high-viscosity liquid, the tail part is separated into several parts, and these separated parts (satellite ink droplets or mist) cause a significant deterioration in image quality.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a liquid ejection device capable of preventing the separation of dots by suppressing the generation of mist and the like when ejecting a highly viscous liquid. And providing a control method thereof.

The present invention has been proposed to achieve the above object, and includes a pressure generation chamber communicating with the nozzle opening, and a pressure generation element that causes a pressure fluctuation in the liquid of the pressure generation chamber. A liquid discharge head capable of discharging liquid from the nozzle opening by operation of the generating element;
A drive signal generator for generating a series of drive signals including a drive pulse for driving the pressure generating element;
With
The nozzle opening is
A first portion in which the liquid discharge side is defined as an opening area smaller than the pressure generation chamber side;
A liquid ejection device having a second portion communicating with the ejection side end of the first portion,
The drive pulse generated by the drive signal generator includes a plurality of expansion elements that expand the pressure generation chamber and draw a meniscus,
A discharge element that discharges a droplet by changing a voltage so as to contract the expanded pressure generation chamber,
The expansion element includes a first expansion element and a second expansion element that draws a meniscus at a voltage change rate different from that of the first expansion element.

  Other features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

2 is a block diagram illustrating an electrical configuration of a printer. FIG. FIG. 3 is a cross-sectional view of a main part for explaining the configuration of a recording head. FIG. 3A is a cross-sectional view illustrating the shape of a nozzle. FIG. 3B is a view of the nozzle as seen from the tapered portion side. It is a figure which shows the list of the evaluation result regarding a taper angle. It is a wave form diagram explaining the structure of an ejection pulse. (A)-(f) is a figure which shows the motion of the meniscus at the time of discharging an ink drop. It is a wave form diagram explaining the modification of an ejection pulse.

=== Summary of disclosure ===
At least the following matters will become clear from the description of the present specification and the accompanying drawings.

  A pressure generating chamber that communicates with the nozzle opening, and a liquid discharging head that has a pressure generating element that causes a pressure fluctuation in the liquid in the pressure generating chamber, and that can discharge liquid from the nozzle opening by the operation of the pressure generating element; A drive signal generator for generating a series of drive signals including a drive pulse for driving the pressure generating element, and the nozzle opening is defined to have an opening area smaller on the liquid discharge side than on the pressure generation chamber side. A liquid discharge apparatus having a first portion and a second portion communicating with a discharge side end portion of the first portion, wherein the pressure generation chamber is expanded by the drive pulse generated by the drive signal generation portion. A plurality of expansion elements that draw the meniscus, and a discharge element that discharges droplets by changing a voltage so as to contract the expanded pressure generation chamber, wherein the expansion element is a first expansion element , Wherein the first expansion element is a liquid discharge apparatus characterized in that it comprises a second expansion component drawing the meniscus at different voltage change rate.

  According to such a liquid ejecting apparatus, a pressure generating chamber communicating with the nozzle opening, a liquid ejecting head having a pressure generating element that causes a pressure fluctuation in the liquid in the pressure generating chamber, and a drive for driving the pressure generating element. A liquid ejection device including a drive signal generation unit that generates a series of drive signals including pulses, and the drive pulse generated by the drive signal generation unit includes a plurality of expansions that expand a pressure generation chamber and draw a meniscus And a discharge element that discharges a droplet by changing a voltage so as to contract the expanded pressure generation chamber, and the expansion element has a voltage change rate different from that of the first expansion element and the first expansion element. And a second expansion element that draws the meniscus. Therefore, when a liquid having a relatively high viscosity (high viscosity liquid) is drawn to the pressure generating chamber side, the peripheral portion of the meniscus (nozzle opening) Side) closer to the inner circumference easily move than the central portion, even if difficult to follow the pressure change, and the liquid in the liquid and the meniscus outer peripheral edge of the central portion of the meniscus, it is possible to match the timing to nestle. This prevents the meniscus central portion at the nozzle opening and the outer peripheral edge side of the meniscus from being out of phase when the liquid droplet is discharged due to the subsequent contraction of the pressure generation chamber. The phenomenon that the end portion extends like a tail can be suppressed, and the shape can be made as close to a sphere as possible. As a result, it is possible to prevent the liquid from being separated and landing on the landing target. In addition, it is possible to suppress a drop in the droplet flying speed caused by the reverse phase.

  Also, the liquid in the nozzle opening can be drawn into the pressure generating chamber side strongly or quickly when the opening area of the nozzle opening is small, and can be drawn into the pressure generating chamber side strongly and quickly when the opening area of the nozzle opening is large. For this reason, a configuration having a first portion in which the liquid discharge side is defined as an opening area smaller than the pressure generation chamber side and a second portion communicating with the discharge side end portion of the first portion, like the nozzle opening. And when the meniscus is located in the first part of the opening area where the liquid discharge side is smaller than the pressure generation chamber side and when the meniscus is located in the second part communicating with the discharge side end of the first part, The meniscus can be drawn by expanding the pressure generating chamber with the first expansion element and the second expansion element having different voltage change rates. That is, the method of drawing the meniscus can be changed according to the opening area of the nozzle opening. By adopting such a configuration, the meniscus is pulled in while maintaining a good state, and the liquid is further separated into a plurality of objects on the landing target by discharging the central portion of the meniscus surface in a good state spread. Landing can be prevented.

In the above configuration, it is desirable that the voltage change rate of the first expansion element is set smaller than the voltage change rate of the second expansion element.
According to this configuration, since the voltage change rate of the first expansion element is set to be smaller than the voltage change rate of the second expansion element, compared with the central portion of the meniscus in the nozzle opening during the voltage of the first expansion element. Thus, the phenomenon that the outer peripheral edge side of the meniscus is delayed can be suppressed. As a result, when droplets are ejected due to contraction of the pressure generation chamber, the center portion of the meniscus and the outer peripheral side of the meniscus are prevented from being in opposite phases, and tail growth associated with the ejected liquid is suppressed. be able to.

The said structure WHEREIN: It is desirable to include the expansion | swelling hold element which maintains a voltage for a fixed time at the rear end of the said 1st expansion element between the said 1st expansion element and the said 2nd expansion element.
According to the above configuration, since the expansion hold element that maintains the voltage for a certain period of time at the rear end of the first expansion element is included between the first expansion element and the second expansion element, The phenomenon that the outer peripheral edge side of the meniscus is delayed as compared with the center portion of the meniscus in the nozzle opening can be further suppressed. As a result, when droplets are ejected due to contraction of the pressure generation chamber, the center portion of the meniscus and the outer peripheral side of the meniscus are prevented from being in opposite phases, and tail growth associated with the ejected liquid is suppressed. be able to.

In the above configuration, it is preferable that the discharge element includes a first discharge element and a second discharge element that contracts the pressure generating chamber at a voltage change rate different from that of the first discharge element.
According to the above configuration, the discharge element includes the first discharge element and the second discharge element that contracts the pressure generating chamber at a voltage change rate different from that of the first discharge element. The center of the meniscus and the outer periphery of the meniscus are close to each other when the liquid droplet is discharged due to the contraction of the pressure generation chamber in a state in which the outer periphery of the meniscus is prevented from being in reverse phase. The timing can be adjusted. Thereby, the growth of the tail accompanying the discharged liquid can be suppressed, and it is possible to prevent the liquid from being separated and landed on the landing target.

In the above-described configuration, it is desirable that a discharge hold element that maintains a voltage for a certain period of time at a rear end of the first discharge element is preferably included between the first discharge element and the second discharge element.
According to the above configuration, since the discharge hold element that maintains the voltage for a certain period of time at the rear end of the first discharge element is included between the first discharge element and the second discharge element, the central portion of the meniscus and the meniscus at the nozzle opening are included. When the liquid droplet is discharged due to the contraction of the pressure generation chamber in a state in which the outer peripheral edge side of the nozzle is prevented from being in an opposite phase, the timing is set so that the central portion of the meniscus at the nozzle opening and the outer peripheral edge side of the meniscus closely Can be matched. Thereby, the growth of the tail accompanying the discharged liquid can be suppressed, and it is possible to prevent the liquid from being separated and landed on the landing target.

In the above-described configuration, the viscosity of the liquid is preferably 8 millipascal seconds or more and 15 millipascal seconds or less, and the first portion of the nozzle opening preferably defines a frustoconical space having a taper angle of 40 degrees or more. .
When the flow path through which the liquid flows is narrowed by the tapered portion, the force applied to the liquid becomes larger and the stress concentrates. For this reason, by pressurizing the liquid in a state where there is little liquid, the applied pressure can be concentrated on the liquid present at the discharge side end of the tapered portion, and the liquid can be strongly pressed locally. When the viscosity of the liquid is 8 millipascal seconds or more and 15 millipascal seconds or less, the taper angle of the first portion of the nozzle opening is set to 40 degrees or more as in the above configuration, so that the liquid can be more effectively discharged. Strong pressure can be applied locally.

In the above configuration, the viscosity of the liquid is preferably 8 millipascal seconds or more and 30 millipascal seconds or less, and the first portion of the nozzle opening preferably defines a frustoconical space having a taper angle of 50 degrees or more. .
As in the above configuration, when the viscosity of the liquid is 8 millipascal seconds or more and 30 millipascal seconds or less, the taper angle of the first portion of the nozzle opening is set to 50 degrees or more, so that the liquid can be more effectively discharged. Strong pressure can be applied locally.

The said structure WHEREIN: It is desirable for the length of the said 1st part in the said nozzle opening to have a length more than the said 2nd part.
According to the above configuration, since the length of the first portion in the nozzle opening has a length equal to or longer than the second portion, the length of the first portion, ie, the portion having the taper, with respect to the entire length of the nozzle opening is tapered. It becomes longer than the 2nd part which does not have. For this reason, the liquid pressure on the discharge side of the first part can be locally increased by pressurizing the liquid of the first part, compared with the case where the length of the first part is shorter than the length of the second part. The high part can be concentrated in the vicinity of the meniscus. For this reason, the pressure change given to the liquid can be used more efficiently for discharging the liquid. As a result, even a highly viscous liquid can be efficiently discharged.

  The control method of the liquid ejection apparatus of the present invention includes a pressure generation chamber communicating with the nozzle opening, and a pressure generation element that causes a pressure fluctuation in the liquid in the pressure generation chamber. A liquid discharge head capable of discharging liquid from the nozzle opening, and a drive signal generation unit that generates a series of drive signals including a drive pulse for driving the pressure generating element, wherein the nozzle opening has a liquid discharge side A control method for a liquid ejection apparatus, comprising: a first portion that is defined as an opening area smaller than a pressure generation chamber side; and a second portion that communicates with a discharge side end of the first portion, wherein the pressure generation chamber is A plurality of expansion steps for expanding and drawing the meniscus; and a discharge step for discharging droplets by changing a voltage so as to contract the pressure generating chamber expanded in the expansion step. A first expansion step, and the first expansion step is a method of controlling a liquid ejecting apparatus which comprises a second expansion step of pulling the meniscus at different voltage change rate.

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

  FIG. 1 is a block diagram showing the electrical configuration of the printer. This printer is schematically composed of a printer controller 1 and a print engine 2. The printer controller 1 includes an external interface (external I / F) 3 that exchanges data with an external device such as a host computer, a RAM 4 that stores various data, a control routine for various data processing, and the like. ROM 5 stored, control unit 6 that controls each unit, oscillation circuit 7 that generates a clock signal, drive signal generation circuit 8 that generates a drive signal to be supplied to the recording head 10, dot pattern data, drive signals, and the like And an internal interface (internal I / F) 9 for outputting to the recording head 10.

  The control unit 6 controls each unit, converts print data received from the external device through the external I / F 3 into dot pattern data, and outputs the dot pattern data to the recording head 10 side through the internal I / F 9. . This dot pattern data is constituted by print data obtained by decoding (translating) gradation data. The control unit 6 supplies a latch signal, a channel signal, and the like to the recording head 10 based on the clock signal from the oscillation circuit 7. The latch pulses and channel pulses included in these latch signals and channel signals define the supply timing of each pulse constituting the drive signal.

The drive signal generation circuit 8 is controlled by the control unit 6 and generates a drive signal for driving the piezoelectric vibrator 20 (see FIG. 2). The drive signal generation circuit 8 in the present embodiment discharges ink droplets (a type of liquid droplets), and discharge pulses for forming dots on recording paper as a type of discharge target, or nozzle openings 32 (FIG. 2). The free surface of the ink (a kind of liquid) exposed to the reference), that is, a drive signal COM including a fine vibration pulse for stirring the ink by slightly vibrating the meniscus within one recording period is generated. Yes.

Next, the configuration on the print engine 2 side will be described. The print engine 2 includes a recording head 10, a carriage moving mechanism 12, a paper feed mechanism 13, and a linear encoder 14. The recording head 10 includes a shift register (SR) 15, a latch 16, a decoder 17, a level shifter 18, a switch 19, and a piezoelectric vibrator 20. The dot pattern data (SI) from the printer controller 1 is serially transmitted to the shift register 15 in synchronization with the clock signal (CK) from the oscillation circuit 7. This dot pattern data is 2-bit data, for example, by gradation information representing four recording gradations (ejection gradations) composed of non-recording (microvibration), small dots, medium dots, and large dots. It is configured. Specifically, non-printing is represented by gradation information “00”, small dots are represented by gradation information “01”, medium dots are represented by gradation information “10”, and large dots are represented by gradation information “11”.

  A latch 16 is electrically connected to the shift register 15. When a latch signal (LAT) from the printer controller 1 is input to the latch 16, the dot pattern data in the shift register 15 is latched. The dot pattern data latched by the latch 16 is input to the decoder 17. The decoder 17 translates 2-bit dot pattern data to generate pulse selection data. This pulse selection data is constituted by associating each bit with each pulse constituting the drive signal COM. Then, supply or non-supply of the ejection pulse to the piezoelectric vibrator 20 is selected according to the contents of each bit, for example, “0” and “1”.

  Then, the decoder 17 outputs pulse selection data to the level shifter 18 when receiving the latch signal (LAT) or the channel signal (CH). In this case, the pulse selection data is input to the level shifter 18 in order from the upper bit. The level shifter 18 functions as a voltage amplifier. When the pulse selection data is “1”, the level shifter 18 outputs an electric signal boosted to a voltage capable of driving the switch 19, for example, a voltage of about several tens of volts. The pulse selection data “1” boosted by the level shifter 18 is supplied to the switch 19. The drive signal COM from the drive signal generation circuit 8 is supplied to the input side of the switch 19, and the piezoelectric vibrator 20 is connected to the output side of the switch 19.

  The pulse selection data controls the operation of the switch 19, that is, the supply of the drive pulse in the drive signal to the piezoelectric vibrator 20. For example, during a period in which the pulse selection data input to the switch 19 is “1”, the switch 19 is in a connected state, and the corresponding ejection pulse is supplied to the piezoelectric vibrator 20 and follows the waveform of the ejection pulse. As a result, the potential level of the piezoelectric vibrator 20 changes. On the other hand, during the period when the pulse selection data is “0”, the level shifter 18 does not output an electrical signal for operating the switch 19. For this reason, the switch 19 is in a disconnected state, and no ejection pulse is supplied to the piezoelectric vibrator 20.

  The decoder 17, level shifter 18, switch 19, control unit 6, and drive signal generation circuit 8 that perform such operations function as a drive unit in the present invention, and are necessary from the drive signal based on the dot pattern data. An ejection pulse is selected and applied (supplied) to the piezoelectric vibrator 20. As a result, the piezoelectric vibrator 20 expands or contracts, and the pressure generating chamber 35 (see FIG. 2) expands or contracts as the piezoelectric vibrator 20 expands or contracts, so that gradation information forming dot pattern data is obtained. A corresponding amount of ink droplet is ejected from the nozzle opening 32.

  FIG. 2 is a cross-sectional view of the main part of the recording head 10 described above. The recording head 10 according to the present embodiment is common to a vibrator unit 25 in which a piezoelectric vibrator group 22, a fixing plate 23, a flexible cable 24, and the like are unitized, and a head case 26 that can store the vibrator unit 25. And a flow path unit 27 that forms a series of ink flow paths (liquid flow paths) from the ink chamber (common liquid chamber) through the pressure generation chamber 35 to the nozzle opening 32.

First, the vibrator unit 25 will be described. The piezoelectric vibrator 20 (a kind of pressure generating element in the present invention) constituting the piezoelectric vibrator group 22 is formed in a comb-like shape elongated in the vertical direction, and is cut into an extremely narrow width of about several tens of μm. . The piezoelectric vibrator 20 is configured as a longitudinal vibration type piezoelectric vibrator that can expand and contract in the vertical direction. Each piezoelectric vibrator 20 is fixed in a so-called cantilever state in which a fixed end portion is joined to a fixing plate 23 so that a free end portion protrudes outward from the tip edge of the fixing plate 23. The distal end of the free end portion of each piezoelectric vibrator 20 is joined to an island portion 40 that constitutes the diaphragm portion 38 of the flow path unit 27, as will be described later. The flexible cable 24 is electrically connected to the piezoelectric vibrator 20 on the side surface of the fixed end opposite to the fixed plate 23. In addition, the fixing plate 23 that supports each piezoelectric vibrator 20 is configured by a metal plate material having rigidity capable of receiving a reaction force from the piezoelectric vibrator 20.

  Next, the flow path unit 27 will be described. The flow path unit 27 includes a nozzle plate 29, a flow path forming substrate 30, and a vibration plate 31. The nozzle plate 29 is on one surface of the flow path forming substrate 30, and the vibration plate 31 is opposite to the nozzle plate 29. Each of the flow path forming substrates 30 is arranged and laminated on the other surface and integrated by bonding or the like. The nozzle plate 29 is a thin plate made of stainless steel in which a plurality of nozzle openings 32 are opened in a row at a pitch corresponding to the dot formation density. In the present embodiment, for example, 180 nozzle openings 32 are formed in a row, and the nozzle rows (nozzle group) are configured by these nozzle openings 32. And this nozzle row is provided two rows side by side. The nozzle opening 32 of the present embodiment includes a straight portion 42 disposed on the opposite side (discharge surface side) of the pressure generating chamber 35 in the nozzle plate 29 joined to the flow path forming substrate 30, and the straight portion 42. And a taper portion 43 whose diameter increases toward the pressure generation chamber 35 side.

  The flow path forming substrate 30 is a plate-like member that forms a series of ink flow paths (a kind of liquid flow path) including the reservoir 33, the ink supply port 34, and the pressure generation chamber 35. More specifically, the flow path forming substrate 30 is formed with a plurality of vacant portions to be the pressure generating chambers 35 corresponding to the respective nozzle openings 32 in a state of being partitioned by the partition walls, and becomes the ink supply port 34 and the reservoir 33. It is a plate-like member in which a void is formed. The flow path forming substrate 30 of this embodiment is manufactured by etching a silicon wafer. The pressure generation chamber 35 is formed as an elongated chamber in a direction orthogonal to the direction in which the nozzle openings 32 are arranged (nozzle row direction), and the ink supply port 34 is provided between the pressure generation chamber 35 and the reservoir 33. It is formed as a narrowed portion with a narrow channel width that communicates. The reservoir 33 is a chamber for supplying ink stored in an ink cartridge (not shown) to each pressure generating chamber 35 and communicates with the corresponding pressure generating chamber 35 through the ink supply port 34. .

  The diaphragm 31 is a composite plate material having a double structure in which a resin film 37 such as PPS (polyphenylene sulfide) is laminated on a metal support plate 36 such as stainless steel, and one opening surface of the pressure generating chamber 35 is formed on the diaphragm 31. This is a member having a diaphragm portion 38 for sealing and changing the volume of the pressure generating chamber 35 and a compliance portion 39 for sealing one opening surface of the reservoir 33. The diaphragm portion 38 is an island portion for etching the portion of the support plate 36 corresponding to the pressure generating chamber 35 and removing the portion in an annular shape to join the tip of the free end of the piezoelectric vibrator 20. 40 is formed. Similar to the planar shape of the pressure generating chamber 35, the island portion 40 has an elongated block shape in a direction perpendicular to the direction in which the nozzle openings 32 are arranged, and the resin film 37 around the island portion 40 serves as an elastic film. Function. Further, the portion functioning as the compliance portion 39, that is, the portion corresponding to the reservoir 33 is formed of only the resin film 37 by removing the support plate 36 by etching according to the opening shape of the reservoir 33.

  In the recording head 10 having the above-described configuration, the corresponding pressure generation chamber 35 contracts or expands by deforming the piezoelectric vibrator 20, and pressure fluctuation occurs in the ink in the pressure generation chamber 35. By controlling the ink pressure, ink (ink droplets) can be ejected from the nozzle openings 32. If the pressure generating chamber 35 having a constant volume is preliminarily expanded prior to discharging ink, ink is supplied into the pressure generating chamber 35 from the reservoir 33 side through the ink supply port 34. Further, when the pressure generating chamber 35 is rapidly contracted after the preliminary expansion, ink is ejected from the nozzle opening 32.

  The shape of the nozzle opening 32 and the shape of the ink supply port 34 will be described.

  As shown in FIGS. 3A and 3B, the nozzle opening 32 has a funnel shape, and includes a tapered portion 43 having a tapered shape and a straight portion 42 communicating with the discharge side end portion of the tapered portion 43. The tapered portion 43 is a portion that defines a frustoconical space, and corresponds to a first portion in the nozzle opening 32. The straight portion 42 corresponds to the second portion of the nozzle opening 32, and is a portion that defines a cylindrical space with a cross-sectional area substantially unchanged on a plane orthogonal to the nozzle direction. In other words, the cross-sectional shape in the direction orthogonal to the discharge direction is a portion that is a constant circle at any location in the discharge direction. The taper portion 43 has a larger opening area toward the pressure generating chamber 35 side (lower side in FIG. 3A). In other words, the opening area on the ink droplet ejection side is set smaller than the opening area on the pressure generation chamber 35 side. For example, the diameter φ32b at the intermediate position in the tapered portion 43 is smaller than the diameter φ32a at the end on the pressure generating chamber 35 side. Further, the diameter φ32c of the discharge side end (the end on the straight portion 32b side) is smaller than the diameter φ32b of the intermediate position.

  In this embodiment, the diameter φ32c of the discharge side end portion corresponds to the diameter of the straight portion 42 and is set to 24 μm. The length L32b of the straight portion 42, that is, the length in the ejection direction is set to 20 μm, and the length L32a of the tapered portion 43 is set to 80 μm. Therefore, the length L32 of the nozzle opening 32 is 100 μm. The taper angle θ32 is set to 50 degrees. On the other hand, the ink supply port 34 has a width W34 of 55 μm, a height H34 of 80 μm, and a length L34 of 600 μm.

  The tapered portion 43 is considered to act as follows. That is, when the pressure generating chamber 35 is contracted to pressurize the ink, the force also acts on the ink in the nozzle opening 32. When this force (pressing force in the discharge direction) is received, it moves along the tapered portion 43. Since the taper portion 43 restricts the flow path through which the ink flows, the force applied to the ink is larger and the stress is concentrated. Thereby, a high pressure part can be concentrated on the boundary part with the straight part 42 in the taper part 43. The timing for pressurizing the ink is determined before the meniscus M drawn to the tapered portion 43 returns to the straight portion 42. In other words, the ink is pressurized in a state where the amount of ink in the straight portion 42 is as small as possible. As a result, the pressure can be concentrated on the ink present at the discharge side end of the tapered portion 43, and the ink can be locally strongly pressurized.

  Based on this idea, the taper angle θ32 was examined. Here, the taper angle θ32 is set to 20 degrees, 25 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees, and 80 degrees, and the viscosity is 8 mPa · s, 10 mPa · s, and 15 mPa · s from the nozzle openings 32 of the respective taper angles. Evaluation was performed by ejecting ink of s, 20 mPa · s, 30 mPa · s, and 40 mPa · s. In this evaluation, the shape of the nozzle opening 32 is determined so that the impedance Z32 of the nozzle opening 32 is smaller than the impedance Z34 of the ink supply port. Further, the nozzle opening 32 having a taper angle θ32 of 80 degrees or more is excluded from the evaluation target. This is because if it is 80 degrees or more (in other words, if a tapered surface having an angle range that does not become an acute angle is provided), the ink flows along the tapered surface, so that an effect of pressure concentration can be obtained. In this case, the maximum taper angle is determined by the width of the pressure generating chamber 35, the pitch of the nozzle openings 32, the length of the nozzle openings 32, and the like.

  FIG. 4 shows a list of evaluation results. In this figure, the vertical item is the viscosity of the ink, and the horizontal item is the taper angle θ32. Regarding the evaluation result, the symbol x means that the ink did not become droplets and was not ejected. Further, the symbol Δ means that the tail portion generated on the rear side in the flight direction of the ink droplet has a length that may cause a trouble for the printer. In this evaluation, Δ is evaluated when the tail portion is longer than 500 μm. Therefore, the symbol “◯” indicates that the tail portion is long enough not to interfere with the printer.

  The following can be said from this evaluation result. That is, there is a correlation between the taper angle θ32 and the viscosity of the ink, and it can be said that it is preferable to increase the taper angle θ32 as the ink has a higher viscosity. This can be understood by paying attention to the evaluation x where ink cannot be ejected. For example, when the taper angle is 20 degrees, the evaluation is x for ink having a viscosity of 20 mPa · s or more, and when the taper angle is 25 degrees and 30 degrees, the evaluation is x for ink having a viscosity of 30 mPa · s or more. It has become. When the taper angle is not less than 40 degrees and not more than 60 degrees, the evaluation is x for the ink having a viscosity of 40 mPa · s. When the taper angle is 80 degrees or more, the evaluation is Δ for ink having a viscosity of 40 mPa · s.

  Focusing on the evaluation o, it can be seen that the taper angle θ32 has an appropriate range according to the viscosity of the ink. For example, if ink having a viscosity of 8 mPa · s or more and 15 mPa · s or less is ejected, the taper angle θ32 may be 40 degrees or more. Further, it is understood that the taper angle θ32 may be 50 degrees or more if the viscosity is 8 mPa · s or more and 30 mPa · s or less is ejected.

  Next, the length L32a of the tapered portion 43 will be examined. In view of the effect of concentrating the stress on the straight portion 42 side in the tapered portion 43, this effect can be obtained if the tapered portion 43 is provided. Therefore, it can be said that the length does not matter. From the viewpoint of more stably ejecting the high-viscosity ink, it can be said that the length L32a preferably has a length equal to or longer than the straight portion 42 (1/2 of the nozzle opening 32 length L32). In addition, the nozzle opening 32 of the present embodiment has a length L32 of 100 μm, of which 80 μm is the length L32a of the tapered portion 43. Then, it can be said that the length L32a of the tapered portion 43 is more preferably 4/5 of the nozzle opening 32 length L32. Thus, if the ratio of the taper part 43 in nozzle opening 32 length L32 is increased, a part with a high pressure can be obtained easily.

In the head 10 used for the above evaluation, the impedance Z32 of the nozzle opening 32 is 1.0 × 10 ¹⁴ Ω and the impedance Z34 of the ink supply port 34 is 1.27 × 10 ¹⁴ Ω in the ink having a viscosity of 30 mPa · s. . That is, the impedance Z32 of the nozzle opening 32 is smaller than the impedance Z34 of the ink supply port 34. Here, the value of the impedance changes according to the viscosity of the ink. For this reason, when the ink of other viscosity is used, the numerical value of each impedance changes. However, the relationship that the impedance Z32 of the nozzle opening 32 is smaller than the impedance Z34 of the ink supply port 34 holds regardless of the viscosity of the ink.

  As described above, when the impedance Z32 of the nozzle opening 32 is made smaller than the impedance Z34 of the ink supply port 34, the ink supply port 34 side having a large impedance is applied to the ink in the pressure generating chamber 35 when the pressure is changed. Is difficult to flow (acousticly becomes heavy), and ink easily flows (acousticly becomes light) on the side of the nozzle opening 32 having a small impedance. Thereby, the meniscus M can be efficiently moved by the pressure change applied to the ink. Further, residual vibration (pressure vibration applied to the ink in the pressure generation chamber 35) generated after the ink droplets are discharged tends to remain in the pressure generation chamber 35, and the ink easily flows from the reservoir 33 into the pressure generation chamber 35. Thereby, the meniscus M can be returned to a steady state at an early stage, and ink droplets can be ejected at a high frequency.

  In order to reduce the impedance Z32 of the nozzle opening 32, the length L32b of the straight portion 42 is preferably shorter than the diameter φ32b. This is because when configured in this manner, inertance and flow path resistance can be reduced. In other words, the inertance is obtained by multiplying the length L32b of the straight portion 42 by the ink density and dividing it by the opening area, so that the value decreases as the opening area increases (the diameter φ32b increases). Further, the flow path resistance becomes smaller as the length L32b of the straight portion 42 is shorter and the opening area is larger. Therefore, making the length L32b of the straight portion 42 shorter than the diameter φ32b can be said to be an effective means for reducing the impedance Z32 of the nozzle opening 32.

  FIG. 5 is a waveform diagram illustrating the configuration of the ejection pulse DP included in the drive signal COM generated by the drive signal generation circuit 8 having the above configuration. The illustrated ejection pulse DP is an ejection pulse for ejecting the smallest ink droplet among the ink droplets that can be ejected by the printer in the present embodiment. The ejection pulse DP includes a first expansion element p1 (corresponding to an expansion element in the present invention) that increases the potential at a constant gradient (voltage change rate) θ1 from the reference potential VHB to the first intermediate potential VM1, and a first expansion element p1. A first hold element p2 (corresponding to the expansion hold element in the present invention) that maintains the first intermediate potential VM1 that is the rear end potential for a short time, and a relatively steep gradient θ2 from the first intermediate potential VM1 to the maximum potential VH ( The second expansion element p3 (corresponding to the expansion element in the present invention) that raises the potential when θ2> θ1), the second hold element p4 that maintains the maximum potential VH for a short time, and from the maximum potential VH to the second intermediate potential VM2. A first contraction element p5 (corresponding to the first discharge element in the present invention) that drops the potential with a relatively steep constant gradient θ3, and a third hold that maintains the second intermediate potential VM2 for a certain period of time. An element p6 (corresponding to the discharge hold element in the present invention) and a second contraction element p7 (second discharge element in the present invention) that drops the potential from the second intermediate potential VM2 to the reference potential VHB with a constant gradient θ4 (θ4 <θ3). Equivalent).

  When the ejection pulse DP is supplied to the piezoelectric vibrator 20, it operates as follows. First, when the first expansion element p1 is supplied to the piezoelectric vibrator 20, the piezoelectric vibrator 20 contracts in the longitudinal direction of the element, whereby the reference volume corresponding to the reference potential VHB is changed to the first intermediate potential VM1. The pressure generation chamber 35 expands to the corresponding volume (first expansion step). The pressure generating chamber 35 is gently contracted in the first expansion step. As a result, as shown in FIG. 6A, the meniscus in the straight portion 42 of the nozzle opening 32 starts to be gradually drawn into the pressure generating chamber 35 side, and as shown in FIG. In the straight portion 42, the central portion is drawn into the pressure generating chamber 35 side before the peripheral portion, and the tip portion on the pressure generating chamber 35 side enters the tapered portion 43. This is because the center portion of the meniscus is easier to move than the peripheral portion of the meniscus (the side closer to the inner periphery of the nozzle opening 32) and easily follows pressure fluctuations. That is, in the first expansion step, the meniscus is located in the straight portion 42 having a small opening area of the nozzle opening 32, so that it is difficult to strongly draw it into the pressure generating chamber 35 side. Therefore, by increasing the potential at a constant gradient (voltage change rate) θ1 from the reference potential VHB to the first intermediate potential VM1 by the first expansion element p1 set so as to gently contract the pressure generation chamber 35. The pressure generation chamber 35 is expanded to eliminate the follow-up delay. Thereby, the expansion of the pressure generation chamber 35 in the first expansion step can suppress the outer peripheral side of the meniscus in the straight portion 42 of the nozzle opening 32 from reaching later than the central portion of the meniscus.

  The expanded state of the pressure generating chamber 35 in the first expansion process is maintained constant over the supply period of the first hold element p2 (expansion maintaining process). Thereby, the expansion of the pressure generation chamber 35 in the first expansion step further suppresses the arrival of the ink on the outer peripheral edge side of the meniscus with a delay compared to the ink in the central portion of the meniscus in the straight portion 42 of the nozzle opening 32. Can be made. Meanwhile, the outer peripheral edge side of the meniscus in the straight portion 42 of the nozzle opening 32 gradually enters the tapered portion 43 following the center portion of the meniscus.

The second expansion element p3 is supplied to the piezoelectric vibrator 20 following the first hold element p2, so that the piezoelectric vibrator 20 contracts more rapidly in the element longitudinal direction than in the first expansion step. Thereby, the pressure generation chamber 35 rapidly expands from the volume corresponding to the first intermediate potential VM1 to the volume defined by the maximum potential VH (second expansion step). At this time, as shown in FIG.
Since the meniscus is located in the taper portion 43 from the straight portion 42 in the nozzle opening 32, it can be strongly pulled into the pressure generating chamber 35 side. That is, the center portion and the outer peripheral surface side of the meniscus can be drawn more largely toward the pressure generation chamber 35 side. Thus, in the second expansion stroke, the first expansion step is performed in a state in which the meniscus that has moved from the straight portion 42 having a small opening area to the tapered portion 43 having a large opening area can be quickly and strongly drawn into the pressure generating chamber 35 side. By contracting the pressure generation chamber 35 more rapidly, the state suitable for ink ejection is obtained without destroying the meniscus. And the expansion state of the pressure generation chamber 35 in this 2nd expansion process is maintained over the supply period of the 2nd hold element p4.

  Thereafter, when the first contraction element p5 is supplied to the piezoelectric vibrator 20, the piezoelectric vibrator 20 expands, and the pressure generating chamber 35 extends from the volume corresponding to the highest potential VH to the volume corresponding to the second intermediate potential VM2. Shrinks rapidly (first discharge shrinkage step). The ink in the pressure generating chamber 35 is pressurized by the rapid contraction of the pressure generating chamber 35, and as a result, as shown in FIG. 6D, the central portion of the meniscus in the tapered portion 43 in the nozzle opening 32 is columnar. Excitement. This is because the outer peripheral side of the meniscus is drawn into the pressure generation chamber 35 side while the central portion of the meniscus advances in a direction away from the pressure generation chamber 35. That is, the center portion of the meniscus and the outer peripheral edge side of the meniscus are in an opposite phase state.

  Then, the third hold element p6 is supplied to the piezoelectric vibrator 20, and the second intermediate potential VM2 is maintained for a certain time (discharge contraction maintaining step). And the contraction state of this pressure generation chamber 35 is maintained for a fixed time over the supply period of the 3rd hold element p6. During this time, as shown in FIG. 6 (e), the center portion of the meniscus and the outer peripheral edge side of the meniscus are in the same phase in the direction away from the pressure generating chamber 35 side, The central portion advances from the tapered portion 43 side toward the straight portion 42, and the tip portion of the columnar central portion enters the straight portion 42 before the surrounding portion.

  Thereafter, when the second contraction element p7 is supplied to the piezoelectric vibrator 20, the piezoelectric vibrator 20 further expands more than the first discharge contraction step, and the volume corresponding to the second intermediate potential VM2 is changed to the reference potential VHB. The pressure generation chamber 35 contracts and returns to the corresponding volume (second discharge contraction step). Here, the gradient θ4 from the second intermediate potential VM2 to the reference potential VHB is set to be gentler than the gradient θ3 from the highest potential VH to the second intermediate potential VM2. Accordingly, it is possible to suppress the outer peripheral edge side of the meniscus that has entered the straight portion 42 due to the contraction of the pressure generation chamber 35 in the first contraction process from reaching later than the center portion of the meniscus. In the meantime, as shown in FIG. 6 (f), the central portion of the meniscus is discharged out of the nozzle opening 32, and then the columnar portion of the central portion of the meniscus is broken, and this is several pl ink droplets corresponding to small dots. From the nozzle opening 32.

By adopting the configuration described above, for example, when ejecting ink (high viscosity liquid) having a higher viscosity than conventional ink, such as a photocurable ink that is cured by irradiation with light energy such as ultraviolet rays. In addition, the discharge pulse DP including the first expansion element p1 and the second expansion element p3 having different rates of change and the first contraction element p5 and the second contraction element p7 is supplied to the piezoelectric vibrator 20, so that Since the center portion of the meniscus and the outer peripheral edge side of the meniscus are suppressed from being in reverse phase, the phenomenon that the rear end of the ejected ink extends like a tail can be suppressed, and it is as close to a sphere as possible. It can be shaped. Thereby, it is possible to prevent the ink from being separated and landed on a landing target such as recording paper, and as a result, it is possible to reduce the deterioration of the image quality of the recorded image. Since the first hold element p2 is included between the first expansion element p1 and the second expansion element p2, and the third hold element p6 is included between the first contraction element p5 and the second contraction element p7, the meniscus is included. It is possible to prevent the central portion of the liquid crystal and the outer peripheral edge side of the meniscus from being in opposite phases, and to suppress tail growth associated with the discharged liquid. Furthermore, it is possible to suppress a decrease in the flying speed of the ink caused by the reverse phase.

  Further, the nozzle opening 32 of the present embodiment has a tapered portion 43 in which the liquid discharge side is set to an opening area smaller than the pressure generation chamber 35 side, and a straight portion 42 communicating with the discharge side end portion of the tapered portion 43. When the meniscus is positioned on the straight portion 42 communicating with the discharge side end of the taper portion 43, the meniscus is gently drawn and the meniscus is formed in the taper portion 43 having a smaller opening area on the liquid discharge side than the pressure generation chamber 35 side. It was set as the structure which draws in quickly and strongly when positioning. For this reason. The straight portion 42 having a small opening area starts to be slowly pulled in, and the taper portion 43 having a large opening area is rapidly pulled in, so that the meniscus is drawn in a good state and spreads to create a good state. By discharging the central portion, it is possible to further prevent the liquid from being separated and landed on the landing target.

  As described above, for example, when the ink viscosity is 8 mPa · s or more and 15 mPa · s or less, the taper angle θ32 is 40 degrees or more, and when the ink viscosity is 8 mPa · s or more and 30 mPa · s or less, the taper angle. By setting the taper angle θ32 to an appropriate range according to the viscosity of the ink such that θ32 is 50 degrees or more, the ink pressure on the discharge side of the tapered portion 43 can be locally increased. Then, by concentrating the high pressure portion in the vicinity of the meniscus, the pressure change applied to the ink can be used more efficiently for ink ejection. As a result, even high viscosity ink can be efficiently discharged.

  Here, in the conventional configuration in which no measures are taken, when forming a medium dot with high-viscosity ink, there is a tendency that the tail of the ink tends to be drawn, and this tail part is separated from the medium dot ink droplet main body. These separated portions (satellite ink droplets or mist) land at different positions on the recording paper, causing a significant deterioration in image quality. In order to prevent such a problem, the gradient θ1 from the reference potential VHB to the first intermediate potential VM1 is set to be gentler than the gradient θ2 from the first intermediate potential VM1 to the maximum potential VH, and from the second intermediate potential VM2. Since the gradient θ4 to the reference potential VHB is set to be gentler than the gradient θ3 from the highest potential VH to the second intermediate potential VM2, the outer peripheral edge side of the meniscus that has entered the straight portion 42 is compared with the central portion of the meniscus. Reaching with a delay can be suppressed.

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

  FIG. 7 is a waveform diagram showing a modified example of the ejection pulse. In the above embodiment, the two contraction elements, the first contraction element p5 and the second contraction element p7, are included as an example of the discharge pulse in the present invention, but the shape of the discharge pulse is not limited to this. For example, the discharge pulse DP ′ shown in FIG. 7 includes, as contraction elements, a third contraction element p8 (corresponding to the discharge element in the present invention) that drops the potential with a constant gradient from the highest potential VH to the third intermediate potential VM3. A fourth hold element p9 (corresponding to the discharge hold element in the present invention) that maintains the third intermediate potential VM3 for a certain period of time, and a fourth contraction element p10 that lowers the potential with a constant gradient from the third intermediate potential VM2 to the fourth intermediate potential VM4. (Corresponding to the ejection element in the present invention), a fifth hold element p11 (corresponding to the ejection hold element in the present invention) for maintaining the fourth intermediate potential VM4 for a certain time, and a constant gradient from the fourth intermediate potential VM4 to the reference potential VHB May include three contraction elements, a second contraction element p12 (corresponding to the discharge element in the present invention) that lowers the potential.

  As a result, when high-viscosity ink is discharged due to contraction of the pressure generation chamber 35, the center portion of the meniscus and the outer peripheral side of the meniscus are further prevented from being in reverse phase, and tail growth associated with the discharged ink is developed. Can be suppressed. Furthermore, it is possible to suppress a drop in the droplet flying speed caused by the reverse phase. That is, the discharge pulse DP has an arbitrary waveform as long as the discharge pulse DP includes at least the first expansion element p1 and the second expansion element p3 having a different rate of change from the first expansion element p1. be able to.

  In the above embodiment, the piezoelectric vibrator 20 in the so-called longitudinal vibration mode is illustrated as the pressure generating unit, but the present invention is not limited to this. For example, the present invention can also be applied when using a so-called flexural vibration mode piezoelectric vibrator. Note that when the piezoelectric vibrator in the flexural vibration mode is employed, the waveform of the ejection pulse DP shown in FIG.

  The present invention is not limited to a printer as long as it is a liquid ejection device that can perform ejection control using a plurality of drive signals, and other than various ink jet recording devices such as plotters, facsimile devices, copiers, and recording devices. The present invention can also be applied to a liquid ejecting apparatus such as a display manufacturing apparatus, an electrode manufacturing apparatus, and a chip manufacturing apparatus.

1 printer controller, 2 print engine, 6 control unit, 7 oscillation circuit,
8 drive signal generation circuit, 10 head, 12 carriage movement mechanism,
13 Paper feed mechanism, 14 Linear encoder, 15 Shift register, 16 Latch, 17 Decoder, 18 Level shifter, 19 Switch, 20 Piezoelectric vibrator,
22 piezoelectric vibrator group, 23 fixing plate, 24 flexible cable,
25 transducer unit, 26 head case, 27 flow path unit,
29 nozzle plate, 30 flow path forming substrate, 31 diaphragm, 32 nozzle opening,
33 Reservoir, 34 Ink supply port, 35 Pressure generating chamber, 36 Support plate,
37 resin film, 38 diaphragm part, 39 compliance part, 40 island part, 42 straight part, 43 taper part, COM drive signal, DP pulse,
p1 first expansion element, p2 first hold element, p3 second expansion element,
p4 second hold element, p5 first contraction element, p6 third hold element,
p7 second contraction element, p8 third contraction element, p9 fourth hold element,
p10 4th contraction element, p11 5th hold element, p12 5th contraction element

Claims (9)

A pressure generating chamber that communicates with the nozzle opening, and a liquid discharging head that has a pressure generating element that causes a pressure fluctuation in the liquid in the pressure generating chamber, and that can discharge liquid from the nozzle opening by the operation of the pressure generating element; ,
A drive signal generator for generating a series of drive signals including a drive pulse for driving the pressure generating element;
With
The nozzle opening is
A first portion in which the liquid discharge side is defined as an opening area smaller than the pressure generation chamber side;
A liquid ejection device having a second portion communicating with the ejection side end of the first portion,
The drive pulse generated by the drive signal generator includes a plurality of expansion elements that expand the pressure generation chamber and draw a meniscus,
A discharge element that discharges a droplet by changing a voltage so as to contract the expanded pressure generation chamber,
The liquid ejection apparatus, wherein the expansion element includes a first expansion element and a second expansion element that draws a meniscus at a voltage change rate different from that of the first expansion element.   The liquid ejection apparatus according to claim 1, wherein a voltage change rate of the first expansion element is set to be smaller than a voltage change rate of the second expansion element.   The expansion hold element that maintains a voltage for a certain time at a rear end of the first expansion element is provided between the first expansion element and the second expansion element. Liquid discharge device.   4. The discharge element according to claim 1, wherein the discharge element includes a first discharge element and a second discharge element that contracts the pressure generating chamber at a voltage change rate different from that of the first discharge element. The liquid ejection device according to any one of the above.   5. The liquid ejection device according to claim 4, further comprising an ejection hold element that maintains a voltage at a rear end of the first ejection element for a certain period between the first ejection element and the second ejection element. . The viscosity of the liquid is 8 millipascal seconds or more and 15 millipascal seconds or less,
6. The liquid ejecting apparatus according to claim 1, wherein the first portion of the nozzle opening defines a frustoconical space having a taper angle of 40 degrees or more. 6. The viscosity of the liquid is 8 millipascal seconds or more and 30 millipascal seconds or less,
6. The liquid ejection apparatus according to claim 1, wherein the first portion of the nozzle opening defines a frustoconical space having a taper angle of 50 degrees or more.   The liquid ejecting apparatus according to claim 1, wherein a length of the first portion in the nozzle opening is equal to or longer than the second portion. A pressure generating chamber that communicates with the nozzle opening, and a liquid discharging head that has a pressure generating element that causes a pressure fluctuation in the liquid in the pressure generating chamber, and that can discharge liquid from the nozzle opening by the operation of the pressure generating element; ,
A drive signal generator for generating a series of drive signals including a drive pulse for driving the pressure generating element;
With
The nozzle opening is
A first portion in which the liquid discharge side is defined as an opening area smaller than the pressure generation chamber side;
And a second part communicating with the discharge side end of the first part.
A plurality of expansion steps for expanding the pressure generating chamber and drawing a meniscus;
A discharge step of discharging a droplet by changing a voltage so as to contract the pressure generating chamber expanded in the expansion step,
The method of controlling a liquid ejection apparatus, wherein the expansion step includes a first expansion step and a second expansion step of drawing a meniscus at a voltage change rate different from that of the first expansion step.