JP2010030119A - Liquid ejection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress such a phenomenon that the rear end of liquid extends like a tail. <P>SOLUTION: The liquid ejection device includes: a pressure chamber communicated with a nozzle; an element performing operation for applying a pressure change to the liquid in the pressure chamber; a pulse producing section producing a pulse for allowing the element to perform the operation; and a controller performing control for applying the pulse to the element. The viscosity of the liquid is 6 mm Pa s or more. The pulse producing section repeatedly produces a non-ejection pulse and an ejection pulse in each repeated period. The controller applies the non-ejection pulse to the element prior to the application of the ejection pulse to the element, when the liquid is ejected by using one ejection pulse and continuously applies the ejection pulse to the element, without applying the non-ejection pulse to the element, when the liquid is ejected by using two or more ejection pulses. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid ejection apparatus.

2. Description of the Related Art There is known a liquid discharge apparatus that applies a pressure change to a liquid in a pressure chamber and discharges the liquid from a nozzle that communicates with the pressure chamber. In such a liquid ejecting apparatus, the amount of ejected liquid is increased by increasing the amplitude of pressure vibration applied to the liquid in the pressure chamber. In other words, the amount of liquid ejected is increased by increasing the drive voltage of the ejection pulse (see, for example, Patent Document 1).
JP 2003-94656 A

  In recent years, an attempt has been made to discharge a liquid having a higher viscosity than a conventionally handled liquid (hereinafter, also referred to as a high-viscosity liquid) by the liquid discharge apparatus. That is, in the past, liquids having a low viscosity such as water were targeted, but attempts have been made to discharge high viscosity liquids of 6 millipascal seconds or more.

  In order to obtain a sufficient discharge amount even with this high-viscosity liquid, it is necessary to give a pressure change having a magnitude corresponding to the discharge amount to the liquid in the pressure chamber. However, if the pressure change is increased, the flying speed of the liquid also increases, and a phenomenon occurs in which the rear end portion of the liquid extends like a tail. Due to this phenomenon, there was a problem that the tail portion did not land at the normal position. For example, an inkjet printer has a problem in that the tail portion becomes a mist and landed out of a normal position, resulting in deterioration of image quality.

  The present invention has been made in view of such circumstances, and an object thereof is to suppress a phenomenon in which a rear end portion of a liquid extends like a tail.

The main invention for achieving the object is as follows:
A pressure chamber in communication with the nozzle;
An element that performs an operation of giving a pressure change to the liquid in the pressure chamber;
A pulse generator for generating a pulse for causing the element to perform the operation;
A controller for controlling the application of the pulse to the element,
The liquid is
The viscosity is 6 millipascal seconds or more,
The pulse generator is
A non-ejection pulse that applies a pressure change that does not cause the liquid to be discharged from the nozzle to the liquid in the pressure chamber, and a discharge that applies a pressure change that causes the liquid to be discharged from the nozzle to the liquid in the pressure chamber. A pulse is repeatedly generated every repetition period,
The controller is
When the liquid is ejected using one ejection pulse in a certain repetition period, the non-ejection pulse is applied to the element prior to application of the ejection pulse to the element,
When the liquid is ejected using two or more ejection pulses in a certain repetition period, the ejection pulse is continuously applied to the element without applying the non-ejection pulse to the element.
A liquid ejection device;

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

  At least the following will be made clear by the description of the present specification and the accompanying drawings.

  That is, a pressure chamber communicated with a nozzle, an element that performs an operation for changing a pressure in a liquid in the pressure chamber, a pulse generation unit that generates a pulse for causing the element to perform the operation, and the pulse to the element And a controller for controlling the application, wherein the liquid has a viscosity of 6 millipascal seconds or more, and the pulse generator generates a pressure change in such a magnitude that the liquid is not discharged from the nozzle. A non-ejection pulse that is applied to the liquid and a discharge pulse that imparts to the liquid in the pressure chamber a pressure change having a magnitude such that the liquid is ejected from the nozzle, and is repeatedly generated for each repetition period. In the case where the liquid is ejected by using the one ejection pulse in step 1, before the non-ejection pulse is applied prior to application of the ejection pulse to the element. When the liquid is ejected using two or more ejection pulses in a certain repetition period, the ejection pulse is continuously applied to the element without applying the non-ejection pulse to the element. It is clarified that a liquid ejecting apparatus can be realized by applying to the liquid crystal.

  According to such a liquid ejecting apparatus, when the liquid is ejected using one ejection pulse, the pressure change in the pressure chamber caused by the application of the non-ejection pulse can be used. For this reason, the flight speed of the liquid can be suppressed as compared with the case where a predetermined amount of liquid is ejected by only one ejection pulse while ensuring the necessary ejection amount. As a result, the phenomenon that the rear end portion of the liquid extends like a tail can be suppressed. In the case where liquid is ejected using two or more ejection pulses, the previous ejection pulse has the same effect as the non-ejection pulse described above. For this reason, in the second and subsequent ejection pulses, a phenomenon in which the rear end portion of the liquid extends like a tail can be suppressed.

In this liquid ejection apparatus, the pulse generation unit generates the ejection pulse used in combination with the non-ejection pulse, and the natural vibration period of the liquid in the pressure chamber from the end of the generation of the non-ejection pulse. It is preferable to start within a period of 1/2 or less.
According to such a liquid ejecting apparatus, it is possible to effectively use the change in the pressure of the liquid generated in the liquid in the pressure chamber by applying the non-ejection pulse to the element.

In this liquid ejection apparatus, the element is operated to change the volume of the pressure chamber by being deformed according to the electric potential, and the ejection pulse deforms the element to expand the pressure chamber. A first expansion element that is generated following the first expansion element and maintains the deformed state of the element; and a pressure chamber that is generated following the first maintenance element and is in an expanded state. A first contraction element that deforms the element to contract, and the non-ejection pulse follows the second expansion element, a second expansion element that deforms the element to expand the pressure chamber. A second sustaining element that is generated in order to maintain the deformed state of the element, and a second contracting element that is generated following the second maintaining element and that deforms the element to contract the pressure chamber in the expanded state. And having the second expansion Variation in potential in element and the second contraction element, it is preferable that the determined smaller than the range of change in potential at the first expansion element and the first contraction element.
According to such a liquid ejecting apparatus, since both the ejection pulse and the non-ejection pulse are constituted by the expansion element, the maintenance element, and the contraction element, the liquid ejection apparatus is suitable for ejecting the liquid at a high frequency.

In this liquid ejection apparatus, the pulse generation unit repeatedly generates these pulses in the order of the non-ejection pulse, the first ejection pulse, and the second ejection pulse, and the controller generates one ejection pulse. When the liquid is ejected using the non-ejection pulse and the first ejection pulse are applied to the element, and when the liquid is ejected using the two ejection pulses, the first ejection pulse and the second ejection pulse are applied. An ejection pulse is preferably applied to the element.
According to such a liquid ejecting apparatus, it is possible to suppress a phenomenon in which the rear end portion of the liquid extends like a tail.

In this liquid ejection apparatus, the first ejection pulse is applied to the element at a timing for exciting a pressure vibration of the liquid in the pressure chamber generated by applying the non-ejection pulse to the element. Is preferred.
According to such a liquid ejecting apparatus, it is possible to effectively use the change in the pressure of the liquid generated in the liquid in the pressure chamber by applying the non-ejection pulse to the element.

In this liquid ejection apparatus, the first ejection pulse is positioned in the liquid ejection direction from the steady state by the pressure vibration of the liquid in the pressure chamber caused by the application of the non-ejection pulse to the element. It is preferable that the voltage is applied to the element at the same timing.
According to such a liquid ejecting apparatus, the amount of ejected liquid can be increased as compared with a case where a predetermined amount of liquid is ejected with only one ejection pulse.

In this liquid ejection apparatus, the second ejection pulse is applied to the element at a timing for exciting the pressure vibration of the liquid in the pressure chamber generated by applying the first ejection pulse to the element. It is preferable.
According to such a liquid ejecting apparatus, it is possible to effectively use the change in pressure of the liquid generated in the liquid in the pressure chamber by applying the first ejection pulse to the element.

In this liquid ejection apparatus, it is preferable that the second ejection pulse has the same shape as the first ejection pulse.
According to such a liquid ejection apparatus, the control for generating each ejection pulse can be simplified.

=== First Embodiment ===
<About the printing system>
The printing system illustrated in FIG. 1 includes a printer 1 and a computer CP. The printer 1 corresponds to a liquid ejecting apparatus, and ejects ink, which is a kind of liquid, toward a medium such as paper, cloth, or film. The medium is an object to which liquid is ejected. The computer CP is communicably connected to the printer 1. In order to cause the printer 1 to print an image, the computer CP transmits print data corresponding to the image to the printer 1.

=== Overview of Printer 1 ===
The printer 1 includes a paper transport mechanism 10, a carriage movement mechanism 20, a drive signal generation circuit 30, a head unit 40, a detector group 50, and a printer-side controller 60.

  The paper transport mechanism 10 transports the paper in the transport direction. The carriage moving mechanism 20 moves the carriage to which the head unit 40 is attached in a predetermined movement direction (for example, the paper width direction). The drive signal generation circuit 30 generates a drive signal COM. This drive signal COM is applied to the head HD (see the piezo element 433, see FIG. 2) at the time of printing on the paper, and as shown in an example in FIG. 5, the pre-pulse PS1 and the ejection pulse (first ejection pulse). A series of signals including PS2 and second ejection pulse PS3). Here, the ejection pulse is a potential change pattern that causes the piezo element 433 to perform a predetermined operation in order to eject droplet-like ink from the nozzles 427 (see FIG. 2) of the head HD. The pre-pulse PS1 is a potential change pattern that causes the piezo element 433 to perform a predetermined operation in order to assist the ejection of ink by the ejection pulse. Since the drive signal COM includes these pulses, the drive signal generation circuit 30 corresponds to a pulse generation unit. The drive signal generation circuit 30 and each pulse will be described later. The head unit 40 includes a head HD and a head controller HC. The head HD discharges ink toward the paper. The head controller HC controls the head HD based on the head control signal from the printer-side controller 60. The detector group 50 includes a plurality of detectors that monitor the status of the printer 1. Detection results by these detectors are output to the printer-side controller 60. The printer-side controller 60 performs overall control in the printer 1. The head HD and the printer-side controller 60 will be described later.

=== Main Parts of Printer 1 ===
<About Head HD>
As shown in FIG. 2, the head HD has a case 41, a flow path unit 42, and a piezo element unit 43. The case 41 has a box shape in which a housing empty portion 411 for housing and fixing the piezoelectric element unit 43 is provided. The case 41 is made of, for example, a resin material. A flow path unit 42 is joined to the front end surface of the case 41.

  The flow path unit 42 includes a flow path forming substrate 421, a nozzle plate 422, and a vibration plate 423. The nozzle plate 422 is bonded to one surface of the flow path forming substrate 421, and the vibration plate 423 is bonded to the other surface. In the flow path forming substrate 421, a pressure chamber 424, an ink supply path 425, a common ink chamber 426, and the like are formed. The flow path forming substrate 421 is made of, for example, a silicon substrate. The pressure chamber 424 is formed as an elongated chamber in a direction orthogonal to the arrangement direction of the nozzles 427. The ink supply path 425 is a narrow channel portion that communicates between the pressure chamber 424 and the common ink chamber 426. The ink supply path 425 corresponds to a liquid supply unit for supplying liquid to the pressure chamber 424. The common ink chamber 426 is a portion that temporarily stores ink supplied from an ink cartridge (not shown), and corresponds to a common liquid storage chamber.

  In the nozzle plate 422, a plurality of nozzles 427 are provided at predetermined intervals in a predetermined arrangement direction. The nozzle plate 422 is made of, for example, a stainless plate or a silicon substrate.

  The vibration plate 423 has a double structure in which a resin elastic film 429 is laminated on a support plate 428 made of stainless steel, for example. A portion of the vibration plate 423 corresponding to each pressure chamber 424 is formed by etching a stainless plate portion in an annular shape. An island 428a is formed in the ring. The island portion 428a and the elastic film 429a around the island portion 428a constitute a diaphragm portion 423a. The diaphragm portion 423 a is deformed by the piezo element 433 included in the piezo element unit 43 and changes the volume of the pressure chamber 424.

  The piezo element unit 43 includes a piezo element group 431 and a fixed plate 432. The piezo element group 431 has a comb shape. Each comb tooth is a piezo element 433. The front end surface of each piezo element 433 is bonded to the corresponding island portion 428a. The fixing plate 432 supports the piezo element group 431 and serves as an attachment portion for the case 41. The fixing plate 432 is made of, for example, a stainless steel plate and is bonded to the inner wall of the housing space 411.

  The piezo element 433 is a kind of electromechanical conversion element, and corresponds to an element that performs an operation (deformation operation) for applying a pressure change to the liquid in the pressure chamber 424. The piezoelectric element 433 shown in FIG. 2 expands and contracts in the element longitudinal direction perpendicular to the stacking direction by applying a potential difference between adjacent electrodes. That is, the electrode includes a common electrode 434 having a predetermined potential and a drive electrode 435 having a potential corresponding to the drive signal COM (prepulse PS1, each ejection pulse PS2, PS3, etc.). The piezoelectric body 436 sandwiched between the two electrodes is deformed at a degree corresponding to the potential difference between the common electrode 434 and the drive electrode 435. The piezoelectric element 433 expands and contracts in the longitudinal direction of the element as the piezoelectric body 436 is deformed. In the present embodiment, the common electrode 434 is set to a ground potential or a bias potential that is higher than the ground potential by a predetermined potential. The piezoelectric element 433 contracts as the potential of the drive electrode 435 becomes higher than the potential of the common electrode 434. On the contrary, it expands as the potential of the drive electrode 435 approaches the potential of the common electrode 434 or becomes lower than the potential of the common electrode 434.

  As described above, the piezo element unit 43 is attached to the case 41 via the fixed plate 432. For this reason, when the piezo element 433 contracts, the diaphragm portion 423 a is pulled in a direction away from the pressure chamber 424. Thereby, the pressure chamber 424 is expanded. On the contrary, when the piezo element 433 is extended, the diaphragm portion 423a is pushed toward the pressure chamber 424 side. As a result, the pressure chamber 424 contracts. The ink in the pressure chamber 424 undergoes a pressure change due to expansion or contraction (volume change) of the pressure chamber 424. That is, the ink in the pressure chamber 424 is pressurized as the pressure chamber 424 contracts, and the ink in the pressure chamber 424 is depressurized as the pressure chamber 424 expands. Since the expansion / contraction state of the piezo element 433 is determined according to the potential of the drive electrode 435, the volume of the pressure chamber 424 is also determined according to the potential of the drive electrode 435. Therefore, the degree of pressurization and the degree of pressure reduction with respect to the ink in the pressure chamber 424 can be determined by the potential change amount per unit time in the drive electrode 435.

<About ink flow path>
In the head HD, a series of ink flow paths (corresponding to liquid flow paths filled with liquid) from the common ink chamber 426 to the nozzles 427 are provided in accordance with the number of nozzles 427. In the ink flow path, the nozzle 427 and the ink supply path 425 communicate with the pressure chamber 424, respectively. Therefore, when analyzing characteristics such as ink flow, the Helmholtz resonator concept is applied. FIG. 3 is a diagram schematically illustrating the structure of the head HD based on this concept.

  In a general head HD, the length L424 of the pressure chamber 424 is determined within a range of 200 μm to 2000 μm. The width W424 of the pressure chamber 424 is determined in the range of 20 μm to 300 μm, and the height H424 of the pressure chamber 424 is determined in the range of 30 μm to 500 μm. The length L425 of the ink supply path 425 is determined in the range of 50 μm to 2000 μm. The width W425 of the ink supply path 425 is determined in the range of 20 μm to 300 μm, and the height H425 of the ink supply path 425 is determined in the range of 30 μm to 500 μm. Further, the diameter φ427 of the nozzle 427 is determined in the range of 10 μm to 35 μm, and the length L427 of the nozzle 427 is determined in the range of 40 μm to 100 μm.

  Regarding the ink supply path 425, the width W425 and the height H425 are determined to be equal to or smaller than the width W424 and the height H424 of the pressure chamber 424. Further, when one of the width W425 and the height H425 of the ink supply path 425 is aligned with one of the width W424 and the height H424 of the pressure chamber 424, the other of the width W425 and the height H425 of the ink supply path 425 The size is determined to be smaller than the other of the width W424 and the height H424 of the chamber 424.

  In such an ink flow path, the ink is ejected from the nozzle 427 by applying a pressure change to the ink in the pressure chamber 424. At this time, the pressure chamber 424, the ink supply path 425, and the nozzle 427 function like a Helmholtz resonator. For this reason, the magnitude of the pressure applied to the ink in the pressure chamber 424 changes in a unique period called a Helmholtz period. That is, pressure vibration occurs in the ink. Therefore, the Helmholtz period is also called the natural vibration period of ink (liquid) in the pressure chamber 424. Due to this Helmholtz period pressure vibration, the meniscus (the free surface of the ink exposed at the nozzle 427) moves periodically within the nozzle 427. Then, by using the pressure change of the natural vibration period, the ink can be efficiently ejected from the nozzle 427, or the pressure change of the ink in the pressure chamber 424 can be canceled efficiently.

  In a general head HD, the natural vibration period in the pressure chamber 424 is determined within a range of 5 μs to 10 μs. For example, in the ink flow path of FIG. 3, the width W424 of the pressure chamber 424 is 100 μm, the height H424 is 70 μm, the length L424 is 1000 μm, the width W425 of the ink supply path 425 is 50 μm, the height H425 is 70 μm, and the length. When L425 is 500 μm, the diameter φ427 of the nozzle 427 is 30 μm, and the length L427 is 100 μm, the natural vibration period in the pressure chamber 424 is about 8 μs. Note that the natural vibration period also varies depending on the thickness of the partition wall that partitions the adjacent pressure chambers 424, the thickness and compliance of the elastic film 429, and the material of the flow path forming substrate 421 and the nozzle plate 422.

<About the printer-side controller 60>
The printer-side controller 60 performs overall control in the printer 1. That is, the control target unit is controlled based on the print data received from the computer CP and the detection result from each detector, and an image is printed on the paper. For example, the pre-pulse PS1 and the ejection pulses PS2 and PS3 included in the drive signal COM are selectively applied to the piezo element 433 according to the amount of ink droplets to be ejected. As shown in FIG. 1, the printer-side controller 60 includes an interface unit 61, a CPU 62, and a memory 63. The interface unit 61 exchanges data with the computer CP. The CPU 62 performs overall control of the printer 1. The memory 63 secures an area for storing a computer program, a work area, and the like. The CPU 62 controls each control target unit according to the computer program stored in the memory 63. For example, the CPU 62 controls the paper transport mechanism 10 and the carriage movement mechanism 20. Further, the CPU 62 transmits a head control signal for controlling the operation of the head HD to the head control unit HC, and transmits a control signal for generating the drive signal COM to the drive signal generation circuit 30.

  Here, the control signal for generating the drive signal COM is also called DAC data, and is, for example, digital data of a plurality of bits. This DAC data defines a change pattern of the potential of the generated drive signal COM. Therefore, the DAC data can be said to be data indicating the drive signal COM and the potential of each pulse included in the drive signal COM. The DAC data is stored in a predetermined area of the memory 63, and is read out when the drive signal COM is generated and output to the drive signal generation circuit 30.

<About the drive signal generation circuit 30>
The drive signal generation circuit 30 functions as a pulse generation unit, and generates a drive signal COM having a pre-pulse PS1 and ejection pulses PS2 and PS3 based on DAC data. As shown in FIG. 4, the drive signal generation circuit 30 includes a DAC circuit 31, a voltage amplification circuit 32, and a current amplification circuit 33. The DAC circuit 31 converts digital DAC data into an analog signal. The voltage amplification circuit 32 amplifies the voltage of the analog signal converted by the DAC circuit 31 to a level at which the piezo element 433 can be driven. In this printer 1, the maximum analog signal output from the DAC circuit 31 is 3.3V, whereas the amplified analog signal output from the voltage amplifier circuit 32 (also referred to as a waveform signal for convenience) is 42V at maximum. It is. The current amplifying circuit 33 amplifies the current of the waveform signal from the voltage amplifying circuit 32 and outputs the amplified signal as a drive signal COM. The current amplifier circuit 33 is configured by, for example, a push-pull connected transistor pair.

<About the head controller HC>
The head control unit HC selects a necessary portion of the drive signal COM generated by the drive signal generation circuit 30 based on the head control signal, and applies it to the piezo element 433. For this reason, as shown in FIG. 4, the head controller HC includes a plurality of switches 44 provided for each piezo element 433 in the middle of the supply line of the drive signal COM. Then, the head controller HC generates a switch control signal from the head control signal. By controlling each switch 44 by this switch control signal, a necessary portion of the drive signal COM, that is, the pre-pulse PS1 and the ejection pulses PS2 and PS3 are applied to the piezo element 433. At this time, the ejection of ink from the nozzles 427 can be controlled depending on how to select the necessary portions. A head control signal that is the basis of the switch control signal is output from the printer-side controller 60. Therefore, the printer-side controller 60 corresponds to a controller that performs control for applying a pulse included in the drive signal COM to the piezo element 433. The head controller HC corresponds to a pulse application unit that is controlled by the controller and applies a pulse included in the drive signal COM to the piezo element 433.

<About the drive signal COM>
Next, the drive signal COM generated by the drive signal generation circuit 30 will be described. This drive signal COM is applied to the drive electrode 435 included in the piezo element 433. As a result, a potential difference corresponding to the potential change pattern is generated between the common electrode 434 and the fixed potential. As a result, the piezo element 433 expands and contracts according to the potential change pattern, and changes the volume of the pressure chamber 424.

  The drive signal COM illustrated in FIG. 5 includes a plurality of pulses that are repeatedly generated for each repetition period. That is, the pre-pulse PS1, the first ejection pulse PS2, and the second ejection pulse PS3 are included in the repetition period T. The pre-pulse PS1 is for giving a pressure change (pressure vibration) that does not eject ink droplets from the nozzle 427 to the ink in the pressure chamber 424, and corresponds to a non-ejection pulse. The first ejection pulse PS <b> 2 and the second ejection pulse PS <b> 3 are for giving the ink in the pressure chamber 424 a change in pressure that causes ink droplets to be ejected from the nozzle 427.

  The repetition period T is a period corresponding to the dot gradation. That is, it is a period necessary for ejecting an amount of ink corresponding to the size of a dot to a unit area where a certain dot is formed. The repetition period T is determined by a period necessary for generating the number of pulses corresponding to the types of dots that can be formed, the moving speed of the head HD, and the like. In the illustrated drive signal COM, the repetition period T is divided into three parts: a first period T1 that is a front period, a second period T2 that is an intermediate period, and a third period T3 that is a rear period. It has been.

  The pre-pulse PS1 is generated in the first period T1, the first ejection pulse PS2 is generated in the second period T2, and the second ejection pulse PS3 is generated in the third period T3. Therefore, the drive signal generation circuit 30 (pulse generation unit) repeatedly generates these pulses in the order of the pre-pulse PS1 (non-ejection pulse), the first ejection pulse PS2, and the second ejection pulse PS3.

  The prepulse PS1 has an expansion element P1, a hold element P2, and a contraction element P3. The expansion element P1 corresponds to a second expansion element, and is a part that increases the potential with a constant gradient θ1 from the lowest potential VL to the intermediate potential VC. In this drive signal COM, the lowest potential VL corresponds to the reference potential corresponding to the reference volume of the pressure chamber 424. As the expansion element P1 is applied to the piezo element 433, the pressure chamber 424 expands from the reference volume to an intermediate volume corresponding to the intermediate potential VC. Thereby, the ink in the pressure chamber 424 is depressurized. The hold element P2 corresponds to a second sustain element, and is a part that maintains the intermediate potential VC. During the application period of the hold element P2, the piezo element 433 maintains a deformed state at the end of application of the expansion element P1, and the pressure chamber 424 maintains an intermediate volume. The contraction element P3 corresponds to the second contraction element P3, and is a part that lowers the potential with a constant gradient θ2 from the intermediate potential VC to the lowest potential VL. With the application of the contraction element P3, the pressure chamber 424 contracts from the intermediate volume to the reference volume. Thereby, the ink in the pressure chamber 424 is pressurized. Along with the application of the pre-pulse PS1, the ink in the pressure chamber 424 undergoes a pressure vibration that does not eject ink. In the pre-pulse PS1, the driving voltage (difference between the intermediate potential VC and the lowest potential VL) is set to ½ of the driving voltage Vh of the ejection pulses PS2 and PS3. In other words, the change width of the potential in the expansion element P1 and the contraction element P3 of the pre-pulse PS1 is the change width of the potential in the expansion elements P4 and P7 and the contraction elements P6 and P9 of the first discharge pulse PS2 and the second discharge pulse PS3 described later. Is set smaller than. When such a pre-pulse PS1 is applied, ink is not ejected, but a sufficiently large pressure vibration is generated. Since the ink flow channel operates like a Helmholtz resonator, this pressure vibration remains even after the application of the prepulse PS1.

  The shapes (potential change patterns) of the first ejection pulse PS2 and the second ejection pulse PS3 are the same. For this reason, it demonstrates collectively. Each ejection pulse PS2, PS3 has expansion elements P4, P7, hold elements P5, P8, and contraction elements P6, P9. The expansion elements P4 and P7 correspond to first expansion elements, and are portions that increase the potential with a constant gradient θ3 from the lowest potential VL to the highest potential VH. As the expansion elements P4 and P7 are applied to the piezo element 433, the pressure chamber 424 expands from the reference volume to the maximum volume corresponding to the maximum potential VH. Thereby, the ink in the pressure chamber 424 is depressurized more than when the expansion element P1 of the pre-pulse PS1 is applied. The hold elements P5 and P8 correspond to the first sustain element and are portions that maintain the maximum potential VH. During the application period of the hold elements P5 and P8, the piezo element 433 maintains the deformed state at the end of the application of the expansion elements P4 and P7, and the pressure chamber 424 maintains the maximum volume. In this period, the ink pressure resulting from the pressure vibration changes from a change in the pressure reduction direction to a change in the pressure direction. The contraction elements P6 and P9 correspond to the first contraction element, and are parts for lowering the potential with a constant gradient θ4 from the highest potential VH to the lowest potential VL. As the contraction elements P6 and P9 are applied, the pressure chamber 424 contracts from the maximum volume to the reference volume. Thereby, the ink in the pressure chamber 424 is pressurized. At this time, the pressure change in the pressurizing direction given to the ink in the pressure chamber 424 and the pressurization of the ink accompanying the contraction of the pressure chamber 424 are combined to greatly pressurize the ink. As a result, ink droplets are ejected from the nozzle 427. Accordingly, the contraction elements P6 and P9 included in these ejection pulses PS2 and PS3 correspond to ejection elements for ejecting ink droplets (a kind of liquid droplets). Even when these ejection pulses PS2 and PS3 are used, pressure vibration remains after ejection of ink droplets.

  All of the pre-pulse PS1, the first ejection pulse PS2, and the second ejection pulse PS3 are composed of trapezoidal waveforms. In this way, when each pulse is constituted by a trapezoidal waveform, the pressure vibration remains strong after the ink droplet is ejected. For this reason, this pressure vibration can be used in the ejection pulses PS2 and PS3 that are subsequently applied to the piezo element 433. The interval between the pre-pulse PS1 and the first ejection pulse PS2 is determined by the generation period of the first constant potential element P11. This interval determines the magnitude of the ink pressure in the pressure chamber 424 after the application of the prepulse PS1. Similarly, the interval between the first ejection pulse PS2 and the second ejection pulse PS3 is determined by the generation period of the second constant potential element P12, and the magnitude of the ink pressure in the pressure chamber 424 after the application of the first ejection pulse PS2 is completed. Determine the size. Therefore, by adjusting the generation period of the first constant potential element P11 and the generation period of the second constant potential element P12, the amount of ink droplets and the flight speed can be adjusted. Further, since each pulse has a trapezoidal waveform, the time required for the waveform can be shortened, which is suitable for high-frequency ejection of ink droplets.

<Ink droplet ejection control>
When the above-described printer 1 ejects ink having a viscosity higher than that of conventionally treated ink, it is necessary to increase the amplitude of pressure vibration applied to the ink in order to ensure a necessary ejection amount. Here, when the amplitude of the pressure vibration is increased, the flying speed of the ink droplet increases in proportion to the amplitude. In the high-viscosity ink, as the flight speed increases, the trailing end portion of the ink droplet extending like a tail becomes longer. Such a tail portion has a high possibility of landing at a position deviated from the normal landing position, and causes deterioration in image quality.

  In order to suppress image quality deterioration due to the tail portion, it is considered effective to shorten the length of the tail portion. As described above, the length of the tail portion is proportional to the flying speed of the ink droplet. Then, in order to shorten the tail portion, it can be said that it is effective to suppress the flying speed of the ink droplet while securing the amount of the ink droplet.

  From this point of view, the printer-side controller 60 and the head controller HC selectively eject ink droplets using the pre-pulse PS1. Specifically, when forming a medium dot using the first ejection pulse PS2, as shown in FIG. 6A, the pre-pulse PS1 is applied to the piezo element prior to the application of the first ejection pulse PS2 to the piezo element 433. Apply to 433. Further, when forming a large dot using the first ejection pulse PS2 and the second ejection pulse PS3, as shown in FIG. 6B, the pre-pulse PS1 is not used, and the first ejection pulse PS2 and the second ejection pulse PS3 are used. The voltage is continuously applied to the piezo element 433.

  With this configuration, when forming a medium dot using the first ejection pulse PS2, the pressure vibration applied to the ink by the pre-pulse PS1 can be used for ejection of the ink droplet by the first ejection pulse PS2. . As a result, the same amount of ink droplets can be ejected with a lower drive voltage than when the ink droplets are ejected only by the first ejection pulse PS2 without using the pre-pulse PS1. Since the flying speed of the ink droplet can be suppressed as the driving voltage is low, the length of the tail portion can be shortened.

  Similarly, when a large dot is formed using the first ejection pulse PS1 and the second ejection pulse PS2, the pressure vibration applied by the first ejection pulse PS1 is used to eject ink droplets by the second ejection pulse PS2. Available. As a result, the ink droplet ejection amount by the second ejection pulse PS2 is suppressed to the same level as the flight speed of the ink droplet by the first ejection pulse PS1, and the ejection amount of the ink droplet by the second ejection pulse PS2 is reduced to the first ejection pulse PS2. The amount of ink droplets ejected by the pulse PS1 can be increased. That is, the discharge amount can be increased without lengthening the tail portion. Details will be described below.

<When forming medium dots>
First, an ink droplet ejection operation when forming a medium dot will be described. Here, FIG. 7A is a diagram showing the position of the meniscus when the medium dot is formed in association with the pre-pulse PS1 and the first ejection pulse PS2. That is, the upper part of FIG. 7A shows the relationship between the potential of the pre-pulse PS1 and the first ejection pulse PS2 and time, and the lower part of FIG. 7A shows the relationship between the meniscus state and time.

  Regarding the state of the meniscus, 0 indicates the position of the meniscus in the steady state. The larger the value on the positive side, the more the meniscus is pushed out in the discharge direction, and the larger the value on the negative side, the more the meniscus is drawn into the pressure chamber 424 side. The meniscus state changes according to the ink pressure in the pressure chamber 424. For this reason, when the meniscus is constant in a steady state, it can be said that the ink pressure in the pressure chamber 424 is not changed by the steady pressure. The state where the meniscus is pushed out can be said to be a state where the ink pressure in the pressure chamber 424 is higher than the steady pressure. On the contrary, the state where the meniscus is drawn can be said to be a state where the ink in the pressure chamber 424 is lower than the steady pressure.

  The expansion element P1 of the prepulse PS1 is applied from timing t1 to t2. Along with this, the pressure chamber 424 expands and the ink pressure decreases, and the meniscus is drawn to the pressure chamber 424 side. The hold element P2 is applied from timing t2 to t3. In this example, the generation period of the hold element P2 is set to be sufficiently shorter than the generation period of the expansion element P1. During this period, the moving direction of the meniscus is reversed. That is, the moving direction of the meniscus is switched from the pulling direction to the pushing direction. The contraction element P3 is applied from the timing t3 to t4. Along with this, the pressure chamber 424 contracts and the ink pressure increases. At this time, since the pressure vibration remaining in the ink is also applied, that is, the pressure vibration excited by the contraction element P3 and the pressure vibration remaining in the ink are in phase, the ink pressure becomes higher due to the vibration. Even after the application of the contraction element P3 is completed, the ink pressure in the pressure chamber 424 increases. Therefore, the meniscus moves in the ejection direction over the application period (timing t4 to t5) of the first constant potential element P11. This is considered because the ink flows into the pressure chamber 424 through the ink supply path 425.

  The expansion element P4 of the first ejection pulse PS2 is applied from timing t5 to t6. Here, the timing t5 is determined in accordance with the timing at which the meniscus returns to the retracting direction. In this example, the meniscus is determined to be pushed out by the ink amount V1. When the expansion element P4 is applied, the ink pressure is greatly reduced due to the pressure vibration remaining in the ink. After the end of the application of the expansion element P4, the hold element P5 is applied from timing t6 to t7. During this period, the ink pressure changes in the increasing direction. That is, the meniscus that has moved in the pull-in direction until then starts moving in the discharge direction. The contraction element P6 is applied from timing t7 to t8. The contraction element P6 is applied while the meniscus is moving in the discharge direction. By applying the contraction element P6, the volume of the pressure chamber 424 contracts, and the ink in the pressure chamber 424 is pressurized. At this time, the pressure vibration remaining in the ink is also added to the pressurization due to the contraction of the pressure chamber 424. For this reason, the ink pressure becomes higher by the vibration. In other words, it is possible to pressurize the ink with a degree stronger than the degree determined by the drive voltage Vh of the first ejection pulse PS2.

  The ink pressure in the pressure chamber 424 increases even after the application of the contraction element P6 is completed. Along with this, the meniscus continues to extend in the ejection direction, and a part of the meniscus tip side is torn off and ejected as ink droplets. The remaining portion of the meniscus quickly returns to the pressure chamber 424 side by the reaction that the tip side portion was torn off, and reciprocates at the natural vibration period.

  Thus, in the printer 1, the pre-pulse PS1 is applied to the piezo element 433 prior to the application of the first ejection pulse PS2 during the formation of the medium dots. Due to the application of the pre-pulse PS1, pressure vibration of such a magnitude that the ink is not ejected is generated in the ink in the pressure chamber 424. Since the application of the first ejection pulse PS2 is started in accordance with the phase of this pressure oscillation, it is possible to give a pressure oscillation having a larger amplitude than the pressure oscillation that can be excited by the drive voltage Vh of the first ejection pulse PS2. it can. Thereby, the potential difference of the contraction element P6 functioning as the ejection element can be suppressed to the minimum necessary. In addition, the application start timing of the first ejection pulse PS2 is determined within a period in which the meniscus is pushed out from the steady state. For this reason, it is possible to increase the ejection amount of the ink droplets as compared with the case where the ink droplets are ejected only by the first ejection pulse PS2. In this example, the amount indicated by the symbol V2 is considered as the ink droplet ejection amount. The discharge amount V2 is considered to increase by the amount indicated by the symbol ΔV1.

  In summary, by applying the pre-pulse PS1 in advance, the flying speed of the ink droplet can be suppressed by the amount that the drive voltage of the first ejection pulse PS2 can be lowered, and at the application start timing of the first ejection pulse PS2. The ink droplet ejection amount can be increased by the amount of meniscus being pushed out. As a result, it is possible to suppress the flight speed while securing the ejection amount necessary for forming the medium dots, and it is possible to shorten the length of the tail portion of the ink droplet.

  Note that, during the formation of medium dots, the pressure vibration applied to the ink in the pressure chamber 424 by the application of the pre-pulse PS1 is used. From this point of view, it is preferable that the generation of the first ejection pulse PS2 is started within a period of ½ or less of the Helmholtz period from the end of the generation of the prepulse PS1. Within this period, the application of the first ejection pulse PS2 is started while the pressure vibration generated by the application of the pre-pulse PS1 is sufficiently large, so that this pressure vibration can be used effectively.

<When forming large dots>
Next, an ink droplet ejection operation when forming a large dot will be described. Here, FIG. 7B is a diagram showing the position of the meniscus when the large dot is formed in association with the first ejection pulse PS2 and the second ejection pulse PS3. The vertical axis and the horizontal axis are the same as those in FIG. 7A. Therefore, the description is omitted.

  In this ejection operation, the pre-pulse PS1 is not applied to the piezo element 433. Then, after the first ejection pulse PS2 is applied, the second ejection pulse PS3 is continuously applied. Accordingly, the first ink droplet is ejected with the application of the first ejection pulse PS2, and the second ink droplet is ejected with the application of the second ejection pulse PS3. The ink droplet ejection operation by the ejection pulses PS2 and PS3 is the same as the ink droplet ejection operation by the first ejection pulse PS2 described above.

  That is, the expansion element P4 of the first ejection pulse PS2 is applied from timing t11 to t12. Accordingly, the meniscus is drawn to the pressure chamber 424 side. The hold element P5 is applied from timing t12 to t13. During this period, the moving direction of the meniscus is reversed, and the meniscus moves in the pushing direction. The contraction element P6 is applied from timing t13 to t14. Along with this, the pressure chamber 424 contracts, and the pressure vibration remaining in the ink is added, so that the ink pressure becomes higher. Then, after the contraction element P6 is applied, ink droplets are ejected. Then, the meniscus rapidly returns toward the pressure chamber 424 by the ejection of the ink droplets.

  The expansion element P7 of the second ejection pulse PS3 is applied from timing t15 to t16 after the ink droplet is ejected. At timing t15, the meniscus returns to the pressure chamber 424 side due to the reaction accompanying the ejection of ink droplets. The expansion element P7 is applied while the meniscus is returning. At this time, since the ink pressure in the pressure chamber 424 is also low, the remaining pressure vibration can be vibrated by the expansion of the pressure chamber 424 accompanying the application of the expansion element P7. Accordingly, it is possible to give a pressure vibration larger than the pressure vibration given by the drive voltage Vh of the second ejection pulse PS3. After application of the expansion element P7, the hold element P8 is applied from timing t16 to t17. During this period, the ink pressure changes in the increasing direction, and the meniscus is reversed in the ejection direction. The contraction element P9 is applied from timing t17 to t18, and the volume of the pressure chamber 424 contracts. Thereby, the ink in the pressure chamber 424 is pressurized. At this time, the remaining pressure vibration is vibrated. As a result, it is possible to press the ink with a degree stronger than the degree determined by the drive voltage Vh of the second ejection pulse PS3.

  The ink pressure in the pressure chamber 424 increases even after the application of the contraction element P9 is completed. Along with this, the meniscus continues to extend in the ejection direction, and a part of the meniscus tip side is torn off and ejected as ink droplets. The remaining portion of the meniscus quickly returns to the pressure chamber 424 side by the reaction that the tip side portion was torn off, and reciprocates at the natural vibration period.

  Thus, although the first ejection pulse PS2 ejects ink droplets, the first ejection pulse PS2 acts on the second ejection pulse PS3 in the same manner as the pre-pulse PS1. That is, pressure vibration is applied to the ink in the pressure chamber 424 prior to the application of the second ejection pulse PS3. Since the application of the second ejection pulse PS3 is started in accordance with the phase of this pressure oscillation, a pressure oscillation having a larger amplitude than the pressure oscillation excited by the drive voltage of the second ejection pulse PS3 can be applied. . Thereby, even if the waveform (drive voltage Vh) of the first ejection pulse PS2 and the second ejection pulse PS3 is the same, the amount of ink droplets ejected by the second ejection pulse PS3 is ejected by the first ejection pulse PS2. The amount of ink droplets can be increased. That is, the amount of ink droplets ejected by the first ejection pulse PS2 is V3, whereas the amount of ink droplets ejected by the second ejection pulse PS3 is V4. Accordingly, the discharge amount can be increased by the amount indicated by the symbol ΔV2.

  Summarizing the above, regarding the ink droplets ejected by the second ejection pulse PS3, while suppressing the flight speed to the same level as that of the ink droplet ejected by the first ejection pulse PS2, the ejection amount is reduced to the first ejection pulse PS2. It is possible to increase the number of ink droplets ejected in step (1). As a result, the flight speed can be suppressed while securing the ejection amount necessary for the formation of large dots, and the length of the tail portion of the ink droplet can be shortened. As schematically shown in FIG. 8, the ink droplet ejected by the second ejection pulse PS3 (the subsequent ink droplet) is in flight with the ink droplet ejected by the first ejection pulse PS2 (the previous ink droplet). Combine and land on the paper as one ink drop. At this time, since the tail portion of the subsequent ink droplet is shortened, the deviation of the landing position of the mist due to the tail portion can be suppressed.

<About simulation results>
Next, the above effect will be described based on the simulation result. 9A and 9B show simulation results when ink having a viscosity of 20 millipascal seconds is ejected. That is, FIG. 9A is a diagram illustrating the pre-pulse PS1 and the first ejection pulse PS2 used for ejecting medium dots. FIG. 9B is a diagram illustrating the state of the meniscus corresponding to each pulse PS1, PS2 of FIG. 9A. 10A and 10B are simulation results of the comparative example. That is, FIG. 10A is a diagram illustrating the first ejection pulse PS2. FIG. 10B is a diagram illustrating the state of the meniscus corresponding to the first ejection pulse PS2 of FIG. 10A.

  In the pre-pulse PS1 shown in FIG. 9A, the lowest potential VL is 0V and the intermediate potential VC is 12.5V. The generation period of the expansion element P1 is 2.5 μs, the generation period of the hold element P2 is 3.0 μs, and the generation period of the contraction element P3 is 2.0 μs. Further, the first ejection pulse PS2 shown in FIGS. 9A and 10A has the same shape, and the lowest potential VL is 0V and the highest potential VH is 25V. The generation period of the expansion element P4 is 2.5 μs, the generation period of the hold element P5 is 3.0 μs, and the generation period of the contraction element P6 is 2.0 μs. Furthermore, the generation period of the first constant potential element P11 generated between the end of the pre-pulse PS1 and the start of the first ejection pulse PS2 is 2.0 μs. The natural vibration period of the pressure chamber 424 in the head HD is 8.5 μs.

  As shown in FIGS. 9A and 9B, at the start of application of the first ejection pulse PS2 (timing t23), the ink in the pressure chamber 424 undergoes pressure vibration due to the application of the prepulse PS1 (timing t21 to t22). Remaining. The expansion element P4 of the first ejection pulse PS2 is applied in phase with this pressure vibration. That is, at timing t23, the ink pressure has just started to drop, and pressure vibration is applied by the pressure reduction accompanying the application of the expansion element P4. As a result, the amount of ejected ink droplets is about 12.5 ng, as indicated by reference numeral V5.

  On the other hand, as shown in FIGS. 10A and 10B, when only the first ejection pulse PS2 is applied (timing t31 to t32), the amplitude of the excited pressure vibration is smaller than in the examples of FIGS. 9A and 9B. As a result, the amount of ejected ink droplets is about 11 ng, as indicated by reference numeral V6. Therefore, if only about 12.5 ng of ink droplets are ejected using only the first ejection pulse PS2 as in the example of FIGS. 9A and 9B, it is necessary to increase the drive voltage Vh accordingly. It can be said. In this case, it can be seen that the flying speed of the ink droplet increases, and the tail portion of the ink droplet becomes longer by that amount.

  FIG. 11A and FIG. 11B show simulation results when ink having a viscosity of 8 millipascal seconds is ejected. 12A and 12B are reference examples having a viscosity of 8 millipascal seconds. In these, the shape of the pre-pulse PS1 and the first ejection pulse PS2 and the application timing of each pulse are the same as in the case of 20 millipascal seconds, and thus the description thereof is omitted.

  When the viscosity is 8 millipascal seconds, by using the pre-pulse PS1, the amount of ink droplets ejected by the first ejection pulse PS2 is about 16 ng as indicated by reference numeral V7. On the other hand, the ejection amount of ink droplets by only the first ejection pulse PS2 without using the pre-pulse PS1 is about 13.5 ng as indicated by reference numeral V8. Accordingly, in this case as well, if only about the first ejection pulse PS2 is used to eject approximately 16 ng of ink droplets as in the examples of FIGS. 11A and 11B, it is necessary to increase the drive voltage Vh accordingly. . Along with this, the flying speed of the ink droplet increases, and it is understood that the tail portion of the ink droplet becomes longer by that amount.

  From the above, it can be understood that by using the pre-pulse PS1, it is possible to suppress the flying speed of the ink droplets while ensuring the necessary ejection amount.

=== About Other Embodiments ===
The above-described embodiment is mainly described with respect to a printing system having the printer 1 as a liquid ejecting apparatus, which includes disclosure of a liquid ejecting method, a liquid ejecting system, and the like. Further, this embodiment is intended to facilitate understanding of the present invention and is not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

<Ink viscosity>
In the above-described embodiment, the simulation results for the ink having the viscosity of 8 millipascal second and the ink having the viscosity of 20 millipascal second are shown. With respect to the viscosity of the liquid, the present invention can be applied as long as the influence is caused by the tail portion of the liquid. Specifically, the present invention can be applied to any liquid having a viscosity of 6 millipascal seconds or more. In addition, regarding the upper limit of the viscosity, the present invention can be applied as long as the viscosity can be discharged from the nozzle 427 as a liquid droplet. At the present time, it is considered that the present invention can be applied to any liquid having a viscosity of 40 millipascal seconds or less.

<Discharge pulse>
In the above-described embodiment, an example in which one pre-pulse PS1 and two ejection pulses PS2 and PS3 are repeatedly generated has been described. However, the number of ejection pulses may be three or four. In short, it may be two or more. Further, the case where the waveforms are the same for each of the ejection pulses PS2 and PS3 has been described, but the shape of the waveform may be varied as necessary. Then, if the waveforms of the first ejection pulse PS2 and the second ejection pulse PS3 are the same as in the above-described embodiment, the DAC data can be shared, so that the control for generating the ejection pulses PS2 and PS3 is simplified. it can. In addition, since the generation periods of the respective ejection pulses PS2 and PS3 are aligned, it is easy to manage the ejection interval when ejecting ink droplets at a high frequency.

  In forming the medium dot, in the above-described embodiment, the first ejection pulse PS2 generated after the pre-pulse PS1 is applied to the piezo element 433 as a set. In this regard, the second ejection pulse PS3 may be applied to the piezo element 433 as a set. When the second ejection pulse PS3 is combined, the period from the end of application of the prepulse PS1 is longer than that in the above-described embodiment. For this reason, it is considered that the amplitude of the residual vibration is reduced, and the ejection amount of the ink droplet is reduced accordingly. Therefore, the first ejection pulse PS2 and the second ejection pulse PS3 may be selectively applied according to the required amount of ink droplets.

<About other heads>
In the head HD of the above-described embodiment, the type that operates to increase the volume of the pressure chamber 424 is used as the piezo element 433 as the potential applied by each pulse is higher. Regarding the piezo element, a type that operates to reduce the volume of the pressure chamber 424 as the electric potential given by each pulse is higher may be used. In this case, each pulse is constituted by, for example, a trapezoidal pulse convex downward.

  An element other than the piezo element 433 may be used. For example, a magnetostrictive element may be used. In short, any element may be used as long as it operates according to the applied potential and gives a pressure change to the liquid in the pressure chamber 424. When the piezo element 433 is used as this element as in the above-described embodiment, the volume of the pressure chamber 424 can be accurately controlled based on the potential of each pulse.

<About other application examples>
In the above-described embodiment, the printer 1 has been described as the liquid ejecting apparatus. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporizer, organic EL manufacturing apparatus (particularly polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied. These methods and manufacturing methods are also within the scope of application.

1 is a block diagram illustrating a configuration of a printing system. It is sectional drawing of a head. It is a figure which illustrates the structure of a head typically. It is a block diagram explaining structures, such as a drive signal generation circuit. It is a figure for demonstrating an example of a drive signal. FIG. 6A is a diagram illustrating medium dot ejection control. FIG. 6B is a diagram illustrating large dot ejection control. FIG. 7A is a diagram illustrating the position of the meniscus at the time of forming the medium dot in association with the pre-pulse and the first ejection pulse. FIG. 7B is a diagram showing the position of the meniscus at the time of forming a large dot in association with the first ejection pulse and the second ejection pulse. It is the figure which showed typically the mode of the ink droplet at the time of large dot discharge. FIG. 9A is a simulation result of ink having a viscosity of 20 millipascal seconds, and is a diagram illustrating the pre-pulse and the first ejection pulse. FIG. 9B is a diagram illustrating the state of the meniscus corresponding to each pulse in FIG. 9A. FIG. 10A is a simulation result of a comparative example using an ink having a viscosity of 20 millipascal seconds, and is a diagram illustrating a first ejection pulse. FIG. 10B is a diagram illustrating the state of the meniscus corresponding to the pulse of FIG. 10A. FIG. 11A is a simulation result with ink having a viscosity of 8 millipascal seconds, and is a diagram illustrating the pre-pulse and the first ejection pulse. FIG. 11B is a diagram illustrating the state of the meniscus corresponding to each pulse in FIG. 11A. FIG. 12A is a simulation result of a comparative example using an ink having a viscosity of 8 millipascal seconds, and is a diagram illustrating the first ejection pulse. FIG. 12B is a diagram for explaining the state of the meniscus corresponding to the pulse of FIG. 12A.

Explanation of symbols

1 printer, 10 paper transport mechanism, 20 carriage movement mechanism,
30 drive signal generation circuit, 31 DAC circuit, 32 voltage amplification circuit,
33 current amplifier circuit, 40 head unit, 41 case,
411 accommodation space, 42 channel unit, 421 channel forming substrate,
422 nozzle plate, 423 diaphragm,
423a Diaphragm part, 424 pressure chamber, 425 ink supply path,
426 common ink chamber, 427 nozzle, 428 support plate,
429 elastic film, 43 piezo element unit,
431 piezo elements, 432 fixing plate, 433 piezo elements,
434 common electrode, 435 driving electrode, 436 piezoelectric body,
44 switches, 50 detector groups, 60 printer side controller,
61 interface unit, 62 CPU, 63 memory,
CP computer, T repetition period, T1 first period,
T2 second period, T3 third period, COM drive signal,
PS1 prepulse, P1 expansion element, P2 hold element,
P3 contraction element, PS2 first discharge pulse, P7 expansion element,
P8 hold element, P9 contraction element, PS3 second ejection pulse,
P7 expansion element, P8 hold element, P9 contraction element,
P11 first constant potential element, P12 second constant potential element,
VH highest potential, VC intermediate potential, VL lowest potential, HD head,
HC head controller

Claims (8)

A pressure chamber in communication with the nozzle;
An element that performs an operation of giving a pressure change to the liquid in the pressure chamber;
A pulse generator for generating a pulse for causing the element to perform the operation;
A controller for controlling the application of the pulse to the element,
The liquid is
The viscosity is 6 millipascal seconds or more,
The pulse generator is
A non-ejection pulse that applies a pressure change that does not cause the liquid to be discharged from the nozzle to the liquid in the pressure chamber, and a discharge that applies a pressure change that causes the liquid to be discharged from the nozzle to the liquid in the pressure chamber. A pulse is repeatedly generated every repetition period,
The controller is
When the liquid is ejected using one ejection pulse in a certain repetition period, the non-ejection pulse is applied to the element prior to application of the ejection pulse to the element,
When the liquid is ejected using two or more ejection pulses in a certain repetition period, the ejection pulse is continuously applied to the element without applying the non-ejection pulse to the element.
Liquid ejection device. The liquid ejection device according to claim 1,
The pulse generator is
Generation of the ejection pulse used in combination with the non-ejection pulse starts within a period of ½ or less of the natural vibration period of the liquid in the pressure chamber from the end of the generation of the non-ejection pulse. apparatus. The liquid ejection device according to claim 1 or 2,
The element is
The operation is to change the volume of the pressure chamber by deforming according to the potential,
The ejection pulse is
A first expansion element that deforms the element to expand the pressure chamber; a first sustaining element that is generated subsequent to the first expansion element and maintains the deformed state of the element; and And a first contraction element that is generated and deforms the element to contract the inflated pressure chamber,
The non-ejection pulse is
A second expansion element that deforms the element to expand the pressure chamber; a second sustaining element that is generated following the second expansion element and maintains the deformed state of the element; and A second contraction element that is generated and deforms the element to contract the pressure chamber in the expanded state, and a potential change width in the second expansion element and the second contraction element is the first contraction element. A liquid ejection apparatus, wherein the liquid ejection device is defined to be smaller than a change width of a potential in one expansion element and the first contraction element. The liquid ejection device according to any one of claims 1 to 3,
The pulse generator is
These pulses are repeatedly generated in the order of the non-ejection pulse, the first ejection pulse, and the second ejection pulse,
The controller is
When ejecting liquid using one ejection pulse, the non-ejection pulse and the first ejection pulse are applied to the element,
A liquid ejecting apparatus that applies the first ejection pulse and the second ejection pulse to the element when ejecting liquid using the two ejection pulses. The liquid ejection device according to claim 4,
The first ejection pulse is:
A liquid ejection apparatus that is applied to the element at a timing for exciting a pressure vibration of the liquid in the pressure chamber generated by applying the non-ejection pulse to the element. The liquid ejection device according to claim 5,
The first ejection pulse is:
Liquid ejection applied to the element at a timing when the meniscus is positioned in the liquid ejection direction from the steady state due to pressure oscillation of the liquid in the pressure chamber caused by application of the non-ejection pulse to the element apparatus. The liquid ejection apparatus according to any one of claims 4 to 6,
The second ejection pulse is:
A liquid ejecting apparatus applied to the element at a timing of exciting a pressure vibration of the liquid in the pressure chamber generated by applying the first ejection pulse to the element. The liquid ejection device according to any one of claims 4 to 7,
The second ejection pulse is:
A liquid ejection apparatus having the same shape as the first ejection pulse.

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