JP4678158B2 - Droplet ejection head driving method, droplet ejection head, and droplet ejection apparatus - Google Patents

Description

  The present invention relates to a droplet ejection head driving method, a droplet ejection head, and a droplet ejection apparatus, and more particularly, a droplet ejection head driving method for ejecting droplets using a piezoelectric element such as a piezoelectric element, and the like. The present invention relates to a droplet discharge head using a driving method, and a droplet discharge apparatus including the droplet discharge head.

  A droplet discharge head that generates a pressure wave for a liquid filled in a pressure chamber using an electromechanical transducer such as a piezo element and discharges a droplet from a nozzle communicating with the pressure chamber by the pressure wave is generally used. Well known. In particular, inkjet recording apparatuses that record ink on recording paper by discharging ink droplets are widely used, and in recent years it has become possible to record high-quality images.

  In a droplet discharge head using an electromechanical conversion element, for example, as in the technique described in Patent Document 1, a meniscus operation of the nozzle portion is performed by applying a complicated drive waveform (analog waveform) to the electromechanical conversion element. It is possible to control with high accuracy. However, the drive circuit using such an analog waveform increases the cost, which increases the cost of the entire apparatus.

Therefore, it is conceivable to use a simple rectangular drive waveform as the drive waveform. For example, Patent Documents 2 to 5 propose a rectangular drive waveform. In this way, the cost of the driving circuit can be greatly reduced by using the rectangular driving waveform.
JP 2001-334659 A Japanese Patent No. 1469531 JP 59-176060 A Japanese Patent No. 3249719 JP 2001-018388 A

  However, in the conventional rectangular drive waveform, the drop volume is modulated by setting the pulse width or the like, but the drop diameter modulation range obtained by the drop volume modulation by setting the pulse width is very narrow (for example, 6 to 6). 10 pl), when performing high-quality printing and high-speed recording, there is a problem that a wide droplet size modulation range (for example, 2 to 20 pl) cannot be obtained.

  In addition, in order to stably discharge droplets at a high frequency, it is necessary to suppress reverberation after droplet discharge. However, in the case of a conventional rectangular drive waveform, the amount of voltage change and the slope at the reverberation suppression unit are reduced. Since it cannot be set freely, there is a problem that appropriate reverberation suppression cannot be performed.

  In addition, the occurrence of unintentional discharge such as satellites and mists depends on the reverberation intensity immediately after discharge, and the voltage change amount and slope in the reverberation suppression unit cannot be set freely, thus preventing the occurrence of satellites and mists. There is a problem that it cannot be performed reliably.

  Further, when ink is applied as the liquid to be ejected, the ink viscosity increases at the meniscus of the nozzle portion due to volatilization of the ink solvent. At this time, if an analog waveform is used, it is possible to apply a weak drive waveform that causes minute vibrations to the meniscus to prevent this, but a rectangular drive waveform is weak like an analog waveform. It is difficult to apply a simple driving waveform, and it is difficult to prevent the influence of an increase in ink viscosity.

  The present invention has been made in consideration of the above facts, and it is possible to ensure a sufficient droplet diameter modulation range, ensure ejection stability at high frequencies, prevent unintentional ejection, and suppress the increase in droplet viscosity. An object of the present invention is to provide a liquid droplet ejection head driving method, a droplet ejection head, and a droplet ejection apparatus.

In order to achieve the above object, the method of driving a droplet discharge head according to claim 1 causes a pressure change in the pressure chamber by applying a drive signal to the electromechanical transducer and deforming the electromechanical transducer. A method of driving a droplet discharge head for discharging a liquid filled in a pressure chamber as droplets from a nozzle communicating with the pressure chamber, wherein the voltage level of the voltage waveform is ternary and rises as the drive signal A rectangular driving wave having a single time and a falling time each having a first driving waveform for discharging a droplet having a first droplet diameter, and a second droplet diameter smaller than the first droplet diameter. Using a rectangular drive wave having one of the drive waveforms selected from the second drive waveform for ejecting the droplet and the third drive waveform for vibrating the liquid surface without ejecting the droplet, Of the lowest and highest voltage levels When the difference is V1, and the potential difference between the maximum voltage and the intermediate voltage is V2, the voltage ratio V2 / V1 between V1 and V2 is set in the range of 0.25 to 0.45 and applied to the electromechanical transducer. It is a feature.

According to the first aspect of the present invention, a rectangular driving wave whose voltage level is ternary is used as the driving signal applied to the electromechanical transducer. By using the rectangular drive wave in this way, the drive circuit can be made inexpensive. In addition, by setting the voltage level of the rectangular driving wave to three values, the degree of freedom in designing the rectangular driving wave waveform can be increased. In the present specification, the “rectangular drive wave” means a drive waveform having one type of rise time and one fall time. The rectangular driving waveform includes a first driving waveform for discharging a droplet having a first droplet diameter, a second driving waveform for discharging a droplet having a second droplet diameter smaller than the first droplet diameter, In addition, the third driving waveform for suppressing the increase in the viscosity of the droplet by vibrating the liquid surface without discharging the droplet can be obtained.

  When the potential difference between the lowest voltage and the highest voltage among the three voltage levels is V1, and the potential difference between the highest voltage and the intermediate voltage is V2, the voltage ratio V2 / V1 between V1 and V2 is 0.25 to 0.45. By setting this range, it is possible to satisfy all the required ranges of sufficient droplet size modulation range, high frequency ejection stability, suppression of unintentional ejection such as satellite and mist, and suppression of increase in droplet viscosity It becomes.

At this time, when discharging the minute droplets by setting the rise time and the fall time of the rectangular driving wave to 1/4 or less of the natural period of the droplet discharge head and applying it to the electromechanical conversion element, It is possible to eject droplets from the nozzles with a droplet volume that enables high-quality recording.

The first drive waveform includes a first voltage changing process in which the applied voltage is changed from the intermediate voltage to the lowest voltage and the meniscus is pulled to the pressure chamber side, and the applied voltage is changed from the lowest voltage to the highest voltage to change the pressure chamber A driving waveform including: a second voltage changing process for discharging a droplet by contracting a volume; and a third voltage changing process for adjusting a reverberation in a pressure chamber by changing an applied voltage from a highest voltage to an intermediate voltage. This makes it possible to discharge a droplet having a first droplet diameter having a larger droplet volume than the second droplet size.

  The second drive waveform includes a first voltage changing process in which the applied voltage is changed from the intermediate voltage to the lowest voltage and the meniscus is pulled to the pressure chamber side, and the applied voltage is changed from the lowest voltage to the intermediate voltage. A fourth voltage changing process for forming a liquid column, a fifth voltage changing process for changing the applied voltage from the intermediate voltage to the lowest voltage, drawing the meniscus to the pressure chamber side, and discharging droplets; and applying the lowest voltage And a sixth voltage changing process for adjusting the reverberation in the pressure chamber by changing the voltage from the voltage to the intermediate voltage, whereby a liquid having a second droplet diameter smaller than the first droplet diameter can be obtained. It becomes possible to discharge droplets.

  Furthermore, the third drive waveform includes a seventh voltage changing process in which the applied voltage is changed from the intermediate voltage to the highest voltage to start generating minute vibrations in the meniscus, and the applied voltage is changed from the highest voltage to the intermediate voltage. And a third voltage change process for adjusting the reverberation in the pressure chamber, thereby suppressing the increase in the viscosity of the droplets by vibrating the liquid surface without ejecting the droplets. Is possible.

Then, the time from the start of the first voltage change process to the start of the second voltage change process of the first drive waveform and the time from the start of the first voltage change process to the start of the fourth voltage change process of the second drive waveform are respectively ejected by droplets. By setting it to ½ of the natural period of the head, the natural vibration generated in each voltage change process is superimposed, so that it is possible to efficiently eject liquid droplets. Further, since the time from the start of the seventh voltage change process to the start of the eighth voltage change process of the third drive waveform is made to coincide with the natural period of the droplet discharge head, the vibration due to each voltage change process is offset, so that the pressure Reverberation in the room can be effectively suppressed, and unintended discharge of satellites and mists can be prevented.

The droplet discharge head of the present invention is deformed when a pressure signal filled with a liquid, a nozzle communicating with the pressure chamber, and a drive signal is applied to generate a pressure wave in the pressure chamber and filled. An electromechanical conversion element that discharges the liquid as droplets from the nozzle, and a drive circuit that applies a drive signal to the electromechanical conversion element by the method of driving a liquid droplet ejection head according to the present invention . .

According to the droplet discharge head of the present invention , a pressure signal is generated in the pressure chamber by applying a drive signal to the electromechanical conversion element and deformed, and the liquid filled in the pressure chamber is discharged as a droplet from the nozzle. Is done.

At this time, since the drive signal is applied to the electromechanical transducer by the driving method of the droplet discharge head of the present invention by the drive circuit, as described above, a sufficient droplet diameter modulation range is ensured and the discharge is performed at a high frequency. It is possible to ensure stability, prevent unintended discharge, and suppress increase in the viscosity of the droplet.

The liquid droplet ejection apparatus of the present invention is characterized by including the liquid droplet ejection head of the present invention .

According to the liquid droplet ejection apparatus of the present invention, since the liquid droplet ejection head of the present invention is provided, as described above, a sufficient droplet diameter modulation range is ensured, ejection stability at high frequencies is ensured, and unintended ejection is performed. And the increase in the viscosity of the droplets can be suppressed.

  As described above, according to the present invention, a rectangular driving wave whose voltage waveform has a ternary voltage level is used as a driving signal applied to the electromechanical transducer, the potential difference between the lowest voltage and the highest voltage is V1, and the highest voltage and the intermediate voltage. By setting the voltage ratio V2 / V1 between V1 and V2 in the range of 0.25 to 0.45 and applying it to the electromechanical transducer when the voltage potential difference is V2, in particular, the voltage between V1 and V2 By setting the ratio V2 / V1 in the range of 0.30 to 0.35, a sufficient droplet diameter modulation range is ensured, ejection stability at high frequencies is ensured, unintentional ejection is prevented, and droplet viscosity is increased. There is an effect that it becomes possible to suppress this.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings. In this embodiment, the present invention is applied to an ink jet recording apparatus.

  FIG. 1 is a diagram showing a head structure per nozzle of an ink jet recording apparatus according to an embodiment of the present invention.

  The head 10 includes an ink tank 12, a supply path 14, a pressure chamber 16, a nozzle 18, and a piezoelectric element 20 as an electromechanical conversion element.

  Ink is stored in the ink tank 12, and the ink stored in the ink tank 12 is filled into the pressure chamber 16 via the supply path 14, and the ink is supplied to the nozzle 18 that communicates with the pressure chamber 16.

  A part of the wall surface of the pressure chamber 16 is composed of a diaphragm 16A. A piezoelectric element 20 such as a piezoelectric element is provided on the diaphragm 16A. The piezoelectric element 20 deforms and vibrates the diaphragm 16A. A pressure wave is generated in the chamber 16. That is, ink stored in the pressure chamber 16 is ejected from the nozzle 18 by the pressure wave generated by the vibration of the piezoelectric element 20, and ink is supplied to the pressure chamber 16 from the ink tank 12 through the supply path 14. It is like that.

  For example, the nozzle 18 records an image in the recording paper width direction by using a plurality of recording heads arranged in the recording paper width direction, and records an image on the recording paper by relatively moving the recording paper and the recording head. Can do.

  FIG. 2 is a diagram showing a drive circuit for driving the head of the ink jet recording apparatus according to the embodiment of the present invention.

  In the present embodiment, a recording head is configured by arranging a plurality of nozzles. That is, a plurality of piezoelectric elements 20 are provided, and the piezoelectric elements 20 are driven by the drive circuit 30.

  As shown in FIG. 2, the drive circuit 30 includes a plurality of piezoelectric elements 20 and a switching circuit 22 for controlling the application of voltage to the piezoelectric elements 20, and each piezoelectric element 20 has one end. The other end is connected to the switching circuit 22.

  Each switching circuit 22 is configured to include three switching elements 22A, 22B, and 22C so that on / off of each switching element 22A, 22B, and 22C is controlled in accordance with a control signal input from a controller (not shown). It has become.

  The switching element 22A of the switching circuit 22 is grounded (GND), the reference voltage V0 (V2-V1 in FIG. 3) is applied to the switching element 22B, and the voltage V1 is applied to the switching element 22C. That is, GND is applied to the piezoelectric element 20 by turning on the switching element 22A using each control signal, and the reference voltage V0 is applied to the piezoelectric element 20 by turning on the switching element 22B, thereby turning on the switching element 22C. Thus, the voltage V1 is applied. Therefore, ternary voltage levels are applied to the piezoelectric element 20 by controlling on / off of the switching elements 22A, 22B, and 22C in accordance with the control signal. Each voltage is V1> V0> GND.

  In the drive circuit 30 of the present embodiment, the droplet diameter of the ink ejected from the nozzles 18 is changed using three voltage levels. More specifically, a large droplet and a small droplet are ejected, and a voltage is applied to the piezoelectric element 20 to such an extent that it is not ejected in order to prevent an increase in ink viscosity.

  FIG. 3 shows an example of a voltage waveform of a drive signal applied to the piezoelectric element 20 by the drive circuit 30 described above. 3A shows a driving waveform for discharging a large drop for discharging a large drop, FIG. 3B shows a driving waveform for discharging a small drop for discharging a small drop, and FIG. FIG. 6 shows a preliminary waveform for preventing thickening to prevent an increase in ink viscosity by causing moderate fine vibrations in the meniscus without discharging droplets. FIG.

  In this embodiment, each of the rising time tr and the falling time tf of the rectangular driving wave is used as one type, and a driving waveform in which the selectable voltage level is fixed to three values is used, and the voltage level is set to three values. This increases the degree of freedom in waveform design. If the voltage level that can be selected is set to 4 or more, the degree of freedom in designing the waveform further increases. However, if the voltage level is set to 4 or more, the drive circuit cost increases, which is lower than the conventional analog waveform. The typical merit will be lost. Therefore, it is most effective to set the selectable voltage level to ternary in order to keep the drive circuit cost low and to ensure the freedom of waveform design.

  Specifically, as shown in FIG. 3A, the large droplet ejection driving waveform is obtained by changing the voltage from the intermediate voltage V0 to the lowest voltage GND in the voltage changing process of (1). By expanding 16, the meniscus is drawn into the nozzle 18. Next, in the voltage change process (2), the voltage is changed from the lowest voltage to the highest voltage V1, and the pressure chamber 16 is contracted, whereby ink droplets are ejected from the nozzle 18. Then, in the voltage change process (3), the voltage is changed from the maximum voltage V1 to the intermediate voltage V0 to adjust the reverberation in the pressure chamber 16 after ink droplet ejection.

  As shown in FIG. 3B, the droplet ejection driving waveform is obtained by changing the voltage from the intermediate voltage V0 to the lowest voltage GND and expanding the pressure chamber 16 in the voltage changing process of (1). The meniscus is drawn into the nozzle 18. Next, in the voltage change process of (2), the voltage is changed from the lowest voltage GND to the intermediate voltage V0 to form a thin liquid column at the center of the nozzle. Then, in the voltage change process (3), the voltage is changed from the intermediate voltage V0 to the lowest voltage GND, and the meniscus is pulled back abruptly, thereby ejecting a fine droplet. Further, in the voltage change process (4), the voltage is changed from the lowest voltage GND to the intermediate voltage V0 to adjust the reverberation of the pressure chamber 16 after droplet discharge.

  Here, FIGS. 4A to 4D show the behavior of the liquid in the nozzle 18 (particularly the change in meniscus) when the droplet ejection drive waveform is applied. When the droplet ejection driving waveform is applied, as shown in FIG. 4 (A), the substantially flat meniscus initially located at the opening of the nozzle 18 is the pressure due to the voltage change process of (1). As the volume of the chamber 16 increases, the chamber is pulled toward the pressure chamber 16, and the central portion of the meniscus is retracted more than the peripheral portion of the meniscus to form a concave meniscus (FIG. 4B). In this state, when the volume of the pressure chamber 16 is reduced by the voltage change process (2), as shown in FIG. 4C, the nozzle 18 (the inner diameter of the ink discharge port) is located at the center of the meniscus. A thin liquid column 32 is formed, and then the tip of the liquid column 32 is separated to form a droplet 34 (FIG. 4D) .The droplet diameter of the droplet at this time is the formed liquid column 32. In other words, by using such a driving method (“meniscus control method” or “strike method”), it is possible to discharge droplets smaller than the nozzle diameter. .

  As shown in FIG. 3C, the preliminary waveform changes the voltage from the intermediate voltage V0 to the maximum voltage V1 in the voltage change process of (1) to generate an appropriate minute vibration in the meniscus. The voltage is changed from the highest voltage V1 to the intermediate voltage V0 in the voltage change process (2) to suppress unnecessary reverberation in the pressure chamber 16.

  Here, various settings of the application time of each voltage level in the drive waveforms for the large droplet discharge, the small droplet discharge drive waveform, and the preliminary waveform will be described.

  In the large droplet ejection driving waveform and the small droplet ejection driving waveform, the natural vibration generated in the head 10 during the voltage change process (1) interferes with the natural vibration generated in the head 10 during the voltage change process (2). It has a great influence on the meniscus.

  Therefore, in the large droplet ejection driving waveform and the small droplet ejection driving waveform, the time from the start of the voltage change process (1) to the start of the voltage change process (2), that is, the pulse width is set for each head 10. ½ of the natural period Tc.

  As described above, by setting the pulse width of the large droplet ejection driving waveform and the small droplet ejection driving waveform to ½ of the natural period Tc of the head 10, in the large droplet ejection driving waveform, the voltage change of (1) is performed. Since the vibration of the head 10 generated by the process and the vibration of the head 10 generated by the voltage change process (2) are superimposed, it is possible to facilitate the discharge of droplets and improve the discharge efficiency of large droplets. be able to. Similarly, the vibration waveform of the head 10 generated by the voltage change process (1) and the vibration of the head 10 generated by the voltage change process (2) are superimposed on the droplet ejection driving waveform. Therefore, the small droplet ejection driving waveform is advantageous for the generation of a thin liquid column, and the micro droplets can be ejected efficiently.

  In the preliminary waveform, the time from the start of the voltage change process (1) to the start of the voltage change process (2), that is, the pulse width is the natural period Tc of the head 10.

  In this way, by setting the pulse width of the preliminary waveform to the natural period Tc, the vibration of the head 10 generated by the voltage change process of (1) and the vibration of the head 10 generated by the voltage fluctuation process of (2). By canceling out, the reverberation in the pressure chamber 16 can be effectively suppressed.

  In the large droplet ejection driving waveform, the small droplet ejection driving waveform, and the preliminary waveform, the potential difference V1 that is the amplitude of the highest voltage V1 and the lowest voltage GND, and the middle that becomes the highest voltage V1 and the reference voltage. By changing the voltage ratio V2 / V1 with the potential difference V2 from the voltage V0, the droplet diameter modulation range, high-frequency ejection stability, satellite / mist generation state, and ink thickening prevention effect are changed.

  Therefore, first, as shown in Table 1, the voltage ratio V2 / V1 was changed, and the droplet diameter modulation range, the high-frequency ejection stability, the satellite / mist generation state, and the ink thickening prevention effect were examined.

  The “drop volume” for large droplet discharge in Table 1 was evaluated as “◎” for 15 pl or more, “◯” for 10 pl to 15 pl, and “x” for 10 pl or less. This is because a droplet volume of 15 pl or more is usually required to cope with a recording resolution of about 400 to 600 dpi that is generally used in an image recording apparatus. The “drop volume” of small droplet ejection was evaluated as “評 価” when 2 pl or less, “◯” when 2 pl to 5 pl, and “x” when 5 pl or more. This is because the recording dots formed with droplets of 2 pl or less are difficult to recognize with the human eye, and high-quality recording with low graininess is possible. In addition, “high frequency ejection” and “satellite” for large droplet ejection and small droplet ejection are evaluated in three stages by observing the ejection state at 20 kHz, landing position accuracy, and dot shape measurement, etc. `` Prevention '' means `` X '' when droplet discharge occurs due to the application of the preliminary waveform, `` ◎ '' when moderate meniscus vibration occurs and sufficient thickening prevention effect is obtained, In the case where there is no discharge of water, but the effect of preventing thickening is small, or the case where there is discharge of liquid droplets (satellite or mist) to the extent that does not cause a problem, the case where the effect of preventing thickening can be obtained was evaluated as “◯”.

  Thus, from Table 1, by setting the voltage ratio V2 / V1 within the range of 0.25 to 0.45, the droplet diameter modulation range, high-frequency ejection stability, satellite / mist generation state, and ink increase It can be seen that it is possible to satisfy all the requirements for the anti-sticking effect. Further, as a more preferable condition, it is desirable to set the voltage ratio V2 / V1 within a range of 0.3 to 0.35.

  Accordingly, each drive waveform is set such that the voltage ratio V2 / V1 is within the range of 0.25 to 0.45 for each of the large droplet ejection drive waveform, the small droplet ejection drive waveform, and the preliminary waveform. Thus, it is possible to perform ink ejection satisfying all the required ranges of the droplet diameter modulation range, high-frequency ejection stability, satellite / mist generation state, and ink thickening prevention effect.

  That is, when discharging a large droplet, it is possible to secure a large droplet volume, and at the same time, it is possible to optimize the reverberation intensity in the pressure chamber 16 and to ensure discharge stability at a high frequency. Occurrence of mist can be prevented.

  In addition, when ejecting small droplets, micro droplets can be ejected, and at the same time, the reverberation intensity in the pressure chamber 16 can be optimized, and ejection stability at high frequencies can be ensured. Occurrence can also be prevented.

  Further, when preventing the increase in viscosity using the preliminary waveform, it is possible to apply a minute vibration to the meniscus without ejecting ink, and it is possible to effectively prevent the increase in viscosity.

  On the other hand, the large droplet ejection driving waveform, the small droplet ejection driving waveform, and the preliminary waveform as described above are not limited to the voltage ratio V2 / V1 described above, and the voltage rise time tr and the rise time during each voltage changing process. The drop volume changes depending on the drop time tf. In particular, when a high-definition image is recorded by droplet ejection, the influence of the voltage rise time tf and the fall time tf during each voltage change process is large.

  Therefore, the droplet volume of the droplet was measured by changing the voltage rise time tr and the fall time tf during droplet ejection.

  FIG. 5 is a graph showing the result of measuring the change in the droplet volume of the microdroplet accompanying the change in the voltage rise time tr and the fall time tf. FIG. 5 shows the result of measurement using an example in which the natural period Tc of the head 10 is 10 μs.

  In order to perform high-quality image recording, it is necessary that the droplet volume of the microdroplet be at least 4 pl or less. That is, as can be seen from FIG. 5, in order to make the voltage 4 pl or less, it is necessary to set the voltage rise time tr and the fall time tf to about 2.5 μs or less. Here, in FIG. 5, the natural period Tc of the head 10 is 10 μs. Therefore, considering the case of using a head with another natural period, the voltage rise time tr and the fall time tf are set to 1 of the natural period Tc. By setting to / 4, the droplet volume of the fine droplets can be reduced to 4 pl or less.

  Therefore, by setting the voltage rise time tr and the fall time tf to ¼ of the natural period Tc of the head 10, it is possible to eject microdroplets and record a high-quality image. Become.

  Here, an example of an ink jet recording apparatus as a droplet discharge apparatus equipped with the above-described head 10 will be described. FIG. 6 is a diagram showing an example of the ink jet recording apparatus according to the embodiment of the present invention.

  The ink jet recording apparatus includes a carriage 36 on which the above-described head 10 is mounted, a main scanning mechanism 38 for scanning the carriage 36 in the main scanning direction X, and a sub scanning direction 40 for conveying a recording paper 40 as a recording medium in the sub scanning direction Y. A scanning mechanism 42 is included.

  The head is mounted on the carriage 36 such that the nozzle surface faces the recording paper 40 and ejects ink droplets as droplets onto the recording paper 40 while being transported in the main scanning direction X, whereby a certain band region 44 is obtained. To record. Next, the recording paper 40 is conveyed in the sub-scanning direction Y, and the next band area is recorded while the carriage 36 is conveyed again in the main scanning direction X.

  Actually, image recording was performed using such an ink jet recording apparatus, and the image quality was evaluated. The driving method described in the above embodiment was used for droplet discharge control for discharging ink droplets. A matrix-like array head having 260 ejectors per color is arranged side by side on the carriage 36 so as to correspond to four colors of yellow, magenta, cyan, and black, and the four color dots are superimposed on the recording paper. By combining them, full color image recording was performed. As a result, stable ejection from each ejector could be realized, and extremely high quality image recording could be performed over the entire recording paper.

  In the above-described ink jet recording apparatus described as the droplet discharge apparatus, the form in which the recording is performed while the head 10 is conveyed by the carriage 36 has been described. It is also possible to apply the present invention to another apparatus form such as performing recording while transporting only the recording medium while fixing the image (in this case, only main scanning is performed).

  In the above embodiment, the example in which the present invention is applied to the head 10 of the ink jet recording apparatus has been described. However, the present invention is not limited to this. It is also possible to apply.

  For example, in the above embodiment, a piezoelectric actuator is used as the pressure generating means. However, an electromechanical conversion element using electrostatic force or magnetic force, an electrothermal conversion element for generating pressure using a boiling phenomenon, or the like. Other pressure generating means may be used. Also, as the piezoelectric actuator, in addition to the single plate type piezoelectric actuator used in the present embodiment, an actuator of another form such as a longitudinal vibration type stacked piezoelectric actuator may be used.

  Further, in the above-described embodiment, the ink jet recording apparatus that records characters, images, and the like by discharging colored ink onto the recording paper has been described as an example. However, the ink jet recording apparatus in this specification refers to an ink jet recording apparatus on the recording paper. It is not limited to the recording of characters and images on That is, the recording medium is not limited to paper, and the liquid to be discharged is not limited to colored ink. For example, it is possible to produce color filters for displays by discharging colored ink onto polymer films or glass, or to form bumps for component mounting by discharging molten solder onto a substrate. It is also possible to use the present invention for the general liquid ejecting apparatus used in the above.

1 is a diagram showing a head structure per nozzle of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 1 is a diagram illustrating a drive circuit that drives a head of an ink jet recording apparatus according to an embodiment of the present invention. An example of the voltage waveform of the drive signal applied to a piezoelectric element by a drive circuit is shown. It is a figure which shows the behavior of the liquid in a nozzle when the drive waveform for small droplet discharge is applied. It is a graph which shows the result of having measured the change of the volume of a micro drop accompanying change of the rise time and fall time of the voltage when the natural period Tc of a head is 10 microseconds. It is a figure which shows an example of the inkjet recording device concerning embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Head 12 Ink tank 14 Supply path 16 Pressure chamber 18 Nozzle 20 Piezoelectric element 22 Switching circuit 30 Drive circuit

Claims (6)

By applying a drive signal to the electromechanical conversion element and deforming the electromechanical conversion element, a pressure change is generated in the pressure chamber, and the liquid filled in the pressure chamber is discharged as a droplet from a nozzle communicating with the pressure chamber. A method of driving a droplet discharge head,
The drive signal is a rectangular drive wave whose voltage waveform has a ternary voltage level and one type of rise time and fall time, and is a first for discharging a droplet having a first droplet diameter. Select from a driving waveform, a second driving waveform for ejecting a droplet having a second droplet diameter smaller than the first droplet size, and a third driving waveform for vibrating the liquid surface without ejecting the droplet Using a rectangular drive wave having any of the drive waveforms
When the potential difference between the lowest voltage and the highest voltage is V1 and the potential difference between the highest voltage and the intermediate voltage is V2, the voltage ratio V2 / V1 between V1 and V2 is in the range of 0.25 to 0.45. A method for driving a droplet discharge head, characterized in that the droplet discharge head is set and applied to an electromechanical transducer. The first driving waveform includes a first voltage changing process in which an applied voltage is changed from an intermediate voltage to a minimum voltage to draw a meniscus toward the pressure chamber side, and an applied voltage is changed from a minimum voltage to a maximum voltage. A second voltage changing process for contracting the volume of the chamber and discharging droplets; and a third voltage changing process for adjusting the reverberation in the pressure chamber by changing the applied voltage from the highest voltage to an intermediate voltage. Configure
The second driving waveform includes the first voltage changing process, a fourth voltage changing process for forming a liquid column by changing the applied voltage from the lowest voltage to the intermediate voltage, and the applied voltage from the intermediate voltage to the lowest voltage. A fifth voltage change process for changing the pressure to draw the meniscus toward the pressure chamber and discharging a droplet, and a sixth voltage change for adjusting the reverberation in the pressure chamber by changing the applied voltage from the lowest voltage to an intermediate voltage. A process comprising,
The third drive waveform includes a seventh voltage change process for changing the applied voltage from an intermediate voltage to a maximum voltage to start generation of minute vibrations in the meniscus, and the third voltage change process. The method for driving a droplet discharge head according to claim 1 . To claim 1 or claim 2, characterized in applying a start-up time and the fall time of the rectangular drive wave to the electromechanical conversion element is set to 1/4 or less of the natural periods of the droplet ejection heads A method of driving the liquid droplet ejection head as described. The first driving waveform includes a time from the start of the first voltage change process to the start of the second voltage change process, and a time from the start of the second voltage change process to the start of the third voltage change process. Set to 1/2 of the natural period of the head,
The second drive waveform sets a time from the start of the first voltage change process to the start of the fourth voltage change process to ½ of the natural period,
The third drive waveform is either from the seventh voltage changing process starts of claims 2 to 4 and sets the time to start the eighth voltage changing process so as to coincide with the natural period A method for driving a droplet discharge head according to claim 1 . A pressure chamber filled with liquid;
A nozzle communicating with the pressure chamber;
An electromechanical transducer that deforms when a drive signal is applied, generates a pressure wave in the pressure chamber, and discharges the filled liquid as droplets from the nozzle;
A driving circuit that applies a driving signal to the electromechanical transducer by the driving method of the droplet discharge head according to any one of claims 1 to 4 ,
Including a droplet discharge head. A droplet discharge device comprising the droplet discharge head according to claim 5 .

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