JP5034309B2 - Droplet discharge device - Google Patents

Description

  The present invention relates to a droplet discharge device, and more particularly, a volume change is generated in a storage chamber in which a liquid is stored by applying a drive voltage having a predetermined drive waveform to a piezoelectric element. The present invention relates to a droplet discharge device that discharges droplets from a nozzle communicated with the nozzle.

  Conventionally, by applying a drive voltage having a predetermined drive waveform to a piezoelectric element such as a piezo element, a volume change (expansion / contraction) is generated in a storage chamber in which a liquid is stored, and communication is made with the storage chamber according to the volume change. 2. Related Art A droplet discharge device such as an ink jet printer that discharges droplets from a formed nozzle is known.

  In this type of droplet discharge device, as shown in FIG. 8A as an example, the liquid level (so-called meniscus) of the liquid supplied from the storage chamber to the nozzle 40 is changed according to the volume change of the storage chamber. As shown in FIG. 8B as an example, one or a plurality of liquid droplets (in FIG. 8B, main droplets and satellite droplets are formed. Are ejected.), And the dots formed by the droplets are recorded at the positions where the flying droplets land on the recording medium.

  By the way, in this type of liquid droplet ejection apparatus, depending on various factors such as the vibration state of the liquid level of the nozzle 40 when a driving voltage is applied, the contamination of foreign matter in the nozzle 40, and the manufacturing error of the nozzle 40, As an example, as shown in FIG. 8C, a deviation (hereinafter referred to as “flying curve”) may occur in the droplet flying direction. In such a droplet discharge device, when such a flying curve occurs, a deviation occurs in the landing position of the droplet, so that the quality of the recorded image is deteriorated.

  Various techniques for preventing the occurrence of flying bends have been proposed for each occurrence factor. Patent Document 1 discloses that when droplets are continuously discharged from a nozzle, the previous discharge occurs on the nozzle surface. The drive voltage is driven so as to generate a vibration having a phase opposite to that of the reverberation vibration on the liquid surface of the nozzle. Techniques have been proposed to cancel the reverberation vibration by adjusting the waveform. In Patent Document 1, the deviation (flying curve) in the flight direction of the droplet shown in FIG. 8C is referred to as “tail curve”.

  That is, as shown in FIG. 9A, for example, when a drive voltage having a drive waveform is applied to the piezoelectric element to cause a volume change in the storage chamber and a droplet is ejected from the nozzle, As an example, as shown by a broken line in FIG. 9C, a reverberation vibration in which the liquid surface vibrates in the internal direction and the external direction of the nozzle is generated even after the drive waveform is finished due to the change in the liquid flow velocity. The vertical axis in FIG. 9C represents the flow rate of the liquid (ink) at the nozzle opening, the positive side moves the liquid in the direction outside the nozzle, and the negative side moves in the direction inside the nozzle. Indicates that it is moving. Note that when a droplet is ejected from the nozzle, the liquid level of the nozzle temporarily retreats by the volume of the ejected liquid droplet, so the vertical axis of FIG. It does not indicate the position.

  For this reason, when droplets are continuously ejected from the nozzles using a drive waveform as shown in FIG. 9A, the flight bends until the reverberation vibration is attenuated to a level that does not affect the ejection of the droplets. May occur.

  Therefore, the driving waveform is adjusted by applying the technique of Patent Document 1 to the driving voltage having the driving waveform as shown in FIG. 9A, and the driving voltage having the driving waveform as shown in FIG. When liquid droplets are ejected from the nozzle by being applied to the element, as shown by the solid line in FIG. 9C, the reverberation vibration can be quickly canceled by the driving voltage, so that no flying bend occurs. The liquid droplets can be accurately discharged from the nozzle in a short cycle.

  Further, Patent Document 2 discloses a natural vibration period of a liquid stored in a storage chamber when a drive voltage having a driving waveform for expanding, holding, and contracting the storage chamber is applied to the piezoelectric element to discharge a droplet from the nozzle. (In Patent Document 2, described as “Helmholtz resonance frequency”) Tc, the period for expanding the storage chamber is set shorter than the natural vibration period Tc, and the period for maintaining the expansion state of the storage chamber is 1 / Tc. By setting it to 2 or less, the reverberation vibration of the liquid level of the nozzle is suppressed to the minimum necessary to prevent the droplet from being bent, and the tailing of the satellite droplet is reduced to stabilize the small droplet at a high driving frequency. Thus, a technique for discharging is proposed.

Further, in Patent Document 3, in an ink jet recording head provided with a wiping mechanism for wiping a nozzle forming surface provided with nozzles, a water repellent treatment is performed on the nozzle forming surface to form a water repellent region, By providing a hydrophilic region at a part of the downstream side in the wiping direction, when the nozzle forming surface is wiped with a wiping mechanism, solid matter generated due to evaporation of ink components is prevented from being pushed into the nozzle, and flight bending is prevented. A technique for preventing the occurrence of the above has been proposed.
JP 2002-361863 A JP-A-9-226106 JP-A-8-39817

  By the way, the inventors of the present invention adopted a driving voltage of a driving waveform that suppresses reverberation vibration by applying the technique of the above-mentioned Patent Document 1, and as a result of performing a flight experiment of a droplet from a nozzle, a flight curve We discovered that defects in different flight directions may occur. As an example, this is a phenomenon in which the tail part of the ejected droplet is bent as shown in FIG. In the present specification, the phenomenon in which the tail part of the ejected droplet is bent is referred to as “tail bending”.

  For example, as shown in FIGS. 10A to 10F, this tail bend is generated when the liquid column formed on the liquid surface of the nozzle 40 is separated in accordance with the volume change of the storage chamber. This is a phenomenon that occurs because only the last tail of the liquid column is dragged to the wall surface of the opening of the nozzle 40 due to various factors such as contamination of foreign matter into the nozzle and manufacturing errors of the nozzle 40 (FIG. 10D). (See (F).)

  In the droplet discharge device, when such a tail bend occurs in the droplet discharged from the nozzle 40, there is a problem that the image quality of the recorded image is deteriorated due to the bent tail portion. .

  The deterioration in image quality due to this tail-bending is less than the above-mentioned flying bend because most of the ejected droplets fly in the assumed direction, but can be ignored when the recorded image is improved in image quality. is not.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a droplet discharge device that can prevent deterioration in the image quality of a recorded image.

In order to achieve the above object, the invention according to claim 1 is communicated with a piezoelectric element that deforms in accordance with an applied drive voltage and generates a volume change in a storage chamber in which a liquid is stored, and the storage chamber. The liquid is supplied, and the liquid column is separated from the liquid surface after the liquid column is formed on the liquid surface according to the volume change of the storage chamber by the piezoelectric element. A first waveform for maintaining the contracted state of the storage chamber at Tc / 3 or more after contracting the storage chamber, where Tc is the natural vibration period of the nozzle from which the droplet is discharged and the liquid stored in the storage chamber. The storage chamber when the storage chamber is contracted by applying the drive voltage having the first waveform to the piezoelectric element to form the liquid column on the liquid surface of the liquid supplied to the nozzle. Generated on the liquid surface due to shrinkage The liquid surface leaves a part of the amplitude of reverberation vibration that vibrates in the internal direction and the external direction of the nozzle, and the separation position of the liquid column from the liquid surface is outside the droplet discharge surface of the nozzle. Generating means for generating a drive voltage having a drive waveform including a second waveform suppressed within a range as a voltage to be applied to the piezoelectric element. The second waveform does not suppress the reverberation vibration in which the first liquid surface moves in the external direction out of the reverberation vibrations, and the reverberation vibration in which the liquid surface immediately after that moves in the internal direction. Suppressed.

According to the first aspect of the present invention, the piezoelectric element is deformed in accordance with the applied drive voltage to generate a volume change in the storage chamber in which the liquid is stored. The liquid is supplied to the nozzle in communication with the storage chamber. A liquid column is formed on the liquid level of the liquid supplied to the nozzle in accordance with a change in the volume of the storage chamber by the element, and then the liquid column is separated from the liquid level, whereby a liquid droplet is discharged from the nozzle. And the generation means maintains the contracted state of the storage chamber at least Tc / 3 after the storage chamber is contracted, where Tc is the natural vibration period of the liquid stored in the storage chamber. The accommodation when the liquid column is formed on the liquid surface of the liquid supplied to the nozzle by contracting the accommodation chamber by applying a driving voltage of the first waveform to the piezoelectric element. Due to the contraction of the chamber The liquid surface is left with a part of the amplitude of the reverberation vibration in which the liquid surface vibrates in the internal direction and the external direction of the nozzle, and the separation position of the liquid column from the liquid surface is outside the droplet discharge surface of the nozzle. A drive voltage having a drive waveform including a second waveform that is suppressed within a certain range is generated as a voltage to be applied to the piezoelectric element. And, by the second waveform, the reverberation vibration in which the first liquid surface moves in the external direction is not suppressed among the reverberation vibrations, and the reverberation vibration in which the liquid surface immediately after moving in the internal direction is not suppressed. It is suppressed.

Thus, according to the first aspect of the present invention, the piezoelectric element is deformed according to the driving voltage to cause a volume change in the storage chamber in which the liquid is stored, and the storage chamber is placed on the liquid level of the liquid supplied to the nozzle. The liquid column is separated from the liquid surface after the liquid column is formed according to the volume change of the liquid, so that the liquid droplets are discharged from the nozzle, and the liquid stored in the storage chamber is unique. When the vibration period is Tc, the first chamber includes a first waveform that maintains the contraction state of the storage chamber after the contraction of the storage chamber by Tc / 3 or more, and a driving voltage having the first waveform is applied to the piezoelectric element. The liquid surface is generated in the liquid surface by contraction of the storage chamber when the liquid column is formed on the liquid surface of the liquid supplied to the nozzle by contracting the storage chamber. Reverberation vibration that vibrates in the direction and outside A drive voltage having a drive waveform including a second waveform that retains a part of the amplitude and suppresses the separation position of the liquid column from the liquid surface within a range outside the droplet discharge surface of the nozzle, Since it is generated as a voltage to be applied to the element, the position where the liquid column is separated from the liquid surface when the drive voltage of the generated driving waveform is applied to the piezoelectric element is outside the liquid droplet ejection surface. Since the last tail can be dragged to the wall surface of the nozzle opening and the tail bend can be prevented, deterioration of the image quality of the recorded image can be prevented. The second waveform does not suppress the reverberation vibration in which the first liquid surface moves in the external direction among the reverberation vibrations, and suppresses the reverberation vibration in which the liquid surface immediately after moving in the internal direction. This waveform cancels reverberation vibration and can be discharged in a short cycle.

Further, generating unit according to claim 1 Symbol mounting, as claimed in claim 2, as the second waveform, to generate vibrations of the reverberation oscillations and opposite phase when it is applied to the piezoelectric element to the liquid surface Thus, it is preferable to generate a waveform that suppresses the reverberation vibration.

As described above, according to the present invention, the piezoelectric element is deformed according to the driving voltage to cause a volume change in the storage chamber in which the liquid is stored, and the liquid level of the liquid supplied to the nozzle Liquid droplets are ejected from the nozzle by separating the liquid column from the liquid surface after the liquid column is formed in accordance with the volume change, and the natural vibration of the liquid stored in the storage chamber When the period is Tc, the first chamber includes a first waveform that maintains the contracted state of the storage chamber after contracting the storage chamber by Tc / 3 or more, and a driving voltage having the first waveform is applied to the piezoelectric element. The liquid surface is generated in the liquid surface by contraction of the storage chamber when the liquid column is formed on the liquid surface of the liquid supplied to the nozzle by contracting the storage chamber. And reverberant vibration that vibrates in the external direction. A drive voltage having a drive waveform including a second waveform that leaves a part of the width and suppresses the separation position of the liquid column from the liquid surface within a range outside the droplet discharge surface of the nozzle is applied to the piezoelectric element. Since it is generated as a voltage to be applied to the element, the position where the liquid column is separated from the liquid surface when the drive voltage of the generated driving waveform is applied to the piezoelectric element is outside the liquid droplet ejection surface. Therefore, the tail of the nozzle can be prevented from being dragged to the wall surface of the opening of the nozzle and the tail bend can be prevented, so that the image quality of the recorded image can be prevented from being lowered. The second waveform does not suppress the reverberation vibration in which the first liquid surface moves in the external direction among the reverberation vibrations, and suppresses the reverberation vibration in which the liquid surface immediately after moving in the internal direction. This waveform cancels reverberation vibration and can be discharged in a short cycle.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a case where the present invention is applied to an inkjet printer will be described.

[First Embodiment]
FIG. 1 shows the configuration of an ink jet printer (hereinafter simply referred to as “printer”) 10 according to the first embodiment.

  As shown in the figure, the printer 10 drives a controller 12 that controls the operation of the entire apparatus, a drive voltage generation circuit 14 that generates a drive voltage having a predetermined drive waveform, and a droplet discharge head 20 described later. A drive control circuit 16 that performs control and a droplet discharge head 20 provided with a plurality of nozzles 40 (see FIG. 2) are provided.

  The controller 12 includes a CPU, RAM, ROM, and the like (not shown). When image data is input from an external device (not shown), the image data is subjected to various image processing such as halftone processing to form pixels. Create dot data for each dot. Then, the controller 12 generates a clock signal having a predetermined period and outputs the clock signal to the drive voltage generation circuit 14 and discharges droplets from each nozzle 40 of the droplet discharge head 20 based on the dot data for each predetermined period. / Control signals for a plurality of lines designating non-ejection are sequentially output to the drive control circuit 16.

  When a clock signal is input from the controller 12, the drive voltage generation circuit 14 generates a drive voltage having a predetermined drive waveform in synchronization with the clock signal and outputs the drive voltage to the drive control circuit 16.

  The drive control circuit 16 is connected to the controller 12 and the drive voltage generation circuit 14, and a drive voltage is supplied from the drive voltage generation circuit 14 at predetermined intervals. Further, the drive control circuit 16 is electrically connected individually to each piezoelectric element 52 (see FIG. 2) provided corresponding to each nozzle 40 of the droplet discharge head 20 described later. Each switch has a built-in switch circuit for individually controlling on / off of energization.

  The drive control circuit 16 controls the application of the drive voltage to each piezoelectric element 52 by turning on / off each switch circuit in accordance with a plurality of lines of control signals input from the controller 12.

  FIG. 2 shows a cross-sectional view of one nozzle portion of the plurality of nozzles 40 provided in the droplet discharge head 20 according to the first embodiment.

  As shown in the figure, the droplet discharge head 20 includes a nozzle 40, an ink tank 42, a supply path 44, a pressure chamber 46, and a piezoelectric element 52.

  An appropriate amount of ink is supplied to the ink tank 42 from an ink cartridge (not shown) and is temporarily stored. The ink tank 42 communicates with the pressure chamber 46 via the supply path 44, and the pressure chamber 46 communicates with the outside via the nozzle 40.

  A part of the wall surface of the pressure chamber 46 is constituted by a pressure adjustment plate 46A, and a piezoelectric element 52 is attached to the pressure adjustment plate 46A.

  The piezoelectric element 52 is deformed by applying a drive voltage supplied from the drive control circuit 16 (see FIG. 1), thereby changing the pressing force on the pressure adjusting plate 46A to generate a volume change in the pressure chamber 46. . The droplet discharge head 20 causes the ink stored in the ink tank 42 to flow from the nozzle 40 via the supply path 44 and the pressure chamber 46 by the vibration wave (pressure wave) of the ink generated by the volume change in the pressure chamber 46. Discharge.

  The pressure chamber 46 has a natural vibration period Tc in which a vibration wave propagates to the ink accommodated in accordance with the size and shape of the pressure chamber 46. In the droplet discharge head 20 according to the present embodiment, the natural vibration period Tc of the pressure chamber 46 is, for example, 13 μsec.

  Next, drive waveforms employed in the first embodiment will be described.

  10A to 10F show changes in the liquid level of the nozzle 40 when the driving voltage having the driving waveform shown in FIG. 9B is applied to the piezoelectric element 52. FIG.

  The liquid level of the nozzle 40 (see FIG. 10A) decreases the applied voltage (points A to B of the drive waveform in FIG. 9B), and the piezoelectric element 52 is deformed to cause a pressure chamber. Since 46 is expanded, it is drawn into the nozzle (see FIG. 10B).

  Then, after the voltage is maintained for a predetermined time (points B to C of the drive waveform in FIG. 9B) and the volume of the pressure chamber 46 is maintained in the expanded state, the applied voltage increases (FIG. 9). Then, since the piezoelectric element 52 is deformed and the pressure chamber 46 is contracted, a liquid column is formed on the liquid surface of the nozzle 40 (see FIG. 10C). .)

  When the voltage is maintained for a predetermined holding time (D point to E point of the driving waveform in FIG. 9B) and the volume of the pressure chamber 46 is maintained in the contracted state, the liquid level of the nozzle 40 is changed to the nozzle 40. A drive voltage having a waveform (points E to G of the drive waveform in FIG. 9B) is applied that generates reverberation vibrations that vibrate in the internal direction and external direction. Then, the reverberation vibration is canceled and the liquid column is separated from the liquid surface (see FIGS. 10D and 10E) and flies (see FIG. 10F).

  In such a drive waveform, when the holding time for maintaining the volume of the pressure chamber 46 in the contracted state (D point to E point of the drive waveform in FIG. 9B) is changed as shown in Table 1 below. When the timing at which the liquid column is separated from the liquid surface of the nozzle 40 is changed and the holding time is Tc / 3 or more (13/3 seconds or more in this embodiment), the position at which the liquid column is separated is the droplet discharge of the nozzle 40. The surface 48 changes from the outside to the inside. In Table 1 below, when the liquid column is separated inside the droplet discharge surface 48 of the nozzle 40, it is unclear because it is difficult to accurately measure the separation timing.

  The tail bend is a phenomenon that occurs because only the last tail of the liquid column is dragged to the wall surface of the opening of the nozzle 40 as shown in FIGS.

  For this reason, even if reverberation vibration is suppressed, if the holding time is set to be less than Tc / 3, the position where the liquid column is separated from the liquid surface is outside the liquid droplet ejection surface 48 of the nozzle 40. Bending can be suppressed. Further, when the holding time is shortened, the tail of the satellite droplet can be shortened, and the droplet amount of the ejected ink droplet can be reduced.

  On the other hand, when the reverberation vibration is suppressed and the holding time is Tc / 3 or more, the tail of the satellite droplet can be lengthened, so that the droplet volume of the ejected ink droplet can be increased. Since the position where the nozzle is separated from the droplet discharge surface 48 of the nozzle 40 is on the inner side, tail bending may occur.

  In the drive voltage generation circuit 14 according to the present embodiment, in order to increase the amount of ejected ink droplets, the contracted state is maintained at Tc / 3 or more (here, 8 μsec) after the pressure chamber 46 is contracted. In addition, a drive voltage having a predetermined drive waveform is generated so that the separation position of the liquid column from the liquid surface is outside the droplet discharge surface 48.

  FIG. 3A shows an example of a drive waveform generated by the drive voltage generation circuit 14 according to the present embodiment. FIG. 3B shows the drive voltage of the drive waveform as a piezoelectric element. The change in the flow rate of the liquid at the nozzle opening when applied to 52 is indicated by a solid line. FIG. 3B shows a change in flow velocity when a drive voltage (see FIG. 9A) having a drive waveform that does not suppress reverberation vibration is applied to the piezoelectric element 52 (FIG. 9C). Is indicated by a broken line.

  4A to 4F show changes in the liquid level of the nozzle 40 when the driving voltage having the driving waveform shown in FIG. 3A is applied to the piezoelectric element 52. FIG. Yes.

  Since points A to E of the drive waveform shown in FIG. 3A are the same waveforms as points A to E of the drive waveform of FIG. 9B, the liquid level of the nozzle 40 changes similarly. (FIGS. 4A to 4C and FIGS. 10A to 10C are the same change).

  When a drive voltage having a waveform such as point E to point G of the drive waveform shown in FIG. 3A is applied to the piezoelectric element 52, the reverberation vibration is completely obtained as shown in FIG. 3B. A portion remains without being canceled, and the separation position of the liquid column from the liquid surface is suppressed in a range outside the droplet discharge surface 48 as shown in FIGS.

  Next, the operation of the printer 10 when image data is input from an external device (not shown) will be described with reference to FIG. FIG. 5 is a flowchart showing the flow of image recording processing executed by the controller 12 when image data is input from an external device (not shown).

  In step 100, various image processing such as halftone processing is performed on image data input from an external device (not shown) to create dot data for each dot constituting the pixel. Generation of the clock signal is started, and output of the clock signal to the drive voltage generation circuit 14 is started.

  When the clock signal is input from the controller 12, the drive voltage generation circuit 14 generates a drive voltage having the drive waveform shown in FIG. 3A in synchronization with the clock signal and outputs the drive voltage to the drive control circuit 16. .

  In the next step 104, a plurality of lines of control signals designating ejection / non-ejection of the droplets of each nozzle 40 of the droplet ejection head 20 based on the created dot data are output to the drive control circuit 16.

  When a plurality of lines of control signals are input, the drive control circuit 16 turns on / off each of the built-in switch circuits according to the control signals. Thereby, the drive voltage supplied from the drive voltage generation circuit 14 is applied to the piezoelectric element 52 connected to the switch circuit that is turned on.

  The piezoelectric element 52 to which the driving voltage is applied is deformed according to the driving waveform of the applied driving voltage to generate a volume change in the pressure chamber 46 and generate a vibration wave in the pressure chamber 46 to thereby generate a nozzle. A droplet is discharged from 40. At this time, since the position where the liquid column is separated from the liquid surface is outside the liquid droplet ejection surface 48 of the nozzle 40, the ejected liquid droplet does not bend.

  In the next step 106, it is determined whether or not the recording of the image indicated by the created dot data has been completed. If the determination is affirmative, the process proceeds to step 108. If the determination is negative, the above-described step 104 is performed. The recording of the image based on the dot data is continued.

  In the next step 108, the output of the clock signal is terminated and the main image recording process is terminated.

  As described above, according to the first embodiment, it is possible to prevent the tail of the ejected droplet from occurring, and thus it is possible to prevent the image quality of the recorded image from being deteriorated. Moreover, since reverberation vibration is suppressed, compared with the case where reverberation vibration is not suppressed, a droplet can also be discharged from the nozzle 40 in a short cycle without causing a flying curve.

  As described above, according to the first embodiment, the piezoelectric element is deformed in accordance with the applied drive voltage, and is stored in the storage chamber (here, the pressure chamber 46) in which liquid (here, ink) is stored. A volume change is generated, the liquid is supplied to the nozzle through communication with the storage chamber, and the liquid column is separated from the liquid level after the liquid column is formed on the liquid level according to the volume change of the storage chamber by the piezoelectric element. As a result, liquid droplets are ejected from the nozzle, and the separation position of the liquid column from the liquid surface is determined by the generation means (here, the drive voltage generation circuit 14). Since the drive voltage having a predetermined drive waveform is applied to the piezoelectric element so as to be outside the liquid crystal, the liquid column is generated when the generated drive voltage having the drive waveform is applied to the piezoelectric element. The position where the liquid is separated from the liquid surface Since the last tail of a outer liquid column can be prevented from being dragged by the wall surface of the opening of the nozzle tail bends occur, it is possible to prevent deterioration in the image quality of the recorded image.

  Further, according to the first embodiment, when the natural vibration period of the liquid stored in the storage chamber is Tc, the generating unit contracts the storage chamber so that the liquid level of the liquid supplied to the nozzle is reduced. A drive waveform including a first waveform (point A to point E of the drive waveform shown in FIG. 3A) that forms a liquid column and maintains the contraction state of the storage chamber at Tc / 3 or more. Since the drive voltage is generated and the image quality of the recorded image is deteriorated due to the noticeable bend in such a drive waveform, the position where the liquid column is separated from the liquid surface is placed outside the liquid droplet ejection surface. By doing so, it is possible to prevent deterioration of the image quality of the recorded image.

  Further, according to the first embodiment, the generation unit generates the liquid surface due to the contraction of the storage chamber when the drive voltage having the first waveform is applied to the piezoelectric element, and the liquid surface is directed in the internal direction of the nozzle. And a second waveform that suppresses reverberation vibration that vibrates in the external direction within a range in which the separation position of the liquid column from the liquid surface is outside the liquid droplet ejection surface of the nozzle (the driving waveform shown in FIG. 3A). Since the drive voltage of the drive waveform including the E point to the G point) is generated, it is possible to prevent the tail bend from occurring and to generate the flight bend as compared with the case where the reverberation vibration is not suppressed. It is also possible to discharge droplets from the nozzles in a short cycle without any problem.

[Second Embodiment]
In the second embodiment, the liquid level generated on the liquid level of the nozzle 40 due to the contraction of the volume of the pressure chamber 46 causes reverberation vibration that vibrates in the internal direction and the external direction of the nozzle 40, and the first liquid level is external. An example of a form to be suppressed after reverberation vibration that vibrates in the direction will be described.

  Since the configurations of the printer 10 and the droplet discharge head 20 according to the second embodiment are the same as those in FIGS. 1 and 2, the description thereof is omitted here.

  Here, for example, a driving voltage having a driving waveform that does not suppress reverberation vibration as shown in FIG. 9A is applied to the piezoelectric element 52 to cause a volume change of the pressure chamber 46 and eject a droplet. In this case, the liquid column formed in accordance with the volume change of the pressure chamber 46 has the nozzle 40 during the period (t1 in FIG. 9C) in which reverberation vibration occurs in which the initial liquid level moves outward. Regardless of the holding time (point D to point E of the drive waveform in FIG. 9A) that separates from the liquid surface and maintains the volume of the pressure chamber 46 in a contracted state, the position where the liquid column is separated is the liquid of the nozzle 40. Outside the droplet ejection surface 48.

  However, when the drive waveform as shown in FIG. 9A is adopted, the reverberation vibration generated on the liquid surface of the nozzle 40 when the drive voltage having the drive waveform is applied to the piezoelectric element 52 as described above is not affected. If it does not wait until it attenuate | damps to a level, since a flight curve may generate | occur | produce, a droplet cannot be accurately discharged from a nozzle 40 with a short period.

  Therefore, in the drive voltage generation circuit 14 according to the second embodiment, as shown in FIG. 6A, the liquid level generated on the liquid level due to the contraction of the pressure chamber 46 is the internal direction and the external direction of the nozzle 40. Among the reverberation vibrations that vibrate in the first direction, the reverberation vibration in which the first liquid level moves in the external direction (t1 in FIG. 9C) is not suppressed, and the next liquid level moves in the internal direction (FIG. 6). A drive voltage having a drive waveform including a waveform that suppresses (t2 of (B)) is generated.

  As a result, when the drive voltage having the generated drive waveform is applied to the piezoelectric element 52, as shown by the solid line in FIG. 6B, the reverberation vibration in which the initial liquid surface moves in the external direction (FIG. 6 ( The reverberation vibration (t2 in FIG. 6B) in which the next liquid level after the occurrence of t1 in B) moves inward is suppressed.

  In this way, the reverberation vibration (t1 in FIG. 6B) in which the first liquid surface moves in the external direction is not suppressed, so that the position of the liquid column separated from the liquid surface of the nozzle 40 is the droplet of the nozzle 40. Since it is outside the ejection surface 48 and the occurrence of tail bending of the ejected liquid droplets can be prevented, it is possible to prevent the image quality of the recorded image from being deteriorated.

  In addition, since the reverberation vibration (t2 in FIG. 6B) is suppressed by suppressing the reverberation vibration in which the next liquid surface moves in the inner direction, the liquid droplets are ejected from the nozzle 40 without causing the flying bend. Can be discharged in a short cycle.

  As described above, according to the second embodiment, the generating unit contracts the storage chamber, forms a liquid column on the liquid surface of the liquid supplied to the nozzle, and discharges droplets from the nozzle. The waveform (points A to E of the drive waveform shown in FIG. 6A) and the first waveform drive voltage applied to the piezoelectric element, the shrinkage of the storage chamber generates the liquid level. Among the reverberation vibrations in which the liquid level vibrates in the internal and external directions of the nozzle, the reverberation vibration in which the first liquid level moves in the external direction is not suppressed, and the reverberation vibration in which the liquid level immediately after that moves in the internal direction Since the drive voltage of the drive waveform including the second waveform (points E to G of the drive waveform shown in FIG. 6A) is generated, deterioration of the image quality of the recorded image is prevented. And can cause flying bends compared to the case where reverberation vibration is not suppressed. Ku can also eject droplets in a short period from the nozzle.

  Note that the drive voltage generation circuit 14 according to the second embodiment does not suppress reverberation vibration (t1 in FIG. 6C) in which the first liquid level vibrates in the external direction, and the next liquid level is inside. Although the case where the drive voltage whose drive waveform is adjusted in advance so as to suppress the reverberation vibration that vibrates in the direction (t2 in FIG. 6B) has been described, the present invention is not limited to this. As long as the reverberation vibration (t1 in FIG. 6C) in which the first liquid surface vibrates in the external direction is generated, it may be any.

  For example, as shown in FIG. 7A, a first waveform in which the storage chamber is contracted to form a liquid column on the liquid surface of the liquid supplied to the nozzle, and droplets are ejected from the nozzle (FIG. 7A). And the liquid level generated on the liquid surface due to the contraction of the storage chamber when the drive voltage of the first waveform is applied to the piezoelectric element. Among the reverberation vibrations that vibrate in the external direction, the reverberation vibration in which the first liquid level moves in the external direction and the reverberation vibration in which the liquid level immediately after that moves inwardly is not suppressed, and then the liquid level moves in the external direction A drive voltage having a drive waveform including a second waveform (points E to G of the drive waveform shown in FIG. 7A) that suppresses reverberation vibrations may be generated. Thereby, as shown by the solid line in FIG. 7B, the reverberation vibration (t1 in FIG. 7B) in which the first liquid level moves in the external direction and the liquid level immediately after that move in the internal direction. The reverberation vibration (t3 in FIG. 7B) in which the next liquid surface after the occurrence of the reverberation vibration (t2 in FIG. 7B) moves outward is suppressed.

  In the first and second embodiments, the case where the drive waveform generated by the drive voltage generation circuit 14 is one type has been described. However, the present invention is not limited to this, and for example, the drive voltage The generation circuit 14 changes the holding time for maintaining the volume of the pressure chamber 46 in the contracted state, and the amount of discharged droplets is different from three types (for example, large droplet, medium droplet, and small droplet), Drive voltages 1 to 3 in which drive waveforms are determined in advance so that the separation position of each liquid column from the liquid surface is outside the droplet discharge surface 48 of the nozzle 40 and output to the drive control circuit 16 respectively. The drive control circuit 16 can selectively apply drive voltages 1 to 3 to each piezoelectric element 52 in accordance with a plurality of lines of control signals input from the controller 12, and the controller 12 can adjust the density of dots to be recorded. According to the system It may alternatively varying the amount of liquid droplets ejected from the nozzle 40 by outputting a signal.

  The present invention may also be applied to the printer 10 that records an image on a recording sheet while the droplet discharging head 20 is reciprocated in the main scanning direction. As a long head having a width wider than the width, a large number of nozzles 40 are provided along the width direction of the recording paper, and while the recording paper is relatively moved in the sub-scanning direction, You may apply to the printer 10 which records the full width of a recording paper collectively by discharging a droplet from each nozzle 40. FIG. Also in this case, the same effects as in the present embodiment can be obtained.

  In addition, the configuration of the printer 10 described in the first embodiment (see FIG. 1) and the configuration of the droplet discharge head 20 (see FIG. 2) are merely examples, and within the scope not departing from the gist of the present invention. Needless to say, it can be changed as appropriate.

  The drive waveforms described in the first and second embodiments (see FIGS. 3A, 6A, and 7A) are also examples, and the scope does not depart from the gist of the present invention. Needless to say, it can be appropriately changed.

  The image recording process (see FIG. 5) described in the first embodiment is also an example, and it is needless to say that the image recording process can be appropriately changed without departing from the gist of the present invention.

  The printer 10 described in the present embodiment records an image (including characters) on a recording medium, but the printer 10 of the present invention is not limited to this. Further, the liquid to be ejected is not limited to ink. For example, the present invention can also be applied to other droplet discharge recording apparatuses such as a pattern forming apparatus that discharges droplets onto a sheet-like substrate for pattern formation of a semiconductor or a liquid crystal display.

1 is a block diagram illustrating a configuration of a printer according to an embodiment. It is sectional drawing of the nozzle which concerns on embodiment. (A) is a wave form diagram which shows the drive waveform of the drive voltage which concerns on 1st Embodiment, (B) is a nozzle opening part at the time of applying the drive voltage of the drive waveform shown to (A) to a piezoelectric element. It is a graph which shows the flow rate of the liquid. It is an enlarged view which shows the change of the liquid level of a nozzle at the time of discharging the droplet which concerns on 1st Embodiment. It is a flowchart which shows the flow of the image recording process which concerns on embodiment. (A) is a wave form diagram which shows the drive waveform of the drive voltage which concerns on 2nd Embodiment, (B) is a nozzle opening part at the time of applying the drive voltage of the drive waveform shown to (A) to a piezoelectric element. It is a graph which shows the flow rate of the liquid. (A) is a wave form diagram which shows another example of the drive waveform of the drive voltage which concerns on 2nd Embodiment, (B) is when the drive voltage of the drive waveform shown to (A) is applied to a piezoelectric element. It is a graph which shows the flow velocity of the liquid in a nozzle opening part. (A) is an enlarged view showing a nozzle, (B) is an enlarged view of a nozzle portion when a droplet is normally ejected, and (C) is when a flying bend occurs in the ejected droplet. (D) is an enlarged view of the nozzle portion when a tail bend occurs in the ejected liquid droplets. (A) is a wave form diagram which shows the drive waveform of the drive voltage which is not adjusted so that reverberation vibration may be suppressed, (B) is a wave form diagram which shows the drive waveform of the drive voltage adjusted so that reverberation vibration may be suppressed. (C) is a graph showing the flow velocity of the liquid at the nozzle opening when the drive voltage having the drive waveform shown in (A) and (B) is applied to the piezoelectric element. It is an enlarged view which shows the change of the liquid level of the nozzle at the time of discharging the conventional droplet.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 14 Drive voltage generation circuit 40 Nozzle 46 Pressure chamber 52 Piezoelectric element

Claims (2)

A piezoelectric element that deforms according to the applied drive voltage and generates a volume change in the storage chamber in which the liquid is stored;
The liquid is supplied in communication with the storage chamber, and the liquid column is separated from the liquid surface after a liquid column is formed on the liquid level of the liquid according to the volume change of the storage chamber by the piezoelectric element. A nozzle from which the liquid droplets are discharged,
When the natural vibration period of the liquid stored in the storage chamber is Tc, the first waveform includes a first waveform for maintaining the contraction state of the storage chamber at Tc / 3 or more after the storage chamber is contracted. Is generated on the liquid surface by contraction of the storage chamber when the liquid column is formed on the liquid surface of the liquid supplied to the nozzle. The liquid surface leaves a part of the amplitude of reverberation vibration that vibrates in the internal direction and the external direction of the nozzle, and the separation position of the liquid column from the liquid surface is outside the droplet discharge surface of the nozzle. Generating means for generating a drive voltage of a drive waveform including a second waveform suppressed within a range as a voltage to be applied to the piezoelectric element;
Equipped with a,
The second waveform is generated on the liquid surface by contraction of the storage chamber when the driving voltage of the first waveform is applied to the piezoelectric element, and the liquid surface vibrates in the internal direction and the external direction of the nozzle. Among the reverberation vibrations that occur, the first liquid level does not suppress the reverberation vibration that moves in the external direction, and the waveform immediately after that suppresses the reverberation vibration in which the liquid level moves in the internal direction.
Droplet discharge device. It said generating means as the second waveform, claim 1 of generating a suppressing waveform the reverberant vibration by generating a vibration of the reverberation oscillations and opposite phase to the liquid surface when it is applied to the piezoelectric element serial mounting of the droplet discharge device.

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