JP3720958B2 - Inkjet recording device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ink jet recording apparatus that records an image by making ink liquid into droplets and flying them onto a recording medium. In particular, the ink droplets are ejected by the pressure of an ultrasonic beam emitted from a piezoelectric element. The present invention relates to an inkjet recording apparatus that flies over a recording medium.
[0002]
[Prior art]
2. Description of the Related Art An apparatus for recording an image by forming image dots by making ink liquid into small particles called droplets and flying it onto a recording medium has been put to practical use as an ink jet printer. This ink jet printer has the advantage that it has less noise than other recording methods and does not require processing such as development and fixing, and is attracting attention as a plain paper recording technique.
[0003]
Many ink jet printer systems have been devised to date, but in particular, a system in which ink droplets are ejected by the pressure of vapor generated by the heat of the heating element and a method in which ink droplets are ejected by pressure pulses due to displacement of the piezoelectric body. Is a typical one.
[0004]
These ink jet printers eject ink from the tip of the nozzle. Therefore, there is a problem that local concentration of the ink occurs due to evaporation or volatilization of the solvent in the ink, and the nozzle is clogged. Further, in the conventional ink jet printer, it is difficult to reduce the particle size of ink droplets to fly (for example, a diameter of 20 μm or less), and it is difficult to increase the resolution.
[0005]
In order to overcome these drawbacks, a method has been proposed in which ink is ejected from the ink surface using the pressure of an ultrasonic beam generated by a piezoelectric element formed of a thin film piezoelectric layer. However, it has been found that in the conventional ultrasonic beam system, the ink flying efficiency tends to decrease due to generation of unnecessary ultrasonic waves caused by mutual induction from the driving piezoelectric element to the non-driving piezoelectric element.
[0006]
[Problems to be solved]
Accordingly, it is an object of the present invention to provide an ink jet recording apparatus that can suppress generation of unnecessary ultrasonic waves due to mutual induction from a driving piezoelectric element to a non-driving piezoelectric element and prevent a decrease in ink flying efficiency. To do.
[0007]
[Means for Solving the Problems]
A plurality of simultaneously driven piezoelectric elements are selected as a simultaneously driven group from the piezoelectric elements constituting the piezoelectric element array that generates ultrasonic waves, and the piezoelectric elements of this simultaneously driven group are assigned to a plurality of simultaneously driven subgroups. When sub-groups are simultaneously driven with a phase difference, and the ultrasonic waves generated from the piezoelectric elements of the simultaneous driving group are focused on the liquid surface of the ink liquid, the flying efficiency and flying stability of the ink droplets It is important not to decrease. In particular, when using a driving method that doubles the resolution by selecting an odd or even number of simultaneously driven piezoelectric elements from the piezoelectric element array, or connecting multiple piezoelectric element arrays in the array direction. In addition, when a long line head is manufactured and the joint portion is driven, the simultaneous drive piezoelectric element is changed from the piezoelectric element so that there is an unselected piezoelectric element in the array of the simultaneous drive piezoelectric elements. Although selection is often performed, it is important that even in such a case, the flying efficiency of the ink droplet does not decrease.
[0008]
As a result of investigating the cause of the drop efficiency of the ink droplet when the piezoelectric element array is driven separately by the piezoelectric element and the non-driving piezoelectric element that are driven simultaneously as described above, the driving piezoelectric element is not driven. It has been found that the cause is that unnecessary ultrasonic waves are generated due to mutual induction to the piezoelectric element. As a result of further examination based on this, one part is simultaneously driven in the same phase in the simultaneous drive group consisting of the selected piezoelectric elements, and the other piezoelectric elements are not driven, and thus, In addition, by grounding a part or all of the non-driven piezoelectric element or applying a DC voltage thereto, the selected simultaneous drive group is divided into a plurality of simultaneous drive subgroups, and each is driven with a phase difference. The present inventors have found that the above problem can be solved by grounding a part or all of the non-driven piezoelectric element or applying a DC voltage thereto, thereby completing the present invention.
[0009]
That is, the present invention firstly includes an ink liquid holding chamber for holding ink liquid and a piezoelectric element array constituted by a plurality of piezoelectric elements arranged at a predetermined interval, and is acoustically connected to the ink liquid. And a plurality of simultaneously driven piezoelectric elements among the piezoelectric elements constituting the piezoelectric element array so that a plurality of ultrasonic beams generated from the piezoelectric elements are focused near the liquid surface of the ink liquid. Element To form one recording dot Select as a simultaneous drive group and drive only a part of the piezoelectric elements of the simultaneous drive group at the same phase simultaneously. And , Of the simultaneous drive group The remaining piezoelectric elements are not driven Set to An ink jet recording apparatus comprising a driving unit is provided.
[0010]
Secondly, the present invention includes an ink liquid holding chamber for holding ink liquid and a piezoelectric element array composed of a plurality of piezoelectric elements arranged at predetermined intervals, and is supersonically connected to the ink liquid. A plurality of simultaneously driven piezoelectric elements from among the piezoelectric elements constituting the piezoelectric element array so that a plurality of ultrasonic beams generated from the sound wave generating means and the piezoelectric elements are focused near the liquid surface of the ink liquid; To form one recording dot Select as a simultaneous drive group, and drive only a part of the piezoelectric elements of the simultaneous drive group at the same phase, The remaining piezoelectric elements of the simultaneous drive group Drive Without There is provided an ink jet recording apparatus comprising driving means for grounding a part or all of a piezoelectric element or applying a DC voltage.
[0011]
Thirdly, the present invention includes an ink liquid holding chamber for holding ink liquid and a piezoelectric element array composed of a plurality of piezoelectric elements arranged at predetermined intervals, and is supersonically connected to the ink liquid. A plurality of simultaneously driven piezoelectric elements from among the piezoelectric elements constituting the acoustic wave generating means and the piezoelectric element array; To form one recording dot Select as a simultaneous drive group, distribute the plurality of simultaneously driven piezoelectric elements to a plurality of simultaneously driven subgroups, apply a drive signal giving a phase difference to each of the simultaneously driven subgroups, and drive simultaneously, And in the simultaneous drive group Piezoelectric element not driven Set Drive means for focusing the ultrasonic waves generated from the simultaneously driven piezoelectric elements of the simultaneously driven group on the liquid surface of the ink liquid by grounding a part or all of the same or applying a DC voltage. An ink jet recording apparatus is provided.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. Throughout the drawings, the same members are denoted by the same reference numerals.
FIG. 1 is a schematic perspective view of a head portion of an ink jet recording apparatus common to the embodiments of the present invention. In the embodiments to be described in detail below, the drive circuit configuration is different, but each has a head portion having the same configuration as the head portion of the ink jet recording apparatus shown in FIG.
[0013]
In FIG. 1, a plate-like piezoelectric body 12 constituting ultrasonic wave generating means is provided across a groove 11a on a support member 11 having a groove 11a described later.
The piezoelectric body 12 is made of a ceramic material such as lead titanate (PT), zircon lead / titanate (PZT), a copolymer of vinylidene fluoride and ethylene trifluoride, etc. It can be formed of a high molecular weight material, a single crystal material such as lithium niobate, or a piezoelectric semiconductor material such as zinc oxide.
[0014]
The support member 11 can be formed of a material such as glass.
A plurality of stripe-like individual electrodes 13 separated from each other are formed on the lower surface of the piezoelectric body 12. The piezoelectric body 12 is functionally divided into a plurality of piezoelectric elements by the individual electrodes 13. On the other hand, an integral common electrode 14 is formed on the entire top surface of the piezoelectric body 12. These electrodes 13 and 14 can be formed as a thin film by vapor deposition or sputtering of a metal material such as titanium, nickel, aluminum, copper, or gold. Alternatively, these electrodes 13 and 14 can also be formed by printing glass frit mixed with silver paste by screen printing and baking it.
[0015]
A plurality of array electrodes 15 are formed on the one end side of the support member 11 at the same interval as the individual electrodes 13 formed on the lower surface of the piezoelectric body 12. The individual electrodes 13 on the lower surface of the piezoelectric body 12 are pressure-bonded and electrically connected with each other through a conductive adhesive (not shown). The array electrode 15 on the support member 11 is connected to a drive circuit 16 disposed on the end of the support member 11 by a bonding wire 17, and the common electrode 14 formed on the upper surface of the piezoelectric body 12 is also connected by a wiring (not shown). Are connected to the drive circuit 16.
[0016]
A one-dimensional Fresnel lens 18 serving as an acoustic lens also serving as an acoustic matching layer is provided on the piezoelectric body 12 via the common electrode 14. The Fresnel lens 18 is formed with a plurality of grooves (six grooves 18a to 18f in FIG. 1) at a predetermined pitch based on Fresnel's ring zone theory, thereby super The phase of the sound wave is shifted by a half wavelength, and each of the grooves 18 a to 18 f is formed in parallel to the arrangement direction (main scanning direction) of the piezoelectric elements divided by the individual electrodes 13. The acoustic matching layer is for acoustic matching between the piezoelectric element and the ink liquid so as to minimize the attenuation of the ultrasonic wave when the ultrasonic wave generated from the piezoelectric element is propagated into the ink liquid. Acoustic impedance Z of the layer _m Is the acoustic impedance Z of the piezoelectric body _p And ink acoustic impedance Z _i The square root of the product (Z _m = (Z _p × Z _i ) ^1/2 It is desirable to form with the material which has the acoustic impedance of the value close | similar to). Examples of such an acoustic matching material include polymer materials such as epoxy resin and polyimide, or those obtained by mixing fibers or powders such as alumina or tungsten in order to adjust acoustic impedance. . In the example of FIG. 1, since the Fresnel acoustic lens 18 also functions as an acoustic matching layer, it is desirable to form it with such a material.
[0017]
In addition, an ink liquid holding chamber 19 is provided on the support member 11 to store and hold the ink liquid 20 with the Fresnel lens 18 as a bottom. The ink liquid holding chamber 19 is inclined so that the side walls surrounding the ink liquid 20 are aligned upward from both ends of the Fresnel lens, and the upper part thereof is closed by a cover plate 21 having a slit 21a. . Note that the upper surface of the ink liquid holding chamber 19 may directly form a slit without providing the cover plate 21.
[0018]
In the ink jet recording apparatus shown in FIG. 1, each individual electrode 13 formed on the lower surface of the piezoelectric body 12 has a length equivalent to the width of the piezoelectric body 12. However, the common electrode 14 formed on the upper surface of the piezoelectric body 12 is formed only on a portion excluding both ends of the piezoelectric body 12 so as to cover the effective width of the Fresnel lens 18 as an acoustic lens. Accordingly, the portion of the piezoelectric body 12 that functions as each piezoelectric element is only a region corresponding to the common electrode 14. In other words, the piezoelectric body 12 extends to both sides of the piezoelectric element, and the piezoelectric body 12 is supported by the support member 11 at the extended portion. Further, the groove 11 a provided in the support member 11 has a width substantially matched with the width of the common electrode 14. That is, the piezoelectric element composed of the portion of the piezoelectric body 11 sandwiched between the individual electrode 13 and the common electrode 14 has a groove 11a on the lower side thereof, that is, the lower side of the piezoelectric element has a hollow structure. Therefore, it is placed in a non-contact state with the support member 11. At the time of recording, a part of driving element groups of a plurality of piezoelectric elements divided by the individual electrodes 13 are simultaneously driven to focus ultrasonic waves near the ink liquid surface and cause ink droplets to fly. The ultrasonic wave radiated from the back surface to the back surface of the piezoelectric element is canceled by the air normally present in the groove 11a located on the back surface of the piezoelectric element, and is not reflected to the ink liquid 20 side. But it is not necessary to provide such a groove | channel 11a.
[0019]
In addition, the piezoelectric element array can be configured by individually manufactured piezoelectric elements. Further, the individual electrode can be disposed on the piezoelectric body, and the common electrode can be disposed below the piezoelectric body.
[0020]
Next, a basic example of a method for focusing an ultrasonic wave generated from a piezoelectric element and a method for driving the piezoelectric element in the inkjet recording apparatus will be schematically described.
First, as a method of focusing ultrasonic waves in the array arrangement direction (main scanning direction) of the piezoelectric elements divided into an array from the individual electrodes 13, a part of the piezoelectric elements in the piezoelectric element array is based on the Fresnel zone theory. At the same time, the phase of the ultrasonic wave emitted from each drive element is controlled to operate so that the intensity of the ultrasonic wave is locally increased in the vicinity of the ink liquid surface, that is, to focus. On the other hand, focusing of ultrasonic waves in a direction (sub-scanning direction) perpendicular to the arrangement direction of the piezoelectric elements is performed by an acoustic lens, here, a Fresnel lens 18.
[0021]
In this way, by focusing ultrasonic waves from two directions, ink droplets are ejected and ejected from any position on the ink liquid surface with ultrasonic pressure. Alternatively, by setting the focal position in the near field where the pressure of the ultrasonic beam is large, focusing of the ultrasonic beam in the main scanning direction is not taken into consideration, and a part of the drive element groups of the piezoelectric element array are in the same phase. There is also a driving method in which ink droplets are ejected by a method of driving simultaneously and focusing the ultrasonic beam by an acoustic lens in the sub-scanning direction. The flying position of the ink droplet can be changed by electronically scanning a group of piezoelectric elements that are simultaneously driven. Furthermore, by providing a plurality of the simultaneous drive element groups among the piezoelectric elements arranged in an array, a plurality of ink droplets can be simultaneously ejected.
[0022]
<First Embodiment>
FIG. 2 shows a configuration according to the first embodiment of the drive circuit 16 in the head section of the ink jet recording apparatus shown in FIG.
[0023]
The driving circuit (driving means) 16 according to the first embodiment includes a burst wave generator 31 that generates a burst wave having a phase of 1 at a predetermined frequency and a predetermined output duration. The burst generator 31 is connected on the one hand to the grounded common electrode 14 via a line L1 and on the other hand to an amplifier (power amplifier) 32 via a line L2.
[0024]
The amplifier 32 is connected to a switch corresponding to each individual electrode 13 via a line L3. In the example shown in FIG. 2, 17 individual electrodes 13 (13 (1) to 13 (17)) are provided, and therefore 17 switches (SW111 to SW127) are also provided. Each switch is connected to an individual electrode 13 (1) to 13 (17). Hereinafter, piezoelectric elements defined by the individual electrodes 13 (1) to 13 (17) will be denoted as T (1) to T (17).
[0025]
In the above configuration, in order to form one recording dot, 16 piezoelectric elements T (1) to T (16) are selected from the 17 piezoelectric elements T (1) to T (17). . Accordingly, the switch SW117 corresponding to the individual electrode 13 (17) of the piezoelectric element T (17) is turned off. Based on the Fresnel zone theory, the piezoelectric element group consisting of these 16 piezoelectric elements T (1) to T (16) is associated with the switches SW111 to SW126 so that the ultrasonic beam is focused in the main scanning direction. By opening and closing, two piezoelectric element subgroups, that is, eight piezoelectric elements T (2), T (4), T (7) to T (10), T (13), which are simultaneously driven in the same phase, A first subgroup switch composed of T (15) and eight piezoelectric elements T (1), T (3), T (5), T (6), T (11), and T (12) that are not driven. , T (14), and T (16).
[0026]
First, the same phase generated from the burst wave generator 31 (this is defined as 0 phase, and in FIG. 2, the individual electrode to which this 0 phase burst wave is applied is given a symbol “0”). The burst wave is amplified by the amplifier 32, and then the piezoelectric elements T (2), T (4), T (7) to T (10), T (13), T (15) belonging to the first subgroup. ) Are applied only to the individual electrodes 13 (2), 13 (4), 13 (7) to 13 (10) and 13 (15), respectively. A burst wave is not applied to the second subgroup, and a non-driving state is set.
[0027]
By driving the piezoelectric element in this manner, the influence of mutual induction between adjacent piezoelectric elements is reduced, and efficient and stable ink droplet flight can be achieved even with a low driving voltage.
[0028]
<Second Embodiment>
FIG. 3 shows a configuration according to the second embodiment of the drive circuit 16 in the head section of the ink jet recording apparatus shown in FIG.
[0029]
The driving circuit (driving means) 16 according to the second embodiment, instead of the zero-phase burst wave generator 31, displays a phase inverted by 180 degrees (this phase is indicated by π, and this is shown in FIG. The individual electrodes to which the π-phase burst wave is applied are given the symbol “π”.) The same configuration as the drive circuit of FIG. Have.
[0030]
In order to drive the piezoelectric element using the drive circuit 16 according to the second embodiment, contrary to the case of the first embodiment, the second that has not been driven in the first embodiment. Burst waves on eight piezoelectric elements T (1), T (3), T (5), T (6), T (11), T (12), T (14), and T (16) in the subgroup Eight piezoelectric elements T (2), T (1) of the first subgroup to which a burst wave of the same phase (π phase) from the generator 41 is applied and a zero-phase burst wave is applied in the first embodiment. 4) T (7) to T (10), T (13), and T (15) are not driven.
[0031]
Also in the second embodiment, as in the first embodiment, the influence of mutual induction between adjacent piezoelectric elements is reduced, and efficient and stable ink droplet flight can be achieved even at a low driving voltage. The
[0032]
<Third Embodiment>
FIG. 4 shows a configuration according to the third embodiment of the drive circuit 16 in the head section of the ink jet recording apparatus shown in FIG.
[0033]
The drive circuit (drive means) 16 according to the third embodiment has a configuration in which a switch connected to the ground line L4 is added to the drive circuit shown in FIG. Switches SW211 to SW227 corresponding to 1) to 13 (17) are added.
[0034]
The method of driving the piezoelectric elements using the drive circuit 16 according to the third embodiment is based on the eight piezoelectric elements T (1) belonging to the second subgroup that were not driven in the first embodiment. , T (3), T (5), T (6), T (11), T (12), T (14) and T (16), and the piezoelectric element T (17) which is not selected are switched to SW211. The same as the driving method in the first embodiment, except that selective grounding is performed by corresponding opening / closing of SW227 (the grounded individual electrode is denoted by “G” in FIG. 4). It is.
[0035]
In this way, by grounding the non-driven piezoelectric element, the piezoelectric element adjacent to the driving piezoelectric element is not applied with a voltage due to mutual induction due to the grounding effect, and therefore unnecessary for hindering the focusing of the ultrasonic wave. Since no ultrasonic waves are generated, efficient and stable flight of ink droplets is achieved.
[0036]
<Fourth embodiment>
FIG. 5 shows a configuration according to the fourth embodiment of the drive circuit 16 in the head unit of the ink jet recording apparatus shown in FIG.
[0037]
The driving circuit (driving means) 16 according to the fourth embodiment is the same as that of the third embodiment shown in FIG. 4 except that a π phase burst wave generator 41 is used instead of the 0 phase burst wave generator 31. The driving circuit has the same configuration.
[0038]
The method of driving the piezoelectric element using the drive circuit 16 according to the fourth embodiment is based on the eight subgroups belonging to the first subgroup that were not driven in the second embodiment. The piezoelectric elements T (2), T (4), T (7) to T (10), T (13), T (15) and the unselected piezoelectric element T (17) correspond to the switches SW211 to SW227. The driving method in the second embodiment is the same as that in the second embodiment except that selective grounding is performed by opening and closing (the grounded individual electrode is denoted by “G” in FIG. 5).
[0039]
In the fourth embodiment, the same effect as in the third embodiment can be obtained.
<Fifth embodiment>
FIG. 6 shows a configuration according to the fifth embodiment of the drive circuit 16 in the head unit of the ink jet recording apparatus shown in FIG.
[0040]
The driving circuit (driving means) 16 according to the fifth embodiment includes an arbitrary waveform burst wave generator 51 that generates a burst wave having an arbitrary waveform at a predetermined frequency and a predetermined output duration. The burst generator 51 is connected on the one hand to the grounded common electrode 14 via a line L11 and on the other hand to a phase inverter 52 via a line L12. From this phase inverter 52, two lines L13 and L14 are branched.
[0041]
On the one hand, the phase inverter 52 is connected to a first amplifier (power amplifier) 53 via a line L13, and this first amplifier 53 is connected to each piezoelectric element (total of 22 in FIG. 6) via a line L15. Are connected to the second amplifier (power amplifier) 54 via the line L14, and this second amplifier 54 is connected via the line L16. Each piezoelectric element is connected to a corresponding switch SW411 to SW432.
[0042]
Further, the drive circuit is provided with a ground line L17, and switches SW511 to SW532 corresponding to the respective piezoelectric elements connected to the line L17 are provided.
The switches SW311 and SW411 and SW511, SW312 and SW412 and SW512,... SW332, SW432 and SW532 are connected in common to the individual electrodes 13 (1) to 13 (22), respectively. Hereinafter, similarly to the above description, the piezoelectric elements defined by the individual electrodes 13 (1) to 13 (22) are denoted by reference characters T (1) to T (22).
[0043]
An example of driving a piezoelectric element using the drive circuit 16 having the above configuration will be described. First, a total of 6 piezoelectric elements at both ends are excluded from the 22 piezoelectric elements T (1) to T (22). The 16 piezoelectric elements T (4) to T (19) arranged continuously in the center are selected as a simultaneous drive group. Then, based on the Fresnel zone theory, the 16 piezoelectric elements are connected to two simultaneously driven subgroups by correspondingly opening and closing the switches SW314 to SW329 and SW414 to SW429 so that the ultrasonic beam is focused in the main scanning direction. That is, the first simultaneous drive subgroup consisting of a total of eight piezoelectric elements T (5), T (7), T (10) to T (13), T (16) and T (18), and the total A second simultaneous consisting of eight piezoelectric elements T (4), T (6), T (8), T (9), T (14), T (15), T (17) and T (19) Sort to drive subgroups.
[0044]
First, the burst wave generated from the burst wave generator 51 is separated into two burst waves whose phases are inverted by 180 degrees by the phase inverter 52. One of the first burst waves (this phase is indicated by 0, and the individual electrode to which the 0-phase burst wave is applied in FIG. And then applied to the individual electrodes 13 (5), 13 (7), 13 (10) to 13 (13), 13 (16) and 13 (18) of the piezoelectric element belonging to the first simultaneous drive subgroup. To do.
[0045]
The other second burst wave (this phase is represented by π, and the individual electrode to which this π phase burst wave is applied in FIG. After amplification, the individual electrodes 13 (4), 13 (6), 13 (8), 13 (9), 13 (14), 13 (15), 13 of the piezoelectric element belonging to the second simultaneous drive subgroup Apply to (17) and 13 (19).
[0046]
At this time, of the piezoelectric elements T (1) to T (3) and T (20) to T (22) that are not selected as the simultaneous driving group, the piezoelectric element T (3) adjacent to the piezoelectric element belonging to the simultaneous driving group. ) And T (20) are selectively grounded by turning on the switches SW513 and 530 (in FIG. 6, the grounded individual electrode is marked with a symbol “G”). The remaining piezoelectric elements T (1), T (2), T (21) and T (22) of the non-selected piezoelectric elements are placed in an electrically floating state.
[0047]
Thus, by grounding the non-driven piezoelectric element, generation of unnecessary ultrasonic waves based on mutual induction is suppressed, and ink droplets fly efficiently and stably.
FIG. 7 is related to FIG. 6 except that all of the non-driven piezoelectric elements T (1) to T (3) and T (20) to T (22) are grounded in the piezoelectric element driving method described with reference to FIG. It is a block diagram of the drive circuit 16 for demonstrating the drive method completely the same as the drive method demonstrated. Thus, by grounding all of the non-driven piezoelectric elements, ink droplets fly efficiently and stably even at a lower voltage.
[0048]
FIG. 8 is a driving method exactly the same as the driving method described with reference to FIG. 6 except that the piezoelectric elements selected as the simultaneous driving group are discontinuous piezoelectric elements in the driving method of the piezoelectric elements described with reference to FIG. FIG. 6 is a configuration diagram of a drive circuit 16 for explaining the above.
[0049]
That is, in this case, for example, piezoelectric elements T (3) to T (10) and T (12) to T (19) are selected as the simultaneous driving group, and the central piezoelectric element T (11) is a non-driving piezoelectric element. Element. As described with reference to FIG. 6, the piezoelectric elements T (3) to T (10) and T (12) to T (19) are used as the first simultaneous drive subgroup to which the zero-phase burst wave is applied. Piezoelectric elements T (4), T (6), T (9), T (10), T (12), T (13), T (16) and T (18) are applied with a π phase burst wave. Piezoelectric elements T (3), T (5), T (7), T (8), T (14), T (15), T (17) and T (19) as the second simultaneous driving subgroup ). As described with reference to FIG. 6, the piezoelectric element adjacent to the piezoelectric element belonging to the simultaneous drive group among the non-drive piezoelectric elements T (1) to T (2) and T (20) to T (22) at both ends. The elements T (2) and T (20) are selectively grounded by turning on the switches SW512 and 530, and similarly, a central non-driving piezoelectric element T (11) which is a piezoelectric element adjacent to the piezoelectric element of the simultaneous driving group. ) Also turns on the switch 521 and grounds it.
[0050]
Even with such a driving method, ink droplets fly efficiently and stably.
FIG. 9 illustrates a piezoelectric element driving method described with reference to FIG. 8. Of the non-driven piezoelectric elements T (1) to T (2) and T (20) to T (22) at both ends, the piezoelectric element T ( 1) and a drive circuit for explaining a drive method exactly the same as the drive method described with reference to FIG. 8 except that all of the non-drive piezoelectric elements are grounded by grounding T (21) and T (22). FIG. Thus, by grounding all of the non-driven piezoelectric elements, ink droplets fly efficiently and stably even at a lower voltage.
[0051]
As mentioned above, although embodiment of this invention was described with reference to drawings, this invention is not limited to this. For example, the same effect can be obtained by applying a DC voltage instead of the grounding means described with reference to FIGS.
[0052]
【Example】
Examples of the present invention will be specifically described below.
Example 1
In this example, an ink jet recording apparatus having a head having the structure shown in FIG. 1 was produced.
[0053]
First, tabular lead titanate (PbTiO _Three ) Ti / Au was formed on one side of the ceramic piezoelectric body by sputtering to a thickness of 0.05 μm and 0.5 μm, respectively. Subsequently, an electric field of 4 kV / mm was applied to perform polarization treatment, thereby producing a piezoelectric ceramic element having ferroelectricity. The relative dielectric constant after polarization was about 215. Thereafter, individual electrodes 13 having a width of 60 μm and an electrode interval of 25 μm (arrangement pitch of 85 μm) were formed by chemical etching. On the other hand, after the Ti / Au array electrode 15 having a width of 60 μm and an electrode interval of 25 μm is formed on the glass support member 11, a depth of 0.1 mm is formed by machining in order to form a hollow structure with the piezoelectric element. A groove 11a having a size of 2 mm and a width of 2.2 mm was formed. Then, while aligning the individual electrode 13 formed on the ceramic piezoelectric body and the array electrode 15 formed on the glass under a microscope, the electrodes were bonded with an epoxy resin, and both electrodes were made conductive. Next, in order to set the frequency of the ultrasonic wave to 50 MHz, the ceramic piezoelectric body was polished to a thickness of 45 μm, and further, Al was electron beam evaporated to form the common electrode 14. At this time, the length of the electrode in the sub-scanning direction, that is, the aperture was 2 mm.
[0054]
For the acoustic matching layer / acoustic lens 18, a mixture of epoxy resin and alumina powder was used. First, the sound speed is 3 × 10 ^Three The mixing ratio is adjusted to be around m / second, and the density is 2.20 × 10 ^Three kg / m ^Three , Speed of sound 2.95 × 10 ^Three m / s was obtained. This was applied to the surface of the common electrode 14 and cured, and was polished to a thickness of about 45 μm. Thereafter, a Fresnel lens 18 was formed by forming a groove having a depth of ½ wavelength (about 30 μm) parallel to the main scanning direction so that the focal length was 1.8 mm. Then, a side wall (ink liquid holding chamber 19) having a distance of about 1.8 mm between the ultrasonic radiation surface and the ink liquid surface is formed, and a drive circuit 16 having the configuration shown in FIG. 2 is further mounted to complete the ink jet recording apparatus. did.
[0055]
Using the ink jet recording apparatus thus manufactured, an ink flight experiment was performed by the driving method according to the present invention.
That is, in order to form one recording dot, as described with reference to FIG. 2, in order to form one recording dot, 16 piezoelectric elements out of 17 piezoelectric elements T (1) to T (17) are formed. Elements T (1) to T (16) were selected. Then, based on the Fresnel zone theory, the simultaneous drive group consisting of these 16 piezoelectric elements T (1) to T (16) is simultaneously driven at 0 phase so that the ultrasonic beam is focused in the main scanning direction. A first subgroup consisting of eight piezoelectric elements T (2), T (4), T (7) to T (10), T (13), T (15), and eight piezoelectric elements that are not driven It was assigned to a second subgroup consisting of T (1), T (3), T (5), T (6), T (11), T (12), T (14), and T (16).
[0056]
A sine wave burst wave having a frequency of 50 MHz and an output duration of 30 μs was generated from the zero-phase burst wave generator 31, amplified by the amplifier 32, and then applied only to the piezoelectric elements of the first simultaneous drive subgroup.
[0057]
When the flying state of ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator 31 was required to be about 1.7 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 17 V was applied to each of the piezoelectric elements.
[0058]
Example 2
An inkjet recording apparatus exactly the same as that of Example 1 was manufactured except that the drive circuit having the configuration shown in FIG.
[0059]
Using the ink jet recording apparatus thus manufactured, an ink flight experiment was performed by the driving method according to the present invention.
That is, as described with reference to FIG. 3, in order to form one recording dot, 16 piezoelectric elements T (1) to T (16) out of 17 piezoelectric elements T (1) to T (17). ) Was selected. Then, based on the Fresnel zone theory, eight simultaneous drive groups composed of these 16 piezoelectric elements T (1) to T (16) are not driven so that the ultrasonic beam is focused in the main scanning direction. A first subgroup consisting of piezoelectric elements T (2), T (4), T (7) to T (10), T (13), T (15), and eight piezoelectric elements T driven by π phase. (1), T (3), T (5), T (6), T (11), T (12), T (14), and the second subgroup consisting of T (16).
[0060]
A sine wave burst wave having a frequency of 50 MHz and an output duration of 30 μs was generated from the π phase burst wave generator 41, amplified by the amplifier 32, and then applied only to the piezoelectric elements of the second simultaneous drive subgroup.
[0061]
When the flying state of the ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generating device 41 was required to be about 1.9 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 19 V was applied to each of the piezoelectric elements.
[0062]
Comparative Example 1
An ink jet recording apparatus having the same configuration as in Example 1 was produced. In this case, the drive circuit includes an arbitrary waveform burst wave generator and a phase inverter.
[0063]
Ink flight experiments were conducted using the ink jet recording apparatus thus manufactured.
That is, as in Example 1, 16 piezoelectric elements T (1) to T (16) were selected from the 17 piezoelectric elements T (1) to T (17). Then, based on the Fresnel zone theory, the simultaneous drive group consisting of these 16 piezoelectric elements T (1) to T (16) is divided into 8 piezoelectric elements T so that the ultrasonic beam is focused in the main scanning direction. (2), T (4), T (7) to T (10), T (13), T (15) and another eight piezoelectric elements T (1), T (3), T (5), T (6), T (11), T (12), T (14), and the second subgroup consisting of T (16).
[0064]
A sine wave burst wave having a frequency of 50 MHz and an output duration of 30 μs is generated from an arbitrary waveform burst wave generator, inverted by a phase inverter, and one zero-phase burst wave is amplified by an amplifier in the same manner as in the first embodiment. Thereafter, the other π-phase burst wave was similarly amplified by an amplifier to all the piezoelectric elements of the first simultaneous driving subgroup and then applied to all the piezoelectric elements of the second simultaneous driving subgroup.
[0065]
When the flying state of the ink droplet was observed with an ultra-high speed camera, the output voltage of the arbitrary waveform burst generator was required to be about 2.0 V in order for the ink droplet to fly stably. It was confirmed that an average voltage of about 15 V was applied to each of the 16 piezoelectric elements.
[0066]
Comparative Example 2
In Example 1, all 16 piezoelectric elements selected as the simultaneous drive group were driven in either 0 phase or π phase. In this case, the voltage applied to each piezoelectric element was 20 V on average with respect to the output voltage 2.0 V of the burst wave generator.
[0067]
As can be seen from the results of Examples 1 and 2, when the piezoelectric elements of the simultaneous drive group are divided into two simultaneous drive subgroups based on Fresnel zonal theory, the ink droplet flying position (focal position) is the most. It was found that ink droplets fly more efficiently when the piezoelectric element group including the closer piezoelectric elements is simultaneously driven in the same phase. Further, when a predetermined piezoelectric element group is driven under the above conditions, a voltage of about 2 V is applied to the non-driving piezoelectric element adjacent to the driven piezoelectric element by the mutual induction with substantially the same phase. It was confirmed that
[0068]
Further, as can be seen from the results of Comparative Example 1 and Comparative Example 2, when the simultaneous drive element groups are all driven at the same phase, and when the two simultaneous drive element groups are distributed and the phases are reversed by 180.degree. In this case, the voltage applied to each piezoelectric element is different. As a cause, when the frequency is 50 MHz, the influence on the adjacent piezoelectric elements cannot be ignored. In particular, the phase between the adjacent piezoelectric elements is 180. When they are inverted, it is presumed that an interaction that lowers the applied voltage occurs.
[0069]
As described above, when Examples 1 and 2 are compared with Comparative Examples 1 and 2, in Comparative Examples 1 and 2, the number of simultaneously driven elements is large. Although the applied voltage may be low, the power supply voltage needs to be increased because the applied voltage is actually affected by the mutual induction between adjacent piezoelectric elements. On the other hand, in Examples 1 and 2, since the adverse effects due to mutual induction are small, stable flying of ink droplets can be achieved with a lower power supply voltage than in Comparative Examples 1 and 2.
[0070]
As described above, according to the present invention, a piezoelectric element group is selected based on the Fresnel zone theory so as to focus an ultrasonic beam in the main scanning direction, and these are simultaneously driven in the same phase, so that adjacent piezoelectric elements are It was confirmed that the influence of mutual induction was reduced and the flying efficiency of ink droplets was improved. Further, since a circuit configuration for giving a predetermined phase difference is not necessary, the drive circuit can be simplified and the manufacturing cost can be reduced.
[0071]
Example 3
An ink jet recording apparatus was manufactured according to the method of Example 1 except that the drive circuit having the configuration shown in FIG.
[0072]
Ink flight experiments were conducted using the ink jet recording apparatus thus manufactured.
That is, as described with reference to FIG. 4, in order to form one recording dot, 16 piezoelectric elements T (1) to T (16) among 17 piezoelectric elements T (1) to T (17). Selected. Then, based on the Fresnel zone theory, the simultaneous drive group consisting of these 16 piezoelectric elements T (1) to T (16) is simultaneously driven at 0 phase so that the ultrasonic beam is focused in the main scanning direction. A first subgroup consisting of eight piezoelectric elements T (2), T (4), T (7) to T (10), T (13), T (15), and eight piezoelectric elements that are not driven It was assigned to a second subgroup consisting of T (1), T (3), T (5), T (6), T (11), T (12), T (14), and T (16).
[0073]
A zero-phase burst wave having a frequency of 50 MHz and an output duration of 30 μs is generated from the zero-phase burst wave generator 31, amplified by the amplifier 32, and then applied only to the piezoelectric elements of the first simultaneously driven subgroup. At this time, the eight piezoelectric elements belonging to the second simultaneous drive subgroup and the piezoelectric element T (17) not selected were selectively grounded.
[0074]
When the flying state of ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator 31 was required to be about 1.4 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 15 V was applied to each of the piezoelectric elements.
[0075]
Example 4
An ink jet recording apparatus was manufactured in the same manner as in Example 1 except that the drive circuit 16 having the configuration shown in FIG. 5 was used.
[0076]
Using the ink jet recording apparatus thus manufactured, an ink flight experiment was performed by the driving method according to the present invention.
That is, as described with reference to FIG. 5, in order to form one recording dot, 16 piezoelectric elements T (1) to T (16) out of 17 piezoelectric elements T (1) to T (17). ) Was selected. Then, based on the Fresnel zone theory, eight simultaneous drive groups composed of these 16 piezoelectric elements T (1) to T (16) are not driven so that the ultrasonic beam is focused in the main scanning direction. A first subgroup consisting of piezoelectric elements T (2), T (4), T (7) to T (10), T (13), T (15), and eight piezoelectric elements T driven by π phase. (1), T (3), T (5), T (6), T (11), T (12), T (14), and the second subgroup consisting of T (16).
[0077]
A sine wave burst wave having a frequency of 50 MHz and an output duration of 30 μs is generated from the π phase burst wave generator 41, amplified by the amplifier 32, and then applied only to the piezoelectric elements of the second simultaneous drive subgroup, At this time, the eight piezoelectric elements belonging to the first subgroup and the piezoelectric element T (17) not selected were selectively grounded.
[0078]
When the flying state of ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator 41 was required to be about 1.6 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 16 V was applied to each of the piezoelectric elements.
[0079]
As can be seen from the results of Examples 3 to 4, when the non-driving piezoelectric element is grounded, the flying efficiency of the ink droplets is further improved as compared with the case where the non-driving piezoelectric element is not grounded (Examples 1 and 2). It was confirmed. Further investigation was conducted to investigate the cause. When a predetermined piezoelectric element group was driven under the above conditions, the grounded piezoelectric element adjacent to the driving piezoelectric element was caused by mutual induction due to the effect of grounding. No voltage application was seen. Therefore, unnecessary ultrasonic waves that disturb the focusing of the ultrasonic waves are not generated, and it is considered that the above-described further improvement in flight efficiency can be achieved. Similarly to the first and second embodiments, when the drive piezoelectric elements are distributed to two simultaneous drive subgroups based on the Fresnel zone theory, the piezoelectric element closest to the ink droplet flight position (focal position). It has been found that the ink droplets fly more efficiently when the piezoelectric element group including the same is simultaneously driven in the same phase.
[0080]
Example 5
An ink jet recording apparatus was manufactured in the same manner as in Example 1 except that the drive circuit having the configuration shown in FIG. 6 was used.
[0081]
Ink flight experiments were conducted using the ink jet recording apparatus thus manufactured.
That is, as described with reference to FIG. 6, in order to form one recording dot, a total of six piezoelectric elements at both ends are removed from the 22 piezoelectric elements T (1) to T (22), and the central continuous line is formed. Sixteen piezoelectric elements T (4) to T (19) arranged were selected as a simultaneous drive group. Then, based on the Fresnel zone theory, the 16 piezoelectric elements are divided into two simultaneously driven subgroups, that is, a total of 8 piezoelectric elements T (5), so that the ultrasonic beam is focused in the main scanning direction. A first simultaneous drive subgroup consisting of T (7), T (10) to T (13), T (16) and T (18), and a total of eight piezoelectric elements T (4), T (6) , T (8), T (9), T (14), T (15), T (17), and T (19).
[0082]
First, a sine burst wave having a frequency of 50 MHz and an output duration of 30 μs is generated from the burst wave generator 51, and this is converted into a zero-phase burst wave and a π-phase burst wave whose phases are inverted by 180 degrees by the phase inverter 52. After separating into two burst waves and amplifying one of the zero-phase burst waves by the amplifier 53, the individual electrodes 13 (5), 13 (7), 13 (10) of the piezoelectric elements belonging to the first simultaneous drive subgroup ) To 13 (13), 13 (16) and 13 (18). The other π-phase burst wave is amplified by the amplifier 54, and then the individual electrodes 13 (4), 13 (6), 13 (8), 13 (9) of the piezoelectric elements belonging to the second simultaneous drive subgroup. , 13 (14), 13 (15), 13 (17) and 13 (19). At this time, of the piezoelectric elements T (1) to T (3) and T (20) to T (22) not selected as the simultaneous drive group, the piezoelectric element T (3) adjacent to the piezoelectric element belonging to the simultaneous drive group. ) And T (20) only were selectively grounded.
[0083]
When the flying state of the ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator 51 was required to be about 1.4 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 14 V was applied to each of the piezoelectric elements.
[0084]
Example 6
An ink flying experiment was performed in the same manner as in Example 5 except that the piezoelectric element was driven by the method described with reference to FIG.
[0085]
That is, under the driving conditions of Example 5, all of the non-driving piezoelectric elements T (1) to T (3) and T (20) to T (22) were grounded.
When the flying state of the ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator was required to be about 1.3 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 13 V was applied to each of the piezoelectric elements.
[0086]
Comparative Example 3
Ink droplets were ejected under exactly the same driving conditions as in Example 5 except that the non-driving piezoelectric elements T (1) to T (3) and T (20) to T (22) were not grounded.
[0087]
When the flying state of the ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator 51 was required to be about 1.7 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 17 V was applied to each of the piezoelectric elements.
[0088]
As can be seen from the results of Examples 5 to 6 and Comparative Example 3, compared to Comparative Example 3 in which all of the non-driving piezoelectric elements are in a floating state, Examples 5 to 5 in which part or all of the non-driving piezoelectric elements are grounded. In No. 6, it was found that the power supply voltage necessary for the ink droplets to stably fly and the voltage applied to the piezoelectric element were small, and the ink droplet flying efficiency was improved. Further, when all non-driving piezoelectric elements are grounded (Example 6) than when a part of the non-driving piezoelectric elements is grounded (Example 5), the ink droplet flying efficiency is further increased. I was able to confirm.
[0089]
Further investigation was conducted to investigate the mechanism of such a phenomenon. As a result, in Example 6, no voltage was applied to the non-driving piezoelectric elements by mutual induction by grounding all the non-driving piezoelectric elements. In Example 5, no voltage was applied to the non-driven piezoelectric element that was grounded, but a voltage of about 0.2 to 0.5 V was applied to the non-driven piezoelectric element that was not grounded. I understood that. On the other hand, in Comparative Example 3, a voltage of about 0.2 to 2 V was applied to the non-driving piezoelectric element by mutual induction from the driving piezoelectric element. It was confirmed that the induced voltage increased as it was closer to the driving piezoelectric element, and in particular, a voltage of 2 V was applied to the non-driving piezoelectric element adjacent to the driving piezoelectric element.
[0090]
From the above examination results, when the non-driving piezoelectric element is electrically floated as in Comparative Example 3, the non-driving piezoelectric element is driven due to the mutual induction from the driving piezoelectric element to the non-driving piezoelectric element. It is considered that the ejection efficiency of ink droplets is lowered because unnecessary ultrasonic waves that disturb the focusing of the ultrasonic waves are generated. On the other hand, by grounding the non-driven piezoelectric element as in Examples 5 to 6, it is considered that the generation of unnecessary ultrasonic waves can be suppressed and the flying efficiency of ink droplets is improved. As described above, the piezoelectric elements of the simultaneous drive group are divided into a plurality of simultaneous drive subgroups based on the Fresnel zone theory so that the ultrasonic beam is focused in the main scanning direction, and a predetermined phase difference is assigned to them. In the case of simultaneous driving by giving, grounding a part or all of the non-driving piezoelectric elements can improve the flying efficiency and flying stability of the ink droplets.
[0091]
Example 7
An ink flying experiment was performed in the same manner as in Example 5 except that the piezoelectric element was driven by the method described with reference to FIG.
[0092]
That is, in order to form one recording dot, as described with reference to FIG. 8, the piezoelectric elements T (3) to T (10) and T (12) to T (19) are selected as the simultaneous drive groups. The central piezoelectric element T (11) is a non-driven piezoelectric element. These piezoelectric elements T (3) to T (10) and T (12) to T (19) are piezoelectric elements T (4), T as a first simultaneous driving subgroup to which a zero-phase burst wave is applied. (6), T (9), T (10), T (12), T (13), T (16) and T (18), and the second simultaneous driving subgroup to which the π-phase burst wave is applied As piezoelectric elements T (3), T (5), T (7), T (8), T (14), T (15), T (17) and T (19). And among the non-driving piezoelectric elements T (1) to T (2) and T (20) to T (22) at both ends, the piezoelectric elements T (2) and T (2) adjacent to the piezoelectric elements belonging to the simultaneous driving group. 20) was selectively grounded, and similarly, the central non-driving piezoelectric element T (11), which is a piezoelectric element adjacent to the piezoelectric element of the simultaneous driving group, was also grounded.
[0093]
When the flying state of the ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator 51 was required to be about 1.8 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 18 V was applied to each of the piezoelectric elements.
[0094]
Example 8
As described with reference to FIG. 9, an ink flight experiment was performed in exactly the same way as in Example 7, except that the non-driving piezoelectric elements T (1), T (21), and T (22) were also grounded.
[0095]
When the flying state of the ink droplets was observed with an ultra-high speed camera, the output voltage of the burst generator 51 was required to be about 1.7 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 17 V was applied to each of the piezoelectric elements.
[0096]
Comparative Example 4
Ink droplets fly under exactly the same driving conditions as in Example 7 except that the non-driving piezoelectric elements T (1) to T (2), T (20) to T (22), and T (11) were not grounded. I let you.
[0097]
When the flying state of ink droplets was observed with an ultra-high speed camera, the output voltage of the burst wave generator 51 was required to be about 2.3 V in order for the ink droplets to fly stably. It was confirmed that an average voltage of about 23 V was applied to each of the piezoelectric elements.
[0098]
As can be seen from the results of Examples 7 to 8, the effect of the present invention is more remarkable when there is a piezoelectric element that is not selected in the array of simultaneously driven elements selected from the piezoelectric element array. That is, when Comparative Example 3 in which all of the non-driving piezoelectric elements are in a floating state is compared with Examples 7 to 8 in which part or all of the non-driving piezoelectric elements are grounded, it is necessary for ink droplets to fly stably. It has been found that the difference between the power supply voltage and the voltage applied to the piezoelectric element is further increased, and the ink droplet flight efficiency is further improved by the effect of the present invention. In addition, it was confirmed that the flying efficiency of the ink droplets was further improved when all the non-driving piezoelectric elements were grounded than when some of the non-driving piezoelectric elements were grounded.
[0099]
Further investigation was conducted to investigate the mechanism of such a phenomenon. As a result, in Example 8, no voltage was applied to the non-driving elements by mutual induction by grounding all the non-driving elements. In Example 7, no voltage was applied to the non-driven element that was grounded, but it was found that a voltage of about 0.2 to 0.5 V was applied to the non-driven element that was not grounded. .
[0100]
From the above examination results, when non-selected piezoelectric elements are generated in the array of simultaneous driving elements selected from the piezoelectric element array, the non-driving piezoelectric elements are brought into an electrically floating state as in Comparative Example 4. In particular, the effect of mutual induction on the non-driving piezoelectric element having the driving piezoelectric element on both sides becomes remarkable, and it is considered that the flying efficiency of the ink droplet is further reduced by increasing the intensity of unnecessary ultrasonic waves. . On the other hand, in Examples 7 to 8, it is considered that the generation of unnecessary ultrasonic waves can be suppressed and the flying efficiency of ink droplets can be improved by grounding the non-driven piezoelectric element.
[0101]
As described above, the simultaneous drive group is selected, and the ultrasonic beam is focused in the main scanning direction, and is distributed to the simultaneous drive subgroup based on the Fresnel annular zone theory. When simultaneously driving with a predetermined phase difference, if there are unselected piezoelectric elements in the array of simultaneous driving groups selected from the piezoelectric element array, ground all or part of the undriven piezoelectric elements. Thus, it was found that the flying efficiency and flying stability of the ink droplets can be further improved.
[0102]
Example 9
In Examples 3 to 8, ink droplets were ejected in the same manner except that a DC voltage was applied instead of grounding. As a result, the same effects as those of the examples were obtained.
[0103]
【The invention's effect】
As described above, according to the present invention, in the simultaneous drive group consisting of the selected piezoelectric elements, a part thereof is simultaneously driven in the same phase and the other piezoelectric elements are not driven, and the non-driven piezoelectric element is also driven. A part or all of them are grounded, or a DC voltage is applied to them, or the selected simultaneous drive group is divided into a plurality of simultaneous drive subgroups to drive each with a phase difference. By grounding all or part or applying a DC voltage, generation of unnecessary ultrasonic waves due to mutual induction from the driving piezoelectric element to the non-driving piezoelectric element is suppressed, and the drop efficiency of ink droplets is prevented from being lowered. be able to.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of a head portion of an ink jet recording apparatus according to the present invention.
FIG. 2 is a diagram showing a configuration of a drive circuit according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a drive circuit according to a second embodiment of the present invention.
FIG. 4 is a diagram showing a configuration of a drive circuit according to a third embodiment of the present invention.
FIG. 5 is a diagram showing a configuration of a drive circuit according to a fourth embodiment of the present invention.
FIG. 6 is a diagram showing a configuration of a drive circuit according to a fifth embodiment of the present invention.
7 is a diagram for explaining another driving method of the piezoelectric element using the driving circuit shown in FIG. 6;
8 is a view for explaining still another method for driving a piezoelectric element using the drive circuit shown in FIG. 6;
FIG. 9 is a view for explaining still another method for driving a piezoelectric element using the drive circuit shown in FIG. 6;
[Explanation of symbols]
11: Support member
11a ... groove
12 ... Piezoelectric material
13 ... Individual electrode
14 ... Common electrode
15 ... Array electrode
16 ... Drive circuit
18 ... Ultrasonic focusing means
19 ... Ink liquid holding chamber
21a ... Slit
20 ... Ink liquid
31, 41, 51 ... Burst wave generator
32, 53, 54 ... amplifier
52. Phase inverter
SW111-SW127 ... switch
SW211 to SW227 ... switch
SW311-332 ... switch
SW411-432 ... switch
SW511-532 ... switch
L4, L17 ... Ground line

Claims (3)

An ink liquid holding chamber for holding ink liquid;
An ultrasonic wave generating means including a piezoelectric element array composed of a plurality of piezoelectric elements arranged at a predetermined interval and acoustically connected to the ink liquid;
A plurality of simultaneously driven piezoelectric elements are arranged as one recording dot from the piezoelectric elements constituting the piezoelectric element array so that a plurality of ultrasonic beams generated from the piezoelectric elements are focused near the liquid surface of the ink liquid. selected as simultaneous driving group to form sets Rutotomoni is simultaneously driven only a part of the piezoelectric element of identity during driving groups in the same phase, the remaining piezoelectric elements of identity during driving groups in the non-driven state drive means An ink jet recording apparatus comprising: An ink liquid holding chamber for holding ink liquid;
An ultrasonic wave generating means including a piezoelectric element array composed of a plurality of piezoelectric elements arranged at a predetermined interval and acoustically connected to the ink liquid;
A plurality of simultaneously driven piezoelectric elements are arranged as one recording dot from the piezoelectric elements constituting the piezoelectric element array so that a plurality of ultrasonic beams generated from the piezoelectric elements are focused near the liquid surface of the ink liquid. Select as a simultaneous drive group to form, drive only a part of the piezoelectric elements of the simultaneous drive group at the same phase simultaneously, and drive a part of the piezoelectric elements without driving the remaining piezoelectric elements of the simultaneous drive group Alternatively, an ink jet recording apparatus comprising driving means for grounding all or applying a DC voltage. An ink liquid holding chamber for holding ink liquid;
An ultrasonic wave generating means including a piezoelectric element array composed of a plurality of piezoelectric elements arranged at a predetermined interval and acoustically connected to the ink liquid;
A plurality of simultaneously driven piezoelectric elements are selected from among the piezoelectric elements constituting the piezoelectric element array as a simultaneously driven group for forming one recording dot, and the plurality of simultaneously driven piezoelectric elements are selected as a plurality of simultaneously driven subgroups. sorting, wherein applying a respective drive signal to give a phase difference to the simultaneously driven sub-group is simultaneously driven by, and to set the piezoelectric element is not driven in of identity when driving group, a DC or to ground the part or all of its An ink jet recording apparatus, comprising: a driving unit configured to focus ultrasonic waves generated from the simultaneously driven piezoelectric elements of the simultaneously driven group on a liquid surface of the ink liquid by applying a voltage.

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