JP5625228B2 - Piezoelectric head, ink discharge device, ink jet recording device - Google Patents

Description

  The present invention includes a deformable diaphragm, a lower electrode formed on one surface of the diaphragm, a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the piezoelectric layer. The present invention relates to a piezoelectric head having a plurality of piezoelectric actuators, an ink discharge apparatus having the piezoelectric head, and an ink jet recording apparatus.

  Currently, there is a piezoelectric actuator using a piezoelectric body as a driving force of an actuator of a micromachine. Actuators used in micromachines continue to be downsized, and piezoelectric actuators are similarly required to be downsized.

  Conventionally, as a piezoelectric element of a piezoelectric actuator, a stacked piezoelectric element in which a structure having electrodes on and below a piezoelectric material is stacked is widely used. The multilayer piezoelectric element can increase the amount of strain, but since it has a multilayer structure, it is not preferable from the viewpoint of miniaturization when used in a micromachine. In addition, in order to use a laminated piezoelectric element, it is necessary to cut a bulk piezoelectric element, which requires advanced technology. A piezoelectric element composed of a thin film PZT (lead zirconate titanate) has a great advantage from the viewpoint of miniaturization over a laminated piezoelectric element. Therefore, some piezoelectric actuators use thin film PZT.

  FIG. 1 is a diagram illustrating a conventional piezoelectric actuator using a thin film PZT. 1A is a perspective view for explaining the outline of the piezoelectric actuator 10, FIG. 1B is a cross-sectional view taken along the line AA of the piezoelectric actuator 10, and FIG. It is AA sectional drawing at the time of displacement.

  The piezoelectric actuator 10 includes a diaphragm 11 and a piezoelectric element 12 formed of a thin film PZT. The piezoelectric element 12 is formed on one side of the diaphragm 11. An electrode 13 is formed between the piezoelectric element 12 and the vibration plate 11, and an electrode 14 is formed on the surface of the piezoelectric element 12 opposite to the surface in contact with the vibration plate 11. A voltage shown in FIG. 2 is applied to the electrode 13 and the electrode 14. FIG. 2 is a diagram for explaining voltages applied to the electrodes 13 and 14. A ground potential is applied to the electrode 13, and a drive potential Vp for driving the piezoelectric element 12 is applied to the electrode 14.

  In the piezoelectric actuator 10, the piezoelectric element 12 is formed at the center of the diaphragm 11. As shown in FIG. 1C, when a drive voltage is applied to the electrode 14, the piezoelectric element 12 expands and contracts one surface of the diaphragm 11 (the surface on which the piezoelectric element 12 is formed). Accordingly, in the piezoelectric actuator 10, the displacement amount in the out-of-plane direction of the diaphragm 11 can be increased while the distortion of the piezoelectric element 12 itself is small.

  In the piezoelectric actuator 10 shown in FIG. 1, by forming the piezoelectric element 12 only at the center of the diaphragm 11, the displacement amount in the out-of-plane direction of the diaphragm 11 can be increased. When it is provided on one entire surface of the plate 11, the amount of displacement in the out-of-plane direction is suppressed. This is because all the one surface of the diaphragm 11 becomes an area that expands or contracts together with the expansion and contraction of the piezoelectric element 12, and the bending does not occur.

  When the degree of integration of the piezoelectric actuators 10 increases, the width of the diaphragm 11 becomes narrow, so that the diaphragm 11 is less likely to be bent.

  In order to increase the amount of displacement in the out-of-plane direction in this state, the drive voltage applied to the piezoelectric element 12 may be increased.

  However, when the drive voltage applied to the piezoelectric element 12 is increased, the piezoelectric element 12 is easily damaged by ion migration. Ion migration occurs mainly when an electrochemical reaction occurs due to moisture in the air and the electrode metal is ionized and dissolved. The frequency of ion migration increases as the temperature is 100 ° C. or lower, the current density is 1 mA / cm 2 or lower, and the humidity is higher. Since the breakdown time due to ion migration becomes shorter as the electric field strength is higher, an electronic component to which a high voltage is applied has a higher failure frequency unless measures are taken to remove the influence of moisture in the air. In addition, Nox, NH3, and Cl present in the air are adsorbed to the water droplets, thereby promoting ion migration. Therefore, when the electronic component is left exposed to the outside air, oxidation, chlorination, and sulfidation easily occur, which may cause migration. For this reason, it can be said that ion migration is likely to occur in the piezoelectric actuator 10 to which a high driving voltage is applied.

  Thus, in recent piezoelectric actuators, the degree of integration can be increased, and a device has been devised to increase the amount of displacement in the out-of-plane direction without increasing the drive voltage.

For example, in Patent Document 1, the piezoelectric element is divided in the short side direction of the diaphragm, and the expansion and contraction of the piezoelectric element in the in-plane direction of the diaphragm is reversed to the expansion and contraction of the piezoelectric element in the out-of-plane direction. Techniques to do this are disclosed. Also, Patent Document 2 discloses a configuration in which individual electrodes of piezoelectric elements divided in each actuator are combined between the actuators to form a common electrode.
JP 2003-8091 A Japanese Patent No. 3750709

  However, the invention described in Patent Document 1 requires substantially two individual electrodes in addition to the common electrode for each actuator, and a significant increase in cost is expected due to an increase in drive drivers and the like. The invention described in Patent Document 2 is not suitable for high-speed driving because it requires two pulses with different timings in order to increase the amount of displacement.

  In view of the above circumstances, the present invention has been made to solve this problem, can increase the amount of displacement at low cost, can cope with high-speed driving, and contributes to further downsizing. An object of the present invention is to provide a piezoelectric head, an ink discharge device, and an ink jet recording apparatus that can be used.

  The present invention employs the following configuration in order to achieve the above object.

The present invention includes a deformable substantially rectangular diaphragm, a lower electrode formed on one surface of the diaphragm, and a piezoelectric formed on a surface of the lower electrode opposite to the surface in contact with the diaphragm. A piezoelectric actuator comprising: a body layer; and an upper electrode formed on the surface of the piezoelectric layer opposite to the surface in contact with the lower electrode and divided into three in a cross section in the short side direction of the diaphragm. a plurality having piezoelectric heads, to the lower electrode of said plurality of piezoelectric actuators, among the first common potential is applied, prior Symbol plurality of the three is split formed in the upper electrode of the piezoelectric actuator , the upper electrode other than the upper electrode positioned in the middle, a second common potential supplied from the common driver common to the plurality of piezoelectric actuators are applied, said plurality of piezoelectric actuators Of the upper electrodes divided into three, the upper electrode located in the middle has a control potential for controlling the deformation of the diaphragm supplied from the drive driver corresponding to the plurality of piezoelectric actuators. When the diaphragm is displaced, a potential having a polarity opposite to the polarity of the second common potential applied in synchronization with the application of the second common potential is applied to suppress the displacement of the diaphragm. In this case, a potential having the same polarity as that of the second common potential applied in synchronization with the application of the second common potential is applied .

  In the piezoelectric head of the present invention, when the first common potential is a reference potential, the second common potential and the control potential are different from the first common potential, The common potential and the control potential are applied synchronously.

  In the piezoelectric head of the present invention, the magnitude of the control potential and the magnitude of the second common potential are substantially the same.

  In the piezoelectric head of the present invention, the upper electrode is formed on the piezoelectric layer with the inflection point of the diaphragm interposed therebetween.

  The present invention provides an ink liquid chamber in which ink is stored, a nozzle hole for ejecting the ink from the ink liquid chamber, a deformable diaphragm that forms part of the ink liquid chamber, and a deformed diaphragm. A piezoelectric head for discharging the ink from the ink liquid chamber by deformation of the vibration plate, wherein the piezoelectric head is any one of the piezoelectric heads. did.

  The present invention is an ink jet recording apparatus that includes an ink liquid ejecting apparatus that ejects ink, and causes the ink to eject from the ink liquid ejecting apparatus and attach the ink to a recording medium. It was set as the structure which is a liquid discharge apparatus.

  According to the present invention, the amount of displacement can be increased at low cost, high-speed driving can be supported, and contribution to downsizing can be achieved.

  In the present invention, among the upper electrodes formed by being divided into three on the piezoelectric element formed on one side of the diaphragm of the piezoelectric actuator constituting the piezoelectric head, the middle upper electrode is used as an individual electrode, The electrode is a common electrode used in common for all piezoelectric actuators constituting the piezoelectric head. A common potential is applied to the common electrode, and an individual potential having the same magnitude as the common potential controlled independently of the common potential is applied to the individual electrode.

  Prior to the description of the piezoelectric head of the present embodiment, the division of the upper electrode when the upper electrode is divided and formed will be described with reference to FIG. FIG. 3 is a diagram illustrating the division of the upper electrode. 3A is a diagram for explaining the bending of the diaphragm 11A, FIG. 3B is a first diagram for explaining the formation position of the upper electrode 14A, and FIG. It is the 2nd figure explaining the formation position of electrode 14A.

  FIG. 3A shows a cross-sectional view in the short-side direction of the diaphragm when the diaphragm 11A supported by the partition wall 15 in the piezoelectric actuator 10A vibrates in the primary vibration mode. The shape of the diaphragm 11A is a substantially rectangular shape similar to that in FIG. 1A, and the cross section in the short side direction of the diaphragm is the same as the AA cross section in FIG. When the diaphragm 11A vibrates in the primary vibration mode, the shape shown in FIG. The shape of the diaphragm 11A depends on the distribution of the applied load, the thickness distribution of the diaphragm 11A, and the like.

  Let us consider the bending in the regions A1 to A5 in the diaphragm 11A. In the diaphragm 11 </ b> A, the deflections of the region A <b> 1, the region A <b> 3, and the region A <b> 5 are particularly greater than the deflections of the region A <b> 2 and the region A <b> 4. By positively applying a force that bends the diaphragm 11A to the portions (area A1, area A3, area A5), the deflection (displacement) of the entire diaphragm 11A can be increased. Moreover, that the bending is large means that the curvature radius of the part is small. In the present invention, it is preferable that a piezoelectric element for bending the vibration plate 11A is formed in a region where the radius of curvature of the vibration plate 11A takes a minimum value. Regions A2 and A4 are portions having the largest curvature radii and include inflection points.

  As shown in FIG. 3B, the piezoelectric elements 12A and 12B, the lower electrodes 13A and 13B, and the upper electrodes 14A and 14B are connected to the piezoelectric element 12A and the piezoelectric element on both sides of the area A2 and the area A4 including the inflection point. The expansion and contraction of the element 12B is reversed. For this reason, as shown in FIG. 1, the displacement amount of the diaphragm 11A can be increased as compared with the case where the piezoelectric element is not divided. The piezoelectric element 12A, the lower electrode 13A, and the upper electrode 14A may be formed so as not to overlap the partition wall 15 as shown in FIG.

  FIG. 4 is a diagram for explaining a method of driving the piezoelectric actuator 10A shown in FIG.

  The lower electrodes 13A and 13B formed on the diaphragm 11A are common electrodes to which a common voltage is applied (hereinafter referred to as a common electrode COM), and 0 V is applied thereto. The drive voltage SEG1 of the piezoelectric element 12A is applied to the upper electrode 14A, and the drive voltage SEG2 of the piezoelectric element 12B is applied to the upper electrode 14B.

  In the piezoelectric actuator 10A, the diaphragm 11A can be displaced by setting the drive voltage SEG1 and the drive voltage SEG2 to opposite polarities. For example, as shown in FIG. 4, when voltages are applied to the piezoelectric elements 12A and 12B, they are applied with the polarities of the drive voltage SEG1 and the drive voltage SEG2 reversed as shown at timing T1. Note that the drive voltage SEG1 and the drive voltage SEG2 are preferably at the same potential.

  When the diaphragm 11A is displaced in this way, a displacement equivalent to the displacement of the diaphragm 11 shown in FIG. 1 is obtained at a voltage half that of the drive voltage Vp shown in FIG. be able to.

  When it is not desired to displace the diaphragm 11A, the drive voltage SEG1 and the drive voltage SEG2 are set to 0V as at the timing T2. This is because when a drive voltage is applied to either one of them, a displacement of about half of the displacement amount δ1 occurs, which is considered undesirable for most applications.

  In the configuration described with reference to FIGS. 3 and 4, since it is necessary to apply drive voltages SEG1 and SEG2 having opposite polarities to the upper electrodes 14A and 14B, independent drive drivers are required for the upper electrodes 14A and 14B.

  In the present invention described below, even when the upper electrode is divided and formed on the diaphragm, an independent drive driver is not required, and a displacement equivalent to the displacement amount δ1 can be obtained with a smaller drive voltage. . For this reason, according to the present invention, it is possible to cope with high-speed driving at low cost, and it is possible to contribute to miniaturization with a long life.

(First embodiment)
A first embodiment of the present invention will be described below with reference to the drawings. FIG. 5 is a diagram for explaining the outline of the piezoelectric head 100 according to the first embodiment.

  The piezoelectric head 100 is used in, for example, an ink jet printing apparatus. The piezoelectric head 100 includes a diaphragm 110 supported by a partition wall 123, a ceramic layer 120 in which an ink liquid chamber 121 and the like are formed, and a stainless steel layer 130 in which nozzle holes 131 from which ink is ejected are formed.

  In the vibration plate 110, a lower electrode 111, a piezoelectric element 112, and an upper electrode 113, which will be described later, are laminated on the vibration plate 110 in the order described above on the surface opposite to the surface on which the ceramic layer 120 is formed. 140 is configured.

  The piezoelectric actuator 140 is provided as the piezoelectric actuator 140 a and the piezoelectric actuator 140 b for each ink liquid chamber 121 provided in the piezoelectric head 100 to constitute the piezoelectric head 100.

  FIG. 6 is an AA cross-sectional view of the piezoelectric head 100 according to the first embodiment.

  Since the piezoelectric actuators 140a, 140b, and 140c shown in FIG. 6 have the same configuration, the configuration of the piezoelectric actuator 140a will be described as a representative example.

  In the piezoelectric actuator 140a, the lower electrode 111 is formed on the surface of the vibration plate 110 opposite to the surface on which the ink liquid chamber 121 is formed. In the lower electrode 111, the piezoelectric element 112 is formed on the surface opposite to the surface in contact with the diaphragm 110. In this embodiment, the diaphragm 110 is commonly used in the piezoelectric actuators 140a, 140b, and 140c. Similarly to the diaphragm 110, the lower electrode 111 and the piezoelectric element 112 are used in common in the piezoelectric actuators 140a, 140b, and 140c. Therefore, the lower electrode 111 and the piezoelectric element 112 are preferably formed on the diaphragm 110 so as to have the same area as the diaphragm 110.

  In the piezoelectric actuator 140a, the upper electrode 113 is formed on the surface of the piezoelectric element 112 opposite to the surface in contact with the lower electrode 111. The upper electrode 113 is divided into three parts: an upper electrode 113a, an upper electrode 113b, and an upper electrode 113c. The upper electrode 113a, the upper electrode 113b, and the upper electrode 113c are formed with the region H including the inflection point interposed therebetween as described with reference to FIG. The region H is preferably narrow. In addition, the upper electrode 113 a and the upper electrode 113 c of this embodiment are formed so as to overlap with the partition wall 123.

  In the present embodiment, the lower electrode 112 is a first common electrode C1. The common electrode C1 is an electrode that is used in common in each of the piezoelectric actuators 140a, 140b, and 140c constituting the piezoelectric actuator 140, and is connected to the ground and applied with the first common potential COM1.

  Of the upper electrodes 113 divided into three in this embodiment, the upper electrode 113b located in the middle is referred to as an individual electrode S. The individual electrodes S are electrically independent in the piezoelectric actuators 140a, 140b, and 140c. An individual potential SEG that is a control potential for controlling the driving of the piezoelectric element 112 is applied to the upper electrode 113b.

  Of the upper electrode 113 divided into three in this embodiment, the upper electrode 113a and the upper electrode 113c disposed on both sides of the upper electrode 113b across the region H are referred to as a second common electrode C2. The common electrode C2 is an electrode that is used in common in each of the piezoelectric actuators 140a, 140b, and 140c constituting the piezoelectric actuator 140, and is applied with the second common potential COM2.

  Thus, in the present embodiment, among the upper electrode 113 divided into three, the upper electrodes 113a and 113c are used as the common electrode C2 in the plurality of piezoelectric actuators constituting the piezoelectric actuator 140. In this embodiment, with this configuration, the drive driver required for each piezoelectric actuator can be only the drive driver for the individual electrode S.

  Hereinafter, a driving method of the piezoelectric actuator 140 of this embodiment will be described with reference to FIG. FIG. 7 is a diagram for explaining a driving method of the piezoelectric actuator 140.

  In the present embodiment, the common electrode C1 is connected to the ground. Therefore, the common potential COM1 applied to the common electrode C1 is 0V.

  A common voltage COM2, which is a pulse signal supplied at a predetermined interval, is applied to the common electrode C2. In the present embodiment, the diaphragm 110 is displaced by applying the individual voltage SEG applied to the individual electrode S in synchronization with the common voltage COM2.

  For example, when the diaphragm 110 is displaced, the individual voltage SEG may be a voltage having a polarity opposite to that of the common voltage COM2. If the diaphragm 110 is not displaced, the individual voltage SEG may be a voltage having the same polarity as the common voltage COM2.

  For example, at the timing Ta shown in FIG. 7, the common voltage COM2 applied to the common electrode C2 is the voltage value Vpa. At the timing Ta, the voltage value of the individual voltage SEG applied to the individual electrode S is the voltage value Vpb having the same polarity as the voltage value Vpa. Therefore, it can be seen that the diaphragm 110 is not displaced at the timing Ta.

  At the timing Tb, the voltage value of the individual voltage SEG applied to the individual electrode S is a voltage value −Vpb having a polarity opposite to the voltage value Vpa. Therefore, it can be seen that the diaphragm 110 is displaced at the timing Tb.

  In the present embodiment, the voltage value Vpa of the common voltage COM2 and the voltage value Vpb of the individual voltage SEG are preferably approximately the same.

  As described above, in the piezoelectric actuator 140a of the present embodiment, a voltage signal common to the other piezoelectric actuators 140b and 140c constituting the piezoelectric actuator 140 is applied to the common electrode COM1 and the common electrode COM2. An individual voltage SEG for controlling the driving of the piezoelectric actuator 140a is applied to the individual electrode S. That is, the driving of the piezoelectric actuator 140a of this embodiment is controlled only by the individual voltage SEG.

  The above configuration is the same for each piezoelectric actuator 140b and piezoelectric actuator 140c constituting the piezoelectric head 100. In the present embodiment, the piezoelectric actuator 140 has been described as including three piezoelectric actuators 140a, 140b, and 140c. However, the present invention is not limited to this. The piezoelectric actuator 140 can be composed of any number of piezoelectric actuators.

  As described above, in this embodiment, in the piezoelectric head 100 including the plurality of piezoelectric actuators 140, the upper electrodes 113a and 113c adjacent to another piezoelectric actuator among the upper electrodes 113 of the piezoelectric actuator 140 are used as the common electrode C2. use.

  Therefore, when driving the piezoelectric head 100 of the present embodiment, one common driver that applies the common voltage COM2 to the common electrode C2 and the individual voltage SEG to the individual electrode S of each piezoelectric actuator that constitutes the piezoelectric head 100 are used. Any configuration may be used as long as each piezoelectric actuator has the same number of drive drivers.

  For this reason, in this embodiment, it is not necessary to provide an independent drive driver for each of the upper electrodes divided into three, and the number of drive drivers can be reduced and the cost can be reduced. In the present embodiment, the drive is controlled in synchronization with the individual voltage SEG applied to the individual electrode S in synchronization with the common voltage COM2 applied to the common electrode C2, so that the common electrode COM2 and the individual electrode SEG It is not necessary to control each independently, and it is possible to cope with high-speed driving.

  In the present embodiment, the driving of the piezoelectric element 112 is controlled by the individual voltage SEG having the opposite polarity to the common voltage COM2. For this reason, in this embodiment, the diaphragm 110 can be greatly displaced even if the drive voltage value of the piezoelectric element 112 is set to a low value. Therefore, in this embodiment, deterioration of the piezoelectric element 112 can be suppressed, and the use of the piezoelectric element 112 over a long period of time can be performed.

  Next, with reference to FIG. 8, the result of driving simulation of the piezoelectric actuator 140 of this embodiment will be described. In FIG. 8, a simulation using the piezoelectric actuator 150 for simulation was performed as a drive simulation of the piezoelectric actuator 140 of the present embodiment. 8A is a diagram illustrating the piezoelectric actuator 150, FIG. 8B is a diagram illustrating a drive voltage during simulation, and FIG. 8C is a diagram illustrating a simulation result.

  The piezoelectric actuator 150 is formed with three divided lower electrodes 151a, 151b, and 151c on the diaphragm 110A held by the partition wall 123A. Piezoelectric elements 152a, 152b, and 152c are formed on the lower electrodes 151a, 151b, and 151c, and upper electrodes 153a, 153b, and 153c are further formed thereon. The lower electrode 151a, the piezoelectric element 152a, the upper electrode 153a, the lower electrode 151c, the piezoelectric element 152c, and the upper electrode 153c are formed so as not to overlap the partition wall 123A.

  In the piezoelectric actuator 150, the upper electrodes 153a and 153c contract the diaphragm 110A by the piezoelectric elements 152a and 152c, and the upper electrode 153b extends the diaphragm 110A by the piezoelectric element 152b.

  As material constants, the vibration plate 110A and the piezoelectric elements 152a, 152b, and 152c all have Young's modulus = 210 Gpa, Poisson's ratio = 0.29, and the thickness is also 0.5 μm. In addition, the diaphragm 110A has a short side length of 60 μm, the piezoelectric elements 152a and 152c have a width Ld1 = 15 μm, and the piezoelectric element 152b has a width Ld2 = 30 μm, and the gap between the divided piezoelectric elements 152a, 152b, and 152c. Calculated with no configuration. On the other hand, as the expansion / contraction amounts of the piezoelectric elements 152a, 152b, and 152c, the lengths extending in the short side direction of the diaphragm when there is no load are expressed as ratios FL1 and FL2 with respect to the original lengths Ld1 and Ld2. In this model, as shown in FIG. 8B, the common voltage COM3 (0 V) is applied to the lower electrodes 151a, 151b, and 151c, the common voltage COM4 is applied to the upper electrodes 153a and 153c, and the drive voltage SEG3 is applied to the upper electrode 152b. Assumed. Note that the voltage value Vp3 of the common voltage COM4 and the voltage value Vp4 of the drive voltage SEG3 have substantially the same magnitude.

  FIG. 8C shows the simulation result under these conditions. Case 0 is a calculation result for comparison and assumes a case where a drive waveform at timing Tc in FIG. 8B is applied. Case 1 is a calculation result assuming a case where the drive waveform at timing Td in FIG. 8B is applied, and case 2 is a calculation result assuming a case where the drive waveform at timing Te in FIG. 8B is applied. .

  The displacement amount in case 1 is four times that in case 0, and 1/9 times in case 2, and the displacement amount in case 1 is 18 times the displacement amount in case 2. That is, it is understood that when the expansion / contraction directions of the piezoelectric elements 152a, 152c and the piezoelectric element 152b are reversed, the displacement amount of the vibration plate 110A increases, but when the expansion / contraction directions are the same, the displacement amount of the vibration plate 110A greatly decreases.

  Also in the piezoelectric actuator 140 of this embodiment, similarly to the piezoelectric actuator 150, the displacement amount of the diaphragm 110 at the timing Tb shown in FIG. 7 is about 18 times the displacement amount at the timing Ta.

  As in the piezoelectric actuator 140 of the present embodiment, when the difference between the small displacement amount and the large displacement amount is 18 times, the change in the displacement amount can be used as ON / OFF. That is, the piezoelectric actuator 140 of the present embodiment can be used as a switch for switching ON / OFF.

  Next, a manufacturing method of the piezoelectric actuator 140 of this embodiment will be described with reference to FIG. FIG. 9 is a diagram illustrating a method for manufacturing the piezoelectric actuator 140.

  First, high-concentration boron is implanted into one surface of the Si substrate 30 (FIG. 9A) by time control to form a high-concentration boron layer 31 of about 2 μm (FIG. 9B). Next, an SiO2 film is formed on the surface opposite to the high-concentration boron layer by CVD (Chemical Vapor Deposition), and then the SiO2 film in the portion that becomes the ink liquid chamber 121 of each piezoelectric actuator 140 is removed. Next, using KOH, Si in the portion that becomes the ink liquid chamber 121 is etched until it reaches the high-concentration boron layer, thereby forming the diaphragm 110 (FIG. 9C). Next, an SiO 2 film 32 is formed on the upper surface of the high-concentration boron layer (FIG. 9D). Thereafter, as shown in FIG. 9E, the lower electrode 111, the piezoelectric element 112, and the upper electrode 113 of the piezoelectric element 112 are sequentially stacked to form the piezoelectric actuator 140. In the example of FIG. 9 of the present embodiment, the lower electrode 111 and the piezoelectric element 112 are solid films, but the upper electrode forms a pattern to form a piezoelectric element 112 that is electrically independent of each piezoelectric actuator. .

  As described above, the piezoelectric actuator 140 according to this embodiment can contribute to the miniaturization of the piezoelectric head 100 because the piezoelectric element can be formed of a thin film.

  In the piezoelectric actuator 140 of the present embodiment, the lower electrode 111 and the piezoelectric element 112 are formed of a solid film, but the present invention is not limited to this. 10 to 12 show modifications of the piezoelectric actuator 140. FIG.

  FIG. 10 is a diagram illustrating a first modification of the piezoelectric actuator 140. In the piezoelectric actuator 140, for example, as in the piezoelectric actuator 140A shown in FIG. 10, only the lower electrode 111 may be formed of a solid film, and the piezoelectric element 112a may be divided into three like the upper electrode 113.

  FIG. 11 is a diagram illustrating a second modification of the piezoelectric actuator 140. The piezoelectric actuator 140 may be formed by dividing the lower electrode 111a, the piezoelectric element 112a, and the upper electrode 113 into three, like the piezoelectric actuator 140B shown in FIG.

  FIG. 12 is a view showing a third modification of the piezoelectric actuator 140. The piezoelectric actuator 140 is formed by dividing the lower electrode 111b, the piezoelectric element 112b, and the upper electrode 113A into three parts as in the piezoelectric actuator 140C shown in FIG. 12, and there is a portion that does not overlap the partition wall 123. It may be formed as follows.

  Next, an operation when the piezoelectric head 100 of the present embodiment is applied to the ink liquid ejecting apparatus 200 will be described with reference to FIG. FIG. 13 is a diagram illustrating a case where the piezoelectric head 100 is applied to the ink liquid ejecting apparatus 200.

  In the ink liquid ejecting apparatus 200, the ink liquid is stored in the ink liquid chamber 121 surrounded by the partition wall 123 and the vibration plate 110 of the piezoelectric actuator 140. In the ink liquid chamber 121, a nozzle hole 131 through which ink is ejected is formed on the side opposite to the side on which the vibration plate 110 is formed.

  In the ink liquid ejecting apparatus 200, when a voltage is applied to the piezoelectric element 112 by the lower electrode 111 and the upper electrode 113 and the diaphragm 110 is bent, the volume of the ink liquid chamber 121 changes. In the ink liquid chamber 121, the internal ink is ejected as a droplet 30 from the nozzle hole 131 with a pressure due to a change in volume. An image or the like can be formed on the recording medium 40 by the ejected droplets 30 adhering to the recording medium 40.

  Since the ink liquid ejecting apparatus 200 uses the piezoelectric head 100, the displacement of the diaphragm 110 can be greatly displaced with a driving voltage lower than that in the prior art. For this reason, the pressure to the ink liquid chamber 121 also increases. Therefore, the ink liquid ejecting apparatus 200 can eject ink with a low driving voltage.

(Second embodiment)
A second embodiment of the present invention will be described below with reference to the drawings. In the second embodiment of the present invention, in the following description of the second embodiment for explaining an ink jet recording apparatus to which the ink liquid ejection device 200 is applied, the same functional configuration as that of the first embodiment is used. The same reference numerals as those used in the description of the first embodiment are assigned, and the description thereof is omitted.

  FIG. 14 is a perspective view illustrating the ink jet recording apparatus 300 according to the second embodiment, and FIG. 15 is a side view of a mechanism portion of the ink jet recording apparatus 300 according to the second embodiment.

  The ink jet recording apparatus 300 includes a carriage 360 that can move in the main scanning direction inside the ink jet recording apparatus 300, a recording head 307 that includes a cartridge 305 mounted on the carriage, a drive device that drives and controls the recording head 307, and a recording head 307. The printing mechanism 310 and the like having the same are accommodated. In the recording head 307, the ink liquid ejection device 200 held by the carriage 360 is disposed below the cartridge 305.

  In addition, a paper feed cassette (or a paper feed tray) 320 on which a large number of recording media (paper sheets) 40 can be loaded from the front side can be detachably attached to the lower part of the ink jet recording apparatus 300.

  Further, the ink jet recording apparatus 300 can turn over the manual feed tray 330 for manually feeding the paper 40. The ink jet recording apparatus 300 takes in the paper 40 fed from the paper feed cassette 320 or the manual feed tray 330, records a required image by the print mechanism unit 320, and then discharges the paper onto a paper discharge tray 350 mounted on the rear side. To do.

  Further, during recording, the inkjet recording apparatus 300 drives the recording head 307 according to the image signal while moving the carriage 360, thereby ejecting ink onto the stopped sheet 40 to record one line, After the predetermined amount 40 is conveyed, the next line is recorded. The ink jet recording apparatus 300 ends the recording operation and discharges the paper 40 by receiving a recording end signal or a signal that the trailing edge of the paper 40 reaches the recording area.

  As mentioned above, although this invention has been demonstrated based on each embodiment, this invention is not limited to the requirements shown in the said embodiment. With respect to these points, the gist of the present invention can be changed without departing from the scope of the present invention, and can be appropriately determined according to the application form.

It is a figure explaining the conventional piezoelectric actuator using thin film PZT. It is a figure explaining the voltage applied to the electrodes 13 and 14. FIG. It is a figure explaining division | segmentation of an upper electrode. It is a figure explaining the drive method of 10 A of piezoelectric actuators shown in FIG. It is a figure explaining the outline of the piezoelectric head 100 of 1st embodiment. It is AA sectional drawing of the piezoelectric head 100 of 1st embodiment. FIG. 5 is a diagram illustrating a method for driving a piezoelectric actuator 140. FIG. 4 is a diagram for explaining a drive simulation of a piezoelectric actuator 140. 5 is a diagram illustrating a method for manufacturing the piezoelectric actuator 140. FIG. FIG. 6 is a diagram showing a first modification of the piezoelectric actuator 140. FIG. 10 is a diagram showing a second modification of the piezoelectric actuator 140. FIG. 10 is a diagram showing a third modification of the piezoelectric actuator 140. 6 is a diagram illustrating a case where a piezoelectric head 100 is applied to an ink liquid ejecting apparatus 200. FIG. It is a perspective view explaining the inkjet recording device 300 of 2nd embodiment. It is a side view of the mechanism part of the inkjet recording device 300 of 2nd embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Piezoelectric head 110 Diaphragm 111 Lower electrode 112 Piezoelectric element 113, 113a, 113b, 113c Upper electrode 121 Ink liquid chamber 123 Partition 131 Nozzle hole 140, 140a, 140b, 140c Piezoelectric actuator 200 Ink liquid discharge apparatus 300 Inkjet recording apparatus

Claims (5)

A deformable substantially rectangular diaphragm, a lower electrode formed on one surface of the diaphragm, and a piezoelectric layer formed on a surface of the lower electrode opposite to the surface in contact with the diaphragm; A piezoelectric head having a plurality of piezoelectric actuators having an upper electrode divided into three in a cross section in the short side direction of the diaphragm on a surface opposite to a surface in contact with the lower electrode in the piezoelectric layer Because
A first common potential is applied to the lower electrodes of the plurality of piezoelectric actuators,
Among previous SL plurality of the three is split formed in the upper electrode of the piezoelectric actuator, the upper electrode other than the upper electrode located within N true, is supplied from the common driver common to the plurality of piezoelectric actuators A second common potential is applied ,
Of the upper electrodes divided into three of the plurality of piezoelectric actuators, the upper electrode located in the middle is deformed by a diaphragm supplied from a drive driver corresponding to the plurality of piezoelectric actuators. As a control potential for controlling,
When displacing the diaphragm, a potential having a polarity opposite to the polarity of the second common potential applied in synchronization with the application of the second common potential is applied,
When suppressing the displacement of the diaphragm, a piezoelectric head having a polarity that is the same as the polarity of the second common potential applied in synchronization with the application of the second common potential . Wherein the magnitude of said control voltage magnitude of the second common potential, substantially the same magnitude as claimed in claim 1 piezoelectric head according. The upper electrode, according to claim 1 or 2 piezoelectric head according formed on the diaphragm the piezoelectric layer to sandwich the inflection point. An ink liquid chamber in which ink is stored; a nozzle hole for discharging the ink from the ink liquid chamber; a deformable diaphragm that forms part of the ink liquid chamber; and a piezoelectric head that deforms the diaphragm. An ink liquid ejecting apparatus for ejecting the ink from the ink liquid chamber by deformation of the diaphragm,
The piezoelectric head, the ink ejection device is a piezoelectric head according to any one of claims 1 to 3. An ink jet recording apparatus having an ink liquid ejecting apparatus for ejecting ink, and ejecting ink from the ink liquid ejecting apparatus to attach the ink to a recording medium,
5. The ink jet recording apparatus according to claim 4 , wherein the ink liquid ejecting apparatus is an ink liquid ejecting apparatus.

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