Piezoelectric actuator and manufacturing method thereof

Abstract

A piezoelectric actuator is provided. The piezoelectric actuator according to one embodiment of the present invention comprises: a piezoelectric layer including a polarized first piezoelectric body and a polarized second piezoelectric body having a predetermined separation distance in a horizontal direction from the first piezoelectric body; and an electrode layer including a first electrode disposed on at least one surface of the first piezoelectric body and a second electrode electrically connected to the first electrode and disposed on at least one surface of the second piezoelectric body. Accordingly, the effects of a high resonance frequency, an appropriate interval between a first resonance frequency and a second resonance frequency, and excellent piezoelectric characteristics can be simultaneously exhibited.

Description

Piezoelectric actuator and manufacturing method thereof

[0001] The present invention relates to a piezoelectric actuator, and more particularly, to a piezoelectric actuator and a method for manufacturing the same.

[0002] With the recent development of the precision machinery and information industries, piezoelectric actuators, which control micro-displacement or vibration, are widely used in precision optical devices, semiconductor equipment, gas flow control pumps, valves, and other applications. This is because piezoelectric actuators offer advantages over conventional mechanical actuators, such as miniaturization, precision control, and fast response times.

[0003] Therefore, with the advancement of mechatronics, micro-displacement control components will transition from conventional stepper motors to piezoelectric actuators. Consequently, materials capable of generating high displacement are needed for piezoelectric actuator applications using piezoelectric ceramics.

[0004] Current actuators are largely made of PZT (Pb(ZrTi)O3) or other Pb-containing relaxor ferroelectric materials. These materials present challenges for practical applications because their specimen displacement in a disk shape is less than 1%.

[0005] To solve this problem, various types of cantilever, flextensional, and laminated actuators have been developed.

[0006] In the case of multilayer actuators, since the disk-shaped PZT deforms under high voltage, the thickness of each layer is made thin to lower the operating voltage, and electrodes are placed in parallel inside each disk to generate a large electric field even at low voltage. In the case of these multilayer actuators, there is a cut and bonding method for simple multi-layer actuators and a simultaneous sintering method of tape-casting and printing.

[0007] The cutting and bonding method involves bonding thinly formed piezoelectric PZT materials using copper foil and silver epoxy. This method is easy to manufacture, as the piezoelectric material is processed to a thickness of 0.3 to 1 mm and then bonded, but requires a relatively high operating voltage.

[0008] Tape casting and printing involves mixing PZT and polymer, extruding them into thin tapes, printing electrode materials such as Pd onto them, bonding multiple layers, burning off the polymer, and simultaneous sintering. This method involves a complex process for forming tape-cast ceramic-polymer composites into thin tapes, and the printing process itself is difficult, making manufacturing costs expensive. However, it offers the advantage of producing extremely thin layers.

[0009] Meanwhile, when sintering at high temperatures (approximately 1200℃ or higher) using the HTCC (High Temperature Co-firing Ceramic) process, expensive rare metals (mainly Pt, Pd, etc.) are typically unavoidable. This is because rare metals such as Pt and Pd are the only ones that can withstand high temperatures and exhibit good conductivity. Furthermore, the volatilization of PbO during high-temperature sintering makes it difficult to reproduce, and it can cause environmental pollution and human health problems.

[0010] In addition, conventional piezoelectric actuators had the problem of a significantly low resonant frequency.

[0011]

[0012] Accordingly, there is an urgent need to develop a piezoelectric actuator that can increase the resonant frequency, has an appropriate gap between the first and second resonant frequencies, and exhibits excellent piezoelectric properties.

[0013] The present invention has been devised to solve the above-mentioned conventional problems, and aims to provide a piezoelectric actuator with improved resonance frequency through a predetermined arrangement and a method for manufacturing the same.

[0014] In addition, another object of the present invention is to provide a piezoelectric actuator having a high first resonant frequency, an appropriate interval between the first resonant frequency and the second resonant frequency, and excellent piezoelectric properties, and a method for manufacturing the same.

[0015] In order to solve the above-described problem, the present invention provides a piezoelectric actuator having a piezoelectric layer including a polarized first piezoelectric body, a polarized second piezoelectric body having a predetermined horizontal distance from the first piezoelectric body, and an electrode layer including a first electrode disposed on at least one surface of the first piezoelectric body, and a second electrode electrically connected to the first electrode and disposed on at least one surface of the second piezoelectric body.

[0016] According to one embodiment of the present invention, the polarized first piezoelectric body and the polarized second piezoelectric body can be formed by individually polarizing the first piezoelectric body and the second piezoelectric body, respectively.

[0017] In addition, the first piezoelectric body and the second piezoelectric body can each be independently formed of a piezoelectric ceramic containing 65.0 to 70.0 wt% of Pb2O4, 11.0 to 16.0 wt% of ZrO2, 9.5 to 10.5 wt% of TiO2, 1.0 to 1.2 wt% of ZnO, 0.3 to 0.4 wt% of NiO, 4.0 to 6.0 wt% of Nb2O5, 1.5 to 3.5 wt% of La2O3, and less than 0.5 wt% of MnO2.

[0018] Additionally, the first piezoelectric element and the second piezoelectric element may each independently have a horizontal and vertical length of 15 to 31 mm.

[0019] Additionally, the electrode layer may be formed by including one or more metals among silver, copper, and aluminum.

[0020] Additionally, it may further include a connecting portion that electrically connects the first electrode layer and the second electrode layer.

[0021] Additionally, the ratio of the first resonant frequency to the second resonant frequency may be 1:1.35 or less.

[0022] Additionally, the first resonant frequency may be 55 kHz or higher.

[0023]

[0024] In addition, the present invention provides a method for manufacturing a piezoelectric actuator, including the steps of: arranging a first laminate including a polarized first piezoelectric body and a first electrode disposed on at least one surface of the first piezoelectric body, and a second laminate including a polarized second piezoelectric body and a second electrode disposed on at least one surface of the second piezoelectric body, with a predetermined distance between them in a horizontal direction; and electrically connecting the first electrode and the second electrode.

[0025] According to one embodiment of the present invention, before the disposing step, a step of polarizing each of the first piezoelectric body and the second piezoelectric body may be further included.

[0026]

[0027] The term "first resonant frequency" used in the present invention refers to the frequency of the first rising inflection point of the impedance value that decreases with increasing frequency in a frequency (x-axis) - impedance (y-axis) graph, and the term "second resonant frequency" refers to the frequency of the second rising inflection point of the impedance value that decreases with increasing frequency in a frequency (x-axis) - impedance (y-axis) graph.

[0028] The piezoelectric actuator of the present invention and its manufacturing method can simultaneously exhibit the effects of a high resonant frequency, an appropriate interval between the first and second resonant frequencies, and excellent piezoelectric characteristics.

[0029] FIG. 1 is a photograph of a piezoelectric actuator according to one embodiment of the present invention;

[0030] Figures 2 to 6 are frequency characteristic measurement graphs of Examples 1 to 5, and

[0031] Figures 7 and 8 are frequency characteristic measurement graphs of Comparative Examples 1 and 2.

[0032] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0033]

[0034] A piezoelectric actuator according to the present invention is implemented by including a piezoelectric layer including a polarized first piezoelectric body, a polarized second piezoelectric body having a predetermined distance in the horizontal direction from the first piezoelectric body, and an electrode layer including a first electrode disposed on at least one surface of the first piezoelectric body, and a second electrode electrically connected to the first electrode and disposed on at least one surface of the second piezoelectric body.

[0035] Hereinafter, each component of the piezoelectric actuator of the present invention will be described.

[0036] The polarized first piezoelectric element and the polarized second piezoelectric element are each polarized, and the first piezoelectric element and the second piezoelectric element may be individually polarized or simultaneously polarized. However, it is preferable that the first piezoelectric element and the second piezoelectric element are individually polarized, which is advantageous in that it has a high resonant frequency, an appropriate interval between the first resonant frequency and the second resonant frequency, and exhibits excellent piezoelectric properties.

[0037] In addition, the first piezoelectric body and the second piezoelectric body may each independently include one of a known lead-based piezoelectric ceramic component and a lead-free piezoelectric ceramic component that does not contain lead, a mixture thereof, or an alloy thereof, and preferably may be at least one selected from the group consisting of lead titanate zirconate (PZT), lead magnesium niobate (PMN), lead nickel niobate (PNN), lead titanate (PT), modified lead titanate (MPT), lead magnesium tungstate (PMW), PNN-PZT, PMN-PT, PMW-PZT, BS-PT, and lanthanum-doped lead zirconate titanate (PLZT), more preferably may be at least one selected from the group consisting of lead titanate zirconate (PZT), lead magnesium niobate (PMN), lead nickel niobate (PNN), and modified lead titanate (MPT), and even more preferably may be modified lead titanate (MPT). There is. More preferably, it may be more advantageous to achieve the purpose of the present invention if the first piezoelectric body and the second piezoelectric body are each independently formed of a piezoelectric ceramic containing 65.0 to 70.0 wt% of Pb2O4, 11.0 to 16.0 wt% of ZrO2, 9.5 to 10.5 wt% of TiO2, 1.0 to 1.2 wt% of ZnO, 0.3 to 0.4 wt% of NiO, 4.0 to 6.0 wt% of Nb2O5, 1.5 to 3.5 wt% of La2O3, and less than 0.5 wt% of MnO2.

[0038] Meanwhile, the first piezoelectric body and the second piezoelectric body can each be formed by sintering a predetermined composition including the above-described piezoelectric ceramic.

[0039] At this time, the composition may further include a sintering aid. The sintering aid serves the function of assisting the sintering of ceramics, and any sintering aid commonly used in the art may be used without limitation, and thus the present invention does not specifically limit it.

[0040] In addition, the composition may further include a binder. The binder performs the function of improving the formability and shape retention when the composition is formed into a sheet, and the interlayer adhesion of the laminate when implemented as a multilayer. Any binder commonly used in the art may be used without limitation, but preferably, including a polyvinyl butyral (PVB)-based binder may be more advantageous in achieving the purpose of the present invention.

[0041] In addition, the binder may be further included in an amount of 3 to 12 parts by weight, preferably 4 to 10 parts by weight, based on 100 parts by weight of the piezoelectric ceramic, but is not limited thereto.

[0042] Meanwhile, the composition may further include a solvent. The solvent may be any known solvent that is advantageous in dispersing the piezoelectric ceramic powder and sintering agent described above while not inhibiting the dissolution of the binder. For example, the solvent may be a mixed solvent containing one or more organic solvents such as toluene or ethanol.

[0043] In addition, the composition may further include known plasticizers, dispersants, antifoaming agents, etc. in addition to the described components, and the present invention is not particularly limited thereto. Non-limiting examples of the plasticizer may include phthalic acid esters such as dioctyl-4,5-epoxy-hexahydrophthalate, tris-(octoxycarbonylethyl)isocyanurate, tristearin, epoxidized soybean oil, or other similar ones, or mixtures thereof.

[0044] Meanwhile, the first piezoelectric member and the second piezoelectric member may each independently have a horizontal and vertical length of 15 to 31 mm, and preferably, the horizontal and vertical lengths of the first piezoelectric member and the second piezoelectric member may each independently be 20 to 30 mm. If the horizontal and vertical lengths of the first piezoelectric member and the second piezoelectric member are each less than 15 mm, the first resonant frequency may become excessively large, and if the horizontal and vertical lengths of the first piezoelectric member and the second piezoelectric member exceed 31 mm, the resonant frequency may be low or the ratio of the first resonant frequency to the second resonant frequency may not be appropriate.

[0045] The above electrode layer may be formed by including a known metal that can be applied to a piezoelectric actuator, and preferably may be formed by including at least one metal selected from the group consisting of silver, copper, and aluminum, and more preferably, including silver may be more advantageous in achieving the purpose of the present invention.

[0046] In addition, a piezoelectric actuator according to one embodiment of the present invention may further include a connecting portion that electrically connects the first electrode layer and the second electrode layer.

[0047] The above connecting part may be made of any known material capable of electrically connecting the first electrode layer and the second electrode layer, and thus the present invention does not specifically limit this.

[0048] Meanwhile, the piezoelectric actuator of the present invention may have a ratio of the first resonant frequency to the second resonant frequency of 1:1.35 or less, and preferably, the ratio of the first resonant frequency to the second resonant frequency may be 1:1.35 or less. If the ratio of the first resonant frequency to the second resonant frequency of the piezoelectric actuator exceeds 1:1.35, the effects intended by the present invention may not be simultaneously exhibited.

[0049] In addition, the piezoelectric actuator of the present invention may have a primary resonant frequency of 55 kHz or more, and preferably, the primary resonant frequency may be 60 to 70 kHz. If the primary resonant frequency of the piezoelectric actuator is less than 55 kHz, the effects intended by the present invention may not be simultaneously achieved.

[0050]

[0051] A piezoelectric actuator according to the present invention is manufactured through a manufacturing method including a step of arranging a first laminate including a polarized first piezoelectric body and a first electrode disposed on at least one surface of the first piezoelectric body, and a second laminate including a polarized second piezoelectric body and a second electrode disposed on at least one surface of the second piezoelectric body so as to have a predetermined distance apart in a horizontal direction, and a step of electrically connecting the first electrode and the second electrode.

[0052] Meanwhile, the method for manufacturing a piezoelectric actuator according to the present invention may further include a step of polarizing each of the first piezoelectric body and the second piezoelectric body before the step of disposing.

[0053] The above-described step of polarizing each of the first and second piezoelectric elements separately polarizes them, indicating that the composition including the piezoelectric ceramic powder is sintered and then separated to polarize them individually. In this case, compared to polarizing simultaneously and then separating them, it may be more advantageous in terms of the effects aimed at by the present invention.

[0054] Meanwhile, the first piezoelectric body and the second piezoelectric body may be sintered piezoelectric ceramics as described above, and since known conditions can be applied to the sintering conditions, the present invention does not specifically limit them.

[0055] Additionally, when the composition forming the piezoelectric body includes a binder, a step of removing the binder before performing sintering may be further included.

[0056] The step of removing the above binder can be performed under conditions commonly available in the art, and is preferably performed at a temperature of 240 to 285°C, more preferably at a temperature of 245 to 280°C.

[0057] In addition, before performing the step of removing the binder, the method may further include a step of manufacturing a composition forming a piezoelectric body in a sheet form, and / or a step of laminating a composition manufactured in a sheet form.

[0058] At this time, the step of manufacturing in the form of a sheet can be performed without limitation by any sheet manufacturing method commonly used in the art, and is preferably performed through a casting or pressing method, but is not limited thereto.

[0059] In addition, since the above-mentioned laminating step can be performed by a method commonly available in the art, the present invention does not specifically limit it.

[0060]

[0061] The present invention will be described in more detail through the following examples, but the following examples do not limit the scope of the present invention, and should be interpreted as helping to understand the present invention.

[0062] [Example]

[0063] <Example 1>

[0064] First, a composition was prepared containing 7 parts by weight of a polyvinyl butyral (PVB) binder for 100 parts by weight of a piezoelectric ceramic powder having a composition of 67.5 wt% of Pb2O4, 13.5 wt% of ZrO2, 10 wt% of TiO2, 1.1 wt% of ZnO, 0.35 wt% of NiO, 5.0 wt% of Nb2O5, 2.5 wt% of La2O3, and 0.05 wt% of MnO2.

[0065] The prepared composition was manufactured into multiple sheets with an average thickness of 45 μm using a doctor blade method, laminated in 11 layers and half-cut, heat-treated at a temperature of 295°C for 120 minutes while applying heat at a heating rate of 3°C / min in a furnace to remove the binder, and sintered by maintaining the temperature at 1130°C for 3 hours while applying heat at a heating rate of 3°C / min, and then cooled under natural cooling conditions to manufacture two piezoelectric elements each having a thickness of 0.3 mm and a length and width of 26 mm (a first piezoelectric element and a second piezoelectric element). Thereafter, silver (Ag) paste was screen-printed and baked on both surfaces of the first piezoelectric element and the second piezoelectric element, respectively, to form first and second electrodes each having a thickness of 20 μm on the upper and lower portions of the first piezoelectric element and the second piezoelectric element, respectively (the first electrode on the upper and lower portions of the first piezoelectric element, and the second electrode on the upper and lower portions of the second piezoelectric element). At this time, the first electrode was placed in the central portion of the upper and lower surfaces of the first piezoelectric body, and the second electrode was placed in the central portion of the upper and lower surfaces of the second piezoelectric body.

[0066] Then, the first piezoelectric element and the second piezoelectric element were individually polarized to manufacture a polarized first piezoelectric element and a polarized second piezoelectric element, and the first piezoelectric element and the second piezoelectric element were arranged with a horizontal distance of 4.5 mm, and the first electrode layer and the second electrode layer were electrically connected through a connecting wire to manufacture a piezoelectric actuator.

[0067]

[0068] <Example 2>

[0069] A piezoelectric actuator was manufactured in the same manner as in Example 1, except that the piezoelectric body was not polarized individually, but the first electrode layer and the second electrode layer were electrically connected through a connecting wire, and then the piezoelectric body was polarized simultaneously.

[0070]

[0071] <Example 3>

[0072] A piezoelectric actuator was manufactured in the same manner as in Example 1, except that the upper left vertex of the first electrode on the upper surface of the first piezoelectric body was arranged so that the upper left vertex of the first electrode on the lower surface of the first piezoelectric body was in contact with the lower left vertex of the first electrode on the lower surface of the first piezoelectric body was in contact with the lower left vertex of the lower surface of the first piezoelectric body, and the upper right vertex of the second electrode on the upper surface of the second piezoelectric body was in contact with the upper right vertex of the upper surface of the second piezoelectric body, and the lower right vertex of the second electrode on the lower surface of the second piezoelectric body was in contact with the lower right vertex of the lower surface of the second piezoelectric body.

[0073]

[0074] <Example 4>

[0075] A piezoelectric actuator was manufactured in the same manner as in Example 2, except that the upper left vertex of the first electrode on the upper surface of the first piezoelectric body was arranged so that the upper left vertex of the first electrode on the lower surface of the first piezoelectric body was in contact with the lower left vertex of the first electrode on the lower surface of the first piezoelectric body was in contact with the lower left vertex of the lower surface of the first piezoelectric body, and the upper right vertex of the second electrode on the upper surface of the second piezoelectric body was in contact with the upper right vertex of the upper surface of the second piezoelectric body, and the lower right vertex of the second electrode on the lower surface of the second piezoelectric body was in contact with the lower right vertex of the lower surface of the second piezoelectric body.

[0076]

[0077] <Example 5>

[0078] A piezoelectric actuator was manufactured in the same manner as in Example 2, except that four piezoelectric bodies each having a horizontal and vertical length of 26 mm (respectively referred to as the first to fourth piezoelectric bodies) were manufactured and then electrode layers (respectively referred to as the first to fourth electrodes) were formed.

[0079]

[0080] <Comparative Example 1>

[0081] A piezoelectric actuator was manufactured in the same manner as in Example 1, except that one piezoelectric body having a length and width of 60 mm each was manufactured and then an electrode layer was formed.

[0082]

[0083] <Comparative Example 2>

[0084] A piezoelectric actuator was manufactured in the same manner as in Example 1, except that the piezoelectric bodies were manufactured so that the horizontal and vertical lengths of the piezoelectric bodies were each 9.8 mm, and the first piezoelectric body and the second piezoelectric body were bonded with epoxy without a gap between them.

[0085]

[0086] <Experimental Example: Measuring Resonant Frequency>

[0087] For each piezoelectric actuator manufactured according to the examples and comparative examples, the resonant frequency was measured in the frequency band of 100 Hz to 100 kHz under the OSC 500 mVolt condition using a test fixture (Agilent 16034G) in an impedance analyzer (Agilent 4294A), and the results are shown in Tables 1 to 2 and Figs. 2 to 8.

[0088] Classification Example 1 Example 2 Example 3 Example 4 Example 5 Resonant frequency (kHz) 1st 6 1.5 3 26.60 26.59 26.50 32.48 2nd 7 5.99 5 5.31 6 1.5 36 0.73 8 8.5 1 1st and 2nd ratio 1:1.23 5 1:2.07 9 1:2.31 4 1:2.29 2 1:2.72 5 3rd 9 2.46 6 0.5 38 5.0 38 5.43 9 1.52

[0089] Classification Comparison Example 1 Comparison Example 2 Resonant Frequency (kHz) 1st 30.59 163 2nd 44.90 - 1st and 2nd ratio 1:1.468 - 3rd 85.01 -

[0090] As a result, as shown in Tables 1 to 2 and FIGS. 2 to 8, it can be confirmed that Example 1, which satisfies all of the number of piezoelectric elements, the length and width of the piezoelectric elements, the presence or absence of individual polarization, and the electrode positions according to the present invention, has a higher first resonance frequency and an appropriate ratio of the first resonance frequency to the second resonance frequency compared to Examples 2 to 5 and Comparative Examples 1 to 2, which do not satisfy even one of these.

[0091]

[0092] Although one embodiment of the present invention has been described above, the spirit of the present invention is not limited to the embodiment presented in this specification, and a person skilled in the art who understands the spirit of the present invention will be able to easily propose other embodiments by adding, changing, deleting, or adding components within the scope of the same spirit, but this will also be considered to fall within the spirit of the present invention.

Claims

1. A piezoelectric layer including a polarized first piezoelectric body and a polarized second piezoelectric body having a predetermined distance in the horizontal direction from the first piezoelectric body; and A piezoelectric actuator comprising: an electrode layer including a first electrode disposed on at least one surface of the first piezoelectric body; and a second electrode electrically connected to the first electrode and disposed on at least one surface of the second piezoelectric body.

2. In paragraph 1, The polarized first piezoelectric element and the polarized second piezoelectric element are piezoelectric actuators formed by individually polarizing the first piezoelectric element and the second piezoelectric element, respectively.

3. In paragraph 1, The first and second piezoelectric elements are each independently Pb 2 O 4 65.0 to 70.0 wt%, ZrO 2 11.0 ~ 16.0 wt%, TiO 2 9.5 to 10.5 wt%, ZnO 1.0 to 1.2 wt%, NiO 0.3 to 0.4 wt%, Nb 2 O 5 4.0 to 6.0 wt%, La 2 O 3 1.5 to 3.5 wt% and MnO 2 A piezoelectric actuator formed of a piezoceramic containing less than 0.5 wt% of 4. In paragraph 1, The first piezoelectric actuator and the second piezoelectric actuator are piezoelectric actuators each having an independent horizontal and vertical length of 15 to 31 mm.

5. In paragraph 1, A piezoelectric actuator formed by including at least one metal selected from the group consisting of silver, copper, and aluminum.

6. In paragraph 1, A piezoelectric actuator further comprising a connecting portion electrically connecting the first electrode layer and the second electrode layer.

7. In paragraph 1, A piezoelectric actuator having a ratio of the first resonant frequency to the second resonant frequency of 1:1.35 or less.

8. In paragraph 1, A piezoelectric actuator having a first resonant frequency of 55 kHz or higher.

9. A step of arranging a first laminate including a polarized first piezoelectric body and a first electrode arranged on at least one surface of the first piezoelectric body, and a second laminate including a polarized second piezoelectric body and a second electrode arranged on at least one surface of the second piezoelectric body, with a predetermined distance between them in the horizontal direction; and A method for manufacturing a piezoelectric actuator, comprising: a step of electrically connecting the first electrode and the second electrode.

10. In paragraph 9, before the step of placing, A method for manufacturing a piezoelectric actuator, further comprising the step of polarizing each of the first piezoelectric element and the second piezoelectric element.

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