JP6619515B2 - Multilayer piezoelectric element, injection device including the same, and fuel injection system - Google Patents

Multilayer piezoelectric element, injection device including the same, and fuel injection system Download PDF

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JP6619515B2
JP6619515B2 JP2018519194A JP2018519194A JP6619515B2 JP 6619515 B2 JP6619515 B2 JP 6619515B2 JP 2018519194 A JP2018519194 A JP 2018519194A JP 2018519194 A JP2018519194 A JP 2018519194A JP 6619515 B2 JP6619515 B2 JP 6619515B2
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piezoelectric element
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JPWO2017204015A1 (en
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山元　堅
堅 山元
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M51/00—Fuel-injection apparatus characterised by being operated electrically
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M61/00—Fuel-injectors not provided for in groups F02M39/00 - F02M57/00 or F02M67/00
    • F02M61/16—Details not provided for in, or of interest apart from, the apparatus of groups F02M61/02 - F02M61/14
    • F02M61/20—Closing valves mechanically, e.g. arrangements of springs or weights or permanent magnets; Damping of valve lift
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/02—Forming enclosures or casings
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/20—Piezoelectric or electrostrictive devices with electrical input and mechanical output, e.g. functioning as actuators or vibrators
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/50—Piezoelectric or electrostrictive devices having a stacked or multilayer structure
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/88—Mounts; Supports; Enclosures; Casings

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Fuel-Injection Apparatus (AREA)

Description

本開示は、例えば、圧電駆動素子（圧電アクチュエータ），圧力センサ素子および圧電回路素子等として用いられる積層型圧電素子およびこれを備えた噴射装置ならびに燃料噴射システムに関する。  The present disclosure relates to a laminated piezoelectric element used as, for example, a piezoelectric driving element (piezoelectric actuator), a pressure sensor element, a piezoelectric circuit element, and the like, an injection device including the same, and a fuel injection system.

積層型圧電素子として、圧電体層および内部電極層が交互に積層された活性部および圧電体層が積層された不活性部を有する積層体と、該積層体の側面を取り囲むように設けられた被覆層とを備えたものが知られている。  As a laminated piezoelectric element, a laminated body having an active portion in which piezoelectric layers and internal electrode layers are alternately laminated and an inactive portion in which piezoelectric layers are laminated, and a side surface of the laminated body are provided. What is provided with the coating layer is known.

なお、被覆層は例えば内部電極層間のマイグレーションや放電を抑制することを目的として設けられている。  The covering layer is provided for the purpose of suppressing migration and discharge between the internal electrode layers, for example.

特開２０００−３２３７６２号公報JP 2000-323762 A

本開示の積層型圧電素子は、圧電体層および内部電極層が交互に積層された活性部および圧電体層が積層された不活性部を有する積層体と、該積層体の側面を取り囲むように設けられた被覆層とを備え、該被覆層は内側の第１の層と外側の第２の層とからなる２層構造を有しており、前記第１の層の外面が複数の凸部または複数の凹部を有しており、前記複数の凸部または前記複数の凹部が格子状に配置されている。 The multilayer piezoelectric element of the present disclosure includes a multilayer body having an active portion in which piezoelectric layers and internal electrode layers are alternately stacked, and an inactive portion in which piezoelectric layers are stacked, and a side surface of the multilayer body. Provided with a coating layer, and the coating layer has a two-layer structure including an inner first layer and an outer second layer, and the outer surface of the first layer has a plurality of convex portions. Or it has a some recessed part, and the said some convex part or the said some recessed part is arrange | positioned at the grid | lattice form .

また、本開示の噴射装置は、噴射孔を有する容器と、上記の積層型圧電素子とを備え、該積層型圧電素子の駆動によって前記噴射孔が開閉されるようになっている。  Moreover, the injection device of the present disclosure includes a container having an injection hole and the multilayer piezoelectric element described above, and the injection hole is opened and closed by driving the multilayer piezoelectric element.

また、本開示の燃料噴射システムは、高圧燃料を蓄えるコモンレールと、該コモンレールに蓄えられた前記高圧燃料を噴射する上記の噴射装置と、前記コモンレールに前記高圧燃料を供給する圧力ポンプと、前記噴射装置に駆動信号を与える噴射制御ユニットとを備えている。  The fuel injection system of the present disclosure includes a common rail that stores high-pressure fuel, the above-described injection device that injects the high-pressure fuel stored in the common rail, a pressure pump that supplies the high-pressure fuel to the common rail, and the injection An injection control unit for supplying a drive signal to the apparatus.

本実施形態の積層型圧電素子の一例を示す概略斜視図である。It is a schematic perspective view which shows an example of the laminated piezoelectric element of this embodiment. 図１に示す積層型圧電素子の一部破断概略斜視図である。It is a partially broken schematic perspective view of the multilayer piezoelectric element shown in FIG. 図１に示す積層型圧電素子のiii−iii線で切断した概略縦断面図である。It is the schematic longitudinal cross-sectional view cut | disconnected by the iii-iii line | wire of the multilayer piezoelectric element shown in FIG. 本実施形態の積層型圧電素子の他の例の概略縦断面図である。It is a schematic longitudinal cross-sectional view of the other example of the multilayer piezoelectric element of this embodiment. 本実施形態の積層型圧電素子の他の例の概略縦断面図である。It is a schematic longitudinal cross-sectional view of the other example of the multilayer piezoelectric element of this embodiment. 本実施形態の積層型圧電素子の他の例の概略縦断面図である。It is a schematic longitudinal cross-sectional view of the other example of the multilayer piezoelectric element of this embodiment. 本実施形態の積層型圧電素子の他の例の概略縦断面図である。It is a schematic longitudinal cross-sectional view of the other example of the multilayer piezoelectric element of this embodiment. 本実施形態の積層型圧電素子の他の例の側面透視図である。It is side surface perspective drawing of the other example of the laminated piezoelectric element of this embodiment. 本実施形態の積層型圧電素子の他の例の側面透視図である。It is side surface perspective drawing of the other example of the laminated piezoelectric element of this embodiment. 本実施形態の積層型圧電素子の他の例の概略縦断面図である。It is a schematic longitudinal cross-sectional view of the other example of the multilayer piezoelectric element of this embodiment. 本実施形態の積層型圧電素子の他の例の概略縦断面図である。It is a schematic longitudinal cross-sectional view of the other example of the multilayer piezoelectric element of this embodiment. 本実施形態の噴射装置の一例を示す概略断面図である。It is a schematic sectional drawing which shows an example of the injection device of this embodiment. 本実施形態の燃料噴射システムの一例を示す概略図である。It is the schematic which shows an example of the fuel-injection system of this embodiment.

従来の積層型圧電素子において、積層体の側面に被覆層を形成する際に塗布された被覆層の形成材料は、表面から硬化が進行する。そのため、被覆層の表面は硬く緻密な構造になる。したがって、被覆層を多層構造にする（２回に分けて形成する）ことで、被覆層の内部にも硬く緻密な構造の領域を有する構成とすることができ、この構成によりさらに放電を生じにくくすることができるようにも思われる。  In the conventional multilayer piezoelectric element, the coating layer forming material applied when the coating layer is formed on the side surface of the multilayer body is cured from the surface. Therefore, the surface of the coating layer has a hard and dense structure. Therefore, by forming the coating layer into a multilayer structure (formed in two steps), the coating layer can have a structure having a hard and dense structure, and this configuration further prevents discharge. Seems to be able to.

しかしながら、上述の積層型圧電素子は例えば固定されて使用される。被覆層の内部には硬く緻密な構造の領域が積層体の積層方向に沿って存在していて当該積層方向への柔らかさが低下しているので、このような状態で積層型圧電素子を長期間駆動させると、被覆層と積層体との界面に応力負荷がかかってクラックが入り、このクラックを通して放電し、積層型圧電素子の変位量が低下するおそれがあった。  However, the laminated piezoelectric element described above is used, for example, by being fixed. A hard and dense structure region exists in the coating layer along the stacking direction of the laminate, and the softness in the stacking direction is reduced. When driven for a period of time, a stress load is applied to the interface between the coating layer and the laminate, causing cracks, and discharging through the cracks may reduce the displacement of the multilayer piezoelectric element.

本開示は上記事情に鑑みてなされたもので、被覆層と積層体との界面への応力負荷が抑制され、放電の生じにくい積層型圧電素子およびこれを備えた噴射装置ならびに燃料噴射システムを提供することを目的とする。  The present disclosure has been made in view of the above circumstances, and provides a multilayer piezoelectric element in which stress load on the interface between the coating layer and the multilayer body is suppressed and discharge is less likely to occur, an injection device including the multilayer piezoelectric element, and a fuel injection system The purpose is to do.

以下、本実施形態の積層型圧電素子の一例について図面を参照して説明する。  Hereinafter, an example of the multilayer piezoelectric element of the present embodiment will be described with reference to the drawings.

図１は本実施形態の積層型圧電素子の一例を示す概略斜視図、図２は図１に示す積層型圧電素子の一部破断概略斜視図、図３は本実施形態の積層型圧電素子の一例の概略縦断面図である。  1 is a schematic perspective view showing an example of the multilayer piezoelectric element of the present embodiment, FIG. 2 is a partially broken schematic perspective view of the multilayer piezoelectric element shown in FIG. 1, and FIG. 3 is a diagram of the multilayer piezoelectric element of the present embodiment. It is a schematic longitudinal cross-sectional view of an example.

図１乃至図３に示す積層型圧電素子１は、圧電体層１１および内部電極層１２が交互に積層された活性部１３および圧電体層１１が積層された不活性部１４を有する積層体１０と、該積層体１０の側面を取り囲むように設けられた被覆層１６とを備えている。そして、該被覆層１６は内側の第１の層１６１と外側の第２の層１６２とからなる２層構造を有しており、第１の層１６１の外面が複数の凹部１６３を有している。  A laminated piezoelectric element 1 shown in FIGS. 1 to 3 includes a laminated body 10 having an active portion 13 in which piezoelectric layers 11 and internal electrode layers 12 are alternately laminated and an inactive portion 14 in which piezoelectric layers 11 are laminated. And a coating layer 16 provided so as to surround the side surface of the laminate 10. The covering layer 16 has a two-layer structure including an inner first layer 161 and an outer second layer 162, and the outer surface of the first layer 161 has a plurality of recesses 163. Yes.

積層型圧電素子１を構成する積層体１０は、圧電体層１１および内部電極層１２が交互に複数積層されてなる活性部１３と、活性部１３の積層方向外側に位置するように積層体１０の積層方向両端部に設けられた圧電体層１１が積層されてなる不活性部１４とを有している。ここで、活性部１３は駆動時に圧電体層１１が積層方向に伸長または収縮する部位であり、不活性部１４は駆動時に圧電体層１１が積層方向に伸長または収縮しない部位である。この積層体１０は、例えば縦０．５〜１０ｍｍ、横０．５〜１０ｍｍ、高さ１〜１００ｍｍの直方体状に形成されている。また、活性部１３の高さは、例えば積層体１０の高さの７５〜９５％の高さとされる。なお、積層体１０としては六角柱形状や八角柱形状などであってもよい。  The multilayer body 10 constituting the multilayer piezoelectric element 1 includes an active portion 13 in which a plurality of piezoelectric layers 11 and internal electrode layers 12 are alternately stacked, and the multilayer body 10 so as to be positioned outside the active portion 13 in the stacking direction. And inactive portions 14 formed by laminating piezoelectric layers 11 provided at both ends in the laminating direction. Here, the active portion 13 is a portion where the piezoelectric layer 11 extends or contracts in the stacking direction during driving, and the inactive portion 14 is a portion where the piezoelectric layer 11 does not extend or contract in the stacking direction during driving. The laminated body 10 is formed in a rectangular parallelepiped shape having a length of 0.5 to 10 mm, a width of 0.5 to 10 mm, and a height of 1 to 100 mm, for example. The height of the active portion 13 is, for example, 75 to 95% of the height of the stacked body 10. The laminate 10 may have a hexagonal column shape, an octagonal column shape, or the like.

積層体１０を構成する圧電体層１１は、圧電特性を有するセラミックスで形成されたもので、このようなセラミックスとして、例えばチタン酸ジルコン酸鉛（ＰｂＺｒＯ３−ＰｂＴｉＯ３）からなるペロブスカイト型酸化物、ニオブ酸リチウム（ＬｉＮｂＯ３）、タンタル酸リチウム（ＬｉＴａＯ３）などを用いることができる。この圧電体層１１の厚みは、例えば３〜２５０μｍとされる。The piezoelectric layer 11 constituting the laminated body 10 is formed of ceramics having piezoelectric characteristics. As such ceramics, for example, a perovskite oxide made of lead zirconate titanate (PbZrO 3 -PbTiO 3 ), Lithium niobate (LiNbO 3 ), lithium tantalate (LiTaO 3 ), or the like can be used. The thickness of the piezoelectric layer 11 is, for example, 3 to 250 μm.

積層体１０を構成する内部電極層１２は、圧電体層１１を形成するセラミックスと同時焼成により形成されたもので、圧電体層１１と交互に積層されて圧電体層１１を上下から挟んでおり、積層順に正極および負極が配置されることにより、それらの間に挟まれた圧電体層１１に駆動電圧を印加するものである。この形成材料として、例えば銀−パラジウム合金を主成分とする導体、あるいは銅、白金などを含む導体を用いることができる。図に示す例では、正極および負極（もしくはグランド極）がそれぞれ積層体１０の対向する一対の側面に互い違いに導出されて、積層体１０の側面に設けられた一対の外部電極１５と電気的に接続されている。この内部電極層１２の厚みは、例えば０．１〜５μｍとされる。  The internal electrode layer 12 constituting the multilayer body 10 is formed by simultaneous firing with ceramics forming the piezoelectric body layer 11, and is alternately laminated with the piezoelectric body layers 11 so as to sandwich the piezoelectric body layers 11 from above and below. By arranging the positive electrode and the negative electrode in the order of lamination, a driving voltage is applied to the piezoelectric layer 11 sandwiched between them. As this forming material, for example, a conductor mainly composed of a silver-palladium alloy or a conductor containing copper, platinum, or the like can be used. In the example shown in the figure, the positive electrode and the negative electrode (or the ground electrode) are alternately led out to a pair of opposing side surfaces of the stacked body 10 and electrically connected to the pair of external electrodes 15 provided on the side surfaces of the stacked body 10. It is connected. The internal electrode layer 12 has a thickness of 0.1 to 5 μm, for example.

なお、積層体１０には、応力を緩和するための層であって内部電極層１２として機能しない金属層等が含まれていてもよい。  Note that the laminate 10 may include a metal layer that is a layer for relaxing stress and does not function as the internal electrode layer 12.

そして、内部電極層１２の正極または負極（もしくはグランド極）が導出された積層体１０の対向する一対の側面には、それぞれ外部電極１５が設けられ、導出された内部電極層１２と電気的に接続されている。この外部電極１５は、活性部１３から不活性部１４にかけてそれぞれ設けられている。外部電極１５は、例えばＡｇやＣｕなど金属の金属を含んだ導電性ペーストを焼き付けてなるのが好ましい。ここで、外部電極１５を積層体１０の側面に垂直な横断面で見たときに、外部電極１５の厚みは５〜７０μｍの厚さに形成される。  External electrodes 15 are respectively provided on a pair of opposing side surfaces of the laminate 10 from which the positive electrode or negative electrode (or ground electrode) of the internal electrode layer 12 is derived, and are electrically connected to the derived internal electrode layer 12. It is connected. The external electrodes 15 are provided from the active portion 13 to the inactive portion 14 respectively. The external electrode 15 is preferably formed by baking a conductive paste containing a metal such as Ag or Cu. Here, when the external electrode 15 is viewed in a cross section perpendicular to the side surface of the multilayer body 10, the thickness of the external electrode 15 is formed to a thickness of 5 to 70 μm.

そして、外部電極１５にリード部材１７が接合され、リード部材１７が引き出されることで、外部回路との電気的な接続がなされる。  Then, the lead member 17 is joined to the external electrode 15 and the lead member 17 is pulled out, so that electrical connection with an external circuit is made.

また、積層体１０の側面を取り囲むように、被覆層１６が設けられている。被覆層１６は、内部電極層１２の正極および負極の両方の端部が達する積層体１０の側面におけるマイグレーションや放電を抑制する効果を奏する。この被覆層１６は、内部電極層１２の端部を覆って露出させないように設けられたものであり、図に示す例では外部電極１５も含めて積層体１０の側面を取り囲むように被覆している。  Moreover, the coating layer 16 is provided so that the side surface of the laminated body 10 may be surrounded. The covering layer 16 has an effect of suppressing migration and electric discharge on the side surface of the multilayer body 10 where both ends of the positive electrode and the negative electrode of the internal electrode layer 12 reach. The covering layer 16 is provided so as to cover the end portion of the internal electrode layer 12 so as not to be exposed. In the example shown in the figure, the covering layer 16 is covered so as to surround the side surface of the laminate 10 including the external electrode 15. Yes.

被覆層１６は、複数の層が重なって構成されていて、内側の第１の層１６１と外側の第２の層１６２とからなる２層構造を有している。第１の層１６１は例えばシリコーン樹脂、エポキシ樹脂などにより形成され、第２の層１６２は例えばシリコーン樹脂、エポキシ樹脂などで形成される。複数の層が重なって被覆層１６が構成されていることにより、被覆層１６と積層体１０との界面に加わる応力が、被覆層１６を構成する各層に分散されて低減される。  The covering layer 16 is formed by overlapping a plurality of layers, and has a two-layer structure including an inner first layer 161 and an outer second layer 162. The first layer 161 is formed of, for example, a silicone resin or an epoxy resin, and the second layer 162 is formed of, for example, a silicone resin or an epoxy resin. Since the coating layer 16 is configured by overlapping a plurality of layers, the stress applied to the interface between the coating layer 16 and the laminate 10 is dispersed and reduced in each layer constituting the coating layer 16.

そして、被覆層１６において、第１の層１６１の外面が複数の凹部１６３を有している。これにより、第１の層１６１の表面が硬く緻密な構造であっても、複数の凹部１６３に沿って硬く緻密な構造が屈曲していることから、被覆層１６が積層体１０の積層方向への柔軟性を備えつつ、内部に硬く緻密な構造の領域を有することとなる。したがって、被覆層１６と積層体１０との界面への応力負荷が抑制され、長期間にわたって放電の生じにくい積層型圧電素子を実現することができる。  In the covering layer 16, the outer surface of the first layer 161 has a plurality of recesses 163. Thereby, even if the surface of the first layer 161 has a hard and dense structure, the hard and dense structure bends along the plurality of recesses 163, so that the coating layer 16 extends in the stacking direction of the stacked body 10. Thus, a region having a hard and dense structure is provided inside. Therefore, a stress applied to the interface between the coating layer 16 and the laminate 10 is suppressed, and a multilayer piezoelectric element that is less likely to cause discharge over a long period of time can be realized.

複数の凹部１６３を除く領域での第１の層１６１の厚みは例えば１０〜１５０μｍ、第２の層１６２の厚みは例えば２０〜２００μｍである。複数の凹部１６３の幅は例えば５０〜５００μｍ、深さは５〜６０μｍである。また、複数の凹部１６３は第１の層１６１の周方向にわたってあるのがよく、周方向に一様にあるのがよい。  The thickness of the first layer 161 in the region excluding the plurality of recesses 163 is, for example, 10 to 150 μm, and the thickness of the second layer 162 is, for example, 20 to 200 μm. The width | variety of the some recessed part 163 is 50-500 micrometers, for example, and the depth is 5-60 micrometers. In addition, the plurality of recesses 163 may extend in the circumferential direction of the first layer 161, and may be uniformly in the circumferential direction.

内側の第１の層１６１がシリコーン樹脂のように柔らかい素材からなる場合、複数の凹部１６３では、第１の層１６１を構成するシリコーン樹脂が表面の硬い部分はあまり変形しなくても内部の柔らかい部分が変形自在であるので、例えば積層型圧電素子１を高速で伸縮させても複数の凹部１６３に応力を集中させないようにすることができる。  When the inner first layer 161 is made of a soft material such as a silicone resin, the plurality of recesses 163 are soft inside even if the hard portion of the surface of the silicone resin constituting the first layer 161 is not significantly deformed. Since the portion is freely deformable, for example, stress can be prevented from being concentrated in the plurality of recesses 163 even when the stacked piezoelectric element 1 is expanded and contracted at high speed.

なお、上述の複数の凹部１６３にかえて、後述する図７に示すような複数の凸部１６４であってもよい。  Instead of the above-described plurality of concave portions 163, a plurality of convex portions 164 as shown in FIG.

ここで、図３は、不活性部１４の側方に複数の凹部１６３が配置されているものであるが、図４に示すように、活性部１３の側方に複数の凹部１６３が配置されているのがよい。この構成によれば、駆動時に変形しやすい活性部１３の側方に複数の凹部１６３があることで、被覆層１６と積層体１０との界面への応力負荷を抑制する効果が大きくなる。なお、複数の凹部１６３にかえて複数の凸部１６４であってもよい。  Here, in FIG. 3, a plurality of concave portions 163 are arranged on the side of the inactive portion 14, but as shown in FIG. 4, a plurality of concave portions 163 are arranged on the side of the active portion 13. It is good to have. According to this configuration, since there are the plurality of concave portions 163 on the side of the active portion 13 that is easily deformed during driving, the effect of suppressing the stress load on the interface between the coating layer 16 and the laminate 10 is increased. A plurality of convex portions 164 may be used instead of the plurality of concave portions 163.

また、図５に示すように、複数の凹部１６３が活性部１３を積層方向に３等分したときの中央部の側方に配置されているのがよい。複数の凹部１６３が活性部１３を積層方向に３等分したときの中央部は活性部１３の中でも最も伸縮変形しやすい部分であるので、この部分の側方に複数の凹部１６３があることで、被覆層１６と積層体１０との界面への応力負荷を抑制する効果がより大きくなる。なお、複数の凹部１６３にかえて複数の凸部１６４であってもよい。  Further, as shown in FIG. 5, the plurality of recesses 163 are preferably arranged on the side of the central portion when the active portion 13 is equally divided into three in the stacking direction. The central portion when the plurality of concave portions 163 divide the active portion 13 into three equal parts in the stacking direction is the portion most easily deformed in the active portion 13. In addition, the effect of suppressing the stress load on the interface between the coating layer 16 and the laminate 10 is further increased. A plurality of convex portions 164 may be used instead of the plurality of concave portions 163.

また、図６に示すように、複数の凹部１６３が第１の層１６１の第２の層１６２との界面の全域に一様に設けられていてもよい。また、図７に示すように、複数の凸部１６４が第１の層１６１の第２の層１６２との界面の全域に一様に設けられていてもよい。  Further, as shown in FIG. 6, the plurality of recesses 163 may be provided uniformly over the entire interface between the first layer 161 and the second layer 162. Further, as shown in FIG. 7, the plurality of convex portions 164 may be provided uniformly over the entire interface between the first layer 161 and the second layer 162.

また、図８および図９に示すように、複数の凹部１６３が格子状に配置されているのがよい。ここで、複数の凹部１６３が格子状に配置されるとは、仮想的に互いに交わる格子を描いたときのそれぞれの格子の互いに交わる点（格子点）に相当する位置に複数の凹部１６３が配置されることである。  Also, as shown in FIGS. 8 and 9, a plurality of recesses 163 are preferably arranged in a lattice pattern. Here, the plurality of recesses 163 are arranged in a lattice form that the plurality of recesses 163 are arranged at positions corresponding to points (lattice points) where each lattice intersects when a lattice that virtually intersects each other is drawn. It is to be done.

これらの構成によれば、被覆層１６が縦にも横にも自在に変形するので、被覆層１６と積層体１０との界面への応力負荷を抑制する効果が大きく、より長期間変位量が安定する。  According to these configurations, since the covering layer 16 is freely deformed both vertically and horizontally, the effect of suppressing the stress load on the interface between the covering layer 16 and the laminate 10 is large, and the displacement amount is longer. Stabilize.

また、図１０に示すように、複数の凹部１６３および複数の凸部１６４は、被覆層１６に垂直な断面で見て台形状の凹凸が連続したような形状であるのがよい。これにより、複数の凹部１６３および複数の凸部１６４が積層体１０の伸縮に追従しやすく、被覆層１６と積層体１０との界面への応力負荷をさらに抑制する効果が高まる。なお、断面台形状の他に、断面半円状、断面半楕円状、断面三角形状などの先細り形状とすることもできる。  Further, as shown in FIG. 10, the plurality of concave portions 163 and the plurality of convex portions 164 may have a shape in which trapezoidal irregularities are continuous when viewed in a cross section perpendicular to the coating layer 16. Thereby, the some recessed part 163 and the some convex part 164 follow the expansion-contraction of the laminated body 10, and the effect which further suppresses the stress load to the interface of the coating layer 16 and the laminated body 10 increases. In addition to the trapezoidal cross section, a tapered shape such as a semicircular cross section, a semi-elliptical cross section, and a triangular cross section may be employed.

また、図１１に示すように、複数の凹部１６３の底および複数の凸部１６４の天面は丸みを帯びているのがよい。これにより、応力が集中しにくく、被覆層１６にクラックを入りにくくすることができる。  In addition, as shown in FIG. 11, the bottoms of the plurality of concave portions 163 and the top surfaces of the plurality of convex portions 164 are preferably rounded. Thereby, it is difficult for stress to concentrate and it is possible to prevent cracks in the coating layer 16.

次に、本実施形態の積層型圧電素子１の製造方法の一例について説明する。  Next, an example of a method for manufacturing the multilayer piezoelectric element 1 of the present embodiment will be described.

まず、圧電体層１１となるセラミックグリーンシートを作製する。具体的には、圧電セラミックスの仮焼粉末と、アクリル系，ブチラール系等の有機高分子からなるバインダーと、可塑剤とを混合してセラミックスラリーを作製する。そして、ドクターブレード法、カレンダーロール法等のテープ成型法を用いることにより、このセラミックスラリーを用いてセラミックグリーンシートを作製する。圧電セラミックスとしては圧電特性を有するものであればよく、例えば、チタン酸ジルコン酸鉛（ＰｂＺｒＯ３−ＰｂＴｉＯ３）からなるペロブスカイト型酸化物等を用いることができる。また、可塑剤としては、フタル酸ジブチル（ＤＢＰ），フタル酸ジオクチル（ＤＯＰ）等を用いることができる。First, a ceramic green sheet to be the piezoelectric layer 11 is produced. Specifically, a ceramic slurry is prepared by mixing a calcined powder of piezoelectric ceramic, a binder made of an organic polymer such as acrylic or butyral, and a plasticizer. And a ceramic green sheet is produced using this ceramic slurry by using tape molding methods, such as a doctor blade method and a calender roll method. As the piezoelectric ceramic, any material having piezoelectric characteristics may be used. For example, a perovskite oxide made of lead zirconate titanate (PbZrO 3 —PbTiO 3 ) can be used. As the plasticizer, dibutyl phthalate (DBP), dioctyl phthalate (DOP), or the like can be used.

次に、内部電極層１２となる導電性ペーストを作製する。具体的には、銀−パラジウム合金の金属粉末にバインダーおよび可塑剤を添加混合することによって導電性ペーストを作製する。この導電性ペーストを上記のセラミックグリーンシート上に、スクリーン印刷法を用いて内部電極層１２のパターンで塗布する。さらに、この導電性ペーストが印刷されたセラミックグリーンシートを複数枚積層し、所定の温度で脱バインダー処理を行なった後、９００〜１２００℃の温度で焼成し、平面研削盤等を用いて所定の形状になるよう研削処理を施すことによって、交互に積層された圧電体層１１および内部電極層１２を備えた活性部１３を作製する。不活性部１４は内部電極層１２となる導電性ペーストを塗布していないシートを積層することで作製する。活性部１３と不活性部１４とを組み合わせることで積層体１０を製造する。  Next, a conductive paste to be the internal electrode layer 12 is produced. Specifically, a conductive paste is prepared by adding and mixing a binder and a plasticizer to a silver-palladium alloy metal powder. This conductive paste is applied on the ceramic green sheet in the pattern of the internal electrode layer 12 using a screen printing method. Furthermore, after laminating a plurality of ceramic green sheets printed with this conductive paste and performing a binder removal treatment at a predetermined temperature, firing at a temperature of 900 to 1200 ° C., using a surface grinder or the like The active part 13 provided with the piezoelectric body layers 11 and the internal electrode layers 12 that are alternately laminated is manufactured by performing a grinding process so as to have a shape. The inactive portion 14 is produced by laminating sheets that are not coated with the conductive paste that becomes the internal electrode layer 12. The laminated body 10 is manufactured by combining the active part 13 and the inactive part 14.

なお、積層体１０は、上記の製造方法によって作製されるものに限定されるものではなく、圧電体層１１と内部電極層１２とを複数積層してなる積層体１０を作製できれば、どのような製造方法によって作製されてもよい。  The laminate 10 is not limited to the one produced by the above manufacturing method, and any laminate 10 can be produced as long as the laminate 10 formed by laminating a plurality of piezoelectric layers 11 and internal electrode layers 12 can be produced. It may be produced by a manufacturing method.

次に、外部電極１５は、ＡｇやＣｕのような金属を含んだ導電性ペーストを用い、これを積層体１０の側面における内部電極層１２の両極のうちの一方の端部が導出された領域に焼き付けて５〜７０μｍの厚さに形成する。スクリーン印刷やディスペンス方式により、所定の厚みや幅に制御して形成することができる。  Next, a conductive paste containing a metal such as Ag or Cu is used for the external electrode 15, and this is a region where one end of both electrodes of the internal electrode layer 12 on the side surface of the laminate 10 is derived. To form a thickness of 5 to 70 μm. It can be formed by controlling to a predetermined thickness or width by screen printing or dispensing.

次に、被覆層１６を構成する第１の層１６１は、例えばナイロンやシリコーンの樹脂を使用し、印刷やディスペンス方式により、所定の厚みや幅に制御して形成することができる。乾燥硬化後に、第２の層１６２を同様に、印刷やディスペンス方式により、所定の厚みや幅に制御して形成することができる。  Next, the first layer 161 constituting the coating layer 16 can be formed by using, for example, nylon or silicone resin and controlling the thickness and width to a predetermined thickness by printing or dispensing. After drying and curing, the second layer 162 can be similarly formed by controlling to a predetermined thickness or width by printing or dispensing.

ここで、第１の層１６１の外面が複数の凸部１６４または複数の凹部１６３を有している構成（第１の層１６１と第２の層１６２との界面に凹凸がある構成）とするには、凹凸を設けたい箇所にディスペンサーで塗布重量を調整し塗布厚みを制御しつつ塗布することで作製することができる。また、メッシュのサイズを変更して重ね塗りすることで、凹凸を作製することもできる。  Here, a configuration in which the outer surface of the first layer 161 has a plurality of convex portions 164 or a plurality of concave portions 163 (a configuration in which the interface between the first layer 161 and the second layer 162 is uneven) is employed. Can be prepared by adjusting the coating weight with a dispenser at a location where unevenness is to be provided and controlling the coating thickness. Moreover, unevenness | corrugation can also be produced by changing the size of a mesh and recoating.

その後、外部電極１５に０．１〜３ｋＶ／ｍｍの直流電界を印加し、積層体１０を構成する圧電体層１１を分極することによって、積層型圧電素子１が完成する。この積層型圧電素子１は、外部電極１５を介して外部の電源と接続して、圧電体層１１に電圧を印加することにより、各圧電体層１１を逆圧電効果によって大きく変位させることができる。これにより、例えばエンジンに燃料を噴射供給する自動車用燃料噴射弁として機能させることが可能となる。  Thereafter, a direct current electric field of 0.1 to 3 kV / mm is applied to the external electrode 15 to polarize the piezoelectric layer 11 constituting the multilayer body 10, thereby completing the multilayer piezoelectric element 1. The multilayer piezoelectric element 1 is connected to an external power source via an external electrode 15 and applies a voltage to the piezoelectric layer 11 so that each piezoelectric layer 11 can be largely displaced by the inverse piezoelectric effect. . This makes it possible to function as an automobile fuel injection valve that injects and supplies fuel to the engine, for example.

次に、本実施形態の噴射装置の一例について説明する。図１２は、本実施形態の噴射装置の一例を示す概略断面図である。  Next, an example of the injection device of the present embodiment will be described. FIG. 12 is a schematic cross-sectional view illustrating an example of the injection device of the present embodiment.

図１２に示すように、本例の噴射装置１９は、一端に噴射孔２１を有する収納容器（容器）２３の内部に上記の例の積層型圧電素子１が収納されている。  As shown in FIG. 12, in the injection device 19 of this example, the multilayer piezoelectric element 1 of the above example is stored inside a storage container (container) 23 having an injection hole 21 at one end.

収納容器２３内には、噴射孔２１を開閉することができるニードルバルブ２５が配設されている。噴射孔２１には流体通路２７がニードルバルブ２５の動きに応じて連通可能になるように配設されている。この流体通路２７は外部の流体供給源に連結され、流体通路２７に常時高圧で流体が供給されている。従って、ニードルバルブ２５が噴射孔２１を開放すると、流体通路２７に供給されていた流体が外部または隣接する容器、例えば内燃機関の燃料室（図示せず）に、噴射孔２１から吐出されるように構成されている。  A needle valve 25 that can open and close the injection hole 21 is provided in the storage container 23. A fluid passage 27 is disposed in the injection hole 21 so as to be able to communicate with the movement of the needle valve 25. The fluid passage 27 is connected to an external fluid supply source, and fluid is constantly supplied to the fluid passage 27 at a high pressure. Therefore, when the needle valve 25 opens the injection hole 21, the fluid supplied to the fluid passage 27 is discharged from the injection hole 21 to the outside or an adjacent container, for example, a fuel chamber (not shown) of the internal combustion engine. It is configured.

ニードルバルブ２５の上端部は内径が大きくなっており、収納容器２３に形成されたシリンダ２９と摺動可能なピストン３１になっている。そして、収納容器２３内には、上述した例の積層型圧電素子１がピストン３１に接して収納されている。  The upper end of the needle valve 25 has a large inner diameter, and is a piston 31 that can slide with a cylinder 29 formed in the storage container 23. In the storage container 23, the multilayer piezoelectric element 1 of the above-described example is stored in contact with the piston 31.

このような噴射装置１９では、積層型圧電素１子の駆動によって噴射孔２１が開閉される。具体的には、積層型圧電素子１が電圧を印加されて伸長すると、ピストン３１が押圧され、ニードルバルブ２５が噴射孔２１に通じる流体通路２７を閉塞し、流体の供給が停止される。また、電圧の印加が停止されると積層型圧電素子１が収縮し、皿バネ３３がピストン３１を押し返し、流体通路２７が開放され噴射孔２１が流体通路２７と連通して、噴射孔２１から流体の噴射が行なわれるようになっている。  In such an injection device 19, the injection hole 21 is opened and closed by driving the laminated piezoelectric element 1. Specifically, when the multilayer piezoelectric element 1 is extended by applying a voltage, the piston 31 is pressed, the needle valve 25 closes the fluid passage 27 leading to the injection hole 21, and the supply of fluid is stopped. When the voltage application is stopped, the laminated piezoelectric element 1 contracts, the disc spring 33 pushes back the piston 31, the fluid passage 27 is opened, and the injection hole 21 communicates with the fluid passage 27. Fluid injection is performed.

なお、積層型圧電素子１に電圧を印加することによって流体通路２７を開放し、電圧の印加を停止することによって流体通路２７を閉鎖するように構成してもよい。  Note that the fluid passage 27 may be opened by applying a voltage to the multilayer piezoelectric element 1, and the fluid passage 27 may be closed by stopping the application of the voltage.

また、積層型圧電素子１が必ずしも容器２３の内部にある必要はなく、積層型圧電素子１の駆動によって容器２３の内部に流体の噴射を制御するための圧力が加わるように構成されていればよい。なお、本例の噴射装置１９において、流体とは、燃料，インク等の他、導電性ペースト等の種々の液体および気体が含まれる。本例の噴射装置１９を用いることによって、流体の流量および噴出タイミングを長期にわたって安定して制御することができる。  In addition, the multilayer piezoelectric element 1 does not necessarily have to be inside the container 23, as long as the multilayer piezoelectric element 1 is configured to apply pressure for controlling the ejection of fluid to the inside of the container 23 by driving the multilayer piezoelectric element 1. Good. In the injection device 19 of the present example, the fluid includes various liquids and gases such as conductive paste in addition to fuel, ink, and the like. By using the ejection device 19 of this example, the flow rate and ejection timing of the fluid can be stably controlled over a long period of time.

上記の例の積層型圧電素子１を採用した本例の噴射装置１９を内燃機関に用いれば、従来の噴射装置に比べてエンジン等の内燃機関の燃焼室に燃料をより長い期間にわたって精度よく噴射させることができる。  If the injection device 19 of the present example employing the multilayer piezoelectric element 1 of the above example is used for an internal combustion engine, the fuel is accurately injected into the combustion chamber of the internal combustion engine such as an engine over a longer period of time compared to the conventional injection device. Can be made.

次に、本開示の燃料噴射システムの実施の形態の例について説明する。図１３は、本実施形態の燃料噴射システムの一例を示す概略図である。  Next, an example of an embodiment of the fuel injection system according to the present disclosure will be described. FIG. 13 is a schematic diagram illustrating an example of the fuel injection system of the present embodiment.

図１３に示すように、本例の燃料噴射システム３５は、高圧流体としての高圧燃料を蓄えるコモンレール３７と、このコモンレール３７に蓄えられた高圧流体を噴射する複数の上記の例の噴射装置１９と、コモンレール３７に高圧流体を供給する圧力ポンプ３９と、噴射装置１９に駆動信号を与える噴射制御ユニット４１とを備えている。  As shown in FIG. 13, the fuel injection system 35 of the present example includes a common rail 37 that stores high-pressure fuel as a high-pressure fluid, and a plurality of injection devices 19 of the above-described examples that inject the high-pressure fluid stored in the common rail 37. A pressure pump 39 for supplying a high-pressure fluid to the common rail 37 and an injection control unit 41 for supplying a drive signal to the injection device 19 are provided.

噴射制御ユニット４１は、外部情報または外部からの信号に基づいて高圧流体の噴射の量およびタイミングを制御する。例えば、エンジンの燃料噴射に本例の燃料噴射システム３５を用いた場合であれば、エンジンの燃焼室内の状況をセンサ等で感知しながら燃料噴射の量およびタイミングを制御することができる。圧力ポンプ３９は、燃料タンク４３から流体燃料を高圧でコモンレール３７に供給する役割を果たす。例えばエンジンの燃料噴射システム３５の場合には１０００〜２０００気圧（約１０１ＭＰａ〜約２０３ＭＰａ）、好ましくは１５００〜１７００気圧（約１５２ＭＰａ〜約１７２ＭＰａ）の高圧にしてコモンレール３７に流体燃料を送り込む。コモンレール３７では、圧力ポンプ３９から送られてきた高圧燃料を蓄え、噴射装置１９に適宜送り込む。噴射装置１９は、前述したように噴射孔２１から一定の流体を外部または隣接する容器に噴射する。例えば、燃料を噴射供給する対象がエンジンの場合には、高圧燃料を噴射孔２１からエンジンの燃焼室内に霧状に噴射する。  The injection control unit 41 controls the amount and timing of high-pressure fluid injection based on external information or an external signal. For example, if the fuel injection system 35 of this example is used for engine fuel injection, the amount and timing of fuel injection can be controlled while sensing the state of the combustion chamber of the engine with a sensor or the like. The pressure pump 39 serves to supply fluid fuel from the fuel tank 43 to the common rail 37 at a high pressure. For example, in the case of an engine fuel injection system 35, fluid fuel is fed into the common rail 37 at a high pressure of 1000 to 2000 atmospheres (about 101 MPa to about 203 MPa), preferably 1500 to 1700 atmospheres (about 152 MPa to about 172 MPa). In the common rail 37, the high-pressure fuel sent from the pressure pump 39 is stored and sent to the injection device 19 as appropriate. As described above, the ejection device 19 ejects a certain fluid from the ejection holes 21 to the outside or an adjacent container. For example, when the target for injecting and supplying fuel is an engine, high-pressure fuel is injected from the injection hole 21 into the combustion chamber of the engine in the form of a mist.

本例の燃料噴射システム３５によれば、高圧燃料の所望の噴射を長期にわたって安定して行なうことができる。  According to the fuel injection system 35 of this example, desired injection of high-pressure fuel can be stably performed over a long period of time.

以下、本開示の実施例について説明する。  Hereinafter, examples of the present disclosure will be described.

積層型圧電素子を以下のようにして作製した。まず、平均粒径が０．４μｍのチタン酸ジルコン酸鉛（ＰｂＺｒＯ３−ＰｂＴｉＯ３）を主成分とする圧電セラミックスの仮焼粉末、バインダーおよび可塑剤を混合したセラミックスラリーを作製した。このセラミックスラリーを用いてドクターブレード法により厚み５０μｍの圧電体層となるセラミックグリーンシートを作製した。A multilayer piezoelectric element was produced as follows. First, a ceramic slurry was prepared by mixing a calcined powder of a piezoelectric ceramic mainly composed of lead zirconate titanate (PbZrO 3 —PbTiO 3 ) having an average particle size of 0.4 μm, a binder and a plasticizer. Using this ceramic slurry, a ceramic green sheet serving as a piezoelectric layer having a thickness of 50 μm was prepared by a doctor blade method.

次に、銀−パラジウム合金にバインダーを加えて、内部電極層となる導電性ペーストを作製した。  Next, a binder was added to the silver-palladium alloy to produce a conductive paste to be an internal electrode layer.

次に、セラミックグリーンシートの片面に、内部電極層となる導電性ペーストをスクリーン印刷法により印刷し、導電性ペーストが印刷されたセラミックグリーンシートを２００枚積層した。また、内部電極層となる導電性ペーストが印刷されたセラミックグリーンシート２００枚を中心にして、その上下に、内部電極層となる導電性ペーストが印刷されていないセラミックグリーンシート合計１５枚を積層した。そして、９８０〜１１００℃で焼成し、平面研削盤を用いて所定の形状に研削して、５ｍｍ角の積層体を得た。  Next, a conductive paste serving as an internal electrode layer was printed on one side of the ceramic green sheet by a screen printing method, and 200 ceramic green sheets printed with the conductive paste were laminated. Further, a total of 15 ceramic green sheets on which the conductive paste serving as the internal electrode layer is not printed are stacked on the top and bottom of 200 ceramic green sheets on which the conductive paste serving as the internal electrode layer is printed. . And it baked at 980-1100 degreeC, it ground to the predetermined shape using the surface grinder, and obtained the 5 mm square laminated body.

次に、積層体の表面にＡｇを含む導電性ペーストを外部電極としてスクリーン印刷により形成した。  Next, a conductive paste containing Ag was formed on the surface of the laminate by screen printing as an external electrode.

次に、図５に示す２層構造の被覆層を形成した。具体的には、ディスペンサーにて積層体の側面にシリコーンからなる樹脂を、積層体中央部の側方に幅１００μｍおよび高さ３０μｍの凸部ができるように塗布し、１５０℃で硬化させて第１の層を形成した。さらに、その上から同様にシリコーンからなる同じ樹脂を同様に塗布して第２の層を形成した。なお、第１の層における凸部を除く領域の厚みは１００μｍ、第２の層における第１の層の凸部に対応する凹部を除く領域の厚みは１５０μｍとした。  Next, a coating layer having a two-layer structure shown in FIG. 5 was formed. Specifically, a resin made of silicone is applied to the side surface of the laminate with a dispenser so that a convex portion having a width of 100 μm and a height of 30 μm is formed on the side of the central portion of the laminate, and cured at 150 ° C. One layer was formed. Furthermore, the same resin made of silicone was similarly applied from above to form a second layer. In addition, the thickness of the area | region except the convex part in a 1st layer was 100 micrometers, and the thickness of the area | region except the recessed part corresponding to the convex part of the 1st layer in the 2nd layer was 150 micrometers.

そして、外部電極に溶接で接合されたリード部材を介して、外部電極に３ｋＶ／ｍｍの直流電界を１５分間印加して、分極処理を行ない、実施例（試料１）の積層型圧電素子を作製した。  Then, a 3 kV / mm direct current electric field is applied to the external electrode for 15 minutes through a lead member joined to the external electrode by welding, and polarization treatment is performed to produce the stacked piezoelectric element of the example (sample 1). did.

一方、比較例（試料２）として、凹凸のない２層構造の被覆層を備えた積層型圧電素子を作製した。  On the other hand, as a comparative example (sample 2), a laminated piezoelectric element provided with a coating layer having a two-layer structure without unevenness was produced.

これらの積層型圧電素子に１６０Ｖの直流電圧を印加したところ、積層体の積層方向に３０μｍの変位量が得られた。  When a DC voltage of 160 V was applied to these stacked piezoelectric elements, a displacement of 30 μm was obtained in the stacking direction of the stacked body.

さらに、３０℃、９０％の湿度内で０Ｖ〜＋１６０Ｖの交流電圧を１５０Ｈｚの周波数で印加して、連続駆動した耐久性試験を行なった。  Furthermore, an endurance test was performed in which an alternating voltage of 0 V to +160 V was applied at a frequency of 150 Hz in a humidity of 30 ° C. and 90% and continuously driven.

その結果、比較例である試料２の積層型圧電素子は、１×１０５回の連続駆動で被覆層と積層体との界面にクラックが入り、内部電極層の端部が空気中に露出して放電することで変位量が低下した。As a result, the laminated piezoelectric element of Sample 2 as a comparative example cracked at the interface between the coating layer and the laminated body by 1 × 10 5 continuous driving, and the end of the internal electrode layer was exposed to the air. The amount of displacement decreased due to discharge.

これに対し、実施例である試料１の積層型圧電素子は、連続駆動１×１０７回をすぎても変位量は変わらず駆動していた。なお、駆動後にシリコンリムーバー（樹脂溶解剤）でシリコーン樹脂を溶かし、積層体の表面を観察してみたところ、内部電極層の放電の跡がなく、クラックもなかった。On the other hand, the laminated piezoelectric element of Sample 1 as an example was driven without changing the displacement even after continuous driving 1 × 10 7 times. In addition, when the silicone resin was melted with a silicon remover (resin solubilizer) after driving and the surface of the laminate was observed, there was no trace of discharge of the internal electrode layer and no cracks.

以上の結果から、本開示によれば、長期間の耐久性に優れた積層型圧電素子を実現することができることがわかる。  From the above results, it can be seen that according to the present disclosure, a multilayer piezoelectric element having excellent long-term durability can be realized.

１・・・積層型圧電素子
１０・・・積層体
１１・・・圧電体層
１２・・・内部電極層
１３・・・活性部
１４・・・不活性部
１５・・・外部電極
１６・・・被覆層
１６１・・・第１の層
１６２・・・第２の層
１６３・・・凹部
１６４・・・凸部
１７・・・リード部材DESCRIPTION OF SYMBOLS 1 ... Laminated piezoelectric element 10 ... Laminated body 11 ... Piezoelectric layer 12 ... Internal electrode layer 13 ... Active part 14 ... Inactive part 15 ... External electrode 16 ... · Coating layer 161 ··· first layer 162 ··· second layer 163 ··· concave portion 164 ··· convex portion 17 ··· lead member

Claims (5)

圧電体層および内部電極層が交互に積層された活性部および圧電体層が積層された不活性部を有する積層体と、該積層体の側面を取り囲むように設けられた被覆層とを備え、該被覆層は内側の第１の層と外側の第２の層とからなる２層構造を有しており、前記第１の層の外面が複数の凸部または複数の凹部を有しており、前記複数の凸部または前記複数の凹部が格子状に配置されている積層型圧電素子。 A laminated body having an active portion in which piezoelectric layers and internal electrode layers are alternately laminated and an inactive portion in which piezoelectric layers are laminated; and a covering layer provided so as to surround a side surface of the laminated body, the coating layer has a two-layer structure consisting of an inner first layer and an outer second layer, and an outer surface of said first layer has a plurality of protrusions or a plurality of recesses A multilayer piezoelectric element in which the plurality of convex portions or the plurality of concave portions are arranged in a lattice shape . 前記複数の凸部または前記複数の凹部が前記活性部の側方に配置されている請求項１に記載の積層型圧電素子。   The multilayer piezoelectric element according to claim 1, wherein the plurality of convex portions or the plurality of concave portions are arranged on a side of the active portion. 前記複数の凸部または前記複数の凹部が前記活性部を積層方向に３等分したときの中央部の側方に配置されている請求項２に記載の積層型圧電素子。   The multilayer piezoelectric element according to claim 2, wherein the plurality of convex portions or the plurality of concave portions are arranged on a side of a central portion when the active portion is divided into three equal parts in the stacking direction. 噴射孔を有する容器と、請求項１乃至請求項３のうちのいずれかに記載の積層型圧電素子とを備え、該積層型圧電素子の駆動によって前記噴射孔が開閉される噴射装置。 An injection apparatus comprising a container having an injection hole and the multilayer piezoelectric element according to any one of claims 1 to 3 , wherein the injection hole is opened and closed by driving the multilayer piezoelectric element. 高圧燃料を蓄えるコモンレールと、該コモンレールに蓄えられた前記高圧燃料を噴射する請求項４に記載の噴射装置と、前記コモンレールに前記高圧燃料を供給する圧力ポンプと、前記噴射装置に駆動信号を与える噴射制御ユニットとを備えた燃料噴射システム。 5. A common rail for storing high-pressure fuel; an injection device according to claim 4 for injecting the high-pressure fuel stored in the common rail; a pressure pump for supplying the high-pressure fuel to the common rail; and a drive signal for the injection device. A fuel injection system comprising an injection control unit.
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