JP2005019860A

JP2005019860A - Laminated piezoelectric element

Info

Publication number: JP2005019860A
Application number: JP2003185347A
Authority: JP
Inventors: Akio Iwase; 昭夫岩瀬; Tetsuji Ito; 鉄次伊藤; Terukazu Fukaya; 輝和深谷; Kenji Suzuki; 健治鈴木
Original assignee: Denso Corp
Current assignee: Denso Corp
Priority date: 2003-06-27
Filing date: 2003-06-27
Publication date: 2005-01-20

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated piezoelectric element which is prevented from exfoliation of an insulating coating layer. <P>SOLUTION: There are provided a piezoelectric lamination 100 wherein a piezoelectric layer 11 and internal electrode layers 121, 122 are alternately laminated, a pair of side surface electrodes 141, 142 formed on the peripheral surface 10 of the piezoelectric lamination 100, and the insulating coating layer 15 formed covering the peripheral surface 10 of the piezoelectric lamination 100 along with the side surface electrodes 141, 142 to surely insulate these from exterior. The insulating coating layer forming surface which makes contact with the insulating coating layer 15 on the peripheral surface 10 of the piezoelectric lamination 100 consists of an uneven surface. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【技術分野】
本発明は，車両用エンジンの燃料噴射用インジェクタ駆動源の圧電アクチュエータ等として使用可能な積層型圧電体素子に関する。
【０００２】
【従来技術】
積層型圧電体素子として，圧電層と内部電極層とを交互に積層してなる圧電積層体と，該圧電積層体の外周面に形成した一対の側面電極と，該側面電極ごと上記圧電積層体の外周面を覆って外部と絶縁を確保するよう形成した絶縁被覆層とを有する構成が知られている。
【０００３】
【特許文献１】
特開２００１−１３５８７２号公報
【特許文献２】
特開２００１−２４４５１４号公報
【特許文献３】
特開平５−１６０４５８号公報
【特許文献７】
特開平７−７１９３号公報
【０００４】
【解決しようとする課題】
しかしながら積層型圧電体素子は駆動時に積層方向に伸張するため，圧電積層体から絶縁被覆層の剥離が生じやすい。
特に車両用エンジンの燃料噴射用インジェクタの駆動源として積層型圧電体素子を使用する際は，使用環境温度が１５０℃〜２００℃と高温であり，圧電積層体を構成する圧電層と絶縁被覆層の熱膨張係数が異なる等，剥離しやすい条件が揃っている。
【０００５】
本発明は，かかる従来の問題点に鑑みてなされたもので，絶縁被覆層の剥離が生じ難い積層型圧電体素子を提供しようとするものである。
【０００６】
【課題の解決手段】
本発明は，圧電層と内部電極層とを交互に積層してなる圧電積層体と，該圧電積層体の外周面に形成した一対の側面電極と，該側面電極ごと上記圧電積層体の外周面を覆って外部と絶縁を確保するよう形成した絶縁被覆層とを有する積層型圧電体素子において，
上記圧電積層体の外周面で，上記絶縁被覆層と接触する絶縁被覆層形成面は凹凸面からなることを特徴とする積層型圧電体素子にある（請求項１）。
【０００７】
本発明にかかる圧電積層体の外周面で，絶縁被覆層と接触する絶縁被覆層形成面は凹凸面からなり，従って絶縁被覆層と絶縁被覆層形成面との接触面積が増え，両者の接合強度が大きくなって剥離が生じ難くなる。
また，絶縁被覆層が凹凸面の凹状となった部分に入り込むことでアンカー効果を得て，両者の接合強度が大きくなって剥離が生じ難くなる。
【０００８】
以上，本発明によれば，絶縁被覆層の剥離が生じ難い積層型圧電体素子を提供することができる。
【０００９】
【発明の実施の形態】
一般に積層型圧電体素子は，圧電層の断面形状と内部電極層の断面形状とが同程度に構成され，内部電極層の側端面が圧電積層体の外周面に露出した全面電極タイプと，圧電層の断面形状よりも内部電極層の断面形状が小さく，側面電極と電気的に導通したい内部電極層の側端面のみが圧電積層体の外周面に露出した部分電極タイプとがあるが，本発明はいずれのタイプに対しても適用することができる。なお，上記断面形状とは積層方向に略直交する方向で切断した際の断面形状である。
【００１０】
また，積層型圧電体素子として，圧電層と内部電極層とを多数枚，交互に積層して所望の高さに構成した一体型のタイプと，圧電層と内部電極層を例えば２０層や３０層等と適当な枚数で積層して圧電ユニットを作製して，該圧電ユニットを積層し，所望の高さに構成したユニット式のタイプとが知られている。
本発明は一体型，ユニット式のいずれに対しても適用することができる。
【００１１】
また，上記凹凸面における凹部や凸部は，円，楕円，十字，星型，クロス溝等，特に限定せず適当な形状で形成することができる。
また，上記凹凸面の形成は実施例にて詳述するが，レーザー加工，切削加工（圧電積層体の焼成後），型押し加工（圧電積層体の焼成前）など，種々の方法を利用することができる。
【００１２】
更に凹凸面は，絶縁被覆形成面の全面に設けることが好ましいが，部分的に設けることでも本発明の効果を得ることができる。しかし凹凸面形成の手間を考慮すると，圧電積層体の外周面の全体に設けることが好ましい。
ここに圧電積層体の外周面とは積層方向と平行な側面である。絶縁被覆層とは，内部電極層や側面電極と，積層型圧電体素子の外にある各種部材との間で絶縁を確保したり，積層型圧電体素子における沿面放電を防止するために設ける被覆材で，樹脂やゴムのモールド等で形成することができる。具体的にはシリコーンゴムやエポキシ樹脂で絶縁被覆層を形成することができる。
【００１３】
また，上記絶縁被覆層形成面の面積Ｓ０と上記凹凸面からなる絶縁被覆層形成面の表面積Ｓ１との間には，Ｓ０よりＳ１の表面積が増加するという関係が成立することが好ましい（請求項２）。
【００１４】
これにより絶縁被覆層形成面において絶縁被覆層との実質的な接触面積がより増えるため，両者の接合強度がより大きくなる。
ここに絶縁被覆層形成面の面積Ｓ０とは，絶縁被覆層形成面が凹凸面が存在しない平べったい状態であると仮定した場合の面積である。また，絶縁被覆層形成面の表面積Ｓ１とは，凹凸面に沿って測定された実質的な表面積である。
表面積の測定は、断面形状を走査型顕微鏡あるいはマイクロスコープ等にて形状を観察計測しそれを基に概略計算して算出することができる。
【００１５】
また，本発明にかかる凹凸面は，後述する図９に示すごとく平坦部が殆どなく山部と谷部とからなるパターン，図１０に示すごとく平坦部に窪みが形成されるパターン，図１１に示すごとく平坦部に突部が形成されるパターン等がある。
図９にかかるパターンにおいて，凹部は谷部からなる。図１０にかかるパターンにおいて，凹部は窪みからなる。図１１にかかるパターンにおいて，凹部は平坦部からなる。
【００１６】
そして，上記凹凸面における凹部の深さは３〜６０μｍであることが好ましい（請求項３）。
凹部の深さを上記範囲とすることで，絶縁被覆層との実質的な接触面積がより増え、さらに凹み部の接合方向が違うことから，両者の接合が有効に作用する、また絶縁被覆層が凸凹となり被覆層の弾力性も増加する効果を得ることができる。
【００１７】
また，凹部の深さとは，図９〜図１１に示すｆ１〜ｆ５のように，凸部の最高点から，該凸部に隣接する凹部の最低点との間の距離である。凸部や凹部が平坦部からなる場合は平坦部の中心位置を最高点や最低点とする。
凹部の深さが３μｍ未満である場合は，凹部の効果が小さく，またこのように浅い凹部を加工することは困難となるおそれがある。凹部の深さが６０μｍより大である場合は，表面積に対して凹部の数が小さく，本発明の効果が得難くなるおそれがある。
【００１８】
また，上記凹凸面の凸部間距離は４〜８０μｍであることが好ましい（請求項４）。
凸部間距離を上記範囲とすることで，絶縁被覆層との実質的な接触面積がより増え、さらに凹み部の接合方向が違うことから，両者の接合が有効に作用する、また絶縁被覆層が凸凹となり被覆層の弾力性も増加する作用効果を得ることができる。
【００１９】
ここに凸部間距離とは，図９〜図１１に示すＰ１〜Ｐ４のように，ある凸部の最高点から，該凸部に隣接する他の凸部における最高点との間の距離である。凸部が平坦部からなる場合は平坦部の中心位置を最高点とする。
凸部間距離が４μｍ未満である場合は，凹部の深さに対して間隔が狭くなりすぎて，凹部の加工が困難となるおそれがある。凸部間距離が８０μｍより大である場合は，表面積に比べて凹部の数が少なくなるおそれがある。
【００２０】
【実施例】
以下に，図面を用いて本発明の実施例について説明する。
（実施例１）
本発明にかかる積層型圧電体素子について，図１〜図８を用いて説明する。
本例にかかる積層型圧電体素子１は，図１に示すごとく，圧電層１１と内部電極層１２１，１２２とを交互に積層してなる圧電積層体１００と，該圧電積層体１００の外周面１０に形成した一対の側面電極１４１，１４２と，該側面電極１４１，１４２ごと上記圧電積層体１００の外周面１０を覆って外部と絶縁を確保するよう形成した絶縁被覆層１５とを有する。
そして，上記圧電積層体１００の外周面１０で，上記絶縁被覆層１５と接触する絶縁被覆層形成面は凹凸面からなる。
【００２１】
以下，詳細に説明する。
本例にかかる積層型圧電体素子１は，ディーゼルエンジンの燃料噴射用インジェクタの駆動源として用いるもので，図６に示すごとき側面電極１４１，１４２を有する積層型圧電体素子１を図７に示す封入ホルダー３を組み込んでレーザー溶接にて封入し，図８に示すごとくディーゼルエンジン用のインジェクタ４に組み付ける。
【００２２】
封入ホルダー３は，図７に示すごとく，内部に積層型圧電体素子１を組み付ける封入筒３４と，該封入筒３４の端部には，底部材３１と外周をベローズパイプ３３で覆われた伝達棒３２を設ける。封入筒３４のもう一方の端部には，内部に電極３６１を配置した電極ユニット３６を差し込む。電極ユニット３６の側面には取り付けナット３７を配置する。また，電極ユニット３６の端部にはコネクタ３８を設けて，該コネクタ３８を図示を略した電源装置に取り付ける。
また，封入筒３４は図８（ｂ）に示すような形状である。
【００２３】
封入ホルダ３を収納するインジェクタ４は，図８に示すごとく，インジェクタ４の中空筒型のボデー４３に封入ホルダ３が導入され，封入ホルダ３の図面下方にはピストン４２が内蔵されたシリンダ４１が配置され，ボデー４３の図面上方における側面から突出して燃料口４４が設けてある。
なお，インジェクタ４に対する封入ホルダ３の組み付けは上記取り付けナット３７によって行う。
【００２４】
そして，図１〜図５に示すごとく，本例の積層型圧電体素子１における圧電積層体１００は，断面がたる型の圧電層１１と，該圧電層１１と同じ断面形状を備えた内部電極層１２１，１２２とを交互に積層してなる。
圧電積層体１００の外周面１０は対向する平面部分１０１，１０２と対向する曲面部分１０３，１０４とからなり，平面部分１０１，１０２に側面電極１４１，１４２を配置する。
上記平面部分１０１，１０２に側面電極１４１，１４２を形成する前に，平面部分１０１に露出する内部電極層１２１，１２２の側端面１２３，１２４のうち，内部電極層１２２の側端面１２４を絶縁層１３１で覆って，内部電極層１２１と側面電極１４１とが導通するように構成する。
【００２５】
また，平面部分１０２に露出する内部電極層１２１，１２２の側端面１２３，１２４のうち，内部電極層１２１の側端面１２３を絶縁層１３２で覆って，内部電極層１２２と側面電極１４２とが導通するように構成する。
これによって，側面電極１４１と側面電極１４２とを異なる電位として，圧電層１１に電圧を印加した際に，圧電層１１が印加した電圧の大きさに応じて伸張して，積層型圧電体素子１を駆動することができる。
【００２６】
本例において，外周面１０における絶縁層１３１，１３２と側面電極１４１，１４２とを設けてない部分が絶縁被覆層形成面となるが，該絶縁被覆層形成面のみに凹凸面２１を設けるのは製造工程上面倒であるため，上記圧電積層体１００の外周面１０の全体が，図３〜図５に示すごとく，平坦部２１２と窪み２１１とからなる凹凸面２１になっている。窪み２１の開口形状は略円形である。
そして，上記圧電積層体１００の外周面１０と絶縁層１３１，１３２と，側面電極１４１，１４２とが絶縁被覆層１５で覆われ，圧電積層体１００の積層方向の端面は絶縁被覆層１５で覆われていない。
【００２７】
そして，図５に示すごとく，本例にかかる凹凸面２１における凹部とは，窪み２１１からなり，その深さはｆ１，ｆ２・・・等であり，略２０μｍである。
また，図５に示すごとく，本例にかかる凹凸面２１における凸部間距離は，平坦部２１２の中央から隣接する別の平坦部２１２の中央への距離であり，例えばＰ１，Ｐ２・・・・等であり，略３０μｍである。
なお，これらの深さや凸部間距離は絶縁層１３１，１３２や側面電極１４１，１４２を形成する前の圧電積層体１００の状態において，外周面や外周面を含む断面を走査型電子顕微鏡等で観察して測定した。
【００２８】
また，本例にかかる絶縁被覆層形成面の面積Ｓ０は絶縁被覆層形成面の表面積Ｓ１が概算で約２倍に増加していた。
表面積Ｓ１の測定は，断面形状を走査型電子顕微鏡やマイクロスコープ等を用いて観察計測し，それに基いて概略計算から算出した。
面積Ｓ０は積層型圧電体素子１の寸法から算出した。
【００２９】
本例にかかる積層型圧電体素子１において，圧電積層体１００の外周面１０で，絶縁被覆層１５と接触する絶縁被覆層形成面は凹凸面２１からなり，従って絶縁被覆層１５と絶縁被覆層形成面との接触面積が増え，両者の接合強度が大きくなって剥離が生じ難くなる。
また，絶縁被覆層１５が凹凸面２１の凹部に入り込むことでアンカー効果を得て，両者の接合強度が大きくなって剥離が生じ難くなる。
更に，凹凸面２１を外周面１０に設けた分，内部電極層１２１，１２２における側端面１２３と１２４との間の経路長が長くなり，これら側端面１２３，１２４間の沿面放電が生じ難くなる。
以上，本例によれば，絶縁被覆層の剥離が生じ難い積層型圧電体素子を提供することができる。
【００３０】
（実施例２）
本例は圧電積層体の外周面に設けた各種の凹凸面２２〜２４について説明する。
図９に示すごとく，外周面に垂直な断面において平坦部が殆どなく山部２２２と谷部２２１とが交互に繰り返されるような凹凸面２２がある。山部２２２が凸部に，谷部２２１が凹部となる。凹部の深さは同図に記載したｆ１，ｆ２・・・となり，凸部間距離は山部２２２の頂点と谷部２２１を挟んで隣接する別の山部２２２の頂点との距離で，同図に記載したＰ１，Ｐ２・・・となる。
【００３１】
また，図１０に示すごとく，外周面に垂直な断面において平坦部２３２と該平坦部２３２から後退した窪み２３１とからなる凹凸面２３がある。平坦部２３２が凸部に，窪み２３１が凹部となる。凹部の深さは同図に記載したｆ１，ｆ２・・・となり，凸部間距離は平坦部２３２の中央と，窪み２３１を一つ挟んで隣接する他の平坦部２３２の中央との最短距離で，同図に記載したＰ１，Ｐ２・・・となる。
【００３２】
また，図１１に示すごとく，外周面に垂直な断面において平坦部２４１と該平坦部２４１から突出した突部２４２とからなる凹凸面２４がある。平坦部２４１が凹部に，突部２４２が凹部となる。凹部の深さは突部２４２の最高点から平坦部２４１までの距離であり，ｆ１，ｆ２・・・となる。また，凸部間距離は突部２４２の最高点から平坦部２４１を挟んで隣接する別の突部２４２の最高点との最短距離で，同図に記載したＰ１，Ｐ２・・・となる。
【００３３】
上記いずれのタイプの凹凸面２２〜２４を外周面に設けた場合であっても，実施例１と同様に，絶縁被覆層と外周面における絶縁被覆層形成面との接触面積が増え，両者の接合強度が大きくなって剥離が生じ難くなる。
その他詳細は実施例１の作用効果を有する。
【００３４】
（実施例３）
本例は圧電積層体の外周面に設けた凹凸面２１における窪み２１１の形状が異なるものについて説明する。
図１２に示すごとく，断面がたる型の圧電積層体１０において，外周面１０に平坦部２１２と窪み２１１とからなる凹凸面２１が形成され，窪み２１の開口形状は長円形である。また，図１３に示すごとく，断面がたる型の圧電積層体１０において，外周面１０に平坦部２１２と窪み２１１とからなる凹凸面２１が形成され，窪み２１の開口形状は十字型である。また，図１４に示すごとく，断面がたる型の圧電積層体１０において，外周面１０に平坦部２１２と窪み２１１とからなる凹凸面２１が形成され，窪み２１はクロス溝からなる。
【００３５】
上記いずれのタイプの凹凸面２１を外周面に設けた場合であっても，実施例１と同様に，絶縁被覆層と外周面における絶縁被覆層形成面との接触面積が増え，両者の接合強度が大きくなって剥離が生じ難くなる。
その他詳細は実施例１の作用効果を有する。
なお，実施例１も本例も，各窪み２１１は略同形状で，略同寸法で，規則正しく設けてあるが，窪みの形状や大きさ等が不均一で，ランダムに設けて形成した凹凸面であっても，実施例１にかかる作用効果を得ることができる。
【００３６】
（実施例４）
図１５に示すごとく，積層型圧電体素子を構成する圧電積層体１００として，断面形状が正方形の圧電層１１と内部電極層１２１，１２２を交互に積層してなるものを用いることができる。
圧電層１１や内部電極層１２１，１２２の断面形状にかかわらず，外周面１０に凹凸面を設けることで，実施例１と同様に，絶縁被覆層と外周面における絶縁被覆層形成面との接触面積が増え，両者の接合強度が大きくなって剥離が生じ難くなる。
その他詳細は実施例１の作用効果を有する。
【００３７】
（実施例５）
本例は，図１７に示す圧電積層体１０からなる積層型圧電体素子の製造方法について説明する。図１７に示す圧電積層体１０は，外周面１０に平坦部が殆どなく山部２２２と谷部２２１とが交互に繰り返されるような凹凸面２２を有する。
【００３８】
次に，製造方法について説明する。
まず，チタン酸ジルコン酸鉛に所定量の有機バインダ及び溶剤を混合してスラリーを作製し，ドクターブレード法により圧電層用のグリーンシートとする。グリーンシートに銀・パラジウムのペーストをスクリーン印刷法により塗布して内部電極層用の印刷部を形成し，乾燥する。その後，チタン酸ジルコン酸鉛を含む接着用スラリーを印刷部の上から塗布し，上記印刷部付きグリーンシートを所定形状に打ち抜くと共に所定枚数を積層して，プレスして圧着する。その後，５００℃で数百時間電気炉中に保持し脱バインダを行って，約１２００℃数時間の条件で焼成し，図１６に示すごとき積層焼結体４９を得る。
【００３９】
この積層焼結体４９の外周面４９０に図１７に示すごとき凹凸面２２を図１８に示すレーザー加工機４を用いて形成する。
このレーザー加工機４は，パルスレーザーを発信するレーザー発信器４１と該レーザー発信器４１から発信されたレーザー４０のビーム径を拡張するビームエキスパンダ４２と，該ビームエキスパンダ４２を通過したレーザー４０をミラーにより反射する２台のガルバノメーター４３１，４３２とを有し，最後のガルバノメーター４３１，４３２を通過したレーザー４０を集光レンズ４４で収束させ，外周面４９０に当てて，ここに窪みを多数形成して，図１７に示すごとく，凹凸面２２を有する外周面１０を備えた圧電積層体１００となす。
【００４０】
ここで，レーザー４０の照射法について説明すると，図１９（ａ）に示すごとく，外周面４９０に破線４９０で示した部分を除去するように，略等間隔にレーザー４０を照射する。図１９（ｂ）に示すごとく，第１の窪み４９２を形成した後，該窪み４９２間の平坦な領域に対し，図１９（ｃ）に示すごとく，破線４９３で示した部分を除去するように，再びレーザー４０を照射する。その結果，図１９（ｄ）に示すように，第１の窪み４９２の間に第２の窪み４９４を得る。
このようにして，図１７に示すごとき圧電積層体１００を得た。
【００４１】
次いで，上記圧電積層体１００について，内部電極層を一層おきに側面電極に接続することができるように（詳細は実施例１参照），外周面の平面部分に露出した内部電極層の側端部に対して，電気泳動法により一層おきにガラス粉末を被着させ，約６００℃で熱処理し，絶縁層を形成する（図１参照）。
その後，絶縁層で覆われていない側端部を電気的に接続するように，波形状に加工したステンレス材からなる板状の側面電極を導電性接着剤を用いて接着する。
これにより実施例１等に示すような積層型圧電体素子を得た。
【００４２】
また，図２０に示すように，外周面４９０に形成したい凹凸面の形状の雛形となるマスク４５を置いて，マスク４５を介してレーザー４０を照射することもできる。
この場合は，例えば，実施例１の図３に示すような凹凸面を得ることができる。
【００４３】
いずれにしても本例にかかる製造方法によれば，圧電積層体の外周面で，絶縁被覆層と接触する絶縁被覆層形成面は凹凸面からなり，従って絶縁被覆層と絶縁被覆層形成面との接触面積が増え，両者の接合強度が大きくなって，絶縁被覆層の剥離が生じ難い積層型圧電体素子を得ることができる。
【００４４】
（実施例６）
本例は，圧電積層体を焼成する前に凹凸面を形成する方法について説明する。すなわち，まず，チタン酸ジルコン酸鉛に所定量の有機バインダ及び溶剤を混合してスラリーを作製し，ドクターブレード法により圧電層用のグリーンシートとする。グリーンシートに銀・パラジウムのペーストをスクリーン印刷法により塗布して内部電極層用の印刷部を形成し，乾燥する。その後，チタン酸ジルコン酸鉛を含む接着用スラリーを印刷部の上から塗布し，上記印刷部付きグリーンシートを所定形状に打ち抜くと共に所定枚数を積層して，プレスして圧着して，圧着体を得る。
【００４５】
続いて，図２１に示すごとく，回転ホルダー５２１で支持され，外表面に多数の突起５２２を備えた回転部５２３からなる凹凸面形成用ローラー５２を準備する。
そして圧着体５８の積層方向の両端面を回転ホルダー５１で支持する。回転部５２３を圧着体５８の未乾燥の外表面５８０に押し当てる。回転ホルダー５１ごと圧着体５８を矢線Ｒ１の方向に，該Ｒ１と反対方向の矢線Ｒ２の方向に凹凸面形成用ローラー５２を回転する。これにより，外表面５８０は突起５２２に押されて，多数の窪みが形成される。
その後，圧着体を乾燥させ，５００℃で数百時間電気炉中に保持し脱バインダを行って，約１２００℃数時間の条件で焼成し，前述した図１６に示すごとき積層焼結体４９を得る。
この積層焼結体４９から本発明にかかる積層型圧電体素子を製造することができる。
【００４６】
または，図２２，図２３に示すように，静止した圧着体５９の外表面５９０に対し，凹凸面形成用ローラー５２を矢線Ｒ３方向に回転させつつ，外表面５９０と平行方向に矢線Ｒ４に沿って移動させ，突起５２２によって外表面５９０に多数の窪みを形成した。
その後，圧着体を乾燥させ，５００℃で数百時間電気炉中に保持し脱バインダを行って，約１２００℃数時間の条件で焼成し，前述した図１６に示すごとき積層焼結体４９を得る。この積層焼結体４９から本発明にかかる積層型圧電体素子を製造することができる。
なお，ここで示した圧着体５９は断面形状が正方形で，外表面５９０は直方体の４つの側面からなる。
【００４７】
以上，本例にかかる製造方法によれば，圧電積層体の外周面で，絶縁被覆層と接触する絶縁被覆層形成面は凹凸面からなり，従って絶縁被覆層と絶縁被覆層形成面との接触面積が増え，両者の接合強度が大きくなって，絶縁被覆層の剥離が生じ難い積層型圧電体素子を得ることができる。
【図面の簡単な説明】
【図１】実施例１における，積層型圧電体素子の要部斜視図。
【図２】実施例１における，積層型圧電体素子の積層方向に沿った断面の説明図。
【図３】実施例１における，外周面に凹凸面を設けた圧電積層体の説明図。
【図４】実施例１における，外周面に凹凸面を設けた圧電積層体の積層方向に沿った断面の説明図。
【図５】実施例１における，凹凸面の説明図。
【図６】実施例１における，積層型圧電体素子の斜視図。
【図７】実施例１における，積層型圧電体素子を組み込んだ封入ホルダーの説明図。
【図８】実施例１における，積層型圧電体素子を組み込んだディーゼルエンジン用インジェクタの説明図。
【図９】実施例２における，山部と谷部とが交互に繰り返される凹凸面の説明図。
【図１０】実施例２における，平坦部と該平坦部から後退した窪みとからなる凹凸面の説明図。
【図１１】実施例２における，平坦部と該平坦部から突出した突部とからなる凹凸面の説明図。
【図１２】実施例３における，窪みの形状が長円形からなる凹凸面を外周面に設けた圧電積層体の説明図。
【図１３】実施例３における，窪みの形状が十字型からなる凹凸面を外周面に設けた圧電積層体の説明図。
【図１４】実施例３における，窪みの形状がクロス溝からなる凹凸面を外周面に設けた圧電積層体の説明図。
【図１５】実施例４における，断面形状が正方形の圧電積層体の斜視図。
【図１６】実施例５における，積層焼結体の説明図。
【図１７】実施例５における，圧電積層体と外周面の凹凸面の状態を示す断面説明図。
【図１８】実施例５における，レーザー加工機の構成を示す線図。
【図１９】実施例５における，レーザーによる凹凸面の形成に関する説明図。
【図２０】実施例５における，マスクを用いたレーザー加工機の構成を示す線図。
【図２１】実施例６における，凹凸面形成用ローラーによる未焼成の圧着体に対する窪み形成の説明図。
【図２２】実施例６における，凹凸面形成用ローラーによる未焼成の断面正方形の圧着体に対する窪み形成の説明図。
【図２３】実施例６における，凹凸面形成用ローラーによる未焼成の断面正方形の圧着体に対する窪み形成の説明図。
【符号の説明】
１．．．積層型圧電体素子，
１０．．．外表面，
１００．．．圧電積層体，
１１．．．圧電層，
１２１，１２２．．．内部電極層，
１４１，１４２．．．側面電極層，
１５．．．絶縁被覆層，
２１．．．凹凸面，[0001]
【Technical field】
The present invention relates to a multilayer piezoelectric element that can be used as a piezoelectric actuator or the like of an injector drive source for fuel injection of a vehicle engine.
[0002]
[Prior art]
As a laminated piezoelectric element, a piezoelectric laminated body in which piezoelectric layers and internal electrode layers are alternately laminated, a pair of side electrodes formed on the outer peripheral surface of the piezoelectric laminated body, and the piezoelectric laminated body together with the side electrodes The structure which has the insulation coating layer which covered the outer peripheral surface of this and was formed so that insulation was ensured with the exterior is known.
[0003]
[Patent Document 1]
JP 2001-135872 A [Patent Document 2]
JP 2001-244514 A [Patent Document 3]
JP-A-5-160458 [Patent Document 7]
Japanese Patent Application Laid-Open No. 7-7193
[Problems to be solved]
However, since the laminated piezoelectric element expands in the laminating direction when driven, the insulating coating layer is easily peeled off from the piezoelectric laminated body.
In particular, when a laminated piezoelectric element is used as a drive source for a fuel injection injector of a vehicle engine, the operating environment temperature is as high as 150 ° C. to 200 ° C., and the piezoelectric layer and the insulating coating layer constituting the piezoelectric laminated body Conditions that are easy to peel off, such as different thermal expansion coefficients, are available.
[0005]
The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a multilayer piezoelectric element in which an insulating coating layer is hardly peeled off.
[0006]
[Means for solving problems]
The present invention provides a piezoelectric laminate in which piezoelectric layers and internal electrode layers are alternately laminated, a pair of side electrodes formed on the outer peripheral surface of the piezoelectric laminate, and the outer peripheral surface of the piezoelectric laminate together with the side electrodes. A laminated piezoelectric element having an insulation coating layer formed to cover the outside and to ensure insulation;
The laminated piezoelectric element is characterized in that, on the outer peripheral surface of the piezoelectric laminate, the insulating coating layer forming surface that comes into contact with the insulating coating layer is an uneven surface.
[0007]
In the outer peripheral surface of the piezoelectric laminate according to the present invention, the insulating coating layer forming surface that is in contact with the insulating coating layer is an uneven surface, so that the contact area between the insulating coating layer and the insulating coating layer forming surface is increased, and the bonding strength between the two is increased. Becomes larger and peeling is less likely to occur.
In addition, the anchoring effect is obtained by the insulating coating layer entering the concave portion of the concavo-convex surface, and the joint strength between the two is increased, so that the separation hardly occurs.
[0008]
As described above, according to the present invention, it is possible to provide a multilayer piezoelectric element in which the insulation coating layer hardly peels off.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In general, a laminated piezoelectric element has a cross-sectional shape of a piezoelectric layer and a cross-sectional shape of an internal electrode layer, and a side electrode surface of the internal electrode layer is exposed on the outer peripheral surface of the piezoelectric laminated body. There is a partial electrode type in which the cross-sectional shape of the internal electrode layer is smaller than the cross-sectional shape of the layer, and only the side end surface of the internal electrode layer that is to be electrically connected to the side electrode is exposed on the outer peripheral surface of the piezoelectric laminate. Can be applied to any type. In addition, the said cross-sectional shape is a cross-sectional shape at the time of cut | disconnecting in the direction substantially orthogonal to the lamination direction.
[0010]
In addition, as the laminated piezoelectric element, an integrated type in which a large number of piezoelectric layers and internal electrode layers are alternately laminated to have a desired height, and 20 or 30 piezoelectric layers and internal electrode layers are formed, for example. There is known a unit type in which a piezoelectric unit is manufactured by laminating an appropriate number of layers and the like, and the piezoelectric units are laminated to have a desired height.
The present invention can be applied to both an integral type and a unit type.
[0011]
In addition, the concave and convex portions on the concave and convex surface can be formed in an appropriate shape without particular limitation, such as a circle, an ellipse, a cross, a star shape, and a cross groove.
In addition, although the formation of the uneven surface is described in detail in the examples, various methods such as laser processing, cutting (after firing the piezoelectric laminate), embossing (before firing the piezoelectric laminate), etc. are used. be able to.
[0012]
Further, the uneven surface is preferably provided on the entire surface of the insulating coating forming surface, but the effect of the present invention can also be obtained by providing it partially. However, considering the trouble of forming the uneven surface, it is preferable to provide the entire outer peripheral surface of the piezoelectric laminate.
Here, the outer peripheral surface of the piezoelectric laminate is a side surface parallel to the lamination direction. An insulation coating layer is a coating provided to ensure insulation between internal electrode layers and side electrodes and various members outside the multilayer piezoelectric element, and to prevent creeping discharge in the multilayer piezoelectric element. It can be formed of a material such as a resin or rubber mold. Specifically, the insulating coating layer can be formed of silicone rubber or epoxy resin.
[0013]
Further, it is preferable that the relationship that the surface area of S1 is increased from S0 is established between the area S0 of the insulating coating layer forming surface and the surface area S1 of the insulating coating layer forming surface composed of the uneven surface. 2).
[0014]
As a result, the substantial contact area with the insulating coating layer on the surface of the insulating coating layer is increased, so that the bonding strength between the two is increased.
Here, the area S0 of the insulating coating layer forming surface is an area when it is assumed that the insulating coating layer forming surface is flat without an uneven surface. The surface area S1 of the insulating coating layer forming surface is a substantial surface area measured along the uneven surface.
The surface area can be calculated by observing and measuring the cross-sectional shape with a scanning microscope or a microscope and roughly calculating the cross-sectional shape.
[0015]
Further, the uneven surface according to the present invention has a pattern having almost no flat portion as shown in FIG. 9 to be described later, and a pattern composed of peaks and valleys, a pattern in which depressions are formed in the flat portion as shown in FIG. As shown, there are patterns in which protrusions are formed on flat portions.
In the pattern according to FIG. 9, the concave portion is formed by a valley portion. In the pattern according to FIG. 10, the concave portion is a depression. In the pattern according to FIG. 11, the concave portion is a flat portion.
[0016]
And it is preferable that the depth of the recessed part in the said uneven surface is 3-60 micrometers (Claim 3).
By setting the depth of the recess in the above range, the substantial contact area with the insulating coating layer is further increased, and the bonding direction of the concave portion is different, so that the bonding of both functions effectively, and the insulating coating layer As a result, the effect of increasing the elasticity of the coating layer can be obtained.
[0017]
Moreover, the depth of a recessed part is the distance between the highest point of a convex part and the lowest point of the recessed part adjacent to this convex part like f1-f5 shown in FIGS. When a convex part or a recessed part consists of a flat part, let the center position of a flat part be the highest point or the lowest point.
When the depth of the recess is less than 3 μm, the effect of the recess is small, and it may be difficult to process such a shallow recess. When the depth of the recess is greater than 60 μm, the number of recesses is small with respect to the surface area, and it may be difficult to obtain the effect of the present invention.
[0018]
Moreover, it is preferable that the distance between convex parts of the said uneven surface is 4-80 micrometers.
By making the distance between the convex portions within the above range, the substantial contact area with the insulating coating layer is further increased, and the bonding direction of the concave portions is different, so that the bonding between the two functions effectively, and the insulating coating layer As a result, the effect of increasing the elasticity of the coating layer can be obtained.
[0019]
Here, the distance between the convex portions is a distance between the highest point of a certain convex portion and the highest point of other convex portions adjacent to the convex portion, as in P1 to P4 shown in FIGS. is there. When a convex part consists of a flat part, let the center position of a flat part be the highest point.
When the distance between the convex portions is less than 4 μm, the interval becomes too narrow with respect to the depth of the concave portion, and it may be difficult to process the concave portion. When the distance between convex parts is larger than 80 micrometers, there exists a possibility that the number of recessed parts may decrease compared with a surface area.
[0020]
【Example】
Embodiments of the present invention will be described below with reference to the drawings.
(Example 1)
The laminated piezoelectric element according to the present invention will be described with reference to FIGS.
As shown in FIG. 1, the multilayer piezoelectric element 1 according to this example includes a piezoelectric multilayer body 100 in which piezoelectric layers 11 and internal electrode layers 121 and 122 are alternately stacked, and an outer peripheral surface of the piezoelectric multilayer body 100. 10 and a pair of side surface electrodes 141 and 142, and an insulating coating layer 15 that covers the outer peripheral surface 10 of the piezoelectric laminate 100 together with the side surface electrodes 141 and 142 so as to ensure insulation from the outside.
And the insulating coating layer forming surface which contacts the said insulating coating layer 15 in the outer peripheral surface 10 of the said piezoelectric laminated body 100 consists of an uneven surface.
[0021]
This will be described in detail below.
The multilayer piezoelectric element 1 according to this example is used as a drive source for a fuel injection injector of a diesel engine. The multilayer piezoelectric element 1 having side electrodes 141 and 142 as shown in FIG. 6 is shown in FIG. The enclosure holder 3 is assembled and sealed by laser welding, and is assembled to the injector 4 for a diesel engine as shown in FIG.
[0022]
As shown in FIG. 7, the enclosing holder 3 includes an enclosing cylinder 34 for assembling the laminated piezoelectric element 1 therein, and a transmission having a bottom member 31 and an outer periphery covered with a bellows pipe 33 at the end of the enclosing cylinder 34. A bar 32 is provided. An electrode unit 36 having an electrode 361 disposed therein is inserted into the other end of the enclosing cylinder 34. A mounting nut 37 is disposed on the side surface of the electrode unit 36. A connector 38 is provided at the end of the electrode unit 36, and the connector 38 is attached to a power supply device (not shown).
The enclosing cylinder 34 has a shape as shown in FIG.
[0023]
As shown in FIG. 8, the injector 4 for housing the enclosure holder 3 is introduced into a hollow cylindrical body 43 of the injector 4, and a cylinder 41 with a built-in piston 42 is provided below the enclosure holder 3 in the drawing. The fuel port 44 is provided so as to protrude from the side surface of the body 43 above the drawing.
The assembly holder 3 is assembled to the injector 4 by the mounting nut 37.
[0024]
As shown in FIGS. 1 to 5, the piezoelectric laminated body 100 in the laminated piezoelectric element 1 of this example includes a piezoelectric layer 11 having a cross-sectional shape and an internal electrode having the same cross-sectional shape as the piezoelectric layer 11. Layers 121 and 122 are alternately stacked.
The outer peripheral surface 10 of the piezoelectric laminate 100 is composed of opposing flat portions 101 and 102 and opposing curved surface portions 103 and 104, and side electrodes 141 and 142 are disposed on the flat portions 101 and 102.
Before the side electrodes 141 and 142 are formed on the planar portions 101 and 102, the side end surfaces 124 of the internal electrode layers 122 out of the side end surfaces 123 and 124 of the internal electrode layers 121 and 122 exposed on the planar portion 101 are insulating layers. 131, and the internal electrode layer 121 and the side electrode 141 are electrically connected.
[0025]
In addition, of the side end surfaces 123 and 124 of the internal electrode layers 121 and 122 exposed to the planar portion 102, the side end surface 123 of the internal electrode layer 121 is covered with the insulating layer 132, and the internal electrode layer 122 and the side electrode 142 are electrically connected. To be configured.
Accordingly, when the side electrode 141 and the side electrode 142 are set to different potentials and a voltage is applied to the piezoelectric layer 11, the piezoelectric layer 11 expands in accordance with the magnitude of the applied voltage, and the stacked piezoelectric element 1 Can be driven.
[0026]
In this example, the portion of the outer peripheral surface 10 where the insulating layers 131 and 132 and the side electrodes 141 and 142 are not provided becomes the insulating coating layer forming surface, but the uneven surface 21 is provided only on the insulating coating layer forming surface. Since the manufacturing process is overlying, the entire outer peripheral surface 10 of the piezoelectric laminate 100 is an uneven surface 21 composed of a flat portion 212 and a recess 211 as shown in FIGS. The opening shape of the recess 21 is substantially circular.
The outer peripheral surface 10, the insulating layers 131 and 132, and the side electrodes 141 and 142 of the piezoelectric laminate 100 are covered with the insulating coating layer 15, and the end surface in the stacking direction of the piezoelectric laminate 100 is covered with the insulating coating layer 15. I have not been told.
[0027]
And as shown in FIG. 5, the recessed part in the uneven surface 21 concerning this example consists of the hollow 211, The depth is f1, f2, ..., etc., and is about 20 micrometers.
Further, as shown in FIG. 5, the distance between the convex portions on the uneven surface 21 according to this example is a distance from the center of the flat portion 212 to the center of another flat portion 212 adjacent thereto, for example, P1, P2,. -It is about 30 μm.
Note that these depths and the distances between the protrusions are measured with a scanning electron microscope or the like in the state of the piezoelectric laminate 100 before forming the insulating layers 131 and 132 and the side electrodes 141 and 142 using a scanning electron microscope or the like. Observed and measured.
[0028]
In addition, the area S0 of the insulating coating layer forming surface according to this example was approximately double the surface area S1 of the insulating coating layer forming surface.
The surface area S1 was measured by observing and measuring the cross-sectional shape using a scanning electron microscope, a microscope, or the like, and calculating from the rough calculation based on the measurement.
The area S0 was calculated from the dimensions of the multilayer piezoelectric element 1.
[0029]
In the multilayer piezoelectric element 1 according to the present example, the insulating coating layer forming surface that comes into contact with the insulating coating layer 15 on the outer peripheral surface 10 of the piezoelectric multilayer body 100 is composed of the uneven surface 21. The contact area with the forming surface increases, and the bonding strength between the two increases, making it difficult for separation to occur.
Further, the insulating coating layer 15 enters the concave portion of the concave and convex surface 21 to obtain an anchor effect, and the bonding strength between the two becomes large, so that the peeling hardly occurs.
Further, since the uneven surface 21 is provided on the outer peripheral surface 10, the path length between the side end surfaces 123 and 124 in the internal electrode layers 121 and 122 becomes longer, and the creeping discharge between these side end surfaces 123 and 124 hardly occurs. .
As described above, according to this example, it is possible to provide a multilayer piezoelectric element in which the insulation coating layer hardly peels off.
[0030]
(Example 2)
In this example, various uneven surfaces 22 to 24 provided on the outer peripheral surface of the piezoelectric laminate will be described.
As shown in FIG. 9, there is an uneven surface 22 in which there are almost no flat portions in a cross section perpendicular to the outer peripheral surface, and the peak portions 222 and the valley portions 221 are alternately repeated. The peak portion 222 is a convex portion, and the valley portion 221 is a concave portion. The depths of the recesses are f1, f2,... Shown in the figure, and the distance between the protrusions is the distance between the apex of the peak 222 and the apex of another peak 222 adjacent to the valley 221. P1, P2... Described in the figure.
[0031]
Further, as shown in FIG. 10, there is an uneven surface 23 composed of a flat portion 232 and a recess 231 retreated from the flat portion 232 in a cross section perpendicular to the outer peripheral surface. The flat part 232 becomes a convex part, and the hollow 231 becomes a concave part. The depths of the recesses are f1, f2,... Shown in the figure, and the distance between the protrusions is the shortest distance between the center of the flat part 232 and the center of another flat part 232 adjacent to each other with one recess 231 in between. Thus, P1, P2,.
[0032]
In addition, as shown in FIG. 11, there is an uneven surface 24 composed of a flat portion 241 and a protrusion 242 protruding from the flat portion 241 in a cross section perpendicular to the outer peripheral surface. The flat portion 241 becomes a concave portion and the protrusion 242 becomes a concave portion. The depth of the recess is the distance from the highest point of the protrusion 242 to the flat portion 241 and is f1, f2,. Further, the distance between the convex portions is the shortest distance from the highest point of the protruding portion 242 to the highest point of another protruding portion 242 adjacent to the flat portion 241 and is P1, P2,.
[0033]
Even when any of the above-described uneven surfaces 22 to 24 is provided on the outer peripheral surface, as in Example 1, the contact area between the insulating coating layer and the insulating coating layer forming surface on the outer peripheral surface increases. Bonding strength increases and peeling is less likely to occur.
Other details have the effects of the first embodiment.
[0034]
Example 3
In this example, a case where the shape of the recess 211 in the uneven surface 21 provided on the outer peripheral surface of the piezoelectric laminate is different will be described.
As shown in FIG. 12, in the piezoelectric laminate 10 having a barrel-shaped cross section, an uneven surface 21 including a flat portion 212 and a recess 211 is formed on the outer peripheral surface 10, and the opening shape of the recess 21 is an oval. Further, as shown in FIG. 13, in the piezoelectric laminated body 10 having a cross section, an uneven surface 21 including a flat portion 212 and a recess 211 is formed on the outer peripheral surface 10, and the opening shape of the recess 21 is a cross shape. Further, as shown in FIG. 14, in the piezoelectric laminated body 10 having a cross section, an uneven surface 21 including a flat portion 212 and a recess 211 is formed on the outer peripheral surface 10, and the recess 21 is formed of a cross groove.
[0035]
In any case where the uneven surface 21 of any type is provided on the outer peripheral surface, as in Example 1, the contact area between the insulating coating layer and the insulating coating layer forming surface on the outer peripheral surface is increased, and the bonding strength between the two is increased. Becomes larger and peeling is less likely to occur.
Other details have the effects of the first embodiment.
In each of Example 1 and this example, each of the recesses 211 is substantially the same shape, approximately the same size, and regularly provided. However, the shape and size of the recesses are not uniform, and the uneven surface is formed randomly. Even so, the operational effects of the first embodiment can be obtained.
[0036]
(Example 4)
As shown in FIG. 15, as the piezoelectric laminate 100 constituting the multilayer piezoelectric element, a laminate in which the piezoelectric layers 11 having the square cross section and the internal electrode layers 121 and 122 are alternately laminated can be used.
Regardless of the cross-sectional shape of the piezoelectric layer 11 and the internal electrode layers 121 and 122, by providing an uneven surface on the outer peripheral surface 10, contact between the insulating coating layer and the insulating coating layer forming surface on the outer peripheral surface is the same as in Example 1. The area increases, the joint strength between the two increases, and peeling does not easily occur.
Other details have the effects of the first embodiment.
[0037]
(Example 5)
In this example, a method of manufacturing a multilayer piezoelectric element composed of the piezoelectric multilayer body 10 shown in FIG. 17 will be described. The piezoelectric laminate 10 shown in FIG. 17 has an uneven surface 22 in which there are almost no flat portions on the outer peripheral surface 10 and the ridges 222 and the valleys 221 are alternately repeated.
[0038]
Next, the manufacturing method will be described.
First, a slurry is prepared by mixing a predetermined amount of an organic binder and a solvent with lead zirconate titanate, and a green sheet for a piezoelectric layer is obtained by a doctor blade method. A silver / palladium paste is applied to the green sheet by screen printing to form a printed part for the internal electrode layer and dried. Thereafter, an adhesive slurry containing lead zirconate titanate is applied from above the printing part, and the green sheet with the printing part is punched into a predetermined shape, and a predetermined number of sheets are stacked, pressed and pressed. Thereafter, it is held in an electric furnace at 500 ° C. for several hundred hours, and is subjected to binder removal, and fired under conditions of about 1200 ° C. for several hours to obtain a laminated sintered body 49 as shown in FIG.
[0039]
An uneven surface 22 as shown in FIG. 17 is formed on the outer peripheral surface 490 of the laminated sintered body 49 by using the laser processing machine 4 shown in FIG.
The laser processing machine 4 includes a laser transmitter 41 that transmits a pulse laser, a beam expander 42 that expands the beam diameter of the laser 40 transmitted from the laser transmitter 41, and a laser 40 that has passed through the beam expander 42. The two galvanometers 431 and 432 are reflected by the mirror, and the laser 40 that has passed through the last galvanometer 431 and 432 is converged by the condensing lens 44 and applied to the outer peripheral surface 490. As shown in FIG. 17, a large number of piezoelectric laminates 100 having an outer peripheral surface 10 having an uneven surface 22 are formed.
[0040]
Here, the irradiation method of the laser 40 will be described. As shown in FIG. 19A, the laser 40 is irradiated at substantially equal intervals so as to remove the portion indicated by the broken line 490 on the outer peripheral surface 490. After forming the first depression 492 as shown in FIG. 19B, the portion indicated by the broken line 493 is removed from the flat region between the depressions 492 as shown in FIG. The laser 40 is irradiated again. As a result, as shown in FIG. 19D, a second recess 494 is obtained between the first recesses 492.
In this way, a piezoelectric laminate 100 as shown in FIG. 17 was obtained.
[0041]
Next, with respect to the piezoelectric laminate 100, the side edges of the internal electrode layer exposed at the planar portion of the outer peripheral surface so that the internal electrode layers can be connected to the side electrodes every other layer (for details, see Example 1). On the other hand, glass powder is deposited every other layer by electrophoresis and heat-treated at about 600 ° C. to form an insulating layer (see FIG. 1).
Thereafter, a plate-like side electrode made of a stainless material processed into a corrugated shape is bonded using a conductive adhesive so as to electrically connect the side end portions not covered with the insulating layer.
Thereby, a multilayer piezoelectric element as shown in Example 1 or the like was obtained.
[0042]
In addition, as shown in FIG. 20, a laser 45 can be irradiated through the mask 45 by placing a mask 45 that is a template having an uneven surface shape to be formed on the outer peripheral surface 490.
In this case, for example, an uneven surface as shown in FIG.
[0043]
In any case, according to the manufacturing method according to this example, the insulating coating layer forming surface that is in contact with the insulating coating layer on the outer peripheral surface of the piezoelectric laminate is an uneven surface, and therefore the insulating coating layer, the insulating coating layer forming surface, This increases the contact area, increases the bonding strength between the two, and makes it possible to obtain a laminated piezoelectric element in which the insulation coating layer hardly peels off.
[0044]
(Example 6)
In this example, a method for forming an uneven surface before firing a piezoelectric laminate will be described. That is, first, a slurry is prepared by mixing a predetermined amount of an organic binder and a solvent with lead zirconate titanate, and a green sheet for a piezoelectric layer is obtained by a doctor blade method. A silver / palladium paste is applied to the green sheet by screen printing to form a printed part for the internal electrode layer and dried. Thereafter, an adhesive slurry containing lead zirconate titanate is applied from above the printing portion, the green sheet with the printing portion is punched into a predetermined shape, a predetermined number of layers are stacked, pressed and pressure bonded, obtain.
[0045]
Subsequently, as shown in FIG. 21, an uneven surface forming roller 52 that is supported by a rotation holder 521 and includes a rotation unit 523 provided with a large number of protrusions 522 on the outer surface is prepared.
Then, both end surfaces of the crimping body 58 in the stacking direction are supported by the rotation holder 51. The rotating part 523 is pressed against the undried outer surface 580 of the crimping body 58. The uneven surface forming roller 52 is rotated in the direction of the arrow R1 together with the rotary holder 51 in the direction of the arrow R2 opposite to the R1. As a result, the outer surface 580 is pushed by the protrusions 522 to form a number of depressions.
Thereafter, the pressure-bonded body is dried, held in an electric furnace at 500 ° C. for several hundred hours, debindered, fired under conditions of about 1200 ° C. for several hours, and the laminated sintered body 49 as shown in FIG. obtain.
From this laminated sintered body 49, a laminated piezoelectric element according to the present invention can be manufactured.
[0046]
Or, as shown in FIG. 22 and FIG. 23, an arrow R4 is formed in a direction parallel to the outer surface 590 while rotating the concave-convex surface forming roller 52 in the direction of the arrow R3 with respect to the outer surface 590 of the stationary pressure body 59. A number of depressions were formed on the outer surface 590 by the protrusions 522.
Thereafter, the pressure-bonded body is dried, held in an electric furnace at 500 ° C. for several hundred hours, debindered, fired under conditions of about 1200 ° C. for several hours, and the laminated sintered body 49 as shown in FIG. obtain. From this laminated sintered body 49, a laminated piezoelectric element according to the present invention can be manufactured.
In addition, the crimping | compression-bonding body 59 shown here has a square cross-sectional shape, and the outer surface 590 consists of four side surfaces of a rectangular parallelepiped.
[0047]
As described above, according to the manufacturing method of this example, the insulating coating layer forming surface that contacts the insulating coating layer on the outer peripheral surface of the piezoelectric laminate is an uneven surface, and therefore the contact between the insulating coating layer and the insulating coating layer forming surface is The laminated piezoelectric element in which the area increases, the bonding strength between the two increases, and the insulating coating layer hardly peels off can be obtained.
[Brief description of the drawings]
FIG. 1 is a perspective view of a main part of a multilayer piezoelectric element according to a first embodiment.
FIG. 2 is an explanatory view of a cross section in the stacking direction of the stacked piezoelectric element in the first embodiment.
FIG. 3 is an explanatory diagram of a piezoelectric laminate having an uneven surface on the outer peripheral surface in Example 1.
4 is an explanatory view of a cross section along the stacking direction of a piezoelectric laminate having an uneven surface on the outer peripheral surface in Example 1. FIG.
5 is an explanatory diagram of an uneven surface in Example 1. FIG.
6 is a perspective view of a multilayer piezoelectric element in Example 1. FIG.
7 is an explanatory diagram of an enclosing holder incorporating a multilayer piezoelectric element in Example 1. FIG.
FIG. 8 is an explanatory diagram of an injector for a diesel engine incorporating a laminated piezoelectric element according to the first embodiment.
FIG. 9 is an explanatory diagram of a concavo-convex surface in which peaks and valleys are alternately repeated in the second embodiment.
FIG. 10 is an explanatory diagram of a concavo-convex surface including a flat portion and a recess retreated from the flat portion in Embodiment 2.
FIG. 11 is an explanatory diagram of a concavo-convex surface including a flat portion and a protrusion protruding from the flat portion in the second embodiment.
12 is an explanatory view of a piezoelectric laminate in Example 3 in which a concave and convex surface having an indentation in the shape of an ellipse is provided on the outer peripheral surface. FIG.
FIG. 13 is an explanatory diagram of a piezoelectric laminate in Example 3 in which a concave and convex surface having a dent shape having a cross shape is provided on the outer peripheral surface.
FIG. 14 is an explanatory view of a piezoelectric laminate in Example 3 in which a concave and convex surface whose depression shape is a cross groove is provided on the outer peripheral surface.
15 is a perspective view of a piezoelectric laminate having a square cross-sectional shape in Example 4. FIG.
16 is an explanatory diagram of a laminated sintered body in Example 5. FIG.
17 is a cross-sectional explanatory view showing the state of the piezoelectric laminate and the uneven surface of the outer peripheral surface in Example 5. FIG.
18 is a diagram showing the configuration of a laser beam machine in Example 5. FIG.
FIG. 19 is an explanatory diagram regarding the formation of an uneven surface by a laser in Example 5.
20 is a diagram showing a configuration of a laser processing machine using a mask in Example 5. FIG.
FIG. 21 is an explanatory diagram of formation of a recess for an unfired pressure-bonded body by a concavo-convex surface forming roller in Example 6.
FIG. 22 is an explanatory diagram of formation of a depression on a pressed body having an unfired cross-sectional square shape by a concavo-convex surface forming roller in Example 6.
FIG. 23 is an explanatory diagram of formation of a recess on a pressed body having an unfired cross-sectional square shape by a concavo-convex surface forming roller in Example 6.
[Explanation of symbols]
1. . . Laminated piezoelectric element,
10. . . Outer surface,
100. . . Piezoelectric laminate,
11. . . Piezoelectric layer,
121, 122. . . Internal electrode layer,
141, 142. . . Side electrode layer,
15. . . Insulation coating layer,
21. . . Uneven surface,

Claims

圧電層と内部電極層とを交互に積層してなる圧電積層体と，該圧電積層体の外周面に形成した一対の側面電極と，該側面電極ごと上記圧電積層体の外周面を覆って外部と絶縁を確保するよう形成した絶縁被覆層とを有する積層型圧電体素子において，
上記圧電積層体の外周面で，上記絶縁被覆層と接触する絶縁被覆層形成面は凹凸面からなることを特徴とする積層型圧電体素子。Piezoelectric laminates formed by alternately laminating piezoelectric layers and internal electrode layers, a pair of side electrodes formed on the outer peripheral surface of the piezoelectric laminate, and the outer peripheral surface of the piezoelectric laminate together with the side electrodes And a laminated piezoelectric element having an insulating coating layer formed to ensure insulation,
A laminated piezoelectric element, wherein an outer peripheral surface of the piezoelectric laminated body is an uneven surface on an insulating coating layer forming surface that comes into contact with the insulating coating layer.

請求項１において，上記絶縁被覆層形成面の面積Ｓ０と上記凹凸面からなる絶縁被覆層形成面の表面積Ｓ１との間には，Ｓ０よりＳ１の表面積が増加するという関係が成立することを特徴とする積層型圧電体素子。2. The relationship according to claim 1, wherein the surface area S1 of the insulating coating layer forming surface and the surface area S1 of the insulating coating layer forming surface comprising the concavo-convex surface are such that the surface area of S1 increases from S0. A laminated piezoelectric element.

請求項１または２において，上記凹凸面における凹部の深さは３〜６０μｍであることを特徴とする積層型圧電体素子。3. The multilayer piezoelectric element according to claim 1, wherein a depth of the concave portion on the concave / convex surface is 3 to 60 μm.

請求項１〜３のいずれか１項において，上記凹凸面の凸部間距離は４〜８０μｍであることを特徴とする積層型圧電体素子。The multilayer piezoelectric element according to any one of claims 1 to 3, wherein a distance between the convex portions of the concavo-convex surface is 4 to 80 µm.