JP2004090067A

JP2004090067A - Machining method for sliding surface, and cylinder block

Info

Publication number: JP2004090067A
Application number: JP2002257073A
Authority: JP
Inventors: Shinji Nishino; 西野　眞司; Yoshinori Izawa; 伊澤　佳典
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2002-09-02
Filing date: 2002-09-02
Publication date: 2004-03-25
Anticipated expiration: 2022-09-02
Also published as: JP4134645B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sliding surface machining method capable of improving the seizure resistance without degrading any friction characteristic of a sliding surface, and to provide a cylinder block. <P>SOLUTION: In the sliding surface machining method for forming very small recessed parts 32 to function as oil sumps by irradiating laser beams on a sliding surface 31 forming a circumferential surface, when a plurality of recessed parts are formed along the circumferential direction at the position where a work is moved in the axial direction after the plurality of recessed parts are formed along the circumferential direction, laser beams are irradiated so that the phases of the adjacent recessed parts along the circumferential direction are deviated from each other along the axial direction of the work. The sliding surface is finished by the grinding thereafter. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、ワークにおける円周面をなす摺動面にレーザ光を照射することにより油溜まりとして機能する微細な窪み部を形成する摺動面の加工方法および摺動面としてのボア内周面にレーザ光を照射することにより油溜まりとして機能する微細な窪み部が形成されたシリンダブロックに関する。
【０００２】
【従来の技術】
ワークにおける円周面をなす摺動面、例えば、シリンダブロックのボア内周面は、ピストンの焼き付きを防止する耐焼き付き性が良好であることが要求されるため、油溜まりとして機能する微細な窪み部が形成されている。
【０００３】
油溜まりを形成する加工方法として、ホーニング砥石により微小な網目状の油溜まりを形成するホーニング加工が知られているが、ホーニング砥石を回転および昇降させながらボア内周面の全領域を加工するため、潤滑油を積極的に保持させる必要がある一部の領域の窪みのみを深く形成することは難しい。
【０００４】
そこで、ボア内周面のうち潤滑油を積極的に保持させる必要がある一部の領域にレーザ光を照射して微細な窪み部を形成するレーザ微細加工による摺動面の加工方法も提案されている。レーザ微細加工によれば、所望形状の窪み部を必要な領域にだけ簡単に形成することができる。レーザ微細加工による摺動面の加工方法は、例えば、特開平７−４００６８号公報、特開平６−８１０３０号公報、特開２００１−２７９４２１号公報に示されている。
【０００５】
【特許文献１】
特開平７−４００６８号公報
【特許文献２】
特開平６−８１０３０号公報
【特許文献３】
特開２００１−２７９４２１号公報
【０００６】
【発明が解決しようとする課題】
レーザ微細加工を行うと、当該レーザ微細加工を行った部分（以下、「レーザ加工部」という）の両側に、盛り上がり部位が生じる。この盛り上がり部位を除去するとともに面粗度を向上させるために、レーザ微細加工の後には、ボア内周面の仕上げ加工が行われている。仕上げ加工は、一般に、ホーニング砥石を用いた研削加工により行われている。
【０００７】
しかしながら、研削加工を行うと、レーザ加工部に比べて、レーザ微細加工を行っていない部分（以下、「レーザ未加工部」という）が優先的に研磨されてしまい、研削加工が完了した後に、ボア内周面は、レーザ加工部が凸形状に、レーザ未加工部が凹形状になり、全体的にうねった凹凸形状になることがある。うねりの発生原因としては、主として、レーザ加工部の周辺に発生する数ミクロン厚さの硬化された部分とレーザ未加工部の硬化されていない部分との間の硬度差によって砥石の磨耗が不均一になるため、および、砥石の目詰まりが不均一になるためであると考えられる。ボア内周面が全体的にうねった凹凸形状になると、凸形状になった部分の面圧が不均一に高くなる。これにより、摺動面のフリクション特性が悪影響を受け、耐焼き付き性が低下する。
【０００８】
したがって、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図るためには、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部を形成する必要がある。
【０００９】
本発明は、このような背景の下になされたものであり、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部を形成でき、もって、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図り得る摺動面の加工方法およびシリンダブロックを提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明の目的は、下記する手段により達成される。
【００１１】
本発明は、ワークにおける円周面をなす摺動面にレーザ光を照射することにより油溜まりとして機能する微細な窪み部を形成する摺動面の加工方法において、複数の窪み部を円周方向に沿って形成した後に前記ワークの軸心方向に移動した位置において複数の窪み部を円周方向に沿って形成するときに、前記ワークの軸心方向に沿って隣り合う円周方向に沿う窪み部の位相がずれるようにレーザ光を照射し、その後に、研削加工により前記摺動面を仕上げ加工することを特徴とする摺動面の加工方法である。
【００１２】
また、本発明は、摺動面としてのボア内周面にレーザ光を照射することにより油溜まりとして機能する微細な窪み部が形成されたシリンダブロックにおいて、軸心方向に沿う複数の位置で、複数の窪み部が円周方向に沿って形成され、さらに、軸心方向に沿って隣り合う円周方向に沿う窪み部の位相がずれていることを特徴とするシリンダブロックである。
【００１３】
【発明の効果】
本発明によれば、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部を形成でき、もって、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図り得る。
【００１４】
【発明の実施の形態】
以下、本発明の実施形態を図面を参照しつつ説明する。
【００１５】
（第１の実施形態）
図１は、レーザ加工装置１０からボア内周面３１にレーザ光を照射して微細な窪み部３２を形成している状況を示す図、図２は、ボア内周面３１のうちレーザ加工が施される領域を示す斜視図である。なお、図２おいて、レーザ加工が施される領域は二点鎖線にて表される。図３は、図２の３−３線に沿う断面図であり、図３（Ａ）は、レーザ加工後のボア内周面３１を示す断面図、図３（Ｂ）は、研削加工後のボア内周面３１を示す断面図である。
【００１６】
図１に示すように、レーザ加工装置１０は、レーザ発振器１１と、伝達ミラー１２と、集光レンズ１３が内蔵された集光部１４と、集光部１４の図中下端に設けられた折り返しミラー１５と、集光部１４を軸心Ｏを中心に回転するとともに軸心Ｏに沿う方向に昇降駆動する駆動装置１６と、を有する。レーザ発振器１１から出力されたレーザ光２０は、伝達ミラー１２により集光部１４に向けて折り返され、集光レンズ１３で集光され、折り返しミラー１５により折り返され、シリンダブロック３０におけるシリンダボアのボア内周面３１（ワークにおける円周面をなす摺動面に相当する）に照射される。レーザ光２０を所定パルス周波数（レーザ光２０の照射の繰り返し数）で照射しつつ駆動装置１６により集光部１４を回転させることにより、油溜まりとして機能する複数の窪み部３２がシリンダボアの円周方向に沿ってボア内周面３１に形成される。その後、駆動装置１６により集光部１４を軸心方向に移動し、その位置において、再び、レーザ光２０を所定パルス周波数で照射しつつ集光部１４を回転させることにより、複数の窪み部３２が円周方向に沿ってボア内周面３１に形成される。
【００１７】
図２に示すように、レーザ光２０による微細な窪み部３２の加工は、シリンダヘッド側開口端から所定寸法の領域に対して施される。この領域は、ピストンの上死点近傍に相当するため熱衝撃が大きく、耐焼き付き性をもっとも向上させなければならない領域である。
【００１８】
図３（Ａ）に示すように、レーザ微細加工を行うと、加熱による膨張や蒸発によって、レーザ加工部の両側に、盛り上がり部位３３（「デブリ」と称される）が必然的に形成されてしまう。このような盛り上がり部位３３がボア内周面３１に残ったままでは、ピストンの円滑な摺動が阻害される。
【００１９】
そこで、図３（Ｂ）に示すように、レーザ微細加工の後に、盛り上がり部位３３（同図に破線で示される）を除去し、さらに、レーザ加工部以外の平滑部での面粗度を高めるために、仕上げ加工が行われている。仕上げ加工は、例えば、ホーニング砥石を用いた研削加工により行われる。ホーニング砥石は、回転駆動される円筒状の工具に、径方向外方に拡張自在に取り付けられている。
【００２０】
図４は、シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相を同位相とした対比例の場合および窪み部３２の位相をずらした第１の実施形態の場合のそれぞれにおける、窪み部３２の配置状況、レーザ微細加工後のボア内周面３１を示す断面図、研削加工後のボア内周面３１を示す断面図である。符号４０は、ホーニング砥石を示している。研削加工時には、ホーニング砥石４０は、円筒状の工具とともに回転されながら、シリンダボアの軸心方向に進退移動される。矢印４１は、ボア内周面３１の円周方向に沿うホーニング砥石４０の相対的な移動方向を示し、矢印４２は、シリンダボアの軸心方向に沿うホーニング砥石４０の相対的な移動方向を示している。
【００２１】
図４に示すように、対比例の場合には、研削加工において、レーザ加工部５０に比べてレーザ未加工部５１が優先的に研磨されてしまう。このため、研削加工が完了した後に、ボア内周面３１は、レーザ加工部５０が凸形状に、レーザ未加工部５１が凹形状になり、全体的にうねった凹凸形状になる。うねりの発生原因としては、前述したように、レーザ加工部５０の周辺に発生する硬化された部分とレーザ未加工部５１の硬化されていない部分との間の硬度差によって砥石４０の磨耗が不均一になるため、および、砥石４０の目詰まりが不均一になるためであると考えられる。ボア内周面３１が全体的にうねった凹凸形状になると、凸形状になった部分の面圧が不均一に高くなり、摺動面のフリクション特性が悪影響を受け、耐焼き付き性が低下する。
【００２２】
これに対して、第１の実施形態の場合には、研削加工が完了した後に、ボア内周面３１は全体的にうねった凹凸形状にならない。うねりを抑制できたのは、矢印４１、４２で示される砥石４０の移動方向に沿って位置する窪み部３２の分布が砥石４０の移動方向に沿ってほぼ均一になって砥石４０の磨耗が研削面の全面にわたってほぼ均一になるため、および、砥石４０の目詰まりが研削面の全面にわたってほぼ均一になるためであると考えられる。ボア内周面３１が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成できるため、面圧が周方向に均一になり、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図ることができる。
【００２３】
第１の実施形態におけるボア内周面３１の加工手順を説明する。
【００２４】
まず、レーザ光２０を所定パルス周波数で照射しつつ駆動装置１６により集光部１４を回転し、油溜まりとして機能する複数の窪み部３２を円周方向に沿ってボア内周面３１に形成する。
【００２５】
次いで、駆動装置１６により集光部１４をシリンダボアの軸心方向に所定距離だけ移動する。その位置において、再び、レーザ光２０を所定パルス周波数で照射しつつ集光部１４を回転し、複数の窪み部３２を円周方向に沿ってボア内周面３１に形成する。
【００２６】
複数の窪み部３２を円周方向に沿って形成した後にシリンダボアの軸心方向に移動した位置において複数の窪み部３２を円周方向に沿って形成するときには、シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相がずれるようにレーザ光を照射する。窪み部３２の位相をずらすために、レーザ発振器１１からのレーザ光２０の出力タイミングをずらす制御が行われる。
【００２７】
上述した集光部１４の軸心方向への移動と、その位置での円周方向に沿う複数の窪み部３２の形成とを繰り返し、図２に二点鎖線で示される領域に対してレーザ微細加工を施す。レーザ光の平均出力、加工速度は適宜選択できるが、一例を挙げれば、レーザ平均出力は１０Ｗ〜５０Ｗ、加工速度は５ｍ／ｍｉｎ〜１５ｍ／ｍｉｎである。
【００２８】
レーザ平均出力が１０Ｗよりも小さいと、油溜まりの窪みとして機能させるのに十分な深さの窪み部３２を形成することができない。また、レーザ平均出力が５０Ｗよりも大きいとき、例えば１００Ｗのときには、レーザ光の発振効率が低くなり、使用できるのはせいぜい５０Ｗ程度である。また、現状の生産時には、レーザ平均出力の範囲として１０Ｗ〜５０Ｗの範囲が、通常、使用されている。以上のことから、さらには省エネルギーについても考慮して、レーザ平均出力は１０Ｗ〜５０Ｗが好ましい。
【００２９】
また、加工速度が５ｍ／ｍｉｎよりも小さいと、従来の加工時間に対して遅くなるので、生産効率（単位時間当たりの加工数）がきわめて低くなる。また、加工速度が１５ｍ／ｍｉｎよりも大きいと、パルス周波数をより大きくする必要があるが、パルス周波数が大きすぎると、レーザ加工装置１０の消耗が激しく、装置寿命が短くなる。以上のことから、実際の生産時に採用し得る加工速度の下限値および上限値を考慮して、加工速度は５ｍ／ｍｉｎ〜１５ｍ／ｍｉｎが好ましい。
【００３０】
レーザ微細加工が終了したシリンダブロック３０は、軸心方向に沿う複数の位置で、複数の窪み部３２が円周方向に沿って形成され、さらに、軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相がずれている。図４に示される窪み部３２は、半球凹部のような点形状を有している。窪み部３２の円周方向のピッチは約０．６ｍｍ、軸心方向のピッチは約０．３ｍｍである。
【００３１】
レーザ微細加工が完了した後、ホーニング砥石４０を用いた研削加工により、ボア内周面３１を仕上げ加工する。研削加工時には、ホーニング砥石４０は、円筒状の工具とともに回転されながら、シリンダボアの軸心方向に進退移動される。さらに、ホーニング砥石４０は、径方向外方に向けて拡張され、ボア内周面３１に押圧される。ホーニング砥石４０は、比較的高速で回転される一方、比較的低速で進退移動される。
【００３２】
研削加工が完了すると、レーザ微細加工により生じた盛り上がり部位３３が除去され、ボア内周面３１は、所定の面粗度を有する平滑面に仕上げられる。
【００３３】
ここで、シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相をずらしたため、レーザ未加工部５１が優先的に研削されることがなくなり、ボア内周面３１が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成できる。このように、油溜まりの機能を有する窪み部３２と平滑面とを合わせ持つボア内周面３１によれば、面圧が周方向に均一になり、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図ることができる。
【００３４】
以上説明したように、第１の実施形態における摺動面の加工方法によれば、複数の窪み部３２を円周方向に沿って形成した後にシリンダボアの軸心方向に移動した位置において複数の窪み部３２を円周方向に沿って形成するときに、シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相がずれるようにレーザ光２０を照射し、その後に、研削加工により摺動面を仕上げ加工している。このため、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成でき、もって、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図ることが可能となる。
【００３５】
摺動面として、シリンダブロック３０におけるシリンダボアの内周面の場合には、ボア内周面３１のフリクション特性を悪化させず、耐焼き付き性の向上を図ることが可能となる。
【００３６】
また、第１の実施形態におけるシリンダブロック３０は、軸心方向に沿う複数の位置で、複数の窪み部３２が円周方向に沿って形成され、さらに、軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相がずれている。このため、円周面をなす摺動面としてのボア内周面３１が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成でき、もって、ボア内周面３１のフリクション特性を悪化させず、耐焼き付き性の向上を図ることが可能となる。
【００３７】
なお、窪み部３２は、図４に示した点形状に限られものではなく、油溜まりとして機能し得る限りにおいて、適宜の形状を選択できる。例えば、図５に示すように、窪み部３２は、長溝のような線形状を有するものでもよい。また、窪み部３２は、楕円のような線形状であってもよい。
【００３８】
線形状の窪み部３２の場合、当該窪み部３２の長手方向（円周方向）の範囲内に溜められた潤滑油が流動ないし移動する。これに対して、点形状の窪み部３２における油溜まりは、線形状の窪み部３２に比べて潤滑油の流動が少ない。このため、ボア内周面３１の単位面積当たりにおける窪み部３２の面積が同じ場合には、点形状の窪み部３２は、線形状の窪み部３２に比べて、油溜まりの途切れる領域が少なくなる。したがって、点形状の窪み部３２は、線形状の窪み部３２に比べて、焼き付きが生じる焼き付き面圧が高くなり、より効率よく焼き付きを防止することができる。
【００３９】
なお、本明細書において、「円周方向に沿う窪み部３２」とは、複数の窪み部３２がワークの軸心に対して直交する方向に配置される場合のみならず、複数の窪み部３２がワークの軸心に対して傾斜する方向に配置される場合をも含む概念である。
【００４０】
（第２の実施形態）
第２の実施形態は、ボア内周面３１のフリクション特性を悪化させず、耐焼き付き性の向上を図り得る摺動面の加工方法およびシリンダブロック３０を提供する点において、上述した第１の実施形態と同じである。但し、第２の実施形態は、レーザ光２０を照射して微細な窪み部３２を形成するレーザ微細加工を行った後に、レーザ微細加工を行った部分５０とレーザ微細加工を行っていない部分５１との硬度差を吸収するレーザ焼き入れを行うことにより、ボア内周面３１が研削加工後にうねった凹凸形状となることを抑制している。この点で、シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相をずらすことにより、ボア内周面３１が研削加工後にうねった凹凸形状となることを抑制した第１の実施形態と相違している。
【００４１】
第２の実施形態では、図１に示したレーザ加工装置１０を使用して、図２に二点鎖線で示された領域に対してレーザ光を照射し、油溜まりとして機能する微細な窪み部３２を形成する。このレーザ微細加工を行った後に、レーザ微細加工を行ったレーザ加工部５０とレーザ微細加工を行っていないレーザ未加工部５１との硬度差を吸収するレーザ焼き入れが行われる。
【００４２】
レーザ微細加工により発生する盛り上がり部位３３は硬化されているので、この盛り上がり部位３３にレーザ焼き入れをさらに施すと、前記硬度差を吸収することができなくなる。このため、レーザ焼き入れは、前記硬度差を吸収するという目的に合致した領域、具体的には、レーザ微細加工を行った部分５０以外の部分５１に対して行う。ここで、「レーザ微細加工を行った部分５０」には、窪み部３２と、当該窪み部３２周辺の盛り上がり部位３３とが含まれている。
【００４３】
レーザ焼き入れにより前記硬度差を吸収した後に、第１の実施形態と同様に、研削加工によりボア内周面３１が仕上げ加工される。
【００４４】
レーザ焼き入れは、専用の機械を用いてもよいが、図１に示したレーザ加工装置１０を使用して行うこともできる。つまり、レーザ加工装置１０から照射されるレーザ光２０のパワー密度がほぼ同じでも、レーザ光２０の焦点がボア内周面３１から離れるように駆動装置１６により集光部１４を移動することにより、ボア内周面３１を溶融することなくレーザ焼き入れを行うことができる。図６には、レーザ光の照射によって、微細加工、焼き入れ、衝撃硬化および溶接のそれぞれを行うときに設定されるレーザ光の照射時間とパワー密度との関係の一例が概略で示される。
【００４５】
図７は、研削加工による仕上げ加工の前にレーザ焼き入れを行わない対比例の場合とレーザ焼き入れを行う第２の実施形態の場合のそれぞれにおける、窪み部３２の配置状況、レーザ微細加工後のボア内周面３１を示す断面図、第２の実施形態の場合のレーザ焼き入れ後のボア内周面３１を示す断面図、研削加工後のボア内周面３１を示す断面図である。図示するように、シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相は、対比例および第２の実施形態ともに同位相である。
【００４６】
図７に示すように、対比例の場合には、研削加工において、レーザ加工部５０に比べてレーザ未加工部５１が優先的に研磨されてしまう。このため、研削加工が完了した後に、ボア内周面３１は、レーザ加工部５０が凸形状に、レーザ未加工部５１が凹形状になり、全体的にうねった凹凸形状になる。うねりの発生原因としては、前述したように、レーザ加工部５０の周辺に発生する硬化された部分とレーザ未加工部５１の硬化されていない部分との間の硬度差によって砥石４０の磨耗が不均一になるため、および、砥石４０の目詰まりが不均一になるためであると考えられる。ボア内周面３１が全体的にうねった凹凸形状になると、凸形状になった部分の面圧が不均一に高くなり、摺動面のフリクション特性が悪影響を受け、耐焼き付き性が低下する。
【００４７】
これに対して、第２の実施形態の場合には、研削加工が完了した後に、ボア内周面３１は全体的にうねった凹凸形状にならない。うねりを抑制できたのは、レーザ焼き入れによりレーザ未加工部５１が硬化されて前記硬度差が吸収され、砥石４０の磨耗が研削面の全面にわたってほぼ均一になるため、および、砥石４０の目詰まりが研削面の全面にわたってほぼ均一になるためであると考えられる。ボア内周面３１が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成できるため、面圧が周方向に均一になり、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図ることができる。
【００４８】
第２の実施形態におけるボア内周面３１の加工手順を説明する。
【００４９】
まず、レーザ光２０を所定パルス周波数で照射しつつ駆動装置１６により集光部１４を回転し、油溜まりとして機能する複数の窪み部３２を円周方向に沿ってボア内周面３１に形成する。
【００５０】
次いで、駆動装置１６により集光部１４をシリンダボアの軸心方向に所定距離だけ移動する。その位置において、再び、レーザ光２０を所定パルス周波数で照射しつつ集光部１４を回転し、複数の窪み部３２を円周方向に沿ってボア内周面３１に形成する。
【００５１】
上述した集光部１４の軸心方向への移動と、その位置での円周方向に沿う複数の窪み部３２の形成とを繰り返し、図２に二点鎖線で示される領域に対してレーザ加工を施す。レーザ光の平均出力、加工速度は適宜選択できるが、一例を挙げれば、レーザ平均出力は１０Ｗ〜５０Ｗ、加工速度は５ｍ／ｍｉｎ〜１５ｍ／ｍｉｎである。
【００５２】
レーザ微細加工を行った後、レーザ加工部５０（微細な窪み部３２と、盛り上がり部位３３との両者が含まれる）以外のレーザ未加工部５１に対してレーザ焼き入れを行う。このとき、レーザ加工装置１０は、レーザ光２０の平均出力を一定にしたまま、レーザ光２０の焦点がボア内周面３１から離れるように集光部１４が移動される。また、レーザ未加工部５１の領域にレーザ焼き入れを行うように、レーザ発振器１１の作動および集光部１４の移動が制御される。
【００５３】
レーザ焼き入れが完了した後、第１の実施形態と同様に、ホーニング砥石４０を用いた研削加工により、ボア内周面３１を仕上げ加工する。
【００５４】
研削加工が完了すると、レーザ微細加工により生じた盛り上がり部位３３が除去され、ボア内周面３１は、所定の面粗度を有する平滑面に仕上げられる。
【００５５】
ここで、研削加工による仕上げ加工の前にレーザ焼き入れを行ったため、レーザ未加工部５１が優先的に研削されることがなくなり、ボア内周面３１が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成できる。このように、油溜まりの機能を有する窪み部３２と平滑面とを合わせ持つボア内周面３１によれば、面圧が周方向に均一になり、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図ることができる。
【００５６】
以上説明したように、第２の実施形態における摺動面の加工方法によれば、レーザ光２０を照射して微細な窪み部３２を形成するレーザ微細加工を行った後に、レーザ微細加工を行った部分５０とレーザ微細加工を行っていない部分５１との硬度差を吸収するレーザ焼き入れを行い、その後に、研削加工により摺動面を仕上げ加工している。このため、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成でき、もって、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図ることが可能となる。
【００５７】
レーザ焼き入れを、レーザ微細加工を行った部分５０以外の部分５１に対して行ったため、前記硬度差を吸収するという目的に合致した領域に対してレーザ焼き入れが行われる。このため、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを確実に抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成でき、もって、摺動面のフリクション特性を悪化させず、耐焼き付き性の向上を図ることが可能となる。
【００５８】
レーザ微細加工を行った部分５０には、窪み部３２と、当該窪み部３２周辺の盛り上がり部位３３とが含まれており、盛り上がり部位３３にレーザ焼き入れを施さないようにしている。このため、レーザ微細加工により硬化された盛り上がり部位３３の硬度がさらに高められることはなく、前記硬度差を吸収して、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを確実に抑制できる。
【００５９】
摺動面として、シリンダブロック３０におけるシリンダボアの内周面の場合には、ボア内周面３１のフリクション特性を悪化させず、耐焼き付き性の向上を図ることが可能となる。
【００６０】
また、第２の実施形態におけるシリンダブロック３０は、レーザ光を照射して微細な窪み部３２を形成するレーザ微細加工を行った部分５０と当該レーザ微細加工を行っていない部分５１との硬度差を吸収するレーザ焼き入れが施されている。このため、円周面をなす摺動面としてのボア内周面３１が研削加工後にうねった凹凸形状となることを抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成でき、もって、ボア内周面３１のフリクション特性を悪化させず、耐焼き付き性の向上を図ることが可能となる。
【００６１】
なお、窪み部３２は、半球凹部のような点形状の場合を示したが、図５に示した線形状、または、楕円のような線形状であってもよい。点形状の窪み部３２は、線形状の窪み部３２に比べてより効率よく焼き付きを防止することが可能である
さらに、第１の実施形態と第２の実施形態とを組み合わせた形態とすることもできる。つまり、シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部３２の位相をずらし、かつ、レーザ微細加工を行った部分５０とレーザ微細加工を行っていない部分５１との硬度差を吸収するレーザ焼き入れを研削加工の前に行ってもよい。かかる形態によれば、円周面をなす摺動面が研削加工後にうねった凹凸形状となることを一層確実に抑制しつつ、油溜まりとして機能する微細な窪み部３２を形成でき、もって、摺動面のフリクション特性を悪化させず、耐焼き付き性のさらなる向上を図ることが可能となる。
【図面の簡単な説明】
【図１】レーザ加工装置からボア内周面にレーザ光を照射して微細な窪み部を形成している状況を示す図である。
【図２】ボア内周面のうちレーザ加工が施される領域を示す斜視図である。
【図３】図３（Ａ）は、レーザ加工後のボア内周面を示す断面図、図３（Ｂ）は、研削加工後のボア内周面を示す断面図である。
【図４】シリンダボアの軸心方向に沿って隣り合う円周方向に沿う窪み部の位相を同位相とした対比例の場合および窪み部の位相をずらした第１の実施形態の場合のそれぞれにおける、窪み部の配置状況、レーザ微細加工後のボア内周面を示す断面図、研削加工後のボア内周面を示す断面図である。
【図５】点形状の窪み部を示す図である。
【図６】レーザ光の照射によって、微細加工、焼き入れ、衝撃硬化および溶接のそれぞれを行うときに設定されるレーザ光の照射時間とパワー密度との関係の一例を示す概略図。
【図７】研削加工による仕上げ加工の前にレーザ焼き入れを行わない対比例の場合とレーザ焼き入れを行う第２の実施形態の場合のそれぞれにおける、窪み部の配置状況、レーザ微細加工後のボア内周面を示す断面図、第２の実施形態の場合のレーザ焼き入れ後のボア内周面を示す断面図、研削加工後のボア内周面を示す断面図である。
【符号の説明】
１０…レーザ加工装置
２０…レーザ光
３０…シリンダブロック（ワーク）
３１…ボア内周面（円周面をなす摺動面）
３２…窪み部
３３…盛り上がり部位
４０…砥石
５０…レーザ加工部５０（レーザ微細加工を行った部分、窪み部３２と盛り上がり部位３３とを含む）
５１…レーザ未加工部５１（レーザ微細加工を行っていない部分）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for processing a sliding surface that forms a fine recess that functions as an oil reservoir by irradiating a laser beam onto a sliding surface that forms a circumferential surface of a work, and a bore inner peripheral surface as a sliding surface It is related with the cylinder block in which the fine hollow part which functions as an oil sump was formed by irradiating a laser beam to.
[0002]
[Prior art]
The sliding surface that forms the circumferential surface of the workpiece, for example, the bore inner circumferential surface of the cylinder block, is required to have good seizure resistance to prevent seizure of the piston. The part is formed.
[0003]
As a processing method for forming an oil reservoir, honing processing is known in which a fine mesh-like oil reservoir is formed by a honing grindstone. In order to process the entire area of the bore inner surface while rotating and lifting the honing grindstone In addition, it is difficult to form deeply only the depressions in some areas where it is necessary to actively hold the lubricating oil.
[0004]
In view of this, a method of processing a sliding surface by laser micromachining has been proposed in which a portion of the bore inner peripheral surface that needs to actively retain lubricating oil is irradiated with laser light to form a fine recess. ing. According to laser microfabrication, a recess having a desired shape can be easily formed only in a necessary region. For example, Japanese Patent Application Laid-Open No. 7-40068, Japanese Patent Application Laid-Open No. 6-81030, and Japanese Patent Application Laid-Open No. 2001-279421 disclose methods for processing a sliding surface by laser fine processing.
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-40068
[Patent Document 2]
JP-A-6-81030
[Patent Document 3]
JP 2001-279421 A
[0006]
[Problems to be solved by the invention]
When laser micromachining is performed, raised portions are generated on both sides of the laser micromachining portion (hereinafter referred to as “laser machining portion”). In order to remove the swelled portion and improve the surface roughness, finishing processing of the inner peripheral surface of the bore is performed after the laser micromachining. The finishing process is generally performed by grinding using a honing grindstone.
[0007]
However, when grinding is performed, a portion that is not subjected to laser micromachining (hereinafter referred to as “laser unprocessed portion”) is preferentially polished as compared with the laser processing portion, and after the grinding processing is completed, The bore inner peripheral surface may have a convex and concave shape as a whole, with the laser-processed portion having a convex shape and the laser non-processed portion having a concave shape. The main cause of waviness is uneven wear of the grindstone due to the hardness difference between the hardened part of the thickness of several microns generated around the laser machined part and the unhardened part of the laser unmachined part. This is considered to be because the clogging of the grindstone becomes uneven. When the bore inner circumferential surface has a generally undulating uneven shape, the surface pressure of the convex portion becomes unevenly high. As a result, the friction characteristics of the sliding surface are adversely affected and the seizure resistance is reduced.
[0008]
Therefore, in order to improve the seizure resistance without deteriorating the frictional characteristics of the sliding surface, it is possible to prevent the oil from being retained while suppressing the sliding surface forming the circumferential surface from becoming an uneven shape after grinding. It is necessary to form a fine depression that functions as
[0009]
The present invention has been made under such a background, and a fine recess that functions as an oil reservoir while suppressing the sliding surface forming the circumferential surface from becoming a undulating uneven shape after grinding. Therefore, an object of the present invention is to provide a method of processing a sliding surface and a cylinder block that can improve seizure resistance without deteriorating the friction characteristics of the sliding surface.
[0010]
[Means for Solving the Problems]
The object of the present invention is achieved by the following means.
[0011]
The present invention relates to a sliding surface processing method for forming a fine recess that functions as an oil reservoir by irradiating a sliding surface forming a circumferential surface of a workpiece with a laser beam. Dents along the circumferential direction adjacent to each other along the axial direction of the workpiece when the plurality of dent portions are formed along the circumferential direction at positions moved in the axial direction of the workpiece after being formed along the axis. This is a sliding surface processing method characterized by irradiating a laser beam so that the phase of the portion is shifted, and then finishing the sliding surface by grinding.
[0012]
Further, the present invention provides a cylinder block in which fine depressions functioning as oil reservoirs are formed by irradiating laser light to the bore inner peripheral surface as a sliding surface, at a plurality of positions along the axial direction. The cylinder block is characterized in that a plurality of depressions are formed along the circumferential direction, and the phases of the depressions along the circumferential direction adjacent to each other along the axial direction are shifted.
[0013]
【The invention's effect】
According to the present invention, it is possible to form a fine recess functioning as an oil reservoir while suppressing the sliding surface forming the circumferential surface from becoming a wavy uneven shape after grinding, and thus the friction of the sliding surface can be formed. The seizure resistance can be improved without deteriorating the characteristics.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0015]
(First embodiment)
FIG. 1 is a diagram showing a situation where a laser beam is radiated from a laser processing apparatus 10 to a bore inner peripheral surface 31 to form a fine recess 32. FIG. It is a perspective view which shows the area | region to which it is given. In FIG. 2, the region where laser processing is performed is represented by a two-dot chain line. 3 is a cross-sectional view taken along line 3-3 in FIG. 2, FIG. 3 (A) is a cross-sectional view showing the bore inner peripheral surface 31 after laser processing, and FIG. 3 (B) is a diagram after grinding. 3 is a cross-sectional view showing a bore inner peripheral surface 31. FIG.
[0016]
As shown in FIG. 1, the laser processing apparatus 10 includes a laser oscillator 11, a transmission mirror 12, a condensing unit 14 including a condensing lens 13, and a folding provided at the lower end of the condensing unit 14 in the figure. The mirror 15 and the drive unit 16 that rotates the light collecting unit 14 about the axis O and drives it to move up and down in the direction along the axis O are included. The laser beam 20 output from the laser oscillator 11 is folded back toward the condensing unit 14 by the transmission mirror 12, collected by the condenser lens 13, folded back by the folding mirror 15, and within the bore of the cylinder bore in the cylinder block 30. Irradiated to the circumferential surface 31 (corresponding to a sliding surface forming a circumferential surface of the workpiece). By rotating the condensing unit 14 by the driving device 16 while irradiating the laser beam 20 at a predetermined pulse frequency (the number of repetitions of the irradiation of the laser beam 20), the plurality of depressions 32 functioning as oil reservoirs are arranged around the cylinder bore. It is formed in the bore inner peripheral surface 31 along the direction. Thereafter, the condensing unit 14 is moved in the axial direction by the driving device 16, and the condensing unit 14 is rotated while irradiating the laser beam 20 at a predetermined pulse frequency again at that position, whereby a plurality of depressions 32 are obtained. Is formed on the bore inner circumferential surface 31 along the circumferential direction.
[0017]
As shown in FIG. 2, the processing of the fine recess 32 by the laser beam 20 is performed on a region having a predetermined dimension from the cylinder head side opening end. Since this region corresponds to the vicinity of the top dead center of the piston, the thermal shock is large, and the seizure resistance must be improved most.
[0018]
As shown in FIG. 3A, when laser microfabrication is performed, a bulge portion 33 (referred to as “debris”) is inevitably formed on both sides of the laser processing portion due to expansion and evaporation due to heating. End up. If such a raised portion 33 remains on the bore inner peripheral surface 31, smooth sliding of the piston is hindered.
[0019]
Therefore, as shown in FIG. 3B, after the laser fine processing, the swelled portion 33 (shown by a broken line in the same figure) is removed, and the surface roughness in the smooth portion other than the laser processed portion is further increased. For this reason, finishing is performed. The finishing process is performed by, for example, grinding using a honing grindstone. The honing grindstone is attached to a rotationally driven cylindrical tool so as to be expandable radially outward.
[0020]
FIG. 4 shows a case in which the phase of the recess 32 along the circumferential direction adjacent to the axial direction of the cylinder bore is the same phase and a case of the first embodiment in which the phase of the recess 32 is shifted. FIG. 4 is a cross-sectional view showing an arrangement state of recesses 32, a bore inner peripheral surface 31 after laser micromachining, and a bore inner peripheral surface 31 after grinding, respectively. The code | symbol 40 has shown the honing grindstone. At the time of grinding, the honing grindstone 40 is moved back and forth in the axial direction of the cylinder bore while being rotated together with the cylindrical tool. An arrow 41 indicates the relative movement direction of the honing grindstone 40 along the circumferential direction of the bore inner peripheral surface 31, and an arrow 42 indicates the relative movement direction of the honing grindstone 40 along the axial direction of the cylinder bore. Yes.
[0021]
As shown in FIG. 4, in the case of proportionality, the unmachined laser part 51 is preferentially polished in comparison with the laser machined part 50 in the grinding process. For this reason, after the grinding process is completed, the bore inner peripheral surface 31 has a convex shape with the laser-processed portion 50 and a concave shape with the laser-unprocessed portion 51, and has an overall uneven shape. As described above, the cause of the waviness is that the grindstone 40 is not worn due to the hardness difference between the hardened portion generated around the laser processed portion 50 and the uncured portion of the laser unprocessed portion 51. This is considered to be due to the uniformity and clogging of the grindstone 40 to be non-uniform. When the bore inner peripheral surface 31 has a generally undulating uneven shape, the surface pressure of the convex portion becomes unevenly high, the friction characteristics of the sliding surface are adversely affected, and the seizure resistance decreases.
[0022]
On the other hand, in the case of the first embodiment, after the grinding process is completed, the bore inner peripheral surface 31 does not have an overall wavy uneven shape. The waviness could be suppressed because the distribution of the depressions 32 positioned along the moving direction of the grindstone 40 indicated by the arrows 41 and 42 became substantially uniform along the moving direction of the grindstone 40 and the wear of the grindstone 40 was ground. This is considered to be because the surface is substantially uniform over the entire surface, and clogging of the grindstone 40 is substantially uniform over the entire surface of the grinding surface. While the bore inner peripheral surface 31 can be formed to have a concave and convex shape that undulates after grinding, a fine recess 32 that functions as an oil reservoir can be formed, so that the surface pressure becomes uniform in the circumferential direction, and the sliding surface The seizure resistance can be improved without deteriorating the friction characteristics.
[0023]
A processing procedure for the bore inner peripheral surface 31 in the first embodiment will be described.
[0024]
First, the condensing unit 14 is rotated by the driving device 16 while irradiating the laser beam 20 at a predetermined pulse frequency, and a plurality of depressions 32 functioning as oil reservoirs are formed on the bore inner circumferential surface 31 along the circumferential direction. .
[0025]
Next, the condensing unit 14 is moved by a predetermined distance in the axial direction of the cylinder bore by the driving device 16. At that position, the condensing unit 14 is rotated again while irradiating the laser beam 20 with a predetermined pulse frequency, and a plurality of depressions 32 are formed on the bore inner circumferential surface 31 along the circumferential direction.
[0026]
When the plurality of depressions 32 are formed along the circumferential direction at positions moved in the axial direction of the cylinder bore after the plurality of depressions 32 are formed along the circumferential direction, they are adjacent along the axial direction of the cylinder bore. Laser light is irradiated so that the phase of the indented portion 32 along the circumferential direction is shifted. In order to shift the phase of the hollow portion 32, control for shifting the output timing of the laser light 20 from the laser oscillator 11 is performed.
[0027]
The above-described movement of the condensing unit 14 in the axial direction and the formation of the plurality of depressions 32 along the circumferential direction at that position are repeated, and laser fine processing is performed on the region indicated by the two-dot chain line in FIG. Apply processing. The average output and processing speed of the laser beam can be selected as appropriate. For example, the average laser output is 10 W to 50 W, and the processing speed is 5 m / min to 15 m / min.
[0028]
If the average laser output is less than 10 W, the recess 32 having a depth sufficient to function as an oil reservoir recess cannot be formed. Further, when the laser average output is larger than 50 W, for example, 100 W, the oscillation efficiency of the laser beam becomes low and can be used at most about 50 W. Further, in the current production, a range of 10 W to 50 W is usually used as the range of laser average output. From the above, the laser average output is preferably 10 W to 50 W in consideration of energy saving.
[0029]
On the other hand, when the machining speed is lower than 5 m / min, the production efficiency (the number of machining per unit time) becomes extremely low because the machining speed becomes slower than the conventional machining time. Further, if the machining speed is higher than 15 m / min, it is necessary to increase the pulse frequency. However, if the pulse frequency is too high, the laser processing apparatus 10 is consumed very much and the life of the apparatus is shortened. From the above, the machining speed is preferably 5 m / min to 15 m / min in consideration of the lower limit value and the upper limit value of the machining speed that can be adopted during actual production.
[0030]
The cylinder block 30 that has been subjected to the laser micromachining has a plurality of recesses 32 formed along the circumferential direction at a plurality of positions along the axial direction, and further in the circumferential direction adjacent to the axial direction. The phase of the indented portion 32 is shifted. The recess 32 shown in FIG. 4 has a point shape like a hemispherical recess. The pitch of the hollow portions 32 in the circumferential direction is about 0.6 mm, and the pitch in the axial direction is about 0.3 mm.
[0031]
After the laser fine processing is completed, the bore inner peripheral surface 31 is finished by grinding using the honing grindstone 40. At the time of grinding, the honing grindstone 40 is moved back and forth in the axial direction of the cylinder bore while being rotated together with the cylindrical tool. Further, the honing grindstone 40 is expanded outward in the radial direction and is pressed against the bore inner peripheral surface 31. The honing grindstone 40 is rotated at a relatively high speed, and is moved forward and backward at a relatively low speed.
[0032]
When the grinding process is completed, the raised portion 33 generated by the laser micromachining is removed, and the bore inner peripheral surface 31 is finished to a smooth surface having a predetermined surface roughness.
[0033]
Here, since the phase of the recessed portions 32 along the circumferential direction adjacent to each other along the axial direction of the cylinder bore is shifted, the laser unmachined portion 51 is not preferentially ground, and the bore inner circumferential surface 31 is ground. The fine hollow part 32 which functions as an oil sump can be formed, suppressing becoming a wavy uneven shape after processing. As described above, according to the bore inner peripheral surface 31 having the recess 32 having the function of the oil sump and the smooth surface, the surface pressure becomes uniform in the circumferential direction, and the friction characteristics of the sliding surface are not deteriorated. The seizure resistance can be improved.
[0034]
As described above, according to the method for processing a sliding surface in the first embodiment, a plurality of depressions are formed at positions moved in the axial direction of the cylinder bore after the plurality of depressions 32 are formed along the circumferential direction. When the portion 32 is formed along the circumferential direction, the laser beam 20 is irradiated so that the phases of the recessed portions 32 along the circumferential direction adjacent to each other along the axial direction of the cylinder bore are shifted, and then grinding is performed. The sliding surface is finished by For this reason, it is possible to form a fine recess 32 that functions as an oil reservoir while suppressing the sliding surface forming the circumferential surface from becoming a wavy uneven shape after grinding, thereby reducing the friction characteristics of the sliding surface. It becomes possible to improve the seizure resistance without deteriorating.
[0035]
In the case of the inner peripheral surface of the cylinder bore in the cylinder block 30 as the sliding surface, it is possible to improve the seizure resistance without deteriorating the friction characteristics of the inner peripheral surface 31 of the bore.
[0036]
Further, the cylinder block 30 in the first embodiment has a plurality of recesses 32 formed along the circumferential direction at a plurality of positions along the axial direction, and a circumference adjacent to the axial direction. The phase of the dent 32 along the direction is shifted. For this reason, it is possible to form a fine recess 32 that functions as an oil reservoir while suppressing the bore inner peripheral surface 31 as a sliding surface forming a circumferential surface from becoming a wavy uneven shape after grinding, It is possible to improve the seizure resistance without deteriorating the friction characteristics of the bore inner peripheral surface 31.
[0037]
In addition, the hollow part 32 is not restricted to the point shape shown in FIG. 4, An appropriate | suitable shape can be selected as long as it can function as an oil sump. For example, as shown in FIG. 5, the recess 32 may have a linear shape like a long groove. Moreover, the hollow part 32 may be a linear shape such as an ellipse.
[0038]
In the case of the linear recess 32, the lubricating oil stored in the longitudinal direction (circumferential direction) of the recess 32 flows or moves. On the other hand, the oil reservoir in the point-shaped depression 32 has less lubricating oil flow than the linear depression 32. For this reason, when the area of the hollow portion 32 per unit area of the bore inner peripheral surface 31 is the same, the dot-shaped hollow portion 32 has fewer regions where the oil reservoir is interrupted than the linear hollow portion 32. . Therefore, the point-shaped dent 32 has a higher seizure surface pressure where seizure occurs than the linear dent 32, and can more effectively prevent seizure.
[0039]
In addition, in this specification, "the hollow part 32 along the circumferential direction" means not only the case where the plurality of hollow parts 32 are arranged in a direction orthogonal to the axis of the workpiece, but also the plurality of hollow parts 32. This is a concept that includes a case where is arranged in a direction inclined with respect to the axis of the workpiece.
[0040]
(Second Embodiment)
The second embodiment is the first embodiment described above in that it provides a sliding surface processing method and a cylinder block 30 that can improve the seizure resistance without deteriorating the friction characteristics of the bore inner peripheral surface 31. The form is the same. However, in the second embodiment, after performing laser micromachining to irradiate the laser beam 20 to form a fine recess 32, a portion 50 subjected to laser micromachining and a portion 51 not subjected to laser micromachining. By performing laser quenching that absorbs the difference in hardness, the inner peripheral surface 31 of the bore is restrained from being undulated after grinding. In this regard, by shifting the phase of the recessed portions 32 along the circumferential direction adjacent to each other along the axial direction of the cylinder bore, the bore inner circumferential surface 31 is prevented from becoming a concavo-convex shape after grinding. This is different from the embodiment.
[0041]
In the second embodiment, the laser processing apparatus 10 shown in FIG. 1 is used to irradiate the laser beam to the region indicated by the two-dot chain line in FIG. 32 is formed. After performing this laser micromachining, laser quenching is performed to absorb the hardness difference between the laser machined portion 50 that has undergone laser micromachining and the laser unmachined portion 51 that has not undergone laser micromachining.
[0042]
Since the raised portion 33 generated by the laser micromachining is hardened, if the laser-hardened portion 33 is further subjected to laser quenching, the hardness difference cannot be absorbed. For this reason, laser quenching is performed on a region that matches the purpose of absorbing the hardness difference, specifically, on a portion 51 other than the portion 50 on which laser micromachining has been performed. Here, the “part 50 subjected to laser micromachining” includes a recess 32 and a raised portion 33 around the recess 32.
[0043]
After absorbing the hardness difference by laser quenching, the bore inner peripheral surface 31 is finished by grinding as in the first embodiment.
[0044]
Laser quenching may be performed using a dedicated machine, but can also be performed using the laser processing apparatus 10 shown in FIG. That is, even if the power density of the laser beam 20 irradiated from the laser processing apparatus 10 is substantially the same, the condensing unit 14 is moved by the drive unit 16 so that the focal point of the laser beam 20 is separated from the bore inner peripheral surface 31. Laser quenching can be performed without melting the bore inner peripheral surface 31. FIG. 6 schematically shows an example of the relationship between the laser beam irradiation time and the power density set when performing fine processing, quenching, impact hardening, and welding by laser beam irradiation.
[0045]
FIG. 7 shows the arrangement state of the dents 32 in the case of the comparative example in which laser quenching is not performed before the finishing process by grinding and the case of the second embodiment in which laser quenching is performed, after laser fine processing FIG. 6 is a cross-sectional view showing a bore inner peripheral surface 31, a cross-sectional view showing a bore inner peripheral surface 31 after laser hardening in the case of the second embodiment, and a cross-sectional view showing a bore inner peripheral surface 31 after grinding. As shown in the figure, the phase of the recessed portion 32 along the circumferential direction adjacent to the cylinder bore in the axial direction is the same phase in both the proportional and second embodiments.
[0046]
As shown in FIG. 7, in the case of proportionality, the unmachined laser beam 51 is preferentially polished in comparison with the laser machined portion 50 in the grinding process. For this reason, after the grinding process is completed, the bore inner peripheral surface 31 has a convex shape with the laser-processed portion 50 and a concave shape with the laser-unprocessed portion 51, and has an overall uneven shape. As described above, the cause of the waviness is that the grindstone 40 is not worn due to the hardness difference between the hardened portion generated around the laser processed portion 50 and the uncured portion of the laser unprocessed portion 51. This is considered to be due to the uniformity and clogging of the grindstone 40 to be non-uniform. When the bore inner peripheral surface 31 has a generally undulating uneven shape, the surface pressure of the convex portion becomes unevenly high, the friction characteristics of the sliding surface are adversely affected, and the seizure resistance decreases.
[0047]
On the other hand, in the case of the second embodiment, after the grinding process is completed, the bore inner peripheral surface 31 does not have an overall wavy uneven shape. The waviness could be suppressed because the laser unmachined portion 51 was hardened by laser hardening and the hardness difference was absorbed, and the wear of the grindstone 40 became almost uniform over the entire grinding surface. This is thought to be because clogging is almost uniform over the entire grinding surface. While the bore inner peripheral surface 31 can be formed to have a concave and convex shape that undulates after grinding, a fine recess 32 that functions as an oil reservoir can be formed, so that the surface pressure becomes uniform in the circumferential direction, and the sliding surface The seizure resistance can be improved without deteriorating the friction characteristics.
[0048]
A processing procedure of the bore inner peripheral surface 31 in the second embodiment will be described.
[0049]
First, the condensing unit 14 is rotated by the driving device 16 while irradiating the laser beam 20 at a predetermined pulse frequency, and a plurality of depressions 32 functioning as oil reservoirs are formed on the bore inner circumferential surface 31 along the circumferential direction. .
[0050]
Next, the condensing unit 14 is moved by a predetermined distance in the axial direction of the cylinder bore by the driving device 16. At that position, the condensing unit 14 is rotated again while irradiating the laser beam 20 with a predetermined pulse frequency, and a plurality of depressions 32 are formed on the bore inner circumferential surface 31 along the circumferential direction.
[0051]
The above-described movement of the light collecting portion 14 in the axial direction and the formation of the plurality of hollow portions 32 along the circumferential direction at that position are repeated, and laser processing is performed on the region indicated by the two-dot chain line in FIG. Apply. The average output and processing speed of the laser beam can be selected as appropriate. For example, the average laser output is 10 W to 50 W, and the processing speed is 5 m / min to 15 m / min.
[0052]
After performing the laser micromachining, laser quenching is performed on the laser unmachined part 51 other than the laser machined part 50 (including both the fine hollow part 32 and the raised part 33). At this time, in the laser processing apparatus 10, the condensing unit 14 is moved so that the focal point of the laser light 20 is separated from the bore inner peripheral surface 31 while keeping the average output of the laser light 20 constant. Further, the operation of the laser oscillator 11 and the movement of the condensing unit 14 are controlled so that laser quenching is performed in the region of the laser unprocessed part 51.
[0053]
After the laser quenching is completed, the bore inner peripheral surface 31 is finished by grinding using the honing grindstone 40 as in the first embodiment.
[0054]
When the grinding process is completed, the raised portion 33 generated by the laser micromachining is removed, and the bore inner peripheral surface 31 is finished to a smooth surface having a predetermined surface roughness.
[0055]
Here, since laser hardening was performed before finishing by grinding, the laser unmachined portion 51 is not preferentially ground, and the bore inner peripheral surface 31 has a concavo-convex shape after grinding. It is possible to form a fine recess 32 that functions as an oil reservoir while suppressing the above. As described above, according to the bore inner peripheral surface 31 having the recess 32 having the function of the oil sump and the smooth surface, the surface pressure becomes uniform in the circumferential direction, and the friction characteristics of the sliding surface are not deteriorated. The seizure resistance can be improved.
[0056]
As described above, according to the sliding surface processing method in the second embodiment, the laser micromachining is performed after the laser micromachining to form the fine recess 32 by irradiating the laser beam 20. Laser quenching is performed to absorb the difference in hardness between the portion 50 and the portion 51 that has not been subjected to laser micromachining, and then the sliding surface is finished by grinding. For this reason, it is possible to form a fine recess 32 that functions as an oil reservoir while suppressing the sliding surface that forms the circumferential surface from becoming a wavy uneven shape after grinding, and thereby to improve the friction characteristics of the sliding surface. It becomes possible to improve the seizure resistance without deteriorating.
[0057]
Since the laser quenching is performed on the portion 51 other than the portion 50 on which the laser micromachining has been performed, the laser quenching is performed on a region that meets the purpose of absorbing the hardness difference. For this reason, it is possible to form the fine recess 32 functioning as an oil reservoir while reliably suppressing the sliding surface forming the circumferential surface from becoming a wavy uneven shape after the grinding process. It is possible to improve the seizure resistance without deteriorating the characteristics.
[0058]
The portion 50 that has been subjected to laser micromachining includes a hollow portion 32 and a raised portion 33 around the hollow portion 32 so that the raised portion 33 is not subjected to laser quenching. For this reason, the hardness of the raised portion 33 hardened by laser micromachining is not further increased, and the hardness difference is absorbed, and the sliding surface forming the circumferential surface becomes a concavo-convex shape wavy after grinding. Can be reliably suppressed.
[0059]
In the case of the inner peripheral surface of the cylinder bore in the cylinder block 30 as the sliding surface, it is possible to improve the seizure resistance without deteriorating the friction characteristics of the inner peripheral surface 31 of the bore.
[0060]
In addition, the cylinder block 30 in the second embodiment has a hardness difference between a portion 50 that has been subjected to laser micromachining to form a fine recess 32 by irradiating laser light and a portion 51 that has not been subjected to the laser micromachining. The laser hardening which absorbs is given. For this reason, it is possible to form a fine recess 32 that functions as an oil reservoir while suppressing the bore inner peripheral surface 31 as a sliding surface forming a circumferential surface from becoming a wavy uneven shape after grinding, It is possible to improve the seizure resistance without deteriorating the friction characteristics of the bore inner peripheral surface 31.
[0061]
In addition, although the hollow part 32 showed the case of the point shape like a hemispherical recessed part, the linear shape shown in FIG. 5 or the linear shape like an ellipse may be sufficient. The point-shaped dent 32 can prevent burn-in more efficiently than the linear dent 32.
Furthermore, it can also be set as the form which combined 1st Embodiment and 2nd Embodiment. That is, the hardness difference between the portion 50 that has been subjected to laser micromachining and the portion 51 that has not been subjected to laser micromachining is shifted by shifting the phase of the recessed portion 32 along the circumferential direction adjacent to the axial direction of the cylinder bore. Absorbing laser quenching may be performed prior to grinding. According to such a configuration, it is possible to form the fine recess 32 functioning as an oil reservoir while further reliably suppressing the sliding surface forming the circumferential surface from becoming a wavy uneven shape after grinding. It is possible to further improve the seizure resistance without deteriorating the friction characteristics of the moving surface.
[Brief description of the drawings]
FIG. 1 is a view showing a situation in which a fine recess is formed by irradiating a laser beam to a bore inner peripheral surface from a laser processing apparatus.
FIG. 2 is a perspective view showing a region where laser processing is performed on an inner peripheral surface of a bore.
FIG. 3A is a cross-sectional view showing a bore inner peripheral surface after laser processing, and FIG. 3B is a cross-sectional view showing a bore inner peripheral surface after grinding.
FIGS. 4A and 4B are a case where the phase of the recesses along the circumferential direction adjacent to each other along the axial direction of the cylinder bore is the same phase, and a case of the first embodiment where the phase of the recess is shifted. FIGS. FIG. 5 is a cross-sectional view showing a state of arrangement of recesses, a bore inner peripheral surface after laser fine processing, and a cross-sectional view showing a bore inner peripheral surface after grinding.
FIG. 5 is a diagram showing a point-shaped depression.
FIG. 6 is a schematic diagram showing an example of a relationship between a laser beam irradiation time and a power density set when performing fine processing, quenching, impact hardening, and welding by laser beam irradiation.
FIG. 7 shows an arrangement state of the recesses in each of a case where the laser quenching is not performed before the finishing process by the grinding process and a case where the laser quenching is performed in the second embodiment, and after the laser micromachining. FIG. 6 is a cross-sectional view showing a bore inner peripheral surface, a cross-sectional view showing a bore inner peripheral surface after laser hardening in the case of the second embodiment, and a cross-sectional view showing a bore inner peripheral surface after grinding.
[Explanation of symbols]
10 ... Laser processing device
20 ... Laser light
30 ... Cylinder block (workpiece)
31 ... Bore inner peripheral surface (sliding surface forming the peripheral surface)
32 ... depression
33 ... Swelling part
40 ... Whetstone
50... Laser processing unit 50 (including a portion subjected to laser fine processing, including a recess 32 and a raised portion 33)
51 ... Laser unprocessed portion 51 (portion where laser fine processing is not performed)

Claims

In the processing method of the sliding surface that forms a fine recess that functions as an oil reservoir by irradiating the sliding surface forming the circumferential surface of the workpiece with laser light,
When the plurality of depressions are formed along the circumferential direction at a position moved in the axial direction of the workpiece after the plurality of depressions are formed along the circumferential direction, along the axis direction of the workpiece. Irradiate the laser beam so that the phase of the recesses along the circumferential direction adjacent to each other is shifted,
Thereafter, the sliding surface is processed by grinding to finish the sliding surface.

In the processing method of the sliding surface that forms a fine recess that functions as an oil reservoir by irradiating the sliding surface forming the circumferential surface of the workpiece with laser light,
After performing laser micromachining to form a fine recess by irradiating with laser light, laser quenching is performed to absorb the hardness difference between the portion subjected to laser micromachining and the portion not subjected to laser micromachining,
Thereafter, the sliding surface is processed by grinding to finish the sliding surface.

3. The sliding surface processing method according to claim 2, wherein the laser quenching is performed on a portion other than the portion subjected to laser micromachining.

4. The method for processing a sliding surface according to claim 3, wherein the laser-micromachined portion includes a recess and a raised portion around the recess.

The sliding surface processing method according to claim 1, wherein the plurality of depressions are in a dot shape or a line shape.

The method of processing a sliding surface according to claim 1, wherein the sliding surface is a bore inner peripheral surface of a cylinder block.

In the cylinder block in which a fine recess that functions as an oil reservoir is formed by irradiating the inner peripheral surface of the bore as a sliding surface with a laser beam,
At a plurality of positions along the axial direction, a plurality of depressions are formed along the circumferential direction,
Furthermore, the phase of the hollow part along the circumferential direction which adjoins along an axial center direction has shifted | deviated, The cylinder block characterized by the above-mentioned.

In the cylinder block in which a fine recess that functions as an oil reservoir is formed by irradiating the inner peripheral surface of the bore as a sliding surface with a laser beam,
Laser quenching that absorbs a difference in hardness between a portion that has been subjected to laser micromachining to form a fine recess by irradiation with laser light and a portion that has not been subjected to the laser micromachining is provided. Cylinder block.

The cylinder block according to claim 7 or 8, wherein the plurality of depressions have a dot shape or a line shape.