JPH0337023B2

JPH0337023B2 -

Info

Publication number: JPH0337023B2
Application number: JP61285639A
Authority: JP
Inventors: Kazuo Tanaka; Yoichiro Yoneda; Kanji Shimizu
Original assignee: Kobe Steel Ltd
Current assignee: Kobe Steel Ltd
Priority date: 1986-11-29
Filing date: 1986-11-29
Publication date: 1991-06-04
Also published as: JPS63138141A

Description

【発明の詳細な説明】［産業上の利用分野］本発明は内燃機関のピストンの製造方法に関
し、特に、ヘツド部がAl基複合材料からなり、
スカート部がAl又はAl合金からなる内燃機関の
ピストンの製造方法に係る。［従来技術］（背景）内燃機関のピストンには燃費向上のため軽量化
が要求される。かかる要求に応じるためピストンの材質として
Al合金を使用することが検討された。しかし、ピストンのヘツド部には高い耐熱性、
高い耐摩耗性、高強度、高耐性、熱膨張率が小さ
いことが要求されるので、ピストンの材質として
Al合金を使用した場合にはかかる要求を満たす
ことはできない。そこで、高い耐熱性、高い耐摩耗性、高強度、
高剛性、小熱膨張性を満たすために、ピストンの
材質としてAl基複合材料を使用することが検討
された。しかし、Al基複合材料は冷間加工性が悪いた
め、ピストンの材質としてAl基複合材料を使用
する場合には、Al基複合材料をピストン形状に
冷間加工することが困難となる。また、Al基複
合材料自体が高価なためピストンが高価になつて
しまうという問題がある。そのため、ピストンのヘツド部のみをAl基複
合材料とし、他の部分はAl合金とする試みがな
されている（特開昭58−100642号公報）。（従来技術の構成）ところで、ピストンのヘツド部のみをAl基複
合材料とし、他の部分はAl合金としたピストン
の製造方法としては次の技術が知られている。第５図に示すように、鋳型２０キヤビテイー
２２内に、ヘツド部形状に成形された複合材料
（プリフオーム２４）を予め配置し、このプリ
フオーム２４が配置された鋳型２０内にAl金
属あるいはAl合金の溶湯２６を鋳込み、鋳込
み後、静水的高圧力を加えたまま凝固させるこ
とにより造ピストンを製造するいわゆる溶湯鍛
造法。 Al基複合材料よりなるヘツド部とAl金属あ
るいはAl合金よりなるスカート部とをアーク
溶接又はフラツシユバツト溶接することにより
ピストンを製造する方法。［発明が解決しようとする問題点］しかし、上記従来技術には次のような問題点が
ある。上記した溶湯鍛造法においては、製品コスト
が高く、実用的でない。アーク溶接又はフラツシユバツト溶接する方
法においては、溶接時のアーク熱又はフラツシ
ングによる熱でAl基複合材料中の強化材（例
えばSiCウイスカ）が分解し、分解により発生
するガスのため溶接部にブローホールを生じた
り、酸化物を生じたりするという問題点。［問題点を解決するための手段］上記問題点は、ヘツド部が、Al金属又はAl合
金よりなるマトリクスを粒子又は繊維で強化して
なるAl基複合材料からなり、スカート部がAl又
はAl合金からなる内燃機関のピストンの製造方
法において、該ヘツド部と該スカート部とを摩擦
溶接により接合することを特徴とする内燃機関の
ピストンの製造方法によつて解決される。以下に本発明を詳細に説明する。本発明においてはヘツド部がAl基複合材料か
らなる。 Al基複合材料としては、Al金属又はAl合金の
マトリツクスを各種の繊維もしくは粒子で強化し
たものならば特に限定されない。マトリクスのAl合金としては、特に限定され
ないが、例えば、AC8A，6061，2024，2219，
7075，4032，AC8B，AC8C，AC9A，AC9B，
AC5A等を用いればよい。強化材の粒子としては、例えば、SiC、Al₂O₃、
Si₃N₄、ZrO₂、TiC、TiO₂等のセラミツク粒子を
用いればよい。また、強化材の繊維としては、例えば、SiCウ
イスカ、Si₃N₄等のウイスカ、Ｃ、Al₂O₃、Al₂O₃
−SiO₂、SiC等の短繊維、および長繊維を用いれ
ばよい。なお、以上の強化材例のうち、繊維としては
SiCが好ましい。さらに、次の性状を有するSiCウイスカを用い
ることがより好ましい。 ●直径 0.1μm〜2μm ●長さ 10〜1000μm これは、この範囲の直径のSiCウイスカが製
造容易であり、経済的であるからである。 ●アスペクト比 100以上アスペクト比が100以上の場合に強度の向上
が特に著しいからである。 ●Vf ５〜40％５％未満では強度の向上効果があまり期待で
きず、一方、40％を超えると強度の向上効果は
飽和するので、経済的に損だからである。ここで、アスペクト比＝ウイスカ長さ／ウイスカ直径 Vf＝ウイスカ体積／ウイスカ体積＋マトリクス体積である。なお、Al基複合材料からなるヘツド部の製造
方法は特に問わないが、例えば、粉末法、溶湯鍛
造法等によればよい。一方、スカート部はAl金属又はAl合金からな
る。ここで、スカート部のAl合金としては、特に
限定されないが、例えば、AC8A，6061，2024，
2219，7075，4032，AC8B，AC8C，AC9A，
AC9B，AC5A等を用いればよい。本発明では、あらかじめピストンのヘツド部の
みを健全なAl基複合材料で作成し（製造方法は
問わない）、このヘツド部を、Al金属又はAl合金
からなるスカート部と摩擦溶接にて接合すること
により、部分強化ピストンを製造する。なお、摩擦溶接後は必要に応じ、機械加工およ
び熱処理を施す。接合部の形状は、後述する第１図、第２図、第
３図、第４図等に示す形状が考えられるが、これ
らの形状に限定されるものではない。また、ピストン形状にも限定されるものではな
い。接合位置も特に制限されるものではないが、ピ
ストンリングはめ込み部分は、Al基複合材料の
方に設けることが好ましい。なぜならば、ピスト
ンリングはめ込み部分は、エンジン作動時に高温
になる。従つて、ピストンリングはめ込み部分を、高温強度の
高いAl基複合材料の方に設けることによりピ
ストンリングはめ込み部分の高温強度を高くす
ることができる。ピストンリングはめ込み部分は熱膨張する
が、ピストンリングはめ込み部分を、熱膨張率
の小さなAl基複合材料の方に設けると、ピス
トンリングはめ込み部分の熱膨張率は小さくな
るのでピストンリングを固定してしまうことが
なく、従つて、ピストンリングは耐えずシリン
ダ壁面にあたり、シール性が良くなるからであ
る。［発明の実施例］以下実施例を参照して本発明を詳細に説明す
る。（第１実施例）第１図に第１実施例を示す。第１図中、ヘツド部１はAl基複合材料（繊
維：SiCウイスカ、マトリツクス：6061合金）よ
りなり、スカート部２はAl合金（6061合金又は
AC8A）よりなる。なお、SiCウイスカとしては次のものを用い
た。 ●径 0.5μm ●長さ 50〜100μm ●アスペクト比 100〜200 Vf値 20％なお、ピストンの外径は40mm、長さは60mmであ
る。本例では、スカート部２の摩擦溶接すべき接合
面２ａ，２ｂを円環状に形成し、ヘツド部２の摩
擦溶接すべき接合面１ａ，１ｂを、スカート部２
の摩擦溶接すべき接合面２ａ，２ｂと略同面積で
且つ円環状に形成すべく、ヘツド部１及びスカー
ト部２の軸心方向にそれぞれ凹部３，４を設けて
いる。ヘツド部１とスカート部２の接合面をこのよう
に薄肉化すると、摩擦溶接する際に両者のヒート
バランスがとれ、両者のうちの一方（熱容量の大
きな方）のみの温度が上がりにくくなることを防
止することができる。従つて、熱容量の大きい方
の接合面に付着した酸化物あるいは油脂等の汚れ
も十分に外に押出され、酸化物あるいは油脂等の
汚れに起因する欠陥の発生をも防止することがで
きる。スカート部２を回転させながら、ヘツド部１に
接触させ、摩擦熱より加熱し、設定より代に達し
た時点でブーキを付加し、スカート部２を急停止
させると共に加圧し、摩擦溶接を行なつた。溶接は、加熱圧力P₁（摩擦中の推力のゲージ圧
力）、アツプセツト圧力P₂（停止後の推力のゲー
ジ圧力）、回転数Ｎ、加熱時設定より代Se₁を変え
実施した。第１比較例として、摩擦溶接時に用いて材料と
同じものを用いて第１図の接合面１ａと２ａと
を、また、接合面１ｂと２ｂとを相対させ、開先
部とし、テイグにて周溶接し、ピストンを製造し
た。以下本方法をアーク溶接法と呼ぶ。また、第２比較例として、摩擦溶接時に用いた
材料と同じものを用いて、第１図の接合面１ａと
２ａとを、また、接合面１ｂと２ｂを相対させ、
フラツシユバツト溶接し、ピストンを製造した。
以下本方法をフラツシユバツト溶接法と呼ぶ。以上の条件を表１に示す。また完成したピスト
ンについてAl基複合材料、Al合金界面の顕微鏡
観察、界面強度を測定し、その結果についても表
１に示す。実施例Ａ〜Ｅはスカート部材質が6061、実施例
Ｆ〜Ｇはスカート部材質がAC8Aであるが、いず
れも界面強度は28Kgｆ／mm²以上で、界面近傍の
6061又はAC8Aの母材で破断した。また顕微鏡観
察によつても界面は健全であつた。一方、比較例Ｈはアーク溶接法、比較例はフ
ラツシユバツト溶接法によるものであるが、界面
に酸化膜、酸化物、ブローホール、割れ等の欠陥
が認められ、界面強度も12〜15Kgｆ／mm²程度と低
く、実用にはならない。（第２実施例）第２図に第２実施例を示す。本例では、スカート部２側に突出し、かつ、ス
カート部２の凹部４の内径より小さな外径を有す
る円筒状の突出部５をヘツド部部１の摩擦溶接す
べき接合面１ａ，１ｂに設け、該突出部の根元近
傍において、直径方向内側にへこんだ溝部６を該
突出部５の外周に設けてある。かかる溝部６を設けることにより、摩擦溶接す
る際に発生するバリはこの溝部６に収納され、ピ
ストン内部にはバリははみださない。すなわち、
第１実施例の場合は、バリはピストンの内部にも
はみだし、このバリが脱落するとピストン内部に
入り込み、ピストンのトラブルを生じせしめるこ
とがあるが、本例ではかかる事態を防止すること
ができる。他の点は第１実施例と同様である。（第３実施例）第３図に第３実施例を示す。本例では、スカート部２に設けた凹部４が有底
で且つ当該底部７に軸心方向に該凹部４とスカー
ト部２の内部８とを連通する連通孔９を設けてあ
る。本例ではこのように凹部４が有底であるので、
摩擦溶接の際に内バリが生じ、それが脱落したと
してもこの底部７に脱落したバリがたまるので、
ピストン内部８に入りこむのを防止している。なお、連通孔９を設けたのは、ヘツド部１の凹
部３とスカート部２の凹部４とで形成される空間
内の空気が、摩擦溶接時の摩擦熱あるいは使用時
の熱のため膨張するのでこの膨張した空気を外部
に逃がすためである。従つて、連通孔９を設ける
位置。形状は特に問わない。第４図に示すように
直線状でもよいし、また、曲折せしめてもよい。
曲折せしめた場合には空気は通過するが、脱落し
たバリはピストン内部に入りにくくなるので好ま
しい。なお、他の点は第１実施例と同様である。（第４実施例）第４図に第４実施例を示す。本例では、ヘツド部１及び／又はスカート部２
の摩擦溶接すべき接合面１ａ，１ｂを突起形状と
した。第４図ではヘツド部１の摩擦溶接すべき接合面
１ａを突起形状としている。 Al基複合材料とAl又はAl合金との間には硬度
差があるため、両者の接合面とともに平面とする
と、ヘツド部とスカート部の中心軸と回転軸とが
少しでもずれた場合、相対速度の速い外周部が最
初に接触し、その部分が優先的に変形するため、
回転中心部に酸化物が残り、接合不良が発生す
る。しかるに、本例のように少なくともいずれか
の接合面を突起形状とすると、両者は回転中心部
から接触していくため、中心部の酸化物は外周部
へ押出され健全な接合が行なわれる。なお、突起形状は、第４図では円錐状のものを
示しているが、円錐状に限らない。要は、回転中
心部より徐々に接触する形状（たとえば半球状）
であればよいことは以上の説明より明らかであ
る。なお、突起形状の先端面積としては10mm²以下が
好ましい。10mm²を超える場合には、接合面中心部
に酸化膜が残り、融合不良が生じる場合があるか
らである。これらの結果から本発明方法によれば、Al基
複合材料、Al材料間界面に脆弱な金属間化合物
や酸化膜を形成させずに、充分な強度を持つ部分
強化ピストンを製造可能なことがわかる。［発明の効果］本発明は以上のように構成したので以下のもろ
もろの効果が得られる。軽量のピストンが製造できる。ヘツド部が、優れた耐熱性、優れた耐摩耗
性、高強度、高剛性、熱膨張率の小さいピスト
ンを製造することができる。素材費、加工費が安価となる。ヘツド部とスカート部との界面に酸化物、割
れ、ラミネーシヨン等の欠陥が存在しないピス
トンを製造することができる。溶接部にブローホール、酸化物の存在しない
ピストンを製造することができる。【表】[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a piston for an internal combustion engine, and in particular, the present invention relates to a method for manufacturing a piston for an internal combustion engine, and in particular, the head portion is made of an Al-based composite material,
The present invention relates to a method of manufacturing a piston for an internal combustion engine whose skirt portion is made of Al or Al alloy. [Prior Art] (Background) Pistons for internal combustion engines are required to be lightweight in order to improve fuel efficiency. In order to meet these demands, we have developed
The use of Al alloy was considered. However, the head of the piston has high heat resistance,
High wear resistance, high strength, high durability, and low coefficient of thermal expansion are required, so it is recommended as a material for pistons.
Such requirements cannot be met if Al alloy is used. Therefore, high heat resistance, high wear resistance, high strength,
In order to achieve high rigidity and low thermal expansion, the use of an Al-based composite material as the material for the piston was considered. However, since the Al-based composite material has poor cold workability, when the Al-based composite material is used as the material of the piston, it is difficult to cold-work the Al-based composite material into a piston shape. Furthermore, since the Al-based composite material itself is expensive, there is a problem in that the piston becomes expensive. Therefore, an attempt has been made to make only the head portion of the piston an Al-based composite material and the other portions to use an Al alloy (Japanese Patent Laid-Open No. 100642/1982). (Constitution of Prior Art) By the way, the following technique is known as a method of manufacturing a piston in which only the head portion of the piston is made of an Al-based composite material and the other portions are made of an Al alloy. As shown in FIG. 5, a composite material (preform 24) molded into a head shape is placed in advance in the mold 20 cavity 22, and Al metal or Al alloy is placed in the mold 20 in which the preform 24 is placed. This is a so-called molten metal forging method in which a molten metal 26 is poured and solidified while applying high hydrostatic pressure after casting to produce a piston. A method of manufacturing a piston by arc welding or flash butt welding a head part made of an Al-based composite material and a skirt part made of Al metal or Al alloy. [Problems to be Solved by the Invention] However, the above prior art has the following problems. In the above-described molten metal forging method, the product cost is high and it is not practical. In the arc welding or flash butt welding method, the reinforcing material (for example, SiC whiskers) in the Al-based composite material decomposes due to the arc heat during welding or the heat from flashing, and the gas generated by the decomposition causes blowholes to be created in the welded part. The problem is that oxidants are formed or oxides are formed. [Means for solving the problem] The above problem is such that the head part is made of an Al-based composite material made of a matrix made of Al metal or Al alloy reinforced with particles or fibers, and the skirt part is made of Al or Al alloy. The present invention is solved by a method for manufacturing a piston for an internal combustion engine, characterized in that the head portion and the skirt portion are joined by friction welding. The present invention will be explained in detail below. In the present invention, the head portion is made of an Al-based composite material. The Al-based composite material is not particularly limited as long as it is a matrix of Al metal or Al alloy reinforced with various fibers or particles. Examples of the matrix Al alloy include, but are not limited to, AC8A, 6061, 2024, 2219,
7075, 4032, AC8B, AC8C, AC9A, AC9B,
AC5A etc. may be used. Examples of reinforcing material particles include SiC, Al ₂ O ₃ ,
Ceramic particles such as Si ₃ N ₄ , ZrO ₂ , TiC, TiO ₂ may be used. In addition, examples of reinforcing fibers include SiC whiskers, Si ₃ N ₄ whiskers, C, Al ₂ O ₃ , Al ₂ O ₃
- Short fibers such as SiO ₂ and SiC, and long fibers may be used. In addition, among the above examples of reinforcing materials, as fibers
SiC is preferred. Furthermore, it is more preferable to use SiC whiskers having the following properties. ●Diameter: 0.1 μm to 2 μm ●Length: 10 to 1000 μm This is because SiC whiskers with a diameter in this range are easy to manufacture and economical. ●Aspect ratio: 100 or more This is because the improvement in strength is particularly remarkable when the aspect ratio is 100 or more. ●Vf 5-40% If it is less than 5%, no significant strength improvement effect can be expected, whereas if it exceeds 40%, the strength improvement effect will be saturated, resulting in an economic loss. Here, aspect ratio=whisker length/whisker diameter Vf=whisker volume/whisker volume+matrix volume. The method of manufacturing the head made of the Al-based composite material is not particularly limited, but may be, for example, a powder method, a molten metal forging method, or the like. On the other hand, the skirt portion is made of Al metal or Al alloy. Here, the Al alloy for the skirt portion is not particularly limited, but examples include AC8A, 6061, 2024,
2219, 7075, 4032, AC8B, AC8C, AC9A,
AC9B, AC5A, etc. may be used. In the present invention, only the head portion of the piston is made in advance from a sound Al-based composite material (the manufacturing method does not matter), and this head portion is joined to the skirt portion made of Al metal or Al alloy by friction welding. A partially reinforced piston is manufactured using the following methods. After friction welding, machining and heat treatment are performed as necessary. The shape of the joint may be the shapes shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, etc., which will be described later, but is not limited to these shapes. Moreover, it is not limited to the shape of a piston. Although the joining position is not particularly limited, it is preferable that the piston ring fitting portion be provided on the Al-based composite material. This is because the part where the piston ring is fitted becomes hot during engine operation. Therefore, by providing the piston ring fitting portion in an Al-based composite material having high high temperature strength, the high temperature strength of the piston ring fitting portion can be increased. The piston ring fitting part expands thermally, but if the piston ring fitting part is made of an Al-based composite material with a small coefficient of thermal expansion, the piston ring will be fixed because the thermal expansion coefficient of the piston ring fitting part will be small. This is because the piston ring does not withstand it and comes into contact with the cylinder wall surface, improving the sealing performance. [Examples of the Invention] The present invention will be described in detail below with reference to Examples. (First Example) FIG. 1 shows a first example. In Fig. 1, the head part 1 is made of Al-based composite material (fiber: SiC whisker, matrix: 6061 alloy), and the skirt part 2 is made of Al alloy (6061 alloy or
AC8A). Note that the following SiC whiskers were used. ●Diameter 0.5μm ●Length 50-100μm ●Aspect ratio 100-200 Vf value 20% The outer diameter of the piston is 40mm and the length is 60mm. In this example, the joint surfaces 2a and 2b of the skirt portion 2 to be friction welded are formed in an annular shape, and the joint surfaces 1a and 1b of the head portion 2 to be friction welded are formed in the skirt portion 2.
Recesses 3 and 4 are provided in the axial direction of the head portion 1 and the skirt portion 2, respectively, so as to have approximately the same area as the joint surfaces 2a and 2b to be friction welded and to form an annular shape. By making the joint surface between the head part 1 and the skirt part 2 thinner in this way, the heat balance between the two parts can be maintained during friction welding, and the temperature of only one of the two parts (the one with larger heat capacity) will not rise easily. It can be prevented. Therefore, dirt such as oxides or fats and oils adhering to the bonding surface having a larger heat capacity is sufficiently pushed out, and defects caused by dirts such as oxides or fats can also be prevented from occurring. While rotating the skirt part 2, it is brought into contact with the head part 1, heated by frictional heat, and when it reaches the set point, a boot is added, and the skirt part 2 is suddenly stopped and pressurized to perform friction welding. Ta. Welding was carried out by changing the heating pressure P ₁ (gauge pressure of thrust during friction), upset pressure P ₂ (gauge pressure of thrust after stopping), rotation speed N, and temperature Se ₁ from the settings during heating. As a first comparative example, the same material used during friction welding was used to make the joining surfaces 1a and 2a in Fig. 1, and the joining surfaces 1b and 2b were made to face each other to form a groove, and Teig was used to The piston was manufactured by circumferential welding. Hereinafter, this method will be referred to as the arc welding method. In addition, as a second comparative example, using the same material as that used in friction welding, the joint surfaces 1a and 2a in FIG. 1 were made to face each other, and the joint surfaces 1b and 2b were made to face each other
The piston was manufactured by flash butt welding.
Hereinafter, this method will be referred to as the flash butt welding method. The above conditions are shown in Table 1. In addition, the completed piston was observed under a microscope at the interface between the Al-based composite material and the Al alloy, and the interface strength was measured, and the results are also shown in Table 1. In Examples A to E, the skirt member material is 6061, and in Examples F to G, the skirt member material is AC8A, but in both cases, the interface strength is 28 Kgf/mm ² or more, and the material near the interface is
It broke in the base material of 6061 or AC8A. The interface was also found to be sound by microscopic observation. On the other hand, Comparative Example H uses the arc welding method, and Comparative Example uses the flash butt welding method, but defects such as oxide films, oxides, blowholes, and cracks are observed at the interface, and the interface strength is also 12 to 15 Kgf/mm ² The degree is too low to be of practical use. (Second Embodiment) FIG. 2 shows a second embodiment. In this example, a cylindrical protrusion 5 that protrudes toward the skirt portion 2 and has an outer diameter smaller than the inner diameter of the recess 4 of the skirt portion 2 is provided on the joint surfaces 1a and 1b of the head portion 1 to be friction welded. A groove 6 recessed diametrically inward is provided on the outer periphery of the protrusion 5 near the base of the protrusion. By providing such a groove 6, burrs generated during friction welding are accommodated in the groove 6, and the burrs do not protrude into the piston. That is,
In the case of the first embodiment, the burr protrudes into the interior of the piston, and if the burr falls off, it may enter the interior of the piston and cause trouble with the piston, but in this embodiment, such a situation can be prevented. Other points are similar to the first embodiment. (Third Embodiment) FIG. 3 shows a third embodiment. In this example, the recess 4 provided in the skirt portion 2 has a bottom, and a communication hole 9 is provided in the bottom portion 7 to communicate the recess 4 and the interior 8 of the skirt portion 2 in the axial direction. In this example, since the recess 4 has a bottom,
Internal burrs are generated during friction welding, and even if they fall off, the burrs will accumulate on this bottom 7.
This prevents it from entering the piston interior 8. The communication hole 9 is provided because the air in the space formed by the recess 3 of the head part 1 and the recess 4 of the skirt part 2 expands due to frictional heat during friction welding or heat during use. This is to allow this expanded air to escape to the outside. Therefore, the position where the communication hole 9 is provided. The shape is not particularly important. It may be straight as shown in FIG. 4, or it may be bent.
If the piston is bent, air will pass through it, but the burrs that have fallen off will be difficult to enter inside the piston, which is preferable. Note that other points are the same as in the first embodiment. (Fourth Example) FIG. 4 shows a fourth example. In this example, the head part 1 and/or the skirt part 2
The joint surfaces 1a and 1b to be friction welded were formed into a protrusion shape. In FIG. 4, the joint surface 1a of the head portion 1 to be friction welded has a protruding shape. Since there is a hardness difference between the Al-based composite material and Al or Al alloy, if the joint surfaces of both are flat, the relative speed will increase if the central axis of the head and skirt parts and the axis of rotation are even slightly deviated. The faster outer periphery of the metal contacts first and deforms preferentially, so
Oxide remains at the center of rotation, resulting in poor bonding. However, if at least one of the bonding surfaces is formed into a protruding shape as in this example, since the two come into contact from the center of rotation, the oxide in the center is pushed out to the outer periphery and a sound bond is achieved. Although the shape of the protrusion is conical in FIG. 4, it is not limited to the conical shape. The key is to have a shape that gradually comes into contact with the center of rotation (for example, hemispherical)
It is clear from the above explanation that it is sufficient. Note that the area of the tip of the protrusion shape is preferably 10 mm ² or less. This is because if it exceeds 10 mm ² , an oxide film may remain at the center of the joint surface, resulting in poor fusion. These results show that according to the method of the present invention, it is possible to manufacture a partially reinforced piston with sufficient strength without forming fragile intermetallic compounds or oxide films at the interface between the Al-based composite material and the Al material. . [Effects of the Invention] Since the present invention is configured as described above, the following various effects can be obtained. Lightweight pistons can be manufactured. It is possible to manufacture a piston whose head portion has excellent heat resistance, excellent wear resistance, high strength, high rigidity, and a small coefficient of thermal expansion. Material costs and processing costs are low. It is possible to manufacture a piston that is free from defects such as oxides, cracks, and laminations at the interface between the head portion and the skirt portion. Pistons can be manufactured without blowholes or oxides in the welds. 【table】

[Brief explanation of drawings]

第１図は本発明の第１実施例を説明するための
正面断面図である。第２図は本発明の第２実施例
を説明するための正面断面図である。第３図は本
発明の第３実施例を説明するための正面断面図で
ある。第４図は本発明の第４実施例を説明するた
めの正面断面図である。第５図は従来例を説明す
るための正面断面図である。１……ヘツド部、２……スカート部、１ａ，１
ｂ，２ａ，２ｂ……接合面、３，４……凹部、５
……突出部、６……溝部、７……底部、８……ピ
ストン内部、９……連通孔、２０……鋳型、２２
……キヤビテイ、２４……プリフオーム、２６…
…溶湯。 FIG. 1 is a front sectional view for explaining a first embodiment of the present invention. FIG. 2 is a front sectional view for explaining a second embodiment of the present invention. FIG. 3 is a front sectional view for explaining a third embodiment of the present invention. FIG. 4 is a front sectional view for explaining a fourth embodiment of the present invention. FIG. 5 is a front sectional view for explaining a conventional example. 1...Head part, 2...Skirt part, 1a, 1
b, 2a, 2b...joint surface, 3, 4...recess, 5
...Protrusion, 6...Groove, 7...Bottom, 8...Piston interior, 9...Communication hole, 20...Mold, 22
...Cavity, 24...Preform, 26...
...molten metal.

Claims

[Claims] 1. Manufacture of an internal combustion engine piston in which the head portion is made of an Al-based composite material made by reinforcing a matrix made of Al metal or Al alloy with particles or fibers, and the skirt portion is made of Al or Al alloy. In the method,
A method of manufacturing a piston for an internal combustion engine, comprising joining the head portion and the skirt portion by friction welding. 2. Form the joint surface of the skirt part to be friction welded into an annular shape, and form the joint surface of the head part to be friction welded into an annular shape.
A piston for an internal combustion engine according to claim 1, wherein a concave portion is provided in the axial direction of the head portion and the skirt portion so as to have approximately the same area as the joint surface of the skirt portion to be friction welded and to be formed in an annular shape. manufacturing method. 3. A cylindrical protrusion that protrudes toward the skirt and has an outer diameter smaller than the inner diameter of the recess in the skirt is provided on the joint surface of the head to be friction welded, and near the base of the protrusion, the cylindrical protrusion has a diametrically inner side. 3. The method of manufacturing a piston for an internal combustion engine according to claim 2, wherein a recessed groove is provided on the outer periphery of the protrusion. 4. Either claim 2 or 3, wherein the recess provided in the skirt portion has a bottom, and the bottom portion is provided with a communication hole that communicates the recess and the inside of the skirt portion in the axial direction. A method for manufacturing a piston for an internal combustion engine as described in . 5. The method of manufacturing a piston for an internal combustion engine according to claim 1, wherein the joint surface to be friction welded is a head portion and/or a skirt portion in a protrusion shape. 6. The method for manufacturing a piston for an internal combustion engine according to claim 5, wherein the tip area of the protrusion is 10 mm ² or less. 7. The method for manufacturing a piston for an internal combustion engine according to any one of claims 1 to 6, wherein the fibers are SiC whiskers. 8 SiC whiskers have a diameter of 0.1 μm to 2 μm, a length of 10 to 1000 μm, an aspect ratio of 100 or more, and a volume fraction Vf in the Al-based composite material of 5 to 40%. Claim 7 which is
A method for manufacturing a piston for an internal combustion engine as described in .