JPH0236357B2

JPH0236357B2 -

Info

Publication number: JPH0236357B2
Application number: JP61203412A
Authority: JP
Inventors: Motomasa Atsui; Kyoshi Kotobuki; Yasuhisa Kimura
Original assignee: Daihatsu Diesel Manufacturing Co Ltd
Current assignee: Daihatsu Infinearth Mfg Co Ltd
Priority date: 1986-08-28
Filing date: 1986-08-28
Publication date: 1990-08-16
Also published as: JPS6360081A

Description

【発明の詳細な説明】＜産業上の利用分野＞本発明は、デイーゼル機関の燃料噴射ポンプか
ら燃料噴射ノズルへ燃料油を送給する燃料噴射高
圧管の製造方法に関する。＜従来の技術＞従来、このような燃料噴射高圧管は、第８図に
示す工程を経て製造されている。即ち、(a)例え
ば、クロムモリブテン鋼（JIS G4105SCM435）
からなるパイプ２１を所定寸法に切断し、(b)パイ
プの一端をプレスで軸方向に据込加工して突起２
２を作り、(c)この突起を径方向にスエージングし
て縮径し、(d)さらに軸方向に仕上げ据込加工して
頭部２３を形成し、(e)頭部先端からパイプ中心穴
へ抜ける穴２４を明け、この穴をリーマ加工した
後、(f)頭部２３外周を旋削して円錐状のニツプル
２５を形成している。そして、めねじを外側に向
けた図示しない一対のユニオン継手をパイプの他
端から外挿し、一方のユニオン継手を上記頭部２
３に外嵌させた後、パイプ２１の他端を上記(b)〜
(f)と同じ工程で加工して、他端にも円錐状のニツ
プルを形成している。＜発明が解決しようとする問題点＞ところが、上記従来の燃料噴射高圧管の製造方
法では、３回もの冷間あるいは熱間鍛造(b)、(c)、
(d)を行なう必要がある。また、３回の鍛造で押し
潰されたパイプ内面が(d)に示すように複雑に褶曲
して、穴明け時にドリルが曲がり、ドリル穴とパ
イプの中心穴がずれたりし、穴明け後も上記押し
潰されたパイプ内面が穴内周面に欠陥として残る
という欠点がある。第９図は、このような欠陥の実例を示してお
り、STS鋼製パイプ（外径12.2mm×内径4.2mm）
から製造された燃料噴射高圧管の頭部の内周面に
は、(a)に示すように深さ1.5mm程度の環状切欠き
が認められ、この切欠き底には(b)に示すような
0.42mmの亀裂が夫々認められる。この切欠きや亀
裂は上記鍛造によつて生じたもので、これらの欠
陥を避けることができないのである。そして、こ
の欠陥が使用時に燃料噴射高圧管の破壊をもたら
すことは論ずるまでもなく、このことは燃料がよ
り高圧で圧送される現在において重大な問題とな
る。そこで、本発明の目的は、頭部の穴明けが正確
かつ容易にでき、明けられた穴の内周面等に欠陥
を残すことのない燃料噴射高圧管の能率的で安価
な製造方法を提供することである。＜問題点を解決するための手段＞上記目的を達成するため、本発明の燃料噴射高
圧管の製造方法は、小径のパイプの一端に、この
パイプと略同径の小径部と大径部からなる段付丸
棒の上記小径部端を突き合わせて軸方向に加圧
し、両者を相対運動させて摩擦熱により突き合わ
せ面を摩擦圧接した後、上記パイプの中心に一直
線をなすように上記段付丸棒に穴を貫設し、この
穴の先端に残つた溶着物の残渣を上記パイプの他
端側から一端側に向けて棒で押し出して除去し、
次いで摩擦圧接部分の外周のバリを旋削除去する
とともに、上記段付丸棒の大径部の外周に円錐状
のニツプルを旋削加工することを特徴とする。＜作用＞パイプと段付丸棒を摩擦圧接して頭部を形成し
ているので、従来の鍛造に比べて、加工工数が低
減し、加工時間がはるかに短く高能率で、形状・
寸法精度も高く、さらに頭部中心に押し潰され褶
曲したパイプ内面ができることもなく、中心穴を
正確、容易かつ欠陥なく明けることができ、使用
時に高圧管の破壊を惹起する虞れもない。さら
に、上記段付丸棒の小径部がパイプと略同径であ
るので、接合される部分の温度場が略対称となつ
て良好な摩擦圧接ができ、かつ圧接部が使用時に
応力進中を生じるニツプル部から離れるため、使
用時の破壊に対してもより安全になる。＜実施例＞以下、本発明を図示の実施例により詳細に説明
する。第１図は燃料噴射高圧管の製造方法を部材の加
工手順図と共に示したフローチヤートであり、ス
テツプ(a)は細棒としてのパイプ１を所定寸法に切
断するパイプ切断工程、ステツプ(b)は上記パイプ
１の外径D₁と同一径の小径部２ａと大径部２ｂ
からなる段付丸棒２，２を旋削加工する段付丸棒
加工工程、ステツプ(c)は上記パイプ１の一端１ａ
に段付丸棒２の小径部２ａ端を突き合わせて軸方
向に加圧し、両者を相対運動させて摩擦熱で圧接
する摩擦圧接工程、ステツプ(d)は上記段付丸棒２
にパイプ１の中心穴１ｃと一直線をなすようにこ
の中心穴１ｃよりも0.2mm程度大径の穴３を貫設
する穴明け工程、ステツプ(e)は上記穴３先端に残
つた溶着物の残渣４を、パイプ１の他端１ｂ側か
ら中心穴１ｃに図示しない針金等を挿入して押し
出す残渣除去工程である。そして、この段階で、
両端の段付丸棒の大径部２ｂに外嵌させるべき一
対のユニオン継手８，８（ステツプ(h)参照）等
を、各めねじ外側に向けてパイプ１の他端１ｂよ
り予め挿入しておく。また、続くステツプ(f)はパイプ１の他端１ｂに
ステツプ(c)と同様にして段付丸棒２を圧接する摩
擦圧接工程、ステツプ(g)は摩擦圧接部５，５の材
質改善のための熱処理加工、ステツプ(h)は他端１
ｂの段付丸棒にステツプ(d)、(e)と同様にして貫通
穴６を明け、溶着物の残渣を除去し、摩擦圧接部
材５，５の外周のバリを旋削除去するとともに、
段付丸棒の大径部２ｂ，２ｂの外周に円錐状のニ
ツプル７，７を旋削加工する工程である。上記パイプ１および段付丸棒２の材質は、クロ
ムモリブテン鋼SCM435（JIS Ｇ 4105）とし、
パイプの外径12mm×内径３mm、段付丸棒は小径部
長さ10mm、大径部長さ20mm、大径部外径19mmとし
た。上記摩擦圧接は、第２図に示す手順で次のよう
に行なわれる。 (a) 固定台の回転チヤツク１０に段付丸棒２を、
移動台上のチヤツク１１にパイプ１を夫々挿入
する。 (b) 両チヤツク１０，１１を夫々矢印Ａ，Ｂの如
く閉じ、ワーク２、１をクランプする。 (c) 回転チヤツク１０を矢印Ｃの如く回転させる
とともに、チヤツク１１を矢印Ｄの如く急速前
進させる。このとき、回転チヤツクの回転数
は、第３図ａに示すように、時刻Tcか２秒位
で一定値Ｒ＝1800rpmに達する。 (d) パイプ１がチヤツク１１の前進により、第３
図ｂに示す時刻Tdにおいて、段付丸棒２に接
触すると、回転チヤツク１０を上記一定回転数
Ｒで回し続けながら、パイプ１を矢印Ｅの如く
段付丸棒に向けて加熱圧力P₁＝４Kgｆ／mm²で
押し付け、時間t₁＝６秒の間接触面を摩擦熱で
加熱する。この間、チヤツク１１は、第３図ｃ
に示すように加熱しろδ₁だけ前進する。 (e) 時刻Teにおいて、第３図に示すように、回
転チヤツク１０の回転を急停止し、パイプ１を
さらに高いアプセツト圧力P₂＝12Kgｆ／mm²で
段付丸棒２に向けて押し付け、チヤツク１１を
アプセツトしろδ₂だけさらに前進させ、摩擦圧
接を完了する。このアプセツト時間t₂は４秒位
で、加熱時間t₁とアプセツト時間t₂を加えた圧
接時間t₃は略10秒、また、加熱しろδ₁とアプセ
ツトしろδ₂を加えたよりしろδは略５mmであ
る。 (f) 最後に、回転チヤツク１０を矢印Ｆの如く開
き、チヤツク１１を、矢印Ｇの如く後退させた
後、矢印Ｈの如く開いて、段付丸棒２２が圧接
されたパイプ１を取り出す。このような摩擦圧接によるパイプ頭部の形成
は、第８図に示した従来の鍛造法に比べて、加工
工数が３（第８図ｂ，ｃ，ｄ参照）から１に低減
し、加工時間がt₃＝10秒とはるかに短く高能率
で、加工の形状・寸法精度も高く、さらに頭部中
心に第８図ｄの如き押し潰され褶曲したパイプ内
面ができないので、中心穴３を真直に容易かつ欠
陥なく明けることができ、従つて使用時に高圧管
の破壊を惹起する虞れもない。その上、パイプ１
と同径の段付丸棒２の小径部２ａの長さを上記パ
イプ径とほぼ同寸法としているので、両者の温度
場が対称的になつて、良好な摩擦圧接が行なえ、
かつ圧接部が使用時に応力集中を生じるニツプル
部から離れていて、使用時の破壊に対してもより
安全である。さらに、容易にニツプルの旋削加工
および中心穴明けを行なうことができ、作業能率
を一層向上させることができる。また、他の接合
法であるフラツシユバツト溶接に比べても、消費
電力が1/10程度と格段に少なく、アプセツトしろ
δも半分程度で材料節約ができ、火花が飛ばす安
全である。第４図、第５図は夫々第１図のｇ熱処理前後の
摩擦圧接部付近のマクロ組織とミクロ組織を示し
ている。熱処理前にマクロ組織である第４図ａ
は、左から順に段付丸棒部、圧接部、パイプ部を
示している。これら各部の顕微鏡組織を第４図
ｂ，ｃ，ｄに順に示した。図から分かるように、
段付丸棒部はフエライト・パーライトの縞状組
織、圧接部はマルテンサイトの焼入組織、パイプ
部はソルバイト組織を呈している。一方、550℃
で２時間保持する焼戻し熱処理後のマクロ組織を
第５図ａに示し、段付丸棒部、圧接部、パイプ部
の顕微鏡組織を第５図ｂ，ｃ，ｄに同様に示し
た。図から分かるように、段付丸棒部とパイプ部
は同様にフエライト・パーライトおよびソルバイ
ト組織を呈し、圧接部はマルテンサイトが消失し
て焼戻し組織となつている。第６図は熱処理前後の摩擦圧接部付近の硬さ分
布を示している。熱処理前は圧接部が前述の如く
マルテンサイト組織であるため、図中の破線で示
すようにこの部分が著しく硬化しているが、熱処
理によつて焼戻し組織となるため、図中の実線で
示すように段付丸棒部やパイプ部と略同じ硬さま
で軟化し、図中の２点鎖線で示すJIS G4105に規
定されるSCM435鋼の硬さ（H_B：269〜331）よ
りもわずかに低い。末尾に掲げた第１表は、摩擦圧接によつて製造
された燃料噴射高圧管の硬性試験結果を示してい
る。引張試験では、圧接部以外の母材パイプ部で
破断し、引張り強さσ_Bも80Kgｆ／mm²以上で、圧接
部の強度に問題はない。曲げ試験や扁平試験で
も、圧接部は傷や割れを生ぜず、良好である。ま
た、衝撃試験では、圧接部はJIS規格値以上の衝
撃値を示し、優れた靭性を有している。さらに、
燃料噴射に伴つてパイプに加わる繰返し応力に対
する強度については、小野式回転曲げ疲労試験を
行なつた。試験結果は、第７図の如きＳ−Ｎ曲線
となり、圧接パイプの10⁷回疲労限は、略24.5
Kg／mm²を示し、母材パイプの疲労限30Kg／mm²と大
差なく、十分な疲労強度を有することが確かめら
れた。これらの確性試験および前述のミクロ、マクロ
組織と硬さ試験の結果から、頭部加工方法として
前述の種々の利点を有する摩擦圧接法が、接合部
の強度や機械的性質の面からも何ら問題のないこ
とが明らかである。なお、上記実施例ではパイプの両端に段付丸棒
を摩擦圧接したが、一端のみに段付丸棒を摩擦圧
接してもよい。さらに、本発明が図示の実施例に限られないの
はいうまでもない。＜発明の効果＞以上の説明で明らかなように、本発明の燃料噴
射高圧管の製造方法は、小径のパイプの一端に、
このパイプと略同径の小径部と大径部からなる段
付丸棒の上記小径部端を突き合わせて軸方向に加
圧し、両者を相対運動させて摩擦熱により突き合
わせ面を摩擦圧接した後、上記パイプの中心に一
直線をなすように上記段付丸棒に穴を貫設し、こ
の穴の先端に残つた溶着物の残渣を上記パイプの
他端側から一端側に向けて棒で押し出して除去
し、次いで摩擦圧接部分の外周のバリを旋削除去
するとともに、上記段付丸棒の大径部の外周に円
錐状のニツプルを旋削除去するので、従来の鍛造
法に比べて、加工工数が低減し、加工時間がはる
かに短く高能率なうえ、頭部の穴明けが真直かつ
容易にでき、明けられた穴の内周面等に欠陥を残
さず、また、接合される細棒と小径部の温度場が
略対称となつて良好な圧接ができるとともに、圧
接部が使用時に応力集中を生じるニツプル部から
離れて、使用時の破壊に対してもより安全にで
き、製品品質と製造能率の向上および製造コスト
の低減に絶大な効果を奏する。【表】DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a high-pressure fuel injection pipe for feeding fuel oil from a fuel injection pump to a fuel injection nozzle of a diesel engine. <Prior Art> Conventionally, such a fuel injection high pressure pipe has been manufactured through a process shown in FIG. That is, (a) For example, chromium molybdenum steel (JIS G4105SCM435)
(b) cut one end of the pipe in the axial direction with a press to form the protrusion 2;
2, (c) swaging this protrusion in the radial direction to reduce the diameter, (d) further finishing swaging in the axial direction to form the head 23, and (e) moving the center of the pipe from the tip of the head. After drilling a hole 24 that passes through the hole and reaming this hole, (f) the outer periphery of the head 23 is turned to form a conical nipple 25. Then, a pair of union joints (not shown) with the female threads facing outward are inserted from the other end of the pipe, and one union joint is attached to the head 2 of the pipe.
3, then attach the other end of the pipe 21 to the above (b)~
A conical nipple is also formed at the other end using the same process as in (f). <Problems to be Solved by the Invention> However, in the above-mentioned conventional method for manufacturing a fuel injection high-pressure pipe, cold or hot forging is performed three times (b), (c),
It is necessary to do (d). In addition, the inner surface of the pipe, which has been crushed by three forgings, becomes complicatedly folded as shown in (d), causing the drill to bend during drilling, causing the drill hole to be misaligned with the center hole of the pipe, and even after drilling. There is a drawback that the crushed inner surface of the pipe remains as a defect on the inner peripheral surface of the hole. Figure 9 shows an example of such a defect, and shows an STS steel pipe (outer diameter 12.2 mm x inner diameter 4.2 mm).
As shown in (a), an annular notch with a depth of approximately 1.5 mm was observed on the inner circumferential surface of the head of the high-pressure fuel injection pipe manufactured from Na
A crack of 0.42mm was observed in each case. These notches and cracks are caused by the forging process, and these defects cannot be avoided. Needless to say, this defect will lead to destruction of the fuel injection high pressure pipe during use, and this is a serious problem in today's world where fuel is pumped under higher pressure. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an efficient and inexpensive manufacturing method for a fuel injection high-pressure pipe in which the head hole can be accurately and easily drilled and no defects are left on the inner peripheral surface of the drilled hole. It is to be. <Means for Solving the Problems> In order to achieve the above object, the method for manufacturing a high-pressure fuel injection pipe of the present invention provides a method for manufacturing a high-pressure fuel injection pipe of the present invention. The ends of the small diameter portions of the stepped round bars are brought together and pressurized in the axial direction, and the two are moved relative to each other to create a friction welding of the abutted surfaces due to frictional heat. A hole is formed in the rod, and the residue of the welded material remaining at the tip of the hole is removed by pushing it out from the other end of the pipe toward one end with the rod,
Next, the burr on the outer periphery of the friction welded portion is removed by turning, and a conical nipple is machined on the outer periphery of the large diameter portion of the stepped round bar. <Function> Since the head is formed by friction welding the pipe and the stepped round bar, compared to conventional forging, the number of machining steps is reduced, the machining time is much shorter, and it is highly efficient, allowing for shape and shape.
The dimensional accuracy is high, and there is no crushed or folded inner surface of the pipe in the center of the head, the center hole can be drilled accurately, easily and without defects, and there is no risk of breaking the high-pressure pipe during use. Furthermore, since the small diameter part of the stepped round bar is approximately the same diameter as the pipe, the temperature field of the welded part is approximately symmetrical, allowing for good friction welding, and the welding part is prevented from developing stress during use. Since it is separated from the nipple part that occurs, it becomes safer from breakage during use. <Examples> Hereinafter, the present invention will be explained in detail with reference to illustrated examples. FIG. 1 is a flowchart showing a method for manufacturing a high-pressure fuel injection pipe together with a diagram of the processing steps for the parts, in which step (a) is a pipe cutting process in which a pipe 1 as a thin rod is cut into a predetermined size, and step (b) are a small diameter part 2a and a large diameter part 2b having the same diameter as the outer diameter _D1 of the pipe 1.
Step (c) is a stepped round bar processing step in which the stepped round bars 2, 2 are turned, and step (c) is one end 1a of the pipe 1
The step (d) is a friction welding process in which the ends of the small diameter part 2a of the stepped round bar 2 are butted against each other and pressurized in the axial direction, and the two are moved relative to each other and pressed together by frictional heat.
Step (e) is a drilling process in which a hole 3 with a diameter approximately 0.2 mm larger than the center hole 1c is inserted so as to be in line with the center hole 1c of the pipe 1. Step (e) is to remove the welded material remaining at the tip of the hole 3. This is a residue removal step in which a wire or the like (not shown) is inserted into the center hole 1c from the other end 1b side of the pipe 1 to push out the residue 4. And at this stage,
Insert the pair of union joints 8, 8 (see step (h)), etc. that should be fitted onto the large diameter portions 2b of the stepped round bars at both ends from the other end 1b of the pipe 1 in advance toward the outside of each female thread. I'll keep it. Further, the following step (f) is a friction welding process in which the stepped round bar 2 is welded to the other end 1b of the pipe 1 in the same manner as in step (c), and step (g) is a friction welding process in which the material of the friction welded parts 5, 5 is improved. For heat treatment processing, step (h) is the other end 1
Drill a through hole 6 in the stepped round bar of step b in the same manner as in steps (d) and (e), remove the welded material residue, and remove the burr on the outer periphery of the friction welding members 5, 5 by turning.
This is a process of turning conical nipples 7, 7 on the outer periphery of the large diameter portions 2b, 2b of the stepped round bars. The material of the pipe 1 and stepped round bar 2 is chromium molybdenum steel SCM435 (JIS G 4105),
The outer diameter of the pipe was 12 mm x inner diameter 3 mm, and the stepped round bar had a small diameter part length of 10 mm, a large diameter part length 20 mm, and a large diameter part outer diameter of 19 mm. The above-mentioned friction welding is performed in the following manner according to the procedure shown in FIG. (a) Attach the stepped round bar 2 to the rotary chuck 10 of the fixed base.
The pipes 1 are each inserted into the chucks 11 on the moving table. (b) Close both chucks 10 and 11 as shown by arrows A and B, respectively, and clamp the works 2 and 1. (c) The rotary chuck 10 is rotated as shown by arrow C, and the chuck 11 is rapidly advanced as shown by arrow D. At this time, the rotation speed of the rotary chuck reaches a constant value R=1800 rpm at about 2 seconds from time Tc, as shown in FIG. 3a. (d) Pipe 1 moves to the third position due to the advance of chuck 11.
At time Td shown in FIG. b, when the pipe 1 comes into contact with the stepped round bar 2, the pipe 1 is directed toward the stepped round bar as shown by the arrow E while the rotary chuck 10 continues to rotate at the constant rotation speed R, and the heating pressure P ₁ = It is pressed at 4 kgf/mm ² and the contact surface is heated by frictional heat for a time t ₁ =6 seconds. During this time, the chuck 11 is
Heat it and move forward by δ ₁ as shown in . (e) At time Te, as shown in Fig. 3, the rotation of the rotary chuck 10 is abruptly stopped, and the pipe 1 is pressed against the stepped round bar 2 at an even higher upset pressure P ₂ =12 Kgf/mm ² . The chuck 11 is upset and further advanced by δ ₂ to complete the friction welding. The upsetting time _t2 is about 4 seconds, the pressing time _t3 , which is the sum of the heating time _t1 and the upsetting time _t2 , is about 10 seconds, and the width δ, which is the sum of the heating time _δ1 and the upsetting time _δ2 , is about 10 seconds. It is 5mm. (f) Finally, open the rotary chuck 10 as shown by the arrow F, move the chuck 11 backward as shown by the arrow G, and then open it as shown by the arrow H to take out the pipe 1 to which the stepped round bar 22 is pressed. Forming the pipe head by such friction welding reduces the number of processing steps from 3 (see Fig. 8 b, c, d) to 1 compared to the conventional forging method shown in Fig. 8, and reduces the processing time. The time is much shorter at t ₃ = 10 seconds, which is highly efficient, the shape and dimensional accuracy of the machining is also high, and the center hole 3 is straight because there is no crushed and folded inner surface of the pipe as shown in Fig. 8 (d) in the center of the head. It can be opened easily and without defects, and therefore there is no risk of causing damage to the high pressure pipe during use. Besides, pipe 1
Since the length of the small diameter portion 2a of the stepped round bar 2 having the same diameter as that of the pipe is approximately the same as the diameter of the pipe, the temperature field of the two becomes symmetrical, and good friction welding can be performed.
In addition, the pressure welding portion is located away from the nipple portion where stress is concentrated during use, making it safer from breakage during use. Further, turning the nipple and drilling the center hole can be easily performed, and work efficiency can be further improved. Furthermore, compared to other joining methods, such as flash butt welding, the power consumption is significantly lower at about 1/10, the upset margin δ is also about half, which saves on materials, and it is safe with no sparks. FIGS. 4 and 5 show the macrostructure and microstructure in the vicinity of the friction welding portion before and after the heat treatment shown in FIG. 1, respectively. Figure 4a shows the macrostructure before heat treatment.
shows, from left to right, a stepped round bar part, a pressure welding part, and a pipe part. The microscopic structure of each of these parts is shown in FIG. 4b, c, and d in order. As you can see from the figure,
The stepped round bar part has a striped structure of ferrite/pearlite, the pressure weld part has a quenched martensite structure, and the pipe part has a sorbite structure. On the other hand, 550℃
The macrostructure after the tempering heat treatment held for 2 hours is shown in FIG. 5a, and the microstructures of the stepped round bar portion, pressure welding portion, and pipe portion are similarly shown in FIGS. 5b, c, and d. As can be seen from the figure, the stepped round bar portion and the pipe portion similarly exhibit a ferrite-pearlite and sorbite structure, and the martensite in the pressure welded portion has disappeared and has become a tempered structure. FIG. 6 shows the hardness distribution near the friction welded portion before and after heat treatment. Before heat treatment, the pressure welded part has a martensitic structure as mentioned above, so this part is significantly hardened as shown by the broken line in the figure, but as it becomes a tempered structure by heat treatment, it is shown by the solid line in the figure. It softens to approximately the same hardness as the stepped round bar and pipe parts, and is slightly lower than the hardness of SCM435 steel specified in JIS G4105 (H _B : 269 to 331), shown by the two-dot chain line in the figure. . Table 1 listed at the end shows the hardness test results of fuel injection high pressure pipes manufactured by friction welding. In the tensile test, it broke at the base material pipe part other than the pressure welded part, and the tensile strength σ _B was also 80 Kgf/mm ² or more, so there was no problem with the strength of the pressure welded part. Even in the bending test and the flattening test, the pressure welded part showed no scratches or cracks and was in good condition. In addition, in an impact test, the pressure welded part showed an impact value that exceeded the JIS standard value, demonstrating excellent toughness. moreover,
An Ono rotary bending fatigue test was conducted to test the strength against repeated stress applied to the pipe during fuel injection. The test result was an S-N curve as shown in Figure 7, and the ^107- cycle fatigue limit of the pressure welded pipe was approximately 24.5.
Kg/mm ² , which was not much different from the fatigue limit of the base material pipe, 30 Kg/mm ² , and it was confirmed that it had sufficient fatigue strength. From the results of these accuracy tests and the micro-, macro-structure and hardness tests mentioned above, the friction welding method, which has the various advantages mentioned above as a head processing method, has no problems in terms of the strength and mechanical properties of the joint. It is clear that there is no In the above embodiment, the stepped round rods were frictionally welded to both ends of the pipe, but the stepped round rods may be frictionally welded to only one end. Furthermore, it goes without saying that the present invention is not limited to the illustrated embodiment. <Effects of the Invention> As is clear from the above explanation, the method for manufacturing a high-pressure fuel injection pipe of the present invention has the following advantages:
The ends of the small diameter part of a stepped round bar consisting of a small diameter part and a large diameter part having approximately the same diameter as this pipe are butted against each other and pressurized in the axial direction, the two are moved relative to each other, and the abutting surfaces are frictionally welded by frictional heat. A hole is made in the stepped round rod so as to form a straight line in the center of the pipe, and the residue of the welded material remaining at the tip of this hole is pushed out from the other end of the pipe toward one end with the rod. Then, the burr on the outer periphery of the friction welded part is removed by turning, and the conical nipple is removed by turning on the outer periphery of the large diameter part of the stepped round bar, so the number of processing steps is reduced compared to the conventional forging method. In addition, the machining time is much shorter and the efficiency is high, and the hole in the head can be drilled straight and easily, leaving no defects on the inner circumferential surface of the drilled hole. The temperature field of the parts becomes almost symmetrical, allowing for good pressure welding, and the pressure welding part is separated from the nipple part, where stress is concentrated during use, making it safer from breakage during use, improving product quality and manufacturing efficiency. This has a tremendous effect on improving performance and reducing manufacturing costs. 【table】

[Brief explanation of drawings]

第１図は本発明の燃料噴射高圧管の製造方法を
加工手順図と共に示したフローチヤート、第２図
は第１図ｃの摩擦圧接工程の手順を示す図、第３
図は第２図の圧接サイクルを示す図、第４図、第
５図は第１図ｇの熱処理前、後の摩擦圧接部付近
のマクロ組織およびミクロ組織を示す図、第６図
は熱処理前後の摩擦圧接部付近の硬さ分布図、第
７図は本発明の高圧管の疲労試験結果を示す図、
第８図は従来の燃料噴射高圧管の製造方法を示す
図、第９図は従来法による高圧管の欠陥例のマク
ロ組織、ミクロ組織および形状を示す図である。１……パイプ（SCM435）、２……段付丸棒、
２ａ……小径部、２ｂ……大径部、３，６……
穴、４……パイプ内溶け込み物、５……摩擦圧接
部、７……ニツプル、８……ユニオン継手。 Fig. 1 is a flowchart showing the manufacturing method of the high pressure fuel injection pipe of the present invention together with processing procedure diagrams, Fig. 2 is a diagram showing the procedure of the friction welding process of Fig. 1c, and Fig. 3
The figure shows the pressure welding cycle in Figure 2, Figures 4 and 5 show the macrostructure and microstructure near the friction welding part before and after the heat treatment in Figure 1g, and Figure 6 shows the before and after heat treatment. Fig. 7 is a diagram showing the fatigue test results of the high pressure pipe of the present invention.
FIG. 8 is a diagram showing a conventional method for manufacturing a high-pressure fuel injection pipe, and FIG. 9 is a diagram showing a macrostructure, microstructure, and shape of an example of a defect in a high-pressure pipe produced by the conventional method. 1... Pipe (SCM435), 2... Stepped round bar,
2a...Small diameter part, 2b...Large diameter part, 3, 6...
Hole, 4...Pipe melt, 5...Friction welding part, 7...Nipple, 8...Union joint.

Claims

[Claims]

1. The end of the small diameter part of a stepped round bar consisting of a small diameter part and a large diameter part with approximately the same diameter as the pipe is butted against one end of a small diameter pipe and pressurized in the axial direction, and the two are moved relative to each other to cause frictional heat. After friction welding the mating surfaces, a hole is made in the stepped round bar in a straight line with the center of the pipe, and the welding residue left at the tip of this hole is removed from the other end of the pipe. The burr is removed by pushing it out toward the side with a rod, and then the burr on the outer periphery of the friction welded part is removed by turning, and a conical nipple is machined on the outer periphery of the large diameter part of the stepped round bar. A method of manufacturing a fuel injection high pressure pipe.