JP6719142B2 - Hollow engine valve manufacturing method - Google Patents

Hollow engine valve manufacturing method Download PDF

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Publication number
JP6719142B2
JP6719142B2 JP2019570144A JP2019570144A JP6719142B2 JP 6719142 B2 JP6719142 B2 JP 6719142B2 JP 2019570144 A JP2019570144 A JP 2019570144A JP 2019570144 A JP2019570144 A JP 2019570144A JP 6719142 B2 JP6719142 B2 JP 6719142B2
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cylindrical portion
spinning
engine valve
processing roller
hollow engine
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JPWO2020004286A1 (en
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敏夫 池田
敏夫 池田
守利 木村
守利 木村
豊 渡部
豊 渡部
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TOA FORGING CO., LTD.
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D53/00—Making other particular articles
    • B21D53/84—Making other particular articles other parts for engines, e.g. connecting-rods
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/14—Spinning
    • B21D22/16—Spinning over shaping mandrels or formers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/28—Deep-drawing of cylindrical articles using consecutive dies
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
    • B21K1/00—Making machine elements
    • B21K1/20—Making machine elements valve parts
    • B21K1/22—Making machine elements valve parts poppet valves, e.g. for internal-combustion engines
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/60—Aqueous agents
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0062—Heat-treating apparatus with a cooling or quenching zone
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L3/00—Lift-valve, i.e. cut-off apparatus with closure members having at least a component of their opening and closing motion perpendicular to the closing faces; Parts or accessories thereof
    • F01L3/12—Cooling of valves
    • F01L3/14—Cooling of valves by means of a liquid or solid coolant, e.g. sodium, in a closed chamber in a valve
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2301/00—Using particular materials
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2303/00—Manufacturing of components used in valve arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2303/00—Manufacturing of components used in valve arrangements
    • F01L2303/01—Tools for producing, mounting or adjusting, e.g. some part of the distribution
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L2820/00—Details on specific features characterising valve gear arrangements
    • F01L2820/01—Absolute values

Description

本発明は、中空エンジンバルブの製造方法に関し、更に詳しくは、軸部及び該軸部の軸端側に連なる傘状部を備え、軸部及び傘状部にわたって中空孔が形成された中空エンジンバルブの製造方法に関する。 The present invention relates to a method for manufacturing a hollow engine valve, and more specifically, a hollow engine valve including a shaft portion and an umbrella-shaped portion connected to the shaft end side of the shaft portion, and a hollow hole formed in the shaft portion and the umbrella-shaped portion. Manufacturing method.

従来の中空エンジンバルブの製造方法として、鍛造加工により、円筒状部及び該円筒状部の軸端側に連なる半傘状部を備える中間部品を製造し、その中間部品の円筒状部をスピニング加工した後に絞り加工して縮径することで、中空エンジンバルブを製造する方法が記載されている（特許文献１の請求項５及び明細書の段落〔００２３〕等参照）。 As a conventional method of manufacturing a hollow engine valve, an intermediate part having a cylindrical part and a semi-umbrella part connected to the shaft end side of the cylindrical part is manufactured by forging, and the cylindrical part of the intermediate part is spun. After that, a method for manufacturing a hollow engine valve by drawing and reducing the diameter is described (see claim 5 of Patent Document 1 and paragraph [0023] of the specification, etc.).

国際公開第２０１１／１０４９０３号公報International Publication No. 2011/104903

しかし、上記従来の中空エンジンバルブの製造方法では、鍛造加工により得られた中間部品を文献・資料等と作業者の経験に基づいて決められる加熱保持時間で熱処理し、その熱処理された中間部品の円筒状部をスピニング加工しているため、スピニング加工時に中間部品の円筒状部が伸び難くい場合がある。その場合、中間部品の円筒状部において加工面（すなわち、円筒状部の外周面）と加工用ツールが接触しない内周面との間で表面状態が異なる。具体的に、中間部品の円筒状部の内周面、ひいては中空エンジンバルブの中空孔を形成する内面には肌荒れが生じて表面状態が悪くなる。そのため、中空エンジンバルブの強度が低下してしまう。さらに、中空エンジンバルブの中空孔内に冷却用の金属ナトリウムを入れることがあるが、その場合、中空孔内での金属ナトリウムの流動性が低く冷却機能が低下してしまう。
なお、上述の問題は、特にオーステナイト系耐熱材料（例えば、ニッケル基超合金、オーステナイト系ステンレス鋼等）の難加工材を加工する場合に顕著に現れる。However, in the above-described conventional method for manufacturing a hollow engine valve, the intermediate part obtained by forging is heat-treated for a heating and holding time determined based on the experience of the operator, such as documents and materials, and the heat-treated intermediate part is Since the cylindrical portion is processed by spinning, it may be difficult for the cylindrical portion of the intermediate part to stretch during the spinning process. In that case, in the cylindrical portion of the intermediate part, the surface state is different between the processing surface (that is, the outer peripheral surface of the cylindrical portion) and the inner peripheral surface with which the processing tool does not contact. Specifically, the inner peripheral surface of the cylindrical portion of the intermediate component, and by extension, the inner surface forming the hollow hole of the hollow engine valve, is roughened to deteriorate the surface condition. Therefore, the strength of the hollow engine valve is reduced. Further, although metallic sodium for cooling may be put in the hollow hole of the hollow engine valve, in that case, the fluidity of metallic sodium in the hollow hole is low and the cooling function is deteriorated.
In addition, the above-mentioned problem becomes remarkable especially when processing a difficult-to-machine material such as an austenitic heat-resistant material (for example, nickel-base superalloy, austenitic stainless steel, etc.).

ここで、中空エンジンバルブでは、軽量化等のために中空孔の容積を大きくすることが求められる。しかしながら、上記従来の中空エンジンバルブの製造方法では、上述のように、鍛造加工により得られた中間部品を文献・資料等と作業者の経験に基づいて決められる加熱保持時間で熱処理し、その熱処理された中間部品の円筒状部をスピニング加工しているため、スピニング加工に加えて絞り加工時にも中間部品の円筒状部が伸び難い。そのため、加圧力が大きくなるように、中間部品の円筒状部の底端側まで深く金型で絞り加工する必要がある。その結果、中空エンジンバルブの傘状部の中空孔の外周側が潰れ易く、傘状部の中空孔の容積を大きくできない。 Here, in the hollow engine valve, it is required to increase the volume of the hollow hole in order to reduce the weight. However, in the above-described conventional method for manufacturing a hollow engine valve, as described above, the intermediate parts obtained by the forging process are heat-treated for a heating and holding time determined based on the literature/materials and the experience of the operator, and the heat treatment is performed. Since the cylindrical part of the formed intermediate part is processed by spinning, it is difficult for the cylindrical part of the intermediate part to stretch during drawing as well as spinning. Therefore, it is necessary to deep-draw with a die to the bottom end side of the cylindrical portion of the intermediate component so that the pressing force becomes large. As a result, the outer peripheral side of the hollow hole of the umbrella-shaped portion of the hollow engine valve is easily crushed, and the volume of the hollow hole of the umbrella-shaped portion cannot be increased.

本発明は、上記現状に鑑みてなされたものであり、中空孔を形成する内面での表面状態が良好であるとともに、中空孔の容積を大きくすることができる中空エンジンバルブの製造方法を提供することを目的とする。 The present invention has been made in view of the above circumstances, and provides a method for manufacturing a hollow engine valve that has a good surface condition on the inner surface forming a hollow hole and can increase the volume of the hollow hole. The purpose is to

本発明は以下の通りである。
１．軸部及び該軸部の軸端側に連なる傘状部を備え、前記軸部及び前記傘状部にわたって中空孔が形成された中空エンジンバルブの製造方法であって、鍛造加工により、円筒状部及び該円筒状部の軸端側に連なる半傘状部を備える中間部品を得る鍛造工程と、前記中間部品を軟化させるために前記円筒状部の肉厚に応じて決められる加熱保持時間で熱処理する熱処理工程と、熱処理された前記中間部品の前記円筒状部をスピニング加工により軸方向に延伸するスピニング工程と、軸方向に延伸された前記円筒状部を絞り加工により縮径することで、前記軸部及び前記傘状部を形成するネッキング工程と、を備えることを要旨とする。
２．前記中間部品は、オーステナイト系耐熱材料で形成されており、前記熱処理工程は、前記中間部品を１０００〜１１００℃に加熱保持した後に水冷する上記１．記載の中空エンジンバルブの製造方法。
３．前記熱処理工程は、加熱された前記中間部品を前記円筒状部の肉厚の１ｍｍ当りに対して３〜８分となる加熱保持時間で保持する上記２．記載の中空エンジンバルブの製造方法。
４．前記熱処理工程は、前記中間部品を、容器内で攪拌される冷却水中又は容器に対して循環される冷却水中に投入して水冷する上記２．又は３．に記載の中空エンジンバルブの製造方法。
５．前記冷却水の水温は、１５〜３５℃である上記４．記載の中空エンジンバルブの製造方法。
６．前記スピニング工程は、前記円筒状部の外周面に加工ローラの外周円弧面を所定の切込み量で押し当てながら、前記加工ローラを前記円筒状部に対して軸方向に移動させて前記円筒状部を軸方向に延伸し、前記加工ローラの外周円弧面の曲率半径は、スピニング加工前の前記円筒状部の肉厚の３〜５倍の値であり、前記スピニング加工時に、前記円筒状部の軸方向に沿う断面において、前記加工ローラの外周円弧面が前記円筒状部の外周面と接する円弧の一端と他端とを結ぶ直線は、前記円筒状部の軸方向に対して５〜７度の傾斜角度で傾斜している上記１．乃至５．のいずれか一項に記載の中空エンジンバルブの製造方法。
７．前記中空エンジンバルブは、前記中空孔を形成する内面の表面粗さＲａが４．０〜２２．０である上記１．乃至６．のいずれか一項に記載の中空エンジンバルブの製造方法。
８．前記鍛造工程は、前記中間部品の前記円筒状部の内周面の底端側に円弧面を形成し、前記ネッキング工程は、前記円筒状部を上側とし且つ前記半傘状部を下側としたときに、前記円筒状部の軸方向で前記円弧面よりも上側の部分を絞り加工する上記１．乃至７．のいずれか一項に記載の中空エンジンバルブの製造方法。
９．前記スピニング工程は、加工ローラを用いて前記中間部品の前記円筒状部をスピニング加工し、前記加工ローラは、該加工ローラを挟んで該加工ローラの軸方向に沿って配置される前後の軸受を介して支持部材に回転自在に支持されている上記１．乃至８．のいずれか一項に記載の中空エンジンバルブの製造方法。The present invention is as follows.
1. A method for manufacturing a hollow engine valve, comprising a shaft portion and an umbrella-shaped portion connected to the shaft end side of the shaft portion, wherein a hollow hole is formed over the shaft portion and the umbrella-shaped portion, the cylindrical portion being forged. And a forging step for obtaining an intermediate part including a semi-umbrella part connected to the axial end side of the cylindrical part, and a heat treatment for a heating and holding time determined according to the wall thickness of the cylindrical part in order to soften the intermediate part. By a heat treatment step of, a spinning step of axially stretching the cylindrical portion of the heat-treated intermediate part by spinning, and a diameter reduction of the axially stretched cylindrical portion by drawing, And a necking step for forming the shaft portion and the umbrella-shaped portion.
2. The intermediate part is formed of an austenitic heat resistant material, and in the heat treatment step, the intermediate part is heated and held at 1000 to 1100° C. and then water-cooled. A method for manufacturing the hollow engine valve described.
3. In the heat treatment step, the heated intermediate part is held for a heating holding time of 3 to 8 minutes per 1 mm of the wall thickness of the cylindrical portion. A method for manufacturing the hollow engine valve described.
4. In the heat treatment step, the intermediate component is put into cooling water stirred in a container or cooling water circulated in the container to perform water cooling. Or 3. A method for manufacturing a hollow engine valve according to.
5. The water temperature of the cooling water is 15 to 35°C. A method for manufacturing the hollow engine valve described.
6. In the spinning step, the processing roller is moved in the axial direction with respect to the cylindrical portion while pressing the outer circumferential arc surface of the processing roller against the outer circumferential surface of the cylindrical portion with a predetermined cut amount. In the axial direction, the radius of curvature of the outer circumferential arc surface of the processing roller is 3 to 5 times the wall thickness of the cylindrical portion before spinning, and during the spinning, In a cross section along the axial direction, a straight line connecting one end and the other end of an arc where the outer circumferential arc surface of the processing roller contacts the outer circumferential surface of the cylindrical portion is 5 to 7 degrees with respect to the axial direction of the cylindrical portion. Inclined at an inclination angle of 1. Through 5. A method for manufacturing a hollow engine valve according to any one of 1.
7. In the hollow engine valve, the surface roughness Ra of the inner surface forming the hollow hole is 4.0 to 22.0. Through 6. A method for manufacturing a hollow engine valve according to any one of 1.
8. The forging step forms an arc surface on the bottom end side of the inner peripheral surface of the cylindrical portion of the intermediate component, and the necking step defines the cylindrical portion as an upper side and the semi-umbrella portion as a lower side. In this case, the portion above the circular arc surface is drawn in the axial direction of the cylindrical portion. Through 7. A method for manufacturing a hollow engine valve according to any one of 1.
9. In the spinning step, a spinning roller is used to spin the cylindrical portion of the intermediate part, and the spinning roller includes front and rear bearings arranged along the axial direction of the spinning roller with the spinning roller interposed therebetween. The above-mentioned 1. which is rotatably supported by the support member via Through 8. A method for manufacturing a hollow engine valve according to any one of 1.

本発明の中空エンジンバルブの製造方法によると、鍛造加工により、円筒状部及び該円筒状部の軸端側に連なる半傘状部を備える中間部品を得る鍛造工程と、中間部品を軟化させるために前記円筒状部の肉厚に応じて決められる加熱保持時間で熱処理する熱処理工程と、熱処理された中間部品の円筒状部をスピニング加工により軸方向に延伸するスピニング工程と、軸方向に延伸された円筒状部を絞り加工により縮径することで、軸部及び傘状部を形成するネッキング工程と、を備える。このように、鍛造加工により得られた中間部品を熱処理して軟化させることで、スピニング加工時及び絞り加工時に中間部品の円筒状部が伸び易くなるため、スピニング加工及び絞り加工の加工性に優れる。その結果、中空エンジンバルブの中空孔を形成する内面での表面肌荒れの発生が抑制されて表面状態が良好となる。よって、中空エンジンバルブの強度の低下が抑制される。さらに、中空エンジンバルブの中空孔内に冷却用の金属ナトリウムを入れる場合には、中空孔内で金属ナトリウムが円滑に流動して効果的に冷却機能を発揮する。さらに、絞り加工の加工性に優れるため、傘状部の中空孔の外周側の潰れが抑制されるように、絞り加工の型締め時の金型の高さ位置を容易に調整できる。その結果、中空エンジンバルブの中空孔の容積を大きくすることができる。
また、前記中間部品が、オーステナイト系耐熱材料で形成されており、前記熱処理工程が、前記中間部品を１０００〜１１００℃に加熱保持した後に水冷する場合は、中間部品を固溶化熱処理して効果的に軟化させることができる。
また、前記熱処理工程が、加熱された前記中間部品を前記円筒状部の肉厚の１ｍｍ当りに対して３〜８分となる加熱保持時間で保持する場合は、中間部品の加熱保持時間を比較的短くでき、熱処理後の中間部品の表面での酸化膜の発生を低減できる。
また、前記熱処理工程が、前記中間部品を、容器内で攪拌される冷却水中又は容器に対して循環される冷却水中に投入して水冷する場合は、冷却水の温度上昇が抑えられるため、熱処理工程で中間部品を効果的に急冷できる。
また、前記冷却水の水温が、１５〜３５℃である場合は、熱処理工程で中間部品を効果的に急冷できる。
また、前記スピニング工程が、前記円筒状部の外周面に加工ローラの外周円弧面を所定の切込み量で押し当てながら、前記加工ローラを前記円筒状部に対して軸方向に移動させて前記円筒状部を軸方向に延伸し、前記加工ローラの外周円弧面の曲率半径が、スピニング加工前の前記円筒状部の肉厚の３〜５倍の値であり、前記スピニング加工時に、前記円筒状部の軸方向に沿う断面において、前記加工ローラの外周円弧面が前記円筒状部の外周面と接する円弧の一端と他端とを結ぶ直線が、前記円筒状部の軸方向に対して５〜７度の傾斜角度で傾斜している場合は、切込み量の最大値と最小値を想定考慮して加工ローラの外周円弧面の曲率半径を設定することとなるため、スピニング加工時に中間部品の円筒状部を効果的に延伸できる。
また、前記中空エンジンバルブが、前記中空孔を形成する内面の表面粗さＲａが４．０〜２２．０である場合は、中空エンジンバルブの中空孔を形成する内面の表面状態が極めて良好である。
また、前記鍛造工程が、前記中間部品の前記円筒状部の内周面の底端側に円弧面を形成し、前記ネッキング工程が、前記円筒状部を上側とし且つ前記半傘状部を下側としたきに、前記円筒状部の軸方向で前記円弧面よりも上側の部分を絞り加工する場合は、中空エンジンバルブの中空孔の最大外径が鍛造加工で得られる中間部品の円筒状部の開口の内径と略同じにできる。その結果、中空エンジンバルブの中空孔の容積を更に大きくできる。
さらに、前記スピニング工程が、加工ローラを用いて前記中間部品の前記円筒状部をスピニング加工し、前記加工ローラが、該加工ローラを挟んで該加工ローラの軸方向に沿って配置される前後の軸受を介して支持部材に回転自在に支持されている場合は、加工ローラの倒れ込みが抑制されるため、中間部品の円筒状部が効果的にスピニング加工される。According to the method for manufacturing a hollow engine valve of the present invention, a forging step for softening the intermediate part by a forging process to obtain an intermediate part including a cylindrical part and a semi-umbrella part connected to the axial end side of the cylindrical part. A heat treatment step of heat-treating for a heating and holding time determined according to the thickness of the cylindrical portion, a spinning step of axially stretching the cylindrical portion of the heat-treated intermediate part by spinning, and an axial stretching. The necking step of forming the shaft portion and the umbrella-shaped portion by reducing the diameter of the cylindrical portion by drawing. In this way, by heat-treating and softening the intermediate part obtained by the forging process, the cylindrical part of the intermediate part is easily stretched during the spinning process and the drawing process, so that the workability of the spinning process and the drawing process is excellent. .. As a result, the occurrence of surface roughening on the inner surface forming the hollow hole of the hollow engine valve is suppressed, and the surface condition is improved. Therefore, the decrease in strength of the hollow engine valve is suppressed. Further, when metallic sodium for cooling is put into the hollow holes of the hollow engine valve, the metallic sodium smoothly flows in the hollow holes to effectively exhibit the cooling function. Further, since the drawability is excellent, it is possible to easily adjust the height position of the mold at the time of clamping the die for drawing so that the outer peripheral side crush of the hollow hole of the umbrella-shaped portion is suppressed. As a result, the volume of the hollow hole of the hollow engine valve can be increased.
In addition, when the intermediate component is formed of an austenitic heat-resistant material and the heat treatment step involves water cooling after heating and holding the intermediate component at 1000 to 1100° C., the intermediate component is effectively subjected to solution heat treatment for solution treatment. It can be softened.
In the case where the heat treatment step holds the heated intermediate part for a heating and holding time of 3 to 8 minutes per 1 mm of the wall thickness of the cylindrical portion, the heating and holding time of the intermediate part is compared. It can be made shorter, and the generation of an oxide film on the surface of the intermediate component after heat treatment can be reduced.
Further, in the heat treatment step, when the intermediate part is put into cooling water stirred in a container or cooling water circulated with respect to the container for water cooling, the temperature rise of the cooling water is suppressed, so that the heat treatment The intermediate parts can be cooled effectively in the process.
Further, when the water temperature of the cooling water is 15 to 35° C., the intermediate part can be effectively rapidly cooled in the heat treatment process.
In the spinning step, the outer peripheral arc surface of the processing roller is pressed against the outer peripheral surface of the cylindrical portion with a predetermined cut amount, and the processing roller is moved in the axial direction with respect to the cylindrical portion to form the cylinder. The cylindrical portion is extended in the axial direction, the radius of curvature of the outer circumferential arc surface of the processing roller is 3 to 5 times the wall thickness of the cylindrical portion before spinning, and the cylindrical shape is used during the spinning. In a cross section along the axial direction of the portion, a straight line connecting one end and the other end of an arc where the outer circumferential arc surface of the processing roller contacts the outer circumferential surface of the cylindrical portion is 5 to the axial direction of the cylindrical portion. When inclining at an inclination angle of 7 degrees, the radius of curvature of the outer peripheral arc surface of the processing roller is set by considering the maximum and minimum values of the depth of cut, so the cylinder of the intermediate part during spinning is processed. The shaped portion can be effectively stretched.
Further, when the surface roughness Ra of the inner surface forming the hollow hole of the hollow engine valve is 4.0 to 22.0, the surface condition of the inner surface forming the hollow hole of the hollow engine valve is extremely good. is there.
Further, the forging step forms an arc surface on the bottom end side of the inner peripheral surface of the cylindrical portion of the intermediate component, and the necking step sets the cylindrical portion as an upper side and the semi-umbrella portion as a lower side. In the case of drawing the upper part of the cylindrical portion above the arc surface in the axial direction, the maximum outer diameter of the hollow hole of the hollow engine valve is the cylindrical shape of the intermediate part obtained by forging. The inner diameter of the opening of the portion can be made substantially the same. As a result, the volume of the hollow hole of the hollow engine valve can be further increased.
Further, in the spinning step, the cylindrical portion of the intermediate component is subjected to a spinning process by using a processing roller, and the processing roller is arranged before and after the processing roller is arranged along the axial direction of the processing roller. When it is rotatably supported by the support member via the bearing, the working roller is prevented from falling down, so that the cylindrical portion of the intermediate component is effectively subjected to spinning.

本発明について、本発明による典型的な実施形態の非限定的な例を挙げ、言及された複数の図面を参照しつつ以下の詳細な記述にて更に説明するが、同様の参照符号は図面のいくつかの図を通して同様の部品を示す。
本実施例に係る中空エンジンバルブの製造方法を説明するための説明図である。 本実施例に係る中空エンジンバルブの製造方法を説明するための説明図であり、（ａ）は素材の縦断面を示し、（ｂ）は第１鍛造工程で得られる中間部品の縦断面を示し、（ｃ）はしごき工程を経た中間部品の縦断面を示す。 上記中空エンジンバルブの製造方法を説明するための説明図であり、（ａ）は第２鍛造工程を経た中間部品の縦断面を示し、（ｂ）はスピニング工程を経た中間部品の縦断面を示し、（ｃ）はネッキング工程で得られる中空エンジンバルブの縦断面を示す。 本実施例に係る熱処理工程を説明するための説明図である。 上記熱処理工程を説明するための説明図である。 上記スピニング工程を説明するための説明図である。 上記ネッキング工程を説明するための説明図であり、中心線の左側が絞り加工の直前の中間部品の縦断面を示し、中心線の右側が絞り加工の完了時の中空エンジンバルブの縦断面を示す。 他の形態のネッキング工程を説明するための説明図である。 本実施例に係る中空エンジンバルブの表面状態を説明するための説明図であり、（ａ）はスピニング工程を経た中間部品の要部の縦断面画像処理図を示し、（ｂ）は中空エンジンバルブの要部の縦断面画像処理図を示す。 比較例に係る中空エンジンバルブの表面状態を説明するための説明図であり、（ａ）はスピニング工程を経た中間部品の要部の縦断面画像処理図を示し、（ｂ）は中空エンジンバルブの要部の縦断面画像処理図を示す。 実験例１〜７に係る中空エンジンバルブの製造方法の実験結果を示す表である。 実験例８〜１３に係る中空エンジンバルブの製造方法の実験結果を示す表である。 実験例１４〜１９及び比較例に係る中空エンジンバルブの製造方法の実験結果を示す表である。 他の形態のスピニング工程を説明するための説明図である。 図１４の要部拡大図である。 実験例に係るスピニング工程の実験結果を示す表であり、（ａ）は実験例２０〜２４の実験結果を示し、（ｂ）は実験例２５〜２７の実験結果を示す。 The present invention will be further explained in the following detailed description with reference to the several drawings referred to, by way of non-limiting examples of typical embodiments according to the present invention, wherein like reference numerals are used in the drawings. Similar parts are shown through several figures.
It is explanatory drawing for demonstrating the manufacturing method of the hollow engine valve which concerns on a present Example. 4A and 4B are explanatory views for explaining a method for manufacturing the hollow engine valve according to the present embodiment, where FIG. 6A is a vertical cross section of a raw material, and FIG. 6B is a vertical cross section of an intermediate part obtained in the first forging step. , (C) shows a vertical cross section of the intermediate component that has undergone the ironing process. It is explanatory drawing for demonstrating the manufacturing method of the said hollow engine valve, (a) shows the longitudinal cross section of the intermediate component which passed the 2nd forging process, (b) shows the longitudinal cross section of the intermediate component which passed the spinning process. , (C) show a vertical cross section of the hollow engine valve obtained in the necking step. It is explanatory drawing for demonstrating the heat processing process which concerns on a present Example. It is an explanatory view for explaining the above-mentioned heat treatment process. It is explanatory drawing for demonstrating the said spinning process. It is explanatory drawing for demonstrating the said necking process, The left side of a centerline shows the vertical cross section of the intermediate component immediately before drawing, and the right side of a centerline shows the vertical cross section of the hollow engine valve at the time of completion of drawing. .. It is explanatory drawing for demonstrating the necking process of another form. It is explanatory drawing for demonstrating the surface condition of the hollow engine valve which concerns on a present Example, (a) shows the longitudinal cross-section image processing figure of the principal part of the intermediate component which passed the spinning process, (b) shows a hollow engine valve. The longitudinal section image processing figure of the important section of is shown. It is explanatory drawing for demonstrating the surface condition of the hollow engine valve which concerns on a comparative example, (a) shows the longitudinal cross-section image processing figure of the principal part of the intermediate component which passed the spinning process, (b) shows a hollow engine valve. The longitudinal section image processing figure of the important section is shown. It is a table which shows the experimental result of the manufacturing method of the hollow engine valve which concerns on Experimental Examples 1-7. It is a table which shows the experimental result of the manufacturing method of the hollow engine valve which concerns on Experimental Examples 8-13. It is a table which shows the experimental result of the manufacturing method of the hollow engine valve which concerns on Experimental Examples 14-19 and a comparative example. It is explanatory drawing for demonstrating the spinning process of other forms. It is a principal part enlarged view of FIG. It is a table which shows the experimental result of the spinning process which concerns on an experimental example, (a) shows the experimental result of Experimental examples 20-24, (b) shows the experimental result of Experimental examples 25-27.

ここで示される事項は例示的なものおよび本発明の実施形態を例示的に説明するためのものであり、本発明の原理と概念的な特徴とを最も有効に且つ難なく理解できる説明であると思われるものを提供する目的で述べたものである。この点で、本発明の根本的な理解のために必要である程度以上に本発明の構造的な詳細を示すことを意図してはおらず、図面と合わせた説明によって本発明の幾つかの形態が実際にどのように具現化されるかを当業者に明らかにするものである。 The matters shown here are for the purpose of exemplifying the exemplary embodiments and the embodiments of the present invention, and are the explanations by which the principle and conceptual features of the present invention can be most effectively and effortlessly understood. It is mentioned for the purpose of providing what you think. In this respect, it is not intended to present the structural details of the invention more than to the extent necessary for a fundamental understanding of the invention, and the description taken in conjunction with the drawings may explain some aspects of the invention. It will be clear to those skilled in the art how it will actually be implemented.

本実施形態に係る中空エンジンバルブの製造方法は、軸部（２）及び該軸部の軸端側に連なる傘状部（３）を備え、軸部（２）及び傘状部（３）にわたって中空孔（４）が形成された中空エンジンバルブ（１）の製造方法であって、鍛造加工により、円筒状部（８Ｂ）及び該円筒状部の軸端側に連なる半傘状部（９Ｂ）を備える中間部品（７Ｃ）を得る鍛造工程（Ｓ３）と、中間部品（７Ｃ）を軟化させるために円筒状部（８Ｂ）の肉厚（ｔ）に応じて決められる加熱保持時間（ｔ２）で熱処理する熱処理工程（Ｓ４）と、熱処理された中間部品（７Ｃ）の円筒状部（８Ｂ）をスピニング加工により軸方向に延伸するスピニング工程（Ｓ５，Ｓ５’）と、軸方向に延伸された円筒状部（８Ｂ）を絞り加工により縮径することで、軸部（２）及び傘状部（３）を形成するネッキング工程（Ｓ６）と、を備える（例えば、図１〜図３等参照）。 The method for manufacturing a hollow engine valve according to the present embodiment includes a shaft portion (2) and an umbrella-shaped portion (3) connected to the shaft end side of the shaft portion, and extends over the shaft portion (2) and the umbrella-shaped portion (3). A method for manufacturing a hollow engine valve (1) having a hollow hole (4), comprising a cylindrical portion (8B) and a semi-umbrella portion (9B) connected to the axial end side of the cylindrical portion by forging. In the forging step (S3) for obtaining the intermediate part (7C) provided with, and the heating holding time (t2) determined according to the wall thickness (t) of the cylindrical part (8B) for softening the intermediate part (7C). A heat treatment step (S4) of heat treatment, a spinning step (S5, S5') of axially stretching the cylindrical portion (8B) of the heat treated intermediate part (7C) by a spinning process, and a cylinder stretched in the axial direction. A necking step (S6) of forming the shaft portion (2) and the umbrella-shaped portion (3) by reducing the diameter of the shaped portion (8B) by drawing (see, for example, FIGS. 1 to 3). ..

本実施形態に係る中空エンジンバルブの製造方法としては、例えば、上記中間部品（７Ｃ）は、オーステナイト系耐熱材料で形成されており、熱処理工程（Ｓ４）は、中間部品（７Ｃ）を１０００〜１１００℃（好ましくは１０３０〜１０７０℃、特に１０４０〜１０６０℃）に加熱保持した後に水冷する形態（例えば、図１１〜図１３等参照）が挙げられる。なお、上記オーステナイト系耐熱材料としては、例えば、ＮＣＦ７５１（インコネル７５１（登録商標））等のニッケル基超合金、ＳＵＳ３０４等のステンレス鋼、ＳＵＨ３５、ＳＵＨ３８等の耐熱鋼等が挙げられる。 As a method of manufacturing the hollow engine valve according to the present embodiment, for example, the intermediate component (7C) is formed of an austenitic heat-resistant material, and the heat treatment step (S4) is performed on the intermediate component (7C) by 1000 to 1100. Examples include a mode of heating and holding at 0° C. (preferably 1030 to 1070° C., particularly 1040 to 1060° C.) and then water cooling (see, for example, FIGS. 11 to 13). Examples of the austenitic heat resistant material include nickel-based superalloys such as NCF751 (Inconel 751 (registered trademark)), stainless steel such as SUS304, heat resistant steels such as SUH35 and SUH38, and the like.

上述の形態の場合、例えば、上記熱処理工程（Ｓ４）は、加熱された中間部品（７Ｃ）を円筒状部（８Ｂ）の肉厚（ｔ）の１ｍｍ当りに対して３〜８分（好ましくは４〜６分）となる加熱保持時間（ｔ２）で保持することができる（例えば、図１１〜図１３等参照）。この場合、例えば、上記中間部品（７Ｃ）の円筒状部（８Ｂ）の肉厚（ｔ）は１〜３ｍｍであり、熱処理工程（Ｓ４）は、加熱された中間部品（７Ｃ）を３〜２４分（好ましくは４〜１８分、特に５〜１５分）の加熱保持時間で保持することができる。 In the case of the above-mentioned form, for example, in the heat treatment step (S4), the heated intermediate part (7C) is 3 to 8 minutes (preferably, 3 to 8 minutes) per 1 mm of the wall thickness (t) of the cylindrical portion (8B). The heating and holding time (t2) is 4 to 6 minutes) (for example, see FIGS. 11 to 13). In this case, for example, the wall thickness (t) of the cylindrical portion (8B) of the intermediate component (7C) is 1 to 3 mm, and the heat treatment step (S4) is performed by heating the heated intermediate component (7C) to 3 to 24. It can be held for a heating and holding time of minutes (preferably 4 to 18 minutes, especially 5 to 15 minutes).

上述の形態の場合、例えば、上記熱処理工程（Ｓ４）は、中間部品（７Ｃ）を、容器（２２）内で攪拌される冷却水（２３）中又は容器に対して循環される冷却水中に投入して水冷することができる（例えば、図５等参照）。この場合、例えば、上記冷却水の水温は、１５〜３５℃（好ましくは２０〜３０℃）であることができる（例えば、図１１〜図１３等参照）。 In the case of the above-mentioned form, for example, in the heat treatment step (S4), the intermediate component (7C) is put into cooling water (23) stirred in the container (22) or cooling water circulated to the container. It can be cooled with water (see, for example, FIG. 5). In this case, for example, the temperature of the cooling water may be 15 to 35°C (preferably 20 to 30°C) (see, for example, Figs. 11 to 13).

本実施形態に係る中空エンジンバルブの製造方法としては、例えば、図１４及び図１５に示すように、スピニング工程（Ｓ５’）は、円筒状部（８Ｂ）の外周面に加工ローラ（１３２）の外周円弧面（１３２ａ）を所定の切込み量（ｄ）で押し当てながら、加工ローラ（１３２）を円筒状部（８Ｂ）に対して軸方向に移動（相対的に移動）させて円筒状部（８Ｂ）を軸方向に延伸することができる。この場合、例えば、加工ローラ（１３２）の外周円弧面（１３２ａ）の曲率半径（Ｒ）は、スピニング加工前の円筒状部（８Ｂ）の肉厚（ｔ）の３〜５倍の値であり、スピニング加工時に、円筒状部（８Ｂ）の軸方向に沿う断面において、加工ローラ（１３２）の外周円弧面（１３２ａ）が円筒状部（８Ｂ）の外周面と接する円弧の一端（ｐ１）と他端（ｐ２）とを結ぶ直線（Ｌ１）は、円筒状部（８Ｂ）の軸方向に対して５〜７度の傾斜角度（θ１）で傾斜していることができる。 As a method of manufacturing the hollow engine valve according to the present embodiment, for example, as shown in FIGS. 14 and 15, in the spinning step (S5′), the processing roller (132) is formed on the outer peripheral surface of the cylindrical portion (8B). While pressing the outer circumferential arc surface (132a) with a predetermined cut amount (d), the processing roller (132) is moved (relatively moved) in the axial direction with respect to the cylindrical portion (8B) so that the cylindrical portion ( 8B) can be stretched in the axial direction. In this case, for example, the radius of curvature (R) of the outer circumferential arc surface (132a) of the processing roller (132) is a value that is 3 to 5 times the wall thickness (t) of the cylindrical portion (8B) before spinning. During spinning, in the cross section along the axial direction of the cylindrical portion (8B), the outer peripheral arc surface (132a) of the processing roller (132) is connected to the outer peripheral surface of the cylindrical portion (8B) at one end (p1) of the arc. The straight line (L1) connecting to the other end (p2) can be inclined at an inclination angle (θ1) of 5 to 7 degrees with respect to the axial direction of the cylindrical portion (8B).

本実施形態に係る中空エンジンバルブの製造方法としては、例えば、上記中空エンジンバルブ（１）は、中空孔（４）を形成する内面の表面粗さＲａが４．０〜２２．０（好ましくは４．０〜１２．０、特に４．０〜８．０、更に４．０〜６．０）である形態（例えば、図９等参照）が挙げられる。なお、上記表面粗さは算術平均粗さ（Ｒａ）を採用した。また、上記表面粗さＲａは、ネッキング工程後の表面粗さを示す。 As a method for manufacturing the hollow engine valve according to the present embodiment, for example, in the hollow engine valve (1), the surface roughness Ra of the inner surface forming the hollow hole (4) is 4.0 to 22.0 (preferably, 4.0 to 12.0, particularly 4.0 to 8.0, and further 4.0 to 6.0) (for example, see FIG. 9). As the surface roughness, arithmetic mean roughness (Ra) was adopted. The surface roughness Ra indicates the surface roughness after the necking step.

本実施形態に係る中空エンジンバルブの製造方法としては、例えば、上記鍛造工程（Ｓ３）は、中間部品（７Ｃ）の円筒状部（８Ｂ）の内周面の底端側に円弧面（１７）を形成し、ネッキング工程（Ｓ６）は、円筒状部（８Ｂ）を上側とし且つ半傘状部（９Ｂ）を下側としたときに、円筒状部（８Ｂ）の軸方向で円弧面（１７）よりも上側の部分を絞り加工する形態（例えば、図８等参照）が挙げられる。この場合、例えば、上記中空エンジンバルブ（１）は、中空孔（４）の最大外径（Ｄ１’）が鍛造工程（Ｓ３）で得られる中間部品（７Ｃ）の円筒状部（８Ｂ）の開口の内径（Ｄ２）と同じであることができる。
なお、上記同じとは、略同じであることを意図しており、±５％程度の相違も含むものとする。As a method for manufacturing the hollow engine valve according to the present embodiment, for example, in the forging step (S3), the circular arc surface (17) is provided on the bottom end side of the inner peripheral surface of the cylindrical portion (8B) of the intermediate component (7C). In the necking step (S6), the arcuate surface (17) is formed in the axial direction of the cylindrical part (8B) when the cylindrical part (8B) is on the upper side and the semi-umbrella part (9B) is on the lower side. ) Is drawn (for example, see FIG. 8). In this case, for example, in the hollow engine valve (1), the maximum outer diameter (D1′) of the hollow hole (4) is the opening of the cylindrical portion (8B) of the intermediate part (7C) obtained in the forging step (S3). Can be the same as the inner diameter (D2) of
Note that the same as above is intended to mean substantially the same, and includes a difference of about ±5%.

本実施形態に係る中空エンジンバルブの製造方法としては、例えば、上記スピニング工程（Ｓ５、Ｓ５’）は、加工ローラ（３２、１３２）を用いて中間部品（７Ｃ）の円筒状部（８Ｂ）をスピニング加工し、加工ローラ（３２、１３２）は、加工ローラ（３２、１３２）を挟んで加工ローラの軸方向に沿って配置される前後の軸受（３４、１３４）を介して支持部材（３５、１３５）に回転自在に支持されている形態（例えば、図６及び図１４等参照）が挙げられる。 As a method of manufacturing the hollow engine valve according to the present embodiment, for example, in the spinning step (S5, S5′), the cylindrical portion (8B) of the intermediate component (7C) is processed by using the processing rollers (32, 132). The spinning roller (32, 132) is subjected to the spinning process, and the supporting member (35, 32) is attached to the supporting member (35, 37) via front and rear bearings (34, 134) arranged along the axial direction of the processing roller (32, 132). 135) rotatably supported (see, for example, FIGS. 6 and 14).

本実施形態に係る中空エンジンバルブの製造方法としては、例えば、中実円柱状の素材（６）を鍛造加工して、杯状拡径部（８Ａ）及び該杯状拡径部の縮径する軸端側に連なる円柱状部（９Ａ）を備える中間部品（７Ａ）を得る第１鍛造工程（Ｓ１）と、杯状拡径部（８Ａ）をしごき加工により円筒状部（８Ｂ）とするしごき工程（Ｓ２）と、を備え、上記鍛造工程は、円柱状部（９Ａ）を鍛造加工により半傘状部（９Ｂ）とする第２鍛造工程（Ｓ３）である形態（例えば、図１〜図３等参照）が挙げられる。 As a method of manufacturing the hollow engine valve according to the present embodiment, for example, the solid cylindrical material (6) is forged to reduce the cup-shaped expanded portion (8A) and the cup-shaped expanded portion. A first forging step (S1) for obtaining an intermediate part (7A) having a cylindrical portion (9A) continuous to the shaft end side, and an ironing process for forming a cup-shaped expanded portion (8A) into a cylindrical portion (8B) And a step (S2), wherein the forging step is a second forging step (S3) in which the columnar portion (9A) is forged into a semi-umbrella portion (9B) (for example, FIGS. 3 etc.).

なお、上記実施形態で記載した各構成の括弧内の符号は、後述する実施例に記載の具体的構成との対応関係を示すものである。 It should be noted that the reference numerals in parentheses of the respective constituents described in the above embodiment indicate the corresponding relationship with the concrete constituents described in the examples described later.

以下、図面を用いて実施例により本発明を具体的に説明する。 Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

（１）中空エンジンバルブの構成
本実施例に係る中空エンジンバルブ１は、図３（ｃ）に示すように、軸部２及び該軸部２の軸端側に連なる傘状部３を備えている。これら軸部２及び傘状部３にわたって中空孔４が形成されている。この中空孔４の最大外径Ｄ１は、後述の鍛造工程Ｓ３で得られる中間部品７Ｃの円筒状部８Ｂの開口の内径Ｄ２（図３（ａ）参照）より僅かに小さな値とされている。さらに、中空エンジンバルブ１は、中空孔４を形成する内面の表面粗さＲａが約４．０とされている（図９参照）。(1) Configuration of Hollow Engine Valve The hollow engine valve 1 according to the present embodiment, as shown in FIG. 3C, includes a shaft portion 2 and an umbrella-shaped portion 3 connected to the shaft end side of the shaft portion 2. There is. A hollow hole 4 is formed over the shaft portion 2 and the umbrella-shaped portion 3. The maximum outer diameter D1 of the hollow hole 4 is set to be a value slightly smaller than the inner diameter D2 (see FIG. 3A) of the opening of the cylindrical portion 8B of the intermediate component 7C obtained in the forging step S3 described later. Further, the hollow engine valve 1 has a surface roughness Ra of the inner surface forming the hollow hole 4 of about 4.0 (see FIG. 9).

（２）中空エンジンバルブの製造方法
本実施例に係る中空エンジンバルブの製造方法は、図１に示すように、第１鍛造工程Ｓ１、しごき工程Ｓ２、第２鍛造工程Ｓ３、熱処理工程Ｓ４、スピニング工程Ｓ５及びネッキング工程Ｓ６を備えている。(2) Method for Manufacturing Hollow Engine Valve As shown in FIG. 1, the method for manufacturing a hollow engine valve according to the present embodiment includes a first forging step S1, an ironing step S2, a second forging step S3, a heat treatment step S4, and spinning. The process S5 and the necking process S6 are provided.

上記第１鍛造工程Ｓ１は、図２（ａ）（ｂ）に示すように、ニッケル基超合金製で中実円柱状の素材６を熱間鍛造加工して中間部品７Ａを得る工程である。この中間部品７Ａは、杯状拡径部８Ａと、杯状拡径部８Ａの縮径する軸端側に連なる円柱状部９Ａと、を備えている。さらに、第１鍛造工程Ｓ１では、杯状拡径部８Ａの内壁を形成するための凸状部１１ａを有する金型１１と、素材６を保持するとともに杯状拡径部８Ａの外壁を形成するための凹状部１２ａを有する金型１２と、が用いられる。 As shown in FIGS. 2A and 2B, the first forging step S1 is a step of hot forging the solid cylindrical raw material 6 made of nickel-base superalloy to obtain the intermediate component 7A. The intermediate component 7A includes a cup-shaped enlarged diameter portion 8A and a columnar portion 9A which is continuous with the shaft end side where the cup-shaped enlarged diameter portion 8A is reduced in diameter. Further, in the first forging step S1, the die 11 having the convex portion 11a for forming the inner wall of the cup-shaped expanded portion 8A, the material 6 is held, and the outer wall of the cup-shaped expanded portion 8A is formed. And a mold 12 having a concave portion 12a for use.

上記しごき工程Ｓ２は、図２（ｂ）（ｃ）に示すように、主に、中間部品７Ａの杯状拡径部８Ａを冷間しごき加工により円筒状部８Ｂとして中間部品７Ｂを得る工程である。この円筒状部８Ｂの外径は、円柱状部９Ａの外径と略同じとされている。さらに、しごき工程Ｓ２では、杯状拡径部８Ａをしごくための貫通孔１４ａが形成された金型１４と、円柱状部９Ａを押圧するための突起部１５ａを備える金型１５と、が用いられる。 As shown in FIGS. 2B and 2C, the ironing step S2 is a step of obtaining the intermediate component 7B as a cylindrical portion 8B mainly by cold-ironing the cup-shaped expanded portion 8A of the intermediate component 7A. is there. The outer diameter of the cylindrical portion 8B is substantially the same as the outer diameter of the cylindrical portion 9A. Further, in the ironing step S2, a mold 14 having a through hole 14a for squeezing the cup-shaped expanded portion 8A and a mold 15 having a protrusion 15a for pressing the columnar portion 9A are used. To be

上記第２鍛造工程Ｓ３は、図２（ｃ）及び図３（ａ）に示すように、主に、中間部品７Ｂの円柱状部９Ａを熱間鍛造加工して傘状部３の半完成品である半傘状部９Ｂとして中間部品７Ｃを得る工程である。すなわち、第２鍛造工程Ｓ３で得られる中間部品７Ｃは、円筒状部８Ｂと、円筒状部８Ｂの軸端側に連なる半傘状部９Ｂと、を備えている。この円筒状部８Ｂの内周面の底端側には、円弧面１７が形成されている。さらに、第２鍛造工程Ｓ３では、円柱状部９Ａの底面を押圧するための凸状部１８ａを備える金型１８と、円柱状部９Ａ及び円筒状部８Ｂの外周側を保持する貫通孔１９ａが形成された金型１９と、貫通孔１９ａに挿入されて円筒状部８Ｂの底端側に当接するピン２０と、が用いられる。
なお、上記第２鍛造工程Ｓ３で得られる中間部品７Ｃの円筒状部８Ｂの肉厚ｔは、約２ｍｍとされている。In the second forging step S3, as shown in FIGS. 2(c) and 3(a), a semi-finished product of the umbrella-shaped portion 3 is mainly formed by hot forging the cylindrical portion 9A of the intermediate component 7B. Is a step of obtaining the intermediate component 7C as the semi-umbrella-shaped portion 9B. That is, 7 C of intermediate components obtained by the 2nd forging process S3 are equipped with the cylindrical part 8B and the semi-umbrella-shaped part 9B connected to the axial end side of the cylindrical part 8B. An arcuate surface 17 is formed on the bottom end side of the inner peripheral surface of the cylindrical portion 8B. Further, in the second forging step S3, the die 18 including the convex portion 18a for pressing the bottom surface of the cylindrical portion 9A and the through hole 19a for holding the outer peripheral side of the cylindrical portion 9A and the cylindrical portion 8B are provided. The formed mold 19 and the pin 20 that is inserted into the through hole 19a and comes into contact with the bottom end side of the cylindrical portion 8B are used.
The thickness t of the cylindrical portion 8B of the intermediate component 7C obtained in the second forging step S3 is about 2 mm.

上記熱処理工程Ｓ４は、中間部品７Ｃを軟化させるために円筒状部８Ｂの肉厚ｔに応じて決められる加熱保持時間ｔ２で固溶化熱処理する工程である。この熱処理工程Ｓ４では、図４に示すように、中間部品７Ｃが所定の加熱温度Ｔ１（例えば、１０５０℃）に加熱保持された後に水冷される。具体的に、常温Ｔ２（例えば、２０℃）の中間部品７Ｃは、所定の昇温時間ｔ１（例えば、５分）で加熱温度Ｔ１まで昇温され、その加熱温度Ｔ１に所定の加熱保持時間ｔ２（例えば、１０分）の間保持される。その後、中間部品７Ｃは、所定の冷却時間ｔ３（例えば、１０秒）で常温Ｔ２まで急冷される。なお、上記加熱保持時間ｔ２は、中間部品７Ｃの円筒状部８Ｂの肉厚ｔの１ｍｍ当りに対して約５分となる値とされている。 The heat treatment step S4 is a step of performing solution heat treatment for a heating and holding time t2 determined according to the wall thickness t of the cylindrical portion 8B in order to soften the intermediate component 7C. In this heat treatment step S4, as shown in FIG. 4, the intermediate component 7C is heated and held at a predetermined heating temperature T1 (for example, 1050° C.) and then water-cooled. Specifically, the intermediate component 7C at room temperature T2 (for example, 20° C.) is heated to the heating temperature T1 in a predetermined heating time t1 (for example, 5 minutes), and the heating temperature T1 is maintained for a predetermined heating time t2. Hold for (eg, 10 minutes). After that, the intermediate component 7C is rapidly cooled to the room temperature T2 in a predetermined cooling time t3 (for example, 10 seconds). The heating and holding time t2 is set to a value of about 5 minutes per 1 mm of the wall thickness t of the cylindrical portion 8B of the intermediate component 7C.

上記水冷では、図５に示すように、容器２２内に貯留される冷却水２３（例えば、水道水等）が用いられる。この容器２２内には、ポンプ２４に接続されて水の噴射可能なノズル２５が配置されている。このノズル２５は、水の噴射により冷却水２３を攪拌するように配置されている。よって、容器２２内に多数（例えば、２０〜３０個）の中間部品７Ｃを投入しても、冷却水２３の水温は２０〜３０℃に保たれる。 In the water cooling, as shown in FIG. 5, cooling water 23 (for example, tap water or the like) stored in the container 22 is used. A nozzle 25, which is connected to a pump 24 and can inject water, is arranged in the container 22. The nozzle 25 is arranged so as to agitate the cooling water 23 by jetting water. Therefore, even if many (for example, 20 to 30) intermediate components 7C are put into the container 22, the water temperature of the cooling water 23 is maintained at 20 to 30°C.

上記スピニング工程Ｓ５は、図３（ａ）（ｂ）に示すように、熱処理された中間部品７Ｃの円筒状部８Ｂを冷間スピニング加工により軸方向に延伸して薄肉化して中間部品７Ｄを得る工程である。このスピニング工程Ｓ５では、図６に示すように、半傘状部９Ｂを把持して中間部品７Ｃを軸回りに回転させるチャック機構３１と、その外周面が円筒状部８Ｂの外周面に押し当てられる加工ローラ３２と、が用いられる。この加工ローラ３２の軸方向に延びる支持軸３３は、加工ローラ３２の両表面側のそれぞれで軸受３４を介して支持部材３５に回転自在に支持されている。言い替えると、加工ローラ３２は、該加工ローラ３２を挟んで加工ローラ３２の軸方向に沿って配置される前後の軸受３４を介して支持部材３５に回転自在に支持されている。この支持部材３５は、図示しない移動機構により、円筒状部８Ｂの径方向及び軸方向に移動可能とされている。なお、上記加工ローラ３２は、１つが用いられてもよいし、複数が用いられてもよい。 In the spinning step S5, as shown in FIGS. 3(a) and 3(b), the cylindrical portion 8B of the heat-treated intermediate component 7C is axially stretched by cold spinning to be thinned to obtain the intermediate component 7D. It is a process. In this spinning step S5, as shown in FIG. 6, a chuck mechanism 31 that holds the semi-umbrella portion 9B and rotates the intermediate component 7C around the axis, and its outer peripheral surface is pressed against the outer peripheral surface of the cylindrical portion 8B. The processing roller 32 is used. The support shaft 33 extending in the axial direction of the processing roller 32 is rotatably supported by a support member 35 via bearings 34 on both surface sides of the processing roller 32. In other words, the processing roller 32 is rotatably supported by the support member 35 via front and rear bearings 34 that are arranged along the axial direction of the processing roller 32 with the processing roller 32 sandwiched therebetween. The support member 35 is movable in the radial direction and the axial direction of the cylindrical portion 8B by a moving mechanism (not shown). The number of the processing roller 32 may be one or plural.

上記スピニング工程Ｓ５では、中間部品７Ｃの円筒状部８Ｂの内側に保持ピン３７が挿入されるが、保持ピン３７は、その先端が円筒状部８Ｂの底端側に当接しているのみで、円筒状部８Ｂの内周面には当接していない。すなわち、スピニング加工Ｓ５では、中間部品７Ｃの円筒状部８Ｂの内周面にはツールが何ら当接していない。 In the spinning step S5, the holding pin 37 is inserted inside the cylindrical portion 8B of the intermediate component 7C, but the tip of the holding pin 37 is only in contact with the bottom end side of the cylindrical portion 8B. It is not in contact with the inner peripheral surface of the cylindrical portion 8B. That is, in the spinning process S5, no tool is in contact with the inner peripheral surface of the cylindrical portion 8B of the intermediate component 7C.

ここで、第２鍛造工程Ｓ３で得られる中間部品７Ｃの円筒状部８Ｂの肉厚に不揃いが生じることがあるが、その場合であっても、スピニング加工後の円筒状部８Ｂでは肉厚の不揃いが解消される。これに対して、スピニング加工の代わりにスウェージング加工を採用した場合、円筒状部８Ｂの肉厚の不揃いを解消し難い。 Here, the thickness of the cylindrical portion 8B of the intermediate component 7C obtained in the second forging step S3 may be uneven, but even in that case, the thickness of the cylindrical portion 8B after spinning is The misalignment is resolved. On the other hand, when swaging is adopted instead of spinning, it is difficult to eliminate the uneven thickness of the cylindrical portion 8B.

上記ネッキング工程Ｓ６は、図３（ｂ）（ｃ）に示すように、軸方向に延伸された円筒状部８Ｂを複数段階（例えば、９段階）の冷間絞り加工により徐々に縮径することで、軸部２及び傘状部３を形成する工程（即ち、中空エンジンバルブ１を得る工程）である。具体的に、円筒状部８Ｂの底端側以外の縮径された部分で軸部２が形成されるとともに、円筒状部８Ｂの底端側の縮径された部分と半傘状部９Ｂとで傘状部３が形成される。このネッキング工程Ｓ６では、中間部品７Ｄの半傘状部９Ｂを保持する金型３８と、円筒状部８Ｂを絞り加工するための成形孔３９ａを有する金型３９と、が用いられる。この金型３９としては、複数段階の絞り加工に応じて成形孔３９ａの穴径等が異なる複数種のものが使用される。 In the necking step S6, as shown in FIGS. 3B and 3C, the cylindrical portion 8B stretched in the axial direction is gradually reduced in diameter by a plurality of stages (for example, 9 stages) of cold drawing. Then, the step of forming the shaft portion 2 and the umbrella-shaped portion 3 (that is, the step of obtaining the hollow engine valve 1). Specifically, the shaft portion 2 is formed by a reduced diameter portion other than the bottom end side of the cylindrical portion 8B, and the reduced diameter portion on the bottom end side of the cylindrical portion 8B and the semi-umbrella portion 9B. The umbrella-shaped portion 3 is formed by. In this necking step S6, a mold 38 holding the semi-umbrella-shaped portion 9B of the intermediate component 7D and a mold 39 having a molding hole 39a for drawing the cylindrical portion 8B are used. As the mold 39, plural kinds of molds having different hole diameters of the molding holes 39a in accordance with plural stages of drawing are used.

上記ネッキング工程Ｓ６では、図７に示すように、中間部品７Ｄの円筒状部８Ｂの軸方向で円弧面１７を含む部分が絞り加工される。具体的に、最終段階（例えば、９段階目）の絞り加工の型締め時において、金型３９の下端面は、絞り加工前の中間部品７Ｄの円筒状部８Ｂの円弧面１７の上端（図７中に一点鎖線で示す高さ。）より下方に位置している。 In the necking step S6, as shown in FIG. 7, a portion including the arcuate surface 17 in the axial direction of the cylindrical portion 8B of the intermediate component 7D is drawn. Specifically, at the final stage (for example, the ninth stage) of the drawing process, the lower end surface of the die 39 is the upper end of the arc surface 17 of the cylindrical portion 8B of the intermediate component 7D before the drawing process (see FIG. 7 is located below the height indicated by the alternate long and short dash line).

（３）実施例の効果
本実施例の中空エンジンバルブの製造方法によると、鍛造加工により、円筒状部８Ｂ及び該円筒状部８Ｂの軸端側に連なる半傘状部９Ｂを備える中間部品７Ｃを得る鍛造工程Ｓ３と、中間部品７Ｃを軟化させるために円筒状部８Ｂの肉厚ｔに応じて決められる加熱保持時間ｔ２で熱処理する熱処理工程Ｓ４と、熱処理された中間部品７Ｃの円筒状部８Ｂをスピニング加工により軸方向に延伸するスピニング工程Ｓ５と、軸方向に延伸された円筒状部８Ｂを絞り加工により縮径することで、軸部２及び傘状部３を形成するネッキング工程Ｓ６と、を備える。このように、鍛造加工により得られた中間部品７Ｃを熱処理して軟化させることで、スピニング加工時及び絞り加工時に中間部品７Ｃの円筒状部８Ｂが伸び易くなるため、スピニング加工及び絞り加工の加工性に優れる。その結果、中空エンジンバルブ１の中空孔４を形成する内面での表面肌荒れの発生が抑制されて表面状態が良好となる。よって、中空エンジンバルブ１の強度の低下が抑制される。さらに、中空エンジンバルブ１の中空孔４内に冷却用の金属ナトリウムを入れる場合には、中空孔４内で金属ナトリウムが円滑に流動して効果的に冷却機能を発揮する。さらに、絞り加工の加工性に優れるため、傘状部３の中空孔４の外周側の潰れが抑制されるように、絞り加工の型締め時の金型３９の高さ位置を容易に調整できる。その結果、中空エンジンバルブ１の中空孔４の容積を大きくすることができる。(3) Effect of Embodiment According to the method for manufacturing the hollow engine valve of this embodiment, the intermediate component 7C including the cylindrical portion 8B and the semi-umbrella-shaped portion 9B connected to the axial end side of the cylindrical portion 8B by forging. Forging step S3 for obtaining the heat treatment, heat treatment step S4 for heat treatment for a heating and holding time t2 determined according to the wall thickness t of the cylindrical portion 8B for softening the intermediate component 7C, and the cylindrical portion of the heat treated intermediate component 7C. A spinning step S5 of axially stretching 8B by spinning, and a necking step S6 of forming the axial portion 2 and the umbrella-shaped portion 3 by reducing the diameter of the axially stretched cylindrical portion 8B. , Is provided. Thus, by heat-treating and softening the intermediate component 7C obtained by forging, the cylindrical portion 8B of the intermediate component 7C is easily stretched during the spinning process and the drawing process. Therefore, the spinning process and the drawing process are performed. Excellent in performance. As a result, the occurrence of surface roughening on the inner surface forming the hollow hole 4 of the hollow engine valve 1 is suppressed, and the surface condition is improved. Therefore, the decrease in strength of the hollow engine valve 1 is suppressed. Further, when metallic sodium for cooling is put into the hollow hole 4 of the hollow engine valve 1, the metallic sodium smoothly flows in the hollow hole 4 to effectively exhibit the cooling function. Further, since the drawing workability is excellent, the height position of the mold 39 can be easily adjusted at the time of clamping the drawing work so that the outer peripheral side crush of the hollow hole 4 of the umbrella-shaped portion 3 is suppressed. .. As a result, the volume of the hollow hole 4 of the hollow engine valve 1 can be increased.

また、本実施例では、中間部品７Ｃは、ニッケル基超合金で形成されており、熱処理工程Ｓ４は、中間部品７Ｃを１０５０℃に加熱保持した後に水冷する。これにより、中間部品７Ｃを固溶化熱処理して効果的に軟化させることができる。 Further, in this embodiment, the intermediate component 7C is made of a nickel-base superalloy, and in the heat treatment step S4, the intermediate component 7C is heated and held at 1050° C. and then water-cooled. As a result, the intermediate component 7C can be effectively softened by solution heat treatment.

また、本実施例では、熱処理工程Ｓ４は、加熱された中間部品７Ｃを円筒状部８Ｂの肉厚ｔ（具体的に、２ｍｍ）の１ｍｍ当りに対して５分となる加熱保持時間ｔ２（具体的に、１０分）で保持する。これにより、中間部品７Ｃの加熱保持時間ｔ２を比較的短くでき、熱処理後の中間部品７Ｃの表面での酸化膜の発生を低減できる。 Further, in the present embodiment, in the heat treatment step S4, the heated holding time t2 (specifically, 5 minutes per 1 mm of the wall thickness t (specifically, 2 mm) of the cylindrical portion 8B of the heated intermediate component 7C (specifically, For 10 minutes). As a result, the heating holding time t2 of the intermediate component 7C can be made relatively short, and the generation of an oxide film on the surface of the intermediate component 7C after the heat treatment can be reduced.

また、本実施例では、熱処理工程Ｓ４は、中間部品７Ｃを、容器２２内で攪拌される冷却水２３中に投入して水冷する。これにより、冷却水２３の温度上昇が抑えられるため、熱処理工程Ｓ４で中間部品７Ｃを効果的に急冷できる。特に、本実施例では、冷却水２３の水温は、２０〜３０℃であるので、熱処理工程Ｓ４で中間部品７Ｃを効果的に急冷できる。 Further, in the present embodiment, in the heat treatment step S4, the intermediate component 7C is put into the cooling water 23 which is stirred in the container 22 and water-cooled. As a result, the temperature rise of the cooling water 23 is suppressed, so that the intermediate component 7C can be effectively rapidly cooled in the heat treatment step S4. Particularly, in the present embodiment, the water temperature of the cooling water 23 is 20 to 30° C., so that the intermediate component 7C can be effectively and rapidly cooled in the heat treatment step S4.

また、本実施例では、中空エンジンバルブ１は、中空孔４を形成する内面の表面粗さＲａが４．０である。これにより、中空エンジンバルブ１の中空孔４を形成する内面の表面状態が極めて良好である。 Further, in the present embodiment, the hollow engine valve 1 has a surface roughness Ra of 4.0 on the inner surface forming the hollow hole 4. Thereby, the surface condition of the inner surface forming the hollow hole 4 of the hollow engine valve 1 is extremely good.

さらに、本実施例では、スピニング工程Ｓ５は、加工ローラ３２を用いて中間部品７Ｃの円筒状部８Ｂをスピニング加工し、加工ローラ３２は、加工ローラ３２を挟んで加工ローラ３２の軸方向に沿って配置される前後の軸受３４を介して支持部材３５に回転自在に支持されている。これにより、加工ローラ３２の倒れ込みが抑制されるため、中間部品７Ｃの円筒状部８Ｂが効果的にスピニング加工される。 Further, in the present embodiment, in the spinning step S5, the processing roller 32 is used to spin the cylindrical portion 8B of the intermediate component 7C, and the processing roller 32 sandwiches the processing roller 32 and extends in the axial direction of the processing roller 32. It is rotatably supported by the support member 35 via the front and rear bearings 34 that are arranged. As a result, the working roller 32 is prevented from falling down, so that the cylindrical portion 8B of the intermediate component 7C is effectively spun.

さらに、本実施例では、中実円柱状の素材６を鍛造加工して、杯状拡径部８Ａ及び該杯状拡径部８Ａの縮径する軸端側に連なる円柱状部９Ａを備える中間部品７Ａを得る第１鍛造工程Ｓ１と、杯状拡径部８Ａをしごき加工して円筒状部８Ｂとするしごき工程Ｓ２と、円柱状部９Ａを鍛造加工して半傘状部９Ｂとする第２鍛造工程Ｓ３と、を備える。これにより、比較的小さな加圧力で比較的肉厚の薄い円筒状部８Ｂを容易に形成できる。 Further, in the present embodiment, the solid columnar material 6 is forged to form the cup-shaped expanded portion 8A and the column-shaped portion 9A continuous to the shaft end side where the cup-shaped expanded portion 8A is reduced in diameter. The first forging step S1 for obtaining the part 7A, the ironing step S2 for ironing the cup-shaped expanded portion 8A to form the cylindrical portion 8B, and the forging process for the columnar portion 9A to form the semi-umbrella portion 9B. 2 forging step S3. As a result, the cylindrical portion 8B having a relatively thin wall can be easily formed with a relatively small pressure.

（４）実験例１〜１９及び比較例について
次に、図１１〜図１３に基づいて、実験例１〜１９及び比較例に係る中空エンジンバルブの製造方法の試験結果について説明する。これら実験例１〜１９では、上述の実施例の中空エンジンバルブの製造方法と同様にして、第１鍛造工程Ｓ１、しごき工程Ｓ２、第２鍛造工程Ｓ３、熱処理工程Ｓ４、スピニング工程Ｓ５及びネッキング工程Ｓ６を経て中空エンジンバルブを製造した。一方、比較例では、上述の各工程Ｓ１〜Ｓ６のうちで熱処理工程Ｓ４を省略して中空エンジンバルブを製造した。そして、実験例１〜１９及び比較例の各製法で得られた中空エンジンバルの表面状態を確認するとともに、スピニング加工の加工性を確認して、総合評価を下した。(4) Experimental Examples 1 to 19 and Comparative Example Next, the test results of the hollow engine valve manufacturing method according to Experimental Examples 1 to 19 and Comparative Example will be described with reference to FIGS. 11 to 13. In these Experimental Examples 1 to 19, the first forging step S1, the ironing step S2, the second forging step S3, the heat treatment step S4, the spinning step S5, and the necking step are performed in the same manner as in the hollow engine valve manufacturing method of the above-described embodiment. A hollow engine valve was manufactured through S6. On the other hand, in the comparative example, the heat treatment step S4 was omitted from the above steps S1 to S6 to manufacture a hollow engine valve. Then, while confirming the surface state of the hollow engine valve obtained by each of the manufacturing methods of Experimental Examples 1 to 19 and Comparative Example, the workability of the spinning process was confirmed, and a comprehensive evaluation was made.

ここで、実験例１〜７では、ニッケル含有率が約５０％であるニッケル基超合金製の素材を用い、実験例８〜１３では、ニッケル含有率が約８０％であるニッケル基超合金製の素材を用い、実験例１４〜１９及び比較例では、ニッケル含有率が約３０％であるニッケル基超合金製の素材を用いた。また、実験例１〜１９の熱処理工程では、加熱温度、加熱保持時間、冷却方法及び処理量等を変更した。特に、実験例１〜１７では、攪拌されない冷却水中に中間部品を投入して水冷し、実験例１８及び１９では、攪拌中の冷却水中に中間部品を投入して水冷した。さらに、実験例１〜１６では、１個の中間部品を冷却水中に投入して水冷し、実験例１７〜１９では、１０〜２０個の中間部品を冷却水中に投入して水冷した。 Here, in Experimental Examples 1 to 7, a nickel-based superalloy having a nickel content of about 50% was used, and in Experimental Examples 8 to 13, a nickel-based superalloy having a nickel content of about 80% was used. In Experimental Examples 14 to 19 and Comparative Example, a nickel-base superalloy material having a nickel content of about 30% was used. Moreover, in the heat treatment process of Experimental Examples 1 to 19, the heating temperature, the heating holding time, the cooling method, the treatment amount, and the like were changed. Particularly, in Experimental Examples 1 to 17, the intermediate component was put into uncooled cooling water and water-cooled, and in Experimental Examples 18 and 19, the intermediate component was put into cooling water being stirred and water-cooled. Further, in Experimental Examples 1 to 16, one intermediate component was put into cooling water for water cooling, and in Experimental Examples 17 to 19, 10 to 20 intermediate components were put into cooling water for water cooling.

その結果、比較例の製法で得られた中空エンジンバルブでは、中空孔を形成する内面に顕著な肌荒れが発生し、その表面粗さＲａが約２２．０であった（図１０参照）。さらに、スピニング加工での材料の伸びが悪く、加工性が極めて低かった。 As a result, in the hollow engine valve obtained by the manufacturing method of the comparative example, the inner surface forming the hollow hole was significantly roughened, and the surface roughness Ra was about 22.0 (see FIG. 10). Furthermore, the elongation of the material during spinning was poor, and the workability was extremely low.

これに対して、実験例１、２、６、９及び１１の製法で得られた中空エンジンバルブでは、中空孔を形成する内面に少々の肌荒れが発生するが、比較例に比べて表面状態が良好であった。また、実験例３−５、７、８、１０及び１２−１９の製法で得られた中空エンジンバルブでは、中空孔を形成する内面に肌荒れが発生せず、表面状態が極めて良好であった。特に、実験例１９の製法で得られた中空エンジンバルブでは、中空孔を形成する内面での酸化膜の発生が少なかった。 On the other hand, in the hollow engine valves obtained by the manufacturing methods of Experimental Examples 1, 2, 6, 9 and 11, some skin roughness occurs on the inner surface forming the hollow holes, but the surface condition is better than that of the comparative example. It was good. Further, in the hollow engine valves obtained by the production methods of Experimental Examples 3-5, 7, 8, 10 and 12-19, the inner surface forming the hollow holes did not have rough skin, and the surface condition was extremely good. In particular, in the hollow engine valve obtained by the manufacturing method of Experimental Example 19, the generation of an oxide film on the inner surface forming the hollow hole was small.

また、実験例１−１５及び１７の製法では、スピニング加工での材料の伸びがやや悪かったが、比較例に比べて加工性が高かった。また、実験例１６、１８及び１９の製法では、スピニング加工での材料の伸びが良く、加工性が極めて高かった。 Further, in the manufacturing methods of Experimental Examples 1-15 and 17, the elongation of the material in the spinning process was slightly poor, but the workability was higher than that of the comparative example. In addition, in the manufacturing methods of Experimental Examples 16, 18 and 19, the elongation of the material during spinning was good, and the workability was extremely high.

ここで、実験例１８及び１９の製法では、多数の中間部品を一度に処理しても効果的に水冷された。これは、攪拌を伴う冷却水で冷却することで、冷却水の温度上昇が抑制されるためである。さらに、実験例１９の製法では、中空エンジンバルブの中空孔を形成する内面での酸化膜の発生が少なかった。これは、加熱保持時間ｔ２が１０分と極めて短いためである。この点から、鍛造工程Ｓ３で得られた中間部品７Ｃを円筒状部８Ｂの肉厚ｔの１ｍｍ当りに対して５分程度の加熱保持時間ｔ２で保持することで、スピニング加工に必要な成分組織の改質が得られると言える。 Here, in the manufacturing methods of Experimental Examples 18 and 19, even if a large number of intermediate parts were treated at once, they were effectively water-cooled. This is because the temperature rise of the cooling water is suppressed by cooling with the cooling water accompanied by stirring. Further, in the manufacturing method of Experimental Example 19, the generation of the oxide film on the inner surface forming the hollow hole of the hollow engine valve was small. This is because the heating holding time t2 is extremely short at 10 minutes. From this point, by holding the intermediate part 7C obtained in the forging step S3 for a heating holding time t2 of about 5 minutes per 1 mm of the wall thickness t of the cylindrical portion 8B, the component structure necessary for the spinning process is obtained. It can be said that the modification can be obtained.

＜他の形態のスピニング工程＞
次に、他の形態のスピニング工程Ｓ５’について説明するが、上述のスピニング工程Ｓ５と略同じ構成の部位には同じ符号を付けて詳説を省略する。<Other forms of spinning process>
Next, the spinning process S5′ of another embodiment will be described, but the portions having substantially the same configurations as those of the spinning process S5 described above will be denoted by the same reference numerals and detailed description thereof will be omitted.

（１）スピニング工程について
上記スピニング工程Ｓ５’は、図３（ａ）（ｂ）に示すように、熱処理された中間部品７Ｃの円筒状部８Ｂを冷間スピニング加工により軸方向に延伸して薄肉化して中間部品７Ｄを得る工程である。このスピニング工程Ｓ５’では、図１４に示すように、半傘状部９Ｂを把持して中間部品７Ｃを軸回りに回転させるチャック機構１３１と、その外周円弧面１３２ａが円筒状部８Ｂの外周面に押し当てられる加工ローラ１３２と、が用いられる。この加工ローラ１３２は、その軸方向に延びる支持軸１３３（すなわち、支持部材１３５）に対して、加工ローラ１３２を挟んで加工ローラ１３２の軸方向に沿って配置される前後の軸受１３４（具体的に、スラスト軸受１３４）を介して回転自在に支持されている。この支持部材１３５は、図示しない移動機構により、円筒状部８Ｂの径方向及び軸方向に移動可能とされている。(1) Spinning Step In the spinning step S5′, as shown in FIGS. 3(a) and 3(b), the cylindrical portion 8B of the heat-treated intermediate component 7C is axially stretched by cold spinning to obtain a thin wall. It is a process of obtaining the intermediate component 7D by liquefying. In this spinning step S5′, as shown in FIG. 14, a chuck mechanism 131 that holds the semi-umbrella portion 9B and rotates the intermediate component 7C around the axis, and its outer peripheral arc surface 132a is the outer peripheral surface of the cylindrical portion 8B. And a processing roller 132 that is pressed against. The processing roller 132 has front and rear bearings 134 (specifically, the bearings 134 (specifically, those arranged along the axial direction of the processing roller 132 with the processing roller 132 sandwiched between the support shaft 133 (that is, the support member 135) extending in the axial direction). Is rotatably supported by a thrust bearing 134). The support member 135 is movable in the radial direction and the axial direction of the cylindrical portion 8B by a moving mechanism (not shown).

なお、上記加工ローラ１３２は、１つが用いられてもよいし、複数が用いられてもよい。また、図１４中の円筒状部８Ｂにおいて、中心線より上側の部分がスピニング加工前の肉厚（例えば、１．６５ｍｍ）を示し、中心線より下側の部分がスピニング加工後の肉厚（例えば、１．０ｍｍ）を示す。 The number of the processing rollers 132 may be one or plural. In addition, in the cylindrical portion 8B in FIG. 14, the portion above the center line shows the thickness before spinning (for example, 1.65 mm), and the portion below the center line shows the thickness after spinning ( For example, 1.0 mm) is shown.

上記スピニング加工Ｓ５’では、図１５に示すように、円筒状部８Ｂの外周面に加工ローラ１３２の外周円弧面１３２ａを所定の切込み量ｄで押し当てながら、加工ローラ１３２を円筒状部８Ｂの軸方向に沿う加工方向Ｐに移動させてこれを繰り返すことで、円筒状部８Ｂが軸方向に延伸される。なお、上記スピニング加工Ｓ５’における切込み量ｄ及び延伸させる方向Ｐへの移動回数等は特に問わない。また、スピニング加工Ｓ５’では、通常、スピニング加工時に切込み量ｄよりも小さな量の戻りが生じる。 In the spinning process S5′, as shown in FIG. 15, while the outer peripheral arc surface 132a of the processing roller 132 is pressed against the outer peripheral surface of the cylindrical portion 8B with a predetermined cut amount d, the processing roller 132 is moved to the cylindrical portion 8B. The cylindrical portion 8B is stretched in the axial direction by moving in the processing direction P along the axial direction and repeating this. The cutting amount d and the number of movements in the stretching direction P in the spinning process S5' are not particularly limited. Further, in the spinning process S5', a return amount smaller than the depth of cut d usually occurs during the spinning process.

ここで、加工ローラ１３２の外周円弧面１３２ａの曲率半径Ｒは、スピニング加工前の円筒状部８Ｂの肉厚ｔの３〜５倍の値とされている。そして、スピニング加工時に、円筒状部８Ｂの軸方向に沿う断面において、加工ローラ１３２の外周円弧面１３２ａが円筒状部８Ｂの外周面と接する円弧の一端ｐ１と他端ｐ２とを結ぶ直線Ｌ１は、円筒状部８Ｂの軸方向に対して５〜７度の傾斜角度θ１で傾斜している。これにより、切込み量ｄの最大値と最小値を想定考慮して加工ローラ１３２の外周円弧面１３２ａの曲率半径Ｒを設定することとなるため、スピニング加工時に中間部品７Ｃの円筒状部８Ｂを効果的に延伸できる。 Here, the radius of curvature R of the outer circumferential arc surface 132a of the processing roller 132 is set to a value that is 3 to 5 times the wall thickness t of the cylindrical portion 8B before spinning. Then, at the time of spinning, in the cross section along the axial direction of the cylindrical portion 8B, the straight line L1 connecting the one end p1 and the other end p2 of the circular arc where the outer peripheral arc surface 132a of the processing roller 132 contacts the outer peripheral surface of the cylindrical portion 8B is , With an inclination angle θ1 of 5 to 7 degrees with respect to the axial direction of the cylindrical portion 8B. Accordingly, the radius of curvature R of the outer circumferential arc surface 132a of the processing roller 132 is set in consideration of the maximum value and the minimum value of the depth of cut d, so that the cylindrical portion 8B of the intermediate component 7C is effective during spinning. Can be stretched.

なお、上記一端ｐ１は、通常、スピニング加工時に、円筒状部８Ｂの軸方向に沿う断面において、加工ローラ１３２の外周円弧面１３２ａの曲率半径Ｒの中心を通り且つ円筒状部８Ｂの軸心と直交する直線Ｌ２が円筒状部８Ｂの外周面と交差する点である。また、上記スピニング工程Ｓ５の加工ローラ３２の曲率半径Ｒ及び傾斜角度θ１として、スピニング工程Ｓ５’の加工ローラ１３２の曲率半径Ｒ及び傾斜角度θ１と同じ条件を採用している。 Note that the one end p1 normally passes through the center of the radius of curvature R of the outer circumferential arc surface 132a of the processing roller 132 and the axial center of the cylindrical portion 8B in the cross section along the axial direction of the cylindrical portion 8B during spinning. The orthogonal straight line L2 intersects with the outer peripheral surface of the cylindrical portion 8B. Further, as the curvature radius R and the inclination angle θ1 of the processing roller 32 in the spinning step S5, the same conditions as the curvature radius R and the inclination angle θ1 of the processing roller 132 in the spinning step S5' are adopted.

（２）実験例２０〜２７について
次に、図１６に基づいて、実験例２０〜２７に係るスピニング工程の試験結果について説明する。これら実験例２０〜２７では、上述の第１鍛造工程Ｓ１、しごき工程Ｓ２、第２鍛造工程Ｓ３、熱処理工程Ｓ４（実験例１９）を経た中間部品７Ｃに対して、円筒状部８Ｂの肉厚ｔが１．６５ｍｍから１ｍｍとなるまで複数回のスピニング加工を行った。各実験例２０〜２４では、円筒状部８Ｂに対する加工ローラ１３２の切込み量ｄを０．１５ｍｍとした。さらに、各実験例２５〜２７では、円筒状部８Ｂに対する加工ローラ１３２の切込み量ｄを０．１ｍｍとした。そして、スピニング加工後の中間部品７Ｄの表面状態を確認し、その表面状態及びスピニング回数に基づいて評価を下した。(2) About Experimental Examples 20 to 27 Next, test results of the spinning process according to Experimental Examples 20 to 27 will be described with reference to FIG. In these Experimental Examples 20 to 27, the wall thickness of the cylindrical portion 8B is different from that of the intermediate part 7C that has undergone the above-described first forging step S1, ironing step S2, second forging step S3, and heat treatment step S4 (Experimental Example 19). The spinning process was performed multiple times until t became 1.65 mm to 1 mm. In each of Experimental Examples 20 to 24, the cutting amount d of the processing roller 132 with respect to the cylindrical portion 8B was set to 0.15 mm. Further, in each of Experimental Examples 25 to 27, the cut amount d of the processing roller 132 with respect to the cylindrical portion 8B was set to 0.1 mm. Then, the surface state of the intermediate component 7D after the spinning process was confirmed, and the evaluation was made based on the surface state and the number of spinnings.

なお、上記実験例２０〜２７では、汎用のＮＣ旋盤を用いて、中間部品７Ｃの回転数を１２００ｒｐｍとし、加工ローラ１３２の送り速度を０．１３ｍｍ／ｓとした。 In Experimental Examples 20 to 27, a general-purpose NC lathe was used, the rotation speed of the intermediate component 7C was 1200 rpm, and the feed speed of the processing roller 132 was 0.13 mm/s.

実験例２１〜２３、２５及び２６では、その外周円弧面１３２ａの曲率半径Ｒがスピニング加工前の円筒状部８Ｂの肉厚ｔの３〜５倍の値であり、直線Ｌ１が円筒状部８Ｂの軸方向に対して５〜７度の傾斜角度θ１で傾斜する加工ローラ１３２を採用した。その結果、実験例２１〜２３で得られた中間部品７Ｄの表面状態は滑らかで良く、スピニング回数が１０回であり加工性にも優れる。また、実験例２５及び２６で得られた中間部品７Ｄの表面状態は滑らかで良く、スピニング回数が１３回であり加工性にも優れる。 In Experimental Examples 21 to 23, 25, and 26, the radius of curvature R of the outer circumferential arc surface 132a is 3 to 5 times the wall thickness t of the cylindrical portion 8B before spinning, and the straight line L1 is the cylindrical portion 8B. A processing roller 132 that is inclined at an inclination angle θ1 of 5 to 7 degrees with respect to the axial direction of is used. As a result, the intermediate parts 7D obtained in Experimental Examples 21 to 23 have a smooth surface condition, the number of spinning times is 10, and the workability is excellent. Further, the surface condition of the intermediate component 7D obtained in Experimental Examples 25 and 26 is smooth, and the number of spinning is 13 times, which is excellent in workability.

一方、実験例２０では、その外周円弧面１３２ａの曲率半径Ｒがスピニング加工前の円筒状部８Ｂの肉厚ｔの約１．８倍の値であり、直線Ｌ１が円筒状部８Ｂの軸方向に対して９度の傾斜角度θ１で傾斜する加工ローラ１３２を採用した。その結果、実験例２０で得られた中間部品７Ｄの表面状態はやや荒れた肌を示したが、スピニング回数が１０回であり加工性に優れる。 On the other hand, in Experimental Example 20, the radius of curvature R of the outer circumferential arc surface 132a is about 1.8 times the wall thickness t of the cylindrical portion 8B before spinning, and the straight line L1 is the axial direction of the cylindrical portion 8B. A processing roller 132 that inclines at an inclination angle θ1 of 9 degrees is used. As a result, the surface condition of the intermediate component 7D obtained in Experimental Example 20 showed a slightly rough skin, but the number of spinnings was 10 and the workability was excellent.

また、実験例２４では、その外周円弧面１３２ａの曲率半径Ｒがスピニング加工前の円筒状部８Ｂの肉厚ｔの約６倍の値であり、直線Ｌ１が円筒状部８Ｂの軸方向に対して４．５度の傾斜角度θ１で傾斜する加工ローラ１３２を採用した。その結果、実験例２４で得られた中間部品７Ｄの表面状態は滑らかで良いが、スピニング回数が１６回であった。 Further, in Experimental Example 24, the radius of curvature R of the outer circumferential arc surface 132a is about 6 times the wall thickness t of the cylindrical portion 8B before spinning, and the straight line L1 with respect to the axial direction of the cylindrical portion 8B. A processing roller 132 that inclines at an inclination angle θ1 of 4.5 degrees is adopted. As a result, the intermediate part 7D obtained in Experimental Example 24 had a smooth surface condition, but the spinning frequency was 16 times.

さらに、実験例２７では、その外周円弧面１３２ａの曲率半径Ｒがスピニング加工前の円筒状部８Ｂの肉厚ｔの５倍の値であり、直線Ｌ１が円筒状部８Ｂの軸方向に対して４．５度の傾斜角度θ１で傾斜する加工ローラ１３２を採用した。その結果、実験例２７で得られた中間部品７Ｄの表面状態は滑らかで良いが、スピニング回数が２０回であった。 Furthermore, in Experimental Example 27, the radius of curvature R of the outer circumferential arc surface 132a is 5 times the wall thickness t of the cylindrical portion 8B before spinning, and the straight line L1 is in the axial direction of the cylindrical portion 8B. A processing roller 132 that is inclined at an inclination angle θ1 of 4.5 degrees is used. As a result, the intermediate part 7D obtained in Experimental Example 27 had a smooth surface condition, but the spinning frequency was 20 times.

なお、本発明においては、上記実施例に限られず、目的、用途に応じて本発明の範囲内で種々変更した実施例とすることができる。すなわち、上記実施例では、熱間鍛造加工、冷間しごき加工、冷間スピニング加工、及び冷間絞り加工等を例示したが、これに限定されず、例えば、これら各加工は、熱間、温間、冷間加工のうちから適宜選択できる。さらに、これら各加工は、１回の加工であってもよいし、複数回の加工であってもよい。 It should be noted that the present invention is not limited to the above-described embodiments, and various modifications may be made within the scope of the present invention according to the purpose and application. That is, in the above examples, hot forging, cold ironing, cold spinning, cold drawing and the like are illustrated, but the present invention is not limited to this. It can be appropriately selected from cold working and cold working. Further, each of these processes may be performed once or may be performed multiple times.

また、上記実施例では、オーステナイト系耐熱材料（具体的に、ニッケル基超合金）により形成される中間部品７Ｃを例示したが、これに限定されず、例えば、ＳＵＨ３、ＳＵＨ１１等のマルテンサイト系耐熱材料により形成される中間部品７Ｃとしてもよい。この場合、熱処理工程Ｓ４では、中間部品７Ｃの材料に適した熱処理が行われる。 Further, in the above-mentioned embodiment, the intermediate component 7C formed of an austenitic heat-resistant material (specifically, nickel-base superalloy) is exemplified, but the invention is not limited to this, and for example, martensitic heat-resistant materials such as SUH3 and SUH11. The intermediate component 7C made of a material may be used. In this case, in the heat treatment step S4, a heat treatment suitable for the material of the intermediate component 7C is performed.

また、上記実施例では、鍛造加工により杯状拡径部８Ａを備える中間部品７Ａを形成し、その杯状拡径部８Ａをしごき加工により円筒状部８Ｂとして円筒状部８Ｂを備える中間部品７Ｂを得るようにしたが、これに限定されず、例えば、杯状拡径部８Ａを形成することなく、鍛造加工により円筒状部８Ｂを備える中間部品７Ｂを得るようにしてもよい。 Further, in the above embodiment, the intermediate part 7A having the cup-shaped expanded portion 8A is formed by forging, and the cup-shaped expanded portion 8A is ironed to form the intermediate part 7B as the cylindrical portion 8B. However, the present invention is not limited to this, and for example, the intermediate component 7B including the cylindrical portion 8B may be obtained by forging without forming the cup-shaped enlarged diameter portion 8A.

また、上記実施例では、ノズル２５の水の噴射により容器２２内で冷却水２３を攪拌するようにしたが、これに限定されず、例えば、攪拌羽根又は攪拌スクリュウの回転により容器２２内で冷却水２３を攪拌するようにしてもよい。さらに、例えば、容器２２に循環経路を接続し、容器２２に対して冷却水２３を循環させるようにしてもよい。この場合であっても、冷却水２３の温度上昇が抑えられるため、熱処理工程Ｓ４で中間部品７Ｃを効果的に急冷できる。 Further, in the above embodiment, the cooling water 23 is stirred in the container 22 by jetting water from the nozzle 25, but the invention is not limited to this. For example, the cooling water is cooled in the container 22 by rotating a stirring blade or a stirring screw. The water 23 may be stirred. Furthermore, for example, a circulation path may be connected to the container 22 and the cooling water 23 may be circulated through the container 22. Even in this case, since the temperature rise of the cooling water 23 is suppressed, the intermediate component 7C can be effectively rapidly cooled in the heat treatment step S4.

また、上記実施例では、スピニング工程Ｓ５、Ｓ５’で、その外周円弧面１３２ａの曲率半径Ｒがスピニング加工前の円筒状部８Ｂの肉厚ｔの３〜５倍の値である加工ローラ１３２を用いる形態を例示したが、これに限定されず、例えば、その外周円弧面１３２ａの曲率半径Ｒが、スピニング加工前の円筒状部８Ｂの肉厚ｔの３倍未満の値又は５倍を超える値である加工ローラ１３２を用いてもよい。 Further, in the above-described embodiment, in the spinning steps S5 and S5′, the processing roller 132 in which the radius of curvature R of the outer circumferential arc surface 132a is 3 to 5 times the wall thickness t of the cylindrical portion 8B before spinning is used. Although the form used is illustrated, the present invention is not limited to this, and for example, the radius of curvature R of the outer peripheral arc surface 132a is less than 3 times or more than 5 times the wall thickness t of the cylindrical portion 8B before spinning. You may use the processing roller 132 which is.

また、上記実施例では、スピニング工程Ｓ５、Ｓ５’で、直線Ｌ１が円筒状部の軸方向に対して５〜７度の傾斜角度θ１で傾斜する加工ローラ１３２を用いる形態を例示したが、これに限定されず、例えば、直線Ｌ１が、円筒状部８Ｂの軸方向に対して５度未満又は７度を超える傾斜角度θ１で傾斜する加工ローラ１３２を用いてもよい。 Further, in the above embodiment, in the spinning steps S5 and S5′, the processing roller 132 in which the straight line L1 is inclined at the inclination angle θ1 of 5 to 7 degrees with respect to the axial direction of the cylindrical portion is used. For example, the processing roller 132 in which the straight line L1 is inclined at an inclination angle θ1 of less than 5 degrees or more than 7 degrees with respect to the axial direction of the cylindrical portion 8B may be used.

また、上記実施例では、中間部品７Ｄの円筒状部８Ｂの軸方向で円弧面１７を含む部分を絞り加工するネッキング工程Ｓ６を例示したが、これに限定されず、例えば、図８に示すように、中間部品７Ｄの円筒状部８Ｂを上側とし且つ半傘状部９Ｂを下側としたきに、円筒状部８Ｂの軸方向で円弧面１７よりも上側の部分を絞り加工するネッキング加工Ｓ６としてもよい。この場合、絞り加工の型締め時において、金型３９の下端面は、絞り加工前の中間部品７Ｄの円筒状部８Ｂの円弧面１７の上端（図８中に一点鎖線で示す高さ。）より上方に位置している。これにより、中空エンジンバルブ１の中空孔４の最大外径Ｄ１’が鍛造工程Ｓ３で得られる中間部品７Ｄの円筒状部８Ｂの開口の内径Ｄ２（図３（ａ）参照）と同じにできる。その結果、中空エンジンバルブ１の中空孔４の容積を更に大きくできる。 Further, in the above-described embodiment, the necking step S6 of drawing the portion including the arcuate surface 17 in the axial direction of the cylindrical portion 8B of the intermediate component 7D has been illustrated, but the present invention is not limited to this and, for example, as shown in FIG. In addition, when the cylindrical portion 8B of the intermediate component 7D is on the upper side and the semi-umbrella portion 9B is on the lower side, a necking process S6 for drawing a portion of the cylindrical portion 8B above the arc surface 17 in the axial direction. May be In this case, at the time of clamping of the drawing process, the lower end surface of the mold 39 is the upper end of the circular arc surface 17 of the cylindrical portion 8B of the intermediate component 7D before the drawing process (the height indicated by the dashed line in FIG. 8). It is located above. Thereby, the maximum outer diameter D1' of the hollow hole 4 of the hollow engine valve 1 can be made equal to the inner diameter D2 (see FIG. 3A) of the opening of the cylindrical portion 8B of the intermediate component 7D obtained in the forging step S3. As a result, the volume of the hollow hole 4 of the hollow engine valve 1 can be further increased.

さらに、上記実施例では、前後の軸受３４により両持ち支持された加工ローラ３２を例示したが、これに限定されず、例えば、片持ち支持された加工ローラ３２としてもよい。さらに、例えば、加工ローラ３２に替えて又は加えて、加工へらを用いるスピニング工程Ｓ５としてもよい。 Furthermore, in the above embodiment, the processing roller 32 supported by both the front and rear bearings 34 was illustrated, but the present invention is not limited to this, and the processing roller 32 may be supported by a cantilever. Further, for example, instead of or in addition to the processing roller 32, a spinning step S5 using a processing spatula may be performed.

本発明は、軽量で且つ耐熱性に優れた中空エンジンバルブを製造する技術として好適に利用される。 INDUSTRIAL APPLICABILITY The present invention is suitably used as a technique for manufacturing a hollow engine valve that is lightweight and has excellent heat resistance.

１；中空エンジンバルブ、２；軸部、３；傘状部、４；中空孔、７Ｃ；中間部品、８Ｂ；円筒状部、９Ｂ；半傘状部、１７；円弧面、２２；容器、２３；冷却水、３２，１３２；加工ローラ、３３；支持軸、３４，１３４；軸受、３５，１３５；支持部材、３９，１３９；金型、Ｓ３；第２鍛造工程、Ｓ４；熱処理工程、Ｓ５，Ｓ５’；スピニング工程、Ｓ６；ネッキング工程、Ｔ１；加熱温度、ｔ２；加熱保持時間。 1; Hollow engine valve, 2; Shaft part, 3; Umbrella part, 4; Hollow hole, 7C; Intermediate part, 8B; Cylindrical part, 9B; Semi-umbrella part, 17; Arc surface, 22; Container, 23 Cooling water, 32, 132; processing roller, 33; support shaft, 34, 134; bearing, 35, 135; support member, 39, 139; mold, S3; second forging step, S4; heat treatment step, S5 S5': spinning step, S6: necking step, T1: heating temperature, t2: heating holding time.

Claims (5)

軸部及び該軸部の軸端側に連なる傘状部を備え、前記軸部及び前記傘状部にわたって中空孔が形成された中空エンジンバルブの製造方法であって、
鍛造加工により、円筒状部及び該円筒状部の軸端側に連なる半傘状部を備える中間部品を得る鍛造工程と、
前記中間部品を軟化させるために前記円筒状部の肉厚に応じて決められる加熱保持時間で熱処理する熱処理工程と、
熱処理された前記中間部品の前記円筒状部をスピニング加工により軸方向に延伸するスピニング工程と、
軸方向に延伸された前記円筒状部を絞り加工により縮径することで、前記軸部及び前記傘状部を形成するネッキング工程と、を備え、
前記スピニング工程は、前記円筒状部の外周面に加工ローラの外周円弧面を所定の切込み量で押し当てながら、前記加工ローラを前記円筒状部に対して軸方向に移動させて前記円筒状部を軸方向に延伸し、
前記加工ローラの外周円弧面の曲率半径は、スピニング加工前の前記円筒状部の肉厚の３〜５倍の値であり、
前記スピニング加工時に、前記円筒状部の軸方向に沿う断面において、前記加工ローラの外周円弧面が前記円筒状部の外周面と接する円弧の一端と他端とを結ぶ直線は、前記円筒状部の軸方向に対して５〜７度の傾斜角度で傾斜しており、
前記中空エンジンバルブは、前記中空孔を形成する内面の表面粗さＲａが４．０〜２２．０であることを特徴とする中空エンジンバルブの製造方法。 A method of manufacturing a hollow engine valve, comprising a shaft portion and an umbrella-shaped portion continuous to a shaft end side of the shaft portion, wherein a hollow hole is formed over the shaft portion and the umbrella-shaped portion,
A forging step for obtaining an intermediate part including a cylindrical portion and a semi-umbrella portion connected to the shaft end side of the cylindrical portion by forging,
A heat treatment step of performing heat treatment for a heating and holding time determined according to the wall thickness of the cylindrical portion in order to soften the intermediate component,
A spinning step of axially stretching the cylindrical portion of the heat-treated intermediate part by spinning.
A necking step of forming the shaft portion and the umbrella-shaped portion by reducing the diameter of the cylindrical portion stretched in the axial direction by drawing.
In the spinning step, the processing roller is moved in the axial direction with respect to the cylindrical portion while pressing the outer circumferential arc surface of the processing roller against the outer circumferential surface of the cylindrical portion with a predetermined cut amount. Is stretched in the axial direction,
The radius of curvature of the outer circumferential arc surface of the processing roller is 3 to 5 times the wall thickness of the cylindrical portion before spinning.
At the time of the spinning process, in a cross section along the axial direction of the cylindrical portion, a straight line connecting one end and the other end of an arc where the outer peripheral arc surface of the processing roller contacts the outer peripheral surface of the cylindrical portion is the cylindrical portion. Is inclined at an inclination angle of 5 to 7 degrees with respect to the axial direction of
The hollow engine valve has a surface roughness Ra of 4.0 to 22.0 on an inner surface forming the hollow hole . 前記中間部品は、オーステナイト系耐熱材料で形成されており、The intermediate component is formed of an austenitic heat resistant material,
前記熱処理工程は、前記中間部品を１０００〜１１００℃に加熱し、加熱された前記中間部品を前記円筒状部の肉厚の１ｍｍ当りに対して３〜８分となる加熱保持時間で保持した後に水冷する請求項１に記載の中空エンジンバルブの製造方法。In the heat treatment step, after heating the intermediate part to 1000 to 1100° C. and holding the heated intermediate part for a heating holding time of 3 to 8 minutes per 1 mm of the wall thickness of the cylindrical portion, The method for manufacturing a hollow engine valve according to claim 1, wherein the method is water cooling. 前記熱処理工程は、前記中間部品を、容器内で攪拌される冷却水中又は容器に対して循環される冷却水中に投入して水冷する請求項２に記載の中空エンジンバルブの製造方法。 The method of manufacturing a hollow engine valve according to claim 2 , wherein in the heat treatment step, the intermediate component is put into cooling water stirred in a container or cooling water circulated with respect to the container to perform water cooling. 前記冷却水の水温は、１５〜３５℃である請求項３に記載の中空エンジンバルブの製造方法。 The method for manufacturing a hollow engine valve according to claim 3 , wherein the temperature of the cooling water is 15 to 35°C. 前記スピニング工程は、加工ローラを用いて前記中間部品の前記円筒状部をスピニング加工し、
前記加工ローラは、該加工ローラを挟んで該加工ローラの軸方向に沿って配置される前後の軸受を介して支持部材に回転自在に支持されている請求項１乃至４のいずれか一項に記載の中空エンジンバルブの製造方法。 The spinning step includes spinning the cylindrical portion of the intermediate component using a processing roller,
5. The processing roller is rotatably supported by a support member via front and rear bearings arranged along the axial direction of the processing roller with the processing roller interposed therebetween. A method for manufacturing the hollow engine valve described.
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