JPH05337603A - Mold for cast iron-made piston - Google Patents

Abstract

PURPOSE:To improve true dimensional accuracy of a cast iron-made piston having thin thickness part by arranging a gate to the position corresponding to below a pin boss part of the product, in a mold flowing molten metal into a mold cavity for casting the product through the gate arranged at the intermediate part in a runner. CONSTITUTION:The runner 3 to the halfway of a sand mold core 6 assembled in the inner part of a vessel with bottomed metal mold 2 having the opening part 1 at the top part is arranged, and the molten metal flows into the mold cavity 5 through the gate 4 arranged in the intermediate part of the runner 3. As the gate 4 is arranged to the position corresponding to below the pin boss part 7 of the product, the molten metal starting the pouring is once stored in the bottom part of the runner and thereafter, the molten metal flows into the mold cavity for casting the product having the thin thickness part. By this method, the molten metal starting the pouring has little spattering developed by rebounding and further, the molten metal having little temp. drop is supplied into the part having the thin thickness at the upper part of the product, and the casting defect of cold shut, etc., is difficult to develop.

Description

【発明の詳細な説明】 （産業上の利用分野）本発明は内燃機関に用いる肉薄の
例えば球状黒鉛鋳鉄のような鋳鉄製ピストンを鋳造する
ための鋳型に関する。Description: TECHNICAL FIELD The present invention relates to a mold for casting a thin-walled cast iron piston such as spheroidal graphite cast iron used in an internal combustion engine.

（従来の技術）古くは内撚機関のピストンは鋳鉄製であ
った。しかしながら、鋳鉄製のピストンは重量が重く、
慣性モーメントが大きくエンジンの効率を低下させると
ともに、その内燃機関を搭載した車両の重量を増加さ
せ、車両の燃費を増加させる。このため、最近の自動車
用エンジンには軽合金製のピストンが採用されている。(Prior Art) In the old days, the piston of an internal twist engine was made of cast iron. However, the cast iron piston is heavy,
The inertia moment is large and the efficiency of the engine is reduced, and the weight of the vehicle equipped with the internal combustion engine is increased to increase the fuel consumption of the vehicle. For this reason, light alloy pistons have been adopted in recent automobile engines.

（発明が解決しようとする問題点）ところが、軽合金製
のピストンは強度が低いため、高出力エンジンへの対応
がしにくい他、公害対策のために燃焼温度を高めるに
は、耐熱製が十分でない。また、一般にはシリンダライ
ナが鉄製であるため、ピストンが軽合金製であると、熱
膨張率が異なり、その結果ピストンスラップに起因する
騒音が大きくなっていた。さらに、軽合金製ピストンは
鋳鉄製のピストンに較べ耐摩耗性が低いという欠点があ
る。また、鋳鉄製のピストンは前記のように重量増加と
撚費の増加の問題の他、製作工数が多いという問題点が
ある。そして、ピストンを砂型鋳造で製造すると、寸法
精度が低く、そのため、肉簿のものが鋳造し難いなどの
問題点がある。(Problems to be solved by the invention) However, since the piston made of light alloy is low in strength, it is difficult to cope with a high-power engine, and a heat-resistant product is sufficient to increase the combustion temperature for pollution control. Not. Further, since the cylinder liner is generally made of iron, if the piston is made of a light alloy, the coefficient of thermal expansion is different, and as a result, the noise caused by the piston slap is increased. Further, the light alloy piston has a drawback that it has lower wear resistance than the cast iron piston. Further, the cast iron piston has a problem that the number of manufacturing steps is large in addition to the problems of weight increase and twisting cost increase as described above. When the piston is manufactured by sand mold casting, the dimensional accuracy is low, which makes it difficult to cast a meat book.

（問題点を解決するための手段）本発明の鋳鉄製ピスト
ンの鋳型は、上記のような問題点を解決するためになさ
れたもので、上部に開口部を有する有底容器状金型の内
部に組込まれた砂型中子に途中までの湯道が通じてお
り、湯道の中間部に設けられた堰を通じて溶湯が製品が
鋳造される鋳型空間へ流入する形状となっている鋳鉄製
ピストンの鋳型において、その堰が製品のピンボス部の
下にあたる位置に設けられていることを必須の構成とす
るものである。(Means for Solving Problems) The mold of the cast iron piston of the present invention is made in order to solve the above problems, and the inside of a bottomed container-shaped mold having an opening at the upper part. A sand iron core built into the runner runs up to the middle, and a cast iron piston with a shape that allows molten metal to flow into the mold space where the product is cast through a weir provided in the middle of the runner In the mold, it is essential that the weir is provided at a position below the pin boss of the product.

（作用と実施例）本発明の鋳鉄製ピストンの鋳型は、第
１図に示すように、上部に開口部（１）を有する有底容
器状金型（２）の内部に組込まれた砂型中子（６）に途
中までの湯道（３）が通じており、湯道（３）の中間部
に設けられた堰（４）を通じて溶湯が製品が鋳造される
鋳型空間（５）へ流入する形状となっている鋳鉄製ピス
トンの鋳型において、その堰（４）が製品のピンボス部
（７）の下にあたる位置に設けられているから、注ぎ始
めの溶湯は一且湯道の底部に貯留されてから、製品が肉
薄に鋳造される鋳造空間へ溶湯が流入する。このため注
ぎ始めの溶湯が跳ね返って生ずるトバッチリ、いわゆる
境玉を生ずることが少なく、さらに製品の上部肉薄の部
分に温度低下の少ない溶湯が供給され、湯境などの鋳造
欠陥が生じにくいことになる。しかも、ピストンの摺動
面側となる部分が金型により鋳造されるので、鋳肌が奇
麓で仕上加工が少なくて済み、また、金型により急冷さ
れるのでこの摺動面側には微細な黒鉛粒子が析出する。
しかも、中子には砂型中子が組込まれているので、ガス
はこの砂型中子から十分に抜けてガスによる欠陥を生じ
ないという作用がある。さらに、鋳型の開口部が上に向
いており、中子が砂型であるから、一層このガス抜き作
用を発揮できる。(Operations and Examples) As shown in FIG. 1, the cast iron piston mold of the present invention is a sand mold assembled inside a bottomed container-shaped mold (2) having an opening (1) at the top. The child (6) is connected to the runway (3) up to the middle, and the molten metal flows into the mold space (5) where the product is cast through the weir (4) provided in the middle part of the runway (3). In the cast iron piston mold having the shape, since the weir (4) is provided at the position below the pin boss (7) of the product, the molten metal at the beginning of pouring is once stored at the bottom of the runner. Then, the molten metal flows into the casting space where the product is thinly cast. For this reason, the molten metal at the beginning of pouring is less likely to be bounced off, that is, a so-called boundary ball, and the molten metal with less temperature drop is supplied to the thin part of the upper part of the product, and casting defects such as the boundary of the molten metal are less likely to occur. . Moreover, since the part on the sliding surface side of the piston is cast by the die, the casting surface is odd and the finishing process is small, and since it is rapidly cooled by the die, the sliding surface side is fine. Graphite particles are deposited.
Moreover, since the sand core is incorporated in the core, the gas has a function of sufficiently escaping from the sand core and causing no defect due to the gas. Further, since the opening of the mold is directed upward and the core is a sand mold, the degassing action can be further exerted.

（発明の効果）本発明の鋳鉄製ピストンの鋳型を用いて
鋳鉄でピストンを鋳造すると、従来は鋳鉄では鋳造でき
なかったような肉薄で軽量な製品を鋳造することがで
き、金型をピストンの摺動面側の鋳型とすることによ
り、寸法精度を高くすることができ、かつ、肉薄の鋳鉄
製ピストンをガス欠陥なく製作することができるという
効果があるものである。このように本発明は産業の発達
に寄与するところ極めて大なるものがある。(Effect of the invention) When a piston is cast with cast iron using the cast iron piston mold of the present invention, it is possible to cast a thin and lightweight product that cannot be cast with cast iron in the past, and the die is used for the piston. By using the mold on the sliding surface side, it is possible to increase the dimensional accuracy and to manufacture a thin cast iron piston without gas defects. As described above, the present invention has an extremely great contribution to the development of industry.

【図面の簡単な説明】[Brief description of drawings]

第１図は本発明の鋳鉄製ピストンの鋳型の一部切欠縦断
面図である。 １．．．．開口部，２．．．．有底容器状金型，
３．．．．湯道，４．．．．堰，５．．．．鋳型空間，
６．．．．砂型中子，７．．．．ピンボス部．FIG. 1 is a partially cutaway vertical sectional view of a mold of a cast iron piston of the present invention. 1. ． ． ． Opening, 2. ． ． ． Bottomed container mold,
3. ． ． ． Runner, 4. ． ． ． Weir, 5. ． ． ． Mold space,
6. ． ． ． Sand core, 7. ． ． ． Pin boss part.

Claims (1)

【特許請求の範囲】[Claims] 上部に開口部を有する有底容器状金型の内部に組込まれ
た砂型中子に途中までの湯道が通じており、湯道の中間
部に設けられた堰を通じて溶湯が製品が鋳造される鋳型
空間へ流入する形状となっている鋳鉄製ピストンの鋳型
において、その堰が製品のピンボス部の下にあたる位置
に設けられていることを特徴とする鋳鉄製ピストンの鋳
型。A sand runner that is built into a bottomed container-like die that has an opening at the top has a runway up to the middle, and the molten metal is cast through a weir provided in the middle of the runner. A cast iron piston mold, wherein a weir is provided at a position below a pin boss portion of a product in a cast iron piston mold which is shaped to flow into a mold space.