EP0870919B1 - Brennkraftmaschinenkolben und Verfahren zu seiner Herstellung - Google Patents

Brennkraftmaschinenkolben und Verfahren zu seiner Herstellung Download PDF

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Publication number
EP0870919B1
EP0870919B1 EP19980106754 EP98106754A EP0870919B1 EP 0870919 B1 EP0870919 B1 EP 0870919B1 EP 19980106754 EP19980106754 EP 19980106754 EP 98106754 A EP98106754 A EP 98106754A EP 0870919 B1 EP0870919 B1 EP 0870919B1
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EP
European Patent Office
Prior art keywords
piston
main body
weight
piston main
aluminum alloy
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP19980106754
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English (en)
French (fr)
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EP0870919A1 (de
Inventor
Toshikatsu Koike
Kazuo Miyazawa
Hirotaka Kurita
Hiroshi Yamagata
Seiji Inoue
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Yamaha Motor Co Ltd
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Yamaha Motor Co Ltd
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Publication date
Priority claimed from JP9108170A external-priority patent/JPH10288085A/ja
Priority claimed from JP10817397A external-priority patent/JP3705676B2/ja
Priority claimed from JP10817297A external-priority patent/JPH10288082A/ja
Application filed by Yamaha Motor Co Ltd filed Critical Yamaha Motor Co Ltd
Publication of EP0870919A1 publication Critical patent/EP0870919A1/de
Application granted granted Critical
Publication of EP0870919B1 publication Critical patent/EP0870919B1/de
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/0015—Multi-part pistons
    • F02F3/003—Multi-part pistons the parts being connected by casting, brazing, welding or clamping
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F3/00—Pistons 
    • F02F3/0015—Multi-part pistons
    • F02F3/003—Multi-part pistons the parts being connected by casting, brazing, welding or clamping
    • F02F2003/0061—Multi-part pistons the parts being connected by casting, brazing, welding or clamping by welding
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02F—CYLINDERS, PISTONS OR CASINGS, FOR COMBUSTION ENGINES; ARRANGEMENTS OF SEALINGS IN COMBUSTION ENGINES
    • F02F2200/00—Manufacturing
    • F02F2200/04—Forging of engine parts
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2201/00—Metals
    • F05C2201/02—Light metals
    • F05C2201/021—Aluminium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05C—INDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2251/00—Material properties
    • F05C2251/04—Thermal properties
    • F05C2251/042—Expansivity

Definitions

  • This invention relates to a piston for an internal combustion engine according to the preamble of independent claim 1 and to a method of manufacturing a piston for an internal combustion engine according to the preamble of independent claim 9.
  • a piston for use in a reciprocating engine for internal combustion engine such as a 2 cycle or 4 cycle gasoline engine or diesel engine
  • a material for the piston is required to be light in, to permit the formation into a thin wall, to be low in permanent set at a high temperature when molded into a thin wall, to be high in strength and to be high in abrasion resistance.
  • an aluminum alloy containing light weight aluminum (Al) as a substrate, silicon (Si) for increasing abrasion resistance and resistance to baking and copper (Cu) and magnesium (Mg) for increasing strengths has been hitherto used.
  • Al light weight aluminum
  • Si silicon
  • Cu copper
  • Mg magnesium
  • Such an aluminum alloy is generally cast into a primary molded article of a piston main body.
  • the reaction force from a conrod during the operation of the engine acts on a pin bore portion of the piston main body from a piston pin, so that a periphery of the pin bore portion which provides a sliding contacting surface of the piston pin is deteriorated (plastic deformation).
  • the pin bore portion has been conventionally reinforced by casting a high strength member in the pin boss section of the piston main body.
  • a head section thereof which is exposed in a combustion chamber is required to have a very high heat resistance
  • a skirt section thereof which is adapted for slidably contacting with an inside wall of a cylinder is required to have a very high abrasion resistance.
  • the material cost should be saved and the weight should be reduced.
  • various proposals have been hitherto made to form a composite piston main body having different portions made of different materials, rather than to uniformly improve the piston as a whole using the same material. (Refer, for example, JP-A-Sho-63-126661, JP-A-Hei-1-180927 and JP-A-Hei-5-320788)
  • a piston of an internal combustion engine and such a method of manufacturing a piston as above described are known from US-A-4 364 159, wherein two different aluminium alloys are used for forming said piston by forging.
  • an objective of the present invention to provide an improved piston as indicated above having an improved strength and abrasion resistance as well as an excellent bonding strength between the different materials.
  • the pin bore portion may be reinforced by casting a high strength member in the pin boss section of the piston main body, it is necessary to enlarge the pin boss section. This is not advantageous in attempting to reduce the weight of the piston main body by making the pin boss section compact. Additionally, there is a problem that the bonding strength between the piston base material and the high strength member because of casting is adopted.
  • a head section and a ring groove portion(or only the ring groove portion) are made of a high strength material because of limitations in manufacturing such as friction welding and weld padding, while the pin boss section is retained as the piston base material.
  • the pin bore portion serving as a sliding contacting surface of the piston pin which is subjected to a high temperature because of the flow of heat from a head section, is not improved in its strength and abrasion resistance at a high temperature.
  • an explosion pressure P mainly acts on an upper surface of a head section of the piston main body at the time of explosion combustion.
  • a reaction force F from the conrod acts on the pin hole portion, so that a reaction force from the cylinder acts on the outer peripheral surface of a right half of the piston main body as a distribution load f.
  • a driving force F' from the conrod side mainly acts on the pin hole portion from the lower right side.
  • a force of inertia Ma (a product of the mass M of the piston main body 1 and an acceleration a) acts on the center of gravity of the piston main body, so that a reaction force from the cylinder acts on the outer peripheral surface of a left half of the piston main body as a distribution load f'.
  • the top land of the piston main body is enlarged (elongated in the direction of the sliding movement of the piston) for the purpose of improving the strength for withstanding such a force of pressing the outer peripheral surface of the piston main body to the cylinder wall, the amount of the exhaust gas remaining in the gap between the top land and the cylinder wall is increased, so that the exhaust gas from the engine has an increased amount of HC, etc.
  • the material of the piston main body is partially changed to a material having high strength and abrasion resistance.
  • a material has generally a high material unit cost for reasons of special constituting elements.
  • the alloy has a large specific gravity because of a large content of large specific gravity elements. Thus, it is necessary to reduce the amount of such a material per one piston in order to save the material costs and to reduce the weight of the piston.
  • one of said materials having a higher strength extends in an outer periphery of said piston main body from an upper end of a head section to at least a skirt section below a ring groove portion and in that said piston main body is prepared by forging such that the length of said material having a higher strength from said upper end of said head section is greater in an intermediate portion between a pair of pin bosses than in a vicinity of each of said pair of pin bosses.
  • said skirt section has a lower end provided with cut away portions so that the entire region of the outer peripheral surface of said piston main body is made of said material having a higher strength.
  • At least an outer peripheral portion of said upper end of said head section is made of said material having a higher strength.
  • said material having a higher strength is an aluminum alloy which is obtained by solidifying a rapidly solidified powder, which contains silicon (Si) in an amount of 10-22 % by weight and which has initial crystal silicon with an average particle diameter of not greater than 10 ⁇ m.
  • said aluminum alloy obtained by solidifying the rapidly solidified powder contains non-metallic component particles, harder than silicon (Si) and having an average particle diameter of not greater than 10 ⁇ m, in an amount of 1-10 % by weight.
  • said material having a higher strength is an aluminum alloy obtained by solidifying the rapidly solidified powder and containing non-metallic component particles, harder than silicon (Si) and having an average particle diameter of not greater than 10 ⁇ m, in an amount of 1-10 % by weight.
  • said material having a higher strength is an aluminum alloy which is obtained by solidifying the rapidly solidified powder, which contains iron (Fe) in an amount of 1-10 % by weight and in which the average particle diameter of a compound of the iron is not greater than 10 ⁇ m.
  • this objective is solved by a method of manufacturing a piston for an internal combustion engine as indicated above according to independent claim 9.
  • a rapidly solidified powder of an aluminum alloy provided around said extruded continuous casting material is coextruded, with heating and under a pressure, together with said continuous casting material through a second die having a greater diameter than said first die to obtain a columnar body composed of a core material made of said material of said continuous casting material and an outer peripheral material integrally bonded to said core and made of the material of said rapidly solidified powder, in that said columnar body is cut into a predetermined size to obtain a raw material for forging, and in that said raw material for forging is subjected to a primary molding step and to a succeeding processing, thereby obtaining said piston main body as a finished article.
  • said rapidly solidified powder of an aluminum alloy contains silicon (Si) in an amount of 10-22 % by weight and in that the average particle diameter of initial crystal silicon is not greater than 10 ⁇ m.
  • said rapidly solidified powder of an aluminum alloy contains a non-metallic component particles, harder than silicon (Si) and having an average particle diameter of not greater than 10 ⁇ m, in an amount of 1-10 % by weight.
  • said component particles harder than silicon (Si) are at least one of those selected from silicon carbide (SiC), aluminum oxide (Al 2 O 3 ) and aluminum nitride (AlN).
  • said rapidly solidified powder of an aluminum alloy contains iron (Fe) in an amount of 1-10 % by weight and in that the average particle diameter of a compound of the iron is not greater than 10 ⁇ m.
  • Fig. 1 shows a piston main body of one embodiment of the piston of an internal combustion engine according to the present invention
  • (A) is a side view as seen in the axial direction of a pin bore portion
  • (B) shows an upper surface of a head section as seen from above
  • (C) shows a vertical cross-section taken along the line C-C in Fig. (B).
  • the piston main body 1 is obtained by integrally molding by forging a thick cylindrical material into a primary molded article having a head section 2 having an upper surface to be exposed in a combustion chamber and a skirt section 3 to be slidably contacted with an inside surface of a cylinder such that the thickness of the wall is large in a side provided with a pin boss 4 and gradually decreases downward from the pin boss 4 in a side having no pin boss 4, the primary molded article being mechanically processed to chip unnecessary portions and to form a piston ring groove 5 and a pin bore portion 6, followed by, if necessary, a surface treatment such as plating, thereby finishing into a final product.
  • the whole piston main body 1 is made of two kinds of materials 1A and 1B having different strengths and integrally bonded by forging in their boundaries.
  • the high strength material 1A distributes to occupy from an upper surface of the head section 2 to a ring groove portion 5, while the material 1 B with a lower strength than the material 1A distributes to occupy from a back surface of the head section 2 to the skirt section 3.
  • the high strength material 1A extends to an upper part of the pin boss 4 located below the ring groove portion 5, so that a part of an upper side of the pin bore portion 6 formed in the pin boss 4 is made of the high strength material 1A.
  • the piston main body 1 of the present embodiment is produced by, as shown in Figs. 4(A) and 4(B), primary molding by forging of a composite piston raw material 10 obtained, as shown in Fig. 2, by simply superimposing two kinds of different materials 1A and 1B or by directly pressure bonding materials 1A and 1B after destroying oxidized surfaces at their boundaries by expanding small outer diameter materials by primary forging.
  • the high strength material 1A and the lower strength material 1B are extended by forging at their bonding surfaces, so that the area of the direct contact between them except the oxidized surfaces is increased, providing more tightly integrated state than that before forging.
  • the forging is performed with a lower mold 22 previously heated while controlling the temperature between 250-450°C and an upper mold (punch) 21 similarly heated while controlling the temperature between 250-450°C.
  • a primary molded article of the piston main body can be molded with a good dimensional accuracy by sufficient utilization of the ductility of the aluminum alloy.
  • the material having a high strength 1A for forming the above-described piston main body there may be used, for example, an aluminum alloy obtained by solidification of rapidly solidified powder and containing aluminum (Al) as a base material and, additionally, 10-22 % by weight of silicon (Si), 1-10 % by weight of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-5 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni), 1 % by weight or less of chromium (Cr), 2 % by weight or less of zirconium (Zr) and 1 % by weight or less of molybdenum (Mo).
  • Al aluminum
  • Si silicon
  • Fe iron
  • Cu 0.5-5 % by weight of copper
  • Mg magnesium
  • Mn manganese
  • Ni nickel
  • Cr chromium
  • Zr zirconium
  • Mo molybdenum
  • Such material an aluminum alloy obtained by solidification of rapidly solidified powder and containing 17 % by weight of silicon (Si), 5 % by weight of iron (Fe), 1 % by weight of copper (Cu), 0.5 % by weight of magnesium (Mg), 0.01 % by weight of manganese (Mn), 0.01 % by weight of nickel (Ni), 0.01 % by weight of chromium (Cr), 1 % by weight of zirconium (Zr) and 0.01 % by weight of molybdenum (Mo).
  • Si silicon
  • Fe iron
  • Cu copper
  • Mg magnesium
  • Mn manganese
  • Ni nickel
  • Cr chromium
  • Zr zirconium
  • Mo molybdenum
  • an aluminum alloy obtained by solidification of rapidly solidified powder and containing aluminum (Al) as a base material and 10-22 % by weight of silicon (Si), 1-10 % by weight of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-5 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni), 1 % by weight or less of chromium (Cr), 2 % by weight or less of zirconium (Zr), 1 % by weight or less of molybdenum (Mo) and, additionally, 1-10 % by weight of silicon carbide (SiC) which is used for improving the abrasion resistance and which is a component harder than silicon (Si).
  • SiC silicon carbide
  • an aluminum alloy obtained by solidification of rapidly solidified powder and containing 17 % by weight of silicon (Si), 5 % by weight of iron (Fe), 1 % by weight of copper (Cu), 0.5 % by weight of magnesium (Mg), 0.01 % by weight of manganese (Mn), 0.01 % by weight of nickel (Ni), 0.01 % by weight of chromium (Cr), 1 % by weight of zirconium (Zr), 0.01 % by weight of molybdenum (Mo) and 5 % by weight of silicon carbide (SiC).
  • silicon (Si) and silicon carbide (SiC) are added to improve the abrasion resistance and resistance to baking by the existence of hard particles in the metal texture.
  • Iron (Fe) is added to obtain a high strength at 200°C or more by dispersing and strengthening the metal texture.
  • Copper (Cu) and magnesium (Mg) are added to improve the strength at 200°C or less. The amounts of these components outside the above-described ranges fail to obtain desired abrasion resistance, resistance to baking and required strengths at high temperatures.
  • an aluminum alloy conventionally used for casting as a melt production-type (continuous casting material), namely an aluminum alloy of a melt production-type containing aluminum (Al) as a base material and additionally 10-22 % by weight of silicon (Si), 1 % by weight or less of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-2 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni) and 1 % by weight or less of chromium (Cr).
  • Such a material is an aluminum alloy of the melt production-type containing 19 % by weight of silicon (Si), 0.2 % by weight of iron (Fe), 4 % by weight of copper (Cu), 1 % by weight of magnesium (Mg), 0.1 % by weight of manganese (Mn), 0.1 % by weight of nickel (Ni) and 0.1 % by weight of chromium (Cr).
  • an ingot of an aluminum alloy is melted at about 700°C or more and the melt is sprayed like a fog to rapidly cool and solidify same at a cooling rate of at least 100°C/sec, thereby obtaining rapidly solidified powder (powder metal) of the aluminum alloy having an average particle diameter of about 100 ⁇ m.
  • the rapidly solidified powder of the aluminum alloy is, as shown in Fig. 3, heated to 400-500°C and extruded into a round rod and solidified. The rod is cut into a predetermined size, thereby obtaining a disc-like material 1A, as shown in Fig. 2, of a composite piston material 10.
  • each of the constituents such as silicon (Si) and iron (Fe) is dispersed in a finely divided state of an average particle diameter of 10 ⁇ m or less.
  • silicon carbide (SiC) since the silicon carbide (SiC) is dispersed uniformly in the texture of the aluminum alloy in a finely divided state, an improved abrasion resistance can be obtained.
  • iron (Fe) since a rapidly solidified powder aluminum alloy containing iron (Fe) in a finely divided state is molded by forging, the formation of coarse iron compounds is prevented so that a uniform metal texture free of coarse iron compounds which would cause stress concentration is obtainable. Therefore, the iron component can be added in a larger amount in comparison with the case in which a piston main body is primary molded by a conventional casting process, enabling the preparation of an alloy having a high strength.
  • the other constituting components are also contained in the aluminum allow powder as fine powder and since the aluminum alloy powder is formed in to a dense crystal texture through solidification and forging, these components do not cause a decrease in strength due to concentration of the stress in the crystal grain boundaries, thereby to improve the fatigue strength.
  • Fig. 13 shows the results of fretting abrasion test (A test sample is used as a rotor). A rider of a predetermined material is repeatedly pressed against the rotor which is maintained in a swung state. The area of the abrasion marks in the contact surfaces represents the degree of abrasion) performed at a test temperature of 250°C to compare the abrasion resistance of each example of the material 1A having a high strength (Example A1 containing SiC, and Example A-2 containing no SiC) with an example (Example B) of the material having a lower strength 1B, from which it is appreciated that both materials 1A (Example A1 and Example A2) give higher abrasion resistance at a high temperature as compared with the material 1B (Example B).
  • Fig. 14 shows the results of fatigue test (A sinuous load is applied to a test sample).
  • the fatigue limit represents the number of repetition (one number represents one period of the sinuous curve) until the test sample has been broken) performed at test temperatures of 25°C, 150°C and 250°C to compare the fatigue strength of each example of the material having a high strength 1A (Example A1 containing SiC, and Example A-2 containing no SiC) with an example (Example B) of the material having a lower strength 1B, from which it is appreciated that both materials 1A (Example A1 and Example A2) give higher fatigue strength as compared with the material 1B (Example B) at any test temperature.
  • Described above is one embodiment (first embodiment) of the piston for an internal combustion engine according to the present invention.
  • Figs. 5 and 9 illustrate other embodiments (second and third embodiments) of the piston for an internal combustion engine according to the present invention.
  • the same materials 1A and 1B as those shown as examples in the above embodiment (first embodiment) are used. But the state of the distribution of the materials 1A and 1B of the piston main body is different.
  • the material having a high strength 1A distributes to occupy an area from the peripheral portion of the head section 2 to the ring groove portion 5 of the piston main body 1, whereas the material having a lower strength 1B distributes to occupy an area from the central portion of the head section 2 to the skirt section 3.
  • the material having a high strength 1A extends up to an upper portion of the pin boss 4 located below the ring groove portion 5, so that a part of the upper side of the pin bore 6 formed in the pin boss 4 is made of the material having a high strength A.
  • the piston main body 1 according to the second embodiment is obtained by hot forging of a composite piston material 10 composed of the two kinds of the materials 1A and 1B having different strengths as shown in Fig. 6 between a lower mold 22 preheated under a controlled state to 250-450°C and an upper mold (punch) 21 preheated under a controlled state to 250-450°C, as shown in Fig. 8, thereby to obtain a primary molded article.
  • This is subjected to a machining treatment by mechanical processing such as for the chipping of unnecessary portions and for the formation of a piston ring groove 5 and a pin bore portion 6 and, if desired, to a surface treatment such as plating, thereby to form the final product.
  • a composite piston material 10 as shown in Fig. 6 may be produced by heating and extruding a rapidly solidified powder of an aluminum alloy (containing powder of respective constituting components) into a hollow bar as shown in Fig. 7. After solidification, the bar is cut into a predetermined size to obtain a ring material 1A. This is then fitted to the material 1 B.
  • the fitting is suitably interference fitting using an interference.
  • transition fitting or running fitting may be adopted. In this case, the fitting engagement surfaces are extended by the generation of a surface pressure in the direction normal to the fitting engagement surfaces by forging, so that the oxidized film on the surfaces are broken to permit the direct bonding of the material 1A and 1B.
  • the material having a high strength 1A distributes to occupy an area from the peripheral portion of the head section 2 to the skirt section 3 located outside the ring groove portion 5 and the pin boss 4 of the piston main body 1, whereas the material having a lower strength 1 B distributes on the axis side of the piston main body 1 to occupy an area from the central portion of the head section 2 to the inside of the pin boss 4.
  • the material having a high strength 1A extends the entire periphery of the outside the pin bore portion 6 formed in the pin boss 4.
  • the piston main body 1 according to the third embodiment is obtained by hot forging of a composite piston material 10 composed of the two kinds of the materials 1A and 1B having different strengths as shown in Fig. 10 between a lower mold 22 preheated under a controlled state to 250-450°C and an upper mold (punch) 21 preheated under a controlled state to 250-450°C, as shown in Fig. 12, thereby to obtain a primary molded article.
  • This is subjected to a machining treatment by mechanical processing such as for the chipping of unnecessary portions and for the formation of a piston ring groove 5 and a pin bore portion 6 and, if desired, to a surface treatment such as plating, thereby to form the final product.
  • a composite piston material 10 as shown in Fig. 10 may be produced by extruding an aluminum alloy of a melt production material with heating into a round rod as shown in Fig. 11 and, at the same time, heating and extruding a rapidly solidified powder of an aluminum alloy (containing powder of respective constituting components) so as to cover the periphery of the round rod of an aluminum alloy of a melt production material.
  • the two extruded portions are integrally solidified.
  • the resulting composite column having central and peripheral portions made of different materials is cut into a predetermined size to obtain the composite material.
  • a pin bore portion 6 which serves as a sliding contacting surface of a piston pin is formed of a material having a high strength 1A, the pin bore portion has improved strength and abrasion resistance without resorting to casting of a specific reinforcing member into the pin boss 4.
  • the material 1A used in each of the above-described embodiments has a higher unit cost as compared with the material 1B, because of the mixing with silicon carbide (SiC) and iron (Fe), because of a high content of silicon (Si), because of necessity of mixing a variety of ingredients while controlling the amounts thereof, because of the use of special constituting components and because necessity of manufacturing step for producing rapidly solidified powder. Therefore, it is necessary to save the amount of the material used per one piston. Additionally, since the material 1A contains greater amount of elements having a high specific gravity and, hence, the resulting alloy has a greater specific gravity in comparison with the material 1B, it is necessary to save the amount of the material used per one piston.
  • each of the above-described embodiments can reduce the material costs and the weight of the piston main body 1 by using the material 1A only in a portion surrounding the pin bore portion 6.
  • the material 1A is used in the head section 2 and a peripheral portion of the head section 2 of the pin bore portion 6 on which the reaction force of the conrod at the time of explosion combustion and the operating force from the conrod during the up stroke of the piston, so that the piston main body 1 has a reduced weight while improving the rigidity and strengths around the ring groove portion 5 and the pin bore portion 6.
  • the top land portion extending from a vicinity of the ring groove portion 5 to the head section 2 is made of the material having a high strength 1A, the top land portion can withstand the force caused when the piston main body is swung about the piston pin by the reaction force of the conrod and piston slap at the time of the explosion combustion and when the top land is thereby strongly pressed against the cylinder wall.
  • top land Because of the top land has a high strength, it is possible to make the top land portion small, so that the amount of an exhaust gas remaining in a gap between the top land and the cylinder wall can be reduced, resulting in the reduction of HC.
  • the piston main body 1 has a more reduced weight because only the peripheral portion of the head section is made of the material 1A in view of the fact that the inside stress and the inside distortion generated in the head section 2 by the explosion combustion pressure acted on the upper surface of the head section 2 is larger in the outer peripheral portion than in the central portion of the head section 2.
  • an aluminum alloy of an ingot material having a high thermal conductivity is used as a material having a low strength 1B which is distributed to occupy an area from the central portion of the head section 2 to the skirt section 3, the heat of the head section 2 can be transmitted through the material 1B from the skirt section 3 to the cylinder wall with high efficiency, so that the temperature of the head section is lowered to release the thermal strength of the head section.
  • the head section 2 thin so that the piston main body 1 can be reduced in weight.
  • the piston main body 1 is primary molding obtained by forging a composite piston material 10 obtained by integrally bonding or simply superimposing the two kinds of materials 1A and 1B having different strengths, the bonding interface of the material 1A and material 1B of the piston main body 1 is extended by forging so that the resulting article is in a more tightly integrated state as compared with that before forging.
  • the strengths and abrasion resistance of a pin bore portion which provides a sliding contacting surface for a piston pin can be improved without preventing the reduction of the weight of the piston main body which would be caused by enlarging a pin boss.
  • Fig. 15 shows a piston main body of one embodiment of the piston of an internal combustion engine according to the present invention
  • (A) is a side view as seen in the axial direction of a pin bore portion
  • (B) shows an upper surface of a head section as seen from above
  • (C) shows a vertical cross-section taken along the line C-C in Fig. (B).
  • the piston main body 1 is obtained by integrally molding by forging a thick cylindrical material into a primary molded article having a head section 2 having an upper surface to be exposed in a combustion chamber and a skirt section 3 to be slidably contacted with an inside surface of a cylinder such that the thickness of the wall is large in a side provided with a pin boss 4 and gradually decreases downward from the pin boss 4 in a side having no pin boss 4, the primary molded article being mechanically processed to chip unnecessary portions and to form a piston ring groove 5 and a pin bore portion 6, followed by, if necessary, a surface treatment such as plating, thereby finishing into a final product.
  • the piston main body 1 is made of two kinds of materials 1A and 1B having different strengths and integrally bonded by forging in their boundaries.
  • the high strength material 1A extends from an upper surface of the head section 2 to a skirt section 3 below a ring groove portion 5, such that the length from the upper portion of the head section 2 is longer in an intermediate portion between two pin hole portions (pin bosses 4) than that in a vicinity of the pin bore portions (pin bosses 4).
  • the high strength material 1A which is exposed on the outer peripheral surface of the piston main body 1 distributes, as shown in Fig. 15(C), in a periphery (outer peripheral surface side) of the piston main body, while the material with a lower strength 1B than the material 1A distributes to occupy from a center portion (axis side) to a lower end portion of the skirt section 3.
  • the piston main body 1 of the present embodiment may be produced by primary molding by forging, as shown in Fig. 16, from a composite piston material 10, as shown in Fig. 17, composed of two kinds of materials 1A and 1 B fitted to each other and having different strengths.
  • the material having a high strength 1A and the material having a low strength 1B are bonded to each other such that the fitting engagement surfaces by forging are extended while being subjected to a tangential load and tightly integrated into a unitary structure.
  • the fitting of the material 1A into the material 1B is suitably by interference fitting using an interference.
  • transition fitting or running fitting may be adopted.
  • the fitting engagement surfaces are extended by the generation of a surface pressure in the direction normal to the fitting engagement surfaces by forging, so that the oxidized film on the surfaces are broken to permit the direct bonding of the materials 1A and 1B.
  • the forging of the composite piston material 10 into a primary molding of the piston as shown in Fig. 16 is carried out in a lower mold 22 composed of side molds 22a and a bottom mold 22b and preheated under a controlled state to 250-450°C and an upper mold (punch) 21 preheated under a controlled state to 250-450°C.
  • a primary molded article of the piston main body having a precise dimension can be obtained sufficiently utilizing the ductility of the aluminum alloy.
  • the material having a high strength 1A for forming the above-described piston main body there may be used, for example, an aluminum alloy obtained by solidification of rapidly solidified powder and containing aluminum (Al) as a base material and, additionally, 10-22 % by weight of silicon (Si), 1-10 % by weight of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-5 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni), 1 % by weight or less of chromium (Cr), 2 % by weight or less of zirconium (Zr) and 1 % by weight or less of molybdenum (Mo).
  • Al aluminum
  • Si silicon
  • Fe iron
  • Cu 0.5-5 % by weight of copper
  • Mg magnesium
  • Mn manganese
  • Ni nickel
  • Cr chromium
  • Zr zirconium
  • Mo molybdenum
  • Such material is an aluminum alloy obtained by solidification of rapidly solidified powder and containing 17 % by weight of silicon (Si), 5 % by weight of iron (Fe), 1 % by weight of copper (Cu), 0.5 % by weight of magnesium (Mg), 0.01 % by weight of manganese (Mn), 0.01 % by weight of nickel (Ni), 0.01 % by weight of chromium (Cr), 1 % by weight of zirconium (Zr) and 0.01 % by weight of molybdenum (Mo).
  • Si silicon
  • Fe iron
  • Cu copper
  • Mg magnesium
  • Mn manganese
  • Ni nickel
  • Cr chromium
  • Zr zirconium
  • Mo molybdenum
  • an aluminum alloy obtained by solidification of rapidly solidified powder and containing aluminum (Al) as a base material and 10-22 % by weight of silicon (Si), 1-10 % by weight of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-5 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni), 1 % by weight or less of chromium (Cr), 2 % by weight or less of zirconium (Zr), 1 % by weight or less of molybdenum (Mo) and, additionally, 1-10 % by weight of silicon carbide (SiC) which is used for improving the abrasion resistance and which is a component harder than silicon (Si).
  • SiC silicon carbide
  • an aluminum alloy obtained by solidification of rapidly solidified powder and containing 17 % by weight of silicon (Si), 5 % by weight of iron (Fe), 1 % by weight of copper (Cu), 0.5 % by weight of magnesium (Mg), 0.01 % by weight of manganese (Mn), 0.01 % by weight of nickel (Ni), 0.01 % by weight of chromium (Cr), 1 % by weight of zirconium (Zr), 0.01 % by weight of molybdenum (Mo) and 5 % by weight of silicon carbide (SiC).
  • silicon (Si) and silicon carbide (SiC) are added to improve the abrasion resistance and resistance to baking by the existence of hard particles in the metal texture.
  • Iron (Fe) is added to obtain a high strength at 200°C or more by dispersing and strengthening the metal texture.
  • Copper (Cu) and magnesium (Mg) are added to improve the strength at 200°C or less.
  • an aluminum alloy conventionally used for casting as a melt production-type (continuous casting material), namely an aluminum alloy of a melt production-type containing aluminum (Al) as a base material and additionally 10-22 % by weight of silicon (Si), 1 % by weight or less of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-2 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni) and 1 % by weight or less of chromium (Cr).
  • Such a material is an aluminum alloy of the melt production-type containing 19 % by weight of silicon (Si), 0.2 % by weight of iron (Fe), 4 % by weight of copper (Cu), 1 % by weight of magnesium (Mg), 0.1 % by weight of manganese (Mn), 0.1 % by weight of nickel (Ni) and 0.1 % by weight of chromium (Cr).
  • an ingot of an aluminum alloy is melted at about 700°C or more and the melt is sprayed like a fog to rapidly cool and solidify same at a cooling rate of at least 100°C/sec, thereby obtaining rapidly solidified powder (powder metal) of the aluminum alloy having an average particle diameter of about 100 ⁇ m.
  • the rapidly solidified powder of the aluminum alloy is, as shown in Fig. 18, heated to 400-500°C and extruded into a hollow cylinder and solidified.
  • the cylinder is cut into a predetermined size, thereby obtaining a ring-like material 1A.
  • the material 1B is then fitted in the ring material 1A to obtain a composite piston material 10 as shown in Fig. 17.
  • each of the constituents such as silicon (Si) and iron (Fe) is dispersed in a finely divided state of an average particle diameter of 10 ⁇ m or less in the powder aluminum alloy having an average particle diameter of about 100 ⁇ m.
  • silicon carbide (SiC) since the silicon carbide (SiC) is dispersed uniformly in the texture of the aluminum alloy in a finely divided state, an improved abrasion resistance can be obtained.
  • iron (Fe) since a rapidly solidified powder aluminum alloy containing iron (Fe) in a finely divided state is molded by forging, the formation of coarse iron compounds is prevented so that a uniform metal texture free of coarse iron compounds which would cause stress concentration is obtainable. Therefore, the iron component can be added in a larger amount in comparison with the case in which a piston main body is primary molded by a conventional casting process, enabling the preparation of an alloy having a high strength.
  • the other constituting components are also contained in the aluminum allow powder as fine powder and since the aluminum alloy powder is formed in to a dense crystal texture through solidification and forging, these components do not cause a decrease in strength due to concentration of the stress in the crystal grain boundaries, thereby to improve the fatigue strength.
  • Fig. 13 again shows the results of fretting abrasion test (A test sample is used as a rotor. A rider of a predetermined material is repeatedly pressed against the rotor which is maintained in a swung state. The area of the abrasion marks in the contact surfaces represents the degree of abrasion) performed at a test temperature of 250°C to compare the abrasion resistance of each example of the material 1A having a high strength (Example A1 containing SiC, and Example A-2 containing no SiC) with an example (Example B) of the material having a lower strength 1B, from which it is appreciated that both materials 1A (Example A1 and Example A2) give higher abrasion resistance at a high temperature as compared with the material 1B (Example B).
  • Fig. 14 shows the results of fatigue test (A sinuous load is applied to a test sample.
  • the fatigue limit represents the number of repetition (one number represents one period of the sinuous curve) until the test sample has been broken.) performed at test temperatures of 25°C, 150°C and 250°C to compare the fatigue strength of each example of the material having a high strength 1A (Example A1 containing SiC, and Example A-2 containing no SiC) with an example (Example B) of the material having a lower strength 1B, from which it is appreciated that both materials 1A (Example A1 and Example A2) give higher fatigue strength as compared with the material 1B (Example B) at any test temperature.
  • Fig. 19 illustrates another embodiment of the piston for an internal combustion engine according to the present invention.
  • the same materials 1A and 1B as those shown as examples in the above embodiment are used. But the state of the distribution of the materials 1A and 1B of the piston main body is different.
  • the skirt section 3 is continuously formed in an elongated state throughout the periphery of the piston main body, with a lower end side of the skirt section 3 being formed of the material 1 B having a low strength.
  • the skirt section 4 is provided with portions cut away from the lower end at positions corresponding to a pair of pin bosses 4 so that the skirt section 3 does not exist at a greater part of the portions outside the pin bosses 4.
  • the piston main body 1 according to the second embodiment is obtained by hot forging of a composite piston material 10, composed of the two kinds of the materials 1A and 1B having different strengths as shown in Fig. 21, between a lower mold 22 preheated under a controlled state to 400-500°C and an upper mold (punch) 21 preheated under a controlled state to 400-500°C, as shown in Fig. 20, thereby to obtain a primary molded article.
  • This is subjected to a machining treatment by mechanical processing such as for the chipping of unnecessary portions and for the formation of a piston ring groove 5 and a pin bore portion 6 and, if desired, to a surface treatment such as plating, thereby to form the final product.
  • a composite piston material 10 as shown in Fig. 21 may be produced by extruding an aluminum alloy of an ingot material with heating into a round rod and, at the same time, heating and extruding a rapidly solidified powder of an aluminum alloy (containing powder of respective constituting components) so as to cover the periphery of the round rod of the ingot aluminum alloy.
  • the two extruded portions are integrally solidified.
  • the resulting composite column having central and peripheral portions made of different materials is cut into a predetermined size to obtain the composite material.
  • the outer peripheral side of the piston main body 1 is formed of the material having a high strength 1A in the long area from the head section 2 to the lower portion of the skirt section 3 through the ring groove section 5 on an intermediate portion side between the both pin bosses 4 of the piston main body 1, namely on the side at which the piston main body is pressed against the cylinder wall by a reaction from a conrod at the time of explosion combustion and by an operating force, although a weak force, from the conrod during the up stroke of the piston, it is possible to ensure a sufficient strength for withstanding the pressing of the piston main body 1 to the cylinder wall.
  • the material 1A used in each of the above-described embodiments has a higher unit cost as compared with the material 1B, because of the mixing with silicon carbide (SiC) and iron (Fe), because of a high content of silicon (Si), because of necessity of mixing a variety of ingredients while controlling the amounts thereof, because of the use of special constituting components and because necessity of manufacturing step for producing rapidly solidified powder. Therefore, it is necessary to save the amount of the material used per one piston. Additionally, since the material 1A contains greater amount of elements having a high specific gravity and, hence, the resulting alloy has a greater specific gravity in comparison with the material 1B, it is necessary to save the amount of the material used per one piston.
  • each of the above-described embodiments can reduce the material costs and the weight of the piston main body 1 as compared with the case in which a portion made of the material 1A is elongated throughout the circumference of the outer peripheral surface of the piston main body by elongating a portion made of the material 1A only in an intermediate portion between the two pin bosses 4. Yet, as described above, the strength for withstanding the pressing of the piston main body to the cylinder wall can be sufficiently ensured.
  • the weight of the skirt section 3 can be more reduced by reducing the thickness thereof as compared with the case in which the skirt section is made only of the material B. Since at least a small thickness is required in the production by forging, there is a limitation in reducing the thickness of the skirt section when the skirt section is made only of the material A.
  • the reduction of the weight of and the material costs for the piston main body can be achieved while ensuring abrasion resistance, at least necessary degree of strength and rigidity.
  • the piston main body 1 is primary molding obtained by forging a composite piston material 10 obtained by integrally bonding the two kinds of materials 1A and 1B having different strengths, the bonding interface of the material 1A and material 1 B of the piston main body 1 is extended by forging so that the resulting article is in a more tightly integrated state as compared with that before forging.
  • the piston main body having an appearance and a shape as shown in Fig. 15 may be prepared by forging the composite piston material 10 as shown in Fig. 21 obtained by the step shown in Fig. 22 with the use of a forging mold as shown in Fig. 16.
  • the pin boss 4 is thick, a structure is adopted in which the material 1A does not sufficiently extend to the skirt section 3 below the pin bore portion 6.
  • the piston main body having an appearance and a shape as shown in Fig. 19 may be prepared by forging the composite piston material 10 as shown in Fig. 17 obtained by the step shown in Fig. 18 with the use of a forging mold as shown in Fig. 20.
  • the portion made of the material 1A does not extend to a lower end of the skirt section 3, it is possible that the surface of the skirt section made of the material 1A extend to the lower portion of the pin bore portion 6.
  • the two kinds of materials 1A and 1B having different strengths are not limited to those exemplified in the above embodiments.
  • the present invention can be practiced using any other suitable materials.
  • the method of producing the piston main body 1 is not limited to the specific forging method as illustrated in the above embodiments, but, rather, any other suitable method can be utilized for the manufacture thereof.
  • the strengths for withstanding the pushing of a piston main body to a cylinder wall and the abrasion resistance of a skirt section can be improved while saving material costs for the production of the piston main body and reducing the weight of the piston main body without increasing a top land of the piston main body and increasing the amount of a residual exhaust gas.
  • Fig. 24 shows a piston main body of one embodiment of the piston of an internal combustion engine according to the present invention
  • (A) is a side view as seen in the axial direction of a pin bore portion
  • (B) shows an upper surface of a head section as seen from above
  • (C) shows a vertical cross-section taken along the line C-C in Fig. (B).
  • the piston main body 1 is obtained by integrally molding by forging a thick disc-like piston forging material into a primary molded article having a head section 2 having an upper surface to be exposed in a combustion chamber and a skirt section 3 to be slidably contacted with an inside surface of a cylinder such that the thickness of the wall is large in a side provided with a pin boss 4 and gradually decreases downward from the pin boss 4 in a side having no pin boss 4, the piston forming material thus primary molded (primary molding article) being mechanically processed to chip unnecessary portions and to form a piston ring groove 5 and a pin bore portion 6, followed by, if necessary, a surface treatment such as plating, thereby finishing into a final product.
  • the piston main body 1 is made of two kinds of materials 1A and 1B having different strengths and integrally bonded by forging in their boundaries.
  • the material 1A formed of a rapidly solidified powder (powder metal) of an aluminum alloy, as a high strength material, distributes in an outer peripheral portion (side wall portion) of the head section 2 to occupy from a periphery of the head section 2 to a ring groove portion 5, an outer side of the pin boss 4 and the skirt section 3, while the material 1B formed of a continuous casting material (ingot material) of an aluminum alloy, as material with a lower strength than the material 1A, distributes in a center part (axis portion) of the piston main body 1 to occupy from a center part of the head section 2 to an inner side of the pin boss 4.
  • the rapidly solidified powder for forming one material 1A of the above-described piston main body there may be used, for example, an aluminum alloy obtained by solidification of rapidly solidified powder and containing aluminum (Al) as a base material and, additionally, 10-22 % by weight of silicon (Si), 1-10 % by weight of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-5 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni), 1 % by weight or less of chromium (Cr), 2 % by weight or less of zirconium (Zr) and 1 % by weight or less of molybdenum (Mo).
  • Al aluminum
  • Si silicon
  • Fe iron
  • Cu 0.5-5 % by weight of copper
  • Mg magnesium
  • Mn manganese
  • Ni nickel
  • Cr chromium
  • Zr zirconium
  • Mo molybdenum
  • Such a material is an aluminum alloy obtained by solidification of rapidly solidified powder and containing 17 % by weight of silicon (Si), 5 % by weight of iron (Fe), 1 % by weight of copper (Cu), 0.5 % by weight of magnesium (Mg), 0.01 % by weight of manganese (Mn), 0.01 % by weight of nickel (Ni), 0.01 % by weight of chromium (Cr), 1 % by weight of zirconium (Zr) and 0.01 % by weight of molybdenum (Mo).
  • Si silicon
  • Fe iron
  • Cu copper
  • Mg magnesium
  • Mn manganese
  • Ni nickel
  • Cr chromium
  • Zr zirconium
  • Mo molybdenum
  • SiC silicon carbide
  • an aluminum alloy obtained by solidification of rapidly solidified powder and containing 17 % by weight of silicon (Si), 5 % by weight of iron (Fe), 1 % by weight of copper (Cu), 0.5 % by weight of magnesium (Mg), 0.01 % by weight of manganese (Mn), 0.01 % by weight of nickel (Ni), 0.01 % by weight of chromium (Cr), 1 % by weight of zirconium (Zr), 0.01 % by weight of molybdenum (Mo) and 5 % by weight of silicon carbide (SiC).
  • silicon (Si) and silicon carbide (SiC) are added to improve the abrasion resistance and resistance to baking by the existence of hard particles in the metal texture.
  • Iron (Fe) is added to obtain a high strength at 200°C or more by dispersing and strengthening the metal texture.
  • Copper (Cu) and magnesium (Mg) are added to improve the strength at 200°C or less. The amounts of these components outside the above-described ranges fail to obtain desired abrasion resistance, resistance to baking and required strengths at high temperatures.
  • the continuous casting material (ingot material) for forming the other part made of the material 1B of the piston main body there may be used an aluminum alloy of continuous casting material conventionally used for casting, namely an alloy containing aluminum (Al) as a base material and additionally 10-22 % by weight of silicon (Si), 1 % by weight or less of iron (Fe), 0.5-5 % by weight of copper (Cu), 0.5-2 % by weight of magnesium (Mg), 1 % by weight or less of manganese (Mn), 1 % by weight or less of nickel (Ni) and 1 % by weight or less of chromium (Cr).
  • Al aluminum
  • Si silicon
  • Fe iron
  • Cu copper
  • Mg magnesium
  • Mn manganese
  • Ni nickel
  • Cr chromium
  • Such a material is an aluminum alloy of a continuous casting material containing 19 % by weight of silicon (Si), 0.2 % by weight of iron (Fe), 4 % by weight of copper (Cu), 1 % by weight of magnesium (Mg), 0.1 % by weight of manganese (Mn), 0.1 % by weight of nickel (Ni) and 0.1 % by weight of chromium (Cr).
  • Fig. 13 shows the results of fretting abrasion test (A test sample is used as a rotor. A rider of a predetermined material is repeatedly pressed against the rotor which is maintained in a swung state. The area of the abrasion marks in the contact surfaces represents the degree of abrasion) performed at a test temperature of 250°C to compare the abrasion resistance of each example of the material 1A of a rapidly solidified powder (Example A1 containing SiC, and Example A-2 containing no SiC) with an example (Example B) of the material 1B of a continuous casting material, from which it is appreciated that both materials 1A (Example A1 and Example A2) give higher abrasion resistance at a high temperature as compared with the material 1B (Example B).
  • Fig. 14 shows the results of fatigue test (A sinuous load is applied to a test sample.
  • the fatigue limit represents the number of repetition (one number represents one period of the sinuous curve) until the test sample has been broken.) performed at test temperatures of 25°C, 150°C and 250°C to compare the fatigue strength of each example of the material 1A of the rapidly solidified powder (Example A1 containing SiC, and Example A-2 containing no SiC) with an example (Example B) of the material 1B of the continuous casting material, from which it is appreciated that both materials 1A (Example A1 and Example A2) give higher fatigue strength as compared with the material 1B (Example B) at any test temperature.
  • a method of manufacturing a piston for an internal combustion engine of the present embodiment will be described below, in which the whole piston main body 1 is made of a composite of two kinds of materials 1A and 1B having different strengths is manufactured using, as raw materials, the above-described rapidly solidified powder of an aluminum alloy and the continuous casting material of an aluminum alloy.
  • the continuous casting material of an aluminum alloy used as a raw material for the production of the piston main body 1 is obtained by, for example, as shown in Fig. 25, (B) melting and continuously casting (A) an aluminum alloy ingot and (C) cutting into a predetermined size.
  • the rapidly solidified powder of an aluminum alloy used is produced by, for example, as shown in Fig. 26, (B) melting (A) an aluminum alloy ingot and spraying like a fog to rapidly cool at a cooling rate of at least 100°C/sec and to solidify, thereby obtaining a rapidly solidified powder (powder metal) having an average particle diameter of about 100 ⁇ m.
  • Respective constituting components in the rapidly solidified powder of an aluminum alloy are contained therein in the form of a fine powder formed either by rapidly solidifying an aluminum alloy ingot containing such components or by mixing fine powder of such components with rapidly solidified powder of an aluminum alloy.
  • a composite piston forging material 10 is produced by means of a material producing device 11 as shown in Fig. 27 using, as a raw material, the above-described rapidly solidified powder and the continuous casting material.
  • the material producing device 11 has a first accommodating chamber 12 for containing the continuous casting material 1B and a second accommodating chamber 13 for containing the rapidly solidified powder 1A in juxtaposition with the first chamber.
  • a first die 14 opens in a partition wall between the first and second accommodating chambers 12 and 13, while a second die 15 having a diameter greater than that of the first die 14 opens outward in the second accommodating chamber 13 at a position opposite the first die 14.
  • the continuous casting material 1 B accommodated in the first accommodating chamber 12 is heated at 400-500°C and pressurized and extruded through the first die 14 toward the second accommodating chamber 13 to form a columnar body.
  • the rapidly solidified material 1A accommodated in the second accommodating chamber 13 is heated at 400-500°C and pressurized and extruded through the second die 15 having a larger diameter than the first die 14.
  • a columnar body of a composite material composed of a core material made of the material 1B of the continuous casting material and an outer peripheral material made of the material 1A of the rapidly solidified powder is coextruded through the second die 15 out of the device 11.
  • the columnar body of the composite material is cut into a predetermined size to obtain a raw forging material 10 of a composite piston for the formation of a primary molded article of the piston main body by forging.
  • the oxidized film thereof is destroyed during the passage of the continuous casting material 1B through the first die 14 so that the base material of the continuous casting material 1B is exposed. Since the heated, rapidly solidified powder 1A is bonded to the exposed portion under a pressure, the bonding strength between the columnar core material 1B and the outer peripheral material 1A has a high value. Therefore, in the composite piston forging material 10, the bonding between the core material 1B and the outer peripheral material 1A is not easily destroyed during transportation or during the preparation of the succeeding forging step, thereby providing good handling property.
  • the composite piston forging material 10 is shaped to have a lower height (thickness) than the that of the piston main body 1 after forging.
  • the outer peripheral material rapidly solidified powder 1A
  • the outer peripheral material has a smaller thickness than the diameter of the core material (continuous casting material 1B).
  • the core material 1B and the outer peripheral material 1A are aligned concentrically.
  • the thickness of the outer peripheral material 1A may be partly changed or a protrusion 10a for use in determining the position thereof relative to a mold for forging may be formed, as shown in Fig. 29.
  • Such a change in the shape of the core material 1B and the outer peripheral material 1A can be easily achieved by changing the shape of the first and second dies 14 and 15 of the above-described device 11.
  • the thus produced composite piston forging material 10 is, in the present embodiment, subjected to hot forging using, as shown in Fig. 30, a lower mold 22 preheated under a controlled state to 250-450°C and an upper mold (punch) 21 preheated under a controlled state to 250-450°C, thereby to obtain a primary molded article.
  • This is subjected to a machining treatment by mechanical processing such as for the chipping of unnecessary portions and for the formation of a piston ring groove 5 and a pin bore portion 6 and, if desired, to a surface treatment such as plating, thereby to form the final product.
  • a primary molded article of the piston main body can be molded with a good dimensional accuracy by sufficient utilization of the ductility of the aluminum alloy. Further, since the bonding boundaries between the material 1A and the material 1B of the composite piston forging material are extended by forging, the area of the direct contact between the base materials of the material 1A and the material 1B is increased, so that, in the forged piston main body 1, the bonding boundaries between the material 1A and the material 1B is in a more enhanced state than that before forging.
  • the step of molding the rapidly solidified powder of an aluminum alloy by solidification can simultaneously produce a composite material piston forging material 10 composed of a core material of the continuous casting material 1B and an outer peripheral material of the rapidly solidified powder 1A without significantly increasing manufacturing steps and manufacturing time so that the cost up is prevented.
  • the bonding boundaries between the material 1A (of the rapidly solidified powder) and the material 1B (of the continuous casting material) of the thus produced composite piston forging material 10 are extended by forging, the bonding strength between the material 1A and the material 1B of the forged piston main body 1 can be.
  • the material 1A forged by solidifying the rapidly solidified powder distributes in an outer peripheral portion of the piston main body 1, the strength and the abrasion resistance of the piston main body 1 can be improved.
  • each of the constituents such as silicon (Si) and iron (Fe) is dispersed in the aluminum alloy powder having an average particle diameter of about 100 ⁇ m and is in a finely divided state of an average particle diameter of 10 ⁇ m or less.
  • iron (Fe) since a rapidly solidified powder aluminum alloy containing iron (Fe) in a finely divided state is molded by forging, the formation of coarse iron compounds is prevented so that a uniform metal texture free of coarse iron compounds which would cause stress concentration is obtainable. Therefore, the iron component can be added in a larger amount in comparison with the case in which a piston main body is primary molded by a conventional casting process, enabling the preparation of an alloy having a high strength.
  • silicon carbide (SiC) is contained in the rapidly solidified powder 10A, since the silicon carbide (SiC) is dispersed uniformly in the texture of the aluminum alloy in a finely divided state, an improved abrasion resistance can be obtained.
  • the other constituting components are also contained in the aluminum alloy powder as fine powder when the material 1A is the rapidly solidified powder of an aluminum alloy.
  • the aluminum alloy powder is formed in to a dense crystal texture through solidification and forging, these components do not cause a decrease in strength due to concentration of the stress in the crystal grain boundaries, thereby to improve the fatigue strength.
  • the top land portion extending from the vicinity of the ring groove portion 5 to the head section 2 is made of the material 1A, even when the top land of the piston is strongly pressed to the cylinder wall during the operation of the engine, the top land can withstand such a pressing force. Thus, it is possible to make the top land portion small, so that the amount of an exhaust gas remaining in a gap between the top land and the cylinder wall can be reduced, resulting in the reduction of HC.
  • a method of manufacturing a piston for an internal combustion engine according to the present invention has been described in the foregoing.
  • the present invention is, however, not limited to the above embodiment.
  • the rapidly solidified powder of an aluminum alloy and the continuous casting material of an aluminum alloy used as a raw material are not limited to those specifically shown as an example in the above embodiment.
  • the specific method for forging the composite piston forging material into a primary molded article of a piston main body and the specific shape of the piston main body finally produced are not limited to those shown in the above-described embodiment.
  • the strength and abrasion resistance of a piston main body are improved by using a rapidly solidified powder aluminum alloy as a material for constituting the piston main body. Further, a composite piston forging material composed of such a rapidly solidified powder is produced without significantly increasing manufacturing steps and manufacturing time so that the cost up is prevented. At the same time, such a composite piston forging material is integrally forged so that the bonding strength between different materials of the piston main body is improved.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)
  • Forging (AREA)

Claims (19)

  1. Kolben für eine Brennkraftmaschine, mit einem Kolbenhauptkörper (1), der aus zumindest zwei unterschiedlichen Materialien (1A,1B), die unterschiedliche Festigkeiten aufweisen, gebildet ist, wobei die Materialien (1A,1B) einstückig durch Schmieden miteinander haftverbunden sind, dadurch gekennzeichnet, daß der Kolbenhauptkörper (1) durch primäre Formgebung durch Schmieden des Verbundmateriales (10), bestehend aus einem Kolbengrundmaterial und einem Material, das eine höhere Festigkeit als das Kolbengrundmaterial aufweist, erhalten wird, derart, daß zumindest ein Abschnitt eines Bolzenbohrungsabschnittes (6) des Kolbenhauptkörpers (1), der eine Gleitkontaktoberfläche eines Kolbenbolzens bildet, aus dem Material gebildet ist, das eine höhere Festigkeit aufweist.
  2. Kolben nach Anspruch 1, dadurch gekennzeichnet, daß eines der Materialien, das eine höhere Festigkeit besitzt, sich in einen Außenumfang des Kolbenhauptkörpers (1) von einem oberen Ende eines Kopfabschnittes (2) zu zumindest einem Mantelabschnitt (3) unterhalb eines Ringnutabschnittes (5) erstreckt, und daß der Kolbenhauptkörper (1) durch Schmieden derart hergestellt ist, daß eine Länge des Materiales, das eine höhere Festigkeit besitzt, von dem oberen Ende des Kopfabschnittes (2) größer in einem Zwischenabschnitt zwischen einem Paar von Bolzennaben (4) größer ist als in einer Nähe jedes einzelnen des Paares von Bolzennabenabschnitten (4).
  3. Kolben nach Anspruch 2, dadurch gekennzeichnet, daß der Mantelabschnitt (3) ein unteres Ende aufweist, das mit ausgesparten Abschnitten versehen ist, so daß ein ganzer Bereich einer äußeren Umfangsoberfläche des Kolbenhauptkörpers (1) aus dem Material hergestellt ist, das eine höhere Festigkeit besitzt.
  4. Kolben nach Anspruch 2 oder 3, dadurch gekennzeichnet, daß zumindest ein äußerer Umfangsabschnitts des oberen Endes des Kopfabschnittes (2) aus dem Material hergestellt ist, das eine höhere Festigkeit aufweist.
  5. Kolben nach zumindest einem der vorhergehenden Ansprüche 1 bis 4, dadurch gekennzeichnet, daß das Material, das eine höhere Festigkeit besitzt, eine Aluminiumlegierung ist, die durch Verfestigen eines rapide erstarrendes Pulvers erhalten wird, das Silizium (Si) in einer Menge von 12 - 22 Gew.% enthält und das ein Primärkristallsilizium mit einem durchschnittlichen Partikeldurchmesser von nicht mehr als 10 µm hat.
  6. Kolben nach zumindest einem der vorhergehenden Ansprüche 1 bis 5, dadurch gekennzeichnet, daß das Material, das eine höhere Festigkeit besitzt, eine Aluminiumlegierung ist, die durch Verfestigen des rasch erstarrenden Pulvers erhalten wird und das nicht metallische Komponententeilchen enthält, die härter als Silizium (Si) sind und die einen durchschnittlichen Teilchendurchmesser als 10 µm aufweisen, in einer Menge von 1 - 10 Gew.%.
  7. Kolben nach Anspruch 6, dadurch gekennzeichnet, daß die nicht metallischen Komponententeilchen zumindest solche sind, ausgewählt unter Siliziumkarbid (SiC), Aluminiumoxid (Al2O3) oder Aluminiumnitrid (AIN).
  8. Kolben nach zumindest einem der vorhergehenden Ansprüche 1 bis 7, dadurch gekennzeichnet, daß das Material, das eine höhere Festigkeit aufweist, eine Aluminiumlegierung ist, die erhalten wird durch Verfestigen des rapide erstarrenden Pulvers, das Eisen (Fe) in einer Menge von 1 - 10 Gew.% enthält und in dem der durchschnittliche Teilchendurchmesser einer Verbindung des Eisens nicht größer als 10 µm ist.
  9. Verfahren zur Herstellung eines Kolbens für eine Brennkraftmaschine, der einen Kolbenhauptkörper (1), gebildet aus zumindest zwei Materialien (1A,1B), die unterschiedliche Festigkeiten aufweisen, besitzt und die Schritte aufweist des Zusammenbringens unter einstückigen Haftverbindens der Materialien (1A,1B) durch Schmieden, gekennzeichnet durch Schmieden eines Verbundmateriales (10) bestehend aus einem Kolbengrundmaterial und einem Material, das eine höhere Festigkeit als das Kolbengrundmaterial aufweist, derart, daß zumindest ein Bereich eines Bolzenbohrungsabschnittes (6) des Kolbenhauptkörpers (1), der eine Gleitkontaktoberfläche eines Kolbenbolzens bildet aus dem Material gebildet ist, das eine größere Festigkeit besitzt.
  10. Verfahren nach Anspruch 9, dadurch gekennzeichnet, daß die Materialien (1A,1B) in einer unteren Form (22) durch eine obere Form oder Stempel (21) geschmiedet sind.
  11. Verfahren nach Anspruch 10, dadurch gekennzeichnet, daß beide Formen (22,21) auf eine gesteuerte Temperatur von 250°C - 450°C vorerwärmt werden.
  12. Verfahren nach zumindest einem der vorhergehenden Ansprüche 9 bis 11, dadurch gekennzeichnet, daß während des Extrudierens eines Stranggießmateriales aus einer Aluminiumlegierung durch ein erstes Werkzeug (12) ein rapide sich verfestigendes Pulver oder eine Aluminiumlegierung, die um das extrudierte Stranggießmaterial vorgehesen ist, so unter Erwärmen und unter Druck zusammen mit dem Stranggießmaterial durch ein zweites Werkzeug (15), das einen größeren Durchmesser als das erste Werkzeug (14) hat, koextrudiert wird, um einen säulenförmigen Körper zu erhalten, der aus einem Kemmaterial, bestehend aus dem Material des Stranggießmateriales und einem äußeren Umfangsmaterial, einstückig haftverbunden mit dem Kern, besteht und dasaus dem Material des rapide sich verfestigenden Pulvers gebildet ist, und daß der säulenförmige Körper in eine vorbestimmte Größe geschnitten wird, um ein Rohmaterial (10) zum Schmieden zu erhalten, und daß das Rohmaterial (10) zum Schmieden einem primären Formgebungsschritt und einer anschließenden Verarbeitung unterzogen wird, um hierdurch den Kolbenhauptkörper (1) als einen Endartikel zu erhalten.
  13. Verfahren nach zumindest einem der vorhergehenden Ansprüche 9 bis 11, dadurch gekennzeichnet, daß das eine der Materialien, das eine höhere Festigkeit besitzt, sich in einen Außenumfang des Kolbenhauptkörpers (1) von einem oberen Ende eines Kopfabschnittes (2) zu zumindest einem Mantelabschnitt (3) unterhalb eines Ringnutabschnittes (5) erstreckt und daß der Kolbenhauptkörper (1) derart geschmiedet wird, daß eine Länge des Materiales, das eine höherer Festigkeit besitzt, von dem oberen Ende des Kopfabschnittes (2) größer ist in einem Zwischenabschnitt zwischen einem Paar von Bolzennaben (4) als in einer Nähe jeder einzelnen des Paares von Bolzennaben (4).
  14. Verfahren nach Anspruch 13, dadurch gekennzeichnet, daß der Mantelabschnitt (3) ein unteres Ende besitzt, das mit Aussparungen versehen ist, so daß der gesamte Bereich einer äußeren Umfangsoberfläche des Kolbenhauptkörpers (1) aus dem Material besteht, das eine höhere Festigkeit besitzt.
  15. Verfahren nach Anspruch 13 oder 14, dadurch gekennzeichnet, daß zumindest ein äußerer Umfangsabschnitt des oberen Ende des Kolbenabschnittes (2) aus einem Material besteht, das eine höhere Festigkeit besitzt.
  16. Verfahren nach zumindest einem der vorhergehenden Ansprüche 9 bis 15, dadurch gekennzeichnet, daß das Material, das eine höhere Festigkeit besitzt, eine Aluminiumlegierung ist, die durch Verfestigen eines rapide erstarrenden Pulvers erhalten wird, daß Silizium (Si) in einer Menge von 10-22 Gew.% enthält und das ein Primärkristallsilizium mit einem durchschnittlichen Teilchendurchmesser von nicht mehr als 10 µm hat.
  17. Verfahren nach zumindest einem der vorhergehenden Ansprüche 9 bis 16, dadurch gekennzeichnet, daß das Material, das eine höhere Festigkeit besitzt, eine Aluminiumlegierung ist, die durch Verfestigen des rapide erstarrenden Pulvers erhalten wird und das nicht metallische Komponententeilchen enthält, die härter als Silizium (Si) sind und einen durchschnittlichen Teilchendurchmesser von nicht mehr als 10 µm in einer Menge von 10 - 10 Gew.% aufweist.
  18. Verfahren nach Anspruch 17, dadurch gekennzeichnet, daß die nicht metallischen Komponententeilchen zumindest welche sind, die ausgewählt sind, aus Siliziumkarbid (SiC), Aluminiumoxid (Al2O3) oder Aluminiumnitrid (AIN).
  19. Verfahren nach zumindest einem der vorhergehenden Ansprüche 9 bis 18, dadurch gekennzeichnet, daß das Material, das eine höhere Festigkeit besitzt, eine Aluminiumlegierung ist, die erhalten wird durch Verfestigen des rapide erstarrenden Pulvers, das Eisen (Fe) in einer Menge von 1 - 10 Gew.% enthält und in dem der durchschnittliche Teilchendurchmesser einer Verbindung des Eisens nicht größer als 10 µm ist.
EP19980106754 1997-04-10 1998-04-14 Brennkraftmaschinenkolben und Verfahren zu seiner Herstellung Expired - Lifetime EP0870919B1 (de)

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JP108172/97 1997-04-10
JP10817397 1997-04-10
JP9108170A JPH10288085A (ja) 1997-04-10 1997-04-10 内燃機関用ピストン
JP10817397A JP3705676B2 (ja) 1997-04-10 1997-04-10 内燃機関用ピストンの製造方法
JP108170/97 1997-04-10
JP10817097 1997-04-10
JP108173/97 1997-04-10
JP10817297 1997-04-10
JP10817297A JPH10288082A (ja) 1997-04-10 1997-04-10 内燃機関用ピストン

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KR20020029402A (ko) * 1999-09-27 2002-04-18 미쯔이 고오헤이 예비 성형체, 성형품 및 내연 기관용 부품
DE60014328D1 (de) * 2000-05-26 2004-11-04 Technodop Ltd Soc De Droit Irl Herstellung eines festes Werkstoffes in quader- oder zylindrischer Form, der laminiert, gesintert, geschnitten und wärmebehandelt wird
WO2003010429A1 (en) * 2001-07-23 2003-02-06 Showa Denko K.K. Forged piston for internal combustion engine and manfacturing method thereof
DE102007052499A1 (de) * 2007-11-02 2009-05-07 Mahle International Gmbh Verfahren zur Herstellung eines Kolbens für einen Verbrennungsmotor sowie mit diesem Verfahren herstellbarer Kolben
DE102008018850A1 (de) * 2007-11-30 2009-06-04 Andreas Borst Kolben und Verfahren zu dessen Herstellung
CN101966586B (zh) * 2010-10-27 2012-02-01 河南科技大学 内燃机活塞毛坯制造方法

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FR2105375A5 (de) * 1970-09-03 1972-04-28 Nova Werke Ag
AU6744381A (en) * 1980-02-27 1981-09-03 British Internal Combustion Engine Research Institute Limited, The Sintered piston
MX157562A (es) * 1980-07-14 1988-12-02 Trw Inc Metodo mejorado para un piston motor de aleacion de aluminio que tiene un anillo ferroso de refuerzo su extremo de cabeza
JPS63243245A (ja) * 1987-03-30 1988-10-11 Toyota Motor Corp 鍛造性に優れたアルミニウム合金部材
JPH03290047A (ja) * 1990-04-04 1991-12-19 Sumitomo Light Metal Ind Ltd 内燃機関のピストン
DE69724035T2 (de) * 1996-05-20 2004-02-19 Yamaha Hatsudoki K.K., Iwata Verfahren zur Herstellung einen Kolben für eine Brennkraftmaschine

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