Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
  • B22D19/00—Casting in, on, or around objects which form part of the product
  • B22D19/0009—Cylinders, pistons
• • 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 
  • F02F3/10—Pistons  having surface coverings
  • F02F3/12—Pistons  having surface coverings on piston heads
• • 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
  • F05C2201/00—Metals
  • F05C2201/04—Heavy metals
  • F05C2201/0433—Iron group; Ferrous alloys, e.g. steel
  • F05C2201/0448—Steel

Definitions

• the invention relates to the connection of aluminium or aluminium alloys to other metal materials and particularly, but not exclusively, to such connections in pistons for internal combustion engines.
• aluminium and aluminium alloys find wide use in many engineering applications, for example, in the manufacture of pistons for internal combustion engines. They suffer,- however, from the disadvantages that, as compared with many other metal materials, such as ferrous materials, they do not wear well and are not well able to withstand elevated temperatures. In the case of pistons for internal combustion engines, for example, aluminium and aluminium alloys are not well able to withstand the temperatures found in the combustion chambers of internal combustion engines and cannot readily resist the wear of steel piston rings commonly carried by such pistons.
• Such a casting technique may not, however, create a secure bond between the aluminium or aluminium alloy and the ferrous material.
• the bond has been sought to be improved by use of processes such as the 'Al-Fin* process but this requires further manufacturing steps.
• casting is not suitable where it is not possible to surround the majority of the material with the aluminium or aluminium alloy.
• a piston of aluminium or aluminium alloy is provided with
• a method of connecting aluminium or aluminium alloy to another metal material comprising locating tne other metal material relatively to a porous metal material, inserting the other metal material and the porous metal material into a die, gravity filling the die with molten aluminium or aluminium alloy and then solidifying the molten aluminium or aluminium alloy under pressure so that the molten aluminium or aluminium alloy penetrates at least a portion of the porous material to connect the aluminium or aluminium alloy to the other metal material.
• a piston for an internal combustion engine having a body of aluminium or aluminium alloy connected to a reinforcement of another metal material by the method of the first aspect of the invention.
• QMPl WIPO having a body of aluminium or aluminium alloy and including a reinforcement of another metal material, the reinforcement being connected by a braze or a weld to a porous metal material and the aluminium or aluminium alloy body penetrating the porous material, at least partially, to connect the reinforcement to the body.
• Figure 1 is a cross-section of a first embodiment of a piston for an internal combustion engine and including a crown reinforcement
• Figure 2 is a cross-section of a second embodiment of a piston for an internal combustion engine and including a combustion bowl reinforcement,
• Figure 3 is a cross-section of a third embodiment of a piston for an internal combustion engine and including a combined crown and combustion bowl reinforcement,
• Figure 4 is a cross-section of a fourth embodiment of a piston for an internal combustion engine, and including a reinforcement around an entrance of a combustion bowl,
• Figure 5 is a cross-section through a crown end of a fifth embodiment of a piston for an internal combustion engine and including a reinforced crown and combustion bowl and reinforcements for forming piston ring grooves,
• Figure 6 is a cross-section of a sixth embodiment of a piston for an internal combustion engine and including a reinforced crown having a heat-insulating barrier,
• Figure 7 is a cross-section of a seventh embodiment of a piston for an internal combustion engine and including a reinforced crown having a heat-insulating barrier,
• Figure 8 is a cross-section of a eighth form of piston for an internal combustion engine and including a reinforced crown and combustion bowl and a insulating heat barrier, and
• Figure 9 is a cross-section of a ninth form of piston for an internal combustion engine and including a reinforced crown separated from the remainder of the piston by a heat-insulating barrier.
• the piston body is produced by a squeeze casting process in which molten aluminium or aluminium alloy is passed under gravity (not under pressure) into a closed die where the molten metal is solidified under a high load which may be many tonnes. Prior to the filling by molten metal, a required reinforcement is placed in the die and may take any of the forms described below with reference to the drawings.
• the piston may be cast 'crown-up' (i.e. with the crown end uppermost) or, preferably, 'crown-down' (i.e. with the crown end lowermost).
• a piston body 10 produced by squeeze casting is strong because voids, gas pockets and other forms of porosity are almost non- existent so that the material is uniform and homogenous.
• the piston body shrinks very little on being removed from the die so reducing the problems associated with such shrinkage.
• OMPI metal material* This material may be a metallic three- dimensional mesh, or a knitted metal material or a material sold under the trade mark 'RETIMET' or any other suitable material which, while being capable of being shaped into a body of predetermined form, allows molten metal under pressure to penetrate the body and can withstand the temperatures and pressures of casting.
• Tne metal may be a ferrous metal or a copper base metal such as a copper alloy.
• a reinforcement is formed by brazing or welding one face of a generally circular steel plate 13 to an end face of a cylindrical body of porous metallic material 12, whose area is generally the area of the plate 13.
• the steel plate 13 and the porous metal material 12 are then placed in the die and the piston-forming squeeze casting step is performed as described above to produce the piston body 10.
• a piston is produced in which the steel plate 13 covers completely the crown end 11 of the piston body 10.
• the aluminium or aluminium alloy within the porous metal material forms an interlocked connection between these two parts which thus joins the steel plate 13 firmly to the body 10. Since the crown is the portion of the piston which is subjected to the highest temperatures, when the piston is in operation in an internal combustion engine, the steel plate 13, being more heat-resistant than the aluminium or aluminium alloy, protects the aluminium or aluminium alloy of the body from the elevated temperatures.
• a reinforcement is formed by brazing an exterior face of a sheet steel combustion bowl 14 to a cup-shaped body of porous metal material 12.
• the bowl 14 and the porous metal material 12 are both inserted in a squeeze casting die and a piston body 10 is squeeze cast around them, as described above. Since the solidification of molten aluminium or aluminium alloy takes place under load, the aluminium or aluminium alloy penetrates completely the porous metal material 12.
• a piston is formed having a combustion bowl 14 which is securely locked to the body 10 by the solidified aluminium or aluminium alloy within the body o porous metal material. Since combustion takes place, in this combustion bowl, tne steel plate 13 forms a heat- resistant barrier which protects the piston body 10 from the elevated temperatures encountered in the bowl.
• a reinforcement is prepared in which a sheet steel member 15 is formed with a central bowl 16 and a peripheral flange 17.
• the outer surface of the bowl and the flange are brazed to a correspondingly shaped surface of a body of porous metal material 12 and the reinforcement is then inserted in a squeeze casting die and has the piston body 10 squeeze cast therearound as described above.
• the pressure applied to the aluminium or aluminium alloy during solidification ensures that the molten aluminium or aluminium alloy penetrates throughout the body of porous metal material 12.
• a piston is produced in which the sheet steel member 15 forms a combustion bowl and covers the remainder of the crown between the edge of the combustion bowl and the outer periphery of the piston. This protects the whole crown end 11 of the piston body 10 from tne temperatures encountered in use in a combustion chamber of an internal combustion engine.
• the solidified aluminium or aluminium alloy within the porous metal material 12 forms a firm interlock between the steel members and the piston body.
• a reinforcement is formed by an annular steel member 18 which is of generally triangular section and which has one surface brazed to a correspondingly shaped surface of an annular body of porous metal material 19. This is then placed in a squeeze casting die with the annular member 18 concentric with the axis of the piston to be cast.
• the die is provided with a hemispherical core (not shown) around which the insert 18 extends.
• the piston body 10 is then squeeze cast as described above.
• the molten material penetrates the porous metal material 12 so that, on solidification, the steel member 18 is securely locked to the piston body 10.
• the insert thus forms an entrance extending ar ⁇ uud a combustion bowl 20 formed by the core.
• the entrance to the combustion bowl is subjected to the highest temperatures and is susceptible to heat damage because of the comparative thinness of the material at this point.
• the steel insert 18 is well able to withstand these temperatures; thus protecting the aluminium or aluminium alloy of the piston body 10.
• the reinforcement is formed by a greater amount of porous metal material 12 than in the Figure 3 embodiment and this material is of substantial thickness in an axial direction.
• the porous metal material 12 is brazed to two annular members 21, 22 which are arranged concentric with the centre of the generally circular sheet steel member 17.
• the two annular members 21, 22 are of a ferrous material and are axially spaced from one another and from the sheet steel member 17.
• the upper surface of the sheet steel member 17 is connected to a member 23 of similar shape, also made of sheet steel, via an annular washer 24; the connections being by welding.
• the chamber formed between the two members 17, 23 may be evacuated.
• This reinforcement assembly is inverted and placed in the squeeze casting die, and the piston body is squeeze cast therearound so that the molten aluminium or aluminium alloy penetrates the porous metal material to connect the assembly securely to the piston body 10. upon removal from the die, one or more piston ring grooves are machined in the first insert 21.
• the second insert 22 acts as an expansion control insert for the piston and the second sheet steel member 23 provides a combustion bowl 24.
• the chamber between the two sheet steel members 17, 23 provides an insulating heat barrier gap so isolating the piston body 10 from the effects of heat in the combustion chamber.
• a reinforcement is formed by a closed annular steel box welded from steel plates with upper and lower circular ends 25, 26 and an annular wall 27.
• the ends 25, 26 and the wall 27 are brazed to a porous metal material 12_ contained within the box.
• the outer surface of the lower end 26 is also brazed to a cylindrical body of porous metal material 12b.
• This assembly is placed in a squeeze casting die and the piston body 10 is squeeze cast from molten aluminium or aluminium alloy, as described above.
• the molten aluminium or aluminium alloy penetrates the porous metal material 12b. and, on solidification, connects firmly the piston body 10 the steel box. Plainly, the molten material does not reach the porous metal material 12a, because it is contained within the box formed by the steel plates.
• the upper end 25 of the assembly forms a heat-resistant crown surface of the piston.
• the annular wall 27 is subsequently formed with one or more wear-resistant piston ring grooves (not shown) .
• the unfilled porous metal material 12a. within the box forms an heat- insulating barrier between the crown end of the piston and the aluminium or aluminium alloy body.
• a reinforcement is formed by two generally circular steel plates 28, 29 which have sandwiched between them a layer of porous metal material 12a which is brazed thereto.
• the other surface of one of the sheet steel members 29 is brazed to a cylindrical body of porous metal material 12J2.
• the two plates 28, 29 may be formed with registering central depressions so that the upper plate 28 defines a combustion bowl in the completed piston.
• the upper plate 28 need not be of steel, it could be of any other suitable material.
• This assembly is placed in a squeeze casting die, and the piston body 10 is squeeze cast from molten aluminium or aluminium alloy, as described above, with the molten aluminium or aluminium alloy penetrating the porous metal material 12&. It will be understood that, of course, the molten aluminium or aluminium alloy cannot pass the steel plate 29 and so the porous metal material 12a. remains unpenetrated by the molten aluminium or aluminium alloy.
• a piston is formed in which one steel piace 28 forms a heat-resistant surface to the crown of the piston while the unpenetrated porous metal material 12a. forms an insulating layer between the crown end of the piston and the body 10 of the piston.
• the porous metal material 12J2 forms a secure connection between the piston body 10 and the plates 28, 29.
• this embodiment is similar to the embodiment of Figure 5 and parts common to Figures 5 and 8 will not be described in detail.
• the two annular inserts 21, 22 are dispensed with and the porous metal material 12 is provided simply for attaching the two spaced steel sheets 17, 23 to the piston body 10.
• the porous metal material 12 has, extending partially into the material from one surface thereof, a filling of a water-soluble salt.
• the circular steel plate 13 is brazed to this surface.
• the aluminium or aluminium " alloy piston body is then squeeze cast around this assembly with aluminium or aluminium alloy penetrating the unfilled porous metal material and the salt preventing penetration of the filled portion.
• the cast piston is then removed from the squeeze casting die and the salt flushed away with water. In this way, the unpenetrated porous metal material forms a heat barrier 31 between the sheet steel crown 13 and the aluminium or aluminium alloy body 10.
• the region below the crown is reinforced by the porous metal material. It may therefore be advantageous to arrange that the porous metal material extends to the piston ring band so that one or more of the piston ring grooves is formed in the porous metal material reinforced portion of the piston.
• a further advantage of crown-down squeeze casting such assemblies is that the molten metal often contains impurities such as dross and oxides which rise to the surface of the molten metal during pouring. In crown- down casting these only affect the lower end of the skirt, which is generally of little significance. In crown-up squeeze casting with an insert assembly, the impurities can enter the assembly and this is undesirable since it could weaken the connection formed during casting.
• OMPI the die.
• crown-down squeeze casting this means that the crown solidifies first and this reduces the possibility of differential solidification rates across the cross-section of the piston from distorting the piston, because at the lower end of the die any differences are minimal.
• crown-up casting the crown is at the upper end of the die, where maximum differential solidification occurs, so giving the possibility of distortion of the assembly by such differential solidification.

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

Applications Claiming Priority (2)

Publications (1)

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• 1983
  • 1983-11-22 GB GB08331135A patent/GB2132524A/en not_active Withdrawn
  • 1983-11-23 IT IT23831/83A patent/IT1167008B/it active
  • 1983-11-23 AU AU22656/83A patent/AU2265683A/en not_active Abandoned
  • 1983-11-23 EP EP83903814A patent/EP0126748A1/de not_active Withdrawn
  • 1983-11-23 WO PCT/GB1983/000299 patent/WO1984002096A1/en unknown

Non-Patent Citations (1)

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