EP0127366A1 - Method of die casting a piston - Google Patents
Method of die casting a piston Download PDFInfo
- Publication number
- EP0127366A1 EP0127366A1 EP84303241A EP84303241A EP0127366A1 EP 0127366 A1 EP0127366 A1 EP 0127366A1 EP 84303241 A EP84303241 A EP 84303241A EP 84303241 A EP84303241 A EP 84303241A EP 0127366 A1 EP0127366 A1 EP 0127366A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- metal
- mold cavity
- molten metal
- plunger
- cavity
- 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.)
- Withdrawn
Links
Images
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D15/00—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor
- B22D15/02—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor of cylinders, pistons, bearing shells or like thin-walled objects
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
- B22D27/11—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of mechanical pressing devices
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/15—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using vacuum
Definitions
- This invention relates to a method of die casting an internal combustion engine piston of the type used in automobiles, and particularly to a method involving the formation of wrist pin openings in die cast pistons.
- a trunk-type piston typically forms the movable end of a cylinder in an internal combustion engine. Rapid expansion of vapors and gases within the cylinder following combustion causes displacement of the piston.
- Conventional trunk-type pistons include a closed "face" end and an opposing skirt to align the piston properly in the cylinder.
- a piston rod communicates with both the piston skirt and a conventional connecting rod.
- the piston rod is one link in a conventional mechanical engine linkage. The linkage transforms the rectilinear motion of the piston within the cylinder into the rotational motion required to drive a shaft.
- One end of a conventional piston rod includes a pair of opposing inwardly facing wrist pins.
- the piston skirt includes a pair of internal bosses having opposing outwardly facing openings to receive and support the wrist pins of the piston rod.
- the piston material surrounding the wrist pin opening is subjected to immense compressive, tensile, and shear stresses due to the alternating load transmitted by the wrist pins during engine operation, particularly in automobiles. Accordingly, the fatigue strength of the material adjacent the wrist pin opening should be maximized to guard against catostrophic stress-related failure after an unacceptably low number of operating cycles.
- porosity is present in the finished product.
- Two types of porosity are present: (1) gas porosity caused by trapped gas or air; and (2) porosity formed by shrinkage of the metal. Either one of these types of porosity may cause a piston to expand, blister, and explode at operating temperatures encountered in automobile internal combustion engines. For these reasons, die casting techniques have not heretofore been used to produce pistons for automobile internal combustion engines.
- Automobile pistons are presently cast without wrist pin openings using a permanent mold casting process since the die casting industry has been unable to increase the fatigue strength of the material surrounding the opening to tolerable levels using a die casting process.
- An aluminum alloy is the most commonly selected piston material.
- secondary drilling and reaming operations must be performed on every cast or machined piston to provide the wrist pin openings.
- steel struts have been used as mold inserts in an attempt to increase the fatigue strength of the aluminum.
- the steel struts have been used in the permanent mold casting process primarily to strengthen . the area around the wrist pin openings. It is also known to use steel struts in the area of the ring groove cut in the closed "face" end of the piston to increase strength in the permanent mold casting process.
- An apparatus for producing dense articles from molten materials is disclosed in U.S. Patent No. 3,268,960 (Morton).
- the apparatus disclosed in Morton comprises a vacuum die casting machine in combination with means for forging selected portions of molten material within the mold cavity to produce articles of high-density character. The forging is accomplished by initial and continuing pressure on the molten material until it has solidified and cooled.
- Morton does not teach a method of ramming a plunger into the molten material in the mold cavity in order to form an opening and intensify certain mechancial properties of the cast item surrounding the opening. Accordingly, significant secondary machining operations would still be required to fabricate wrist pin openings in a die cast trunk-type piston.
- the present invention provides a method of die casting pistons for automobile internal combustion engines in which intensifying plungers are used to form wrist pin openings.
- the plungers can be hydraulically thrust into the semi-molten metal already injected into the mold cavity to simultaneously displace the metal to form the wrist pin openings and compress the displaced metal within the mold cavity to intensify the critical mechancial properties of the metal surrounding the wrist pin openings.
- the present invention provide a unitary method of forming wrist pin openings in die cast pistons, but it concurrently maximizes the fatigue strength of the metal surrounding the wrist pin opening to forestall ruinous piston failure due to stress fracture during engine operation. The need for costly, labor-intensive secondary machining is minimized and intensifying procedures are not required to form wrist pin openings in pistons produced using the method of the present invention.
- a method of die casting a piston for an internal combustion engine includes the steps of forming a mold cavity for casting the piston, introducing a molten metal into the mold cavity through gates in order to substantially fill the cavity, cooling the introduced molten metal until it solidifies in the gates to close the cavity, and thrusting a plunger into the mold cavity to displace and compress the molten metal within the cavity.
- the plunger forms an opening in the piston and compresses the displaced metal to intensify mechanical properties of the metal surrounding the opening.
- the introducing step can include the steps of transferring a predetermined quantity of molten metal from a reservoir maintained at a predetermined pressure to a channel in communication with the reservoir, by producing a pressure in the mold cavity below the predetermined pressure.
- the lower pressure in the mold cavity will induce molten metal to leave the reservoir and enter the channel.
- a plunger pushes the metal from the channel into the mold cavity through relatively small gates.
- the molten metal is allowed to solidify or •freeze * in the gates to close the cavity and prevent metal from being forced back into the channel.
- the time required for the metal to "freeze" in the gates will depend upon the gate size, the freeze curve of the metal alloy, and the thickness of the casting.
- the thrusting step can include the steps of moving the plunger in a cylinder communicating with the mold cavity, actuating a fluid motor connected to the plunger so that the plunger is moved from a first position within the cylinder to a second position within the cavity, retaining the plunger within the cavity for at least a predetermined interval of time, and thereafter actuating the fluid motor so that the plunger is retracted to its first position within the cylinder.
- the thrusting step can also include the step of ramming two opposing plungers into the molten metal to displace the metal to form a pair of wrist pin openings in the cast piston. In the thrusting step, the plungers are moved into the cavity until back pressure from the compressed molten metal stops the motion of the plunger. The plunger should be stopped by the back pressure before it reaches a predetermined limit to ensure that adequate pressure is created on the molten metal and maintained during the solidification of the metal.
- the casting method of the present invention produces a die cast piston 10 having internal bores or wrist pin openings 12 formed and intensified by a pair of thrustable intensifying plungers 14.
- the wrist pin openings 12 are formed in opposing faces of the piston skirt 16 to receive and support the inwardly projecting wrist pins of a conventional piston rod (not shown).
- the intensifying plungers 14 cooperate with a metal die 18 in a cold chamber vertical die casting machine to form and intensify the wrist pin openings as shown in Figs. 2, 3, and 4.
- the metal die 18 includes a stationary die 20 seated in a cover holding block 22 and an opposing movable die 24 seated in an ejector holding block 26.
- Each of the dies 20, 24 includes a cut-away portion 27 suitably configured and located so that they cooperate to form a mold cavity'28 having the shape of a piston when the dies 20, 24 are mated.
- the piston skirt 16 is molded in the cut-away portion 27 of the movable die 24, the closed "face" end 29 being molded in the cut-away portion 27 of the stationary die 20.
- the movable die 24 and the adjacent ejector holding block 26 include plunger-receiving passageways 30, 32 so that intensifying plungers 14 can be thrust into the mold cavity 28 after the dies 20, 24 are mated and molten metal 31 has been allowed to substantially fill the mold cavity 28.
- Each plunger 14 is normally housed within a first cylindrical passageway or portion 30 formed in the ejector holding block 26 and is movable therein.
- Each first cylindrical passageway 30 communicates with the mold cavity 28 via a coaxial second cylindrical passageway or portion 32 of a smaller cross-sectional area formed in the movable die 24, as shown in Fig. 3.
- Each plunger 14 includes a flat-faced tip portion 34 and a base portion 36.
- the tip portion 34 is movable to a position within the movable die 24 to form a wall portion of the mold cavity 28 during introduction of molten metal, as shown in Fig. 3.
- the tip portions 34 are held approximately tangent to the outside diameter of the mold cavity 28 so that very little molten metal 31 will enter the passageway 32. Thereafter, the tip portion 34 is thrust into the mold cavity 28, thereby piercing the molten metal 31 contained therein to form and intensify the wrist pin openings 12 as shown in Fig. 4.
- the cross-sectional area of the tip portion 34 must be of sufficient size to pass through the second cylindrical passageway 32 to enter the mold cavity 28.
- the diameter of the plunger tip portion 34 of the plunger 14 is about 0.004 inch to 0.005 inch smaller than the diameter of the passageways 32 in the dies through which they pass.
- the base portion 36 is provided with an annular flange 38 having a cross-sectional area of sufficient size to engage the outer surface 40 of the movable die 24 to thereby limit travel of the tip portion 34 into the mold cavity 28 to a predetermined distance.
- Each plunger 14 is propelled by a fluid motor 42.
- the fixed portion of the fluid motor 42 is securely mounted to the ejector holding block 26 as shown in F ig. 2 at 44 and the movable portion is attached to the plunger base portion 36 to selectably move the plunger 14 within passageways 30, 32 to thrust the tip portion 34 into the mold cavity 28.
- the fluid motor 42 is a conventional hydraulic piston and cylinder mechanism. As will be explained later, the hydraulic pressure generated by the fluid motor 42 should be adequate to generate a force that will create effective pressures in the molten metal 31 of about 15,000 psi to 30,000 psi.
- a vacuum pump (not shown) is used to induce a partial vacuum in the mold cavity 28 and in the molten metal feed conduits 46 that connect the mold cavity 28 to a molten metal reservoir (not shown).
- the vacuum pump communicates with the mold cavity 28 and molten metal feed conduit 46 via a vacuum chill block and pull gate combination as shown in dotted lines in Fig. 2 at 48. Vacuum is pulled through the chill block and gate combination 48 to pull molten metal from the reservoir into the feed conduit 46. In one embodiment, 28 inches of mercury vacuum is pulled in the cavity 28.
- the method of the present invention can best be understood by reference to Figs. 2, 3, and 4.
- the cover and ejector holding blocks 22, 26 are preferably mounted on a vertical die casting machine, and the movable and stationary dies 20, 24 are mounted in the blocks 22, 26, respectively.
- a partial vacuum is induced in the mold cavity 28 and feed conduits 46.
- the vacuum is transmitted through the feed conduits 46 to the molten metal reservoir through a conventional shot sleeve and transfer tube (not shown).
- the molten metal 31 is drawn into the shot sleeve through the transfer tube by the vacuum. Use of the vacuum prevents air bubbles from forming in the molten metal.
- a shot cylinder/plunger apparatus pushes the molten metal into the mold cavity 28 through a plurality of gates 50, resulting in a pressure of about 2,500 psi to 5,500 psi on the molten metal 31. Excess metal is captured in overflows 49.
- the gates 50 are formed in the lowermost portion of the movable die 24 just above the parting line 52, shown in Figs. 3 and 4.
- fluid motors 42 Prior to filling the cavity 28 with molten metal, fluid motors 42 are activated to move the plungers 14 in the movable die passageways 30, 32 so that the flat face of the tip portion 34 forms a portion of the wall of the mold cavity, thereby preventing flow of molten metal 31 into the movable die passageway 32.
- the pressure of 2,500 psi to 5,500 psi is exerted on the molten metal 31 in the mold cavity 28 until the metal 31 in the gates 50 solidifies or freezes.
- the cavity 28 is filled with molten metal 31 and the freezing in the gates 50 begins approximately one to two seconds after the vacuum is induced in the mold cavity 28.
- the solidification of the metal in gates 50 closes the mold cavity 28 to prevent backflow of metal into the shot sleeve when plungers 14 are thrust into the cavity 28.
- the fluid motors 42 are once again activated to thrust the intensifying plungers 14 under high pressure directly into the molten mass of the casting as soon as the metal in the gates 50 has frozen.
- the plunger tip portion 34 will pierce the molten metal 31 about one-half second after the mold cavity 28 is full of metal.
- the plunger tip portion 34 could be thrust into the cavity 28 up to eight seconds after the cavity 28 is full. The exact time interval depends upon port 48 size, the freeze curve of the alloy being cast, and the thickness of the section of casting into which the plunger 14 is being thrust.
- the plungers 14 are thrust as far as possible into the semi-molten metal 31 in the cavity 28.
- the plungers 14 help to create effective pressures of about 15,000 psi to 30,000 psi in the molten metal 31 within the mold cavity 28. Normal pressures achieved in conventional die casting range from about 4,000 psi to 10,000 psi.
- the plunger 14 pierces and compresses the semi-molten metal 31 until the pressure within the mass of metal 31 becomes great enough so that back pressure on the plunger tip 34 stops forward notion of the plunger 14 into the cavity 28.
- forward motion of the plunger 14 be stopped by back pressure on the tip 34 before the annular flange 38 of the plunger base portion 36 bottoms out on the outer surface 40 of the movable die 24 to ensure that adequate pressure is created in the molten metal mass 31 and held throughout the freezing process. Accordingly, the depth of penetration of the plunger tip 34 will vary but will be equal to or less than the predetermined distance of travel of the plungers 14.
- the plungers 14 are subsequently retracted from the mold cavity 28 to allow the molded piston to be ejected from the separated dies 20, 24 by a plurality of ejector pins 54.
- the plungers 14 remain in the mold cavity 28 at least until the metal has cooled and frozen and the plungers 14 are therefore no longer effective.
- the plungers 14 are not withdrawn until just before the die 18 is opened. Following ejection, the fully formed piston 10 having wrist pin openings 12 can be machined to conform to operating specifications.
Abstract
A method (Figure 4) of die casting an automobile engine piston includesthe steps of moving one (24) of two halves (20, 24) to form a mould cavity (28) having the shape of a piston, introducing molten metal (31) into the cavity (28) through gates, cooling the metal for an interval of time sufficient for the metal to solidify in the gates, and thrusting a plunger (14) into the cavity (28) to displace the molten metal to form an opening in the piston and to compress the displaced metal to intensify mechanical properties of the metal surrounding the opening. The plunger (14) is moved from a first position outside the cavity (28) until pressure within the displaced metal stops the plunger in a second position in the cavity. The plunger is retained in the cavity for a predetermined time and is then retracted to the first position.
Description
- This invention relates to a method of die casting an internal combustion engine piston of the type used in automobiles, and particularly to a method involving the formation of wrist pin openings in die cast pistons.
- A trunk-type piston typically forms the movable end of a cylinder in an internal combustion engine. Rapid expansion of vapors and gases within the cylinder following combustion causes displacement of the piston. Conventional trunk-type pistons include a closed "face" end and an opposing skirt to align the piston properly in the cylinder. A piston rod communicates with both the piston skirt and a conventional connecting rod. The piston rod is one link in a conventional mechanical engine linkage. The linkage transforms the rectilinear motion of the piston within the cylinder into the rotational motion required to drive a shaft.
- One end of a conventional piston rod includes a pair of opposing inwardly facing wrist pins. Typically, the piston skirt includes a pair of internal bosses having opposing outwardly facing openings to receive and support the wrist pins of the piston rod. Not unexpectedly, the piston material surrounding the wrist pin opening is subjected to immense compressive, tensile, and shear stresses due to the alternating load transmitted by the wrist pins during engine operation, particularly in automobiles. Accordingly, the fatigue strength of the material adjacent the wrist pin opening should be maximized to guard against catostrophic stress-related failure after an unacceptably low number of operating cycles. These engineering requirements cannot be achieved at present using die casting techniques due to process limitations that have hindered development of the piston die casting art.
- In conventional die casting techniques, porosity is present in the finished product. Two types of porosity are present: (1) gas porosity caused by trapped gas or air; and (2) porosity formed by shrinkage of the metal. Either one of these types of porosity may cause a piston to expand, blister, and explode at operating temperatures encountered in automobile internal combustion engines. For these reasons, die casting techniques have not heretofore been used to produce pistons for automobile internal combustion engines.
- Automobile pistons are presently cast without wrist pin openings using a permanent mold casting process since the die casting industry has been unable to increase the fatigue strength of the material surrounding the opening to tolerable levels using a die casting process. An aluminum alloy is the most commonly selected piston material. Presently, secondary drilling and reaming operations must be performed on every cast or machined piston to provide the wrist pin openings.
- Even in the permanent mold casting process, steel struts have been used as mold inserts in an attempt to increase the fatigue strength of the aluminum. The steel struts have been used in the permanent mold casting process primarily to strengthen . the area around the wrist pin openings. It is also known to use steel struts in the area of the ring groove cut in the closed "face" end of the piston to increase strength in the permanent mold casting process.
- Methods of altering mechanical properties of die cast items are known. An apparatus for producing dense articles from molten materials is disclosed in U.S. Patent No. 3,268,960 (Morton). The apparatus disclosed in Morton comprises a vacuum die casting machine in combination with means for forging selected portions of molten material within the mold cavity to produce articles of high-density character. The forging is accomplished by initial and continuing pressure on the molten material until it has solidified and cooled. However, Morton does not teach a method of ramming a plunger into the molten material in the mold cavity in order to form an opening and intensify certain mechancial properties of the cast item surrounding the opening. Accordingly, significant secondary machining operations would still be required to fabricate wrist pin openings in a die cast trunk-type piston.
- The present invention provides a method of die casting pistons for automobile internal combustion engines in which intensifying plungers are used to form wrist pin openings. The plungers can be hydraulically thrust into the semi-molten metal already injected into the mold cavity to simultaneously displace the metal to form the wrist pin openings and compress the displaced metal within the mold cavity to intensify the critical mechancial properties of the metal surrounding the wrist pin openings. Not only does the present invention provide a unitary method of forming wrist pin openings in die cast pistons, but it concurrently maximizes the fatigue strength of the metal surrounding the wrist pin opening to forestall ruinous piston failure due to stress fracture during engine operation. The need for costly, labor-intensive secondary machining is minimized and intensifying procedures are not required to form wrist pin openings in pistons produced using the method of the present invention.
- In accordance with the present invention, a method of die casting a piston for an internal combustion engine includes the steps of forming a mold cavity for casting the piston, introducing a molten metal into the mold cavity through gates in order to substantially fill the cavity, cooling the introduced molten metal until it solidifies in the gates to close the cavity, and thrusting a plunger into the mold cavity to displace and compress the molten metal within the cavity. The plunger forms an opening in the piston and compresses the displaced metal to intensify mechanical properties of the metal surrounding the opening.
- The introducing step can include the steps of transferring a predetermined quantity of molten metal from a reservoir maintained at a predetermined pressure to a channel in communication with the reservoir, by producing a pressure in the mold cavity below the predetermined pressure. The lower pressure in the mold cavity will induce molten metal to leave the reservoir and enter the channel. A plunger pushes the metal from the channel into the mold cavity through relatively small gates. Before thrusting the plungers into the mold cavity, the molten metal is allowed to solidify or •freeze* in the gates to close the cavity and prevent metal from being forced back into the channel. The time required for the metal to "freeze" in the gates will depend upon the gate size, the freeze curve of the metal alloy, and the thickness of the casting.
- The thrusting step can include the steps of moving the plunger in a cylinder communicating with the mold cavity, actuating a fluid motor connected to the plunger so that the plunger is moved from a first position within the cylinder to a second position within the cavity, retaining the plunger within the cavity for at least a predetermined interval of time, and thereafter actuating the fluid motor so that the plunger is retracted to its first position within the cylinder. The thrusting step can also include the step of ramming two opposing plungers into the molten metal to displace the metal to form a pair of wrist pin openings in the cast piston. In the thrusting step, the plungers are moved into the cavity until back pressure from the compressed molten metal stops the motion of the plunger. The plunger should be stopped by the back pressure before it reaches a predetermined limit to ensure that adequate pressure is created on the molten metal and maintained during the solidification of the metal.
- This invention may best be understood by a reference to the following descripton of a preferred embodiment and the accompanying drawings. In the drawings:
- Fig. 1 is an isometric view of a pair of intensifying plungers received within the wrist pin openings of a die cast piston of the present invention;
- Fig. 2 is a top plan view, partly broken away and cross-sectioned, of the die casting apparatus showing the relationship of the intensifying plunger conduits to the mold cavity of the present invention;
- Fig. 3 is a sectional detail view, partly cross-sectioned, of an embodiment of the present invention showing the intensifying plungers prior to entry into the mold cavity taken generally along line 3-3 of Fig. 2;
- Fig. 4 is a sectional detail view, partly cross-sectional, of an embodiment of the present invention showing the intensifying plunger thrust into the molten metal within the mold cavity to form the wrist pin openings and compress the metal surrounding the wrist pin openings taken generally along line 3-3 of Fig. 2.
- Throughout the following detailed description of the present invention and the claims, reference is made to the formation of a .piston.8 In the description and the claims, it is intended that the word "piston" mean a large internal combustion engine piston of the type used in vehicles such as automobiles.
- As shown in Fig. 1, the casting method of the present invention produces a
die cast piston 10 having internal bores orwrist pin openings 12 formed and intensified by a pair of thrustable intensifyingplungers 14. As is customary, thewrist pin openings 12 are formed in opposing faces of thepiston skirt 16 to receive and support the inwardly projecting wrist pins of a conventional piston rod (not shown). Preferably, theintensifying plungers 14 cooperate with ametal die 18 in a cold chamber vertical die casting machine to form and intensify the wrist pin openings as shown in Figs. 2, 3, and 4. - The metal die 18 includes a
stationary die 20 seated in acover holding block 22 and an opposing movable die 24 seated in anejector holding block 26. Each of thedies portion 27 suitably configured and located so that they cooperate to form a mold cavity'28 having the shape of a piston when thedies piston skirt 16 is molded in the cut-away portion 27 of themovable die 24, the closed "face"end 29 being molded in the cut-away portion 27 of thestationary die 20. Therefore, themovable die 24 and the adjacentejector holding block 26 include plunger-receivingpassageways plungers 14 can be thrust into themold cavity 28 after thedies molten metal 31 has been allowed to substantially fill themold cavity 28. - Each
plunger 14 is normally housed within a first cylindrical passageway orportion 30 formed in theejector holding block 26 and is movable therein. Each firstcylindrical passageway 30 communicates with themold cavity 28 via a coaxial second cylindrical passageway orportion 32 of a smaller cross-sectional area formed in themovable die 24, as shown in Fig. 3. - Each
plunger 14 includes a flat-faced tip portion 34 and abase portion 36. Thetip portion 34 is movable to a position within themovable die 24 to form a wall portion of themold cavity 28 during introduction of molten metal, as shown in Fig. 3. Thetip portions 34 are held approximately tangent to the outside diameter of themold cavity 28 so that very littlemolten metal 31 will enter thepassageway 32. Thereafter, thetip portion 34 is thrust into themold cavity 28, thereby piercing themolten metal 31 contained therein to form and intensify thewrist pin openings 12 as shown in Fig. 4. - Accordingly, the cross-sectional area of the
tip portion 34 must be of sufficient size to pass through the secondcylindrical passageway 32 to enter themold cavity 28. Preferably, the diameter of theplunger tip portion 34 of theplunger 14 is about 0.004 inch to 0.005 inch smaller than the diameter of thepassageways 32 in the dies through which they pass. Thebase portion 36 is provided with anannular flange 38 having a cross-sectional area of sufficient size to engage theouter surface 40 of themovable die 24 to thereby limit travel of thetip portion 34 into themold cavity 28 to a predetermined distance. - Each
plunger 14 is propelled by afluid motor 42. The fixed portion of thefluid motor 42 is securely mounted to theejector holding block 26 as shown in Fig. 2 at 44 and the movable portion is attached to theplunger base portion 36 to selectably move theplunger 14 withinpassageways tip portion 34 into themold cavity 28. In one embodiment, thefluid motor 42 is a conventional hydraulic piston and cylinder mechanism. As will be explained later, the hydraulic pressure generated by thefluid motor 42 should be adequate to generate a force that will create effective pressures in themolten metal 31 of about 15,000 psi to 30,000 psi. - A vacuum pump (not shown) is used to induce a partial vacuum in the
mold cavity 28 and in the moltenmetal feed conduits 46 that connect themold cavity 28 to a molten metal reservoir (not shown). The vacuum pump communicates with themold cavity 28 and moltenmetal feed conduit 46 via a vacuum chill block and pull gate combination as shown in dotted lines in Fig. 2 at 48. Vacuum is pulled through the chill block andgate combination 48 to pull molten metal from the reservoir into thefeed conduit 46. In one embodiment, 28 inches of mercury vacuum is pulled in thecavity 28. - The method of the present invention can best be understood by reference to Figs. 2, 3, and 4. The cover and ejector holding blocks 22, 26 are preferably mounted on a vertical die casting machine, and the movable and stationary dies 20, 24 are mounted in the
blocks mold cavity 28 andfeed conduits 46. The vacuum is transmitted through thefeed conduits 46 to the molten metal reservoir through a conventional shot sleeve and transfer tube (not shown). Themolten metal 31 is drawn into the shot sleeve through the transfer tube by the vacuum. Use of the vacuum prevents air bubbles from forming in the molten metal. - As soon as enough
molten metal 31 is in the shot sleeve, a shot cylinder/plunger apparatus (not shown) pushes the molten metal into themold cavity 28 through a plurality ofgates 50, resulting in a pressure of about 2,500 psi to 5,500 psi on themolten metal 31. Excess metal is captured inoverflows 49. Thegates 50 are formed in the lowermost portion of themovable die 24 just above theparting line 52, shown in Figs. 3 and 4. Prior to filling thecavity 28 with molten metal,fluid motors 42 are activated to move theplungers 14 in themovable die passageways tip portion 34 forms a portion of the wall of the mold cavity, thereby preventing flow ofmolten metal 31 into themovable die passageway 32. The pressure of 2,500 psi to 5,500 psi is exerted on themolten metal 31 in themold cavity 28 until themetal 31 in thegates 50 solidifies or freezes. In a preferred embodiment, thecavity 28 is filled withmolten metal 31 and the freezing in thegates 50 begins approximately one to two seconds after the vacuum is induced in themold cavity 28. The solidification of the metal ingates 50 closes themold cavity 28 to prevent backflow of metal into the shot sleeve whenplungers 14 are thrust into thecavity 28. - The
fluid motors 42 are once again activated to thrust theintensifying plungers 14 under high pressure directly into the molten mass of the casting as soon as the metal in thegates 50 has frozen. Preferably, theplunger tip portion 34 will pierce themolten metal 31 about one-half second after themold cavity 28 is full of metal. However, theplunger tip portion 34 could be thrust into thecavity 28 up to eight seconds after thecavity 28 is full. The exact time interval depends uponport 48 size, the freeze curve of the alloy being cast, and the thickness of the section of casting into which theplunger 14 is being thrust. - The
plungers 14 are thrust as far as possible into thesemi-molten metal 31 in thecavity 28. Theplungers 14 help to create effective pressures of about 15,000 psi to 30,000 psi in themolten metal 31 within themold cavity 28. Normal pressures achieved in conventional die casting range from about 4,000 psi to 10,000 psi. Theplunger 14 pierces and compresses thesemi-molten metal 31 until the pressure within the mass ofmetal 31 becomes great enough so that back pressure on theplunger tip 34 stops forward notion of theplunger 14 into thecavity 28. It is preferred that forward motion of theplunger 14 be stopped by back pressure on thetip 34 before theannular flange 38 of theplunger base portion 36 bottoms out on theouter surface 40 of themovable die 24 to ensure that adequate pressure is created in themolten metal mass 31 and held throughout the freezing process. Accordingly, the depth of penetration of theplunger tip 34 will vary but will be equal to or less than the predetermined distance of travel of theplungers 14. - The
plungers 14 are subsequently retracted from themold cavity 28 to allow the molded piston to be ejected from the separated dies 20, 24 by a plurality of ejector pins 54. Preferably, theplungers 14 remain in themold cavity 28 at least until the metal has cooled and frozen and theplungers 14 are therefore no longer effective. In the present invention, theplungers 14 are not withdrawn until just before the die 18 is opened. Following ejection, the fully formedpiston 10 havingwrist pin openings 12 can be machined to conform to operating specifications. - Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.
Claims (6)
1. A method of die casting a piston comprising the steps of:
(a) moving a movable die having a first cut-away portion to mate with a stationary die having a second cut-away portion, the cut-away portions of the mated dies cooperating to form a mold cavity having the shape of a piston,
(b) introducing a molten metal through gates into the mold cavity to substantially fill the cavity,
(c) cooling the introduced molten metal to solidify the metal in the gates, and
(d) subsequent to solidification of the metal in the gates, thrusting a plunger into the molten metal admitted into the mold cavity to displace the molten metal to form an opening in the piston and to compress the displaced metal to intensify mechanical properties of the metal surrounding the opening.
2. The method of claim 1 wherein the thrusting step further comprises the steps of:
(a) moving the plunger in a cylinder communicating with the mold cavity,
(b) actuating a fluid motor connected to the plunger to extend the plunger into the mold cavity from a first position within the cylinder,
(c) moving the plunger into the mold cavity until pressure within the displaced metal stops the plunger in a second position,
(d) retaining the plunger within the cavity for a predetermined interval of time, and
. (e) thereafter actuating the fluid motor to retract the plunger to the first position.
3. The method of claim 2 wherein the actuating step further comprises moving the plunger from the first position in a first cylinder portion to the second position in the mold cavity through a coaxial second cylinder portion, the second cylinder portion having a smaller cross-sectional area than the first cylinder portion to engage a flange of the plunger to limit the movement of the plunger into the mold cavity to a predetermined distance.
4. A method of forming wrist pin openings in die cast pistons comprising the steps of:
(a) moving a movable die having a first cut-away portion to mate with a stationary die having a second cut-away portion, the cut-away portions of the mated dies cooperating to form a cavity having the shape of a piston,
(b) introducing a molten metal into the cavity through a plurality of gates so that the molten metal substantially fills the cavity,
(c) cooling the introduced molten metal for an interval of time sufficient for the metal to solidify in the gates, and
(d) ramming two opposing plungers into the semi-molten metal to displace the metal to form a pair of wrist pin openings and to compress the displaced metal to intensify the mechanical properties of the metal surrounding the openings.
5. A method of forming wrist pin openings in a piston comprising the steps of:
(a) forming a mold cavity for casting the piston,
(b) transferring at least a predetermined quantity of molten metal from a reservoir maintained at a predetermined pressure to a channel in communication with the reservoir,
(c) introducing a predetermined quantity of molten metal from the channel through gates into the mold cavity to substantially fill the mold cavity,
(d) cooling the introduced molten metal for an interval of time sufficient for the metal to solidify in the gates,
(e) driving two opposing plungers into the mold cavity to displace the molten metal contained therein,
(f) moving the plungers into the mold cavity until pressure within the displaced metal stops the plungers,
(g) retaining the displaced molten metal within the mold cavity, and -
(h) retracting the plungers from the mold cavity to a position external to the mold cavity to produce two wrist pin openings in the piston.
6. A method of forming wrist pin openings in a die cast piston comprising the steps of
(a) moving a movable die having a first cut-away portion to mate with a stationary die having a second cut-away portion, the cut-away portions of the mated dies cooperating to form a mold cavity having the shape of a piston,
(b) inducing a partial vacuum in the cavity to cause the molten metal to flow from a molten metal source to a channel,
(c) forcing a quantity of metal through the channel and gates under pressure into the cavity,
(d) cooling the molten metal to solidify the metal in the gates, and
(e) thrusting a plunger into the molten metal admitted into the mold cavity to displace the molten metal to form a wrist pin opening and to compress the displaced metal to intensify mechanical properties of the metal surrounding the opening.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US49961183A | 1983-05-31 | 1983-05-31 | |
US499611 | 1983-05-31 |
Publications (1)
Publication Number | Publication Date |
---|---|
EP0127366A1 true EP0127366A1 (en) | 1984-12-05 |
Family
ID=23985960
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP84303241A Withdrawn EP0127366A1 (en) | 1983-05-31 | 1984-05-14 | Method of die casting a piston |
Country Status (2)
Country | Link |
---|---|
EP (1) | EP0127366A1 (en) |
JP (1) | JPS59229270A (en) |
Cited By (24)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102008054718A1 (en) | 2008-12-16 | 2010-06-17 | Federal-Mogul Nürnberg GmbH | Casting mold for gravity casting, comprises wall section that is displaceable after beginning the filling of metal melt in direction of opposite-lying wall section, so that thin wall is producible compared with other areas of casting part |
CN103949491A (en) * | 2014-05-13 | 2014-07-30 | 四川中邦模具有限公司 | Automobile aluminum piston workblank extrusion forming equipment |
CN104338917A (en) * | 2014-11-11 | 2015-02-11 | 山东滨州渤海活塞股份有限公司 | Quick cooling die for aluminum pistons produced through gravity casting |
WO2015042437A1 (en) * | 2013-09-19 | 2015-03-26 | California Institute Of Technology | Systems and methods for fabricating structures including metallic glass-based material using low pressure casting |
US9328813B2 (en) | 2013-02-11 | 2016-05-03 | California Institute Of Technology | Systems and methods for implementing bulk metallic glass-based strain wave gears and strain wave gear components |
US9610650B2 (en) | 2013-04-23 | 2017-04-04 | California Institute Of Technology | Systems and methods for fabricating structures including metallic glass-based materials using ultrasonic welding |
US9783877B2 (en) | 2012-07-17 | 2017-10-10 | California Institute Of Technology | Systems and methods for implementing bulk metallic glass-based macroscale compliant mechanisms |
US10151377B2 (en) | 2015-03-05 | 2018-12-11 | California Institute Of Technology | Systems and methods for implementing tailored metallic glass-based strain wave gears and strain wave gear components |
US10155412B2 (en) | 2015-03-12 | 2018-12-18 | California Institute Of Technology | Systems and methods for implementing flexible members including integrated tools made from metallic glass-based materials |
US10174780B2 (en) | 2015-03-11 | 2019-01-08 | California Institute Of Technology | Systems and methods for structurally interrelating components using inserts made from metallic glass-based materials |
US10471652B2 (en) | 2013-07-15 | 2019-11-12 | California Institute Of Technology | Systems and methods for additive manufacturing processes that strategically buildup objects |
US10487934B2 (en) | 2014-12-17 | 2019-11-26 | California Institute Of Technology | Systems and methods for implementing robust gearbox housings |
US10941847B2 (en) | 2012-06-26 | 2021-03-09 | California Institute Of Technology | Methods for fabricating bulk metallic glass-based macroscale gears |
US10968527B2 (en) | 2015-11-12 | 2021-04-06 | California Institute Of Technology | Method for embedding inserts, fasteners and features into metal core truss panels |
US11014162B2 (en) | 2017-05-26 | 2021-05-25 | California Institute Of Technology | Dendrite-reinforced titanium-based metal matrix composites |
US11077655B2 (en) | 2017-05-31 | 2021-08-03 | California Institute Of Technology | Multi-functional textile and related methods of manufacturing |
US11123797B2 (en) | 2017-06-02 | 2021-09-21 | California Institute Of Technology | High toughness metallic glass-based composites for additive manufacturing |
US11155907B2 (en) | 2013-04-12 | 2021-10-26 | California Institute Of Technology | Systems and methods for shaping sheet materials that include metallic glass-based materials |
US11185921B2 (en) | 2017-05-24 | 2021-11-30 | California Institute Of Technology | Hypoeutectic amorphous metal-based materials for additive manufacturing |
US11198181B2 (en) | 2017-03-10 | 2021-12-14 | California Institute Of Technology | Methods for fabricating strain wave gear flexsplines using metal additive manufacturing |
US11400613B2 (en) | 2019-03-01 | 2022-08-02 | California Institute Of Technology | Self-hammering cutting tool |
US11591906B2 (en) | 2019-03-07 | 2023-02-28 | California Institute Of Technology | Cutting tool with porous regions |
US11680629B2 (en) | 2019-02-28 | 2023-06-20 | California Institute Of Technology | Low cost wave generators for metal strain wave gears and methods of manufacture thereof |
US11859705B2 (en) | 2019-02-28 | 2024-01-02 | California Institute Of Technology | Rounded strain wave gear flexspline utilizing bulk metallic glass-based materials and methods of manufacture thereof |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2057074A (en) * | 1932-10-24 | 1936-10-13 | Nat Bronze & Aluminum Foundry | Method and apparatus for making cast metal articles |
US3068539A (en) * | 1960-08-04 | 1962-12-18 | Thompson Ramo Wooldridge Inc | High pressure permanent molding |
US3268960A (en) * | 1964-09-08 | 1966-08-30 | Glenn R Morton | Method of and means for producing dense articles from molten materials |
-
1984
- 1984-05-14 EP EP84303241A patent/EP0127366A1/en not_active Withdrawn
- 1984-05-29 JP JP10766384A patent/JPS59229270A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2057074A (en) * | 1932-10-24 | 1936-10-13 | Nat Bronze & Aluminum Foundry | Method and apparatus for making cast metal articles |
US3068539A (en) * | 1960-08-04 | 1962-12-18 | Thompson Ramo Wooldridge Inc | High pressure permanent molding |
US3268960A (en) * | 1964-09-08 | 1966-08-30 | Glenn R Morton | Method of and means for producing dense articles from molten materials |
Cited By (35)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102008054718B4 (en) * | 2008-12-16 | 2012-11-22 | Federal-Mogul Nürnberg GmbH | Casting mold for gravity casting and gravity casting |
DE102008054718A1 (en) | 2008-12-16 | 2010-06-17 | Federal-Mogul Nürnberg GmbH | Casting mold for gravity casting, comprises wall section that is displaceable after beginning the filling of metal melt in direction of opposite-lying wall section, so that thin wall is producible compared with other areas of casting part |
US11920668B2 (en) | 2012-06-26 | 2024-03-05 | California Institute Of Technology | Systems and methods for implementing bulk metallic glass-based macroscale gears |
US10941847B2 (en) | 2012-06-26 | 2021-03-09 | California Institute Of Technology | Methods for fabricating bulk metallic glass-based macroscale gears |
US9783877B2 (en) | 2012-07-17 | 2017-10-10 | California Institute Of Technology | Systems and methods for implementing bulk metallic glass-based macroscale compliant mechanisms |
US9328813B2 (en) | 2013-02-11 | 2016-05-03 | California Institute Of Technology | Systems and methods for implementing bulk metallic glass-based strain wave gears and strain wave gear components |
US9791032B2 (en) | 2013-02-11 | 2017-10-17 | California Institute Of Technology | Method for manufacturing bulk metallic glass-based strain wave gear components |
US11155907B2 (en) | 2013-04-12 | 2021-10-26 | California Institute Of Technology | Systems and methods for shaping sheet materials that include metallic glass-based materials |
US9610650B2 (en) | 2013-04-23 | 2017-04-04 | California Institute Of Technology | Systems and methods for fabricating structures including metallic glass-based materials using ultrasonic welding |
US10471652B2 (en) | 2013-07-15 | 2019-11-12 | California Institute Of Technology | Systems and methods for additive manufacturing processes that strategically buildup objects |
WO2015042437A1 (en) * | 2013-09-19 | 2015-03-26 | California Institute Of Technology | Systems and methods for fabricating structures including metallic glass-based material using low pressure casting |
US9868150B2 (en) | 2013-09-19 | 2018-01-16 | California Institute Of Technology | Systems and methods for fabricating structures including metallic glass-based materials using low pressure casting |
CN103949491A (en) * | 2014-05-13 | 2014-07-30 | 四川中邦模具有限公司 | Automobile aluminum piston workblank extrusion forming equipment |
CN104338917B (en) * | 2014-11-11 | 2016-08-24 | 山东滨州渤海活塞股份有限公司 | A kind of gravitational casting aluminium recovery quickly cools down mould |
CN104338917A (en) * | 2014-11-11 | 2015-02-11 | 山东滨州渤海活塞股份有限公司 | Quick cooling die for aluminum pistons produced through gravity casting |
US10487934B2 (en) | 2014-12-17 | 2019-11-26 | California Institute Of Technology | Systems and methods for implementing robust gearbox housings |
US10151377B2 (en) | 2015-03-05 | 2018-12-11 | California Institute Of Technology | Systems and methods for implementing tailored metallic glass-based strain wave gears and strain wave gear components |
US10690227B2 (en) | 2015-03-05 | 2020-06-23 | California Institute Of Technology | Systems and methods for implementing tailored metallic glass-based strain wave gears and strain wave gear components |
US10883528B2 (en) | 2015-03-11 | 2021-01-05 | California Institute Of Technology | Systems and methods for structurally interrelating components using inserts made from metallic glass-based materials |
US10174780B2 (en) | 2015-03-11 | 2019-01-08 | California Institute Of Technology | Systems and methods for structurally interrelating components using inserts made from metallic glass-based materials |
US10953688B2 (en) | 2015-03-12 | 2021-03-23 | California Institute Of Technology | Systems and methods for implementing flexible members including integrated tools made from metallic glass-based materials |
US10155412B2 (en) | 2015-03-12 | 2018-12-18 | California Institute Of Technology | Systems and methods for implementing flexible members including integrated tools made from metallic glass-based materials |
US10968527B2 (en) | 2015-11-12 | 2021-04-06 | California Institute Of Technology | Method for embedding inserts, fasteners and features into metal core truss panels |
US11198181B2 (en) | 2017-03-10 | 2021-12-14 | California Institute Of Technology | Methods for fabricating strain wave gear flexsplines using metal additive manufacturing |
US11839927B2 (en) | 2017-03-10 | 2023-12-12 | California Institute Of Technology | Methods for fabricating strain wave gear flexsplines using metal additive manufacturing |
US11185921B2 (en) | 2017-05-24 | 2021-11-30 | California Institute Of Technology | Hypoeutectic amorphous metal-based materials for additive manufacturing |
US11905578B2 (en) | 2017-05-24 | 2024-02-20 | California Institute Of Technology | Hypoeutectic amorphous metal-based materials for additive manufacturing |
US11014162B2 (en) | 2017-05-26 | 2021-05-25 | California Institute Of Technology | Dendrite-reinforced titanium-based metal matrix composites |
US11077655B2 (en) | 2017-05-31 | 2021-08-03 | California Institute Of Technology | Multi-functional textile and related methods of manufacturing |
US11123797B2 (en) | 2017-06-02 | 2021-09-21 | California Institute Of Technology | High toughness metallic glass-based composites for additive manufacturing |
US11773475B2 (en) | 2017-06-02 | 2023-10-03 | California Institute Of Technology | High toughness metallic glass-based composites for additive manufacturing |
US11680629B2 (en) | 2019-02-28 | 2023-06-20 | California Institute Of Technology | Low cost wave generators for metal strain wave gears and methods of manufacture thereof |
US11859705B2 (en) | 2019-02-28 | 2024-01-02 | California Institute Of Technology | Rounded strain wave gear flexspline utilizing bulk metallic glass-based materials and methods of manufacture thereof |
US11400613B2 (en) | 2019-03-01 | 2022-08-02 | California Institute Of Technology | Self-hammering cutting tool |
US11591906B2 (en) | 2019-03-07 | 2023-02-28 | California Institute Of Technology | Cutting tool with porous regions |
Also Published As
Publication number | Publication date |
---|---|
JPS59229270A (en) | 1984-12-22 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
EP0127366A1 (en) | Method of die casting a piston | |
US3106002A (en) | Die-casting method | |
EP0120649B1 (en) | Improvements in or relating to the squeeze casting of articles | |
CN102527997B (en) | Controlled pressure casting | |
EP0772278B1 (en) | Apparatus for casting conductor of rotor of induction motor | |
US4779665A (en) | Die casting apparatus and process comprising in-die plunger densification to form a bore through a product casting | |
EP0546664A1 (en) | Closed shot die casting | |
JP3418027B2 (en) | Molten forging equipment | |
US6499530B2 (en) | Apparatus and method of forming battery parts | |
US6363996B1 (en) | Apparatus and method of forming battery parts | |
US4779666A (en) | Die casting process and apparatus comprising in-die plunger densification | |
EP0438279A1 (en) | A method and system for gas injection moulding a hollow object | |
US4562875A (en) | Die-casting method and apparatus | |
US3387646A (en) | Method and apparatus for highpressure permanent molding | |
US4836267A (en) | Vertical die casting method and apparatus | |
GB2056338A (en) | Die-casting method and apparatus | |
US6651727B1 (en) | Method and apparatus for injecting molten metal into a mold | |
US4846252A (en) | Secondary pressurization casting method | |
US6684935B2 (en) | Intensification through displacement of a coacting mold member | |
US4399859A (en) | Diecasting assembly | |
EP1640088B1 (en) | Pressure castings of battery terminals | |
US3118225A (en) | Method of casting | |
JP3417988B2 (en) | Molten forging equipment | |
US2866240A (en) | Mechanism for reducing porosity of die castings | |
JPS59309B2 (en) | Injection molding method with degassing inside the mold and degassing device for mold |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PUAI | Public reference made under article 153(3) epc to a published international application that has entered the european phase |
Free format text: ORIGINAL CODE: 0009012 |
|
AK | Designated contracting states |
Designated state(s): DE FR GB IT |
|
STAA | Information on the status of an ep patent application or granted ep patent |
Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN |
|
18D | Application deemed to be withdrawn |
Effective date: 19850806 |
|
RIN1 | Information on inventor provided before grant (corrected) |
Inventor name: LINDSEY, JOHN L. |