Hybrid cam bore sand core with metal chills for cast aluminum block

A system for making a hybrid cam bore sand core with metal chills for an engine block includes an engine block cast of an aluminum material. A camshaft bore extends through the engine block. A cam bore sand core with at least one metal chill is positioned within the camshaft bore. A body portion of the at least one metal chill is positioned in direct contact with a cam bearing surface of at least one cam bearing member during casting of the engine block to increase a cooling rate of the at least one cam bearing member and create a crystalline material depth of the cam bearing member having enhanced mechanical properties.

INTRODUCTION

The present disclosure relates to cast engine blocks and methods for casting engine blocks.

Automobile vehicle engine blocks may be cast from metals such as iron and aluminum. The use of aluminum reduces a weight of the engine block compared to iron and therefore reduces vehicle weight which provides improved fuel efficiency for the vehicle. The mechanical properties of aluminum are not equivalent to those of iron, therefore processes have been developed to locally enhance the mechanical properties of aluminum in high load areas of the engine block, particularly in the areas of the crankshaft and crankshaft bearing journals.

Casting molds commonly use casting sand to define a negative volume defining a desired geometry for the metal to be subsequently poured into the mold. It is desirable in aluminum casting to locally enhance the mechanical properties of the aluminum in areas of increased loading such as at the crankshaft bearing journals. It is known that increasing a cooling rate of the aluminum provides localized enhancement of the mechanical properties of the aluminum. Casting sand however acts as a thermal insulator which retards the cooling rate of aluminum at the areas of contact of the casting sand with the aluminum. Casting “chills” are therefore introduced into the mold prior to pour which are made of a material such as iron having a heat transfer coefficient that enhances a cooling rate of the aluminum at the contact locations of the aluminum and the chill. Known chills extend for an entire length of the engine block in an area of the crankshaft bearing journals, which are subsequently removed from the mold after the cast aluminum cools. A geometry of the camshaft area of known engine block designs inhibits the removal of chills in the camshaft journal bearing areas, therefore enhancement of the aluminum material at the camshaft journal bearings has through the use of chills not been achievable. Such enhancement would permit increased horsepower output from the engine with no weight penalty.

Thus, while current aluminum engine block casting processes achieve their intended purpose, there is a need for a new and improved system and method for casting aluminum engine blocks.

SUMMARY

According to several aspects, a system for making a hybrid cam bore sand core with metal chills for an automobile vehicle engine block includes an automobile vehicle engine block cast of an aluminum material. A camshaft bore extends through the engine block. A cam bore sand core with at least one metal chill is positioned within the camshaft bore. A body portion of the at least one metal chill is positioned in direct contact with a cam bearing surface of at least one cam bearing member during casting of the engine block to increase a cooling rate of the at least one cam bearing member and create a crystalline material depth of the cam bearing member having enhanced mechanical properties.

In another aspect of the present disclosure, the at least one metal chill defines a first metal chill and a second metal chill individually having an outward directed body portion, an inward directed body end, and a connecting body portion positioned between the inward directed body end and the outward directed body portion.

In another aspect of the present disclosure, the outward directed body portion includes a first tapering surface positioned to directly contact the cam bearing surface of a first one of the at least one cam bearing member.

In another aspect of the present disclosure, the inward directed body end includes a second tapering surface positioned to directly contact the cam bearing surface of a second one of the at least one cam bearing member.

In another aspect of the present disclosure, the first tapering surface defines a first angle with respect to a horizontal plane and the second tapering surface defines a second angle with respect to a second horizontal plane.

In another aspect of the present disclosure, the connecting body portion includes a smaller diameter inward directed body end and a larger diameter of the outward directed body portion.

In another aspect of the present disclosure, a first sand core surrounds the connecting body portion of the first metal chill and a second sand core surrounds the connecting body portion of the second metal chill.

In another aspect of the present disclosure, a first extension member is integrally created on the inward directed body end of the first metal chill and a second extension member integrally is created on the inward directed body end of the second metal chill.

In another aspect of the present disclosure, a third sand core is positioned between the first metal chill and the second metal chill, the first extension member is embedded in and retains the third sand core in contact with the inward directed body end of the first metal chill during molding, and the second extension member is embedded in and retains the third sand core in contact with the inward directed body end of the second metal chill during molding.

In another aspect of the present disclosure, the first metal chill is removed from the camshaft bore after molding in a first direction and the second metal chill is removed from the camshaft bore in a second direction opposite to the first direction.

According to several aspects, a system for making a hybrid cam bore sand core with metal chills for an automobile vehicle engine block includes an automobile vehicle engine block casting of an aluminum material. A camshaft bore extends through the engine block casting. A cam bore sand core with a first metal chill and a second metal chill is positioned within the camshaft bore during pouring of the engine block casting. A body portion of the first metal chill is positioned in direct contact with a cam bearing surface of a first cam bearing member during pouring of the engine block casting and a body portion of the second metal chill positioned in direct contact with a cam bearing surface of a second bearing member during pouring of the engine block casting. The first metal chill and the second metal chill are provided of a metal to increase a cooling rate of the aluminum material and to create a crystalline material depth of the first cam bearing member and the second cam bearing member having enhanced mechanical properties. The body portion of the first metal chill includes a first tapering surface and the body portion of the second metal chill includes a second tapering surface, the first tapering surface and the second tapering surface allowing sliding removal of the first metal chill in a first direction and sliding removal of the second metal chill in a second direction opposite to the first direction.

In another aspect of the present disclosure, the first metal chill and the second metal chill individually include an inward directed body end and a connecting body portion positioned between the inward directed body end and the body portion.

In another aspect of the present disclosure, the inward directed body end includes a third tapering surface defining an angle.

In another aspect of the present disclosure, the first metal chill and the second metal chill further include a central body portion directly connected to the body portion via a first connecting body portion and an inward directed body end integrally connected to the central body portion by a second connecting body portion.

In another aspect of the present disclosure, the inward directed body end of the first metal chill is in direct contact with the inward directed body end of the second metal chill.

In another aspect of the present disclosure, the inward directed body end of the first metal chill is separated from the inward directed body end of the second metal chill by a gap.

In another aspect of the present disclosure, the inward directed body end of the first metal chill and the inward directed body end of the second metal chill are in direct contact with a portion of a cam bearing surface of a third cam bearing member.

According to several aspects, a method for making a hybrid cam bore sand core with metal chills for a cast aluminum engine block includes: preparing an automobile vehicle engine block mold negative portion having a sand core; positioning a cam bore sand core with at least one metal chill within a camshaft bore of the sand core; and casting an automobile vehicle engine block from an aluminum material using the engine block mold negative having a body portion of the at least one metal chill in direct contact with a cam bearing surface of at least one cam bearing member during the casting of the engine block to increase a cooling rate of the at least one cam bearing member and to create a crystalline material depth of the cam bearing member having enhanced mechanical properties.

In another aspect of the present disclosure, the method further includes forming the at least one metal chill as a first metal chill and a second metal chill further individually having an inward directed body end and a connecting body portion positioned between the inward directed body end and the body portion.

In another aspect of the present disclosure, the method further includes forming the at least one metal chill as a first metal chill and a second metal chill further individually having a central body portion directly connected to the body portion via a first connecting body portion and an inward directed body end integrally connected to the central body portion by a second connecting body portion.

DETAILED DESCRIPTION

Referring toFIG.1, a system and method for making a hybrid cam bore sand core with metal chills for a cast aluminum engine block10includes an aluminum as-cast engine block12. The as-cast engine block12is shown prior to machining and includes multiple cylinder bores14and a crankcase cavity16having multiple crankshaft bearing supports18(only one is visible in this view). According to several aspects, the as-cast engine block12includes a camshaft bore20with a cam bore sand core with metal chills22positioned within the camshaft bore20, shown after casting and prior to removal of the cam bore sand core with metal chills22. The cam bore sand core with metal chills22is further discussed in reference toFIGS.2and4through6.

Referring toFIG.2and again toFIG.1, a mold negative portion24is shown which is formed within an engine block mold (not shown) prior to pour of a molten aluminum into the mold. The mold negative portion24includes a crankcase sand core26with a crankshaft chill28extending throughout a lower portion of the crankcase sand core26. After the aluminum pour into the mold is complete with aluminum cooling and crystallization which produces the as-cast engine block12discussed in reference toFIG.1, the crankcase sand core26is broken apart and removed from the as-cast engine block12and the crankshaft chill28is removed for example in a downward direction30for reuse.

The mold negative portion24further includes the cam bore sand core with metal chills22. According to several aspects, the cam bore sand core with metal chills22includes a camshaft sand core32together with a first metal chill34and a second metal chill36. After the aluminum pour and aluminum cooling and crystallization, the camshaft sand core32is broken apart and removed from the as-cast engine block12and the first metal chill34and the second metal chill36are individually slidably removed from the as-cast engine block12as discussed in further detail in reference toFIG.4for reuse.

Referring toFIG.3and again toFIGS.1and2, the as-cast engine block12described in reference toFIG.2is shown after machining to produce a finished engine block38. The finished engine block38includes multiple machined cylinder bores40. The crankshaft bearing supports18are machined to receive multiple individual bearing journals42, and multiple crankshaft bearing caps44are fastened onto the finished engine block38and are ready to receive a crankshaft (not shown). After finish machining of the camshaft bearing members in the camshaft bore20, which are described in greater detail in reference toFIG.5, multiple individual camshaft journal bearings46(only one is visible in this view) are installed. Multiple machined surfaces including a cylinder block deck surface48are also provided at this time.

Referring toFIG.4and again toFIGS.2and3, according to several aspects the cam bore sand core with metal chills22includes the first metal chill34and the second metal chill36. The first metal chill34includes a first metal chill body50, and the second metal chill36includes a second metal chill body52which is substantially identical to the first metal chill body50and oppositely directed. The first metal chill body50and the second metal chill body52include an outward directed body portion54, an inward directed body end56, and a connecting body portion58positioned between the inward directed body end56and the outward directed body portion54and having a diameter smaller than a diameter of the inward directed body end56and a diameter of the outward directed body portion54.

A first tapering surface60of the outward directed body portion54is positioned to directly contact a first cam bearing surface62of a first cam bearing member64during casting. The first cam bearing member64is created as the aluminum material cools in the mold. A second tapering surface66of the inward directed body end56is positioned to directly contact a second cam bearing member68created as the aluminum material cools in the mold to form the second cam bearing member68. The second metal chill36is similarly created and includes a third tapering surface70positioned to directly contact a third cam bearing surface72and a fourth tapering surface74positioned to directly contact a fourth cam bearing surface76.

A first sand core78surrounds the connecting body portion58of the first metal chill34. A third sand core80is positioned between the first metal chill34and the second metal chill36. A second sand core82surrounds a connecting body portion58′ of the second metal chill36. According to several aspects, a first extension member84may be integrally created on the inward directed body end56of the first metal chill34and a second extension member86may be integrally created on an inward directed body end56′ of the second metal chill36. The first extension member84is embedded in and helps retain the third sand core80in contact with the inward directed body end56during molding, and the second extension member86is embedded in and helps retain the third sand core80in contact with the inward directed body end56′ of the second metal chill36during molding.

To assist with removal of the first metal chill34from the as-cast engine block12after the aluminum casting material cools, a first release member88may be provided as an integral extension of the outward directed body portion54. The first metal chill34is removed from the as-cast engine block12in a removal direction90by grasping or coupling a removal tool (not shown) to the first release member88. Similarly, to assist with removal of the second metal chill36from the as-cast engine block12after the aluminum casting material cools, a second release member92may be provided as an integral extension of the outward directed body portion54′. The second metal chill36is removed from the as-cast engine block12in a removal direction94, opposite to the removal direction90, by grasping or coupling a removal tool (not shown) to the second release member92.

Referring toFIG.5and again toFIGS.1through4, the first tapering surface60of the outward directed body portion54defines an angle alpha (α) with respect to a horizontal plane96. The first cam bearing surface62directly abuts the first tapering surface60during aluminum material pour and therefore permits an enhanced cooling rate of the first cam bearing surface62to a crystalline material depth98which creates enhanced mechanical properties of the first cam bearing surface62compared to aluminum material cooling at a normal cooling rate with air exposure or a retarded cooling rate if the aluminum is in contact with a sand core. Due to the crystalline material depth98of the first cam bearing surface62, as the first cam bearing surface62is subsequently machined to be parallel with the horizontal plane96and to accept a bearing journal the enhanced mechanical properties of the first cam bearing surface62are retained.

According to several aspects, because the inward directed body end56is embedded between the first sand core78and the second sand core80which may retard a cooling rate of the second cam bearing member68, the inward directed body end56may have a greater length than the outward directed body portion54, which further enhances heat transfer between the inward directed body end56and the second cam bearing member68. The inward directed body end56may therefore include a cylindrical portion100having a major diameter102which transitions into a conical portion104having a third tapering surface106which defines a portion of the second tapering surface66. The third tapering surface106may define an angle beta (β) with respect to a horizontal plane108. According to several aspects the angle β may be equal to the angle α or may vary from the angle α as desired to enhance removal of the first metal chill34and the second metal chill36. A second cam bearing surface110directly abuts the third tapering surface106during aluminum material pour and therefore permits an enhanced cooling rate of the second cam bearing surface110to a crystalline material depth112which creates enhanced mechanical properties of the second cam bearing surface110. Due to the crystalline material depth112of the second cam bearing surface110, as the second cam bearing surface110is subsequently machined to be parallel with the horizontal plane108and to accept a bearing journal the enhanced mechanical properties of the second cam bearing surface110are retained.

Referring toFIG.6and again toFIGS.1through5, according to several aspects a cam bore sand core with metal chills114is modified from the cam bore sand core with metal chills22to extend lengths of a third metal chill116and an oppositely directed fourth metal chill118such that the third metal chill116and the fourth metal chill118in combination extend for substantially an entire length of the camshaft bore20of the as-cast engine block12. The third metal chill116includes an outward directed body portion120, a central body portion122directly connected to the outward directed body portion120via a first connecting body portion124, and an inward directed body end126directly connected by a second connecting body portion128to the central body portion122. A metal material such as iron, steel, or other alloys used for the third metal chill116creates crystalline material depths of the aluminum material present at a first cam bearing surface130directly contacting the outward directed body portion120, a cam bearing surface132directly contacting the central body portion122, and a cam bearing surface134directly contacting the inward directed body end126.

Similar to the third metal chill116the fourth metal chill118includes an outward directed body portion136, a central body portion138directly connected to the outward directed body portion136via a first connecting body portion140, and an inward directed body end142directly connected by a second connecting body portion144to the central body portion138. A metal material such as iron, steel or other alloys used for the fourth metal chill118creates crystalline material depths of the aluminum material present at a fourth cam bearing surface146directly contacting the outward directed body portion136, a cam bearing surface148directly contacting the central body portion138, and a portion of the cam bearing surface134directly contacting the inward directed body end142.

According to several aspects the inward directed body end126and the inward directed body end142may directly contact each other, or a gap150may be provided between the inward directed body end126and the inward directed body end142. After the aluminum material cools in the mold, the third metal chill116is removed from the as-cast engine block12in a direction152and the fourth metal chill118is removed from the as-cast engine block12in a direction154oppositely directed with respect to the direction152. Similar to the cam bore sand core with metal chills22, sand cores are provided for the cam bore sand core with metal chills114. A first sand core156surrounds the first connecting body portion124and a second sand core158surrounds the second connecting body portion128of the third metal chill116. A fourth sand core160surrounds the second connecting body portion144of the fourth metal chill118and a third sand core162surrounds the first connecting body portion140. According to several aspects, any or all of the metal chills of the present disclosure may be solid, or may include a bore156, therefore making the metal chills hollow for all or a portion of a length of the metal chills.

With continuing reference toFIGS.4,5and6, the metal chills of the present disclosure, including the first metal chill34, the second metal chill36, the third metal chill116and the fourth metal chill118are made of a material having a high coefficient of thermal transfer, and preferably with a melting point above the melting point of aluminum. The metal chills of the present disclosure may therefore be provided of a metal such as but not limited to iron, steel or other alloys. This material selection for the metal chills permits localized rapid cooling of the aluminum material at the cam bearing surfaces in direct contact with the metal chills after aluminum pour into the engine block mold, with consequent formation of the crystalline material depths at the cam bearing surfaces described herein.

A system and method for making a hybrid cam bore sand core with metal chills for a cast aluminum engine block10of the present disclosure adds chills to the block or crankcase which are embedded in the cam core to improve the aluminum micro-structure in high stress transition areas between the cam tunnel and bulkheads. Metal chills of the present disclosure are positioned in the cam core to improve the aluminum material properties near a bottom of the cam tunnel which transitions into the bulkhead, which is a high stress region in a V8 cylinder block.

The metal chills of the present disclosure may be applied to all cam journals of the engine block. The metal chills may be single piece or multiple pieces. Metal chill materials can be ductile or cast iron, steel, or other alloys. The metal chills may be solid or may also be hollow.

A system and method for making a hybrid cam bore sand core with metal chills for a cast aluminum engine block10of the present disclosure offers several advantages. These include provision of a hybrid cam bore sand core with metal chills to increase local cooling rate during solidification and to improve mechanical properties of the cast aluminum in areas below the cam tunnel. The metal chills directly contact surfaces of the cam bore bearing journals. The configuration including angled surfaces of the metal chills of the present disclosure promote easy removal after casting solidification and casting sand shakeout.