Casting of engine blocks

Information

  • Patent Grant
  • 6527040
  • Patent Number
    6,527,040
  • Date Filed
    Monday, June 11, 2001
    23 years ago
  • Date Issued
    Tuesday, March 4, 2003
    21 years ago
Abstract
In assembly of engine block mold package, a water jacket slab core is assembled on a barrel crankcase core having a plurality of barrels on which cylinder bore liners are positioned. Some of the barrels include a core print on a distal end thereof. The water jacket slab core includes a plurality of core prints each in mating relation with a respective barrel core print and a plurality of bore liner positioning surfaces that each engage a respective distal end of a respective cylinder bore liner when the water jacket slab core is assembled on the barrels.
Description




FIELD OF THE INVENTION




The present invention relates to precision sand casting of engine cylinder blocks, such as engine cylinder V-blocks, with cast-in-place cylinder bore liners.




BACKGROUND OF THE INVENTION




In the manufacture of cast iron engine V-blocks, a so-called integral barrel crankcase core has been used and consists of a plurality of barrels formed integrally on a crankcase region of the core. The barrels form the cylinder bores in the cast iron engine block without the need for bore liners.




In the precision sand casting process of an aluminum internal combustion engine cylinder V-block, an expendable mold package is assembled from a plurality of resin-bonded sand cores (also known as mold segments) that define the internal and external surfaces of the engine V-block. Each of the sand cores is formed by blowing resin-coated foundry sand into a core box and curing it therein.




Traditionally, in past manufacture of an aluminum engine V-block with cast-in-place bore liners, the mold assembly method for the precision sand process involves positioning a base core on a suitable surface and building up or stacking separate crankcase cores, side cores, barrel cores with liners thereon, water jacket cores, front and rear end cores, a cover (top) core, and other cores on top of the base core or on one another. The other cores can include an oil gallery core, side cores and a valley core. Additional cores may be present as well depending on the engine design.




During assembly or handling, the individual cores may rub against one another at the joints therebetween and result in loss of a small amount of sand abraded off the mating joint surfaces. Abrasion and loss of sand in this manner is disadvantageous and undesirable in that the loose sand may fall onto the base core, or may become trapped in small spaces within the mold package, contaminating the casting.




Additionally, when fully assembled, the typical engine V-block mold package will have a plurality of parting lines (joint lines) between mold segments, visible on the exterior surface of the assembled mold package. The external parting lines typically extend in myriad different directions on the mold package surface. A mold designed to have parting lines extending in myriad directions is disadvantageous in that if contiguous mold segments do not mate precisely with each other, as is often observed, molten metal can flow out of the mold cavity via the gaps at the parting lines. Molten metal loss is more prone to occur where three or more parting lines converge.




The removal of thermal energy from the metal in the mold package is an important consideration in the foundry process. Rapid solidification and cooling of the casting promotes a fine grain structure in the metal leading to desirable material properties such as high tensile and fatigue strength, and good machinability. For those engine designs with highly stressed bulkhead features, the use of a thermal chill may be necessary. The thermal chill is much more thermally conductive than foundry sand. It readily conducts heat from those casting features it contacts. The chill typically consists of one or more steel or cast iron bodies assembled in the mold in a manner to shape some portion of the bulkhead features of the casting. The chills may be placed into the base core tooling and a core formed about them, or they may be assembled into the base core or between the crankcase cores during mold assembly.




It is difficult to remove chills of this type from the mold package after the casting is solidified, and prior to heat treatment, because the risers are encased by the sand of the mold package, and may also be entrapped between the casting and some feature of the runner or risering system. If the chills are allowed to remain with the casting during heat treatment, they can impair the heat treatment process. The use of slightly warm chills at the time of mold filling is a common foundry practice. This is done to avoid possible condensation of moisture or core resin solvents onto the chills, which can lead to significant casting quality problems. It is difficult to “warm” the type of chill described above, as a result of the inherent time delay from mold assembly to mold filling.




Another method to rapidly cool portions of the casting involves using the semi-permanent molding (SPM) process. This method employs convective cooling of permanent mold tooling by water, air or other fluid. In the SPM process, the mold package is placed into the SPM machine. The SPM machine includes an actively cooled permanent (reusable) tool designed to shape some portion of the bulkhead features. The mold is filled with metal. After several minutes have passed, the mold package and casting are separated from the permanent mold tool and the casting cycle is repeated. Such machines typically employ multiple molding stations to make efficient use of the melting and mold filling equipment. This leads to undesirable system complexity and difficulty in achieving process repeatability.




In past manufacture of an aluminum engine V-block with cast-in-place bore liners using separate crankcase cores and barrel cores with liners thereon, the block must be machined in a manner to insure, among other things, that the cylinder bores (formed from the bore liners positioned on the barrel features of the barrel cores) have uniform bore liner wall thickness, and other critical block features are accurately machined. This requires the liners to be accurately positioned relative to one another within the casting, and that the block is optimally positioned relative to the machining equipment.




The position of the bore liners relative to one another within a casting is determined in large part by the dimensional accuracy and assembly clearances of the mold components (cores) used to support the bore liners during the filling of the mold. The use of multiple mold components to support the liners leads to variation in the position of the liners, due to the accumulation, or “stack-up” of dimensional variation and assembly clearances of the multiple mold components.




To prepare the cast V-block for machining, it is held in either a so-called OP10 or a “qualification” fixture while a milling machine accurately prepares flat, smooth reference sites (machine line locator surfaces) on the cast V-block that are later used to position the V-block in other machining fixtures at the engine block machining plant. The OP10 fixture is typically present at the engine block machining plant, while the “qualification” fixture is typically present at the foundry producing the cast blocks. The purpose of either fixture is to provide qualified locator surfaces on the cast engine block. The features on the casting which position the casting in the OP10 or qualification fixture are known as “casting locators”. Typically, the OP10 or qualification fixture for V-blocks with cast-in-place bore liners uses as casting locators the curved inside surface of at least one cylinder bore liner from each bank of cylinders. Using curved surfaces as casting locators is disadvantageous because moving the casting in a single direction causes a complex change in spatial orientation of the casting. This is further compounded by using at least one liner surface from each bank, as the banks are aligned at an angle to one another. As a practical matter, machinists prefer to design fixtures that first receive and support a casting on three “primary” casting locators that establish a reference plane. The casting then is moved against two “secondary” casting locators, establishing a reference line. Finally, the casting is moved along that line until a single “tertiary” casting locator establishes a reference point. The orientation of the casting is now fully established. The casting is then clamped in place while machining is performed. The use of curved and angled surfaces to orient the casting in the OP10 or “qualification” fixture can result in less precise positioning in the fixture and ultimately in less precise machining of the cast V-block, because the result of moving the casting in a given direction, prior to clamping in position for machining, is complex and potentially non-repeatable.




An object of the invention is to use an integral barrel crankcase core in the production of aluminum and other engine V-blocks that include cast-in-place bore liners where the barrel features are adapted to receive cylinder bore liners in a manner that the liners and casting locators are accurately positioned one to the other in the mold package and in the cast engine block produced in the mold package.




Another object of the present invention is to provide method and apparatus for sand casting of engine cylinder blocks in a manner that overcomes one or more of the above disadvantages.




SUMMARY OF THE INVENTION




The present invention involves method and apparatus for assembling an engine block mold package as well as a mold package wherein a water jacket slab core is assembled on an integral barrel crankcase core having a plurality of barrels on an integral crankcase region. Each barrel includes a cylinder bore liner disposed thereon. One or more of the barrels includes a core print on a distal end thereof. The water jacket slab core includes one or more core prints in cooperating relation with a barrel core print and a plurality of bore liner positioning surfaces that each engage a respective distal end region of a respective bore liner.




Pursuant to an illustrative embodiment of the invention, the core prints of the water jacket slab core comprise core print openings that are disposed proximate a respective barrel distal end to receive a respective elongated barrel core print. The water jacket slab core includes a conical bore liner positioning surface proximate each core print opening to engage the upper distal end of each cylinder bore liner on each barrel. The conical bore liner positioning surfaces on the water jacket slab core cooperate with conical bore liner positioning surfaces on the barrels proximate the crankcase region to center the cylinder bore liners on the barrels. For a V-engine block mold package, a pair of such water jacket slab cores is used with one for each bank of barrels on the integral barrel crankcase core.




Advantages and objects of the present invention will be better understood from the following detailed description of the invention taken with the following drawings.











DESCRIPTION OF THE DRAWINGS





FIG. 1

is a flow diagram illustrating practice of an illustrative embodiment of the invention to assemble an engine V block mold package. The front end core is omitted from the views of the assembly sequence for convenience.





FIG. 2

is a perspective view of an integral barrel crankcase core having bore liners on barrels thereof and casting locator surfaces on the crankcase region pursuant to an embodiment of the invention.





FIG. 3

is a sectional view of an engine block mold package pursuant to an embodiment of the invention where the right-hand cross-section of the barrel crankcase core is taken along lines


3





3


of

FIG. 2 through a

central plane of a barrel feature and where the left hand cross-section of the barrel crankcase core is taken along lines


3


′—


3


′ of

FIG. 2

between adjacent barrels.





FIG. 3A

is an enlarged sectional view of a barrel of the barrel crankcase core and a water jacket slab core assembly showing a cylinder bore liner on the barrel.





FIG. 3B

is a perspective view of a slab core having core print features for engagement to core prints of the barrels, lifter core, water jacket core, and end cores.





FIG. 3C

is a sectional view of a subassembly (core package) of cores residing on a temporary base.





FIG. 3D

is a sectional view of the subassembly (core package) positioned by a schematically shown manipulator at a cleaning station.





FIG. 3E

is an enlarged sectional view of a barrel of the barrel crankcase core and a water jacket slab core showing a cylinder bore liner with a taper only on an upper portion of its length.





FIG. 3F

is an enlarged sectional view of a barrel of the barrel crankcase core and a water jacket slab core showing an untapered cylinder bore liner on the barrel.





FIG. 4

is a perspective view of the engine block mold after the subassembly (core package) has been placed in the base core and the cover core is placed on the base core with chills omitted.





FIG. 5

is a schematic view of core box tooling for making the integral barrel crankcase core of

FIG. 2

showing closed and open positions of the barrel-forming tool elements.





FIG. 6

is a partial perspective view of core box tooling and resulting core showing open positions of the barrel-forming tool elements.











DESCRIPTION OF THE INVENTION





FIG. 1

depicts a flow diagram showing an illustrative sequence for assembling an engine cylinder block mold package


10


pursuant to an embodiment of the invention. The invention is not limited to the sequence of assembly steps shown as other sequences can be employed to assemble the mold package.




The mold package


10


is assembled from numerous types of resin-bonded sand cores including a base core


12


mated with an optional chill


28




a


, optional chill pallet


28




b


, and optional mold stripping plate


28




c


, an integral barrel crankcase core (IBCC)


14


having metal (e.g. cast iron, aluminum, or aluminum alloy) cylinder bore liners


15


thereon, two end cores


16


, two side cores


18


, two water jacket slab core assemblies


22


(each assembled from a water jacket core


22




a


, jacket slab core


22




b


, and a lifter core


22




c


), tappet valley core


24


, and a cover core


26


. The cores described above are offered for purposes of illustration and not limitation as other types of cores and core configurations may be used in assembly of the engine cylinder block mold package depending upon the particular engine block design to be cast.




The resin-bonded sand cores can be made using conventional core-making processes such as a phenolic urethane cold box or Furan hot box where a mixture of foundry sand and resin binder is blown into a core box and the binder cured with either a catalyst gas and/or heat. The foundry sand can comprise silica, zircon, fused silica, and others. A catalyzed binder can comprise Isocure binder available from Ashland Chemical Company.




For purposes of illustration and not limitation, the resin-bonded sand cores are shown in

FIG. 1

for use in assembly of an engine cylinder block mold package to cast an aluminum engine V8-block. The invention is especially useful, although not limited to, assembling mold packages


10


for precision sand casting of V-type engine cylinder blocks that comprise two rows of cylinder bores with planes through the centerlines of the bores of each row intersecting in the crankcase portion of the engine block casting. Common configurations include V6 engine blocks with 54, 60, 90, or 120 degrees of included angle between the two rows of cylinder bores and V8 engine blocks with a 90 degree angle between the two rows of cylinder bores, although other configurations may be employed.




The cores


14


,


16


,


18


,


22


, and


24


initially are assembled apart from the base core


12


and cover core


26


to form a subassembly


30


of multiple cores (core package), FIG.


1


. The cores


14


,


16


,


18


,


22


, and


24


are assembled on a temporary base or member TB that does not form a part of the final engine block mold package


10


. The cores


14


,


16


,


18


,


22


, and


24


are shown schematically in

FIG. 1

for convenience with more detailed views thereof in

FIGS. 2-5

.




As illustrated in

FIG. 1

, integral barrel crankcase core


14


is first placed on the temporary base TB. The core


14


includes a plurality of cylindrical barrels


14




a


on an integral crankcase core region


14




b


as shown in

FIGS. 2-3

and


5


-


6


. The barrel crankcase core


14


is formed as an integral, one-piece core having the combination of the barrels and the crankcase region in core box tooling


100


shown in

FIGS. 5-6

. A cam shaft passage-forming region


14




cs


may also be integrally formed on the crankcase region


14




b.






The core box tooling


100


comprises a base


102


on which first and second barrel-forming tool elements


104


are slidably disposed on guide pins


105


for movement by respective hydraulic cylinders


106


. A cover


107


is disposed on a vertically movable, accurately guided core machine platen


110


for movement by a hydraulic cylinder


109


toward the barrel-forming tool elements


104


. The elements


104


and cover


107


are moved from the solid positions of

FIG. 5

to the dashed line positions to form a cavity C into which the sand/binder mixture is blown and cured to form the core


14


. The ends of the core


14


are shaped by tool elements


104


and/or


107


. The core


14


then is removed from the tooling


100


by moving the tool elements


104


and cover


107


away from one another to expose the core


14


, the crankcase region


14




b


of which is shown somewhat schematically in

FIG. 6

for convenience.




The barrel-forming tool elements


104


are configured to form the barrels


14




a


and some exterior crankcase core surfaces, including casting locator surfaces


14




c


,


14




d


, and


14




e


. The cover


107


is configured to shape interior and other exterior crankcase surfaces of the core


14


. For purposes of illustration and not limitation, the tool elements


104


are shown including working surfaces


104




c


for forming two primary casting locator surfaces


14




c


. These two primary locator surfaces


14




c


can be formed at one end E


1


of the crankcase region


14




b


and a third similar locator surface (not shown but similar to surfaces


14




c


) can be formed at the other end E


2


of the crankcase region


14




b


, FIG.


2


. Three primary casting locator surfaces


14




c


establish a reference plane for use in known 3−2−1 casting location method. Two casting secondary locator surfaces


14




d


can be formed on one side CS


1


of the crankcase region


14




b


,

FIG. 2

, of the core


14


to establish a reference line. The right-hand tool element


104


in

FIG. 5

is shown including working surfaces


104




d


(one shown) for forming secondary locator surfaces


14




d


on side CS


1


of the core


14


. The left-hand tool element


104


optionally can include similar working surfaces


104




d


(one shown) to optionally form secondary locating surfaces


14




d


on the other side CS


2


of the core


14


. A tertiary casting locator surface


14




e


adjacent locator surface


14




c


,

FIG. 2

, can be formed on the end E


1


of crankcase region


14




b


by the same tool element that forms locator surface


14




c


at core end E


1


. The single tertiary locator surface


14




e


establishes a reference point. The six locating surfaces


14




c


,


14




d


,


14




e


will establish the three axis coordinate system for locating the cast engine block for subsequent machining operations.




In actual practice, more than six such casting locator surfaces may used. For example, a pair of geometrically opposed casting locator surfaces may optionally be “equalized” to function as a single locating point in the six point (3+2+1) locating scheme. Equalization is typically accomplished by the use of mechanically synchronized positioning details in the OP10 or qualification fixture. These positioning details contact the locator surface pairs in a manner that averages, or equalizes, the variability of the two surfaces. For example, an additional set of secondary locator surfaces similar to locator surfaces


14




d


optionally can be formed on the opposite side CS


2


of the core


14


by working surfaces


104




d


of the left-hand barrel forming tool element


104


in FIG.


5


. Moreover, additional primary locator and tertiary locator surfaces can be formed as well for a particular engine block casting design.




The locator surfaces


14




c


,


14




d


,


14




e


can be used to orient the engine block casting in subsequent aligning and machining operations without the need to reference one or more curved surfaces of two or more of the cylinder bore liners


15


.




Since the locator surfaces


14




c


,


14




d


,


14




e


are formed on the crankcase core region


14




b


using the same core box barrel-forming tool elements


104


that also form the integral barrels


14




a


, these locator surfaces are consistently and accurately positioned relative to the barrels


14




a


and thus the cylinder bores formed in the engine block casting.




As mentioned above, the integral barrel crankcase core


14


is first placed on the temporary base TB. Then, a metal cylinder bore liner


15


is placed manually or robotically on each barrel


14




a


of the core


14


. Prior to placement on a barrel


14




a


, each liner exterior surface may be coated with soot comprising carbon black, for the purpose of encouraging intimate mechanical contact between the liner and the cast metal. The core


14


is made in core box tooling


100


to include a chamfered (conical) lower annular liner positioning surface


14




f


at the lower end of each barrel


14




a


as shown best in FIG.


3


A. The chamfered surface


14




f


engages the chamfered annular lower end


15




f


of each bore liner


15


as shown in

FIG. 3A

to position it relative to the barrel


14




a


before and during casting of the engine block.




The cylinder bore liners


15


each can be machined or cast to include an inside diameter that is tapered along the entire length, or a portion of the length, of the bore liner


15


to conform to a draft angle A (outside diametral taper),

FIG. 3A

, present on the barrels


14




a


to permit removal of the core


14


from the core box tooling


100


in which it is formed. In particular, each barrel-forming element


104


of tooling


100


includes a plurality of barrel-forming cavities


104




a


having a slight reducing taper of the inside diameter along the length in a direction extending from the crankcase-forming region


104




b


thereof toward the distal ends of barrel-forming cavities


104




a


to permit movement of the tool elements


104


away from the cured core


14


residing in tooling


100


; i.e., movement of the tool elements


104


from the dashed line positions to the solid positions of FIG.


5


. The outside diametral taper of the formed core barrels


14




a


thus progresses (reduces in diameter) from proximate the core crankcase region


14




b


toward the distal ends of the barrels. The taper on the outside diameter of the barrels


14




a


typically is up to 1 degree and will depend upon the draft angle used on the barrel-forming tool elements


104


of core box tooling


100


. The taper of the inside diameter of the bore liners


15


is machined or cast to be complementary to the draft angle (outside diametral taper) of barrels


14




a


,

FIG. 3A

, such that the inside diameter of each bore liner


15


is lesser at the upper end than at the lower end thereof, FIG.


3


A. Tapering of the inside diameter of the bore liners


15


to match that of the outside diameter of the barrels


14




a


improves initial alignment of each bore liner on the associated barrel and thus with respect to water jacket slab core


22


that will be fitted on the barrels


14




a


. The matching taper also reduces, and makes uniform in thickness, the space or gap between each bore liner


15


and associated barrel


14




a


to reduce the likelihood and extent to which molten metal might enter the space during casting of the engine block mold. The taper on the inside diameter of the bore liners


15


is removed during machining of the engine block casting.




The inside diametral taper of the bore liners


15


may extend along their entire lengths as illustrated in

FIG. 3 and 3A

or only along a portion of their lengths as illustrated in FIG.


3


E. For example, the inside diametral taper of each bore liner


15


can extend only along an upper tapered portion


15




k


of its length proximate a distal end of each said barrel


14




a


adjacent the core print


14




p


as illustrated in

FIG. 3E

proximate to where the upper end of the bore liner


15


mates with the water jacket slab core assembly


22


. For example, the tapered portion


15




k


may have a length of one inch measured from its upper end toward its lower end. Although not shown, a similar inside diametral tapered region can be provided locally at the lower end of each bore liner


15


adjacent the crankcase region


14




b


, or at any other local region along the length of the bore liner


15


between the upper and lower ends thereof.




The invention is not limited to use of bore liners


15


with a slight taper of the inside diameter to match the draft angle of the barrels


14




a


since untapered cylinder bore liners


15


with constant inside and outside diameters can be used to practice the invention, FIG.


3


F. The untapered bore liners


15


are positioned on barrels


14




a


by chamfered positioning surfaces


14




f


,


22




g


engaging chamfered bore liner surfaces


15




f


,


15




g


that are like surfaces


15




f


,


15




g


described herein for the tapered bore liners


15


.




Following assembly of the bore liners


15


on the barrels


14




a


of core


14


, the end cores


16


are assembled manually or robotically to core


14


using interfitting core print features on the mating cores to align the cores, and conventional means of attaching them, such as glue, screws, or other methods known to those experienced in the foundry art. A core print comprises a feature of a mold element (e.g. a core) that is used to position the mold element relative to other mold elements, and which does not define the shape of the casting.




After the end cores


16


are placed on the barrel crankcase core


14


, a water jacket slab core assembly


22


is placed manually robotically on each row of barrels


14




a


of the core


14


, FIG.


3


. Each water jacket slab core assembly


22


is made by fastening a water jacket core


22




a


and a lifter core


22




c


to a slab core


22




b


using conventional interfitting core print features of the cores such as recesses


22




q


and


22




r


on the slab core


22




b


, FIG.


3


B. These receive core print features of the water jacket core


22




a


and lifter core


22




c


, respectively. Means of fastening/securing the assembled cores include glue, screws, or other methods known to those experienced in the foundry art. Each water jacket slab core


22




b


includes end core prints


22




h


,

FIG. 3B

, that interfit with complementary features on the respective end cores


16


. The intended function of core prints


22




h


is to pre-align the slab core


22




b


during assembly on the barrels and to limit outward movement of the end cores during mold filling. Core prints


22




h


do not control the position of slab core


22




b


relative to the integral barrel crankcase core


14


other than to reduce rotation of the slab core


22




b


relative to the barrels.




Water jacket slab core assemblies


22


are assembled on the rows of barrels


14




a


as illustrated in FIG.


3


. At least some of the barrels


14




a


include a core print


14




p


on the upper, distal end thereof formed on the barrels


14




a


in the core box tooling


100


,

FIG. 2 and 5

. In the embodiment shown for purposes of illustration only, all of the barrels


14




a


include a core print


14




p


. The elongated barrel core print


14




p


is illustrated as a flat-sided polygonal extension including four major flat sides S separated by chamfered corners CC and extending upwardly from an upwardly facing flat core surface S


2


. The water jacket slab core assembly


22


includes a plurality of complementary polygonal core prints


22




p


each comprising four major sides S′ extending from a downwardly facing core surface S


2


′, FIG.


3


A. The core prints


22




p


are illustrated as flat-sided openings to receive core prints


14




p


and having annular chamfered (conical) liner positioning surfaces


22




g


at their lower ends. When each core assembly


22


is positioned on each row of barrels


14




a


, each core print


14




p


of the barrels


14




a


is cooperatively received in a respective core print


22




p


. One or more of the flat major sides or surfaces of some of core prints


14




p


typically are tightly nested (e.g. clearance of less than 0.01 inch) relative to a respective core print


22




p


of the core assembly


22


. For example only, the upwardly facing core surfaces S


2


of the first barrel


14




a


(e.g. #


1


in

FIG. 2

) and the last barrel


14




a


(e.g. #


4


) in a given bank of the barrels could be used to align the longitudinal axis of the water jacket slab core assembly


22


using downwardly facing surfaces S


2


′ of the core prints (e.g. #


1


A and #


4


A in

FIG. 3B

) of assembly


22


parallel to an axis of that bank of barrels (the terms upwardly and downwardly facing being relative to FIG.


3


A). The forward facing side S of core print


14




p


of the second barrel (e.g. #


2


in

FIG. 2

) of a given bank of barrels could be used to position the core assembly


22


along the “X” axis,

FIG. 2

, using the rearwardly facing side S′ of core print


22




p


(e.g. #


2


A in

FIG. 3B

) of assembly


22


.




As assembly of the jacket slab assembly


22


to the barrels nears completion, each chamfered surface


22




g


engages a respective chamfered upper annular end


15




g


of each bore liner


15


as shown in

FIGS. 3 and 3A

. The upper, distal ends of the bore liners


15


are thereby accurately positioned relative to the barrels


14




a


before and during casting of the engine block. Since the locations of the barrels


14




a


are accurately formed in core box tooling


100


and since the water jacket slab core


22


and barrels


14




a


are closely interfitted at some of the core prints


14




p


,


22




p


, the bore liners


15


are accurately positioned on the core


14


and thus ultimately the cylinder bores are accurately positioned in the engine block casting made in mold package


10


.




Regions of the core prints


14




p


and


22




p


are shown as flat-sided polygons in shape for purposes of illustration only, as other core print shapes can be used. Moreover, although the core prints


22




p


are shown as flat-sided openings that extend from an inner side to an outer side of each core assembly


22


, the core prints


22




p


may extend only part way through the thickness of the core assembly


22


. Use of core print openings


22




p


through the thickness of core assembly


22


is preferred to provide maximum contact between the core prints


14




p


and the core prints


22




p


for positioning purposes. Those skilled in the art will also appreciate that core prints


22




p


can be made as male core prints that are each received in a respective female core print on upper, distal end of each barrel


14




a.






Following assembly of the water jacket slab core assemblies


22


on the barrels


14




a


, the tappet valley core


24


is assembled manually or robotically on the water jacket slab core assemblies


22


followed by assembly of the side cores


18


on the crankcase barrel core


14


to form the subassembly (core package)


30


,

FIG. 1

, on the temporary base TB. The base core


12


and the cover core


26


are not assembled at this point in the assembly sequence.




The subassembly (core package)


30


and the temporary base TB then are separated by lifting the subassembly


30


using a robotic gripper GP or other suitable manipulator,

FIG. 3D

, off of the base TB at a separate station. The temporary base TB is returned to the starting location of the subassembly sequence where a new integral barrel crankcase core


14


is placed thereon for use in assembly of another subassembly


30


.




The subassembly


30


is taken by robotic gripper GP or other manipulator to a cleaning (blow off) station BS,

FIGS. 1 and 3D

, where it is cleaned to remove loose sand from the exterior surfaces of the subassembly and from interior spaces between the cores thereof. The loose sand typically is present as a result of the cores rubbing against one another at the joints therebetween during the subassembly sequence described above. A small amount of sand can be abraded off of the mating joint surfaces and lodge on the exterior surfaces and in narrow spaces between adjacent cores, such narrow spaces forming the walls and other features of the engine block casting where their presence can contaminate the engine block casting made in the mold package


10


.




The cleaning station BS can comprise a plurality of high velocity air nozzles N in front of which the subassembly


30


is manipulated by the robotic gripper GP such that high velocity air jets J from nozzles N impinge on exterior surfaces of the subassembly and into the narrow spaces between adjacent cores to dislodge any loose sand particles and blow them out of the subassembly as assisted by gravity forces on the loose sand particles. In lieu of, or in addition to, moving the subassembly


30


, the nozzles N may be movable relative to the subassembly to direct high velocity air jets at the exterior surfaces of the subassembly and into the narrow spaces between adjacent cores. The invention is not limited to use of high velocity air jets to clean the subassembly


30


since cleaning may be conducted using one or vacuum cleaner nozzles to suck loose particles off of the subassembly.




The cleaned subassembly (core package)


30


includes multiple parting lines L on exterior surfaces thereof, the parting lines being disposed between the adjacent cores at joints therebetween and extending in various different directions on exterior surfaces as schematically illustrated in FIG.


4


.




The cleaned subassembly (core package)


30


then is positioned by robotic gripper GP on base core


12


residing on optional chill pallet


28


,

FIGS. 1 and 3

. Chill pallet


28


includes mold stripper plate


28




c


disposed on pallet plate


28




b


to support base core


12


, FIG.


3


. The base core


12


is placed on the chill pallet


28


having a plurality of upstanding chills


28




a


(one shown) that are disposed end-to-end on a lowermost pallet plate


28




b


. The chills


28




a


can be fastened together end-to-end by one or more fastening rods (not shown) that extend through axial passages in the chills


28




a


in a manner that the ends of the chills can move toward one another to accommodate shrinkage of the metal casting as it solidified and cools. The chills


28




a


extend through an opening


280


in mold stripper plate


28




c


and an opening


120


in the base core


12


into the cavity C of the crankcase region


14




b


of the core


14


as shown in FIG.


3


. The pallet plate


28




b


includes through holes


28




h


through which rods R,

FIG. 1

, can be extended to separate the chills


28




a


from the mold stripper plate


28




c


and mold package


10


. The chills


28




a


are made of cast iron or other suitable thermally conductive material to rapidly remove heat from the bulkhead features of the casting, the bulkhead features being those casting features that support the engine crankshaft via the main bearings and main bearing caps. The pallet plate


28




b


and the mold stripper plate


28




c


can be constructed of steel, thermal insulating ceramic plate material, combinations thereof, or other durable material. Their function is to facilitate the handling of the chills and mold package, respectively. They typically are not intended to play a significant role in extraction of heat from the casting, although the invention is not so limited. The chills


28




a


on pallet plate


28




b


and mold stripper plate


28




c


are shown for purposes of illustration only and may be omitted altogether, depending upon the requirements of a particular engine block casting application. Moreover, the pallet plate


28




b


can be used without the mold stripper plate


28




c


, and vice versa, in practice of the invention.




Cover core


26


then is placed on the base core


12


and subassembly (core package)


30


to complete assembly of the engine block mold package


10


. Any additional cores (not shown) not part of subassembly (core package)


30


can be placed on or fastened to the base core


12


and cover core


26


before they are moved to the assembly location where they are united with the subassembly (core package)


30


. For example, pursuant to an assembly sequence different from that of

FIG. 1

, core package


30


can be assembled without side cores


16


, which instead are assembled on the base core


12


. The core package


30


sans side cores


16


is subsequently placed in the base core


12


having side cores


16


therein. The base core


12


and cover core


26


have inner surfaces that are configured complementary and in close fit to the exterior surfaces of the subassembly (core package


30


). The exterior surfaces of the base core and cover core are illustrated in

FIG. 4

as defining a flat-sided box shape but can be any shape suited to a particular casting plant. The base core


12


and cover core


26


typically are joined together with core package


30


therebetween by exterior peripheral metal bands or clamps (not shown) to hold the mold package


10


together during and immediately following mold filling.




Location of the subassembly


30


between base core


12


and cover core


26


is effective to enclose the subassembly


30


and confine the various multiple exterior parting lines L thereon inside of the base core and cover core, FIG.


4


. The base core


12


and cover core


26


include cooperating parting surfaces


14




k


,


26




k


that form a single continuous exterior parting line SL extending about the mold package


10


when the base core and cover core are assembled with the subassembly (core package)


30


therebetween. A majority of the parting line SL about the mold package


10


is oriented in a horizontal plane. For example, the parting line SL on the sides LS, RS of the mold package


10


lies in a horizontal plane. The parting line SL on the ends E


3


, E


4


of the mold package


10


extends horizontally and non-horizontally to define a nesting tongue and groove region at each end E


3


, E


4


of the mold package


10


. Such tongue and groove features may be required to accommodate the outside shape of the core package


30


, thus minimizing void space between the core package and the base and cover cores


12


,


26


, to provide clearance for the mechanism used to lower the core package


30


into position in the base core


12


, or to accommodate an opening through which molten metal is introduced to the mold package. The opening (not shown) for molten metal may be located at the parting line SL or at another location depending upon the mold filling technique employed to provide molten metal to the mold package, which mold filling technique forms no part of the invention. The continuous single parting line SL about the mold package


10


reduces the sites for escape of molten metal (e.g. aluminum) from the mold package


10


during mold filling.




The base core


12


includes a bottom wall


12




j


, a pair of upstanding side walls


12


m joined by a pair of upstanding opposite end walls


12




n


, FIG.


4


. The side walls and end walls of the base core


12


terminate in upwardly facing parting surface


14




k


. The cover core includes a top wall


26




j


, a pair of depending side walls


26




m


joined by a pair of depending opposite end walls


26




n


. The side and end walls of the cover core terminate in downwardly facing parting surface


26




k


. The parting surfaces


12




k


,


26




k


mate together to form the mold parting line SL when the base core


12


and cover core


26


are assembled with the subassembly (core package)


30


therebetween. The parting surfaces


14




k


,


26




k


on the sides LS, RS of the mold package


10


are oriented solely in a horizontal plane, although the parting surfaces


12




k


,


26




k


on the end walls E


3


, E


4


of the mold package


10


could reside solely in a horizontal plane. The completed engine block mold package


10


then is moved to a mold filling station MF,

FIG. 1

, where it is filled with molten metal such as molten aluminum using in an illustrative embodiment of the invention a low pressure filling process with the mold package


10


inverted from its orientation in

FIG. 1

, although any suitable molding filling technique such as gravity pouring, may be used to fill the mold package. The molten metal (e.g. aluminum) is cast about the bore liners


15


prepositioned on the barrels


14




a


such that when the molten metal solidifies, the bore liners


15


are cast-in-place in the engine block. The mold package


10


can include recessed manipulator-receiving pockets H, one shown in

FIG. 4

, formed in the end walls of the cover core


26


by which the mold package


10


can be gripped and moved to the filling station MF. During casting of molten metal in the mold package


10


, each bore liner


15


is positioned at its lower end by engagement between the chamfer


14




f


on the barrel


14




a


and the chamfered surface


15




f


on the bore liner and at its upper distal end by engagement between the chamfered surface


22




g


on the water jacket slab core assembly


22


and the chamfered surface


15




g


on the bore liner. This positioning keeps each bore liner


15


centered on its barrel


14




a


during assembly and casting of the mold package


10


when the bore liner


15


is cast-in-place in the cast engine block to provide accurate cylinder bore liner position in the engine block. This positioning in conjunction with use of tapered bore liners


15


to match the draft of the barrels


14




a


also can reduce entry of molten metal into the space between the bore liners


15


and the barrels


14




a


to reduce formation of metal flash therein. Optionally, a suitable sealant can be applied to some or all of the chamfered surfaces


14




f


,


15




f


,


22




g


, and


15




g


to this end as well when the bore liners


15


are assembled on the barrels


14




a


of core


14


, or when the jacket slab assembly


22


is assembled to the barrels.




The engine block casting (not shown) shaped by the mold package


10


will include cast-on primary locator surfaces, secondary locator surfaces and optional tertiary locator surface formed by the respective primary locator surfaces


14




c


, secondary locator surfaces


14




d


, and tertiary locator surface


14




e


provided on the crankcase region


14




b


of the integral barrel crankcase core


14


. The six locating surfaces on the engine block casting are consistently and accurately positioned relative to the cylinder bore liners cast-in-place in the engine block casting and will establish a three axis coordinate system that can be used to locate the engine block casting in subsequent aligning (e.g. OP10 alignment fixture) and machining operations without the need to locate on the curved cylinder bore liners


15


.




After a predetermined time period following casting of molten metal into the mold package


10


, it is moved to a next station illustrated in

FIG. 1

where vertical lift rods R are raised through holes


28




h


of pallet plate


28




b


to raise and separate the mold stripper plate


28




c


with the cast mold package


10


thereon from the pallet plate


28




b


and chills


28




a


thereon. Pallet plate


28




b


and chills


28




a


can be returned to the beginning of the assembly process for reuse in assembling another mold package


10


. The cast mold package


10


then can be further cooled on the stripper plate


28




c


. This further cooling of the mold package


10


can be accomplished by directing air and/or water onto the now exposed bulkhead features of the casting. This can further enhance the material properties of the casting by providing a cooling rate greater than can be achieved by the use of a thermal chill of practical size. Thermal chills become progressively less effective with the passage of time, due to the rise in the temperature of the chill and the reduction in casting temperature. After removal of the cast engine block from the mold package by conventional techniques, the inside diametral taper, if present, on the inside diameter of the bore liners


15


is removed during subsequent machining of the engine block casting to provide a substantially constant inside diameter on the bore liners


15


.




While the invention has been described in terms of specific embodiments thereof, it is not intended to be limited thereto but rather only to the extent set forth in the following claims.



Claims
  • 1. An engine block mold package, comprising a barrel crankcase core having a plurality of barrels on an integral crankcase region, said barrels each having a cylinder bore liner thereon, a barrel core print proximate a distal end of one of said barrels, and a water jacket slab core on said barrels and having a core print cooperating with said barrel core print.
  • 2. The mold package of claim 1 wherein said water jacket slab core includes a cylinder bore liner positioning surface proximate said core print thereof.
  • 3. The mold package of claim 2 wherein said barrels each includes a cylinder bore liner positioning surface.
  • 4. The mold package of claim 1 wherein said core print of said water jacket slab core comprises an opening that receives said barrel core print.
  • 5. The mold package of claim 4 wherein said opening extends from an inner side to an outer side of said water jacket slab core and wherein said barrel core print extends through said opening from said inner side to said outer side.
  • 6. The mold package of claim 4 wherein said opening comprises a flat-sided polygonal opening and said barrel core print comprises a flat-sided polygonal extension.
  • 7. An engine V-block mold package, comprising a barrel crankcase core having first and second banks of a plurality of barrels on an integral crankcase region, said barrels each having a cylinder bore liner thereon, a barrel core print proximate a distal end of one of said barrels of each of said first and second banks, and first and second water jacket slab cores disposed on the respective first and second banks of said barrels, said first and second water jacket slab cores each having a core print cooperating with a respective barrel core print.
  • 8. The mold package of claim 7 wherein said first and second water jacket slab cores each includes a cylinder bore liner positioning surface proximate a respective said core print thereof.9.The mold package of claim 8 wherein said barrels each includes a cylinder bore liner positioning surface.
  • 10. The mold package of claim 7 wherein each said core print of said first and second water jacket slab cores comprises an opening that receives said respective barrel core print.
  • 11. The mold package of claim 10 wherein said opening comprises a flat-sided polygonal opening and said barrel core print comprises a flat-sided polygonal extension.
  • 12. A method of assembling an engine block mold package, comprising the steps of providing a barrel crankcase core having a plurality of barrels formed integrally on a crankcase region with said barrels each having a cylinder bore liner thereon and one or more of said barrels having a barrel core print proximate a distal end thereof, and placing a water jacket slab core on said barrels with a respective core print on said slab core cooperating with a respective barrel core print.
  • 13. The method of claim 12 wherein said respective barrel core print is received in said respective core print of said water jacket slab core.
  • 14. The method of claim 12 including mating a flat side of said respective barrel core print with a flat side of said respective core print of said water jacket slab core.
  • 15. The method of claim 12 including positioning each said cylinder bore liner on a respective one of said barrels by engaging an end region of said bore liner with a positioning surface of said water jacket slab core and by engaging an opposite end region of said bore liner with a positioning surface of said barrel crankcase core.
  • 16. A method of assembling an engine V-block mold package, comprising the steps of providing a barrel crankcase core having first and second banks of a plurality of barrels formed integrally on a crankcase region with said barrels each having a cylinder bore liner thereon, one or more of said barrels of each of said first and second banks having a barrel core print proximate a distal end thereof, and placing a respective first and second water jacket slab core on a respective one of said first and second banks of said barrels with a respective core print on each said first and second water jacket slab core cooperating with a respective barrel core print on said first and second banks.
  • 17. The method of claim 16 wherein each said respective core print on said first and second water jacket slab cores receives said respective barrel core print.
  • 18. The method of claim 16 including mating a flat side of said respective barrel core print with a flat side of said respective core print of a respective one of said first and second water jacket slab cores.
  • 19. The method of claim 16 including positioning each said cylinder bore liner on a respective one of said barrels by engaging an end region of said bore liner with a positioning surface on a respective said first and second water jacket slab core and by engaging an opposite end region of said bore liner with a positioning surface of said barrel crankcase core.
US Referenced Citations (12)
Number Name Date Kind
4693292 Campbell Sep 1987 A
4938183 Field et al. Jul 1990 A
4967827 Campbell Nov 1990 A
5163500 Seaton et al. Nov 1992 A
5215141 Kuhn et al. Jun 1993 A
5320158 Helgesen Jun 1994 A
5361823 Kuhn et al. Nov 1994 A
5365997 Helgesen et al. Nov 1994 A
5477906 Legge et al. Dec 1995 A
5558152 Anderson Sep 1996 A
5771955 Helgesen et al. Jun 1998 A
5924470 Costilla-Vela et al. Jul 1999 A
Foreign Referenced Citations (1)
Number Date Country
1002602 May 2000 EP