US3166992A - Engine block - Google Patents

Description

P. L. FRANCIS ENGINE BLOCK Jan. 26, 1965 3 Sheets-Sheet 1 Filed Nov. 2, 1962 R O N E V m ATTORNEY Jan. 26, 1965 P. 1.. FRANCIS 3,165,992

ENGINE BLOCK Filed Nov. 2, 1962 3 Sheets-Sheet 2 A TTORNE Y P. L. FRANCIS Jan. 26, 1965 ENGINE BLOCK 3 Sheets-Sheet 3 Filed Nov. 2, 1962 INVENTOR.

ATTORNEY United States Patent 3,1663% ENtGll lE BLQ'CK Philip L. Francis, Rochester, Mich, assignor to General Motors Corporation, Detroit, Mich, a corporatien of Delaware Filed Nov. 2, 1?:52, Ser. No. 234,980 7 (Zlaims. (El. 92-149) The present invention relates to an internal combustion engine and more particularly to the cylinder block structure therefor.

In recent years cast iron engine blocks have given way in some cases to light metal alloy fabrication. These light metals, such as aluminum and magnesium alloys are readily die castable due to their lower melting points and other properties. But, die casting opens up entirely new foundry problems not present in sand casting. in die casting, permanent molds and cores are used to form the surfaces of the casting and the internal design of the part must be such that the cores can be pulled after the metal has solidified. That is, there must be no undercut interior surfaces to interfere with core drawing. For example, even in sand casting it is sometimes easier to drill the oil gallery after forming the block because of the difiiculty in casting this interior passage.

Despite these problems, numerous advantages inherent in die casting may convince the manufacturer that light weight alloys should be used. Some of these advantages are closer tolerances and smoother finishes through the use of permanent molds, also light metals are good conductors of heat and have high strength to weight ratios. One ofthe chief disadvantages, however, of die castable metals is that though they have a good strength to weight ratio, their maximum strength is below cast iron and other ferrous alloys. The strength of the cylinder block is critical because under the conditions a present day high compression engine is required to operate, the burning gases in the engine cylinders develop pulsating pressures of considerable magnitude. This in turn creates large forces that tend to force the cylinder head. in one direction oil of the cylinder block and the crankshaft in an opposite direction out of the crankcase. Where the cylinder head is bolted directly to the cylinder block and the crankshaft is carried by hearing caps bolted to the bottom of the bulkheads in the crankcase, clearly the cylinder block is subjected to high tensile loads. The cylinder block is placed in severe strain especially in the crankshaft bearing area. It is customary, therefore, to beef up the bulkheads in light metal alloy engines and, for this reason, the bearing caps are usually formed as separate cast iron members bolted to the bottom of the bulkheads to absorb forces delivered to the main bearings by the connecting rods. Damaging forces also develop in the upper portion of a block where the cylinder head bolts are anchored. To compensate, extra metal is added in these areas to withstand the strain. These metal masses are objectionable for one reason in particular, because they absorb and hold heat which creates a hot spot in the engine.

It is now proposed to provide a cylinder block structure that is relieved of excessive tensile loads. This, in turn, will permit the wider use of die castable metals in much diminished quantities while at the same time streamlining the cylinder block structure so that the various members and wall portions may be of a thickness considerably less than has been possible in the past. This brings about an increase in the cooling efliciency of the block, lowers the cost of casting due to the savings in metal and, more particularly, eliminates the need for 3, 1 65,9 92 Patented Jan. 26, 1955 cast iron bearing caps formerly required in the light metal alloy blocks.

Furthermore, it is the usual practice in cylinder block constructions to have relatively deep, thick side walls or skirts for the crankcase portion of the block. A bolting flange is provided extending laterally from the free ends of these walls to which an oil pan is attached. These thick walls and the bolting flange thereon are thought essential to provide rigidity to the crankcase and upper block frame. Numerous bolts are used in securing the oil pan to the bolting flange in order to insure sufiicient unit pressure on the oil pan gasket.

In the present block design, I eliminate the crankcase skirt portions without loss of overall block strength and close the crankcase by an oil pan construction using a single stud to fasten it to a crankcase bulkhead without sacrificing the required seal between the mating flanges of the oil pan and the block.

These and other objectives are accomplished by the development of an engine block castable in right and left cylinder block halves which may be assembled to form a complete engine block. The block halves are held together by long U-bolts surrounding the lower extremities of each bisectionally split bulkhead and extending upwardly therefrom, terminating above the top surface of the block. A cylinder head and gasket are assembled on the block closing the cylinders using the U-bolts in place of the normal head bolts for securing the head. Head nuts are threadably received on the Ubolt ends and when tightened place the bolts in tension. The entire intervening block frame is thus prestressed in compression to counterbalance the tensile stresses developed during engine operation and the destructive forces on the main bearings are minimized by the structural backing provided by the U-bolts.

It will be appreciated by those familiar with foundry practice that by casting the block in equal halves, die casting equipment may be reduced in size and weight from that presently required. Furthermore, the oil gallery and branch passages, camshaft gallery, valve lifter openings, crankshaft main bearing openings, cylinder barrels, and other previously difficult to cast internal surfaces may now be die cast because they are more accessible for coring.

Further advantages and objects of the present invention will become more apparent by reference tothe fol lowing detailed description and drawings wherein:

FIGURE 1 is a transverse crosssectional view of an engine embodying the present invention;

FIGURE 2 is a longitudinal cross-sectional view of FIGURE 1 taken along the lines 2-2;

FIGURE 3 is a view along the lines 33 of FIGURE 1 with a portion of the block broken away to show the oil gallery and valve lifter openings; and

FIGURE 4 is an exploded cross-sectional View of a cylinder block, cylinder heads, and an oil pan for the engine, as shown in FIGURE 1.

Referring to FIGURE 1 of the drawings, the engine includes a cylinder block ll) of aluminum having inclined cylinders 12 disposed in parallel rows opening downwardly into a crankcase area 14 which is closed by oil pan lie. The cylinders are closed at the top by cylinder heads 17 and normally contain pistons connectable to the crankshaft 29. Gaskets 18 seal between the cylinder heads and the block. A valve operating mechanism including valve springs 23, rocker arms and mounts Z5, pushrods 2'7, and hydraulic valve lifters 29 operates valves 31 in timed sequence from a camshaft 33 driven from 3 the crankshaft 20. Valve covers 34 enclose the rocker arm mechanism. 7

At first glance, it will appear that a normal V-type internal combustion engine is disclosed. On closer examination it will be found that the cylinder block 10 is split along a vertical plane passing through the center 35 of the engine. The axes of the crankshaft 20 and camshaft 33 lie in this plane. Left and right cylinder block halves 4t) and 41 complement each other when assembled to form circular openings 42 and 43 for receiving bearings 44 and 45 to journal the camshaft and crankshaft, respectively. Since the left cylinder block half 49 is similar to the right half 41, our attention will be devoted to its description, keeping in mind that what is said applies equally to the right half.

As seen in FIGURE 2, the left block half 40 has an upper cylinder block portion 46 supported from the block base 48 and has a row of cylinders 47 opening downwardly into the crankcase area 14. The crankcase area is divided into crank throw regions by intermediate bulkhead partitions 50, 51 and 52 extending downwardly from the block base 48 and lying in a plane that passes between the adjacent cylinders 47. As will appear later, there are no crankcase skirt portions along the side and the crankcase end walls 55 and 56 complete the lower walls of the assembled cylinder block. In addition to the camshaft and crankshaft openings 42 and 43 being 'half formed in the bulkheads and end walls, vertical semicircular grooves 60 are formed in the mating surfaces thereof and mate with equivalent semi-circular grooves in block half 41 .to form oil passages feeding the bearings 44 and 45. These passages connect with the oil gallery 62 running the length of the block, shown half formed in block base 48. It will be seen by inspection of FIG- URE 3 that the oil gallery 62 also communicates with hydraulic valve lifter openings 64 formed in the block base 48 and opening downwardly into the camshaft gallery.

Since the block halves are die castable, the mold parting line is along a plane containing the axes of cylinders 49 audit is important to realize that since only one half of the block is being cast, the path of movement of the cores for valve lifter openings 64 is unobstructed in a direction downwardly out of the camshaft gallery and that the die projections for forming the oil gallery 62 may be pulled freely along a plane passing through the block base 48 perpendicular to the mold parting plane. more clearly seen in the broken away section of FIG- URE 3, the withdrawal of cores and mold projections is not inhibited by re-entrant angles or pockets. The semicircular oil grooves 60, and camshaft and crankshaft openings 42 and 43 also may be cast by appropriate design of the mold; these openings too being virtually exterior surfaces when casting a bisectionally split block. Hence, the main interior spaces of the engine block are initially cast, eliminating the need of machining openings after the casting is formed.

The upper cylinder block portion 46 includes the water jacket 66 and cylinder barrels 68 cast integrally with the block base 48. The cylinder barrels 68 define cylinders 47 opening through the block base 48 into the crankcase area 14. The water jacket 66 is a thin shelled structure and forms a continuous wall encircling the cylinder barrels 68, being narrowest at 69. Cooling water from a radiator is circulated around each cylinder barrel to carry away the heat resulting from combustion. The present block structure having thin wall portions is more efficiently cooled than present engines and, since there is no head bolt anchoring problem, hot spots are eliminated as will hereinafter appear.

The assembled bulkheads arch downwardly from the full block base 48-49 and each has a pair of cast circular ears 70 and 71 formed on the radial bottom surface thereof. In illustration, intermediate bulkhead 51 has a greater portion of an ear 70 formed in the left bisection with only a short mating extension in the right and,

similarly, the majority of car 71 is formed in the opposite alternate side of the right bisection with only a short mating extension in the left. The ears and 71 are of a radius r having the crankshaft axis for a center and receive steel U-bolts 72 and 74, respectively. The U portion of (the bolts has a curvature inscribed by the radius r and seats in the ears 70 and 71 so that the leg portions extend upwardly through the full block base 4849 and straddle the narrowed region 69 of water jacket 66. Bore holes 73 and 75 open through the block base to permit the legs of the bolts to be inserted. Bore holes 73 pass diagonally through an upper portion of the bulkheads while holes 75 pass through the block base near its outer edge. The bolt legs lie on the outside of the water jacket 66 intermediate adjacent cylinder barrels 68 and are arranged cross-fashion to run alternately, first through one block half and then the other. This arrangement is possible because in a V-type engine the cylinder axes are laterally offset so that a single crankshaft can be used. The bolts are directed more or less parallel with the cylinders of the engine because the maximum firing forces occur in this plane. In the illustrated engine, ten bolts are used but the requirement is that a suflicient number be used so that a balanced prestress force distribution may be obtained without overloading any portion of the block frame. It may be seen by inspection that when the bolts are in place they extend above the top surface of the cylinder block a sufficient distance to mount cylinder heads 17 and gaskets 18 and are provided with threads to receive head nuts 19. When the block halves are assembled with the bearings in position and the crankshaft and camshaft in place, the block may be prestressed by torquing all of the head nuts 19 to the same degree in both cylinder heads. This places an equal tensile strain on the U-bolts and secures the block halves tightly together. A sealing compound may be applied to the meeting surfaces of the block halves, if desired.

When any internal combustion engine is running, force impulses of considerable magnitude are transmitted from the pistons to the crank arms of the crankshaft. These forces are absorbed in the usual case in the main bearing areas and in the head bolt anchor locations of the block. In the present invention the U-bolts largely eliminate these force concentrations in the block and distribute the load. The prestressed condition of the U-bolts and block frame counterbalances these pulsating forces and, as a consequence, the intervening block structure can be designed with much thinner wall sections since the primary structural support members are actually the U-bolts. No head bolt anchor structure in the upper portion of the block is needed since the U-bolts serve instead to secure the cylinder heads to the block and thus eliminate potential hot spots in the block.

Furthermore, the usual engine, and this includes one made of a light metal, must have sturdy bearing caps usually made of cast iron to journal the crankshaft. This is because the pulsating forces transmitted to the crank shaft from the connecting rods will, in time, deform bearing caps made of lesser strength material. Cast iron bearing caps naturally add considearble weight to the engine and where the Weight to horsepower ratio is important, this is not a negligible factor. Also, the need for any bearing caps adds an additional assembly operation which, of course, is costly. The U-bolt construction of the present invention besides anchoring the cylinder heads, loops behind each main bearing opening and backs up the bulkheads and end walls to prevent deformation otherwise resulting from the repeated pounding these areas normally undergo. The need for bearing caps is obviated, as may be readily appreciated referring to FIG- URE 4; where in the present streamlined block, the familiar horizontally split main bearing is replaced by the' vertical split line assembly strikingly shown illustrated with bulkhead 51.

It is also apparent in FIGURE 4 that the assembled block has no vertical crankcase side walls upon which to mount a conventional oil pan. The oil pan 16 has an arched transverse cross-sectional shape similar to the shape defined by the lower bulkhead and end wall surfaces. To ensure a tight fit, the pan 16 has longitudinal flanges 80 which may be sprung outwardly to mate with the lower outer edges of the assembled block base 48-49. A wedging action takes place when sliding the pan into position since the beam of the block base is greater than the transverse distance between the flanges 80. End flanges 82 of the pan 16 meet with the lowermost projections 85 of arched end walls 55 and 56. A sealing gasket 36 is positioned between the oil pan flanges and mating block surfaces. A hanger 90 is fitted beneath the bulkhead 51 prior to assembly of the U-bolts and is held in place by them after assembly. The hanger 98 has internal threads to receive the stud 92 passing through the bottom of the oil pan to mount it on the block closing and sealing the crankcase. The innovation of mounting an oil pan with a single stud, where in the past numerous boits were required, is an important consequence stemming from the ability to eliminate crankcase side walls or skirts;

In the usual engine block these skirts serve to strengthen the block and add beam-like rigidity to the super-structure. In the present block, the tensioned U-bolts place the block frame in rigid compression; this prestressed condition greatly increasing the strength capabilities of the block and completely eliminating the need for crankcase side walls.

Having now described my invention in detail in relation to a V-type internal combustion engine, it will be apparent that the inventive features of the described embodiments may easily be adapted for use in a straight six-cylinder engine; a pancake-type engine where the cylinders are opposed and lie in a horizontal plane; a radial engine; or even a single-cylinder engine. Plainly, the features of my invention are so related in design, operation, and effect as to be dependent as disclosed, but it should be clear that certain portions are sufficiently distinct so as to be capable of adaptation and use separately. Accordingly, I do not Wish to be limited to a V-8 type construction or to an isolated subcombination where to one skilled in the art, it would be obvious to make certain changes without deviating from the spirit and scope of the appended claims.

What is claimed is:

1. In a V-type engine, a block having parallel rows of inclined cylinders opening downwardly into a common crankcase, aligned bearing portions formed in the block, a crankshaft journaled in the bearing portions and having crank arms lying in the paths of the cylinders, and cylinder heads connectable to the top of the block closing the cylinders, the improvement comprising;

a plurality of high tensile strength U-bolts having their closed ends looping behind each bearing portion and their free ends inclining upwardly in planes parallel with the rows of cylinders and terminating beyond the top of the block, said U-bolts adapted to adjustably secure the cylinder heads to the block whereby the Ubolts are placed in tension and absorb oppositeiy directed firing stresses acting on said cylinder heads and bearing portions thus relieving the cylinder block of such stress.

2. In a V-type engine, a block having parallel rows of inclined cylinders opening downwardly into a common crankcase, aligned bearing portions formed in the block, a crankshaft journaled in the bearing portions and having crank arms lying in the paths of the cylinders, and cylinder, heads connectable to the top of the block closing the cylinders, the improvement comprising;

a plurality of high tensile strength U-bolts having their closed ends looping behind each bearing portion and their free ends inclining upwardly in planes parallel with the rows of cylinders and terminating beyond the top of the block, said U-bolts arranged in pairs on each bearing portion with the free ends extending cross-fashion alternately first parallel with one row of cylinders and then the other and being adapted to adjustablysecure the cylinder heads to the block whereby the U-bolts are placed in tension and absorb oppositely directed firing stresses acting on said cylinder heads and bearing portions thus relieving the cylinder block of such stresses.

3. In a -type engine, a block according to claim 2 wherein said block is made of aluminum and has an arcuate portion below each bearing portion adapted to be cradled by the closed ends of said U-bolts whereby said bearing portions are locally reinforced below the crankshaft eliminating the need for hearing caps.

4. In an engine having a crankcase closed by the mating edges of a cylinder block and oil pan, said oil pan comprising;

a flexible body portion having peripheral edges configured so as to mate with the block edges, said body portion characterized by being of lesser transverse dimension than the beam of the block at the point where the edges mate; and

means to force said peripheral edges against the block edges whereby upon assembly the oil pan body is sprung sufficiently to effect a seal between the oil pan and block.

5. A V-type internal combustion engine comprising;

a split engine frame castable in equal halves and assembled along a common plane, said frame defining interior spaces opening in complementary fashion through the assembly plane and being characterized by the absence of undercut portions, said interior spaces including aligned bearing portions formed in the lower portion of the frame;

cylinder heads connectable to the top of the frame closing cylinders formed therein;

a crankshaft journaled in the bearing portion with the crank throws thereof in the axial path of opposite adjacent cylinders;

high tensile strength U-bolts having their closed ends looping behind each bearing portion and their free ends inclining upwardly in planes parallel with the cylinders and terminating beyond the top of the respective frame halves, said U-bolts adapted to hold said frame halves together at the assembly plane and to adjustably secure the cylinder heads thereon;

a flexible oil pan having an inclined peripheral edge adapted to mate with the frame; and

means for forcing the oil pan edges against the frame, said oil pan having a lesser transverse dimension than the beam of said frame where said edges mate so that the pan is sprung outwardly upon being assembled to the frame causing a seal between the oil pan and frame.

6. In an internal combustion engine, a cylinder block including a cylinder and having a bearing journaling a crankshaft adjacent one end of the cylinder;

a cylinder head adapted to be secured to the cylinder block and to close the cylinder at the end opposite from the crankshaft; and

a high tensile strength U-bolt having its closed end partially surrounding and reinforcing the bearing portion and its free ends extending to and adjustably securing the cylinder head to the block whereby oppositely directed firing stresses acting on the cylinder head and the bearing portion are taken in tension by the U-bolt thus relieving the cylinder block of such stresses.

7. A V-type internal combustion engine comprising;

a split engine frame casta-ble in equal halves and assembled along a common plane, said frame defining interior spaces opening in complementary fashion If through the assembly plane, said interior spaces including aligned bearing portions formed in the lower portion of the frame;

cylinder heads connectable to the top of the frame closing cylinders formed therein;

a crankshaft journaled in the bearing portions; and

high tensile strength U-bolts each having its closed end looping beneath one of the bearing portions and its free ends inclining upwardly in a plane parallel with one of the cylinders and terminating beyond the top of one of the respective frame halves, said U-bolts being adapted to hold said frame halves together at the assembly plane and to adjustably secure the cylinder heads thereon.

7 References Cited in g the file of this patent UNITED STATES PATENTS Johansen June 24, Mason et al. Aug. 20, Meyer Dec. 24, Kahn Sept. 21, Bugatti Nov. 7, De Long July 23, Arden Dec. 10, Bouvy Mar. 14,

FOREIGN PATENTS France Sept. 27,

Claims (1)

1. IN A V-TYPE ENGINE, A BLOCK HAVING PARALLEL ROWS OF INCLINED CYLINDERS OPENING DOWNWARDLY INTO A COMMON CRANKCASE, ALIGNED BEARING PORTIONS FORMED IN THE BLOCK, A CRANKSHAFT JOURNALED IN THE BEARING PORTIONS AND HAVING CRANK ARMS LYING IN THE PATHS OF THE CYLINDERS, AND CYLINDER HEADS CONNECTABLE TO THE TOP OF THE BLOCK CLOSING THE CYLINDERS, THE IMPROVEMENT COMPRISING; A PLURALITY OF HIGH TENSILE STRENGTH U-BOLTS HAVING CLOSED ENDS LOOPING BEHIND EACH BEARING PORTION AND THEIR FREE ENDS INCLINING UPWARDLY IN PLANES PARALLEL WITH THE ROWS OF CYLINDERS AND TERMINATING BEYOND THE TOP OF THE BLOCK, SAID U-BOLTS ADAPTED TO ADJUSTABLY SECURE THE CYLINDER HEADS TO THE BLOCK WHEREBY THE U-BOLTS ARE PLACED IN TENSION AND ABSORB OPPOSITELY DIRECTED FIRING STRESSES ACTING ON SAID CYLINDER HEADS AND BEARING PORTIONS THUS RELIEVING THE CYLINER BLOCK OF SUCH STRESS.

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