Composite Engine Block Having High Strength to Weight Ratio

This invention relates to engine block designs for internal combustion engines. More particularly, this invention relates to a composite engine block for a compression ignition engine wherein each component part of the block is configured to maximize its own strength to weight ratio while cooperating with the configuration of the other components in a way to synergistically increase the strength to weight ratio of the composite block. The disclosed invention is further concerned with the technology of mechanical vibration reduction in the operation of internal combustion engines.

Greater fuel efficiency and lower operating noise have traditionally been important objectives in the design of internal combustion engines, but the rising cost of fossil fuel and increasing concern over noise pollution has greatly intensified the need to achieve higher levels of performance in these areas. One fundamental approach for improving strength to weight ratio has been to provide specialized load bearing structure within the engine block to enable the engine block to better withstand concentrated loads without substantially increasing the overall weight of the block. For example, U.S. Pat. No. 3,046,952 to Dolza discloses a light weight engine block wherein elongated steel bolts extending through the block are each connected at one end to the engine head and at the other end to a respective main bearing cap. In addition to increased assembly and manufacturing costs, the use of such elongated bolts requires an overall increase in the size of the engine block by necessitating increased spacing between cylinder cavities. This increased spacing is required, in part, because the bolts are under tension at all times and the block must accordingly be strengthened in the vicinity of the bolts to withstand the bolt tension. One proposed solution to this problem illustrated in U.S. Pat. No. 4,059,085 to Mansfield et al has been to provide an internal combustion structure in which the cylinder head and main bearing caps are linked by a framework of members including pairs of tension members. While useful in some circumstances, the disclosed framework includes members angled obliquely to the direct line between head and caps which unduly enlarges the overall engine size.

A variety of composite engine block designs have also been proposed in attempts to optimize the often conflicting goals of high strength, low cost and compact size. For instance, U.S. Pat. No. 3,351,044 to Pomeroy discloses an internal combustion engine including an upper unit containing plural cylinder cavities and a lower unit containing a crankshaft to which the engine oil pan is attached on the lower side. While some advantages may be achieved with this design, such as facilitating engine assembly, no strength improving advantages are disclosed by the use of this composite design. The Pomeroy patent also discloses a pair of bolt-on water jackets for use on the respective sides of the upper unit thereby achieving a streamlined outer engine configuration and simplified coolant system. However, this patent fails to suggest any way in which the advantages of such a bolt on jacket can be used while simultaneously reducing the number of component parts and avoiding at least some of the increased seal leakage potential which naturally attends the use of two separate bolt on water jackets.

The use of cylinder liners in internal combustion engines has long been recognized as desirable as a means for improving internal combustion engine design and is especially desirable because it allows greatly simplified engine overhaul. One particularly desirable liner design is disclosed in British Pat. No. 615,045, accepted Dec. 31, 1948, wherein the liner is provided with an exterior stop positioned intermediate the ends of the liner for engagement with a liner stop located within the cylinder cavity at a substantial distance from the head engaging surface of the engine block. This design affords numerous advantages over liner designs employing a liner stop located at the top of the liner by allowing, for example, improved head gasket sealing during engine operation. The provision of mid stop liners, however, creates complications in routing the coolant and lubrication fluid flow passages through the engine without substantially increasing the size or complexity of the engine block design. U.S. Pat. No. 2,681,054 to Boghassian discloses an integral cast block for receiving mid stop cylinder liners wherein the camshaft and crankshaft bearing supports are cast integrally within the block. However, no portion of the space between the cylinder liners is utilized for the lubrication fluid return flow passage requiring other portions of the engine block to provide this function. Provision of an integral oil gallery within the disclosed engine block design of the Boghassian patent permits supply of lubrication fluid to both the crankshaft and camshaft bearing supports through passageways integral with the engine block but plural angularly arranged passageways are required for each set of interlinked crankshaft and camshaft bearing supports.

A great variety of engine block designs are known which employ cross walls extending between the cylinder cavities of the engine to provide support to the outer side walls of the engine block. One example of such a cross wall design is disclosed in U.S. Pat. No. 2,129,906 wherein a large aperture is provided in the cross wall as illustrated in the drawings of this patent. While such a cross wall design will reduce engine weight as compared with solid cross wall designs, there is no disclosure in this patent which would suggest how a cross wall design of the type illustrated could be used to provide sufficient strength to the liner stops within the engine block. In short, the prior art of engine block design is devoid of an optimum engine design which simultaneously provides high strength, low cost and compact size.

The basic object of this invention is to overcome the disadvantages of the prior art as listed above and, in particular, to provide an engine block design characterized by light weight, compact size and high strength as well as low operating noise characteristics.

A more specific object of this invention is to provide a composite engine block structure wherein each component is designed for maximum strength to weight ratio taken by itself as well as being designed to synergistically increase the strength to weight ratio of the composite block. To achieve this result, the composite engine block design includes a cylinder block or main frame containing plural cylinder cavities combined with a plurality of internally disposed, cross frames interleaved with the cylinder cavities. A ladder frame encompassing in part the crankshaft receiving cavity of the engine block is also provided wherein the ladder frame is designed to concentrate additional rigidifying support on the base of each cross frame of the main frame to increase synergistically the strengthening effect of connecting the main and ladder frames.

Yet another object of this invention is to provide an engine block design including vibration control or reducing structure for reducing the level of vibration of the block during engine operation wherein the vibration control structure includes a plurality of concavities formed in the outer side wall of the composite engine block in registry with the rigidifying structure of both the main engine block or frame and the base supporting ladder frame.

Still another object of this invention is to provide a composite engine block design characterized by a light weight and streamlined configuration wherein the coolant and lubrication flow paths are formed integrally within the composite engine block in such a way as to provide unobstructed flow throughout. The composite engine block structure is adapted to receive cylinder liners having stops located intermediate the ends of the liners and further is characterized by specially designed coolant and lubrication flow paths arranged to pass between the spaces formed by the cylinder liners when placed within the engine block.

A still more specific object of this invention is to provide a composite engine block design including inlet and outlet coolant manifolds formed in parallel adjacent relationship along one side wall of the composite engine block. The inlet coolant manifold communicates with a coolant flow chamber surrounding each cylinder liner, and the outlet coolant manifold receives return coolant from each coolant flow chamber through a path including the engine head and discharge openings formed in the top wall of the engine block. This arrangement causes the return coolant to flow downwardly from the engine head into the outlet coolant manifold.

Still another object of this invention is to provide a composite engine block design including a crankshaft receiving cavity adjacent the lower side of the engine block and a camshaft receiving cavity adjacent the upper side of the engine block wherein lubrication fluid is supplied to the bearing supports located in the respective crankshaft and camshaft receiving cavities by means of a parallel linear supply passage positioned intermediate the crankshaft and camshaft cavities. A linear supply branch extends from the linear supply passage upwardly to each camshaft bearing support and downwardly to a corresponding crankshaft bearing along a single linear path, thereby causing lubrication fluid to move in opposite directions along each linear supply branch from the intermediate linear supply passage to the respective bearing supports.

Another object of this invention is to provide a composite engine block including a main frame containing a plurality of closely spaced cylinder cavities for receiving cylinder liners having mid stops with each cylinder cavity being separated by a cross frame formed by connecting pillars extending between corresponding head bolt bosses and cap screw bosses. Each cross frame includes a cross wall intersecting and connecting with the upper wall of the engine block, the head bolt bosses, the connecting pillars, the cap screw bosses and the crank shaft bearing supports. While the cross wall is considerably thinner than the pillars and bosses to which it is connected, the arrangement of such elements into a single cross frame extending generally perpendicularly to the side walls and the top or head engaging wall of the engine block results in an extremely rigid overall structure in which the major loading forces tend to be concentrated within the connecting pillars. During the casting of the main frame of the composite engine block, the design and location of the connecting pillars provides a convenient flow path for molten casting metal. Accordingly, the disclosed engine block design not only achieves a high strength to weight ratio but also achieves this result without complicating the process of casting the engine block.

Still another object of this invention is to provide a ladder frame for providing significant additional support to the main frame of the composite engine block. In particular, the ladder frame is adapted for connection with the lower portion of the engine block main frame wherein the ladder frame includes first and second side walls forming extensions of the main frame side walls and a plurality of pairs of strengthening pillars, one pillar of each pair being connected to the inside surface of the first side wall and the other pillar of each pair being connected to the inside surface of the second side wall. A plurality of struts are also provided with each strut being connected at one end to one pillar and at the other end to another pillar of each pair of strengthening pillars thereby forming a plurality of rigidifying base frames within the ladder frame of the composite engine block. By positioning the rigidifying base frames within extensions of the planes defined by the cross frames, the rigidifying frames can be formed to extend into the interior of the engine block while still clearing the rotating counter weights of the crankshaft.

Yet another object of the subject invention is to provide a very compact, composite engine block structure having an exterior which is unobstructed by fluid flow conduits. In particular, the ladder frame described above includes an integrally formed lubrication pump housing interconnected with the lubrication fluid flow passage in the main frame of the composite engine block by fluid passages formed in the side walls of the ladder and main frames.

Still other and more specific objects of this invention may be appreciated by consideration of the following Brief Description of Drawings and the following description of the Best Mode for Carrying Out the Invention.

FIG. 1 is a cross sectional view of the composite engine block structure designed in accordance with the subject invention.

FIG. 2 is a partially cut-away perspective view of the main frame or cylinder block of the composite engine block design illustrated in FIG. 1.

FIG. 3 is a cross sectional view of the main frame taken along lines 3--3 of FIG. 2.

FIG. 4 is a cross sectional view of the main frame taken along lines 4--4 of FIG. 2.

FIG. 5A is a composite of a top elevational view and a pair of cross sectional views taken along lines D--D and E--E of the main frame illustrated in FIG. 1.

FIG. 5B is a composite of a pair of cross sectional views taken along lines F--F and G--G of the main frame illustrated in FIG. 1.

FIG. 6 is a broken elevational view of the left side of the main frame illustrated in FIG. 1.

FIG. 7 is a broken elevational view of the right side of the main frame illustrated in FIG. 1.

FIG. 8 is a broken bottom elevational view of the main frame illustrated in FIGS. 1 and 2.

FIG. 9 is an end elevational view of the main frame illustrated in FIG. 1.

FIG. 10 is an end elevational view of the ladder frame illustrated in FIG. 1.

FIG. 11 is an elevational view of the opposite end of the ladder frame illustrated in FIG. 10.

FIG. 12 is a broken top elevational view of the ladder frame illustrated in FIGS. 10 and 11.

FIG. 13 is a cross sectional view taken along the lines 13--13 of the ladder frame illustrated in FIG. 12.

FIG. 14 is a cross sectional view taken along lines 14--14 of the ladder frame illustrated in FIG. 12.

FIG. 15 is a cross sectional view taken along lines 15--15 of the ladder frame illustrated in FIG. 17.

FIG. 16 is a cross sectional view taken along lines 16--16 of the ladder frame illustrated in FIG. 12.

FIG. 17 is a broken bottom elevational view of the ladder frame illustrated in FIG. 10.

FIG. 18A is an elevational view of one portion of the right side of the ladder frame illustrated in FIG. 10.

FIG. 18B is an elevational view of the remaining portion of the right side of the ladder frame illustrated in FIG. 10, and

FIG. 19 is a broken elevational view of the left side of the ladder frame illustrated in FIG. 10.

The development of an extremely light weight streamlined and high strength durable engine block has long been a desire of internal combustion engine designers. With the ever increasing costs of fossil fuels, the need for a light weight internal combustion engine for over-the-road vehicles has become acute particularly among commercial users of heavy duty vehicles such as trucks, tractors and other heavy road equipment. Normally engines used in such vehicles are of the compression ignition (diesel) type which inherently operate at a higher cylinder pressure levels than do spark ignition type internal combustion engines and thus require higher strength, heavier engine blocks. Moreover, engines of this type must be designed for extremely rugged use under greater strain and for longer periods than passenger vehicle engines. It is the purpose of this invention to provide a composite engine block design especially well suited for heavy duty compression ignition engines characterized by great strength, light weight and long term durability without in any way sacrificing the fuel efficiency and simplicity of operation normally associated with compression ignition internal combustion engines. Moreover, the disclosed design is expressly adapted to reduce the audible vibration associated with the operation of conventional compression ignition internal combustion engines.

Reference is made to FIG. 1 wherein a cross sectional view of a composite engine block 2 designed in accordance with the subject invention is illustrated. In particular, the disclosed engine block includes a main frame 4 having a head engaging surface 6 and a crankshaft receiving cavity 8 on an opposed side of the main frame 4. An oil pan adaptor frame or ladder frame 5 is mounted on the base of main frame 4 for providing added strength to the composite engine block as will be explained in greater detail hereinbelow. A plurality of closely spaced cylinder cavities 10, only one of which is illustrated in FIG. 1, are provided in the main frame 4 extending from the head engaging surface 6 toward the crankshaft receiving cavity 8. Within each cylinder cavity 10, a piston liner 12 is positioned to receive an engine piston (not shown) for reciprocating motion during engine operation.

The cylinder liners 12 are of the type illustrated in U.S. patent application Ser. No. 959,702, filed Nov. 13, 1978, and assigned to the same assignee as the subject invention. A cylinder liner 12 of the type disclosed in the above noted co-pending patent application is illustrated partially in cross section in FIG. 1. Each such cylinder liner 12, having a generally hollow cylindrical body, is provided with an external liner stop 14 intermediate the liner ends 16 and 18. Corresponding liner engaging stop means 21 are formed inside main frame 4 for engaging the external liner stops 14 of the cylinder liners 12 to support or retain the liners in a position in which each liner is free of all direct contact with the main frame 4 along a substantial portion of the axial length of the liner commencing at end 18 and extending up to the liner engaging or stop means 21. This axial distance is generally denoted by the letter "a" in FIG. 1. As will be described in greater detail hereinbelow, the main frame cylinder cavities 10 are arranged such that a plurality of interliner spaces are formed between the liners disposed within the respective cylinder cavities 10 of the main frame 4.

Referring now jointly to FIGS. 1 and 2, it is apparent that the cylinder cavities 10 are rather closely spaced in generally parallel, vertically aligned positions above the crankshaft receiving cavity 8. The upper surface 6 of the main frame 4 is formed by a head wall 20, the outer surface of which forms the head engaging surface 6. Disposed within the crankshaft receiving cavity 8 are a plurality of crankshaft bearing supports 22 for receiving and supporting the crankshaft bearings, not illustrated, which are adapted to support the crankshaft for rotation about axis 24. Surrounding the top end of each cylinder cavity 10 are a plurality of spaced head bolt bosses 26 containing threaded holes 28 opening into surface 6 for receiving head bolts adapted to attach the engine head to the head engaging surface 6, thereby capping the cylinder cavities. Each crankshaft bearing support 22 is provided with a pair of cap screw bosses 30 containing threaded holes 32 for receiving bearing cap bolts 35 for attaching a bearing cap 36 to each corresponding bearing support 22. A pair of head bolt bosses 26 is provided at each end of the main frame and between each of the cylinder cavities 10 within the inter cavity spaces referred to above. A connecting pillar 34 extends between each cap screw boss 30 and one of the pair of head bolt bosses 26 arranged in a position generally vertically above the corresponding cap screw bosses 30 of each crankshaft bearing support 22. Since main frame 4 is normally formed by a metal casting operation, flow passageways need to be provided within the casting mold to insure that molten metal reaches all portions of the block being molded. The portions of casting mold forming pillars 34, can be used to function as passages for metal flow during the casting operation while the resulting pillars perform a strengthening function. Thus, pillars 34 tend to transmit the thrust forces resulting from fuel combustion within each cylinder from the engine head through the head bolts to the crankshaft by means of the cap screw bosses 30 and the crankshaft bearing supports 22. As is illustrated in FIG. 1, and more clearly in FIG. 2, each crankshaft bearing support 22 includes a pair of cap screw bosses 30 linked to a pair of connecting pillars 34, and a pair of head bolt bosses 26 to form one of a plurality of cross frames interleaved with the cylinder cavities 10 of the main frame 4. The central axis of the bosses and pillars forming each cross frame are positioned within a single cross plane which is parallel to the remaining cross planes and which is perpendicular to the rotational axis 24 of the crankshaft.

Extending along the left side of the main frame 4, as illustrated in FIG. 1, is an outer side wall 36 aligned generally with the cylinder cavities 10. Outer side wall 36 extends in a generally perpendicular direction downwardly from the head wall 20 toward the crankshaft receiving cavity 8. Disposed on the opposite side of the cylinder cavities 10 from side wall 36 is an inner side wall 38 which similarly extends in a generally perpendicular direction downwardly from the head wall 20 toward the crankshaft receiving cavity 8. The liner stop means 21 is formed in a support wall 40 parallel to and spaced from head wall 20. The support wall 40 intersects with and is connected to outer side wall 36 and inner side wall 38 as is best illustrated in FIG. 1. Support wall 40 also intersects and connects with connecting pillars 34 to form an extremely strong and rigid integral unit. Within each cylinder cavity 10, the support wall 40 contains a circular aperture 42 having a diameter slightly greater than the diameter of the portion of each cylinder liner indicated by "X" in FIG. 1. The diameter of circular aperture 42 is less than the diameter of the external liner stop 14 and the upper side of each circular aperture 42 is counter bored at 44 to provide a recess for receiving the external liner stop 14 all as illustrated in FIG. 1.

On the right side of main frame 4 is provided an auxiliary side wall 46 having a generally V-shaped cross section as illustrated in FIGS. 1 and 2. The upper half 48 of the auxiliary side wall 46 is spaced from the inner side wall 38 to define a camshaft receiving cavity 50 extending along the aligned cylinder cavities 10 from one end 52 to the other end (not illustrated) of the main frame 4. A plurality of spacing webs 56 are connected with and extend generally perpendicularly between inner side wall 38 and the upper half 48 of the auxiliary side wall 46. As is clearly illustrated in FIG. 2, spacing webs 56 reside generally within the plane defined by the rigidifying frames respectively associated with each crankshaft bearing support 22. An aperture 58 contained in each spacing web 56 is configured to receive and support a bearing for a conventional camshaft receiving cavity 50 and to rotate about an axis 59 parallel to the rotational axis 24 of the crankshaft.

In order to further strengthen the main frame 4, each rigidifying frame includes a cross wall 60 interconnecting each pair of head bolt bosses 26, associated connecting pillars 34 and cap screw bosses 30. The cross wall 60 is further connected with the head wall 20, the support wall 40 and the associated crankshaft bearing support 22. As illustrated in FIGS. 1 and 2, the lower half 62 of the auxiliary side wall 46 is flared outwardly away from the crankshaft bearing supports 22 in order to provide sufficient room within the crankshaft receiving cavity 8 for rotational movement of the cranks and connecting rods of the internal combustion engine. As is also apparent in FIGS. 1 and 2, outer side wall 36 includes an outwardly flared lower half 64 which is also designed to provide sufficient room for rotational movement of the cranks and connecting rods of the internal combustion engine. To provide further rigidity to this portion of the engine structure, the cross walls 60 of each rigidifying frame are extended outwardly beyond cap screw bosses 30 into engagement with the lower halves 62 and 64 of the auxiliary side wall 46 and the outer side wall 36, respectively. The thickness of the cross walls 60 is substantially less than the cross sectional diameters of the bosses (26 and 30) and connecting pillars 34 to which the respective cross walls 60 are connected in order to reduce the total weight of the composite engine block. In this regard, rounded apertures 66 are formed in the portion of each cross wall 60 extending between the support wall 40 and each respective crankshaft bearing support 22. The rounded aperture is shaped as illustrated in FIG. 3 to leave upper support webs 68 interconnecting each connecting pillar 34 with support wall 40 and a lower support web 70 interconnecting the cap screw bosses 30 and the associated connecting pillars 34 of each rigidifying frame. Upper and lower support webs 68 and 70 will be described in greater detail hereinbelow. Provision of aperture 66 not only lightens the engine block but also facilitates easier casting of main frame 4 by providing an opening through which the mold cores necessary to form cavities 10 may be interlinked for added stability and positional accuracy during the molding process. To further assist in rigidifying the crankshaft bearing supports 22, horizontally oriented interconnecting webs 72 are provided between the respective sides of each crankshaft bearing support 22 and the corresponding side wall of the main frame 4.

The composite engine block of FIGS. 1 and 2 is provided with coolant passage forming means for directing cooling fluid through the main frame 4 along a coolant path shaped to bring the flow into direct contact with the cylinder liners 12 only along a portion of the axial length of each liner extending between the projection 74 formed by the counter bored aperture 42 and the head wall 20. Because the inside surfaces of the outer side wall 36, the cross walls 60 and the inner side wall 38 surrounding each cylinder liner between head wall 20 and support wall 40 are spaced from the exterior surface of the cylinder liner, a coolant flow chamber 76 having a generally cylindrical configuration is formed within the main frame 4 in surrounding relationship with the upper section of each cylinder liner. As is explained in co-pending application Ser. No. 959,702, filed Nov. 13, 1978, it has been found that only the upper section "b" of each cylinder liner 12 need be brought into contact directly with the coolant fluid flowing through the main frame in order to provide sufficient cooling of the cylinder liner 12 during engine operation. Cooling fluid is supplied to each coolant flow chamber 76 through a pair of inlet ports 78 formed in the outer side wall 36 adjacent the intersection of the outer side wall 36 and support wall 40 as illustrated in FIGS. 1 and 2. As will be explained in further detail hereinbelow, all of the inlet ports 78 are interconnected with an inlet coolant manifold 80 formed in part, by a linear inlet channel 82 formed on the outside surface of the outer side wall 36 adjacent to and slightly below the intersection of the outer side wall 36 and support wall 40. A pair of outlet ports 81 (FIG. 2) are formed in the head wall 20 for communication with each coolant flow chamber 76. Note that the outlet ports 81 are formed generally adjacent the intersection of the head wall 20 with the inner side wall 38. Although not illustrated in the drawings, the outlet ports 81 cause coolant to flow from the coolant flow chambers 76 into the engine head formed with a plurality of flow paths, one of each being positioned to register with one of the outlet ports. After flowing through the engine head, the coolant from each outlet port 81 is discharged from the head into a discharge port 83, formed in the head wall 20 adjacent the intersection of the head wall 20 with the outer side wall 36. As can be noted in FIG. 2, discharge ports 83 are arranged to cause coolant to flow downwardly from the engine head into an outlet manifold 84 formed in part by an outlet channel 86 located on the outside surface of outer side wall 36. The inlet coolant manifold 80 and outlet coolant manifold 84 are arranged generally in a parallel position along the upper portion of outer side wall 36. The respective manifolds are sealed by means of a jacket including a single integral cover member 88 which may be attached in sealing relationship with the inlet channel 82 and the outer channel 86, respectively. The inlet and outlet manifolds are connected to a radiator and coolant pump system, not illustrated, as is conventional in internal combustion engines.

As can be appreciated from a consideration of FIGS. 1 and 2, the flow path of coolant within each coolant flow chamber 76 includes a directional component oriented from outer side wall 36 toward inner side wall 38 and another directional component oriented from the support wall 40 toward the head wall 20. While cross walls 60 contain a large aperture 66 below support wall 40, it has been found that the portion of cross wall 60 extending between head wall 20 and support wall 40 is preferably solid and free of any voids which would allow passage of cooling fluid therethrough. Tests have shown that the provision of a large weight reducing aperture in this portion of cross walls 60 can result in damaging distortion in the main frame 4 although a small pressure equalizing hole could possibly be employed.

The composite engine block of FIGS. 1 and 2 includes a lubrication flow passage forming means for directing lubrication fluid through the main frame 4 along a lubrication flow path which bypasses entirely the portion of the interliner spaces extending between the head engaging surface 6 and the projection 74 of the liner stop means 21. In particular, the lubrication flow passage forming means includes a lubrication fluid entry passage 90 formed in the flared section 64 of the outer side wall 36, whereby the entry passage 90 may receive lubrication fluid from a lubrication fluid pump mounted within the ladder frame 5 as will be discussed in further detail hereinbelow. Lubrication filter mounting means 92 are formed on the outside surface of the flared portion 64 of outer side wall 36 such that lubrication fluid received in lubrication fluid entry passage 90 is passed into a lubrication filter (not illustrated) mounted on the side of the main frame 4. After passing through the filter, the lubrication fluid is passed back into the main frame 4 through a main lubrication fluid supply port 94 into a cross flow passage 96 lying within the plane defined by a cross frame bisecting the entire main frame 4. Flow passage 96 connects with a linear supply passage 98 formed in a lubrication fluid supply rifle 100 extending horizontally along the main frame at the intersection of the inner side wall 38 and the auxiliary side wall 46.

For structural rigidity purposes, the lubrication fluid rifle 100 is integrally connected with the inner side wall 38. As can be seen most clearly in FIG. 1, the lubrication fluid rifle 100 is positioned substantially intermediate the crankshaft receiving cavity 8 and the camshaft receiving cavity 50. To supply lubricating fluid to the crankshaft breaking supports 22 and the corresponding camshaft bearing supports defined by spacer webs 56, a linear supply branch 102 is positioned in the plane defined by the corresponding cross frame. Each linear supply branch 102 intersects at one end with the camshaft bearing aperture 58 of the corresponding spacing web 56 and at the other end with the bearing receiving surface of the bearing support 22. Each linear supply branch 102 also intersects with linear supply passage 98 to cause lubrication fluid supplied to the linear supply passage 98 to travel in opposed directions from the linear supply passage 98 upwardly through each linear supply branch 102 to the corresponding camshaft aperture 58 and downwardly through the same linear supply branch 102 to supply the corresponding crankshaft bearing support 22. By forming the supply branches in this manner, a single drilling of the cast main frame 4 may be made in order to form each linear supply branch 102. Savings in machining costs result from this construction.

Oil returns by gravity flow from the camshaft receiving cavity 50 as indicated by arrows 104 through a plurality of openings 106 formed in the inner side wall 38 between support wall 40 and lubrication fluid rifle 100. Openings 106 (illustrated in FIGS. 1, 2) communicate with the inter cylinder cavity spaces formed between the portion of the cylinder liners extending below support wall 40. By this arrangement, a substantially unobstructed and wide open lubrication fluid return path is formed within the main frame 4 with more than sufficient capacity to handle the volume of returning lubrication fluid which could be expected under all engine operating conditions. This wide open return path is achieved without interferring with the coolant flow path around the cylinder liner and without expanding the main frame size in either the axial or cross axial direction.

The ladder frame means 5, illustrated in FIG. 1, serves the critically important function of strengthening the main frame 4 by providing localized support to the cross frames and of forming an extension of the crankshaft receiving cavity 8 to substantially encompass the crankshaft and to provide sufficient space for rotational movement of the cranks of the crankshaft. The ladder frame means 5 includes a hollow skirt member 108 having an lower surface 112 for engaging the oil pan 114. The hollow skirt member 108 includes a first side wall 116 forming an extension of the lower portion 64 of outer side 36 of the main frame 4 and a second side wall 118 forming an extension of the lower portion 62 of auxiliary side wall 46 of the main frame 4. A plurality of pairs of strengthening pillars 120 extend between upper surface 110 and the lower surface 112 with one strengthening pillar of each pair being integrally connected with the inside surface of the first side wall 116 and the other strengthening pillar 120 of each pair being integrally connected with the inside surface of the second side wall 118. Located adjacent the lower surface 112 are a plurality of struts 122, each strut being connected at one end to one strengthening pillar of a pair of strengthening pillars and at the other end to the other strengthening pillar of a pair of strengthening pillars, whereby each pair of strengthening pillars and the interconnected strut form a rigidifying base frame. As will be illustrated in greater detail hereinbelow, the various rigidifying base frames formed along the axial length of the ladder frame means 5 are positioned to coincide with the cross frames of the main frame 4 to thereby provide localized support to the cross frames.

Reference is now made to FIGS. 3 and 4 which show, respectively, cross sectional views of the main frame taken along lines 3--3 and 4--4 of FIG. 2. The corresponding elements referred to in FIGS. 1 and 2 are identified by the same reference numerals in FIGS. 3 and 4. Reference is particularly made to FIG. 3 which discloses one of the cross frames formed by the interconnection of a pair of head bolt bosses 26, connecting pillars 34 and cap screw bosses 30 which together interlink head wall 20 with crankshaft bearing supports 22. The lubrication fluid entry passage 90 formed in the lower half 64 of side wall 36 is also illustrated with greater clarity in FIG. 3. The return flow of oil illustrated by arrows 104 through opening 106 in inner side wall 38 is further clearly illustrated in FIG. 3.

Referring now particularly to FIG. 4, the cross flow passage 96 is illustrated as being formed in the cross wall 60 positioned at the bisecting cross section of main frame 4. This cross fluid passage 96 interconnects the main lubricating fluid supply port 94 with the linear supply passage 98 in order to transfer oil received through an oil filter unit, not illustrated, to the lubrication fluid rifle 100. Surrounding the main lubricating fluid support port 94 is a flat 95 forming part of the lubrication mounting means 92 which functions to assist in mounting an oil filter on the main frame as discussed above.

Referring now to FIGS. 5A and B, the configuration of the side walls of the main frame and their interconnection with the cross frames is illustrated. In particular FIGS. 5A and B include a top elevational and a plurality of cross sectional views of the main frame taken along lines D--D, E--E, F--F, and G--G of FIG. 1. In these Figures, the inlet ports 78 leading from the inlet manifold 80 are clearly illustrated particularly in cross sectional views D--D and E--E, FIG. 5A. The outlet ports 81 and the discharge ports 83 are clearly shown in the top elevational section at the left hand side of FIG. 5A.

Turning now to FIG. 6, the auxiliary side wall 46 is illustrated in broken side elevational view. FIG. 6 clearly illustrates the vibration reducing means 123 employed in the subject composite engine block design for reducing the audible level of vibration caused by operation of an engine. In particular, FIG. 6 illustrates a plurality of concavities 124 formed in the auxiliary side wall 46 in registry, respectively, with the cross frames of the type illustrated in FIG. 4. The cross sectional shape of these concavities 124 can be better understood by reference to sections E--E, F--F, and G--G of FIG. 5 wherein the shape of the concavities 124 is best illustrated. The purpose of these concavities is to raise the natural frequency of the composite engine block to a level above the frequency of the most audible vibrational perturbations produced by engine operation thereby forming a quieter running internal combustion engine.

FIG. 7 is a side elevational view of the outer side wall 36 which clearly discloses the inlet and outlet coolant channels 82 and 86, respectively. Outlet coolant channel 86 is formed on the upper side by an extension 126 (See FIG. 4) of head wall 20 extending outwardly beyond the intersection of head wall 20 and outer side wall 36. The lower section of inlet coolant channel 82 is formed by an extension 128 parallel to extension 126. A common undulating extension 130 divides the outlet coolant channel 86 and the inlet coolant channel 82. The undulating configuration of extension 130 permits inlet ports 78 to be formed by drilling at a perpendicular orientation with respect to the outer side wall 36 of the main frame 4. By thus avoiding the necessity for drilling the main frame side wall at an acute angle, manufacturing costs can be saved. Extensions 126, 128 and 130 terminate in a planar surface adapted to form a seal with a jacket means formed by integral cover 88, illustrated in FIG. 1.

The side elevational view of FIG. 7 also clearly illustrates the lubrication mounting means 92 which consist of projections 132 and 134 surrounding, respectively, the outlet 101 of the lubrication entry passage 90 and the main lubrication fluid supply port 94. Projections 132 and 134 terminate in planar surfaces 136 and 95, respectively, for sealing engagement with an oil filter unit, not illustrated.

FIG. 8 is a bottom elevational view of the main frame 4 illustrating the relative positions of cylinder cavities 10, outer side wall 36 and auxiliary side wall 46. As is clearly illustrated in FIG. 8, each of the crankshaft bearing supports 22 is interconnected with the respective side walls 36 and 46 by a pair of interconnecting webs 72 extending into integral connection with the respective side walls. The threaded holes 32 of each cap screw boss 30 is shown in this bottom elevational view of the main frame 4. Each interconnecting web 72 contains a threaded opening 138 for receiving connecting bolts 140 (FIG. 1) for attaching the ladder frame 5 to the bottom surface of the main frame 4. As is illustrated best in FIG. 1 threaded apertures 138 extend upwardly into connecting bosses 142 formed integrally with the corresponding interconnecting web 72 and cross wall 60.

FIG. 9 is an end elevational view of the main frame 4 which clearly illustrates the relative positions of the various elements identified by reference numerals corresponding to those elements illustrated in FIGS. 1-8.

Turning now to FIG. 10, an end view is illustrated of the oil pan adaptor or ladder frame means 5. As was noted with reference to FIG. 1, the ladder frame 5 is formed by a hollow skirt member 108 including a first side wall 116 and a second side wall 118 formed between an upper surface 110 for engaging the base of main frame 4 and a bottom surface 112 for attachment to the oil pan of the internal combustion engine. As is clearly illustrated in FIG. 10, the ladder frame includes a lubrication fluid pump housing 143 including a cylindrical cavity 144 adapted to receive a lubrication fluid pump for supplying lubricating fluid to the internal combustion engine. A lubrication fluid discharge passage 146 extends from the cylindrical cavity 144 to a point on upper surface 110 registering with the lubrication fluid entry passage 90 of the main frame. By this arrangement, the lubrication fluid pump may force lubrication fluid through passage 146 into the main frame 4. A lubrication fluid intake passage formed in first side wall 116 extends from the oil pan engaging lower surface 112 into the cylindrical cavity 144 of the pump housing 143. The fluid intake passage 148 opens into the cylindrical cavity 144 of the lubrication fluid pump housing 143 at a point 149 substantially above the lowest point in the housing to permit lubrication fluid to be trapped within the housing when the lubrication fluid pump ceases operation. This arrangement causes the lubrication fluid pump to be self-priming upon start-up of the engine.

FIG. 11 is an elevational view of the opposite end of the ladder frame 5 illustrated in FIG. 10 wherein a pair of strengthening pillars 120 are illustrated. To understand the function of these pillars, reference is also made to FIG. 12 which discloses a top elevational view of the ladder frame 5 and the pairs of strengthening pillars 120. As is apparent in FIG. 12, one strengthening pillar of each pair is integrally connected with first side wall 116 while the other pillar of each pair is connected integrally with the second side wall 118. As previously noted, each pillar is positioned to register with a corresponding interconnecting web 72. Each pair of strengthening pillars is connected along the lower surface 112 by a strut 150 connected at one end to one pillar of a pair and at another end to the other pillar of a pair to form a rigidifying base frame designed to strengthen a corresponding cross frame within main frame 4. FIG. 12 discloses that each strengthening pillar 120 contains an aperture 152 for receiving a connecting bolt 140 (FIG. 1). The threaded ends of bolts 140 are received within threaded apertures 138 (FIG. 8) of the main frame 4 such that the ladder frame 5 may be securely connected at each point of contact between a connecting web 72. A plurality of strengthening webs 154 are formed in the plane of lower surface 112 and are integrally formed with struts 150 and the ladder frame side walls 116 and 118. The configuration of webs 154 has been designed to maximize the rigidifying effect which such webs have on the connection of the individual strengthening pillars 120 and the corresponding side walls of the ladder frame 5. Strengthening webs 154 take a triangular form filling the corner intersection of each strengthening pillar 120 and the corresponding side wall over a substantial area of the lower surface 112. Adjacent webs 154 join integrally at the mid point between adjacent pillars as illustrated by dashed line 156 to form a single integral web extending inwardly from each side wall. Strengthening webs 154 may include extensions 158 from one side wall to the other side wall along each strut 150. The width of such extensions 158 in the axial direction of the ladder is limited, however, to insure sufficient clearance of the rotating counterweight attached to the crankshaft of the engine.

FIGS. 13 and 14 disclose various cross sectional views of the ladder frame taken along corresponding lines in FIG. 12. In particular, FIG. 13 illustrates the dip stick boss 159 for receiving a dip stick assembly, not illustrated. FIG. 14 discloses an oil fill opening 161 for the crankcase of the engine.

FIG. 15 discloses a cross sectional view of the lubrication fluid pump housing 143 taken along lines 15--15 of FIG. 17 including the lubrication fluid intake passage 148 communicating with the cylindrical cavity 144 through channel 160 extending from point 149 to the lower section of the cavity 144.

FIG. 16 is a cross sectional view taken along lines 16--16 of FIG. 12 illustrating a lubrication fluid pressure regulator housing 162 containing an aperture 164 for receiving a lubrication fluid regulator assembly, not illustrated. The regulator housing 162 includes an inlet opening 166 connected with the lubrication fluid discharge passage 146 and a return opening 168 for returning lubrication fluid to the interior of the ladder frame 5 from which the return fluid may be dumped into the oil pan connected with the lower surface 112.

Referring now to FIG. 17, a bottom elevational view of the ladder frame is illustrated. A plurality of oil pan connecting bosses 170 are shown containing threaded apertures 172 for receiving oil pan connecting bolts, not illustrated, for attaching an oil pan to the lower surface 112 of the ladder frame 5. Each oil pan connecting boss 170 is spaced from the center of a corresponding strengthening pillar by a distance "d" substantially less than one half the distance between each strengthening pillar. By this arrangement, the mass of each oil pan connecting boss 170 is moved away from the center of the panel portions of the respective side walls extending between each succeeding pair of strengthening pillars 120. Since struts 150 tend to create vibrational nodes along the length of each ladder frame side wall, the natural frequency of the ladder frame means is increased by positioning the respective oil pan connecting bosses 170 adjacent such vibrational nodes rather than in a position intermediate the vibrational nodes.

Reference is now made to FIGS. 18A, 18B and 19 which disclose, respectively, elevational views of the left side wall 116 and right side wall 118 of the ladder frame as illustrated in FIG. 10. In particular, FIG. 18A discloses oil fill opening 161 positioned between a pair of ladder frame concavities 174 in side wall 116. Similar ladder frame concavities 176 are also formed in side wall 116 as illustrated in FIG. 18B. However, concavities 176 are tapered to permit the oil filter assembly (not illustrated) to be mounted along side wall 116 and to accommodate apertured flat 177. The ladder frame concavities 174 and 176 register with the rigidifying base frames formed by corresponding pairs of strengthening pillars 120 and interconnecting struts 150 as illustrated in FIG. 17.

FIG. 19 similarly discloses a plurality of ladder frame concavities 118 formed in right side wall 118. These ladder frame concavities perform the same functions as cavities 174 and 176 by tending to increase the natural frequency of the ladder frame 5 in the same manner as the main frame concavities 124 illustrated in FIGS. 6 and 8.

A composite engine block structure has thus been disclosed having extremely light weight, high strength characteristics and operational noise reducing capability. The high strength, yet light weight and compact size, of the composite engine block structure makes the subject design ideal for compression ignition engines of the type generally employed in over-the-road vehicles. The light weight of the subject design, of course, improves the overall fuel efficiency of any vehicle equipped with an engine employing the disclosed composite engine block design. The light weight, low noise characteristics and the compact size also make the disclosed engine block design ideal for other applications such as portable compression units, marine propulsion systems and other types of industrial applications in which portability and/or low noise operated characteristics are desired.