Patent Abstract:
An automotive reciprocating engine design is disclosed preferably including an extruded cylinder bore block with cylinder bores and a surrounding coolant passage extending from a top flat surface to a bottom flat surface; a cast, closed bottom, open top crankcase with vertical walls having flat upper surfaces; and a stamped metal mid-plate interposed in sealing relationship between the bottom surface of the cylinder block and the flat top surfaces of the crankcase. The crankcase contains bearing supports for a crankshaft and the mid-plate contains holes for connecting rods attached to pistons in the cylinder bores. The design facilitates low cost manufacture of strong, light weight components and easier assembly of the engine, and permits flexible manufacture of a family of engines with different displacements by substitution of a cylinder block of different length or of different bore diameter.

Full Description:
TECHNICAL FIELD 
     This invention pertains to the design of reciprocating internal combustion engines for simplified manufacturing. More specifically, this invention pertains to an engine component design which permits the flexible manufacture of engines of similar but varying cylinder bore and piston stroke dimensions. 
     BACKGROUND OF THE INVENTION 
     The modern four cycle, spark ignition, gasoline powered automobile engine is an elegant and increasingly fuel-efficient machine. Because of the wide ranging needs of vehicle owners, engines of widely different torque and power outputs must be produced. But each different engine size (or displacement) is of complicated construction and requires a large investment to design and manufacture. 
     In simplest terms, these internal combustion engines comprise a plurality of round pistons reciprocating within cylindrical bores and connected to a crankshaft with connecting rods. During a combustion pressure induced power stroke each piston applies torque to the crankshaft to provide the motive power of the engine. The torque and power delivered through the crankshaft is a function of the pressure surface area of the pistons and the length of their power strokes. 
     This assembly of pistons, connecting rods and crankshaft is housed in an engine block. The engine block defines the cylinders in which the pistons reciprocate and it locates and supports the crankshaft and connecting rods. It is open at the bottom. The pistons, connecting rods and crankshaft are assembled from the bottom of the block after inverting it. Finally the bottom of the block is closed with an oil pan. The engine block also contains engine coolant and lubricating oil passages. A cylinder head closes the tops of the cylinders in the block to define therein each respective combustion chamber with the enclosed piston head. The cylinder head also typically contains two air or fuel/air inlet ports and valves, two exhaust gas ports and valves, a spark plug and, often, a fuel injector. It also contains coolant and oil passages. Both the engine block and the cylinder head are metal castings of complex design. And each casting must be designed for the specified displacement of the engine. 
     As observed, it is very expensive to manufacture such engines with specifically designed and cast engine blocks and cylinder heads. It is foreseen that large savings could be realized in the manufacture of automobile engines if the design and manufacture of the engine block could be simplified. It is an object of this invention to provide a modular approach to making the engine structural components that contain the piston, connecting rod, and crankshaft assembly. It is a further object of the invention to separate the cylinder block portion of engine construction from the crankcase containing and assembling portion of the engine. 
     SUMMARY OF THE INVENTION 
     This invention focuses on the redesign of the engine block and oil pan portion of current automobile engines. Current production engines consist of a cylinder head and an engine block. These two components are bolted together with a head gasket in-between for sealing purposes. This configuration has been in production since internal combustion engines became available. The engine block itself is a big casting and requires a new design when either the bore diameter or stroke of the engine is changed. The production of a new engine block requires substantial tooling costs and its design delays new engine development. 
     This invention provides a new modularity in constructing automotive engines. In accordance with the invention, conceptually the current engine block is divided into two distinct sections: an upper cylinder bore block, which is preferably an extrusion, and a lower crankcase which will typically be a casting. The extruded cylinder block defines the cylinder bores and provides coolant passages around the cylinders. It has flat upper and lower surface portions for sealing purposes which will be described. The cast crankcase is shaped to contain and support the crankshaft and its bearing supports and bearing caps. It contains a closed bottom and side walls for these purposes. The side walls end in flat top surfaces also for a sealing function. A mid-plate separates the cylinder block and crankcase structures and provides openings for the connecting rods joining the pistons in the respective cylinder bores to the crankshaft in the crankcase. 
     The upper surface of the mid-plate has a gasket shaped to seal coolant in the cylinder block while the bottom surface of the mid-plate has another gasket to seal oil and blow-by gases in the crankcase. The mid-plate separator thus allows a single crankcase to be matched with varying sizes of cylinder bores for a family of engines. 
     The overall engine architecture then includes a conventional cylinder head and the extruded cylinder block and separate closed crankcase provided by this invention. A head gasket provides sealing between the cylinder head and upper surface of the cylinder block. Gaskets on both sides of the mid-plate provide sealing between the cylinder block and mid-plate and between the mid-plate and crankcase. These engine structural components from cylinder head to crankcase are bolted together by a set of long bolts into a suitably rigid and strong structure. 
     The open top of the crankcase permits easy placement of the crankshaft on its bearing supports and the positioning of the bearing caps on the journals of the crankshaft. Moreover, the continuous cylinder openings through the length of the extruded cylinder block and the cooperating holes in the mid-plate permit easy assembly of the connecting rods and pistons in and between the cylinder block and crankcase. Such placements and assembly can be accomplished without turning the engine over during this part of its construction. And the architecture requires no oil pan. 
     Generally, both the cylinder head and crankcase are cast parts. But the cylinder bore block is preferably an extrusion and can be cut to the length to meet the piston stroke needed. Extruded alloys are often stronger than cast alloys and, therefore, extrusions can sometimes be made smaller and lighter then the same part made by casting. Further, cylinder block extrusions can be made with lower cost tooling than cast blocks and can be extruded to close to net shape, thus requiring less machining. 
     With the cylinder bore block and crankcase being separated by the mid-plate, the sizes of the cylinder bores or lengths in a cylinder block are not rigidly tied to a specific crankcase or even a specific cylinder head. The selection of bore diameter and stroke may be limited by valve size, valve bridge width (e.g., minimum of 4 mm) or bore wall distance (e.g., minimum of 5.5 mm). Under these constraints, a modular engine construction as provided by this invention can accommodate approximately a 40% variation in engine displacement using the same cylinder head and crankcase. Thus, a modular engine architecture as provided herein can be utilized for designing and manufacturing a family of engines where the engine displacements vary within a range, for example 1.8 L, 2.0 L, and 2.2 L. For these three engines, a manufacturer could use the same cylinder head, crankcase, mid-plate and the gasket for lower mid-plate surface. Variations in engine displacement can be achieved by varying bore diameter, piston stroke, or a combination of both, in the extrusion of the cylinder block, which would be a commodity part. This family of engines could be produced on the same production line. The number of engines produced for each displacement could be quickly tuned to reflect the market needs for these engines. 
     The use of the extruded cylinder bore block and cast crankcase is also applicable in V-engine designs. In this embodiment, two extruded cylinder blocks would be bolted through two mid-plates to a single crankcase having wall sections to seal against the two V-legs formed by the cylinder blocks. The bearing caps would be shaped to accommodate this architecture. 
     In preferred embodiments of the invention, water cooling of the cylinder head and the cylinder block are managed separately. An electric water pump is employed with water flow circuits that enable the head and cylinder blocks to be cooled independent of engine speed and of each other. The object of this arrangement is to maintain uniform engine temperature at all speeds. 
     Just as different engine segments can be cooled with different coolant flow rates, lubricant flow to the cylinder head and the crankcase can also be separately controlled using an oil pump mounted outside the engine structure. 
     Other objects and advantages of the invention will become apparent from a detailed description of a preferred embodiment which follows. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective assembly view of a modular engine architecture comprising an extruded cylinder bore block, a mid-plate and cast crankcase in assembled relationship. A front engine cover casting for enclosing a timing chain is illustrated in the FIG. 1 view. 
     FIG. 2 is an exploded view of several of the modular engine elements of FIG.  1 . In this figure the elements are shown turned end-for-end from their position in FIG. 1 for further illustration. 
     FIG. 3A is a perspective view of the extruded cylinder bore block of FIGS. 1 and 2. 
     FIG. 3B is a bottom view of a broken-off portion of the cylinder block of FIG.  3 A. 
     FIG. 4 is a perspective view of the mid-plate element of FIGS. 1 and 2. 
     FIG. 5 is a top perspective view of the cast crankcase modular element of FIGS. 1 and 2. 
     FIG. 6 is a perspective view of a bearing cap of FIG.  2 . 
     FIG. 7 is a perspective view of an assembly of the crankcase and bearing caps without the crankshaft. 
     FIG. 8 illustrates a coolant intake/outlet manifold for bolting to the extruded engine bore block. 
     FIG. 9 is a top view of an extruded engine block illustrating coolant flow around the cylinders. 
    
    
     When a part is shown in different drawing figures it is identified by the same number. 
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The practice of the invention will be illustrated in the case of an in-line, four-cylinder, spark ignition engine. Engines of this type are manufactured in large numbers throughout the world. Moreover, they are designed and manufactured with displacement values that vary over a relatively narrow range, for example, 1.8 to 2.2 liters. In accordance with this invention, a family of engines with similar modular components could be designed and manufactured at relatively low cost and capital investment. In a preferred, but optional, embodiment the illustrated design contemplates detached engine accessories such as the oil pump, water pump, starter and alternator. 
     In FIG. 1 an assembly  10  of modular engine structural components is illustrated. The assembly  10  includes an extruded cylinder bore block  12  that has a front end  20  (referring to the arrangement in FIG. 1) and a rear end  22 . Below the cylinder block  12  is a crankcase  16  that also has a front end  24  and rear end  26 . Cylinder block  12  and crankcase  16  are separated by mid-plate  14 . Enclosing the front of the engine (as shown in FIG. 1) is engine cover  18 . As shown cylinder block  12  has four cylindrical bores  28 ,  30 ,  32 , and  34 , respectively, from the front  20  to the rear  22  of the cylinder block. 
     The cylinder block  12 , crankcase  16 , and mid-plate  14  are structural parts of the modular engine architecture of this invention. In an assembled engine these parts cooperate to enclose a crankshaft in crankcase  16 , four pistons in cylinder bores  28 ,  30 ,  32 ,  34  and four connecting rods extending from the cylinder bores through holes ( 74 , in FIG. 4) in midplate  14  into crankcase  16 . In order to simplify the illustration of the modular engine elements of this invention, the pistons, connecting rods and crankshaft are not shown. These engine components are well known and neither their design nor manufacture need be changed by the practice of this invention. 
     Front plate  18  forms a space  35  between the front end  20  of cylinder block  12  and front end  24  of crankcase  16  to accommodate a timing sprocket and timing chain. These parts are not shown in FIG.  1 . But as is well known, the timing sprocket is turned by one end of the crankshaft and drives a timing chain that drives a camshaft for intake and exhaust valve actuation. Front plate  18  also provides a bearing support opening  19  for the front end of the crankshaft. 
     The top surface  36  of cylinder bore block  12  is flat for sealing engagement with a cylinder head, not shown. Again, as is well known, the cylinder head of the engine closes the top of the cylinder bores  28 - 34  to provide a combustion chamber in each bore in cooperation with the respective piston reciprocating in the bore. The cylinder head contains inlet and exhaust ports, and positions and supports intake and exhaust valves. The cylinder head also contains a spark plug, in the case of a spark ignition engine, and it often contains a fuel injector. The cylinder head and its components are not illustrated, for purposes of simplicity of disclosure, because their design, construction and operation does not necessarily have to be altered by the use of the modular engine components of this invention. 
     FIG. 2 shows cylinder block  12 , mid-plate  14  and crankcase  16  turned end-for-end and in exploded view. In this view (and in FIGS.  1  and  3 ), cylinder bore block  12  is recognizable as an extruded article of manufacture. Its vertical surfaces extending from top surface  36  to bottom surface  38  are straight. The cylinder bores  28 - 34  and cooling passage  40  also extend vertically straight throughout their length. Cylinder block  12  may be extruded using an aluminum alloy such as AA6063. 
     Crankcase  16  is preferably a casting of suitable aluminum or ferrous alloy. It is basically an elongated bowl structure, symmetrical about its central longitudinal vertical plane. Its rounded bottom  42  is closed, except for an oil drain hole  44 . The length and spacing of sidewalls  46  and  48  accommodate the crankshaft for the four cylinder engine. The journals of the crankshaft are supported on semi-circular cradle portions  51  of bearing supports  50  (as seen in FIG. 2) and bearing supports  52 ,  54 ,  56  and  58  as best seen in FIG.  5 . Preferably, these five bearing supports are integrally cast portions of crankcase  16 . 
     Referring to FIG. 2 the upper halves of the bearing structures for the crankshaft are bearing caps  60 ,  62 ,  64 ,  66  and  68 . They are shown in exploded view prior to engine assembly. Thus, in the assembly of the engine, a crankshaft with connecting rods attached can be readily laid on bearing supports  50 - 58  through the open top of the crankcase structure. Bearing caps  60 ,  62 ,  64 ,  66 ,  68  are then placed upon the respective bearing supports on top of the journals of the crankshaft. The bearing caps are secured partly by five bolts on each side of the crankcase extending through bolt holes  70  into complementary holes  72  in the ends of the bearing caps. This assembly is easily accomplished through the open top of the crankcase  16 . 
     Mid-plate  14  is then laid on top of the bearing caps  60 - 68 . As seen in FIGS. 2 and 4, the mid-plate has holes  74  for the extension of the connecting rods from the crankshaft in the crankcase  16  up into the cylinder bores  28 - 34  of the cylinder block  12 . Pistons can then be inserted into the bores  28 - 34  and the cylinder block  12  placed on top of the mid-plate  14  which in turn rests on the top surfaces  76  of walls  46 ,  48  of the crankcase  16  and the top surfaces  78  of bearing caps  60 ,  62 ,  64 ,  66 ,  68  (see also FIG.  6 ). As best seen in exploded view FIG. 2, ten bolts  82  of suitable length extend through the cylinder block  12 , mid-plate  14 , and bearing caps  60 - 68  and are screwed into and anchored in the bearing support portions  50 - 58  of the crankcase  16 . In FIG. 5, ten threaded bolt holes  80  in the respective bearing supports receive the bolts  82 . Actually, in the assembly of an engine these through bolts  82  could also extend through the cylinder head (not shown) to be located on top of the cylinder block  12 . 
     Thus, FIG. 2 illustrates, in uncluttered outline, the relative positions of the modular structural engine elements of this invention. In an engine assembly operation, a gasket would be inserted between the cylinder head and the extruded cylinder bore block  12 . Also in the assembled engine there would be a gasket (not shown) on top of mid-plate  14  to provide a coolant seal between mid-plate  14  and the lower surface  38  of the cylinder block  12 . Similarly a second gasket (not shown) would be located as a lubricating oil seal below mid-plate  14  on the top surfaces  76  of the crankcase  16 . In a preferred embodiment, mid-plate  14  is stamped from a stainless steel sheet and thin sheets (0.25 mm) of coated steel gasket material are riveted or welded to each side of the plate. 
     FIG. 3A is a perspective of the cylinder bore block  12 . It shows the cylinder bores  28 ,  30 ,  32 ,  34  with the surrounding cooling passage  40 . Bolt holes  84  for through bolts  82  are shown as well as additional bolt holes for rigidly securing the cylinder block to mid-plate  14  and crankcase  16 . Machined in the side  86  wall of cylinder bore block  12  are an engine coolant inlet slot  88  and a coolant outlet slot  90 . Coolant slots  88  and  90  extend through wall  86  to region of the coolant passage  40  on the immediate opposite side of the wall  86 . Bolt holes  107  are for attaching a coolant inlet/outlet manifold casting  94 , shown in FIG.  8 . 
     FIG. 3B shows more detail of the bottom of a portion of extruded cylinder block  12  adjacent end  24 . Cylinder bores  28 ,  30  and  32  are seen as well as part of the cooling passage  40  surrounding these cylinder bores. In the bottom of the extruded block are ten webs  92  (seven are shown in FIG. 3B) that locate and retain the cylinder bore  28 - 34  containing structure within the extruded block  12  while leaving ample coolant flow passage  40  volume in the upper hotter portion of the engine component. In this embodiment, two webs are formed on each side of the central two bores  30  and  32  and three webs are extruded between the end cylinder bores (only bore  28  shown) and the adjoining portion of cooling passage  40 . The material of the ten webs is initially formed the full length of the cylinder block during extrusion of this component. About 80% of the length of each web material is machined away from passage  40  before engine assembly so that the finished webs  92  extend only about 20% of the height of cylinder block  12 . Coolant flow in the upper portion of passage  40  is to remain unimpeded because this flow is adjacent the heated portion of the cylinder bores. 
     FIG. 9 is a plan view of the top surface  36  of the cylinder bore block. The principal purpose of FIG. 9 is to show a preferred embodiment of the flow of coolant within coolant passage  40  of the cylinder block. It will be recalled that the coolant flow is isolated in the cylinder bore block by suitable gaskets at both its upper surface  36  and lower surface  38 . Coolant is circulated with an electric water pump separate from the engine structure and the coolant circulation system is arranged so that coolant flow to the cylinder block and the cylinder head can be controlled separately. 
     Coolant enters inlet port  88  (FIG. 3A) through a coolant inlet-outlet manifold  94  attached to the side of cylinder block  12  and described below with reference to FIG.  8 . As seen in FIG. 9 a rod  96  inserted into coolant passage  40  adjacent bore  28  serves as a coolant inlet-outlet separator. Rod  96  extends vertically the full height of the passage  40  at that location. Thus, the coolant flow is directed from left to right (as seen in FIG. 9) successively past each cylinder bore  28 ,  30 ,  32 ,  34  and around the outside of each cylinder. Since there is no coolant flow channel between the cylinders this cylinder block design is referred to as a Siamese twin design. Preferably, the incoming coolant is directed past the exhaust gas port side of the cylinder bank because the exhaust side is hotter than the intake port side. The coolant thus traverses the length of the block, flowing around end cylinder  34  and then coming back down the intake port side of the block  12  (i.e., U flow path) and around the first cylinder  28  to coolant outlet slot  90 . The coolant exits the coolant manifold and is directed to the vehicle radiator. 
     As stated, an advantage of this modular construction utilizing the extruded cylinder block and mid-plate construction is that segregated or segmented cooling can be employed in the block itself with a separate cooling flow in the cylinder head. Flow can be permitted or stopped separately in each of the cylinder block and the cylinder head in order to maintain more uniform temperature in these components throughout engine operation. 
     FIG. 8 illustrates a coolant inlet-outlet manifold  94  casting for attachment to cylinder block  12 . It is a simple two part manifold structure with an inlet hole  98 , a partition  100  forming two coolant flow volumes within the manifold body  104  an outlet hole  102 . Bolt holes  106  of the manifold  94  are shown for accommodating bolting of the manifold  94  to the side  86  of block  12  over slots  88 ,  90 . Corresponding bolt holes  107  are provided in a flat machined region of side wall  86 . A gasket should be interposed between the manifold and block for a coolant tight connection. Suitable hoses or the like would be attached to the inlet  98  and outlet  102  for coolant circulation between the water pump, cylinder block and radiator. 
     FIG. 4 is a perspective plan view of a stamped ferrous or aluminum alloy mid-plate  14 . As stated, the mid-plate component is for suitably separating portions of the cylinder block  12  and crankcase  16 . It is a flat plate through which round holes  74  are permitted to accommodate the four moving connecting rods. Obviously, one end of each rod is connected to a piston in the cylinder bore and the other end of each rod is connected to the crankshaft in the crankcase. The holes  74  in the mid-plate  14  must be large enough to accommodate the sweep of each connecting rod as it follows its reciprocating piston and contributes to the rotation of the crankshaft. 
     Mid-plate  14  contains ten bolt holes  108  for through bolts  82  and additional bolt holes for additional bolt connections with the cylinder block and crankcase during engine assembly. 
     FIG. 6 is a perspective view of a representative bearing cap  60 . Each cap has a flat upper surface  78  for engagement with mid-plate  14  or an interposed gasket. Each bearing cap also has a half round cylindrical lower surface  109  for engagement with the bearing surface of a crankshaft. Bolt holes  72  are provided in each end for attachment to the wall of the crankcase and bolt holes  110  for through bolt  82  attachment to the underlying bearing support during engine assembly. A crankcase oil channel  112  is formed in top surface  78  of each cast bearing cap  60 - 68  extending from the channel in the surface to cylindrical surface  109 /crankshaft journal interface. 
     Each bearing cap  60 - 68  is shaped with ventilation windows  114  to provide fluid flow communication between crankcase volumes created between the bearing supports  50 - 58 /bearing caps  60 - 68  barriers. These windows in the bearing caps permit crankcase ventilation. 
     FIG. 7 is a perspective view of the bearing caps  60 - 68  assembled on the corresponding bearing supports  50 - 58 . This view also shows the crankcase oil channel  116  formed in the top surface of one of the vertical walls of crankcase  16 . Thus, lubricating oil is delivered through an oil line (not shown) to channel  116  by a remote oil pump (not shown). The oil flows along channel  116  and into the individual channels  112  on the bearing caps and then to the crankshaft bearing sites. Except for the connecting rod hole  74  openings in the mid-plate  14 , the top of the crankcase assembly is closed by mid-plate  14  in the assembled engine. Oil flowing from the crankshaft bearings is thrown upwardly through the openings  74  to provide some lubrication of the piston ring cylinder wall surfaces. 
     Thus, it is seen that the combination of the cylinder bore block, the mid-plate and the closed bottom crankcase permits these components to be manufactured simply and inexpensively. The separate manufacture of the cylinder bore block, mid-plate and crankcase means that these modular components can each be made of preferred materials and processes for better individual properties. 
     The modular engine combination also provides for flexibility in the extrusion of cylinder bores of varying length and varying diameters in order to form cylinder blocks accommodating varying engine displacement values. As shown above there can be a variation of 10%-40% in displacement range without requiring a change in the design of the crankcase and without requiring substantial change in the design of the cylinder head. Thus a whole family of engines can be made with simply made structural components to produce engines that are just as efficient and elegant in their operation as the modern automotive engine. Further, the combination of the extruded cylinder bore block and open-top crankcase permits easy assembly of the pistons, connecting rods, crankshaft and crankshaft bearing cups during engine manufacture. 
     While this invention has been described in terms of a few specific embodiments it will be appreciated if other forms could be readily adapted by those skilled in the art. Accordingly, the scope of the invention is to be limited only by the following claims.

Technology Classification (CPC): 5