Method of Making Air Engine Housing

It is desirable to operate the engine at temperatures as close to the limits imposed by oil properties and strength of the materials as possible. Removing too much heat through the cylinder walls and head lowers engine thermal efficiency. However, prior art cooling systems have tended to overcool in some zones and undercool in others; the prior art systems have been a rough compromise designed to remove approximately 30 to 35% of the heat produced in the combustion chambers resulting from the combustion of an air-fuel mixture. The systems have typically been of the forced circulation type utilizing a water jacket placed around the engine cylinders. Through the years, the water jacket has evolved as an immensely intricate casting with intersecting channels and intersecting bosses delicately cored within the metal casting. Principal emphasis has been to allow water to circulate freely within a bath adjacent the cylinders and head valves. On some engines, water distributing tubes or nozzles have been used to direct the flow of the cooling water into the water jacket reservoir in the hopes of regulating heat transfer. Because of the need to extend bolts, shafts and shanks through the water jacket cavity, flow therein is interrupted and detrimentally affected. The water jacket has now become a labyrinth of passages which do not contribute to controlled fluid flow.

The need to improve the cooling system, increase fuel economy, and economize on the use of cast material has only recently become acute. Prior to this there was greater emphasis given to ease of casting and the benefit of having a large safety factor in block strength by making the engine block large and relatively heavy. Now there is a clear necessity to reduce the weight of the engine, utilize less casting material, while at the same time increase the efficiency of the cooling system.

To economize on weight as well as improve thermal efficiency, several problems must be simultaneously overcome, including: (a) elimination of turbulent cooling flow within the engine block resulting from improper passage wall design; (b) design and cast thinner wall sections throughout the engine, which sections are more closely designed to the material strength limit thereby eliminating excess weight; (c) substitute lighter materials having a higher thermal conductivity without sacrificing strength; and (d) reduce the volume and thereby the weight of cooling fluid while still maintaining a uniform engine wall temperature. These problems of flow, thickness, material and fluid volume must be overcome together.

A primary object of this invention is to provide a new cooling system for an internal combustion engine which extracts heat energy more closely programmed to that which is best adapted for maintaining the metal temperature of the engine housing at a desirable level within design limits and at a more uniform operating temperature throughout while at the same time allowing for a significant reduction in weight of the engine.

A further object, in conformity with the above, is to provide a unique cooling system which increases engine fuel economy, increases horsepower for an equivalent sized engine, and enables the engine to use a leaner combustible mixture while meeting stringent emission standards.

Still another object of this invention is to permit engine design to be more flexible providing for design tradeoffs between the hot strength of the materials utilized, the hot wear resistance capability of the materials employed, and cost factors, to obtain the best combination thereof.

Yet still another object of this invention is to provide a novel head and block construction for an internal combustion engine housing characterized by a cooling system (a) arranged to convey fluid in a singular series relationship between the fluid flowing in the block and that flowing in the head; (b) the flow is arranged to move in consecutive series relationship from cylinder to cylinder within the block or within the head, (c) the flow is programmed to have a relatively low velocity in conjunction with a material having a lower thermal conductivity and low heat rejection, such as in the block, and a higher velocity in the head which is comprised of a material having a much higher thermal conductivity and higher heat rejection (the result being that the highest heat concentration zones will be reduced in temperature more effectively to provide a better overall uniform wall temperature for the engine housing).

Specific features pursuant to the above objects comprise: (a) use only a pair of thin bands of fluid to cool the block and use only three narrow laminar flow paths of fluid to cool the head, one of the latter being a critically placed cylindrical boring passage disposed between the exhaust gas passages and valve guide cylinders; (b) casting the head and block each with a mating deck surface having open grooves extending from said deck thereinto to define a passage for a continuous band of laminar or controlled flow extending successively along one side of each of the engine cylinders; by use of a specially designed block to head gasket, the flow will be directed to pass substantially throughout the entire transverse length of the engine block before being permitted to pass transversely through the head; (c) the gasket separating the deck surfaces of said head and block have a slot at one end to act as an ingate for flow to the head; (d) small apertures are defined in the gasket to short circuit or shunt a small pencil-sized flow of fluid to the head at the inner-most undulations of the band of water so as to act as vortex shedder at each such location; (e) controlling the size of the slot in said gasket and head grooves to insure a velocity flow ratio between said head and block of at least 5:1 with the fluid flow through said head being typically in the velocity range of about 120-130 inches per second; (f) the cooling fluid passages, particularly those in the block, provide controlled flow producing a higher coefficient of heat transfer and less energy loss; (g) the system reduces or holds back pressure equivalent to back pressures of current systems while providing said other advantages; (h) the volume of coolant flowing through said system is reduced to 1/5 that of current systems; and (i) walls separating the cooling channel and a combustion cylinder have a thinner section and are more uniform in dimension thereby providing more controlled heat transfer in those areas requiring increased cooling and in those areas requiring decreased cooling .

FIG. 1 is an exploded perspective view of part of the engine housing of FIG. 6; the housing being broken away along a sectional plane;

FIG. 2 is a schematic composite view of the bodies of cooling fluid, detached from the engine of FIG. 6, showing the fluid paths and flow character for this system of this invention;

FIG. 3 is a schematic elevational view, partly broken away, of an internal combustion engine depicting a conventional cooling system in accordance with the prior art;

FIG. 4 is a composite view of several separated core clusters used to define passages in a prior art head and of their nested or stacked position;

FIG. 5 schematically illustrates the body of cooling fluid, detached from the engine of FIG. 3, with flow lines disclosing the character of flow;

FIG. 6 is a partial sectional elevational view of an internal combustion engine embodying the invention herein;

FIG. 7 is a view looking directly down upon one galley of cylinders of the head illustrated in FIG. 7 together with the sealing gasket superimposed thereon;

FIG. 8 is a plan view looking directly down upon the galleys of cylinders in the engine block;

FIG. 9 is an exploded perspective of various sectioned portions of an engine head constructed in accordance with the prior art;

FIG. 10 is a view similar to FIG. 9 but depicting a head constructed according to this invention;

FIG. 11 is a top view of the engine head of FIG. 10 and taken in the direction of the arrows shown in FIG. 10;

FIGS. 12-15 are graphical illustrations of various physical parameters of the cooling system for the embodiment of FIG. 1;

FIG. 16 is a composite diagram and chart depicting valve guide and seat temperature conditions in a head employing this invention and for a head employing conventional principles.

One of the principal features of this invention is the use of an engine housing water jacket which is significantly decreased in volume and yet is arranged to provide improved cooling over that of conventional engines. This is brought about in part by a series flow concept, and in part by using different flow velocities in different portions thereof, including a critically placed cylindrical boring to carry fast laminar cooling flow between the exhaust gas passages and the valve guide cylinders. For the series flow concept, the fluid is allowed to enter the engine block at one end, separate into two wide bands of fluid which move parallel to each other and along opposite contours of the cylinder gallery without merging except at the opposite end; at such end the paths are permitted to merge and turn upwardly into the engine head where the flow again proceeds to separate into two, three or four channels which move back transversely across the head, two of which are located similarly but oppositely to that in the block. Fluid in said bands is design to move in a laminar or controlled flow manner, the bands being so thin that they appear as convoluted sheets of fluid. The fluid bands are differential in size so as to provide a relatively low fluid flow velocity in the block from a given pump source and a higher fluid velocity in the head. When the series flow concept and differential velocity system is combined with a system of using high thermally conductive material about the high velocity flow and a lower thermal conductivity material about the relatively lower velocity flow, the new total cooling system herein emerges and obtains optimization of energy useage.

The series flow concept can best be appreciated by comparing the schematic illustration in FIG. 2 (representing the invention) and the schematic illustration in FIG. 5 (representing prior art), and also comparing the structure of FIG. 1 with that of FIGS. 3 and 4.

Grooves or passages 10a and 10b are defined in the block 11 to provide primarily two fluid paths 12 and 13 (indicated by arrows in FIG. 1 for each cylinder galley) which begin at one end of the block and are supplied through an inlet 17 from a conventional engine pump (not shown). The fluid flows in said grooves consecutively along each series or galley of in-line cylinders 14, the paths being so defined that the body of cooling fluid, if separated from the engine would appear as wide bands 15 and 16 of fluid which move in a laminar or controlled flow manner toward the remote or opposite end of the block. The bands are thin and adapted to conform to the undulating contour of one hemi-cylindrical side of each of said cylinders in the galley. Upon reaching the opposite end, the fluid paths merge and the fluid is directed upwardly through arcuately aligned slots 18, 19 and 20 in a gasket 21 (see FIG. 7) separating the block 11 and head 9, such slots being dimensioned to place an ingate effect upon said fluid flow stimulating an increase in velocity for the head. Fluid flow passes through the slots and again divides into three paths 44-45 and 25 providing two fluid bands 22-23 and one fluid cylinder 52, all shorter in height and or smaller in area than the bands in the block. The bands 22-23 proceed back along the undulating contours of the cylinder galley to the end 9a (see FIG. 10) where they are permitted to return to the radiating system through outlet 24. In the head 9, the third path 25 provides a most important function; the path is defined by a central boring 8 located at the top of the head and spaced above and midway between the two fluid bands 22-23 and is adjacent to the engine valve guide cylinders 51. The boring defines the fluid cylinder 52 which is fed by a column 32 of fluid. In addition, small volumes 26-27-28-29-30-31 of fluid are permitted to be sequestered from the first two fluid bands 15 and 16 before reaching the end 11b of the block (see FIG. 7) thereof in minute quantity and only for purposes of acting as vortex shedders at the inner contours of the upper two bands 22-23. These small volumes do not form a part of the normal cooling flow, but rather are hydrodynamic flow guides.

The block 11 is made from a casting having grooves extending from the casting parting surface 43 downwardly along each of the cylinder walls 14, the cylinder walls being defined as rather thin sectioned walls (about 0.15 inches thick) which stand free except for a solid connection 42 (about 0.3 inches thick) between each of the cylinders in a siamese fashion. The walls surrounding the cooling grooves are exposed to ambient temperature conditions and are about 0.12 inches thick. The two paths of fluid 12 and 13 through the block undulate around the hemi-cylindrical shaped groovings 10a and 10b. In the head, paths 44 and 45 are formed by groovings 46 and 47 extending upwardly substantially the same height as the roof wall 48 or closure for each cylinder. The third path 25 defining a straight cylinder of fluid 52 extends substantially along the area of the casting which is above the intake and exhaust passages 49-50 and between the exhaust gap passages 50 and the valve guide cylinders 51.

Such series flow concept is dramatically different than that which is now experienced within conventional engine cooling jackets (turn to FIGS. 3-5). Here, fluid is permitted to enter the block casting at one station 33 and because of the design of the passages of the water jacket, fluid is permitted to tumble and turbulate within the fluid body 35 of block 40, such as at 34, to result in a turbulant bath with no specific requirement that the fluid pass along a streamline flow to the opposite end of the housing before being permitted to move upwardly into the body of fluid 36 in the head 9. In fact, openings throughout the entire gasket 21 separating the head 9 and block 11, permit fluid to be short circuited in large quantities at several points, such as at 37, insuring that substantially all of the fluid will not move from one end 11a of the block to the other end 11b before entering the head 9 or exiting at 24. Thus, fluid flow can be considered, in FIGS. 3 and 5, to be the opposite of series flow. Over 90% of the fluid traverses the full length of each of the block and head for the present invention, whereas in the prior, only up to 65% of the fluid may do so. The rather wide bulky passages in the block and head 9 are incorporated more for convenience of casting than for control of fluid flow. Such passages are best illustrated, for example, by viewing the sand core clusters 54 and 53 used to define the cooling passages in the head (see FIG. 4). These components are nested with the core cluster 55 used to define the intake and exhaust passages (as shown at the right).

In prior art constructions, there is no intention or desire to create only a thin sheet of fluid which is directed along the walls of the cylinders. To the contrary, a flooding concept is employed where as much fluid as possible is placed as a bath adjacent the cylinders without specific regard to the volume of fluid or the character of the flow induced as a result of the unavoidable interruptions of such fluid bath. In some prior art constructions, the bath approach is modified to achieve a thermal siphon action, but the latter lacks adequate response to the variable cooling needs. As a result, heat is extracted at a rate which is non-uniform and difficult to assess; usually the rate results in under-cooling at some portions of the cylinder walls and overcooling at other portions; a non-uniform wall temperature is created which prevents attainment of the goals of this invention.

A preferred method of cooling an internal combustion engine according to the invention would comprise at least two essential aspects: (a) providing a housing with first walls (such as 66-71) and second walls (such as 58-59) together defining a series of cylinders for carrying out combustion, the second walls surrounding that portion of the cylinders within which ignition of a combustible mixture takes place and said first walls providing for expansion of said combusted mixture, said second walls being comprised of a material having a higher thermal conductivity than said first walls by a factor of at least 1.5, and (b) conveying cooling fluid through at least one continuous passage (such as 10 in the block and 46-47-48 in the head) extending through and between both said first and second walls, said passage having a smaller throat area for the flow in said second walls than in said first walls to establish a higher velocity fluid flow through said second walls than through said first walls (compare visually cross-sectional area of grooves 10-46-47 and hole 8 shown in FIG. 6). The passages should extend in a manner to carry fluid consecutively along each of the cylinders in the first walls before extending in series into the second walls where again the passages split and extend consecutively along each of the cylinder portions and each of the valve guides in the second walls. The flow velocity of fluid flow in the second walls should be higher than the flow velocity in the first walls by a ratio of about 5:1. The weight of the fluid system in a 5 liter engine when incorporating such cooling method, can be about 8 lbs.; this is significantly low when compared to 17.9 lbs., the weight of fluid required in a conventional engine for an equivalent application. This is a net weight saving in fluid of 9.9 lbs.

The placement of the inlet 17 will influence the velocity distribution between the inboard flow 12 and the outboard flow 13 in the block. For example, if the inlet 17 is located as in the schematic inset for FIG. 13, then the velocity distribution in the block will be as plotted in the graph for FIG. 13. Depending on whether there is a need for greater or less cooling on one side or the other, the inlet can be relocated to render coolent velocity tailored to such needs or establish equal velocities in both passages.

Since the effective inlet to the head is slots 18-19-20 at one end of the head gasket and since the slots direct flow upwardly therethrough, the velocity distribution will substantially be similar to that in the block and as shown in FIG. 12, but of much higher value due to throat area. Moreover, the drilled passage 8 in the head will exhibit an even greater increase in its velocity pattern with the same flow in the head, indicated in FIG. 14; the passage 8 must do a superior cooling job in a remote region of the head and does so in conjunction with the right metal material. For example, the throat area of passage 8 is about 0.55 in..sup.2, and the throat area of passage 46 or 47 is about 0.6 in.sup.2. The total throat area of the head passages is about 1.70 in..sup.2 compared to 8.5 in..sup.2 for the block. This will typically result in flow velocities of 120-130"/sec. in the head and about 20"/sec. in the block, assuming the liquid coolant has a viscosity of about 0.81 centipose at 190.degree. F.

Turning now to FIG. 15, the pressure head loss resulting from using this method of increasing flow velocity in the head (see plot 63) is less than that experienced by merely limiting the cooling volume (see plot 60) when compared with a conventional 1975 302 CID production system (see plot 61) or a conventional 1966 428 CID production system (see plot 62).

The passages 46-47 and 8 in the head play a key role in controlling wall temperature. They are comparatively small, but flow velocity is high. This in conjunction with the high thermal conductivity of aluminum diffuses heat more uniformly. Passages 46 and 47 are joined by small bleeding flows at the inner undulation; this is necessary to drive away any formation of vapor at these locations generated by cavitation and to act as a compressor on the fluid above to retard boiling.

Turning now to FIGS. 6-11, a preferred engine housing, incorporating the cooling system herein, comprises a V-type cast iron block 11, two aluminum alloy cylinder heads 9, an aluminum intake manifold 65, preferably a double-walled exhaust manifold 66, conventional 4-barrel carburetor 67 and air cleaner 68, and aluminum alloy pistons 69. The pistons 69, movable within the cylinders of the block, are preferably comprised of aluminum of conventional design having typical sealing rings. The cast iron block is preferably constructed by way of a sand cast method using the cavityless method of casting whereby a foam pattern is surrounded by unbonded sand. Deep grooves, defining the inboard and outboard water passages, as well as the cylinders, are by a common sand core cluster which is introduced from one side of the pattern. The resulting casting should have thin walls defining a first galley of cylinders 65 on one side of the block and a second galley 66 of cylinders on the other side, in a V-8 configuration. The cylinder walls 67 and 68 are open at both ends, one end (67a or 68a) terminating at the parting surface 43 and being exposed to the gasket 21 mounted thereon separating the block from the head. The other end (67 b or 68b) is exposed to the crankcase chamber. Additional walls outboard walls 70 and 71, and inboard walls 72 or 73, define the cooling fluid channels or grooves 10a and 10b. Other wall portions 74-75-76 respectively define sleeves 74a for rocker arm actuator rods 77, webbing and walls for mounting the engine crankshaft, mounting feet for the block, and cylinders 78 for mounting tension bolts (not shown), and auxiliary equipment.

One feature of the cast iron block of this invention is the open deck access to all of the cooling passages therein; sand cluster corings may be employed in the casting pattern and are readily removable. It is desirable that the pattern for such block be formed of a material that is consumed and burned upon contact with molten metal, such as polystyrene. This should be carried out according to the technique of cavityless or evaporative casting procedures.

The head 9a is preferably comprised of aluminum material thereby rendering thermal conductivity in excess of 0.28 calory-centimeter per second-centimeter squared-.degree.C., a minimum for purposes of this invention.

Prior art heads have been constructed of aluminum, but their configurations have consistently required or contained cooling passages which prevented controlled series flow. For example, in FIG. 9, a prior art head 80 is illustrated having non-straight intake and exhaust passages 81-82. Water passages were created wherever space would permit; this resulted in non-uniform and interrupted passages 83, 84 and 85, which in some cases provided excessive flooding of some head zones and in other cases provided inadequate cooling flow. The cooling passages are not of the open deck type, but rather are cored passages which do not have any regular or uniform cross-section. The passages 83, 84 and 85 occupy any available space in the solid walls adjacent the heat centers, such as the roof of the cylinder and exhaust passages. Very little, if any, of the cylinder roof is exposed to ambient air conditions for radiation, but rather is substantially enclosed by a water jacket. Each of the passages have intersecting portions; fluid passing through such varying passages will experience a non-laminar flow and considerable turbulence causing a deficient heat exchange relationship with the casting material.

The head of this invention (FIG. 10) eliminates such cooling disadvantages. It is preferably constructed by way of a semi-permanent mold die-casting technique again having an open deck by deck by which one sand core cluster may be deployed to define the intake passages while three mating permanent dies define all other aspects of the head. More specifically, a bottom die is used to define the deck surface 86, grooves 46-47, cylinder roof walls 48 and other contours, such as 87, of the lower portion of the head. The upper right die piece is used to define the various bolt cylinders 78 and rocker arm bosses or walls 74, and other upper surfaces 88. The upper left hand die piece is used to define the exhaust passages 50, sloping wall surface 89 and bolt bosses 90.

The grooves 10 extend substantially to the general height of the roof wall 48; the grooves are spaced apart on opposite sides of the cylinders and are spaced from the boring 8 by at least 3 inches. The grooves are adapted to closely conform to the periphery defined by the aligned hemi-cylindrical shapes at one side of each cylinder galley. In a sense, the location of the three fluid paths passages (44-45-25) form an equilateral triangle which, when incorporated with a high thermal conductivity material, provides more efficient heat extraction and maintenance, a more uniform and desirable wall temperature without the necessity for greater cooling fluid volume and greater weight of the solid mass.

After casting of the head, a longitudinally extending passageway 8 is drilled through the head material and interconnected with the grooves 10 by way of upright passage (not shown). The head casting has an outlet opening 24 which when compared to the outlet opening 87 of the prior art head side of the head housing, illustrates the velocity difference necessary to render an equal volume displacement. The walls are of a predetermined thickness substantially surrounding the roof portion of each of the cylinders and are consistently thin throughout the remainder of the casting. For example, the thickness across 7 (FIG. 10) is about 0.25-0.3 inches and the thickness across 6 (FIG. 16) is no less than 0.28 inches, and typically about 0.3 inches.

Saddle between the V-shaped block and heads for said engine is a cast aluminum intake manifold 65 which employs intake passages emanating from a series of four apertures in the top wall thereof (not shown), two of which communicate with a first labyrinth of passage 88 leading to the series of four intake passages at one side and the other communite with a second labyrinth of passages 89 leading to the four intake passages on the other side. The intake manifold is of a crossflow construction whereby exhaust gases are sequestered and allowed to pass through passages 90-91 underneath the labyrinth of passages 88-89 in heat exchange relationshiop for facilitating vaporization of the combustible mixture on its delivery to the intake passages. The heat exchange surface 92 is provided with a series of extended heat absorbing surfaces in the form of ribs 93-94.

Mounted at outwardly facing sides of each of the heads 9a is an exhaust manifold 66 of the double-walled (96-97) insulated construction type, where exhaust gases are permitted to enter a recirculating or turbulizer chamber 95 and finally exhausted through a central aperture 98 at the far end and where the exhaust gases are then brought forward of the engine to be exited through an exhaust system which may include emission control elements.

An additional thermal control feature of the head 9 is the exhaust port shape. As previously stated, this port can be formed during the casting process by a metal die piece. This is possible because of the elimination of the conventional water jacket passage or core as used in conventional head construction which allows a large size straight in exhaust port to be used. Because of the exhaust port size (or area) and straight in design, a thin metal exhaust port liner (100) can be slipped into the exhaust port during engine assembly. The inner surface of the slip-in liner shape conforms to that of an ideal exhaust port surface configuration and has excellent gas flow properties. The liner is insulated against heat transfer to the aluminum head by a gasket (101) at the head face and an air gap (102) between the liner and the aluminum exhaust port wall. The liner, because it is thin and well insulated from the aluminum head, heats up very fast and speeds up the oxidation reaction process of the exhaust gases for better emission control. Exhaust ports, which are surrounded by water, as in conventional cylinder heads, cannot be as large in area or as straight, thus making it difficult, if not impossible, to design a good flowing slip-in liner. Most of the prior art designs try to cast in the exhaust port liner; this is inferior because the liner and aluminum head will be in contact at several points including the forward and rear ends; this results in a considerable increase in heat transfer over the insulated slip-in design. Excessive heat transfer results in increased heat rejection to the coolant, which requires a larger radiator, and also results in a lower exhaust gas temperature which reduces the gas oxidation process which in turn results in higher emission feed gas levels.

As a result of the unique cooling concept of this invention, an engine will not emit more hydrocarbons at somewhat less compression ratios; the octane rating of the required fuel does not need to be lowered to accommodate slightly lower compression ratios. Furthermore, the adjustment of the air/fuel ratio for the engine need not be resorted to in order to run the engine at a lower wall temperature level. The latter has been a typical remedial measure to reduce the severity of cooling problems, since the combustion temperature is lower if the air/fuel ratio is richer.