Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~n~4l7
The present invention relates to engine heads and
to cooling the same.
This application is a division of copending appli-
cation Serial No. 290,629 ~iled November 10, 1977.
It is desirable to operate an engine at temperatures
as close to t~e 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 ef~cienc~ However, prior art cooling systems
have tended to overcool in some zones and undercool in
others; the pr~or art systems have been a rough compromise
des~gned to remove approximately 30 to 35~ of the heat
produced in the com~ustion chambers resulting from the com-
~ustion of an air-fuel mixture. The systems have typically
been oE 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 ead valves. On some engines,
water distributing tubes or nozzles have been used to
direct the-flow of the cooling water into the water
jacket reserwir in the hopes of regulating heat transfer.
~ecause of the need to extend bolts, shafts and shanks
through the water jacket cavity, flow therein is interrup-
; ted and detrimentally affected. The water jacket has now
become a labyrinth of passages which do not con~ribute to
controlled fluid flow.
The need to improve the cooling system, increase fuel
economy, and economize on the use of cast material has only
,
10~17
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.
The present invention is directed to an engine head
and to a method of cooling the same. The engine head forms
part of an engine housing which forms the subject of the
parent appplication referred to above.
In accordance with one aspect of the present invention,
there is provided an engine head for an internal combustion
engine, com~rising: (a) an elongate housing comprised
entirely of aluminum and having walls defining a top
closure for a galley of aligned cylinders opening onto the
bottom face of the housing, the housing having walls
defining passages for inducting a combustible mixture
and exhausting combusted gases, the closure wall extending
upwardly from the bottom face of the housing, (bl means
defining a series of interconnected hemicylindrical grooves
in the housing extending upwardly from the bottom face of
the housing and consecutively along aach of the cylinders,
the grooves limiting the lower portion of the top closure
walls to a thin-sectioned cylinder, the grooves being so
interconnected as to leave a solid siamese connection
between each of the thin-sectioned cylinders.
In accordance with another aspect of the invention,
there is provided a method of cooling the head of an
internal combustion engine, comprising: (a~ form the
head as a cast body consisting of a metal having a thermal
1094417
conductivity exceeding .~8 cal-cm./sec.-cm2-C, the body
being provlded with a flat bottom, opposed sides, first
walls defining a series of cylindrical portions arranged
side-by-side with each portion extending through the
bottom, having second walls defining a plurality of gas
passages with each extending between one cylindrical portion
and one side of the head, and third walls defining a
plurality o~ valve guide cylinders each extending ~rom the
top of the head into one cylindrical portion, the third
walls having a portion serving as a separation between the
exhaust gas passages and the valve guide cylinders, (b~
convey cooling fluid through the first walls in at least
one laminar non-turbulent first flow path extending from
: one end of ~he head along the sides of each of the
cylindrical portio.ns to the opposite end of the head, and
convey cooling fluid through a cylindrical boring in the
pQrtion of the third walls in a laminar non-turbulent
manner while in parallel flow with the first flow path,
the flow rate and flow area of the flow paths being
2~ adjusted to carry heat away from the metal at a rate
equal to or greater than the thermal conductivity of the
metal whereby any nucleate boiling at the interface
between the flow and metal is limited and controlled to
increase the thermal heat transfer thereacross.
The invention is described further, by way of
illustration, with reference to the accompanying drawings,
:: in which:
: .
Figure 1 is an. exploded perspective view of part of
the engine housing of Figure 6; the housing being broken
:- 30 away alony a sectional plane;
Figure 2 is a schematic composite view of the bodies
4 ~
10~4417
of cooling fluid, detached from the engine of Figure 6,
showin~ the fluid paths and flow character for the
overall cooling system;
Figure 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;
Figure 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;
Figure 5 schematically illustrates the body of
cooling fluid, detached from the engine of Figure 3, with
flow lines disclosing the character of flow;
Figure 6 is a partial sectional elevational view
of an internal combustion engine embodying the invention
herein;
Figure 7 is a view looking directly down upon one
galley of c~rlinders of the head illustrated in Figure 7
together with the sealing gasket superimposed thereon;
Figure 8 is a plan view looking directly down upon
the galleys of cylinders in the engine block;
Figure 9 is an exploded perspective of various
sectioned portions of an engine head constructed in
accordance with the prior art;
Figure 10 is a view similar to Figure 7 but depicting
a head constructed according to this invention;
Figure ll is a top view of the engine head of
Figure 7 and taken in the direction of the arrows shown in
Figure 7;
~igures 12 15 are graphical illustrations of various
physical parameters of the cooling system for the embodiment
10944~ 7
of Figure l;
Figure 16 is a composite diagram and chart depicting
valve guide and seat temperature conditions in a hea~
employing this invention and for a head employing con-
ventional principles; and
-- Figures 17-23 are graphical illustrations of various
engine parameters plotted against engine speed for an
engine according to this invention.
One of the principal features of this invention is
the ability to provide 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 ~oring to carry fast laminar cooling flow
between the exhaust gas passages and the valve guide
cylinders in the engine head. For the series flow concept,
the fluid is allowed to enter the engine block at one end,
20 ~ 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 designed 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
-- 6 --
1~)94417
in the block from a given pump source and a higher 1uid
velocity in the head. ~hen 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 usage.
The series flow concept can best be appreciated
by comparing the schematic illustration in Figure 2 (repre-
senting the invention) and the schematic illustration in
Figure 5 (representing the prior art), and also comparing
the structure of Figure l with that of Figures 3 and 4.
~ Grooves or passages lOa and lOb are defined in the
block 11 to pro~ide primarily two fluid paths 12 and I3
~indicated by arrows in Figure 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 moye in a laminar or controlled
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 Figure 7) separating the block 11 and head 9, such
slots being dimensioned to place an ingate effect upon said
- 7 ~
109~417
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 52 providing two fluid
bands 22-23 and one fluid cylinder 52, all shorter in height
and/or smaller in area than the bands iIl the block. The
bands 22-23 proceed back along the undulating contours of
the cylinder galley to the end 9a (see Figure 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 sequestexed from the first two fluid bands
15 and 16 before reaching the end llb of the block (see
Figure 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 hydro-
dynamic flow guides.
The block 11 is made from a casting having grooves
extending from the casting parting surface 43 downwardly
along each of the cylindex walls 14, the cylinder walls
being defined as rather thin-sectioned walls ~about .15
inches thick~ which stand free ~xcept for a solid connection
42 (about .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 .12 inches thick. The two paths of fluid 12 and 13
10~4417
through the block undulate around the hemi-cylindrical
shaped groovings lOa and lOb. 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 Figures 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 turbulent bath with no specific requirement that the
1uid pass along a streamline flow to the opposite end of
the housing before being permitted to move upwardly into
the ~ody 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 lla of the block to the other end llb before entering
the head ~ or exiting at 24. Thus, fluid flow can be
considered, in Figures 3 and 5, to be the opposite of
series flow. 0~7er 90~ of the fluid traverses the full
length of each of the block and head for the present
~ - 30 invention, whereas in the prior, only up to 65~ of the fluid
- may do so. The rather widr bulky passages in the bloc]c and
.. g _
10~417
head 9 are incorporated more for convenience of casting
than for control of ~luid 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 Figure 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 need~. As a result, heat
is extracted at a rate which is non-uniform and difficult
to assess; usually the rate results in undercooling at
some portions of the cylinder walls and overcooling at
other portions; a non-uniform wall temperature is created
which prévents 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 aspect's: (a~ providing a housing with first
walls (such as 56-58~ and second walls (such as 57-59)
; 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
:
- ~ lQ
1094417
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 ~6-47-48 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 ~ shown
in Figure 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 incor-
porating such cooling method, can be about 8 lbs.; this i8
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 Figure 13,
then the velocity distribution in the block will be as
plotted in the graph for Figure 13. ~epending on whether
10~4417
there is a need for greater or less cooling on one side
or the other, the inlet can be relocated to render coolant
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 Figure 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 velccity pattern
with the same flow in the head, indicated in Figure 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 .55 in2, and the throat area of passage
46 or 47 is about .6 in2. The total throat area of the
head passages is about 1.70 in2 compared to 8.5 in2 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 .81 centipose at 190F.
Turning now to Figure 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 603 when compared with a conventional 1~75 302 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
- 12 -
10~4417
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 Figures 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 oam
pattern is surrounded by unbonded sand. Deep grooves,
defining the inboard and out~oard water passages, as well
as the cylinders, are by a comm~n sand core cluster which
is introduced from one side of the pattern. The
resulting casting should have thin walls defining a first
galley o~ cylinders 65 on one side o the block and a second
; galley 66 of cylinders on the other side, in a V-8 configur-
ation. The bylinder 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 69 mounted
thereon separating the block from the head. The other
end (67b or 68b) is exposed to the crankcase chamber.
~dditional walls outboard walls 70 and 71, and inboard walls
109~417
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 ~eet for
the block, and cylinders 78 for mounting tension bolts
(not shown), and auxiliary equipment.
One ~eature 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 o~ 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 thereb~ rendering thermal conductivity in excess
of .28 calory-centimeter per second-centimeter squared-C,
a minimum for purposes of this invention.
Prior art heads have been constructed o~ aluminum,
but their configurations have consistently required or
contained cooling passages which prevented controlled
:
series flow. For example, in Figure 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;ithis 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
- 30 passages are not of the open deck type, ~ut rather are
~ cored passages which do not have any regular or uniform
- ~ ~4 -
'
,
~09~l~17
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 e~change relationship with the casting
material.
The head of this invention (Figure 10~ eliminates
such cooling disadvantages~ It is preferably constructed
by wa~ of a semi-permanent mold die-casting technique
again having an open 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 ~9 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 b~ 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 loc~tion of the three fluid paths
- 15 -
10944~7
passages (~4-45-25) 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
- 10 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 (Figure lO) is about .25-.3 inches and the
thickness across 6 (Figure 1~) is no less than .28 inches,
and typically about .3 inches.
Saddled 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 passages 88
leading to the seriés 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 cross~low con-
struction whereby exhaust gases are sequestered and
allowed to pass through passages 90-91 underneath the
- 16 -
.0~
labyrinth of passages 88-89 in heat exchange relationship
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 ~ 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 elimina-
tion of the conventional water jacket passage or core as
used in conventional head construction which allows a
large size straight in exha~st 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
surfac~ of the slip-in liner shape conform 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
- 30 liner and the alumlnum exhaust port wall. The liner,
because it is thin and well insulated from the aluminum
- 17 -
~9~417
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 ga~s oxidation process which in turn~results
in~ higher emission feed~gas levels.
As a result~of the unique cooling concept of this
inVent~ion~ an engine~will not emit more hydrocarbons at
0mewhAt~less compression ratios;~the~octane rating of
20~ ;the~required~fue1 does~ not need to ~be lowered to accommodate
slightly~lower~campresslon ratlos. Furthermore, the
adjustment: of~the~air~fuel ratio for the engine need not
e~resorted;to~in order ~to run the engine at a lower wall
temperature~level~ The~latter has been a typical remedial
méAsure~to reduce~the sever~ity of cooling problems, since
the combustion température lS lower if the air/fuel ratio
s~ri~her.
30~ ~
18 -
