Internal combustion engine cylinder head method of manufacture

Manufacture of a liquid cooled cylinder head for an internal combustion engine is described which reduces incidence of casting fins that may block or impede coolant flow through the cylinder head. The head is cast without internal liquid coolant passages to interconnect the first and second cooling cavities. An opening is machined through an outer surface of the head to define a passage interconnecting the first and second cooling cavities to provide for communication of cooling liquid therebetween. The opening formed by machining through the outer surface of the head is closed. Throat area of the the passage may be selected to control coolant exchange between the first and second cooling cavities and additional passages may be machined in each head to provide additional coolant interchange or to vent air from the cooling cavities.

BACKGROUND OF THE INVENTION 
The present invention relates to the manufacture of internal combustion 
engines, and more particularly, but not exclusively, the formation of 
cooling structures for a cylinder head. 
The use of overhead valves in internal combustion engines is a common 
practice. In one configuration, multiple intake and exhaust valves are 
employed to improve engine performance and efficiency. Such cylinder heads 
are ordinarily cast from metal with a complex labyrinth of passageways and 
chambers in order to accomodate the multiple valve structure. U.S. Pat. 
Nos. 5,222,464 to Oyaizu and 2,710,602 are cited as examples of the 
intricate internal structure of various types of cylinder heads. 
Frequently, the intricate structure of a cylinder head requires utilization 
of multi-core casting techniques. Furthermore, optimum performance of this 
type of structure usually requires fluid interconnection between cooling 
jacket chambers formed by different cores with relatively small passages. 
Properly casting these small interconnections can be difficult. Sometimes 
"casting fins" result within the interconnecting passages which threaten 
to block or impede desired coolant flow. The geometry of cooling jackets 
often makes casting fins difficult to detect and remove--leading to labor 
intensive rework. This rework adversely impacts producability of the 
cylinder head. 
Thus, there is a need to improve cylinder head producability by reducing 
the occurrence of undesired casting fins. 
SUMMARY OF THE INVENTION 
One feature of the present invention is a method for making a liquid cooled 
cylinder head for a multi-valve internal combustion engine. This head has 
an outer surface that includes a first cooling cavity and a second cooling 
cavity. The method includes casting the head without integral liquid 
coolant passages connecting the first and second cooling cavities within 
the head. An opening is machined through the outer surface of the head to 
form a passage intersecting the first and second cooling cavities to 
provide for liquid coolant communication between the first and second 
cooling cavities within the head. The opening formed by machining in the 
outer surface of the head is then closed. 
In another feature of the present invention, manufacture of a liquid cooled 
cylinder head for an internal combustion engine includes casting the head 
with a number of exhaust ports and a number of intake ports. A lower 
cooling jacket and an upper cooling jacket are also cast in the head. A 
first opening is machined through the outer surface of the head after 
casting to define a first passage interconnecting the upper and lower 
cooling jackets to provide for the flow of coolant therebetween. In 
addition, a second opening is machined through the outer surface of the 
head after the casting to define a second passage interconnecting the 
upper and lower cooling jackets to vent air when coolant is introduced. 
The first and second openings are then closed. The first passage has a 
larger throat area then the second passage with the second passage being 
positioned generally above the first passage. 
Among the advantages of these features is that small interconnecting 
passages prone to the formation of casting fins typically do not need to 
be cast between the first and second cooling cavities. Instead, these 
passages are machined through the outer surface of the head. Generally, 
this approach improves cylinder head producability. 
Accordingly, one object of the present invention is to provide a method of 
manufacture of a cylinder head which avoids the need to cast cooling 
jacket passages prone to rework. Instead, passages are machined through an 
outer surface of the head to provide desired interconnections. 
Another object of the present invention is to improve producability of the 
cylinder head for an internal combustion engine by reducing occurrence of 
casting fins within passages interconnecting cylinder head cooling 
jackets. 
Further objects, features, and advantages of the present invention will 
become apparent from the detailed description and drawings herein.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
For the purposes of promoting an understanding of the principles of the 
invention, reference will now be made to the embodiment illustrated in the 
drawings and specific language will be used to describe the same. It will 
nevertheless be understood that no limitation of the scope of the 
invention is thereby intended. Any alterations and further modifications 
in the described device, and any further applications of the principles of 
the invention as described herein are contemplated as would normally occur 
to one skilled in the art to which the invention relates. 
FIG. 1 is a partial cross-sectional view of the multi-valve internal 
combustion engine 10 of the present invention. Engine 10 includes cylinder 
block 12 which defines cylinder bore 14 having a longitudinal axis 15. 
Cylinder block 12 also defines cooling chambers 18a, 18b. Piston 16 is 
situated within bore 14 and configured to reciprocate along axis 15 in a 
conventional manner. Bore 14 includes combustion chamber 17a situated 
between piston 16 and head assembly 20. Preferably, engine 10 includes a 
number of cylinder/piston assemblies (not shown) which are configured for 
conventional four cycle operation. 
Head assembly 20 includes cast member 22 defining head 30a Preferably, cast 
member 22 is integrally cast from metal using a multi-core technique. U.S. 
Pat. No. 3,558,808 to Koziara is cited as an example of various coring 
techniques applied to cylinder heads. Cast member 22 includes outer walls 
24a, 24b generally opposing each other and defining outer surface 26. In 
addition, cast member 22 includes a number of inner walls 28, 29 defining 
various chambers in head 30a. 
Referring additionally to FIGS. 2 and 4, further details concerning the 
structure of cast member 22 are depicted. FIGS. 2 and 4 illustrate a 
portion of engine 10 including not only head 30a, but also heads 30b, 30c. 
The partial view of engine 10 in FIGS. 2 and 4 show heads 30a, 30b, 30c 
(collectively designated heads 30) integrally connected to each other in 
an in-line arrangement. Preferably, engine 10 has six in-line cylinder 
heads with corresponding cylinder/piston assemblies (not shown). In other 
embodiments, a different number of cylinder heads or different cylinder 
head arrangement may be employed as would occur to one skilled in the art. 
Cylinder heads 30 define a number of bolt bores 32. Bolt bores 32 are each 
configured to receive a corresponding head bolt 34 to secure cast member 
22 to block 12. FIG. 1 provides an example of the interconnection of block 
12 and member 22 with bolt 34 extending through a typical bolt bore 32. 
FIG. 2 illustrates a number of bolt bores 32 without corresponding head 
bolts 34 for clarity. 
Each head 32 also defines an injector passage 36 configured to receive a 
fuel injector 38. Each injector 38 is configured to inject fuel into a 
corresponding combustion chamber 17a, 17b, 17c (collectively designated 
combustion chambers 17) in a conventional manner. FIGS. 2 and 4 depict 
combustion chambers 17 in phantom. 
FIGS. 1, 2, and 4 also depict intake manifold 40 defining intake chamber 
41. Head 30a includes two intake ports 42a, 44a in fluid communication 
with intake chamber 41. Similarly, heads 30b, 30c include intake ports 
42b, 44b and 42c, 44c, respectively, in fluid communication with intake 
chamber 41. Intake passage 46a connects intake port 42a with intake 
chamber 41 as partially shown in phantom in FIG. 4. FIG. 4 also depicts, 
in phantom, intake passage 46b interconnecting intake ports 44a and 42b to 
intake chamber 41, intake passage 46c interconnecting intake ports 44b and 
42c to intake chamber 41, and intake passage 46d interconnecting intake 
port 44c to intake chamber 41. 
Referring additionally to FIG. 3, each cylinder head 30 defines exhaust 
exit 50a, 50b, 50c, (collectively designated exhaust exits 50), 
respectively. As illustrated in phantom by FIG. 4, exhaust exit 50a is 
interconnected to exhaust ports 54a, 52a of cylinder head 30a via exhaust 
passage 56a, exhaust exit 50b is interconnected to exhaust ports 52b, 54b 
of head 30b via exhaust passage 56b, and exhaust exit 50c is 
interconnected to exhaust ports 52c, 54c of cylinder head 30c via exhaust 
passage 56c. 
Referring specifically to FIGS. 1 and 2, a number of valve assemblies 60 
are illustrated. Each intake port 42a, 42b, 42c, 44a, 44b, 44c includes a 
valve assembly 60 to control the flow of air from intake manifold 40 into 
the corresponding combustion chamber 17. Similarly, each exhaust port 52a, 
52b, 52c, 54a, 54b, 54c includes a valve assembly 60 to control the 
exhaust of combustion products from the corresponding combustion chamber 
17. 
FIG. 1 depicts valve assembly 60 corresponding to intake port 42a in 
greater detail. Valve assembly 60 includes valve seat 62 which receives 
valve head 64. Valve stem 66 is integrally connected to valve head 64 and 
extends through head 30a. Opposing valve head 64 is terminal portion 67 of 
stem 66 which passes through spring 68. Spring 68 is situated in spring 
recess 69 on the top portion of head 30a opposite the lower portion 
containing seat 62. Spring 68 and stem 66 are configured to bias valve 
head 64 into seat 62 to prevent flow of air through intake port 42a. Valve 
assembly 60 is opened and closed by rocker load assembly 70 via push rods 
(not shown) or other appropriately timed means synchronized to the 
combustion cycle of engine 10. For each head 30, the opening and closing 
of the corresponding valve assemblies 60 is performed by a rocker load 
assembly 70 in a conventional manner. Similarly, injectors 38 are also 
timed to inject fuel into combustion chambers 17 as appropriate. Head 
assembly 20 includes valve cover 72 connected to cast member 22 with an 
intervening orificed head gasket 74. 
Preferably, the four overhead valve, fuel injection arrangement of in-line 
heads 30 is configured for diesel fueling with conventional compression 
ignition. In other embodiments, more or fewer valves may be employed and 
fuel may be introduced by other techniques besides injection. Furthermore, 
other types of fuel or engine ignition schemes may be used as would occur 
to one skilled in the art. 
Referring specifically to FIGS. 1 and 4, cooling spaces for each cylinder 
head 30 are depicted. Cast member 22 defines a lower cooling jacket 80 
depicted as an interconnected cooling chamber or cavity from one cylinder 
head to the next. Lower cooling jacket 80 is particularly depicted in 
FIGS. 1 and 4 which illustrate that lower cooling jacket 80 is generally 
positioned between outer wall 24a and inner wall 28. Upper cooling jacket 
90 has portion 90a located generally above lower cooling jacket 80 and 
between outer wall 24a and inner wall 29. Upper jacket 90 also includes 
portion 90b generally positioned opposite cooling jacket 80 and between 
outer wall 24b and inner wall 29. 
Lower cooling jacket 80 is in fluid communication with cooling chamber 18a 
of cylinder block 12 via passages 88. Similarly, upper cooling jacket 90 
is in fluid communication with cooling chamber 18b of block 12 via 
passages 98. Passages 88, 98 interconnect cooling chambers 18a, 18b of 
block 12 through orificed head gasket 74, respectively, 
Initially, cast member 22 is formed by a multi-core casting process with 
lower cooling jacket 80 and upper cooling jacket 90 being formed by 
separate cores. As cast, lower cooling jacket 80 and upper cooling jacket 
90 lack any interconnecting passages between lower cooling jacket 80 and 
upper cooling jacket 90 within heads 30. As a result, liquid coolant 
cannot be exchanged between lower cooling jacket 80 and upper cooling 
jacket 90 within heads 30. Nonetheless, it is desirable to provide an 
interconnection between lower cooling jacket 80 and upper cooling jacket 
90. In one preferred embodiment, this interconnection is provided by 
machining lower passage 82a, 82b, 82c (collectively designated passages 
82) in each head 30a, 30b, 30c, respectively. Each lower passage 82 
intersects lower cooling jacket 80 and upper cooling jacket 90 along a 
corresponding longitudinal axis 86a, 86b, 86c (collectively designated 
axes 86). Longitudinal axes 86 of passages 82 are generally horizontal and 
approximately perpendicular to longitudinal axis 15. Each lower passage 82 
intersects upper cooling jacket portion 90c. Portion 90c is situated 
generally between exhaust ports 52 and 54 in the vicinity of injector 
passage 36 for each head 30. Also, upper jacket portion 90c is generally 
located between wall 28 and wall 29 for each head 30. Preferably, lower 
passage 82 is formed by machining an opening 84a, 84b, 84c (collectively 
designated openings 84) through outer surface 26 of cast member 22. In one 
embodiment, this machining is performed by drilling a generally horizontal 
bore through cast member 22. In other embodiments different machining 
methods are contemplated as would occur to one skilled in the art. 
After lower cooling jacket 80 and upper cooling jacket 90 are 
interconnected, plug 89 is secured within opening 84, providing a seal to 
prevent loss of coolant from lower cooling jacket 80 or upper cooling 
jacket 90. Plug 89 may be joined with cast member 22 by welding, brazing, 
an adhesive, a threaded connection, or such other means as would occur to 
one skilled in the art. 
Interconnection by passages 82 facilitates coolant flow along path P80 from 
chamber 18a, through lower cooling jacket 80, and into upper cooling 
jacket 90 as illustrated in FIG. 1. Similarly, FIG. 1 depicts path P90 
corresponding to coolant flow from chamber 18b into upper cooling jacket 
90 to combine with coolant received in upper cooling jacket 90 along path 
P80. This combined coolant then flows forward through the head where it 
exits (not shown). The exiting coolant excounters a thermostat and is 
processed through a heat exchanger, such as a radiator; and then 
circulates back to cylinder block 12 (not shown). 
FIG. 1 also depicts vertical passage 92 formed by machining through surface 
26 to form a second interconnection between lower cooling jacket 80 and 
upper cooling jacket 90. This vertical orientation generally aids in the 
venting of air when cooling fluid is introduced into jackets 80 and 90. 
Plug 99 is configured to be securely held in opening 94 to seal jackets 80 
and 90, and may be secured within opening 94 using techniques utilized to 
secure plug 89 in opening 84. Vertical longitudinal axis 96 of passage 92 
is generally parallel to longitudinal axis 15 and approximately 
perpendicular to axes 86. 
Notably, the exchange of coolant between jackets 80 and 90 is generally 
controlled by the throat area of the interconnecting passages. As used 
herein, "throat area" refers to the minimum planar cross-sectional area of 
a passage perpendicular to the longitudinal axis of the passage. For 
example, as depicted by FIG. 1, the throat area of passage 82a corresponds 
to a plane containing the cross-sectional area of passage 82a and axis 83; 
where that plane is perpendicular to axis 86a. Similarly, the throat area 
of passage 92 corresponds to a cross-sectional planar area perpendicular 
to axis 96 which contains axis 93. 
Preferably, the minimum throat area of lower passages 82 is considerably 
larger than the throat area of passage 92. In one preferred embodiment, 
the throat area of lower passages 82 is at least twice the minimum throat 
area of passage 92. In a more preferred embodiment, the minimum throat 
area of passages 82 are at least eight times the throat area of passage 
92. In a most preferred embodiment, the minimum throat area of passages 82 
are each at least twelve times the throat area of passage 92. 
By machining passages 82, 92, the problems attendant to casting 
interconnections between lower cooling jacket 80 and upper cooling jacket 
90 are avoided, including the difficulty of detecting and removing casting 
fins to assure adequate coolant communication within the labyrinthine 
cooling jackets required to optimize engine performance. In other 
embodiments, more or fewer externally machined interconnections may be 
used to provide adequate fluid communication between cooling spaces. In 
still other embodiments, external machining techniques may be combined 
with integrally casted interconnecting passages or other techniques to 
assure adequate fluid communication between desired spaces in the 
manufacture of a cylinder head. 
All publications and patent applications cited in this specification are 
herein incorporated by reference as if each individual publication or 
patent application were specifically and individually indicated to be 
incorporated by reference. 
While the invention has been illustrated and described in detail in the 
drawings and foregoing description, the same is to be considered as 
illustrative and not restrictive in character, it being understood that 
only the preferred embodiment has been shown and described and that all 
changes and modifications that come within the spirit of the invention are 
desired to be protected.