Internal combustion engine

Improved internal combustion engine, particularly, an improved two-stroke, diesel aircraft engine. The invention includes a new wrist pin/connecting rod connection, a new cooling system for fuel injectors, a new cylinder head cooling arrangement, a new cooling jacket cross-feed arrangement, and a new combustion seal arrangement.

BACKGROUND OF THE INVENTION

The present invention relates generally to internal combustion engines. More particularly, the present invention relates to two-stroke, diesel aircraft engines.

Internal combustion engines generally include an engine block defining a cylinder which includes a reciprocally operating piston. A cylinder head is generally mounted to the engine block over the cylinder. As generally known, the overall operation, reliability and durability of internal combustion engines depends on a number of design characteristics. One such design characteristic involves the piston pin or wrist pin/connecting rod connection. Uneven wear, excessive deflection or other structural deformities of the wrist pin will adversely affect the performance of an engine. Another design characteristic involves providing adequate cooling for fuel injectors. Generally, fuel injectors are in close proximity to the high heat regions of the combustion chambers. Without proper cooling, a fuel injector can malfunction and, in some cases, completely fail. Another design characteristic involves sufficiently cooling the cylinder heads. Thermal failure or cracking of a cylinder head results in costly repairs to the engine. Yet another design characteristic involves providing coolant to cooling jackets in multiple cylinder engines having a plurality of cylinder banks. Inadequate flow or obstructed flow of the coolant through the cooling jacket can result in engine failure.

A heat conducting fireplate or deck is typically provided beneath the cylinder head, and a combustion chamber is defined between the piston and the fireplate. Many internal combustion engines utilize a plurality of head bolts to secure the cylinder head to the engine block so as to provide a clamping force that seals the cylinder head to the engine block to prevent the undesirable escape of by products created by combustion within the combustion chamber.

SUMMARY OF THE INVENTION

The present invention provides an internal combustion engine having many advantages over prior art engines. In particular, the present invention provides certain improvements that are particularly well suited for use in two-stroke, diesel aircraft engines. The invention includes a new wrist pin/connecting rod connection, a new cooling system for fuel injectors, a new cylinder head cooling arrangement, a new cooling jacket cross-feed arrangement, and a new combustion seal arrangement.

The wrist pin, especially in two-stroke diesel engines, is nearly continuously under load. It is not uncommon for wrist pins to deflect under heavy or continuous loads. A heavy or thick walled wrist pin reduces the deflection, but at the cost of a substantial increase in weight. Thus, there is a need for a new wrist pin/connecting rod assembly which makes it less likely that the wrist pin will deflect under heavy or continuous loads, yet which does not appreciably add to the overall weight of the engine.

Providing a wrist pin/connecting rod assembly in which the wear on the bearing surface of the wrist pin is evenly distributed is difficult at best. Uneven wear of the wrist pin bearing surface can result in poor engine performance. Thus, there is a need for a wrist pin/connecting rod assembly which minimizes uneven wear on the wrist pin bearing surface.

Accordingly, the invention provides a connecting rod with a cradle-like upper end. In other words, the upper end of the connecting rod has an arcuate portion and does not encircle the wrist pin. The wrist pin has an outer surface in engagement with the arcuate portion of the connecting rod, and a plurality of fasteners (e.g., screws) secure the wrist pin to the arcuate portion of the connecting rod by extending through the wall of the wrist pin and into an insert within the wrist pin. Because the arcuate portion of the connecting rod does not completely encircle the wrist pin, the entire “top” of the wrist pin (the side of the wrist pin farthest from the crank-shaft and nearest the piston crown) can bear against the piston. In other words, a longitudinal portion of the wrist pin that does not engage the arcuate portion of the connecting rod can bear against the piston. This results in the load and the wear being more evenly distributed across substantially the entire longitudinal length of the wrist pin and, therefore, a lighter wrist pin than would otherwise be necessary can be used. Moreover, the wrist pin insert stiffens the wrist pin, also allowing the use of a thinner wrist pin. In addition, because the wrist pin cannot pivot relative to the connecting rod, the forced movement or rocking of the wrist pin as the connecting rod pivots during operation of the engine aids in oiling and minimizes uneven wear on the wrist pin bearing surface.

Fuel injectors are subject to intense thermal conditions because of their general proximity to the cylinder heads. One way to cool fuel injectors is to install the fuel injectors through cooling jackets which are adjacent the cylinder heads. The cooling jackets can cool both the cylinder heads and the fuel injectors. However, cooling jackets are not always sufficient to cool the fuel injectors. Moreover, in some engine designs, cooling jackets are not located in positions which allow them to be used to cool the fuel injectors. Thus, there is a need for a new fuel injector cooling system which enhances operation of or operates independent from a cooling jacket.

Fuel pumps generally deliver more fuel than the fuel injection system and engine can utilize at any given moment. As a result, the excess fuel is typically returned to a fuel supply tank for further use. Rather than returning the overflow fuel from the fuel pump directly to the fuel supply tank, the present invention utilizes the overflow fuel to cool the fuel injectors. Circulating the overflow or bypass fuel from the fuel pump through the fuel injectors for the purpose of cooling the fuel injectors makes use of an existing liquid flow not previously used to cool the fuel injectors. The overflow fuel flows into each fuel injector via a newly-provided inlet port and flows out through the known leak-off port. It is not uncommon for engine coolant in a cooling jacket to reach temperatures in excess of 240° F. The overflow fuel is significantly cooler than the engine coolant running through the cooling jacket, thereby providing an improved method of cooling the fuel injector to increase fuel injector life. In those engines which do not use a cooling jacket, the fuel injector cooling system of the present invention provides a new way of cooling the fuel injectors.

Accordingly, the invention also provides a fuel injection system having a fuel injector for injecting fuel into a combustion chamber. The fuel injector includes a fuel inlet port, a fuel outlet port and a fuel passage communicating between the fuel inlet port and the fuel outlet port. The fuel injector further includes a cooling fuel inlet port, a leak-off fuel outlet port and a cooling fuel passage communicating between the cooling fuel inlet port and leak-off fuel outlet port. The fuel injection system includes a bypass fuel line which communicates between a fuel pump and the cooling fuel inlet port of the fuel injector. Overflow fuel from the fuel pump flows through the bypass fuel line and through the fuel injector to cool the fuel injector. Using the excess fuel from the fuel pump to cool the fuel injector simplifies or supplants the cooling jacket.

A problem particularly prevalent with aircraft engines concerns ice build-up on the fuel filter due to cold outside temperatures. The overflow fuel which cools the fuel injectors is warmed as it flows through the fuel injectors. The warmed overflow fuel is recirculated through the fuel injection system to travel through the fuel filter so as to provide the additional benefit of resisting ice build-up on the fuel filter in cold weather.

Radiant and conductive heating of a cylinder head can raise the temperature of the cylinder head above its metallurgical and structural limits. Traditionally, cylinder heads are bolted or otherwise secured to the cylinder block or engine block with a suitable head gasket therebetween to effectively seal the cylinder heads and provide the cooling means for the cylinder head. According to a preferred embodiment of the present invention, the cylinder head threads into the engine block. Because of this, cooling passages normally provided between the engine block and the cylinder head cannot be utilized. Thus, there is a need for a cylinder head cooling arrangement which is not dependent on the location of the cylinder head with respect to the engine block, as is the case with prior engine designs.

Accordingly, in another aspect of the present invention, a cooling cap is mounted on the cylinder head. The cooling cap and the cylinder head combine to define a substantially annular cooling passageway. The cooling cap further includes inlet and outlet ports which communicate with the cooling passageway, so that cooling fluid can flow through the cooling passageway to cool the cylinder head. According to one aspect of the present invention, the inlet and outlet ports of the cooling cap communicate with the cooling passageway, so that the cooling fluid is caused to flow from the inlet port, substantially all the way around the cooling passageway, and then out the outlet port to provide enhanced cooling effectiveness. The cooling cap is adjustably positionable on the cylinder head, such that the inlet and outlet ports of the cooling cap can be properly aligned with ports in the engine block. In other words, the cooling cap is connectable to a cooling jacket in the engine block regardless of the position of the cylinder head with respect to the cylinder block or engine block. Because the cylinder head threads into the engine block, it is not known exactly where the cylinder head will be positioned in terms of the engine block. Thus, the adjustable cooling cap of the present invention is especially advantageous in an engine in which the cylinder head threads into the engine block.

Threading the cylinder head into the engine block according to the present invention provides the added benefit of eliminating the bolt and head gasket system of prior engines. This eliminates a possible point of failure, while at the same time reducing the number of parts to assemble the engine. According to one aspect of the present invention, the engine block includes female threads concentric with the cylinder and the cylinder head includes male threads which engage the female threads on the engine block. Because the traditional bolt and head gasket assembly can be eliminated, in order to provide a proper combustion seal, the present invention provides, according to one aspect thereof, a biasing spring between a cylinder head and a fireplate. The spring provides a downward force against the fireplate to offset an upward force created by combustion within the combustion chamber, thereby substantially ensuring that a proper cylinder head combustion seal is maintained.

In V-type engines, a cooling jacket and an associated thermostat are typically provided for each cylinder bank. A problem with such prior arrangements is that if one thermostat fails, there is no mechanism to allow cooling fluid to flow through the associated cooling jacket. Another problem with such prior designs is that the temperature gradient between the hot cylinder heads and the cooler lower crankcase can be significant, thereby adding undesirable stress to the engine block and other engine components. Thus, there is a need for a new system which provides redundancy of thermostat operation and thermal coupling between the cylinder heads and the lower portion of the engine.

Accordingly, the invention also provides a cross-feed cooling passageway in the engine block of a V-type engine. The cooling passageway extends between a first cooling jacket adjacent a first cylinder bank and a second cooling jacket adjacent a second cylinder bank. The first thermostat communicates with the first cooling jacket and a second thermostat communicates with the second cooling jacket. The cooling passageway provides cooling fluid flow between the cooling jackets. This is particularly advantageous in the event that one of the thermostats fails. The cross-feed passageway will allow the cooling fluid to continue to flow if one thermostat fails, so as to reduce the possibility of damage to the engine from over-heating. Another advantage of the cooling passageway is that it reduces the temperature gradient between the cylinder heads and the lower crankcase.

The present invention addresses the above mentioned problems and other problems. In addition, other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings in which like numerals are used to designate like features.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Illustrated inFIG. 1is an internal combustion engine10in which the present invention is employed. It should be understood that the present invention is capable of use in other engines, and the engine10is merely shown and described as an example of one such engine. The engine10is a two-stroke, diesel aircraft engine. More particularly, the engine10is a V-type engine with four-cylinders. The improvements described herein are particularly well suited for use in such engines, but may be used in other internal combustion engines.

FIG. 2shows a section view of a portion of the engine10of FIG.1. An engine block14at least partially defines a crankcase18(see also,FIG. 9) and two banks of four cylinders (only two are illustrated and have reference numerals21and22in FIG.1). The four cylinders are generally identical, and only one cylinder22will be described in detail. A crankshaft (not shown) is rotatably supported within the crankcase18. A piston26reciprocates in the cylinder22and is connected to the crankshaft via connecting rod30. As the piston26reciprocates within the cylinder22, the crankshaft rotates.

The connecting rod30includes a first end34which is connected to the crankshaft. The connecting rod30further includes a second end38which includes an arcuate portion42that does not completely encircle the wrist pin46. Preferably, the arcuate portion42of the connecting rod30has an arcuate extent that is about or slightly less than 180°. The wrist pin46has an annular wall50including a cylindrical inner surface54(FIG. 3) and a cylindrical outer surface58, which engages the arcuate portion42of the connecting rod30, and is pivotally connected to the piston26. A plurality of fasteners62extend through the annular wall50of the wrist pin46and into a wrist pin insert66(see also,FIG. 3) to secure the wrist pin46to the arcuate portion42of the connecting rod30. Preferably, the wrist pin insert66is cylindrical. Preferably, the fasteners are screws and thread into the wrist pin insert.

As shown inFIG. 3, since the upper or second end38of the connecting rod30does not encircle the wrist pin46, the piston26bears against the wrist pin46along the entire top of the wrist pin46, thereby more evenly distributing the load on the wrist pin46. The use of the wrist pin insert66further increases the strength and stability of the wrist pin46. The forced rocking of the wrist pin46as the connecting rod30pivots, and the increased bearing surface area of the wrist pin46minimizes uneven wear on the wrist pin46bearing surface during operation of the engine10.

As shown schematically inFIG. 6, the engine10includes four fuel injectors69,70,71and72, one for each cylinder. The fuel injectors are substantially identical, and only one will be described in detail.FIG. 7illustrates in section, among other things, the fuel injector70, which injects fuel into a combustion chamber74defined by a cylinder head78, the cylinder22and the piston26(not shown in FIG.7). The fuel injector70includes a fuel injector nut86which is received by an appropriately sized tapered bore in the cylinder head78. Inside the nut86is a fuel injector tip90housing a pressure responsive, movable pintle (not shown). The nut86and the tip90define a main fuel outlet92communicating with the combustion chamber74. A fuel injector body82is threaded into the upper end of the nut86. As best shown inFIGS. 4 and 5, the fuel injector body82includes a main fuel inlet port98, a portion of a fuel passage106which communicates between the main fuel inlet port98and the main fuel outlet port92(FIG.7), a cooling fuel inlet port110, a leak-off fuel outlet port114, an upstream portion118of a cooling fuel passage which communicates between the cooling fuel inlet port110and the leak-off fuel outlet port114, and a downstream portion120of the cooling fuel passage. Although not shown, the fuel injector further includes a flow straightener, a check valve, a check valve receiver, a spring mechanism and a spring guide, all of which are positioned within the hollow space94of the fuel injector nut86between the body82and the tip90. Except for the cooling fuel inlet port110and the passage portion118, the fuel injector70is conventional and known to those skilled in the art. The addition of the port110and the passage portion118allows cooling of the fuel injector as described below.

FIG. 6illustrates a fuel flow schematic for a fuel injection system122. Shown is fuel supply tank126, fuel line128, fuel filter130, fuel pump132which includes delivery pump134and high pressure pump138, fuel lines142, bypass fuel line146, fuel injectors69,70,71and72, return fuel line148and return fuel tank150. Referring also toFIGS. 4-5and7, overflow fuel expelled from the fuel pump132flows through the bypass fuel line146, into the cooling fuel inlet port110of the fuel injector69, through the inlet portion118of the cooling fuel passage in the fuel injector body82, into the space below the fuel injector nut86, where leak-off fuel normally flows, and around the flow straightener, the check valve, the check valve receiver, the spring mechanism and the spring guide, to commingle with the leak-off fuel, through the outlet portion120of the cooling fuel passage in the fuel injector body82, and out the leak-off fuel outlet port114of the fuel injector body82where the leak-off fuel normally exits. The fuel flowing out of the port114of the fuel injector69then flows into the port110of the fuel injector70and flows through the fuel injector70in the same manner, and so on.

As can be appreciated, as the overflow fuel cools the fuel injectors, the overflow fuel is warmed. The overflow fuel is recirculated through the fuel injection system122by way of return fuel line148. The warmed overflow fuel will flow through the fuel filter130on its way back to the fuel pump132to resist excessive build-up of ice on the fuel filter130during cold weather.

FIGS. 7 and 8illustrate a cooling cap154mounted on the cylinder head78to cool the cylinder head78. The cooling cap154has an annular coolant groove158which mates with an annular coolant groove162of the cylinder head78to define an annular cooling passageway166when the cooling cap154is mounted on the cylinder head78. In other embodiments, such as the embodiment which is illustrated inFIGS. 10-13, only one of the cooling cap154and the cylinder head78includes a groove such that the combination of the cooling cap154and the cylinder head78define an annular cooling passageway166. The cooling cap154includes inlet170and outlet174ports which communicate with the annular cooling passageway166, so that cooling fluid can flow into the inlet port170, through the annular cooling passageway166and out the outlet port174, thereby cooling the cylinder head78. As used within the claims, “substantially annular” includes a completely enclosed loop similar to that illustrated inFIGS. 7 and 8, and a partial loop similar to that illustrated inFIGS. 10-13(e.g., an annular groove that is separated by a divider pin, or projection406).

The engine block14includes a cooling jacket178with an outlet182and an inlet (not shown). The cooling cap154is placed on the cylinder head78with the inlet port170in alignment with the outlet port182of the cooling jacket178and the outlet port174in alignment with the inlet port of the cooling jacket178. A first transfer tube186communicates between the inlet port170of the cooling cap154and the outlet port182of the cooling jacket178, and a second transfer tube (not shown) communicates between the outlet port174of the cooling cap154and the inlet port of the cooling jacket178.

As shown, the inlet port170and the outlet port174of the cooling cap154are not diametrically opposed around the annular cooling passageway166. Thus, a first portion of the annular cooling passageway166extends in one direction from the inlet port170to the outlet port174(representatively shown as arrow190inFIG. 8) and a second portion of the annular cooling passageway166extends in an opposite direction from the inlet port170to the outlet port174(representatively shown as arrow194in FIG.8). The first portion of the annular cooling passageway166is shorter in length than the second portion of the annular cooling passageway166. So that the flow rate through the annular cooling passageway166in either direction is proportional to the distance traveled, the first portion of the annular cooling passageway166is restricted. In this way, cooling fluid travels in both directions through the annular cooling passageway166to cool the cylinder head78.

The cooling cap154is adjustably positionable around the cylinder head78, so that the inlet port170and the outlet port174are properly alignable with the associated inlet and outlet ports of the cooling jacket178. This is especially advantageous for a preferred embodiment of the present invention in which the cylinder head78threads into the cylinder block or engine block14. As shown, the engine block14includes female threads concentric with the cylinder22, and the cylinder head78includes male threads which engage the female threads of the engine block14. Because the cylinder head78threads into the engine block14, it is not exactly known where the cylinder head78will be located with respect to the engine body14. Once the adjustable cooling cap154is properly located on the cylinder head78, a plurality of clamping members198, preferably equally spaced apart, span across the top of the cooling cap154to secure the cooling cap154to the cylinder head78. Each of the clamping members198has opposite ends202and206, and is secured to the cylinder head78by a pair of fasteners210. One fastener210is located adjacent end202and the other fastener210is located adjacent end206. Preferably, the fasteners210thread into the top of the cylinder head78. Preferably, the cylinder head78includes a plurality of sets of pre-drilled, threaded holes such that each fastener210can be located in a plurality of positions relative to the cylinder head78. Preferably, end202of each clamping member198is received by an annular groove214in the fuel injector nut86, thereby also securing the fuel injector70to the cylinder head78.

In the embodiment illustrated inFIGS. 7 and 8, the coolant initially flows from a pump (not shown) into the cooling jacket178. From the cooling jacket178, the coolant flows into the annular cooling passageway166through the outlet port182of the cooling jacket178, the first transfer tube186, and the inlet port170of the cooling cap154. From the inlet port170, the coolant travels through the cooling passageway166to the outlet port174of the cooling cap154removing heat from the cylinder head78. The coolant then flows from the outlet174of the cooling cap154through the second transfer tube and inlet port of the cooling jacket178to return to the cooling jacket178. From the cooling jacket178, the heated coolant is returned to the pump of the coolant system to be cooled and returned to the cooling jacket178.

Another embodiment of the cooling cap154is illustrated inFIGS. 14 and 15. This embodiment is substantially similar to the embodiment shown inFIGS. 7 and 8except that the embodiment illustrated inFIGS. 14 and 15includes a different coolant flow path. Reference numbers used with respect to the embodiment illustrated inFIGS. 7 and 8are also used inFIGS. 14 and 15to indicate like components.

With reference toFIGS. 14 and 15, the coolant initially flows from a pump (not shown), through a supply conduit172, and into the cooling jacket178. From the cooling jacket178, the coolant flows into through the outlet port182of the cooling jacket178, through the first transfer tube186, through the inlet port170of the cooling cap154, and into the annular cooling passageway166. From the inlet port170, the coolant travels through the cooling passageway166in the direction of arrow194to the outlet port174of the cooling cap154removing heat from the cylinder head78. In this embodiment, the coolant is blocked from flowing toward the outlet174in a direction opposite to the arrow194. The coolant then flows from the outlet174of the cooling cap154through a second transfer tube184and into a return port188. From the return port188, the coolant is directed back to the pump through the return line192to be cooled and returned to the cooling jacket178through the supply conduit172. As just described, the coolant flows into the cooling jacket178, then flows into the cooling cap154, and then returns to the pump. In contrast, the coolant used with the embodiment illustrated inFIGS. 7 and 8flows into the cooling jacket178, then flows into the cooling cap154, then flows back into the cooling jacket178, and then finally returns to the pump.

FIG. 9illustrates a cross-feed cooling passageway218which extends between a first cooling jacket178and a second cooling jacket222of the V-type engine of FIG.1. The cross-feed cooling passageway218provides cooling fluid flow between the cooling jackets178and222. The cross-feed cooling passageway218is drilled through the portion of the engine block14supporting the main bearing support for the crankshaft. The cutaway portion ofFIG. 1shows the general location of the cross-feed passageway218in the engine10. If a thermostat communicating with the one of the cooling jackets178and122fails, the cross-feed cooling passageway218enables cooling fluid to continue to flow to minimize or prevent damage to the associated cylinder head78. The cross-feed cooling passageway218also reduces the thermal gradient between the cylinder heads78and the lower crankcase of the engine10to increase engine life.

Illustrated inFIG. 10is another internal combustion engine310in which the present invention is employed. It should be understood that the present invention is capable of use in other engines, and the engine310is merely shown and described as an example of one such engine. The engine310is a two-stroke, diesel aircraft engine, which is substantially similar to the engine10of FIG.1. More particularly, the engine310is a V-type engine with four cylinders.

As shown inFIG. 10, an engine block314at least partially defines two banks of four cylinders (only two are illustrated and have reference numerals316and318). The four cylinders are generally identical, and only one cylinder318will be described in detail.FIGS. 11-13show various views of portions of the engine310of FIG.10.

A cylindrical sleeve322is positioned within the cylinder318. Preferably, the sleeve322is an aluminum sleeve that is shrink fitted into the cylinder318and bonded to the engine block314with an epoxy resin having an aluminum filler. The sleeve322includes a shoulder326. A piston330reciprocates within the sleeve322.

A gasket334is positioned on the shoulder326of the sleeve322. The gasket334is preferably made of a compliant material which can form to the shape of mating components, and which is also made of a material which is highly conductive for rapid heat dissipation. In a highly preferred embodiment, the gasket334is a copper gasket. As will be further explained below, the, gasket334acts as both a sealing mechanism and a shimming device.

A fireplate338is positioned between a cylinder head342and the gasket334. A bottom side346of the fireplate338cooperates with the piston330to define a combustion chamber350. An annular ledge354on the fireplate338receives an O-ring358to provide a seal between the side wall356of the fireplate338and the cylinder318. In a preferred design, the cylinder head342is made of aluminum and the fireplate338is made of stainless steel.

A head spring362is positioned between the cylinder head342and the fireplate338. A bottom side366of the cylinder head342has an annular groove370which receives the head spring362, and a top side374of the fireplate338has a recess378which also receives the head spring362. The head spring362is preferably a belleville spring. The head spring362is also preferably made of stainless steel. As generally known in the art, belleville springs take the form of a shallow, conical disk with a hole through the center thereof. A very high spring rate or spring force can be developed in a very small axial space with these types of springs. Predetermined load-deflection characteristics can be obtained by varying the height of the cone to the thickness of the disk. The importance of being able to obtain a predetermined spring force in regards to the present invention will be made clear below.

As can be observed with reference toFIGS. 11-13, the cylinder head342threads into a portion of the engine block314. When the cylinder head342is threaded into the engine block, the cylinder head342compresses the head spring362against the fireplate338to provide a downward force against the top side374of the fireplate338to offset an upward force created by combustion within the combustion chamber350. The downward force provided by the spring362substantially ensures that the fireplate338will remain in contact with the gasket334, and that the gasket334will remain in contact with the shoulder326of the sleeve322to provide an appropriate combustion seal during operation of the engine310.

The head spring362also acts to allow for the expansion and contraction of the relevant mating engine components during changing thermal conditions of the engine310without adversely affecting the combustion seal, much like traditional head bolts act. As noted above, head bolts can be used to provide a clamping force that seals a cylinder head to an engine block. Because the head bolts are allowed to expand and contract with the associated engine components as the temperature of the engine varies, the head bolts are capable of maintaining the clamping force during operation of the engine. However, in the case of the present invention, the threaded cylinder head342does not generally have the stretching capabilities of typical head bolts because of its relatively large diameter and short thread length. Thus, the head spring362provides the desired clamping force in lieu of traditional head bolts to create the proper combustion seal.

As suggested above, the load provided by the head spring362can be calculated based on the deflection of the spring362. In this way, a guaranteed amount of downward force can be provided to ensure a proper combustion seal. To obtain the desired deflection for the head spring362, the cylinder head342and associated components are assembled as follows.

The piston330is located in its top dead center position. The gasket334is positioned on the shoulder326of the sleeve322. The fireplate338is positioned on the gasket334to create a predetermined volume for the combustion chamber350. The gasket334is appropriately sized to obtain the desired volume for the combustion chamber350. The gasket334accommodates the assembly stack up tolerances associated with the engine block314, the cylinder head342, the sleeve322, and the piston330. After the fireplate338is positioned on the gasket334, the cylinder head342is threaded into the engine block314until such time as the bottom side366of the cylinder head342contacts the top side374of the fireplate338. Once contact is made between the cylinder head342and the fireplate338, the final assembly position of the cylinder head342with respect to the engine block314is known. The final assembly position of the cylinder head342is then marked or otherwise recorded for future reference. Thereafter, the cylinder head342is unthreaded from the engine block314and the head spring362is positioned between the cylinder head342and the fireplate338. The cylinder head342is then threaded a second time into the engine block314until the cylinder head342is located in the final assembly position. The threading of the cylinder head342into the engine block compresses the spring362between the cylinder head342and the fireplate338. Knowing the desired deflection amount for the spring362and where the final assembly position will be for the cylinder head342, ensures that a sufficient load will be applied against the fireplate338to offset the upward force generated by the combustion within the combustion chamber in order to provide the desired combustion seal.

Another feature of the present invention concerns providing a cooling system for the cylinder head342. A cooling cap382is mounted on the cylinder head342. The cooling cap382cooperates with an annular groove390of the cylinder head342to define a cooling passageway394. The cooling cap382includes an inlet port398and an outlet port402. The inlet port398is adapted to receive a cooling fluid flowing through the engine310, and the outlet port402is adapted to send the cooling fluid on through the engine310after the cooling fluid has been used to cool the cylinder head342. As best shown inFIG. 11, the inlet port398and the outlet port402are practically adjacent to one another. A divider pin, or projection406extends from the cooling cap382into the cooling passageway394to substantially close the short passageway between the inlet port398and the outlet port402. In this way, the cooling fluid is only allowed to flow around the cooling passageway394in a single direction to cool the cylinder head342. Although allowing the cooling fluid to flow in both directions around the cooling passageway394between the inlet port398and an outlet port402would cool the cylinder head342, it has been determined that causing the cooling fluid to flow in one direction around substantially the entire cooling passageway394also provides effective cooling. In other embodiments, the divider pin406is eliminated and only a partial annular groove is formed in the cylinder head342and/or the cooling cap382such that the combination of the cylinder head342and the cooling cap382define a unidirectional cooling passage without the need for a divider pin406.

The manner of attaching the cooling cap382to the cylinder head342is substantially described above in relation to engine10. Reference is also made to the description above in relation to engine10for the description and manner of operating the fuel injector410. One difference worth noting between engine10and engine310is that the cylinder head342of the subject application includes nine sets of holes414for the associated clamping members418, as compared to the six sets of holes as shown for engine10. It was determined that nine sets of holes is preferred to enable the desired positioning of the cooling cap382with respect to the cylinder head342.

The foregoing description of the present invention has been presented for purposes of illustration and description. Furthermore, the description is not intended to limit the invention in the form disclosed herein. Consequently, variations and modifications commensurate with the above teachings in skill or knowledge of the relevant art, are within the scope of the present invention. The embodiments described herein are further intended to explain the best modes known for practicing the invention and to enable others skilled in the art to utilize the invention as such, or other embodiments and with various modifications required by the particular applications or uses of the present invention. It is intended that the appended claims are to be construed to include alternative embodiments to the extent permitted by the prior art. It is understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text and/or drawings. All of these different combinations constitute various alternative aspects of the present invention.