Patent Publication Number: US-RE41335-E

Title: Internal combustion engine

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/220,787, filed Jul. 25, 2000. 
    
    
     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. 
     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. 
     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 and a new cooling jacket cross-feed 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 crankshaft 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 in 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 includes an annular coolant groove which mates with an annular coolant groove in the cylinder head to define an 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. 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. 
     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. A 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. 
     Other features and advantages of the present 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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an elevational view of an internal combustion engine in which the present invention is employed. 
         FIG. 2  is a sectional view illustrating, among other things, a cylinder head, a cylinder, a piston and a connecting rod of the engine of FIG.  1 . 
         FIG. 3  is a cross-sectional view taken along line III—III of  FIG. 2   
         FIG. 4  is a perspective view of a fuel injector body of the engine of FIG.  1 . 
         FIG. 5  is a cross-sectional view taken along line V—V of FIG.  4 . 
         FIG. 6  is a schematic of a fuel injection system for the engine of FIG.  1 . 
         FIG. 7  is a cross-sectional view taken along line VII—VII of FIG.  8 .  FIG. 7  is also an enlarged view of a portion of  FIG. 2  illustrating in greater detail, among other things, the cylinder, the cylinder head, the fuel injector and the cooling cap. 
         FIG. 8  is a top-view of FIG.  7 . 
         FIG. 9  is a sectional view illustrating the cross-feed passageway between the cylinder banks of the engine of FIG.  1 . 
     
    
    
     Before the embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein are for the purpose of description and should not be regarded as limiting. The use of “including” and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items and equivalents thereof. The use of “consisting of” herein is meant to encompass only the items listed thereafter and the equivalents thereof. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Illustrated in  FIG. 1  is an internal combustion engine  10  in which the present invention is employed. It should be understood that the present invention is capable of use in other engines, and the engine  10  is merely shown and described as an example of one such engine. The engine  10  is a two-stroke, diesel aircraft engine. More particularly, the engine  10  is 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. 2  shows a section view of a portion of the engine  10  of FIG.  1 . An engine block  14  at least partially defines a crankcase  18  (see also,  FIG. 9 ) and two banks of four cylinders (only two are illustrated and have reference numerals  21  and  22  in FIG.  1 ). The four cylinders are generally identical, and only one cylinder  22  will be described in detail. A crankshaft (not shown) is rotatably supported within the crankcase  18 . A piston  26  reciprocates in the cylinder  22  and is connected to the crankshaft via connecting rod  30 . As the piston  26  reciprocates within the cylinder  22 , the crankshaft rotates. 
     The connecting rod  30  includes a first end  34  which is connected to the crankshaft. The connecting rod  30  further includes a second end  38  which includes an arcuate portion  42  that does not completely encircle the wrist pin  46 . Preferably, the arcuate portion  42  of the connecting rod  30  has an arcuate extent that is about or slightly less than 180°. A wrist pin  46  having an annular wall  50  including a cylindrical inner surface  54  ( FIG. 3 ) and a cylindrical outer surface  58 , which engages the arcuate portion  42  of the connecting rod  30 , is pivotally connected to the piston  26 . A plurality of fasteners  62  extend through the annular wall  50  of the wrist pin  46  and into a wrist pin insert  66  (see also,  FIG. 3 ) to secure the wrist pin  46  to the arcuate portion  42  of the connecting rod  30 . Preferably, the wrist pin insert  66  is cylindrical. Preferably, the fasteners are screws and thread into the wrist pin insert. 
     As shown in  FIG. 3 , since the upper or second end  38  of the connecting rod  30  does not encircle the wrist pin  46 , the piston  26  bears against the wrist pin  46  along the entire top of the wrist pin  46 , thereby more evenly distributing the load on the wrist pin  46 . The use of the wrist pin insert  66  further increases the strength and stability of the wrist pin  46 . The forced rocking of the wrist pin  46  as the connecting rod  30  pivots, and the increased bearing surface area of the wrist pin  46  minimizes uneven wear on the wrist pin  46  bearing surface during operation of the engine  10 . 
     As shown schematically in  FIG. 6 , the engine  10  includes four fuel injectors  69 ,  70 ,  71  and  72 , one for each cylinder. The fuel injectors are substantially identical, and only one will be described in detail.  FIG. 7  illustrates in section, among other things, the fuel injector  70 , which injects fuel into a combustion chamber  74  defined by a cylinder head  78 , the cylinder  22  and the piston  26  (not shown in FIG.  7 ). The fuel injector  70  includes a fuel injector nut  86  which is received by an appropriately sized tapered bore in the cylinder head  78 . Inside the nut  86  is a fuel injector tip  90  housing a pressure responsive, movable pintle (not shown). The nut  86  and the tip  90  define a main fuel outlet  92  communicating with the combustion chamber  74 . A fuel injector body  82  is threaded into the upper end of the nut  86 . As best shown in  FIGS. 4 and 5 , the fuel injector body  82  includes a main fuel inlet port  98 , a portion of a fuel passage  106  which communicates between the main fuel inlet port  98  and the main fuel outlet port  92  (FIG.  7 ), a cooling fuel inlet port  110 , a leak-off fuel outlet port  114 , an upstream portion  118  of a cooling fuel passage which communicates between the cooling fuel inlet port  110  and the leak-off fuel outlet port  114 , and a downstream portion  120  of 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 space  94  of the fuel injector nut  86  between the body  82  and the tip  90 . Except for the cooling fuel inlet port  110  and the passage portion  118 , the fuel injector  70  is conventional and known to those skilled in the art. The addition of the port  110  and the passage portion  118  allows cooling of the fuel injector as described below. 
       FIG. 6  illustrates a fuel flow schematic for a fuel injection system  122 . Shown is fuel supply tank  126 , fuel line  128 , fuel filter  130 , fuel pump  132  which includes delivery pump  134  and high pressure pump  138 , fuel lines  142 , bypass fuel line  146 , fuel injectors  69 ,  70 ,  71  and  72 , return fuel line  148  and return fuel tank  150 . Referring also to  FIGS. 4-5  and  7 , overflow fuel expelled from the fuel pump  132  flows through the bypass fuel line  146 , into the cooling fuel inlet port  110  of the fuel injector  69 , through the inlet portion  118  of the cooling fuel passage in the fuel injector body  82 , into the space below the fuel injector nut  86 , 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 portion  120  of the cooling fuel passage in the fuel injector body  82 , and out the leak-off fuel outlet port  114  of the fuel injector body  82  where the leak-off fuel normally exits. The fuel flowing out of the port  114  of the fuel injector  69  then flows into the port  110  of the fuel injector  70  and flows through the fuel injector  70  in 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 system  122  by way of return fuel line  148 . The warmed overflow fuel will flow through the fuel filter  130  on its way back to the fuel pump  132  to resist excessive build-up of ice on the fuel filter  130  during cold weather. 
       FIGS. 7 and 8  illustrate a cooling cap  154  mounted on the cylinder head  78  to cool the cylinder head  78 . The cooling cap  154  has an annular coolant groove  158  which mates with an annular coolant groove  162  of the cylinder head  78  to define an annular cooling passageway  166  when the cooling cap  154  is mounted on the cylinder head  78 . The cooling cap  154  includes inlet  170  and outlet  174  ports which communicate with the annular cooling passageway  166 , so that cooling fluid can flow into the inlet port  170 , through the annular cooling passageway  166  and out the outlet port  174 , thereby cooling the cylinder head  78 . 
     The engine block  14  includes a cooling jacket  178  with an outlet  182  and an inlet (not shown). The cooling cap  154  is placed on the cylinder head  78  with the inlet port  170  in alignment with the outlet port  182  of the cooling jacket  178  and the outlet port  174  in alignment with the inlet port of the cooling jacket  178 . A first transfer tube  186  communicates between the inlet port  170  of the cooling cap  154  and the outlet port  182  of the cooling jacket  178 , and a second transfer tube (not shown) communicates between the outlet port  174  of the cooling cap  154  and the inlet port of the cooling jacket  178 . 
     As shown, the inlet port  170  and the outlet port  174  of the cooling cap  154  are not diametrically opposed around the annular cooling passageway  166 . Thus, a first portion of the annular cooling passageway  166  extends in one direction from the inlet port  170  to the outlet port  174  (representatively shown as arrow  190  in  FIG. 8 ) and a second portion of the annular cooling passageway  166  extends in an opposite direction from the inlet port  170  to the outlet port  174  (representatively shown as arrow  194  in FIG.  8 ). The first portion of the annular cooling passageway  166  is shorter in length than the second portion of the annular cooling passageway  166 . So that the flow rate through the annular cooling passageway  166  in either direction is proportional to the distance traveled, the first portion of the annular cooling passageway  166  is restricted. In this way, cooling fluid travels in both directions through the annular cooling passageway  166  to cool the cylinder head  78 . 
     The cooling cap  154  is adjustably positionable around the cylinder head  78 , so that the inlet port  170  and the outlet port  174  are properly alignable with the associated inlet and outlet ports of the cooling jacket  178 . This is especially advantageous for a preferred embodiment of the present invention in which the cylinder head  78  threads into the cylinder block or engine block  14 . As shown, the engine block  14  includes female threads concentric with the cylinder  22 , and the cylinder head  78  includes male threads which engage the female threads of the engine block  14 . Because the cylinder head  78  threads into the engine block  14 , it is not exactly known where the cylinder head  78  will be located with respect to the engine body  14 . Once the adjustable cooling cap  154  is properly located on the cylinder head  78 , a plurality of clamping members  198 , preferably equally spaced apart, span across the top of the cooling cap  154  to secure the cooling cap  154  to the cylinder head  78 . Each of the clamping members  198  has opposite ends  202  and  206 , and is secured to the cylinder head  78  by a pair of fasteners  210 . One fastener  210  is located adjacent end  202  and the other fastener  210  is located adjacent end  206 . Preferably, the fasteners  210  thread into the top of the cylinder head  78 . Preferably, the cylinder head  78  includes a plurality of sets of pre-drilled, threaded holes such that each fastener  210  can be located in a plurality of positions relative to the cylinder head  78 . Preferably, end  202  of each clamping member  198  is received by an annular groove  214  in the fuel injector nut  86 , thereby also securing the fuel injector  70  to the cylinder head  78 . 
       FIG. 9  illustrates a cross-feed cooling passageway  218  which extends between a first cooling jacket  178  and a second cooling jacket  222  of the V-type engine of FIG.  1 . The cross-feed cooling passageway  218  provides cooling fluid flow between the cooling jackets  178  and  222 . The cross-feed cooling passageway  218  is drilled through the portion of the engine block  14  supporting the main bearing support for the crankshaft. The cut-away portion of  FIG. 1  shows the general location of the cross-feed passageway  218  in the engine  10 . If a thermostat communicating with the one of the cooling jackets  178  and  122  fails, the cross-feed cooling passageway  218  enables cooling fluid to continue to flow to minimize or prevent damage to the associated cylinder head  78 . The cross-feed cooling passageway  218  also reduces the thermal gradient between the cylinder heads  78  and the lower crankcase of the engine  10  to increase engine life. 
     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. 
     Various features of the invention are set forth in the following claims.