Abstract:
Internal combustion engines have been developed having regeneration mechanisms for increasing efficiency and reducing emissions. Previous regeneration mechanisms have been complicated and costly. The present invention provides a simple regeneration member which is attached within a piston assembly. Thus the apparatus for attaching the regeneration member within the internal combustion engine greatly reduces the cost of the engine.

Description:
TECHNICAL FIELD 
     This invention relates generally to an internal combustion engine and more specifically to a piston having a thermal regenerator attached therein. 
     BACKGROUND 
     Thermal regeneration has been developed for increasing the thermal efficiency of internal combustion engines. Thermal regeneration consist of the introduction of a heat exchanger within the engine. The heat exchanger includes a porous core that is capable of withstanding high temperatures. During the exhaust stroke of the engine, the core absorbs exhaust gas heat. The exhaust gas heat is then transferred from the core to working fluid (air/fuel mixture) following the compression stroke, but prior to or during the combustion of fuel. 
     A regenerative internal combustion engine is disclosed in U.S. Pat. No. 5,540,191 issued to Caterpillar, Inc. on Jul. 30, 1996, wherein a regenerator captures a portion of unutilized heat normally expelled with exhaust gas, and transfers the captured heat to the fresh working fluid. The above identified patent includes a regenerative member moveably positioned in the cylinder of the engine between the piston and the cylinder head. The regenerator is adapted to reciprocate in relationship to the piston movement. 
     Obstacles to using a regenerator as described above include the need to construct an internal combustion engine having an additional mechanism for moving the regenerator between the piston and the cylinder head. Previous designs required a separate reciprocating mechanism for moving the regenerator. The separate reciprocating mechanism requires additional features to be cast into the engine components, additional parts, a sealing arrangement to prevent compression loss in the cylinder and additional assembly time. 
     The above identified invention is directed to overcoming one or more of the above identified problems. 
     SUMMARY OF THE INVENTION 
     In an aspect of the present invention a piston assembly for an internal combustion engine is provided. The internal combustion engine includes a combustion cylinder, a predefined cycle including an intake stroke and a compression stroke. The piston assembly includes a piston head having a top surface. The top surface defines a recessed portion. A regeneration member having a porous structure is positioned within the recessed portion. 
     In another aspect of the present invention an internal combustion engine is provided. The internal combustion engine has a predefined cycle including a combustion stroke and an intake stroke prior to the compression stroke. The piston assembly having a top surface defining a recessed portion. A regeneration member is provided in the recessed portion and has a porous structure. The regeneration member is adapted to absorb heat from the combustion stroke and release the heat during the intake stroke. 
     In another aspect of the present invention a method for operating an internal combustion engine is provided. The internal combustion engine has a combustion cylinder and a predefined cycle including an intake stroke and an compression stroke. The method includes the steps of providing a regeneration member within a piston assembly, providing air to said combustion cylinder during the intake stroke, pushing an intake air through the regeneration member, introducing fuel, mixing fuel and intake air, igniting the fuel and intake air mixture, creating heat and absorbing heat with the regeneration member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a sectional illustration of a combustion cylinder of an internal combustion engine having a regeneration member disposed within a recessed portion of a piston, a cycle of the internal combustion engine is illustrated as the piston begins a compression stroke. 
     FIG. 2 is a sectional illustration of the combustion cylinder of the internal combustion engine having a regeneration member disposed within the recessed portion of the piston, a cycle of the internal combustion engine is illustrated as the piston nears top-dead-center. 
     FIG. 3 is a sectional illustration of the combustion cylinder of the internal combustion engine having the regeneration member disposed within a recessed portion of the piston, a cycle of the internal combustion engine is illustrated as it moves away from top dead center. 
     FIG. 4 is an enlarged sectional illustration of the present invention illustrating one embodiment of a mounting arrangement the regeneration member within a piston assembly. 
     FIG. 5 is an enlarged sectional illustration of the piston of the present invention illustrating another embodiment of a mounting arrangement a regeneration member within the piston assembly. 
     FIG. 6 is an enlarged sectional illustration of the present invention illustrating another embodiment of a mounting arrangement of the regeneration member within a piston. 
     FIG. 7 is a top view of a piston having a regeneration member of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIGS. 1,  2  and  3 , a sectional illustration of an internal combustion engine is depicted generally as  10 . The internal combustion engine  10  may be either a two cycle or a four cycle engine. In either case, there is at least an intake stroke and an compression stroke. The internal combustion engine  10  includes a cylinder head  11  and a block  12  having a plurality of combustion cylinders  14  therein, only one being shown. A piston assembly  16  is positioned within the combustion cylinder  14 . The piston assembly reciprocates within the combustion cylinder  14  and has a regeneration member  18  positioned therein. 
     The combustion cylinderl 4  defines a cylinder wall  24  having a top end  26  and a bottom end  28 . The cylinder head  11  is positioned at the top end  26  and has an intake valve  34 , an exhaust valve  36  and a fuel injector  38  positioned therein. The fuel injector  38  has a plurality of nozzles  39  that are adapted to direct fuel into the combustion cylinder  14 . 
     The piston assembly  16  is primarily of conventional construction, but the geometry may be modified slightly to accommodate the required thickness of the regeneration member  18 . Although the piston assembly  16  is shown as a multi-piece construction, a single piece piston could be used without varying the inventive concept, as is show in FIG.  6 . The piston assembly  16  is a substantially cylindrical member having an outer wall  40  and an inner wall  42 , a top end  46  and a bottom end  48 . The outer wall  40  extends from the top end  46  to the bottom end  48 . A plurality of ring grooves  60  are defined in the outer wall  40  near the top end  46 , as with a conventional piston assembly  16 . A top surface  52  is defined on the top end  48 . An underside surface  53  is spaced away from the top surface  52 . The top surface  52  may be integral of the piston assembly  16  or may be a removable portion  54  as illustrated. A recessed portion  56  is defined in the top surface  52 , the recessed portion  56  forms a bottom surface  57  and an inner-side surface  58 . The regeneration member  18  is positioned within the recessed portion  56  and defines a cavity  59  between the regeneration member  18  and the bottom surface  57 . 
     The regeneration member  18  may be manufactured from a ceramic material or a metal foam material. The regeneration member  18  has a porous structure  70  that withstands high temperatures. The regeneration member  18  is a disk shaped member having a top portion  62  and a bottom portion  64 . An outer edge  66  extends between the top portion  62  and the bottom portion  64 . At least a passage  72  is provided in the regeneration member and extends from the top portion  62  to the bottom portion  64 . The passage(s)  72  is/are aligned with the nozzle(s)  39  provided in the fuel injector  38 . An expansion member  76  is disposed between the outer edge  66  and the inner-side surface  58  of the piston assembly  16 . 
     As illustrated in FIGS. 4,  5  and  6 , the expansion member  76  is a substantially ring shaped member. FIGS. 4 and 6 illustrate the expansion member  76  constructed from a metallic material. The expansion member  76  as illustrated in FIGS. 4 and 6 may be attached to the recessed portion  56  of the piston assembly  16  using conventional welding or bonding technologies that are capable of withstanding high temperatures. Alternately, FIG. 5 illustrates the expansion member  76  manufactured from an flexible heat resistant material. The expansion member as illustrated in FIG. 5 may include a chemical bonding adhesive. The expansion member  76  provides an isolation means  78  which in this application uses a gap, between the outer edge  66  of the regeneration member  18  and the recessed portion  56  of the piston assembly  16 . As illustrated, the expansion member  76  includes a “U” portion  82  disposed about the outer edge  66  of the regeneration member  18 . The “U” portion includes an inner vertical leg  84 , an outer vertical leg  86  and a joint portion  88  that extends between the vertical legs  84 , 86 . A horizontal member  90  extends radially inward from the inner vertical leg  84 . As an alternative and illustrated in FIG. 4, two or more horizontal members  90  can be used without changing the intent of the invention. FIG. 6 illustrates a single horizontal member  76  extending into the regeneration member  18  whish is interposed the top portion  62  and the bottom portion. 
     INDUSTRIAL APPLICABILITY 
     In operation the present invention provides an internal combustion  10  engine having the regeneration member  18 . During the intake stroke, intake valve  34  is opened and the piston assembly  16  moves toward bottom dead center in the combustion cylinder  14 . As the piston assembly  16  moves toward bottom dead center, intake air is drawn into the combustion cylinder  14 . At the end of the intake stroke, the intake valve  34  closes and the piston assembly  16  begins the compression stroke, moving toward top dead center. 
     During the compression stroke, the intake valve  34  and the exhaust valve  36  are closed. As the piston assembly  16  moves toward the cylinder head  11 , the intake air in the combustion cylinder  14  is compressed and pushed through the porous construction of the regeneration member  18 , and into the cavity  59 . Near top dead center of the compression stroke, the nozzle  39  of the fuel injector  38  sprays fuel through the passage  72  of the regeneration member  18  and into the cavity  59 . Thus, the fuel and intake air in the cavity reaches the appropriate temperature, combustion occurs within the cavity  59  and combustion cylinder  14 . 
     After combustion and expansion occurs, the exhaust valve  36  opens and allows exhaust gas to exit the combustion cylinder  14  and cavity  59 . Heat from the combustion process and exhaust gas is absorbed by the regeneration member  18 . During the next cycle of the intake stroke, fresh intake air again passes through the porous structure of the regeneration member  18  and extracts heat from the regeneration member  18 . 
     By providing a simple method and apparatus to capture heat from exhaust gases and transfer that heat to air before combustion, the efficiency and emissions of the internal combustion engine  10  is affordably improved. 
     Other aspects, objects and advantages of this invention can be obtained from a study of the drawings, the disclosure and the appended claims.