Two-cycle engine with improved scavenging

Abstract

A two-cycle internal combustion engine having an "open" combustion chamber/poppet valve arrangement that produces improved scavenging. The combustion chamber has a generally oblate configuration and is slanted with respect to the cylinder axis in such a manner that the air flowing therein converges and is directed downward in a collimated column into the cylinder. The placement of overhead cam operated poppet valves in combination with the combustion chamber produces a scavenging method of the reverse return-flow type. A displacer piston having a displacer with a peripheral wall corresponding in configuration to that of the combustion chamber and defining a recess of predetermined volume that forms the floor of the combustion chamber when the piston is located in its upper most position may be advantageously employed. Variable valve timing is achieved by opening and closing the exhaust and inlet valves unsymmetrically in order to improve the scavenging efficiency and asymmetrically to cause an increase in the effective expansion ratio.

What I claim is: 
     
       1. An improved two-cycle internal combustion engine comprising: a cylinder;   a cylinder head having an exhaust valve and an open type combustion chamber located therein, said chamber and exhaust valve being located in side-by-side relationship on opposite sides of a central axis of the cylinder;   an air inlet valve located within and in the top of the combustion chamber, said inlet valve having a valve stem located overhead said cylinder;   a piston reciprocally disposed within the cylinder;   means for converging a flow of scavenging air beneath the inlet valve into a colimated column as it enters the cylinder, said converging means comprising the combustion chamber having a generally oblate configuration with sides converging downwardly to form an opening which overlies the cylinder, the combustion chamber having diametrically opposed sides with predetermined different angles of curvature; and   wherein the inlet valve and the combustion chamber are coaxially aligned and oriented to the central axis of the cylinder at a predetermined angle and wherein the flow of scavenging air is directed toward and along an inside wall of the cylinder, said inside wall being on the same side of the cylinder axis as the combustion chamber.   
     
     
       2. The engine of claim 1 further comprising a fuel injector located adjacent to the combustion chamber and oriented with respect to the cylinder axis at an angle equal approximately to said predetermined angle plug 90°. 
     
     
       3. The engine of claim 2 wherein the opening of the combustion chamber has an area equal approximately to one-third of the cross-sectional area of the cylinder. 
     
     
       4. The engine of claim 3 wherein said injector comprises a single orifice nozzle type fuel injector, said inlet and exhaust valves comprise poppet valves, and wherein said exhaust valve has a lower face which is substantially flush with the underside of the cylinder head when the exhaust valve is closed. 
     
     
       5. The engine of claim 4 wherein the inlet and exhaust valves are operated in accordance with an asymmetric, unsymmetric timing sequence such that the major portion of scavenging occurs after the piston reaches a bottom dead center position. 
     
     
       6. The engine of claim 5 wherein said piston comprises a displacer piston. 
     
     
       7. The engine of claim 6 wherein said displacer piston comprises: a piston having a top surface; and   a displacer supported on said top surface for projecting into the combustion chamber when the piston nears a top dead center position.   
     
     
       8. The engine of claim 7 wherein said displacer comprises an upwardly extending peripheral wall surrounding a recess, the recess being of a generally hemispherical configuration and forming the floor of the combustion chamber when the piston is in its firing position. 
     
     
       9. the engine of claim 8 wherein the wall of the displacer includes a first notch therethrough configured to induce a high degree of turbulence in the combustion chamber. 
     
     
       10. The engine of claim 9 wherein said first notch is configured to produce a venturi effect in the combustion chamber. 
     
     
       11. The engine of claim 10 wherein the wall of the displacer is provided with a second notch facilitating entry of spray from the fuel injector into the combustion chamber when the piston is located in the vicinity of said top dead center position. 
     
     
       12. The engine of claim 1 wherein said piston comprises a displacer piston. 
     
     
       13. The engine of claim 12 wherein said displacer piston comprises: a piston having a top surface; and   a displacer supported on said top surface for projecting into the combustion chamber when the piston nears a top dead center position.   
     
     
       14. The engine of claim 13 wherein said displacer comprises an upwardly extending peripheral wall surrounding a recess, the recess being of a generally hemispherical configuration and forming the floor of the combustion chamber when the piston is in its firing position. 
     
     
       15. The engine of claim 14 wherein the wall of the displacer includes a first notch therethrough configured to induce a high degree of turbulence in the combustion chamber. 
     
     
       16. The engine of claim 15 wherein said first notch is configured to produce a venturi effect in the combustion chamber. 
     
     
       17. The engine of claim 16 wherein the wall of the displacer is provided with a second notch facilitating entry of spray from the fuel injector into the combustion chamber when the piston is located in the vicinity of said top dead center position. .Iadd. 
     
     
       18.  A two-cycle internal combustion engine, comprising (a) an engine block containing at least one cylinder cavity defined in part by a cylindrical sidewall;   (b) a piston mounted for reciprocal movement within said cylinder cavity;   (c) an engine head positioned across one end of said cylinder cavity to define a cylinder cavity end wall, said head containing an open combustion chamber communicating directly with said cylinder cavity through a combustion chamber outlet opening contained in said cylinder cavity end wall, said combustion chamber outlet opening being radially offset with respect to the central axis of said cylinder cavity and immediately adjacent one portion of the perimeter of said end wall;   (d) at least one inlet valve and one exhaust valve mounted within said head, said inlet valve being positioned within said combustion chamber; and   (e) valve actuating means for operating said inlet and exhaust valves in timed sequence with said piston motion to produce two cycle engine operation including a scavenging period during which said valves are both open to produce a reverse-return-flow of scavenging air through said cylinder cavity; wherein the location of said inlet valve within said combustion chamber is selected and said combustion chamber is shaped in parts with predetermined differing radii of curvature such that air admitted into said combustion chamber by said inlet valve is collected and directed into a converged, single column, collimated air stream passing through said combustion chamber outlet opening into said cylinder cavity axially along and closely adjacent the axial portion of said cylindrical sidewall which extends axially away from said one portion of the perimeter of said end wall, and wherein said opening is shaped and is sufficiently large in size to cause said collimated air stream to proceed axially along said axial portion of said cylindrical sidewall and to have a sufficient flow area and flow velocity to remain unbroken and substantially collimated until it reaches said piston and to cause said scavenging air stream to sweep the internal solid surfaces of said cylinder cavity. .Iaddend. .Iadd.   
     
     
       19.  An engine as defined in claim 18, wherein said inlet valve is a poppet valve, said combustion chamber walls contain a valve seat against which said poppet valve head is moved when said poppet valve is closed, at least one perimeter edge of said valve seat being positioned in substantial axial alignment with said one portion of the perimeter of said end wall. .Iaddend. .Iadd.20. An engine as defined in claim 19, wherein said inlet valve seat is positioned within the radial extent of said cylinder cavity. .Iaddend. .Iadd.21. An engine as defined in claim 19, wherein the head of said inlet poppet valve is moved away from said valve seat into said combustion chamber when said inlet poppet valve is opened, said head of said inlet poppet valve residing within the radial extent of said cylinder cavity when in its open position. .Iaddend. .Iadd.22. An engine as defined in claim 18, wherein said combustion chamber is located substantially entirely within the radial extent of said cylinder cavity. .Iaddend. .Iadd.23. An engine as defined in claim 18, wherein said inlet valve is a poppet valve having a central axis which is oriented at a non-parallel angle with respect to the central axis of said cylinder cavity. .Iaddend. .Iadd.24. An engine as defined by claim 23, wherein the central axis of said inlet valve and said cylinder cavity intersect. .Iaddend. .Iadd.25. An engine as defined in claim 24, wherein a pair of exhaust valves are positioned on a side of said cylinder cavity opposite of said inlet valve relative to the central axis of said cylinder cavity. .Iaddend. .Iadd.26. An engine as defined in claim 24, wherein the stem of said inlet poppet valve extends from the head of said inlet poppet valve away from said central axis of said cylinder cavity. .Iaddend. .Iadd.27. An engine as defined in claim 24, wherein said angle of intersection is approximately 20 degrees. .Iaddend. .Iadd.28. An engine as defined in claim 21, wherein said inlet valve is a poppet valve having a central axis which is oriented at a non-parallel angle with respect to the central axis of said cylinder cavity. .Iaddend. .Iadd.29. An engine as defined in claim 28, wherein the central axis of said inlet valve and said cylinder cavity intersect. .Iaddend. .Iadd.30. An engine as defined by claim 29, wherein the stem of said inlet poppet valve extends from the head of said inlet poppet valve away from said central axis of said cylinder cavity. .Iaddend. .Iadd.31. An engine as defined in claim 18, wherein said combustion chamber outlet opening has an area equal to approximately one-third of the cross sectional area of said cylinder cavity. .Iaddend. .Iadd.32. An engine as defined in claim 18, wherein said combustion chamber has a radial diameter which is greater than about 45 percent of the radial diameter of said cylinder cavity. .Iaddend. .Iadd.33. An engine as defined in claim 18, wherein said combustion chamber has a radial diameter which is less than 55 percent of the radial diameter of said cylinder cavity. .Iaddend. .Iadd.34. An engine as defined in claim 18, wherein said combustion chamber has an extent in the axial direction of said cylinder cavity of greater than 25 percent of the diameter of the cylinder cavity. .Iaddend. .Iadd.35. An engine as defined in claim 18, wherein said combustion chamber has an extent in the axial direction of said cylinder cavity of less than 35 percent of the diameter of the cylinder cavity. .Iaddend. .Iadd.36. An engine as defined in claim 18, wherein said combustion chamber has a volume greater than 5 percent of the displacement volume of said piston in said cylinder cavity. .Iaddend. .Iadd.37. An engine as defined in claim 18, wherein said combustion chamber has a volume less than 16 percent of the displacement volume of said piston in said cylinder cavity. .Iaddend. .Iadd.38. An engine as defined in claim 18, wherein said combustion chamber has a volume between 5 and 6 percent of the displacement volume of said piston in said cylinder cavity when said engine is operated as a diesel engine. .Iaddend. .Iadd.39. An engine as defined in claim 18, wherein said combustion chamber has a volume of between 12 and 16 percent when said engine is operated as a spark ignition engine. .Iaddend. .Iadd.40. An engine as defined in claim 18, wherein said combustion chamber and said exhaust valve are positioned on opposite sides of the cylinder cavity central axis. .Iaddend. .Iadd.41. An engine as defined in claim 30, wherein said combustion chamber outlet opening has an area equal to approximately one-third of the cross sectional area of said cylinder cavity. .Iaddend. .Iadd.42. An engine as defined in claim 30, wherein said combustion chamber has a radial diameter which is greater than 45 percent of the radial diameter of said cylinder cavity. .Iaddend. .Iadd.43. An engine as defined in claim 30, wherein said combustion chamber has a radial diameter which is less than 55 percent of the radial diameter of said cylinder cavity. .Iaddend. .Iadd.44. An engine as defined in claim 30, wherein said combustion chamber has an extent in the axial direction of said cylinder cavity of greater than 25 percent of the diameter of the cylinder cavity. .Iaddend. .Iadd.45. An engine as defined in claim 30, wherein said combustion chamber has an extent in the axial direction of said cylinder cavity of less than 35 percent of the diameter of the cylinder cavity. .Iaddend. .Iadd.46. An engine as defined in claim 30, wherein said combustion chamber has a volume greater than 5 percent of the displacement volume of said piston in said cylinder cavity. .Iaddend. 
     
     
        .Iadd.47.  An engine as defined in claim 30, wherein said combustion chamber has a volume less than 16 percent of the displacement volume of said piston in said cylinder cavity. .Iaddend. .Iadd.48. An engine as defined in claim 30, wherein said combustion chamber has a volume between 5 and 6 percent of the displacement volume of said piston in said cylinder cavity when said engine is operated as a diesel engine. .Iaddend. .Iadd.49. An engine as defined in claim 30, wherein said combustion chamber has a volume of between 12 and 16 percent when said engine is operated as a spark ignition engine. .Iaddend. .Iadd.50. An engine as defined in claim 30, wherein said combustion chamber and said exhaust valve are positioned on opposite sides of the cylinder cavity central axis. .Iaddend. .Iadd.51. An engine as defined in claim 18, wherein said valve actuating means includes variable timing means for varying the timing of opening and closing of at least one of said inlet and exhaust valves relative to the reciprocal motion of said piston. .Iaddend. .Iadd.52. An engine as defined in claim 51, wherein said piston is connected with a crankshaft and said valve actuating means includes a camshaft rotationally driven by said crankshaft and having cams for operating said inlet and exhaust valves, and wherein said variable timing means includes means for rotating said camshaft with respect to said crankshaft in order to change the timing of opening and closing of said inlet and exhaust valves simultaneously relative to the reciprocal motion 
     
     
        of said piston. .Iaddend. .Iadd.53.  An engine as defined in claim 52, wherein said valve actuating means is designed to produce unsymmetric valve timing of said valves by opening and closing said valves at different crank angles before and after the bottom dead center position of said piston, respectively. .Iaddend. .Iadd.54. An engine as defined in claim 53, wherein said valve actuating means is designed to open said exhaust valve before opening said inlet valve and for closing said exhaust valve before closing said inlet valve to achieve blow down and supercharging of said cylinder cavity. .Iaddend. .Iadd.55. An engine as defined in claim 54, wherein said valve actuating means is designed to produce asymmetric valve timing by skewing the opening and closing of said valves in a retarded direction with respect to the bottom dead center position of said piston in order to lengthen the power stroke and shorten the compression stroke. .Iaddend. .Iadd.56. An engine as defined in claim 18, wherein said valve actuating means is designed to produce unsymmetric valve timing of said valves by opening and closing said valves at different crank angles before and after the bottom dead center position of said piston, respectively. .Iaddend. .Iadd.57. An engine as defined in claim 56, wherein said valve actuating means is designed to open said exhaust valve before opening said inlet valve and for closing said exhaust valve before closing said inlet valve to achieve blow down and 
     
     
        supercharging of said cylinder cavity. .Iaddend. .Iadd.58.  An engine as defined in claim 57, wherein said valve actuating means is designed to produce asymmetric valve timing by skewing the opening and closing of said valves in a retarded direction with respect to the bottom dead center position of said piston in order to lengthen the power stroke and shorten the compression stroke. .Iaddend. .Iadd.59. An engine as defined in claim 30, wherein said piston is connected with a crankshaft and said valve actuating means includes a camshaft rotationally driven by said crankshaft and having cams for operating said inlet and exhaust valves, and wherein said variable timing means includes means for rotating said camshaft with respect to said crankshaft in order to change simultaneously the timing of opening and closing of said inlet and exhaust valves relative to the reciprocal motion of said piston and wherein said variable timing means is designed to produce asymmetric valve timing by skewing the opening and closing of said valves in a retarded direction with respect to the bottom dead center position of said piston in order to lengthen the power stroke and shorten the compression stroke. .Iaddend. .Iadd.60. An engine as defined in claim 30, wherein said valve actuating means includes variable timing means for varying the timing of opening and closing of at least one of said inlet and exhaust valves relative to the reciprocal motion of said piston. .Iaddend. .Iadd.61. An engine as defined in claim 60, wherein said piston is connected with a crankshaft and said valve actuating means includes a camshaft rotationally driven by said crankshaft and having cams for operating said inlet and exhaust valves, and wherein said variable timing means includes means for rotating said camshaft with respect to said crankshaft in order to change the timing of opening and closing of said inlet and exhaust valves simultaneously relative to the reciprocal motion of said piston. .Iaddend. .Iadd.62. An engine as defined in claim 61, wherein said valve actuating means is designed to produce unsymmetric valve timing of said valves by opening and closing said valves at different crank angles before and after the bottom dead center position of said piston, respectively. .Iaddend. .Iadd.63. An engine as defined in claim 62, wherein said valve actuating means is designed to open said exhaust valve before opening said inlet valve and for closing said exhaust valve before closing said inlet valve to achieve blow down and supercharging of said cylinder cavity. .Iaddend. .Iadd.64. An engine as defined in claim 63, wherein said valve actuating means is designed to produce asymmetric valve timing by skewing the opening and closing of said valves in a retarded direction with respect to the bottom dead center position of said piston in order to lengthen the power stroke and shorten the compression stroke. .Iaddend. .Iadd.65. An engine as defined in claim 30, wherein said valve actuating means is designed to produce unsymmetric valve timing of said valves by opening and closing said valves at different crank angles before and after the bottom dead center position of said piston, respectively. .Iaddend. .Iadd.66. An engine as defined in claim 65, wherein said valve actuating means is designed to open said exhaust valve before opening said inlet valve and for closing said exhaust valve before closing said inlet valve to achieve blow down and supercharging of said cylinder cavity. .Iaddend. .Iadd.67. An engine as defined in claim 66, wherein said valve actuating means is designed to produce asymmetric valve timing by skewing the opening and closing of said valves in a retarded direction with respect to the bottom dead center position of said piston in order to lengthen the power stroke and shorten the compression stroke. .Iaddend. .Iadd.68. An engine as defined in claim 30, wherein said piston is connected with a crankshaft and said valve actuating means includes a camshaft rotationally driven by said crankshaft and having cams for operating said inlet and exhaust valves, and wherein said variable timing means includes means for rotating said camshaft with respect to said crankshaft in order to change the timing of opening and closing of said inlet and exhaust valves simultaneously relative to the reciprocal motion of said piston and wherein said variable timing means is designed to produce asymmetric valve timing by skewing the opening and closing of said valves in a retarded direction with respect to the bottom dead center position of said piston in order to lengthen the power stroke and shorten the compression stroke. .Iaddend. .Iadd.69. A two-cycle internal combustion engine, comprising (a) an engine block containing at least one cylinder cavity defined in part by a cylindrical sidewall;   (b) a piston mounted for reciprocal movement with in said cylinder cavity;   (c) an engine head positioned across one end of said cylinder cavity to define a cylinder cavity end wall, said head containing a non-spherical open combustion chamber communicating directly with said cylinder cavity through a combustion chamber outlet opening contained in said cylinder cavity end wall, said combustion chamber outlet opening being radially offset with respect to the central axis of said cylinder cavity and immediately adjacent one portion of the perimeter of said end wall;   (d) at least one inlet valve and one exhaust valve mounted within said head, said inlet valve being positioned within said combustion chamber; and   (e) valve actuating means for operating said inlet and exhaust valves in timed sequence with said piston motion to produce two cycle engine operation including a scavenging period during which said valves are both open to produce a reverse return flow of scavenging air through said cylinder cavity;   wherein the location of said inlet valve within said combustion chamber is selected and said combustion chamber is shaped such that air admitted into said combustion chamber by said inlet valve is collected and directed into a collimated air stream passing through said combustion chamber outlet opening into said cylinder cavity axially along and closely adjacent the axial portion of said cylindrical sidewall which extends axially away from said one portion of the perimeter of said end wall,   wherein said opening is shaped and is sufficiently large in size to cause said collimated air stream to proceed axially along said axial portion of said cylindrical sidewall and to have a sufficient flow area and flow velocity to remain unbroken and substantially collimated until it reaches said piston and to cause said scavenging air stream to sweep the internal solid surfaces of said cylinder cavity; and   wherein said inlet valve is a poppet valve having a valve head located in said combustion chamber and having a valve stem extending from said combustion chamber in a non-parallel direction with respect to the central axis of said cylinder cavity, said combustion chamber walls contain a valve seat against which said poppet valve head is moved when said poppet valve is closed, at least one perimeter edge of said valve seat being positioned in substantial axial alignment with said one portion of the perimeter of said end wall. .Iaddend.  .Iadd.70. An engine as defined in claim 69, wherein said inlet valve seat is positioned within the radial extent of said cylinder cavity. .Iaddend. .Iadd.71. An engine as defined in claim 69, wherein the head of said inlet poppet valve is moved away from said valve seat into said combustion chamber when said inlet poppet valve is opened, said head of said inlet poppet valve residing within the radial extent of said cylinder cavity when in its open position. .Iaddend. .Iadd.72. An engine as defined by claim 69, wherein the central axis of said inlet valve and said cylinder cavity intersect. .Iaddend. .Iadd.73. An engine as defined by claim 72, wherein the stem of said inlet poppet valve extends from the head of said inlet poppet valve away from said   
     
     
        central axis of said cylinder cavity. .Iaddend. .Iadd.74.  A two-cycle internal combustion engine, comprising (a) an engine block containing at least one cylinder cavity defined in part by a cylindrical sidewall;   (b) a piston mounted for reciprocal movement within said cylinder cavity;   (c) an engine head positioned across one end of said cylinder cavity to define a cylinder cavity end wall, said head containing an open combustion chamber communicating directly with said cylinder cavity through a combustion chamber outlet opening contained in said cylinder cavity end wall, said combustion chamber outlet opening being radially offset with respect to the central axis of said cylinder cavity and immediately adjacent one portion of the perimeter of said end wall;   (d) at least one inlet valve and one exhaust valve mounted within said head, said inlet valve being positioned within said combustion chamber; and   (e) valve actuating means for operating said inlet and exhaust valves in timed sequence with said piston motion to produce two cycle engine operation including a scavenging period during which said valves are both open to produce a reverse-return-flow of scavenging air through said cylinder cavity;   wherein the location of said inlet valve within said combustion chamber is selected and said combustion chamber is shaped such that air admitted into said combustion chamber by said inlet valve is collected and directed into a collimated air stream passing through said combustion chamber outlet opening into said cyinder cavity axially along and closely adjacent the axial portion of said cylindrical sidewall which extends axially away from said one portion of the perimeter of said end wall,   wherein said opening is shaped and is sufficiently large in size to cause said collimated air stream to proceed axially along said axial portion of said cylindrical sidewall and to have a sufficient flow area and flow velocity to remain unbroken and substantially collimated until it reaches said piston and to cause said scavenging air stream to sweep substantially all of the internal solid surfaces of said cylinder cavity; and   wherein said valve actuating means includes variable timing means for varying the timing of opening and closing of at least one of said inlet and exhaust valves relative to the reciprocal motion of said piston. .Iaddend. .Iadd.75. An engine as defined in claim 74, wherein said piston is connected with a crankshaft and said valve actuating means includes a camshaft rotationally driven by said crankshaft and having cams for operating said inlet and exhaust valves, and wherein said variable timing means includes means for rotating said camshaft with respect to said crankshaft in order to change the timing of opening and closing of said inlet and exhaust valves simultaneously relative to the reciprocal motion of said piston. .Iaddend. .Iadd.76. An engine as defined in claim 74, wherein said valve actuating means is designed to produce unsymmetric valve timing of said valves by opening and closing said valves at different crank angles before and after the bottom dead center position of said piston, respectively. .Iaddend. .Iadd.77. An engine as defined in claim 76, wherein said valve actuating means is designed to open and close said exhaust valve before opening and closing, respectively, said inlet valve to achieve blow down and supercharging of said cylinder cavity. .Iaddend. .Iadd.78. An engine as defined in claim 77, wherein said valve actuating means is designed to produce asymmetric valve timing by skewing the opening and closing of said valves in a retarded direction with respect to the bottom dead center position of said piston in order to lengthen the power stroke and shorten the compression stroke. .Iaddend.