Moment-cancelling 4-stroke engine

Abstract

A moment-cancelling, four-stroke engine is disclosed. The engine includes a first cylinder having a first piston and a second cylinder having a second piston, a first crankshaft operably connected to the first piston and a second crankshaft operably connected to the second piston. The first crankshaft rotates in a first direction and the second crankshaft rotates in a second direction that is opposite the first direction to cancel the moments applied to the engine and reduce engine vibration.

1 - 8 . (canceled) 
     
     
         9 . An internal combustion engine, comprising:
 a first cylinder having a first piston;   a second cylinder having a second piston;   a first crankshaft operably connected to the first piston;   a second crankshaft operably connected to the second piston;   a cylinder head comprising at least one intake port and at least one exhaust port per cylinder, said at least one intake port connected to the first cylinder such that fluid can pass through the at least one intake port into the first cylinder and said at least one exhaust port connected to the first cylinder such that fluid can pass from the first cylinder through the at least one exhaust port;   a movable intake valve positioned at least partially within the at least one intake port configured to control the flow of fluid through the at least one intake port, a diameter of the intake valve greater than 0.55 inches and less than 2.56 inches;   a movable exhaust valve positioned at least partially within the at least one exhaust port configured to control the flow of fluid through the at least one exhaust port, a diameter of the exhaust valve greater than 0.44 inches and less than 2.06 inches;   wherein the at least one intake port has a minimum intake port diameter and a first inside radius positioned toward an intake port valve seat from the minimum intake port diameter smoothly transitions to a second inside radius positioned toward the intake port valve seat from the first radius so that the intake port expands to meet the intake port valve seat to allow a maximum flow volume into the cylinder, the first inside radius being greater than 0.8 inches and less than 1.2 inches, the second inside radius being greater than 0.3 inches and less than 0.5 inches;   wherein the cylinder bore diameter is greater than 1.5 inches and less than 7 inches and a sum of twice the intake valve diameter and twice the exhaust valve diameter is greater than 1.5 inches and less than 7 inches; and   wherein the first crankshaft rotates in a first direction and the second crankshaft rotates in a second direction such that the second direction is an opposite direction from the first direction.   
     
     
         10 . The engine of  claim 9 , wherein the engine is water-cooled. 
     
     
         11 . The engine of  claim 9  further comprising a third cylinder and a fourth cylinder, wherein the first and third cylinders are operably connected to the first crankshaft and the second and fourth cylinders are operably connected to the second crankshaft, each of the third and fourth cylinders having at least one intake valve and at least one exhaust valve. 
     
     
         12 . The engine of  claim 11  further comprising a fifth cylinder and a sixth cylinder, wherein the first, third, and fifth cylinders are operably connected to the first crankshaft and the second, fourth, and sixth cylinders are operably connected to the second crankshaft, each of the fifth and sixth cylinders having at least one intake valve and at least one exhaust valve. 
     
     
         13 . The engine of  claim 12  further comprising a seventh cylinder and an eighth cylinder, wherein the first, third, fifth, and seventh cylinders are operably connected to the first crankshaft and the second, fourth, sixth, and eighth cylinders are operably connected to the second crankshaft, each of the seventh and eighth cylinders having at least one intake valve and at least one exhaust valve. 
     
     
         14 . The engine of  claim 9 , wherein the cylinders are displaced a nominal distance forward and aft from intersections between a centerline of each of the cylinders and a crankshaft axis to allow a connecting rod of each cylinder to be straighter on a firing stroke of each cylinder. 
     
     
         15 . The engine of  claim 9 , wherein the engine is mounted perpendicular to a longitudinal axis of the vehicle and the engine further comprises dual overhead cams. 
     
     
         16 . The engine of  claim 9  further comprising a throttle valve configured to control air flow to the first cylinder and the second cylinder by receiving signals from an electronic engine management system, the electronic engine management system configured to transmit signals to the throttle valve such that a first position of the throttle valve corresponds to a high mileage mode of operation of the engine and a second position of the throttle valve corresponds to a high power mode of operation of the engine. 
     
     
         17 . An internal combustion engine, comprising:
 a first cylinder having a first piston;   a second cylinder having a second piston;   a first crankshaft operably connected to the first piston and a second crankshaft operably connected to the second piston;   a cylinder head comprising at least one intake port and at least one exhaust port per cylinder, said at least one intake port connected to the first cylinder such that fluid can pass through the at least one intake port into the first cylinder and said at least one exhaust port connected to the first cylinder such that fluid can pass from the first cylinder through the at least one exhaust port;   a movable intake valve positioned at least partially within the at least one intake port configured to control the flow of fluid through the intake ports;   a movable exhaust valve positioned at least partially within the at least one exhaust port configured to control the flow of fluid through the at least one exhaust port;   wherein the at least one intake port has a minimum intake port diameter and a first inside radius positioned toward an intake port valve seat from the minimum intake port diameter, said first inside radius smoothly transitioning to a second inside radius positioned toward the intake port valve seat from the first radius so that the intake port expands to meet the intake port valve seat, the first inside radius being greater than 0.4 inches and less than 1.5 inches, the second inside radius being greater than 0.13 inches and less than 0.7 inches;   wherein the at least one intake port has an intake bowl radius positioned between the minimum intake port diameter and an intake valve seating surface, the intake bowl radius being greater than 0.45 inches and less than 2.1 inches;   wherein the first crankshaft rotates in a first direction and the second crankshaft rotates in a second direction such that the second direction is an opposite direction from the first direction.   
     
     
         18 . The engine of  claim 17 , wherein a bore of each of the first and second cylinders is greater than 3.0 inches. 
     
     
         19 . The engine of  claim 17 , wherein a compression ratio of the engine is between 9.1 and 13.5 and an oversquare ratio of the engine is greater than 1.0. 
     
     
         20 . The engine of  claim 17 , wherein a squish area of each piston is between 24%-35% of an area of the piston. 
     
     
         21 . The engine of  claim 17 , wherein the engine is water-cooled. 
     
     
         22 . An internal combustion engine, comprising:
 a first cylinder having a first piston;   a second cylinder having a second piston;   a first crankshaft operably connected to the first piston and a second crankshaft operably connected to the second piston;   a cylinder head comprising at least one intake port and at least one exhaust port per cylinder, said at least one intake port connected to the first cylinder such that fluid can pass through the at least one intake port into the first cylinder and said at least one exhaust port connected to the first cylinder such that fluid can pass from the first cylinder through the at least one exhaust port;   a movable intake valve positioned at least partially within the at least one intake port configured to control the flow of fluid through the intake ports;   a movable exhaust valve positioned at least partially within the at least one exhaust port configured to control the flow of fluid through the at least one exhaust port;   wherein the at least one intake port has a minimum intake port diameter and a first inside intake radius positioned toward an intake port valve seat from the minimum intake port diameter, said first inside intake radius smoothly transitioning to a second inside intake radius positioned toward the intake port valve seat from the first inside intake radius so that the intake port expands to meet the intake port valve seat, the first inside intake radius being greater than 0.4 inches and less than 1.5 inches, the second inside intake radius being greater than 0.13 inches and less than 0.7 inches;   wherein the at least one exhaust port has a minimum exhaust port diameter and a first inside exhaust radius positioned toward an exhaust port valve seat from the minimum exhaust port diameter, said first inside exhaust radius smoothly transitioning to a second inside exhaust radius positioned toward the exhaust port valve seat from the first inside exhaust radius so that the exhaust port expands to meet the exhaust port valve seat, the first inside exhaust radius being greater than 0.2 inches and less than 0.98 inches, the second inside exhaust radius being greater than 0.12 inches and less than 0.56 inches;   wherein the at least one intake port has an intake bowl radius positioned between the minimum intake port diameter and an intake valve seating surface, the intake bowl radius being greater than 0.45 inches and less than 2.1 inches;   wherein the first crankshaft rotates in a first direction and the second crankshaft rotates in a second direction such that the second direction is an opposite direction from the first direction.   
     
     
         23 . The engine of  claim 22 , wherein a bore of each of the first and second cylinders is greater than 3.0 inches. 
     
     
         24 . The engine of  claim 22 , wherein a compression ratio of the engine is between 9.1 and 13.5 and an oversquare ratio of the engine is greater than 1.0. 
     
     
         25 . The engine of  claim 22 , wherein a squish area of each of the first and second pistons is between 24%-35% of an area of the piston. 
     
     
         26 . The engine of  claim 22 , wherein the engine is water-cooled. 
     
     
         27 . The engine of  claim 22  further comprising a throttle valve configured to control air flow to the first cylinder and the second cylinder by receiving signals from an electronic engine management system, the electronic engine management system configured to transmit signals to the throttle valve such that a first position of the throttle valve corresponds to a high mileage mode of operation of the engine and a second position of the throttle valve corresponds to a high power mode of operation of the engine.