Opposed piston engine cam shape
First Claim
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1. An internal combustion engine comprising:
- a driveshaft having a first end and a second end and disposed along a driveshaft axis;
a first cam mounted on the driveshaft, the first cam having a cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the hub, the cam shoulder having a first cam diameter and a first segmented polynomial shape, the shoulder having at least two lobes formed by the polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough and a lobe wavelength between the two troughs, the peak having a maximum amplitude for the lobe, where the wavelength distance from the first trough to peak of an ascending shoulder portion of the lobe is greater than the wavelength distance from the peak to the second trough of a descending shoulder portion of the lobe;
a second cam mounted on the driveshaft spaced apart from the first cam, the second cam having a cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the hub, the cam shoulder having a second segmented polynomial shape of constantly changing slope which second segmented polynomial shape has the same frequency as the first segmented polynomial shape, the shoulder having at least two lobes formed by the second polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough and a lobe wavelength between the two troughs, the peak having a maximum amplitude for the lobe, where the wavelength distance from the first trough to peak of an ascending shoulder portion of the lobe is greater than the wavelength distance from the peak to the second trough of a descending shoulder portion of the lobe,wherein the number of lobes of the second cam corresponds with the number of lobes of the first cam;
a first combustion cylinder defined along a center cylinder axis, the combustion cylinder having a first end and a second end with an intake port formed in the cylinder between the first and second ends and an exhaust port formed in the cylinder between the intake port and the second end, the center cylinder axis being parallel with but spaced apart from the driveshaft axis, wherein a combustion chamber is defined within the cylinder between the two cylinder ends;
a first piston assembly disposed in the first cylinder end of the first combustion cylinder and an opposing second piston assembly disposed in the second cylinder end of the first combustion cylinder, the first piston assembly engaging the segmented polynomial shaped shoulder of the first cam and the second piston assembly engaging the segmented polynomial shaped shoulder of the second cam, each piston assembly movable between an inner dead center (IDC) position in which the piston assembly is fully extended in the combustion chamber away from its corresponding cam and an outer dead center position in which the piston assembly is fully retracted in the combustion chamber away from the inner dead center position; and
at least one fuel injector disposed adjacent a center of the combustion cylinder and in communication with said combustion chamber,andwherein the cams oppose one another so that the peak of a lobe of the first cam is substantially aligned with the peak of a lobe of the second cam, but no portion of first segmented polynomial shaped shoulder is parallel with a portion of second segmented polynomial shaped shoulder.
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Abstract
An opposed piston engine has a driveshaft with a spaced apart cams mounted thereon. Each cam has a circumferential cam shoulder of a curvilinear shape selected to enhance flow through intake and exhaust ports. The curvilinear shape may be a segmented polynomial shape forming lobes which lobes are asymmetrical so that the lobe wavelength distance from a first trough to the lobe peak of an ascending shoulder portion of the lobe is greater than the lobe wavelength distance from the peak to a second trough of a descending shoulder portion of the lobe. Opposing cam shoulders may be shaped so as to always be converging or diverging from one another.
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Citations
30 Claims
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1. An internal combustion engine comprising:
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a driveshaft having a first end and a second end and disposed along a driveshaft axis; a first cam mounted on the driveshaft, the first cam having a cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the hub, the cam shoulder having a first cam diameter and a first segmented polynomial shape, the shoulder having at least two lobes formed by the polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough and a lobe wavelength between the two troughs, the peak having a maximum amplitude for the lobe, where the wavelength distance from the first trough to peak of an ascending shoulder portion of the lobe is greater than the wavelength distance from the peak to the second trough of a descending shoulder portion of the lobe; a second cam mounted on the driveshaft spaced apart from the first cam, the second cam having a cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the hub, the cam shoulder having a second segmented polynomial shape of constantly changing slope which second segmented polynomial shape has the same frequency as the first segmented polynomial shape, the shoulder having at least two lobes formed by the second polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough and a lobe wavelength between the two troughs, the peak having a maximum amplitude for the lobe, where the wavelength distance from the first trough to peak of an ascending shoulder portion of the lobe is greater than the wavelength distance from the peak to the second trough of a descending shoulder portion of the lobe, wherein the number of lobes of the second cam corresponds with the number of lobes of the first cam; a first combustion cylinder defined along a center cylinder axis, the combustion cylinder having a first end and a second end with an intake port formed in the cylinder between the first and second ends and an exhaust port formed in the cylinder between the intake port and the second end, the center cylinder axis being parallel with but spaced apart from the driveshaft axis, wherein a combustion chamber is defined within the cylinder between the two cylinder ends; a first piston assembly disposed in the first cylinder end of the first combustion cylinder and an opposing second piston assembly disposed in the second cylinder end of the first combustion cylinder, the first piston assembly engaging the segmented polynomial shaped shoulder of the first cam and the second piston assembly engaging the segmented polynomial shaped shoulder of the second cam, each piston assembly movable between an inner dead center (IDC) position in which the piston assembly is fully extended in the combustion chamber away from its corresponding cam and an outer dead center position in which the piston assembly is fully retracted in the combustion chamber away from the inner dead center position; and at least one fuel injector disposed adjacent a center of the combustion cylinder and in communication with said combustion chamber, and wherein the cams oppose one another so that the peak of a lobe of the first cam is substantially aligned with the peak of a lobe of the second cam, but no portion of first segmented polynomial shaped shoulder is parallel with a portion of second segmented polynomial shaped shoulder. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. An internal combustion engine comprising:
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a driveshaft having a first end and a second end and disposed along a driveshaft axis; a piston disposed to reciprocate along a piston axis, the piston axis being parallel with but spaced apart from the driveshaft axis, and a first cam mounted on the driveshaft, the first cam comprising; a first cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the first cam hub, the cam shoulder having a first cam diameter and a first segmented polynomial shape, the shoulder having at least one lobe formed by the polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough and a lobe wavelength between the two troughs, the peak having a maximum amplitude for the lobe, where the wavelength distance from the first trough to peak of an ascending shoulder portion of the lobe is greater than the wavelength distance from the peak to the second trough of a descending shoulder portion of the lobe; and a second cam mounted on the driveshaft and spaced apart from the first cam, the second cam comprising; a second cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the second cam hub, the cam shoulder having a second segmented polynomial shape which second segmented polynomial shape has the same frequency as the first segmented polynomial shape, the second cam hub shoulder having at least one lobe formed by the second polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough and a lobe wavelength between the two troughs, the peak having a maximum amplitude for the lobe, where the wavelength distance from the first trough to peak of an ascending shoulder portion of the lobe is greater than the wavelength distance from the peak to the second trough of a descending shoulder portion of the lobe, wherein the number of lobes of the second cam corresponds with the number of lobes of the first cam; and wherein the cams oppose one another so that the peak of a lobe of the first cam is substantially aligned with the peak of a lobe of the second cam, but no portion of first segmented polynomial shaped shoulder is parallel with a portion of second segmented polynomial shaped shoulder. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19)
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20. An internal combustion engine comprising:
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a driveshaft having a first end and a second end and disposed along a driveshaft axis; a piston disposed to reciprocate along a piston axis, the piston axis being parallel with but spaced apart from the driveshaft axis, and a first cam mounted on the driveshaft, the first cam comprising a cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the hub, the cam shoulder having a first cam diameter and a first segmented polynomial shape, the shoulder having at least one lobe formed by the polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough, the lobe having an ascending shoulder portion between the first trough and the peak and a descending shoulder portion between the peak and the second trough, wherein the average slope of the ascending shoulder portion is greater than the average slope of the descending shoulder portion; and a second cam mounted on the driveshaft and spaced apart from the first cam, the second cam comprising a cam hub attached the driveshaft, and a circumferential cam shoulder extending around a periphery of the hub, the cam shoulder having a second segmented polynomial shape which second segmented polynomial shape has the same frequency as the first segmented polynomial shape, the shoulder having at least one lobe formed by the second polynomial shape, each lobe characterized by a peak positioned between a first trough and a second trough, the lobe having an ascending shoulder portion between the first trough and the peak and a descending shoulder portion between the peak and the second trough, wherein the average slope of the ascending shoulder portion is greater than the average slope of the descending shoulder portion, wherein the number of lobes of the second cam corresponds with the number of lobes of the first cam; and wherein the first segmented polynomial shaped shoulder and the second segmented polynomial shaped shoulder oppose one another so as to be constantly diverging or converging from one another. - View Dependent Claims (21, 22)
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23. A method for operating an internal combustion engine comprising:
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moving a first cam follower along a first cam from a first position on the first cam in which a first piston is at inner dead center within a combustion cylinder to a second position on the first cam in which the first piston blocks flow through an intake port in the cylinder, and simultaneously moving a second cam follower along a second cam from a first position on the second cam in which a second piston is at inner dead center within the combustion cylinder to a second position on the second cam, so as to cause the second piston to open an exhaust port in the cylinder, wherein the respective piston move axially away from one another as the respective cam followers move from the first position to the second position; continuing to move the first cam follower along the first cam from the second position to a third position on the first cam so as to cause the first piston to continue to move away from inner dead center and to open the intake port, and simultaneously moving the second cam follower along the second cam from the second position to a third position so as to cause the second piston to move away from the first piston while the exhaust port remains open to outer dead center for the second piston; continuing to move the first cam follower along the first cam from the third position to a fourth position in which the intake port remains open, and simultaneously moving the second cam follower along the second cam from the third position to a fourth position so as to cause the second piston to close the exhaust port in the cylinder, wherein the respective piston move axially towards one another as the respective cam followers move from the third position to the fourth position; continuing to move the first cam follower along the first cam from the fourth position to a fifth position so as to cause the first piston to move axially towards second piston and inner dead center, whereby movement of the first piston closes the intake port in the cylinder, and simultaneously moving the second cam follower along the second cam from the fourth position to a fifth position so as to cause the second piston to move axially towards the first piston and inner dead center; and continuing to move the first cam follower along the first cam from the fifth position to the first position on the cam so as to cause the first piston to move axially towards second piston and inner dead center, and simultaneously moving the second cam follower along the second cam from the fifth position to the first position on the cam so as to cause the second piston to move axially towards the first piston and inner dead center. - View Dependent Claims (24, 25, 26, 27, 28, 29, 30)
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Specification