USING VALVE TIMING TO IMPROVE ENGINE ACOUSTICS
First Claim
1. A method of controlling sound of an engine having a crankshaft, a camshaft and a plurality of cylinders, each cylinder having an associated piston that is driven by the crankshaft, an associated exhaust valve, and an associated exhaust path length, wherein the respective exhaust path lengths associated with at least some of the plurality of cylinders differ and wherein at least some of the exhaust valves are driven by the camshaft, the method comprising:
- operating an engine in a skip fire mode; and
dynamically varying a phase of the camshaft between different exhaust events during a sequence of skip fire operation in a manner that at least partially compensates for differences in the exhaust path lengths associated with fired cylinders to thereby help suppress audible beats that would otherwise occur in the event that the camshaft phase was held substantially constant during the sequence of skip fire operation.
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Accused Products
Abstract
A method for improving the operation of an internal combustion engine implementing cylinder deactivation is described. Generally, the pattern of combustion events that are fired and skipped together with the geometry of the exhaust and/or intake system can create unpleasant acoustic issues. By slightly altering the timing of the cylinder intake and exhaust valves, these acoustic issues can be mitigated. The valve timing can be altered on a combustion event by combustion event basis. Alternatively, valve timing for different groups of cylinders can be modified together.
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Citations
20 Claims
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1. A method of controlling sound of an engine having a crankshaft, a camshaft and a plurality of cylinders, each cylinder having an associated piston that is driven by the crankshaft, an associated exhaust valve, and an associated exhaust path length, wherein the respective exhaust path lengths associated with at least some of the plurality of cylinders differ and wherein at least some of the exhaust valves are driven by the camshaft, the method comprising:
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operating an engine in a skip fire mode; and dynamically varying a phase of the camshaft between different exhaust events during a sequence of skip fire operation in a manner that at least partially compensates for differences in the exhaust path lengths associated with fired cylinders to thereby help suppress audible beats that would otherwise occur in the event that the camshaft phase was held substantially constant during the sequence of skip fire operation. - View Dependent Claims (2, 3)
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4. A method of controlling sound of an engine having a crankshaft and a plurality of cylinders, each cylinder having an associated piston that is driven by the crankshaft, an associated exhaust valve and an associated exhaust path length, wherein the respective exhaust path lengths associated with at least some of the plurality of cylinders differ, the method comprising:
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operating the engine in a skip fire mode; and dynamically varying the relative timing of the exhaust valve opening events relative to crankshaft angle between different cylinder exhaust events during skip fire operation. - View Dependent Claims (5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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- 16. A method of controlling acoustic characteristics of an engine having a plurality of cylinders, a crankshaft, a camshaft and a cam phaser, the method comprising applying an periodic signal to the cam phaser to adjust the phase of the camshaft relative to the crankshaft, wherein the periodic signal has a frequency that substantially corresponds to a characteristic acoustic frequency associated with a current operational condition of the engine and wherein the periodic signal is arranged to help suppress such acoustic frequency.
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18. An engine comprising:
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a crankshaft; at least one camshaft; a plurality of cylinders, each cylinder having an associated piston that is driven by the crankshaft and an associated exhaust valve driven by the at least one camshaft; at least one exhaust manifold; and an exhaust pipe that receives exhaust gases expelled from the cylinders through the at least one exhaust manifold, each cylinder having an associated exhaust path length from the cylinder through the at least one exhaust manifold to the exhaust pipe and wherein the respective exhaust path lengths associated with at least some of the plurality of cylinders differ; and wherein the at least one camshaft includes a plurality of exhaust valve cam lobes, each exhaust valve cam lobe being arranged to actuate an associated exhaust valve, wherein the phases of the exhaust valve cam lobes relative to their associated pistons vary in accordance with the exhaust path length associated with their respective cylinders such that the sound associated with each exhaust event exits the exhaust path in a more evenly spaced manner than would occur in the event that the phases of the exhaust valve cam lobes were consistent relative to their associated pistons. - View Dependent Claims (19, 20)
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Specification