Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
2001-11-09
2003-11-18
Dolinar, Andrew M. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C123S090170
Reexamination Certificate
active
06650992
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a system and method for selecting a camshaft in an engine having dual camshafts to reduce engine torque fluctuations.
BACKGROUND OF THE INVENTION
Known engines have utilized variable cam timing (VCT) mechanisms to control the opening and closing of intake valves and exhaust valves communicating with engine cylinders. In particular, each VCT mechanism is utilized to adjust a position of a camshaft (which actuates either an intake valve or exhaust valve or both) with respect to a crankshaft position. By varying the position of the camshaft (i.e., camshaft angle) with respect to the position of the crankshaft, engine fuel economy can be increased and engine emissions can be decreased.
In known engines having VCT mechanisms, it is desired to shift the position of camshafts in the VCT mechanisms synchronously (i.e., at the same speed) to a desired phase angle with respect to the crankshaft. However, the inventors herein have recognized that first and second camshafts associated with first and second VCT mechanisms, respectively, in an engine, may not move to the desired phase angle at the same speed. For example, the first VCT mechanism may be actuated at a lower pressure that a second VCT mechanism due to a clogged oil line communicating with the first VCT, resulting in slower movement of the first camshaft. Still further, the first VCT mechanism may “stick” at cold temperatures resulting in slower movement of the first camshaft as compared to the second camshaft of the second VCT mechanism. During non-synchronous movement of the first and second camshafts, the air charge delivered to first and second cylinder banks, respectively, are different. The difference in air charge can result in a differing torques being produced by the first and second cylinder banks resulting in undesirable engine shaking and increased engine noise.
The inventors herein have recognized that there is a need for a system and method for selecting one of the first and second camshafts when attempting to reduce engine torque fluctuations. In particular, the inventors herein have recognized that a first camshaft moving at a slower speed than a second camshaft toward a scheduled phase angle—cannot physically move faster to reduce engine torque fluctuations. Therefore, the faster camshaft must be selected when modifying the speed of one of the camshafts to reduce engine torque fluctuations.
SUMMARY OF THE INVENTION
The foregoing problems and disadvantages are overcome by a system and method for selecting one of first and second camshafts in a variable cam timing engine. The first and second camshafts control air flow communicating with first and second cylinders, respectively, of the engine. The engine further includes a crankshaft driven by first and second pistons within the first and second cylinders, respectively. The method includes determining which of the first and second camshafts is moving at a faster rate of movement toward a first scheduled phase angle with respect to the crankshaft. Finally, the method includes selecting one of the first and second camshafts having the faster rate of movement for reducing engine torque fluctuations.
A system for selecting one of first and second phase shiftable camshafts in a variable cam timing engine is also provided. The system includes a first sensor generating a first signal indicative of a position of the first camshaft. The system further includes a second sensor generating a second signal indicative of a position of the second camshaft. The system further includes a third sensor generating a third signal indicative of a position of a crankshaft. Finally, the system includes a controller configured to determine which of the first and second camshafts is moving toward a first scheduled phase angle with respect to the crankshaft at a faster rate of movement based on the first, second, and third signals. The controller is further configured to select one of the first and second camshafts having the faster rate of movement for reducing torque fluctuations when changing the faster rate of movement.
The inventive system and method for selecting one of first and second camshafts of an engine solves the problem of which camshaft to use to reduce engine torque fluctuations. In particular, the inventive system and method selects the faster camshaft when modifying the speed of one of the camshafts to reduce engine torque fluctuations.
REFERENCES:
patent: 5245968 (1993-09-01), Kolias et al.
patent: 6219611 (2001-04-01), Russell
Cooper Stephen Lee
Jankovic Mrdjan J.
Magner Stephen William
Buckert John
Dolinar Andrew M.
Ford Global Technologies LLC
Lippa Allan J.
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