System and method for improved cam retard
First Claim
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1. A system for regulating flow to a cylinder of an internal combustion engine, the system comprising:
- a valve operating mechanism capable of opening at least one intake valve at an opening position that is after top-dead-center, relative to an intake stroke of a cylinder, said intake valve opening position also being in advance of a closing of an exhaust valve in said cylinder;
a cam profile switching device that is capable of changing the amount of intake valve lift produced by said valve operating mechanism; and
a controller constraining cam retard so that a desired level of manifold vacuum is observed when said cam profile switch is in a low lift position and when said valve operating mechanism is in a retarded position wherein the opening of said at least one intake valve is after top-dead-center, relative to the intake stroke of said cylinder, and where the opening of said at least one intake valve is in advance of the exhaust valve closing in said cylinder.
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Abstract
A system and method to control valve timing and valve lift of an engine is described. The intake valve timing can be retarded while the valve is in a low lift or high lift mode. The method can lower engine friction and reduce fuel consumption, at least under some conditions.
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Citations
19 Claims
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1. A system for regulating flow to a cylinder of an internal combustion engine, the system comprising:
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a valve operating mechanism capable of opening at least one intake valve at an opening position that is after top-dead-center, relative to an intake stroke of a cylinder, said intake valve opening position also being in advance of a closing of an exhaust valve in said cylinder; a cam profile switching device that is capable of changing the amount of intake valve lift produced by said valve operating mechanism; and a controller constraining cam retard so that a desired level of manifold vacuum is observed when said cam profile switch is in a low lift position and when said valve operating mechanism is in a retarded position wherein the opening of said at least one intake valve is after top-dead-center, relative to the intake stroke of said cylinder, and where the opening of said at least one intake valve is in advance of the exhaust valve closing in said cylinder. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for regulating flow to a cylinder of an internal combustion engine, the system comprising:
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an electronically controlled throttle; a variably operable valve mechanism capable of opening at least one intake valve at an opening position that is after top-dead-center, relative to an intake stroke of said cylinder, said intake valve opening position also being in advance of a closing of an exhaust valve in said cylinder; a cam profile switching device that is capable of changing the amount of valve lift produced by said valve operating mechanism; and a controller to adjust throttle position, retard spark timing, and increase torque converter slip during a switching of said cam profile switching device from a low lift state to a high lift state when said variably operated valve mechanism is positioned such that said at least one intake valve opens after top-dead-center, relative to the intake stroke of said cylinder, and while said intake valve opening position being in advance of a closing of said exhaust valve. - View Dependent Claims (9, 10, 11)
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12. A method for regulating flow to a cylinder of an internal combustion engine, the method comprising:
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retarding intake valve opening and exhaust valve closing to a crankshaft angle that is after top-dead-center, relative to an intake stroke of a cylinder, said intake valve opening position also being in advance of a closing of an exhaust valve in said cylinder; varying the state of a cam profile switching device as engine speed varies and while said intake valve opening and said exhaust valve closing are retarded after top-dead-center, relative to said intake stroke; and constraining cam retard so that a desired level of intake manifold vacuum is observed while said intake valve opening is retarded from top-dead-center of the intake stroke of said cylinder. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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Specification