Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
2000-07-06
2001-10-30
Denion, Thomas (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090110, C123S406290, C123S406410, C123S406430
Reexamination Certificate
active
06308670
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a system and method for valve timing and more particularly, a valve timing system and method which compensates for variation in the compression ratios of cylinders within a camless internal combustion engine, effective to provide uniform knock sensitivity among the cylinders.
BACKGROUND OF THE INVENTION
Valve timing systems and assemblies are used in internal combustion engines in order to alter the timing of the opening and closing of the engine's intake and/or exhaust valves. Prior valve timing systems typically include one or more camshafts and one or more cam timing assemblies which selectively advance and/or delay the rotation of the one or more camshafts relative to the crankshaft, thereby controlling the actuation of the intake and exhaust valves.
These prior systems and the valve timing profiles used by these systems suffer from several drawbacks. For example and without limitation, due to their inherent physical limitations, these prior cam-driven systems are ineffective to adjust or compensate for variations in the compression ratios of the various cylinders of a vehicle's engine. Due to manufacturing variability, the compression ratios of the various cylinders of many vehicle engines often vary significantly. The higher the compression ratio of a cylinder, the more susceptible that cylinder is to knock. Hence, many conventional engines have cylinders with varying susceptibility to knock. When one or more cylinders have a greater susceptibility to knock, the calibration of the ignition or “spark” system is typically retarded in order to prevent engine knock and excessive activation of the vehicle's knock control system. Particularly, due to the inability of these prior systems to independently adjust the valve timing of particular cylinders, the spark calibration of engines utilizing these prior cam-driven systems must be undesirably reduced.
Efforts have been made to increase the efficiency of vehicle engines and reduce emissions by eliminating the camshafts and operating the intake and exhaust valves by use of selectively controllable electromagnetic or electrohydraulic actuators. These types of systems eliminate many problems related to the physical characteristics of cam-driven systems and offer additional precision in valve timing. However, these prior systems are typically implemented using conventional valve timing profiles or strategies, and thus, suffer from many of the same previously delineated drawbacks associated with cam-driven systems. For example and without limitation, the valve timing profiles used within these systems and strategies cannot compensate for variation in the compression ratios of the various cylinders of the engine. As a result, the spark calibration of these engines is likewise undesirably reduced to prevent knocking and excessive activation of the engine's knock control system.
There is therefore a need for a new and improved system and method for valve timing for use with a camless engine including several cylinders having varying compression ratios.
SUMMARY OF THE INVENTION
It is a first object of the invention to provide a system and method for valve timing which overcomes at least some of the previously delineated drawbacks of prior systems, assemblies and methodologies, which is adapted for use with a camless internal combustion engine having several cylinders, and which is effective to compensate for variations in the compression ratios of the cylinders.
It is a second object of the invention to provide a valve timing system and method for use in combination with a camless internal combustion engine which is effective to provide substantially uniform cylinder knock sensitivity throughout the various cylinders of the engine.
It is a third object of the invention to provide a valve timing system and method for use within an engine which utilizes several electromagnetic or electrohydraulic valve actuating assemblies which are adaptively and independently controlled to provide uniform knock sensitivity among the various cylinders of the engine.
It is a fourth object of the invention to provide a method for valve timing which is effective to bias a particular cylinder within an engine to be more sensitive to knock that the other cylinders of the engine.
According to a first aspect of the present invention, a valve timing system is provided for use within a camless engine of the type including a first cylinder having a first valve and a first compression ratio, and a second cylinder having a second valve and a second compression ratio. The valve timing system includes a first actuator which selectively actuates the first valve; a second actuator which selectively actuates the second valve; and a controller which is communicatively coupled to the first and second actuators, the controller being effective to selectively communicate a first signal to the first actuator effective to actuate the first valve and a second signal to the second actuator effective to actuate the second valve, the controller being further effective to vary the first signal based upon the first compression ratio and to vary the second signal based upon the second compression ratio, thereby causing the first cylinder and the second cylinder to have a substantially similar susceptibility to knock.
According to a second aspect of the present invention, a valve timing method is provided for use within a camless engine including a plurality of cylinders each having at least one valve which is selectively actuated according to a unique timing profile. The method includes the steps of measuring a compression ratio for each of the plurality of cylinders; comparing the measured compression ratios; and altering at least one of the timing profiles based upon the comparison, effective to cause the plurality of cylinders have a substantially uniform sensitivity to knock.
These and other features, aspects, and advantages of the invention will become apparent by reading the following specification and by reference to the following drawings.
REFERENCES:
patent: 4104991 (1978-08-01), Abdoo
patent: 5009203 (1991-04-01), Seki
patent: 5072700 (1991-12-01), Kawamura
patent: 5117790 (1992-06-01), Clarke et al.
patent: 5161497 (1992-11-01), Simko et al.
patent: 5255637 (1993-10-01), Schechter
patent: 5271229 (1993-12-01), Clarke et al.
patent: 5450824 (1995-09-01), Yamane et al.
patent: 5469818 (1995-11-01), Yoshioka et al.
patent: 5496229 (1996-03-01), Miyamoto
patent: 5626109 (1997-05-01), Yasumura et al.
patent: 5679094 (1997-10-01), Nakamura et al.
patent: 5845613 (1998-12-01), Yoshikawa
patent: 6135086 (2000-10-01), Clarke
Haghgooie Mohammad
Hammoud Mazen
Corrigan Jaime
Denion Thomas
Ford Global Tech. Inc.
Ford Global Tech., Inc.
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