Engine with hydraulic variable valve timing
AssigneeFord Global Technologies, LLC
InventorsJonathan Denis Crowe, Jamie Charles Hanshaw
Life of this patent
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Abstract
In one example, a method is described for an engine with a hydraulically actuated phaser for adjusting cam timing. The phaser is controlled by a hydraulic spool valve, for example, having a de-energized position that results in hydraulic force urging the phaser to a base timing. When it is desired to operate the cam timing at base timing, rather then leave the spool valve in a de-energized position that can generate leakage, the spool valve is adjusted to near a null position to reduce the hydraulic pressure drop across the cam journal and thus reduce oil leakage. In this way, it is possible to maintain base timing, while also reducing leakage.
Claims20
A method of controlling an engine including a hydraulically actuated cylinder valve actuator controlled by a hydraulic valve adjustable among a plurality of ranges including a first range generating hydraulic force in a first direction on the actuator toward a first end position, a second range generating hydraulic force in a second, opposite direction on the actuator toward a second, opposite end, position, and a neutral range between the first and second ranges, comprising:
- when the actuator is at the first end position, adjusting the hydraulic valve to within the first range and closer to the neutral range than to a full actuation boundary of the first range.
A method of hydraulically controlling a variable cam timing actuator of an engine through an electromechanically actuated solenoid spool valve, the spool valve adjustable among a plurality of ranges including a first range generating a hydraulic force in a retard direction on the variable cam timing actuator toward a first retarded end position, a second range generating a hydraulic force in a second advance direction on the variable cam timing actuator toward a second, advanced end, position, and a neutral range between the first and second ranges, the method comprising:
- during engine operation and when the variable cam timing actuator is maintained in a fully retarded position, adjusting the spool valve to be within the first range closer to the neutral range than to a full retard end of the first range;
- and
- during engine operation and when the variable cam timing actuator is away from the fully retarded position, adjusting the spool valve based on feedback cam timing to maintain a desired cam timing position.
A system for an engine, comprising:
- a hydraulically actuated variable cam timing actuator;
- a cam with oil passages used to deliver oil from oil passages in a cam cap to the variable cam timing actuator coupled to the cam;
- a cylinder having at least a cylinder valve actuated by the cam;
- a hydraulic spool valve coupled to the variable cam timing actuator, the spool valve adjustable among a plurality of ranges including a first retard range generating a hydraulic force in a first direction on the variable cam timing actuator toward a fully retarded timing position, a second advance range generating a hydraulic force in a second, opposite direction on the variable cam timing actuator toward a fully advanced timing position, and a neutral range between the first and second ranges;
- and
- computer readable storage medium having instructions encoded therein, including:
- instructions for operating in a first mode during selected conditions and when the variable cam timing actuator is held at the fully retarded timing position, adjusting the spool valve to within the first retard range and closer to the neutral range;
- and
- instructions for operating in a second mode that includes advancing the cam timing from the fully retarded timing position by adjusting the spool valve from within the first retard range and closer to the neutral range, to the second advance range.
A method of hydraulically controlling a VCT-actuator through a spool valve comprising:
- during engine operation and when the VCT-actuator is maintained in a fully retarded position, adjusting the spool valve to be closer to a neutral range than to the fully retarded position;
- and
- during engine operation and when the VCT-actuator is away from the fully retarded position, adjusting the spool valve based on feedback of cam timing to maintain a desired cam timing.
Dependencies are inferred from the claim text.