Variable cycle engine
AssigneeFord Motor Company
InventorsDavid L. Boggs, Michael M. Schechter
Life of this patent
Estimating the term…
Abstract
A method of phaseshifting a variable cycle engine utilizing the Otto cycle engine timing schedule for full-load and the Atkinson cycle engine timing schedule for part-load operation, the engine having multiple intake valves and an exhaust valve, phaseshifting of the intake and exhaust events coupled with adjustment of the clearance volume and the use of residual gas in the cylinder as a determinant of the intake charge volume and the compression end temperature level, to provide a high engine operating efficiency while concurrently lowering nitrogen oxide emissions and eliminating the need for an external exhaust gas recirculating system.
Claims15
In an internal combustion engine having multiple valves per cylinder including primary and secondary intake valves and an exhaust valve, a method of operating the engine on an Otto cycle engine timing during full load operation and an Atkinson cycle engine timing during part load operation, to improve the fuel efficiency of the engine while controlling the nitrogen oxide emissions, comprising the steps of:
- operating the engine with unthrottled air intake to eliminate engine pumping losses,
- operating the multiple intake and exhaust valve opening and closing events on a conventional Otto cycle schedule at full load, and
- operating the engine under the Atkinson cycle at part load
- by varying the timing of the primary and the secondary intake valve events independently of each other to control the intake charge volume and to assure that the engine effective expansion ratio is significantly higher than the effective compression ratio, and
- by independently varying the timing of the exhaust valve event to control the amount of residual gas, and
- by varying the cylinder clearance volume to maintain adequately high effective compression ratio.
In an internal combustion engine having multiple intake and exhaust valves per cylinder and multiple camshafts for actuating the valves including primary and secondary intake valves and primary and secondary intake camshafts, a method of operating the engine on the Otto cycle engine timing during full load operation and the Atkinson cycle engine timing during part load operation, to improve the fuel efficiency of the engine while controlling the nitrogen oxide emissions, comprising the steps of:
- operating the engine with unthrottled air intake to eliminate engine pumping losses,
- operating the multiple intake and exhaust valve opening and closing events in a first stage of operation on a conventional Otto cycle schedule at full load, and as the load decreases,
- operating the engine in a second stage of operation on an Atkinson cycle by varying the engine piston stroke/clearance volume and variably retarding the secondary intake and the exhaust valve events as a function of the load without changing the timing of the primary intake valve openings and closings to thereby variably reduce the intake charge volume and control the increase in the residual gas content in the cylinder to control dilution of the charge as a function of the load, while maintaining adequate effective compression ratio and increased effective expansion ratio.
In an internal combustion engine having multiple intake and exhaust valves per cylinder including primary and secondary intake valves, a method of operating the engine on the Otto cycle engine timing during full load operation and the Atkinson cycle engine timing during part load operation, to improve the fuel efficiency of the engine while controlling the nitrogen oxide emissions, comprising the steps of:
- operating the engine with unthrottled air intake to eliminate engine pumping losses,
- operating the multiple intake and exhaust valve opening and closing events in a first stage of operation at full load on a conventional Otto cycle schedule, and as the load decreases,
- operating the engine in a second stage of operation on an Atkinson cycle by varying the engine piston stroke/clearance volume and variably retarding the primary and secondary intake and exhaust valve events as a function of the load to thereby variably reduce the intake charge volume and control the increase in the residual gas content in the cylinder to control dilution of the charge as a function of the load, while maintaining adequate effective compression ratio and increased effective expansion ratio.
Dependencies are inferred from the claim text.