Internal-combustion engines – Accessories – Covers – trays – vibrators – corrosion inhibitors – air filters
Reexamination Certificate
2002-03-22
2004-08-31
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Accessories
Covers, trays, vibrators, corrosion inhibitors, air filters
Reexamination Certificate
active
06782865
ABSTRACT:
TECHNICAL FIELD
The present invention relates to the control of internal combustion engines. More specifically, the present invention relates to a method and apparatus to control a variable displacement internal combustion engine.
BACKGROUND OF THE INVENTION
Present regulatory conditions in the automotive market have led to an increasing demand to improve fuel economy and reduce emissions in present vehicles. These regulatory conditions must be balanced with the demands of a consumer for high performance and quick response for a vehicle. Variable displacement internal combustion engines (ICEs) provide for improved fuel economy and torque on demand by operating on the principal of cylinder deactivation. During operating conditions that require high output torque, every cylinder of a variable displacement ICE is supplied with fuel and air to provide torque for the ICE. During operating conditions at low speed, low load, and/or other inefficient conditions for a fully displaced ICE, cylinders may be deactivated to improve fuel economy for the variable displacement ICE and vehicle. For example, in the operation of a vehicle equipped with an eight cylinder variable displacement ICE, fuel economy will be improved if the ICE is operated with only four cylinders during low torque operating conditions by reducing throttling losses. Throttling losses, also known as pumping losses are the extra work than an ICE must perform to pump air from the relatively low pressure of an intake manifold, across a throttle body or plate, through the ICE and out to the atmosphere. The cylinders that are deactivated will not allow air flow through their intake and exhaust valves, reducing pumping losses by forcing the ICE to operate at a higher intake manifold pressure. Since the deactivated cylinders do not allow air to flow, additional losses are avoided by operating the deactivated cylinders as “air springs” due to the compression and decompression of the air in each deactivated cylinder.
In past variable displacement ICEs, the switching between a partially displaced and fully displaced operating condition for a variable displacement internal combustion engine was problematic due to the disturbances associated with varying the displacement of the ICE.
SUMMARY OF THE INVENTION
The present invention is a method and apparatus for the control of cylinder deactivation in a variable displacement engine. In the preferred embodiment of the present invention, an eight-cylinder internal combustion engine (ICE) may be operated as a four-cylinder engine by deactivating four cylinders. The cylinder deactivation occurs as a function of load or torque demand by the vehicle. Torque reserve can be estimated using vacuum pressure determined by subtracting engine manifold pressure from the barometric pressure. As seen in
FIG. 1
, there is a generally linear relationship between vacuum pressure and reserve engine torque. An engine or power train controller will monitor vacuum pressure and determine if the ICE should enter four-cylinder mode. If the ICE is in a condition where it can deliver the desired torque with partial displacement to improve efficiency, the controller will deactivate the mechanisms operating the valves for the selected cylinders and also shut off fuel to the selected cylinders. The deactivated cylinders will thus function as air springs.
Fuel economy for a variable displacement ICE is maximized by operating in a partially displaced mode or configuration. The present invention maximizes the amount of time spent in a partially displaced operation while maintaining the same performance and driveability of a fully displaced ICE. Fuel economy improvement is maximized by entering a partially displaced configuration as quickly as possible, and staying in the partially displaced configuration for as long as possible in the operation of a variable displacement ICE. To make the change from variable to full displacement imperceptible to the driver, the ICE must be able to maintain some torque reserve when partially displaced (as detected by vacuum) to allow the generation of any additional torque that may be requested during the time delay of a switching cycle. The switching cycle requires approximately 1000 engine crank degrees during a change from partial to full displacement or vice versa. Continued switching or cycling (busyness) between partial and full displacement should also be reduced as it will compromise fuel economy and emissions for a variable displacement ICE.
The present invention reduces the busyness of operating mode switching or cycling by monitoring the amount of time operating with partial displacement. Busyness is detected if this partial displacement operating time does not exceed a calibrated time, and a non-busy condition is detected if the operating time exceeds a second calibrated time. When operating conditions that generate busyness are detected, the vacuum threshold to switch to partial displacement is incremented by a calibration value to decrease the potential for cycling. Whenever a non-busy condition is detected, the threshold is reduced by a calibrated amount. This allows the system to quickly increase the threshold to reduce cycling and slowly reduce the threshold when busyness is not detected.
REFERENCES:
patent: 4305355 (1981-12-01), Jordan
patent: 5568795 (1996-10-01), Robichaux et al.
patent: 5721375 (1998-02-01), Bidner
patent: 5826563 (1998-10-01), Patel et al.
patent: 6209526 (2001-04-01), Sun et al.
patent: 6499449 (2002-12-01), Michelini et al.
patent: 6585621 (2003-07-01), Matthews et al.
Matthews Gregory Paul
Rayl Allen B.
Ali Hyder
Argenbright Tony M.
DeVries Christopher
General Motors Corporation
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