Method and apparatus for control of a variable displacement engine for fuel economy and performance

#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.

#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.

#FIG. 1 is a torque versus manifold pressure graph;

#FIG. 2 is a diagrammatic drawing of the control system of the present invention;

#FIG. 3 is a graph of the different operating conditions of the present invention;

#FIG. 2 is a diagrammatic drawing of the vehicle control system 10 of the present invention. The control system 10 includes a variable displacement ICE 12 having fuel injectors 14 and spark plugs 16 (in the case of a gasoline engine) controlled by an engine or powertrain controller 18. The ICE 12 crankshaft 21 speed and position are detected by a speed and position detector 20 that generates a signal such as a pulse train to the engine controller 18. The ICE 12 may comprise a gasoline ICE or any other ICE known in the art. An intake manifold 22 provides air to the cylinders 24 of the ICE 10, the cylinders having valves 25. The valves 25 are further coupled to an actuation apparatus such as used in an overhead valve or overhead cam engine configuration that may be physically coupled and decoupled to the valves 25 to shut off air flow through the cylinders 24. An air flow sensor 26 and manifold air pressure (MAP) sensor 28 detect the air flow and air pressure within the intake manifold 22 and generate signals to the powertrain controller 18. The airflow sensor 26 is preferably a hot wire anemometer and the MAP sensor 28 is preferably a strain gauge.

#An electronic throttle 30 having a throttle plate controlled by an electronic throttle controller 32 controls the amount of air entering the intake manifold 22. The electronic throttle 30 may utilize any known electric motor or actuation technology in the art including, but not limited to, DC motors, AC motors, permanent magnet brushless motors, and reluctance motors. The electronic throttle controller 32 includes power circuitry to modulate the electronic throttle 30 and circuitry to receive position and speed input from the electronic throttle 30. In the preferred embodiment of the present invention, an absolute rotary encoder is coupled to the electronic throttle 30 to provide speed and position information to the electronic throttle controller 32. In alternate embodiments of the present invention, a potentiometer may be used to provide speed and position information for the electronic throttle 30. The electronic throttle controller 32 further includes communication circuitry such as a serial link or automotive communication network interface to communicate with the powertrain controller 18 over an automotive communications network 33. In alternate embodiments of the present invention, the electronic throttle controller 32 may be fully integrated into the powertrain controller 18 to eliminate the need for a physically separate electronic throttle controller.

#A brake pedal 36 in the vehicle is equipped with a brake pedal sensor 38 to determine the amount of pressure generated by an operator of the vehicle on the brake pedal 36. The brake pedal sensor 36 generates a signal to the powertrain controller 18 to determine a braking condition for the vehicle. A braking condition will indicate a low torque/low demand condition for the variable displacement ICE 12. An accelerator pedal 40 in the vehicle is equipped with a pedal position sensor 42 to sense the position of the accelerator pedal. The pedal position sensor 42 signal is also communicated to the powertrain controller 18. In the preferred embodiment of the present invention, the brake pedal sensor 38 is a strain gauge and the pedal position sensor 42 is an absolute rotary encoder.