Abstract:
An engine control system in a vehicle including a variable displacement internal combustion engine, an intake manifold coupled to the variable displacement internal combustion engine, a first turbocharger supplying air to the intake manifold, a first waste gate regulating the boost of the turbocharger, and a controller for controlling the displacement of the variable displacement internal combustion engine.

Description:
TECHNICAL FIELD  
         [0001]    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 equipped with at least one turbocharger.  
         BACKGROUND OF THE INVENTION  
         [0002]    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 principle 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 a six cylinder variable displacement ICE, fuel economy will be improved if the ICE is operated with only three cylinders during relatively low torque operating conditions by reducing throttling losses. Throttling losses, also known as pumping losses, are the extra work that 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.  
           [0003]    Turbocharging may also improve fuel economy by utilizing wasted energy in engine exhaust gas to increase the performance of an ICE. A turbocharger generally includes a turbine and a compressor. Exhaust gases from an ICE are directed to the turbine housing, causing the turbine to rotate. The turbine concomitantly rotates the compressor to force more air into the engine air intake, increasing the power output of the ICE. The additional pressure generated by the compressor is known as boost pressure, which is typically controlled by a wastegate. The wastegate regulates the flow of exhaust gas over the turbine, controlling the speed of the turbine and the compressor. When high engine power is not needed, the wastegate can bypass the turbine dropping the boost pressure, allowing the engine to run closer to atmospheric intake manifold pressure to minimize the need for throttling and improving fuel economy.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention is a method and apparatus for the control of cylinder deactivation and turbocharging in a variable displacement ICE to improve fuel economy and maintain performance. In the preferred embodiment of the present invention, a six-cylinder internal combustion engine (ICE) may be operated as a three-cylinder engine by deactivating three cylinders. The cylinder deactivation occurs as a function of load or torque demand by the vehicle as determined by variables such as manifold pressure. 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 and spark to the selected cylinders. The deactivated cylinders will then function as air springs.  
           [0005]    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.  
           [0006]    Turbocharging can further improve the operation of a variable displacement engine operating in a partially-displaced mode by providing a larger torque range within which the engine can operate in the partially-displaced mode and/or by further reducing throttling losses if the engine displacement is reduced from its original size. A turbocharger can assist in engine transient operation by its ability to regulate air flow. For example, when the engine switches from partially-displaced to fully-displaced mode, the turbocharger can provide immediate increase in air flow without throttle movement. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    [0007]FIG. 1 is a diagrammatic drawing of a variable displacement engine equipped with twin turbochargers;  
         [0008]    [0008]FIG. 2 is a diagrammatic drawings of a turbocharger wastegate of the present invention; and  
         [0009]    [0009]FIG. 3 is a diagrammatic drawing of a spool in the turbocharger wastegate of the present invention.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0010]    [0010]FIG. 1 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  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  1 - 2 - 3 - 4 - 5 - 6  of the ICE  10 ; the cylinders include valves  24 , as is known in the art. The valves  24  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 to shut off air flow through the cylinders  1 - 2 - 3 - 4 - 5 - 6 . 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 normally installed in the air flow passage leading to the intake manifold  22  and is preferably a hot wire anemometer and the MAP sensor  28  is preferably a strain gauge.  
         [0011]    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.  
         [0012]    The engine  12  includes exhaust manifolds  40  and  42  which provide exhaust flow to drive turbochargers  44  and  46 . Cylinders  1 - 2 - 3  are coupled to exhaust manifold  40 , and cylinders  4 - 5 - 6  are coupled to exhaust manifold  42 . The turbochargers  44  and  46  include compressors  45  and  47  having bypass valves  48  and  50 , turbines  41  and  43 , and waste gate valves  52  and  54 . Compressors  45  and  47  are coupled to the turbines  41  and  43  by bearing couplings  61  and  63 . A compressor charge cooler  56  is included to cool the air injected into the intake manifold  22  by the turbochargers  44  and  46 .  
         [0013]    During normal bi-turbo operation of the ICE  12  in a fully displaced configuration, the firing order of the cylinders will be  1 - 5 - 3 - 6 - 2 - 4 . During normal boosted operation of the turbochargers  44  and  46 , a portion of the engine exhaust flow can bypass the turbines in the turbochargers  44  and  46  to maintain the desired boost level. Generally, this is a fraction of the total flow such that most of the exhaust gas flows through the turbines. The waste gate valves  52  and  54  are regulated by the powertrain controller  18  using rotary actuation and pulse width modulation to control the position of the wastegate valves  52  and  54  and control the boost.  
         [0014]    The ICE  12  of the present invention enters a partially-displaced configuration during relatively low power demand/light load driving conditions. The engine  12  will operate on three cylinders  1 - 2 - 3  of the six cylinders with cylinders  4 - 5 - 6  deactivated. The firing order in a partially-displaced configuration will be  1 - 3 - 2 . In such a partially-displaced operating configuration, there are reduced friction losses and no pumping losses for the deactivated cylinders  4 - 5 - 6 . The waste gate  52  is a three-position valve and is positioned and modulated such that exhaust gas may be ported to the exhaust of turbocharger  44  or to the turbine  43  of turbocharger  46 . The turbine  43  of turbocharger  46  continues to rotate from the gated gas of turbocharger  44  in a partially-displaced configuration, and since there is no flow to cylinders  4 - 5 - 6  the compressor  47  of turbocharger  46  is bypassed using the bypass valve  50  such that there is no compression of the air created by the compressor  47  of turbocharger  46 . Furthermore, the turbine  43  of turbocharger  46  is still maintained or rotated such that bi-turbo operation in a fully-displaced configuration can be entered quickly from the partially-displaced configuration. A differential valve  60  closes in the partially-displaced mode to prevent air flow through the exit port of the compressor  45  of turbocharger  44  to the compressor  47  of turbocharger  46 . The necessary turbocharging boost supplied by the turbocharger  44  to maintain relatively light loads with only cylinders  1 - 2 - 3  activated is determined empirically on a dynamometer. Waste gate  52  regulation for turbocharger  46  is also calibrated for a partially-displaced configuration.  
         [0015]    The reactivation of cylinders  4 - 5 - 6  is executed after a predetermined rate of change of accelerator pedal position is reached or any other indication of a high torque command or load. Both turbochargers  44  and  46  are active in a fully-displaced configuration for the ICE  12  and the waste gate  52  in a fully-displaced configuration bypasses to the exhaust instead of turbocharger  46  with the second waste gate  54  resuming normal operation.  
         [0016]    [0016]FIGS. 2 and 3 are a more detailed illustration of the three-way waste gate  52 . During deactivation of cylinders  4 - 5 - 6 , the three-way waste gate  52  bypasses exhaust gas from turbocharger  44  to turbocharger  46  such that the turbine  43  of turbocharger  46  remains spinning. The three-way waste gate valve  52  includes a ported ceramic spool  62 , a containment housing  64  which is integral to the turbine housing, a pipe  66  with bellows connected fluidly to turbo  46  and an aperture  65  connected to the outlet of turbine  41 . A second aperture  67  fluidly couples the waste gate  52  to the inlet of the turbine  41  of turbo  44 . The spool  62  is rotated by a rotary actuator by an extension shaft  68 . As the spool  62  is rotated counterclockwise, increasing port area  70  and  72  is exposed until maximum flow to turbocharger  46  is reached. When turbocharger  46  is deactivated along with cylinders  4 - 5 - 6 , the spool  62  can be rotated such that the bypass flow now feeds the inlet of turbocharger  46  to maintain the rotational speed of the turbine  43  of turbocharger  46 . In this way, turbocharger  46  may be reactivated relatively quickly with the activation of cylinders  4 - 5 - 6 , eliminating turbo lag.  
         [0017]    While this invention has been described in terms of some specific embodiments, it will be appreciated that other forms can readily be adapted by one skilled in the art. Accordingly, the scope of this invention is to be considered limited only by the following claims.