Adaptive fuel strategy for a hybrid electric vehicle

Details Adaptive fuel strategy for a hybrid electric vehicle Adaptive fuel strategy for a hybrid electric vehicle

2000-12-21

2002-08-27

Cuchlinski, Jr., William A. (Department: 3663)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

Electric vehicle

C701S001000, C701S086000, C701S084000, C701S085000, C701S083000, C701S109000, C701S101000, C701S102000, C701S112000, C701S103000, C701S104000, C123S179160, C123S179180, C123S1950HC, C123S192200, C123S19800E, C123S179300, C123S673000, C123S681000, C123S674000, C123S698000, C123S575000, C123S478000, C180S065230, C180S065510, C180S065800, C180S065310, C290S016000, C290S04000F, C322S016000, C322S022000

Reexamination Certificate

active

06442455

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a Hybrid Electric Vehicle (HEV), and specifically to a method and system to optimize emissions using an adaptive fuel strategy for a hybrid electric vehicle (HEV).
2. Discussion of the Prior Art
The need to reduce fossil fuel consumption and emissions in automobiles and other vehicles predominately powered by Internal Combustion Engines (ICEs) is well known. Vehicles powered by electric motors attempt to address these needs.
Another alternative solution is to combine a smaller ICE with electric motors into one vehicle. Such vehicles combine the advantages of an ICE vehicle and an electric vehicle and are typically called Hybrid Electric Vehicles (HEVs). See generally, U.S. Pat. No. 5,343,970 to Severinsky.
The HEV is described in a variety of configurations. Many HEV patents disclose systems where an operator is required to select between electric and internal combustion operation. In other configurations, the electric motor drives one set of wheels and the ICE drives a different set.
Other, more useful, configurations have developed. For example, a Series Hybrid Electric Vehicle (SHEV) configuration is a vehicle with an engine (most typically an ICE) connected to an electric motor called a generator. The generator, in turn, provides electricity to a battery and another motor, called a traction motor. In the SHEV, the traction motor is the sole source of wheel torque. There is no mechanical connection between the engine and the drive wheels. A Parallel Hybrid Electrical Vehicle (PHEV) configuration has an engine (most typically an ICE) and an electric motor that work together in varying degrees to provide the necessary wheel torque to drive the vehicle. Additionally, in the PHEV configuration, the motor can be used as a generator to charge the battery from the power produced by the ICE.
A Parallel/Series Hybrid Electric Vehicle (PSHEV) has characteristics of both PHEV and SHEV configurations and is sometimes referred to as a “powersplit” configuration. In one of several types of PSHEV configurations, the ICE is mechanically coupled to two electric motors in a planetary gear-set transaxle. A first electric motor, the generator, is connected to a sun gear. The ICE is connected to a carrier. A second electric motor, a traction motor, is connected to a ring (output) gear via additional gearing in a transaxle. Engine torque can power the generator to charge the battery. The generator can also contribute to the necessary wheel (output shaft) torque if the system has a one-way clutch. The traction motor is used to contribute wheel torque and to recover braking energy to charge the battery. In this configuration, the generator can selectively provide a reaction torque that may be used to control engine speed. In fact, the engine, generator motor and traction motor can provide a continuous variable transmission (CVT) effect. Further, the HEV presents an opportunity to better control engine idle speed over conventional vehicles by using the generator to control engine speed.
The desirability of combining an ICE with electric motors is clear. There is great potential for reducing vehicle fuel consumption and emissions with no appreciable loss of vehicle performance or drivability. The HEV allows the use of smaller engines, regenerative braking, electric boost, and even operating the vehicle with the engine shut down. Nevertheless, new ways must be developed to optimize the HEV's potential benefits.
One such area of HEV development is HEV engine operations. In an HEV, the engine has many functions. Its primary function is to provide drive torque. Other functions can include the following: charging the battery, purging a vapor canister, learning the shifts in the fuel delivery system to an adaptive fuel table, powering. an air conditioning (“A/C”) compressor if the compressor is mechanically driven by a front end accessory drive (FEAD) belt, replenishing vacuum to a vacuum reservoir, maintaining catalyst temperature (for optimal emissions), and maintaining engine temperature (for climate control system to provide heat to the passenger compartment). While performing these functions, the HEV engine must optimize emissions and fuel consumption without negatively impacting drivability and performance.
One of the techniques available in an HEV to reduce emissions and fuel consumption is to turn the engine off when it is not needed. If the engine is not running, the electric motor provides the required driving torque.
When running, the engine is used in both drive and vehicle idle conditions. Idle conditions exist when the vehicle is not moving. In an HEV, the engine is generally and ideally off during idle conditions. However, some HEV functions require the engine to remain on even in vehicle idle conditions. One such function can be the maturing of an HEV engine's adaptive fuel table. Adaptive fuel tables are known in the prior art to optimize emissions from internal combustion engines. See generally, Fuel Controller with an Adaptive Adder, U.S. Pat. No. 5,464,000 to Pursifull, et al. (Ford Motor Company).
As discussed in this referenced patent and known in the prior art, electronic fuel control systems are used predominantly today in most vehicles. The fuel controller systems vary the amount of fuel delivered to the engine cylinders based on the engine speed, mass airflow rate, and the oxygen content of the exhaust. These fuel controllers typically try to maintain the ratio of air and fuel at or near stoichiometry (considered to be approximately 14.6:1 A/F ratio for most types of gasoline) by implementing a closed loop fuel controller. Maintaining A/F at or near stoichiometry allows the catalytic converter to convert the exhaust gas into clean byproducts at an optimal level.
A typical prior art closed loop fuel controller determines the proper amount of fuel to deliver to the engine cylinders as follows. First, the airflow entering the engine is measured and then converted to an estimate of the amount of air charge entering each cylinder. This estimate is then modified by the concentration of oxygen in the exhaust gas (as measured by an exhaust gas oxygen (EGO) sensor). The oxygen content of the exhaust gas directly reflects the A/F ratio of the previous combustion event so that, if the A/F ratio was not near stoichiometry, a correction factor can be applied to the fuel amount delivered for the next combustion event. For example, if the EGO indicates a rich A/F mixture (less then stoichiometry), then the fuel amount will be reduced for the next combustion event. If the EGO indicates a lean A/F mixture, then the fuel amount will be increased for the next combustion event.
The adaptive fuel control feature, as discussed in the referenced patent and known in the prior art, enhances the closed loop fuel controller by learning the long-term “shifts” in the fuel delivery system. The amount of fuel required during closed loop fuel operation varies from engine to engine within a given engine configuration. The variation is due to differences in fuel system components such as fuel injectors and mass airflow sensors, the different degrees to which these components age, and the conditions under which the vehicle is driven. The adaptive fuel controller “learns” these long-term fuel adjustments for the many combinations of engine speed and engine air charge (or airflow) that can occur in the operation of an engine. The adaptive fuel controller learns a fuel shift if the actual A/P ratio is outside of a calibratable range relative to stoichiometry. The amount of the adjustment learned is proportional to how far from stoichiometry the actual A/F was and how quickly the gains used for adaptive corrections are calibrated. These learned or “adapted” adjustments in A/F are then stored in an adaptive fuel table for future use by the closed loop fuel controller when those same engine speed and air charge conditions are encountered again. Once the actual A/F returns to stoichiometry, the adaptive fuel cell i

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