Motor vehicles – Power – Electric
Reexamination Certificate
1999-09-09
2002-01-15
Swann, J. J. (Department: 3611)
Motor vehicles
Power
Electric
C060S602000
Reexamination Certificate
active
06338391
ABSTRACT:
FIELD OF THE INVENTION
This application relates to improvements in hybrid vehicles, that is, vehicles in which both an internal combustion engine and one or more electric motors are provided to supply torque to the driving wheels of the vehicle, and wherein turbocharging is employed under certain circumstances. A preferred method of sizing the power-producing components of the hybrid vehicle is also disclosed.
BACKGROUND OF THE INVENTION
This application discloses a number of improvements over and enhancements to the hybrid vehicles disclosed in U.S. Pat. No. 5,343,970 (the “'970 patent”) to one of the present inventors, which is incorporated herein by this reference. Where differences are not mentioned, it is to be understood that the specifics of the vehicle design shown in the '970 patent are applicable to the vehicles shown herein as well. Discussion of the '970 patent herein is not to be construed to limit the scope of its claims.
Generally speaking, the '970 patent discloses hybrid vehicles wherein a controllable torque transfer unit is provided capable of transferring torque between an internal combustion engine, an electric motor, and the drive wheels of the vehicle. The direction of torque transfer is controlled by a microprocessor responsive to the mode of operation of the vehicle, to provide highly efficient operation over a wide variety of operating conditions, and while providing good performance.
The flow of energy—either electrical energy stored in a substantial battery bank, or chemical energy stored as combustible fuel—is similarly controlled by the microprocessor. For example, in low-speed city driving, the electric motor provides all torque needed responsive to energy flowing from the battery. In high-speed highway driving, where the internal-combustion engine can be operated efficiently, it typically provides all torque; additional torque may be provided by the electric motor as needed for acceleration, hill-climbing, or passing. The electric motor is also used to start the internal-combustion engine, and can be operated as a generator by appropriate connection of its windings by a solid-state, microprocessor-controlled inverter. For example, when the state of charge of the battery bank is relatively depleted, e.g., after a lengthy period of battery-only operation in city traffic, the internal combustion engine is started and drives the motor at between 50 and 100% of its maximum torque output, for efficient charging of the battery bank. Similarly, during braking or hill descent, the kinetic energy of the vehicle can be turned into stored electrical energy by regenerative braking.
The hybrid drive train shown in the '970 patent has many advantages with respect to the prior art which are retained by the present invention. For example, the electric drive motor is selected to be of relatively high power, specifically, equal to or greater than that of the internal combustion engine, and to have high torque output characteristics at low speeds; this allows the conventional multi-speed vehicle transmission to be eliminated. As compared to the prior art, the battery bank, motor/generator, and associated power circuitry are operated at relatively high voltage and relatively low current, reducing losses due to resistive heating and simplifying component selection and connection.
Application Ser. No. 09/264,817 filed Mar. 9, 1999 (the “'817 application”), now U.S. Pat. No. 6,209,672, also incorporated herein by reference, discloses and claims certain further improvements in hybrid vehicles, described below, with respect to the vehicles of the '970 patent. The present patent application represents further improvements over the hybrid vehicle described in the '817 application.
OBJECTS OF THE INVENTION
It is an object of the present invention to provide further improvements over the hybrid vehicles shown in the '970 patent and the '817 application.
It is a more specific object of the present invention to provide a hybrid drive system for vehicles that does not require the controllable torque-transfer unit shown in the '970 patent, while providing the functional advantages of the hybrid vehicles shown in the '970 patent and the '817 application, together with further improvements.
Other aspects of and improvements provided by the present invention will appear below.
SUMMARY OF THE INVENTION
According to the invention of the '817 application, the controllable torque-transfer unit shown in the '970 patent is eliminated by replacing the single electric motor shown therein by two separate motors, both operable as generators when appropriate, connected by a functionally-conventional clutch or mechanical interlock operated by the microprocessor responsive to the vehicle's mode of operation and to input commands provided by the operator of the vehicle. As in the '970 patent, an internal combustion engine is provided, sized to provide sufficient torque for the maximum cruising speed desired without requiring a multi-speed transmission, and is used for battery charging as needed. According to the invention of the '817 application, a relatively high-powered “traction” motor is connected directly to the output shaft of the vehicle; the traction motor provides torque to propel the vehicle in low-speed situations, and provides additional torque when required, e.g., for acceleration, passing, or hill-climbing during high-speed driving. A relatively low-powered starting motor is also provided, and can be used to provide torque propelling the vehicle when needed. This second motor is connected directly to the internal combustion engine for starting the engine. Unlike a conventional starter motor, which rotates an internal combustion engine at low speed (60-100 rpm) for starting, necessitating provision of a rich fuel/air mixture for starting, the starter motor according to the invention spins the engine at relatively high speed (typically 300 rpm) for starting; this allows starting the engine with a near-stoichiometric mixture, significantly reducing undesirable emissions and improving fuel economy at start-up.
As noted, the two motors are separated by a functionally-conventional clutch, that is, a clutch which either joins the two motors together for rotation at the same speed, or separates them completely. As the motor shafts can be controlled to rotate at essentially the same speed when the clutch is engaged, the clutch need not allow for significant slipping before engagement. Accordingly, a friction clutch, as normally provided for road vehicles, may not be required, and a less-expensive simple mechanical interlock may alternatively be employed. Engagement of the clutch is controlled by the microprocessor, e.g., controlling a hydraulic actuator, responsive to the state of operation of the vehicle and the current operator input.
For example, during low-speed operation, the clutch will be disengaged, so that the traction motor is disconnected from the engine; the vehicle is then operated as a simple electric car, i.e., power is drawn from the battery bank and supplied to the traction motor. If the batteries become depleted, the starter motor is used to start the internal combustion engine, which then runs at relatively high torque output (e.g., between about 50-100% of its maximum torque), for efficient use of fuel, and the starting motor is operated as a high-output generator to recharge the battery bank. If the operator calls for more power than available from the traction motor alone, e.g., in accelerating onto a highway, the starter motor starts the internal combustion engine, and the clutch is engaged, so that the engine and starter motor can provide additional torque. The engine is sized so that it provides sufficient power to maintain a suitable highway cruising speed while being operated in a torque range providing good fuel efficiency; if additional power is then needed, e.g., for hill-climbing or passing, the traction and/or starter motors can be engaged as needed. Both motors can be
Louckes Theodore
Severinsky Alex J.
Angeli Michael de
Dunn David R.
Paice Corporation
Swann J. J.
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