1. Field of the Invention
This invention relates to prime movers such as may be used in vehicle propulsion systems, for example, and more particularly to self-contained prime mover systems employing rotating flywheels for energy storage.
2. Description of the Prior Art
The driving conditions, customs, and practices experienced by the general public place demands upon the power plant of the conventional automobile which render it inherently inefficient. For a long time the driving public, Americans in particular, have opted for larger, heavier automobiles with the capability of operating satisfactorily under low-speed city traffic and high-speed turnpike conditions with a substantial degree of acceleration in all speed ranges. Meeting these demands has resulted in large high-powered engines which are only rarely exercised to full capacity or even operated within their range of most efficient operation. Until recently, the internal combustion engine was the only power plant capable of providing these performance capabilities and automobiles produced for sale to the American public have almost exclusively contained internal combustion engines, predominantly fueled by gasoline.
However, the recent adoption of ever more stringent restrictions on engine exhaust and other emissions has required the emasculation of the performance capabilities of the conventional American automobile engine, and the various pollution control devices which are now required to be combined with such engines have further degraded their performance and exacerbated their inefficiencies. With the current emphasis on goals of pollution-free operation and conservation of energy, it appears that the era of the conventional internal combustion engine as an automobile power plant is nearing an end. Work on other types of propulsion systems will doubtless result in the internal combustion engine being phased out as such alternative systems are developed.
Even before the recent shift in emphasis on design considerations which has militated in favor of less polluting, more fuel-economical propulsion systems, work was done on the development of hybrid power plants for vehicle propulsion and for stationary power sources as well. The objective of such systems was to combine a standard engine or like power source generally sized to the load normally encountered in its use with an auxiliary power source capable of supplying additional power or torque under relatively transient, larger load conditions. One such system is disclosed in the Henry U.S. Pat. No. 707,230 directed to a combination steam engine and electric motor propulsion system for driving an automobile through a planetary gearing mechanism. Another such system utilizing a flywheel in combination with a plurality of electric motors is disclosed in the Thomas U.S. Pat. No. 1,076,614, entitled Winding Apparatus. Other systems utilizing a flywheel for energy storage are disclosed in the Heins U.S. Pat. No. 2,672,566 which combines a flywheel and an electric motor coupled together through a planetary gear system, and the Kasschau U.S. Pat. No. 2,443,770 and the Cuny U.S. Pat. No. 2,567,636, both of which combine a flywheel with an internal combustion engine. Split path, power transmission systems combining an internal combustion engine with an electric drive unit are the subject of the Berman et al U.S. Pat. No. 3,566,717 and an article entitled "An Electromechanical Transmission for Hybrid Vehicle Power Trains--Design and Dynamometer Testing" by Gelb et al, Society of Automotive Engineers (Automotive Engineering Congress, Jan. 11-15, 1971). The Chirgwin U.S. Pat. No. 3,851,232 discloses an electrical propulsion system for rapid transit cars or trains utilizing third rail electric power in combination with an energy storing flywheel during certain modes of operation of the system.
As may be surmised form the variety of combination systems and loads epitomized in the examples referenced above, the demands of different utilization systems dictate different types of power plants. For example, for the purposes of the present invention, a prime mover system such as may be used to provide propulsion for individual vehicles such as personal automobiles or small rail cars, an internal combustion engine is undesirable. The split electromechanical transmission and control system of the present invention is particularly adpated to the use of an energy storing flywheel as a power source.