DOE/N ASA/1044-12 NASA TM-81642 ^ Design Studies of Continuously Variable Transmissions for Electric Vehicles (NASA-TM-81642) DESIGN STUDIES OF Illllllllilllllllllllllll COHIINOOUSL* VARIABLE TRANSMISSIONS FOE : lin111111111111111111111 ELECI3IC VEHICLES (NASA) 18 p HC A02/MF A01 CSCL 131 Dncias G3/37 29446 Richard J. Parker, Stuart H. Loewenthal, and George K. Fischer National Aeronautics and Space Administration Lewis Research Center Work performed for U.S. DEPARTMENT OF ENERGY Conservation and Solar Energy Office of Transportation Programs Prepared for Society of Automotive Engineers Congress Detroit, Michigan, February 23-27, 1981 NOTICE This report was prepared to document work sponsored by the Uniled Slates Government Neither the United States nor its agent, the United Slates Department of Energy, nor any Federal employees, nor any ol their contractors, subcontractors or their employees, makes any warranty, express or implied, or assumes any legal liability or responsioility (or the accuracy, completeness, or usefulness ol any information, apparatus, product or process disclosed, or represenis that its use would not infringe privately owned rights GENERAL DISCLAIMER This document may be affected by one or more of the following statements • This document has been reproduced from the best copy furnished by the sponsoring agency. It is being released in the interest of making available as much information as possible. • This document may contain data which exceeds the sheet parameters. It was furnished in this condition by the sponsoring agency and is the best copy available. • This document may contain tone-on-tone or color graphs, charts and/or pictures which have been reproduced in black and white. • This document is paginated as submitted by the original source. • Portions of this document are not fully legible due to the historical nature of some of the material. However, it is the best reproduction available from the original submission. 1. Report No. 2 Government Accession No. 3. Recipient's Catalog No. NASA TM-81642 4. Title and Subtitle 5. Report Date DESIGN STUDIES OF CONTINUOUSLY VARIABLE TRANSMISSIONS FOR ELECTRIC VEHICLES 6. Performing Organization Code 778-36-06 7. Author(s) 8. Performing Organization Report No. Richard J. Parker. Stuart H. Loewenthal, and George K. Fischer E-588 10. Work Unit No. 9. Performing Organization Name and Address National Aeronautics and Space Administration Lewis Research Center 11. Contract or Grant No. Cleveland, Ohio 44135 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address Technical Memorandum U.S. Department of Energy Office of Transportation Programs 14. Sponsoring Agency -6e*- Report No. Washington, D.C. 20545 DOE/NASA/1044-12 15. Supplementary Notes Prepared under Interagency Agreement EC-77-A-31-1044. Prepared for Society of Automotive Engineers Congress, Detroit, Michigan, February 23-27, 1981. 16. Abstract Preliminary design studies were performed on four continuously variable transmission (CVT) concepts for use in advanced electric vehicles. A 1700 kg (3750 Ib) vehicle with an energy stor- age flywheel was specified. Requirements of the CVTs were a maximum torque of 450 N-m (330 lb-ft), a maximum output power of 75 kW (100 hp), and a flywheel speed range of 28 000 to 14 000 rpm. The design of each concept was carried through the design layout stage. Power losses were determined over the ranges of operating conditions, and transmission efficiencies were calculated. The design studies were performed under contracts to NASA for DOE by Garrett/AiResearch (toroidal traction CVT), Battelle Columbus Labs (steel V-belt CVT). Kumm Industries (flat belt variable diameter pulley CVT), and Bales-McCoin Tractionmatic (cone- roller traction CVT). 17.. Key Words (Suggested by Author(s)) 18. Distribution Statement Transmissions; Traction drives; Belt drives; Unclassified - unlimited Continuously variable transmissions; Electric STAR Categor> 37 vehicles; Flywheel vehicles DOE Category UC-96 19. Security Classif. lof this report) 20. Security Classil. lof this pagel 21. No. of Pages 22. P''ce' Unclassified Unclassified ' Foi snle by !he Nnlion.il Technic.il Information Sc:vicc. Sprin^liM'!. Viip.iiu.i ?2!6I DOE/N ASA/1044-12 NASA TM-81642 Design Studies of Continuously Variable Transmissions for Electric Vehicles Richard J. Parker, Stuart H. Loewenthal, and George K. Fischer National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio 44135 Performed for U.S. DEPARTMENT OF ENERGY Conservation and Solar Energy Office of Transportation Programs Washington, D.C. 20545 Under Interagency Agreement EC-77-A-31-1044 Society of Automotive Engineers Congress Detroit, Michigan, February 23-27, 1981 DESIGN STUDIES OF CONTINUOUSLY VARIABLE TRANSMISSIONS FOR ELECTRIC VEHICLES Richard J. Parker, Stuart H. Loewenthal, and George K. Fischer National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio vehicles. A significant factor in this applica- tion is the broad ratio range required of the CVT for a system with a flywheel, since the flywheel ABSTRACT speed may be at its maximum value when the vehi- cle speed is lowest. Other concerns raised in Preliminary design studies were performed on the propulsion system design studies of (7 and 8) four continuously variable transmission (CVT) are life, weight, and cost of CVTs suitable for concepts for use in advanced electric vehicles. electric vehicles. A 1700 kg (3750 Ib) vehicle.with an energy stor- To initiate a development program for CVTs, age flywheel was specified. Requirements of the preliminary design studies were performed on four CVTs were a maximum torque of 450 N-m (330 CVT concepts which include traction and variable Ib-f t) , a maximum output power of 75 kW (100 hp) , belt types. These studies were performed as a and a flywheel speed range of 28 000 to 14 000 part of the DOE- Electric and Hybrid Vehicle Pro- rptn. The design of each concept was carried gram under contract to NASA Lewis Research Center. through the-design layout stage. Power losses by the contractors listed in table I. Each study were determined over the ranges of operating con- was for the preliminary design of a specific CVT ditions, and transmission efficiencies were cal- for a 1700-kg (3750-lb) vehicle containing a culated. The design studies were performed under 1.8-MJ (0.5 kWh) energy storage flywheel. Re- . contracts to NASA for DOE by Garrett/AiResea rch quirements of the CVTs were a flywheel speed (toroidal traction CVT), Battelle Columbus Labs range of 28 000 to 14 000 rpm, a maximum output (steel V-belt CVT), Kumm Industries (flat belt torque of 450 N-m (330 Ib-ft) , a maximum output variable diameter pulley CVT), and Bales-McCoin power of 75 kW (100 hp) , and an output speed Tractionmatic (cone-roller traction CVT). range of zero to 5000 rpm. Following these pre- liminary design studies, two or more of the CVT concepts are to be selected for detailed design, fabrication, and testing with a goal of making an FLYWHEEL ENERGY STORAGE can improve the perform- advanced CVT available for use in electric vehi- ance of electric and hybrid vehicles (1 to 4).* cles by the year 1985. Also, the flywheel offers short-term energy stor- The objective of each of the design studies age and leveling of current draw on the batter- was to determine the best arrangement of a speci- ies. With a flywheel, electric vehicle perform- fic CVT concept, select and size the components ance can be maintained over the life of the bat- for a 90-percent survival life of 2600 hours, and tery regardless of age or depth of discharge of determine power losses and efficiencies over the the battery (5). Actual performance tests show range of operating conditions. A preliminary that regenerative braking can increase the range design layout of each CVT was completed. The of electric vehicles (6). A flywheel can be used results of these design studies were published in for regenerative braking by transferring kinetic references (9 to 12). In this paper, the results energy from the vehicle to the flywheel. of the studies are summarized, and the CVTs are Studies have recently been completed on the compared based on such criteria as efficiency, conceptual design of several advanced electric size, weight, cost, and the extent of new tech- vehicle propulsion systems (7 and 8). Three of nology advancements required to make each CVT the four systems studied include flywheels. The suitable for electric vehicles. flywheels are either mechanically or electrically coupled to the drive train. For flywheels me- DESIGN REQUIREMENTS AND CRITERIA chanically coupled, a continuously variable transmission (CVT) is required to provide match- The preliminary design of each CVT concept ing of the independent flywheel and vehicle was performed within certain design requirements speeds. CVTs are also being considered for elec- and criteria specified in each contract statement tric vehicle systems without flywheels and have of work. These design requirements were not se- shown some advantages, such as reducing the re- lected for any specific vehicle but as a common quired battery weight (8). basis for comparisons among the various CVT con- At present, CVTs have not been sufficiently cepts. The CVT was to be arranged .in the vehicle- developed for immediate application to electric drive train shown in figure 1. A 1700-kg (3750- *Numbers in parentheses designate References at lb) vehicle was specified which included a 1.8-MJ end of paper. (0. 5-kWh) maximum usable energy flywheel. Selec- Parker, Loewenthal, and Fischer tion and sizing of components was based on Che unavoidably generated was to be contained within following factors: the housing. 1. The speed ratio of the CVT was to be con- 6. Controls - The control system used to tinuously controllable over the range of input operate the CVT was to be stable and reliable, speeds (flywheel output) of 28 000 to 14 000 rpm was to provide driver "feel" and response similar and output speed (differential input) of zero to to that of a current automatic transmission 5000 rpm.