Popular Science August 1992, page 30
Automotive Newsfront
Gearing For the Infinite
by Stuart Brown
IVT Invented by Paul Pires
Developed by Epilogics Inc.
Los Gatos, Ca
August 2, 1994
US Patent 5334115 granted to Inventor Pires, Paul B.
Assignee: Epilogics
- able to handle large amounts of torque
- the gears are never disengaged
- no friction clutches with low torque and high heat
- no fluid couplings to leak or require pressure
Other References:
Fitz, Frank A., “The Epilogics infinitely variable transmission,” Automotive Technology, pp. 215-220, 1992. ;, pp. 215-220, 1992.
Puttré, Michael, “Continuously Variable Transmissions,” Mechanical Engineering, pp. 64-67, 1991. ;, pp. 64-67, 1991.
Fitz, Frank A. and Paul B. Pires, “A Geared Infinitely Variable Transmission for Automotive Applications,” Society of Automotive Engineers paper presented at the SAE International Congress & Exposition, pp. 1-7, 1991.
Fitz, Frank A. and Paul B. Pires, “A High Torque, High Efficiency CVT for Electric Vehicles,” Electric Vehicle Design and Development SP-862 paper for Society of Automotive Engineers, ISBN: 1-56091-126-3, pp. 111-116, 1991.
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Picture a housing full of gears with shafts emerging at both ends. Imagine twisting the input shaft with one hand
while grasping the output shaft with the other hand. Now ponder this mystery: Though all the gears are meshed - and
there are no friction clutches or fluid couplings in the gear train - the output shaft stays stationary, and no
torque is felt on the output side.
So where on earth did the motion go? Even a master clockkmaker could get a little crazy bending his mind around the
elusive interplay of movement, inside the purely mechanical, infinitely variable (IVT) transmission developed by
Epilogics Inc. in Los Gatos, Calif."
The IVT is the invention of Paul Pires, a soft-spoken mechanical designer who puzzled the complex mechanism out in
his head before building a model of it - and when he did build it, it worked! Pires's background is in designing
equipment used in electronics manufacturing, which may account for his preference for thinking about mechanisms and
describing them in the lingo of circuitry; "Dealing with things on a symbolic level helps me come up with the
concept, then I backtrack through the hardware," he explains. "I think of an overrunning clutch as a diode, for
instance."
In characteristically electronic metaphors, Pires offers this description of the IVT's workings: "We take a DC signal,
turn it into an AC signal, rectify it, and sum it - but we do it mechanically."
Pires, works out refinements to the IVT concept using a kinematic analysis computer program introduced recently by
Rasna Corp. in nearby Sari Jose, Calif. Developed to help mechanical designers model the inter-relationships between
moving parts. The software predicts collisions and problems of fit without the heartbreak of destroying actuual
prototype components. The accompanying [color] illustrations were generated on the Rasna system.
The ultimate dream of these transmission developers is licensing their designs to, auto makers for production by the
millions. Cars with engines optimized for steady-state operation at their most efficient speed could have fuel
consumption and exhaust emissions reduced by as much as 30 percent, according to some estimates, But new devices like
the IVT run up against the fact that auto makers already have transmissions they are happy with. The huge expense and
risk of tooling up for a radically different design is unappealing to them in times of inexpensive fuel and relaxed
government regulation.
As a result, it's possible that the first IVT-geared car to hit the pavement will do so at supra-legal speeds. An engineer with a major team active in several classes of motor racing (who insisted on anonymity) says they have concluded from computer simulations that a "shiftless" race car could turn lap times several seconds quicker than conventionnal machines, providing the IVT doesn't add appreciable weight - and race rules permit its use.
Among the beltless transmission's characteristics are its ability to handle large amounts of torque - a severe shortcoming of most continnuously variable transmissions (CVTs) - and its lack of wear-prone sliding parts or fluid couplings that waste energy in the form of heat. It can shift steplessly from a "geared neutral" up to an input-to-output speed ratio of five to one.
Together, these features have caught the attention of manufacturers of machinery ranging from truck transmissions to electricity generators. They see the infinitely variable transmission as a potential route to sizable fuel efficiency and performance improvements.
One of the first projects Epilogics tackled was building a large IVT into a heavy diesel tractor, which it demonstrated to a group of truck engineers. At present, though, it appears that the first commercial applications of the IVT may be relatively miniature in scale, according to Wayne Higashi, president of Epilogics. He says a maker of fan clutches for truck engines is showing customers a small prototype IVT that keeps the cooling fan running at a constant speed for better temperaature control.
Another component maker, C.E Niehoff & Co. of Evanston, Ill., wants to apply an IVT to the heavy-duty alternators it builds for transit buses and military vehicles. Currently, such vehicles require very large alternators in order to power accessories, such as air conditioners and electronic equipment, when the engine idling. Niehoff is using the IVT to drive a much smaller alternator at a constant speed to save engine fuel and keep the electrical components at a stable temperature for " longer life. "I happen to believe in this set of weird gears," says George Buhrfeind, the company's president.
Detroit Diesel Corp. has surveyed the continuously variable transmission field for years, found fatal drawbacks to existing designs, and now would like to test an IVT. "We want to be able to get more power, when it's needed, by increasing the speed of our diesel engines used in constant-rpm applications like emergency generator sets for hospitals. A smaller engine can do the job under varying load conditions, if you can somehow keep its output speed constant," says Rob Sisk, vice president of power systems.
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original column 1 (from pop.sci.)
original column 2 (from pop.sci.)
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