Heavy-duty CVT works without a belt
Mart Molle
Recently, there has been another flurry of discussion in rec.autos about
the pros and cons of continuously variable automatic transmissions (CVTs).
The concensus seemed to be that CVTs, though a good idea in theory, are of
only limited value in practice because nobody has designed one that can
transmit a useful amount torque without self destructing.
Below is an article from _Machine_Design_ (November 9, 1989) that describes
a new CVT design that looks as if it might solve this problem. Perhaps
someone in Los Gatos area can follow up on this and post more information....
Mart L. Molle
Computer Systems Research Institute
University of Toronto
Toronto, Canada M5S 1A4
(416)978-4928
Heavy-duty CVT works without a belt
A continuously variable transmission (CVT) that works without a belt is said
to be the first suitable for heavy-duty applications. Called an infinitely
variable transmission (IVT) by developer Epilogics, Inc., Los Gatos, CA, the
new transmission is not restricted by the traction limits of belt-drive CVTs.
The first prototype IVT, installed in a class VII diesel truck, can handle
an input torque of 600 lb-ft and will provide output torque of up to 4,000
lb-ft. Previous attemts to introduce transmissions with a continous range
of gear ratios like the IVT, rather than discrete steps of gears, have been
limited to light-duty vehicles.
Epilogics' IVT is completely made up of fully engaged gears. It does not
use belts, pulleys or frictional components such as clutched or fluid
couplings. In addition to a continuous range of gear ratios, the transmission
can be adjusted to neutral without disengaging the power source. The IVT
can also be designed to operate in a locked-up mode, a predetermined speed
within the transmission's operating range to minimize wear.
The IVT uses a linear actuator to adjust ratios. The transmission converts
an input rotational motion into a modifiable reciprocating motion (MRM),
then reconverts the MRM back into a rotational output. The Epilogics
transmission can be compared to a crankshaft with a continously adjustable
stroke. By regulating the stroke, output speed is adjusted.
Benefits of the IVT include an estimated 30% fuel savings because the engine
operates continuously at its maximum efficiency point. An efficient engine
outputs less harmful gases, reducing the need for emissions controls.
Inventors expect IVT life to be five times longer than conventional trans-
missions because the gears are constantly engaged. This eliminates
operator error as a source of transmission failure. Also, no energy wasting
frictional components mean no heat buildup. Applications include automobiles,
motorcycles, construction equipment, and bicycles.
[Caption beside a fuzzy picture of a desk top hand cranked working model
in which some random gears and a rotating squirrel cage containging several
gears are held in alignment by three nicely machined flat plates...]
Model of an infinitely variable transmission first demonstrated
in a diesel tractor. Driven by a 210-hp engine with maximum
output speed of 2,600 rpm, the transmission provided continuously
selectable input/output ratios from zero output to 1:1.
Newsgroups: rec.autos,rec.autos.tech
Subject: Heavy-duty CVT works without a belt
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Recently, there has been another flurry of discussion in rec.autos about
the pros and cons of continuously variable automatic transmissions (CVTs).
The concensus seemed to be that CVTs, though a good idea in theory, are of
only limited value in practice because nobody has designed one that can
transmit a useful amount torque without self destructing.
Below is an article from _Machine_Design_ (November 9, 1989) that describes
a new CVT design that looks as if it might solve this problem. Perhaps
someone in Los Gatos area can follow up on this and post more information....
Mart L. Molle
Computer Systems Research Institute
University of Toronto
Toronto, Canada M5S 1A4
(416)978-4928
Heavy-duty CVT works without a belt
A continuously variable transmission (CVT) that works without a belt is said
to be the first suitable for heavy-duty applications. Called an infinitely
variable transmission (IVT) by developer Epilogics, Inc., Los Gatos, CA, the
new transmission is not restricted by the traction limits of belt-drive CVTs.
The first prototype IVT, installed in a class VII diesel truck, can handle
an input torque of 600 lb-ft and will provide output torque of up to 4,000
lb-ft. Previous attemts to introduce transmissions with a continous range
of gear ratios like the IVT, rather than discrete steps of gears, have been
limited to light-duty vehicles.
Epilogics' IVT is completely made up of fully engaged gears. It does not
use belts, pulleys or frictional components such as clutched or fluid
couplings. In addition to a continuous range of gear ratios, the transmission
can be adjusted to neutral without disengaging the power source. The IVT
can also be designed to operate in a locked-up mode, a predetermined speed
within the transmission's operating range to minimize wear.
The IVT uses a linear actuator to adjust ratios. The transmission converts
an input rotational motion into a modifiable reciprocating motion (MRM),
then reconverts the MRM back into a rotational output. The Epilogics
transmission can be compared to a crankshaft with a continously adjustable
stroke. By regulating the stroke, output speed is adjusted.
Benefits of the IVT include an estimated 30% fuel savings because the engine
operates continuously at its maximum efficiency point. An efficient engine
outputs less harmful gases, reducing the need for emissions controls.
Inventors expect IVT life to be five times longer than conventional trans-
missions because the gears are constantly engaged. This eliminates
operator error as a source of transmission failure. Also, no energy wasting
frictional components mean no heat buildup. Applications include automobiles,
motorcycles, construction equipment, and bicycles.
[Caption beside a fuzzy picture of a desk top hand cranked working model
in which some random gears and a rotating squirrel cage containging several
gears are held in alignment by three nicely machined flat plates...]
Model of an infinitely variable transmission first demonstrated
in a diesel tractor. Driven by a 210-hp engine with maximum
output speed of 2,600 rpm, the transmission provided continuously
selectable input/output ratios from zero output to 1:1.