Christopher GREENWOOD, et al.
Torotrak Infinitely Variable Transmission
Easy ascent/descent 25% slope...
Low revs in cruising... Optimal engine use...
Mileage improved by 20%... &c...
http://www.thecarconnection.com/Auto_News/Daily_Auto_News/Torotrak_The_Next_CVT.S173.A5029.html
Sunday, June 23, 2002
Torotrak: The Next CVT?
by Ian Norris
Britain comes up with a new kind of infinitely
variable transmission for the off-road crowd.
A British firm has developed a new form of automatic
transmission that it says can cut fuel consumption on SUVs and
trucks by 20 percent when compared with a conventional automatic
gearbox.
The company, Torotrak, says that the cost of its Infinitely
Variable Transmission is comparable to a conventional auto box,
and it is looking for an American company interested in building
the units for sale to American manufacturers. GM has already
tested the Torotrak system and approved it, and although the
company is not prepared to build the transmissions itself, it
would be prepared to look at proposals from any of its Tier 1
component suppliers who were prepared to undertake manufacture
of the gearboxes.
The Torotrak transmission differs from a conventional automatic
in that it has no torque converter. The torque converter
transfers the drive from the engine to the gearbox by means of a
fluid coupling that takes the place of the mechanical clutch
used in manual transmissions. The fluid allows the drive from
the engine to "slip" while the car is at rest or while shifts
are being made, thus making it unnecessary to disengage the
drive using the clutch.
Slipping into economy
Torque converters are convenient for drivers, but are
inherently inefficient because of the slippage, and this
inefficiency makes itself felt in gas mileage.
In place of the torque converter, the Torotrak has a system of
two clutches in which the drive is transmitted by variators. The
variators are discs that run in contact between two dished
clutch plates, transferring the drive from the input plate to
the output plate and performing the job carried out by the
transmission fluid in a torque converter. Slippage is minimal,
however, and the power losses and consequent fuel consumption
associated with the torque converter are drastically reduced. By
varying the angles of the variators, the drive ratio can be
changed infinitely, and by using a system of lockable clutches
and a planetary gearset, the drive transmitted to the road
wheels is totally seamless, unlike that of a conventional
automatic, in which fixed ratios are engaged as required. The
Torotrak thus combines the advantages of the torque converter -
clutchless drive - and the CVT, or Constantly Variable
Transmission, which achieves seamless power transmission through
belts - which can be prone to slippage - running on variable
circumference pulleys.
The Torotrak's increased fuel efficiency comes partly from the
absence of the torque converter and partly from the fact that
the gearbox is capable of sustaining very high overdrive ratios,
with 70 mph per 1000 engine revolutions being easily achievable.
Another advantage of the system is that it is capable of
'slipping' without the overheating that comes from running a
torque converter in this way for any extended period of time.
Although a car with a conventional automatic can be held on a
hill by leaving it in Drive and applying the throttle gently, if
this is done for too long the transmission fluid will overheat.
With no fluid present, the Torotrak can be held on the throttle
for much longer periods. An advantage of this quality - which
has great potential for off-road vehicles - is the fact that the
gearbox can slow the vehicle on descents. This is done by
engaging reverse and allowing the slippage of the clutches to
work against the weight of the vehicle. The engine is
effectively trying to drive the vehicle back up the hill, and
the rate of descent can be controlled very precisely.
In production vehicles, it would not be necessary to select
reverse gear physically. Since the gearbox is completely
controlled by software, it would be a simple matter to write the
software in such a manner that when 'Hill Descent' is selected
with a dashboard switch, the gearbox takes over automatically.
Another advantage of software control is that the gearbox
software settings can be controlled by a "smart key." In the
same way that the keys of individual drivers can now set seat
positions and radio selections to personal tastes, the gearbox
can also be controlled for individual drivers. The possibility
of setting maximum speeds for teenage drivers is an obvious
advantage of this system.
Principles in motion
Torotrak has been in existence as a company since 1998, and the
Torotrak system has been under development since 1988, but up
till now only a few industry engineers have had the opportunity
to drive Torotrak-equipped vehicles. I was among the first
journalists to sample the system, fitted to one of fifteen Ford
Expedition SUVs that Torotrak has converted to demonstrate its
capabilities. Torotrak has identified the SUV/truck market in
the U.S. as a major opportunity, and it was to show how the
system worked in such a vehicle that the firm chose to work with
the Expedition. For the moment, the work is concentrated on
rear-drive vehicles, which constitute the biggest proportion of
the market, but an all-wheel-drive Torotrak system is feasible.
On the road, the Torotrak behaves like any other automatic. The
PrNDL selector is the same, and after selecting Drive the
Expedition moved off quite normally. Acceleration is no swifter
than a standard automatic, but the big vehicle, with its
5.4-liter engine, was soon able to reach a good freeway cruising
speed, blending in with other traffic from the entry-ramp easily
and smoothly. Smoothness is the keyword with the Torotrak, which
gave totally seamless acceleration, with none of the clunks or
jumps that can come with a badly-adjusted automatic.
Once at cruising speed on the freeway, it was fascinating to
see the rev-counter hovering around the 1000 mark as the
speedometer indicated 70+ mph. In town and on country roads, the
drive was smooth, and torque was always available for moving off
or acceleration. Where engine braking is required, the company's
engineers have built in low-range locks similar to those found
on conventional automatics.
Torotrak has measured the consumption of the Expedition, not on
the road, but in statutory fuel-consumption tests that are more
reliable and repeatable, and has found that the Expedition
equipped with the company's transmission is consistently 20
percent more fuel-efficient than the standard vehicle.
Descending power
Off the road and on the test track, I was able to sample the
Torotrak's ability to control speed on a steep descent. With
reverse selected, the big SUV could be held stationary on a
25-percent downward incline just by gentle pressure on the
accelerator. When the accelerator was released, and the
vehicle's weight took over, the Expedition rolled slowly
downhill. It was strange to see the way it started to reverse
when it arrived on level ground. Naturally, in a production
model, software would select reverse when required for this
purpose and release it as soon as it was not needed. Going back
up the 25-percent grade, the Expedition could again be held
stationary on the throttle, this time with Drive selected.
The Torotrak company has no plans to start producing gearboxes
using its technology. It is structured purely as a technology
provider, and it licenses specialist manufacturers to develop
and produce their own gearboxes using Torotrak principles.
Currently, Getrag of Germany and Japan's Aisin AW hold licenses,
but no U.S. manufacturer has yet joined them, hence Torotrak's
work on proving the feasibility of the transmission for SUVs and
trucks, which are currently seen as the world's largest
potential market for the unit.
http://findarticles.com/p/articles/mi_qn4158/is_19970915/ai_n14133066
Copyright 1997 Newspaper Publishing PLC
Let's Get this Invention on the Road
Sameena Ahmad
Around the world the giant car makers are pouring billions of
pounds into designing the latest models. But it has taken a
small, British hot-house developer to come up with potentially
one of the most significant innovations in the motor industry.
The Torotrak transmission system, the brainchild of the patent
licensing group BTG, changes gear automatically without the use
of a clutch, solving one of the motor industry's last
unconquered technological problems. BTG claims it costs
one-fifth less to produce than a normal automatic transmission,
uses at least 15 per cent less fuel and, according to those
allowed a test ride in prototype cars, gives an unbelievably
smooth ride. So much so that the company is introducing an
artificial lurch to remind drivers when they are racing up a
hill.
Transmissions, the parts on the underside of a car that we
never see, are, crudely, what makes the engine drive the wheels.
The area has been a graveyard for technological advance despite
years of research effort. Engineers have long understood that
fixed speed gearboxes are inefficient. To optimise fuel
consumption drivers must be skilled enough to match engine speed
with the car's speed, using the gears. In theory, the solution
should be continuous variable transmissions (CVT), with an
infinity of gear ratios. But despite decades of research there
have been few successes. The best-known CVT, and still something
of a joke in the motor world, was the infamous Daf, Holland's
only independent car maker until its takeover by Volvo in the
mid-Seventies. Launched in the 1950s, the Dafodil (later
abbreviated to Daf), used rubber bands in its transmission,
which became legendary for high-pitched whirring noises and
delayed acceleration. In the 1980s car giants such as Ford and
Fiat developed the idea using steel belts which expanded or
shrank as the speed changed. According to BTG, Torotrak's
so-called infinitely variable transmission (IVT) looks quite
different, using discs and rollers to dispense with the clutch.
For the first time the engine is directly connected to the
wheels, dramatically improving efficiency. A car with Torotrak
can be driving at 60 mph, but at such low revolutions that the
engine is effectively idling. Though no car company has yet
committed to produce a car fitted with Torotrak, Ford, Toyota
and Getrag, which supplies BMW with transmissions, have all
signed licences with full production in mind. General Motors
should be next to sign. Ian Harvey, BTG's chief executive,
predicts that Torotrak could become the industry standard by
2010: "Fuel efficiency and low production costs are crucial to
car manufacturers. And Torotrak gives the same handling as
current cars. No other system has all that." The potential of
Torotrak has not been lost on investors. Since BTG was floated
at pounds 40m two years ago, its value has risen almost 20-fold.
Some overexcited observers even estimate that Torotrak alone
justifies BTG's current pounds 705m market valuation.
Shareholders should not underestimate the difficulty of
persuading the conservative car market to adopt such a radical
new product. Maurice Martin, Torotrak's chief executive, admits
that car manufacturers are formidably tough customers. He tells
of painstaking instructions from one licensee to position the
transmission at a precise distance from the engine casing. "We
spent so much time and effort getting it just right. In the end,
the distance was too big. They told us to readjust it by hitting
it with a hammer. We had to grit our teeth," he laughs. "But no
car maker wants even the remotest risk that they will have to
recall their vehicles." Funding is another concern. BTG, yet to
make sustained profits, is having to invest huge sums in
research and in kitting out the factory at Leyland in
Lancashire. Torotrak has cost more than pounds 10m to develop so
far and will not be in production in a car before 2001. Half of
BTG's recent pounds 25m placing proceeds are allocated to
Torotrak to fund two years' research, yet, as Mr Martin admits,
Torotrak's appetite for cash is growing. That Torotrak dominates
BTG's valuation also raises a serious issue. BTG is
fundamentally a patent licensing group, brimming with more than
9,000 patented inventions. For investors wary of one-product
biotechnology companies, BTG has been marketed as a safe and
unique way to invest in UK technology. But the innovation has
changed that. As Mr Harvey says: "Torotrak is some 40 per cent
of our valuation, which exposes us to the risk of failure.
Torotrak is also a development company, taking BTG out of just
licensing." The solution, and an option under review, says Mr
Harvey, is to demerge Torotrak. Whatever happens, Torotrak's
progress is one roadshow to keep watching.
http://www.histomobile.com/dvd_histomobile/histomo/tech/110-2.asp
Test drive of the Torotrak IVT (4)
by François Dovat
DRIVING
Engine at 1200 rpm the big Ford Expedition moves forward or
backwards at will, cm by cm on the 25 % grade. It could make it
until it runs out of fuel without overheating or wearing its
transmission. Full throttle: it rushes forward, the revs quickly
rising to 3600 before stabilizing gradually at 4200, speed at
which the big V8 already pumps out all his power.
On the other hillside, the descent is as slow as wished,
without brakes, shifter on R, the Ford even willingly and
gradually restarting in reverse on demand. Then, on the oval of
the Leyland Technical Center test track it accelerates as a
plane taking off, its 265 hp not weakening until the wished
speed is reached. When lifting the foot a 130 kph, the revs
falls to 1100. They rise immediately again according to the
required power, but without the slightest feel of delay in the
pulling force.
Torotrak do not intend to re-teach the driving to the drivers.
The tested prototype has a single program only, which simulate
the behavior of an hydrodynamic converter. A creep identical to
that of the production Ford AOD is programmed. However the
passage of D to R or conversely doesn't produce any jerk… of
course! The shift lever under the steering wheel remains that of
the production vehicle with the P-R-N-D-2-1 positions. The last
two provide an effective engine brake, the deceleration
occurring with a perfect progressiveness. Whether it's in the
traffic or on the track, the Torotrak transmission is extremely
pleasant. The engine winds up in revs only if the driver asks
for real power. Most of the times it revs at less than 1500 rpm
and becomes virtually inaudible, but stays ready to pounce like
an eager cat if necessary. The computer constantly chooses the
optimal ratio and the driver is freed of any concern about what
the transmission does or is going to do. In brief: sensational!
SOON IN PRODUCTION?
9 OEMs and transmission manufacturers acquired licenses, among
which quite recently ZF Friedrichshafen AG and the Japanese
tractor maker Iseki. It is said that several prototypes equipped
with Torotrak transmissions are being tested on the road and the
rumor runs that BMW might be the first car manufacturer to
market the Torotrak IVT. The British firm equipped in 2001 some
Chevrolet Suburban/Tahoe and Ford Expedition for evaluation by
their OEMs, amongst them the one the author had the privilege to
test drive. Those impressive SUV of 2.3 T are propelled by 5 to
5,4 liters V8s; their trials were satisfactory in every
respects. GM declared the concept production ready, but prefers
to leave the manufacture to specialized Tier 1s like Aisin AW.
At least Getrag and probably ZF might also produce the
transmission under license. Ford and ZF seem convinced of the
advantages of the Torotrak IVT as it sprang out of recent
official declarations.
The efficiency of this pre-production type would exceed the 91
% with a slip in the order of 1 %. If the ratio span of the
variator itself reaches 5, it is widened up to the infinite
(vehicle stopped) and inversion by the regrouping epicyclical
gear set.
TOROTRAK
Founded in 1988 as a BTG department, the firm employs at
present a hundred highly qualified persons and holds more than
250 patents. It took up the technology developed separately by
different teams – notably Leyland Trucks – brought together the
engineers and the competent executives, invested in a building
and brand new installations involving notably a workshop
equipped to assemble simultaneously 10 transmissions, 7
transmission test benches, 2 rollers test benches for vehicles,
4 vehicles lifts and an assembly hall. Its funds results mainly
from the £ 50 million obtained in 1998 at a stock exchange
flotation during its demerger from BTG.
Since the beginning of 2002 more than 300 engineers and
executives of different OEMs and transmission manufacturers
test-drove the prototypes during demonstrations in Germany, in
Japan and at the factory itself. Torotrak engineers presented
their latest developments at the CVT 2002 Congress in Munich and
at the SAE 2003 Transmission & Driveline Systems Symposium
in March 2003 at Detroit. They stated that the power
recirculation in low regime had been greatly reduced toghether
with a largely improved acceleration from standing still.
See : http://www.torotrak.com/technical_papers.html
ADVANTAGES
Absolute progressiveness
Outstanding creeping ability up and downhill
Lightning fast transient response
Relaxed driving
Low revs in cruising
Optimal engine use
Mileage improved by 20%
DRAWBACKS
Not yet in production
Lack of a direct drive
Power recirculation in low regime
http://fourwheelsteer.blogspot.com/2007/06/formula-1-in-new-technology-shock-long.html
Monday, 11 June 2007
Formula 1 in New Technology Shock
At the risk of sounding like a scene from The Life of Brian I
have to ask, “What has Formula 1 racing ever done for us?”
It is a valid question; I cannot think of any significant
technological advance that to come from Formula 1 racing. Anyone
who knows different is welcome to leave a comment by way of a
correction.
There is always hope that one day Formula 1 will give the world
of motoring something worthwhile; whether it is developing a new
technology or embodying some desirable system. It may be that
2009 will be the year for good to be done, as Formula 1 cars
incorporate a Torotrak transmission within the driveline.
What is a Torotrak drive?
It is a vehicle transmission that does not rely on fixed gear
ratios but offers a stepless spread of gear ratios between fixed
upper and lower limits. It is not a new idea; the basic
principles can be traced back to the 1930s, when it was known as
the Perbury drive, but it needed materials and particularly
lubricants that were not developed until the 1980s in order to
work properly. To understand how the Torotrak works imagine an
axle with two flat-faced discs mounted so that both are free to
spin independently. Between the faces of the disks - parallel to
the axle - is a roller, fixed in space but free to spin, with
the circumference of the roller touching both disks. If you turn
one disk the other disk will rotate in the opposite direction at
the same speed. The principle is similar to the differential
gear but relying on friction rather than meshing gears to
transmit drive.
If the roller was not parallel to the axle but at an angle so
that the roller described a larger circle on the face of one
disk than the other then the two disks will turn at different
speeds and there will be a torque multiplication or reduction
depending on which disk is driven. Flat-faced disks are no good
for a variable ratio transmission so the opposing faces of the
disks are machined with circular tracks of curved cross section.
The curved tracks mean that the roller (usually the real
Torotrak has 2 or 3 to reduce wear) remains in contact with the
opposing faces as it is tilted. To reduce stress on the friction
components the output disk has the curved tracks on both faces
and is sandwiched between two sets of rollers and facing input
disks. The Torotrak transmission also incorporates an epicyclic
gear set and a couple of clutches (which can be engaged or
disengaged but never slip). One of the input disks drives the
planet carrier, the output disk drives the sunwheel and the
annulus drives the car.
It would be too much to hope that the Torotrak was going to
replace the conventional transmission of a Formula 1 racing car.
There is no reason why it wouldn’t work; back in 1994 or 5
Williams tried a Van Doorne CVT drive in their then current F1
car and David Coulthard lapped Silverstone two seconds faster
than he managed in an identical car with conventional
transmission. Two seconds, thanks to the oft derided “rubber
band” transmission was a considerable and worthwhile advantage.
Before Williams could incorporate the transmission in a racing
car the rules were changed and such transmissions were banned.
The Torotrak would offer similar advantages and probably enjoys
similar prohibition.
So how is the Torotrak to be incorporated? In some sort of
effort to appeal to or appease the environmental movement
Formula 1 want to be seen as more ecologically aware and
incorporate energy saving devices into F1 cars. One idea is a
kinetic energy recovery system (KERS) which is another old idea
brought up to date. Rather than “wasting” energy converting
kinetic energy to heat when braking, kinetic energy is used to
spin up a flywheel which can be disconnected from the drive line
and reconnected when the stored energy can be put to good use
driving the car. It is an old idea because the Swiss used it in
busses working in hilly areas; energy “gained” running down one
hill could be stored and used to assist the climb up the next
hill. By using a Torotrak drive rather than a simple clutch the
energy sent to or recovered from the flywheel can be controlled
with greater subtlety.
Torotrak PLC (the name of the British company owning the rights
to the Torotrak drive) have granted a license to Xtrax, the
transmission specialists, to incorporate the Torotrak drive in a
gearbox with a KERS. The idea is to provide a more compact,
lighter, more efficient means of energy storage than electrical
batteries. The hope is that not only will racing teams adopt the
technology but that it will find its way into road cars too.
My hope is that the publicity given to the Torotrak
transmission as a result of the F1 association will act as a
catalyst for someone to put a Torotrak transmission in a car
that people can buy. Just imagine an automatic transmission that
overcomes all the limitations of conventional automatics. With
luxury cars adopting seven and eight speed automatics a
transmission that can be in the right gear all the time by
eschewing the established conventions of fixed ratios has to be
a good idea.
http://www.greencarcongress.com/2005/12/torotrak_infini.html
(2 October 2007)
http://www.typepad.com/t/trackback/22062/22088090
Application of Torotrak IVT to
Optare Bus Delivers 19% Improvement in Fuel Economy
Torotrak, a developer of full-toroidal traction drive technology,
and Optare UK, one of Europe’s largest bus manufacturers, have
recently achieved a 19% improvement in fuel economy in an Optare
Solo Bus by replacing the standard fit 5-speed automatic
transmission with a prototype Infinitely Variable Transmission
(IVT).
Computer simulation of an optimized “production intent” IVT
design demonstrates further efficiencies that increase the
improvement in fuel economy to 23%.
An Optare Solo European Midi-Bus was selected as the IVT test
vehicle. The 11,300 kg gross design weight Solo accommodates up
to 60 passengers and is fitted with a Euro-3 compliant
four-cylinder diesel engine and a 5-speed automatic
transmission.
The standard fit 5 speed automatic transmission was replaced
with a prototype IVT, originally developed for a Sports Utility
Vehicle (SUV), with gearing modified to suit the Optare
application. Testing was independently performed on the
“Millbrook London Transport Bus” (MLTB) Cycle, at Millbrook
Proving Ground, UK. The MLTB is an intensive stop-start cycle
replicating a demanding urban bus route.
The core of the IVT is Torotrak’s ‘variator’, which comprises
four identically shaped discs, being two input discs (shaded
green in figure above) and two opposing output discs (shaded
yellow), that form two symmetrical cavities. Each disc is formed
so that the space created between the opposing pair of input and
output discs is doughnut shaped; that is, the toroidal surfaces
on each disc form the toroidal cavity.
Each cavity contains three rollers, positioned so that the
outer edge of each roller is in contact with the toroidal
surfaces of the input and the output discs. When power is
supplied to the input disc, the disc rotates and the power is
transferred via the rollers to the output disc, which rotates in
the opposite direction to the input disc.
The full-toroidal traction drive variator is torque controlled,
meaning that the required system torque is set by hydraulic
pressure and the variator follows the ratio automatically. Force
is applied to the rollers via hydro-mechanical actuation which
determines the output torque, and the variator is clamped
together via a simple hydraulic end-load arrangement.
The transfer of power through the contacting surfaces of the
discs and rollers takes place via a microscopic film of traction
fluid. This fluid separates the rolling surfaces of the discs
and rollers at their contact points and prevents metal-to-metal
contact, increasing the durability and life of the variator
components. The hydraulic forces and clamping pressures act at
the contact points between the rollers and discs to make the
traction fluid highly viscous, creating an efficient traction
drive mechanism for transferring power between the rotating
discs and rollers, both smoothly and quietly.
The variator alone cannot provide neutral and reverse drive,
nor can it provide the ratio spread to achieve high overdrive.
However, the torque control capability of Torotrak’s IVT allows
the variator to be incorporated within a “two regime mechanical
shunt” transmission arrangement to provide forward and reverse
operation, generation of high output torques and extraordinary
overdrive capabilities (approximately 60 mph / 1000 rpm). In
addition, the IVT employs a geared neutral function which
provides a zero output speed with the engine rotating so
eliminating the need for an inefficient starting device such as
a slipping clutch or torque converter.
Due to the ratio range and the torque controlled nature of the
transmission, the IVT is able to decouple engine speed from
vehicle wheel speed while accurately defining the load demand
placed upon the engine. These features enable the engine to be
operated at its optimum engine speed and load condition,
regardless of the vehicle speed or power demand, so maximizing
fuel efficiency and reducing emissions.
The result of this driveline control strategy is a vehicle
which is simple to drive and that offers a smooth, gear shift
free ride for the passengers, while delivering excellent fuel
economy with a steadier and lower engine speed.
In addition to the power train efficiency benefits, the IVT
also provides additional functionality including:
An automatic anti-rollback feature, without making use of the
foundation brakes, where sufficient torque is applied to the
wheels to ensure a stationary vehicle. A safety feature that can
only be applied with a ‘geared neutral’ system.
An enhanced engine braking feature mimicking the electric
retarder fitted on the base vehicle—the IVT increases the engine
speed to fully exploit the overrun torque absorbing capability
of the engine whilst maintaining the desired vehicle speed.
Hence the retarder can be deleted.
The IVT decouples the engine speed from the vehicle speed
enabling engine design to exploit new combustion regimes, such
as HCCI, that are not easily accessed when using fixed ratio
transmissions.
By operating the engine at the most efficient point then,
depending upon application, the IVT may enable downsizing of the
engine leading to further efficiency, fuel economy and carbon
improvements.
For ultimate fuel economy, the IVT can itself be incorporated
into a hybrid driveline. With the torque controlled nature of
the transmission and the ability to manage power flow in either
direction, the IVT is able to transfer power to and from any
energy storage system—not only an electrical hybrid arrangement
but also enabling mechanical hybrid systems.
Torotrak and Optare are now in exploratory discussions with
partners regarding series production.
http://www.typepad.com/t/trackback/22062/3864560
Torotrak Infinitely Variable
Transmission Finds Business in Outdoor Power, Targets Hybrids
for the Future
15 December 2005
Torotrak, the UK developer of a fuel-efficient toroidal
“infinitely variable transmission” (IVT), has formed a 50–50
joint venture with MTD Holdings Inc to apply technology to the
Outdoor Power Equipment (OPE) market.
The new venture, named Infinitrak, will boost Torotrak’s
revenue while the company continues to work on placing its IVT
not just in conventional vehicles, but in new parallel-hybrid
systems as well. An IVT-based parallel hybrid can, according to
the company, provide a greater than 35% increase in fuel
efficiency over conventional vehicles, thereby matching the fuel
efficiency gains of more complex and expensive series-parallel
hybrid drives.
The outdoor power deal. Under the terms of the joint
venture, Torotrak will vest in Infinitrak exclusive global
rights to IVT technology in the 0-25kw power range, and
exclusive North American rights in the 25-45kW power range for
certain products.
Infinitrak expects to commence manufacture of IVT units in
2006. Production in the first full year of manufacture is
expected to exceed 100,000 units. The OPE Market includes annual
sales of more than 2 million powered ride-on products in the
United States alone.
The automotive market. Automotive, however, remains the
key target market for Torotrak, which has been working with
Equos and Koyo for a number of years to develop production
prototypes of the IVT, although the company has yet to ink a
volume distribution deal with an auto major. (Hence the
importance of the outdoor power market as a revenue stream.)
Equos is the company within the Aisin AW group that undertakes
new product development. Aisin is the world’s largest
tier 1 supplier of automatic transmissions, and a key early
partner with Toyota in the development of the Hybrid Synergy
Drive.
According to Torotrak CEO Dick Elsy, the company is making
progress with its automotive work.
The current three-way project to develop a transmission with
Equos and Koyo is now focused on the calibration of the compact
IVT in the unnamed target customer’s vehicle.
The calibration process is crucial to getting the best out
of the transmission in the eyes of their customer, one of the
world’s foremost car companies. This involves a
comprehensive optimization of engine and transmission, to
achieve the optimum combination of fuel economy, performance
and driving feel. This is a normal but critical development
process for any new transmission.
The continued extensive evaluation of IVT by another global
car company has led to a program of work to understand the
performance of IVT in a specific vehicle which they
manufacture. This vehicle, which features a large diesel
engine, already enjoys good fuel economy but we have been able
to demonstrate that a further improvement of 9.5% is possible
with the IVT design considered for this application.
The competitive bidding process started last year by a
further car company has reached the point where that company
has informed the bidders that it wishes to consider working
with another car company using the same transmission
manufacturer to build IVTs. Torotrak is assisting in this
process to bring together interested parties to realize this
goal. --- Dick Elsy, CEO
A decision by Toyota Motor in 2000 to terminate a licence
agreement with Torotrak sent the company’s shares
plummeting more than 60%. Toyota gave as its reason
“unacceptable driveability” in the form of
vibration in the Toyota IVT-equipped prototype.
At the time, Torotrak's potential had pushed the
company’s valuation to nearly £400 million (US$705
million). A similar decision by GM early in 2002 had a similar
effect, precipitously knocking down the stock price even
further.
The IVT. Torotrak was created in 1998 out of the BTG
Group, although work on what would become the Torotrak IVT began
in 1988. This type of approach to a transmission has a long
history, reaching back to an 1877 patent by Charles Hunt.
Key elements of the IVT are:
The input gearset. The input gearset transmits the power
from the engine via the low regime clutch to the planet gear in
the epicyclic gear train.
The variator. The variator is the means by which the IVT
can deliver an infinite range of ratios. It effects the speed of
rotation of the sun gear in the epicyclic and is responsible for
the smooth variation of ratios which the Torotrak transmission
produces.
Inside the variator are two pairs of discs. The space between
each pair of discs forms a hollow doughnut shape or toroid.
Within each toroidal space there are three rollers. These
rollers transmit drive from the outer, engine driven, discs to
the output discs located in the centre. The rollers transfer
power between the input discs and the output discs via a traction
fluid.
Each roller is attached to a hydraulic piston. The pressure in
the pistons can be increased or decreased to create a range of
reaction torque within the variator.
When the rotational velocities of the input and/or output discs
change, the rollers automatically alter their inclination in
order to adjust to the new operating conditions.
By varying the angles of the variators, the drive ratio can be
changed infinitely, and by using a system of lockable clutches
and the epicyclic gearset, the drive transmitted to the road
wheels is totally seamless, unlike that of a conventional
automatic, in which fixed ratios are engaged as required.
Traction fluid. The traction fluid --- a special oil ---
separates the rollers from the discs. Long chain molecules used
in the traction fluid interlock with each other when the fluid
is compressed, becoming highly viscous (glassy) under pressure.
As pressure is exerted at the contact points between the rollers
and the discs the oil resists the tendency to slide and
transmits the power effectively.
Thus, power transmission in the IVT is achieved by traction,
(by shearing the thin, elasto-hydrodynamic fluid film) and not
through metal-to-metal friction.
Epicyclic (planetary) gearset. The central gear (sun
gear) is driven by the output of the variator. The planet gears
are driven directly by the engine. The outer annulus gear is
connected to the wheels. The change of ratio in the variator
(the speed it transmits) alters the relative speeds of the sun
and planet gears.
Fixed ratio chain. This takes the drive from the output
discs and transmits it to the sun gear of the epicyclic gearset
and the input of the high regime clutch.
High regime clutch. The Torotrak IVT operates in two
regimes activated by the engagement and disengagement of
clutches which act as on/off switches. In low regime the
epicyclic gearset is included in the power path from the engine.
In high regime the output from the variator is directly
connected to the road wheels.
The basic IVT offers four main benefits:
Torque-Based Control. The IVT is torque controlled,
which essentially means that the required system torque is set
by hydraulic pressure and the variator follows the ratio
automatically. This control approach eliminates the need for a
starting device such as a torque converter or friction clutch
(also adding to the increased fuel efficiency).
High Overdrive. Very high levels of overdrive have been
demonstrated in vehicles equipped with Torotrak-IVT -- the
Expedition test vehicles have achieved 74mph @ 1,000 rpm.
Optimized Engine Running. The ratio range of the IVT
provides an almost total decoupling of engine and vehicle speed.
Thus a control line can be set which, for any given power
demand, will operate the engine at a pre-determined torque and
speed, largely independent of vehicle speed. This control line
ensures that the engine always operates at minimum specific fuel
consumption, i.e. at maximum efficiency. Typically, this means
that the engine operates at low speed (reduced friction losses)
and high torque (reduced throttling losses).
Fixed ratio transmissions, with a smaller ratio range, must
operate at higher speed and lower torque when delivering the
same power to the wheels—hence their inferior fuel
economy. In practice, the control line is the result of a
multi-variable optimization, to ensure emissions and NVH are
also controlled to provide the optimum trade-off. The result is
that the IVT delivers a validated fuel economy benefit of 20%
over a conventional four-speed automatic transmission, and more
than 10% over a six-speed automatic transmission with emissions
well within requirements.
Low-Speed Control. The IVT is able to provide sensitive,
safe control of vehicle speed under extreme conditions, without
the need for a low range gearset.
Torotrak has recently developed a lower-cost variator control
mechanism—Epicycloidal Roller Control
(ERC)—that promises further significant cost
reductions for the transmission.
The IVT in Hybrids. On the hybrid front, Torotrak is
collaborating with Cranfield University in developing a
parallel-hybrid IVT applied in the Ford Expedition.
We are able to offer a 20% fuel economy improvement from the
fitment of IVT to a conventional vehicle growing to more than
35% improvement with the parallel hybrid IVT derivative.
Our results also show that the hybrid IVT is capable of
producing very significant fuel economy gains whilst the
vehicle is cruising at speed --- an area where many current
generation hybrid vehicles perform relatively poorly. These
results bode well for "real-world" fuel economy
improvement. --- Dick Elsy.
Achieving reductions in fuel consumption at highway speeds is
one of the design rationales behind the GM-Chrysler-BMW work on
a two-mode hybrid system.
Basically, Torotrak's contention is that a parallel-hybrid
drive (a "mild" hybrid where the electric motor provides
additive traction but does not drive the vehicle on its own)
built with an IVT could match the increased fuel efficiency
benefit of a more complex, series-parallel ("power split")
hybrid architecture (e.g., the Prius), but at lower cost and
less complexity -- primarily through the efficiencies gained
from the optimum control of the engine.
In other words, Torotrak is suggesting that although its IVT
hybrid wouldn’t have an all-electric mode, its
increased base engine efficiency combined with the boost from
the electric motor would match the fuel efficiency of
series-parallel hybrids on the market (and be less expensive).
To test this out, Torotrak is working with Cranfield University
and Newage (an electric motor company) with support from UK
Government program, Foresight Vehicle. The purpose of the
project --- Electrically Assisted Infinitely Variable
Transmission --- is to quantify the combined benefits in
combining a mild parallel hybrid system with IVT, first through
modelling and then in a physical vehicle.
Resources:
http://www.torotrak.com/press/interim2005.pdf
Torotrak IVT ---
Variator ---
http://www.torotrak.com/IVT/
What is an IVT
The IVT moves away from the constraints of stepped ratio
automatic transmissions and unlike Continuously Variable
Transmissions there is no torque limitation. The ratio range is
provided not by a system of gears, as found in a conventional
automatic transmission, but by a variator which consists of a
set of discs and rollers and is termed a 'full toroidal'
variator (more information on how the variator works can be
found here).
The IVT technology allows control of the complete powertrain
enabling optimisation of the efficiency of the engine. In
conventional transmissions the engine and transmission are
controlled separately.
The IVT is torque controlled rather than ratio controlled. The
software determines the torque required at the road wheels and
then requests torque from the transmission rather than setting a
specific ratio. The engine can then be used to deliver the power
at its most efficient operating point. In conventional
automatics where the gear ratios are fixed the engine only runs
at its most efficient operating points for short periods of
time.
This optimisation of the entire powertrain brings about a fuel
economy benefit in three ways:
* Due to the geared neutral feature of the
IVT the engine can be directly connected to the road wheels
whilst the vehicle is stationary. There is no need for a
separate starting device such as an inefficient torque
converter.
* Due to its wide ratio spread the IVT
provides the ability for the engine to run at a high overdrive
of 74mph/1000rpm.
* Because the IVT does not have discrete
ratio steps it can run the engine at optimum conditions for fuel
economy and emissions.
http://www.torotrak.com/IVT/ivtbenefits.htm
Core IVT benefits
Running an engine at optimum conditions
The exceptional ratio range of the IVT provides an almost total
decoupling of engine and vehicle speed. For any given power
demand the IVT will operate the engine at a pre-determined
torque and speed, largely independent of vehicle speed. This
ensures that the engine always operates at minimum specific fuel
consumption, i.e. at maximum efficiency. Typically, this means
that the engine operates at low speed (reduced friction losses)
and high torque (reduced throttling losses).
‘Geared neutral’
The IVT has a feature termed ‘geared neutral’ where the engine
can be connected to the road wheels whilst the vehicle is
stationary (for information on how this is achieved please see
the epicyclic page in the ‘How It Works’ section). This feature
delivers a number of benefits including:
No need for an inefficient starting device such as a torque
converter.
Continuous torque at the wheels.
Accurate control of the vehicle at low speeds.
http://www.torotrak.com/IVT/works/
Overview of the IVT system
A generic simplified layout of the IVT is shown below, this
represents a layshaft layout, a coaxial layout is also possible.
Beneath the diagram a brief description of each component is
given.
The variator - is how the Torotrak IVT creates its
continuous variation of ratio.
The input gearset - transmits the power from the engine
via the low regime clutch to the planet gear in the epicyclic
gear train.
The epicyclic gearset - is the means by which the
running engine can be connected to the stationary road wheels
without a slipping clutch or torque converter.
Fixed ratio chain - takes the drive from the output
discs and transmits it to the sun gear of the epicyclic gearset
and the input of the high regime clutch. An idling gear can be
used instead of a chain.
High regime clutch - engaged for all forward speeds
above the equivalent of a second gear.
The IVT facilitates the optimum management of the engine by use
of computer control.
Full Toroidal Variator
Variator
Above is the Torotrak variator, it affects the speed of
rotation of the sun gear and is responsible for the smooth
variation of ratios, which the Torotrak transmission produces.
Inside the variator are two pairs of discs. The space between
each pair of discs forms a hollow doughnut shape or 'toroid'.
Within each toroidal space there are three rollers. These
rollers transmit drive from the outer, engine driven, discs to
the output discs located in the centre. The rollers transfer
power between the input discs and the output discs via a
traction fluid.
Each roller is attached to a hydraulic piston. The pressure in
the pistons can be increased or decreased to create a range of
reaction torque within the variator.
The variator shown on this page is an inline piston design,
where the packaging requirements require a compact lever
arrangement can be used as shown in the picture below.
Compact levers variator
A new even more compact version of the variator has recently
been developed where the rollers are all controlled by one
piston. Torotrak have termed this design 'Epicycloidal Roller
Control' (ERC). A movie clip showing the basic operation can be
accessed form the bottom of the related links section. More
details on this new design will be added to this website early
in 2006.
Video Links
3D CAD Model:
QuickTime:
http://www.torotrak.com/NR/rdonlyres/64ACEA5D-4D84-4AE9-88C1-287CB6BE4E32/0/varqtvr.qt
MPEG: http://www.torotrak.com/NR/rdonlyres/5419F6FB-5DFE-4608-83DF-B3B703E5BFDE/0/variator_spin.mpeg
Individual Components: http://www.torotrak.com/NR/rdonlyres/8FDD408D-D38F-4B0F-94C3-53EB8814E102/0/varfly.qt
http://www.torotrak.com/NR/rdonlyres/70C42329-53B2-4073-9DD4-EF948A25DCE8/0/varfly.mpeg
Explanation: http://www.torotrak.com/NR/rdonlyres/83BE8388-8000-43BB-8A9E-3921FEA54072/0/variatorhi.wmv
Epicycloidal Roller Control:
http://www.torotrak.com/NR/rdonlyres/9BCCCFA5-9444-47C9-B958-AA63D1D5AE99/0/ERC5.mpg
... 
...
Patents Held By Torotrak
Christopher GREENWOOD, et al.
Continously Variable Toroidal Transmission
Inventor: GREENWOOD CHRISTOPHER JOHN
US2008153659
2008-06-26
Continuously Variable Ratio Transmission
Inventor: OLIVER ROBERT ANDREW (GB); FIELDING ALAN
US2008146399
2008-06-19
CONTINUOUSLY-VARIABLE-RATIO TRANSMISSION OF THE TOROIDAL-RACE
ROLLING-TRACTION TYPE
Inventor: GREENWOOD CHRISTOPHER JOHN
MX9710354
1998-07-31
DRIVING AND STEERING OF MOTOR VEHICLES
Inventor: GREENWOOD CHRISTOPHER JOHN (GB); CORNWELL IAN DAVID
EP1924484
2008-05-28
ARRANGEMENTS FOR DRIVING AND STEERING OF MOTOR VEHICLES
Inventor: CORNWELL IAN DAVID (GB); GREENWOOD CHRISTOPHER JOHN
CA2620116
2007-03-01
RATIO LIMITING ARRANGEMENT
Inventor: MURRAY STEPHEN WILLIAM
KR20080021615
2008-03-07
POWER TAKE OFF ARRANGEMENT FOR A MOTOR VEHICLE
Inventor: OLIVER ROBERT ANDREW
KR20080016582
2008-02-21
VARIATOR
Inventor: DUTSON BRIAN JOSEPH
AT394613T
2008-05-15
HYDRAULIC VARIATOR CONTROL ARRANGEMENT
Inventor: FULLER JOHN
DE602004008475T
2008-05-15
CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: GREENWOOD CHRISTOPHER JOHN
WO2008038043
2008-04-03
IMPROVEMENTS IN OR RELATING TO CONTINOUSLY-VARIABLE-RATIOS
TRANSMISSIONS
Inventor: FELLOWS THOMAS GEORGE (GB); GREENWOOD CHRISTOPHER JOHN
MX9706904
1997-11-29
DRIVE MECHANISM FOR INFINITELY VARIABLE TRANSMISSION
Inventor: GREENWOOD CHRISTOPHER JOHN (GB); DE FREITAS ANDREW
DAMIAN
WO2008017881
2008-02-14
CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: TSUCHIYA SAOTO (JP); HASEBE MASAHIRO
DE112006000791T
2008-02-07
DRIVE MECHANISM FOR INFINITELY VARIABLE TRANSMISSION
Inventor: GREENWOOD CHRISTOPHER JOHN (GB); DE FREITAS ANDREW
DAMIAN
KR20070102615
2007-10-18
POWERTRAIN CONTROL METHOD AND SYSTEM
Inventor: FIELD MATTHEW GIBSON (GB); BURKE MATTHEW PIERS
KR20070099044
2007-10-08
ARRANGEMENT FOR CONTROL OF A CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: OLIVER ROBERT ANDREW
WO2007141564
2007-12-13
Continuously variable transmission with two opposing biasing
devices
Inventor: FULLER JOHN WILLIAM EDWARD
GB2438412
2007-11-28
Continuously variable transmission system
Inventor: DEFREITAS ANDREW DAMIAN
ZA200406126
2006-09-27
TOROIDAL TYPE CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: TSUCHIYA SADAI; FULLER JOHN
JP2007271060
2007-10-18
TOROIDAL TYPE CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: TSUCHIYA SADAI; FULLER JOHN
JP2007271059
2007-10-18
HYDRAULIC CONTROL DEVICE AND TOROIDAL TYPE CONTINUOUSLY
VARIABLE TRANSMISSION PROVIDED WITH THE SAME
Inventor: TSUCHIYA SADAI; FULLER JOHN
JP2007271058
2007-10-18
CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: HASEBE MASAHIRO; TACHIBANA TAKUMI
JP2007271057
2007-10-18
Hydraulic control of a continuously-variable ratio transmission
Inventor: MURRAY WILLIAM
DE60126808T
2007-11-15
CONTINOUSLY VARIABLE TOROIDAL TRANSMISSION
Inventor: GREENWOOD CHRISTOPHER JOHN
EP1846673
2007-10-24
CONTINUOUSLY VARIABLE RATIO TRANSMISSION SYSTEM
Inventor: GREENWOOD CHRISTOPHER JOH
ES2276068T
2007-06-16
IMPROVEMENTS RELATING TO CONTINUOUSLY VARIABLE TRANSMISSIONS
Inventor: GREENWOOD CHRISTOPHER JOHN
ES2270268T
2007-04-01
CONTINUOUSLY VARIABLE RATIO TRANSMISSION SYSTEM
Inventor: WINTER PHILIP DUNCAN
EP1800026
2007-06-27
VARIATOR
Inventor: DUTSON BRIAN
WO2007065900
2007-06-14
CONTINUOUSLY VARIABLE TRANSMISSION AND METHOD OF OPERATION
THEREOF
Inventor: FULLER JOHN WILLIAM
DE60215855T
2007-06-06
Method and device for determining motor vehicle acceleration
Inventor: MURRAY STEPHEN
US2007112495
2007-05-17
CONTINUOUSLY VARIABLE RATIO TRANSMISSION DRIVE
Inventor: GREENWOOD CHRISTOPHER JOHN
WO2007051827
2007-05-10
Method for controlling a motor vehicle powertrain
Inventor: FIELD MATTHEW GIBSON (GB); BURKE MATTHEW PIERS
GB2430718
2007-04-04
HYDRAULIC CIRCUIT FOR CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: TSUCHIYA SADAI; FULLER JOHN
JP2007024076
2007-02-01
METHOD OF CONTROLLING A CONTINUOUSLY VARIABLE TRANSMISSION
Inventor: BURKE MATTHEW PIERS
DE602004002765T
2008-01-31
TRANSMISSION OF THE TOROIDAL RACE ROLLING TRACTION TYPE
Inventor: DUTSON BRIAN JOSEPH (GB); ROBINSON LESLIE KENDRICK
KR20050117584
2005-12-14
Method of controlling a continuously variable transmission
Inventor: WILLIAM FIELD MATTHEW GIBSON
CN1860315
2006-11-08
CONTINUOUSLY VARIABLE RATIO TRANSMISSION SYSTEM
Inventor: GREENWOOD CHRISTOPHER JOHN
KR20060034251
2006-04-21
CVT OF THE TOROIDAL RACE ROLLING TRACTION TYPE
Inventor: FELLOWS THOMAS GEORGE
KR0174566B
1999-02-18
TOROIDAL-RACE ROLLING-TRACTION TYPE TRANSMISSION
Inventor: GREENWOOD CHRISTOPHER JOHN
KR100191849B
1999-06-15
TRANSMISSION OF THE TOROIDAL-RACE ROLLING TRACTION TYPE
Inventor: FELLOWS THOMAS GEORGE
KR0173673B
1999-02-18
TRANSMISSION
Inventor: FELLOWS THOMAS GEORGE
KR0137405B
1998-04-24
HYDRAULIC CONTROL CIRCUIT FOR CONTINUOUSLY VARIABLE RATIO
TRANSMISSION
Inventor: GREENWOOD CHRISTOPHER JOHN
KR0127146B
1997-12-26
A continuously variable ratio transmission unit
Inventor: ADRIAN DEFREITAS ANDREW DAMIAN
CN1849474
2006-10-18
Control method and controller for a motor vehicle drive train
Inventor: WILLIAM MURRAY STEPHEN
CN1849473
2006-10-18
Continuously variable transmission
Inventor: EDWARD FULLER JOHN WILLIAM
CN1788172
2006-06-14
HYDRAULIC CONTROL CIRCUIT FOR A VARIATOR
Inventor: GREENWOOD JOHN (GB); FULLER WILLIAM
DE60206609T
2006-07-20
Asymmetric roller crown
Inventor: NEWALL JONATHAN PAUL
GB2421771
2006-07-05
A HYDRAULIC CONTROL CIRCUIT FOR A CONTINUOUSLY VARIABLE
TRANSMISSION
Inventor: FULLER WILLIAM
DE60205892T
2006-06-08
FLUID SUPPLY ARRANGEMENT FOR A ROLLING-TRACTION CONTINUOUSLY
VARIABLE RATIO TRANSMISSION UNIT
Inventor: GREENWOOD CHRISTOPHER JOHN
DE60301328T
2006-06-01
Continuously variable ratio transmission unit and method of
assembly thereof
Inventor: JOSEPH DUTSON BRIAN
CN1723354
2006-01-18
CONTROL OF THE LINE PRESSURE IN A MULTI-REGIME CONTINUOUSLY
VARIABLE TRANSMISSION
Inventor: FULLER JOHN
WO2005047738
2005-05-26
Multi-regime CVT with coaxial input and output shafts
Inventor: GREENWOOD CHRISTOPHER
GB2410302
2005-07-27
Hydraulic control circuit for a continuously variable
transmission
Inventor: FULLER JOHN WILLIAM EDWARD
US2004171457
2004-09-02
HYDRAULIC ACTUATOR AND CONTINUOUSLY VARIABLE RATIO TRANSMISSION
UNIT
Inventor: ROBINSON LESLIE KENDRICK
WO2004027293
2004-04-01
Roller control unit
Inventor: ROBINSON LESLIE KENDRICK
US2004038773
2004-02-26
CONTINUOUSLY VARIABLE RATIO TRANSMISSION SYSTEM
Inventor: GREENWOOD CHRISTOPHER JOHN
EP1507991
2005-02-23
Roller and bearing assembly for a rolling-traction continuously
variable transmission
Inventor: GREENWOOD CHRISTOPHER JOHN
EP1486700
2004-12-15
A multi-regime CVT system with coaxial input and output shafts
Inventor: GREENWOOD CHRISTOPHER
GB2397630
2004-07-28
Continously variable transmission and method of operation
thereof
Inventor: FULLER JOHN WILLIAM EDWARD
EP1457716
2004-09-15
Continuosusly variable ratio transmission system
EP1369624
2003-12-10
A HYDRAULIC CONTROL CIRCUIT FOR A CONTINUOUSLY VARIABLE
TRANSMISSION
Inventor: FULLER JOHN WILLIAM EDWARD
EP1392990
2004-03-03
Multi-regime CVT with coaxial input and output shafts
Inventor: GREENWOOD CHRISTOPHER
GB2384531
2003-07-30
Control system of speed variator
Inventor: GRINUD C J (GB); YINNUG M
CN1368610
2002-09-11
ROLLER CONTROL UNIT
Inventor: ROBINSON LESLIE KENDRICK (GB); CORNWELL IAN DAVID
EP1337770
2003-08-27
Bearing support for infinitely-variable-ratio transmission
output discs
Inventor: GREENWOOD CHRISTOPHER
US6666791
2003-12-23
A hydraulic control circuit for a continuously variable
transmission
EP1273833
2003-01-08
Hydraulic supply for infinitely variable transmission
Inventor: DUTSON BRIAN JOSEPH
US2001001938
2001-05-31
TEST APPARATUS
Inventor: GREENWOOD CHRISTOPHER JOHN
WO0127609
2001-04-19
An Hydraulic control circuit for a
continously-variable-transmission
Inventor: GREENWOOD CHRISTOPHER JOHN
ZA200005511
2001-05-22
Cooling fluid supply to hydraulically actuated rollers in a
continuously-variable-ratio transmission
Inventor: DUTSON BRIAN JOSEPH
US6306060
2001-10-23
Roller control unit for a continuously-variable-ratio
transmission
Inventor: DUTSON BRIAN JOSEPH
US6273839
2001-08-14
Drive mechanism for infinitely variable transmission
Inventor: GREENWOOD CHRISTOPHER JOHN
US6312356
2001-11-06
DRIVE MECHANISM FOR INFINITELY VARIABLE TRANSMISSION
Inventor: GREENWOOD CHRISTOPHER JOHN (GB); HOUGH MICHAEL
WO0079150
2000-12-28
A continuously-variable-ratio, toroidal race rolling traction
transmission
Inventor: SMITH MARTIN JOHN (GB); DE FREITAS ANDREW DAMIEN
GB2361510
2001-10-24
Continuously variable ratio transmission apparatus
Inventor: SMITH MARTIN JOHN (GB); DE FREITAS ANDREW DAMIAN
EP1148270
2001-10-24
HYDRAULIC SUPPLY FOR INFINITELY VARIABLE TRANSMISSION
Inventor: DUTSON BRIAN JOSEPH
WO0015980
2000-03-23
Drive mechanism for infinitely variable transmission
EP1061286
2000-12-20
SHAFT SUPPORT FOR AN INFINITELY-VARIABLE-RATIO TRANSMISSION
Inventor: ROBINSON LESLIE KENDRICK
WO9934134
1999-07-08
Variator control system
Inventor: GREENWOOD CHRISTOPHER JOHN
US6030310
2000-02-29
CVT Control System
Inventor: GREENWOOD CHRISTOPHER JOHN
US5938557
1999-08-17
81
Roller assembly
Inventor: GREENWOOD CHRISTOPHER JOHN
US5971885
1999-10-26
Position servo systems
Inventor: GREENWOOD CHRISTOPHER JOHN
US6066067
2000-05-23
STEPLESSLY ADJUSTABLE GEARBOX CONTROL SYSTEM
Inventor: GRINVUD KRISTOFER DZHON
RU2178109
2002-01-10
Flow valve
Inventor: GREENWOOD CHRISTOPHER JOHN
EP0959269
1999-11-24
Roller assembly for piston actuator
Inventor: GREENWOOD CHRISTOPHER JOHN
EP0930449
1999-07-21
ROLLER ASSEMBLY
Inventor: ROBINSON LESLIE KENDRICK (GB); GREENWOOD CHRISTOPHER
JOHN
CA2249441
1997-10-09
Continuously variable transmission capable of torque control
Inventor: FELLOWS THOMAS GEORGE (GB); GREENWOOD CHRISTOPHER JOHN
US5766105
1998-06-16
Method of controlling vehicular drivelines including a
continuously variable transmission
Inventor: GREENWOOD CHRISTOPHER JOHN
US5820513
1998-10-13
IMPROVEMENTS IN OR RELATING TO POSITION SERVO SYSTEMS
Inventor: GREENWOOD CHRISTOPHER JOHN
WO9718982
1997-05-29
DISPOSICION DE TRANSMISION COAXIAL
Inventor: GREENWOOD CHRISTOPHER JOHN
ES2181331T
2003-02-16
Co-axial gear arrangement
Inventor: GREENWOOD CHRISTOPHER JOHN
ES2139250T
2000-02-01
IMPROVEMENTS IN OR RELATING TO POSITION SERVO SYSTEMS
Inventor: GREENWOOD CHRISTOPHER JOHN
EP0861183
1998-09-02
Continuously-variable-ratio transmissions in my patents
Inventor: GREENWOOD CHRISTOPHER JOHN (GB); FELLOWS THOMAS GEORGE
US5643121
1997-07-01
Continuously-variable-ratio-transmissions
Inventor: FELLOWS THOMAS G
US5564998
1996-10-15
Continuously-variable-ratio transmission having an improved
starting arrangement
Inventor: FELLOWS THOMAS GEORGE
US5667456
1997-09-16
CONTINUOUSLY-VARIABLE-RATIO TRANSMISSION OF THE TOROIDAL-RACE
ROLLING-TRACTION TYPE
Inventor: RHOBINSEN RESLY CANDRIC
KR100235977B
2000-03-02
Continuously-variable-ratio transmissions
Inventor: FELLOWS THOMAS GEORGE; GREENWOOD CHRISTOPHER JOHN
ZA9410131
1996-06-20
Transmissions of the toroidal-race rolling-traction type
Inventor: FELLOWS THOMAS G (GB); GREENWOOD CHRISTOPHER
US5395292
1995-03-07
Transmission of the toroidal-race rolling-traction type
Inventor: FELLOWS THOMAS G
US5423727
1995-06-13
Continuously-variable-ratio transmission of the toroidal-race
rolling-traction type
Inventor: ROBINSON LESLIE KENDRICK
GB2282196
1995-03-29
Transmission of the toroidal-race rolling-traction type
Inventor: FELLOWS THOMAS GEORGE
GB2267133 - 1993-11-24
IMPROVEMENTS IN OR RELATING TO CONTROL SYSTEMS FOR DRIVELINES
INCLUDING CONTINUOUSLY-VARIABLE-RATIO TRANSMISSIONS
Inventor: GREENWOOD CHRISTOPHER JOHN
WO9321031
1993-10-28
Transmission of the toroidal-race, rolling-traction type having
a mixer and a reducer epicyclic type gearing with clutches
brakes
Inventor: FELLOWS THOMAS GEORGE (GB); SOAR GEOFFREY BERNARD
US5401221
1995-03-28
IMPROVEMENTS IN OR RELATING TO TRANSMISSIONS OF THE
TOROIDAL-RACE,ROLLING-TRACTION TYPE
Inventor: FELLOWS THOMAS GEORGE (GB); SOAR GEOFFREY BERNARD
GB2263142
1993-07-14
Hydraulic control systems
Inventor: LAMBERT DAVID R
US5308298
1994-05-03
Transmission of the toroidal-race rolling-traction type
Inventor: FELLOWS THOMAS
US5263907
1993-11-23
Transmissions of the toroidal-race rolling-traction type
Inventor: GREENWOOD CHRISTOPHER
US5308297
1994-05-03
TRANSMISSIONS OF THE TOROIDAL-RACE ROLLING-TRACTION TYPE
Inventor: FELLOWS THOMAS G (GB); SOAR GEOFFREY
US5232414
1993-08-03
IMPROVEMENTS IN OR RELATING TO TRANSMISSIONS OF THE
TOROIDAL-RACE ROLLING TRACTION TYPE
Inventor: FELLOWS THOMAS GEORGE; SOAR GEOFFREY BERNARD
GB2256015
1992-11-25
CONTINUOUSLY-VARIABLE-RATIO TRANSMISSIONS OF THE TOROIDAL-RACE
ROLLING-TRACTION TYPE
Inventor: GREENWOOD CHRISTOPHER
US5242337
1993-09-07
IMPROVEMENTS IN OR RELATING TO CONTINUOUSLY-VARIABLE-RATIO
TRANSMISSIONS OF THE TOROIDAL-RACE ROLLING-TRACTION TYPE
Inventor: GREENWOOD CHRISTOPHER JOHN
GB2253252
1992-09-02
A variator for a continuously-variable ration transmission of
the toroiodal-race rolling¦-traction type
Inventor: GREENWOOD CHRISTOPHER JOHN
IN184863
2000-09-30
DRIVELINES FOR WHEELED VEHICLES
Inventor: FELLOWS THOMAS G (GB); WINTER PHILIP
US5217418
1993-06-08
STEPLESS TRANSMISSION
Inventor: TOMAS DZHORDZH FELLOUZ (GB); KRISTOFER DZHON GRINVUD
RU2004863
1993-12-15
TRANSMISSIONS OF THE TOROIDAL-RACE ROLLING-TRACTION TYPE
Inventor: FELLOWS THOMAS G (GB); GREENWOOD CHRISTOPHER
CA2008770 - 1990-07-30
TRANSMISSIONS OF THE TOROIDAL-RACE ROLLING-TRACTION TYPE
Inventor: FELLOWS THOMAS G (GB); GREENWOOD CHRISTOPHER
DD297864
1992-01-23
GETRIEBE MIT ROLLREIBUNG VOM TOROIDFLAECHENTYP
Inventor: FELLOWS THOMAS GEORGE GREENBRO; GREENWOOD CHRISTOPHER
JOHN
AT84602T
1993-01-15
HYDRAULIC RAM IN ANNULAR RACE, ROLLING TRACTION TYPE GEARING
Inventor: RESURII KENDORITSUKU ROBINSON Applicant:
TOROTRAK DEV LTD
JP2154863
1990-06-14
Continuously variable transmission
Inventor: GREENWOOD CHRISTOPHER
US4922788
1990-05-08
AUTOMOTIVE TRANSMISSIONS COMPRISING A VARIATOR AND ANOTHER
GEARING UNIT
Inventor: FELLOWS THOMAS GEORGE
GB2200175 - 1988-07-27
