rexresearch.com


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

 



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