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.
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).
VIDEOS:
Torotrak | How the IVT works | Full toroidal variator
Toroidal Continuously Variable Transmission (TCVT)
Torotrak has developed the Toroidal Continuously Variable Transmission (TCVT) – based on the proven technology of rolling contact ‘disc and roller’ traction drive, rather than the more expensive belt or chain variators, and offering significant benefits and competitive advantages. TCVT is a low cost, lightweight, fuel efficient, compact transmission with excellent torque capacity which offers high levels of drivability, refinement and fuel economy.
Components of the TCVT
To achieve the package, cost and simplicity targets the TCVT comprises of only four elements:
The Full Toroidal Traction Drive Variator
A hydraulic block
A clutch pack
A final drive
This has resulted in:
A stepless automatic transmission - with a wide ratio spread of 6.25
Overall transmission reduction ratio in forward and reverse of 16:1 – delivering excellent gradeability and low speed performance
A large overdrive capability – for optimised fuel economy and relaxed cruising
A transmission weighing less than 50Kg – for example offering a design length of 345mm with torque capacity of 150Nm to satisfy typical 'A', 'B' and 'C' sectors.
Torotrak | TCVT for automotive | TCVT for passenger cars
Xtrac Sees a Number of Applications for Flywheel Hybrids in Road Cars
Transmission technology specialist Xtrac says the flywheel kinetic energy recovery systems (KERS) currently being developed for Formula One could be applied to road vehicles in a number of ways.
By providing an additional boost of power, the F1 technology is particularly relevant to the trend to fit cars with smaller engines in pursuit of better fuel efficiency and lower CO2 output. The technical challenge with engine downsizing is compensating for the loss of engine torque and driveability, which could be restored by applying flywheel technology. It is also possible that a mechanical KERS system could be used as a range extender in a battery electric hybrid vehicle or even to power vehicle auxiliaries.
“All are potential applications of the technology, subject to the size of the flywheel, compactness of the system and vehicle packaging requirements,” says Xtrac technical director Adrian Moore. “These are all resolvable technical issues. The intent of the KERS technology in F1 is to consider energy recovery, storage and discharge, and to demonstrate that technology in a novel and effective way.”
Complementing its work in F1, the transmission technology provider is also an active partner in a new project to develop a flywheel hybrid system for premium cars. Xtrac forms part of a consortium supported by the UK government’s Technology Strategy Board, which recently announced funding of £23 million for 16 innovative low carbon vehicle development projects.
The flywheel hybrid project will involve the design and development of a mechanical KERS system for use in a premium segment passenger car as an alternative solution to other hybrid systems, and to prove its effectiveness and viability for production. Jaguar is leading the project, which will be carried out by a consortium made up of Flybrid Systems, Ford, Prodrive, Ricardo, Torotrak and Xtrac.
“We are very excited about being part of a consortium that has successfully secured funding to undertake one of the major UK low carbon vehicle programmes,” said Peter Digby, managing director of Xtrac. “Taking a technology that has been developed for motorsport and implementing it for road vehicles in order to improve fuel economy and reduce carbon emissions so quickly after the emergence of the base technology shows how rapidly the UK motorsport industry can react. It is no surprise that a number of our consortium members are successful motorsport engineering companies who have taken up the challenge.”
Xtrac has been involved in energy efficient motorsport initiatives since 2001 and more recently has played a key role in designing, developing and integrating a mechanical KERS system for F1 with partners Flybrid and Torotrak. Xtrac’s role is to provide the toroidal continuously variable transmission (CVT) between the flywheel and the vehicle powertrain.
Given the need to develop systems in time for the 2009 season, the CVT has already undergone rigorous bench testing on Torotrak and Flybrid test rigs. The three F1 project collaborators all strongly believe that the mechanics of this system can be transferred to other technology areas including road vehicles.
“There are some peculiarities which are distinct to F1 due to the regulations, such as the control system, integration of the ECU and the operating parameters,” says Moore, “but as the original Torotrak CVT concept was intended for road vehicle transmissions, the flywheel KERS opportunity readily allows for the use of toroidal CVTs in cars.”
“Historically, there are many instances where a new technology initially looks challenging to install in certain applications only to find a few years later that it is smaller, lighter and performs better than anyone ever envisaged. F1 will certainly help advance this process.”
The energy recovery rate and storage requirements of a flywheel for a road car could be considerably less than that required in F1 where the energy which could be recovered from 5g braking is significant. As the flywheel is required to be charged, some preliminary motion may be required; though road cars could store energy in the flywheel directly from the engine, which is not currently permissible under F1 regulations. Road driving conditions also vary from the stop-start conditions experienced in a town environment to constant speed cruising found on motorways.
“Although still maturing, KERS has stimulated the introduction of radical new technologies to F1 and ultimately to other engineering sectors,” says Moore. “The mechanical based concept offers one such solution and indeed could offer significant energy efficient benefits to the driveline of both race and road vehicles.”
Moore is presenting a paper outlining the design and development of the CVT used in Flybrid Systems F1 flywheel KERS this week to leading automotive engineers and technical experts attending the 10th Global Powertrain Congress being held in Vaals in the Netherlands.
This is not the first time that Xtrac has presented a paper at this high level conference demonstrating the potential crossover of transmission technology between motorsport and road vehicles.
Last year it presented details of its gearbox developed for the world's first commercially viable diesel-electric drivetrain for automotive engineering consultancy Zytek. The low-cost energy-efficient system had been prepared for assessment by carmakers in a vehicle fully meeting the requirements of the UK government’s Ultra Low Carbon Car Challenge (ULCCC).
A published copy of Xtrac’s latest paper on the CVT development for the flywheel KERS for F1 and its potential for road vehicles is available from the International Council for Powertrain Engineering and Management (ICPEM), the non-profit organisation that organises the conference. Information is available at
Global Powertrain Congress 2007.
The Global Powertrain Congress (GPC), currently celebrating its 10th anniversary, has established itself as an international event focused exclusively on the needs of the powertrain community. The event is sponsored by IPCEM to help advance knowledge of science, engineering and safety related powertrain technologies.
June 11, 2008
The Use of Mechanically Based KERS in Motorsport and Beyond
During 2007, the FIA agreed that kinetic energy recovery systems (KERS) had relevance to Formula 1. Road car electrical systems were probably thought the obvious solution, however mechanical high speed flywheel systems are giving the teams some choice. Xtrac are key to the design, development and integration of the CVT (Continuously Variable Transmission), into a mechanical flywheel KERS, initially for F1 but also for Sportscar and ultimately for mainstream automotive use.
Within the F1 regulations, KERS means energy that can be recovered from braking events only and is intended to promote overtaking and improved lap time by driver decision. It is to provide a platform to demonstrate technology for automotive interest, in a highly interesting and demanding environment. The developments by specialist technology companies of high speed flywheels in a very low pressure vacuum suggest an exciting combination of a flywheel based energy storage device, a clutch, a speed controller and a mechanical linkage. As the system is very high speed and thus low torque, linking the elements requires very high quality gearing – hence Xtrac!
Flybrid Systems, a British company supplying complete KERS solutions, utilise a flywheel that rotates at over 60,000rpm. This requires a speed transform between 11:1 and 80:1, and in conjunction with a number of fixed gears the CVT provides a continuous variation to absolutely match the required flywheel (high speed) and vehicle (low speed) requirements. Xtrac have partnered with Torotrak, the toroidal CVT experts, whose designs are road vehicle based, and Xtrac have developed their own ‘racing’ CVT.
The Flybrid Kinetic Energy Recovery System (KERS) is a very small and light device that meets the FIA regulations for the 2009 season.
The key system features are:
A flywheel made of steel and carbon fibre which rotates at over 60,000 RPM inside an evacuated chamber
The flywheel casing features containment to avoid the escape of any debris in the unlikely event of a flywheel failure
The flywheel is connected to the transmission of the car on the output side of the gearbox via several fixed ratios, a clutch and the CVT
60 kW power transmission in either storage or recovery
400 kJ of usable storage (after accounting for internal losses)
A total system weight of 25 kg
A total packaging volume of 13 litres
The layout of the device is tailored exactly to meet the customer's requirement resulting in a truly bespoke solution that fits within the tight packaging constraints of a F1 car.
http://www.flybridsystems.com/F1System.html
The key element of the CVT is the variator, and Xtrac’s two toroidal cavity solution consists of identically contoured toroidal discs configured as two inputs and two outputs mounted back to back. Arranged as opposing pairs to create the two working chambers, each cavity contains three roller elements which contact the toroidal discs at the periphery, but separated by an oil film of traction fluid producing no metal to metal contact. The speed ratio of the variator is dependent upon the angle of the rollers within the toroidal cavities. Axial load is applied to the variator to create a contact normal force at the contacts between the rollers and the discs. Power is transmitted from the two input discs through the six rollers to the two output discs by shearing a traction fluid in the twelve elastohydrodynamic contacts between the discs and the rollers. The traction fluid is under pressure, which enables it to transmit force by shear, whilst also preventing metal-to-metal contact. The inner toroidal output discs in this case have a spur gear cut around the periphery, which permits drive to be taken out of the unit.
Xtrac have made the assemblies super lightweight and encased the discs in shrouds which feed the oil up through the lever arms exactly where it is required, at the contact patch. The unit also uses a common oil system for both the traction and the hydraulic system and weighs around 6.5kg which is very low for a transmission that can transmit over 60kW across its entire speed range.
The CVT is torque controlled. Applying a force to the rollers of the variator causes a reaction torque at the variator discs and consequently an acceleration or deceleration of the flywheel and the vehicle inertia. This will change the speed of the flywheel and / or vehicle resulting in a change of variator ratio. The application of a castor angle to the roller carriages enables the rollers to ‘steer’ to a new angle of inclination or ratio. This happens automatically – only the variator disc speeds and reaction force are defined externally – not the ratio itself. Xtrac’s engineers have further simplified the unit by designing the lever arms as common and symmetrical parts removing the need for additional levels of feedback control and damping.
Ultimately, it will be for Flybrid Systems and the race car constructors to control the final integration and operation of the system. Given the need to develop systems in time for the 2009 season, the unit has already undergone rigorous bench testing and can be readily mated to an existing transmission.
Although still maturing, KERS has stimulated the introduction of radical new technologies to F1, other Motorsport sectors such as Sportscar racing and ultimately for mainstream automotive use. The mechanical based concept offers one such solution and indeed could offer significant energy efficient benefits to the driveline of both race and road vehicles. Flybrid, Torotrak and Xtrac together are positioned to deliver this, with the planned launch of a KERS unit for Sportscar racing.
Xtrac-Flybrid-Torotrak partnership recognised with a motorsport industry Business Excellence Award
Three British companies – Xtrac, Flybrid Systems and Torotrak - jointly received this year’s prestigious ‘Teamwork Award’ at the Motorsport Industry Association (MIA) annual Awards Dinner for their close working relationship in the development of a groundbreaking mechanical kinetic energy recovery system (KERS) for motor sport applications.
It is the first time this award has been presented simultaneously to three companies, who were also nominated for the prestigious ‘Technology and Innovation Award’. Each award is decided upon through a process of voting by MIA members in the weeks leading up to the event.
The three business partners were singled out from other influential motorsport organisations - McLaren Mercedes F1 Racing Team, M-Sport World Rally Team and Shell Racing Solutions - nominated for the teamwork award, which was in one of eight categories recognising the industry’s highest achievers from the past year.“We are delighted that the motorsport industry has chosen to recognise that three very different businesses have successfully applied their respective areas of technical expertise to develop a new and innovative technology,” said technical director Adrian Moore, who collected the award on behalf of Xtrac.
“We too are delighted the motorsport industry has chosen to recognise the combined effort of our three businesses to step up to the KERS challenge,” said Doug Cross, who received the award on behalf of Flybrid Systems, the company he co-founded with managing partner Jon Hilton. “This latest accolade clearly highlights the recognition KERS is receiving as a major motorsport innovation, which addresses the demands being made of the industry to become more energy efficient and to help lead in the development of ‘greener’ engineering solutions,” said business manager Chris Brockbank, who received the award on behalf of Torotrak.
Torotrak CEO Dick Elsy added: “This is the first time that the MIA award for teamwork has been given to three independent companies working together. It is indicative of how a change in regulations can lead to opportunities for specialist UK companies from different areas of the industry to work together to create groundbreaking technology for F1, and in particular a technology that I expect to cascade into general automotive applications.”
This latest motorsport industry accolade closely follows all three companies receiving the ‘Engine Innovation of the Year’ award at the Professional MotorSport Awards Dinner held in Cologne in November 2007. The three businesses have combined their different but complementary technical capabilities to provide the new mechanical KERS innovation following the decision by the FIA to permit energy recovery in F1 from the 2009 season.
Each company has played an important role in the development of the KERS system. Xtrac has a license from Torotrak to design and manufacture a continuously variable transmission (CVT), incorporating Torotrak’s traction drive technology, which matches the speed between a flywheel and vehicle drivetrain. The KERS assembly is completed by Flybrid with the addition of electronic controls, mechanical flywheel and containment system. As the final system integrator, Flybrid also carries out the calibration, testing and installation of KERS for the customer.
The mechanical KERS system utilises a flywheel to recover and store a moving vehicle’s kinetic energy, which is otherwise wasted when the vehicle is decelerated. The energy is received from the driveline through the CVT as the vehicle decelerates, and is subsequently released back into the driveline, again through the CVT, as the vehicle accelerates. The FIA has defined the amount of energy recovery for the F1 2009 season as 400kJ per lap giving the driver an extra 80hp over a period of approximately seven seconds.
The role played by Flybrid, Torotrak and Xtrac in designing a KERS solution for F1 could be highly instrumental in developing this pioneering vehicle technology for more fuel efficient road cars, especially important at a time of spiralling fuel prices and tighter emission regulations, without resorting to the expense and complexity of battery systems. Compared with hybrid electric vehicles, which use batteries for energy storage, a mechanical KERS system utilises flywheel technology as a highly efficient alternative to recover and store a moving vehicle’s kinetic energy.
Applied to road cars the system supports the industry trend for smaller powertrains and hybrid vehicles. Flybrid, Torotrak and Xtrac believe that compared to the alternative of battery systems, a mechanical flywheel-based KERS system can provide a more compact, lighter and environmentally-friendly solution.
First presented in 1995, the MIA Awards were created to recognise excellence at all levels within the motorsport and high performance engineering industry and Xtrac has previously won MIA awards for Business of the Year and Export Achievement (twice). Taking place on the evening of the first day of the Autosport International Show (NEC, Birmingham, January 10th-13th 2008), the sell-out dinner was attended by an audience of some 500 representatives of the international motorsport community.
In its official statement the MIA comments that ‘all motorsport companies are eligible to win one of these sought-after awards; nominations for which are made by the MIA membership thereby demonstrating that the winners have earned the respect and support of their industry peers, which makes the awards especially meaningful to the recipients.’
The ‘Teamwork Award’ was sponsored by MIRA, whose chief executive John Wood presented the award.
16th January 2008
Latest News
Magneti Marelli and Flybrid systems to collaborate 29th April 2009 on KERS energy storage for motorsport
Italian Motorsport electronics specialist Magneti Marelli and British high-speed flywheel specialists Flybrid Systems today announce the collaboration to develop a new energy storage solution for the Kinetic Energy Recovery System (KERS). The new product will deliver a high power electrical storage system for hybrid racing cars capable of deep depths of discharge with no performance degradation and a long service life.
The new product named Flywheel Capacitor consists of a high-speed carbon fibre flywheel incorporating Flybrid® technology connected to a high-speed electric motor generator using technology from Magneti Marelli, all managed by Magneti Marelli’s control electronics.
The device works by applying to the electric motor generator the recovered electrical energy captured from the vehicle during braking events. The energy is stored into the Flywheel Capacitor by speeding up the flywheel. During the acceleration events of the vehicle, the energy stored into the flywheel capacitor is returned to the vehicle by transforming the kinetic energy of the flywheel into electrical energy via the motor generator.
The Flywheel capacitor will not use chemical battery based energy storage systems.
The first Flywheel Capacitor to be developed will have a specification of 60 kW power and 600 kJ total storage capacity but the specification can be readily adapted to any vehicle requirements. Both partners will draw upon extensive experience with their own KERS products to deliver a working prototype in the next few months.
The electric motor and flywheel will rotate at up to 60,000 RPM and the flywheel will sit inside an evacuated chamber that includes special containment features to ensure complete safety. A small electric pump will occasionally top up the vacuum so that no regular maintenance is required.
State of the art magnetic design of the motor generator and high efficiency electronics are expected to deliver round trip storage efficiencies approaching 80%. The device has a low cooling requirement and contains no flammable materials. The complete flywheel capacitor including the associated electronics is expected to weigh just 20 kg.
Commenting on the collaboration Flybrid Systems Managing Partner Jon Hilton said “This is an exciting new development that will deliver a high end product capable of exploitation in F1 but also suitable for more widespread use in motorsport. As well as offering low running costs the flywheel capacitor is a green alternative to regularly replacing batteries.”
Managing Director of Magneti Marelli Motorsport Roberto Dalla said: “We are very excited to apply our technology and our deep experience in developing KERS solutions to create an alternative energy storage system. This project lies within our strategy of continuous innovation and research for efficiency and performance”.
The new flywheel capacitor product will be commercially available from both Magneti Marelli and Flybrid Systems. Both companies will continue to develop, manufacture and distribute their own existing KERS products.
http://www.flybridsystems.com/News.html
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