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Toyo Tire & Rubber Co, Ltd President and CEO Takashi Shimizu says the company has been conducting research to realise new possibilities for automobile tyres with an eye on future changes in a mobile society. Toyo Tires recently announced the development of ‘noair’, a neo-futuristic airless concept tyre that does not require any filling of air.
Toyo Tires undertook a fundamental review of the existing ‘basic structure of pneumatic tyres’ that cushions road impacts by supporting the vehicle weight by filling the inside with air. It has researched airless tyres since 2006 under a new concept of ensuring the fundamental performance of a tyre without the need for it to be filled with air. In May 2012, Toyo Tires introduced a prototype as a reference exhibit at Automotive Engineering Exposition 2012 to demonstrate some of the technological developments that were amassed up to that point.
Fundamental changes in the tyre structure from previous prototypes and moving forward with resolving issues led to substantial improvements in multiple performance indexes as well as making it possible to drive the tyres at a practical level. Naming it the ‘noair’ concept tyre, Toyo Tires says it would continue to engage in research with the aim of practical application as well as efforts to advance technological developments.
Characteristics of noair
For the inner core side, the basic tyre structure comprises special high-rigidity resin spokes to ensure sufficient strength to support the load. Basic tyre performance, namely ‘drive, turn, stop’, is achieved by using a rubber material for the outer tread that comes into contact with the road. The section between the spokes and rubber tread, the outer diameter ring is reinforced with carbon fibre reinforced plastic (CFRP) that serves to reduce the load imposed on the spokes.
Previous prototypes supported the load through an ‘elliptical spoke configuration’ but the latest version has evolved into an ‘X-shaped spoke configuration’ that alternately crosses the width of the noair tyre from the outside to the inside and vice-versa. Durability is improved by achieving a completely unique support configuration form.
Furthermore, the number of spokes is doubled (100 pitch) compared to the previous model, distributing contact pressure, reducing impact sounds from the spokes that are generated when they come into contact with the ground, and achieving an even more quieter ride.
Evaluation of characteristic values
Durability is said to vastly exceed the equivalent legal and regulatory requirements for Toyo Tires commercial products* (pneumatic tyres) and at least eight times better than previous prototypes.
‘Rolling resistance’ – which expresses the amount of force that opposes the rotation of the tyres – is reduced by at least half compared to previous prototypes and is 25 per cent better when compared to Toyo Tires commercial products. On the other hand, superior environment and safety performance levels were also achieved, such as reducing ‘wet braking distance’ – which measures braking performance on wet roads – by 4 per cent. One of the factors underscoring this result was the adoption of fuel efficient tread rubber composed through ‘Nano Balance Technology’, a unique material design core technology used by Toyo Tires when commercialising fuel-efficient tyres.
Road noise is significantly improved compared to previous prototypes, with a level similar to that of current pneumatic tyres.
*Toyo Tires commercial products ‘TOYO TEO+ (Toyo Teo Plus)’: tyre size 155/65R13, rim: 13×4.5-J, air pressure: 200/220 kPa
*Airless tyre: external diameter 540mm; width 140mm; rim equivalent to 14 inches
*Evaluations were conducted in-house at a Toyo Tires tyre proving ground (Tsuno-cho, Koyu-gun, Miyazaki prefecture).
Performance on actual cars
According to the results of performance tests conducted by driving the tyres on actual cars, where evaluations were made by a designated driver from the Tire Evaluation Development Department, although there are still some issues related to noise within the vehicle and ride quality, handling stability and noise outside the vehicle were found to be significantly improved, with progress made in narrowing the gap with Toyo Tires commercial products (pneumatic tyres) for a majority of the indexes.
Toyo Tires believes it has made dramatic advances from previous prototypes in tyre-related possibilities through technological breakthroughs, such as material selection, unique structural design, enhancement and integration of various technologies, and optimisation of the overall balance.
Bearing in mind that this concept tyre would soon reach a level where it could be fitted to actual vehicles and driven, in addition to giving this concept tyre a name, Toyo Tires is considering shifting from the laboratory-level to a market perspective, such as creating colour variations for the spokes.
When considering a society where futuristic mobility, such as EVs and compact cars, would start forming a section of the market, it is currently expected that the need for maintenance-free tyres would increase. Furthermore, as it is thought that transportation vehicles that do not run the risk of flat tyres would be more effective from a safety perspective, airless tyres that do not require filling up with air show great potential.
Although there are some outstanding issues to be resolved before they enter practical use, Toyo Tires says it would continue to acquire knowledge from multiple fields through the disclosure of current technological levels as well as further advance research and technological development to open up possibilities in a mobile society.
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