The tyre is a highly complex product packed with advanced material engineering. Continuing just-auto/QUBE’s series of research snapshots, this one focuses on some recent advances in the tyres arena.
A breath of fresh air
The term ‘green tyres’ has been talked about for years in engineering circles, referring to a breed of environmentally friendly rubber. Goodyear has taken this to a new level with its so-called Oxygene concept, a ‘breathing’ tyre that cleans the air around it. The tyre’s structure features living moss growing within the sidewall. This open structure and the tyre’s tread design absorbs and circulates moisture and water from the road surface, allowing photosynthesis to occur and therefore releasing oxygen into the air. Its non-pneumatic construction is 3D-printed with rubber powder from recycled tyres. Additional safety is ensured by the tyre’s open structure, which improves wet grip by helping absorb water from the tread. If that’s not enough, Goodyear claims this concept can generate electricity. Oxygene harvests the energy generated during photosynthesis to power its embedded electronics, including onboard sensors, an artificial intelligence processing unit, and a customisable light strip in the tyre’s sidewall that switches colours, warning both road users and pedestrians of upcoming manoeuvres, such as lane changes or braking.
Continuing the airless theme, other suppliers are rolling out their tyre concepts. Toyo Tyre and Rubber’s research into this area began way back in 2006. The tyre maker says its latest non-pneumatic tyre concept, dubbed Noair, resolves certain technical issues and can support a practical application. Buried under the tread rubber, the concept incorporates highly-rigid resin spokes to support the load demands placed on the tyre. An outer diameter ring between the spokes and the tread, made from carbon fibre reinforced plastic, serves to reduce the load imposed on the spokes.
Lightweighting
With automakers under pressure to produce more fuel-efficient cars, it is hardly surprising to see them eliminating the spare wheel, thereby shedding up to 30 pounds in one stroke. A good number of automakers now supply a tyre sealant and tyre-inflator pack instead of a full-size or temporary spare wheel (also known as a space-saver tyre). The sealant and compressed air are injected through the tyre valve but the result achieved will depend on the cause of the puncture and how far and fast the flat tyre has been driven on. In other words, tyre inflator kits only work on small punctures over short distances. A major blow-out cannot be repaired using an inflator kit. Other ways to reduce tyre weight are continually under focus though. For example, Yokohama Rubber recently revealed its so-called BluEarth-air EF21, a concept designed to reduce tyre weight and environmental impact. Claimed benefits include a thin yet rigid structure and a weight reduction of about 25 percent in the tyre’s mass.
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By GlobalDataGreener tyres
It is estimated that it takes half a barrel of crude oil to make one truck tyre. So a Goodyear team of scientists and engineers have created a tread compound, or formulation, using soybean oil. By employing soybean oil in tyres, Goodyear says it has found a new way to help keep the rubber compound pliable in changing temperatures, a key performance achievement in maintaining and enhancing the vehicle’s grip on the road surface. The tyre maker’s tests have shown rubber made with soybean oil mixes more easily in the silica-reinforced compounds used in manufacturing certain tyres. This also improves manufacturing efficiency and reduces energy consumption.
Safer tyres
A sudden aquaplaning is always a frightening moment behind the wheel but how would it feel like in an autonomous vehicle? Aquaplaning occurs when the tread cannot quickly enough deflect the water from the road. To detect this excessive water displacement, Continental relies on images from the surround-view cameras. These wide-angle cameras are installed in the wing mirrors, grille and on the rear. “When there is a lot of water on the road, the camera images show a specific splash and spray pattern from the tyres that can be detected as aquaplaning in its early phase,” said project manager Bernd Hartmann.
The supplier also plans to use information from the tyres to identify the risk of aquaplaning. Here, the sensor signals will be analysed directly in the tyres. “We use the accelerometer signal from the electronic tyre information system to look for a specific signal pattern,” said Andreas Wolf, head of Continental’s body and security business unit. As the eTIS sensor can also identify the tyre’s remaining tread, this data can be used to determine a safe speed for specific wet road conditions and pass this on to the driver.
With connectivity, vehicles that are still far behind a potential aquaplaning spot can be informed of the danger immediately via vehicle to vehicle communication and the digital map.
In future, says Continental, it will be possible to evaluate all sensor data in a central vehicle computer for the aquaplaning warning system. If the system detects a danger at the current speed, the driver will be notified of a safe speed. With connectivity, vehicles that are still far behind a potential aquaplaning spot can be informed of the danger immediately via vehicle to vehicle communication and the digital map based on the electronic horizon. This is how the traffic control systems also receive information about relevant danger areas. The aquaplaning warning system is especially important for automated vehicles. They must avoid aquaplaning situations without human driving experience.
Looking around motor shows nowadays, it seems that everything is connected to everything. Tyres are no exception. Pirelli used the most recent Geneva motor show to unveil its Cyber Car tyre technology. It enables the tyre to directly interact with the car’s on-board electronics and, in particular, with driver assistance systems in order to deliver information about the car’s operation. Pirelli says the technology will be on the road by the end of this year.
Tyres for electric vehicles
Goodyear also used this year’s Geneva show to unveil its latest tyre innovations for electric vehicles. Known as EfficientGrip Performance with Electric Drive Technology, it is a prototype tyre for the growing electric vehicle market that will be on the road by 2019 in Europe. Goodyear testing reveals that traditional tyres can wear out up to 30 percent faster on electric vehicles due to the powerful, instant torque from electric motors and the additional vehicle weight from heavy battery packs.
In addition to tyre durability requirements, automakers are pressing for enhanced rolling resistance on EVs. Increasing range is a high priority for consumers due to an underdeveloped electric recharging infrastructure in most countries. Quiet and comfort from tyres is another consideration as, at low speeds, EVs generate as little as half the amount of noise as traditional vehicles.
For its part, Hyundai Motor recently formed a technology partnership with Michelin. The partners are developing a new all-season tyre for EVs. The use of Michelin’s next-generation tyre material and structural technology will help Hyundai Motor optimise overall vehicle efficiency and performance. Michelin will also collaborate in the development of a bespoke tyre for a successor model to the Genesis G80 luxury sedan. Co-operative testing and analysis will help determine tyre vibration characteristics at high speeds, both in a laboratory setting and using evaluation conditions set to match the Nürburgring circuit.
New development processes
Toyo Tyre and Rubber is pushing back the technical boundaries of Nano Balance Technology (NBT), the indigenous rubber material development technology developed in 2011. NBT is used for developing rubber materials with high precision through observation, prediction, material design and production control at the molecular (nano) level. The supplier has developed a new process development technology contributing to reduction in fuel consumption from the “nano processing” aspect of NBT. It uses this to achieve an improved level of tyre rolling resistance (low fuel consumption performance) and braking performance (wet grip performance).
All the above reminds us that tyres remain a key technology within chassis engineering. Quite apart from the fact that vehicle grip and handling behaviour ultimately depends entirely on the physics and mechanics of what happens within the four tyre contact patches, the tyres also make significant contributions towards determining ride comfort, internal and external vehicle noise, and economy.