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“Mobility Aerodynamics" Technology

June 11, 2018

Precision “Aerodynamic Flow” simulations: Another key to reducing fuel consumption and increasing electric vehicle range

Hyogo, Japan – 11 June, 2018 – Toyo Tire & Rubber Co., Ltd. (HQ: Itami, Hyogo Prefecture, President & CEO : Takashi Shimizu) is pleased to report it has developed its own “Mobility Aerodynamics” (aerodynamic simulation) technology through the application of aerodynamic flow simulations. The technology will be effective in designing “tires having the excellent aerodynamic characteristics※1” required to further reduce fuel consumption and increase electric vehicle range.

※1) Aerodynamic characteristics: The attributes of air forces (air resistance) and airflow exerted on a body when it moves through air.

Our new “Mobility Aerodynamics” technology lets us predict the aerodynamic characteristics of tires and vehicles under rolling tire contact patch conditions.※2 We use actual tire pattern designs to combine tire use conditions when a vehicle is in motion (primarily the load on the tires and the vehicle’s speed) with conditions of various wheel and vehicle shapes, after considering how tire shape deforms under those conditions.

※2) Rolling tire contact patch conditions:
Conditions exerted when the tire is rolling on an actual road surface (conditions at point of contact).

By combining the various conditions, mobility aerodynamics will offer our company an advantage when proposing ideas suited to achieving the aerodynamic characteristics required by vehicles developed by manufacturers for improved fuel consumption and extended range. This breakthrough also lets us develop “tires that have excellent aerodynamic characteristics”, based on high-precision simulations yielding numerical data consistent with the results of wind tunnel tests using actual vehicles,※3 so that we can offer such tires to the market.

※3) Wind tunnel tests using actual vehicles: Tests performed at a specially designed facility that generates air currents invisible to the naked eye. Flow fields around an actual vehicle are made visible and air resistance is measured quantitatively.
Complex tire, including individual tread patterns, were combined with those of actual vehicles and wheels. Tire deforms caused by differences in applied load, speed, running attitude angle and other factors were considered in order to develop techniques for aerodynamic characteristic simulations. The breakthrough represents an advance never seen in the industry before.

・ Importance of aerodynamic characteristics

Drag force is the resistance a vehicle is bound to be subjected to when it moves. Reducing that force can result in improving fuel efficiency. Under social pressure to raise environmental performance, automotive manufacturers are striving to develop new vehicle designs that result in better aerodynamic characteristics. Meanwhile, electric vehicle makers faced with the challenge of extending the per-charge range, so improving aerodynamic characteristics has become a significant aim for them as well.

・ The relationship between tires and aerodynamics
As they rotate, tires on a moving vehicle keep deforming their shape while supporting the load. A rotating object has an effect on the air around it, changing the flow fields. They generated around the tire have a direct effect※4 on the vehicle’s aerodynamic characteristics. Minimizing this effect by optimizing a cross-sectional contour of a tire profile will reduce fuel consumption. To achieve this aim, it is necessary to analyze flow fields generated around rotating tires, and then develop ways to control that flow fields.
※4) Direct effect: It is estimated that the tires are responsible for about 15% of the total air resistance faced by a moving vehicle.

・Harmonization of global standards for measuring fuel consumption
In 2014, the United Nations’ World Forum for Harmonization of Vehicle Regulations (WP29) adopted unified global technical rules for “measuring passenger vehicle fuel consumption and emissions (WLTP※5)”. This globally standardized the measurement and testing procedures for automotive fuel consumption, emissions regulations and safety, which had until then differed by country or region. The WLTP, which mandates resistance assessments of individual motor vehicles, includes wind tunnel tests to determine tire air resistance as well, and this will have a direct bearing on regulated levels for tire aerodynamic characteristics. This means that efforts to improve flow fields around tires will be the focus of much attention.
※5) WLTP: Worldwide-harmonized Light vehicles Test Procedure
In consideration of the above three points, as a tire manufacturer we recognize the social significance and industrial benefits of “being able to demonstrate in more concrete terms how to raise aerodynamic characteristics to their optimum level”. We can expect to gain an “advantage for our company through this type of tire development”. We can achieve these goals through techniques that permit high precision   prediction.

We have developed numerical simulations methods “using supercomputers for tire analysis”, and our tire designers are using these methods to design products for the market. Through application of our own “T-mode” Design Technology, which combines tire analysis with driving simulations, we have been able to significantly shorten design time and achieve high precision design.

Our newly developed Mobility Aerodynamics technology represents T-mode advances that have permitted the establishment of approaches in areas unattainable by previous research. And so, through the use of various numerical simulations methods to quantify motion and conditions affected by the aerodynamics of actually running vehicles — such as “how tire shape deforms due to load and driving conditions”, “how tire rotation is affected by discontinuous tire patterns”, and “how flow fields are impacted by tire-road contact conditions” — and by combining these various factors, we have been able to simulate and visualize flow fields around tires and moving vehicles.

Toyo Tire & Rubber will continue to take tires to higher levels by applying our “design technologies for future road mobility”.

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