Anti-vibration solutions (AVS) are used throughout vehicles to improve driveability, economy, emissions and comfort. Alain Guillaume, engineering manager at Trelleborg Automotive, looks into the technology, and how it can withstand extreme conditions and meet current legislation.
Anti-vibration solutions (AVS) for the automotive industry are used primarily to reduce vehicle vibration and noise. They are vital for improving the drivability, durability, economy and emissions of a car, as well as for optimising passenger comfort and safety.
A comprehensive range of anti-vibration solutions are used throughout the vehicle, from the engine and exhaust mounts to the chassis and suspension. While the variety and design of AVS is continually developing, they have been used in various forms right from the design of the very first car.
Critical to the quality of the ride and handling of the vehicle, the vehicle suspension system, or shock absorber, is an integral automotive component and its efficiency and performance is heavily dependent on a number of anti-vibration solutions.
Anti-vibration solutions must be able to withstand extreme conditions on a daily basis. As such, there are a variety of environmental conditions that must be considered in the design of these solutions to ensure they can perform in any situation and withstand the following conditions:
• Movement: Anti-vibration solutions, and the vehicle chassis in general, must withstand constant vehicle movement, throughout the lifetime of the vehicle, which is generally considered to be at least ten years.
• Climate: Anti-vibration solutions must also withstand extreme climatic conditions, ranging from temperatures of -40°C to over +120°C.
• Environment: Vehicles are often exposed to a variety of elements, such as heavy rain, water, snow and sand, as well as rough terrain.
Changing industry requirements
In addition to meeting the needs of extreme environmental and climatic conditions, the design of anti-vibration solutions must continually evolve to meet changing industry needs and demands. These include:
• Weight: As metal prices continue to rise, OEMs are looking to source alternative materials and solutions that can reduce the quantity of metal parts required. Even a small weight reduction can enable significant savings during production. As a consequence, we are seeing an increasing move from steel to aluminium parts, with growing demand for more plastic components. The use of plastic also allows greater design freedom for inserts supporting elastomer-based parts. This is an efficient way to increase car durability as plastic components aren’t susceptible to rust, don’t require painting and are also easier to recycle.
• CO2 emissions: A reduction in vehicle weight can also help the car manufacturer to meet the CO2 Emissions Standards, which define the acceptable limits for exhaust emissions of new vehicles across the EU. This is something that is generally adhered to by manufacturers across the globe, as they seek to gain a competitive advantage.
• Recycling: As the 2015 deadline for the European Union’s 95% recycling rate for end-of-life vehicles becomes ever closer, car manufacturers are looking for more easily recyclable components. New material developments, such as MDI-based PU, rather than less environmental NDI-based materials, have been developed to help OEMs reach these targets.
• A global market: Environmental and climatic conditions vary dramatically between countries. However, it is important for a car manufacturer to be able to sell the same vehicle platform right across the globe without incurring the cost of re-designing various components to meet different conditions. It’s therefore essential that AVS designs are flexible, robust and that the components can be sourced easily.
• Developing technology: As car technology evolves and we see the increase of more refined and quieter vehicles, especially with the emergence of electric vehicles, anti-vibration solutions must work harder to optimise noise dampening performance.
In order to meet the needs of the manufacturer, changing industry requirements and the wide range of environmental and climatic conditions that anti-vibration solutions are exposed to, constant material development and design is critical.
Improvements in AVS durability, temperature resistance, stiffness, creep and noise reduction, are heavily dependent on compound and polymer design and selection.
The importance of material development to the industry can be demonstrated through innovations such as the Trelleborg Noise-Free Rubber, a self-lubricated, low-friction rubber formulation that overcomes noise from AVS components – such as suspension bushings, engine mounts and anti-roll bar isolators – while the vehicle is in motion. In addition, this material has been engineered to meet stringent fatigue requirements, resulting in an increased durability of around 50%.
Meeting future demands
Vehicle design has evolved so much in recent years, yet from the outside it’s easy to forget that the finished product is dependent on the pioneering new design and material developments of integral components, such as anti-vibration solutions, which are critical to the safety, comfort and durability of the entire vehicle. Continued and collaborative design, across all vehicle components, is essential to meet the evolving needs of the industry, the environment and the end-user.
The key to suspension
Top strut mount & spring seat
The Trelleborg top strut mount is designed to prevent sudden excitation of the car body through road input, bumps, obstacles and pot holes, etc. Due to the forces it absorbs, the mount needs to be soft in the axial direction but hard in the radial direction. As well as performing a damping function, the strut mount can also help to isolate tyre and spring induced noise and vibration.
A key driver for innovations in top strut and spring seat technology is the recent pedestrian shock legislation. The legislation requires the reduction in height of the shock absorber mounts to create increased clearance between the bonnet and the strut, in order to provide a crumple zone to absorb pedestrian energy in the event of impact and reduce the possibility of serious injury. To combat this, Trelleborg has developed compact strut mounting solutions and retuned surrounding components, such as the bearing, spring seat, spring, bumper and dust cover.
PU bump stop
The strength of the bump stop lies in its damping abilities, absorbing and isolating extreme shock, noise and vibration. Trelleborg Automotive use PU materials for bushing and bump stop applications.
Polyurethane (PU) elastomers are a useful and cost-effective alternative to rubber in several applications. Elastomeric properties are determined by the material mix. Polyurethane can offer strength, rigidity, softness and flexibility. PU can perform better than rubber in terms of abrasion resistance and the injection moulding process makes the component easier to shape.