During wind-tunnel testing they focused their attentions on maintaining a draught-free interior, as this was crucial to creating an effective system of neck-level heating. The result is a seating position which is matched to the height of the windscreen frame so that the airflow is directed over the heads of the SLK passengers; this means they are truly screened from the wind when seated in the car, making the journey a much more comfortable one. The new SLK-Class also comes with a draught-stop as standard. The draught-stop is simply pulled over the two roll-over bars and secured by means of press studs. The fine-mesh structure results in a uniform distribution of air to avoid the high flow speeds which could otherwise be sensed as a draught. The same function is also fulfilled by the three-section, transparent draught-stop which is available as an accessory for the new SLK-Class. Thanks to these aerodynamic measures, the prerequisites for optimising thermal comfort whist driving with the roof down had been fulfilled. However, the SLK developers had no intention of stopping there: as well as smoothing the airflow with the draught-stop, they wanted to warm the air up too. And after a development and testing phase which lasted several years, their efforts were rewarded with the creation of the AIRSCARF system.
Over the course of numerous test runs, the seat development team in Sindelfingen tried out a number of dif
ferent ideas and concepts for the neck-level heating system, and soon came to the conclusion that only a system that was integrated into either the seat or the head restraint could achieve the desired level of heating. In other words, the technology used had to be both small enough to fit into the SLK seats and at the same time powerful enough to generate enough thermal energy to heat the airflow in the roadster interior with the roof down.
The engineers at Mercedes were able to resolve these conflicting technical objectives using state-of-the-art, high-performance ceramic materials: various elements made of barium titanate and other metal oxides are energised, causing them to heat up in a matter of seconds and emit heat continuously. This does not drain the car’s 12-volt power supply though, as once a certain temperature is reached the electrical resis-tance of the ceramic material suddenly jumps, thereby reducing power consumption; heat output remains unchanged, however. This produces an equilibrium between the electrical energy the ceramic material is fed with and the heat output it produces.
The experts refer to this state as a "Positive Temperature Coefficient" or PTC for short. Meanwhile, the ceramic heating element is able to prevent itself from overheating by monitoring its surface temperature and automatically reducing the output if necessary.
As well as the compact design, this technology’s key benefits are its speed when heating up and the constant heat output.
The PTC air heater for the AIRSCARF system measures only a few centimetres in size, allowing it to fit into the backrest of the SLK seat. It consists of a number of rectan-gular ceramic elements with a total heat output of around 216 watts. The heat produced is dissipated into the air through aluminium fins which are positioned between the individual ceramic elements. A blower directs the air though a plastic duct until it reaches the head restraint where it flows out of a special vent to warm up the neck, throat and head of the seat occupant.
AIRSCARF comes equipped with a three-speed switch and an electronic control module that adjusts heating at neck level to meet current requirements. A data bus keeps the micro-computer in contact with the speedometer, the temperature sensor in the centre console and the exterior thermometer of the Mercedes Roadster. The micro-computer then compares this up-to-the-minute data with the stored characteristic curves for particular ambient conditions and driving situations.
Pushing a button starts the system in switch position 3, after which it adjusts automatically depending on ambient temperature and road speed. The AIRSCARF system adapts the blower speed constantly in order to achieve optimal distribution of the warm air in all situations. This adaptive control based on stored characteristic data is active up to a speed of 120 km/h. At higher speeds, the system operates at a constant setting. Anyone preferring to regulate the heating effect individually can also select three different output settings manually via the buttons in the centre console.
As well as the AIRSCARF, the seat experts at the Mercedes-Benz Technology Centre (MTC) worked on the development of further special technical features which are geared towards boosting ride comfort and increasing practicality. The sports seats boast a number of distinguishing features, including core springing and a layer of foam which provides a precise level of cushioning. Both of these elements – the core springs and the layer of foam – are incorporated into a robust cushion shell made from fibre-reinforced plastic. When it came to the seat backrests, the engineers opted for magnesium. By combining low weight with high strength, this high-tech material helps to boost occupant safety by providing extra lateral bracing for the side wall in the event of a side-on collision, for example. In addition to this, the silver-painted magnesium frame provides a solid basis for attaching the standard head/thorax sidebags. The backrests’ foam cushioning is applied directly onto cush-ion holders made from glass-fibre reinforced plastic. These are in turn supported by the magnesium frame.
The seats fitted in the SLK-Class feature fore-and-aft, height and squab-angle adjustment, allowing all occupants to find their ideal position. Compared to the predecessor model, the engineers at Mercedes have been able to increase the fore-and-aft adjustment range by nine millimetres to a total of 247 millimetres. The seat squab angle is adjusted automatically as the seat is moved forwards and backwards. The height adjustment range of the integral head restraints is 80 millimetres, whilst the slot in the seat backrest for the head restraint is concealed by a gaiter.
Yet another novel feature is the facility for folding the driver’s and passenger’s seat backrests forwards to improve access to the practical luggage net attached to the rear wall behind the seat. A coat hook can also be found on the rear of each seat backrest in the new SLK.
Mercedes-Benz is also able to supply electrically adjustable seats with a memory function as an option for the new SLK-Class: in this case, a microchip stores the individual setting data for the driver’s seat and relays the data to the electronic ignition key. Every time drivers insert their key in the ignition, the seat, steering wheel and exterior mirrors will automatically adjust to the stored positions.
The second electronic key included as standard with the SLK-Class is also compatible with this highly convenient memory function, while a third memory setting can be programmed using the button on the seat base without data transfer to an ignition key.
The memory facility includes an extra, automatic function which offers drivers even greater convenience: as soon as the door of the SLK-Class is opened or the electronic key is removed from the ignition, the driver’s seat slides back automatically and the steering column moves upwards to make getting into and out of the car easier.
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