CLS-Part Two
Bodywork: Stable conditions
Modern lightweight construction of high-strength steel and aluminium
High long-term quality owing to more scratch-resistant paintwork based on nano-technology
Aerodynamic body with a Cd figure of 0.30
Bi-xenon headlamps with Active Light System and cornering lights
High-strength steel and aluminium are the major lightweight materials used for the CLS bodyshell. Aluminium is used wherever it has the most advantages over steel, namely for the bonnet, parcel shelf, front-end module member and the panel behind the rear seat backrests.
All the other components of the bodyshell are of sheet steel, with high-strength alloys accounting for 47.5 percent by weight. Among these is an innovative dual-phase steel, which has a special two-phase microstructure for high dynamic strength and resistance to extremely high loading forces. Various parts of the underbody and the reinforcements around the bumpers and suspension springs are of this high-tech material. The spare wheel recess of fibre-reinforced plastic makes a further contribution to weight-saving.
The engineers in Sindelfingen have also adopted the well-proven modular concept for the front and rear end used in other Mercedes models, thereby improving ease of repair and at the same time simplifying the body assembly process. The front and rear-end modules are bolted to the body structure, therefore they can be replaced without lengthy welding operations when accident repairs are called for. The front-end module mainly consists of a robust cross member which is not only used to attach the bumper, but also carries out an important function during an offset frontal impact by diverting the forces to the unaffected side of the vehicle and thereby significantly helping to dissipate the impact energy. Two special crash boxes of high-strength steel create a connection to the front side members and absorb most of the impact energy in the event of a frontal collision at up to 15 km/h. The structural members behind them remain unaffected as a result.
In addition to the repair-friendly front-end module, the new CLS-Class features highly resistant structural members which make a major contribution to the exemplary occupant protection provided by the four-door Coupé. The integral member, to which parts of the front axle, the steering gear and the engine mountings are attached, also deforms during a severe frontal collision and absorbs impact energy.
The mainstay of the rear-end module is a high-strength flexural cross member connected to the rear-end structure by two crash boxes. Here too, damaged components can be quickly and therefore inexpensively replaced following an accident.
The foam impact absorbers of the plastic bumpers are made from energy-absorbing polypropylene which deforms during a collision and absorbs the entire impact energy up to a maximum speed of 4 km/h, leaving the downstream metal components undamaged. After such a collision the plastic automatically reverts to its original shape.
Boot lid: opened and closed at the touch of a button
Mercedes-Benz offers a convenient remote control function for the boot lid: pressing a button on the electronic ignition key or in the switch array on the interior panel of the driver’s door unlocks the boot lid, which automatically swings open with the assistance of two electric motors and two springs. To close it, the driver operates a key in the boot lid or interior door panel to set the electric motor in motion again. This causes the boot lid to lower slowly and engage the lock under its own weight, after which it is secured by a servo locking system.
Paintwork: more scratch-resistant and shiny thanks to nano-technology
With its innovative, more scratch-resistant clearcoat based on nano-technology, Mercedes-Benz has made a major contribution to long-term quality and outstanding value retention. This innovative paint system is standard on the new CLS-Class, and is used for both metallic and non-metallic paint finishes.
Thanks to remarkable advances in the science of nano-technology it has been possible to integrate ceramic particles measuring less than one millionth of a millimetre into the molecular structure of the paint binder. These particles initially float freely in the clear liquid paint, but form a network during the drying process in the paintshop, creating a very dense, regular structure on the surface of the paintwork. These nano-particles achieve a three-fold increase in the scratch-resistance of the paint finish, ensuring a visibly improved and lasting sheen.
Corrosion protection: 70 percent of all sheet metal galvanised
The 30-year MobiloLife warranty which Mercedes-Benz offers its customers in many European countries is based on a sophisticated system of corrosion protection: galvanised sheet metal accounts for 70 percent of the bodyshell weight. The electrolytically galvanised sheets are additionally coated with an organic paint containing rust-resistant zinc pigments. This paint has a layer thickness of only two to four micrometres, however it stands up to the stresses arising during pressing and spot-welding and provides lasting protection.
For the front end, side members, A-pillars and the inner shells of the doors, bonnet and boot lid Mercedes-Benz even uses sheet metal with an organic coating on both sides, and also preserves the cavities in the body structure by means of a special wax.
Thanks to full plastic cladding of the underbody it is possible to dispense with the PVC underbody protection used previously. This effectively protects the body against stone chipping and also has an important aerodynamic effect, as it allows the airstream to pass beneath the vehicle body with practically no turbulence.
Aerodynamics: successful fine-tuning in the wind tunnel
The underbody cladding therefore contributes to the good Cd figure of only 0.30 for the vehicle body. At 0.66 square metres the wind resistance of the body is also extremely favourable, with resulting beneficial effects on fuel consumption and performance.
Aerodynamic data for the CLS-Class
CLS-Class
Coefficient of drag Cd 0.30
Frontal area A 2.22 sq. m.
Wind resistance (Cd x A) 0.66 sq. m.
These good results are not only due to painstaking, detailed work in the wind tunnel, but also to intensive cooperation between the designers and aerodynamics engineers which began right back at the early styling phase for the new four-door Coupé. This meant that the design specialists were able to take major factors into consideration from the very start when creating the body lines, leading to a highly respectable overall result. Examples:
The shape of the front and rear aprons not only characterises the sporty, elegant nature of the new CLS-Class, but also proves to be very aerodynamically efficient.
The design of the bonnet allows a practically unimpeded airflow around the windscreen wipers.
The designers and aerodynamics specialists precisely coordinated the recessed C-pillars – a typical Mercedes design feature – with the shape of the rear end, ensuring optimal guidance of the airstream.
The attractively integrated spoiler lip at the rear of the boot lid makes hardly any visual impact, however it has a very positive aerodynamic effect in reducing both wind resistance and lift.
In addition the Mercedes specialists have developed a number of technical features which contribute to the good aerodynamics of the new CLS-Class:
The smooth panelling on the engine compartment, transmission and underbody directs the airstream beneath the vehicle and prevents turbulence.
Aerodynamically shaped plastic elements in front of the front wheel arches improve the airflow across the front axle linkages. In addition the spring links on the rear axle feature aerodynamic cladding.
Mini-spoilers in front of each wheel reduce dynamic pressure at the tyres and improve the airflow around the wheels.
The engineers in Sindelfingen have achieved a two-fold benefit with many of these detailed aerodynamic measures, namely reducing wind resistance while at the same time improving handling stability at high speeds or when braking. By means of the underbody cladding, wheel spoilers, air deflectors in front of the front wheel arches and the spoiler lip on the boot lid, the specialists have influenced the aerodynamic forces acting perpendicular to the direction of travel, which tend to lift the body on its springs at high speed. The result is a favourable coefficient of lift at the front and rear axle, namely CAV 0.10 to 0.13 (front) and CAH 0.11 to 0.13 (rear, provisional figures).
The speed-related body lowering function of AIRMATIC DC (standard in the CLS 500) also improved handling stability: at higher speeds the air suspension system automatically lowers the body by 15 millimetres at both axles, ensuring even better roadholding – and a more favourable fuel consumption.
Headlamps: projection technology with high lighting power
In the field of lighting technology the new CLS-Class shines with one of the most efficient headlamp systems available: as standard equipment, H7 halogen lamps provide low-beam lighting behind clear plastic lenses.
The headlamps are based on the latest projection technology, which occupies less space in the front end than a conventional reflector system, allows the designers more latitude and also offers perceptibly more lighting power.
On request bi-xenon headlamps are available in which only one lamp is required for main and low beam: in contrast to main-beam lighting when the full light output is used, whenever low-beam is selected, a shutter is inserted between the lamp and the lens which obscures part of the beam of light. With bi-xenon headlamps on their main-beam setting, the H7 spotlights also come into play. A dynamic headlamp range adjustment unit automatically adapts the angle of the light beam to the prevailing body attitude and also compensates for brief dips and rises caused whenever the vehicle brakes or accelerates: this forms part of the optional bi-xenon equipment package.
In both versions - halogen and bi-xenon technology – the standard Headlamp Assist function automatically switches on the headlamps whenever the CLS Coupé drives into a tunnel or underground car park – provided the rotary light switch is in the "Auto" position.
Road safety: significant advances with Active Light System and cornering light function
Mercedes-Benz combines bi-xenon headlamps with the newly developed cornering light function and steering-dependent lighting, making a further important contribution to visibility and safety in the hours of darkness:
Thanks to the automatic cornering light function, cyclists, pedestrians and other road users can be seen more clearly when cornering, and even tight bends are more efficiently illuminated when driving slowly. Whenever the low-beam headlamps are on, and up to a maximum speed of 40 km/h, the cornering lights switch on automatically when the driver uses the indicators or turns the steering wheel. When turning right or taking a right-hand bend the right cornering light is switched on, and vice versa. At this point, the cornering light illuminates the area to one side of the vehicle to an angle of up to 65 degrees and a distance of up to 30 metres, thereby lighting up areas of the road which would normally not be visible with conventional headlamp technology. The intelligent electronic control unit does not switch the cornering lights on or off abruptly: instead they fade in or out with a dimmer function. This operates more rapidly when fading in than when fading out. This gives the human eye time to adapt to a change in lighting conditions. There is intelligence at work again in the design of the cornering lights. This skilful arrangement enables Mercedes-Benz to combine two lighting functions in a single housing: the halogen lamp in the cornering light also acts as a fog lamp.
The Active Light System causes the headlamps to follow the steering movements made by the driver, immediately pivoting the light beam to the relevant side when entering a bend. This improves road illumination by up to 90 percent: whereas the normal illumination range when entering a bend with a radius of 190 m is approx. 30 m, this increases to 55 m with the Active Light System. The system operates in both the low and high-beam functions and continuously adapts itself to the vehicle speed. A microprocessor integrated into the electronic data network of the Coupé controls the Active Light System on the basis of continuous information concerning on steering angle and vehicle speed.
The attractively styled rear light clusters of the new CLS-Class also use the latest lighting technology: a total of 54 light-emitting diodes (LEDs) ensure instant attention when braking, while modern HP bulbs are used for the rear lights. HP stands for High Performance and indicates that these bulbs have a particularly long operating life. While conventional bulbs need to be replaced after an average of approx. 70,000 kilometres, HP bulbs last much longer.
The standard features of the CLS-Class also entry/exit lights integrated into the exterior mirror housings, which are switched on when the doors are opened or the central locking system is operated by remote control and illuminate the ground area next to the Coupé - a helpful feature that increases the safety and convenience of passengers when entering or leaving the vehicle.
Windscreen wipers: aero system with continuously variable wipe intervals
Mercedes engineers have developed an efficient two-arm wiper system with special kinematics for the new CLS-Class: while the wiper arm on the driver’s side moves around a fixed axis, its counterpart on the passenger side executes an additional lifting movement to wipe an even larger area of the windscreen. The system is powered by a reversing motor whose drive shaft periodically changes its direction of rotation, thereby also driving the wipers on the reverse sweep. This means that the wiping frequency and intervals can be continuously varied according to need – either manually or with the help of the standard rain sensor.
The two wiper blades were developed in the wind tunnel and are therefore known as aero wipers. Instead of the articulated retention system used for conventional wiper blades, in which the rubber blades are claw-mounted, the aero wiper consists of a one-piece rubber section with an integral spoiler and externally mounted spring rails. The advantages are significantly better wiping quality and less noise, which is particularly noticeable when driving at high speed.
Safety: Comprehensive concept
Occupant protection on three levels during a frontal crash
Adaptive airbags and belt force limiters
PRE-SAFE preventive occupant protection system
Stuttgart, Mar 02, 2004
The innovative occupant protection systems in the new CLS-Class also underpin the traditional Mercedes-Benz claim to leadership in the field of car safety. This means that thanks to a comprehensive concept, the four-door Coupé is prepared for virtually every conceivable eventuality and offers its occupants an outstanding level of all-round protection.
Large deformation zones at the front end optimise the flow of forces during a collision, leaving the passenger cell substantially undamaged even during severe accidents. As in all recent Mercedes car models, impact protection is based on a three-stage concept which is wholly or only partly initiated depending on the severity of the accident:
Up to approx. 4 km/h impact speed the plastic bumpers and foam elements absorb the impact energy and regain their original shape after the crash.
Up to approx. 15 km/h impact speed the front cross members and the crash boxes on the front-end module absorb the energy, so that the structure behind them remains undamaged. Thanks to repair-friendly connections, the elements making up the front-end module can be replaced at low cost.
At more than 15 km/h impact speed, occupant protection is assured by a sophisticated system of structural members. These include the robust steel sections above the wheel arches, which form a second tier of side members and ensure efficient load distribution during an offset collision. They are braced against the A-pillars. The lower side members in the front-end structure feature an additional, third skin on the inside surface. These direct the impact forces into the robust firewall cross member, which acts together with the pedal floor members to ensure that the energy is widely distributed right to the transmission tunnel and outer side members. Like the lower elements of the front axle, the integral member, to which parts of the front axle, the steering gear and engine mountings are attached, is also involved in energy absorption during a severe frontal impact. If the Coupé is in a frontal collision with a one-sided overlap, the special impact-absorbing elements in front of the side members perform an important function. They brace the wheels at an early stage in the collision, so that impact forces can also be transferred to the lateral body structure along this path.
The fact that 47.5 percent of all the sheet metal components in the bodyshell are of high-strength steel alloys is a further indication of the high safety level in the new CLS-Class. These high-strength components provide maximum dynamic resistance despite a low material thickness.
Passenger cell: effective all-round occupant protection
The passenger cell is designed to withstand all kinds of accident situations – frontal or rear collisions, side impacts or roll-overs – and provides a very robust structure for a very high level of occupant protection even at high impact speeds. The sophisticated floor structure, robust longitudinal and cross members, flexurally rigid struts, three-walled A, B and C-pillars and tubular reinforcements in the B-pillars form the strong backbone of this "protection zone".
In the event of a rear-end collision, the same three-phase, speed-related safety concept as is found in the front-end structure of the new CLS-Class take effect, based on the plastic bumper, a flexing cross member and deformable crash boxes. The rear side members consist of a continuous, closed box section with specifically graduated material thicknesses, and are able to absorb large forces. The plastic fuel tank is installed in a crash-protected location in front of the rear axle.
Front airbags: two-stage control depending on accident severity
Mercedes-Benz has already been making a major contribution to improved occupant safety for many years, with intelligent restraint systems which adapt to the current occupant and accident situation. The new CLS-Class likewise features such an adaptive protection concept. The aim of these measures is to reduce the loads acting on the occupants even further during serious accidents, and to optimise the protective function during accidents in the medium speed range.
The sensors of the restraint system are supplemented with two upfront sensors on the radiator cross member. Their remote positioning in the front end of the body enables them to detect the severity of a collision even earlier and with greater accuracy than the central crash sensor on the transmission tunnel. The information from the upfront sensors is used by the electronic control module to shorten the time that elapses between the moment of impact and the deployment of the belt tensioners, to adapt the operation of the belt force limiters to the severity of the collision and to trigger the airbags both earlier and in two stages, depending on the situation. During a minor frontal impact the electronic control unit only ignites one stage of the two-stage airbag gas generators, and the airbag inflates more gently. Should the control unit detect a severe frontal collision, however, it deploys the second stage of the gas generator after a slight delay. As a result, the airbag inflates at a higher pressure to provide the occupants with the level of protection required in a collision of this severity.
Side airbags: combination of windowbags and sidebags
The restraint system in the new CLS-Class offers two further, highly effective systems with standard-fitted sidebags in the front seat backrests as well as windowbags. These complement each other in their protective effect: while the sidebags mainly protect the thorax area of the occupants, the windowbags deploy from the front to the rear roof pillar like a large curtain, providing head protection over a wide area. The windowbags and belt tensioners are also activated in the event of a roll-over.
PRE-SAFE: pioneering system for preventive occupant protection
The preventive occupant protection system PRE-SAFE will also be available for the new Mercedes Coupé in future. This is based on the principle of prevention: PRE-SAFE is able to detect critical driving situations in advance and intervenes to prepare both the occupants and the vehicle for an impending collision:
The seat belts of the driver and front passenger are tensioned as a precaution.
If the front passenger seat is in an unfavourable position in terms of longitudinal adjustment and cushion/backrest angle, it is moved to a better position.
The sunroof is automatically closed.
Thanks to these precautionary PRE-SAFE measures the vehicle occupants are in a better seating position even before the accident occurs, enabling the seat belts and airbags to work more efficiently. If the accident is avoided, the preventive tensioning of the seat belt is automatically relaxed and the front passenger is able to adjust the seat to its previous position.
With this unique system Mercedes-Benz has responded to accident research findings which indicate that more than two thirds of all traffic accidents follow critical driving situations – skidding, emergency braking or sudden evasive action – which allow the conclusion to be drawn that a collision is imminent. This valuable time before a crash, which can be several seconds, has previously been wasted for passive occupant protection purposes – well-proven protective systems such as seat belts, airbags or belt tensioners have only gone into action during an impact.
In contrast, PRE-SAFE is able to detect impending accident situations in good time, and uses the time before a possible collision to put preventive safety measures in place. In other words, PRE-SAFE gives the vehicle "reflexes". Just as every living being reacts reflexively to the threat of danger and takes preventive measures, this innovative safety technology activates systems almost instantly to reduce the risk of injury to the occupants.
Early accident detection is possible because PRE-SAFE represents a so far unique synergy of active and passive safety. It is linked to the anti-lock , whose?braking system, Brake Assist and the Electronic Stability Program ESP sensors constantly send information concerning the current driving situation to the control units. The micro-processors use these data to recognise hazardous driving manoeuvres and respond within milliseconds by issuing the appropriate commands. Mercedes-Benz also uses these sensor data for the preventive occupant protection system PRE-SAFE, opening up a new dimension in car safety.
For Mercedes-Benz this system is the logical continuation of its long-pursued philosophy of practically focused car safety. Based on the knowledge and experience of the in-house accident research department, PRE-SAFE builds a bridge between active and passive vehicle safety.