Mercedes Benz

OFFICIAL PRESS RELEASE

Stuttgart, Germany, Apr 22, 2009

Passive safety: Reflexes, airbags and actuators - Comprehensive commitment to comprehensive protection

*
PRE-SAFE® occupant protection for the first time in this vehicle category
*
Substantially enlarged front and rear crumple zones
*
Active Bonnet with reversible actuator control as standard


In the new E-Class Coupé, occupant protection actually begins in the phase leading up to a possible accident thanks to the Mercedes PRE-SAFE® invention, which is specified as standard for the two-door model. If there is a risk of an accident, the system activates protective measures as a precaution, allowing the seat belts and airbags to deploy with maximum effect in the event of a collision. This early accident detection is possible because PRE-SAFE® is an intelligent synergy of active and passive safety. It is linked to Brake Assist and the Electronic Stability Program (ESP®), whose sensors detect critical driving situations and send the relevant information to the electronic control units within a matter of milliseconds. PRE-SAFE® also uses these sensor data.

Anticipatory occupant protection is activated in the event of emergency braking or high lateral acceleration - heavy understeer or oversteer, for example, or fast, sudden movements of the steering wheel by the driver:

PRE-SAFE® In the event of emergency braking
· Driver and front-passenger seat belts are tensioned by means of electric motors
· Electrically adjustable front-passenger seat** is moved backwards or forwards into the optimum position whilst the cushion angle and backrest inclination are also optimised

PRE-SAFE® In the event of high lateral acceleration
· Side windows at the front and rear are closed
· Sunroof** is closed

*In addition to the emergency-braking measures
**Optional equipment

All PRE-SAFE®protective measures are reversible: if the accident is averted, the advance tensioning of the seat belts is halted automatically, and the occupants are able to reset the positions of the seats and the sunroof. The anticipatory
occupant protection system is then ready for action again straightaway.

The technology used for the PRE - SAFE ® belt tensioners enables a further protective measure to be activated as a precaution: once the driver and front passenger have put on their seat belts, the electric motors tighten the belt straps to reduce belt slack right at the start of a trip.

For the first time, PRE-SAFE® also uses the information provided by the short-range radar sensors (optional) in the front bumper to tension the front seat belts at the very last moment before an unavoidable collision, thus reducing the loads exerted on the driver and front passenger during a collision. This PRE-SAFE® function is literally the "ultima ratio" of anticipatory occupant protection, since the accident occurs around 200 milliseconds later.

Analyses performed during crash tests show just how important and effective this safety system can be. In the case of precautionary belt tensioning, for example, the measures mean that the driver and front passenger are held in their seats in the best possible position and so do not move forwards as much before the impact, thus reducing the load exerted on the head and neck area. These tests showed that the head was subjected to around 30 per cent less stress, while the Mercedes engineers recorded a reduction of around 40 per cent in the neck area.

Front-end structure: further enlarged crumple zone on four levels

Compared to the previous model series, the Mercedes engineers have enlarged the deformation zones substantially in the front and rear sections of the new E‑Class Coupé as well as improving the energy flows. The front crumple zone has four independently-acting impact levels, meaning that the forces can be distributed over a wide area while bypassing the passenger cell.

1) Sectional panels above the wheel arches form the upper side-member level. From here, the impact forces are channelled into the A-pillars and, subsequently, into the roof frame.
2) An aluminium crossmember connects the forward-extended side members and ensures that the forces are transferred to the side facing away from the impact. The crossmember and the forward-extended side members form the central impact zone.
3) The subframe to which the engine, steering and front axle are attached also serves as an impact level in the event of a frontal collision. It is made of high-strength steel and, depending on the engine variant, can be connected to the newly developed floor side members by means of special supporting tubes. As a consequence, the subframe can deform in a predetermined manner and absorb energy in the event of a crash on the one hand and channel high impact forces straight into the vehicle floor on the other.
4) The side skirts have been extended forwards to support the wheel and prevent it from entering the footwell in the event of an offset frontal collision. In order to provide specifically targeted front-wheel support and location, Mercedes-Benz has also developed special struts and additional energy-absorbing elements for the wheel arches. The struts are arranged diagonally and prevent the passenger cell from sinking in the event of an impact.

The firewall is a four-part construction. This design enables Mercedes engineers to vary the material thickness according to the level of vulnerability in an accident. As the load acting on the firewall during a frontal crash is greatest in the lower section, the sheet steel used here is almost 50 percent thicker.

Side wall: two-shell construction with reinforcements

Like the designers, the body specialists and safety engineers at the Mercedes-Benz Technology Centre (MTC) in Sindelfingen played a major part in creating one of the new E-Class Coupé's most attractive design features: the elegant side lines, along with the continuous strip of the side windows and the filigree roof pillars were only made possible thanks to a series of complex body manufacturing processes. All of which enables the Coupé to meet the most stringent of test requirements with respect to torsional stiffness and occupant protection, even though it has no upper B-pillars.

The single-piece sidewalls feature individually welded inner shells which provide strong, stiff cross-sections for the roof pillars, the roof frame and the side members. All of the load-bearing components feature additional panel reinforcements in the A-, B- and C-pillars, stretching across their entire length in each case. In addition to this, the A-pillars contain high-strength steel tubing which is capable of withstanding high impacts of the kind experienced in the roof-drop test.

Likewise, high-strength panelling is welded into the (non-visible) B-pillars which, together with numerous other reinforcement measures, provides effective resistance in the event of a side impact. Below the dashboard, there is also a solid square section which is bolted to both the A-pillars.

Materials: around 60 percent of all panels are made from high-strength steel

These examples show that, more so than ever before, Mercedes-Benz has given preference to ultra-high-strength steel alloys for the body construction because they offer maximum strength whilst minimising weight and, therefore, are essential for meeting the strict safety and durability requirements. Around two thirds of all the bodyshell panels for the new E-Class Coupé are made from these grades of steel. These ultra-high-strength alloys, which boast three to four times the tensile strength of conventional high-strength steel grades, account for around 20 percent of the weight (previous model: one percent). They are used in those areas where the material can be subjected to extreme stresses during an accident.

Mercedes-Benz's intelligent material concept also involves the specifically targeted use of aluminium and plastic, both of which help to save weight above all. Hence the front end, bonnet, front wings and boot lid of the new Coupé are made from aluminium, while the front end is a hybrid constructionmade from sheet aluminium and fibreglass-reinforced plastic. The front single-section aluminium crash boxes are inserted into the side members and bolted to them at the side. The other front-end components are likewise bolted together and can therefore be replaced cost-effectively following an accident. Glass fibre matting-reinforced plastic has been used to produce the spare-wheel well.

Passenger cell: custom-designed floor panels and robust load-bearing
sections

The passenger cell of the new two-door model is a robust structure which is virtually immune to deformation and keeps the passengers' survival space intact, even at high impact speeds, regardless of whether the collision is head-on, from the rear or from the side, or whether the vehicle rolls over. The use of high-strength steel and thicker panels plays as important a role here as the installation of additional load-bearing members.

The main floor assembly consists of custom-designed steel sheets that either undergo flexible rolling or are laser-welded and subsequently shaped. Flexible in this sense means that the high-strength steel can be processed in such a way that areas with different steel thicknesses can be produced within a single component. The extremely thick middle blank forms the tunnel - the actual backbone of the passenger cell. Other new features which are equally crucial for both occupant protection and the rigidity of the bodyshell include the continuous floor side members, the insides of which are reinforced with additional sections. Their front sections connect to the side members, thereby lengthening the load-bearing paths along which forces can be distributed in the event of an impact. At the rear, the floor side members extend as far as the crossmember beneath the rear seat unit to stabilise the entire floor structure.

The Mercedes engineers have also incorporated sturdy aluminium transverse sections - known as transmission tunnel braces - into the floor assembly. One is located beneath the transmission, and is designed to direct forces to the side of the vehicle facing away from the impact in the event of a side-on collision. The second forms a connection between the two side members. It likewise braces the floor assembly and is able to channel impact forces into the floor structure at an early stage following a side-on collision.

Rear-end structure has successfully passed the toughest of crash tests

Multi-piece side members and a robust crossmember made from ultra-high-strength steel form the key components of the rear-end structure. The rear side members are continuous, closed box sections with carefully graduated material thicknesses. These are able to absorb high forces, thereby making a decisive contribution to occupant safety in the event of a rear impact. The bolt-on flexible crossmember is manufactured using a flexible rolling process which likewise allows the material thickness to be varied as required. Accordingly, the material thickness on the outside of the crossmember - where impact loads are highest - is greater than on the inside. The new Coupé therefore also meets the world’s most stringent crash regulations where rear impact protection is concerned, for example the 80-km/h test in the US.

Typically for a Mercedes-Benz car, the fuel tank is located in a protected position beneath the rear seats, in other words ahead of the rear axle and, therefore, outside of the impact zone.

Body torsional stiffness increased by around 24 percent

As well as being a major reason behind the high level of impact resistance, this intelligently designed bodyshell enhances ride comfort or, to be more precise,
reduces noise and vibration. The Sindelfingen engineers paid particular attention to the connecting points between the chassis and the bodyshell, which are required to withstand very high forces. These were specifically reinforced to ensure that road-induced vibrations are not transferred to the body at the expense of driving enjoyment.

A reliable indicator of the excellent cumulative effect of these measures is the
body's static torsional stiffness, which has been increased by around 24 percent compared to the outgoing model.

Restraint systems: seven airbags as standard

With seven airbags fitted as standard, not to mention four seat-belt tensioners and belt-force limiters as well as NECK-PRO crash-responsive head restraints for the driver and front passenger, the new E-Class Coupé offers an even more extensive package of safety equipment than its predecessor.

The airbags, which can deploy in a matter of milliseconds in the event of an accident, include two adaptive airbags (for the driver and front passenger), a kneebag for the driver, two sidebags in the front-seat backrests and two large windowbags which extend from the A-pillar to the C‑pillar during a side impact. Plus the E-Class Coupé is the only coupé in this vehicle category to also offer the option of sidebags for the rear passengers.

Three-point inertia-reel seat belts with belt tensioners and belt-force limiters are fitted as standard for all the occupants. The Mercedes engineers have developed practical technology in the form of automatic belt feeders in order to make it even easier for the driver and front passenger to put on these seat belts. As soon as the occupants are seated, an electric motor extends plastic sections from the side panels on both sides, bringing the seat belt to within easy reach.

The belt feeders retract again once the seat belts have been put on; the belt feeder on the front-passenger side retracts automatically after around five seconds if the seat is unoccupied. A push of a button on the dashboard is all it takes to re-activate the belt feeders.

The standard occupant restraint system at a glance:


Crash-responsive head restraints for driver and front passenger

NECK-PRO is the name Mercedes-Benz has given to a crash-responsive head
restraint whose development, like that of PRE-SAFE® and other Mercedes innovations, is based on analyses of real accidents. NECK-PRO is an effective means of reducing the risk of whiplash injuries during a rear-end collision. If the sensor system detects a rear-end collision with a defined impact severity, it releases pre-tensioned springs inside the head restraints, causing the head restraints to move forward by about 40 millimetres and upwards by 30 millimetres within a matter of milliseconds.

Pedestrian protection: extensive raft of measures including Active Bonnet

The protection of those road users who are most at risk has always been a top priority during the development of Mercedes passenger cars. Smooth-surfaced bodies, energy-absorbing bumpers, flush-mounted door handles, laminated-glass windscreens, folding exterior mirrors and recessed windscreen wipers are pedestrian-protection measures that have been features of Mercedes models for many years. But, as ever, another top priority for the safety engineers is accident prevention. So systems such as Brake Assist and the cornering light function play crucial roles. Fitting Brake Assist as standard alone has reduced the rate of serious accidents involving collisions between pedestrians and Mercedes passenger cars by 13 percent.

The additional protective measures Mercedes-Benz has introduced for the E‑Class, including the new Coupé model, are based on these high standards. Top of the bill is an Active Bonnet, which enlarges the deformation area, reducing the risk of injury to pedestrians. This system, fitted as standard, includes three impact sensors in the front section as well as special bonnet hinges pretensioned and arrested by powerful springs. Upon impact with a pedestrian, the sensors send information to the electronic control unit which, in turn, activates two solenoids in the hinges instantaneously. These solenoids release the arresters so that the rear section of the bonnet is pushed upwards by 50 millimetres by means of spring force. It all takes just a fraction of a second.

As well as being extremely fast, the newly developed technology has a further crucial benefit: the Active Bonnet is reversible. If the bonnet is released in another type of collision, for example, Mercedes customers can reset it to its original position and, therefore, reactivate the system themselves, allowing them to continue driving.

In addition to this, the Mercedes engineers have increased the deformation space between the bonnet and the assemblies beneath it by raising the Coupé's exterior contours and lowering the engine, shock absorber towers, reservoirs and control units. As on all the latest Mercedes models, the front bumper incorporates a flush spoiler lip with a bracing function, which provides a pedestrian with uniform cushioning at an early stage in a collision.











Copyright © 2009, Mercedes-Benz-Blog. All rights reserved.