Mercedes Benz

OFFICIAL PRESS RELEASE

Stuttgart, Germany, Mar 03, 2009

Passive safety: Preventive action and on-demand protection: exceptional occupant safety based on intelligent systems and designs

* Test programme: 150 crash tests and over 17,000 crash simulations

* PRE-SAFE®: even more comprehensive anticipatory occupant protection

* Body structure: larger front and rear crumple zones

* Restraint systems: seven airbags and four seat-belt tensioners as
standard

* Pedestrian protection: Active Bonnet with reversible actuator control

The pioneering work carried out by Béla Barényi enabled Mercedes-Benz to develop the basic principles of passenger-car safety in the 1940s and 1950s. And these principles still apply to this day. Barényi's ideas first came to fruition in the "Ponton" (three-box body) Mercedes (model series W 120) around 56 years ago in autumn 1953. This precursor to the E-Class was the world's first car to feature a crash-stable floor assembly, which enhanced occupant safety in the event of a frontal or side impact.


Model series W 111/112 with the distinctive tail fins provided the next milestone in the field of safety technology. From 1959 onwards, these Saloons were the first models into which Mercedes-Benz incorporated front and rear crumple zones. In the event of an accident, these zones absorb energy in a predetermined manner and distribute the impact forces, thus greatly reducing the forces exerted on the occupants. The precursor to the E-Class from the 1960s, the "tail fin" Mercedes (W 110), likewise featured this safety body.

Béla Barényi's successors at the Mercedes-Benz Technology Centre in Sindelfingen have continued to further develop the concepts devised by their mentor based on the latest development and calculation methods and the use of state-of-the-art bodyshell materials. Their level of dedication has reached a new pinnacle with the new E-Class. During the course of its many years of development to date, the Saloon has come through over 150 crash tests and, if the complex pedestrian protection calculations are included, a total of more than 17,000 realistic crash test simulations. The test programme included around 30 different crash tests, which the Saloon had to pass in order to achieve the prescribed ratings and gain world-wide approval, not to mention nine exceptionally demanding, in-house impact tests, some of which go well beyond the statutory requirements. Only cars that pass these tests receive the highest accolade in automotive safety: the Mercedes star.

PRE-SAFE®: anticipatory system incorporating additional protective measures

In the new E-Class, occupant protection actually begins in the phase leading up to a possible accident. The Mercedes PRE-SAFE® invention activates protective measures if there is a risk of an accident, allowing the seat belts and airbags to deploy with maximum effect in the event of a collision. This multi-award-winning technology is fitted as standard in the E-Class, where it offers even more functions than previously.

The Mercedes PRE-SAFE® system takes its lead from nature in that it activates protective measures as a precaution to protect the occupants and the car from an imminent collision, just as living things react instinctively and search for cover when they are in danger. PRE-SAFE® is able to recognise an impending accident because it offers an intelligent synergy of active and passive safety features. It is networked to Brake Assist and the Electronic Stability Program (ESPÒ), whose sensors recognise potentially dangerous driving situations and then transmit this information to the electronic control units within milliseconds. PRE-SAFE® also uses these sensor data for anticipatory occupant protection.

What's more, the 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 new E-Class features even more measures aimed at preventing an imminent accident than its predecessor:

Whereas PRE - SAFE ® previously responded to emergency or panic braking – in other words when the driver hit the brake pedal reflexively – the system in the new E-Class can also be activated if the optionally available DISTRONIC PLUSsystem's short- and long-range radars have detected an impending head-to-tail collision and a certain level of deceleration is exceeded when braking. The occupants are prepared for the collision by tensioning of the seat belts and repositioning of the optionally available, fully electrically adjustable front-passenger seat, enabling the seat belts and airbags to be activated and deployed with maximum effect.

The newly developed active multicontour seat (optional, also see page 67) ensures that the driver and front passenger are seated even more securely, thereby limiting dangerous whiplash movements of the upper body in the event of an accident. If the PRE-SAFE® control unit detects a critical driving situation, it activates the air chambers in the seat cushions and backrests instantaneously. These then envelope the seat occupants and lend them extra support. Tests at the Mercedes-Benz Technology Centre have shown that this PRE-SAFE® function and preventive belt tensioning increase the distance between the shoulder and the inner door lining by up to 40 millimetres at a lateral acceleration of 0.6 g, enabling the sidebag to fulfil its protective function even more effectively.

When installed in combination with the Driver Assistance package, which includes DISTRONIC PLUS and Brake Assist PLUS, PRE-SAFE® also uses the information provided by the short-range radar sensors in the front bumper to tension the front seat belts at the very last moment before an unavoidable collision, thus reducing the forces exerted on the driver and front passenger during the crash.

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 anticipatory occupant protection can be. In the case of belt tensioning, for example, the precautionary 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.

When installed in combination with the Driver Assistance package, which includes DISTRONIC PLUS and Brake Assist PLUS, PRE-SAFE® also uses the information provided by the short-range radar sensors in the front bumper to tension the front seat belts at the very last moment before an unavoidable collision, thus reducing the forces exerted on the driver and front passenger during the crash.

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 anticipatory occupant protection can be. In the case of belt tensioning, for example, the precautionary 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: 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 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 level.

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, has been 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 twice as thick.

Materials: around 72 percent of all body parts made from high-strength steel

Key aspects of the safety concept at the heart of the new E-Class include intelligent design and meticulous material selection. More so than ever before,
Mercedes-Benz has given preference to ultra-high-strength steel alloys because they offer maximum strength whilst minimising weight and, therefore, are essential for meeting the strict safety and durability requirements.

Around 72 percent of all the bodyshell panels for the new E-Class are made from these grades of steel – a new record in passenger-car development. These ultra-high-strength, high-tech alloys, which boast three to four times the tensile strength of conventional high-strength steel grades, account for around eight percent of the weight. They are used at points where the material can be exposed to exceptionally high stresses during an accident – as a material for the B-pillars and the side roof frames to provide side impact protection, for example, or at the rear to produce a robust crossmember.

If these sophisticated alloys were not used, far more material would be required in order to meet the stringent safety requirements. The B-pillar is a perfect case in point: the body components which have to absorb high forces and transfer these into the body structure in the event of a side impact consist of sheet-metal shells and an extensive reinforcement which reaches as far as the upper edge of the belt deflector. One of the shells and the reinforcement are made from ultra-high-strength, hot-formed steel. Were they made using conventional sheet steel, however, the B-pillars would be more than a third heavier. In other words, the ultra-high-strength, high-tech alloy enhances safety whilst also reducing weight.

Doors: sophisticated design for a high level of crash safety

The doors also predominantly consist of high-strength and ultra-high-strength steel and, therefore, likewise enable the new E-Class to provide a even higher level of crash safety than the outgoing model – by some considerable margin. The inner door shells comprise steel blanks reinforced by additional sections in the area of the frame and the waistline as well as at bumper height. Additional members made from ultra-high-strength cold-formed steel, located in the lower area between the doors' inner and outer shells, complement the design measures implemented to enhance side-impact protection. Each of the rear doors houses two of these diagonally arranged sectional panels.

On top of all this, the Mercedes engineers have devoted special attention to the hinges by developing mounting areas with a high load-bearing capacity to create a robust side-structure assembly that provides the occupants with effective protection in the event of a collision.

Aluminium bonnet, wings and boot lid

Finally, the intelligent material concept involved the specifically targeted use of aluminium and plastic, both of which help to save weight above all. Aluminium is used for the bonnet, front wings, boot lid, parcel shelf and various load-bearing sections, for example, while the front end is a hybrid construction made 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.

Body torsional stiffness increased by over 30 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 body, which have to withstand extremely high loads. These were specifically reinforced to prevent road-induced vibrations from being transferred to the body and so as not to spoil the driving experience.

A reliable indicator of the excellent cumulative effect of these measures is the body's static torsional stiffness, which has been increased by over 30 percent compared to the outgoing model.

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

The passenger cell of the new E-Class 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 sheet-metal plates that either undergo flexible rolling or are welded together by laser beam 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 middle blank forms the tunnel – the actual backbone of the passenger cell. Here the thickness of the custom-designed panels varies between 0.7 and 1.1 millimetres, or between 1.55 and 2.0 millimetres in the case of the additionally fitted tunnel reinforcements, depending on the stresses and loads to which they are exposed.

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 further 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 that has come through the toughest of crash tests

Multi-piece side members and a robust, flexible 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 E-Class 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.

As is usual at Mercedes-Benz, the fuel tank is located in a protected position beneath the rear seats, in other words in front of the rear axle and, therefore,
outside of the impact zone.

Restraint systems: seven airbags as standard

With seven airbags fitted as standard, not to mention four seat-belt tensioners, belt-force limiters and NECK-PRO crash-responsive head restraints for the driver and front passenger, the new E-Class 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.

In addition, rear sidebags can be ordered as optional extras, giving the new E‑Class at total of up to nine airbags for occupant protection.
Three-point inertia-reel seat belts with belt tensioners and belt-force limiters are fitted as standard for the driver, the front passenger and the occupants of the outer rear seats.

The occupant restraint system for the new E-Class at a glance:

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. This setup ensures that the heads of the driver and front passenger are protected at an early stage.

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, the cornering light function and Night View Assist PLUS 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 new E‑Class are based on these high standards. Top of the bill is a newly developed 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 Active Bonnet technology has a further crucial benefit in that it 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 Saloon's exterior contours and lowering the engine, shock absorber towers, reservoirs and control units. Like all the latest Mercedes models, the front bumper on the new E‑Class incorporates a flush spoiler lip with a bracing function, which provides a pedestrian with uniform cushioning at an early stage in a collision.