The new Mercedes-Benz GLE Coupé: Body shell: Weighty advantages, lightweight design

Dec 5, 2019
Stuttgart

The body shell of the new GLE Coupé largely shares its structure with the GLE SUV. The development focused on the high requirements on the rigidity of the body shell and on the noise insulation, which benefit the handling, safety and comfort. A host of lightweight construction measures were employed in order to keep the vehicle weight as low as possible at the same time.

For certain assemblies, the body shell of the new GLE Coupé combines high-strength sheet steel with lightweight materials such as aluminium where they achieve the desired characteristics. The bonnet and front wings are made of sheet aluminium, the strut towers at the front and rear axles are made of die-cast aluminium, and the side members at the rear are in part reinforced with die-cast aluminium. All components are sized optimally in order to achieve the desired strength at a low weight.

The floorpan of the passenger cell uses a so-called tailored rolled blank. These metal sheets are rolled to different thicknesses, so that the finished stamped component has the ideal wall thickness in every area. Large wall thicknesses only occur where they are really needed, e.g. in the area of the transmission tunnel that forms the backbone of the floorpan and greatly influences the rigidity of the body shell in a crash.

The main differences of the body shell structure of the coupé are the wheelbase shorter by 60 mm, and the larger tailgate. Because the latter has a larger cross-section than that of the SUV, the coupé is fitted with additional structural foams in the rear roof frame, which increase the torsional rigidity. The floorpan and the rear end of the plug-in hybrid variant were reinforced further in light of the weight of the battery and in order to protect it from damage in a crash.

For the greatest possible rigidity, the body shell components are for the most part bonded and spot-welded, and the flanges connecting the parts are designed to allow joining with minimal tension so that tolerances between the panels are compensated during assembly.

A haven of quiet

The rigidity of the body shell structure of the new GLE Coupé is a key reason for the high level of noise and vibration comfort. It ensures that the typical excitation frequencies of wheels and powertrain can be dampened effectively and do not produce resonance vibrations. The load application points at the bearings of the powertrain and the axle carrier newly developed from scratch have a particularly rigid design and a new geometry. This means that these assemblies and their vibrations are very effectively isolated from the body shell.

The dampening of sound transmitted from the powertrain to the passenger cell has also been optimised. The firewall insulation to the engine bay is injection moulded rather than deep drawn and its wall thicknesses and basis weights are dimensioned to ensure that there are no acoustic weak points, but also to avoid dragging around unnecessary weight. The same is true for the insulation on the vehicle floor and the wheel arches. The measures are rounded off by insulation membranes, foamed-filled cavities and vibration-damping vehicle carpets.

The quiet is even more pronounced in the GLE Coupé when the optional Acoustics Comfort package is ordered. This includes laminated safety glass with a sound and infrared-absorbing membrane, as well as numerous additional insulation measures right up to special tyres. They are fitted with a layer of foam on the inside of the treads to absorb low-frequency noises originating in the tyre itself, and reduce the rolling noise.

Crash safety up to the latest standards

Protecting the occupants from the consequences of an accident is one of the most important development goals of Mercedes-Benz. In-house safety standards are applied in all models which in many cases go well beyond the legal requirements. Especially the crash-related requirements are aligned to the so-called Real Life Safety philosophy. These take findings from in-house accident research into account in the development specifications, e.g. the roof drop test. Alongside verification of crash behaviour, all Mercedes-Benz vehicles undergo additional component tests at system level. For many years PRE-SAFE®, the preventive occupant protection system, has supplemented the classic design measures. The result is all-round protection that commences well before an accident and is still effective afterwards, as in the new GLE Coupé.

The basis for occupant protection is the body structure with a particularly rigid passenger cell, whose strength is suited to the deformation resistance of the front-end and rear-end structures. To this end all structures within the vehicle body are optimised in terms of dimensions and materials, either by virtue of material strength or the wall thickness of the panels. This gives the occupants sufficient protective space and protects them from excessive deceleration forces, which are as far as possible reduced by intelligently responding restraint systems.

In addition to the passenger cell, the area of the body structure that accommodates the fuel tank is of particularly rigid design to limit the consequences of a serious collision. To this end, the new GLE Coupé has die-cast aluminium components with steel inserts which limit deformation of this area in front of the rear axle even in very severe accidents. The transmission tunnel and rear end are constructed even more rigidly for the battery of the plug-in hybrid.

Restraint systems: state-of-the-art belts and airbags

The GLE Coupé has three-point inertia-reel seat belts with belt tensioners and belt force limiters on all outer seats. The centre belt in the second row is a standard three-point seat belt. In addition, reversible PRE-SAFE® reel tensioners are available for the front seats, so that the belts can be pre-tensioned as a precaution in certain hazardous situations. For child seats, the two outer rear seats have anchorages for i‑Size or ISOFIX child seat attachment systems, depending on the country.

For severe frontal collisions, the airbags in the new GLE Coupé include a knee airbag for the driver, a driver airbag and a front passenger airbag. As standard, a sensor system in the front passenger seat automatically deactivates the front passenger airbag when a rear-facing child seat or an unoccupied seat is detected. The window airbags can also be activated in a frontal collision involving a lateral component.

During a severe lateral collision, only the airbags on the impact side are normally activated: Window airbags are available as a head protection system extending down from the roof to cover the side windows between the A, B and C-pillars. This enables the passengers on the outer rear seats to be protected as well. Combined thorax-pelvis side airbags are also available for the driver and front passenger, and optionally also side airbags for the outer rear seats.

In addition the airbag control unit is equipped with rollover sensors. These can activate belt tensioners and window airbags for example when a rollover is detected.

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