The new EQE: passive safety

Apr 13, 2022
Stuttgart

The principles of Integral Safety, in particular accident safety, apply regardless of the platform. Like all other Mercedes-Benz models, the EQE therefore has a rigid passenger cell, special deformation zones and modern restraint systems.

The fact that the EQE is based on an all-electric architecture also opened up new design possibilities for its safety concept. It meant, for example, that a favourable location could be chosen for the installation of the battery, in a crash-protected area in the underbody. And because there is no large crankcase on board, the behaviour in a frontal crash could be modelled even better. In addition to the standard crash tests, the car's performance in various additional load situations was verified and extensive component tests carried out at the Vehicle Safety Technology Centre (TFS). Internally the new body structure bears the designation "flat-floor concept".

Material concept: the backbone of accident safety

The body structure is predominantly made of steel. To reduce weight, the steel grades were selected to match the respective load. Hot-formed, ultra-high-strength steels are used in the critical areas. Furthermore, some components of the bodyshell are made of aluminium, for example the energy absorbers in the sill and the shock absorber strut brackets at the front and rear. Doors, bonnet, boot lid and front wings are also made of aluminium.

Frontal impact

The energy management of the EQE in a frontal impact meets several requirements: in the case of minor damage, an inexpensive repair is possible. And in the event of more serious accidents, the concept takes the protection of other road users into account in addition to self-protection, as is the case with every Mercedes‑Benz model.

In the front area behind the plastic trim of the bumper and an absorber foam are removable crash boxes. In the case of minor accident severity, these can be replaced at low cost. A large-area crossmember connects the crash structures in such a way that the impact energy can also be dissipated to the other side of the vehicle in the event of a staggered accident. In a severe frontal impact, the energy is then mainly absorbed by the two longitudinal members, supplemented by an upper and a lower load path. The upper load path is supported by the damper leg bracket, the lower load path is formed by the integral carrier. This houses the lower suspension links, torsion bar, steering gear and front eATS.

Side impact

In principle, in a side impact only a very small deformation path is available. Highly stable structures in the EQE therefore serve to protect the occupants, but also the battery. The outer shell of the side wall assembly is formed by the one-piece outer panelling. The inner shells are partly made up of several components, with particularly large areas for the nodal points between the pillars, roof frame and side members according to the potential loads. For a side impact, the sills are designed in a shell construction made of steel with an aluminium insert profile that is specifically deformable to avoid critical damage to battery modules as far as possible. The lateral battery profiles additionally support the sill when supporting the front wheel. At the same time, they reinforce the floor structure and thus the passenger cell. The B-pillar is designed to provide particularly good protection for occupants in the event of a crash.

Rear impact

The EQE is also equipped for rear impact. Unlike the EQS, the EQE has a boot lid, which allows the use of a crossmember from suspension strut tower to suspension strut tower. Flanged crossmembers with crash boxes under the bumper panelling help to distribute the energy of a one-sided impact to both rear side members. Thanks to the specific design of the structural components and the rear axle carrier, the requirements in terms of battery safety have been fulfilled.

Rollover

In a rollover it is particularly important that sufficient headroom is retained. At Mercedes-Benz, strict global standards in terms of survival space are applied, which are checked by means of the roof-drop test, for example. Of course, these also apply to the EQE.

High-voltage (HV) system: automatic shut-off in accidents

The battery, high-voltage cables and other HV components have been designed and protected in such a way that they meet the high safety requirements of Mercedes-Benz in the event of an accident. You can read more about this in the chapter "Under the magnifying glass: high-voltage safety".

The multi-stage protection concept of the high-voltage (HV) system has already proven itself in the other Mercedes-EQ models. In case of danger, the HV system can be automatically switched off and disconnected from the battery. A distinction is made between a reversible and an irreversible shut-off. The reversible shut-off occurs in more minor accidents. Afterwards, reconnection of the high-voltage system is possible if an insulation measurement automatically carried out by the vehicle does not detect a fault. This means that slightly damaged vehicles can still be moved. Only in severe accidents, in which as a rule the vehicle is in any case no longer capable of being driven, is the high-voltage system irreversibly switched off. It can no longer be activated without repair. When switching off, it should be ensured that no injury-relevant residual electrical voltage is present in the high-voltage system outside the battery within a few seconds.

There are also shut-down points where emergency teams can deactivate the high-voltage system manually. In addition, the EQE has crash monitoring as standard during the charging process, to enable this to be terminated in the event of an accident.

Acoustic presence indicator: special sound as a warning for pedestrians

The electric car-specific innovations include an acoustic presence indicator (standard). This allows pedestrians to better perceive the EQE at low speeds. One sound generator sits weatherproof in the front right wheel arch and in the rear underbody respectively. A Mercedes-EQ-specific sound is produced up to approx. 30 km/h vehicle speed. Initially it becomes louder and higher with increasing speed. This change allows conclusions to be drawn about the driving status (braking/acceleration).

Above 20 km/h the sound is then already gradually reduced, since the vehicle can then be perceived by its tyre and wind noise. If the speed drops from a higher speed back down to 30 km/h, the sound is faded in again. When reversing, an intuitively recognisable interval tone sounds regardless of the speed.

Modern restraint systems

In addition to driver and front passenger airbags, a knee airbag on the driver's side is also standard. It protects the legs from contact with the steering column or instrument panel in a severe frontal crash. This is to prevent or mitigate injuries.

The standard window airbags can reduce the risk of head impact with the side window or penetrating objects. In the event of a serious side collision, the window airbag on the side of the impact extends from the A- to the C-pillar like a curtain over the front and rear side windows. If a rollover is detected, the window airbags can be activated on both sides.

Vehicles in certain countries also have a centre airbag to meet new rating requirements. It positions itself between the driver and front passenger in the event of a severe side impact, depending on the direction of impact, severity of the accident and occupancy status, and can thus further reduce the very low risk of head-to-head contact. The centre airbag is integrated into the backrest of the driver's seat on the side of the centre console.

Side airbags in the rear are available as optional equipment. They can supplement the effect of the standard windowbags on the outer rear seats.

The EQE has i-Size child seat attachments as standard on the two outer rear seats. With two anchors each between the seat back and the seat cushion, corresponding child seats are installed particularly quickly and securely. Top tether attachment points behind the rear head restraints provide additional support.

PRE-SAFE®: precautionary preparation for an accident

The PRE-SAFE® preventive occupant protection system is also available for the EQE. Together with the familiar precautionary measures in the event of a potential frontal and rear-end crash, PRE-SAFE® Impulse Side (available in conjunction with the Driving Assistance package Plus) forms a kind of virtual crumple zone that extends around the vehicle.

As only a limited crumple zone is available in a side impact, PRE-SAFE® Impulse Side (availability depending on selected equipment) can move the affected driver or front passenger away from the danger even before the crash as soon as the system detects that a side collision is immediately imminent. For this purpose, air chambers in the side bolsters of the front seat backrest are inflated in fractions of a second.

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