0 The new Mercedes-Benz S-Class: Extended protection in the rear - Top safety level in the rear

Mercedes-Benz is further reinforcing the safety system for passengers in the rear with the seat belt buckle extender, the beltbag and the cushionbag. In contrast to many other manufacturers, the seat belts in the rear already include belt tensioners and belt force limiters today.

Both systems were furthermore developed with a particular view toward new markets in Asia. There, the occupancy rate in the rear is as much as 30 percent, making it much higher than in Europe.

Reducing the belt slack: the seat belt buckle extender

With the seat belt buckle extender, an electric motor extends and retracts the belt buckle automatically. In this way, buckling up can be made more convenient, and any belt slack in the area of the pelvis and thorax can be reduced even when belting up so that passengers are secured more firmly in both the sideways and the lengthways direction. The seat belt buckle extender fits in with Mercedes-Benz's integral safety concept. In keeping with an all-embracing approach to safety, this concept covers all phases of automotive safety: from safety while driving through safety in hazardous situations and protection in the event of an accident to minimisation of the consequences of accidents.

The innovation is classic Mercedes-Benz, improving safety and comfort in one. This is because fastening seat belts in the rear is also made much simpler: the seat belt buckle emerges from the upholstery when the rear doors are opened and is provided with an illuminated insertion slot. Simplifying use of the seat belt in this manner may increase the percentage of rear passengers who buckle up. It also makes it easier to assist children or people who require help in fastening their seat belts.

The seat belt buckle extender is furthermore integrated in the PRE-SAFE® anticipatory safety system. This means that whenever PRE-SAFE® becomes active in critical driving situations or when the system detects the vehicle approaching other objects at a critical speed, reversible belt tensioning is also performed in the rear via the seat belt buckle extender function. The restraint system and the passengers are thus better prepared for a possible accident situation. In this way, the seat belt buckle extender complements the pyrotechnic belt tensioning which has featured as standard on all outer rear seats in Mercedes-Benz vehicles for many years now, and is triggered in the event of an impact exceeding a certain severity.

The seat belt buckle extender is a motorised belt buckle which can be extended upwards by up to 50 millimetres and retracted by up to 40 millimetres. The belt buckle is attached via a cable to a nut which runs on a spindle, translating the electric motor's rotary movement into a linear movement.

The following functions are carried out by means of this movement:

- Seat belt reminder/fastening aid: the seat belt buckle extender is provided with an illuminated insertion slot, attracting the occupants' attention to the buckle. Particularly in the dark, this makes it easier to find the belt buckle and connect it with the seat belt tongue. In addition, the belt buckle is extended by up to 50 millimetres when occupants enter the rear of the vehicle, to facilitate fastening of the seat belt. When extended, the belt buckle is more readily accessible and it is easier to insert the belt tongue. Both functions are activated when the doors are opened by passengers entering the rear of the vehicle.

- Minimised belt slack: after the belt tongue has been inserted, the belt buckle returns to its original position. This reduces any belt slack in the area of the pelvis and thorax, and ensures that the belt fits correctly in the pelvis area.

- PRE-SAFE® function for rear occupants: the seat belt buckle extender is fully integrated in the vehicle's PRE-SAFE® system. Whenever PRE‑SAFE® becomes active in critical driving situations or when the system detects the vehicle approaching other objects at a critical speed, reversible belt tensioning is now also performed in the rear via the seat belt buckle extender function. The restraint system and the passengers are thus better prepared for a possible accident system. In contrast to its extended position to facilitate fastening of the seat belt, the belt buckle is retracted by approx. 40 millimetres instead. This reversible function tightens the belt on the occupant by up to 80 millimetres. In addition, the belt buckle branches off at a lower point at the occupant's hip. This reduces the risk of the pelvis submarining under the belt. Securing the occupants more effectively in this way can reduce the strain to which they are exposed in the event of an accident. The seat belt buckle extender complements the pyrotechnic belt tensioning which has featured as standard in Mercedes-Benz vehicles for many years now and is triggered in the event of an actual impact.

- POST-SAFE functionality: to facilitate the rescue of occupants and to assist rescue personnel or the occupants themselves in unbuckling the seat belts, the belt buckle is extended once again as soon as the doors are opened by rescue personnel or the occupants themselves after the system has detected a crash and the vehicle has come to a standstill, provided that the on-board electrical system is intact. The raised belt buckle position allows better access from inside the vehicle, while illumination of the buckle draws attention to the opening mechanism.

An airbag for seat belts: the beltbag

The beltbag is an inflatable seat-belt strap that reduces the load on the ribcage in a head-on collision and is thus able to reduce the risk of injury to passengers in the rear. Because dummy measurement technology is not capable of quantifying the benefits resulting from a wider belt strap, such as the lower force exerted on occupants in the rib area in particular, the safety experts at Mercedes have been working intensely with virtual human models too, as such computer-generated models make it possible to obtain detailed findings on the biomechanical strain during a collision.

Should the crash sensors detect a severe frontal impact, the airbag control unit will trigger deployment and inflation of the beltbag. A gas generator then inflates the multi-layered belt strap with Velcro seams to nearly three times its normal width. The resulting larger surface area is able to better distribute the force acting on the seat occupant, thereby reducing the risk of injury.

The beltbag is used in exactly the same way as a conventional seat belt. The belt strap's design is different from that of the standard belt though, and received top marks in practical trials for being extremely comfortable to wear and for its extra-soft belt strap edge.

An airbag for the seat: cushionbag

If the S-Class is equipped with the Executive seat (reclining seat), the seat includes the innovative cushionbag as standard. The airbag is located under the seat cushion upholstery, but on top of the plastic seat shell, which is moved by the seat mechanisms. This means that the airbag is always in the right position relative to the occupant.

In an accident, with the occupant in a reclined position on a flat seat cushion, without additional measurers there would be a danger of the pelvic area sliding beneath the seat belt (submarining). This can be prevented by the cushionbag, as it raises the front section of the seat cushion upholstery. The airbag is only activated if the seat is in the reclined position during a crash. It is not activated in the upright position, as there is then no danger of submarining.

Credits: Daimler AG

Copyright © 2013, Mercedes-Benz-Blog. All rights reserved.

Detail: The new Mercedes-Benz S-Class: Extended protection in the rear - Top safety level in the rear

0 The new Mercedes-Benz S-Class: Extended PRE-SAFE® protection - Prevention is better than cure

Ten years ago, Mercedes-Benz unveiled a groundbreaking safety concept in the form of the PRE-SAFE® anticipatory occupant protection system, which has been undergoing continuous refinement ever since. Now, the safety pioneer is increasing protection levels once again.

The new PRE-SAFE® functions can help to prevent collisions with pedestrians and vehicles in front in city traffic, defuse dangerous situations caused by traffic behind and enhance the protection offered by the seat belts.

The PRE-SAFE® Brake now also can detect pedestrians and initiate autonomous braking to avoid a collision at speeds up to 50 km/h.

PRE-SAFE® PLUS can recognise an imminent rear-end collision and warn the following traffic by activating the rear hazard warning lights at a high frequency. If the danger of a collision persists, the system can also firmly apply the stationary vehicle's brakes and thus minimise the risk of whiplash injuries by reducing the forward jolt caused by the impact. This additionally can reduce the risk of secondary accidents. Immediately before impact, the PRE-SAFE® anticipatory occupant protection measures, especially the reversible belt tensioners, are deployed.

With PRE-SAFE® Impulse, the driver and front passenger are pulled away from the direction of impact by their seat belts at an early phase of the crash before the resulting occupant deceleration sets in. This can substantially reduce the risk and severity of injuries in a frontal collision.

Including pedestrian detection and City Brake function: BAS PLUS with Cross-Traffic Assist and PRE-SAFE® Brake

Pedestrian detection has been added to the BAS PLUS with Cross-Traffic Assist and PRE-SAFE® Brake functions, while autonomous braking for vehicles in front has undergone a major enhancement too.

Thanks to the combination of stereo camera and radar sensors, it is now possible to detect pedestrians in front of the vehicle. Visual and acoustic warnings are triggered when a hazard is spotted. If the driver then reacts by braking, the braking power will be boosted by BAS PLUS with Cross-Traffic Assist as the situation requires, right up to a full brake application. Should the driver fail to react, the PRE-SAFE® Brake triggers autonomous vehicle braking. The PRE‑SAFE® Brake with pedestrian detection is active up to approx. 72 km/h, and is able to prevent collisions with pedestrians autonomously up to an initial speed of 50 km/h.

Evaluations of GIDAS accident data by Mercedes-Benz indicate that this new technology could avoid six percent of pedestrian accidents and reduce the severity of a further 41 percent. The operating range of the autonomous braking function for stationary vehicles has been optimised so that rear-end collisions can likewise be avoided at speeds of up to 50 km/h.

BAS PLUS with Cross-Traffic Assist and the PRE-SAFE® Brake with pedestrian detection rely on the same sensors employed for the adaptive cruise control DISTRONIC PLUS with Steering Assist: the new stereo camera plus the multistage radar sensor system.

Safety measures in response to an imminent rear impact: PRE-SAFE® PLUS

PRE-SAFE® PLUS offers an extension of the familiar occupant protection measures in situations where traffic behind poses a danger. A radar sensor in the rear bumper monitors the traffic behind the vehicle. If the risk of an impact from the rear is detected, the rear hazard warning lights are activated with a high frequency (5 Hz) to alert the driver of the vehicle behind (not on vehicles with USA/Canada coding). If the vehicle is stationary and the driver wishes it to remain so (e.g. by applying the brakes, activating the HOLD function or engaging "P" using the selector lever), if the danger of a collision persists PRE-SAFE® PLUS comes to the driver's aid by increasing the brake pressure in order to keep the vehicle firmly braked. In addition, immediately before impact the PRE-SAFE® anticipatory occupant protection measures, especially the reversible belt tensioners, are deployed.

Keeping the vehicle firmly braked when another vehicle hits it from behind greatly reduces the strain placed on the occupants, such as the risk of whiplash injuries. At the same time, it serves to protect other road users too by restricting uncontrolled vehicle movements after the initial impact that could lead to secondary collisions, such as running into a vehicle in front or colliding with pedestrians or other road users at junctions.

Intelligent countermovement: PRE-SAFE® Impulse

Mercedes-Benz is extending the front seat belt's protective function with the introduction of PRE-SAFE® Impulse: at an early phase of the crash, before the resulting deceleration sets in, the front occupants are pulled away from the direction of impact and deeper into their seats by their seat belts. By the time the accident enters the phase when loads peak, the extra distance they are retracted by can be used while dissipating energy in a controlled fashion thanks to additional force limiting in the belt buckle. Pre-acceleration and force limitation allow the occupants to be temporarily isolated from the effects of the crash, significantly reducing the risk and severity of injuries in a frontal collision.

With PRE-SAFE® Impulse, the seat belt strap can be retracted by pyrotechnic means at all three belt anchorage points, both in the pelvis and chest area, and released again with controlled force at the buckle and in the shoulder area. The fundamental difference compared to conventional belt tensioners is that the force for retracting the belt strap is maintained more consistently for a much longer time. The deployment logic fires the seat belt system's belt tensioners progressively depending on the seriousness of the accident. In this way, the tensioning force can be adapted as required. The PRE-SAFE® Impulse system is integrated in the seat's structure and supplements the pyrotechnic reel tensioner with a pyrotechnic buckle and anchor fitting tensioner including central gas generator.

Credits: Daimler AG

Copyright © 2013, Mercedes-Benz-Blog. All rights reserved.

Detail: The new Mercedes-Benz S-Class: Extended PRE-SAFE® protection - Prevention is better than cure