The present invention relates to a vehicle-mounted crash energy absorbing arrangement that includes at least one inflatable airbag which is normally in a collapsed state but which can be quickly inflated to form an external protection with respect to part of the vehicle in the event of the risk of the vehicle colliding with another object, and means for detecting when such risk is imminent and activating bag inflation means.

The use of vehicle-mounted crash energy absorbing bags is known from GB-1 367 954, GB-1 371145 and DE 2 020 360 for instance.

These known arrangements include one or more energy absorbing bags mounted on one or more sides of a vehicle. The bags are normally kept in a collapsed state tucked away behind a vehicle fender, bumper, for instance. This enables the external shape and the standard outer dimensions of the vehicle to be maintained, which is important with respect to parking the vehicle and other vehicle maneuvers.

Gas-filled bags of this kind will successively absorb the energy generated by a collision with another object and therewith lessen the extent to which the vehicle is damaged and also reduce the risk of injury to the driver and passengers of the vehicle.

One problem with crash bags of this nature is that in order to obtain the best effect the bags should be inflated to different pressures in different situations, depending upon the speed at which the vehicle is moving at the moment of collision, among other things. A bag which is too softly inflated will result in poor protection or in no protection at all, especially when the vehicle is travelling at a high speed, and will not in such case prevent direct contact of the vehicle with the object with which it is in collision. On the other hand, if the bag is inflated to an excessively high pressure, no appreciable crash

energy will be successively absorbed and the result will be relatively similar to the result obtained in the event of a direct collision between vehicle and object, particularly when the vehicle is travelling slowly. The bag would rupture at high vehicle speeds.

Accordingly, the main object of the present invention is to provide a vehicle-mounted crash-energy absorbing arrangement that includes at least one inflatable crash bag or airbag which enables crash energy to be absorbed gradually over a wider range of vehicle speeds.

The invention is based on the realization that this object can be achieved by dividing the crash bag into at least one outer and at least one inner chamber that have mutually different properties, so that crash energy will be transferred from the outer chamber to the vehicle via the inner chamber.

An inventive arrangement of the kind defined in the first paragraph is therewith particularly characterized in that the bag includes at least one outer and at least one inner chamber which are so arranged that the force generated by impact of the vehicle with an object will first be received by the outer chamber which transfers the force to the inner chamber from which a resultant force is transferred to the vehicle, and in that when activated, said inflating devices function to generate a lower pressure in one chamber than in the other chamber.

Such an arrangement will reduce the collision force by deforma¬ tion firstly of the chamber that has the lowest pressure, while compressing the gas in this chamber, and thereafter by common deformation of both chambers when the pressures in both chambers are mutually equal, so that only a minor part of the original crash energy will be transferred to the vehicle. The chambers will thus function as an extension of the deformation zone incorporated in the majority of modern cars.

It is preferred that at least one of the chambers includes valve means that can be opened to the ambient atmosphere, and that these valve means are designed to open in response to a pre-determined pressure in their associated chamber. This enables the chamber to absorb larger forces in a relatively controlled fashion, e.g. in conjunction with a high speed collision, without risk of rupturing or giving rise to a catapult effect.

Suitably both chambers are provided with valve means that can open to the surroundings and that will open in the two chambers at mutually different pressure levels. In this regard, each chamber may incorporate several valve means that can open to the surroundings, wherewith different valve means in each chamber can open at different pressure levels.

This in combination with the chambers being inflated initially to different pressures enables the arrangement to be adapted to function as an effective crash energy absorbing deformation zone in a number of very different situations.

To enable the speed at which an approaching vehicle moves and its distance from the vehicle to be indicated both quickly and precisely, the arrangement conveniently includes electronic speed and distance detecting means which operate with ultra¬ sonic waves, light waves or electromagnetic waves. This enables inflation of the bag to be initiated when an approaching vehicle is located at a given distance from the vehicle, this distance being determined by the relative speed between said object and said vehicle so as to ensure that the bag will be inflated prior to the collision occurring.

Other features of the invention are set forth in the following claims.

The invention will now be described in more detail with reference to exemplifying embodiments thereof and also with

reference to the accompanying drawings.

Figure 1 illustrates from above a car which incorporates the inventive crash-energy absorbing arrangements. Figures 2 and 3 illustrate schematically the manner in which an inventive crash bag can be mounted at the rear of a car. Figure 4 illustrates schematically means for inflating both chambers of the crash bag. Figures 5 and 6 illustrate an inflated bag from one side and from above respectively.

Figures 7, 8 and 9, 10 illustrate compression of the bag at two collision stages, seen from one side and from above respective¬ ly. Figures 11 and 12 illustrate the car of Figure 1 from one side and from above respectively, subsequent to inflation of an inventive crash bag mounted at the front of the vehicle.

The car 1 shown in Figure 1 is equipped with front and rear crash bags which are folded-up in an inactive state and tucked away behind respective front and rear fenders 2, 3 of the vehicle. The vehicle may also be equipped with crash bags that are tucked away along the sides 4 and 5 of said vehicle in their respective rest states.

Although not shown, the car is also equipped with means for sensing the distance from an object with which a collision risk is imminent. These detecting means are also suitably designed to sense the relative speed between car and object. When there is risk of the car colliding with a foreign object, the detecting means activate inflation of one or more vehicle- mounted crash bags. This activation must take place in good time before the moment of collision, so that the bags will be inflated before the collision takes place.

The detecting means are suitably electronic and operate with ultrasound. Short range radar or opto-electronic sensors using laser may also be used for instance. Detectors of this kind are

already known and are included, for instance, in collision inhibiting or collision warning systems for vehicles. It is also possible to determine the relative speed of an object with this type of detector, wherewith inflation of the bag is initiated at a distance from said object and at a time determined by the speed relative thereto. Mechanical detectors can also be used in certain cases.

The bags can be inflated in response to a pyrotechnical, gas- generated reaction initiated upon indication of an approaching collision. Alternatively, the bags can be inflated from one or more gas containers that contain non-inflammable gas under high pressure. In this case, inflation is commenced by penetrating a sealing element on the gas container.

One type of serious injury caused in car accidents are the so- called whiplash injuries caused to the cervical vertebrae when a vehicle is involved in a tail-end collision among other things. The invention will be described below in conjunction with a crash bag that is intended to prevent or substantially reduce such injuries.

In accordance with the present invention, there is mounted on the rear of the car a crash bag that is inflated immediately prior to another vehicle colliding with the rear of said car.

Figures 2 and 3 illustrate schematically a folded bag 6 stowed in a space, for instance in the rear fender 3 of the car 1. The reference numeral 7 identifies two ultrasonic sensors which transmit ultrasonic waves and receive the echoes that are reflected by a vehicle approaching from behind. The number of sensors or detectors 7 installed and the positioning of said sensors is chosen to achieve the best possible coverage.

When the sensors 7 establish that the relative speed and distance between a vehicle approaching from behind and said car is such that a collision is unavoidable, the sensors send an

activating signal to a device 8 which initiates inflation of the bag 6.

When the bag is comprised of an outer and an inner chamber that are intended to be inflated at different pressures, the car will conveniently be equipped with two gas-generating devices 9 and 10 having respective separate gas conduits 11 and 12 that deliver gas to respective bag chambers, as indicated in Figure 4. The device 8 is able to initiate the two gas-generating devices simultaneously or with a short time difference therebetween, such that, e.g. , inflation of one chamber will be commenced slightly earlier than inflation of the other chamber. When the gas-generating devices are mounted in the car luggage space, or boot, the car passengers will not be injured or influenced negatively by the explosive noise that occurs in conjunction with gas generation.

Figures 5 and 6 illustrate what takes place when the car 1 equipped with a crash bag is about to be hit by another car 13 from behind. Because the sensors 7 have established that the speed of the car 13 and its distance from the car 1 are such that a collision is unavoidable, the gas generating devices 9 and 10 have been activated. The bag, which comprises an outer chamber 14 and an inner chamber 15, has been filled with gas to a pre-deter ined pressure. Although the chambers 14 and 15 have been shown separated from one another for the sake of clarity, it will be understood that they normally constitute two chambers separated by a partition wall in a common bag.

The inner bag 15 may be connected to associated gas-generating device 9 via a fixed pipe 16 or like conduit. The outer chamber 14 is connected to an associated gas generator 10 via a flexible hose 17 that can be collapsed in a concertina fashion, suitably a bellows-like hose, and which is drawn out as the bag inflates as a result of the expansion of the inner chamber 5, if this chamber is the first to be inflated. The ends of the pipe 15 and hose 17 are fitted with one-way valves, suitably

flapper-type valves, as shown at 18. The chambers 14 and 15 are inflated to mutually different pressures, wherewith the inner chamber 15 is suitably inflated to a lower pressure than the outer chamber 14. In the event of a collision, the speed of the colliding vehicle will first be gently retarded while compres¬ sing the chamber 15. When the pressures in the two chambers are identical, the chambers will be compressed commonly to achieve full retardation of the colliding vehicle and absorb the collision energy.

To ensure that retardation of the colliding vehicle is effected in a controlled fashion, at least one chamber, the inner chamber 15 in Figures 7 and 8, is equipped with a number of valve means that allow gas to escape to the surroundings when the pressure in the chamber reaches a given value. In the case of the embodiment illustrated in Figures 7 and 8, the chamber is equipped with two types of valve means 19, 20, which are designed to open at different pressure levels. The openings in the valve means may have different sizes, wherewith the openings in the valve means that open at a higher pressure will have a larger area than the openings in the valve means that open at a lower pressure. The arrangement may include more than two types of valve means, and the number of valve means of each type may be chosen in accordance with requirements.

Figures 9 and 10 illustrate an alternative embodiment in which the outer chamber 14 may be provided with valve means 21 and valve means 22 respectively for allowing gas to flow to the surroundings at pre-determined pressure level. Alternatively, both chambers may be provided with valve means that can open at mutually different pressures for instance. As in the earlier case, each chamber may include valve means that open at mutually different pressure levels.

This provides the designer with a very large number of possible variations. For instance, by determining the inflation pressures for the two chambers and the pressure levels at which

gas shall escape to the surroundings and the volume of gas permitted to escape at each individual pressure level, the designer is able to adapt the crash protection so that, in practice, it will function as an extended deformation zone over a broad range of collision forces. Highly effective protection can be achieved with respect to said whiplash injuries among other injuries in this way. By using the combination of two chambers that are inflated to different pressures, the speed of a colliding vehicle can be retarded gently, both in the case of high and low speeds. The interplay between the two chambers is thus highly significant to the invention.

As mentioned in the introduction, crash bags of this kind can also be mounted at the front of the car, see Figures 11 and 12, and optionally also along the sides thereof. Figures 11 and 12 illustrate an inventive crash bag subsequent to inflation of the two chambers 14 and 15. In this embodiment, the bag has been divided into a plurality of juxtaposed smaller bags each of which includes an outer and an inner chamber. The inner chambers of respective bags have a configuration such as to enable said bags to project in under and up over the car hood, or bonnet, so as to be held securely in place at the moment of collision. The laterally outermost bags are constructed for corresponding purposes, so that they extend at least partially along the sides of the car.

The bags of all embodiments are made of a flexible but non- stretchable material, suitably a reinforced plastic material. The bag surfaces that face towards the ground are suitably provided with a reinforcement layer 23 which prevents the bags from being torn to pieces as they scrape against the ground.

Although the invention has been described above with reference to illustrated embodiments thereof, it will be understood that these embodiments can be varied in several respects within the scope of the following claims. For instance, each bag may be divided into more than two sequential chambers if considered

suitable. Instead of using an outer bag that is inflated to a high pressure, this outer bag may, alternatively, be inflated to a lower pressure than the inwardly lying bag. In addition to two separate gas-generating devices, it is also possible to use one single gas-generator together with a pressure regulator that determines the pressures in the two chambers.