WO1998015435A1

WO1998015435A1 - Improvements relating to vehicle airbag deployment

Info

Publication number: WO1998015435A1
Application number: PCT/GB1997/002673
Authority: WO
Inventors: Graeme Peter Smith
Original assignee: Ford Motor Company Limited; Ford Werke Ag; Ford France S.A.; Ford Motor Company
Priority date: 1996-10-05
Filing date: 1997-09-29
Publication date: 1998-04-16
Also published as: GB9620823D0

Abstract

An airbag deployment system (1) including an impact sensor (3) coupled to an airbag actuator (5) which comprises a pre-arm mechanism coupled to the airbag actuator, the pre-arm mechanism comprising a sensing system (7) arranged to detect the presence of an object in a predetermined area relative to the vehicle to produce a potential collision signal which is fed to a pre-arm control system (9) which pre-arms the airbag actuator (5) in readiness for an impact detected by the impact sensor (3) of the airbag deployment system.

Description

IMPROVEMENTS RELATING TO VEHICLE AIRBAG DEPLOYMENT

Field of the Invention

The invention relates to an improved vehicle airbag deployment system.

Airbags are recognised as an important breakthrough in the protection of vehicle occupants in the event of collision. Driver and passenger airbags are commonly used to protect the occupants of the front seat of a vehicle and further airbag applications are being proposed and introduced including side airbags and airbags for rear passengers.

Traditionally an airbag is actuated to operate once an impact has been sensed. Mounted within a vehicle are impact sensors which sense when a collision has occurred to trigger deployment of the airbag. Sensors are now being developed which detect the position of an occupant and identify the nature of the seat's occupant to allow the airbag actuator to be disabled in certain circumstances. These systems all depend upon the impact sensor within a vehicle operating after a collision has occurred to actuate the airbag.

A number of radar systems have been proposed for installation in motor vehicles for detecting objects around a vehicle. Transmitters and receivers are mounted upon the vehicle to detect the presence or approach of objects in a particular direction to be used to help to warn an occupant of a potential collision. Typically, such systems have been developed for collision warning and parking aids.

Summary of the Invention

According to the invention there is provided an airbag deployment system including an impact sensor coupled to an airbag actuator which comprises a pre-arm mechanism coupled to the airbag actuator, the pre-arm mechanism comprising a sensing system arranged to detect the presence of an object in a pre-determined area relative to the vehicle to produce a potential collision signal which is fed to a pre-arm control system which pre-arms the airbag actuator in readiness for an impact detected by the impact sensor of the airbag deployment system.

The method of sensing the presence of an object approaching the vehicle may be infrared or ultrasonic but preferably the sensing system is a radar sensing system.

In such a system, in theory it would be possible for the airbag actuator to be disabled until a potential collision signal has been received by the pre-arm control system. However, such a system would require an override to be included in the event of a collision occurring due to impact with an object from a position outside the predetermined area scanned by the radar transmitter or receiver.

Preferably however the airbag actuator has two stages in its operation, a pre-arm stage, where the airbag state is changed from non operating to a ready to fill mode, and an actuation stage where the release of the gas to fill the airbag is initiated. The use of the two stages means that the second actuation stage can be made quicker, to reduce the time between impact and the airbag protection being available .

The predetermined area in relation to the vehicle in which the presence of an object is to be detected depends on the nature of the airbag to be deployed. The driver and passenger airbags will operate in different collision conditions than a side airbag, for example.

Preferably the radar sensing system is arranged to detect not only the presence of an object in the pre-determined area relative to the vehicle but also the direction of movement of the object relative to the vehicle body and the velocity of movement relative to the vehicle to more accurately predict the potential of a collision. In such an arrangement the pre arm control receives signals indicative of the position, speed and direction of relative movement of the object and from this indicates if a collision is possible .

Preferably the system includes at least two radar transmitters and receivers, which are impulse radar transmitters and receivers. In this specification, the term 'impulse radar' is intended to encompass any radar signal of short radio frequency without a carrier wave, and includes radar sometimes referred to as 'broadband radar'. A typical impulse radar system is described in published specification WO90/13048.

Because the spectrum of the radiated signal is very broad, the radar cannot be said to operate at a particular frequency. By virtue of transmitting only a short pulse, the reflection from the target arrives after a delay corresponding to the distance from the target.

Such a system can be used to track accurately the path of an object outside the vehicle to accurately predict the potential of a collision, its likely position and time before impact.

Although the radar sensing system may be used in a vehicle, purely for use in the airbag deployment system, the invention is applicable with particular advantage to a vehicle in which the radar sensing system is used also for providing driver information and warnings, such as a parking aid. The advantage is that the same sensors are multifunctional . Preferably the radar sensing system is part of a collision warning system as described in copending PCT application number GB97/01728. Such a system is able to look around the vehicle to detect obstacles about the vehicle and to use the signals detected in a number of collision warning modes.

Brief Description of the Drawings

An airbag deployment system in accordance with the invention will now be described, by way of example only, with reference to the accompanying drawings, in which :-

Figure 1 is a schematic block diagram of the airbag deployment system;

Figure 2 is a schematic view of the predetermined area scanned by the radar receiver; and,

Figure 3 is a schematic plan view of a vehicle illustrating the position of the sensors and receivers.

Description of the Preferred Embodiment

The airbag deployment system 1 illustrated in the drawings includes an impact sensor 3 coupled to an airbag actuator 5. A pre-arm mechanism comprises a radar sensing system 7 includes at least one radar transmitter and receiver arranged to detect the presence of an object in a predetermined area relative to the vehicle to produce a potential collision signal which is fed to a pre-arm control 9 which pre-arms the airbag actuator 5 in readiness for an impact detected by the impact sensor of the airbag deployment system.

The impact sensor 3 is standard, the choice of which will be apparent to the skilled addressee of the specification. The airbag actuator is non standard since it has two operating modes, one putting the airbag mechanism into standby, pre- armed mode ready for impact, and the second to initiate operation .

The radar system 7 comprises four sensors 11 shown in figure 3 mounted at the corners of the vehicle in the region of the bumper. Each sensor 11 comprises an impulse radar transmitter and receiver. This arrangement of four sensors allows the envelope around the vehicle to be monitored. The predetermined areas which need to be monitored for actuation of side airbags, and for driver and passenger airbags are shown in figure 2.

The radar sensing system monitors continually the zones of concern illustrated in figure 2 for intrusion by other vehicles or other obstacles . The predetermined areas are front of vehicle, rear of vehicle, drivers side and passenger side. The sensors 11 are used in pairs to track the trajectory of targets within their field of view. Time to impact is calculated using knowledge of relative velocities of the vehicle and target. If it is determined that a collision greater than a predetermined threshold speed is highly likely given the current dynamics of the situation, and the current driver actions, then a trigger signal (the pre-arm signal) is given to the airbag actuator to arm it in preparation for impact.

Claims

1. An airbag deployment system 1 including an impact sensor 3 coupled to an airbag actuator 5 which comprises a pre-arm mechanism coupled to the airbag actuator, the pre-arm mechanism comprising a sensing system 7 arranged to detect the presence of an object in a pre-determined area relative to the vehicle to produce a potential collision signal which is fed to a pre-arm control system 9 which pre-arms the airbag actuator 5 in readiness for an impact detected by the impact sensor 3 of the airbag deployment system.

2. A system according to claim 1, in which the sensing system 7 is a radar sensing system.

3. A system according to claim 1 or 2, in which the airbag actuator 5 has tow stages in its operation, a pre-arm stage, where the airbag state is changed from a non operating to a ready to fill mode and an actuation stage where the release of gas to fill the airbag is initiated.

4. A system according to any one of the preceding claims in which the sensing system 7, detects the direction and velocity of movement of an object relative to the vehicle to more accurately predict the potential of a collision.

5. A system according to claim 2, in which the sensing system 7 includes at least two impulse radar transmitters and receivers .

6. A system according to any one of the preceding claims, in which the sensing system is used also to providing driver information and warnings .