GB2318325A

GB2318325A - Vehicle occupant restraint system

Info

Publication number: GB2318325A
Application number: GB9621108A
Authority: GB
Inventors: Anthony Pike
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-10-10
Filing date: 1996-10-10
Publication date: 1998-04-22
Also published as: GB9621108D0

Abstract

A vehicle occupant safety system comprising one or more inflatable passive restraint means (2-9), a deceleration sensor (11) for detecting a sudden deceleration of the vehicle and generating a signal to initiate inflation of the passive restraint means; a frangible component (13) forming part of the vehicle and means (12) to shatter the frangible component upon inflation of the passive restraint means to reduce pressure within the vehicle. The shattering may be delayed until inflation of the restraining means is underway. The frangible component may be a window, such as a rear quarter light. The shattering means may be operated by a pyrotechnic charge.

Description

VEHICLE OCCUPANT RESTRAINT SYSTEM This invention relates to a vehicle occupant safety system wherein one or more air bags are employed to cushion and restrain the movement of a vehicle occupant in the event of a sudden deceleration of the vehicle, such as is caused when the vehicle is involved in a collision.

In known safety systems, the air bag is inflated in response to a signal from a deceleration (collision) sensor within a very short time interval after the signal is generated. A typical inflation time for the air bag is in the region of 10-30 milliseconds. This rapid inflation of the air bag causes a corresponding increase in the pressure within the space surrounding the vehicle occupants.

As the demand for increased safety of both vehicle drivers and passengers increases, safety systems have been developed which employ two or more air bags located in appropriate locations within the vehicle. However, the increased pressure generated within the vehicle by the increased number of air bags increases the risk of causing serious injury to the vehicle occupants such as injury to the ears.

The build up of pressure within the vehicle has restricted the number of air bags in vehicle safety systems and hampered the development of improved systems.

The present invention aims to overcome or at least mitigate the problems associated with known vehicle occupant safety systems.

According to one aspect of the present invention there is provided a vehicle occupant safety system comprising one or more inflatable passive restraint means, a deceleration sensor for detecting a sudden deceleration of the vehicle and generating a signal to initiate inflation of the passive restraint means; a frangible component mounted within the vehicle and means to shatter the frangible component upon inflation of the passive restraint means.

Preferably, the shattering means is responsive to a signal generated by the deceleration sensor.

Advantageously, the system further comprises electronic timing means to delay the operation of the shattering means until the inflation of the passive restraint means is underway.

Advantageously also, the frangible component is a window of the vehicle. Most preferably the window is a rear quarter light of the vehicle as this would avoid occupant ejection in the event of operation of the system.

Preferably, the shattering means is a protractive device mounted adjacent the frangible component within the vehicle.

Advantageously, the protractive device is operated by an impulsive force generated by a pyrotechnic charge within the body of the device. This allows the device to respond to the signal in less time than would be taken by a mechanical means.

Advantageously, the system further comprises an electronic control unit which monitors signals from the deceleration sensor and controls the inflation of the passive restraint means and the protractive device.

Preferably, the pyrotechnic charge is provided by a bridge wire sensitive compressed wire pyrotechnic charge which is ignited by a fuse within the protractive device upon receipt of an ignition signal from the control unit.

One embodiment of the present invention will now be described with reference to and as shown in the accompanying drawings in which: FIGURE 1 is a schematic representation of a passive restraint system for a vehicle according to one aspect of the present invention; FIGURE 2 is a cross-sectional view of a pressure relief device of the system of Figure 1; and FIGURE 3 is a schematic representation of the mounting position of the pressure relief device of Figure 2.

Turning now to the figures, there is shown a passive restraint safety system 1 for use in a vehicle. Figure 1 shows a schematic representation of the system. In the example shown air bags 2, 3 are indicated as fitted for the driver and passenger in the front section of the vehicle and also 4, 5 behind each of the driver and front passenger seats in order to cushion the movement of passengers in the rear of the vehicle should a sharp deceleration of the vehicle by necessary.

Further side impact air bags 6, 7 are also shown as mounted in the driver and front passenger doors and knee air bags 8, 9 are shown as mounted within the footwells of the driver and front passenger seats.

An electronic control unit 10 is mounted within the vehicle. It is envisaged that this unit will be an nonintrusive unit perhaps mounted within the engine compartment of the vehicle. The electronic control unit is electronically linked to each of the air bags 2-9 within the vehicle. One or more deceleration sensors 11 is provided within the engine compartment or alternatively may be mounted, for example, on a wheel axle of the vehicle to monitor the acceleration and deceleration of the vehicle or on the extremities of the front or rear bumper of the vehicle.

A pyrotechnic actuator 12 is mounted adjacent a window 13 of the vehicle. This is most preferably a rear quarter light of the vehicle as this both enables the actuator to be mounted without obstructing the view of the driver of the vehicle and is also the most inexpensive window within the vehicle to replace in the event of operation of the system as will be described below. The window 13 may conveniently be of any glass suitable for vehicle window, however, toughened glass is preferred as it can be readily shattered into small fragments.

The preferred actuator 12 for this system is a METRON (RTM) actuator of the DR2000 series available from ICI Explosives. The actuator is shown more clearly in Figure 2, and comprises a hollow body 14 housing a protractible piston rod 15. The piston rod is slideable within a channel 16 in the actuator body. The piston stroke may range from between 3 mm to 20 mm. The piston is shown in the Figures as having a flat end 17 although it may be pointed or profiled if required. The diameter of the channel 16 is slightly larger than the diameter of the piston rod 15 to allow the piston rod to slide into and out of the channel.

The actuator body 14 is provided with a chamber 18 behind the piston rod 15. The chamber is lined with a charge cup 19 into which a pyrotechnic charge 20 is inserted. The pyrotechnic charge may be provided a bridge wire sensitive compressed wire pyrotechnic such as, for example, barium styphnate or a mixture of titanium and potassium perchlorate or zirconium and potassium perchlorate. In the final example the mixture is preferably 60% zirconium perchlorate 40% potassium perchlorate.

Sealing means 21 are provided between the charge cup 19 and the channel 16 in which the piston rod is located. A cap 22 is mounted on the free end of the actuator body 14 remote from the piston rod. The cap provides a fuse head for the actuator and is secured to the body for example by soldering 23 in order to prevent the pyrotechnic charge being accidentally removed from the actuator body. The cap of the actuator is provided with a pair of contacts 24 to allow the actuator to be connected to the electronic control unit 10.

As shown in Figure 3 of the drawings, the actuator 12 is mounted adjacent to the rear quarter light 13 of the vehicle by a mounting pin 25. The actuator body 14 is mounted with the piston rod 15 of the actuator adjacent to the window.

In use of the system, when the vehicle experiences a sharp deceleration such as is caused when the vehicle is involved in a collision, the deceleration is detected by the sensor 11 which generates a signal which is passed to the electronic control unit 10. The control unit receives the signal, process it and generates a signal which is sent to the various air bags 2-9 in the vehicle and causes each air bag inflation mechanism to become operational. A typical response time for the air bags to begin inflating is in the range of 10 to 30 milliseconds.

As the air bags inflate, the pressure within the vehicle increases. Following a pre-set delay time of around 15 milliseconds, while the air bags 2-9 are still inflating, the electronic control unit 9 generates a further signal which is sent to the actuator 12 mounted adjacent to the rear quarter light 13 of the vehicle.

The actuator receives the signal which ignites the pyrotechnic charge 20 within the body 14 of the actuator.

As the actuator body is held against movement by the mounting pin 25, the explosion generated by the combustion of the charge forces the piston 15 to extend from the chamber 16 within the actuator and, due to the force of the charge and the speed of the actuator, which is generally in the order of 5 to 15 milliseconds, the piston rod is forced against the edge of the quarter light 13, shattering the window.

The speed of the actuator ensures that the rear quarter light is shattered whilst the air bags 2-9 are still inflating and therefore before the pressure in the vehicle exceeds a level which would cause injury to the occupants of the vehicle. The shattering of the rear quarter light breaks the closed space within the vehicle and allows the pressure within the vehicle to return quickly to ambient pressure.

The time delay in sending the signal to the actuator 12 allows the pressure within the vehicle to rise slightly thereby ensuring that when the rear quarter light 13 is shattered by the piston rod 15, the debris is displaced outwardly. Shattering of the rear quarter light upon inflation of the air bags, i.e before the pressure in the vehicle is increased, could result in debris being projected into the vehicle and causing injury to one or more of the vehicle occupants.

The total time for the air bags 2-9 in the vehicle to inflate is in the range of 40 to 60 milliseconds from receiving the signal from the electronic control unit. It will be appreciated that the actuator 12 will shatter the rear quarter light before the air bags are fully inflated which eliminates the risk of injury to the vehicle occupants from the pressure caused by the inflating of the one or more air bags in a standard safety system.

It is envisaged that the system described above could be fitted both to new vehicles as a standard system but could also be retro-fitted to older vehicles in order to improve the safety for the vehicle occupants during a collision.

Claims

1. A vehicle occupant safety system comprising one or more inflatable passive restraint means, a deceleration sensor for detecting a sudden deceleration of the vehicle and generating a signal to initiate inflation of the passive restraint means; a frangible component forming part of the vehicle and means to shatter the frangible component upon inflation of the passive restraint means to reduce pressure within the vehicle.

2. A vehicle occupant safety system according to claim 1, wherein the shattering means is responsive to a signal generated by the deceleration sensor.

3. A vehicle occupant safety system according to claim 1 or 2, wherein the system further comprises electronic timing means to delay the operation of the shattering means until the inflation of the passive restraint means is underway.

4. A vehicle occupant safety system according to any one of the preceding claims, wherein the shattering means is a protractive device mounted adjacent the frangible component within the vehicle.

5. A vehicle occupant safety system according to any one of claim 1-4, wherein the frangible component is a window of the vehicle.

6. A vehicle occupant safety system according to claim 5, wherein the window is a rear quarter light of the vehicle.

7. A vehicle occupant safety system according to any one of the preceding claims, wherein the protractive device is operated by an impulsive force generated by a pyrotechnic charge within the body of the device.

8. A vehicle occupant safety system according to any one of the preceding claims, wherein the system further comprises an electronic control unit which monitors signals from the deceleration sensor and controls the inflation of the passive restraint means and the protractive device.

9. A vehicle occupant safety system according to claim 7, wherein the pyrotechnic charge is provided by a bridge wire sensitive compressed wire pyrotechnic charge which is ignited by a fuse within the protractive device upon receipt of an ignition signal from the control unit.

10. A vehicle occupant safety system according to any one of the preceding claims, substantially as hereinbefore described with reference to and as shown in the accompanying drawings.