GB2268128A

GB2268128A - An air bag for a motor vehicle

Info

Publication number: GB2268128A
Application number: GB9213625A
Authority: GB
Inventors: Geoffrey Joseph Clarke
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1992-06-26
Filing date: 1992-06-26
Publication date: 1994-01-05
Anticipated expiration: 2012-06-26
Also published as: GB9213625D0; GB2268128B

Abstract

The air bag comprises an envelope 10 made from outer and inner main panels 12, 13 stitched together at 16 and 17 to form an annular region 18 between the stitching. The envelope 10 includes a bottom panel 14 and a web 25 which define a chamber 21 therebetween. An inlet 20 is provided in the bottom panel 14 for inflation gas which fills the chamber 21 and enters the annular region 18 via holes 15 whereby the annular region takes on a toroidal shape. <IMAGE>

Description

AN AIR BAG FOR A MOTOR VEHICLE The invention relates to an air bag for a motor vehicle.

For increased passenger safety in motor vehicles, air bags have been proposed which will inflate in the event of an accident in order to provide protection.

An air bag is normally inflated by means of a pyrotechnic gas generator and a typical inflation time is around 30m seconds. On the driver side of the vehicle, the air bag is particularly intended to prevent the torso of the driver from coming into contact with the steering wheel. Known air bags tend to take on a pearshape when inflated often due to failure of internal tether straps. Whilst that particular shape is generally satisfactory for many types of saloon car, movement of the torso towards the steering wheel of a cross-country or commercial vehicle where the steering wheel is more upright, can cause a pear-shaped air bag to displace leaving unprotected that part of the steering wheel which is nearest to the torso.

An object of the present objection is to provide an air bag which will help to reduce that particular problem.

According to a first aspect of the invention there is provided an air bag for a motor vehicle having an inlet for inflation gas and an inflatable envelope including a portion which, in the inflated condition, is annular for overlying and extending radially beyond the periphery of the steering wheel.

Such an air bag is less easily displaced than the typical pear-shaped form and, therefore, there is less chance of a relevant section of the steering wheel being left unprotected during an accident.

Preferably, the annular portion is of toroidal shape when the air bag is inflated. The curve of the toroidal shape serves well to absorb the impact of the torso of a person during an accident.

A web section of the envelope may extend between diametrically opposite surfaces of the annular portion. The envelope may also include a panel which extends across the envelope from one side of the annular portion to the other so as to define a gas receiving chamber between itself and the web section.

In that way, the web section can also form a cushion to protect the torso from impact against a hub of the steering wheel.

Preferably, the aforesaid panel is formed with the inlet for admission of gas to the chamber and a passageway may be formed through part of the envelope which defines the annular portion of the air bag to enable gas to pass from the chamber to the annular portion during inflation of the air bag. A plurality of such passageways may be formed so as to be spaced around the annular portion.

Conveniently, the envelope may comprise an outer main panel and an inner main panel which are interconnected both around their outer peripheries and around a section inwardly thereof, eg by machine stitching, to define the annular portion between the interconnections. The or each aforesaid passageway may be formed in the inner main panel between the interconnections. This construction of the air bag dispenses with the need to utilise internal strapping to control inflation shape.

The aforesaid web section may be formed from overlying sections of the outer and inner main panels. Such constructions provides a double thickness web which is ideal for a bodily contact area of the air bag.

The panel which extends across the envelope is preferably connected to the inner main panel, e.g between the peripheral interconnections of the inner and outer panels. The inner main panel may include a portion which is folded over on itself to provide a part to which the panel is connected. A part formed in that way can provide an annular double thickness lip to which the said panel can easily be stitched by machine.

According to a second aspect of the invention there is provided an air bag in a steering wheel of a motor vehicle, the air bag having an inlet adjacent a hub of the steering wheel for inflation gas and an inflatable envelope including a portion which in the inflated condition is of annular shape for overlying and extending radially beyond the periphery of the steering wheel.

The air bag of the second aspect of the invention may include features as set out in any of the consistory clauses relating to the first aspect of the invent ion.

The aforesaid panel which extends across the envelope preferably lies firmly against the steering wheel when the air bag is inflated.

An air bag in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which: Fig.1 is a cross-section through an air bag in accordance with the invention, Fig.2 is a plan view of a main outer panel for the air bag shown in Fig.1, Fig.3 is a plan view of a main inner panel, Fig.4 is a plan view of a bottom panel of the air bag, Fig.5 is a diagrammatic cross section through the panel viewed edgeways to show the way in which the panels can be stitched together, Fig.6 is a perspective view of a motor vehicle having a steering wheel in which the air bag in accordance with the invention is mounted, Fig.7 is a cross-section through the steering wheel showing the way in which the air bag is mounted, and Fig.8 is a cross-section through the steering wheel to a smaller scale than Fig. 7 showing the inflated air bag.

The air bag comprises an envelope 10 having a main outer panel 12, a main inner panel 13 and a bottom panel 14. As shown in Fig.3, the main outer panel 12 is a circular sheet of suitable material (for example a textile reinforced plastics material) and the main inner panel 13 is also a circular sheet of similar material which is formed with a plurality of large openings 15 and two vent openings 11. The outer and inner main panels 12, 13 are held together by machine stitching 19 (Fig. 5) along lines 16, 17 to define an annular region 18 therebetween. To attach the bottom panel 14, an annular section of the inner main panel 13 is folded over on itself to provide an outwardly facing annular lip 13a. The bottom panel can then be held by machine stitching 19a to the lip 13a.It is envisaged that the arrangement of the panels shown in Fig. 5 will enable the stitching together of the envelope to be suitably automated, for example by robotics, to minimise or even eliminate manual construction of the envelope. The bottom panel 14 has an opening 20 therein by which it can be secured to a hub 23 of a steering wheel 24.

It will be noted from Figs.1 and 5 that the stitching 17 for the outer and inner main panels 12, 13 defines a double skinned web 25 extending between opposite inner surfaces of the annular section 18 and a chamber 21 is defined between the web 25 and the bottom panel 14.

In use, the air bag is fitted to the vehicle steering wheel 24 as shown in Figs 6, 7 and 8. The hub 23 carries a pyrotechnic gas generator 26 which operates in response to a crash sensor 33 in the vehicle. The gas generator 26 has a body 27 having a peripheral flange 28. The flange is positioned so as to overlie a margin 29 of the bottom panel 14 around the opening 20. A clamping ring 30 is provided for clamping the margin 29 against the flange 28, clamping bolts 31 being provided for that purpose. The bolts 31 also connect the gas generator 26 to a mounting dish 32 which is bolted to the hub 23 of the steering wheel 24. The gas generator body 27 defines a ring of outlet slits 34 for the gas, which slits are disposed within the chamber 21.

In the event of an impact sufficient to trigger the sensor 33, a diagnostic control unit 35 sends a signal to the gas generator 26 which provides a rush of gas through the outlet slits 34, into the chamber 21 and through the openings 15 into the annular section 18 to inflate the bag from a folded condition, as shown in broken lines in Fig.8, to an inflated condition as shown in full lines in Fig. 8.

In its inflated form, the annular section 18 takes on a toroidal form (also shown in Fig.1 where the air bag is in a semi-inflated condition) to extend around and project radially beyond the rim 24a of the steering'wheel 24. The web 25 forms a dome-shaped surface thereby providing a central cushion to prevent contact with the steering wheel hub 23.

The steering wheel rim 24a is normally set somewhat behind the hub 23 and inflation of the air bag will cause the bottom panel 14 to draw the toroidal section 18 tightly against the rim 24a. The circumferential axis (indicated at 36 in Fig. 8) is set so as to lie outboard of the steering wheel rim 24a. In that way, contact of the annular section by the torso of the driver as shown in Fig. 8 will tend to urge the toroidal section 18 into firm engagement with the rim portion 24a nearest the driver and/or cause it to wrap around the outside of the rim as shown in chain dot lines thereby providing reliable protection against bodily contact with the rim.

The normal pear shaped air bag P (shown in broken lines in Fig.7) does not provide such reliable coverage of the lower rim pprtion and particularly so with steeper angled steering wheels for which an air bag in accordance with the present invention is particularly useful. As the torso T compresses the air bag, gas escapes to atmosphere through the vents 11.

Normal air bags require internal tether straps which are intended to control their shape but often break in use. That problem is substantially avoided with an air bag in accordance with the invention and the method of construction does not require internal tether straps particularly in view of the connections by stitching 19 and 19a.

Claims

1. An air bag for a motor vehicle having an inlet for inflation gas and an inflatable envelope including a portion which in the inflated condition is of annular shape for overlying and extending radially beyond the periphery of a steering wheel.

2. An air bag according to Claim 1 in which the annular portion is of toroidal shape when the air bag is inflated.

3. An air bag according to Claim 1 or 2 in which the envelope includes a web section extending between diametrically opposite surfaces of the annular portion.

4. An air bag according to Claim 3 in which the envelope includes a panel which extends across the envelope from one side of the annular portion to the other to define a gas chamber between itself and the web section.

5. An air bag according to Claim 4 in which the panel is formed with said inlet for admission of gas to the chamber.

6. An air bag according to Claim 4 or 5 in which a passageway is formed through part of the envelope defining the annular portion to enable gas to pass from the chamber to the annular portion during inflation.

7. An air bag according to claim 6 in which a plurality of said passageways in formed around the annular portion.

8. An air bag according to any preceding Claim in which the envelope comprises an outer main panel and an inner main panel which are interconnected around their outer peripheries and around a section inwardly thereof to define the annular portion between the interconnections.

9. An air bag according to claim 8 when appendant to any of claims 3 to 7 in which the web section is formed from overlying sections of the outer and inner main panels.

10. An air bag according to claim 8 or 9 when appendant to claim 4, 5, 6 or 7 in which the panel which extends across the envelope is connected to theinner main panel.

11. An air bag according to claim 10 in which a portion of the inner main panel is folded over itself to provide a part to which the said panel is connected.

12. An air bag according to any of claims 8 to 11 when appendant to Claim 6 or 7 in which the said passageway is formed in the inner main panel between the interconnections.

13. An air bag according to any preceding claim in which the envelope is formed with vent means for venting gas from the inflated air bag.

14. An air bag according to claim 13 when appendant to any of claims 8 to 12 in which the vent means is formed in the inner main panel.

15. An air bag according to any preceding Claim on a steering wheel of a motor vehicle, the air bag having its inlet for inflation gas adjacent a hub of the steering wheel.

16. An air bag according to claim 15 when appendant to any of claims 4 to 7 in which the said panel lies firmly against the steering wheel when the air bag is inflated.

17. An air bag constructed and arranged substantially as described herein with reference to the accompanying drawings.