GB2244378A

GB2244378A - G-Sensors

Info

Publication number: GB2244378A
Application number: GB9010609A
Authority: GB
Inventors: Artur Lennart Haglund
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1990-05-11
Filing date: 1990-05-11
Publication date: 1991-11-27
Anticipated expiration: 2010-05-11
Also published as: GB9010609D0; GB2244378B; DE4115560A1

Abstract

A G-sensor for sensing deceleration or deformation of a motor vehicle responds to a predetermined G-force of at least 100G. The sensor may be mounted in a door of the vehicle and comprises a weight 24 movable against the bias of a spring 23 in response to a sensed G force to cause a plate spring 12 to be flattened thereby completing an electrical circuit between a contact 13 on the plate spring 12 and a contact 10 on a printed circuit board 9. The contacts 10, 13 may also be closed by downward movement of the weight 24 caused by deformation of a housing 26 of the sensor. <IMAGE>

Description

DESCRIPTION OF INVENTION "Improvements in or relating to a G-Sensor" THE

PRESENT INVENTION relates to a G-sensor. A G-sensor is adapted to sense the G-forces generated during acceleration or deceleration.

The present invention relates more particularly to a G-sensor adapted for use in a motor vehicle and particularly to a G-sensor for use to detect a side impact for a motor vehicle.

It has been proposed previously to provide a G-sensor, adapted to respond to a predetermined G-force when a vehicle decelerates rapidly, for example under accident conditions. Such a G-sensor may be used to activate a safety item, such as an air-bag or the like.

It has been proposed to mount a G-sensor on the front of a motor vehicle (see, for example, US-A-4166641) but this prior art G-sensor is found to be responsive to a very low G-force, for example about 10 G. The unit "G" is equal to the force of gravity at the surface of the earth.

According to this invention there is provided a G-sensor for use in sensing deceleration or deformation of an outer part of a vehicle, wherein the sensor is adapted to respond to a G-force, provided that the G-force is in excess of a predetermined limit.

Preferably the limit is at least 100 G.

Conveniently the limit is at least 400 G.

The sensor may be mounted in a door of a motor vehicle.

The sensor may be mounted to move in response to deformation of the outer skin of the motor vehicle.

I Preferably the sensor comprises a mass or weight, the mass or weight being movable against the bias of a spring, in response to the sensed Gforce, movement of the mass causing an electric c5-rcui.t to be completed.

Conveniently the mass moves against the bias of a compression spring.

Advantageously a plate-spring is provided, the plate-spring being adapted to move, in response to movement of the weight, from a first condition in wh--ch the electric circuit is open, to a second condition in which the electric circuit is completed.

Preferably the plate-spring is initially in a substantially arched condition and moves, in response to movement of the weight, to a substantially planar condition.

Conveniently the plate-spring carries a first contact and rests on an element carrying a second contact, the contacts being caused to touch each other when the plate spring moves to the substantially planar condition, the plate spring establishing contact with a further electric contact.

Preferably the further contact comprises a signal track on a printed circuit board.

Conveniently the further contact comprises a signal track on a printed circuit board.

Preferably the weight is mounted in position adjacent a fixed part of the door, so that, in response to movement of the main part of the sensor, the weight will be engaged, directly or indirectly by the said fixed part and will be moved against the bias of said spring to complete said electric circuit.

Conveniently the weight is protected by means of a housing, the part of the housing adajeent the weight being deformable, so that, on deformation of t,his part of the housing, the weight may be moved against the spring to complete said electric circuit.

In one embodiment the weight is a substantially cylindrical weight movable within a bore defined by a housing component.

Preferably part of the weight protrudes through an aperture provided at the end of said bore.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated, the invention will now be described, by way of example, with reference to the accompanying drawings in which FIGURE 1 is a sectional view of a sensor in accordance with the invention, and FIGURE 2 is a plan view, with parts shown in phantom, of the sensor with parts thereof removed for the sake of clarity of illustration.

Referring to the drawings, a sensor in accordance with the invention is adapted to be mounted within the side door of a motor vehicle. The sensor comprises a first housing 1 which defines, in its upper surface, a central circular recess 2. The housing 1 also defines an aperture 3 extending through the housing, by means of which the housing may be secured in position with:n a door of a motor vehicle. The housing may be secured to a plate which is secured to the inner surface of the outer skin of the door of the vehicle, or may be mounted within the door in some other convenient way.

A lower portion of the housing is out-away and provided with an infill 4 formed of, for example, an epoxy resin, or other sealing electrically insulating material. This infill of epoxy resin forms a suitable termination for a cable 5, which is a two-core cable. The two cores of the cable are connected, respectively, to terminals 6 and 7 located within the housing. The terminal 6 establishes contact with a signal track 8 which is formed on the upper surface of a c,rcular printed circuit board 9 which is located at the bottom of the circular recess 2. The signal track establishes contact with a central terminal 10 indicated in phantom in Figure 1.

The second terminal 7 establishes contact w41th a second signal track 11 which is of part circular form, 1 the circle having, as its centre, the middle of the contact 10.

Resting on the signal track 11 is a metal 0 plate-spring 12. This plate-spring 12 comprises a cen- i tral substantially planar region which carries, on its under-surface, a downwardly extending contact 13 element and four equi-angularly spaced, radially outwardly extending and downwardly inclined legs 14. Each leg terminates with a radially outwardly directed substantially planar foot 15. The contact 13 is thus opposed to but slightly spaced from the contact 10. The plate-spring is thus initially in an arched condition.

The plate-spring 12 is located within a recess 16 located above the printed circuit board 9 and defined by a housing 17. The housing 17 has a lower outwardly directed flange 18 which extends to the side wall of the recess 2. The housing 18 has a central upstanding portion 19, having a hollow interior defined by a vertical bore 20 extending upwardly from the recess 16, the portion 19 terminating, at its upper end, with inwardly directed flanges 21 which define an aperture 22.

Received within the bore 20 is a helical compression spring 23, the lower end of which rests on top of the plate-spring 12 and the upper end of which engages the under-surface of a weight 24. The weight 24 is of cylindrical form and substantially fills the bore 20, but the weight is provided with an upwardly extending peg 25 dimensioned to pass through the aperture 22. The peg 25 thus projects above the extension 19.

An outer housing 26 is provided which is mounted within the recess 2. The housing 26 is of generally cylindrical form having an open lower end and a closed upper end. The outer periphery of the housing 26 is provided, adjacent the open lower end, with radially outwardly extending flanges 27 which are inserted between corresponding radially inwardly extending flanges 28 provided, on the housJng 1, at the perinhery of the recess 2. An appropriate adhesive or glue may be inserted between the flanges to secure the housing 26 in position. The housing 26 has a substantially cylindrical or tubular outer wall 29, and a closure at the upper end which comprises a central relatively thick portion 30 of lesser diameter than the cylindrical tubular wall 29, which is connected to the cylindrical tubular wall 29 by a relatively thin web 31 which is inclined upwardly. The housing 26 may be formed of aluminium or the like.

The described sensor may be mounted in the side door of a motor vehicle with the lower part of the housing, as illustrated in Figure 1, directed towards the exterior of the vehicle. Thus any impact on the exterior of the side door of the vehicle will tend to move the housing 1 and all the associated components described above in the direction indicated by the arrow 32. It is also to be appreciated that when the sensor is mounted in position, the central portion 30 of the closure of the housing 26 may be located at a position spaced from the inner surface of the door or spaced from some other part of the door which is relatively fixed in posItion.

I It will be appreciated that the sensor of the invention should be designed to trigger for a speed change greater than 3 metres per second within a very short period of time, i.e. within 2 mill-i-seconds. Also, the sensor should be able to respond to slower inputs, if they are prolonged. The sensor should not, however, respond to brief slower inputs.

The sensor, as described, is intended to operate as follows.

When the sensor senses an acceleration in the direction of the arrow 32, the main housing of the sensor 1 will move in the direction of the arrow 32, but the weight 24 will tend to maintain its initial position due to inertia. Initially this will cause the spring 23 to become compressed. If the acceleration does not exceed a predetermined limit, the spring will subsequently re-expand, thus returning the sensor to the condition illustrated in Figure 1. However, if the predetermined limit is exceeded, the spring 23 will become compressed to such an extent that it will cause the plate spring to become flattened. There is an initial resistance to the flattening of the plate spring, but once the spring starts to flatten it flattens relatively quickly. The contact 13 will thus be brought to a position in which it touches the contact 10 and the legs 14 of the spring will be Jin contact with the signal track 11 on the printed circuit board 9. it will thus be appreciated that there is an electrical connection between the two cores of the cable 5.

The nature of the spring 23 and the plate-spring 12 may be selected so that the device only triggers when subjected to a very high G-force, such as a G-force in excess of 100 G, or preferably, in excess of 400 G. Thus, the side impact sensor will only trigger when subjected to very severe force. This minimises any risk of the side impact sensor being triggered by an inadvertent kick on the side door of the motor vehicle. The nature of the spring is thus such thast the sensor responds rapidly (within the 2 milli-seconds time frame mentioned above) to appropriate inputs, in excess of 3 metres per second.

However, the sensor is also adapted to respond to an impact of less than 3 metres per second, provided that the impact is of sufficient duration to deform the housing 26. In an impact of this type JIG is envIllsaged that the housing 1 will move in the direction of the arrow 32, whereas the central part 30 of the cover of the housing 26 will not move further, because that part of the housing is then in contact with a fixed part of the door. Thus the part of the housing defined by the webs 31 will deform. The under-surface of the central portion 30 of the closure of the housing 26 will thus engage the projecting peg 25 provided on the weight 24, pushing the weight down against the bias of the spring 23, thus causing the plate- spring 12 to pass through the dead-centre condition, thus establishing electrical contact between the contacts 13 and 10.

It will thus be appreciated that the sensor, as described, thus responds even to a relatively low speed impact, provided that the impact Is sufficient to deform the door. Of course, in an accident involving another ormed, and will be deiormed vehicle, the door will be def to a sufficient extent to cause the sensor to be act!vated in the manner described above.

Claims

CLAIMS:

1. A G-sensor for use in sensing deceleration or deformation of an outer part of a vehicle, wherein the sensor is adapted to respond to a G-force, provided that the G-force is in excess of a predetermined limit.

2. A sensor according to Claim 1 wherein the limit is at least 100 G.

A sensor according to Claim 1 wherein the limit is at least 400 G.

4. A sensor according to any one of the preceding Claims mounted in a door of a motor vehicle.

5. A sensor according to Claim 4 mounted to move in response to deformation of the outer skin of the motor vehicle.

6. A sensor according to any one of the preceding Claims wherein the sensor comprises a mass or weight, the mass or weight being movable against the bias of a spring, in response to the sensed G-force, movement of the mass causing an electric circuit to be completed.

7. A sensor according to Claim 6 wherein the mass moves against the bias of a compression spring.

i

8. A sensor according to Claim 6 or 7 wherein a plate-spring is provided, the plate-spring being ad apted to move, in response to movement of the weight, from a first condition in which the electric circuit is open, to a second condition in which the electric cir cuit is completed.

9. A sensor according to Cla-1m 8 wherein the plate-spring is initially in a substantIally arched con dition and moves, in response to movement of the weIght, to a substantially planar condition.

10. A sensor accordIng to Claim 9 where-in the plate-spring carries a first contact and rests on an element carrying a second contact, the contacts being caused to touch each other when the plate spring moves to the substantially planar condition, the plate spring establishing contact with a further electric contact.

11. A sensor according to Claim 10 whereln the further contact comprises a signal track on a printed circuit board.

12. A sensor according to Claim 10 or 11 whereln the further contact comprises a signal track on a printed circuit board.

13. A sensor according to any one Claims 6 to 12 wherein the weight is mounted in position adjacent a fixed part of the door, so that, in response to movement of the main part of the sensor, the weight will be engaged, directly or indirectly by the said fixed part and will be moved against the bias of said spring to cornplete said electric circuit.

14. A sensor according to any one of Claims 6 to 12 wherein the weight is protected by means of a housing, the part of the housing adajcent the weight beIng deformable, so that, on deformation of this part of the housing, the weight may be moved against the spring to complete said electric circuit.

15. A sensor according to any one of Cla!1ns 6 to 14 wherein the weight is a substantially cylindrical weight 1 movable within a bore defined by a housing component.

16. A sensor substantially as herein described with reference to and as shown in the accompanying drawings.

1 Published 1991 at The Patent Office. Concept House, Cardiff Road. Newport, Gwent NP9 I RH. Further copies may be obtauied from Sales Branch. Unit 6. Nine Mile Point. Cwmfelinfach, Cross Keys. Newport, NPI 7HZ. Printed by Multiplex techniques'ltd. St Marv Crav. Kent.

16. A sensor according to Claim 15 wherein part of the weight protrudes through an aperture provided at the end of said bore.

17. A sensor substantially as herein described with reference to and as shown in the accompanying drawings.

18. Any novel feature or combination of features disclosed herein.

- l)-- AMENDMENTS TO THE CLAIMS HAVE BEEN FILED AS FOLLOWS.

A G-sensor for use in sensing acceleration or deformation of an outer part of a vehicle in a side impact, wherei the sensor comprises a houisng mounted in position on or adjacent the outer skin of the vehicle at the side of the vehicle, and adapted to move in response to deformation of the outer part of the vehicle during a side impact, the housing containing means adapted to respond to a sensed G-force and to provide an output when the G-force is in excess of a predetermined limited.

2. A sensor according to Claim 1 wherein the limit is at 'Least 100 G.

A sensor according to Claim 1 wherein the limit is at least 400 G.

4. A sensor according to any one of the preceding Claims mounted in a door of a motor vehic'-'-e.

5. A sensor according to any one of the preceding Claims wherein the sensor comprises a mass or weight the mass or weight being movable against the bias of a spring, in response to the sensed G-force, movement of the mass causing an electric circuit to be completed.

6. A sensor according to Claim 5 wherein the mass moves against the bias of a compression spring.

7. A sensor according to Claim 5 or 6 wherein a plate-spring is provided, the plate-spring being ad apted to move, in response to movement of the weight, from a first condition in which the e'lectric circuit is open, to a second condition in which the electric eir- 1 1 1 -i- cuit is completed.

8. A sensor according to Claim 7 wherein the plate-spring is initially in a substantially arched con dition and moves, in response to movement of the weight, to a substantially planar condition.

9. A sensor according to Claim 8 wherein the plate-spring carries a first contact and rests on an element carrying a second contact, the contacts being caused to touch each other when the plate spring moves to the substantialiy planar condition, the plate spring establishing contact with a further electric contact.

10. A sensor according to Claim 9 wherein the further contact comprises a signal track on a printed circuit board.

11. A sensor according to Claim 9 or 10 wherein the further contact comprises a signal track ona Printed circuit board.

12. A sensor according to any one Claims 5 to 11 wherein the weight is mounted in position adjacent a fixed part of the door, so that, in response to movement of the main part of the sensor, the weight will be en gaged, directly or indirectly by the said fixed part and will be moved against the bias of said spring to com Plete said electric circuit.

13. A sensor according to any one of Claims 5 to 11 wherein the weight is protected by means of a housing, the part of the housing adajoent the weight being de formable, so that, on deformation of this part of the housing, the weight may be moved against the spring to complete said electric circuit.

14. A sensor according to any one of Claims 5 to 13 - lt- wherein the weight is a substantially cylindrical weight movable within a bore defined by a housing component.

15. A sensor according to Claim 14 wherein part of the weight protrudes through an aperture provided at the end of said bore.