WO1999001319A1

WO1999001319A1 - An acceleration detector

Info

Publication number: WO1999001319A1
Application number: PCT/SE1998/001282
Authority: WO
Inventors: Matthew J. Knox
Original assignee: Autoliv Development Ab
Priority date: 1997-07-01
Filing date: 1998-06-30
Publication date: 1999-01-14
Also published as: GB2326813A8; GB9713959D0; GB2326813B; GB2326813A

Abstract

An acceleration sensor for a motor vehicle comprises a platform (24) which is pivotally mounted (25) and which supports a pendulum member (28) which has an enlarged head (32) resting on the platform and a shaft (29) extending through an aperture in the platform, the shaft carrying an inertia mass (30) at its lower end. An operating lever (20) is provided resting on top of the head (31) of the pendulum member (28). A blocking member is provided which is pivotally mounted (34) and which has an inertia mass (37) and forwardly projecting arms (38, 39). On deceleration of the vehicle in excess of a predetermined limit one arm (39) of the blocking member (33) engages the platform (24) and the pendulum member (28) then pivots about a point where the periphery of the head (31) rests on the platform (24) causing the lever (20) to rise.

Description

"AN ACCELERATION DETECTOR"

THE PRESENT invention relates to an acceleration detector and more particularly relates to an acceleration detector to be incorporated into a safety device, such as a retractor mechanism, adapted to be mounted in a motor vehicle.

In particular the invention relates to an acceleration detector for use in a retractor which to be mounted in a vehicle seat.

A typical acceleration detector, for use in connection with a safety device in a motor vehicle, comprises an inertia mass which moves, from an initial position, to an operative position, in response to acceleration or deceleration of the vehicle. In a typical prior proposed acceleration sensor there is a tendency for the inertia member to move, from the initial position to the operative position if the sensor is tilted from its ordinary position. The sensor may, for example, be tilted from its ordinary position if the vehicle is located on a slope.

It has been proposed to mount a retractor mechanism for a safety belt in the back of a vehicle seat. The back of a vehicle seat, typically, may be adjusted between various inclined positions, to provide a position that is comfortable for the occupant of the seat. If a retractor mechanism is mounted in a vehicle seat, the acceleration sensor present within that retractor may have various positions of different inclination with respect to the horizontal, and any acceleration sensor present in the retractor must operate satisfactorily at these various degrees of inclination.

The present invention seeks to provide an acceleration sensor that will operate satisfactorily at various degrees of inclination.

According to this invention there is provided an acceleration sensor for use in a motor vehicle, the acceleration sensor comprising a support platform which is pivotally mounted for pivotal movement, a pendulum member carried by the platform, the pendulum member having a head which is supported by the platform and having an inertia mass located beneath the platform, the pendulum member being tiltable, relative to the platform, about an axis defined by a point where the periphery of the head of the pendulum member engages the platform, the platform being associated with a blocking member, the blocking member being mounted for pivotal movement and having means adapted to engage at least one surface of the platform, the arrangement being such that when the acceleration sensor is subjected to an initial deceleration the combination of the platform and the associated pendulum member will pivot together about the axis of pivotal support of the platform in one sense and the blocking member will also pivot, and on subsequent harder deceleration the blocking member will move to a position in which the blocking member engages at one surface of the platform tending to cause the platform to rotate in the opposite sense about the pivot axis, causing the pendulum member to pivot, relative to the platform, about said point, causing part of the head of the pendulum member to rise above the platform, there being an actuating element engaging the head of the pendulum member. Preferably the head of the pendulum member is of dome-shaped configuration.

Conveniently the centre of curvature of the dome- shaped configuration of the head of the pendulum member is substantially coincident with the pivot axis of pivotal support of the platform.

Advantageously the blocking element is provided with two projecting means, one located above the platform and one located beneath the platform, each of said means being adapted to contact the platform as a consequence of deceleration of the acceleration detector in different senses.

Preferably the blocking member defines an arcuate recess, the recess accommodating one edge of the platform.

Advantageously the radius of curvature of the recess in the blocking member is less than the distance between the edge of the platform accommodated within the recess and the point of pivotal support of the platform.

The invention relates to a retractor mechanism incorporating an acceleration sensor as described above. Also the invention relates to a vehicle seat incorporating an acceleration sensor as described above.

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 diagrammatic view of a vehicle seat provided with a retractor.

Figure 2 is a diagrammatic view of the operative parts of the acceleration sensor of the retractor.

Figure 3 is a part sectional view corresponding to part of Figure 2,

Figure 4 is a view corresponding to Figure 2 showing the acceleration sensor when subject to a predetermined deceleration.

Figure 5 is a view corresponding to Figure 2 illustrating the deceleration sensor when subject to a greater acceleration.

Figure 6 is a view corresponding to Figure 1 illustrating the acceleration sensor when the acceleration sensor is in an inclined position.

Figure 7 is a view corresponding to Figure 6 illustrating the acceleration sensor when subjected to a predetermined deceleration.

Figure 8 is a view corresponding to Figure 7 illustrating the acceleration sensor when subject to a greater deceleration,

Figure 9 is a view corresponding to Figure 8 illustrating the deceleration sensor when subjected to an even greater deceleration, and Figure 10 is a view, corresponding to Figure 2, of an alternative embodiment of the invention.

Referring initially to Figure 1 of the accompanying drawings the vehicle seat 1 comprises a squab 2 and a back 3. The back is pivotally connected to the squab 2 by a recliner mechanism 4. Mounted in the back 3, towards the upper part of the back, is a retractor mechanism 5 on which is wound a safety belt 6. The retractor mechanism, as will be described more fully hereinafter, is provided with an acceleration sensor.

It is to be observed that the back 3 of the seat may have an initial or "ordinary" position, as shown in solid lines, but the seat may be pivoted forwardly about the axis defined by the recliner mechanism 4 to occupy the position 3' as shown in phantom or may be reclined rearwardly to occupy the position 3" as shown in phantom. The acceleration sensor provided in the retractor 5 must operate satisfactorily regardless of the degree of inclination of the back of the seat.

Referring now to Figures 2 and 3 of the accompanying drawings, the principal components of the acceleration sensor provided in the retractor mechanism 5 are illustrated in the position that they occupy when the seat back 3 is in the ordinary position as shown in solid lines in Figure 1, and when the vehicle is stationary, or is travelling at a constant speed.

The acceleration sensor incorporates an actuating lever 20. The actuating lever 20 is of elongate form and is pivotally mounted adjacent one end 21 thereof. The other end of the actuation lever 22 is of pointed configuration and lies adjacent the toothed periphery 23 of a control wheel. As will be described hereinafter in great detail on deceleration of the vehicle in which the acceleration sensor is mounted, with a deceleration rate in excess of a predetermined threshold, the pointed end 22 of the lever 20 engages the toothed periphery 23 of the control wheel, which causes the retractor mechanism to be locked. This is a conventional feature of many retractor mechanisms currently in production, and for one example of how such a retractor mechanism may operate reference may be made to GB-A-2176993.

The acceleration sensor additionally comprises a platform 24 that is mounted for pivotal movement about a horizontal axis 25, that axis extending transversely of the motor vehicle in which the seat 1 is mounted. The axis 25 is aligned with a central region of the platform 24. The platform 24 may be made of a plastics material or other material which is light, so that the platform 24 does not have any significant mass.

The platform 24 is provided with a central aperture 26, aligned with the axis 25 which is located within a recess 27 formed in the upper surface of the platform 24. The aperture 26 is aligned with the axis 25.

A pendulum member 28 is provided comprising a shaft 29, the lower end of which is provided with a mass 30, and the upper end of which is provided with a head 31, the head 31 being of circular form and being provided with domed top 32. The head 31 is received within the recess 27 and the shaft 29 passes through the aperture 26 formed in the platform 24.

Part of the lever 20 rests on top of the domed part 32 of the head 31.

The centre of curvature of the domed head 32 is substantially coincident with the pivot axis 25 of the platform 24.

Located to one side of the platform, is a pivotally mounted blocking member 33. The blocking member 33 is mounted for pivotal movement about an axis 34. The axis 34 and the axis 25 lie in a single horizontal plane 35.

The blocking member 33 is provided with a depending arm 36 which carries a weight or mass 37. The blocking member 33 is provided with two horizontal extending arms 38, 39. The arms 38, 39 are located respectively below and above the forward edge of the platform 24, so that the forward edge of the platform 24 is received between the arms 38 and 39.

Figures 2 and 3 illustrate the various components of the acceleration sensing arrangement in an initial condition. The mass 30 is located beneath the pivot point 25, extending parallel with the vertical axis 40. Similarly the arm 36 and the mass 37 depend beneath the axis 34. The illustrated components will occupy these positions when a vehicle in which the acceleration sensor is mounted is stationary or when a vehicle in which the acceleration sensor is mounted is moving at a substantially constant velocity.

Should a vehicle in which the acceleration sensor is mounted decelerated, the mass 37 and the mass 30 will tend to move forwardly, relatively to the vehicle, in the direction indicated by the arrow 41 in Figure 4 of the accompanying drawings . It can be seen that the combination of the platform 24 and the pendulum member 28 have pivoted about the pivot axis 25, in a clockwise sense so that the mass 30 is no longer directly beneath the pivot axis 25. During this movement, because the centre of curvature of the domed- shaped part 32 of the head 31 of the pendulum member 28 is coincident with the pivot axis 25, the lever 20 has not changed its position at all. All that has happened is that part of the dome has slid beneath the lever 20, without the lever 20 either rising or falling. The blocking member 33 has also pivoted slightly about its axis 34, in a clockwise sense. The upper arm 39 is immediately adjacent platform 24 but does not contact the platform 24.

In the condition illustrated in Figure 4, the retractor mechanism is not locked.

Should the vehicle in which the acceleration sensor is mounted be subjected to a more severe deceleration, that is to say a deceleration in excess of a predetermined threshold the masses 30 and 37 will tend to move further forward, in the direction indicated by the arrow 41. As a consequence of this movement the upper arm 39 of the blocking member engages the forward edge of the platform 24 and causes the platform 24 to pivot, in a counter-clockwise direction, about the pivot axis 25. Thus the direction of movement of the platform 24 is reversed as a consequence of the blocking member 33 engaging the platform 24. The inertia mass 30, however, will tend to continue a movement forwardly of the vehicle, that is to say in the direction indicated by the arrow 41. The pendulum member 28 will consequently pivot about the rearward point of engagement of the head 31, and the platform 24, that is to say about the point 42 as shown in Figure 5. This causes the forward edge of the head 31 of the inertia member, as indicated by the reference numeral 43, to rise above the platform, thus moving the lever 20 upwardly, to a position where the pointed end 22 can engage with the teeth 23.

The teeth 23 are undercut teeth. The control wheel will tend to rotate in an anti-clockwise direction, as indicated by the arrow 44. Thus, as soon as the pointed end 22 of the lever 20 is within the envelope of the teeth 23 the pointed end will be drawn firmly into engagement with one of the teeth, thus causing the toothed wheel to stop rotating and actuating the locking mechanism.

It can be seen, therefore, that the effect of the blocking member 33 is not simply to block movement of the platform 24, but to move the platform 24 in such a direction that the degree of lifting of the head 31 of the pendulum member 28 is enhanced.

Figure 6 illustrates the arrangement described above with reference to Figures 2 to 5, when the vehicle is stationary, but when the back of the seat has been reclined to the position illustrated in phantom at 3" in Figure 1. It is to be noted that in this condition of the apparatus, the plane defined by the pivot axis 25 and 34, that is to say the plane 45 as shown in Figure 6 is no longer coincident with the horizontal 35. The platform 24 occupies an initial horizontal position, with the inertia mass 30 being located immediately beneath the pivot axis 25, and the blocking member 33 also occupies a position as described but with reference to Figure 2, with the mass 37 being located directly beneath the pivot axis 34. However, the upper arm 39 is now spaced a substantial distance above the platform 24 whereas the lower arm 38 is located immediately beneath the platform 34. As shown in Figure 7, when the vehicle is subjected to a predetermined deceleration, pendulum member 28 and the associated platform 24 rotate about the axis 25, and the blocking member 33 rotates about the axis 34.

Referring now to Figure 8 it can be seen that if the vehicle is subjected to an even greater deceleration, the pendulum member 28 and the platform 24 rotate to a greater extent, about the pivot axis 25 and the blocking member 33 rotates, by a greater extent, about the axis 34. When subjected to even greater deceleration, namely deceleration in excess of a predetermined threshold the upper arm 39 of the blocking member again contacts the forward edge of the platform 24, as shown in Figure 9, again forcing the forward edge of the platform 24 to move so that the platform 24 rotates, about the pivot axis 25 in an anti-clockwise direction. The inertia mass 30 will still tend to move forwardly of the vehicle, in the direction shown by arrow 41, with the consequence that the pendulum member 28 will pivot upwardly about the point 42 where the rear part of the head 31 engages the platform 24, causing the front portion 43 of the head 31 to rise, thus again moving the actuating lever 20 to a position in which the pointed end thereof will engage the toothed periphery 23 of the locking wheel.

In the foregoing description reference has been made to the situation that exists when a motor vehicle is decelerated, when the motor vehicle travels in a forward direction. It is to be appreciated that if a motor vehicle decelerates whilst travelling in a rearward direction, the various inertia masses 30 and 37 described above would not move in the direction indicated by the arrow 41, that is to say towards the left in the orientation shown in the accompanying drawings, but instead would move towards the right. Such a movement would cause the platform 24 to pivot initially in an anti-clockwise sense, with the blocking member 33 also moving in an anti-clockwise sense. The lower arm 38 of the blocking member would, after a predetermined movement, engage the lower surface of the platform 24, and would then tend to cause the platform 24 to rotate in a clockwise sense. This rotation of the platform 24 in the clockwise sense, whilst the pendulum member 28 was tending to rotate in the counter-clockwise sense would cause the head 31 of the pendulum member 28 to lift, thus moving the lever 20 upwardly.

It is to be appreciated that if the deceleration sensor were to operate in the described manner only on deceleration of the vehicle when the vehicle is travelling in a forward direction, the blocking member 33 need only be provided with the upper arm 39 and the lower arm 38 could be omitted.

Figure 10 illustrates a modified embodiment of the invention. In this embodiment of the invention the pendulum member 28, and the platform 24, are as described above, but the design of the blocking member 33 has been altered. Instead of the blocking member having two simple projecting arms 38, 39, the blocking member is provided with an arcuate recess 50 which extends between two forwardly extending projections 51, 52. The recess has a radius of curvature which is shorter than the distance between the pivot point 25 and the forward edge of the platform 24. The forward edge of the platform 24 is received within the recess 50.

The arrangement is such that, as can be seen in Figure 10, as the blocking member 33 moves from an initial position to an operative position when subjected to deceleration, the arcuate recess will engage the edge of the platform 24, thus enhancing the consequent movement of the platform 24 in the counter-clockwise direction.

Whilst the invention has been described above with reference to an acceleration sensor primarily intended to be mounted in the adjustable back of a seat, it is to be appreciated that an acceleration sensor as described may be found to be of value in vehicles which are intended for use in mountainous terrain, where steep gradients may be encountered. The acceleration sensor may be used to actuate other safety devices than a retractor reel.

Claims

1. An acceleration sensor for use in a motor vehicle, the acceleration sensor comprising a support platform which is pivotally mounted for pivotal movement, a pendulum member carried by the platform, the pendulum member having a head which is supported by the platform and having an inertia mass located beneath the platform, the pendulum member being tiltable, relative to the platform, about an axis defined by a point where the periphery of the head of the pendulum member engages the platform, the platform being associated with a blocking member, the blocking member being mounted for pivotal movement and having means adapted to engage at least one surface of the platform, the arrangement being such that when the acceleration sensor is subjected to an initial deceleration the combination of the platform and the associated pendulum member will pivot together about the axis of pivotal support of the platform in one sense and the blocking member will also pivot, and on subsequent harder deceleration the blocking member will move to a position in which the blocking member engages at one surface of the platform tending to cause the platform to rotate in the opposite sense about the pivot axis, causing the pendulum member to pivot, relative to the platform, about said point, causing part of the head of the pendulum member to rise above the platform, there being an actuating element engaging the head of the pendulum member.

2. An acceleration sensor according to Claim 1 wherein the head of the pendulum member is of dome-shaped configuration.

3. An acceleration sensor according to Claim 2 wherein the centre of curvature of the dome-shaped configuration of the head of the pendulum member is substantially coincident with the pivot axis of pivotal support of the platform.

4. An acceleration sensor according to any one of the preceding claims wherein the blocking element is provided with two projecting means, one located above the platform and one located beneath the platform, each of said means being adapted to contact the platform as a consequence of deceleration of the acceleration detector in different senses.

5. A deceleration sensor according to any one of the preceding claims wherein the blocking member defines an arcuate recess, the recess accommodating one edge of the platform.

6. An acceleration sensor according to Claim 5 wherein the radius of curvature of the recess in the blocking member is less than the distance between the edge of the platform accommodated within the recess and the point of pivotal support of the platform.

7. A retractor mechanism incorporating an acceleration sensor according to any one of the preceding claims.

8. A vehicle seat incorporating an acceleration sensor according to Claim 7.