GB2400351A

GB2400351A - Load Limiting Arrangement

Info

Publication number: GB2400351A
Application number: GB0308218A
Authority: GB
Inventors: Fredrik Wigstrom; Anders Ingemarsson; Yogen Patel; Andreas Sandahl
Original assignee: Autoliv Development AB; Ford Global Technologies LLC
Current assignee: Autoliv Development AB; Ford Global Technologies LLC
Priority date: 2003-04-09
Filing date: 2003-04-09
Publication date: 2004-10-13
Anticipated expiration: 2023-04-09
Also published as: SE0400979D0; GB2400351B; DE102004018323B4; SE0400979L; SE527927C2; GB0308218D0; DE102004018323A1

Abstract

A load limiting arrangement, for use with a safety belt (1), comprises a rotatable spool (2), a connecting mechanism, a deformable element (13) and a sensor (24). The connecting mechanism is actuated by a signal from the sensor to couple part of the deformable element to the spool for rotation, such that the deformable element deforms as the spool rotates in the pay-out direction, thereby absorbing energy and resisting pay-out of the safety belt. Preferably, the deformable element comprises an elongate bar or wire mounted so as to be pulled through a tortuous path (14) when coupled to the spool. The connecting mechanism may comprise at least one locking element (12) which, when actuated, moves to engage with teeth (3) on the spool in a locking position. An energy absorbing torsion bar (4) may be connected to the spool to further resist rotation in the pay-out direction.

Description

DESCRIPTION OF INVENTION

IMPROVEMENTS IN OR RELATING TO A LOAD LIMITING

ARRANGEMENT

THE PRESENT INVENTION relates to a load limiting arrangement, and more particularly relates to a load limiting arrangement for use with a motor vehicle safety-belt.

A simple safety-belt arrangement, as in widespread use, comprises a lapand-diagonal safety-belt arrangement (or "three-point" safety-belt), with one end of the safety-belt being anchored to part of the vehicle, an intermediate part of the safety-belt being provided with a tongue being releasably engageable with a fixed buckle, and the other end of the safety-belt, which may pass through a pillar-loop, being wound on to the spindle of a retractor mechanism.

The retractor mechanism incorporates a lock which is configured to lock the retractor in the event that the vehicle undergoes substantial deceleration or is involved in a frontal impact. If a safety-belt is locked by such a retractor, a very sudden decelerating force may be applied to the occupant of the vehicle who is wearing the safety-belt.

Consequently, it has been proposed to provide a safety-belt with a load limiting device in the form of a deformable element which will deform, when a substantial load is applied to the safety-belt so that the load applied by the safety-belt to the occupant of the vehicle is modified or restricted. Some previously-proposed load limiting devices for use with vehicle safety-belts comprise a torsion bar fixed at one end to the structure of the retractor mechanism and secured at its other end to the rotatable spool upon which the safety-belt is wound. As the spool is urged to rotate in a pay-out direction, under the load applied to the safety-belt by the inertia of a seat occupant, the torsion bar twists, thereby resisting pay-out of the safety-belt.

Another known type of load limiting arrangement is disclosed in DE10015048 in which the deformable outer element takes the form of a metal band, one end of which is connectable to the spool on which the safety-belt is wound. When a load is applied to the safety-belt in the pay-out direction in a crash situation, the metal band is pulled through a tortuous path defined by a baffle which thereby provides the load limitation through deformation of the metal band.

It has also been proposed previously to provide load limiting arrangements with more than one different type of deformable element so as to provide a multi-stage load limiting effect, for example, to provide an initial stage of high resistance to pay-out of the safety-belt, followed by a second stage of medium resistance and a final soft stop stage.

However, prior proposed load limiting arrangements are such that the or each deformable element is deformed automatically upon loading of the safety- belt in a crash situation. Therefore, none of these prior art arrangements provide a load limiting arrangement in which the load limiting function can be selectively engaged, for example as a consequence of certain parameters associated with the speed and/or force of pay-out of the safety-belt.

It is therefore an object of the present invention to provide an improved load limiting arrangement.

Accordingly, the present invention provides a load limiting arrangement for use with a vehicle safety belt, the load limiting arrangement comprising a rotatable spool, a connecting mechanism, a deformable element, and a sensor, the connecting mechanism being actuable upon receipt of a signal from said sensor to couple part of the deformable element to the spool for co-rotation with the spool in a pay-out direction, the deformable element being configured to deform when coupled to the spool as the spool rotates in said pay-out direction so as to resist pay-out of the safety belt.

Preferably, said sensor is configured to generate said signal in response to the pay-out speed of the safety belt satisfying an activation criterion Advantageously, said sensor is configured to sense the speed of rotation of said spool.

Conveniently, said sensor is configured to generate said signal in response to the position of an occupant wearing the seat-belt satisfying an activation criterion.

Preferably, said sensor is a distance sensor.

Advantageously, said sensor is a weight distribution sensor.

Advantageously, said deformable element comprises an elongate metal bar or wire mounted so as to be pulled through a tortuous path when coupled to said spool as the spool rotates in said pay-out direction.

Conveniently, said deformable element is connected to or comprises a rotor, the connecting mechanism being actuable to connect said rotor to the spool for co-rotation with the spool.

Preferably, said spool comprises a plurality of peripheral teeth and said connecting mechanism comprises at least one locking element, the or each locking element being moveable in response to said signal from a release position in which it is substantially clear of said teeth to a locking position in which it engages said teeth, the or each locking element also engaging said rotor when in said locking position.

Advantageously, the or each said locking element is moved from said release position to said locking position by rotation of an actuating ring.

Conveniently, said connecting mechanism comprises an actuator operable to actuate the mechanism.

Preferably, said actuator is operable to rotate said actuating ring.

Advantageously, said actuator comprises a gas generator.

Conveniently, said actuator comprises a solenoid.

Preferably, the load limiting arrangement further comprises an energy absorbing torsion element connected to the spool to resist rotation of the spool in said pay-out direction before actuation of said connecting mechanism.

Advantageously, the torsion unit comprises a torsion bar.

So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings in which: FIGURE I is a schematic sectional view through a load limiting arrangement in accordance with the present invention, illustrating the operative parts of the arrangement, in their initial positions, prior to actuation of the arrangement; FIGURE 2 is a view corresponding generally to that of Figure 1, but illustrating the operative parts of the arrangement at an initial stage following actuation of the arrangement; FIGURE 3 is a view corresponding generally to Figure 2, but illustrating the operative parts in a further position at a subsequent stage of actuation of the arrangement; FIGURE 4 is a view corresponding generally to that of Figure 1, but illustrating an alternative embodiment of the present invention.

FIGURE 5 illustrates the relationship between belt force and belt pay out for a first mode of operation of the load limiting arrangement of the present invention; and FIGURE 6 shows the relationship between belt force and belt pay-out for a second mode of operation of the load limiting arrangement of the present invention.

Turning initially to consider Figure 1, there is illustrated a load limiting arrangement in accordance with the present invention, which is suitable for use with a vehicle safety-belt 1. One end of the safety-belt 1 is wound on to a rota/ably-mounted spool 2 which, at one or both ends, carries a plurality of outwardly-directed peripheral locking teeth 3. However, it should be appreciated that whilst the arrangement illustrated in Figure l shows the locking teeth 3 formed integrally around the periphery of the spool 2, the teeth 3 could be formed on a separate component which in turn is connected to the spool 2. The important aspect is that the peripheral locking teeth 3 rotate with the spool 2.

The spool 2 is fixed to one end of a torsion element 4 such as a torsion bar of a type known per se. A typical torsion bar 4 suitable for use with the arrangement of the present invention will be made of relatively soft metal or possibly even plastics material, which is plastically deformable when a torque: load is applied to the torsion bar tending to twist the torsion bar along its longitudinal axis 5. At its end opposite to that secured to the spool 3, the torsion bar 4 is secured to a fixed part of the structure or housing of the load limiting arrangement (not shown).

The part of the spool 2 carrying the locking teeth 3 (or the component carrying the locking teeth 3 which is in turn secured to the spool 2) is received I within a central bore 6 of a rotor drum 7. The central bore 6 of the rotor drum 7 1 defines an inner rotor surface 8 which is spaced a short distance away from the locking teeth 3 around its entire extent. The central bore 6 is generally circular in cross-section as illustrated in Figure 1, but is provided with three recesses 9 which are spaced equidistantly around the bore 6. Each recess 9 has an outwardly, generally tangentially extending arcuate part 10 and a substantially planar shoulder surface 11.

Accommodated within each recess 9 provided on the rotor drum 7, is a respective locking element 12 which takes the form of a generally wedge shaped pall. Each locking element 12 has an outer arcuate surface to bear against the inner arcuate part 10 of a respective recess 9, and has a radially directed end surface to engage a respective shoulder 11. The inner surface of each locking element 12 is configured to conform to the peripheral part of the spool or component carrying the locking teeth 3 and is provided with a plurality of complimentary locking teeth to mesh with the peripheral locking teeth provided around the spool 2 in a manner which will be described in more detail hereinafter.

The rotor drum 7 is connected to one end of an elongate deformable element 13 which extends tangentially away from the rotor drum and passes between a plurality of rollers 14 which are arranged to define a tortuous path therebetween, thereby serving as a baffle-type arrangement.

Also provided around the spool 2 is an actuation ring 15 which is located adjacent the rotor drum 7. The actuation ring 15 has a central bore 16 of similar profile to that of the bore 6 of the rotor drum. However, the central bore 16 of the actuation ring 15 has a slightly larger diameter than that of the bore 6; of the rotor drum 7. It will therefore be seen that the central bore 16 of the I actuation ring 15 also defines three equi-spaced recesses 17 (illustrated most I clearly in Figure 2 which shows an alternate position of the actuation ring 15 relative to the rotor drum 7). Each recess 17 of the bore 16 has a similar configuration to that of the recesses 9 formed in the rotor drum 7, but the recesses 17 in the actuation ring 15 are somewhat "shallower". The recesses 17 each define a small radially-extending shoulder 18 which, in the position illustrated in Figure 1 are each aligned with a respective shoulder l l of the recesses 9 formed in the rotor drum 7. In the initial position of the actuation ring 15 illustrated in Figure 1, each shoulder 18 engages the radially-extending surface of a respective locking element 12.

The actuation ring 1 S carries a radially-extending actuation flange 19.

Located adjacent the actuation flange 19, there is provided an actuator arrangement 20. In the arrangement illustrated in Figures 1 to 3, the actuating arrangement 20 comprises a gas generator 21 having a pyrotechnic charge 22 and a firing squib 23. The squib 23 is electrically connected to a sensor 24 which, as will be described in more detail hereinafter, can take one of various forms.

The actuator arrangement 20 illustrated in Figures 1 to 3 includes a piston 25 which is slidably received within a barrel 26. The barrel 26 is oriented such that its longitudinal axis is directed towards the actuation flange 19.

In the position illustrated in Figure 1, it will be seen that the three locking elements 12 are all spaced away from the locking teeth 3 provided around the spool 2. This means that the spool 2 is free to rotate in order to wind-in the safety-belt 1 and to allow pay-out of the safety- belt 1. Upon the application of a predetermined load to the safety-belt 1 in the pay-out direction (illustrated A in Figure 1), the torsion bar 4 becomes coupled to the spool 2 thereby providing some resistance to the pay-out of the safety- belt 1 from the spool 2, and hence providing an energy-absorbing function. However, in certain circumstances, as will be described in more detail hereinafter, it will be desirable to provide a further force limiting or energy absorbing function and so in such circumstances, the deformable element 13 can also be coupled to the spool 2.

Upon receipt of an appropriate signal from the sensor 24, the squib 23 is energised, thereby actuating the gas-generator 21. The generation of a high volume of gas within the barrel 3 urges the piston 25 towards the actuation flange 19 so that the piston 25 strikes the actuation flange l9, thereby causing the actuation ring 15 to rotate relative to the rotor drum 7. This rotation of the actuation ring 15 is illustrated in Figure 2 from which it will be seen that, because the radial flanges 18 of the actuation ring 15 engage respective locking elements 12, the locking elements 12 are also caused to rotate around the spool; 2. However, because the locking elements 12 also bear against the arcuate parts 10 of the recesses 9 provided in the rotor drum 7 (which at this stage of actuation is still stationary), the locking elements 12 are driven inwardly towards the locking teeth 3 as they rotate about the spool 2. There will therefore come a point at which the locking teeth provided on the inner surfaces i of the locking elements 12 engage and mesh with the locking teeth 3 provided around the periphery of the spool 2. Remembering that the locking teeth 3 each engage the arcuate parts 10 of the recesses 9 provided in the rotor drum 7, it will be clear that when the locking elements 12 engage the locking teeth 3 provided around the rotor 2, the rotor drum 7 effectively becomes coupled or keyed to the spool 2. Further pay-out of the safety-belt 1 from the spool 2 thus causes the rotor drum 7 to rotate (as illustrated in Figure 3) which serves to pull; the elongate deformable element 13 through the tortuous path defined by the rollers 14. This causes the deformable element 13 to deform plastically thereby serving a further energy absorption or load limiting effect tending to resist: further pay-out of the safety-belt 1 from the spool 2.

From the foregoing, it should therefore be appreciated that the load I limiting arrangement of the present invention enables the deformable element 13 to be selectively coupled to the spool 2 in order to provide a further load limiting effect in addition to that provided by the torsion bar 4.

Figure 4 illustrates an alternative embodiment of the above-described load limiting arrangement, in which the piston 25, instead of being driven towards the actuation flange 19 by a gas generator, is driven towards the actuating flange 19 by a solenoid 27 which is energised upon receipt of an appropriate signal from the sensor 24. In other respects, the arrangement of Figure 4 is identical to that illustrated in Figures 1 to 3.

In one proposed embodiment of the load circuiting arrangement, the sensor 24 can take the form of a distance sensor, or a weight distribution sensor, or a combination of both. If a distance sensor is used, it can comprise a laser or radar arrangement and is configured to measure the distance between an occupant wearing the safety-belt, and a fixed part of the motor vehicle such as, for example, the steering wheel or dashboard. The position of the occupant relative to the fixed part of the vehicle is compared to an activation criterion which may be a function of the speed and weight of the vehicle and of the weight of the occupant. If the activation criterion is satisfied (for example by the occupant's body bearing sufficiently close to the dashboard or steering wheel), then the sensor generates an actuation signal.

In such an arrangement, it is envisaged that the deformable element 13 will only be coupled to the spool 2 to provide its additional load limiting effect in the event that the sensor 24 produces said actuation signal, indicating, for example, that the safety-belt 1 is restraining a passenger having a weight deemed too great to be safely restrained under the action of the torsion bar 4 alone. In such circumstances, the deformable element 13 will couple with the spool 2 to provide an additional load limiting effect, thereby increasing the overall energyabsorption level and safely restraining the seat occupant.

Figure 5 illustrates a first plot 30 of the tension in the safety-belt, or "belt force", against the amount of safety-belt pay-out under the energy absorbing effect of the torsion bar 4 alone. Plot 31 shows the additional energy-absorption contribution following actuation of the above-described arrangements.

However, in other arrangements, it may be appropriate to fire the actuation mechanism 20 in order to couple the deformable element 13 to the spool2 if the pay-out of the safety-belt 1 from the spool 2 satisfies an activation criterion (such as exceeding a predetermined threshold speed). In such an arrangement, the sensor 24 can therefore take the form of a speed sensor effective to generate an actuation signal upon detecting the rotational speed of the spool 2 satisfying an activation criterion.

Figure 6 illustrates a plot of belt force against a belt pay-out for operation of the load limiting arrangement with a pay-out-speed-sensitive sensor 24. It will be seen from Figure 6 that during an initial period 32 of safety-belt pay-out, the torsion bar 4 provides a first level of energy-absorption.

The energy-absorption provided by the torsion bar 4 then drops suddenly at point 33 and continues at a constant level 34 for a further period of pay-out.

These energy-absorption characteristics are typical of a two-stage torsion bar of a type known per se which provides an initial high level of energy absorption followed by a second, lower level of energy- absorption. However, if the speed sensor 24 thereafter detects that the rotational speed of the spool 2 in the pay- out direction exceeds a safe predetermined limit (with the possible result that the occupant will be moving so quickly as to reach the steering wheel or dash board of a motor vehicle), the sensor 24 generates its actuation signal at point which causes the secondary energy- absorption contribution of the deformable element 13 to be introduced. It will be seen from Figure 6 that the energy-absorption contribution from the deformable element 13 increases (at 36) uniformly as the safety-belt continues to be paid-out. This type of characteristic can be provided by, for example, a tapered deformable element 13 which is configured to provide a progressively increased energy- absorbing function as it is pulled through the tortuous path defined by the rollers 14.

In the present specification "comprises" means "includes or consists of" and "comprising" means "including or consisting of".

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS: 1. A load limiting arrangement for use with a vehicle safety belt,

the load limiting arrangement comprising a rotatable spool, a connecting mechanism, a deformable element, and a sensor, the connecting mechanism being actuable upon receipt of a signal from said sensor to couple part of the deformable element to the spool for co-rotation with the spool in a pay-out direction, the deformable element being configured to deform when coupled to the spool as the spool rotates in said pay-out direction so as to resist pay-out of the safety belt.
2. A load limiting arrangement according to claim 1, wherein said sensor is configured to generate said signal in response to the pay-out speed of the safety belt satisfying an activation criterion.
3. A load limiting arrangement according to claim 2, wherein said sensor is configured to sense the speed of rotation of said spool.
4. A load limiting arrangement according to claim 1, wherein said sensor is configured to generate said signal in response to the position of an occupant wearing the safety belt satisfying an activation criterion
5. A load limiting arrangement according to claim 4, wherein said sensor is a distance sensor.
6. A load limiting arrangement according to claim 4 or 5, wherein said sensor is a weight distribution sensor.
7. A load limiting arrangement according to any preceding claim, wherein said deformable element comprises an elongate metal bar or wire mounted so as to be pulled through a tortuous path when coupled to said spool as the spool S rotates in said pay-out direction.
8. A load limiting arrangement according to any preceding claim, wherein said deformable element is connected to or comprises a rotor, the connecting mechanism being actuable to connect said rotor to the spool for co-rotation with the spool.
9. A load limiting arrangement according to any claim 8, wherein said spool comprises a plurality of peripheral teeth and said connecting mechanism comprises at least one locking element, the or each locking element being moveable in response to said signal from a release position in which it is substantially clear of said teeth to a locking position in which it engages said teeth, the or each locking element also engaging said rotor when in said locking position.
10. A load limiting arrangement according to claim 9, wherein the or each said locking element is moved from said release position to said locking position by rotation of an actuating ring.
11. A load limiting arrangement according to any preceding claim, wherein said connecting mechanism comprises an actuator operable to actuate the mechanism.
12. A load limiting arrangement according to claim 11 as dependent upon claim 10, wherein said actuator is operable to rotate said actuating ring. .
13. A load limiting arrangement according to claim 11 or 12, wherein said actuator comprises a gas generator.
14. A load limiting arrangement according to claim 11 or 12, wherein said actuator comprises a solenoid.
15. A load limiting arrangement according to any preceding claim, further comprising an energy absorbing torsion element connected to the spool to resist rotation of the spool in said pay-out direction before actuation of said connecting mechanism.
16. A load limiting arrangement according to claim 15, wherein the torsion unit comprises a torsion bar.
17. A load limiting arrangement substantially as hereinbefore described with reference to and as shown in Figures 1 to 3 of the accompanying drawings.
18. A limiting arrangement substantially as hereinbefore described with reference to and as shown in Figures 1 to 3 of the accompanying drawings, modified as shown in Figure 4.
19. Any novel feature or combination of features disclosed herein.