GB2345473A

GB2345473A - Deceleration sensor

Info

Publication number: GB2345473A
Application number: GB9900161A
Authority: GB
Inventors: Michael Kenneth Hishon
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 1999-01-05
Filing date: 1999-01-05
Publication date: 2000-07-12
Also published as: WO2000040441A1; GB9900161D0

Abstract

A deceleration sensor which may be utilised in a vehicle seat belt retractor mechanism mounted in a vehicle seat (see figures 1 and 6) comprises a pivotally mounted member 30 which is connected to a support so that it can pivot about a horizontal axis whereby its degree of pivotal movement is limited by stop members 33,34 (see figure 4). The pivotally mounted member carries an inertia element 26 which is moveable relative thereto between an initial position and a second position when subjected to a deceleration in excess of a predetermined threshold (see figure 5). The inertia element moves a control element 24 when subjected to said deceleration whereby the control element may contact the teeth 23 of a control disk (see figure 1) when utilised in a seat belt retractor mechanism so that further pay out of the belt is prevented. When forming part of a seat belt retractor mechanism mounted on a seat pivotal member 30 allows the inertia element 26 to hang vertically without causing engagement of the control element 24 with the control disk. The inertia element may also take the form of a ball or cylindrical member.

Description

DESCRIPTION OF INVENTION: "Improvements In Or Relating To A Deceleration Sensor" THE PRESENT invention relates to a deceleration sensor and more particularly relates to a deceleration sensor for use in a motor vehicle to activate a safety device such as, for example, an inertia reel.

It is known to provide a safety belt in a motor vehicle, the safety belt being retracted automatically onto an inertia reel when not in use. The inertia reel is provided with a deceleration sensor, in the form of an inertia device, which operates to lock the reel, to prevent safety belt being paid out from the reel, when an accident situation arises. It is to be appreciated that in a typical accident situation there is very substantial deceleration of the vehicle.

A typical deceleration sensor comprises a pendulum.

The pendulum is mounted to pivot about a predetermined axis. The pendulum is provided with a head located above the axis. When the pendulum pivots about the axis, the head may engage a lever, and may move the lever to engage, for example, a toothed wheel which is mounted to co-rotate with the spindle of the retractor reel. The engagement of the lever with the toothed wheel causes the movement of the toothed wheel to stop, which can effect locking of the retractor reel.

A problem that has been encountered with prior proposed deceleration sensors is that the sensors are sensitive to inclination of the vehicle. Thus, if the vehicle has been parked on sloping ground, the deceleration sensor could actually be in a position where the lever is moved to engage the toothed wheel, thus preventing the withdrawal of safety belt from the motor vehicle.

This problem has become more acute in connection with retractor mechanisms which are adapted to be mounted within a vehicle seat. It is to be understood that it has been proposed to mount a retractor mechanism in a vehicle seat, at a position within the back of the seat immediately adjacent the shoulder of an occupant of the seat. A typical seat back is of adjustable angle or rake. Thus the seat back may be adjusted between the relatively upright position and a relatively laid back position. It has been difficult to provide an acceleration sensor for use in such an environment that operates satisfactorily, whilst permitting the adjustment of the seat between these alternate positions.

The present invention seeks to provide an improved deceleration sensor and seeks to provide a retractor mechanism provided with such a deceleration sensor.

According to this invention there is provided a deceleration sensor, the deceleration sensor comprising a pivotally mounted member, the pivotally mounted member being connected to a support and being adapted to pivot, relative to said support, about a substantially horizontal axis, stop means being provided to limit the degree of pivotal movement of the pivotally mounted member, the pivotally mounted member carrying an inertia element, the inertia element being movable relative to the pivotally mounted member between an initial position and a second position when subjected to deceleration in excess of a predetermined threshold, the inertia member being adapted to move a control element when the inertia member moves to the second position in response to said deceleration.

Preferably the inertia element comprises a pendulum, the pendulum having a head supported by the upper surface of the pivotally mounted member and a shank passing from the head through the pivotally mounted member, the shank carrying a mass at its lower end.

Conveniently the head of the pendulum is substantially dome-shaped.

Preferably the centre of curvature of said domeshaped head is substantially co-aligned with the axis of pivotal mounting of the pivotally mounted member.

Advantageously the element which is moved by the inertia member comprises a pivotally mounted control lever initially lying immediately adjacent the head of the pendulum.

Conveniently the control lever is adapted to be moved to a position in which the control lever engages the toothed periphery of a control disk.

The invention relates to a retractor mechanism incorporating a deceleration sensor as described above.

Conveniently, in such a retractor mechanism, the control disk is adapted to co-rotate with a shaft of the retractor mechanism, the shaft being adapted to have a safety belt wound down, the arrangement being such that engagement of the control lever with the toothed periphery of the control disk causes locking means to be actuated on continuing rotation of the shaft to prevent the withdrawal of safety belt from the retractor mechanism.

The invention also relates to a vehicle seat provided with a retractor mechanism 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 perspective view of the operative parts of a retractor mechanism provided with a deceleration sensor in accordance with the invention, with the outer cover of the retractor mechanism removed, Figure 2 is a view corresponding to Figure 1 illustrating the retractor of Figure 1 with the locking wheel and the deceleration sensor removed, in order to illustrate more clearly the locking pins, Figure 3 is a view illustrating, on an enlarged scale, the deceleration sensor in an initial position, Figure 4 is a view corresponding to Figure 1 illustrating the deceleration sensor when in a subsequent position, Figure 5 is a view corresponding to Figure 4 illustrating the deceleration sensor when in a subsequent condition, Figure 6 is a diagrammatic view illustrating the back of a seat, showing the possible angles of adjustment of the back of the seat, illustrating the deceleration sensor schematically, Figure 7 is an enlarged view of the deceleration sensor illustrating the condition that the deceleration sensor occupies when the seat back is in a first position, and Figure 8 is a view corresponding to Figure 7 illustrating the position that the acceleration sensor occupies when the seat back is in a second position.

Referring initially to Figures 1 and 2 a retractor reel assembly is illustrated (parts thereof removed for the sake of clarity of illustration), the retractor reel assembly incorporating a deceleration sensor in accordance with the invention.

The reel assembly comprises a support 10 which is adapted to be mounted on a motor vehicle body or on a vehicle seat. The support 10 includes a substantially planar plate having two forwardly extending parallel flanges lOa and lob (Figure 2). The flanges are parallel and are substantially the same shape. A rotatable reel 11 extends between the flanges and is rotatably supported on the flanges. An aperture lia is provided extending through the shaft of the reel 11 to facilitate the attachment of one end of the safety belt to the shaft. The safety belt may be wound on to the shaft.

One end of the shaft extends beyond the flange l0a and is provided with a device (as will be described below) for locking the shaft to prevent rotation of the shaft relative to the support 10, thus preventing the subsequent extraction of any of the safety belt from the reel assembly. The shaft is provided with a helical spring (not shown) for automatic retraction of the belt when the safety belt is not in use. The helical spring is provided at the end of the shaft opposite to the locking device.

The locking device, in this particular embodiment of the invention, comprises various components including two locking pins 12,13. The locking pins extend, parallel with each other, substantially diametrically through the shaft 11. The construction of the shaft and the way in which the pins are located in the shaft will be described hereinafter in greater detail. The pins are adapted to move in opposite directions to a protruding position in which they can engage with fixed abutment means 14 constituted by a circular array of detents securely mounted on the flange l0a of the support 10. The detents may comprise tabs pressed out of the flange 10a. The array of detents 14 is coaxial with the axis of the shaft 11. When the locking pins 12,12 engage the detents 14, the shaft 11 is prevented from further rotation.

Each locking pin 12,13, is provided with a respective guide pin 15,16, constituted by a pin extending from one end of the locking pin in a direction parallel to the axis of the shaft 11. A control disc 19 is provided which is rotatably mounted on the shaft 11 adjacent the locking pins 12,13. Guide grooves 17,18, the side walls of which form guide surfaces to engage the guide pins, are provided in the control disc and the arrangement is such that each of the guide pins 15,16 is accommodated within a respective guide groove 17,18. The guide grooves each include an initial arcuate portion 17a, 18a which extends substantially parallel to the outer circumference of the control disc 19, and the guide grooves have terminal arcuate portions 17b, 18b which extend generally inwardly so that the inner ends of the guide groove portions 17b, 18b are closer to the axis of the shaft 11 than the initial arcuate portions 17a, 18a of the guide grooves.

The control disc 19 is connected to the shaft 11 by means of a resilient interconnection, exemplified by a spring element 20 which extends through a groove 21 formed diametrically in the end of an extension of the shaft 11, opposed ends of the spring element 20 being connected to the control disc 19 at diametrically opposed positions 22.

The arrangement is such that if the shaft 11 is rotated in such a sense that the safety belt is being paid out from the reel (i. e. in an anti-clockwise sense as generally shown in Figure 1) the shaft 11 can rotate slightly relative to the control disc 19, with the spring element 20 being placed under tension.

It is to be understood that the guide grooves 17, 18 and the control disc 19 are so positioned and have such a length and shape that when the shaft is turned relative to the control disc initially the guide pins 15 move through the initial arcuate portions 17a, 18a of the guide grooves and thus the locking pins 12,13 are not moved axially. However, if the shaft 11 moves, relative to the control disc 19, to such an extend that the guide pins 15, 16 enter the secondary arcuate portions 17b, 18b of the guide grooves 17,18, the locking pins are moved axially, the locking pin 12 moving generally upwardly when in the condition illustrated in Figure 2 and the locking pin 13 moving generally downwardly. The locking pins will be moved to such an extent that the ends of the locking pins will engage corresponding detents 14 thus ensuring that there is no further rotation of the shaft 11 and thus preventing a further length of the seat belt being withdrawn.

The locking pins 12,13 are illustrated in the retracted or non-locking position in Figure 2. In this position the centres of gravity of the locking pins are close to the centre of the shaft, so that the pins are, at the worst, only slightly influenced by centrifugal force during rotation of the shaft.

The control disc 19 is provided with a plurality of teeth 23 spaced around the circumference of the disc to form a ratchet. A control lever 24 is provided located adjacent the periphery of the control disc 19. One end of the control lever is pivotally connected to the flange 10a.

The lever can be moved from a position in which it does not engage the teeth of the locking disc 19 to a position in which there is engagement under the influence of a deceleration sensor arrangement 25 which is illustrated in greater detail in Figure 3.

Turning now to Figure 3 the deceleration sensor comprises an inertia member 25 in the form of a pendulum, the inertia member 25 being adapted to move from an initial or"ordinary"position to an inclined position under the influence of a substantial deceleration applied to a vehicle in which the described retractor reel is provided.

The pendulum comprises a lower cylindrical portion 26 of substantial mass which is connected, by means of a relatively narrow shank 27, to a dome-shaped head 28. The dome-shaped head is of a greater diameter than the shank 27 and presents a substantially hemispherical upper surface, and an annular under-surface that surround the shank. The relatively narrow shank 27 of the inertia member 25 passed through a vertical bore 29 provided on a pivotally mounted member 30. The pivotally mounted member 30 presents an upper surface 31 which engages the undersurface of the dome-shaped head 28 of the inertia member 25.

The pivotally mounted member 30 is mounted on the flange 10a of the support 10 for pivoting movement about a horizontal axis 32.

Two stop elements 33,34 are provided located beneath the pivotally mounted member 30 at such a position that if the pivotally mounted member 30 rotates in a clockwise sense about the pivot axis 32, part of the pivotally mounted member 30 engages the stop 33, whereas if the pivotally mounted member 30 rotates in a counterclockwise sense about the pivotal axis 32, part of the pivotally mounted member 30 engages the stop 34. Thus the degree of pivotal movement of the pivotally mounted member 30 about the pivot axis 32 relative to the support 10 is restricted by the stops 30,34.

It is to be observed that the control lever 24 rests on the upper surface of the dome-shaped head 28 of the inertia member 25. It is also to be observed that when the inertia member 25 is in the position illustrated in Figure 3, the inertia member 25 is fully supported by the pivotally mounted member 30, with the undersurface of the dome-shaped head being fully supported by the upper surface 31 of the tiltable member 30, and the centre of curvature of the dome-shaped head is substantially aligned with the axis 32 of pivotal movement of the pivotally mounted member 30.

If the retractor mechanism is inclined, for example if the vehicle in which the retractor mechanism is mounted is parked on a slope, the inertia member will move to a position in which the inertia member is itself vertical, since the mass 26 will always tend to hang downwards. Thus the inertia member will tend to move to the position illustrated in Figure 4, causing the pivotally mounted member 30 to tilt about the pivot axis 32. The movement will be such that the pivotally mounted member 30 engages the stop 34. During this movement of the combination of the pivotally mounted member 30 and the inertia member 25, the control lever has not moved.

Should the vehicle in which retractor is mounted be subject to severe deceleration, the cylindrical portion 26 forming part of the inertia member 25 will tend to move forwardly, because of its inertia, causing the inertia member 25 to pivot, relative to the pivotally mounted member 30, about a point defined by the engagement of the outer periphery of the dome-shaped head 28 and the upper surface 31 of the pivotally mounted member 30. Thus one side of the dome-shaped head 28 will rise relative to the upper surface 31 of the pivotally mounted member 30. The inertia member will then have the position illustrated in Figure 5. It is to be observed that in this position the control lever 24 has been moved to such a position that the end of the locking arm will engage the teeth 23 provided in the periphery of the control disk 19. In the manner described above, the retractor mechanism will be locked.

Figure 6 illustrates a vehicle seat 40 comprising a squab 41 and a back 42. The back 42 is mounted so that it can be adjusted pivotally about a pivot axis 43. The back may have a nominal"ordinary"position as indicted by the line 44, but may be adjusted forwardly of that"normal" position by an angle up to the angle"a", in which case the seat will have a position as indicted by the line 45 and also the angle of inclination of the back 42 of the seat may be adjusted rearwardly of the"normal"position as indicted by the line 44 through an angle"b"and when thus adjusted the back will have a position indicated by the line 46.

When the back of the seat is in the ordinary position as indicated by the line 44, the deceleration sensor of the retractor mechanism will ordinarily have the position illustrated in Figure 3 (the line 44 is shown for reference in Figure 3). Should the back of the seat be tilted forwardly so that the seat occupies the position indicated the line 45, the deceleration sensor will have the condition illustrated in Figure 7. It is to be noted that since the line 45 is displaced by an angle"a" forwardly of the line 44, the stop members 33,34 will define a plane 46 which is offset from the horizontal 47 by an angle"a". Nevertheless, the deceleration sensor will operation in a satisfactory manner.

Similarly, if the seat back is moved back to the position indicated by the line 46, the plane 46 defined by the stop members 33,34 will make an angle"b"with the horizontal 47, but in the opposite sense to the angle"a" illustrated in Figure 7. Nevertheless, the deceleration sensor will still operate in a satisfactory manner.

It is to be understood that in the described embodiment of the invention, the control lever will not move into contact with the control disk during the first movement of the pendulum. This has the advantage that the retractor will work in a satisfactory manner when the vehicle is parked on a slope and will also operate in a satisfactory manner when the retractor mechanism is mounted in the back of the seat and the position of the seat is adjusted away from the"normal"position. Also this feature will help to prevent premature locking of the reel during ordinary braking of the motor vehicle.

Nevertheless, the described arrangement will provide a satisfactory result in the event that an accident should occur.

It is to be understood that the details of the locking mechanism illustrated in Figures 1 and 2 are given by way of example and alternative locking arrangements could be utilised. It is to be understood that there have been various prior proposals as to how locking of a retractor reel can be effected by bringing a control lever into engagement with the toothed periphery of a control disk.

Also it is to be understood that whilst reference has been made to an inertia member in the form of a pendulum, in alternative embodiments of the invention the inertia member could comprise a ball, forming part of a ball-in-cup deceleration sensor or could comprise an inertia member of the"standing-man"type in which a substantially cylindrical member is provided which is normally retained in an upright position within a substantially cylindrical cavity which is of slightly greater diameter than the member, the upper part of the cylindrical member being provided with a recess which receives the lower end of a plunger, the arrangement being such that when the cylindrical member topples over, within the cavity, due to substantial deceleration of a vehicle in which the arrangement is mounted, the plunger is moved upwardly. The plunger may thus engage the undersurface of a lever, such as the control lever 24 to move that lever into engagement with the toothed periphery of a control disk.

Claims

CLAIMS: 1. A deceleration sensor, the deceleration sensor comprising a pivotally mounted member, the pivotally mounted member being connected to a support and being adapted to pivot, relative to said support, about a substantially horizontal axis, stop means being provided to limit the degree of pivotal movement of the pivotally mounted member, the pivotally mounted member carrying an inertia element, the inertia element being movable relative to the pivotally mounted member between an initial position and a second position when subjected to deceleration in excess of a predetermined threshold, the inertia member being adapted to move a control element when the inertia member moves to the second position in response to said deceleration.
2. A deceleration sensor according Claim 1 wherein the inertia element comprises a pendulum, the pendulum having a head supported by the upper surface of the pivotally mounted member and a shank passing from the head through the pivotally mounted member, the shank carrying a mass at its lower end.
3. A deceleration sensor according to Claim 2 wherein the head of the pendulum is substantially dome-shaped.
4. A deceleration sensor according to Claim 3 wherein the centre of curvature of said dome-shaped head is substantially co-aligned with the axis of pivotal mounting of the pivotally mounted member.
5. A deceleration sensor according to any one of Claims 2 to 4 wherein the element which is moved by the inertia member comprises a pivotally mounted control lever initially lying immediately adjacent the head of the pendulum.
6. A deceleration sensor according to Claim 5 wherein the control lever is adapted to be moved to a position in which the control lever engages the toothed periphery of a control disk.
7. A retractor mechanism incorporating a deceleration sensor according to any one of Claims 1 to 6.
8. A retractor mechanism according to Claim 7 as dependent upon Claim 6 wherein the control disk is adapted to co-rotate with a shaft of the retractor mechanism, the shaft being adapted to have a safety belt wound down, the arrangement being such that engagement of the control lever with the toothed periphery of the control disk causes locking means to be actuated on continuing rotation of the shaft to prevent the withdrawal of safety belt from the retractor mechanism.
9. A vehicle seat provided with a retractor mechanism according to Claims 7 to 8.
10. A deceleration sensor substantially as herein described with reference to and as shown in the accompanying drawings.
11. A retractor mechanism substantially as herein described with reference to and as shown in the accompanying drawings.
12. Any novel feature or combination of features disclosed herein.