GB2328184A

GB2328184A - Assembling a vehicle sensor

Info

Publication number: GB2328184A
Application number: GB9717138A
Authority: GB
Inventors: Ian Alexander Gordon; Alan George Smithson
Original assignee: AlliedSignal Ltd
Current assignee: Honeywell UK Ltd
Priority date: 1997-08-12
Filing date: 1997-08-12
Publication date: 1999-02-17
Anticipated expiration: 2017-08-12
Also published as: GB2328184B; GB9717138D0

Abstract

A method of assembling an acceleration sensor 2 in a vehicle safety restraint belt retractor 1, the sensor comprising, a rocking lever 5 for locking the retractor against belt webbing protraction, mounted in the retractor about a pivot point 6, and an inertia mass member 3 which is sensitive to sudden changes in vehicle speed to move the rocking lever into a locking position when a change in vehicle acceleration occurs, comprises the steps of assembling the acceleration sensor in the retractor without the rocking lever 5 and subsequently installing the lever by selecting the pivot point 6 of the lever to match a desired vehicle sensor gap defining the distance through which the lever must move to lock the retractor. The desired gap may be measured before the pivot point is defined. The pivot point may be formed by driving a steel pin first through a lever support member and then through a pre-moulded hole in the lever, and subsequently through a second support member, or alternatively inserting the pin through pre-formed holes. Alternatively, a range of pivot points may be provided. This method enables the clearance distance to be kept small to optimise the sensitivity of the sensor and to minimise lever chatter noise caused by vibrations of the vehicle engine or from uneven road surfaces, without the requirement for tight manufacturing tolerances which increases costs, and also minimises the danger of the retractor locking spuriously.

Description

VEHICLE SENSOR DESCRIPTION The present invention relates to a vehicle sensor for a vehicle safety restraint seat belt retractor.

A vehicle sensor detects sudden changes in vehicle speed which usually indicate an impending emergency situation. The vehicle sensor is mounted in the retractor or closely linked thereto and will lock the retractor against further belt pay out when an emergency situation is detected, thus securing a vehicle occupant against dangerous forward movement under his own momentum if the vehicle stops suddenly.

Typically, a vehicle sensor comprises an inertia mass which moves under the influence of sudden changes in speed, and a pivoted lever moved by the mass to lock the retractor.

The distance through which the lever moves to effect the locking determines the sensitivity of the sensor since it influences the speed with which the retractor is locked in an emergency. Evidently it is desirable to keep this clearance distance small to optimise the sensitivity. A small gap also reduces noise generated in the retractor, for example that caused by vibrations of the vehicle engine or from uneven road surfaces, making the lever chatter.

On the other hand, a small clearance gap means tighter manufacturing tolerances and this leads to increased costs.

With an excessively small gap there is the danger of the retractor locking spuriously or even jamming altogether.

Traditionally the vehicle sensor is assembled on the production line, as a complete unit before it is mounted in the retractor, and hence the vehicle sensor gap is effectively already set by the dimensions of the constituent components.

According to the present invention there is provided a method of assembling an acceleration sensor in a vehicle safety restraint belt retractor, the sensor comprising a rocking lever for locking the retractor against belt webbing extraction, mounted in the retractor about a pivot point, and an inertia mass member which is sensitive to sudden changes in vehicle speed and mounted to move the lever into a locking position when a change in vehicle acceleration of at least a predetermine value occurs, the method comprising assembling the acceleration sensor in the retractor without the lever and, subsequently, installing the lever by selecting the pivot point of the lever to match a desired vehicle sensor gap defining the distance through which the lever must move to lock the retractor.

The method of the present invention allows every retractor to be made with a precisely controlled vehicle sensor gap without the need for unacceptable manufacturing tolerances to be implemented. Hence an optimal balance can be struck between having a larger gap to give easy spool rotation, and a small gap which gives faster locking and lower noise levels.

There is also provided a retractor comprising a vehicle sensor and constructed according to the method of the invention.

Preferably the desired gap is measured before the pivot point is defined.

According to one preferred embodiment the pivot point is formed by driving a steel pin through a lever support member on the retractor, and then through a pre-moulded hole in the lever, and subsequently, for extra support, through a second support member. The pin will, in this embodiment, make its own hole in the support members and thus, within a range predetermined by the size of the parts of the retractor, an infinitely varying size of gap may be relatively easily and cheaply defined in any retractor.

Alternatively a plurality of holes could be pre-moulded or drilled, or otherwise formed in the lever supports so as to give a finite choice of pivot point positions defining a finite choice of gap sizes.

In a further alternative, the trunnion height can be set, using the axis insert, before final assembly.

For a better understanding of the present invention and to show how the same may be carried into effect, reference will now be made to the accompanying drawing in which: Figure 1 is a cut away side view of a retractor with a vehicle sensor constructed according to the method of the present invention; Figure 2 is a schematic cross-sectional view of a vehicle sensor in a retractor illustrating the method of the invention; Figures 3-6 are schematic views of vehicle sensor levers and their supports, illustrating alternative embodiments of the method of the invention.

Figure 1 shows a side view of a retractor 1 fitted with a vehicle sensor indicated generally at 2. The vehicle sensor comprises an inertia mass 3 on a platform 4. Resting on the mass 3 is a pawl 5 pivoted about point 6 on an upstanding arm 7 of the support platform 4. It is fixed to arm 7 by a pin 8 at the pivot point 6.

In the event of an emergency situation, the vehicle usually experiences an abrupt change in speed and this tips the inertia mass 3 out of its normal vertical alignment.

The mass 3 in turn locks the pawl 5, pivoting it upwards into engagement with a toothed wheel attached to the retractor spool (not shown). Engagement of pawl 5 with the teeth on the wheel locked the retractor against further belt extraction.

Figure 2 is a schematic illustration of a vehicle sensor which could be used in the retractor of Figure 1. It comprises an inertial mass 3 with a up-standing finger 9 engaging pawl 5 which is pivoted about point 6. The toothed wheel of the retractor is shown schematically at 10 and the gap between the engaging end 12 of the pawl 5 and the retractor wheel 10 is the distance from which the pawl must move to lock the retractor and is the vehicle sensor clearance gap 11.

If the pivot point 6 is moved higher, i.e. in the direction of arrow A, then the engaging end 12 of pawl 5 is lower and the gap 11 will be larger.

On the other hand if the pivot point 6 is moved downwardly in the direction of arrow B, then the engaging end 12 of pawl 5 moves up and the gap 11 closes.

Figure 3 illustrates one way in which the pivot point 6 can be made during production. The lever 5 is attached between two supports 13, 14 by driving a steel pin 15 through the two supports and through a hole at the end of the pawl 5 opposite to the engaging end 12. The two supports 13, 14 form part of the upstanding arm 7 of vehicle sensor housing 4.

Alternatively, as illustrated in Figure 4, a single support 16 is used and this is sandwiched between two arms of a U-shaped end 17 of pawl 5. The steel pin 15 is driven through holes 18 in the first arm of the U-shaped part of pawl 5, through the support 16 and through a hole in the other arm of U-shape 17. This defines the pivot point for the lever 5.

Figure 5 illustrates another embodiment in which the pin and holes is replaced by a rectangular insert 19 and a rectangular hole 20. The rectangular insert 19 has ridges 21 formed on its sides and these co-operate with cut-outs 22 in the rectangular holes 20 (which is made longer than the rectangular insert) so that a range of possible positions is given.

Figure 6 shows another alternatively embodiment in which the pin 15 is replaced by an eccentric insert 24 with a set of splines 23 along its cylindrical outer surface. In this case the adjustment is given by rotating the eccentric insert 24, as indicated by arrow 25.

Claims

1. A method of assembling an acceleration sensor in a vehicle safety restraint belt retractor, the sensor comprising: a rocking lever for locking the retractor against belt webbing protraction, mounted in the retractor about a pivot point, and an inertia mass member which is sensitive to sudden changes in vehicle speed and is mounted to move the rocking lever into a locking position when a change in - vehicle acceleration of at least a predetermined value occurs, the method comprising: assembling the acceleration sensor in the retractor without the rocking lever and, subsequently, installing the lever by selecting the pivot point of the lever to match a desired vehicle sensor gap defining the distance through which the lever must move to lock the retractor.

2. A method of assembling an acceleration sensor according to claim 1, the method further comprising measuring the desired gap before defining the pivot point.

3. A method of assembling an acceleration sensor according ., to claim 1 or claim 2, the method further comprising forming the pivot point by driving a steel pin first through a lever support s member ea the retractor, and then through a pre-moulded hole in the level std subsequently through a second support member.

4. A method of assembling an acceleration sensor according to claim 1 or claim 2, the method further comprising forming a plurality of holes in the lever by pre-moulding or by predrilling so as to define a finite choice of pivot point positions.

5. A method of assembling an acceleration sensor according to any one of the preceding claims further comprising the step, before final assembly, of setting the trunnion height using the axis insert.

6. A method of assembling an acceleration sensor in a vehicle safety restraint seat belt retractor, substantially as hereinbefore described with reference to figures 1 and 2 and figures 3 , 4, 5 or 6 of the accompanying drawings.

7. A vehicle safety restraint belt retractor comprising a vehicle sensor assembled in accordance with the method of any one of claims 1 to 6.

8. A vehicle safety restraint belt retractor comprising: a spool holding a length of belt webbing wound thereon and being rotatably mounted in the retractor for belt protraction and retraction, and further comprising a vehicle acceleration sensor which has a rocking lever for engaging teeth on the retractor spool to lock the retractor spool against belt protraction, the lever being mounted in the retractor about a pivot point; an an inertia mass member being mounted on the retractor soas to be movable when the accelerator or decelerator of evehicle exceeds a predetermined level, and being coupled to the lever so as to pivot the lever about its pivot point when the mass moves,wherein a range of pivot points are provided in the retractor to provide a corresponding range of clearance gaps defining the distance through which the lever must move to lock the retractor.

9. A vehicle safety restraint belt retractor substantially as hereinbefore described with reference to figures 1 and 2 and figures 3 , 4, 5 or 6 of the accompanying drawings.