GB2369683A

GB2369683A - Position sensor for vehicle seat

Info

Publication number: GB2369683A
Application number: GB0029525A
Authority: GB
Inventors: Bart Dewaele
Original assignee: Autoliv Development AB
Current assignee: Autoliv Development AB
Priority date: 2000-12-04
Filing date: 2000-12-04
Publication date: 2002-06-05
Also published as: GB0029525D0

Abstract

A position sensing arrangement determines the position of a first part of a vehicle, such as a seat, head-rest or steering wheel, mounted for movement relative to a second part, such as the main body. A sensor element 1 incorporating a sensor 5, is positioned for movement relative to a sensed element 10 in the form of an elongate strip. The sensor 5 may be biassed against the strip 10 by a spring 6, or may be mounted to slide along the strip 10 (see fig 3). This minimises any 'interference' from stray objects. The strip 10 has at least one region 11 having a predetermined property, and another region in which the property is not present or has a different value. The sensor 5 can he a Hall effect, inductance or optical sensor. The system is used to alter the inflation characteristics of an air-bag according to the position of an occupant of the vehicle.

Description

DESCRIPTION OF INVENTION "IMPROVEMENTS IN OR RELATING TO A POSITION SENSOR ARRANGEMENT" THE PRESENT INVENTION relates to a position sensor arrangement.

There is a need to be able to sense the position of a first part of a vehicle relative to the second part of the vehicle when the first part is moveably mounted in position. Thus there is a need to be able to sense the position of a vehicle seat, such as, for example, the front seat in a motor vehicle, such as a motor car, where the front seat is mounted on rails or the like for positional adjustment in the longitudinal direction of the vehicle. It is often desirable for a front seat in a motor vehicle to have an adjustable position in this way, for example so that the driver of the vehicle may adjust the position to provide a comfortable driving position having regard to the height of the driver.

If an air-bag is provided in front of such a seat it is desirable for the inflation characteristic of the air-bag to be adjusted in dependence upon the position of the seat. Thus, if the seat is in a forward position, with the occupant of the seat thus being very close to the air-bag, the air-bag should be inflated with a lesser quantity of gas, and if the seat is in a rear-most position, with the

occupant therefore being located a long way away from the air-bag. v Also, it is desirable to be able to sense the position of a seat component, such as a head-rest, relative to the rest of the seat. This may provide an indication of the height of the occupant of the seat. It may be desirable to alter the inflation characteristic of an air-bag in dependence on the height of the occupant of a seat. Additionally it may be desirable to be able to sense the position of other components with a vehicle, such as the position of a height adjustable pillar loop or a steering wheel.

Various proposals have been made as to how the position of a seat can be sensed. It has been proposed to use one or more micro switches. Such switches maybe prone to mechanical failure. It has also been proposed, for example, to sense the position of a seat using a sensor arrangement where the sensor itself has no moving parts, such as a Hall effect sensor and a magnet.

However, it has been found that such a sensor may provide an erroneous output, especially if a ferromagnetic object is located close to the Hall element within the sensor.

The present invention seeks to provide an improved position sensor arrangement.

According to this invention there is provided a position sensor arrangement for sensing the position of a first part of a vehicle which is mounted for movement relative to a second part of the vehicle. The arrangement comprising a sensor element and a sensed element, each element being associated with a respective one of said parts, the sensor element comprising a sensor adapted to sense a predetermined property, the sensed element comprising an elongate strip, the elongate strip having at least one region in which said property is present and has a first value and at least one other region in which the sensed property is not present or has second different value, the sensor being maintained in a substantially predetermined position adjacent the sensed element during the relative movement between the sensor element and the sensed element on movement of the said first part.

The first part may be a part such a vehicle seat, an adjustable pillar loop or a steering wheel mounted for movement relative to the main body the vehicle. Alternatively the first part may be a seat headrest which is moveable relative to the main part of the seat.

In one embodiment the sensor element is resiliently biased into contact with a surface of the sensed element.

Conveniently the sensor element is within a housing, the housing being guided by two parallel guide elements which extend from a support plate, a resilient element being provided located between the support plate and the housing to bias the housing into contact with the said surface of the sensed element.

In an alternative embodiment the sensor element is in the form of a carriage and the elongate strip constituting the sensed element is in the form of a rail, the carriage being mounted on the rail for sliding movement there along.

Conveniently the rail is provided with two axially extending recesses formed in opposed side edges thereof, the carriage of the sensor element having arms which extend adjacent the sides of the rail, the arms carrying inwardly directed fingers received within the recesses.

Various types of sensor may be used, and thus in one embodiment the sensor is a Hall effect sensor and the said predetermined property is a magnetic property.

Alternatively the sensor is an inductive sensor, and the predetermined property is an inductive property.

In a further embodiment the sensor is an optical sensor, and the predetermined property is a light-reflecting property.

The invention relates to an arrangement of the type described above when the first part is a vehicle seat and the second part is the body of the vehicle. In examples of such an embodiment of the invention either the sensed element is fixed to the motor vehicle, and the sensor element is mounted on the vehicle seat, or alternatively, the sensor element is fixed to the motor vehicle, and the sensed element is mounted on the vehicle seat.

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 principal components of a sensor arrangement in accordance with the invention, FIGURE 2 is an end view of the arrangement shown in Figure 1, FIGURE 3 is a view corresponding to Figure I illustrating an alternative embodiment of the invention, FIGURE 4 is an end view of the arrangement shown in Figure 3, FIGURE 5 is a diagrammatic perspective view of part of a vehicle seat illustrating one arrangement in accordance with the invention, and FIGURE 6 is a view corresponding to Figure 5 illustrating an alternate embodiment of the invention.

In embodiments of the invention a sensor element is provided, and a sensed element is provided, in the form of an elongate strip. The sensor element is adapted to sense a specific characteristic present in the sensed element, and has no moving parts, and the sensed element has at least one region where the characteristic is present, and at least one region where the characteristic is not present. One of the elements is fixed in position in the motor vehicle and the other element is mounted on the seat so that, as the seat moves, there is relative movement between the elements. The elements are located in position immediately adjacent each other during the entire movement of the seat, and thus the sensor element is always located adjacent part of the sensed element, minimising the risk of any undesired"interference"if additional objects are present in the motor vehicle.

Referring initially to Figure 1 of the accompanying drawings, a sensor unit 1 comprises a mounting plate 2 by means of which the sensor unit may be mounted in position, the mounting plate 2 carrying two parallel guide arms 3,4 which guide a sensor housing 5 so that the sensor housing 5 may execute a motion towards and away from the plate 2. A compression spring 6 is provided located between the plate and the housing tending to bias the housing away from the plate. The housing 5 contains a sensor which has no moving parts and which is adapted to sense a predetermined characteristic. The sensor may therefore be a Hall sensor, adapted to detect a magnetic field, although the sensor may be an inductive sensor which generates a magnetic field and which responds to changes in the generated magnetic field caused by materials of different reluctance being introduced into the magnetic field. Alternatively again the sensor may be an optical sensor, such as a sensor which includes a source of light, in the form of an infra-red light-emitting diode, and a light sensor adapted to detect reflected light.

Associated with the sensor unit I is an elongate sensed element 10. The sensed element 10 is in the form of an elongate strip having a uniform width, the strip presenting an upper surface which is directed towards the sensor unit 1. The strip 10 has at least two regions. One region 11, herein termed the "target"region, is provided with a first predetermined characteristic which has a predetermine value. The second region, 12, is such that the predetermined characteristic has a second, different, value, or is not present at all.

If the sensor 5 is a Hall effect sensor, the target region 11 may be made of magnetic material. The rest of the strip may be made of a non-magnetic material such as, for example, a plastics material. It will be understood that if the sensor 5 is adjacent the magnetic material present in the target region 11, it will provide a predetermined output, whereas if the sensor is adjacent the plastics material forming the region 12, it will provide a different output. Alternatively the entire strip may be made of magnetic material with only the target region being magnetised. Of course, if the sensor is an inductive sensor, the target region 11 will be of a material having a predetermined iductive property such as a predetermined reluctance, and the region 12 will be of a material having a different reluctance. Alternatively again if the sensor is an optical sensor, the region 11 may be a region in which the surface of the strip is reflective, whereas the region 12 may be a region where the strip is nonreflective.

Whilst the strip 10 shown in Figure 1 is of a simple design, having one target region 11, and with the remainder of the strip constituting a region 12 not having the properties of the target region 11, it is envisaged that in certain embodiments of the invention there may be more than one discrete target region 11.

It is to be appreciated that the components as shown in Figures 1 and 2 will be mounted in position on a vehicle seat and on part of the structure of the vehicle so that, as the position of the vehicle seat is adjusted, so there is a relative movement between the sensor unit 1 and the strip 10. However, the housing 5 is biased by the spring 6 into sliding contact with the upper surface of the strip 10, and thus the sensor within the housing 5 will only be able to sense the strip 10. The provision of a spring biasing the housing into contact with the strip ensures that the sensor housing 5 is biased into contact with the surface of the strip regardless of any manufacturing tolerances that may exist.

The surface of the housing 5 that engages the strip may be provided with rollers or the like to minimise any effects of friction. Because the spring maintains the sensor in a predetermined position adjacent the strip 10, the sensor can only sense the strip and is thus not influenced by other objects.

Figures 3 and 4 illustrate a modified embodiment of the invention which has major components which correspond with the components described above, and in which the sensor housing 5 and the rail 10 are both modified so that the sensor housing 5 is in the form of a carriage sliding along a rail constituted by the elongate strip 10. Thus, the elongate strip 10 is provided with two co aligned recesses 13,14 formed in opposed side walls thereof, so that the side edges of the upper part of the strip 10 constitute two outwardly directed flanges 15,16, and the housing 5 is provided with two depending arms 7,8, each of which carries an inwardly directed finger 9, the fingers being inserted into the recesses 13,14 so that the housing 5 is retained on the rail constituted by the elongate strip 10 but is slidable there along. The other features of the embodiment shown in Figures 3 and 4 are the same as the corresponding features described above with reference to Figures 1 and 2. In the embodiment of Figures 3 and 4, the housing 5 which houses the sensor is retained in a predetermined position adjacent the rail constituted by the elongate strip, with the benefit that the sensor can only sense the rail. Thus the sensor is not influenced by other objects.

Turning now to Figure 5, part of the floor 20 of a motor vehicle is illustrated schematically. Mounted on the floor 20 is a support block 21 which carries, on its upper surface, a rail 22. A carriage 23 slidably engages the rail, and mounted on the carriage 23 is the squab 24 of a vehicle seat. Mounted on the support block 20 is an elongate strip 10 of the type discussed above, and mounted on the under-surface of the squab of the seat is a sensor unit 1 of the type discussed above. Figure 5 is a schematic figure and the sensor unit 5 may be of the type shown in Figure 1 or of the type shown in Figure 3. It is important to note, however, from Figure 5 that the elongate strip 10 is fixed in position relative to the floor of the motor vehicle, and the sensor unit 1 is mounted on the seat and thus moves relative to the fixed elongate strip.

Figure 6 illustrates an alternative embodiment, but is generally equivalent to Figure 5. Figure 6 again illustrates part of the floor 20 of the vehicle and the mounting 21, carrying the rail 22 which engages a carriage 23 mounted on the underside of the squab 24 of the seat. However, in this embodiment the elongate strip 10 is mounted on the underside of the squab of the seat, and the sensor unit 1, which in this case is a sensor unit 1 generally similar to that shown in Figure 1, is mounted on the floor 20 of the motor vehicle. Thus the sensor unit 1 is fixed in position and the housing 5 containing the sensor is resiliently biased upwardly into contact with the strip 10 which is mounted on the seat 24 and moves relative to the fixed sensor unit 1.

An arrangement similar to those described above may be used to determine the position of part of a vehicle seat, such as a head-rest, relative to the rest of the seat. Also arrangements similar to those described above may be used to sense the position of vehicle components such as an adjustable pillar loop or a steering wheel.

In the present specification"comprise"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 position sensor arrangement for sensing the position of a first part of a vehicle which is mounted for movement relative to a second part of the vehicle.

The arrangement comprising a sensor element and a sensed element, each element being associated with a respective one of said parts, the sensor element comprising a sensor adapted to sense a predetermined property, the sensed element comprising an elongate strip, the elongate strip having at least one region in which said property is present and has a first value and at least one other region in which the sensed property is not present or has second different value, the sensor being maintained in a substantially predetermined position adjacent the sensed element during the relative movement between the sensor element and the sensed element on movement of the said first part.
2. An arrangement according to Claim 1 wherein the sensor element is resiliently biased into contact with a surface of the sensed element.
3. An arrangement according to Claim 2 wherein the sensor element is within a housing, the housing being guided by two parallel guide elements which extend from a support plate, a resilient element being provided located between the support plate and the housing to bias the housing into contact with the said surface of the sensed element.
4. An arrangement according to Claim 1 wherein the sensor element is in the form of a carriage and the elongate strip constituting the sensed element is in the form of a rail, the carriage being mounted on the rail for sliding movement there along.
5. An arrangement according to Claim 4 wherein the rail is provided with two axially extending recesses formed in opposed side edges thereof, the carriage of the sensor element having arms which extend adjacent the sides of the rail, the arms carrying inwardly directed fingers received within the recesses.
6. An arrangement according to any one of the preceding Claims wherein the sensor is a Hall effect sensor and wherein said predetermined property, is a magnetic property.
7. An arrangement according to any one of Claims 1 to 5 wherein the sensor is an inductive sensor, and wherein the predetermined property is an inductive property.
8. An arrangement according to any one of Claims 1 to 5 wherein the sensor is an optical sensor, and wherein the predetermined property is a lightreflecting property.
9. An arrangement according to any one of the preceding Claims wherein the first part is a vehicle seat and the second part is the body of the vehicle.
10. An arrangement according to Claim 9 wherein the sensed element is fixed to the motor vehicle, and the sensor element is mounted on the vehicle seat.
11. An arrangement according to Claim 9 wherein the sensor element is fixed to the motor vehicle, and the sensed element is mounted on the vehicle seat.
12. An arrangement for sensing the position of a part of a vehicle substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.
13. An arrangement for sensing the position of a part of a vehicle substantially as herein described with reference to and as shown in Figures 3 and 4 of the accompanying drawings.
14. An arrangement for sensing the position of a part of a vehicle substantially as herein described with reference to and as shown in Figure 5 of the accompanying drawings.
15. An arrangement for sensing the position of a part of a vehicle substantially as herein described with reference to and as shown in Figure 6 of the accompanying drawings.
16. Any novel feature or combination of features disclosed herein.