GB2289106A

GB2289106A - Apparatus for measuring the relative position of two members

Info

Publication number: GB2289106A
Application number: GB9508781A
Authority: GB
Inventors: David William Jackson Kennedy; Phillip James Green; Gordon Frederick Smith
Original assignee: MG Rover Group Ltd
Current assignee: MG Rover Group Ltd
Priority date: 1994-05-06
Filing date: 1995-05-01
Publication date: 1995-11-08
Anticipated expiration: 2015-05-01
Also published as: GB9508781D0; GB9409032D0; GB2289106B

Abstract

A rotary sensor 14 which responds to changes in the distance between two components in a vehicle suspension, one unsprung and one sprung, is driven by a link in the form of a crank part 16 connected to a rod 18 through a hinge 20 formed from flexible material. The link may alternatively be formed as a twisted strip (Fig. 2). The link is intended to reduce the problem of wear that takes place in drive links which include a mechanical articulation joint. <IMAGE>

Description

APPARATUS FOR MEASURING THE RELATIVE POSITION OF TWO MEMBERS This invention relates to apparatus for measuring the distance between two members, and particularly but not exclusively to a apparatus for measuring movement in suspension systems for motor vehicles.

In the field of motor vehicle manufacture, assembly of many small components is a major part of the manufacturing process.

The aim is constantly to simplify construction of motor vehicles without compromising on the ability of the finished article to meet specifications. However, this aim is often difficult to achieve, since many parts must move relative to others.

In addition to this problem, a plurality of moving parts causes reliability problems since even the most durable materials wear due to the effect of friction between two components. In particular, the suspension system of some motor vehicles is controlled actively. One of the main requirements for such a system is that the position of the suspension of the vehicle relative to its chassis must be known, in order to calculate the correct suspension forces for stabilising the vehicle.

At present this is carried out by connecting an articulated strut between the suspension and the chassis of the vehicle.

This articulated strut is pivotally attached at one end to the suspension of the vehicle, and at the other end it is mounted on the axle of a rotary height sensor attached to the chassis. The articulation allows the strut to act like a con rod and crank, when linear movement of the suspension is transferred to arcuate movement of the portion of the strut mounted on the axle of the rotary height sensor. In this way, the relative height of the chassis from the suspension can be calculated.

Due to the somewhat vibratory movement which a chassis can make relative to its suspension the articulating joint can be susceptible to wear and consequent failure. This type of articulated strut commonly comprises five components. This can be complex and time consuming to assemble.

The object of the present invention is to provide a drive link for use in suspension systems which will reduce the problems mentioned above.

According to one aspect of the invention there is provided apparatus for measuring the relative position of two members, the apparatus comprising a rotary sensor for mounting on one of said members and a drive link for connecting the sensor to the other of said members, the drive link comprising a crank part connected to the sensor, a connecting part for connection to said other member, and a hinge comprising a flexible portion joining the crank part and the connecting part.

The apparatus may be arranged to measure the distance between the two members at various points in time, or continuously over a period of time thereby to monitor changes in said distance.

In this way, manufacture of the link can be simplified as a mechanical articulation joint can be omitted, and reliability can be improved.

The hinge may be made from plastics material, and preferably, the entire link is made from plastics material. The hinge may be formed integrally with the remainder of the link and in one preferred embodiment the hinge is co-moulded with the remainder of the link. Manufacture is thus further simplified.

In one preferred embodiment, the link comprises a strip which includes a twist, the strip on one side of the twist comprising said hinge and the strip on the other side of the twist comprising one of said crank part and said connecting part. The twist is preferably a twist through substantially ninety degrees. The strip preferably includes two said twists, the second twist thus connecting the hinge to the other of said crank part and said connecting part. In this way the link can be simply and reliably formed from a single strip of material.

This is a particularly elegant engineering solution.

According to another aspect of the invention there is provided a vehicle including apparatus according to the invention wherein one of said members comprises an unsprung part of the vehicle and the other of said members comprises a sprung part of the vehicle.

Conventional linkages survive abuse loads by mechanical strength. The new linkage can be made to survive abuse loads (i.e. load at the hinge in the direction of the sensor axis or rotation), such as those that occur off road, by bending elastically in that direction. This can be achieved through choice of material and cross-section of at least one of the crank part, the connecting part, and the hinge. Preferably the crank part is made more flexible in a direction parallel to the axis of the sensor than in the direction perpendicular to that axis and its own axis. Alternatively the connecting part can be made more flexible in a direction parallel to the axis of the sensor than in the direction perpendicular to that axis and its own axis.

Two embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig 1 is a perspective view of the drive link in the first embodiment of the invention, and, Fig 2 is a perspective view of the device in the second embodiment.

The measuring apparatus according to the first embodiment of the invention is shown in Fig 1 and comprises a drive link 10 connected between a lower spindle 12 on the suspension of the vehicle and a rotary sensor 14 mounted on a sprung 'part of the vehicle such as the chassis.

The drive link 10 comprises a crank part 16 which is connected to a rod 18 through a hinge 20 formed from flexible material which flexes to allow articulation between the rod 18 and the crank part 16, herein referred to as a "live hinge".

The end of the crank part 16 is connected to the rotary axle 22 of the rotary sensor 14. The rod 18 includes an end piece 24 which defines a journal to pivotally receive the spindle 12.

The crank part 16 is at about ninety degrees to the rod 18 when the vehicle is at rest and carrying no substantial load.

The rod 18 has a generally square cross-section. The crank part 16 has a similar cross-section to the rod 18 where it is attached to the live hinge 20 and broadens, in the direction parallel to the axis of the sensor, towards the end where it is attached to the rotary sensor axle 22. The crank part is therefore more flexible in the direction parallel to the axis of the sensor than in the direction perpendicular to that axis and its own axis. The hinge 20 has a generally square cross-section and is smoothly curved through an angle of about 900.

The end piece 24 may be formed from a flexible material such as plastics so that it can take up cross-vehicle articulations by allowing the spindle 12 to move relative to the rod 18.

The crank part 16 and the rod 18 are made from relatively stiff plastics material and are co-moulded with the live hinge 20. The end piece 24 and the spindle 12 are also made from plastics material and the crank part 16, hinge 20, rod 18, and end piece 24 are injection moulded as a single part. The spindle 12 could also be moulded integrally with the end piece 24.

The rigid components of Fig 1 can be made of glass filled nylon or glass filled polypropylene. The flexible components (hinge 20 and endpiece 24) can be made of thermoplastic elastomers such as styrene-ethylene-butylene-styrene copolymer (S.E.B.S.) e.g. "thermoflex', or polypropylene/rubber alloys e.g.

"santoprene".

In use, movement of the suspension relative to the chassis will cause the spindle 12 to move upwardly which will move the rod 18 upwardly. The hinge 20 will thus be moved in the closing direction and will raise the end of the crank part 16. The crank part 16 will thus rotate the axle 22 of the rotary sensor 14.

Fig 2 shows the drive link 30 of the second embodiment which is connected to the same rotary sensor 14 as before.

The drive link 30 is in the form of a strip which is twisted twice to define three parts 32, 34, 36 separated by the two twists 38, 40. The first part 32 is connected to the axle 22 of the rotary sensor 14 so that the plane of the strip is perpendicular to the axis of the axle 22. The twist 38 from- the first part 32 to the central part 34 is clockwise and through an angle of 900. The central part 34 is curved downwardly through an angle of about 900 from straight. The second twist 40 is also clockwise from the central part 34 to the third part 36 and is also through an angle of 900. The end of the third part 36 defines an aperture 42 for rotatable connection of the third part 36 to the suspension of the vehicle.

The strip is injection moulded from plastics material.

Upwards movement of the suspension will move the third part 36 of the link 30 upwardly substantially along its axis. The central section 34 of the link 30 acts as a live hinge and increases its curvature as the suspension rises. The first part 32 of the link 30 is thus pivoted to turn the axle 22 of the rotary sensor 14. The first part 32 and the third part 36 of the strip thus act rigidly, as the plane of the strip in each case is in the plane of induced flexing. The central part 34 however is arranged to provide minimum resistance to flexure.

The central part 34 of the strip may be co-moulded with the remainder of the strip in a more flexible plastics material.

Each embodiment does away with at least one mechanical articulation joint of known drive link and is reliable while being inexpensive to manufacture.

Claims

1. Apparatus for measuring the relative position of two members, the apparatus comprising a rotary sensor for mounting on one of said members and a drive link for connecting the sensor to the other of said members, the drive link comprising a crank part connected to the sensor, a connecting part for connection to said other member, and a hinge comprising a flexible portion joining the crank part and the connecting part.

2. Apparatus as claimed in claim 1, wherein the hinge is made from plastics material.

3. Apparatus as claimed in claim 2, wherein the entire link is made from plastics material.

4. Apparatus as claimed in any foregoing claim wherein the hinge is formed integrally with at least one of the crank part and the connecting part.

5. Apparatus as claimed in any of the preceding claims, wherein the hinge is co-moulded with at least one of the crank part and the connecting part.

6. Apparatus as claimed in any foregoing claim, wherein the link comprises a strip which includes a twist, the strip on one side of the twist comprising the hinge and the strip on the other side of the twist comprising one of the crank part and the connecting part.

7. Apparatus as claimed in claim 6, wherein the twist is through substantially ninety degrees.

8. Apparatus as claimed in claim 6 or claim 7, wherein the strip includes a further twist which joins the hinge to the other of the crank part and the connecting part.

9. Apparatus as claimed in any foregoing claim wherein at least a part of the link can flex to accommodate movement of said other member relative to said one member in a direction parallel to the axis of the sensor.

10. Apparatus as claimed in claim 9 wherein the hinge can flex to accommodate movement of said other member relative to said one member in a direction parallel to the axis of the sensor.

11. Apparatus as claimed in claim 9 or claim 10 wherein at least one of the crank part and the connecting part is more flexible in a direction parallel to the axis of the sensor than in the direction perpendicular to that axis and its own axis.

12. Apparatus substantially as described herein with reference to Fig 1 or Fig 2 of the accompanying drawings.

13. A vehicle including apparatus as claimed in any preceding claim wherein one of said members comprises an unsprung part of the vehicle and the other of said members comprises a sprung part of the vehicle.