GB2476378A

GB2476378A - Potentiometric position sensor including a ramp enabling slide-on of the slider finger

Info

Publication number: GB2476378A
Application number: GB1021251A
Authority: GB
Inventors: Heiko Bald; Frank Bonarens
Original assignee: GM Global Technology Operations LLC
Current assignee: GM Global Technology Operations LLC
Priority date: 2009-12-19
Filing date: 2010-12-15
Publication date: 2011-06-22
Anticipated expiration: 2030-12-15
Also published as: GB201021251D0; DE102009059151A1; GB2476378B

Abstract

Position sensor 1 generates an electric signal according to the position of a movable element (e.g. a vehicle clutch pedal, steering arrangement or throttle). It comprises: first sensor element 2 with a (e.g. linear, arc-shaped or elliptical) resistive track 5 (and optionally conducting track 4) formed on substrate 3; and second sensor element with slider finger 8 which forms a sliding contact 9 with the track so as to transmit the position of the movable element. The first sensor element comprises functional and dead areas 10, 11, the sliding track being laid in the functional area only; and a filling structure 19 which bridges a difference in level between the track and the substrate (e.g. a metal, plastic or ceramic ramp (14. Fig. 2) in transitional area 15 or a bridge across the entire dead area (19, Figs. 3 and 4)).

Description

A position sensor and use of the position sensor The invention relates to a position sensor for generating an electric signal dependent on the position of a movable ele-ment, e.g. a rotation angle sensor.

Rotation angle sensors are known for example from DE 197 37 063 Al and DE 197 16 321 Cl. They frequently comprise a sta- *:" 15 tor disk and a rotor disk which is rotatable against the sta-tor disk, with the rotor disk comprising at least one slider a..,: finger and the stator disk comprising a sliding track on which the sliding finger slides and with which it forms a * *, sliding contact. The rotor disk is connected with a movable * a * *.* . element. It transmits its motion and determines its position *....* * and rotational angle.

Such position sensors frequently have a functional range which comprises the sliding track and a dead area which does not comprise any sliding track, but in which the slider can move under certain circumstances, e.g. during mounting and repair, or in the case of improper use. For example, the functional range can be 180 degrees in a rotational angle sensor, with the other half of the full angle being the dead zone.

It is problematic in such position sensors that the slider needs to overcome a difference in level when leaving the sliding track and when running onto the sliding track again, which difference in level is the result of the thickness of the sliding track applied as a resistive track and/or as a conducting track. In particular, the slider fingers often hit the edge of the sliding track when running back onto the track and are bent in this process, or the springs holding the contact are destroyed, so that the position sensor will become defective or will at least no longer be reliably func-tional.

It is therefore the object of the present invention to pro-vide a position sensor with which the preliminary damaging of the slider fingers can be prevented especially during mount-: ing. * I * 15

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This object is achieved in accordance with the invention by *..: the subject matter of the independent claim. Advantageous further developments of the invention are the subject matter * ,* of the dependent claims. * S * S.55

* A position sensor in accordance with the invention for gener-ating an electric signal which is dependent on the position of a movable element comprises a first sensor element with at least one sliding track formed by a resistive track on a sub-strate and a second sensor element with at least one slider finger. The slider finger transmits the position of the mov- able element and is movably arranged in relation to the slid-ing track and forms a sliding contact with the same.

The sliding track is laid in a functional area of the first sensor element and the first sensor element does not comprise any sliding track in a dead area. The dead area of the posi-tion sensor shall therefore be understood as being an area in which no sliding track has been laid, but in which the slider may move under certain circumstances, e.g. during mounting and repair or in the case of improper use, as provided by the constructively enabled relative movements of the first and second sensor element.

In other words, the functional area of the position sensor is formed from the quantity of those positions of the slider which correspond in operation to permissible positions of the movable element, and the dead area of the position sensor is formed from the quantity of the positions of the slider which in operation correspond to impermissible positions of the movable element.

S S.... * .

A filling structure is arranged in at least one transitional area between the functional area and the dead area, which structure bridges a difference in level between the resistive track and the substrate. * ..

The filling structure can be arranged as a ramp structure for **..*.

* example which at least partly connects the two different 1ev-els of slider track and substrate.

It can also be arranged as a material bridge between two ends of the sliding track. Combinations of both solutions are also possible.

The invention is based on the consideration that especially during mounting or assembly of the position sensor it may un-der certain circumstances be necessary to move the slider to the dead area as a result of constructional issues. It is thus not desirable in every case to prevent a position of the slider in the dead area.

A movement of the slider from the functional area to the dead area and vice-versa should be enabled rather without any de-struction of the slider finger. This occurs by providing ramp structures which enable the slide-on of the slider fingers, so that the difference in level between the functional area and the dead area can be overcome not abruptly but over a constant path.

The ramp structure in accordance with the invention can be used both in position sensors whose sliding track is arranged in a substantially linear manner, and also in position sen-sors whose sliding track is arranged in a bent manner in a substantially arc-shaped, elliptical or other way. It can therefore be used both in rotational angle sensors and also *:*. in linear displacement transducers.

In one embodiment, at least one conducting track is addition- * ** ally arranged on the substrate, on which at least one slider : 20 finger slides. The conducting track allows tapping the signal **.*..

* in a very simple way.

The conducting track can also comprise a ramp structure in at least one transitional area between the functional area and the dead area on one edge of the conducting track, which structure bridges a difference in level between the conduct-ing track and the substrate.

In one embodiment, the ramp structure is arranged with a wider configuration at its end facing the dead area than the resistive track and/or the conducting track, and it comprises lateral guides which centre the slider finger on the resis-tive track.

The ramp structure can be made both of metal and also of plastic or ceramics, and can be applied either in the same step as the conducting track and the resistive track or in a later process.

The position sensor in accordance with the invention is suit-able for example for detecting the position of a clutch pedal, a steering angle or the opening angle of a throttle of a motor vehicle.

It comes with the advantage that the destruction of the slider fingers on the resistive track edge or the conducting track edge during the movement from the dead area to the functional area is prevented in a simple way. There is no longer any likelihood of installing and using position sen-sors that are not fully functional.

* ** Embodiments of the invention will be explained below in :*s 20 closer detail by reference to the enclosed drawings, wherein: ****** * V Fig. 1 schematically shows a top view of a position sensor according to a first embodiment of the invention; Fig. 2 shows a sectional view through an area of the posi-tion sensor according to Fig. 1; Fig. 3 schematically shows a top view of a position sensor according to a second embodiment of the invention; Fig. 4 schematically shows a top view of a position sensor according to a third embodiment of the invention, and Fig. 5 shows a cross-sectional view through an area of the position sensor according to a fourth embodiment.

The same parts are provided in all drawings with the same reference numerals.

Fig. 1 schematically shows a position sensor 1 which is ar-ranged as a rotational angle sensor and comprises a first sensor element 2 and a second sensor element not shown in further detail in Fig. 1, with the position sensor 1 generat-ing an electric signal which is dependent upon a rotational angle of a movable element, e.g. the clutch pedal of a motor vehicle.

For this purpose, a resistive track 5 is applied to a sub-strate 3 of the first sensor element 2, which jointly form a sliding contact 9 with a slider 7 with slider fingers 8, * *, which slider is associated with the second sensor element. *$ S

I

* In the embodiment of the position sensor 1 as shown in Fig. 1, a conducting track 4 made of a material of good electrical conduction is provided on the substrate 3, by means of which the tapping is performed. For this purpose, the slider 7 corn-prises a plurality of slider fingers 8, of which a few slide on the resistive track 5 and others on the conducting track 4.

The resistive track 5 and the conducting track 4 are depos- ited or printed on the substrate 2 for example, or are ap-plied by etching processes and have a specific thickness on the substrate 2 as a result of the process.

With the position sensor 1 according to the illustrated em- bodiment, rotational angles in an angular range of approxi-mately 1200 can be measured. For this purpose, a functional area of the first sensor element 2 in which the sliding track 6 is laid extends over an angular range of 120°.

The dead area 11 extends outside of the functional area 10 over the remaining 240° of the full angle, in which no resis-tive track 5 and no conducting track 4 has been laid on the substrate.

A transitional area 15 is arranged between the dead area 11 and the functional area 10 at both ends of the sliding track 6, in which both the resistive track 5 and also the conduct-ing track 4 comprise filling structures 19 which are arranged as ramp structures 14. * ** * **

Fig. 2 shows a sectional view through an area of the position : * sensor 1 according to Fig. 1. This illustration clearly shows " 20 the difference in level of thickness d of the resistive track 5 between the resistive track 5 and the substrate 2.

At the resistive track edge 13, this difference in level d is bridged in the transitional area 15 by the ramp structure 14.

In the illustrated embodiment, ramp structures 14 are pro-vided on both conducting track edges 12 and both resistive track edges 13. Depending on the thickness of the resistive track 5 and the conducting track 4 which need not necessarily be equally thick, it is also possible to omit the ramp struc-tures 14 on the conducting track 4 or the resistive track 5.

Fig. 3 schematically shows a top view of a position sensor 1 according to a second embodiment. This embodiment differs from the one already described in that a filling structure 19 for bridging the difference in level between the resistive track 5 and the substrate 2 is provided not only in the tran-sitional area 15 but also in the entire dead area 11.

In this embodiment, the slider 7 no longer needs to overcome any difference in level any more. The material for the fill- ing structure is chosen in such a way that it no longer dis-turbs the function of the sliding contacts 9 and especially the tapping on the resistive track 5.

Fig. 4 schematically shows a top view of a position sensor 1 * 15 according to a third embodiment. The third embodiment differs * ****.

* from the second one in such a way that the filling structure 19 can be made of the material of the resistive track 5 and can thus be produced in the same process step as the same, e.g. by etching. The filling structure 19 is separated from : 20 the resistive track 5 either by an intermediate space 21 which is so narrow that the slider finger 8 will simply slide over the same, or an intermediate space 20 is provided which is filled with a suitable material.

Fig. 5 shows a sectional view through an area of the position sensor 1 according to a fourth embodiment. According to this embodiment, the filling structure 19 is arranged as a ramp structure 14 which in contrast to the first embodiment does not apply merely to the resistive track edge 13 but already slightly before the same. The ramp structure 14 further com-prises a superelevated portion 22.

This embodiment comes with the advantage that the resistive track edge 13 is additionally secured. Especially in the case of glued resistive tracks 5 there is a likelihood over time that the resistive track edge 13 will detach, which is ampli- fied further by frequent passage of the slider 7. The resis-tive track edge 12 is protected from wear and tear by the ramp structure 14 applied over the resistive track edge 13. * * *

S..... * . S. * * S * * S. S S* * . . S.. *

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List of reference numerals 1 Position sensor 2 First sensor element 3 Substrate 4 Conducting track Resistive track 6 Sliding track 7 Slider 8 Slider fingers 9 Sliding contact Functional area 11 Dead area 12 Edge of conducting track **. *..

* 15 13 Edge of resistive track ***** * 14 Ramp structure Transitional area 19 Filling structure Filled intermediate space :.:. 20 21 Intermediate space *:*** 22 Superelevated portion d Thickness