GB2476377A

GB2476377A - Potentiometric position sensor which disables the slider beyond the functional range

Info

Publication number: GB2476377A
Application number: GB1021246A
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: GB2476377B; DE102009059150A1; GB201021246D0

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 (e.g. linear, arc-shaped or elliptical) sliding track 6 formed by resistive track 5 (and optionally conducting track 4) 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 guide 14 arranged on an edge 13 of the track in transitional area 15 to exert bending forces on the slider finger during any movement therein, thus deforming it so that it is no longer able to touch the sliding track.

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 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 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 a dead zone.

The problematic aspect in such position sensors is 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 thick-flCG3 of the sliUiiiy LLdk applied as a resistive track and/or as a conducting track. In particular, the slider fingers of-ten hit the edge of the sliding track when running back onto the track and are bent in this process, or the springs hold-ing the contact are destroyed, so that the position sensor will become defective or will at least no longer be reliably functional, so that malfunctions of the position sensor may occur at least at a later time.

It is therefore the object of the present invention to pro-vide a position sensor with which the installation or the use of not fully functional position sensors can securely be ex-cluded.

S * S S * 0s

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 *** *** * 20 of the dependent claims.

The position sensor in accordance with the invention for gen-erating 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 to be 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, on the basis of 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. * * ** *

A guide is arranged in at least one transitional area between the functional area and the dead area on an edge of the re- * sistive track, which guide exerts bending forces on the :.: slider finger during a movement of the slider finger in the ****** * 20 transitional area, which bending forces deform said finger in such a way that it is unable to touch the sliding track any more.

The invention is based on the consideration that defective slider fingers, when it is not possible to completely avoid them, should be recognised securely at least with a diagnos-tic method, so that they are not inadvertently installed or continued to be used.

It was problematic however that the bending of the slider finger would not automatically lead to an immediate securely recognisable malfunction of the position sensor during the return to the sliding track.

It is therefore proposed in accordance with the invention to destroy the slider finger upon leaving the sliding track and/or upon returning back to the sliding track completely in a defined manner, which means to permanently prevent any con-tact between the slider finger and the sliding track, so that the malfunction is easily recognised with current diagnostic methods.

The guide in accordance with the invention can be used both in position sensors whose sliding track is arranged in a sub-stantially linear manner, and also in position sensors whose sliding track is arranged in a substantially arc-like, ellip- tic or other manner. It can therefore be used both in rota-**S*S. * *

tiorial angle sensors and also in linear displacement trans-S. S *. .: ducers.

* ** The guide is arranged in one embodiment in such a way that it guides the slider finger laterally adjacent to the conducting *S*SS * 20 track. The guide can also be arranged in such a way that it lifts slider finger off the conducting track. Combinations are also possible. Accordingly, the slider finger can be in-herently compressed and/or bent by a guide arranged as a locking element for example.

In one embodiment, at least one conducting track is addition-ally arranged on the substrate, on which at least one slider finger slides. The conducting track allows tapping the signal in a very simple way.

The conducting track can also comprise a guide in at least one transitional area between the functional area and the dead area on one edge of the conducting track, which guide exerts bending forces on the slider finger during a movement of the slider finger in the transitional area, which bending forces will ciefo Lii fiiiyr in such a way that it is no longer able to touch the sliding track.

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 prior damage to the slider fingers on the resistive track edge or other conducting track edge will lead to the complete and securely recognisable de- struction of the sliding contact, so that pre-damaged posi-tion sensors can no longer be installed or be used.

I * * * * S.

Embodiments of the invention will be explained below in : closer detail by reference to the enclosed drawings, wherein: * * 20 Fig. 1 schematically shows a top view of a position sensor according to one embodiment of the invention; Fig. 2 shows a longitudinal sectional view through an area of the position sensor according to a further em-bodiment; Fig. 3 shows a longitudinal sectional view through an area of the position sensor according to a further em-bodiment, and Fig. 4 schematically shows a cross-sectional view through an area of the position sensor according to a fur-ther embodiment.

The same parts are provided in all drawings with the same LeLeL11Lt L1UILtL:d.L.

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 sliding fingers 8, which slider 7 is associated with the second sensor element. S *

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-S.....

* S 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 1200.

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 have been laid on the substrate.

A transitional area 15 is arranged between the dead area 11 and a functional area 10 at one end of the sliding track 6, in which both the resistive track 5 and also the conducting track 4 comprise guides 14.

The guide 14 associated with the resistive track 5 is ar- :.15 ranged as a bending element 17 which bends the slider fingers 8 laterally away from the resistive track to the inside upon leaving the sliding track 6. S. * * . S * *.

The guide 14 associated with the conducting track 4 is ar-ranged as a blocking element 16 which inherently compresses the slider fingers 8 upon leaving the sliding track 6.

*SSS.. * S

Fig. 2 shows a sectional view through an area of the position sensor 1 according to a further embodiment. This illustration clearly shows the difference in level of thickness d of the resistive track 5 between the resistive track 5 and the sub-strate 2.

The guide 14 is provided in the transitional area 15 at the edge 13 of the resistive track, which guide is arranged in this embodiment as a ramp 18 with a final height h. Height h is higher than d, so that the slider fingers 8 are lifted up- wardly away from the resistive track 5 when leaving the slid-ing track 6. Any contact with the sliding track 6 is then no longer possible and the sliding contact 9 has been securely destroyed.

Fig. 3 shows a sectional view through an area of the position sensor 1 according to a further embodiment. In this embodi-ment, the guide 14 is arranged as a blocking element 16 with a height h, with h being higher than d, so that the slider fingers 8 are pressed against the blocking element 16 when leaving the sliding track 6 and are inherently compressed and bent.

The various illustrated concepts for the guides 14 can be combined with one another and can respectively be used both for the resistive track 5 and also for the conducting track S 5 Fig. 4 schematically shows a cross-sectional view through an area of the position sensor 1 according to a further embodi- * *. 20 ment. In this embodiment, the guide 14 is arranged as a * * * bracket 20 which is anchored in pass-through holes 19 of sub-S.....

* strate 2. The bracket 20 is arranged in the transitional area and represents an especially simple, but also reliable possibility to bend the slider fingers 18 in a defined manner when leaving the sliding track 6.

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 13 Edge of resistive track 14 Guide Transitional area 16 Blocking element 17 Bending element 18 Ramp 19 Pass-through holes ***S.* * 20 Bracket d Thickness h Height