FR2596512A1

FR2596512A1 - Inductive position sensor

Info

Publication number: FR2596512A1
Application number: FR8604612A
Authority: FR
Inventors: Guiseppe Apruzzese
Original assignee: MECALECTRO
Current assignee: MECALECTRO
Priority date: 1986-04-01
Filing date: 1986-04-01
Publication date: 1987-10-02

Abstract

Inductive position sensor including a moving magnetic core 3 linked to the displacements of a part 5 whose position it is required to determine and an inductor 1 whose value is a function of the degree of insertion of the moving core in the latter, characterised in that the said inductor 1 is connected in an oscillating circuit 8, 10, 11 whose frequency of oscillation varies with the value of the inductor 1 and therefore constitutes a measure of the position of the said part 5.

Description

La presente invention est relative aux cp- teurs inductifs et se rapporte plus particulièrement
aux capteurs de ce type destinés a mesurer la position angulaire d'un arbre déplaçable en rotation.The present invention relates to inductive sensors and relates more particularly
to sensors of this type intended to measure the angular position of a shaft movable in rotation.

On connaît des capteurs inductifs de position dont le fonctionnement repose sur la variation de la tension entre deux inductances en fonction de la variation de la position d un noyau magnetique dans celles-ci. Inductive position sensors are known, the operation of which is based on the variation of the voltage between two inductors as a function of the variation of the position of a magnetic core therein.

Ces dispositifs de la technique ariterieure fonctionnent generalement a des frequences relativement élevées et sont de ce fait sensibles aux variations de temperature ce qui constitue un inconvénient quand le capteur est utilise notamment dans des dispositifs de commande pour moteurs a combustion interne. These devices of the rear technique generally operate at relatively high frequencies and are therefore sensitive to temperature variations which constitutes a drawback when the sensor is used in particular in control devices for internal combustion engines.

L'invention vise a remédier aux 1nconve- nients des capteurs de la technique antérieure en creant un capteur inductif qui tout en etant d'une construction relativement simple, presente une sensibilité aux variations de température reduite au minimum. The invention aims to remedy the disadvantages of sensors of the prior art by creating an inductive sensor which, while being of a relatively simple construction, presents a sensitivity to temperature variations reduced to the minimum.

Elle a donc pour objet un capteur inductif de position comportant unnoyau magnétique mobile lié aux déplacements d une piece dont il y a lieu de déterminer la position et une inductance dont la valeur est fonction du degre d introduction du noyau mobile dans celle-ci. caracterise en ce que ladite inductance est connectee dans un circuit oscillant dont la fréquence d'oscillation varie avec la valeur de l'inductance et constitue donc une mesure de la position de ladite place. It therefore relates to an inductive position sensor comprising a movable magnetic core linked to the displacements of a part, the position of which must be determined and an inductance, the value of which is a function of the degree of introduction of the movable core therein. characterized in that said inductance is connected in an oscillating circuit whose oscillation frequency varies with the value of the inductance and therefore constitutes a measure of the position of said place.

L'lnvention sera mieux compr;se a laide de la description qui va suivre, donnee uniquement a titre d'exemple et faite en se référant aux dessins annexés. sur lesquels
- la Fig.1 est une vue en elevation d'un mode de realisation d une inductance variable entrant dans la construction du capteur inductif de position suivant l'invention;
- la Fig.2 est une coupe suivant la ligne 2-2 de la Fig.1: et
- la Fig.3 est un schema electrique du circuit du capteur inductif suivant l'invention.The invention will be better understood with the aid of the description which follows, given solely by way of example and made with reference to the accompanying drawings. on which ones
- Fig.1 is an elevational view of an embodiment of a variable inductor used in the construction of the inductive position sensor according to the invention;
- Fig.2 is a section along line 2-2 of Fig.1: and
- Fig.3 is an electrical diagram of the inductive sensor circuit according to the invention.

Aux Fig.1 et 2.on a represente une lnduc- tance variable constituee d'un premier enroulement inductif 1 comprenant un passage axial 2 dans lequel est destine a étre engage un noyau 3 en forme d'arc de circonférence d'une pièce magnétique 4 calée en rotation sur un arbre 5 dont il y a lieu de determiner la position angulaire. In Fig. 1 and 2, a variable inductance is shown, consisting of a first inductive winding 1 comprising an axial passage 2 in which is intended to be engaged a core 3 in the form of an arc of circumference of a magnetic piece. 4 stalled in rotation on a shaft 5 whose angular position should be determined.

L inductance des Fig.1 et 2 comporte en ou- tre un second enroulement 6 pourvu d'un passage axial 7 dans lequel est destiné a etre engage un noyau 8 identique au noyau 3 et dispose de façon diamétrale- ment oppose a celui-ci. The inductance of Fig. 1 and 2 comprises in addition a second winding 6 provided with an axial passage 7 in which is intended to be engaged a core 8 identical to the core 3 and has diametrically opposite to it .

Comme represente a la Fig.3. l'enroulement 1 est connecte dans un circuit oscillant comprenant un condensateur 9 dont une armature est reliez a la masse et dont l'autre armature est reliee par l'lntermedial- re d'une resistance 10 a l'entree negative d'un ampli fixateur opérationnel 11. L'entree positive de l'amplicateur opérationnel 11 est reliee directement a la sortie de celui-ci. Le condensateur 9 forme avec l'en- roulement 1. un circuit LC. As shown in Fig. 3. winding 1 is connected in an oscillating circuit comprising a capacitor 9, one armature of which is connected to ground and the other armature of which is connected by the intermediary of a resistor 10 to the negative input of an amplifier operational fixer 11. The positive input of the operational amplifier 11 is connected directly to the output thereof. The capacitor 9 forms with the winding 1. an LC circuit.

Le circuit oscillant ainsi constitue engendre a sa sortie qui est la sortie de l'amplificateur operationnel I 1. un signal de frequence variable en fonction de la valeur de l'inductance 1. The oscillating circuit thus constitutes generates at its output which is the output of the operational amplifier I 1. a signal of variable frequency as a function of the value of the inductance 1.

Cette valeur est fonction du degré d' intro- diction du noyau 3 dans le passage axial 2 de l enrou-
lement 1.This value is a function of the degree of introduction of the core 3 into the axial passage 2 of the winding.
1.

La position extréme d'introduction du noyau
3 et du noyau 8 diametralement oppose. est indique en
trait mixte a la Fig.2.The extreme position of introduction of the nucleus
3 and the diametrically opposed core 8. is indicated in
dashed line in Fig. 2.

Le deuxième enroulement 6 constitue un moyen
complementaire pour effectuer une mesure distincte de
celle assuree par l'enroulement 1. Il peut étre bran
ché dans un autre circuit oscillant identique a celui
represente a la Fiv.3 et permet d'effectuer une mesure de verification. The second winding 6 constitutes a means
additional to perform a separate measurement of
that provided by the winding 1. It can be bran
ché in another oscillating circuit identical to that
represents Fiv. 3 and allows a verification measurement to be carried out.

t'agencement qui vient d'ëtre décrit permet d obtenir des mesures de position angulaire d'une pré
cision de l'ordre de 1/10 de degré. L'oscillateur uti
lisé est un oscillateur basse frequence dont la fré
quence varie par exemple entre 300 et 1500 Hertz. Cet
te fréquence augmente avec le degré de pénétration du
noyau 3 dans le passage 2 de l'enroulement 1.the arrangement which has just been described makes it possible to obtain angular position measurements of a pre
cision of the order of 1/10 of a degree. The uti oscillator
lisé is a low frequency oscillator whose fre
quence varies for example between 300 and 1500 Hertz. This
The frequency increases with the degree of penetration of the
core 3 in passage 2 of winding 1.

La plage angulaire de mesure du capteur sui
vant l'lnvention est O a 40'. The angular measurement range of the following sensor
Before the invention is 0 to 40 '.

En raison de son fonctionnement a basse fré
quence, le dispositif qui vient d'etre décrit est in
sensible aux variations de temperature.Due to its low fre
quence, the device which has just been described is in
sensitive to temperature variations.

Bien que dans l'exemple decrit en reference aux Fig.1 a 3.le capteur de position soit un capteur de position angulaire, l'invention s'applique egalement a la réalisation d'un capteur de position linéai- re. Although in the example described with reference to Fig.1 to 3.the position sensor is an angular position sensor, the invention also applies to the production of a linear position sensor.

Il suffit pour cela que le noyau plongeur tel que le noyau 3 soit constitue par une pièce rectiligne liée aux déplacements en translation d'une pièce dont il y a lieu de mesurer la position. It suffices for this that the plunger core such as the core 3 is constituted by a rectilinear piece linked to the translational displacements of a piece whose position should be measured.

On donne ci-apres a titre d'exemple non ll- mitatif. les valeurs des composants entrant dans la construction du circuit de la Fig.3. A non-limiting example is given below. the values of the components used in the construction of the circuit in Fig. 3.

- inductance 1 de 70 a 80 mH
- condensateur 9 330 F
- résistance 10 4700 Ohms
- amplificateur opérationnel 11 type LM 1245 fabriqué et vendu par la Société MOTOROLA. - inductance 1 from 70 to 80 mH
- capacitor 9 330 F
- resistance 10 4700 Ohms
- operational amplifier 11 type LM 1245 manufactured and sold by the MOTOROLA Company.

Claims

RtVtNDICATIONS

1. Inductive position sensor comprising a mobile magnetic core (3) linked to the displacements of a part (5) whose position must be determined and an inductor (1) whose value depends on the degree of introduction of the movable core (3) therein, characterized in that said inductor (1) is connected in an oscillating circuit- (9,10.11) whose oscillation frequency varies with the value of the inductor (1) and constitutes therefore a measurement of the position of said part (5).

2. Sensor according to claim 1, characterized in that said core (3) is in the form of an arc of circumference and is part of a magnetic part locked in rotation on a shaft (5) displaceable in rotation. said core (3) being intended to penetrate an axial passage (2) of said inductor (1) during the angular displacements of said shaft (5).

3. Sensor according to one of claims 1 and 2, characterized in that said oscillating circuit comprises a capacitor (9) forming with said inductance (1) an LC circuit. and an operational amplifier (11) connected between the junction of the capacitor (9) with the winding (1) and the terminal of said winding (1) opposite to said junction.

5. Sensor according to claim 2, ca characterized in that it further comprises an additional inductor (6) in which is movable an additional magnetic core (8) in the form of an arc of circumference carried by said magnetic piece (4) , this inductor and its core constituting a verification sensor.