INDUCTIVE POSITION SENSOR

Abstract

An inductive position sensor including a stator element having an exciter coil to which a periodic alternating voltage is applied and having a receiving system, wherein the signal of the exciter coil is inductively coupled into the receiving system. A rotor element influences the strength of the inductive coupling between the exciter coil and the receiving system according to its angular position relative to the stator element. An evaluation circuit determines the angular position of the rotor element relative to the stator element from the voltage signals induced in the receiving system. The position sensor has an unambiguous range E, in which the angular position can be unambiguously determined. The receiving system extends over a first angular range, wherein the first angular range is N.sub.1=n*E where n≥1, and the exciter coil extends over a second angular range, wherein the second angular range is N.sub.2=m*E where m≥2.

Claims

1. An inductive position sensor comprising: comprising a stator element having an exciter coil to which a periodic alternating voltage is applied and having a receiving system, a signal of the exciter coil being inductively coupled into the receiving system; a rotor element that influences a strength of the inductive coupling between the exciter coil and the receiving system according to an angular position relative to the stator element; and an evaluation circuit to determine the angular position of the rotor element relative to the stator element from the voltage signals induced in the receiving system, wherein the position sensor has an unambiguous range E, in which the angular position is unambiguously determined, wherein the receiving system extends over a first angular range, wherein the first angular range is N.sub.1=n*E where n≥1, and wherein the exciter coil extends over a second angular range, wherein the second angular range is N.sub.2=m*E where m≥2, and wherein m and n are positive whole numbers and m>n.

2. The inductive position sensor according to claim 1, wherein m≥n+1, or wherein m=n+1.

3. The inductive position sensor according to claim 1, wherein the geometry of the rotor element is described by two circular paths with different radii around a center point, wherein a first radius of a first of the two circular paths is smaller than a second radius of a second of the two circular paths, and a section of an outer contour extends alternately and uniformly on the first or the second circular path, and the ends of the sections are connected by a radial connection between the circular paths to the respective adjacent sections on the respective other circular path.

4. The inductive position sensor according to claim 3, wherein the section on the circular path with the second radius forms a blade and the section on the circular path with the first radius forms a gap.

5. The inductive position sensor according to claim 1, wherein the unambiguous range E is determined according to the formula:
E=360°/Number of blades of the rotor element(5).

6. The inductive position sensor according to claim 1, wherein the receiving system has at least two or three first conductor loops.

7. The inductive position sensor according to claim 6, wherein the first conductor loops each form a uniformly repeating loop structure.

8. The inductive position sensor according to claim 6, wherein the winding direction of the first conductor loops of the uniformly repeating loop structure changes, wherein an area is spanned by the change of the winding direction.

9. The inductive position sensor according to claim 1, wherein the stator element and the evaluation circuit are arranged on a printed circuit board, wherein the evaluation circuit is arranged inside the exciter coil and outside the conductor loops of the receiving system.

10. An inductive position sensor comprising: a stator element having an exciter coil to which a periodic alternating voltage is applied and having a receiving system, a signal of the exciter coil being inductively coupled into the receiving system; a coupling element that influences the strength of the inductive coupling between the exciter coil and the receiving system according to its linear position relative to the stator element; and an evaluation circuit to determine the linear position of the coupling element relative to the stator element from the voltage signals induced in the receiving system, wherein the position sensor has an unambiguous range E in which the length position is unambiguously determined, wherein the receiving system extends over a first length range, wherein the first length range is L.sub.1=n*E where n≥1, and wherein the exciter coil extends over a second length range, wherein the second length range is L.sub.2=m*E where m≥2, and wherein m and n are positive whole numbers and m>n.

11. The inductive position sensor according to claim 1, wherein the inductive position sensor is a segment sensor.

12. The inductive position sensor according to claim 1, wherein the inductive position sensor is a linear sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0031] FIG. 1 shows a schematic representation of an inductive position sensor;

[0032] FIG. 2 shows a schematic representation of a stator element; and

[0033] FIG. 3 shows a graphical representation of the error in determining the angle for different relations of the receiving system to the exciter coil.

DETAILED DESCRIPTION

[0034] An inductive position sensor 1 constructed according to a preferred exemplary embodiment of the present invention comprises a circuit board 9 on which a stator element 2 is disposed.

[0035] Furthermore, inductive position sensor 1 comprises a rotor element 5. Rotor element 5 is arranged to rotate relative to circuit board 9. The sections can be seen on the outer radius of rotor element 5. These can be assumed to be blades 7. The sections at the inner radius of rotor element 5 can be assumed to be gaps 8. Here, a blade 8 and a gap 9 respectively define the unambiguous range E of position sensor 1. The unambiguous range E is understood to be the range in which an angle can be unambiguously determined by means of position sensor 1. The unambiguous range of the position sensor can be calculated according to the formula

E=360°/Number of blades of the rotor element 5.

[0036] FIG. 2 shows an enlarged detail of stator element 2 from FIG. 1. The stator element, which comprises an exciter coil 3 and a receiving system 4, is arranged on the side of circuit board 9 facing rotor element 5. Circuit board 9 is adapted in its actual design to the shape of stator element 2. Receiving system 4 comprises two first conductor loops 4a, 4b. First conductor loops 4a, 4b form a periodically repeating loop structure, which span an area by a change in the winding direction.

[0037] Inductive position sensor 1 has an oscillator circuit, which during operation of inductive position sensor 1 generates a periodic alternating voltage signal, with which first exciter coil 3 is supplied. In its rotation, rotor element 5 affects the strength of the inductive coupling between exciter coil 3 and receiving system 4.

[0038] By influencing the strength of the inductive coupling between exciter coil 3 and receiving system 4 by rotor element 5 according to its angular position relative to stator element 2, the angle between rotor element 5 and receiving system 4 can be determined. This angle is increasingly important for many applications, especially in a motor vehicle. In order to be able to determine the angle within the unambiguous range E of the sensor, exciter coil 3 and receiving system 4 must extend at least over this angular range of sensor 1. The signals coupled into receiving system 4 are influenced by exciter coil 3 due to the end regions of exciter coil 3. This influence is undesirable, because it can lead to an error in determining the angle. FIG. 2 shows one way of optimally designing the relation between exciter coil 3 and receiving system 4 and minimizing the error. For this purpose, it is possible that both exciter coil 3 and receiving system 4 are larger by a whole number multiple than the unambiguous range E. It applies to receiving system 4 that the multiple can also be 1, which would make receiving system 4 as large as the unambiguous range E. Furthermore, it is a prerequisite that exciter coil 3 must always be larger than receiving system 4. In the present case, the angular range over which receiving system 4 extends corresponds to the unambiguous range E and the angular range over which exciter coil 3 extends is larger by a factor of 2.

[0039] Inductive position sensor 1 further has an evaluation circuit 6 for determining the angular position of rotor element 5 relative to stator element 2 from the signals coupled into receiving system 4. Evaluation circuit 6 is arranged inside exciter coil 3 and outside conductor loops 4a, 4b of receiving system 4. Such an arrangement offers the advantage that unused space on circuit board 9 can be used optimally. If evaluation circuit 6 is located outside exciter coil 3, the required size of circuit board 9 is larger, which increases its cost.

[0040] FIG. 3 shows a graphical representation of the expected error in determining the angle due to the influence of exciter coil 3 on the signals coupled into receiving system 4, for different sizes of exciter coil 3. The percentage error of the sensor is plotted here versus the determined angle of the inductive position sensor. In this case, receiving system 4 is as large as the unambiguous range E of the sensor. The illustration shows a simulation of the expected error. It can be seen that the error becomes minimal for whole number values of m. The graph shows the minima for m=2 and m=3. It is possible to continue the graph showing a minimum for all whole number m. It follows from the graph that the error in determining the angle due to the influence of exciter coil 3 on the signal coupled into receiving system 4 can be minimized by the design of exciter coil 3 and receiving system 4 in relation to the unambiguous range E of the sensor. What is particularly advantageous about this mathematical relationship is the fact that if the unambiguous range E of the sensor is known, which is determined by the geometry of rotor element 5, the design of exciter coil 3 and receiving system 4 can be carried out immediately. This can reduce development effort and ensure optimal results.

[0041] The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.