Path measurement method for a magnetic sensor and sensor

Abstract

A method of path measurement uses eddy current principles and a sensor which interacts with a measuring object. The sensor has an electrical connector and a sensor coil. In accordance with the method, an operating voltage is applied to the sensor such that a magnetic field is built up by an oscillator in cooperation with the sensor coil. A measuring object may be moved in the vicinity of the sensor coil through an opening in the sensor coil to produce field strength changes adjacent to the coil and the oscillator. The field strength changes are detected by an evaluation circuit and transmitted to a microcontroller. The microcontroller processes the signals of the evaluation circuit and provides the evaluation circuit with said signals via an output and protection circuit. The sensor coil consists of a plurality of windings constructed in a planar manner.

Claims

1. A method of path measurement using eddy current comprising: with a sensor that interacts with a measuring object (2), wherein the sensor comprises an electrical connector (4) and an electronic unit cooperating with a sensor coil (3): (i) applying an operating voltage to the sensor in a manner such that a magnetic field is built up by an oscillator (11) disposed in the electronic unit in cooperation with the sensor coil (3); (ii) moving the measuring object (2) axially through an opening in the sensor coil (3) in a manner to generate eddy currents in the measuring object and create changes in a field strength adjacent to the coil (3) and the oscillator (11); and (iii) detecting the field strength changes with an evaluation circuit (14) and transmitting signals indicative of the field strength changes to a microcontroller (13), wherein the microcontroller processes the signals of the evaluation circuit (14) and provides the evaluation circuit with the signals via an output and protection circuit (15); wherein the coil is formed by a multilayer printed circuit board comprising at least two planar windings connected in series to form one continuous coil; wherein the measuring object (2) has at least a portion with a varying geometric cross-section along an axial direction relative to the opening of the sensor coil adapted and configured to generate variations in the eddy currents in the measuring device as the measuring object is moved axially though the opening in the sensor coil when the operating voltage is applied to the sensor.

2. The path measurement method according to claim 1, characterized in that path measurement is one of two modes: (i) continuously in relation to a position of the measuring object (2), and (ii) as a switching function based upon selected operational parameters of the oscillating circuit.

3. The path measurement method according to claim 1, characterized in that the portion of the measuring object with a varying geometric cross-section has a continuously changing cross section.

4. An eddy current sensor for path measurement, wherein the sensor has at least one electronic unit including an oscillator (11) cooperating with a sensor coil (3) that induces eddy currents in a measuring object (2) and an electronic connector (4) for providing the supply voltage and transmitting signals for the sensor, wherein the sensor coil (3) comprises a multilayer printed circuit board upon which a plurality of windings constructed in a planar manner are arranged to form the sensor coil, wherein the sensor coil (3) has an opening through which the measuring object (2) can be moved axially; and wherein the measuring object has a portion with a geometric cross-section having a varying geometry adapted and configured to generate variations in the eddy currents in the measuring device as the measuring object is moved axially though the opening in the sensor coil when the supply voltage is provided to the sensor.

5. The eddy current sensor according to claim 4, characterized in that the portion of the measuring object (2) with the varying geometric cross section has a continuously changing cross section.

6. The eddy current sensor according to claim 5, characterized in that the measuring object (2) has a conical shape.

7. The eddy current sensor according to claim 4, characterized in that the measuring object (2) has a part (5) operatively connected to an object to be detected.

8. The eddy current sensor according to claim 7, characterized in that an elastic structure is associated with the measuring object (2).

9. The eddy current sensor according to claim 8, characterized in that the elastic structure is a compression spring (7).

10. The eddy current sensor according to claim 4, characterized in that the measuring object (2) has a part (5) adapted be in contact with an object to be detected.

11. The eddy current sensor according to claim 4, characterized in that the measuring object (2) is disposed in one of a sleeve (8), a housing (8), and a tubular section (8).

12. The eddy current sensor according to claim 11, characterized in that the measuring object (2) is three-dimensionally supported in the respective sleeve (8), the housing (8), and the tubular section (8).

13. The eddy current sensor according to claim 4, further comprising a housing (16) that encloses the sensor coil (3), the electrical connector (4), and the measuring object (2).

14. The eddy current sensor according to claim 4, characterized in that windings of the sensor coil (3) are each arranged on a carrier.

15. The eddy current sensor according to claim 4, characterized in that the windings of the sensor coil (3) are integrated within the multilayer printed circuit board.

16. The eddy current sensor according to claim 4, characterized in that the sensor contains an evaluation circuit for detecting parameters of the oscillator.

17. The eddy current sensor according to claim 16, characterized in that the electronic unit contains a microcontroller (13) having a memory a stored program configured to receive signals of the evaluation circuit (14), process said signals, and output said signals to an output and protection circuit (15).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will be described below in greater detail with reference to some exemplary embodiments and drawings, in which:

(2) FIG. 1 shows a side view of the basic construction of the sensor;

(3) FIG. 2 shows a rear view of the sensor;

(4) FIG. 3 shows an embodiment of the sensor with a measuring object/transducer element guided within a sleeve;

(5) FIG. 4 shows a further embodiment of the sensor illustrated in FIG. 3; and

(6) FIG. 5 shows a block diagram of the sensor.

DETAILED DESCRIPTION

(7) The path measurement method according to the invention is carried out using a position sensor 1 which cooperates and/or interacts with a measuring object/transducer element 2.

(8) The sensor consists of at least one electronic unit cooperating with a sensor coil 3, and an electronic connector 4 serving for providing the supply voltage and transmitting signals. The aforementioned components are combined in a common housing 16. The housing 16 can be shaped in the manner customary.

(9) The mode of operation of the path measurement method consists in activating at first the electronic unit arranged in the sensor by applying an operating voltage. An oscillator 11 existing in the electronic unit excites an oscillation in cooperation with the sensor coil 3, with an oscillation with a specific frequency being generated as a function of the parameters of the oscillator 11 and the sensor coil 3, and the sensor coil 3 establishing a magnetic field.

(10) A measuring object/transducer element 2 is located in the vicinity of the sensor coil 3 and moved, thus changing the field strength in the area of the coil 10 and, at the same time, the frequency of the oscillating circuit from the sensor coil 3 and the oscillator 11. By means of an evaluation circuit 14, these changes are detected and converted into measured variables suitable for further processing. The information obtained is transmitted by the evaluation circuit 14 to a microcontroller 13. The latter processes the information obtained using, inter alia, a stored programme sequence and develops therefrom control signals which can be further processed in external devices. An output and protection circuit 15 is disposed in the electronic unit for trouble-free operation.

(11) In order to ensure a stable operation and meet the required measurement conditions, a voltage regulator 12 is further assigned to the electronic unit.

(12) Furthermore, the specific feature of the path measurement method is that the sensor coil 3 consists of a plurality of coils constructed in a planar manner.

(13) The path measurement method can be configured in such a way that path measurement is carried out continuously in relation to an actual position of the measuring object/transducer element 2.

(14) In a further embodiment of the path measurement method, when specific parameters are reached, a switching function according to the characteristic of a so-called threshold value switch can be provided, depending on specific parameters reached in the oscillating circuit from the oscillator 11 and the sensor coil 3.

(15) A path measurement method with a sensor according to the invention in which the measuring object/transducer element 2 has geometrical irregularities is particularly preferred. This means that the measuring object/transducer element 2 is present in the area of the sensor coil 3 but can change its position and thus changes in cross section.

(16) Preferred embodiments of such changes in cross section are annular grooves, bores, one-sided flat portions or varying materials.

(17) A further embodiment of the path measurement method may be that a part comes close to the sensor coil 3 at all.

(18) In a particularly preferred embodiment of the path measurement method, the measuring object/transducer element 2 has an area with a continuous transition from a small diameter to a larger diameter, thus enabling a quasi-analogue determination of position.

(19) Furthermore, the measuring object/transducer element 2 can have a part 5 by which it is in contact with or connected to the parts to be measured.

(20) Various measuring tasks can be performed by the path measurement method according to the invention. For example, it can be used for determining the positions of moveable rods, pins, shafts or housing components.

(21) The use in automated manual transmissions or for the determination of position of clutch components is particularly preferable.

(22) Further preferable uses may be the determination of position of hydraulic cylinders, gear racks, linear drives and other parts, provided that the latter's location/position can be detected by means of path measurements.

(23) As already described above, the sensor is composed of at least one sensor coil 3, one electronic unit and one housing 16 (not shown).

(24) According to the invention, the sensor coil 3 consists of a plurality of coils constructed in a planar manner, with the planar coils each being located on a carrier medium.

(25) Thus, by choosing an appropriate number of such coils constructed in a planar manner, the inductance of the sensor coil 3 can be determined over a wide range, whereby, in cooperation with the oscillator 11 disposed in the electronic unit, the possible operating frequency can also be adjusted over a wide range.

(26) An individual planar coil can be implemented in such a way that, as a single element, it has as large an inductance as possible. In this way, it can be achieved that the number of planar coils to be combined with each other can be minimized.

(27) A preferred embodiment may be that a planar coil is arranged on either side of a double-sided printed circuit board.

(28) A further preferred embodiment of the sensor coil 3 is implemented if the planar coils are integrated within a so-called multilayer printed circuit board and more than two planar coils can thereby be interconnected.

(29) Apart from the possibility of adjusting the inductance of the sensor coil 3, a sensor coil 3 having a stable structure is produced by the embodiment according to the invention, which does not require any additional measures for its protection.

(30) The position sensor 1 according to the invention can be developed further in accordance with various operating conditions. Thus, in one embodiment, the measuring object/transducer element 2 can be disposed in a sleeve 8. In this way, it is largely protected against environmental influences.

(31) A compression spring 7 which ensures continuous contact of the part 5 with the parts to be detected can be assigned to the measuring object/transducer element 2.

(32) The part 5 can be guided centrally by means of a duct 6.

(33) In a further embodiment in which the system is not capable of providing the measuring object 2 in the right geometry, location or material, a spring 7 loaded measuring object 2 can be accommodated and enclosed as an integrated sliding object within the sensor housing 16 by extending the housing, in particular the plastic encapsulation 16, by a tubular section 8, with the integrated sliding object being guided through an element 6 which can be placed on either side of the tubular element 8 as shown in FIG. 3. The measuring object 2 remains located on the outside of the encapsulated PCB portion, thus causing the closed and, in particular, sealing system for the electronics portion. The compression spring 7 ensures the continuous contact with the actuating mechanism from the system which, for example, can be a plunger or a cam.

(34) In cases where the arrangement of the electronic unit on the printed circuit board of the sensor coil is not possible, an additional printed circuit board 9 can carry this electronic unit and be connected to the sensor coil 3.

(35) Thus, the invention has the advantage that it allows for carrying out a path measuring method using a sensor with a sensor coil consisting of a plurality of individual planar coils, wherein the sensor can be used over a wide range of parameters, whilst being robust and inexpensive to produce.

LIST OF REFERENCE NUMERALS

(36) 1. 1 position sensor 2. 2 measuring object, transducer element, metal target, shaft 3. 3 sensor coil 4. 4 connector 5. 5 part 6. 6 duct 7. 7 compression spring 8. 8 sleeve, housing, tubular section 9. 9 printed circuit board 10. 10 coil 11. 11 oscillator 12. 12 voltage regulator 13. 13 microcontroller 14. 14 evaluation circuit 15. 15 output and protection circuit 16. 16 housing