Inductive Proximity Switch

Abstract

The invention relates to an inductive proximity switch having a primary coil for generating an alternating magnetic field, with an oscillator for driving the primary coil, with a control and evaluation unit, which is operatively connected to the oscillator and is equipped to acquire and evaluate an amplitude and a phase position of a current in the primary coil and for outputting a detection signal depending on the acquired current in the primary coil, with at least one compensation coil for manipulation of the alternating magnetic field generated by the primary coil. The inductive proximity switch is characterized in that a separate controllable current source is present for controlling the at least one compensation coil.

Claims

1-16. (canceled)

17. An inductive proximity switch comprising: a primary coil for generating an alternating magnetic field, an oscillator for driving the primary coil, a control and evaluation unit, which is operatively connected to the oscillator and is equipped to acquire and evaluate an amplitude and a phase position of a current in the primary coil and for outputting a detection signal depending on the acquired current in the primary coil, at least one compensation coil for manipulating the alternating magnetic field generated by the primary coil, wherein a separate controllable current source is present for controlling the at least one compensation coil.

18. The inductive proximity switch according to claim 17, wherein a plurality of compensation coils are present.

19. The inductive proximity switch according to claim 17, wherein a separate controllable current source is present for each of the compensation coils.

20. The inductive proximity switch according to claim 17, wherein the controllable current sources are equipped to control at least one of: an amplitude or a phase position of the compensation coil current.

21. The inductive proximity switch according to claim 17, wherein a compensation coil surrounds the primary coil at least partially.

22. The inductive proximity switch according to claim 21, wherein the compensation coil surrounding the primary coil has an expansion in an axial direction which is greater than or equal to an expansion of the primary coil or of a coil core of the primary coil in its axial direction.

23. The inductive proximity switch according to claim 17, wherein a compensation coil surrounds the primary coil completely.

24. The inductive proximity switch according to claim 17, wherein a compensation coil is arranged in an axial direction behind the primary coil.

25. The inductive proximity switch according to claim 24, wherein the compensation coil arranged behind the primary coil has a diameter that is greater than or equal to a diameter of the primary coil or the diameter of a coil core of the primary coil.

26. The inductive proximity switch according to claim 17, wherein the primary coil has a coil core.

27. The inductive proximity switch according to claim 26, wherein the coil core is a pot core.

28. The inductive proximity switch according to claim 17, wherein the primary coil is positioned in a tubular housing on a front side.

29. The inductive proximity switch according to claim 17, wherein the primary coil, the compensation coils and the controllable current sources are arranged in a rectangular or cylindrical housing.

30. The inductive proximity switch according to claim 29, wherein the housing is made of at least one of plastic or metal.

31. The inductive proximity switch according to claim 17, wherein the primary coil, the compensation coils and the controllable current sources are arranged in a housing in the shape of a circular cylinder.

32. The inductive proximity switch according to claim 17, wherein the control and evaluation unit is also equipped to control the controllable current sources.

33. The inductive proximity switch according to claim 32, wherein the control and evaluation unit has a programmable logical component with analog and digital functionality.

34. The inductive proximity switch according to claim 32, wherein the control and evaluation unit has a programmable microcontroller with analog and digital functionality.

35. The inductive proximity switch according to claim 17, wherein the control and evaluation unit is equipped to determine when the current in the primary coil falls below a threshold to be specified and depending on that, to output an output signal.

Description

[0042] Further properties and advantages of the invention are described in the following with reference to the attached schematic FIGURE. The FIGURE shows the following:

[0043] FIG. 1 shows an exemplary embodiment of an inductive proximity switch according to the invention.

[0044] The exemplary embodiment schematically represented in FIG. 1 of an inductive proximity switch 10 according to the invention has as essential components a primary coil 2, an oscillator 5, a first compensation coil 3 with an assigned first controllable current source 8 and a second compensation coil 4 with an assigned second current source 6.

[0045] These components are accommodated in a housing 9, which can for example be made of plastic and/or of metal.

[0046] The primary coil 2, which is used to generate an alternating magnetic field, is accommodated in a pot core 1. Within the housing 9, which for example can have a cubic or cylindrical shape, the pot core 1 is arranged with the primary coil 2 directly at a front side. The alternating magnetic field can thus emerge outwardly. The first compensation coil 3 is located radially outward of the pot core 1 and surrounds it completely in the circumferential direction. In the axial direction, which is labeled reference numeral 11 in FIG. 1, the expansion of the of the first compensation coil 3 is about as large as that of the pot core 1. However, it should be noted that, in principle there is a great freedom of design with regard to the specific geometry and the specific positioning of the compensation coils. For example, the compensation coils do not necessarily have to be formed and positioned flush relative to the primary coil in the manner shown in the FIGURE.

[0047] The second compensation coil 4 is a flat coil and, viewed in the axial direction, is located behind the pot core 1. The second compensation coil 4 overlaps essentially the entire rear side of the pot core 1.

[0048] Electronic means are provided in the oscillator 5, with which a current can be acquired.

[0049] In this respect components of the oscillator 5 and the control and evaluation unit 7 overlap. The oscillator 5 is connected to the control and evaluation unit 7 for evaluation of the current by the primary coil 2.

[0050] In the shown exemplary embodiment, the first controllable current source 6 and the second controllable current source 8 are connected to the oscillator 5. This means that, in any event, the frequency of the current through the first compensation coil 3 and the second compensation coil 4 is predetermined by the oscillator 5.

[0051] The first controllable current source 8 and the second controllable current source 6 in each case facilitate an individual adjustment of amplitude and relative phase position of the current through the first compensation coil 3 or the second compensation coil 4. These further controls can, for example, as illustrated by corresponding arrows in the present exemplary embodiment, be performed by the control and evaluation unit 7. For example, the control and evaluation unit 7 can be a microcontroller, which can provide analog and digital functionalities. An interface 12 (schematically represented) is available for outputting a preferably binary switching signal, said interface being able to be connected to a bus system.

[0052] The compensation coils 3 and 4 are used for local field displacement of the alternating magnetic field generated by the primary coil 2. The electrical variables of the primary coil current, in particular amplitude and phase position, are acquired in the process. The compensation coils 3 and 4, controlled by the controllable current sources 6 and 8, respectively, generate local compensation fields. Due to the possibility of the adjustment of amplitude and phase position in the case of the current sources 6 and 8, respectively, with regard to adjoining installation materials, for example on the housing edge, extremely flexible adaptations are possible. As a special advantage, in the case of the invention, the mentioned installation materials on the edges of the housing, which were acquired without compensation by the primary coil 2, can be especially well hidden and accordingly no longer or only slightly acquired by the evaluation unit 7, without the detection sensitivity of the actual target of interest suffering.

[0053] With the present invention a novel inductive proximity switch is provided in which through the basic idea of the individual adaptation of the current of the compensation coils, which takes place in particular independent of a primary current through the transmission coil, significant improvements are achieved with regard to the hiding of objects and materials in the environment of the proximity switch. The reliability of the inductive proximity switch can thus be increased.

LIST OF REFERENCES

[0054] 1 Coil core [0055] 2 Primary coil [0056] 3 Compensation coil [0057] 4 Compensation coil [0058] 5 Oscillator [0059] 6 Controllable current source [0060] 7 Control and evaluation unit [0061] 8 Controllable current source [0062] 9 Housing [0063] 10 Inductive proximity switch [0064] 11 Axial direction [0065] 12 Interface