Proximity switch and method for detecting a trigger

Abstract

The present invention relates to a proximity switch comprising a coil arrangement having at least two receiving coils and at least one transmitting coil, and comprising a control and evaluation unit disposed downstream of said coil arrangement for obtaining a switching signal when a trigger of the coil arrangement approaches the desired response distance, wherein the at least two receiving coils and the at least one transmitting coil are designed as planar coils and are arranged in a common coil plane. The common coil plane is oriented substantially perpendicular to a longitudinal axis of the proximity switch and the coil axes parallel to said longitudinal axis, wherein the at least two receiving coils and the at least one transmitting coil are each applied on a coil base surface, wherein the coil base surfaces do not overlap and do not enclose one another circumferentially in the direction of the longitudinal axis Furthermore, the invention comprises a method for detecting a target, in which the proximity switch mentioned above is used.

Description

[0001] Proximity switch and method for detecting a trigger

[0002] The present invention relates to a proximity switch according to the preamble of claim 1 and a method for detecting a target according to the preamble of claim 9.

[0003] Inductive proximity switches are known in the prior art, in particular those in which at least one of the coils is printed on a circuit board.

[0004] Such an arrangement is shown, for example, in DE 202006 004 158 U1, in which an inductive proximity switch is equipped with at least one receiving coil, an oscillator circuit, and at least two receiving coils arranged in the alternating magnetic field of the transmitting coil. The receiving coil and the transmitting coils are arranged adjacent to one another on a circuit board, with an evaluation circuit connected to the transmitting coils that generates a switching signal when a target approaches the proximity switch. According to DE 20 2006 004 158 U1, the two receiving coils and the transmitting coil each consist of at least one annular, elliptical, polygonal, or spiral-shaped winding, with either the transmitting coil being peripherally surrounded by the first receiving coil, which in turn is peripherally surrounded by the second receiving coil.

[0005] Furthermore, DE 102006 053 023 A1 discloses a proximity switch with a coil arrangement generating an alternating magnetic field, which comprises a main transmitting coil and a compensation coil coaxially surrounding the main transmitting coil. The proximity switch further comprises a receiving coil, wherein the transmitting coil and the compensation coil are supplied with alternating currents of opposite phase. The transmitting coil is connected in the opposite direction to the compensation coil, has a larger number of turns than the compensation coil, and the transmitting coil and the compensation coil are energized by a common alternating voltage generator, so that the magnetic field generated by the transmitting coil is greater than the magnetic field generated by the compensation coil.

[0006] Finally, DE 100 57 773 B4 discloses a proximity switch with a coil arrangement having a coil and an evaluation circuit arranged downstream of the coil arrangement for obtaining a switching signal in the event of a field strength change when a target approaches the coil arrangement to the desired response distance, wherein the at least one coil is formed by partial coils electrically connected in series and axially parallel to one another, characterized in that the partial coils are arranged next to one another in a common plane and connected in series with the same winding direction.

[0007] With these basically suitable proximity switches, there is a need for further development towards more stable, interference-free zero states when there is no target in the detection range, while at the same time maintaining high sensitivity (switching distance) and response characteristics.

[0008] It is the object of the present invention to propose an improved proximity sensor and an associated method for detecting a target, wherein a more stable zero state is present and fewer disturbances occur.

[0009] This object is achieved according to the invention by an inductive proximity switch according to the features of claim 1 and a method according to the features of claim 9. Advantageous embodiments are specified in the respective associated subclaims.

[0010] The invention relates to a proximity switch with a coil arrangement comprising at least two receiving coils and at least one transmitting coil, and a control and evaluation unit arranged downstream of said coil arrangement for obtaining a switching signal when a trigger approaches the coil arrangement to the desired response distance, wherein the at least two receiving coils and the at least one transmitting coil are designed as planar coils and are arranged in a common coil plane, wherein the common coil plane is aligned substantially perpendicular to a longitudinal axis of the proximity switch and the coil axes parallel to this longitudinal axis, wherein the at least two receiving coils and the at least one transmitting coil are each applied to a coil base surface, wherein the coil base surfaces do not overlap in the direction of the longitudinal axis and do not enclose one another circumferentially, in particular do not enclose one another in a ring-like manner.

[0011] In particular, a switching signal is generated when the field strength changes due to the presence of a trigger (target). The arrangement of the individual coils in "a plane" does not mean a mathematically two-dimensional surface. In this case, "a plane" refers to the arrangement on a circuit board or printed circuit board, particularly on the same surface of the board. A plane also refers to individual coils or coil groups being recessed into the board and / or mounted on the back or underside of a board.

[0012] A coil or the coil windings are designed, in particular, as a flat spiral, the first terminal of which is arranged radially outwardly of the respective spiral at one end of the windings, and the second end is arranged in the center, i.e., on a central inner surface of the respective coil. The connection from the second end of the winding to another connection point is made, in particular, through the circuit boards and, in particular, at least along a section on the back of the circuit board.

[0013] In a further improved embodiment, at least one coil or a group of coils is formed in multiple layers by applying an electrically insulating layer (first insulating layer) to a first level with electrically conductive turns (first winding level) and applying a second winding level with an electrically conductive turn to the first insulating layer, which in turn can be covered by a second insulating layer, wherein the structure can be continued in an analogous manner.

[0014] Here, the winding on the second winding level is an electrically conductive, co-directional continuation of the winding on the first, lowest winding level. The winding of the second winding level can be completely congruent with all the windings of the level below or only cover a portion of the windings in the coil's axial direction. Advantageously, at least one of the windings is applied using an additive manufacturing process. Ideally, the winding levels and the insulation levels are applied at least partially using an additive manufacturing process.

[0015] In a further improved embodiment, at least one outer correction or counter winding is applied to at least one winding level, in particular the uppermost winding level, which outer correction or counter winding encloses the base area of ​​the respective coil at least over a partial length of 360°, in particular with a partial length of more than 180°, ideally with a partial length of more than 270°.

[0016] Due to the multi-layer structure, the flat coil cannot be significantly miniaturized while maintaining the same detection performance and the same detection range, as the maximum detection range is always proportional to the overall coil diameter. However, the multi-layer structure can improve the detection performance without increasing the size, for example, by increasing the inductance of the transmitting coil.

[0017] The receiving coils are connected in series. The transmitting coil either has windings in opposite directions to the receiving coils or carries current in the opposite direction to the receiving coils.

[0018] The coil arrangement operates on a transformer coupling factor principle, in which the receiving coils are excited by an oscillator or form an oscillator circuit. At least one transmitting coil is arranged adjacent to the receiving coil in this alternating magnetic field. The control and evaluation unit connected to the transmitting coil generates a switching signal from the changed output or rest signals of the transmitting coil when a trigger approaches within the detection range of the proximity switch.

[0019] In an improved embodiment, it can be provided that the coil axis of the at least one transmitting coil is located radially inward in the common coil plane and the at least two coil axes of the receiving coils are located radially outward

[0020] A further advantage may be that in one embodiment, exactly one transmitting coil is provided, the coil axis of which runs in coincidence with the longitudinal axis, and wherein the coil axes of the at least two receiving coils are at the same distance from the coil axis of the transmitting coil. Advantageously, at least two groups or pairs of receiving coils are arranged symmetrically to the coil axis of the central transmitting coil. Ideally, the receiving coils or their coil axes are arranged at an identical angular distance around the transmitting coil or its coil axis. To create a uniform and stable magnetic field, a particular advantage may be that the coil axes of all receiving coils are at the same or essentially the same distance from the coil axis of the central transmitting coil.

[0021] One transmitting coil is thus positioned at the center of the coil array (Cu layer), and several ring-shaped receiving coils are arranged around it, which, through electrical interconnection, create a differential voltage. This allows for the position detection of metallic triggers (targets), regardless of their conductivity. This creates a factor of 1, which can be evaluated at the standard industrial detection (switching) distance.

[0022] This embodiment can be improved by providing three to six receiving coils, whose coil axes are arranged concentrically around the coil axis of the transmitting coil. The distances between the receiving coils and their coil axes are not necessarily identical, but are advantageously symmetrical to achieve the most uniform distribution of the magnetic field possible.

[0023] It may be advantageous if, in one embodiment, each receiving coil has a number S of turns, and each transmitting coil has a number E of turns, wherein the ratio ZS / ZE is in the range from 0.46 to 0.30, ideally in the range from 0.43 to 0.32. In one advantageous embodiment, for example, four receiving coils each have 3.5 turns, and the one central transmitting coil has 5.5 turns, resulting in a ratio of 0.393.

[0024] It may also be advantageous if, in one embodiment, the ratio of the coil base areas of a receiving coil to a transmitting coil is 1, plus / minus 0.2. In this case, the coil base area is understood to mean only the surface area covered by the spiral windings, in particular; any necessary lines or conductor paths do not define the coil base area.

[0025] Overall, the coil arrangement should be designed such that a differential voltage is generated by the electrical interconnection of the receiving and transmitting coils. To create a very dense magnetic field and to reduce interference, it has been found that it can be advantageous to keep the vertical distance between

[0026] - the outermost turn of a receiving coil and

[0027] - the outermost turn of the transmitting coil, is a multiple of the turn spacing of a receiving coil, whereby the multiple is in the range of 0.8 to 3, ideally in the range of 0.8 to 1.5.

[0028] The coil pitch is the vertical distance in the radial direction between two parallel coils of a spiral. Ideally, the receiving coils are identical or largely identical, at least in terms of the number of coils and their dimensions.

[0029] The invention further includes a method by which a trigger (target) can be detected, wherein a proximity switch with associated circuit and evaluation unit is used, and wherein the proximity switch is designed according to one of the previous variants and embodiments.

[0030] All statements, information and mentions of advantages made regarding the proximity switch apply analogously to the process using the proximity switch.

[0031] A particular advantage has been found to be that the coil system for the inductive proximity sensor described here has a reduction factor of 1 for all metals, a very simple structure and is characterized by high temperature and long-term stability.

[0032] Furthermore, no ferrite core is required, so external magnetic fields cannot interfere with the sensor. Another advantage has been found to be the coil system's ability to withstand any directional bias, allowing detection from both sides of the board with identical sensitivity and effectiveness.

[0033] Further details and advantages of the invention will now be explained in more detail with reference to an embodiment illustrated in the drawings. They show:

[0034] Fig. 1 is a sectional view of the proximity sensor according to the invention as a plan view of the coil arrangement of a first embodiment, Fig. 2 is a second embodiment of the coil arrangement,

[0035] Fig. 3 shows a third embodiment of the coil arrangement,

[0036] Fig. 4 shows a fourth embodiment of the coil arrangement and

[0037] Fig. 5 is a vertical sectional view in the longitudinal direction of the

[0038] Proximity sensor as an overview display.

[0039] Figure 1 shows the proximity switch 100, which has a housing 104 in which a circuit board 106 with a coil arrangement 200 comprising four receiving coils 210 and one transmitting coil 220 is arranged. The top side of the circuit boards 106 forms the coil plane 114 in the illustrated embodiment. The receiving coil 210 has a coil axis 212, and the transmitting coil 220 has a coil axis 222. The coil axis 222 of the transmitting coil 220 is congruent with the longitudinal axis 102 of the coil arrangement 200 or the proximity sensor 100. The axes emerging from the image plane are symbolized as a circle with an inner "X."

[0040] The receiving coils 210 and the transmitting coils 212, or their windings, run concentrically around the respective coil axes 212, 222. The longitudinal axis 102 of the coil arrangement 200 is generally located in the center of all coil axes 212, 222, or forms the center.

[0041] The circuit board 106 is arranged parallel to the section plane (not shown), which is aligned parallel to the image plane. A control and evaluation unit 108 is connected to the circuit board 106 and, in particular, to the electronic components 118 (not shown) arranged thereon (Fig. 5).

[0042] Figure 1 also shows a trigger 110 (target) which moves in the direction 122 of the proximity sensor 100 and, in the position shown, is still outside the response distance 112 of the proximity sensor 100.

[0043] All coils of coil arrangement 200 are designed as planar coils, which are applied to the surface of circuit board 106, for example, using a melting or printing process. The four receiving coils 210 are connected in series and conductively connected to one another on the underside of circuit board 106. The central transmitting coil 220 is positioned in the center of the coil arrangement (Cu layer), and the four receiving coils 210 are arranged around it. The electrical interconnection creates a differential voltage, the change in which represents the detection of a metallic trigger (target). This occurs independently of the trigger's conductivity. Thus, a factor of 1 exists, which can be evaluated at the industrially standard detection (switching) distance.

[0044] The electrical interconnection, as described above, is a series connection of the four receiving coils. It is essential that the individual coils are electrically connected in such a way that the direction of current flow results in a differential voltage across all receiving coils, which can be used to adjust the coil system. This differential voltage, which is to be evaluated, results in a zero crossing.

[0045] The coil base surfaces 230, better seen in Figures 2, 3 and 4, do not overlap. In the example shown in Figure 1, the four receiving coils 210 are not arranged symmetrically with identical angular spacings around the central transmitting coil 220, whereby an angle is meant that has the passage point of the longitudinal axis 102 as its center and runs through the passage points of the respective coil axes. In the present case, the pair of receiving coils 210 shown above encloses a first angle between them that is identical to the angle encloses the lower pair of receiving coils 210. A larger second angle is spanned between the upper left and lower left receiving coils 210, which is designed analogously to the right receiving coils 210.

[0046] The four coil axes 212 of the four receiving coils 210 are arranged at an identical radius from the longitudinal axis 102 and thus also from the coil axis 222 of the transmitting coil 220. Furthermore, the circuit board 106 has guide surfaces 124 as flat surfaces, which serve for positioning within the housing 104.

[0047] The advantage of the embodiment of the proximity sensor 100 shown in Figure 1, and in particular of the coil arrangement 200 on the circuit board 106, is that the receiving coils 210 can be positioned very closely to the central transmitting coil 220, while also providing ample space for necessary soldering in the second angle. The distance 128 between the outermost turn of the transmitting coil 220 and the respective opposite outermost turn of one of the receiving coils 210, along the distance between the respective coil axes 212, is equal to the inner turn spacing of the receiving coil or the transmitting coil.

[0048] Figure 2 shows an arrangement of a coil arrangement 200 with five receiving coils 210 and a central transmitting coil 220, which lie in a common coil plane 114, as can be seen in the sectional view of partial image II.

[0049] Partial image I shows that the receiving coils 210 and their coil axes 212 are arranged symmetrically as petaloids around the central longitudinal axis 102 and the central coil axis 212 of the transmitting coil 220, respectively. Furthermore, reference numeral 130 indicates the direction of the view of the sectional view in partial image II. Instead of a guide surface as an installation and positioning aid, the circuit board 106 has a guide groove 126.

[0050] Figure 3 shows a coil arrangement 200 consisting of six receiving coils 210 arranged symmetrically and at equal angular intervals around a central transmitting coil 220. The embodiment according to Figure 3 differs from that according to Figures 1 or 2, in addition to the number of receiving coils 210, in that the coil plane 114, within the meaning of this invention, can also run centrally in the circuit board 106. In this case, the receiving coils 210 are arranged on one side of the circuit board 106, and the one central transmitting coil 220 is arranged on the opposite side of the (same) circuit board 106 (partial image II). The one central transmitting coil 220 can also consist of a group of several transmitting coils 220, as shown in Figure 4.

[0051] It can also be provided that at least one type of coil (receiving and / or receiving coils) is arranged in a recess or cutout of the circuit board. In partial images I and III, the upper coils 210, 220 are shown as solid (circular) lines, and the rear coils 210, 220 are shown as dashed (circular) lines. The circuit board 106 has two guide grooves 126 on its outer contour, which, analogous to the guide surfaces 124 described for Figure 1, serve for positioning within the housing 104.

[0052] The embodiment according to Figure 4 differs from the previous embodiments in that a group of three transmitting coils 220 is arranged centrally in the middle of three receiving coils 210. The central longitudinal axis 102. The transmitting coils 220 are connected in series with one another and, as a group, are connected to the receiving coils 210, which are also connected in series.

[0053] In this embodiment, the central longitudinal axis 102 is not congruent with any of the coil axes 212.

[0054] Figure 5 shows the entire proximity sensor 100, wherein the circuit board 106 with the coil arrangement 200 thereon is arranged on the detection side 132 and the connecting cable 116 for the data and current-conducting connection to the circuit board 106 and its components 118 of the control and evaluation unit 108 is arranged on the connection side 134.

[0055] List of reference symbols

[0056] Proximity switch longitudinal axis housing circuit board

[0057] Control and evaluation unit Trigger, target Response distance Coil level Connecting cable Components Guide groove Direction

[0058] Guide surface guide groove distance direction

[0059] Capture page Connection page

[0060] Coil arrangement

[0061] Receiving coils Coil axis of 210 Coil plane

[0062] transmitting coil

[0063] Coil axis of 220

[0064] Coil base area

Claims

Claims: Proximity switch (100) with a coil arrangement (200) comprising at least two receiving coils (210) and at least one transmitting coil (220), and a control and evaluation unit (108) downstream thereof for generating a switching signal when a trigger (110) of the coil arrangement (200) approaches the desired response distance (112), wherein the at least two receiving coils (210) and the at least one transmitting coil (220) are designed as planar coils and arranged in a common coil plane (114), wherein the common coil plane (114) is oriented substantially perpendicular to a longitudinal axis (102) of the proximity switch (100) and the coil axes (212, 222) parallel to this longitudinal axis, characterized in that the at least two receiving coils (210) and the at least one transmitting coil (220) are each located on a coil base. (230) are applied,wherein the coil base surfaces (230) do not overlap in the direction of the longitudinal axis (102) and do not enclose each other completely. Proximity switch according to claim 1, characterized in that the coil axis (222) of the at least one transmitting coil (220) lies radially inside the common coil plane (114) and the at least two coil axes (212) of the receiving coils (210) lie radially outside. Proximity switch according to claim 1 or 2, characterized in that exactly one transmitting coil (220) is provided, the coil axis (222) of which is in alignment with the longitudinal axis (102), and wherein the coil axes (212) of the at least two receiving coils (210) are at the same distance from the coil axis (222) of the transmitting coil (220). Proximity switch according to claim 3, characterized in that 3 to 6 receiving coils (210) are provided, the coil axes (212) of which are arranged concentrically around the coil axis (222) of the transmitting coil (220). Proximity switch according to one of the preceding claims, characterized in that each receiving coil (210) has a number S of turns, and each transmitting coil (212) has a number E of turns, wherein the ratio ZS / ZE is in the range of 0.46 to 0.30, ideally in the range of 0.43 to 0.

32. Proximity switch according to one of the preceding claims, characterized in that the ratio of the coil base areas 230 of a receiving coil (210) to a transmitting coil (212) is 1, plus / minus 0.

2. Proximity switch according to one of the preceding claims, characterized in that the vertical distance (116) between the outermost turn of a receiving coil (210) and the outermost turn of the transmitting coil (220) is a multiple of the turn spacing of a receiving coil (210) and is in the range of 0.8 to 3, ideally in the range of 0.8 to 1.5.Proximity switch according to one of the preceding claims, characterized in that at least one coil and / or a group of coils is designed in multiple layers and has at least the following layer sequence:. - a first winding level with electrically conductive windings, - a first electrical insulating level or insulating layer and - a second winding level with an electrically conductive winding, and wherein, in particular, the layer sequence comprises further winding and / or insulating levels in an analogous manner. Method for detecting a trigger (110) by means of a proximity switch (100), characterized in that the proximity switch (100) is configured according to one of the preceding claims.

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