DE102022121645A1 - Inductive proximity sensor and method for detecting objects - Google Patents

Abstract

The present invention relates to an inductive proximity sensor with a transmitter coil arrangement generating an alternating magnetic field, which has the following: a coil axis, a carrier plate, a transmitter coil with a compensation coil coaxially surrounding it, a receiver coil arrangement with a receiver coil, the transmitter coil and the compensation transmitter coil having alternating currents of opposite phase can be fed, whereby the transmitter coil is connected in series and in opposite directions to the compensation transmitter coil and the transmitter coil and compensation transmitter coil are energized by a common AC voltage generator or can be excited by natural oscillation, so that the magnetic field generated by the transmitter coil is greater than the magnetic field generated by the compensation transmitter coil, and wherein the transmitting coil is arranged on a support plate, and wherein the receiving coil arrangement comprises a compensation receiving coil which is connected in series with the receiving coil. The invention further includes a method for detecting an object using this proximity sensor.

Description

The present invention relates to a proximity sensor according to the preamble of claim 1 and a detection method for metallic elements according to the preamble of claim 12.

Inductive proximity sensors are known in the prior art, for example, describes DE 44 29 314 B4 such a proximity sensor in which an alternating magnetic field is generated in a coil so that a penetrating metallic object influences the vibration state. The detected change in the oscillation state is evaluated using a circuit, with two receiving coils arranged in a direct differential circuit in the alternating field to detect the induced voltages. The differential voltage of the receiving coils becomes zero at the response distance. In the solution after DE 44 29 314 B4 the wound coils are arranged in three levels or in three corridors. The disadvantage of this solution is that the wound coils tend to age, so that the switching distance drifts over time. In particular, the maximum achievable switching distance with wound coils is severely limited.

Therefore, already in the DE 10 2006 053 023 A1 An improved inductive proximity sensor with a planar transmitter coil arrangement generating an alternating magnetic field is proposed, which has a transmitter coil and a compensation coil coaxially surrounding it. Furthermore, a receiving coil is provided, the transmitting coil and the common compensation coil being fed with alternating currents of opposite phases, and the transmitting coil being connected in opposite directions to the compensation coil and having a larger number of turns. The common compensation coil and the external field and its field lines generated by it result in a compensation of the field lines of the transmitting coil in the surrounding area, so that overall the flux in the surrounding area can be brought to zero or essentially zero. According to the DE 10 2006 053 023 A1 The receiving coil is arranged between the transmitting coil and the compensation transmitting coil, and a planar arrangement is proposed as the ideal solution, in which the transmitting, receiving and compensation windings are ideally located on one plane. In this way, however, the system only achieves standard switching distances; extended switching distances cannot be achieved.

It is the object of the present invention to propose an improved coil arrangement in which extended switching distances can be achieved.

This object is achieved according to the invention by an inductive proximity sensor according to the features of claim 1 and a method for detecting objects according to the features of claim 12. Advantageous refinements are specified in the respective, associated subclaims.

• - eine Spulenachse
• - eine Trägerplatte mit einer ersten Seite und einer zweiten Seite,
• - eine Sendespule mit einer diese koaxial umgebenden Kompensationsspule,
• - eine Empfangsspulenanordnung (130(Empfangsspulenanordnung) mit einer Empfangsspule, wobei die Sendespule die Kompensationssendespule mit Wechselströmen entgegengesetzter Phasen gespeist werden können. Die Sendespule ist in Reihe und gegensinnig zur Kompensationssendespule geschaltet, wobei Sendespule und Kompensationssendespule von einem gemeinsamen Wechselspannungsgenerator bestromt angeregt werden können und/oder durch Eigenschwingung angeregt werden können. Das von der Sendespule erzeugte Magnetfeld ist hierbei größer als das von der Kompensationssendespule erzeugte Magnetfeld. Die Sendspule und die Kompensationssendespule sind auf einer Trägerplatte angeordnete.

The task is then solved by an inductive proximity sensor with a transmitter coil arrangement that generates an alternating magnetic field and which has the following:

• - a coil axis
• - a carrier plate with a first side and a second side,
• - a transmitter coil with a compensation coil coaxially surrounding it,
• - a receiving coil arrangement (130 (receiving coil arrangement) with a receiving coil, whereby the transmitting coil and the compensating transmitting coil can be fed with alternating currents of opposite phases. The transmitting coil is connected in series and in opposite directions to the compensating transmitting coil, with the transmitting coil and the compensating transmitting coil being able to be excited by a common alternating voltage generator and/ or can be excited by natural oscillation. The magnetic field generated by the transmitter coil is larger than the magnetic field generated by the compensation transmitter coil. The transmitter coil and the compensation transmitter coil are arranged on a carrier plate.

Here, the receiving coil arrangement comprises a compensation receiving coil, wherein the receiving coil and the compensation receiving coil are connected in series, and wherein each coil has at least one connection field (126, 128, 136, 138) to which it is conductively connected.

Advantageously, the coils mentioned are soldered as a conductor track, printed or applied to the carrier plate as an adhesively placed wire made of a current-conducting material.

So that the magnetic field generated by the transmitter coil is greater than the magnetic field generated by the compensation transmitter coil, the transmitter coil has a larger number of turns than the compensation transmitter coil.

Advantageously, the transmitting coil arrangement and the receiving coil arrangement are arranged one behind the other (stacked) in the axial direction of the sensor axis.

A further advantage here can be that the transmitting coil arrangement and the receiving coil arrangement are arranged on a common carrier plate, and in a further improved embodiment it can be provided that the transmitting coil arrangement is arranged on a first side of the carrier plate and the receiving coil arrangement is arranged on a second side of the same carrier plate .

“Side” here means a broad side of the carrier plate, not the narrow peripheral edge of the carrier plate.

Furthermore, an advantage for a very compact coil arrangement can be that the transmitting coil arrangement and the receiving coil arrangement are arranged on a common support plate and are arranged stacked one above the other on the same first or second side. At least one electrically insulating intermediate layer is arranged between the transmitting coil arrangement and the receiving coil arrangement. This intermediate layer can be a film or plate, which is ideally glued and/or rests on a casting material. Alternatively, the separating layer can be formed entirely from a potting material, such as an acrylic resin or an epoxy resin.

Advantageously and depending on the field of application, the transmitter coil has two or more turns, in particular more than 4 turns. In an advantageous embodiment, the compensation transmitter coil has one or two turns.

Here, “a turn” means not only the line path, which is guided 360° in the circumferential direction around a center and/or the longitudinal axis of the proximity sensor, but also partial lengths of a turn in the circumferential direction. Thus, half a turn means a conductor track that circles a center and/or the longitudinal axis of the proximity sensor by 180°. Furthermore, information about “one turn” should not necessarily be understood as a 360° circumnavigation, but rather as a largely complete circumnavigation.

Although a turn is described as “circulating”, “circumferential” or “circumferentially” around a center, this does not mean a circular shape in the mathematical sense. Even if a substantially circular shape and winding is advantageous, other shapes can also be provided, in particular polygonal shapes or an elliptical shape. In an analogous way, a circular shape or wreath shape does not mean a circular or wreath shape that is round in the mathematical sense. The course of the winding can have lateral deviations on a section of the respective coil in order to bypass elements arranged in the occupancy area of the respective coil, such as a connecting element of a coil, so that in this respect too a circle or a ring is essentially, i.e. averaged, as should be understood as circular or wreath-shaped.

Typically, the ratio of the number of turns of the transmitter coil to the number of turns of the compensation transmitter coil is in the range of 5/1 to 50/1, whereby this depends in particular on the possible size and the intended use. Advantageously, the ratio of the number of turns is 25/1. The number of turns of the compensation transmitter coil is advantageously, for example, 1 to 3. Large ratios are particularly advantageous if the transmitter coil cannot be accommodated on one level and/or in a single area due to a high number of turns, so that further levels for turns of the Transmitting coil can be provided. Thus, for example, 5 turns of the transmitter coil can be arranged on 5 levels, so that the transmitter coil has a total of 25 turns.

Even if a clear distinction is generally made here between the different coils or types of coils and their functions, the term “coil” is intended to mean all types of coils, i.e. in particular the transmitter coil, the compensation transmitter coil, the receiver coil and the compensation receiver coil, unless it is is executed something different.

Advantageously, the compensation transmitter coil is immediately radially enclosed by the compensation receiver coil and furthermore the compensation receiver coil is directly radially enclosed by the compensation transmitter coil. In this context, this directly means that no further coil consisting of at least one turn and/or with a different or the same function is arranged between them.

In a further improved embodiment, it can be provided that the ratio of the number of turns of the receiving coil to the compensation receiving coil is in the range from 0.5 to 1.6, in particular in the range from 0.8 to 1.2. This ensures, in particular, that the main detection space on the detection side of the proximity sensor is sharply demarcated from the external scattering space.

In a further improved embodiment, it can be provided that the compensation receiving coil has at least a first turning region, in which a change of direction occurs at least in a partial number of the turns of the compensation receiving coil, and in particular the compensation receiving coil has a first turning region and a second turning region.

In the present case, a “turning area” means the area or the coil section on the carrier plate or in the course of the compensation transmission coil in which a change in direction of at least one turn, in particular all turns of the compensation transmission coil, takes place. In other words, in the turning area there is a change of direction from “clockwise” to “counterclockwise” and vice versa, so that the KPS has a group of turns that run in the circumferential direction and a second group through one or two turning areas at least on a section of the compensation transmitter coil of turns that run counterclockwise.

In a very compact, advantageous embodiment, it is provided that the connection field of the compensation receiving coil lies in the turning area, in particular is surrounded by at least a partial length of a section of a turn in which the 180° deflection takes place. Advantageously, the connection field of the compensation receiving coil is surrounded by at least a partial length of all sections of the windings that are deflected by 180°.

In this case, the section of the conductor path of coils that covers the transition from the series-connected transmitter coil to the compensation transmitter coil or the receiver coil to the compensation receiver coil should not be viewed as a turning area.

In a further improved embodiment, it can be provided that the compensation receiving coil is electrically conductively connected to a connection field at one end of the compensation receiving coil and the connection field is arranged in one of the turning areas, in particular in the middle of the turning area. The term “middle” is not to be understood in the mathematical sense, but simply means an essentially centrally arranged area. This also refers in particular to the variant explained above, in which the connection field of the compensation receiving coil is enclosed by all sections of the windings that are deflected by 180°.

In an alternative embodiment, it can be advantageous if a direct line or line track to the interconnection unit is provided via fillet soldering, for which purpose the connection panels are connected via additional conductor tracks. Furthermore, with very large proximity switches, it can be advantageous if the interconnection unit is arranged directly on the circuit board.

In a further improved embodiment, it can be provided that the turn spacing of the first group of turns of the compensation receiving coil, which run in the first direction (clockwise), corresponds to the turn spacing of a second group of turns of the compensation receiving coil, which run in the second, opposite direction , in particular the turn spacing of the adjacent turns of the first group and that of the second group is equal or substantially equal to the turn spacing within the respective groups.

In the smallest expansion stage, an aforementioned group can only include one turn.

• - der Sendespule und der Kompensationssendespule und
• - der Empfangsspule und der Kompensationsempfangsspule

jeweils eine Freifläche mit einer Breite angeordnet ist.In a further improved embodiment it can be provided that the transmission coil, the compensation transmission coil, the reception coil and the compensation reception coil each have a signal cover the supply surface on the carrier plate, in particular with a substantially fixed width, with between

• - the transmitter coil and the compensation transmitter coil and
• - the receiving coil and the compensation receiving coil

an open space with a width is arranged in each case.

The occupancy surfaces advantageously have the shape of a ring or a wreath, having an inner radius and an outer radius. The occupancy area can also have the shape of an ellipse or a polygon, in which case all statements that refer to a substantially circular or round shape are to be applied in an analogous manner. The respective open area results in its overarching geometric shape and dimensions essentially from the adjacent coils, so that what has been said above finds an analogous application.

The term “occupancy area” means the area on the carrier plate or the shadow area on the carrier plate, on or above which the respective turns of the respective coil are essentially arranged. What was said at the beginning also applies to a round or ring-shaped geometry or shape.

The transmitting coil and the receiving coil have a circular core surface in the center, which is formed from the central, for example circular, surface in the middle of the coil, an advantageous embodiment being that the transmitting coil is completely in the area of the core surface without overlapping in the direction of the coil axis the receiving coil.

In a further improved embodiment, it can be provided that the occupancy area of the transmitting coil at least partially covers the open area of the receiving coil arrangement, in particular is arranged to completely cover the area of the open area of the receiving coil arrangement.

Here, “covering” or “covering” a first coil means that its shadow area is arranged in a surface area, such as an occupancy area or the core area, of another coil in the direction of view of the coil axis.

• - eine Breite einer ersten Überdeckung von der Kompensationssendespule mit der Kompensationsempfangsspule,
• - eine Breite einer zweiten Überdeckung von der Sendespule mit der Kompensationsempfangsspule und/oder
• - eine Breite einer dritten Überdeckung von der Sendespule mit der Empfangsspule gegeben ist, die nicht größer als die Breite von zwei Windung, insbesondere nicht größer als die Breite von einer Windung beträgt und idealerweise Null ist. Hierbei kann eine Verbesserung darin bestehen, dass in radialer Richtung ein Abstand zwischen der Sendespule und der Kompensationsempfangsspule ausgebildet ist., der 0,5 bis 2 Windungsbreiten beträgt.

In a further improved embodiment it can be provided that

• - a width of a first overlap of the compensation transmission coil with the compensation reception coil,
• - a width of a second overlap between the transmitting coil and the compensation receiving coil and/or
• - There is a width of a third overlap between the transmitting coil and the receiving coil, which is not greater than the width of two turns, in particular not greater than the width of one turn and is ideally zero. An improvement here can be that a distance is formed in the radial direction between the transmitting coil and the compensation receiving coil, which is 0.5 to 2 turn widths.

• - wenn nur eine (einzige) Windung betroffen ist, wird die „Breite einer Windung“ identisch gebildet aus der Breite der elektrisch leitenden Leitungsbahn mit ggf. deren Isolierungsmaterial in radialer Richtung und/oder insbesondere der Fuß- oder Grundfläche der Leitungsbahn, nachstehend kurz „Fußbreite“ genannt und
• - wenn zwei oder mehr Windungen überdeckt werden, ist die summarische Windungsbreite die Summe aus der Fußbreite der ersten Windung plus dem freien Windungsabstand mal der Anzahl der Windungen.

The “width” of a turn means the following:

• - if only one (single) turn is affected, the “width of a turn” is formed identically from the width of the electrically conductive conductor track with, if applicable, its insulation material in the radial direction and/or in particular the foot or base area of the conductor track, hereinafter referred to as “ Foot width” called and
• - if two or more turns are overlapped, the total turn width is the sum of the foot width of the first turn plus the free turn spacing times the number of turns.

For example, if a receiving coil has 3 turns, the total turn width of the receiving coil is the sum of 3 times the foot width plus 2 times the distance between the turns.

The following applies to all information and values: in the event of different winding distances and/or base widths of the coils considered with one another, the values of that coil are used as the basis should be laid which has the smaller winding spacing and/or the larger ratio of turns to the width of the coil. The background here is that the influence of a possibly additional turn in the overlapping area of two coils has a greater influence than the distance between the turns alone. The decisive factor here is the capacitive coupling of two conductor tracks (conductor surfaces) of the transmitter and receiver to one another. The larger the overlapping conductor areas, usually copper tracks or copper surfaces, the more detrimental the overall effect is.

• - eine Breite einer erste Überdeckung von der Kompensationssendespule mit der Kompensationsempfangsspule kleiner als das 0,75-fache, insbesondere kleiner als das 0,5-fache der Windungsbreite beträgt,
• - eine Breite einer zweiten Überdeckung von der Sendespule mit der Kompensationsempfangsspule kleiner als das 2-fache, insbesondere kleiner als das 1 ,5-fache einer Windungsbreite beträgt,

und/oder

• - eine Breite einer dritten Überdeckung von der Sendespule mit der Empfangsspule nicht größer als 40% der Belegungsfläche ist, vorteilhafterweise die Breite kleiner als das 0,5-fachen der Windungsbreite beträgt, insbesondere Null ist.

In a further improvement of this embodiment it can be provided that

• - a width of a first overlap between the compensation transmitter coil and the compensation receiver coil is less than 0.75 times, in particular less than 0.5 times the winding width,
• - a width of a second overlap between the transmitting coil and the compensation receiving coil is less than 2 times, in particular less than 1.5 times, a turn width,

and or

• - a width of a third overlap between the transmitting coil and the receiving coil is not greater than 40% of the occupancy area, advantageously the width is less than 0.5 times the winding width, in particular zero.

In a particularly advantageous embodiment, there is an uncovered distance area between the occupancy area of the receiving coil and the occupancy area of the overlapping transmitter coil arranged in the core area of the receiving coil, which has a width of at least 0.15 times a turn width and/or a foot width.

The coverage in the edge area of two coils can be particularly advantageous for design reasons and should not exceed 20% coverage of an occupancy area of one of the two coils. Furthermore, it is advantageous if, of the two coils involved, which overlap each other, at least 60% of the occupancy areas of both coils are not covered by another coil.

Overall, it is advantageous if the base width of the turns of the transmitter coil has a width of, for example, 0.2mm to 0.6mm, with wide conductor tracks (foot width) being advantageous due to the associated low resistance and thus a high coil quality. Furthermore, it is advantageous if the windings of the receiving coil have a width of 0.1mm to 0.2mm, for example. Overall, it is advantageous if the receiving coil has conductor tracks that are as narrow as possible, so that the capacitive coupling between the transmitter and receiver is advantageously reduced. In other words, it is advantageous if the ratio of the base width of the turns of the transmitting coil to the base width of the turns of the receiving coil is in the range of 1 to 0.15, in particular if it is in the range of 0.35 to 0.15.

The exact dimensioning must be adapted depending on the intended use or object size and distance to the object as well as the type of object, in particular the material of the object.

• - ein Anschlussfeld der Kompensationssendespule mit mindestens einer Teilfläche in der Belegungsfläche der Kompensationsempfangsspule liegt und ein Anschlussfeld der Sendespule mit mindestens einer Teilfläche in der Belegungsfläche der Empfangsspule liegt.

In a further improved embodiment, it can be provided that the transmitting coil arrangement and the receiving coil arrangement are arranged on a support plate, with at least one connection field of the transmitting coil and/or the compensating transmitting coil with at least one partial area in the area of the occupancy area of the compensating receiving coil, in particular

• - a connection field of the compensation transmission coil with at least one partial area lies in the occupancy area of the compensation reception coil and a connection field of the transmission coil with at least one partial area lies in the occupancy area of the reception coil.

In the present case, the “connection field” refers in particular to the soldering or connection area in which the conductor track of the first turn or the last turn of a coil is electrically conductively connected to the outside, in particular with a circuit.

This connection field is, for example, regularly routed through the carrier plate in the case of a common carrier plate. The background is that connection panels are regularly formed by filling a hole or opening in the carrier plate with a soldering material and in parallel connecting the respective turn (conductor track) and a supply line in an electrically conductive manner. So at least At least one of the connection panels, in particular all connection panels, of the transmitting coil arrangement and the receiving coil arrangement are arranged on both sides of the carrier plate and can be contacted on both sides by the carrier plate. Contacting on both sides is necessary for measurement and maintenance purposes as well as for the production side to coordinate the transmitting coil arrangement and the receiving coil arrangement with one another.

In the connection panels, the windings of other coils are "insulated", in particular by means of a lacquer or a casting material, such as an acrylic resin and an epoxy resin, electrically insulated and protected against environmental influences.

The invention also includes a method for detecting an object, in particular a metallic object (target), using an inductive proximity sensor according to one of the previous variants and embodiments.

The method advantageously includes a separation of a scattering space and main detection space by arranging the transmitting coil between an inner receiving coil and an outer, circumferential compensation receiving coil, with only field lines that enter within the compensation receiving coil generating a receiving voltage.

This means within the compensation receiving coil the theoretical core area of the compensation receiving coil, which would result if no transmitting coil and no receiving coil were arranged there.

In this way, the scattering space outside the transmitter coil is advantageously sharply separated from the main detection space, within the aforementioned theoretical core area.

All advantages and aspects of the proximity sensor apply identically or in an analogous manner to the method of detecting an object, so they will not be repeated here.

Further details and advantages of the invention will now be explained in more detail using an exemplary embodiment shown in the drawings.

• 1 eine schematische (horizontale) Schnittdarstellung des Näherungssensors in einer ersten Ausführungsform,
• 2 eine Draufsicht auf die Spulenanordnungen gem. der ersten Ausführungsform,
• 3 eine weitere Draufsicht auf die Spulenanordnungen gem. der ersten Ausführungsform,
• 4 eine weitere (vertikale) Schnittdarstellung durch die Trägerplatte mit den beiden Spulenanordnungen,
• 5 eine zur 4 alternative Schnittdarstellung für eine weitere Ausführungsform und
• 6 eine schematische Darstellung von zwei Ausführungsformen für eine Verschaltung des Näherungssensors.

Show it:

• 1 a schematic (horizontal) sectional view of the proximity sensor in a first embodiment,
• 2 a top view of the coil arrangements according to the first embodiment,
• 3 a further top view of the coil arrangements according to the first embodiment,
• 4 another (vertical) sectional view through the carrier plate with the two coil arrangements,
• 5 one for 4 alternative sectional view for a further embodiment and
• 6 a schematic representation of two embodiments for connecting the proximity sensor.

The inductive proximity sensor 100, which could also be referred to as an inductive proximity sensor, is in a schematic structure in the 1 shown in a section at the height and parallel to the coil axis 110. The proximity sensor 100 is shown in the installed position in which the housing 114 is guided through an opening in a carrier 300 in a manner not shown and is held there. A carrier plate 102 is arranged in the interior 194 of the housing 114, on which a transmitting coil arrangement 120 and a receiving coil arrangement 130 are applied. The transmitting coil arrangement 120 is connected to an interconnection unit 116 via the lines 196, the receiving coil arrangement 130 is connected to the interconnection unit 116 via the lines 198. The interconnection unit 116 is connected to the outside via the supply line 118 to conduct current and/or data. Details of the interconnection unit 116 are in particular in the 6 shown in more detail. In the present case, a circuit 116 comprises a generator 202 and an amplifier 206, via which the vibration excitation of the transmitter coil 122 and the compensation transmitter coil 124 can be caused. The connection fields 126, 128 of the transmitting coil arrangement 120 and the connection fields 136, 138 of the receiving coil arrangement 130 are arranged on the carrier plate 102 for the current-conducting connection of the respective lines 196, 198.

On the detection side 108 in front of the proximity sensor 100, a central main detection space 304 and a scattering space 306 surrounding the main detection space 304 are formed by switching the coil arrangements. The main detection space 304 can, in particular due to the annular, coaxially arranged coils, approximately have the shape of a cylinder, which is enclosed by the scattering space 306. The coil axis 110 is essentially identical in position to the longitudinal axis of the main detection space 304.

In the example shown, the two coil arrangements 120, 130 are arranged on both sides of the carrier plate 102, with the transmitting coil arrangement 120 being arranged on the side 192 facing the interior 194 and the receiving coil arrangement 130 being arranged on the side 190 facing the detection side 108. In an alternative embodiment, not shown, this position of the coil arrangements on the carrier plate 102 is reversed.

Current flows through the transmitting coil 122 and the receiving coil 132 in opposite directions and the current flows through the transmitting coil 122 and the compensation transmitting coil 124 in opposite directions. In the example shown, current flows through the receiving coil 132 and the compensation receiving coil 134 both in opposite directions and in the same direction, as in particular in FIG 2 , 4 and 5 is shown in detail.

As shown, with a current flow direction, the field lines 210 induced by the transmitting coil 122 occur centrally in the direction of the detection side 108. The field lines 210 surround the receiving coil 132 and the transmitting coil 122 and enter the interior 196 of the proximity sensor in the area of the compensation transmitting coil 134. The field lines 212 induced by the compensation transmission coil 124 surround the compensation transmission coil 124 and, due to the opposite orientation to the transmission coil 122 between the transmission coil 122 and the compensation transmission coil 124, enter from the detection side 108 and run around the outside of the compensation transmission coil 124 in the direction of the detection side. Thus, the compensation receiving coil 134 only receives the magnetic field between the transmitting coil 122 and the compensation transmitting coil 124. The receiving compensation coil 132, on the other hand, only receives the magnetic field within the transmitting coil 122. The penetrating field lines 210, 212 are in opposite directions in the receiving coil 132 and the compensation receiving coil 134.

In an embodiment not shown, the structure is reversed in the viewing direction, in that the transmitting coil arrangement 120 is arranged on the detection side 108 or the second side 192 and the receiving coil arrangement 130 is arranged on the side 192 facing the interior 194.

In the example shown the 1 The diameter of the carrier plate 102 (circuit board) is 25mm with the ones in the 2 15mm can be achieved if the object 302 (target) has a square shape and an object edge length 310 of at least 45mm.

• Wenn:

- Durchmesser der Trägerplatte 25mm x Faktor a, dann - Schaltabstand 15mm x Faktor a, dann - Objektkantenlänge 45mm x Faktor a As the diameter of the carrier plate 102 increases, larger switching distances 308 can be achieved. The embodiment shown is essentially linearly scalable in terms of size and switching distance 308 according to the following general formula:

• If:

- Diameter of the carrier plate 25mm x factor a, then - Switching distance 15mm x factor a, then - Object edge length 45mm x factor a

Here factor a means the respective scaling factor.

Overall, the compensation receiving coil 134 ensures that the switching distance 308 is reduced back to the desired setpoint when the proximity sensor 100 is installed in a metal environment (support 300). Without this compensation receiving coil 134, the proximity sensor 100 would detect the surrounding metal and switch through undesirably.

The intended use is determined by the switching distance, where the switching distance is the maximum distance of the object to be detected (target 310) from the proximity sensor 100.

In the embodiment according to 2 is the top and bottom plan view of the carrier plate 102 1 shown. On the left partial image, the receiving coil arrangement 130 on the first side 190 of the carrier plate 102 is shown in a top view and on the right partial image the second side of the carrier plate 102 is shown in a top view with the transmitting coil arrangement 120 there.

The transmitter coil arrangement 120 includes an inner transmitter coil 122 with a total of 5 turns 112 and an outer compensation transmitter coil 124 which only has one turn 112. Furthermore, a connection field 126 of the transmission coil 122 and a connection field 128 of the compensation transmission coil 124 are provided. As already stated above, the connection fields 136, 138 of the receiving coil arrangement 130 are also arranged on the second side 192 or can be contacted in a current-conducting manner.

In the example shown, the viewing direction is parallel to the coil axis 106 and in the direction of the detection side 108, i.e. from the interior 194 to the outside. Here, the windings 112 of the transmitting coil 122 are traversed by current in a first direction, which runs counterclockwise. The winding of the compensation transmitter coil 124 is traversed by current in a second direction, which runs clockwise.

The top view of the first partial image shows the receiving coil arrangement 130 with an inner receiving coil 132 and an outer compensation receiving coil 134. The receiving coil 132 has 5.5 turns 112 and the compensation receiving coil 134 has 6 turns. Furthermore, a connection field 136 of the receiving coil 132 and a connection field 138 of the compensation receiving coil 134 are provided. As in the right part of the picture, the connection fields 126, 128 of the transmitting coil arrangement 120 are arranged on the first page 190 and can be contacted in a current-conducting manner.

Even if in the common image plane the directional arrows of the current direction point in the same direction to the left, in the aforementioned, selected viewing direction from the interior 194 to the outside and the current flow direction of the transmitting coil 122, the receiving coil 132 flows in opposite directions, excited by the transmitting coil 122, i.e. in clockwise.

The compensation receiving coil 134 rotates or wraps around the receiving coil 132, with two turning areas 140, 142 being provided in which the windings 112 undergo a change of direction by 180°. The compensation receiving coil 134 is thus divided into two groups 214, 216. The first group 214 of three turns 112 is oriented in the opposite direction to the receiving coil 132 and the second group 216 of the further three turns 112 is again oriented in the same direction as the receiving coil 132.

The second group 216 of the compensation receiving coil 134 is oriented opposite to the direction of the winding of the compensation transmitting coil 124. One direction of flow of the current is indicated by the arrows on the turns of the respective coil.

Furthermore, in the 2 It can be seen in detail that the coils do not have a circular or arc shape with only one radius in the strict mathematical sense. As can be seen in particular with the receiving coil 132 and the compensation receiving coil 134, the back sides of the connection fields 126, 128 lie in the occupancy area of one of the two coils and the windings 112 are guided in such a way that they move laterally and thereby run largely parallel to one another. As already stated above, such a sectional, lateral guidance or deflection of one or more turns 112 for a limited section in the longitudinal direction of a coil or turn should not be understood as an interruption of the basic shape of the respective occupancy area or geometry of the occupancy area, as in particular in the 3 is then assumed.

When presented in the 3 , which is the exemplary embodiment of the 2 shows, the carrier plate 102 with the receiving coil arrangement 130 is again shown in the left partial image and the transmitting coil arrangement 120 is shown on the back of the carrier plate 102 in the right partial image. Here, the respective ring-shaped or ring-shaped occupancy surfaces 150, 152, 154 and 156 are shown as such an annular surface for all coils. The carrier plate 102 has the outer radius 208, wherein the carrier plate 102 can have guide and/or fastening sections on the outer edge in a manner not shown, such as flats, guide grooves or other fastening sections or fastening openings.

In the center of the occupancy area 150 of the transmitter coil 122, a core area 184 is arranged and between the occupancy area 150 of the transmitter coil 122 and the outer, annular occupancy area 152 of the compensation transmitter coil 124, a likewise annular open area 158 is arranged.

The occupancy surfaces 150, 152, 154 and 156 and the circular core surfaces 184, 186 of the coils are arranged concentrically to the common coil axis 106, not shown, and parallel to one another.

The annular open area 158 is not occupied by a coil on this side 192 of the carrier plate 102. The section of the line path that forms the transition from the transmitter coil 122 to the series-connected compensation transmitter coil 124 should not be viewed as a coil.

The occupancy area 150 of the transmitter coil 122 has an outer radius 160 and an inner radius 162. The occupancy area 152 of the compensation transmission coil 124 has an outer radius 164 and an inner radius 166. The inner radius of the open area 158 largely corresponds to the outer radius 160 of the transmitter coil 122 and the outer radius of the open area 158 largely corresponds to the inner radius 166 of the compensation transmitter coil 124. The radii of the open areas and/or the core areas are not named further below because they differ in this way can be derived analogously, which also applies to the receiving coil arrangement 130 shown in the left partial image.

In the center of the occupancy area 154 of the receiving coil 132, a core area 186 is arranged and between the occupancy area 154 of the receiving coil 132 and the outer, annular occupancy area 156 of the compensation receiving coil 134, there is also an annular open area 158 arranged, which is not on this side 190 of the carrier plate 102 a coil is occupied. Here, as stated above, the section of the conductor path that forms the transition from the receiving coil 132 to the series-connected compensation receiving coil 134 should not be considered a coil.

The occupancy area 154 of the receiving coil 132 has an outer radius 172 and an inner radius 170. The occupancy area 156 of the compensation transmission coil 134 has an outer radius 176 and an inner radius 166.

Like in the 3 shown in detail, the occupancy areas arranged parallel to one another and axially spaced apart form a portion of the respective areas. The occupancy area 156 of the compensation receiving coil 134 covers, with its radially outer region, the occupancy area 152 of the compensation transmitting coil 124 on the radially inner (ring) region. This coverage has a width 180 of approximately 30% of the occupancy area 152 of the compensation transmission coil 124. The uncovered part of the compensation transmission coil 124 forms the outermost edge of the entire coil arrangement.

Furthermore, the occupancy area 156 of the compensation receiving coil 134 with its radially inner area covers the occupancy area 150 of the transmitting coil 122 on its radially outer (ring) area. This coverage of the transmitter coil 122 on the outer ring area has a width 180 of approximately 10% of the occupancy area 150 of the transmitter coil 122. The dashed auxiliary lines serve as an orientation aid for the position of the respective occupancy areas of the coil arrangements on the two sides 190, 192 of the carrier plate 102. In In the example shown, the occupancy areas 150 of the transmitting coil 122 and the occupancy area 154 of the receiving coil 132 do not overlap because the outer radius 172 is smaller than the inner radius 162 of the occupancy area 150 of the transmitting coil 122.

The sectional view of the 4 shows the exemplary embodiment of a proximity sensor 100 according to the previous figures, with the housing 114 and many other details not being shown. The receiving coil arrangement 130 is arranged on the first side 190 of the carrier plate 102, the detection side 108 of the proximity sensor 100, and the transmitting coil arrangement 120 is attached on the second side. The turns 112 of the coils cut transversely to the longitudinal axis are shown in simplified form as circles. The real cross-sectional geometry can be different and, for example, have a square, rectangular or trapezoidal cut surface. The base surface is regularly the same as or larger than the opposite head surface, which is removed from the support plate. Furthermore, it is advantageous if the height is less than or equal to the width of the foot surface.

In the example shown, the sectional surface of the turns resembles a trapezoid with rounded corners, with the side of the trapezoid that rests on the support plate 102 forming the foot surface and being wider than the width of the opposite head surface. The head surface can still be slightly convexly curved be. The direction of current flow is symbolized by the cross inside the circle or the absence of the cross inside the circle. The cross represents a direction of current flow that leads into the representation plane and the missing cross represents the direction of current flow that exits the representation plane.

Overall, the advantages and aspects mentioned for the device or segment should apply identically or in an analogous manner to the method and vice versa. Starting from the coil axis 110, around which all coils are arranged concentrically, the direction of the current flow in one coil changes to the radially subsequent coil. Furthermore, the partial overlap of the radially outermost turns 112 of the transmission coil 112 with the radially first turn 112 of the compensation reception coil 134 is shown and the partial overlap of the radially outer turn 112 of the compensation reception coil 134 with the opposite turn 112 of the compensation transmission coil 124.

In the 5 is one for 4 alternative embodiment shown. In this embodiment, all coils that do not have to be arranged on the opposite side due to overlapping of occupancy areas are arranged on a common side. This common, one side can, as in the 5 be the second side 192 of the carrier plate 102, which faces the interior 194 of the proximity sensor 100. In an alternative embodiment it is the other way around.

In the exemplary embodiment 5 the receiving coil 132 is arranged on the second side 192, where the transmitting coil arrangement 120 is also placed. The receiving coil 132 is arranged in the core surface 184 of the transmitting coil 122.

The particular advantage of this solution is that a smaller amount of potting material 312 is required if one side 192 is more densely covered with turns 112 and the side 190 opposite the coil, here the compensation receiving coil 134, can be cast individually.

Like in the 6 shown in the right-hand part of image II, the circuit 116 is such that the transmitter coil 122 together with a capacitor 204 form an LC resonator, which are connected in series with an amplifier 206 via line 314 to form an LC oscillator and generate an alternating field.

In the idle state, a small current is induced in the receiving coil 132 by the transmitting coil 122, so that the amplifier 206 sends a very low value to a downstream low-pass filter and/or evaluation unit (not shown). The output signal of the low-pass filter is amplified and evaluated via the amplifier 206. If a particularly metallic object 302 (target) is introduced within the switching distance 308 to the proximity sensor 100, a disturbance occurs in the alternating field, which is constantly generated in the above-mentioned manner by the transmitter coil 122 or the LC oscillator. The disturbance changes the number of field lines penetrating the receiving coil 132, with the alternating field of the compensation transmitting coil 124 and thus also the compensation receiving coil 134 not being changed or only being changed insignificantly. The resulting change in magnetic flux through the receiving coil 132 causes the current induced in the receiving coil 132 to change significantly. This results in an amplified output and/or switching signal.

Due to the sole detection of the stray field of the transmitting coil by the compensation receiving coil, the change in the reception voltage in the compensation receiving coil caused by the target is only very small and almost approaches zero. On the other hand, the changes in the reception voltages in the reception coil caused by the target are very large. As a result, the entire coil reacts very sensitively to the penetrating target.

Connecting the transmitter coil as an LC oscillator with a capacitor ensures a further increase in sensitivity through increasing subsequent effects. These consist in the fact that the introduction of the target ensures an increase in the reception voltage, which in turn increases the amplitude of the transmitter coil, which subsequently results in an increase in the reception voltage.

In an alternative embodiment of the circuit 116 in the left partial image I, the circuit 116 is connected to a voltage source 200, in which a generator 202 is provided, which is connected via the line 196 to the transmitter coil 122 and excites it in a defined amplitude. The generator 202 may be an alternator. Here, the voltage amplitude present at the receiving coil 132 is evaluated using a voltmeter, not shown. The basic signal response of the receiving coil 132 takes place in an analog manner.

Here, all aspects and advantages of the method should apply identically or in an analogous manner to the device and vice versa.

Reference symbol list

100

Proximity sensor

102

carrier plate (circuit board)

106

Coil axis

108

Entry page

110

Coil axis

112

Winding of a coil

114

Housing

116

Interconnection unit

118

supply line

120

Transmit coil arrangement

122

transmitter coil

124

Compensating transmitter coil

126

Connection panel, first

128

Connection panel, second

130

Receiving coil arrangement

132

Receiving coil

134

Compensation receiving coil

136

Connection panel, first

138

Connection panel, second

140

Turnaround area, first

142

Turning area, second

146

Distance

148

Distance

150

Occupancy area

152

Occupancy area

154

Occupancy area

156

Occupancy area

158

Open space

160

Outer radius

162

Inside radius

164

Outer radius

166

Inside radius

168

Outer radius

170

Inside radius

172

Outer radius

174

Inside radius

176

Outer radius

178

Width

180

Width

182

Width

184

core area

186

core area

190

Page, first

192

pages, second

194

inner space

196

Line

198

Line

200

voltage source

202

generator

204

capacitor

206

amplifier

208

radius

210

Field lines

212

Field lines

214

group of coils'

216

Group of turns

300

Carrier)

302

object

304

Main detection room

306

scatter space

308

Switching distance

310

Object width

312

Potting material

314

Line

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 4429314 B4 [0002]
• DE 102006053023 A1 [0003]

Claims (12)

Inductive proximity sensor (100) with a transmitter coil arrangement (120) that generates an alternating magnetic field, which has the following: - a coil axis (110) - a carrier plate (102) with a first side (190) and a second side (192), - a transmitter coil (122/transmitting coil) with a compensation coil (124/compensating transmitting coil) surrounding it coaxially, - a receiving coil arrangement (130 (receiving coil arrangement) with a receiving coil (132), wherein the transmitting coil (122) and the compensating transmitting coil (124) can be fed with alternating currents of opposite phases , wherein the transmission coil (120) is connected in series and in opposite directions to the compensation transmission coil (124) and the transmission coil (122) and compensation transmission coil (124) can be excited by a common AC voltage generator (104) and / or can be excited by natural oscillation, so that the magnetic field generated by the transmitting coil (122) is greater than the magnetic field generated by the compensating transmitting coil (124), and wherein the transmitting coil (122) is arranged on the carrier plate (102), characterized in that the receiving coil arrangement (130) is a compensation receiving coil (134), wherein the receiving coil (132) and the compensation receiving coil (134) are connected in series, and wherein each coil has at least one connection field (126, 128, 136, 138) to which it is conductively connected. Proximity sensor Claim 1 , characterized in that the ratio of the number of turns (112) of the receiving coil (122) to the number of turns of the compensation receiving coil (132) is in the range from 0.5 to 1.6, in particular in the range from 0.8 to 1.2 lies. Proximity sensor Claim 1 or 2 , characterized in that the compensation receiving coil (134) has at least a first turning area (140), in which a change of direction takes place at least in a partial number of the turns (102) of the compensation receiving coil (134), in particular the compensation receiving coil (134) has a first turning area ( 140) and a second turning area (142). Proximity sensor Claim 3 , characterized in that the compensation receiving coil (134) is electrically conductively connected to a connection panel (138) at one end of the compensation receiving coil (134) and the connection panel (138) is arranged in one of the turning areas (140, 142), in particular in the middle the turning area (140). Proximity sensor Claim 3 or 4 , characterized in that the turn spacing of the first group of turns of the compensation receiving coil (134) running in the first direction (clockwise) corresponds to the turn spacing of a second group of turns of the compensation receiving coil (134) running in the second, opposite direction run, in particular the winding spacing of the adjacent windings of the first group and the second group is the same or substantially the same as the winding spacing within the respective groups. Proximity sensor according to one of the preceding claims, characterized in that the transmitting coil (122), the compensating transmitting coil (124), the receiving coil (132) and the compensating receiving coil (134) each have an occupancy area (150 ... 156) on the carrier plate (102). occupy, whereby an open space (158) with a width (178) is arranged between - the transmission coil (122) and the compensation transmission coil (124) and - the reception coil (132) and the compensation reception coil (134). Proximity sensor Claim 6 , characterized in that the occupancy area (150) of the transmitting coil (132) at least partially covers the open area (158) of the receiving coil arrangement (130), in particular is arranged completely covering the area of the open area (158) of the receiving coil arrangement (130). Proximity sensor according to one of the preceding claims, characterized in that - a width (180) of a first overlap of the compensation transmitting coil (124) with the compensation receiving coil (134), - a width (182) of a second overlap of the transmitting coil (122) with the Compensation receiving coil (134) and/or - There is a width of a third overlap between the transmitting coil (122) and the receiving coil (132), which is not greater than the width of two turns (112), in particular not greater than the width of one turn (112) and ideally zero is. Proximity sensor Claim 7 or 8th , characterized in that - a width (180) of a first overlap between the compensation transmitting coil (124) and the compensation receiving coil (134) is less than 0.75 times, in particular less than 0.5 times the winding width, - a Width (182) of a second overlap of the transmitting coil (122) with the compensation receiving coil (134) is less than 2 times, in particular less than 1.5 times, a turn width, and / or - a width of a third overlap of the Transmitting coil (122) with the receiving coil (132) is given, which is not larger than the width of 0.5 times the winding width, in particular zero, ideally an uncovered area with a width of at least 0.15 times a winding width and /or an occupancy/floor area. Proximity sensor according to one of the Claims 6 until 9 , characterized in that the transmitting coil arrangement (120) and the receiving coil arrangement (130) are arranged on a support plate (102), with at least one connection field (126, 128) of the transmitting coil (122) and / or the compensation transmitting coil (124) with at least one Partial area lies in the area of the occupancy area (152, 156) of the compensation receiving coil (134), in particular - a connection field (128) of the compensation transmitting coil (124) with at least one partial area lies in the occupancy area (156) of the compensation receiving coil (124) and a connection field (126 ) of the transmitting coil (122) lies with at least one partial area in the occupancy area (154) of the receiving coil (132). Proximity sensor according to one of the preceding claims, characterized in that - the ratio of the base width of the turns (102) of the transmitting coil (122) to the base width of the turns (102) of the receiving coil (132) is in the range from 0.15 to 1 and/or - the base width of the transmitting coil (122) is in the range of 0.2mm to 0.6mm and the base width of the receiving coil (132) is in the range of 0.1mm to 0.2mm. Method for detecting an object, in particular a metallic object, characterized in that an inductive proximity sensor (100) according to one of the preceding claims is used.

Images