Miniaturized inductive proximity sensor and method for detecting a detection body

Abstract

The invention relates to an inductive proximity sensor, comprising two receiving coils and one transmitting coil, which are each composed of at least two individual coils arranged in a stack parallel to one another and axially offset as a group on a carrier circuit board along a common sensor axis, wherein the transmitting coil is arranged between the two receiving coils, and wherein the carrier circuit board of the individual coils has a diameter of less than or equal to 10 mm. Here, the turns of the receiving coils and / or the transmitting coil have a cross-sectional geometry, wherein the ratio of the height to the foot width is in the range from 0.2 to 0.3, ideally between 0.23 and 0.27. The invention also comprises a detection method.

Description

Technical Field

[0001] This invention relates to an inductive proximity sensor and a detection method using the inductive proximity sensor. Background Technology

[0002] Inductive proximity sensors are known in the prior art. For example, DE102006053023A1 illustrates such a device, which proposes a planar transmitting coil arrangement having a transmitting coil that generates an alternating magnetic field. Furthermore, DE102006053023A1 suggests that the coil turns are printed on a carrier circuit board. Compensation of the transmitting coil's magnetic field lines occurs in the surrounding region through a common compensation coil and the external field and its field lines generated therefrom, thereby making the overall magnetic flux in the surrounding region zero or substantially zero. According to DE102006053023A1, a receiving coil is arranged between the transmitting coil and the compensation transmitting coil.

[0003] It has been confirmed that such coils can only be miniaturized to a very limited extent because interference effects such as line paths and adjacent contact points become excessive. Summary of the Invention

[0004] The objective of this invention is to propose an improved structural form for very small inductive proximity sensors that avoids the aforementioned drawbacks.

[0005] Therefore, the task is solved by an inductive proximity sensor for detecting a target object, comprising two receiving coils and one transmitting coil, each consisting of a group of at least two individual coils on a carrier circuit board. These individual coils are oriented parallel to each other and arranged as a stack along a common sensor axis, axially offset from each other. The transmitting coil is arranged between the two receiving coils, and the carrier circuit board of each individual coil has a diameter of less than or equal to 10 mm. Here, the coil turns of the receiving and / or transmitting coils have a cross-sectional geometry in which the ratio of height to foot width is in the range of 0.2 to 0.3, ideally between 0.23 and 0.27.

[0006] The coil assembly is excited into an oscillating alternating field by an oscillator and / or generator, especially by applying wiring in such a way that a self-excited alternating field oscillating at the resonant frequency is formed.

[0007] Advantageously, the height of the coil does not exceed 0.05 mm, and in particular, its maximum is 0.04 mm.

[0008] In existing coil systems, printed wire turns typically have a lead width of approximately 0.14 mm and a height of 0.014 mm above the carrier circuit board. It has been proven advantageous that, instead of linearly reducing the cross-section from those known in the prior art, a proportionally larger height is set. This avoids excessively high ohmic resistance in the corresponding coil, and narrower wire turns are possible.

[0009] Below, the terms “single coil” and “carrier circuit board” (a coil of wire mounted therewith a single coil) are used synonymously unless otherwise explicitly stated.

[0010] An improved embodiment specifies that the number of turns of at least one individual coil in the receiving coil is equal to or greater than 3, ideally 4 or 5, and in particular, the number of turns of all individual coils in the receiving coil is equal to or greater than 3, ideally 4 or 5. Unsurprisingly, it has proven optimal to construct sufficient inductance within a very limited footprint. Furthermore, another improved embodiment exists where the number of turns of at least one individual coil in the transmitting coil is equal to or greater than 3, ideally 3 or 4, and in particular, the number of turns of all individual coils in the receiving coil is equal to or greater than 3, ideally 3 or 4.

[0011] Here, the number of turns should not be understood as an even number of absolute 360° cycles, but rather as the number of turns X refers to X times the 360° cycle plus the 360° component. In other words, for example, the number of turns "4" also means an absolute number of turns / cycles of 4.25 or 4.5, but no longer means a number of turns / cycles of "5".

[0012] Advantageously, the stack consisting of individual coils and carrier circuit boards is arranged symmetrically with respect to a central plane of symmetry, which is vertically aligned with the sensor axis. The central individual coil of the transmitting coil can be located within this plane of symmetry. Here, the plane of symmetry of the mechanical structure can be arranged slightly differently with respect to the axial position from a parallel, electrically symmetrical plane of symmetry, which can also be composed of individual coils. This difference can be compensated for by adjusting the voltage difference using parallel-connected, particularly adjustable, resistors.

[0013] Advantageously, the wiring also includes or is connected to a measurement and regulation circuit by means of which the resistance relative to ground can be coupled via at least one single coil, in particular a single coil attached to or opposite to the end plate, to compensate for, in particular, phase shift.

[0014] Advantageously, the measuring and regulating circuit includes a voltage divider. In this way, manufacturing tolerances and material effects, especially in the conductor lines and coils, can be compensated for to ensure zero error in the induced voltage in the receiving coil during specified operation. Combining a single coil at the end of the receiving coil, opposite the end plate, has the significant advantage of having little or no effect on the magnetic field through a short conduction path extending primarily strictly parallel to the stack axis.

[0015] Here, a particularly good adjustable and controllable implementation is that the transmitting coil has a number of n individual coils and the two receiving coils together have a number of at least n+1 individual coils.

[0016] Here, the term "plane" should not be defined mathematically as a simple two-dimensional form, but can also refer to a very flat, theoretical space or corridor that surrounds and / or accommodates the corresponding elements.

[0017] To further reduce space, it is advantageous that at least one carrier circuit board is constructed as a dual-carrier circuit board, having a single coil or coil turn on each of its two surface sides. Advantageously, the at least one carrier circuit board constructed as a dual-carrier circuit board has a single coil of a receiving coil on one side and a single coil of a transmitting coil on the other side.

[0018] A further improved embodiment specifies that a headplate is provided, which serves as an interface with connection pads, in particular exactly four connection pads, for conductive connections to wiring including an oscillator and / or generator, and the headplate does not have a coil (single). In a further improved embodiment, the headplate may have additional connection pads or contact pads for one or more measurement points and / or measurement and adjustment loops, in which at least one single coil, in particular a single coil adjacent to the headplate, is connected.

[0019] As the negative impact of all metal surfaces and conductors (lines) on magnetic fields increases significantly with the continued miniaturization of inductive sensors and individual coils, ideally, there should be no aggregation of conductors or conductive paths on any of the individual coils other than direct connections to adjacent or related individual coils. Only the headplate has metal connection pads for wiring connections, including oscillators, and multiple conductors or conductor lines for different (individual) coils appear only on the headplate. Here, "multiple" means not only two adjacent or related individual coils are conductively connected.

[0020] Therefore, no transverse conductors for continued transmission or connection are provided on each individual coil, especially on the outer individual coil of the receiving coil. In particular, the connection between two individual coils is always achieved through connecting conductors or through contacts guided parallel to the coil axis. For this purpose, the carrier circuit board advantageously has multiple holes or through contacts arranged aligned along the coil axis and, in particular, forming a channel or well for a conductive path extending across multiple circuit boards. Electrical conductors are guided in a number of aligned holes or wells, or the holes or wells are filled with conductive material. Advantageously, at least four of the wells extend into a headplate configured as an interface and terminate directly at the connection pad or on the back side, that is, on the side away from the board stack, via conductors to one of the connection pads.

[0021] On the carrier circuit board, on one side where the (individual) coils to be connected are arranged, the hole opening serves as a soldering point and connection point, or is configured to do so. The individual coils are connected in a known manner to conductors guided in holes or wells parallel to the stack axis via wire lines.

[0022] Here, the headplate advantageously has exactly four connection pads, with every two connection pads used for the inlet and outlet of the series-connected receiving coil and every two connection pads used for the inlet and outlet of the transmitting coil. As explained in detail above, additional connection pads can be provided for measurement points and / or at least one measurement and adjustment loop.

[0023] A particularly advantageous approach in terms of energy is to form a self-excited system. For this purpose, a particularly advantageous implementation specifies the use of only an oscillator without a (active) generator. Here, an LC resonator is formed by a transmitting coil acting as an inductor and a parallel capacitor. This LC resonator is connected in series with an amplifier and a sensor coil or associated compensation coil to form an LC oscillator, wherein an alternating field can be generated. This alternating field is, in particular, a self-excited alternating field oscillating at the resonant frequency.

[0024] The present invention also includes a method for detecting a detection object by means of an inductive proximity sensor having an outer diameter equal to or less than 10 mm and constructed according to one of the aforementioned implementation variations. Attached Figure Description

[0025] Other details and advantages of the invention will now be explained in detail with the aid of embodiments shown in the accompanying drawings.

[0026] The attached diagram shows:

[0027] Figure 1 This shows a proximity sensor with a single coil and its associated wiring;

[0028] Figure 2 A single carrier circuit board is shown;

[0029] Figure 3 A cross-sectional view of the coil stack is shown;

[0030] Figure 4 A single coil of coil stacked coils is shown as a top view; and

[0031] Figure 5a and 5b A top view of the headboard is shown. Detailed Implementation

[0032] Figure 1 A schematic structure of a proximity sensor 1 is shown, which consists of three sets of individual coils. These are two receiving coils 2, with a transmitting coil 3 arranged between them. The inductive proximity sensor 1 is used to detect a metallic object 50 and includes a housing 11, which typically has a cylindrical or quadrangular base. (See also...) Figure 1 As can be seen, proximity sensor 1 is connected to wiring 21 and generates a self-excited alternating field through transmitting coil 3 via oscillator 9. The transmitting coil, acting as an inductor, together with capacitor 17 forms an LC resonant circuit of oscillator 9. Typical oscillation signals are in the range of 3 to 10 MHz. Two anti-winding receiving coils 2 are arranged in a direct differential circuit. The differential AC voltage generated by the two receiving coils 2 is provided to the input of amplifier 9 and detected by voltage measuring device 8. The receiving coils 2 are constructed such that the differential AC voltage UD becomes zero when the trigger approaches the desired response distance, by means of their spatial positions on the two mutually parallel planes and their corresponding number of turns, that the change in oscillation state is detected and converted into a switching signal in a manner not shown. Such circuits are generally known to those skilled in the art, for example, by DE4429314B4 or DE4031252C1. Such circuits are designed for different types of operation, i.e., for detecting different objects 50 depending on the material (metallic, non-metallic), and are known to those skilled in the art, for example, by the aforementioned DE4429314B4.

[0033] In this example, a measurement and adjustment unit 51 is provided, which includes a voltage divider and, in a manner not further shown, integrates a single coil of the forward receiving coil 2 into the measurement and adjustment circuit 52, such that the phase shift between the two reverse-current receiving coils can be compensated. This is done by adjusting the corresponding resistor, particularly an ohmic resistor.

[0034] The characteristic now is that each coil 2.1, 3.1 has a cross-sectional geometry in which the ratio of the height H of each coil to the foot width B is 0.25. In this embodiment, the foot width is 0.14 mm and the height is 0.035 mm. This structure of the conductor circuit is applied using a printing method. The carrier circuit board 4 is made of a non-conductive material such as PCB material. In the example shown, the diameter D of the carrier circuit board is 8 mm, and its height X is 0.068 mm.

[0035] As shown in the detailed view below, the innermost coils 2.1, 3.1 are connected to the internal conductor circuit 13 disposed on the surface and in the hole 22, thus forming a solder point and connection point 15 on the surface. The outer ends of the coils 2.1, 3.1, in the example shown, are similarly connected to the solder point and connection point 15 and the conductor circuit, which continues in an upwardly guiding hole or through contact (not shown) for connection to a single coil (not shown) located thereon. It should be understood that spatial descriptions such as "above it" or "below it" should not be construed as restrictive and should be understood similarly, depending on the overall orientation of the proximity sensor. The outer and inner conductor circuits refer to their radial positions relative to the respective single coil or its coils.

[0036] exist Figure 2 The top view shows a single carrier circuit board 4 for a single coil 2.1 of the receiving coil 2. The seven holes 22 or through-contacts in the carrier circuit board 4 can be provided in all carrier circuit boards 4 of the sensor stack 20, with only one carrier circuit board 4 used for power supply, such that the carrier circuit board is configured on its surface as solder points and connection points 15 and electrically connected to the external conductor circuit 14 and the coil turns of the single coil 2.1. The other six holes 22 serve as conductor circuits guided parallel to the stack axis 20 for connecting other single coils or remaining inactive. Opposite flattened portions 4.2 are used for positional stabilization and as insertion aids, where alternatively, other geometries such as slots, edges, or guide fingers can be provided, which engage in a form-locking manner with the housing or carrier and guide elements (not shown).

[0037] exist Figure 3The sensor stack 20, shown in cross-section, avoids metal surfaces and components on the carrier circuit board 4 and the surface of a single coil configured as a dual carrier circuit board 4.1. Layers L1 to L3 are part of or constitute the first receiving coil 2, and layers L9 to L11 constitute the second receiving coil 2. A transmitting coil 3, comprising layers L4 to L8, is arranged between them. These layers are defined by a single coil. A dielectric is provided between the single coils, which is either the carrier circuit board 4 carrying the single coil or a dual carrier circuit board 4 with single coils on both sides. Furthermore, to create a strictly symmetrical structure, a dielectric is provided as a simple spacer element 16 on the surface of which no single coil is applied. Layer 12 does not have coils but is essentially composed of connecting pads 7, solder points and connection points 15, and laterally extending wire lines for connecting wiring 21 (not shown) and / or measurement and adjustment paths 52 (…). Figure 1 The individual coils 2.1 and 3.1 are respectively integrated with the coiled clips. In the present case, the individual coils of layer 6 form an electrically symmetrical plane 30, wherein the structural mechanical symmetrical plane 30, indicated by the dashed line, is formed by the intermediate plane between layers L1 and L12 and is arranged between layers L6 and L7. End plates 18 are respectively provided at both ends of the stack 20.

[0038] In this example, the axis of symmetry of the plate's structural machinery is detached by the mechanical construction and located at a height of 0.822 mm on the plate or layer stack. For the functionality and adjustability of the coil system to the induced voltage difference of 0 mV at the desired switching point, ideally the number of positions and the total number of turns of the receiving coils L2 and L3 must be the same or nearly the same, and furthermore, the distance between the transmitting coil 3 and the two receiving coils 2 must be the same or nearly the same.

[0039] A certain difference can be compensated for by adjusting the voltage difference using a parallel resistor, ideally constructed as an adjustable resistor or integrated into the adjustment path. In this way, the proximity sensor can have a defined initial state.

[0040] The portion or individual coils of the transmitting coil 3 arranged in layer L6 form an “electrified” plane of symmetry.

[0041] As in Figure 3 In China and especially Figure 4As can be clearly seen, on the carrier circuit board 4, there are no transverse wire connections or couplings to the respective individual coils 2.1, 3.1, other than direct wire connections. The external wire lines 14 shown on the left, guided in holes 22 towards the stack axis 20, are used for connection to external supplies and are guided on the back side of the headplate 5 through the dielectric. Only there are they connected to the connection pads 7, which is typically achieved by soldering.

[0042] Similarly, the connection from the headplate 5 to the individual coil is implemented on layer L11.

[0043] Furthermore, in the example shown, the carrier circuit board 4.1 for layers L3 and L4 is configured with dual functions, such that a single coil of layer L3 functionally belongs to the first receiving coil 2 and a single coil below layer L4 functionally belongs to the transmitting coil 3. Continuous holes 22 or through-contacts connect layers 10 and 11 and are wiring connections used solely for measurement purposes and to make measurement points (not shown) accessible.

[0044] Figure 4 The individual coil and its conductive connection 14.1 between the headplate 5 and its connecting pads 7.1 are shown in detail. The flattened portions 4.2 on both sides are used for positioning and serve as insertion aids. The individual coil shown in top view is associated with layers L1 to L11 or layer L12 of the headplate 5, as shown in... Figure 3 As shown in the diagram. External conductor 14.1 extends from connection pad 7.1 to the single coil of layer L1 and then through conductors 13.1, 14.2 and the single coils of layers L2, L3 to the single coil of layer L9, and after passing through the single coils of layers L10, L11, and through conductors 13.3, 14.5, and 13.4 back to the solder and connection points, which are connected to the connection pad 7.2 of the headboard 5. The transmitting coil 3 utilizes a single coil on layer L4 to connect to the connection pad 7.3 of the headboard 5 via external conductor 14.3, and after simulatingly passing through the single coil and conductor, returns from the single coil / coil of layer L8 to the connection pad 7 via external conductor 14.4. For space reasons, the solder and connection points on the headboard 5 are partially located outside the actual connection pads, as can be seen with respect to connection pads 7.2, 7.4.

[0045] In one embodiment (not shown), measurement and adjustment paths are provided, such as in... Figure 1As outlined herein, these individual coils on the lowest layer L11 are integrated into the measurement and adjustment path. Furthermore, at least one measurement point is arranged, for example, in conductor line 13.2 or external conductor line 14.2, which interacts with or is surrounded by the measurement and adjustment path. Thus, tolerances affecting voltage differences and phases, for example, in the structure, conductor line, or coils, can be compensated for.

[0046] The receiving coil 2 on the left and the transmitting coil 3 in the middle are currently flowing in the same direction, that is, counterclockwise in the direction of the current indicated by the arrow. The receiving coil 2 on the right is flowing in the opposite direction, which is clockwise in the example shown. Through oscillation, the direction of the current naturally changes regularly.

[0047] exist Figure 5a Two headplates 5 are shown in 5a and 5b). Figure 5a The head plate has two flattened portions 5.1, similar to the flattened portion 4.2 of the single plate 4, to ensure a defined orientation, guidance, and position within the housing 11. Here, the larger diameter D1 = 8 mm and the width D2 = 7.5 mm in the flattened area. Figure 5b The smaller of the two head plates 5 has a diameter D1 of 5.5 mm and a width of 5.0 mm at the flattened position D2.

[0048] In the sensor dimensions, the switching distance is approximately 4 mm when the diameter D1 of the carrier circuit board is 8 mm, approximately 2 mm when the diameter D1 is 5 mm, and approximately 1 mm when the diameter D1 is 3 mm.

[0049] In one embodiment (not shown), an additional generator is provided that excites the oscillator 9, which consists of the transmitting coil 3 and the capacitor 17, at its resonant frequency. Alternatively, when the capacitor 17 is removed, the additional generator can excite the transmitting coil 3 at any frequency.

[0050] List of reference numerals

[0051] 1. Proximity switch

[0052] 2. Receiving coil

[0053] 2.1 Single coil

[0054] 3. Transmitting coil

[0055] 3.1 Single coil

[0056] 4. Carrier circuit board

[0057] 4.1 Dual-carrier circuit board

[0058] 4.2 Flattened Section

[0059] 5 headboards

[0060] 5.1 Flattening Section

[0061] 6. Voltage measuring instrument

[0062] 7 Connecting pads

[0063] 8. Voltage measuring instrument

[0064] 9. Oscillator

[0065] 10 Amplifier

[0066] 11. Shell

[0067] 12 Measurement Points

[0068] 13 holes

[0069] 14. Conductor circuits (i.e., 14.1...14.n)

[0070] 15 Welding points and connection points

[0071] 15.1 Conductor Circuits

[0072] 16. Spacer elements, dielectrics

[0073] 17 Capacitors

[0074] 18 end plates

[0075] 20 Stacked Axis Lines

[0076] 21 Wiring

[0077] 22 holes

[0078] 30 symmetrical planes, mechanical

[0079] 31. Plane of symmetry, electric

[0080] 50 objects

[0081] 51 Measurement and Control Unit

[0082] 52 Measurement and Adjustment Path

[0083] B width

[0084] D is the diameter, i.e., D1 and D2.

[0085] H height

[0086] X Height

Claims

1. An inductive proximity sensor (1) for detecting an object (50), the inductive proximity sensor comprising two receiving coils (2) and one transmitting coil (3), the two receiving coils (2) and the one transmitting coil (3) each being composed of a group of at least two individual coils on a carrier circuit board (4), the carrier circuit boards (4) being oriented parallel to each other and arranged in a stacked manner axially offset along a common sensor axis (20), wherein, The transmitting coil (3) is arranged between the two receiving coils (2), and wherein the carrier circuit board (4) has a diameter (D) less than or equal to 10 mm, characterized in that, The coil turns (2.1, 3.1) of the receiving coil (2) and / or transmitting coil (3) have a cross-sectional geometry in which the ratio of height (H) to foot width (B) is in the range of 0.2 to 0.3; The inductive proximity sensor (1) is provided with a head plate (5), which serves as an interface with connecting pads (7) for wiring connection including a generator and / or an oscillator, and the head plate (5) does not have a coil.

2. The inductive proximity sensor (1) according to claim 1, characterized in that, The height (H) shall not exceed 0.05 mm.

3. The inductive proximity sensor (1) according to claim 1 or 2, characterized in that, The number of turns of at least one individual coil in the receiving coil (2) is equal to or greater than 3.

4. The inductive proximity sensor (1) according to claim 1 or 2, characterized in that, The number of turns of at least one individual coil in the transmitting coil (3) is equal to or greater than 3.

5. The inductive proximity sensor (1) according to claim 1 or 2, characterized in that, The stack consisting of a single coil and a carrier circuit board (4) is arranged symmetrically with respect to a central symmetry plane (30) that is vertically arranged relative to the sensor axis (20), wherein the central single coil of the transmitting coil (3) can be located in the symmetry plane (30).

6. The inductive proximity sensor (1) according to claim 1 or 2, characterized in that, The transmitting coil (3) has a number of n individual coils and the two receiving coils (2) together have a number of at least n+1 individual coils.

7. The inductive proximity sensor (1) according to claim 1 or 2, characterized in that, At least one carrier circuit board (4) is configured as a dual carrier circuit board having a single coil on each side.

8. The inductive proximity sensor (1) according to claim 7, characterized in that, At least one carrier circuit board (4) configured as a dual carrier circuit board has a single coil of receiving coil (2) on one side and a single coil of transmitting coil (3) on the other side.

9. The inductive proximity sensor (1) according to claim 1, characterized in that, The headboard (5) has exactly four connection pads (7), two of which are used for receiving coil (2) and the other two are used for transmitting coil (3).

10. The inductive proximity sensor (1) according to claim 1 or 2, characterized in that, Instead of providing transverse wire lines (14) for transfer or connection on each individual coil, only one wire line (14) is provided to the head plate (5), which serves as an interface for connection with the wiring (21).

11. A method for detecting an object (50) using an inductive proximity sensor (1), characterized in that, The inductive proximity sensor (1) has an outer diameter (D1) equal to or less than 10 mm, and the inductive proximity sensor (1) is constructed according to any one of claims 1-10.

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