SCALE ELEMENT FOR AN INDUCTIVE ANGLE MEASURING DEVICE

Abstract

The invention relates to a scale element (2) comprising a substrate (2.1) on which a division track (2.2) is arranged. The division track (2.2) is formed along a circumferential direction (x) from a periodic sequence of alternatingly arranged electrically conductive division areas (2.21) and non-conductive division areas (2.22), wherein the electrically conductive division areas (2.21) are each formed from a layer of electrically conductive material. At least one bore (2.11) is arranged in the substrate (2.1). The electrically conductive division areas (2.21) each have an opening (2.211), wherein the electrically conductive material surrounds the opening (2.211). The bore (2.11) extends through the opening (2.211) in at least one of the electrically conductive division areas (2.21) in the substrate (2.1). In addition, two electrically conductive division areas adjacent in the circumferential direction (x) (2.21) designed such that the angular distances (α, β, γ) between their conductive layers are of different sizes along the radial direction.

Description

AREA OF TECHNOLOGY

[0001] The invention relates to a scale element for an inductive angle measuring device according to claim 1 for determining an angular position of the scale element relative to a scanning element.

[0002] Inductive angle measuring devices are used, for example, to determine the angular position of machine parts that can rotate relative to each other. In inductive angle measuring devices, excitation tracks and receiver tracks, often in the form of conductive traces, are typically mounted on a common, usually multilayer, printed circuit board (PCB) that is rigidly connected to, for example, a stator of the angle measuring device. Opposite this PCB is a scale element with graduations, which is rigidly connected to a moving part of the angle measuring device. When a time-varying electrical excitation current is applied to the excitation tracks, position-dependent signals are generated in the receiver tracks during the relative movement between the scale element and the sensing element. These signals are then processed by evaluation electronics. STATE OF THE ART

[0003] From EP 4 421 454 A1 of the applicant, a scale element for an inductive angle measuring device is known. The scale element described therein comprises two graduation tracks, each consisting of a periodic sequence of alternating electrically conductive and non-conductive graduation areas. The scale element is fastened by means of screws in mounting holes, all of which are arranged within electrically conductive graduation structures. SUMMARY OF THE INVENTION

[0004] The invention is based on the objective of creating a compact and cost-effectively manufactured scale element that offers flexible mounting options and is nevertheless usable for a comparatively accurate inductive angle measuring device.

[0005] This problem is solved according to the invention by the features of claim 1.

[0006] The scale element, suitable and intended for an inductive angle measuring device, comprises a substrate on which a graduation track is arranged. The graduation track is formed along a measuring direction by a periodic sequence of alternating electrically conductive and comparatively non-conductive graduation areas, wherein the electrically conductive graduation areas each consist of a layer of electrically conductive material. The layer or surface of electrically conductive material extends both circumferentially and radially. Furthermore, at least one bore is provided in the substrate, suitable for attaching the scale element to a machine part. At least one electrically conductive graduation area has an opening, the opening being enclosed by the electrically conductive material.Furthermore, at least one bore is arranged in the substrate through the opening in at least one of the electrically conductive partition areas. Two circumferentially adjacent electrically conductive partition areas are designed such that the angular distances between the conductive layers of the electrically conductive partition areas differ along the radial direction.

[0007] Accordingly, adjacent electrically conductive divisions at different distances from the axis exhibit different angular distances (in the circumferential direction). In other words, if one measures a first distance radially inward between two circumferentially opposite points on the respective contour of an electrically conductive division, a second distance at a radially offset point will be different from the first. Opposite points lie, in particular, on one and the same virtual circle whose center lies on the axis. The contours of the electrically conductive divisions or electrically conductive layers in question therefore do not run in a straight radial direction over their entire radial extent.Angular distances between two circumferentially adjacent electrically conductive division areas refer to a respective central angle around the axis and are given here in degrees.

[0008] In particular, a first distance exists between two circumferentially adjacent electrically conductive division areas, and a second distance exists radially offset from this. The first and second distances can be larger than a third distance located radially between the first and second distances.

[0009] The electrically conductive division areas are thus formed from a layer of electrically conductive material. The comparatively non-conductive division areas can be made of plastic (e.g., printed circuit board material). The scale element can preferably have a printed circuit board material made of plastic as its substrate. Alternatively, the substrate can be formed from a layered body comprising a relatively thick steel layer and a non-conductive layer (e.g., a plastic layer), with the steel layer located on the side of the scale element facing away from the division areas. The term "comparatively non-conductive" mentioned above therefore refers to the ratio of the electrical conductivities of the materials of the alternating division areas. This ratio can, in particular, be greater than 10 or greater than 50.The layer of electrically conductive material in the electrically conductive partition areas is advantageously greater than 12 µm or 0.012 mm. On the other hand, it is particularly advantageous for economic reasons if the layer is thinner than 1 mm, especially thinner than 0.5 mm, and preferably thinner than 0.1 mm.

[0010] In the following, the term "bore" refers to a hole that does not necessarily have to be round. In particular, the bore can also be square or elliptical and may have been produced, for example, by a punching or milling process.

[0011] In an angle measuring device, the scale element serves to determine an angular position relative to a scanning element. The scale element is rotatably arranged around an axis relative to the scanning element, so that the measuring direction is the circumferential direction with respect to the axis.

[0012] Advantageously, another bore is also arranged in the substrate in a non-conductive division area.

[0013] Advantageously, the dividing track has n electrically conductive dividing areas and m bores are arranged in the substrate, with n ≠ m. In particular, the scale element can be designed such that the relationship n < m holds.

[0014] In particular, n can be an odd number and m an even number.

[0015] In a further embodiment of the invention, at least one electrically conductive division area is circumferentially bounded by a convex contour. This means that circumferentially opposite electrically conductive division areas are bounded by a convex contour in their opposing sections. In particular, this contour can be circular and, especially, a segment of a circle. In contrast to electrically conductive division areas in conventional inductive scale elements, there is no continuous straight contour extending radially. As an alternative to the aforementioned circular contour, a polygonal contour can also be chosen, e.g., in the form of a half-hexagon. The contour can also be concave.

[0016] Advantageously, the division track is designed in a ring-shaped or circular shape, with the center point of the ring-shaped division track lying on the axis.

[0017] The scale element can be designed such that it has an opening in each of several electrically conductive divisions and / or at least one electrically conductive division has multiple openings. In particular, all electrically conductive divisions of the scale element can have multiple openings.

[0018] It is advantageous if all electrically conductive partition areas are geometrically identical.

[0019] In a further embodiment of the invention, at least some of the openings in the electrically conductive division areas are geometrically identical.

[0020] Advantageously, the division track extends along a division circle with its center point located, in particular, on the axis, wherein the openings are arranged such that they are each equidistant from the center point and are arranged equidistantly along the division circle.

[0021] Advantageously, the scale element comprises several electrically conductive graduation areas, each with holes. The holes are arranged so that they are equidistant from the center point and positioned along the graduation circle.

[0022] The distances between the openings or between the bores are given here in degrees and refer to a respective central angle around the axis or around the center of the division circle.

[0023] In a further embodiment of the invention, the scale element comprises at least one fastening element arranged in the bore. The fastening element can be arranged flush with or recessed from the electrically conductive graduation areas with respect to the axial direction and, in any case, must not project axially beyond the surface of the electrically conductive graduation areas. In the following, "axial direction" is understood to mean a direction oriented parallel to the axis.

[0024] In particular, the fastening element is made of electrically conductive material and can be designed as a screw. Alternatively, a rivet, a metal pin, a spring pin, or the like can serve as the fastening element. It can be advantageous if the scale element is additionally bonded to the machine part to which it is attached. The fastening element can, in particular, serve to create a positive fit, which is important for a functionally reliable arrangement. At the same time, the fastening element can serve to center the scale element. For example, a configuration is also possible in which centering lugs or centering edges are pressed into the bores and the scale element is additionally fixed with an adhesive bond.

[0025] Advantageously, the scale element comprises several fastening elements, wherein the scale element includes several of the electrically conductive division areas which have bores in which the fastening elements are arranged.

[0026] In a further embodiment of the invention, the graduation track n has electrically conductive graduation areas, and the scale element comprises p fastening elements arranged in the bores. The following condition applies: n ≠ p. In particular, the following can hold: n < p, where it may be advantageous if n is an odd number and p is an even number.

[0027] According to another aspect, the invention also includes an inductive angle measuring device with a scale element and a scanning element.

[0028] Advantageous embodiments of the invention can be found in the dependent claims.

[0029] Further details and advantages of the scanning element according to the invention will become apparent from the following description of an exemplary embodiment with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 a top view of one side of a scale element, Fig. 2 a perspective sectional view of the scale element, Fig. 3 a sectional view through a bore of the scale element, Fig. 4 a top view of one side of the scanning element. DESCRIPTION OF THE EXECUTION FORMS

[0030] The invention is described in connection with an angle measuring device which includes a scale element 2 ( Fig. 1, Fig. 2 and Fig. 3) and a scanning element 1 ( Fig. 4) has a feature that can be used to detect the angular position of the scale element 2. The scale element 2 is rotatably arranged about an axis A relative to the scanning element 1. Such an angle measuring device can be used, for example, in a drive system such as in a robot, where the scale element 2 is then connected to a drive shaft of a motor in a rotationally fixed manner.

[0031] The scanning element 1 according to the Fig. Component 4 serves to scan the scale element 2 and is designed as a printed circuit board (PCB) comprising several layers and electronic components. In the presented embodiment, the electronic components are mounted only on one side of the PCB, namely on the side facing away from the scale element 2, and therefore in the Fig. 4 not visible. Alternatively or additionally, both sides of the circuit board could be populated with electronic components.

[0032] To determine the angular information, the scanning element 1 has a first receiver track 1.1 and a second receiver track 1.2. Receiver tracks 1.1 and 1.2 each have a ring shape, with their center point M lying on axis A. Therefore, to a first approximation, receiver tracks 1.1 and 1.2 are arranged concentrically with respect to center point M.

[0033] In the presented embodiment, the first receiver track 1.1 comprises four receiver conductor tracks 1.11. The receiver conductor tracks 1.11 of the first receiver track 1.1 are arranged offset from each other in the circumferential direction x and have a spatially periodic course that is essentially sinusoidal or sinusoidal in design.

[0034] In the presented embodiment, the second receiver track 1.2 comprises eight receiver conductor tracks 1.21, which are arranged offset relative to each other in the circumferential direction x.

[0035] Furthermore, the scanning element 1 comprises a first excitation track 1.3 and a second excitation track 1.4. In the presented embodiment, the excitation tracks 1.3 and 1.4 comprise multiple excitation lines, but can also each be configured as a single excitation line. The first receiver track 1.1 extends radially within the first excitation track 1.3 and radially outside the second excitation track 1.4. The second excitation track 1.4 also extends radially outside the second receiver track 1.2. Both the excitation tracks 1.3 and 1.4 and the receiver tracks 1.1 and 1.2 extend along the circumferential direction x.

[0036] The receiver traces 1.11 of the first receiver track 1.1, as well as the receiver traces 1.21 of the second receiver track 1.2, are connected by vias in different layers of the printed circuit board, thus preventing unwanted short circuits at intersection points. Although, strictly speaking, each of the receiver traces 1.11, 1.21 consists of many conductor segments, each distributed across two layers and arranged in series, such a structure is referred to here collectively as a receiver trace 1.11, 1.21.

[0037] In the Fig. Figure 1 shows the scale element 2 in a top view, with the scale element 2 in the Fig. 1 compared to scanning element 1 of the Fig. Figure 4 is shown enlarged. Scale element 2 has a ring-shaped or circular shape. Scale element 2 comprises a substrate 2.1 ( Fig. 2), on which two partition tracks 2.2, 2.3 are arranged. In the illustrated embodiment, the substrate 2.1 is made of printed circuit board material comprising plastic, in particular epoxy resin. The partition tracks 2.2, 2.3 are annular and arranged concentrically with different radii about axis A on the substrate 2.1. The partition tracks 2.2, 2.3 comprise partition structures consisting of a periodic sequence of electrically conductive partition areas 2.21, 2.31 and non-conductive partition areas 2.22, 2.32 arranged alternately along the circumferential direction x, wherein the electrically conductive partition areas 2.21, 2.31 are each formed from a layer of electrically conductive material. The thickness of this layer is 18 µm. In the example shown, copper was applied to substrate 2.1 as the material for the electrically conductive division areas 2.21, 2.31. In the non-conductive division areas 2.In contrast, substrate 2.1 is not coated in sections 22 and 2.32. The arrangement with two graduation tracks 2.2 and 2.3 allows the angular position of the scale element 2 to be determined absolutely. The second (outer) graduation track 2.3 of the scale element 2 has a greater number of respective division areas 2.31 and 2.32 along the circumferential direction x, thus enabling a higher resolution for measuring the angular position.

[0038] The electrically conductive parting areas 2.21 of the first (inner) parting track 2.2 have openings 2.211, such that the layer of electrically conductive material is open at these locations, or rather, the substrate 2.1 is not coated in these areas. In the presented embodiment, the openings 2.211 each have a circular geometry. The openings 2.211 are arranged such that they are each equidistant from the center point M. In particular, the centers of gravity of the openings 2.211 are each equidistant from the center point M.

[0039] The electrically conductive partition areas 2.21 are designed or arranged such that each opening 2.211 is enclosed by the electrically conductive partition area 2.21, so that there are webs 2.212 made of electrically conductive material on both sides around the opening 2.211, and a closed contour of electrically conductive material exists around the opening 2.211. Two electrically conductive partition areas 2.21 adjacent in the circumferential direction x are designed such that the angular first, second, and third distances α, β, y between their conductive layers are of different sizes along the radial direction x. Thus, for example, the first angular distance α is defined at a first distance r1 to the axis A (radial distance), and the second angular distance β is defined at a second radial distance r2. The following relationship applies: r1≠r2 and α≠β.

[0040] In particular, the third distance y, which lies radially centered in the first division track 2.2 with a third radial distance r3, is smaller than the first distance α, which lies radially further inwards, and also smaller than the second distance β, which lies radially outwards relative to the third distance γ. Therefore, the first distance α and the second distance β are larger than the third distance γ, which lies radially between the first and second distances α and β. It can thus be concluded that the angular distances α, β, γ in the circumferential direction x are of different magnitudes depending on the radial position or radial distance r1, r2, r3.

[0041] In the presented embodiment, the electrically conductive division areas 2.21 each have a shape that is bounded in the circumferential direction x by a round contour, wherein the electrically conductive division areas 2.21 have a convex contour in these areas.

[0042] In the electrically conductive division areas 2.21, bores 2.11 are arranged in the substrate 2.1 through an opening 2.211. The bores 2.11 are thus arranged along the first (inner) division track 2.2 in the substrate 2.1. In the presented embodiment, four bores 2.11 are provided, each at the same distance from the center point M and arranged along the circumferential direction x (here at intervals of 90°). Three bores 2.11 are located within the electrically conductive division areas 2.21 and one bore 2.11 is located within a non-conductive division area 2.22.

[0043] In the presented embodiment, the first graduation track 2.2 has three electrically conductive graduation areas 2.21 (n = 3). The scale element 2 comprises four bores 2.11 in the substrate 2.1 for attaching the scale element to a machine part (m = 4). Therefore, the number n of electrically conductive graduation areas 2.21 differs from the number m of bores 2.11 (n ≠ m). In particular, the number n of electrically conductive graduation areas 2.21 is less than the number m of bores 2.11 in the substrate 2.1 (n < m). In the presented embodiment, the number n of electrically conductive graduation areas 2.21 is an odd number, and the number m of bores 2.11 is an even number.

[0044] In the Fig. 2 is a perspective section along a line E - E ( Fig. 1) shown by the scale element 2, where fastening elements 2.4, here screws, inserted into the bores 2.11 are also depicted. As described above, the graduation track 2.2 has a total of three electrically conductive graduation areas 2.21 (n = 3). In addition, the scale element 2 comprises four fastening elements 2.4 (p = 4). Therefore, the number n of electrically conductive graduation areas 2.21 differs from the number p of fastening elements 2.4 (n ≠ p). In particular, the number n of electrically conductive graduation areas 2.21 is less than the number p of fastening elements 2.4 (n < p). In the presented embodiment, the number n of electrically conductive graduation areas 2.21 is an odd number and the number p of bores 2.11 is an even number.

[0045] In the Fig. Figure 3 shows a detailed section through a part of the scale element 2 in the area of ​​the first division track 2.2, where in the Fig.3. The thickness of the layer of electrically conductive material in the electrically conductive division area 2.21 is exaggerated for illustrative purposes. The bore 2.11 is designed here as a stepped through-hole. In particular, the bore 2.11 has a conical section 2.111, which is produced, for example, by countersinking. The conical section 2.111 is set back by a dimension h with respect to the surface of the substrate 2.1 and in the axial direction. This allows a fastening element 2.4 to be arranged in the respective bore 2.11, which here is designed in particular as a countersunk screw, wherein the fastening element 2.4 is set back with respect to the surface of the substrate 2.1 and with respect to the surface of the respective electrically conductive division area 2.21. The fastening element 2.4 serves to attach the scale element 2 to a machine part and is made of steel and is therefore electrically conductive.

[0046] In the assembled state, the scanning element 1 and the scale element 2 are positioned opposite each other with an axial distance or air gap, such that a relative rotation between the scale element 2 and the scanning element 1 generates a signal in the receiver conductor tracks 1.11, 1.21, dependent on the respective angular position, through induction effects. A prerequisite for the generation of such signals is that the excitation tracks 1.3, 1.4 generate a time-varying electromagnetic excitation field in the region of the respective scanned division structures. In the illustrated embodiment, the excitation tracks 1.3, 1.4 are configured as several planar-parallel, current-carrying individual conductor tracks.

[0047] When the excitation tracks 1.3, 1.4 are energized, a tubular or cylindrical electromagnetic field forms around them. The field lines of the resulting electromagnetic field run around the excitation tracks 1.3, 1.4, with the direction of the field lines depending, in a known manner, on the current direction in the excitation tracks 1.3, 1.4. Eddy currents are induced in the electrically conductive division areas 2.21, 2.31, resulting in a field modulation that depends on the angular position. Accordingly, the relative angular position can be measured by the receiver tracks 1.1, 1.2.

[0048] The scanning element 1 comprises an electronic circuit with electronic components that are electrically interconnected. This electronic circuit can, for example, include an ASIC chip. The signals generated by the receiver tracks 1.1 and 1.2 are further processed by some of the electronic components that form an evaluation circuit. In particular, with the present configuration of the two division tracks 2.1 and 2.2 and the two receiver tracks 1.1 and 1.2, the evaluation ASIC can calculate an absolute position. The electronic circuit of scanning element 1 functions not only as an evaluation element but also as an excitation control element, under whose control the excitation current is generated, which then flows through the excitation tracks 1.3 and 1.4. Thus, the excitation tracks 1.3 and 1.4 are energized by one and the same excitation control element.

[0049] The first receiver track 1.1 is surrounded radially on the outside by the first excitation track 1.3 and simultaneously radially on the inside by the second excitation track 1.4. In contrast, the second receiver track 1.2 is surrounded on only one side by the second excitation track 1.4. By imprinting the excitation field on only one side with respect to the second receiver track 1.2, an extremely space-saving configuration of the scanning element 1 can be achieved.

[0050] The special design of the first electrically conductive division areas 2.21, in particular the positioning and dimensioning of the openings 2.211, ensures a suitable formation of the eddy currents that can flow around the opening 2.211 over 360°, especially in the webs 2.212 made of electrically conductive material.

[0051] In the conventional design of the electrically conductive partition areas 2.21, as disclosed in the prior art, two electrically conductive partition areas 2.21 adjacent in the circumferential direction x are designed such that the angular distances between their conductive layers are equal along the radial direction. This is the case because, in particular, the electrically conductive partition areas 2.21 are each bounded in the circumferential direction x by a contour that extends straight in the radial direction.

[0052] In conjunction with the design of the scale element 2 with bores 2.11, it has proven particularly advantageous with regard to the signal quality achieved and thus with regard to the achievable measurement accuracy if the scale element, in particular the electrically conductive graduation areas 2.21, are designed according to the invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 4 421 454 A1

[0003]

Claims

[1] Scale element (2) for an inductive angle measuring device, which has a substrate (2.1) on which a graduation track (2.2) is arranged, wherein the division track (2.2) along the circumferential direction (x) is formed from a periodic sequence of alternating electrically conductive division areas (2.21) and non-conductive division areas (2.22), wherein the electrically conductive division areas (2.21) are each formed from a layer of electrically conductive material extending along the circumferential direction (x) and the radial direction, wherein in the substrate (2.1) at least one bore (2.11) is arranged for fastening the scale element (2) to a machine part, wherein at least one electrically conductive partition area (2.21) has an opening (2.211), wherein the electrically conductive material surrounds the opening (2.211), wherein in which at least one electrically conductive division area (2.21) through the opening (2.211) the at least one bore (2.11) is arranged in the substrate (2.1), characterized by , that two electrically conductive partition areas (2.21) adjacent in the circumferential direction (x) are designed such that the angular distances (α, β, γ) between their conductive layers are of different sizes along the radial direction. [2] Scale element (2) according to claim 1, wherein a further bore (2.11) is arranged in the substrate (2.1) in a non-conductive division area (2.22). [3] Scale element (2) according to one of the preceding claims, wherein the division track (2.2) has n electrically conductive division areas (2.21) and m bores (2.11) are arranged in the substrate (2.1), wherein: n ≠ m. [4] Scale element (2) according to one of the preceding claims, wherein n < m. [5] Scale element (2) according to any of the preceding claims, wherein n is an odd number and m is an even number. [6] Scale element (2) according to one of the preceding claims, wherein a first distance (α) and a second distance (β) are larger than a third distance (γ) lying radially between the first and the second distance (α, β). [7] Scale element (2) according to one of the preceding claims, wherein at least one electrically conductive division area (2.21) is bounded in the circumferential direction (x) with a convex contour. [8] Scale element (2) according to one of the preceding claims, wherein at least one electrically conductive division area (2.21) is bounded in the circumferential direction (x) with a round contour. [9] Scale element (2) according to one of the preceding claims, wherein the graduation track (2.2) has n electrically conductive graduation areas (2.21) and the scale element (2) comprises p fastening elements (2.4) arranged in the bores (2.11), wherein n ≠ p. [10] Scale element (2) according to claim 9, wherein n < p. [11] Scale element (2) according to claims 9 or 10, wherein n is an odd number and p is an even number.

Images