Scale element for an inductive angle measuring device

Abstract

The invention relates to a scale element (2) for an inductive angle measuring device, comprising a base (2.1) on which an indexing track (2.2) is arranged. The indexing track (2.2) is formed in the circumferential direction (x) from a periodic sequence of electrically conductive indexing regions (2.21) and non-electrically conductive indexing regions (2.22), which are arranged alternately, the electrically conductive indexing regions (2.21) being each formed from a layer of electrically conductive material. At least one hole (2.11) is arranged in the base (2.1). The electrically conductive indexing regions (2.21) each have an opening (2.211), the electrically conductive material surrounding the opening (2.211). A hole (2.11) is arranged in the substrate (2.1) in such a way as to pass through the opening (2.211) at least in one of the electrically conductive indexing regions (2.21). Furthermore, two electrically conductive indexing regions (2.21) adjacent in the circumferential direction (x) are designed such that an angle-dependent distance (alpha, beta, gamma) between the electrically conductive layers of the electrically conductive indexing regions in the radial direction is different.

Description

Technical Field

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

[0002] Inductive angle measuring devices are used, for example, to determine the angular position of relatively rotating mechanical components. In an inductive angle measuring device, excitation and receiving tracks are typically arranged as conductive paths on a common multilayer printed circuit board, which is fixedly connected to the stator of the angle measuring device, for example. A scaling element with an indexing structure is positioned opposite this printed circuit board and is fixedly connected to a movable part of the angle measuring device. When a time-varying excitation current is applied to the excitation track, a position-related signal is generated in the receiving track during the relative movement between the scaling element and the scanning element. These signals are then further processed in an evaluation circuit. Background Technology

[0003] A scaling element for an inductive angle measuring device is known from the applicant's EP 4 421 454 A1. This scaling element comprises two graduated tracks, each track consisting of a periodic sequence of alternating conductive and non-conductive graduated regions. The scaling element is fixed in mounting holes by screws, all of which are located within the conductive graduated structure. Summary of the Invention

[0004] The purpose of this invention is to provide a compact and economically manufacturable scaling element that offers flexible installation options while still being usable in a relatively accurate inductive angle measuring device.

[0005] According to the present invention, this technical problem is solved by the features of the present invention.

[0006] A scaling element suitable for and defined for an inductive angle measuring device includes a substrate on which a graduation track is disposed. The graduation track consists of a periodic sequence of alternating conductive and non-conductive graduation regions along the measurement direction, wherein the conductive graduation regions are each formed of a layer made of a conductive material. This layer or layer surface extends, on the one hand, in a circumferential direction and on the other hand, in a radial direction. Furthermore, at least one hole is disposed and provided in the substrate for securing the scaling element to a mechanical component. At least one conductive graduation region has an opening, wherein the conductive material surrounds the opening. Furthermore, at least one hole is disposed in the substrate through the opening in at least one of the conductive graduation regions. Two circumferentially adjacent conductive graduation regions are designed such that the radially angle-related spacing between the conductive layers of the conductive graduation regions is of different magnitudes in the circumferential direction.

[0007] Therefore, adjacent conductive indexing regions have different angle-dependent spacing (in the circumferential direction) at different distances from the axis. In other words, if a first spacing between two opposing points in the circumferential direction on the contour of a conductive indexing region is measured radially inward, then a second spacing at a radially offset position will have a different magnitude compared to the first spacing. The opposing points are specifically located on the same virtual circumference, the center of which lies on the axis. The contour of the relevant conductive indexing region or conductive layer is not linearly distributed radially along its entire radial extension. The angle-dependent spacing between two adjacent conductive indexing regions in the circumferential direction involves the corresponding central angle around the axis, expressed in degrees.

[0008] Specifically, a first spacing exists between two adjacent conductive indexing regions in the circumferential direction, and a second spacing exists at a radially offset position. The first and second spacings can be greater than a third spacing located radially between the first and second spacings.

[0009] The conductive indexing region is formed of a layer of conductive material. The relatively non-conductive indexing region can be formed of plastic (e.g., printed circuit board material). The scale element can serve as a substrate, preferably a plastic printed circuit board material. Alternatively, the substrate can be composed of a layered structure comprising a relatively thick steel layer and a non-conductive layer (e.g., a plastic layer), wherein the steel layer is disposed on the side of the scale element opposite to the indexing region. The term "relatively non-conductive" refers to the ratio of the electrical conductivity between the alternating indexing region materials. This ratio is particularly likely to be greater than 10 or greater than 50. The thickness of the conductive material layer in the conductive indexing region is preferably greater than 12 µm, i.e., 0.012 mm. Furthermore, particularly for economic reasons, it is advantageous when the layer thickness is less than 1 mm, particularly less than 0.5 mm, preferably less than 0.1 mm.

[0010] In the following description, the concept of a hole refers to an opening that is not necessarily circular. In particular, the hole can also be constructed as square or elliptical, for example, by means of stamping or milling processes.

[0011] In an angle measuring device, a scaling element is used to determine the angular position relative to a scanning element. Here, the scaling element is rotatably arranged about an axis relative to the scanning element, such that the measurement direction represents a circumferential direction relative to that axis.

[0012] Advantageously, additional holes are provided within the substrate in the non-conductive indexing region.

[0013] Advantageously, the indexing track has n conductive indexing regions and m holes arranged in the substrate, where n ≠ m. In particular, the scaling element can be designed to work in the relationship n < m.

[0014] Specifically, n can be odd and m can be even.

[0015] In a further embodiment of the invention, at least one conductive indexing region is defined by a convex profile in the circumferential direction. This means that opposing conductive indexing regions in the circumferential direction are defined by convex profiles in opposing cross-sections. In particular, the profile can be circular, and especially can be an arc segment. Unlike the conductive indexing regions in conventional inductive scaling elements, there is no profile extending in a continuous radial straight line. As an alternative to the aforementioned circular profile, a polygonal profile, such as a semi-hexagonal form, can also be chosen. Similarly, the profile can also be designed to be concave.

[0016] Advantageously, the indexing track is constructed in a ring or circular shape, with the center point of the ring indexing track located on the axis, in particular.

[0017] The scaling element can be constructed such that it has one opening in each of the multiple conductive scale regions and / or at least one conductive scale region has multiple openings. In particular, all conductive scale regions of the scaling element can have multiple openings.

[0018] Advantageously, all conductive indexing regions are designed to have the same geometry.

[0019] In a further embodiment of the invention, at least a portion of the openings in the conductive indexing region are designed to be geometrically identical.

[0020] Advantageously, the indexing tracks extend along the indexing circumference centered on a center point, which is specifically located on the axis, wherein the openings are arranged such that they are each equidistant from the center point and are arranged along the indexing circumference.

[0021] Advantageously, the scaling element comprises multiple conductive indexing regions with holes. These holes are arranged such that they are each equidistant from the center point and are distributed along the indexing circumference.

[0022] The spacing between openings or holes is expressed in degrees and refers to the corresponding central angle around the center point of the axis or the scale circle.

[0023] In a further embodiment of the invention, the scaling element includes at least one fixing element disposed in the hole. This fixing element is configurable to be flush with or recessed relative to the conductive indexing region in the axial direction, and in no case protrudes from the surface of the conductive indexing region in the axial direction. In the following description, the axial direction refers to a direction oriented parallel to an axis.

[0024] Specifically, the fixing element is made of a conductive material and can be designed in the form of a screw. Alternatively, rivets, metal pins, spring pins, or the like can be used as fixing elements, which may be advantageous if the scale element is additionally bonded to the mechanical part it is fixed to. This fixing element is particularly useful for creating form fits, which is important for functionally safe arrangements. Simultaneously, this fixing element can be used for centering the scale element. For example, a configuration can be adopted in which a centering protrusion or centering blade is pressed into a hole and the scale element is additionally fixed by adhesive bonding.

[0025] The scaling element advantageously includes a plurality of fixing elements, wherein the scaling element includes a plurality of conductive indexing regions having holes in which the fixing elements are arranged.

[0026] In a further embodiment of the invention, the indexing track has n conductive indexing regions, and the scale element includes p fixing elements arranged in holes. In this case, the condition n ≠ p applies. Specifically, the condition n < p applies, where it is advantageous when n is odd and p is even.

[0027] According to another aspect, the invention also includes an inductive angle measuring device having the aforementioned scaling element and scanning element.

[0028] Further details and advantages of the scanning element according to the invention can be derived from the following description of the embodiments taken in conjunction with the accompanying drawings. Attached Figure Description

[0029] Figure 1 This is a top view of one side of the scale element.

[0030] Figure 2 It is a three-dimensional cross-sectional view of the scaling element.

[0031] Figure 3 It is a cross-sectional view of the hole passing through the scaling element.

[0032] Figure 4 This is a top view of one side of the scanning element. Detailed Implementation

[0033] The present invention will be described in conjunction with an angle measuring device having a scale element 2 ( Figure 1 , 2 and 3) and scanning element 1 ( Figure 4 The scanning element can be used to detect the angular position of the scaling element 2. The scaling element 2 is rotatably arranged relative to the scanning element 1 about axis A. This angle measuring device can be used, for example, in a drive device, such as in a robot, where the scaling element 2 is torsionally connected to the drive shaft of the motor.

[0034] according to Figure 4 The scanning element 1 shown is used to scan the scaling element 2 and is designed as a printed circuit board having multiple layers and electronic components. In the embodiment, the electronic components are mounted only on one side of the printed circuit board, i.e., the side opposite to the scaling element 2, therefore... Figure 4 It is not visible in the middle. Alternatively or supplementarily, electronic components can be mounted on both sides of the printed circuit board.

[0035] To determine the angle information, the scanning element 1 has a first receiving track 1.1 and a second receiving track 1.2. Both receiving tracks 1.1 and 1.2 are circular, and for both receiving tracks 1.1 and 1.2, the center point M is located on axis A. Therefore, the receiving tracks 1.1 and 1.2 are concentrically arranged with respect to the center point M under a first approximation.

[0036] In the embodiment described, the first receiving track 1.1 includes four receiving conductor paths 1.11. The receiving conductor paths 1.11 of the first receiving track 1.1 are staggered in the circumferential direction x and have a spatial periodic orientation, which is substantially sinusoidal or quasi-sinusoidal in shape.

[0037] In the embodiment, the second receiving track 1.2 includes eight receiving conductor paths 1.21, which are staggered relative to each other in the circumferential direction x.

[0038] Furthermore, the scanning element 1 includes a first excitation track 1.3 and a second excitation track 1.4. In the embodiment described, the excitation tracks 1.3 and 1.4 include multiple excitation wires, but they can also be configured as a single excitation wire each. The first receiving track 1.1 is located radially inside the first excitation track 1.3 and radially outside the second excitation track 1.4. The second excitation track 1.4 is also located radially outside the second receiving track 1.2. The excitation tracks 1.3 and 1.4, as well as the receiving tracks 1.1 and 1.2, all extend along the circumferential direction x.

[0039] The receiving conductor path 1.11 of the first receiving track 1.1 and the receiving conductor path 1.21 of the second receiving track 1.2 are connected by vias and distributed in different layers of the printed circuit board, thereby avoiding unwanted short circuits at the intersection. Although strictly speaking, each receiving conductor path 1.11, 1.21 consists of many conductor segments distributed on two planes or layers and arranged in series, such a structure is collectively referred to here as a receiving conductor path 1.11, 1.21.

[0040] exist Figure 1 The scale element 2 is shown in a top view, where, Figure 1 Compared to scale element 2 in the middle Figure 4 The scanning element 1 is shown magnified. The scaling element 2 has a ring or annular shape. The scaling element 2 includes a substrate 2.1 ( Figure 2 Two indexing tracks 2.2 and 2.3 are arranged on the substrate. In the illustrated embodiment, the substrate 2.1 is made of printed circuit board material, which includes plastic, particularly epoxy resin. The indexing tracks 2.2 and 2.3 are in a ring structure and are concentrically arranged on the substrate 2.1 with different radii relative to axis A. The indexing tracks 2.2 and 2.3 contain an indexing structure consisting of a periodic sequence of conductive indexing regions 2.21 and 2.31 and non-conductive indexing regions 2.22 and 2.32 arranged alternately along the circumferential direction x, wherein the conductive indexing regions 2.21 and 2.31 are each formed of a conductive material layer. The thickness of this layer is 18 µm here. In the illustrated example, the conductive indexing regions 2.21 and 2.31 are made of copper coated on the substrate 2.1. In the non-conductive indexing regions 2.22 and 2.32, the substrate 2.1 is not coated. By arranging the corresponding two indexing tracks 2.2 and 2.3, the angular position of the scale element 2 can be absolutely determined. The second (outer) indexing track 2.3 of the scale element 2 has a greater number of corresponding indexing regions 2.31 and 2.32 along the circumferential direction x, thus enabling higher resolution angular position measurement.

[0041] The conductive indexing region 2.21 of the first (inner) indexing track 2.2 has openings 2.211, thus the conductive material layer is interrupted at these locations, i.e., the substrate 2.1 is not coated in these areas. In the embodiment, the openings 2.211 all have a circular geometry. The openings 2.211 are arranged such that they are each equidistant from the center point M. In particular, the centroids or center points of the openings 2.211 are arranged at the same interval as the center point M.

[0042] The conductive indexing regions 2.21 are designed and arranged such that each opening 2.211 is surrounded by the conductive indexing regions 2.21, thereby forming tabs 2.212 made of conductive material around both sides of the opening 2.211, and forming a closed contour made of conductive material around the opening 2.211. Here, two adjacent conductive indexing regions 2.21 in the circumferential direction x are designed such that the first, second, and third spacings α, β, γ, which are angle-related between the conductive layers in the circumferential direction x, are of different sizes in the radial direction. Therefore, for example, the spacing α related to the first angle is defined at a first spacing r1 (radial spacing) from the axis A, and the spacing β related to the second angle is defined at a second radial spacing r2. The following relationship applies:

[0043] r1 ≠ r2 and a ≠ b.

[0044] Specifically, the third spacing γ is radially centered in the first indexing track 2.2 with the third radial spacing r3, and is smaller than the first spacing α, which is radially located further inward, and also smaller than the second spacing β, which is radially located radially outward relative to the third spacing g. Therefore, both the first spacing α and the second spacing β are larger than the third spacing γ, which is radially located between the first spacing α and the second spacing β. Thus, it can be determined that the angle-related spacings α, β, and γ in the circumferential direction x have different sizes depending on their radial positions or radial spacings r1, r2, and r3.

[0045] In the embodiment, the conductive indexing regions 2.21 each have a shape defined by a circular outline in the circumferential direction x, wherein the conductive indexing regions 2.21 present a convex outline in these regions.

[0046] In the conductive indexing region 2.21, holes 2.11 are arranged in the substrate 2.1 through openings 2.211. The holes 2.11 are arranged in the substrate 2.1 along the first (inner) indexing track 2.2. In this embodiment, four holes 2.11 are provided, each having the same distance from the center point M and arranged along the circumferential direction x (the distance is 90°). Among them, three holes 2.11 are located in the conductive indexing region 2.21, and one hole 2.11 is located in the non-conductive indexing region 2.22.

[0047] In the embodiment described, the first indexing track 2.2 has three conductive indexing regions 2.21 (n = 3). The scale element 2 includes four holes 2.11 in the substrate 2.1 for securing the scale element to the mechanical component (m = 4). Therefore, the number n of conductive indexing regions 2.21 is different from the number m of holes 2.11 (n ≠ m). Specifically, the number n of conductive indexing regions 2.21 is less than the number m of holes 2.11 in the substrate 2.1 (n < m). In the illustrated embodiment, the number n of conductive indexing regions 2.21 corresponds to an odd number and the number m of holes 2.11 corresponds to an even number.

[0048] Figure 2 The EE along the line is shown. Figure 1 The diagram shows a three-dimensional cross-sectional view through the scale element 2, where the fixing element 2.4, here a screw, is shown in the insertion hole 2.11. As described above, the indexing track 2.2 has a total of three conductive indexing regions 2.21 (n = 3). Furthermore, the scale element 2 includes four fixing elements 2.4 (p = 4). Therefore, the number n of conductive indexing regions 2.21 is different from the number p of fixing elements 2.4 (n ≠ p). Specifically, the number n of conductive indexing regions 2.21 is less than the number p of fixing elements 2.4 (n < p). In this embodiment, the number n of conductive indexing regions 2.21 corresponds to an odd number, while the number p of holes 2.11 corresponds to an even number.

[0049] Figure 3 A partial cross-sectional view of the scale element 2 in the region of the first indexing track 2.2 is shown, wherein, Figure 3 The thickness of the conductive material layer in the conductive indexing region 2.21 is exaggerated for ease of explanation. Holes 2.11 are all designed as stepped through holes. Specifically, holes 2.11 have tapered regions 2.111, which are formed, for example, by countersinking. The tapered regions 2.111 are recessed by a distance h relative to the surface of the base 2.1, or in the axial direction. Thus, a fixing element 2.4 can be provided in the corresponding hole 2.11. This fixing element is specifically constructed as a countersunk screw, wherein the fixing element 2.4 is locked in place relative to the surface of the base 2.1 and relative to the surface of the corresponding conductive indexing region 2.21. The fixing element 2.4, used to fix the scale element 2 to the mechanical component, is made of steel and is therefore conductive.

[0050] In the assembled state, scanning element 1 and scale element 2 are arranged opposite each other with an axial spacing or air gap, such that when relative rotation occurs between scale element 2 and scanning element 1, signals dependent on their respective angular positions can be generated in the receiving conductor paths 1.11 and 1.21 through induction. The prerequisite for generating these signals is that excitation tracks 1.3 and 1.4 generate time-varying electromagnetic excitation fields within their respective scanned indexing structure regions. In the illustrated embodiment, excitation tracks 1.3 and 1.4 are constructed as multiple planar parallel current-carrying individual conductors.

[0051] When excitation tracks 1.3 and 1.4 are energized, a tubular or cylindrical electromagnetic field is formed around them. The magnetic field lines of the generated electromagnetic field are distributed around the excitation tracks 1.3 and 1.4, and the direction of the magnetic field lines depends in a known manner on the direction of the current in the excitation tracks 1.3 and 1.4. Eddy currents are generated in the conduction index regions 2.21 and 2.31, thereby achieving angular position-dependent field modulation. Accordingly, the relative angular positions can be measured via receiving tracks 1.1 and 1.2, respectively.

[0052] Scanning element 1 has an electronic circuit with interconnected electronic components. This electronic circuit can, for example, include an ASIC (Application-Specific Integrated Circuit) chip. The signals generated by the receiving rails 1.1 and 1.2 are further processed by the electronic components constituting the evaluation circuit. In particular, in the current configuration with two indexing rails 2.1 and 2.2 and two receiving rails 1.1 and 1.2, the absolute position can be calculated by evaluating the ASIC. The electronic circuit of scanning element 1 operates not only as an evaluation element but also as an excitation control element, under its control generating or producing an excitation current that then flows through excitation rails 1.3 and 1.4. Therefore, excitation rails 1.3 and 1.4 are powered by the same excitation control element.

[0053] The first receiving track 1.1 is radially outer surrounded by the first excitation track 1.3, and radially inner surrounded by the second excitation track 1.4. Conversely, the second receiving track 1.2 is surrounded only on one side by the second excitation track 1.4. By applying a unilateral excitation field relative to the second receiving track 1.2, an extremely compact configuration of the scanning element 1 can be achieved.

[0054] The special configuration of the first conductive indexing region 2.21, especially the positioning and size design of the opening 2.211, ensures the proper formation of eddies that can flow around the opening 2.211 in a 360° manner, particularly in the bridging portion 2.212 made of conductive material.

[0055] In the conventional configuration of the conductive indexing region 2.21 disclosed in the prior art, two adjacent conductive indexing regions 2.21 in the circumferential direction x are constructed such that the angle-dependent spacing between their conductive layers remains equal in the radial direction. This is because, in particular, the conductive indexing regions 2.21 are defined in the circumferential direction x by contours that extend linearly in the radial direction.

[0056] The design of the scaling element 2 with the aperture 2.11 has proven particularly advantageous in terms of the signal quality achieved and therefore the achievable measurement accuracy, when the scaling element, in particular the conductive graduation region 2.21, is designed according to the invention.

Claims

1. A scaling element (2) for an inductive angle measuring device, the scaling element having a base (2.1) on which a graduation track (2.2) is arranged, wherein, The indexing track (2.2) is formed along the circumferential direction (x) by a periodic sequence of alternating conductive indexing regions (2.21) and non-conductive indexing regions (2.22), wherein the conductive indexing regions (2.21) are formed by layers made of conductive material extending along the circumferential direction (x) and the radial direction, respectively. At least one hole (2.11) is arranged in the substrate (2.1) for fixing the scale element (2) to the mechanical component, wherein, At least one of the conductive indexing regions (2.21) has an opening (2.211), wherein a conductive material surrounds the opening (2.211), wherein, In at least one of the conductive indexing regions (2.21), at least one of the holes (2.11) is arranged in the substrate (2.1) such that it passes through the opening (2.211). Its features are, Two adjacent conductive indexing regions (2.21) in the circumferential direction (x) are designed such that the angle-dependent spacing (α, β, γ) between the conductive layers in the conductive indexing regions along the radial direction is of different sizes.

2. The scaling element (2) according to claim 1, wherein, In the non-conductive indexing region (2.22), additional holes (2.11) are arranged in the substrate (2.1).

3. The scaling element (2) according to any one of the preceding claims, wherein, The indexing track (2.2) has n conductive indexing regions (2.21) and m holes (2.11) are arranged in the substrate (2.1), wherein, applicable: n ≠ m.

4. The scaling element (2) according to any one of the preceding claims, wherein, Applicable to: n < m.

5. The scaling element (2) according to any one of the preceding claims, wherein, n is an odd number and m is an even number.

6. The scaling element (2) according to any one of the preceding claims, wherein, The first spacing (α) and the second spacing (β) are greater than the third spacing (γ) located radially between the first spacing and the second spacing (α, β).

7. The scaling element (2) according to any one of the preceding claims, wherein, At least one conductive indexing region (2.21) is defined by a convex profile in the circumferential direction (x).

8. The scaling element (2) according to any one of the preceding claims, wherein, At least one conductive indexing region (2.21) is defined by a circular outline in the circumferential direction (x).

9. The scaling element (2) according to any one of the preceding claims, wherein, The indexing track (2.2) has n conductive indexing regions (2.21), and the scale element (2) includes p fixed elements (2.4) arranged in the hole (2.11), wherein, applicable: n ≠ p.

10. The scaling element (2) according to claim 9, wherein, Applicable when n < p.

11. The scaling element (2) according to claim 9 or 10, wherein, n is odd and p is even.

Images