Scale element for induction angle measuring mechanism

Abstract

The present invention relates to a scale element (2) having a base (2.1) on which a scale track (2.2) is placed. The scale track (2.2) is formed from a periodic sequence of alternately arranged conductive scale regions (2.21) and non-conductive scale regions (2.22) along the circumferential direction (x), where each conductive scale region (2.21) is formed from a layer of conductive material. At least one hole (2.11) is located within the base (2.1). Each conductive scale region (2.21) has an opening (2.211), and the conductive material surrounds the opening (2.211). Within at least one of the conductive scale regions (2.21), the hole (2.11) is located within the base (2.1) through the opening (2.211). In addition, two conductive scale regions (2.21) adjacent to each other in the circumferential direction (x) are formed such that the angular spacing (α, β, γ) between their conductive layers is of different sizes along the radial direction.

Description

Technical Field

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[0001] The present invention relates to a scale element for an inductive angle measuring mechanism according to claim 1 for determining the angular position of a scale element relative to a scanning element. Inductive angle measuring mechanisms are used, for example, to determine the angular position of machine parts that are rotatable relative to each other. In inductive angle measuring mechanisms, excitation tracks and reception tracks are often applied, for example in the form of conductor paths, on a common, usually multi-layer printed circuit board, which is fixedly connected, for example, to the stator of the angle measuring mechanism. Opposite this printed circuit board, there is a scale element, on which a graduation structure is applied, and the scale element is fixedly connected to the movable part of the angle measuring mechanism. When an excitation current that alternates over time is applied to the excitation track, a position-dependent signal is generated in the reception track during the relative movement of the scale element and the scanning element. This signal is then further processed in the evaluation electronics.

Background Art

[0002] From the applicant's EP4421454A1, a scale element for an inductive angle measuring mechanism is known. The scale element described therein includes two graduation tracks each consisting of a periodic sequence of alternately arranged conductive graduation regions and non-conductive graduation regions. The scale element is fixed by screws in fixing holes, all of which are arranged within the conductive graduation structure.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The fundamental problem of the present invention is to provide a compact and inexpensively manufactured scale element that can be used for inductive angle measuring mechanisms that operate relatively accurately, while still allowing for flexible fixing possibilities. [Means for solving the problem]

[0005] This problem is solved by the features of claim 1 in the present invention. Suitable for an inductive angle measuring mechanism, the scale element determined for this purpose includes a base on which a scale track is mounted. The scale track is formed from a periodic sequence of alternately arranged conductive scale regions and relatively non-conductive scale regions along the measurement direction, each of which is formed from a layer of conductive material. The layers or surfaces of the conductive material extend circumferentially on one side and radially on the other. Furthermore, at least one hole suitable for fixing the scale element to a mechanical part is provided within the base. At least one conductive scale region has an opening, and the conductive material surrounds the opening. In addition, at least one hole is provided within the base, passing through the opening within at least one of the conductive scale regions. Two circumferentially adjacent conductive scale regions are formed such that the angle between the conductive layers of these conductive scale regions is of a different magnitude along the radial direction.

[0006] Therefore, adjacent conductive scale regions have different angular spacings (circumferentially) at different distances from the axis. In other words, if the first spacing between two circumferentially opposite points on the contour of each conductive scale region is measured radially inward, then at radially offset locations, the second spacing will be of a different magnitude compared to the first spacing. The opposite points, in particular, have their centers on the same virtual circumference along the axis. That is, the contour of the conductive scale region or conductive layer in question does not run straight radially across its entire radial extent. The angular spacing between two circumferentially adjacent conductive scale regions is relative to their respective central angles around the axis, and is presented here in degrees.

[0007] In particular, a first gap exists between two circumferentially adjacent conductive scale regions, and a second gap exists offset from this gap from the diameter. These first and second gaps can be greater than a third gap that lies between the diameters of the first and second gaps.

[0008] In other words, the conductive scale region is formed from a layer made of conductive material. The relatively non-conductive scale region can be formed from, for example, plastic (e.g., printed circuit board material). Preferably, the scale element may have a printed circuit board material made of plastic as its base. Alternatively, the base can be formed from a layered structure including a relatively thick steel layer and a non-conductive layer (e.g., a plastic layer), with the steel layer positioned on the side of the scale element opposite to the scale region. In other words, the above term "relatively non-conductive" relates to the ratio of conductivity of the materials in the alternately arranged scale regions. This ratio can be greater than 10 or greater than 50, in particular. It is advantageous for the conductive material layer of the conductive scale region to be greater than 12 μm, or 0.012 mm. On the other hand, it is particularly advantageous for economic reasons if this layer is thinner than 1 mm, especially thinner than 0.5 mm, and preferably thinner than 0.1 mm.

[0009] In the following, the term "hole" refers to a void, which does not necessarily have to be round. In particular, the hole may be angular or elliptical and can be manufactured, for example, by punching or milling.

[0010] A scale element is used within the angle measuring mechanism to determine the angular position relative to the scanning element. This scale element is rotatable around an axis relative to the scanning element, and therefore the measurement direction is circumferential with respect to the axis.

[0011] Even within the non-conductive scale region, it is advantageous to have additional holes placed within the base. The graduation track has n conductive graduation regions, and m holes are arranged in the base, and it is advantageous that n≠m. In particular, the scale element can be formed such that the relationship n < m holds.

[0012] In particular, n can be odd and m can be even. In a further form of the present invention, at least one conductive graduation region is defined by a convex contour in the circumferential direction. That is, the conductive graduation regions facing each other in the circumferential direction are defined by a convex contour in the facing section. In particular, this contour can be round and can in particular be a circular arc. That is, unlike the conductive graduation regions in conventional inductive scale elements, there is no contour that is consistently straight and runs radially here. Instead of the round contour given, a polygonal, for example semi-hexagonal, contour may be selected. Similarly, the contour may be formed concave.

[0013] It is advantageous that the graduation track is formed in a ring shape or an annular shape, and in particular, the center point of the ring-shaped graduation track is on the axis. The scale element can be formed such that it has one opening in each of the plurality of conductive graduation regions and / or such that at least one conductive graduation region has a plurality of openings. In particular, all the conductive graduation regions of the scale element can have a plurality of openings.

[0014] It is advantageous that all the conductive graduation regions are geometrically identical. In a further form of the present invention, at least a part of the openings in the conductive graduation regions are geometrically the same.

[0015] It is advantageous that the graduation track extends along a graduation circumference having a center point, particularly on the axis, and in this case, the openings are arranged such that they each have the same distance from the center point and are arranged equidistantly along the graduation circumference.

[0016] It is advantageous for the scale element to include a plurality of conductive graduation regions having holes. The holes are arranged such that they have the same spacing with respect to the center point and are equidistant along the graduation circumference.

[0017] The spacing of the openings or holes is presented here in degrees and relates to each central angle around the axis or the center point of the graduation circumference. In a further form of the invention, the scale element includes at least one fixing element, which is arranged in the hole. This fixing element can be arranged flush with or offset behind the conductive graduation region with respect to the axial direction. In any case, it cannot protrude axially beyond the surface of the conductive graduation region. Hereinafter, the axial direction means the direction oriented parallel to the axis.

[0018] In particular, the fixing element is made of a conductive material and can be formed as a screw. Instead, a stud, a metal pin, a spring pin, or the like can be used as the fixing element. In this case, it may be advantageous if the scale element is additionally adhered to the mechanical part to which the scale element is fixed. The fixing element can be used, in particular, to establish a form-fit, which is important for a functionally reliable arrangement. At the same time, the fixing element can be used to center the scale element. That is, for example, a centering cone or a centering blade can be pushed into the hole and the scale element can be additionally fixed by an adhesive bond.

[0019] It is advantageous for the scale element to include a plurality of fixing elements. In this case, the scale element includes a plurality of conductive graduation regions having holes in which the fixing elements are arranged. In a further form of the invention, the graduation track has n conductive graduation regions and the scale element includes p fixing elements arranged in the holes. In this regard, the following condition applies, namely n≠p. In particular, the following can apply, namely n<p, and in this regard, it may be advantageous if n is odd and p is even.

[0020] According to a further aspect, the invention also includes an inductive angle measuring mechanism having a scale element and a scanning element. Advantageous configurations of the invention are read from the dependent claims.

[0021] Further details and advantages of the scanning element according to the invention are apparent from the following description of exemplary embodiments based on the accompanying drawings.

Brief Description of the Drawings

[0022] [Figure 1] It is a plan view of one side of the scale element. [Figure 2] It is a cross-sectional perspective view of the scale element. [Figure 3] It is a cross-sectional view of the hole of the scale element. [Figure 4] It is a plan view of one side of the scanning element.

Embodiments for Carrying Out the Invention

[0023] The invention will be described in connection with an angle measuring mechanism having a scale element 2 (Figs. 1, 2, and 3) and a scanning element 1 (Fig. 4) that can be used to capture the angular position of the scale element 2. The scale element 2 is arranged to be rotatable relative to the scanning element 1 about an axis A. Such an angle measuring mechanism can be used, for example, in a robot, for example, in a drive mechanism, in which case the scale element 2 is non-rotatably coupled to, for example, the drive shaft of a motor.

[0024] The scanning element 1 based on Fig. 4 is used to scan the scale element 2 and is formed as a printed circuit board having a plurality of layers and electronic components. In the exemplary embodiment presented, the electronic components are attached only to one side of the printed circuit board, specifically the side not facing the scale element 2, and thus are not visible in Fig. 4. However, alternatively or in addition thereto, the printed circuit board may be equipped with electronic components on both sides.

[0025] To determine angular information, the scanning element 1 has a first receiving track 1.1 and a second receiving track 1.2. Receiving tracks 1.1 and 1.2 each have a ring shape, and in this respect, both receiving tracks 1.1 and 1.2 have their center point M on axis A. Therefore, receiving tracks 1.1 and 1.2 are first approximately concentric with respect to the center point M.

[0026] The first receiving track 1.1 includes four receiving conductor paths 1.11 in the exemplary embodiment described. The receiving conductor paths 1.11 of the first receiving track 1.1 are offset from one another in the circumferential x direction and have spatially periodic and substantially sinusoidal or sinusoidal trajectories.

[0027] The second receiving track 1.2, in the exemplary embodiment described, includes eight receiving conductor paths 1.21 that are offset relative to one another in the circumferential x direction. The scanning element 1 further includes a first excitation track 1.3 and a second excitation track 1.4. In the exemplary embodiment described, the excitation tracks 1.3 and 1.4 include multiple excitation conductors, but may each be formed as only one excitation conductor. The first receiving track 1.1 runs inside the diameter of the first excitation track 1.3 and outside the diameter of the second excitation track 1.4. The second excitation track 1.4 runs outside the diameter of the second receiving track 1.2 in addition to the first. Both the excitation tracks 1.3 and 1.4 and the receiving tracks 1.1 and 1.2 run along the circumferential direction x.

[0028] Both 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 run in different layers of the printed circuit board, coupled with vias, thus avoiding undesirable short circuits at intersections. Strictly speaking, each of the receiving conductor paths 1.11 and 1.21 consists of many conductor pieces arranged in two planes or layers, but here we refer to such structures collectively as a single receiving conductor path 1.11, 1.21.

[0029] In Figure 1, the scale element 2 is shown in a plan view, and in this respect, the scale element 2 in Figure 1 is shown enlarged compared to the scanning element 1 in Figure 4. The scale element 2 has a ring-like or annular shape. The scale element 2 includes a base 2.1 (Figure 2) on which two scale tracks 2.2, 2.3 are mounted. In the illustrated exemplary embodiment, the base 2.1 is manufactured from a printed circuit board material, including plastic, particularly epoxy resin. The scale tracks 2.2, 2.3 are formed in a ring shape and are arranged on the base 2.1 concentrically with respect to axis A and at different radii. The scale tracks 2.2, 2.3 each include a scale structure consisting of a periodic sequence of conductive scale regions 2.21, 2.31 and non-conductive scale regions 2.22, 2.32, respectively, which are alternately arranged along the circumferential direction x, and these conductive scale regions 2.21, 2.31 are each formed from layers of conductive material. The thickness of these layers is 18 μm in this case. In the example shown, copper is applied to the base 2.1 as the material for the conductive scale regions 2.21 and 2.31. In contrast, the base 2.1 is not coated within the non-conductive scale regions 2.22 and 2.32. With a configuration having two scale tracks 2.2 and 2.3 respectively, the angular position of the scale element 2 can be determined in an absolute manner. The second (outer) scale track 2.3 of the scale element 2 has more individual scale regions 2.31 and 2.32 along the circumferential x direction, and therefore, higher resolution for measuring angular position can be achieved with respect to the scale regions 2.31 and 2.32.

[0030] The conductive scale region 2.21 of the first (inner) scale track 2.2 has an opening 2.211, meaning that a layer made of conductive material is open at this location, or the base 2.1 is not coated in this region. In the exemplary embodiment presented, each opening 2.211 has a circular geometric shape. Each opening 2.211 is arranged to be equally spaced with respect to the center point M. In particular, the centroids or center points of the openings 2.211 are each equally spaced with respect to the center point M.

[0031] The conductive scale region 2.21 is formed or arranged such that each opening 2.211 is surrounded by the conductive scale region 2.21, and therefore a bridge portion 2.212 made of conductive material exists on both sides around the opening 2.211, and a closed contour made of conductive material exists around the opening 2.211. In this case, two conductive scale regions 2.21 adjacent in the circumferential direction x are formed such that the first, second, and third spacings α, β, and γ, determined by the angle between their conductive layers in the circumferential direction x, are of different magnitudes along the radial direction. That is, for example, at a first distance r1 (radial distance) with respect to axis A, the spacing α due to the first angle is defined, and at a second radial distance r2, the spacing β due to the second angle is defined. In this case, the following relationship applies.

[0032] r1 ≠ r2 and α ≠ β. In particular, at a distance r3 of the third diameter, the third interval γ, which lies in the middle of the diameter within the first scale track 2.2, is smaller than the first interval α, which lies further inside the diameter, and also smaller than the second interval β, which lies outside the diameter relative to the third interval γ. Thus, the first interval α and the second interval β are larger than the third interval γ, which lies between the first and second intervals α and β of the diameter. In other words, it can be determined that the intervals α, β, and γ, which are angled in the circumferential direction x, are of different magnitudes depending on the position of the diameter or the distances r1, r2, and r3 of the diameter.

[0033] In the exemplary embodiment described, each conductive scale region 2.21 has a shape defined by a rounded contour in the circumferential direction x, and in this case, the conductive scale region 2.21 has a convex contour in this region.

[0034] Within the conductive graduation region 2.21, the holes 2.11 are arranged in the base 2.1 through the openings 2.211 respectively. That is, the holes 2.11 are arranged in the base 2.1 along the first (inner) graduation track 2.2. In the exemplary embodiment being introduced, four holes 2.11 are provided, and these holes 2.11 have the same interval with respect to the center point M respectively, and are arranged along the circumferential direction x (here at an interval of 90°). In this regard, three holes 2.11 are within the conductive graduation region 2.21, and one hole 2.11 is within the non-conductive graduation region 2.22.

[0035] In the exemplary embodiment being introduced, the first graduation track 2.2 has three conductive graduation regions 2.21 (n = 3). The scale element 2 includes four holes 2.11 in the base 2.1 for fixing the scale element to the mechanical part (m = 4). Therefore, here it holds that the number n of the conductive graduation regions 2.21 is different from the number m of the holes 2.11 (n ≠ m). In particular, here the number n of the conductive graduation regions 2.21 is smaller than the number m of the holes 2.11 in the base 2.1 (n < m). In the exemplary embodiment being introduced, the number n of the conductive graduation regions 2.21 corresponds to an odd number and the number m of the holes 2.11 corresponds to an even number.

[0036] In FIG. 2, a cross-sectional perspective view along the line E - E (FIG. 1) of the scale element 2 is shown, where the fixing elements 2.4 inserted into the holes 2.11, here screws, are shown together. As described above, the graduation track 2.2 has three conductive graduation regions 2.21 in total (n = 3). In addition to this, the scale element 2 includes four fixing elements 2.4 (p = 4). Therefore, here it holds that the number n of the conductive graduation regions 2.21 is different from the number p of the fixing elements 2.4 (n ≠ p). In particular, here the number n of the conductive graduation regions 2.21 is smaller than the number p of the fixing elements 2.4 (n < p). In the exemplary embodiment being introduced, the number n of the conductive graduation regions 2.21 corresponds to an odd number and the number p of the fixing elements 2.11 corresponds to an even number.

[0037] Figure 3 shows a detailed cross-sectional view of a portion of the scale element 2 within the region of the first scale track 2.2, in which the thickness of the conductive material layer of the conductive scale region 2.21 is shown excessively for illustrative purposes. The holes 2.11 are each formed here as stepped through holes. In particular, the holes 2.11 have a conical region 2.111, which is manufactured, for example, by drilling. The conical region 2.111 is positioned backward by a dimension h in the axial direction relative to the surface of the base 2.1. This allows for the placement of a fixing element 2.4 within each hole 2.11, where the fixing elements 2.4 are each formed, in particular, as countersunk screws, and these fixing elements 2.4 are positioned backward relative to the surface of the base 2.1 and the surface of each conductive scale region 2.21. The fixing elements 2.4 are used to fix the scale element 2 to the machine part, and are made of steel and therefore conductive.

[0038] In the assembled state, the scanning element 1 and the scale element 2 face each other with an axial gap or space between them, and therefore, as the scale element 2 and the scanning element 1 rotate relative to each other, signals dependent on their respective angular positions can be generated by inductive effects within the receiving conductor paths 1.11 and 1.21. The prerequisite for the formation of corresponding signals is that the excitation tracks 1.3 and 1.4 generate electromagnetic excitation fields that alternate over time within the region of the scale structure being scanned. In the illustrated exemplary embodiment, the excitation tracks 1.3 and 1.4 are formed as a plurality of single conductor paths through which current flows in parallel planes.

[0039] When excitation tracks 1.3 and 1.4 are energized, tubular or cylindrically oriented electromagnetic fields are formed around them. The lines of force of this resulting electromagnetic field run around excitation tracks 1.3 and 1.4, and the direction of these lines of force depends, as is known, on the direction of the current within excitation tracks 1.3 and 1.4. Eddy currents are induced in the conductive scale regions 2.21 and 2.31, thereby achieving field modulation that is dependent on the angular position, respectively. Correspondingly, the relative angular positions can be measured by receiving tracks 1.1 and 1.2, respectively.

[0040] Scanning element 1 has an electronic circuit comprising electronic components electrically connected to each other. This electronic circuit may include, for example, an ASIC chip. The signals generated by receiving tracks 1.1 and 1.2 are further processed by some of the electronic components constituting the evaluation circuit. In particular, in this configuration with two scale tracks 2.1 and 2.2 and two receiving tracks 1.1 and 1.2, the absolute position can be calculated by the evaluation ASIC. This electronic circuit of scanning element 1 acts not only as an evaluation element but also as an excitation control element, under the control of this excitation control element an excitation current is generated or produced, which then flows through excitation tracks 1.3 and 1.4. Thus, excitation tracks 1.3 and 1.4 are energized by the same excitation control element.

[0041] The first receiving track 1.1 is surrounded by the first excitation track 1.3 on the outside of its diameter and simultaneously surrounded by the second excitation track 1.4 on the inside of its diameter. In contrast, the second receiving track 1.2 is surrounded by the second excitation track 1.4 on only one side. By applying the excitation field to the second receiving track 1.2 on only one side, an extremely space-saving configuration of the scanning element 1 can be achieved.

[0042] The specific configuration of the first conductive scale region 2.21, particularly the positioning and dimensional determination of the opening 2.211, ensures the proper formation of eddy currents, which can flow around the opening 2.211 over 360°, especially within the bridge portion 2.212 made of conductive material.

[0043] In conventional forms of conductive scale regions 2.21 as disclosed in the current art, two conductive scale regions 2.21 adjacent to each other in the circumferential direction x are formed such that the angular spacing between their conductive layers is the same along the radial direction. This is because, in particular, the conductive scale regions 2.21 are each defined in the circumferential direction x by contours that run linearly in the radial direction.

[0044] In relation to the configuration of the scale element 2 having holes 2.11, it has been found that the case in which the scale element, in particular the conductive scale region 2.21, is formed according to the present invention is particularly advantageous with respect to the signal quality achieved and therefore with respect to the measurement accuracy that can be achieved. [Explanation of Symbols]

[0045] 1 scanning element 1.1, 1.2 Receiving Tracks 1.11, 1.21 Receiving conductor path 1.3, 1.4 Excitation Truck 2 Scale elements 2.1 Base 2.11 hole 2.111 Conical region 2.2, 2.3 Scale Track 2.21, 2.31 Conductive scale area 2.211 Opening 2.212 Bridge section 2.22, 2.32 Non-conductive scale area 2.4 Fixed elements r1, r2, r3: Distances relative to axis A (radial distances) x circumferential direction α, β, γ: Spacing by angle

Claims

1. A scale element (2) for an induction angle measuring mechanism having a base (2.1) on which a scale track (2.2) is positioned, The scale track (2.2) is formed from a periodic sequence of conductive scale regions (2.21) and non-conductive scale regions (2.22) arranged alternately along the circumferential direction (x), wherein each conductive scale region (2.21) is formed from a layer made of a conductive material, and the layers extend along the circumferential direction (x) and the radial direction. Within the base (2.1), there is at least one hole (2.11) for fixing the scale element (2) to the machine part. At least one conductive scale region (2.21) has an opening (2.211), and the conductive material surrounds the opening (2.211). In the scale element (2), within the at least one conductive scale region (2.21), the at least one hole (2.11) is located within the base (2.1) through the opening (2.211), A scale element (2) characterized in that two conductive scale regions (2.21) adjacent to each other in the circumferential direction (x) are formed such that the angular spacing (α, β, γ) between their conductive layers is of different sizes along the radial direction.

2. The scale element (2) according to claim 1, wherein a further hole (2.11) is located within the base (2.1) in the non-conductive scale region (2.22).

3. The scale element (2) according to claim 1 or 2, wherein the scale track (2.2) has n conductive scale regions (2.21), and m holes (2.11) are arranged within the base (2.1), such that n ≠ m.

4. A scale element (2) according to any one of claims 1 to 3, wherein n < m applies.

5. A scale element (2) according to any one of claims 1 to 4, wherein n is odd and m is even.

6. A scale element (2) according to any one of claims 1 to 5, wherein a first interval (α) and a second interval (β) are greater than a third interval (γ) between the diameters of the first and second intervals (α, β).

7. A scale element (2) according to any one of claims 1 to 6, wherein at least one conductive scale region (2.21) is defined by a convex contour in the circumferential direction (x).

8. A scale element (2) according to any one of claims 1 to 7, wherein at least one conductive scale region (2.21) is defined by a rounded contour in the circumferential direction (x).

9. The scale element (2) according to any one of claims 1 to 8, wherein the scale track (2.2) has n conductive scale regions (2.21), and the scale element (2) includes p fixed elements (2.4) disposed within the holes (2.11), such that n ≠ p.

10. The scale element (2) according to claim 9, wherein n < p applies.

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

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