Inductive position measuring device

Abstract

The invention relates to an inductive position measuring device having a scale element (2) and a scanning element (1) which can be moved relative to the scale element. The scanning element (1) has an exciter line (1.6), a first receiver track (1.1) and a second receiver track (1.2). The scale element (2) has a support layer (2.3) made of a first electrically conductive material, a first indexing track (2.11) and a second indexing track (2.12). A first indexing track (2.11) and a second indexing track (2.12) are arranged on the support layer (2.3) and are formed by alternately arranged partitions (2.111, 2.121) and gaps (2.112, 2.122), the partitions (2.111, 2.121) being made of a second electrically conductive material, which is different from the first material of the support layer (2.3). A shielding barrier (2.16) made of an electrically conductive material is arranged between the first indexing track (2.11) and the second indexing track (2.12).

Description

Technical Field

[0001] The present invention relates to an inductive measuring device for determining a relative position.

[0002] An inductive position measuring device serves, for example, as a measuring device for determining the relative position of two elements that can move or rotate relative to one another. In an inductive measuring device, an exciter conductor coil and a receiver conductor coil are, for example, mounted in the form of a conductor circuit on a common, mostly multi-layer printed circuit board, where this unit can be referred to as a scanning element. This scanning element is opposite a scale element, on which, for example, partitions and gaps are arranged as a graduation structure. If a time-varying excitation current is applied to the exciter conductor, a signal that depends on the relative position is generated in the receiver conductor coil or the receiver conductor during the relative movement between the scale element and the scanning element. These signals are then further processed in an evaluation circuit.

[0003] With such a position measuring device, the linear position of the scanning element relative to the scale element can be determined. However, the present invention can also be applied to a position measuring device that measures the angular position of the scanning element relative to the scale element. In particular, the position measuring device can generate absolute position information. Background Art

[0004] An inductive position measuring device is described in the applicant's EP 2515086 A2, which has a measuring rod composed of different metal layers. Summary of the Invention

[0005] The object of the present invention is to create an inductive position measuring device by which the determination of the relative position can be achieved in a simple manner with high measuring accuracy in a first direction that extends along a receiver track.

[0006] According to the present invention, this object is achieved by the features described in the present invention.

[0007] The inductive position measuring device has a scanning element and a scale element, wherein the scanning element can move relative to the scale element either along a first direction or is movably arranged. The first direction can be a linear direction or a circumferential direction in the case of detecting an angular position. The scanning element has at least one exciter conductor. In addition, the scanning element has a first receiver track, which includes at least one receiver conductor that extends along the first direction according to a first periodic model. Similarly, the scanning element has a second receiver track, which includes at least one receiver conductor that extends along the first direction according to a second periodic model, and the second receiver track is arranged offset in a second direction relative to the first receiver track, so that an intermediate strip extends between them along the first direction. The second direction is oriented orthogonally to the first direction. The scale element has a support layer made of a first conductive material and a first graduation track and a second graduation track. The second graduation track is arranged offset in the second direction relative to the first graduation track. The first graduation track and the second graduation track are arranged on the support layer and consist of partitions and gaps that are alternately arranged along the first direction. Here, the partitions include a second conductive material or are made of a second conductive material, and the second conductive material is different from the first material of the support layer, wherein the partitions and the support layer are conductively connected to each other. There is a shielding partition (based on the second direction) or a shielding partition is arranged between the first graduation track and the second graduation track, and the shielding partition also consists of a conductive material. The shielding layer is arranged offset relative to the intermediate strip in a third direction. The third direction is oriented orthogonally to the first direction and the second direction.

[0008] Therefore, the first receiver track is arranged offset in the second direction at a certain distance from the second receiver track, so that an intermediate strip extending in the second direction exists between the first receiver track and the second receiver track. In addition, the intermediate strip also extends along the first direction. In particular, the width of the intermediate strip can extend in the second direction and the length of the intermediate strip can extend in the first direction. The material of the shielding partition corresponds to the second conductive material of the partition.

[0009] Not only the partitions but also the shielding partitions protrude relative to the support layer in the relevant third direction. Advantageously, the partitions and the shielding partitions have the same elongation or height in the third direction. According to an advantageous design of the invention, the partitions have an elongation of at least 5 µm, in particular at least 10 µm, in the third direction.

[0010] Advantageously, the graduation tracks are generated by structuring a first conductive layer, in particular by laser treatment or laser ablation.

[0011] According to an advantageous design of the present invention, the first material of the support layer corresponds to the ferritic stainless steel family. Thus, preferably, the first material of the support body is ferritic stainless steel.

[0012] Advantageously, the first material of the support layer has a permeability value of at least 100, in particular at least 500, or at least 1000. The permeability value is a measure of the magnetic conductivity or magnetic permeability of the first material of the support layer.

[0013] Advantageously, the scale element has a compensation layer, wherein the support layer is arranged between the graduation track and the compensation layer with respect to the relevant third direction. In particular, the compensation layer can be made of the same second material as the partition.

[0014] Advantageously, the first conductive material of the support layer has a higher specific resistance than the second conductive material of the partition and / or the shielding partition. In particular, the specific resistance of the first conductive material of the support layer can be at least 10 times greater than the specific resistance of the second conductive material. On the other hand, the first conductive material of the support layer can have a specific resistance less than 1 Ω·mm 2 / m.

[0015] Advantageously, the total elongation of exactly one partition and exactly one gap of the first graduation track in the first direction or along the first direction has a first period length. In addition, the total elongation of exactly one partition and exactly one gap of the second graduation track in the first direction or along the first direction has a second period length. The first period length and the second period length are of different sizes.

[0016] Advantageously, the first periodic model of the receiver wires of the first receiver track has a first period length, and the second periodic model of the receiver wires of the second receiver track has a second period length. As already mentioned, the first period length and the second period length are of different sizes. The first and / or second periodic model can have a sinusoidal curve. The position measuring device is configured such that the electromagnetic field generated by the exciter wire can be modulated by the graduation track. Thus, a first signal with a first period length can be generated by the receiver wires of the first receiver track, and a second signal with a second period length can be generated by the second receiver wires of the second receiver track. Using the position measuring device, the absolute position of the scale element relative to the scanning element can be determined by the receiver wires of the first receiver track and by the receiver wires of the second receiver track, in particular according to the vernier principle.

[0017] According to an advantageous design of the present invention, the shielding partition extends along the first direction by more than the first period length or the second period length, i.e., more than the larger period length.

[0018] Advantageous improvements of the present invention result from the present invention. Description of the Drawings

[0019] Further details and advantages of the inductive position measuring device according to the invention result from the embodiments described below with reference to the drawings.

[0020] Figure 1 is a sectional view of a blank for a scale element

[0021] Figure 2 is a sectional view of a scale element with a scanning element

[0022] Figure 3 is a further sectional view of the scale element

[0023] Figure 4 is a top view of the scale element

[0024] Figure 5 is a top view of the scanning element

[0025] Figure 6 is a top view of details of the scanning element, in particular of the first and second receiver tracks and the exciter conductor

[0026] Figure 7 is a view in the measuring direction of the position measuring device Detailed Description of the Invention

[0027] The invention is described with the aid of a position measuring device which determines the absolute relative position between a scanning element 1 (see Figure 2 , 5 and 7) which can be moved along a first direction X (measuring direction) and a scale element 2 or a scale.

[0028] The scale element 2 is made of a multi-layer semi-finished product in the embodiment shown, as Figure 1 shown in the sectional view. In the embodiment shown, the scale element 2 comprises a relatively thick support layer 2.3, the thickness T23 of the support layer 2.3 being 0.3 mm in the embodiment shown. The first material from which the support layer 2.3 is made is ferritic stainless steel, the magnetic permeability value of which is between 100 and 2000. For the support layer 2.3, for example, steel EN 1.4016 can be used. Steel EN 1.4016 has a specific resistance of approximately 0.60 Ωmm 2 / m.

[0029] The above-mentioned semi-finished product, or the blank for the scale element 2, also comprises a graduation layer 2.1 on the side of the support layer 2.3 and a compensation layer 2.2 on the opposite side of the support layer 2.3. The graduation layer 2.1 and the compensation layer 2.2 are each made of the same second material, such as aluminium or copper (specific resistance: Al: 0.027 Ωmm 2 / m, Cu: 0.017 Ωmm 2 / m), and have the same thickness or elongation T21 in the third direction Z, here 24 µm. Thus, not only the graduation layer 2.1, but also the support layer 2.3 and the compensation layer 2.2 are electrically conductive. In addition, the graduation layer 2.1 and the support layer 2.3 are in direct contact with each other, so that they are conductively connected.

[0030] During the manufacture of the scale element 2, the graduation layer 2.1 arranged directly on the support layer 2.3 is structured by means of a laser ablation process. Here, the graduation layer 2.1 is partially ablated by the laser beam over the total thickness T21. Subsequently, a first graduation track 2.11, a second graduation track 2.12, a third graduation track 2.13, a fourth graduation track 2.14 and a fifth graduation track 2.15 are then produced (see Figure 2 and 3 ). The graduation tracks 2.11 to 2.15 are arranged offset from each other in the second direction Y.

[0031] Furthermore, an improvement of the graduation tracks 2.11 to 2.15 is described in more detail based on the first graduation track 2.11 and the second graduation track 2.12. The first graduation track 2.11 and the second graduation track 2.12 consist of Figure 4 partition walls 2.111, 2.121 and gaps 2.112, 2.122, and the partition walls and the gaps are arranged staggered or alternately along the first direction X, so that there are gaps 2.112, 2.122 between the partition walls 2.111, 2.121 respectively. Correspondingly, the graduation tracks 2.11, 2.12 each consist of an alternating sequence of partition walls 2.111, 2.121 and gaps 2.112, 2.122. In the first graduation track 2.11, the sum of the lengths of the partition wall 2.111 and the gap 2.112 in the aspect of the first direction X corresponds to the first period length P11. Similarly, in the second graduation track 2.12, the sum of the lengths of the partition wall 2.121 and the gap 2.122 corresponds to the second period length P12. Thus, in the period lengths P11, P12, there is exactly one partition wall 2.111, 2.121 and one gap 2.112, 2.122 respectively.

[0032] In addition, during the structuring of the graduation layer 2.1, so-called shielding partition walls 2.16 are generated or appear during laser ablation. The shielding partition walls 2.16 are arranged between the first graduation track 2.11 and the second graduation track 2.12 in the aspect of the second direction Y and extend along the first direction X. The length of the shielding partition walls 2.16 in the first direction X is much larger than the first period length P11 or the second period length P12.

[0033] The partition plates 2.111, 2.121 and the shielding partition plate 2.16 are made of the same second material and are conductive. The first material of the support layer 2.3 is also conductive. Therefore, an electric current can be obtained between the support layer 2.3 and the partition plates 2.111, 2.121, and similarly, an electric current can also be obtained between the support layer 2.3 and the shielding layer 2.16.

[0034] The third to fifth indexing tracks 2.13 to 2.15 are also designed similarly, and additional shielding partition plates 2.16 are respectively arranged therebetween. The shielding partition plates 2.16 all have the same thickness or elongation T21 in the third direction Z, just like the partition plates 2.111, 2.121 of the first and second indexing tracks 2.11, 2.12. The same also applies to the third to fifth indexing tracks 2.13 to 2.15. The scale element 2 is manufactured in this way, and the scale element is shown in Figure 4 the top view (where the surfaces of the partition plates 2.111, 2.121 and the shielding partition plate 2.16 are emphasized by hatching).

[0035] The support layer 2.3 is located between the indexing tracks 2.11, 2.12 and the compensation layer 2.2 in terms of the relevant third direction Z. The compensation layer 2.2 is basically used to ensure high shape stability and good flatness of the scale element 2.

[0036] Figure 5 The top view of the scanning element 1 is shown. The scanning element is designed as a printed circuit board with multiple layers, and electronic components are mounted on the back surface that is not visible in Figure 5 it. The scanning element 1 is used to scan the scale element 2.

[0037] In order to determine the relative position between the scale element 2 and the scanning element 1, the scanning element 1 has a first receiver track 1.1, a second receiver track 1.2, a third receiver track 1.3, a fourth receiver track 1.4 and a fifth receiver track 1.5. The receiver tracks 1.1 to 1.5 are surrounded by the exciter wire 1.6.

[0038] As Figure 5 shown, the receiver tracks 1.1 to 1.5 are arranged offset from each other in the second direction Y, and there is a spacing in the second direction Y between two adjacent receiver tracks 1.1 to 1.5, so that there is an interval band 1.7 there.

[0039] Figure 6 The enlarged detail view of the first receiver track 1.1 and the second receiver track 1.2 is shown. The first receiver track 1.1 includes a first receiver wire 1.11 and a second receiver wire 1.12. Similarly, the second receiver track 1.2 includes a third receiver wire 1.21 and a fourth receiver wire 1.22.

[0040] Thus, in the illustrated embodiment, the first receiver track 1.1 and the second receiver track 1.2 each have two receiver conductors 1.11, 1.12, 1.21, 1.22, which are arranged offset from each other in the first direction X, so that they can respectively convey two phase-shifted signals in a corresponding offset manner. Here, the receiver conductors 1.11, 1.12, 1.21, 1.22 are designed as conductor circuits and extend in different layers of the circuit board or the scanning element 1 and are connected to vias, so as to avoid undesired short circuits at the intersection points. Although strictly speaking, each of the receiver conductors 1.11, 1.12, 1.21, 1.22 consists of four conductor parts, which are respectively divided or arranged in multiple different planes or layers, such a structure is further generally referred to as the receiver conductors 1.11, 1.12, 1.21, 1.22 respectively.

[0041] The first receiver conductor 1.11 extends along the first direction X according to the first periodic model, and the second receiver conductor 1.12 extends according to the second periodic model. In particular, the receiver conductors 1.11, 1.12, 1.21, 1.22 have a spatially periodic extension, and the receiver conductors are basically designed in a sinusoidal shape or of a sinusoidal type, wherein all the receiver conductors 1.11, 1.12 of the first receiver track 1.1 have a first periodic length P11 ( Figure 6 ). The receiver conductors 1.21, 1.22 of the second receiver track 1.2 have a second periodic length P12. Here, the second periodic length P12 is greater than the first periodic length P11.

[0042] In the illustrated embodiment, among the first receiver track 1.1, the receiver conductors 1.11, 1.12 are arranged offset from each other along the first direction X by 1 / 4 of the first periodic length P11. The receiver conductors 1.11, 1.12 are electrically connected to convey 0° and 90° signals, from which the first position signal can be determined. By means of the first receiver conductors 1.11 and 1.12, a relatively high-resolution incremental signal can be basically generated when the scale element 2 moves relative to the scanning element 1.

[0043] In accordance with Figure 6 the illustrated embodiment, the second receiver track 1.2 includes a third receiver conductor 1.21 and a fourth receiver conductor 1.22, that is, two receiver conductors 1.21, 1.22, which are arranged offset from each other in the first direction X, so that they can provide two signals with an angular offset of 90° according to this offset. The receiver conductors 1.21, 1.22 are designed as conductor circuits and also extend in different layers of the printed circuit board or the scanning element 1 and are connected to vias here.

[0044] In other respects, applicable, on the scanning element 1 the first period length P11 is the smallest period length, which period length is exactly as large as the period length of the fifth receiver track 1.5. The middle third receiver track 1.3 has a period length slightly larger than the first period length P11. The second period length P12 and the period length of the fourth receiver track 1.4 are greater than the first period length P11 and greater than the period length of the third receiver track 1.3. Similarly, the same considerations regarding the period lengths also apply to the graduation tracks 2.11 to 2.15 of the scale element 2.

[0045] In the assembled state of the position measuring device according to Figure 7 , the scanning element 1 and the scale element 2 are opposed to a gap extending in the third direction Z. During the relative movement between the scale element 2 and the scanning element 1, then signals depending on the relative position can be generated by induction effects in the receiver conductors 1.11, 1.12, 1.21, 1.22 respectively. The prerequisite for forming the corresponding signals is that the exciter conductor 1.6 generates a temporally alternating electromagnetic excitation field in the range of the correspondingly scanned graduation tracks 2.11 to 2.15. In the illustrated embodiment, the exciter conductor 1.6 is configured as a single conductor circuit through which a plurality of planar parallel currents pass. The scanning element 1 has a circuit with electronic components. This circuit of the scanning element 1 can also include, for example, an ASIC module. This circuit of the scanning element 1 not only functions as an evaluation element but also as an excitation control element, generating or producing an excitation current under the control of the scanning element, and the excitation current then flows through the exciter conductor 1.6.

[0046] If current flows through the exciter conductor 1.6, then a tubular or cylindrically oriented electromagnetic field is formed around the exciter conductor 1.6. The field lines of the generated electromagnetic field extend around the exciter conductor 1.6, wherein the direction of the field lines depends on the current direction in the exciter conductor 1.6 in a known type and manner. Eddy currents are induced in the range of the partition plates 2.111, 2.121, thereby respectively achieving the modulation of the field depending on the relative position. Accordingly, the relative position can be measured by the receiver conductors 1.11, 1.12, 1.21, 1.22 respectively.

[0047] All the receiver conductors 1.11, 1.12 of the first receiver track 1.1 have the same period length P11 respectively, and the receiver conductors 1.21, 1.22 of the second receiver track 1.2 have the same period length P12 respectively. The scanning of the two receiver tracks 1.1, 1.2 is carried out simultaneously, and this scanning does not require switching between the respective receiver tracks 1.1, 1.2. When sweeping across the partition plates 2.111, 2.121 and the gaps 2.112, 2.122, a signal period is generated by the scanning element 1. The first receiver track 1.1 scans the scale element 2 with its receiver conductors 1.11, 1.12 that extend with a smaller first period length P11, so that a relatively fine determination of the relative position can be achieved through the first receiver track 1.1. At the same time, the adjacent second receiver track 1.2 scans the scale element 2 with its receiver conductors 1.21, 1.22 that extend with a larger second period length P12. Therefore, a relatively rough determination of the relative position can be achieved through the second receiver track 1.2.

[0048] Similarly, when scanning the third, fourth, and fifth graduation tracks 2.13 to 2.15, signals in the third, fourth, and fifth receiver tracks 1.3 to 1.5 are generated or received.

[0049] The received signals are connected by means of a beat or vernier algorithm, so that the relative position between the scanning element 1 and the scale element 2 can be absolutely determined through the signals.

[0050] In addition, the advantages of setting five graduation tracks 2.11 to 2.15 and five receiver tracks 1.1 to 1.5 are as follows: The measurement is relatively insensitive to the flipping of the scale element 2 relative to the scanning element 1 (minimizing the Moiré error).

[0051] In the directly adjacent receiver tracks 1.1, 1.2, crosstalk signals are generated in the graduation tracks 2.11, 2.12 in the design shown here. This crosstalk signal typically has a sinusoidal shape with a crosstalk period length of approximately fifteen second period lengths P12 or sixteen first period lengths P11. The lengths of the receiver conductors 1.21, 1.22 in the first direction X approximately correspond to this crosstalk period length. This design dimension can ensure that the crosstalk is reduced within a certain limit when scanning the directly adjacent graduation tracks 2.11, 2.12. It is shown that although the crosstalk effect can be determined on a conductive substrate when applying a conventional scale element with conductive graduations. Through the present invention, it is possible to significantly minimize the crosstalk and thus optimize the measurement accuracy.

Claims

1. An inductive position measuring device, comprising a scanning element (1) and a scale element (2), wherein the scanning element (1) is arranged in a movable manner in a first direction (X) relative to the scale element (2), and - the scanning element (1) having at least one exciter conductor (1.6), A first receiver track (1.1) is provided, the first receiver track comprising at least one receiver wire (1.11, 1.12), the receiver wire extending along the first direction (X) according to a first periodic pattern, and A second receiver track (1.2) is provided, the second receiver track comprising at least one receiver wire ( 1.21, 1.22), the receiver wire extends along the first direction (X) according to a second periodic model and is arranged offset in a second direction (Y) relative to the first receiver track (1.1), so that the spacing band (1.7) extends in the first direction (X) between the first receiver track and the second receiver track, wherein: - the scale element (2) having a support layer (2.3) made of a first conductive material, includes the first indexing track (2.11), and It comprises a second indexing track (2.12), the second indexing track is arranged offset in the second direction (Y) relative to the first indexing track (2.11), wherein: The first indexing track (2.11) and the second indexing track (2.12) are arranged on the support layer (2.3) and are formed by partitions (2.111, 2.121) and gaps (2.112, 2.122) alternately arranged along the first direction (X), wherein: The separator (2.111, 2.121) is made of a second conductive material, which is different from the first material of the support layer (2.3), wherein: A shielding partition (2.16) made of a conductive material is arranged between the first dividing track (2.11) and the second dividing track (2.12) based on the second direction (Y), wherein the shielding partition is arranged offset relative to the spacing band (1.7) in a third direction (Z), wherein the third direction (Z) is oriented orthogonal to the first direction (X) and the second direction (Y).

2. The inductive position measuring device according to claim 1, wherein: The first material of the support layer (2.3) belongs to the family of ferritic stainless steels.

3. The inductive position measuring device according to claim 1, wherein: The graduation tracks (2.11, 2.12) are produced by structuring the electrically conductive graduation layer (2.1).

4. The inductive position measuring device according to claim 1, wherein: The partition (2.111, 2.121) and the shielding partition (2.16) respectively have the same elongation (T21) in the third direction (Z).

5. The inductive position measuring device according to claim 1, wherein: The separator (2.111, 2.121) has an extension (T21) of at least 5 μm in the third direction (Z).

6. The inductive position measuring device according to claim 1, wherein: The first material of the support layer (2.3) has a magnetic permeability value of at least 100.

7. The inductive position measuring device according to claim 1, wherein: The scale element (2) has a compensation layer (2.2), wherein the support layer (2.3) is arranged between the graduation track (2.11, 2.12) and the compensation layer (2.2) based on the third direction (Z).

8. The inductive position measuring device according to claim 7, wherein: The compensation layer (2.2) comprises a second material which is identical to the second material of the partition (2.111, 2.121).

9. The inductive position measuring device according to claim 1, wherein: The first conductive material of the support layer (2.3) has a higher specific resistance than the second conductive material of the spacer (2.111, 2.121) and / or the shielding spacer (2.16).

10. The inductive position measuring device according to claim 1, wherein: The elongation of the partitions (2.111) and the gaps (2.112) of the first indexing track (2.11) in the first direction (X) has a total first period length (P11), and the elongation of the partitions (2.121) and the gaps (2.122) of the second indexing track (2.12) in the first direction (X) has a total second period length (P12), wherein the first period length (P11) and the second period length (P12) are different in size.

11. The inductive position measuring device according to claim 1, wherein: The first periodic pattern has a first periodic length (P11), and the second periodic pattern has a second periodic length (P12), wherein the first periodic length (P11) and the second periodic length (P12) are different in size.

12. The inductive position measuring device according to claim 1, wherein: The first periodic pattern has a first periodic length (P11), and the second periodic pattern has a second periodic length (P12), wherein the shielding partition (2.16) extends along the first direction (X) by a length greater than the first periodic length (P11) or the second periodic length (P12).

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