Scanning element and induction-type position measurement mechanism including the scanning element

Abstract

To provide a scanning element for an induction-type position measurement mechanism that operates relatively accurately and can be manufactured at a low price.SOLUTION: The present invention relates to a scanning element (1) for an induction-type position measurement mechanism, the scanning element (1) having a foundation (1.3) including excitation tracks (Sa, Si) and reception tracks (Ri, Ra) and formed of metal material, and including a shield layer structure (1.2). The shield layer structure (1.2) includes a first layer (1.21) having dielectric properties, and a conductive second layer (1.22). The shield layer structure (1.2) is arranged between the foundation (1.3) and the reception tracks (Ri, Ra) and / or between the foundation (1.3) and the excitation tracks (Sa, Si).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The invention relates to a scanning element for an inductive position measuring mechanism according to claim 1 for determining the relative position between a scale element and a scanning element, and to a position measuring mechanism comprising such a scanning element. [Background technology]

[0002] Inductive position measuring devices are used, for example, as angle measuring devices for determining the angular position of machine parts that can rotate relative to one another. In inductive position measuring devices, an excitation track and a receiving track are often provided, for example in the form of conductor tracks, on a common, usually multi-layer, printed circuit board, which is, for example, fixedly connected to the stator of the angle measuring device. Opposite this printed circuit board is a scale element, on which a graduation structure is provided and which serves as the rotor of the angle measuring device. If a time-alternating excitation current is applied to the excitation conductor tracks of the excitation track, signals that depend on the angular position are generated in the receiving conductor tracks of the receiving track during the relative rotation between the rotor and the stator. These signals are then further processed in the evaluation electronics.

[0003] Such inductive position measuring mechanisms are often used as measuring devices for electric drives to determine the relative movement or relative position of corresponding machine parts, with the generated angular position values ​​of the subsequent electronics being supplied via a corresponding interface arrangement for controlling the drive.

[0004] Inductive position measuring mechanisms are also often used to directly measure longitudinal displacement along an axis, in which case the same measurement principles apply as in the angle measuring instruments described above, except that in this case the receiving track and the graduation structure run along a linear axis.

[0005] From EP 3 702 737 A1 of the applicant an inductive angle measuring arrangement is known which has a base made of metal material. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] EP3702737A1 Summary of the Invention [Problem to be solved by the invention]

[0007] SUMMARY OF THE DISCLOSURE The object of the invention is to provide a scanning element for an inductive position measuring mechanism which functions relatively accurately and can be manufactured inexpensively. [Means for solving the problem]

[0008] This problem is solved according to the invention by the features of claim 1. The scanning element, which is suitable for and has been determined for an inductive position measuring mechanism for measuring a position along a measuring direction, comprises at least one excitation track and at least one receiving track. The excitation track may comprise one or more excitation conductor paths, and the receiving track may comprise, inter alia, a first receiving conductor path and optionally a second receiving conductor path. The scanning element further comprises a base made of a metallic material. The scanning element additionally comprises a shield layer structure comprising at least one dielectric first layer and an electrically conductive second layer. The shield layer structure is arranged between the base and the at least one receiving track in a direction perpendicular to the measuring direction. Alternatively or additionally, the shield layer structure is arranged between the base and the at least one excitation track.

[0009] The measuring direction can be linear or circumferential or tangential. The excitation track and the receiving track run inter alia along the measuring direction. In a further embodiment of the invention, the first layer has a thickness of less than 1 mm, in particular less than 0.50 mm, advantageously less than 0.10 mm.

[0010] Advantageously, the electrically conductive second layer of the shielding layer structure is applied by physical vapor deposition, in particular onto the dielectric first layer of the shielding layer structure. It is advantageous if the shielding layer structure additionally has a third layer and a fourth layer, whereby the third layer can be arranged between the dielectric layer and the conductive layer of the shielding layer structure.

[0011] In a further embodiment of the invention, the scanning element has a multi-layered sensor structure that corresponds to the structure of a multi-layered printed circuit board or conductor film. In other words, the layer of the scanning element here means a (structured) layer. The sensor structure comprises at least one first conductive layer and a second conductive layer. The excitation track and the receiving track are generated by structuring these conductive layers. The sensor structure thus comprises structured conductive layers, in which at least one excitation track and at least one receiving track are arranged. In a further embodiment of the invention, the sensor structure has exactly two conductive layers, in which at least one excitation track and at least one receiving track run.

[0012] Advantageously, an insulating layer is arranged between the second conductive layer and the shielding layer structure. In addition, a fourth layer may be arranged between this insulating layer and the conductive layer. Advantageously, the conductive second layer of the shielding layer structure is arranged between the third layer and the fourth layer. The material of the third layer and / or the material of the fourth layer may contain chromium. The third and fourth layers are therefore made of a material having a relatively high electrical conductivity, however, the third and fourth layers together have a thickness of less than 50% of the conductive layer.

[0013] It is advantageous for the dielectric first layer of the shielding layer structure to have a thickness of at least 2.5 μm, in particular at least 5 μm, advantageously at least 20 μm. In a further embodiment of the invention, the scanning element comprises at least one electronic component, in which case the shielding layer structure, i.e. the conductive second layer, is arranged between the base and the at least one electronic component, i.e. according to this embodiment, the shielding layer structure, i.e. the conductive second layer, also extends under the area of ​​the at least one electronic component.

[0014] In particular, the at least one electronic component is designed to be able to evaluate signals received by the receiving track with respect to the position information contained therein, i.e. signals that can be generated by the receiving track and that can be further processed by at least one electronic component, which in particular constitutes an evaluation circuit. The scanning element can have several electronic components, which are electrically connected to the (evaluation) circuit. These connections are designed in particular as conductor tracks running in correspondingly structured first and second layers.

[0015] In an advantageous embodiment of the invention, at least one electronic component is suitable for generating or creating an excitation current that can be introduced into the excitation track, i.e. an excitation current can be passed through the excitation track, which typically has a current intensity that alterns over time (alternating current or mixed current). The excitation current can be generated by the at least one electronic component, i.e. the trajectory of the excitation current can be shaped by the electronic component. Due to the physical relationship between current intensity and voltage intensity, the same considerations can of course be made for the excitation voltage.

[0016] The at least one electronic component can be attached to a side of the scanning element facing away from the base, so that the sensor structure and the at least one electronic component are accordingly arranged on the same side with respect to the base.

[0017] Advantageously, the electronic circuit can be connected to ground potential via a conductor (electronic ground), and at least one electrically conductive second layer of the shielding layer structure is electrically connected to this conductor. This conductor can have an ohmic resistor and a capacitor, which are connected in parallel. Advantageously, the shielding layer structure, in particular its electrically conductive second layer, is formed planarly without interruption. Advantageously, the electrically conductive second layer of the shielding layer structure is connected to the conductor via a via. In particular, the conductor can be electrically connected to a connection element, which is used as a terminal for the ground potential as specified. In this case, the second layer is electrically connected to the connection element. The connection element can be, for example, an element of a plug connector, i.e. a plug element, or a solder connection.

[0018] For this purpose, the base can be attached, for example, to a conductive housing, for example a motor housing, so that the base is grounded via the motor housing. It has proven to be particularly preferred if the base and the conductive second layer of the shielding layer structure are not directly electrically connected to each other and in particular are not grounded to each other.

[0019] The shielding layer structure serves to shield noise fields so that no noise is generated in the receiving track and / or in the excitation track and possibly in the electronic components, and at the same time is designed in such a way that the desired signal can still be received with the required strength by means of the shielding layer structure, so that an accurate position determination is possible.

[0020] Advantageously, the base has a thickness of more than 0.5 mm. According to a further aspect, the invention also includes an inductive position measuring mechanism comprising a scanning element and a scale element, the scanning element being arranged opposite and movable relative to the scale element.

[0021] Incidentally, the use of a shielding layer may also be meaningful in the case of scanning elements which work on the basis of optical, capacitive or magnetic principles, in particular for shielding the electronic components of the scanning element from noise fields.

[0022] Advantageous configurations of the invention can be seen from the dependent claims. Further details and advantages of the scanning element according to the invention become apparent from the following description of an exemplary embodiment based on the attached drawings. [Brief description of the drawings]

[0023] [Figure 1] FIG. 2 is an overhead view of a scanning element. [Diagram 2] FIG. 2 is an overhead view of a scale element. [Diagram 3] FIG. 2 is a partial cross-sectional view of a scanning element. [Figure 4] FIG. 2 is a detailed cross-sectional view of a scanning element. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] The invention will be explained by means of a position measuring arrangement with a scanning element 1 according to Figure 1 and a scale element 2 according to Figure 2. In the assembled state of the position measuring arrangement, the scanning element 1 and the scale element 2 are axially spaced apart opposite each other and the scale element 2 is arranged rotatable relative to the scanning element 1 about an axis A, which in Figures 1 and 2 is oriented orthogonally to the drawing plane. The scanning element 1 is used to scan the scale element 2. By means of this position measuring arrangement the circumferential position of the scale element 2, i.e. the angular or rotational position, can thus be determined.

[0025] In Fig. 3, a cross section of a partial region of the scanning element 1 is shown. The scanning element 1 comprises a sensor structure 1.1 with a first conductive layer 1.12 and a second conductive layer 1.14. In the exemplary embodiment shown, the first conductive layer 1.12 and the second conductive layer 1.14 are formed as copper layers with a thickness of about 12 μm. A first insulating layer 1.11 is arranged between the first conductive layer 1.12 and the second conductive layer 1.14. A second insulating layer 1.13 and a third insulating layer 1.15 are also arranged on the sides of the conductive layers 1.12, 1.14, respectively, opposite the first insulating layer 1.11. In the exemplary embodiment shown, the insulating layers 1.11, 1.13, 1.15 each consist of polyimide with a thickness of about 20 μm. In the presented exemplary embodiment, the sensor structure 1.1 is made very thin, having a thickness of about 100 μm, and may therefore be referred to here as a multilayer film, which in principle corresponds to a multilayer (flexible) printed circuit board.

[0026] The first conductive layer 1.12 and the second conductive layer 1.14 are structured in accordance with FIG. 1 such that excitation tracks Sa, Si and reception tracks Ra, Ri are present. In the presented exemplary embodiment, both excitation tracks Sa, Si each comprise a number of parallel excitation conductor paths. The excitation conductor paths or excitation tracks Sa, Si surround the receiving tracks Ra, Ri and run circumferentially around the axis A.

[0027] Each of the receiving tracks Ra, Ri in the presented exemplary embodiment includes four receiving conductors Rax, Rix (see FIG. 1 ), which are arranged with a circumferential offset and thus can provide four phase-shifted signals corresponding to the offset. The receiving conductors Rax, Rix of the respective receiving tracks Ra, Ri run alternately in the first conductive layer 1.12 and in the second conductive layer 1.14 of the sensor structure 1.1 in combination with vias, so that undesired short circuits are avoided at the intersections. The receiving conductors Rax, Rix have a spatially periodic trajectory that is substantially sinusoidally or sinusoidally shaped. The receiving conductors Rix of the inner receiving tracks Ri have a different periodic length than the receiving conductors Rax of the outer receiving tracks Ra. The receiving conductors Rax, Rix are electrically connected with an offset to provide 0° and 90° signals on the one hand and 45° and 135° signals on the other hand. A first position signal can be determined from the 0° and 90° signals, and a second position signal that is redundant to the first position signal can be determined from the 45° and 135° signals.

[0028] In addition to this, the scanning element 1 comprises an electronic circuit with a number of electronic components 1.4 which are only diagrammatically illustrated in Fig. 1. In the presented exemplary embodiment, the electronic circuit also comprises an ASIC chip.

[0029] The signals received by the receiving conductors Rax, Rix are conducted to an electronic circuit, in particular to a region which serves as an evaluation circuit. In addition to this, the scanning element 1 has a connection element 1.7, which in the presented exemplary embodiment is formed as a pin of a plug connector. The connection element 1.7 or the pin is used for connecting to a ground potential GND during operation of the scanning element 1 as specified. Incidentally, the plug connector is intended for connecting a multi-core output cable, which is used, inter alia, for supplying electrical energy to the scanning element and for transmitting signals to the subsequent electronics.

[0030] For mechanical reinforcement, the scanning element 1 has a relatively thick base 1.3 made of metallic material, in particular the base 1.3 can be manufactured from a soft magnetic material. In the presented exemplary embodiment the base 1.3 is made of steel and has a thickness of 1.5 mm.

[0031] As shown in Fig. 3, the shield layer structure 1.2 is arranged between the base 1.3 and the sensor structure 1.1. The shield layer structure 1.2 comprises a dielectric, i.e. electrically insulating, first layer 1.21 and an electrically conductive second layer 1.22. The dielectric first layer 1.21 is applied on the base 1.3 and is a polyimide layer with a thickness of 30 μm in the presented exemplary embodiment. According to Fig. 4, the shield layer structure 1.2 additionally comprises a third layer 1.23 and a fourth layer 1.24. In the course of manufacturing the scanning element 1, the base 1.3 is coated with the dielectric first layer 1.21. Afterwards, the third layer 1.23 is applied on the first layer 1.21, which consists of chromium and has a thickness of only 30 nm. On this third layer 1.23 of chromium, a second layer of copper is applied with a thickness of 200 nm, this second layer being the conductive second layer 1.22. Then on this second layer 1.22, a fourth layer 1.24 is applied, this fourth layer also being of chromium and having a thickness of 30 nm. In the presented exemplary embodiment, the conductive second layer 1.22 and the third and fourth layers 1.23, 1.24 are applied by physical vapor deposition (PVD method). In particular, sputtering or cathodic sputtering methods are carried out here. Then, on this shield layer structure 1.2, an insulating layer 1.15 is applied, then the further components of the sensor structure 1.1. Finally, the mounting of the electronic components 1.4 is carried out.

[0032] The shielding layer structure 1.2 is connected to an electrical conductor 1.6 via a via 1.5. In the presented exemplary embodiment, the electrical conductor 1.6 comprises an ohmic resistor 1.6a and a capacitor 1.6b connected in parallel thereto. The electronic circuit including the electronic component 1.4 is connected to a ground potential GND via the conductor 1.6. For example, the position measuring mechanism can be connected to the subsequent electronics via a plug connector 1.7 (FIG. 1) attached to the scanning element 1. For this purpose, an output cable can be connected to the plug connector 1.7, which has at least one core electrically connected to the ground or earth of the subsequent electronics arranged outside the scanning element 1.

[0033] That is, the conductive second layer 1.22 is electrically connected via the conductor 1.6 to the plug connector 1.7, i.e. to the pin of the plug connector 1.7, which has a ground potential GND as required, which is 0 V in the exemplary embodiment presented. On the one hand, the capacitor 1.6b allows high-frequency noise signals to be conducted away, while on the other hand, the parallel branch with the ohmic resistor 1.6a ensures that the charges can be bled away. This causes the noise energy to be conducted away via the conductor 1.6 (and in the exemplary embodiment presented additionally via the plug connector 1.7 and the connecting cable).

[0034] The third layer 1.23 and the fourth layer 1.24 act as adhesion promoters or as oxygen barriers. In particular, the fourth layer 1.24 prevents oxygen from penetrating beyond the insulating layer 1.15 into the conductive layer 1.22. Oxygen would react with the material of the conductive layer 1.22, here copper. In addition, this reaction would minimize the adhesion properties between the second layer 1.22 and the third layer 1.23 and especially between the second layer 1.22 and the fourth layer 1.24. In particular, the above effects would impair the shielding function.

[0035] The conductive second layer 1.22 is structured by an etching method in such a way that the edge of the second layer 1.22 is offset backwards with respect to the edge of the base 1.3 (see FIG. 1). The conductive second layer 1.22 extends over the entire surface between the base 1.3 and the excitation tracks Sa, Si, the reception tracks Ri, Ra and the electronic components 1.4 of the electronic circuit. In the presented exemplary embodiment, although the third layer 1.23 and the fourth layer 1.24 are made of conductive chromium, an essential part of the shielding effect is achieved by the second layer 1.22 made of copper. This is partly due to the higher electrical conductivity of copper compared to chromium, but especially due to the much larger thickness of the second layer 1.22 (200 nm) compared to the thicknesses of the third layer 1.23 and the fourth layer 1.24 (30 nm each).

[0036] The scanning element 1 is formed in such a way that the electrically conductive second layer 1.22 is arranged electrically insulating with respect to the base 1.3, ie the second layer 1.22 is not electrically connected to the base 1.3.

[0037] In FIG. 2, a scale element 2 having a disk-like shape is shown in a top view. The scale element 2 consists of a support, which in the illustrated exemplary embodiment is made of epoxy resin, on which two graduation tracks 2.1, 2.2 are arranged. The graduation tracks 2.1, 2.2 are ring-shaped and are arranged on the support concentrically with respect to the axis A and with different diameters. The graduation tracks 2.1, 2.2 comprise a graduation structure consisting of a periodic sequence of alternating conductive graduation fields 2.11, 2.21 and non-conductive graduation fields 2.12, 2.22, respectively. As material for the conductive graduation fields 2.11, 2.21, copper was applied to the support in the illustrated example. In contrast, the support was not coated in the non-conductive graduation fields 2.12, 2.22. Due to the configuration with the two graduation tracks 2.1, 2.2, the angular position of the scale element 2 can each be determined in an absolute manner. The outermost graduation track 2.1 of the scale element 2 has a greater number of graduation areas 2.11, 2.12 along the circumference, so that a higher resolution for measuring the angular position can be achieved by means of the graduation areas 2.11, 2.12.

[0038] In the assembled state, the scanning element 1 and the scale element 2 face each other with an axial distance or axial gap (relative to the axis A), so that when the scale element 2 and the scanning element 1 rotate relative to each other, signals that depend on the respective angular position can be generated by inductive effects in the conductor tracks of the receiving tracks Ra, Ri. A prerequisite for the generation of corresponding signals is that the excitation tracks Sa, Si generate an electromagnetic excitation field that alternates over time in the area of ​​the respective scanned graduation structure. In the illustrated exemplary embodiment, the excitation tracks Sa, Si are formed as several single conductor tracks that are pierced by a current in parallel planes. The electronic circuit of the scanning element 1 serves not only as an evaluation element but also as an excitation control element, under the control of which an excitation current is generated or generated, which then pierces the excitation tracks Sa, Si. The excitation tracks Sa, Si are therefore energized by one and the same excitation control element.

[0039] When the excitation tracks Sa, Si are energized, they generate a tubularly or cylindrically oriented electromagnetic field around them. The lines of force of this resulting electromagnetic field run around the excitation tracks Sa, Si, and their direction depends, as is known, on the current direction in the excitation tracks Sa, Si. Eddy currents are induced in the area of ​​the conductive graduation areas 2.11, 2.21, whereby a field modulation is achieved that depends on the angular position. Correspondingly, the relative angular position can be measured by the receiving tracks Ra, Ri. The receiving conductors are arranged in their receiving tracks Ra, Ri in such a way that they provide signals that are phase-shifted by 90°, so that the direction of rotation can also be determined. The signals generated by the receiving tracks Ra, Ri are further processed by an evaluation circuit.

[0040] Although the base 1.3 is made of a metallic material and is normally electrically connected to ground potential during operation of the position measuring mechanism, for example by contact with a grounded metal housing (see FIG. 1), a significant improvement of the measurement signal can be achieved by the additional shielding layer structure 1.2. What is important in this respect is that, on the one hand, a good shielding effect against noise fields is achieved by the shielding layer structure 1.2, but, on the other hand, the shielding layer structure 1.2 must not decisively weaken the desired signal of the inductive position measuring mechanism. With the scanning element 1 according to the invention, a high-quality position signal can be generated. The shielding layer structure 1.2, in particular the electrically conductive second layer 1.22, is electrically connected to the ground potential GND of the circuit of the scanning element 1 and is preferably not electrically connected to the base 1.3, which is grounded during operation, but is electrically insulated and separated from it by the first layer 1.21. [Explanation of symbols]

[0041] 1 Scanning Element 1.1 Sensor structure 1.12 First Conductive Layer 1.14 Second conductive layer 1.15 Insulating Layer 1.2 Shield layer structure 1.21 Dielectric first layer 1.22 Conductive second layer 1.23 The third layer 1.24 The Fourth Layer 1.3 Foundation 1.4 Electronic Components 1.5 Vias 1.6 Conductors / Electrical Conductors 1.6a ohm resistor 1.6b capacitor 1.7 Connecting elements / plug connectors 2 Scale elements 2.1 Scale Track 2.11 Conductive Graduation Area 2.12 Non-conductive graduation areas 2.2 Scale Track 2.21 Conductive Graduation Area 2.22 Non-conductive graduation areas A-axis GND Ground potential Ra, Ri received track Rax, Rix receiving conductor Sa, Si excitation track

Claims

1. A scanning element (1) for an inductive position measuring mechanism, - Includes excitation tracks (Sa, Si) and receiving tracks (Ri, Ra), - Having a base (1.3) made of a metal material, - At least one - A first layer (1.21) having dielectric properties and - Including a second conductive layer (1.22), Including a shield layer structure (1.2), The shield layer structure (1.2) is Between the base (1.3) and the receiving track (Ri, Ra) and / or A scanning element (1) is positioned between the base (1.3) and the excitation track (Sa, Si).

2. The scanning element (1) according to claim 1, wherein the first layer (1.21) has a thickness of less than 1 mm.

3. The scanning element (1) according to claim 1 or 2, wherein the second layer (1.22) of the shield layer structure (1.2) is formed by physical vapor phase growth.

4. The scanning element (1) according to claim 1 or 2, wherein the shield layer structure (1.2) has a third layer (1.23) disposed between the dielectric first layer (1.21) and the conductive second layer (1.22).

5. The scanning element (1) according to claim 1 or 2, wherein the scanning element (1) has a multilayer sensor structure (1.1) including a first conductive layer (1.12) and a second conductive layer (1.14), and at least one excitation track (Sa, Si) and at least one receiving track (Ri, Ra) are generated by the structuring of the conductive layers (1.12, 1.14).

6. The scanning element (1) according to claim 5, wherein an insulating layer (1.15) is disposed between the second conductive layer (1.14) and the shield layer structure (1.2), and a fourth layer (1.24) is disposed between the insulating layer (1.15) and the second layer (1.22).

7. The scanning element (1) according to claim 1 or 2, wherein the shield layer structure (1.2) has a third layer (1.23) and a fourth layer (1.24), and the second layer (1.22) of the shield layer structure (1.2) is disposed between the third layer (1.23) and the fourth layer (1.24).

8. Scanning element (1) according to claim 1 or 2, wherein the shield layer structure (1.2) has a third layer (1.23) and / or a fourth layer (1.24), the second layer (1.22) of the shield layer structure (1.2) is adjacent to the third layer (1.23) and / or the fourth layer (1.24), and the material of the third layer (1.23) and / or the fourth layer (1.24) contains chromium.

9. The scanning element (1) according to claim 1 or 2, wherein the first layer (1.21) of the layer structure (1.2) has a thickness of at least 2.5 μm.

10. The scanning element (1) according to claim 1 or 2, wherein the scanning element (1) includes at least one electronic component (1.4), and the shielding layer structure (1.2) is disposed between the base (1.3) and at least one of the electronic components (1.4).

11. The scanning element (1) according to claim 10, wherein at least one of the electronic components (1.4) is used to evaluate the signal received by the receiving track (Ri, Ra).

12. The scanning element (1) according to claim 10, wherein at least one of the electronic components (1.4) is used to generate an excitation current that can be introduced into the excitation track (Sa, Si).

13. The scanning element (1) according to claim 1 or 2, wherein the scanning element (1) includes at least one electronic component (1.4) assigned to an electronic circuit, the circuit is electrically connected to a connecting element (1.7) used as a terminal for ground potential (GND) as specified, and the second layer (1.22) is electrically connected to the connecting element (1.7).

14. The scanning element (1) according to claim 13, wherein the second layer (1.22) is electrically connected to the connecting element (1.7) via a conductor (1.6), and an ohm resistor (1.6a) and a capacitor (1.6b) are connected in parallel within the conductor (1.6).

15. An inductive position measuring mechanism comprising a scanning element (1) and a scale element (2) according to claim 1 or 2, wherein the scanning element (1) is positioned facing the scale element (2) and is movable relative to the scale element (2).

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