Patent Application
20240077337
The present application claims priority to Application No. 22194068.7, filed in the European Patent Office on Sep. 6, 2022, which is expressly incorporated herein in its entirety by reference thereto.
The present invention relates to a sensing element, e.g., for an inductive position measuring device for determining a relative position between a scale element and the sensing element, and to a position measuring device that includes such a sensing element.
Inductive position measuring devices are used, for example, as angle measuring devices to determine the angular position of machine parts that can be rotated relative to one another. In inductive position measuring devices, excitation tracks and receiving tracks, for example, in the form of conductive paths, are often applied to a common, usually multilayer, printed circuit board, which is firmly connected, for example, to a stator of an angle measuring device. Opposite this printed circuit board is a scale element on which graduation structures are applied and which serves as the rotor of the angle measuring device. When a time-varying electrical excitation current is applied to the excitation conductive paths of the receiving track, signals dependent on the angular position are generated in receiving conductive paths of the receiving track during the relative rotation between rotor and stator. These signals are further processed in an evaluation electronic system.
Such inductive position measuring devices are often used as measuring instruments for electrical drives to determine the relative movement or the relative position of corresponding machine parts. In this instance, the generated angle position values are fed to a downstream electronic system for controlling the drives via a corresponding interface arrangement.
Furthermore, inductive position measuring devices are also frequently used for direct measurement of longitudinal displacements along an axis. The same measuring principle is used as for the angle measuring devices mentioned above, but the receiver coils and the graduation structure extend along the straight-line axis.
An inductive angle measuring device is described in European Patent Document No. 3 702 737 and U.S. Patent Application Publication No. 2020/0278220, which has a substrate made of a metal material.
Example embodiments of the present provide an inductive position measuring device that is accurate and inexpensive to produce.
According to example embodiments, a sensing element, which is, for example, adapted for an inductive position measuring device for measuring a position along a measuring direction, includes at least one excitation track and at least one receiving track. The excitation track may include one or more excitation conductive paths, and the receiving track may include, for example, a first receiving conductive path and, optionally, a second receiving conductive path. Furthermore, the sensing element includes a substrate produced from a metallic material. In addition, the sensing element includes a shield layer structure having dielectric first layer(s) and electrically conductive second layer(s). The shield layer structure is arranged—with respect to a direction perpendicular to the measuring direction—between the substrate and the receiving track. Alternatively or supplementally, the shield layer structure is arranged between the substrate and the excitation track.
The measuring direction may be a linear direction, a circumferential direction, or a tangential direction. The excitation track and the receiving track extend, for example, along the measuring direction.
According to example embodiments, the first layer has a thickness of less than 1 mm, e.g., less than 0.50 mm, less than 0.10 mm, etc.
According to example embodiments, the electrically conductive second layer of the shield layer structure is applied by a physical vapor deposition, e.g., on the dielectric first layer of the shield layer structure.
According to example embodiments, the shield layer structure also has a third layer and a fourth layer. The third layer may be arranged between the dielectric layer and the electrically conductive coat of the shield layer structure.
According to example embodiments, the sensing element includes a multilayer sensor structure that corresponds to a structure of a multilayer printed circuit board or conductive foil. The position of the sensing element should therefore be understood as a (structured) layer. The sensor structure includes at least a first electrically conductive layer and a second electrically conductive layer. The excitation track and the receiving track are produced by structuring the electrically conductive layers. Consequently, the sensor structure includes structured conductive layers in which the excitation track and the receiving track are arranged. For example, the sensor structure has exactly two electrically conductive layers in which the excitation track and the receiving track are arranged.
According to example embodiments, an insulating layer is arranged between the second electrically conductive layer and the shield layer structure. In addition, a fourth layer may be arranged between the insulating layer and the electrically conductive layer. For example, the electrically conductive second layer of the shield 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 include chromium. Thus, the third and fourth layers are made of a material that has a comparatively high electrical conductivity. However, the third layer and the fourth layer together have less than 50% of the thickness of the electrically conductive layer.
According to example embodiments, the dielectric first layer of the shield layer structure has a thickness of at least 2.5 μm, e.g., at least 5 μm, at least 20 μm, etc.
According to example embodiments, the sensing element includes at least one electronic component, and the shield layer structure or the electrically conductive second layer is arranged between the substrate and the electronic component. Accordingly, the shield layer structure or the electrically conductive second layer also extends below the area of the electronic component.
For example, the electronic component is adapted to evaluate signals recorded by the receiving track with regard to the position information contained therein. Thus, the signals that can be generated by the receiving track can be further processed with the aid of the electronic component, which, for example, forms an evaluation circuit. The sensing element may include several electronic components that are electrically connected to form an (evaluation) circuit. For example, the connections are arranged as conductive paths that extend in the correspondingly structured first and second layers.
According to example embodiments, the electronic component is adapted to generate or produce an excitation current that can be conducted into the excitation track. The excitation track may thus be energized with an excitation current, which has a time-varying current intensity (alternating current or mixed current). The excitation current may be generated with the aid of the electronic component, which means that it can be shaped by the electronic component. Since there is a physical relationship between the current and the voltage, the same consideration can be made for the excitation voltage.
The electronic component may be mounted on the side of the sensing element opposite the substrate, so that the sensor structure and the electronic component are arranged on the same side with respect to the substrate.
For example, the electronic circuit can be connected via a line to a ground potential (electronic ground) and the electrically conductive second layer of the shield layer structure is electrically connected to the line. The line may include a resistor and a capacitor that are connected in parallel. The shield layer structure, e.g., its conductive second layer, is, for example, planar without interruptions. The electrically conductive second layer of the shield layer structure is, for example, connected to the line by a via. For example, the line may be electrically connected to a connection element arranged as a connection for the ground potential. The second layer is electrically connected to the connection element. A connection element should be understood, for example, as an element of a connector, i.e., a connector element, or a soldered connection.
In contrast, the substrate may be mounted, for example, on an electrically conductive housing, such as a motor housing, so that the substrate is grounded through the motor housing. For example, the substrate and the electrically conductive second layer of the shield layer structure are not directly electrically connected to each other, e.g., are not grounded to each other.
The shield layer structure is used to shield interference fields so that no interference occurs in the receiving track and/or in the excitation track and, if necessary, in the electronic component. At the same time, the shield layer structure is configured such that useful signals can still be received through it with the required strength, so that accurate position determination is possible.
For example, the substrate has a thickness of more than 0.5 mm.
According to example embodiments, an inductive position measuring device includes the sensing element and a scale element, in which the sensing element is arranged opposite the scale element and is movable relative thereto.
The use of a shield layer may also be beneficial for sensing elements that operate according to an optical, capacitive, or magnetic principle, e.g., for shielding electronic components of the sensing element from interference fields.
Further features and aspects of example embodiments of the present invention are described in more detail below with reference to the appended schematic Figures.
A position measuring device includes a sensing element 1, such as that illustrated in
The first electrically conductive layer 1.12 and the second electrically conductive layer 1.14 are configured such that excitation tracks Sa, Si and receiving tracks Ra, Ri are present, as illustrated in
For example, both excitation tracks Sa, Si include several parallel excitation conductive paths. The excitation conductive paths or the excitation tracks Sa, Si enclose the receiving tracks Ra, Ri and extend along the circumferential direction around the axis A.
For example, each of the receiving tracks Ra, Ri includes four receiving conductive paths Rax, Rix (see, e.g.,
In addition, the sensing element 1 has an electronic circuit with a plurality of electronic components 1.4, illustrated schematically in
The signals received by the receiving conducting paths Rax, Rix are routed to the electronic circuit, e.g., to an area that serves as the evaluation circuit.
In addition, the sensing element 1 has a connection element 1.7, e.g., arranged as a pin of a connector. The connection element 1.7 or the pin is intended for connection to the ground potential GND during operation of the sensing element 1. The connector is also intended for coupling a multi-core output cable and is used, for example, to supply the sensing element with electrical energy and to transmit signals to a subsequent electronic system.
The sensing element 1 has a comparatively thick substrate 1.3 for mechanical reinforcement, including a metallic material. For example, the substrate 1.3 may be produced from a soft magnetic material. The substrate 1.3 may be made of steel and may have a thickness of 1.5 mm.
As illustrated in
The shield layer structure 1.2 is connected to an electrical line 1.6 by a via 1.5. As illustrated in
The electrically conductive second layer 1.22 is electrically connected via the line 1.6 to the connector 1.7 or to a pin of the connector 1.7, which has the ground potential GND, e.g., the ground potential GND is 0 V. The capacitor 1.6b can dissipate high-frequency interference signals, and the parallel connection of the ohmic resistor 1.6a provides that charges can be dissipated. Thus, interference energy is dissipated via the line 1.6 (e.g., also via the connector 1.7 and the connecting cable).
The third layer 1.23 and the fourth layer 1.24 are arranged as adhesion promoters or as oxygen barriers. For example, the fourth layer 1.24 prevents oxygen from penetrating through the insulating layer 1.15 to the electrically conductive layer 1.22. Oxygen would react with the material of the electrically conductive layer 1.22, e.g., copper. Moreover, this reaction would lead to a minimization of 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. The shielding properties would be impaired, e.g., by the aforementioned effects.
The electrically conductive second layer 1.22 is structured by an etching process such that the edge of the second layer 1.22 is set back with respect to the edge of the substrate 1.3 (see, e.g.,
The sensing element 1 is configured such that the electrically conductive second layer 1.22 is arranged electrically isolated from the substrate 1.3, i.e., the second layer 1.22 is not electrically connected to the substrate 1.3.
As illustrated in
In the assembled state, the sensing element 1 and the scale element 2 are opposite one another with an axial distance (relative to the axis A) or with an axial air gap, so that when there is a relative rotation between the scale element 2 and the sensing element 1, a signal depending on the respective angular position can be generated in each of the conductive paths of the receiving tracks Ra, Ri by induction effects. A prerequisite for the formation of corresponding signals is that the excitation tracks Sa, Si generate a time-varying electromagnetic excitation field in the area of the respective sensed graduation structures. For example, the excitation tracks Sa, Si are arranged as a plurality of planar-parallel current-carrying individual conductive paths. The electronic circuit of the sensing element 1 operates not only as an evaluation element, but also as an excitation control element under whose control the excitation current is generated or produced, which flows through the excitation tracks Sa, Si. Thus, the excitation tracks Sa, Si are supplied with current by one and the same excitation control element.
If the excitation tracks Sa, Si are supplied with current, a tubular or cylindrical electromagnetic field is formed around them. The field lines of the resulting electromagnetic field extend around the excitation tracks Sa, Si, and the direction of the field lines depends on the direction of the current in the excitation tracks Sa, Si. Eddy currents are induced in the area of the conductive partial areas 2.11, 2.21, so that a modulation of the field is achieved which is dependent on the angular position. Accordingly, through the receiving tracks Ra, Ri, the relative angular position can be measured. The receiving conductive paths are arranged within their receiving track Ra, Ri such that they each provide signals 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.
Although the substrate 1.3 includes a metallic material that is electrically connected to the ground potential during operation of the position measuring device (see, e.g.,
| Number | Date | Country | Kind |
|---|---|---|---|
| 22194068.7 | Sep 2022 | EP | regional |
