WO2023147851A1

WO2023147851A1 - Transmitter element for a position sensor system

Info

Publication number: WO2023147851A1
Application number: PCT/EP2022/052432
Authority: WO
Inventors: Frank Baumgärtner; Jan Bremer; Thomas THÖLKE
Original assignee: Schunk Sintermetalltechnik Gmbh
Priority date: 2022-02-02
Filing date: 2022-02-02
Publication date: 2023-08-10

Abstract

The invention relates to a transmitter element (1) for a position sensor system (51), said transmitter element being used to allow the current orientation of a rotor shaft in a rapidly rotating electric machine to be ascertained for example. The transmitter element has a main part (3) and multiple sub-surface layers (5). The main part (3) consists of particles which are sintered together. Each of the sub-surface layers (5) is arranged on a main part (3) transmitter surface (7) which is oriented towards the position sensor (53). Adjacent sub-surface layers (5) are mutually spaced at least in some regions. Each of the sub-surface layers (5) has a higher electric conductivity than the main part (3) for electric currents which are induced by an electromagnetic alternating field that is emitted towards the transmitter surface (7) of the main part (3) and has a frequency of more than 0.2 MHz. The transmitter element is inexpensive to produce while still allowing a high degree of detection precision for the position sensor system.

Description

Sensor element for a position sensor system

FIELD OF THE INVENTION

The present invention relates to a transmitter element for a position sensor system. Furthermore, the invention relates to a position sensor system with such a transmitter element and an electric machine with such a position sensor system.

BACKGROUND OF THE INVENTION

Position sensors are used to determine relative positions between two components. A transmitter element is typically arranged on one of the components, whereas a position sensor is arranged on the other of the components. The transmitter element is sometimes also referred to as a target. The position sensor is designed to detect a position and/or orientation of the transmitter element relative to its own position or orientation. Alternatively, the position sensor can detect changes in such relative positions or relative orientations over time. Depending on the area of use, the position sensor system can be configured to determine translatory and/or rotatory positions or changes in position. A rotary position corresponds to an orientation and a rotary position change corresponds to a change in orientation. A position sensor system can be used in particular to determine a current orientation of a rotor relative to a stator or to a stationary reference position in an electrical machine such as a motor or a generator. Up-to-date information about the orientation of the rotor can be required in particular in order to be able to control the electrical machine correctly.

A large number of different position sensor systems have been developed for a wide variety of applications, in particular for determining a rotor orientation in an electrical machine. A position sensor system in which there is direct mechanical contact between a position sensor and a component that is moved relative to this position sensor usually suffers from wear. Position sensor systems have therefore been developed, with the aid of which a relative position or relative orientation between the position sensor and the transmitter element can be detected without contact.

For example, DE 19 738 836 A1 describes an inductive angle sensor with a compact design, high resolution and high insensitivity to manufacturing and installation tolerances. EP 2 446 228 B1 describes an angular position sensor which uses a first electrical track and a second electrical track as well as a movable magnetic target which is connected to a rotating object in order to determine a current angular position of the rotating object. In the angle sensors described, alternating electromagnetic fields are used to generate electric currents in the form of eddy currents in the transmitter element. Physical properties in the transmitter element vary depending on the induced currents, which in turn are dependent on a current relative position between the transmitter element and the inducing sensor. Accordingly, by measuring the changing physical properties, conclusions can be drawn about the current relative position of the encoder element and thus about the current relative position of the rotating object mechanically coupled to it. Conventionally, a transmitter element was typically used in a position sensor system, and high demands were placed on it. For example, the encoder element had to be manufactured with high precision in order to be able to fix it precisely to a rotating object on the one hand and to be able to precisely determine its current position or orientation using the position sensor on the other hand.

In the case of an embodiment of a transmitter element, with the aid of which a position sensor system is intended to be able to determine in particular a current orientation of a rotating rotor in an electrical machine, it must be taken into account that such a rotor rotates at very high speeds of often more than 10,000 revolutions per minute (rpm), in some cases even up to 30,000 rpm or more. Accordingly, considerable centrifugal forces can act on the encoder element coupled to the rotor. The encoder element must therefore be suitably dimensioned and designed to be stable in order to be able to withstand such centrifugal forces during operation of the electrical machine.

Conventionally, the encoder element is usually manufactured from a solid metal material by machining. On the one hand, this enables very precise shaping, but on the other hand, it requires a high manufacturing effort and high costs both because of the solid material blank to be provided and because of material losses that unavoidably occur during machining.

SUMMARY OF THE INVENTION AND ADVANTAGEOUS EMBODIMENTS

There may therefore be a need for a transmitter element for a position sensor system that can be produced simply and inexpensively and that nevertheless allows for sufficient precision when determining the position. Furthermore, there may be a need for a position sensor system equipped with such a transmitter element. In addition, there may be a need for an electric machine in which to help a current orientation of a rotor can be determined using the position sensors described.

Such a need may be met by the subject-matter of any of the independent claims. Advantageous embodiments are defined in the dependent claims and the following description and illustrated in the figures.

A first aspect of the invention relates to a transmitter element for a position sensor system, which has a base body and a plurality of partial surface layers. The base body consists of particles sintered together. Each of the partial surface layers is arranged on a transmitter surface of the base body to be aligned towards the position sensor. Adjacent partial surface layers are spaced apart from one another, at least in partial areas. Each of the partial surface layers has a higher electrical conductivity than the base body for electrical currents which are induced by an alternating electromagnetic field radiated towards the transmitter surface of the base body with a frequency of more than 0.2 MHz.

According to a second aspect of the invention, a position sensor system is described which has a position sensor and a transmitter element according to an embodiment of the first aspect of the invention.

According to a third aspect of the invention, an electrical machine is described which has a stator, a rotor and a position sensor system according to an embodiment of the second aspect of the invention. In this case, the encoder element is mechanically coupled to the rotor. The position sensor is configured to determine a position, in particular an angular position, of the encoder element relative to the stator. Briefly and roughly summarized and without restricting the invention in any way, a basic idea of the idea described here can be seen in forming a transmitter element for a position sensor system using a sintered component made of particles sintered together instead of machining a solid metal material. Such sintered components can be produced very inexpensively and with sufficient precision for many applications by pressing a raw material in the form of a particle-containing powder in a suitably designed mold and then sintering the blank formed in this way at elevated temperature.

It has been observed that a transmitter element that was manufactured as a simple sintered component can be further improved with regard to the accuracy of a position detection when used in a position sensor system. In particular, it was recognized that signals that a position sensor determines in a position sensor system in which the conventionally machined encoder element is replaced by a sintered component can be similarly accurate or even more accurate with a suitable configuration of the sintered component and/or similarly insensitive to any slight incorrect positioning of the encoder element can react to a component such as a shaft of a rotor of an electrical machine, as is the case with position sensors with conventional, machined encoder elements.

In particular, it has been observed that the precision of the position determination can be significantly increased when using an encoder element manufactured as a sintered component if several special layers are formed on its surface facing the position sensor, which are referred to herein as partial surface layers and which are compared to an underlying part of the transmitter element have a higher electrical conductivity, in particular in the event that currents are induced therein by high-frequency electromagnetic alternating fields. The partial surface layers are arranged on a base body sintered together from particles in such a way that they form a pattern in which adjacent partial surface layers are spaced apart from one another at least in partial areas.

A sensor element in which the base body can be produced simply and inexpensively as a sintered component on the one hand and in which partial surface layers with increased electrical conductivity can be produced in a simple manner on the other hand enables a high measuring accuracy of a position sensor system equipped with it.

Possible details on configurations of the encoder element proposed here and the position sensor system equipped therewith or the electric machine equipped therewith are explained below.

The base body of the transmitter element is designed as a sintered component and is composed of particles sintered together. In particular, the particles can be metal particles. Metals, metal mixtures or metal alloys such as Fe, FeCu, FeP, FeMo, Fe(Mo, Cu, Ni), FeCrMo, which can also include carbon, or stainless steel ferritic (e.g. 430), austenitic (e.g. 316L ) or duplex. Aluminum, copper or bronze particles can also be used. The particles can typically have dimensions in a range of between 0 and 300 μm, for example with an average grain size of 120 to 150 μm. The particles can be pressed together. Typically, pressures in a range of up to 1000 MPa, particularly preferably in the range from 600 to 750 MPa, can be used here. For this purpose, the particles can be filled into a mold provided and then pressed in the mold in order to give the blank produced therefrom a desired geometry. The blank is then heated to an elevated temperature, typically in the range above 1100°C in the case of iron-based materials, to sinter it. Through such sintering, the pressed particles enter into a mechanically resilient material connection with one another. In this way, the base body can achieve high mechanical strength. The partial surface layers are arranged in a region of the transmitter element which, when the transmitter element is arranged in a position sensor system, is aligned towards the position sensor or is opposite a sensor surface of the position sensor. In this case, the partial surface layers are arranged on a surface of the base body, which is referred to herein as the encoder surface and which is accordingly directed towards the position sensor.

In this case, a plurality of partial surface layers are provided on the base body, these being spaced apart from one another at least in partial areas. The adjacent partial surface layers are arranged next to one another, that is to say not necessarily orthogonally, but at a distance from one another laterally. Surface areas that are not covered by one of the partial surface layers can thus remain on the donor surface of the base body between adjacent partial surface layers.

The partial surface layers are specifically designed in such a way that electrical currents, in particular eddy currents, which are generated in the partial surface layers by irradiation of an alternating electromagnetic field of high frequency, experience a higher electrical conductivity there than would be the case if the same electrical currents were induced in the base body . In this case, the increased electrical conductivity should apply to alternating currents which are irradiated by alternating electromagnetic fields with a frequency of at least 0.2 MHz, preferably at least 1 MHz and more preferably at least 2 MHz.

Such high-frequency electromagnetic alternating fields are typically generated by position sensors in position sensor systems, with the aid of which the angular positions of a very rapidly rotating rotor in an electrical machine are to be determined. It must be taken into account that high-frequency electrical alternating currents in electrically conductive materials only flow in a layer very close to the surface due to the so-called skin effect. In other words, high-frequency electromagnetic alternating fields have only a small penetration depth in electrically conductive material. The thickness of the layer in which the high-frequency Alternating currents flow depends on their frequency and typically decreases with increasing frequency. At the high frequencies mentioned, such a layer thickness can be less than 1 mm or even less than 0.1 mm.

It is assumed that the higher electrical conductivity for high-frequency alternating currents in the partial surface layers compared to the base body contributes to the fact that a position sensor system equipped with such a transmitter element can be used to determine relative positions with high accuracy and/or less sensitivity to misalignments.

According to one embodiment, the partial surface layers differ from the base body with regard to a material forming them and/or with regard to a material density prevailing in them.

The partial surface layers can in particular be formed with a material which has a high conductivity for electrical direct currents and/or for high-frequency electrical alternating currents, in particular has a higher conductivity than a material used for the base body.

Alternatively or additionally, the material of the partial surface layers can have a different microscopic and/or macroscopic structure than that of the base body. For example, the base body can have a large number of grain boundaries and/or pores between adjacent particles due to its design as a sintered component, whereas the partial surface layers can be provided with fewer or no such grain boundaries and/or pores. Forming the partial surface layers with different materials and/or different porosities than in the base body generally also means that the material density in the partial surface layers differs from that in the base body.

The differences mentioned can contribute to the desired increased electrical conductivity for alternating currents within the partial surface layers and in this way increase a detection accuracy of the position sensor system equipped with the transmitter element.

According to one embodiment, the partial surface layers are each adhered as a separate layer to the encoder surface.

In other words, each of the partial surface layers can first be provided as a separate component and then connected to the base body on its donor surface. The partial surface layers can thus be produced in advance and then attached to the base body. As a result, the partial surface layers can be manufactured using suitable manufacturing processes that may be specially adapted for this purpose, with the properties of the base body not having to be taken into account. The partial surfaces can be provided, for example, as a thin film or thin platelets.

According to one embodiment, the partial surface layers are each adhered to the donor surface by means of an adhesive layer.

The adhesive layer may be formed with an adhesive. The adhesive layer can cover a surface of a partial surface layer that faces the donor surface of the base body over the entire surface or in partial areas. The adhesion layer is typically thinner than the partial surface layer. With the aid of the adhesive layer, the partial surface layers can be fixed to the base body in a simple, reliable and/or mechanically resilient manner.

According to one embodiment, the partial surface layers are each attached to a carrier film.

The carrier film can be made of any material. In particular, the carrier foil can be designed as a plastic foil, metal foil or the like. The carrier foil can be thinner or thicker than the partial surface layers. Each of the partial surface layers can be attached to its own carrier film. Alternatively several partial surface layers can be attached to a common carrier film. Since the partial surface layers are each attached to a carrier film, they can be produced in a simple manner. For example, the partial surface layers can be deposited onto the carrier film from a liquid phase or a gas phase using industrially established layer formation processes.

Alternatively, however, it is also conceivable to provide the partial surface layers without a carrier film, i.e. as self-supporting layers.

According to one embodiment, the partial surface layers are each formed as a full-area layer of an electrically conductive material, in particular of a metal, preferably with copper or aluminum.

In other words, each of the partial surface layers can be formed as an inherently homogeneous layer. The partial surface layer can have a homogeneous layer thickness and/or a homogeneous volume. As a result, an electrical conductivity within the partial surface layer can also be homogeneous, in particular isotropic. This can have an advantageous effect on the measuring accuracy of the position sensor system equipped with the transmitter element. In this case, the partial surface layer is preferably formed with a material that is electrically very well conductive. Metals, in particular metals with high conductivity such as, for example, copper or aluminum, can preferably be used for this purpose. Alternatively, however, a configuration of the partial surface layers with other highly conductive materials, for example a carbon layer, also appears conceivable.

According to another embodiment, the partial surface layers are each formed as a woven fabric or nonwoven fabric made of electrically conductive fibers, in particular carbon fibers or metal fibers.

Such partial surface layers formed with fibers are typically not homogeneous, in particular not isotropic, but can nevertheless have advantageous electrical properties in order to increase the detection accuracy of the position sensor system increase. Furthermore, such fiber-containing partial surface layers can be specifically designed with a fiber orientation and/or applied to the base body in order to impart desired electrical properties and/or mechanical properties to them. An electrically conductive fabric or fleece can also be provided easily and inexpensively.

According to an alternative embodiment, the partial surface layers are pressed onto the sensor surface as small metal plates, in particular as small copper plates.

Metal flakes can be produced in advance with a desired geometry and/or thickness, for example by pressing and/or stamping metal sheets. Manufacturing the metal plates can be very simple here. In addition, the metal plates can have good electrical properties, which improve the detection accuracy of the position sensors. The metal plates can be suitably positioned on the surface of the base body and then pressed onto the base body. This can result in a mechanically resilient connection between the metal plates and the base body. In particular, material of the small metal plate can be pressed into pores in the base body and thus ensure a microscopically form-fitting connection between the two components. Such a mechanically resilient connection can be produced in particular with the help of copper plates, which allow a very strong connection to the base body due to their mechanical properties.

According to one embodiment, material of the partial surface layers is infiltrated at least near the surface in pores in the base body.

Since the material of the partial surface layers engages in pores of the base body formed as a sintered component, a mechanically particularly resilient connection can be brought about between the partial surface layers and the base body. For example, a partial surface layer can be produced on the base body by applying material of the partial surface layer directly to the base body. An intermediate layer, in particular an adhesive layer and/or a carrier layer, can optionally be dispensed with.

Material of the partial surface layer can, for example, be applied from a liquid or viscous phase to the surface of the base body and flow into pores in the base body before it then dries or hardens. For example, flowable material may be brushed, sprayed, painted, printed, spun-bonded, or otherwise applied to the donor surface. Conductive material can also be dissolved in a solution or taken up in a suspension and deposited from this on the surface of the base body, for example galvanically or by electroless plating.

Alternatively, material of the partial surface layer can be applied from a gaseous phase to the surface of the encoder, in particular vapor-deposited or sputtered on. Gas phase deposition processes, in particular CVD processes (Chemical Vapor Deposition) or PVD processes (Physical Vapor Deposition) can be used for this purpose. In general, in such deposition processes, some of the deposited material inevitably infiltrates pores in the base body.

As a further alternative, conductive material can be applied as a solid and then liquefied, in particular melted, in order to be able to flow into the pores of the base body. For example, a metal flake, in particular a copper flake or aluminum flake, can be applied to the surface of the encoder and then partially or completely melted, so that its liquefied material can infiltrate pores on the surface of the encoder.

According to one embodiment, the partial surface layers are formed as near-surface compacted layer areas on the base body. In general, the base body has a certain porosity due to its composition of particles. In the case of the base body originally produced as a sintered component, the porosity is generally largely homogeneous over the entire volume of the base body. However, in a post-processing step or through targeted measures when pressing the particles to form the basic body blank, a layer area close to the surface of the basic body can be specifically compacted in order to reduce the porosity there in this way. For this purpose, the layer area close to the surface can be machined in a targeted manner, for example, in order to locally reduce the number and/or size of pores present there. Alternatively or additionally, additional material can be introduced into the pores in the layer area near the surface in order to compact the layer area. Material with good electrical conductivity, in particular metal, can preferably be additionally introduced. Due to the densification, the layer area close to the surface typically has an increased electrical conductivity and can therefore act as a highly conductive partial surface layer.

According to one embodiment, the base body has a higher porosity than the partial surface layers.

In general, a porosity that prevails in a volume of material to be considered is understood to mean a ratio of a volume of pores that are present in the volume of material to the total volume of the volume of material. The more pores there are and the larger the pores, the higher the porosity in the volume of material.

In the case of the transmitter element presented here, the porosity within the base body sintered from particles should generally be greater than the porosity in the partial surface layers. As already described in detail above, this can be brought about, for example, by the partial surface layers being able to be formed as full-volume layers, ie having essentially no pores, or the existing pores in the base body initially provided are specifically infiltrated close to the surface with material of the partial surface layers or the layers close to the surface are otherwise compacted.

For example, the porosity in the base body can be more than 5%, preferably more than 15%, whereas the porosity in the partial surface layers is less than 10%, preferably less than 5%, or is equal to 0. In particular, the porosity in the base body can be at least 10%, preferably at least 20%, at least 30% or even at least 50% greater than in the partial surface layers.

According to one embodiment, the base body has a greater thickness than the partial surface layers.

In general, the base body serves, among other things, to provide the transmitter element with sufficient mechanical strength in order to be able to withstand the forces acting on it, in particular any high centrifugal forces that may be acting. In addition, the base body is usually used to be able to attach the transmitter element to a component whose position is to be determined. For this purpose, the base body generally has macroscopic dimensions, in particular a thickness of at least 1 mm and usually even several millimeters. The partial surface layers, on the other hand, are intended, inter alia, to impart desired electrical properties to the transmitter element, in particular high electrical conductivity on its transmitter surface. To this end, it may be sufficient to form the part surfaces with a very small thickness, in particular a thickness of less than 1 mm, less than 0.5 mm or even less than 0.1 mm. For example, the thickness of the base body can be more than 50%, more than 100% or even more than 500% greater than the thickness of the partial surface layers.

According to one embodiment, the partial surface layers are planar.

In other words, the partial surface layers can be in the form of planar, ie non-curved, planar structures. opposites In this case, main surfaces of a partial surface layer can run parallel to one another, ie the partial surface layer can have a uniform thickness along its entire extent. This can simplify production of the partial surface layers and/or have a positive effect on their electrical properties.

According to one embodiment, the partial surface layers are flat at least on a surface directed away from the base body.

In other words, at least that surface of a partial surface layer that is directed away from the base body and thus toward the position sensor when used in the position sensor system should preferably be flat. A gap between this surface of the partial surface layer and an opposite surface on the position sensor can thus have a uniform thickness. Among other things, this can positively influence a detection accuracy of the position sensor system.

According to one embodiment, the partial surface layers are arranged in a common plane.

In other words, all partial surface layers of the transmitter element can preferably be flat and arranged laterally next to one another. Laterally adjacent partial surface layers are spaced apart from one another at least in regions, but can also directly adjoin one another in partial regions. The arrangement of the partial surface layers in a common plane can make it possible to align the sensor element in such a way that its partial surface layers can all be aligned parallel to a planar surface of the position sensor. This allows a position detection accuracy to be positively influenced.

According to one embodiment, the base body has a rotationally symmetrical outer contour. A base body with a rotationally symmetrical outer contour can be mounted in a simple manner with respect to an axis of rotation running through the center of the base body, without having to compensate for forces that would otherwise arise due to imbalances. In particular, the outer contour of the base body should preferably have rotational symmetry. The rotational symmetry can be of the nth order (n=1, 2, 3, . . . ), where an even rotational symmetry can be preferred. Away from an outer circumference, in particular near a center, the base body can have structures such as centering recesses, which have no symmetry or a different symmetry than the outer contour of the base body. The base body can, for example, have a cylindrical shape or have a circular outer contour. Alternatively, the base body can have a polygonal outer contour, for example.

According to one embodiment, the partial surface layers are arranged rotationally symmetrically on the base body.

The provision of the partial surface layers in a rotationally symmetrical arrangement can also contribute to avoiding imbalances when the transmitter element rotates as far as possible.

In particular, according to one embodiment, the base body can have a number n of partial regions and overall have a rotational symmetry of the nth order. In this case, one of the partial surface layers is arranged on each of the partial regions.

A body with a rotational symmetry of the nth order is imaged onto itself when rotated about an axis of rotation by an angle of (360°/n). In addition to avoiding imbalances, the arrangement of the partial surface layers on n partial areas of the base body, which are arranged with a rotational symmetry of the nth order, is advantageous in order to be able to draw conclusions about a current orientation of the encoder element based on eddy currents induced in the partial surface layers. According to one embodiment, the main body has a main body base and a plurality of carrier areas protruding from the main body base in a direction toward the position sensor. The encoder surface is arranged on the carrier areas.

In other words, the base body can have a base area. This basic body base can preferably be designed to be rotationally symmetrical, in particular cylindrical. A plurality of support areas protrude from the main body base in a direction parallel to the axis of rotational symmetry. For example, 2, 3, 4, 5, 6 or more carrier areas can be provided. The carrier areas can be arranged equidistantly, in particular at equal angular distances, on the base body. The carrier areas can have an essentially planar configuration, i.e. have a small thickness. A surface of the carrier areas directed away from the base body can form the transmitter surface of the transmitter element. This transmitter surface is preferably flat and plane-parallel to an opposite surface of the base body at the base of the base body. One of the partial surface layers can then be arranged on each of the protruding carrier areas. The distribution of the partial surface layers over a plurality of carrier areas protruding axially from the main body base can improve electrical properties of the transmitter element and, as a result, a detection accuracy of the position sensor system.

According to a specific embodiment, adjacent carrier areas are each spaced apart from one another by a gap running transversely to the transmitter surface.

The gap thus spatially separates the adjacent carrier areas and the partial surface layers arranged on them from one another. Electrically, however, the sub-surfaces arranged on adjacent carrier areas can be connected to one another indirectly via the base body. Due to the spatial separation and in particular due to the gap, however, an electrical resistance between adjacent partial surface layers is generally significantly greater than within a partial surface layer. This influences, among other things, a way in which eddy currents are induced in the transmitter element and in particular in the partial surface layers. From the resulting characteristics of the eddy currents, conclusions can be drawn particularly well about a positioning or orientation of the transmitter element.

According to one embodiment, the donor surface is uneven.

Unevenness on the donor surface can be caused in a targeted manner or result from properties of manufacturing processes that are used to form the base body. In particular, macroscopic bumps can appear on the encoder surface, which are significantly larger than, for example, pores in the base body. For example, asperities in the form of depressions with depths of more than 50 μm or more than 0.1 mm can exist in the encoder surface. Such unevenness can arise, for example, due to pressing surfaces on tools that are used to press the particles to be sintered together.

While it was observed in the case of encoder elements that were produced as a sintered component overall that unevenness on their encoder surface can lead to inaccuracies in the position detection, it was observed in the encoder element presented here that the additional provision of the partial surface layers can largely avoid such a negative effect .

In particular, according to one embodiment, the base body can have a facet shape on the encoder surface, in which case a peripheral, facet-like depression is formed in the base body adjacent to a circumference of the base body.

Such a facet-like indentation can be brought about, for example, if the base body is pressurized when the sintered particles are pressed with a tool which, due to the design, has a Deepening pressed into the body. In this case, the recess can have a conical segment-like shape. Such an indentation is referred to herein as faceted.

According to a specific embodiment, the partial surface layers cover the facet-like depression.

In other words, the partial surface layers can run over the facet-like depression on the donor surface of the base body. The partial surface layers can thus cover the depression in such a way that they can no longer have any significant influence on eddy currents induced within the transmitter element. Rather, such eddy currents are predominantly induced in the partial surface layers which are preferably flat on their surface directed towards the position sensor, i.e. have no indentations. As a result, an overall accuracy of a position detection in the position sensor system can be improved.

According to an alternative specific embodiment, the partial surface layers do not cover the facet-like depression.

In other words, the partial surface layers can be dimensioned and positioned in such a way that they only cover a planar part of the encoder surface of the base body, but leave the facet-like depression free. In this configuration, the facet-like indentation created during production is exposed and can continue to be opposite the sensor surface of the position sensor. However, their influence on eddy currents that form in the transmitter element is small, since these eddy currents form predominantly in the partial surface layers.

According to one embodiment, the base body has a fastening structure which is configured to fasten the encoder element to a shaft of a rotor of an electrical machine. The fastening structure can be designed in such a way that it can be used to fix the base body firmly, in particular non-rotatably, to the shaft of the rotor. The mounting structure may be concentric with an axis of rotation of the rotor.

In particular, according to one embodiment, the fastening structure can be designed as a central through-opening in the base body.

Such a central passage opening can be formed in the base body in a particularly simple manner. With the help of the central passage opening, the base body can be pushed onto the shaft of the rotor and fixed there precisely with regard to its position, orientation and/or inclination.

According to the second aspect of the invention, a position sensor system includes a position sensor and a transmitter element with the properties described herein.

According to one embodiment, the position sensor can be configured to induce eddy currents in the encoder element by irradiating a high-frequency electromagnetic alternating field. In this case, the position sensor is also configured to measure physical parameters which are influenced by the induced eddy currents, and to use this to determine information about a position, in particular an angular position, of the transmitter element.

Such a position sensor system can be used in particular to detect a current angular position of a rotor in an electrical machine according to the third aspect of the invention. The encoder element is mechanically coupled to the rotor, whereas the position sensor is held stationary relative to the stator of the electrical machine. Since the position sensor system described functions without mechanical contact between the position sensor and the transmitter element, it can be operated largely without friction and/or without wear. The sensor element described here enables cost-effective production for the position sensor system while at the same time achieving high detection accuracy. It is pointed out that possible features and advantages of embodiments of the invention are described here partly with reference to a transmitter element and partly with reference to a position sensor system or an electrical machine equipped therewith. A person skilled in the art will recognize that the features described for individual embodiments can be transferred, adapted and/or exchanged in an analogous and suitable manner to other embodiments in order to arrive at further embodiments of the invention and possibly to achieve synergy effects.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, advantageous embodiments of the invention are explained in more detail with reference to the attached drawings, whereby neither the drawings nor the explanations are to be interpreted as restricting the invention in any way.

FIG. 1 shows a perspective view of a transmitter element according to an embodiment of the invention.

FIG. 2 shows a sectional view through the transmitter element from FIG. 1 along section line AA.

FIGS. 3 to 8 are enlarged illustrations of the area B shown in FIG. 2 for different transmitter elements according to different exemplary embodiments of the invention.

FIG. 9 illustrates a position sensor system according to an embodiment of the invention.

Figure 10 illustrates an electric machine according to an embodiment of the present invention. The figures are merely schematic and not true to scale. In the various drawings, the same reference symbols denote the same features or features that have the same effect.

DESCRIPTION OF ADVANTAGEOUS EMBODIMENTS

A transmitter element 1 for a position sensor system 51, as shown in FIG. 9, is illustrated in FIGS.

The transmitter element 1 comprises a base body 3 and a plurality of partial surface layers 5. The base body 3 is a sintered component which is made up of a large number of metal particles sintered together. The main body 3 comprises a main body base 11 and a plurality of carrier areas 13. The main body base 11 has an essentially cylindrical contour and is therefore rotationally symmetrical. In the example shown, four carrier areas 13 protrude from the main body base 11 in a direction parallel to an axis of rotational symmetry of the main body base 11 . All carrier areas 13 each have the same shape and are arranged equidistantly, i.e. at equal angular intervals, on the base body 11 . Accordingly, the carrier areas 13 form four partial areas 9 on the base body 3, which are arranged on the base body 3 overall with fourth-order rotational symmetry.

The partial surface layers 5 are each arranged on a surface of these partial regions 9 referred to as the donor surface 7 and essentially cover the entire surface in the example shown. In particular, an outer surface of the partial surface layers 5 is planar. Adjacent carrier regions 13 and thus also the partial surface layers 5 covering them are spaced apart from one another by a gap 15 running transversely to the surface 7 of the carrier. The gaps 15 each run in the radial direction in the base body 3 . As in the example shown, the gaps 15 can have the same or a similar width as the carrier areas 13 or cover an angle section that is the same or similar. Alternatively, however, such gaps 15 can also be clearly be narrower or cover a significantly smaller angular section than the adjacent support regions 13 spaced apart from one another by the gaps 15.

A through opening 21 is provided in the center of the base body 3, which can serve as a fastening structure 19, with the aid of which the transmitter element 1 can be fastened, for example, to a shaft 67 of a rotating component (see FIG. 10).

The position sensor system 51 shown in simplified form in Figure 9 has a position sensor 53 and a transmitter element 1. The position sensor 53 comprises a field generation device 55 and an evaluation device 57. The field generation device 55 can be used to generate high-frequency electromagnetic alternating fields, for example in a frequency range of one to five megahertz and radiated in a direction towards the transmitter element 1 . Due to electrical conductivities within the transmitter element 1, such alternating fields induce eddy currents in the transmitter element 1. These eddy currents in turn influence physical parameters in the encoder element 1 or interactions between the encoder element 1 and the position sensor 53. Such physical parameters can be measured and analyzed with the evaluation device 57 in order to obtain information about a position, in particular an angular position of the encoder element 1 relative to the position sensor 53 to be able to derive.

It has been observed that a way in which alternating fields generated in the transmitter element 1 produce eddy currents can have an influence on a measuring accuracy with which the positions can be determined in the position sensor system 51 . In particular, it has been observed that the manner in which eddy currents are generated in a sensor element designed as a sintered component appears to result in measurement accuracies when using such a sintered component sensor element being lower, at least in some cases, than when using a conventional sensor element which is characterized by machining was made very precisely from a solid material. In order to overcome the deficit described, the partial surface layers 5 are provided on the surface 7 of the base body 3 manufactured as a sintered component. These partial surface layers 5 are produced or formed in a suitable manner so that they offer a lower electrical resistance to the eddy currents induced by the high-frequency electromagnetic alternating fields irradiated by the position sensor 53 than is the case with the sintered base body 3 . Due to the increased electrical conductivity within the partial surface layers 5, the eddy currents can form there in a more precisely defined manner, as a result of which the measurement accuracy of the position sensor system 51 can be increased overall.

In FIGS. 3 to 8, various possibilities for forming the partial surface layers 5 on the base body 3 and associated properties are illustrated. The figures illustrate the region "B" of a sensor element 1 shown in Figure 2.

FIG. 3 shows a base body 3 on whose surface 7 a separate layer 27 is attached. The separate layer 27 comprises an adhesive layer 25, a carrier film 23 and the partial surface layer 5 deposited on the carrier film 27. The partial surface layer 5 is in turn applied to the side of the carrier film 23 opposite the adhesive layer 25 and is designed, for example, as a full-surface layer made of an electrically conductive material such as copper or aluminum. Alternatively, the partial surface layer 5 can be formed from other conductive materials or with an inhomogeneous structure. In particular, the partial surface layer 5 can be in the form of a woven or non-woven fabric with carbon fibers or metal fibers or other electrically conductive fibers (not illustrated).

Figure 4 shows an alternative embodiment in which the partial surface layer 5 as

Metal plate 29 on the surface 7 of the base body 3 is attached to the encoder. To the When producing a transducer element 1 configured in this way, the small metal plate 29, particularly if it is designed as a small copper plate or aluminum plate, can be pressed onto the porous surface of the sintered base body 3 and thus enter into a mechanically strong connection with it.

FIG. 5 shows a further embodiment in which the material of the partial surface layer 5 is infiltrated into pores 33 in the base body 3 at least near the surface. To produce such a transmitter element 1, electrically conductive material, in particular metal, can be applied directly to the transmitter surface 7 of the base body and at least partially penetrate into the pores 33 there. For example, the metal can be applied to the surface 7 of the encoder in the form of a liquid suspension or a paste containing metal particles. Alternatively, a metallic layer can be evaporated or otherwise deposited from a gas phase.

FIG. 6 illustrates an embodiment in which a compacted layer region 31 is formed on the base body 3 on the encoder surface 7 close to the surface. Pores 33 are present in this compressed layer region 31 just like in an adjoining region of the base body 3 . However, the number and/or size of pores 33' in the compressed layer area 31 is significantly smaller than is the case for pores 33'' in the area of the base body 3 underneath. The compressed layer area 31 can be produced, for example, by special measures during the production of the sintered component or by targeted post-processing of an area of the sintered component close to the surface.

In general, it can be preferred to design the transmitter surface 7 on the base body 3 as flat as possible in order to be able to arrange a partial surface layer 5 that is also flat. However, when producing sintered components, it may be necessary to use tools, for example in the form of pressure dies, which can result in indentations on the surfaces of the sintered component produced. Particularly in the production of a sintered component in the form of a base body 3 for the encoder element 1 presented here, the tool can lead to the formation of facet-like depressions 17 (see Figures 7 and 8) come adjacent to a periphery of the base body 3. Such depressions 17 can have a chamfer, ie a surface which runs obliquely to an adjacent remaining surface of the encoder surface. The indentations 17 can typically be about a tenth of a millimeter deep and several tenths of a millimeter wide.

The additional provision of electrically highly conductive partial surface layers 5 on the encoder surface 3 as described herein can help to avoid a disadvantageous influence of an uneven encoder surface 7 caused by production on the position measurement accuracy that can be achieved with the encoder element 1 .

As shown in FIG. 7, the partial surface layer 5 can cover the facet-like depression 17 in this case. Accordingly, radiated alternating fields lead to induced eddy currents forming mainly within the partial surface layer 5 and the depression 17 underneath having no significant negative influence on the alternating currents formed.

Alternatively, as shown in FIG. 8, the partial surface layer 5 cannot cover the facet-like depression 17 . In this case, the facet-like depression 17 is exposed. Nevertheless, alternating fields radiated in are largely absorbed in the partial surface layer 5 and cause eddy currents there, since their electrical conductivity is considerably higher than in the adjacent area of the base body 3 with the depression 17 formed there.

FIG. 10 illustrates an electrical machine 61 with a stator 63 and a rotor 65. A position sensor system 51, as presented here, is used to determine a current angular position of the rotor 65 relative to the stator 63. For this purpose, the encoder element 1 is mechanically coupled to the rotor 65 . The position sensor 53 is held stationary relative to the stator 63 . Accordingly, the position sensor 53 can determine the angular position of the encoder element 1 relative to the stator 63 in the contactless manner described herein. Finally, it should be noted that terms such as "comprising,""comprising," etc. do not exclude other elements or steps, and terms such as "a" or "an" do not exclude a plurality. Furthermore, it should be pointed out that features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Any reference signs in the claims should not be construed as limiting.

Reference List

I transmitter element

3 basic bodies

5 partial surface layers

7 giver surface

9 section

I I body base

13 carrier area

15 gap

17 deepening

19 mounting structure

21 through hole

23 carrier film

25 adhesive layer

27 separate layer

29 metal plates

31 condensed layer area

33 pores

51 position sensors

53 position sensor

55 field generating device

57 evaluation device

61 electric machine

63 stator

65 rotors

67 wave

Claims

Expectations

1. Transmitter element (1) for a position sensor (51), comprising: a base body (3) and a plurality of partial surface layers (5), wherein the base body (3) consists of particles sintered together, each of the partial surface layers (5) on a towards the transmitter surface (7) of the base body (3) to be aligned with the position sensor (53), with adjacent partial surface layers (5) being spaced apart from one another at least in certain areas, and with each of the partial surface layers (5) for electrical currents which flow through a towards the transmitter surface ( 7) of the base body (3) induced electromagnetic alternating field with a frequency of more than 0.2 MHz, has a higher electrical conductivity than the base body (3).

2. Sensor element according to claim 1, wherein the partial surface layers (5) differ in terms of a material forming them and/or in terms of a material density prevailing in them from the base body (3).

3. Transmitter element according to one of claims 1 and 2, wherein the partial surface layers (5) are each adhered as a separate layer (27) to the transmitter surface (7).

4. The donor element as claimed in one of claims 1 to 3, in which the partial surface layers (5) are each adhered to the donor surface (7) by means of an adhesive layer (25).

5. Transmitter element according to one of claims 1 to 4, wherein the partial surface layers (5) are each attached to a carrier film (23).

6. Transmitter element according to one of claims 1 to 5, wherein the partial surface layers (5) are each formed as a full-surface layer of an electrically conductive material, in particular of a metal, preferably with copper or aluminum.

7. Transmitter element according to one of claims 1 to 5, wherein the partial surface layers (5) are each formed as a woven or non-woven fabric made of electrically conductive fibers, in particular carbon fibers or metal fibers.

8. Transmitter element according to one of Claims 1 to 3, in which the partial surface layers (5) are pressed onto the transmitter surface (7) as small metal plates (29), in particular as small copper plates.

9. Transmitter element according to one of claims 1 and 2, wherein material of the partial surface layers (5) is infiltrated at least near the surface in pores (33) in the base body (3).

10. Transmitter element according to one of claims 1 and 2, wherein the partial surface layers (5) are formed as near-surface compressed layer regions (31) on the base body (3).

11. Transmitter element according to one of the preceding claims, wherein the base body (3) has a higher porosity than the partial surface layers (5).

12. Transmitter element according to one of the preceding claims, wherein the base body (3) has a greater thickness than the partial surface layers (5).

13. A donor element according to any one of the preceding claims, wherein the partial surface layers (5) are planar.

14. Transmitter element according to one of the preceding claims, wherein the partial surface layers (5) are planar at least on one of the base body (3) surface directed away.

15. Transmitter element according to one of the preceding claims, wherein the partial surface layers (5) are arranged in a common plane.

16. Transmitter element according to one of the preceding claims, wherein the base body (3) has a rotationally symmetrical outer contour.

17. Transmitter element according to one of the preceding claims, wherein the partial surface layers (5) are arranged rotationally symmetrically on the base body (3).

18. Transmitter element according to one of the preceding claims, wherein the base body (3) has a number n of partial areas (9) and overall has a rotational symmetry of the nth order, one of the partial surface layers (5) being arranged on each of the partial areas (9). .

19. Transmitter element according to one of the preceding claims, wherein the base body (3) has a base body (11) and a plurality of carrier areas (13) protruding from the base body (11) in a direction towards the position sensor (53), the transmitter surface (7 ) is arranged on the carrier areas (13).

20. Transmitter element according to claim 19, wherein adjacent carrier areas (13) are spaced apart from one another in each case by a gap (15) running transversely to the transmitter surface (7).

21. Transmitter element according to one of the preceding claims, wherein the transmitter surface (7) is uneven.

22. Sensor element according to one of the preceding claims, wherein the base body (3) has a facet shape on the sensor surface (7), in which a facet-like depression (17) in the base body (3) adjoins a circumference of the base body (3). is trained.

23. Transmitter element according to claim 22, wherein the partial surface layers (5) cover the facet-like depression (17).

24. Transmitter element according to claim 22, wherein the partial surface layers (5) do not cover the facet-like depression (17).

25. Transmitter element according to one of the preceding claims, wherein the base body (3) has a fastening structure (19) which is configured to attach the transmitter element (1) to a shaft (67) of a rotor (65) of an electrical machine (61). attach.

26. Transmitter element according to claim 25, wherein the fastening structure (19) is designed as a central through-opening (21) in the base body (3).

27 position sensor (51), comprising: a position sensor (53), and a transmitter element (1) according to any one of the preceding claims.

28. Position sensor system according to claim 27, wherein the position sensor (53) is configured to induce eddy currents in the encoder element (1) by irradiating a high-frequency electromagnetic alternating field and wherein the position sensor (53) is further configured to measure physical parameters which by the induced eddy currents are influenced, and to determine from this information about a position, in particular an angular position, of the transmitter element (1).

29. Electrical machine (61), comprising: a stator (63), a rotor (65), and a position sensor (51) according to any one of claims 27 and 28, wherein the encoder element (1) mechanically coupled to the rotor (65). is, and wherein the position sensor (53) is configured to determine a position, in particular an angular position, of the transmitter element (1) relative to the stator (63).