Electrical machine arrangement

Abstract

An electrical machine arrangement comprising an electric machine for driving an electrically powered motor vehicle, comprising a stator and a rotor, wherein the rotor is rotatably mounted within the electrical machine arrangement via at least one bearing point, wherein the rotor has a rotor shaft (2), one end (3) of which, within the axial longitudinal extent (6) of the rotor shaft (2), comprises a shaft grounding element (8) and a rotor position sensor, wherein the shaft grounding element (8) consists of at least a tap (8a) and grounding elements, characterized in that the rotor position sensor consists of a ring-shaped magnet (4) mounted at the end of the rotor shaft (2) and a sensor element (9), and that the magnet (4) is electrically conductive and the shaft grounding element (8) conducts currents directly via the tap (8a), and that the components are arranged in axial sequence with the rotor shaft (2), the magnet (4),the wave grounding element (8) and the sensor element (9).

Description

The invention relates to an electrical machine arrangement comprising an electric machine for driving an electrically powered motor vehicle, a stator and a rotor, wherein the rotor is rotatably mounted within the electrical machine arrangement via at least one bearing point, wherein the rotor has a rotor shaft, one end of which has a shaft grounding element and a rotor position sensor within the axial extent of the rotor shaft. State of the art In electric motors, the position of the parts through which the magnetic field flows is crucial. This applies both to the mechanical structure of the electric motor, which positions the parts relative to each other, and to precise knowledge of the angular position of the rotating parts, which determines the exact current position of the rotor relative to the stator. A precise, rigid mechanical structure is essential because even slight positional deviations between the parts can significantly affect the magnetic flux (for example, due to changes in air gaps). Furthermore, precise knowledge of the rotor's current position is also critical, as the constantly changing position (angular position) of the magnets integrated into the rotating rotor must always be known exactly relative to the fields present in the stator in order to control the electric motor correctly.Therefore, it is important to integrate a rotor position sensor into the mechanical structure of the electric motor in such a way that the sensor can accurately detect the relative position of the magnetically relevant parts, i.e., with the lowest possible tolerance influence. At the same time, the sensor's size and installation conditions must not negatively affect the mechanical structure of the electric motor, ensuring that all parts and assemblies can be designed with sufficient robustness and dimensional accuracy, as well as precisely aligned during assembly. In addition to the rotor position sensor, most electric motors also require the integration of elements for grounding the rotor or rotor shaft, as well as elements that electrically insulate the rotor relative to the stator. These grounding and / or insulation elements prevent the electrical voltage induced in the mechanical structural elements of the electric motor from discharging through the bearings or being transferred to adjacent components of the electric motor. In an electric machine, the shaft end of the rotor shaft serves various functions: Oil is introduced into the rotor shaft via the shaft end to cool the rotor. A grounding conductor located at the shaft's center, running along the rotor shaft axis, conducts away rotor currents to prevent bearing damage. Additionally, magnetic rotation sensors are used at the shaft end to detect the rotor's position. However, only two shaft ends are available for the three functions. Individual functions can also be placed on the shaft itself, e.g., a slip ring for current conduction as a shaft ground, but this has its disadvantages. From DE 10 2020 122 255 A1, an electrical machine arrangement is known, comprising an electric axial flux machine for driving an electrically powered motor vehicle, with a stator and with a rotor, further comprising - a component supporting the stator, and - an output element in rotationally fixed contact with the rotor, wherein the rotor is rotatably mounted within the electrical machine arrangement via at least one bearing point, wherein a shaft grounding element and / or a rotor position sensor is / are arranged in a spatial area, in the radial direction between the rotor shaft and the stator and in the axial direction within the axial extent of the stator. A rotation sensor is also known from DE 11 2014 006 362 B4. A magnet is attached to the shaft end of the rotor shaft, which is evaluated by a sensor chip installed axially in front of it and mounted on a circuit board in the housing. Document US 2018 / 0152081A1 discloses a rotary machine equipped with a rotor shaft rotatably mounted in a housing. The rotary machine further comprises an end plate arranged axially at one end of the housing; a recessed section formed in the end plate and facing inward toward the housing; a through-hole formed in the recessed section through which an end section of the rotor shaft is inserted; and a shaft grounding device provided in the recessed section, which is brought into contact with the end section of the rotor shaft inserted through the through-hole. The rotary machine also includes a rotor position sensor arranged on the end section. DE 10 2022 107 246 A1 discloses a motor unit with a shaft and a shaft grounding element arranged at the end region, wherein the contact element of the shaft grounding element is brought into contact with the end surface by pre-tensioning a pre-tensioning element. Furthermore, the motor unit includes a resolver as a rotation sensor, which comprises a resolver rotor arranged on the outer circumference of the shaft end. A machine with an integrated rotary encoder is known from DE 10 2004 059 181 A1. The rotary encoder comprises an encoder element that rotates with the rotor shaft and a sensor element that interacts with the encoder element. The encoder element is arranged on a region of the rotor shaft facing the bearing shield, and the sensor element is integrated into a bearing shield of the machine. The object of the invention is to provide an improved combination of the functions of the wave earth electrode and the rotation sensor, which takes up less space in terms of construction. Description of the invention The problem is solved by an electrical machine arrangement comprising an electric machine for driving an electrically powered motor vehicle, a stator, and a rotor, wherein the rotor is rotatably mounted within the electrical machine arrangement via at least one bearing point, wherein the rotor has a rotor shaft, one end of which, within the axial extent of the rotor shaft, has a shaft grounding element and a rotor position sensor, and wherein the shaft grounding element consists of at least a tap and discharge elements, and wherein the rotor position sensor consists of a ring-shaped magnet mounted at the end of the rotor shaft and a sensor element, and wherein the magnet is electrically conductive and the shaft grounding element discharges currents directly via the tap, and wherein the components are arranged in axial sequence with the rotor shaft, the magnet, the shaft grounding element, and the sensor element. The invention consists of a combination of a magnetic rotor position sensor and a shaft grounding element for rotor current dissipation at the same shaft end. The functions are designed such that both can be mounted at one shaft end without interfering with each other. The formulation that the two functions, namely the shaft grounding element and the rotor position sensor, lie within the axial extent of the rotor shaft, means that all relevant components lie within the cross-section of the rotor shaft in an axial extent, whereby a certain radial extent beyond the radius of the rotor shaft may exist. The shaft grounding element consists of at least a tap and wings as discharge elements. The discharge elements can also be a coil spring or any surface. The wave grounding element can also include a contact pin. The rotor position sensor consists of a ring-shaped magnet mounted at the end of the rotor shaft and a sensor element. Alternatively, two individual magnets that generate a similar field or a conductive round magnet can also be used. Description of the characters Fig. 1 shows a shaft end of a rotor of the electrical machine arrangement, Fig. 2 section through the shaft end, Fig. 3 a top view of the shaft end, Fig. 4 shows a solution without a contact pin. The electrical machine arrangement 1 according to the invention comprises an electrical machine consisting of a stator and a rotor, neither of which are shown in Fig. 1. The stator and rotor are installed in a housing of the electrical machine, which has provisions for mounting the components and space for electrical connections. The rotor has a rotor shaft, which in the solution according to the invention can be designed either as a hollow rotor shaft or as a filled rotor shaft. The rotor with the rotor shaft 2 is mounted within the housing and within the stator. Figures 1, 2 to 3 show a shaft end 3 of the rotor of the electrical machine arrangement 1. An annular magnet 4 is mounted on the shaft end 3 of the rotor shaft 2. The annular magnet 4 has two poles 4a and 4b, which run apart along a diameter. The two poles enclose an opening 5 in a semicircle. In this embodiment, the opening 5 serves to receive a contact pin 7 for the shaft grounding electrode 8, so that the contact pin can be guided through the magnet 4 in the middle of the rotor shaft 2. The contact pin, acting as a grounding pin with a spring mechanism, serves to contact the end face of the rotor shaft 2. The entire shaft grounding element 8 is fixedly connected to an electrical conductor, which can be designed as a circuit board or as a housing component. The wave grounding device 8 consists of a metal component comprising a hemispherical tap 8a with three vanes 8b extending outwards from the hemispherical tap 8a beyond the radius of the rotor shaft 2. Currents occurring at the rotor are conducted via the vanes 8b to the housing of the electrical machine assembly. The exact design of the wave ground electrode can also differ from the exemplary embodiment. For example, the tap can be made via any possible shape. The grounding can also be achieved via a coil spring or a geometrically differently designed contact surface. A sensor element 9 is mounted above the magnet 4 in the area of ​​the opening 5 of the magnet 4, for example on a circuit board. The conductive paths from contact pin 7 radiate outwards above magnet 4 in a star-shaped pattern, allowing the sensor element 9 to detect the magnetic field at a suitable distance. Due to its symmetrical design, the conductive path below the sensor element does not affect the sensor accuracy. Figure 2 shows a dashed outline of an installation space extending along the axial alignment 6 of the rotor shaft 2 and the diameter D of the rotor shaft 2. This installation space contains the key components for the shaft grounding element and the rotor position sensor. These consist of the magnet 4 with its central opening 5 and the sensor element 9, as well as the contact pin 7, the shaft grounding electrode 8 with the tap 8a, and the majority of the vanes 8b. In another embodiment, the ring-shaped magnet 4 is sufficiently electrically conductive so that the wave ground 8 can be contacted directly via the magnet 4. Such an embodiment is shown in Fig. 4. The magnet shape can also consist of two individual magnets that generate a similar field to a ring magnet or a conductive round magnet.

Claims

An electrical machine arrangement comprising an electric machine for driving an electrically powered motor vehicle, comprising a stator and a rotor, wherein the rotor is rotatably mounted within the electrical machine arrangement via at least one bearing point, wherein the rotor has a rotor shaft (2), one end (3) of which, within the axial longitudinal extent (6) of the rotor shaft (2), comprises a shaft grounding element (8) and a rotor position sensor, wherein the shaft grounding element (8) consists of at least a tap (8a) and discharge elements, characterized in that the rotor position sensor consists of a ring-shaped magnet (4) mounted at the end of the rotor shaft (2) and a sensor element (9), and that the magnet (4) is electrically conductive and the shaft grounding element (8) discharges currents directly via the tap (8a), and that the components are arranged in axial sequence with the rotor shaft (2), the magnet (4),the wave grounding element (8) and the sensor element (9). Electrical machine arrangement according to claim 1, characterized in that the shaft grounding element (8) also comprises a contact pin (7). Electrical machine arrangement according to one of the preceding claims, characterized in that the discharge elements are wings (8b) or consist of a spiral spring or a contact surface.

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