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DE-102024132862-A1 - Rotor for an electric machine

DE102024132862A1DE 102024132862 A1DE102024132862 A1DE 102024132862A1DE-102024132862-A1

Abstract

Rotor (1) for an electric machine comprising a hollow cylindrical rotor core (2) with a central opening (3) and a rotor shaft (5) arranged along a central axis of rotation (4), wherein the rotor core (2) is rotationally fixed to the rotor shaft (5) in the region of the central opening (3) by means of an interference fit and wherein the rotor core (2) has at least one axial opening (6) which extends at least partially axially through the rotor core (2), wherein the axial opening (6) is formed in the rotor core (2) such that a radial rotor core section (7) which extends radially between the axial opening (6) of the rotor core (2) and the central opening (3) of the rotor core (2) has a radial extent of a maximum of four percent of an outer diameter (d) of the rotor core (2).

Inventors

  • Frank Fabian
  • Ingo Lukas
  • Walter Meindl

Assignees

  • Magna powertrain gmbh & co kg

Dates

Publication Date
20260513
Application Date
20241111

Claims (4)

  1. Rotor (1) for an electric machine comprising - a hollow cylindrical rotor core (2) with a central opening (3) and - a rotor shaft (5) arranged along a central axis of rotation (4), wherein the rotor core (2) is rotationally fixed to the rotor shaft (5) in the region of the central opening (3) by means of an interference fit and wherein the rotor core (2) has at least one axial opening (6) which extends at least partially axially through the rotor core (2), characterized in that the axial opening (6) is formed in the rotor core (2) such that a radial rotor core section (7) which extends radially between the axial opening (6) of the rotor core (2) and the central opening (3) of the rotor core (2) has a radial extent of a maximum of four percent of an outer diameter (d) of the rotor core (2).
  2. Rotor (1) after Claim 1 , characterized in that the axial opening (6) is designed as an elongated opening along a circumferential direction (U) of the rotor (1).
  3. Rotor (1) after Claim 1 or 2 , characterized in that at least three axial openings (6) are formed in the rotor core (2) along the circumferential direction (U) of the rotor (1), spaced at uniform intervals, and the rotor core (2) thus has at least three radial rotor core sections (7).
  4. Rotor (1) according to one of the Claims 1 , 2 or 3 , characterized in that the rotor core (2) has several successive poles (8) in the circumferential direction (U), wherein an axial opening (6) and thus a radial rotor core section (7) is formed in a region between two adjacent poles (8).

Description

Field of invention The present invention relates to a rotor for an electric machine comprising a hollow cylindrical rotor core with a central opening and a rotor shaft arranged along a central axis of rotation, wherein the rotor core is connected to the rotor shaft in the area of the central opening via a press fit in a rotationally fixed manner. State of the art Electrical machines comprise a stationary stator and a movable rotor, the rotor being rotatably mounted within an annular stator in the most common design. The stator has a stator core and at least one stator winding arranged on the stator core, forming a winding head at each end face of the stator core. The rotor has a rotor core fixed to a rotor shaft and, in a common rotor design, permanent magnets arranged in or on the rotor and uniformly distributed around its circumference. The rotationally fixed connection between the rotor shaft and the rotor core can be easily achieved, for example, via an interference fit between the rotor shaft and rotor core. A problematic aspect of this method is that, particularly at high rotor speeds, the rotor core can lift off the rotor shaft, which in turn causes a twist between the rotor core and a resolver (altered angular position) and results in an imbalance. Summary of the invention One object of the invention is to provide an improved rotor for an electric machine, in which, in addition to a simple and cost-effective installation of the rotor core on the rotor shaft, reliable operation is also ensured. This need can be met by the subject matter of the present invention according to independent claim 1. Advantageous embodiments of the present invention are described in the dependent claims. The rotor according to the invention for an electric machine comprises a hollow cylindrical rotor core with a central opening and a rotor shaft arranged along a central axis of rotation. According to the present invention, the rotor core is connected to the rotor shaft in a rotationally fixed manner via a press fit in the area of the central opening. The rotor core has at least one axial opening that extends at least partially axially through the rotor core. According to the invention, the axial opening is formed in the rotor core such that a radial rotor core section, which forms radially between the axial opening of the rotor core and the central opening of the rotor core, has a radial extent of a maximum of four percent of the outer diameter of the rotor core. The direction "axial" essentially corresponds to a direction along or parallel to the central axis of rotation of the rotor. The direction "radial" essentially corresponds to a direction perpendicular to the central axis of rotation of the rotor. The axial opening is preferably designed as an elongated opening along a circumferential direction of the rotor. In a cross-section along a plane perpendicular to a plane formed along the central axis of rotation, the axial opening can, for example, be kidney-shaped, essentially triangular, essentially rectangular, oval, etc. – in principle, other window shapes are also possible. In an advantageous embodiment, at least three axial openings are formed in the rotor core along a circumferential direction of the rotor, spaced at uniform intervals, and the rotor core thus has at least three radial rotor core sections. Particularly preferably, the rotor has several successive poles in the circumferential direction, with each having an axial opening and thus each forming a radial rotor core section in a region between two adjacent poles. In a particularly preferred embodiment of the present invention, the rotor core has several successive poles in the circumferential direction, wherein an axial opening and thus a radial rotor core section is formed in a region between two adjacent poles. If the rotor core is fixed to the rotor shaft via a press fit, the design of the rotor core prevents rotational movement if it lifts off the rotor shaft, at least partially. According to the invention, a self-regenerating press fit between the rotor shaft and the rotor core ensures continued contact between the rotor shaft and the rotor core. Furthermore, the inventive design of the rotor reduces the required pressing force of the rotor core onto the rotor shaft. The self-regenerating press fit between the rotor shaft and the rotor core delays rotor core lift-off to higher rotational speeds. In addition to this positive effect, a smaller overlap between the rotor shaft and rotor core can also be considered, thus reducing assembly problems. Brief description of the drawings The invention is described below by way of example with reference to the drawings. 1 shows a schematic top view of a rotor for an electric machine. 2 shows a representation of a pole of a rotor core and a corresponding section of a rotor shaft of a rotor according to 1 . 3 shows a schematic representation of a region between two poles of a rotor core as well as a corresponding