US-12620880-B2 - Rotor device for an electric motor and method for producing this rotor device

US12620880B2US 12620880 B2US12620880 B2US 12620880B2US-12620880-B2

Abstract

A method for producing a rotor device, including providing a rotor shaft having at least one sheet metal packet joined to the rotor shaft. The at least one sheet metal packet includes magnetic units. The method includes performing a transfer molding process, in which the magnetic units are fixed in position in relation to the at least one sheet metal packet and at least one balancing disk is joined axially on the rotor shaft on at least one side of the at least one sheet metal packet such that a gap of a defined width is ensured between the at least one balancing disk and the at least one sheet metal packet. The gap is filled with a molding compound used for the transfer molding process. The method includes determining an imbalance of the rotor device and compensating the imbalance by removing material from the at least one balancing disk.

Inventors

Peter Wurster
Patrick Knecht
Johannes Lange
Florian Braunbeck
Tobias Engelhardt

Assignees

DR. ING. H.C. F. PORSCHE AKTIENGESELLSCHAFT

Dates

Publication Date: 20260505
Application Date: 20230323
Priority Date: 20220329

Claims (15)

1 . A method for producing a rotor device for an electric motor, comprising: providing a rotor shaft having at least one sheet metal packet joined to the rotor shaft, wherein the at least one sheet metal packet comprises magnetic units, performing a transfer molding process, in which the magnetic units are fixed in their position in relation to the at least one sheet metal packet and at least one balancing disk is joined axially on the rotor shaft on at least one side of the at least one sheet metal packet in such a way that a gap of a defined width is ensured between the at least one balancing disk and the adjacent at least one sheet metal packet, the gap being filled with a molding compound used for the transfer molding process, wherein, at at least one radial position, the molding compound contacts both the at least one balancing disk and the adjacent at least one sheet metal packet, determining an imbalance of the rotor device, and compensating the imbalance by removing material from the at least one balancing disk.
2 . The method according to claim 1 , wherein the defined width of the gap is between 1 mm and 5 mm.
3 . The method according to claim 1 , wherein an inner diameter of the at least one balancing disk is significantly larger than the diameter of the rotor shaft at an axial position at which the at least one balancing disk is provided.
4 . The method according to claim 3 , further comprising bandaging the rotor device, wherein the bandaging additionally fixes the at least one balancing disk in the axial direction.
5 . The method according to claim 3 , wherein the molding compound fills a space between the inner diameter of the at least one balancing disk and the diameter of the rotor shaft at the axial position at which the at least one balancing disk is provided.
6 . The method according to claim 1 , wherein two balancing disks are provided on the rotor shaft, wherein one balancing disk is arranged on one side of the at least one sheet metal packet and the other balancing disk is arranged on an opposite side of the at least one sheet metal packet.
7 . The method according to claim 1 , wherein the removal of the material is carried out by providing bores.
8 . The method according to claim 7 , wherein the bores are drilled through an entire thickness of the at least one balancing disk.
9 . The method according to claim 7 , wherein the bores are parallel to the rotor shaft.
10 . The method according to claim 1 , wherein the molding compound is used in the transfer molding process, and wherein the molding compound has an adhesive effect in conjunction with the at least one balancing disk.
11 . The method according to claim 10 , wherein the molding compound positively locks the at least one balancing disk to the rotor shaft based on the adhesive effect.
12 . The method according to claim 1 , wherein the defined width of the gap is 2 mm.
13 . The method according to claim 1 , wherein performing the transfer molding process further comprises injecting the molding compound into the gap such by that same injection, the molding compound adheres the at least one balancing disk to the adjacent at least one sheet metal packet.
14 . The method according to claim 1 , wherein at each radial position that the molding compound contacts the at least one balancing disk, the molding compound contacts the adjacent at least one metal packet.
15 . A rotor device, comprising: a rotor shaft, at least one sheet metal packet with magnetic units joined on the rotor shaft, and at least one balancing disk arranged axially on the rotor shaft, wherein the magnetic units are fixed in their position in relation to the at least one sheet metal packet by transfer molding and the at least one balancing disk is joined on the rotor shaft by transfer molding, wherein a gap is provided between the at least one sheet metal packet and an adjacent at least one balancing disk, the gap being filled by a molding compound used for the transfer molding, and wherein, at at least one radial position, the molding compound contacts both the at least one balancing disk and the adjacent at least one sheet metal packet.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims benefit to German Patent Application No. DE 10 2022 107 435.8, filed on Mar. 29, 2022, which is hereby incorporated by reference herein. FIELD The invention relates to a rotor device and a method of producing a rotor device. BACKGROUND Rotor devices for electric motors have sheet metal packets arranged around a rotor shaft in which magnetic units are provided. Due to the sometimes very high speeds of rotors in operation, it is necessary that any possible production-related imbalance of the rotor device be compensation up to a specified target value. For this purpose, balancing disks are used in the prior art in order to compensate for the imbalance of the rotor device by selectively removing material at certain locations on the balancing disk. A rotor device 10 according to the prior art is shown in FIGS. 1a and 1b. FIG. 1a shows the rotor device 10 in a side view with a horizontal rotor shaft 11, on which four sheet metal packets 12 are arranged coaxially. In the axial direction of the rotor shaft 11, a balancing disk 13 is arranged next to the two outer sheet metal packets 12. The balancing disks 13 typically have a thickness of 5-10 mm, wherein their outer diameter approximately corresponds to the outer diameter of the sheet metal packets. They are either pressed onto the rotor shaft 11 as positively locking elements or screwed axially onto the rotor shaft 11 as positively locking elements by a retaining nut so that they contact the outer sheet metal packet 12 which faces them. Therefore, they must be made from a paramagnetic material in order to avoid a magnetic short circuit. Embodiments are also known in which the balancing disks 13 are glued to the sheet metal packets 12 for axial fixation. Such or similar rotor devices 10 are known from the following patent documents: EP 3 276 793 A1, U.S. Pat. No. 5,780,945 A, CN 100352143 C, US 2013/0082563 A1, and CN 206180798 U. In order to compensate for the imbalance of the rotor device 10, material of the balancing disks 13 is removed at certain positions in the form of bores 14, as FIG. 1b indicates. FIG. 1b shows the rotor device 10 of FIG. 1a in a top plan view, i.e. a view of FIG. 1a rotated by 90°. Due to the type of attachment of the balancing disk 13 on the rotor shaft 11, by press fit or retaining nut, the inner diameter Di of the balancing disk 13 approximately corresponds to the diameter of the rotor shaft 11. The bores 14 are made in the radial direction relatively far outwards in order to make it necessary only to remove a small amount of material. Care must be taken to ensure that the balancing disk 13 is also not bored completely in order to avoid damage to the abutting sheet metal packet 12. FIG. 2 shows a section of a sheet metal packet 12 of a rotor device 10, which is already known from the prior art, in a top plan view as in FIG. 1b. The cavities designated as pockets 121 can be seen, into which the magnetic units 16 are inserted. The magnetic units 16 comprise a permanent magnet or are configured as such. The magnetic units 16 thus inserted into the pockets 121 of the sheet metal packets 12 are referred to as buried magnetic units. By contrast, there are also external magnetic units, which are mounted on the sheet metal packets 12 radially from the outside. Recesses can also be provided on the outside of the sheet metal packets 12 in order to receive the external magnetic units. In this respect, buried magnetic units and external magnetic units can be used alternatively or additionally in relation to one another. The fixation of the magnetic units 16 takes place in both the external and buried magnetic units by means of transfer molding, in which a molding compound is injected into cavities like the pockets 121, in order to ensure the correct position, even at high speeds of the rotor device 10. Particularly in the case of external magnetic units, additional bandaging is used. Composite materials are typically used as the molding compound. The production of a rotor unit 10 according to the prior art is thus carried out according to the method outlined in FIG. 3. First, the magnetic units are joined to the sheet metal packets before they are joined onto a rotor shaft. Unless stated otherwise, in the context of the application, an attachment of any kind will be described by the term “join.” This can be a positive-locking attachment, for example, by means of a thread, a positive-locking attachment, for example by means of a press-fit, or another type of attachment. After the sheet metal packets 12, including the magnetic units 16, are joined to the rotor shaft 11, the magnetic units 16 are fixed by transfer molding. Furthermore, the balancing disks 13 are added to the rotor shaft 11 and the imbalance of the rotor device 10 is determined. This imbalance is then compensated by removing material from the balancing disks 13, usually by way of bores 14. It is disadvantageous in this m