Patent Application
20220247246
The present application is related and has right of priority to German Patent Application No. 102021200874.7 filed in the German Patent Office on Feb. 1, 2021, which is incorporated by reference in its entirety for all purposes.
The invention relates generally to a rotor for an electric machine having a pack of stacked, magnetically active rotor laminations, the sheet metal section of which has guide webs formed from metal, and open intermediate spaces. The guide webs guide the magnetic flux, whereas the open intermediate spaces act as a flux barrier for the magnetic field lines.
The invention further relates generally to an electric machine having this type of rotor. An electric machine of this type functions, in particular, as an electric motor, although, in principle, it can also be utilized equally well as a generator.
The turning motion of an electric motor is based on the mutual attractive and repulsive forces of the magnetic fields in the stator and the rotor. Usually, the stator is situated on the outside and is mounted in a housing in a rotationally fixed manner. In an internal-rotor electric machine of this type, the stator usually holds a current-carrying winding, which generates a magnetic field. A magnetic field is also built up in the rotating rotor, either in the guide webs of the rotor laminations due to the excitation by the stator currents and/or by permanent magnets buried in the open intermediate spaces.
In the geometric configuration of the sheet contour of the rotor laminations, there is a trade-off, at times, between the magnetic function and the mechanical function. The sheet metal section must form one contiguous area, so that the rotor lamination does not fall apart. Simultaneously, the guide webs formed from metal are to be as narrow as possible and the open intermediate spaces are to be as large as possible, in order to keep the magnetic permeability low. The metal guide webs must be selected to be so large that the arising mechanical forces, in particular centrifugal forces, are absorbed, and so the rotor is not deformed or even damaged during fast rotation.
Specifically in permanently excited synchronous motors or magnet-free reluctance synchronous motors, the intermediate spaces acting as a flux barrier for the magnetic field lines are designed as slots, which extend essentially transversely to the direction of the useful magnetic flux. These slots cannot be designed to be arbitrarily large, however, in particular not too wide, since the sheet-metal webs remaining therebetween can no longer absorb the arising centrifugal forces otherwise. For this reason, the open intermediate spaces or slots are interrupted by narrow connecting webs, which connect the metal guide webs and, as a result, reinforce primarily in the radial direction. These connecting webs result, however, in an undesirable magnetic flux, which is precisely to be prevented by the open intermediate spaces or slots.
Example aspects of the present invention provide a rotor having stacked, magnetically active rotor laminations, configured for preventing the magnetic short circuits in the rotor laminations to the greatest extent possible, while simultaneously ensuring the mechanical strength of the rotor structure, in particular the stability against centrifugal forces.
According to example embodiments, connecting elements are arranged between the individual rotor laminations for transferring radial thrust forces from one rotor lamination onto the adjacent rotor lamination. The connecting elements provided according to example aspects of the invention reinforce the individual rotor laminations, and so the centrifugal forces are not or at least not completely absorbed by the metal guide webs of an individual rotor lamination, but rather are distributed onto multiple rotor laminations situated next to one another. Since the connecting elements are arranged between the individual rotor laminations, the open intermediate spaces between the guide webs formed from metal can be designed to be more open and more ample; in particular, otherwise necessary connecting webs, which interrupt the open intermediate spaces, can be avoided. In this way, the mechanical strength of the rotor is significantly increased, without the need to accept additional magnetic short circuits, which would reduce the power of the machine.
In one preferred example embodiment, the connecting elements are designed as connecting bodies integrally formed with the rotor laminations, and corresponding receptacles, wherein the connecting bodies and receptacles extend in the axial direction, and wherein the connecting bodies of one rotor lamination form-lockingly engage into the receptacles of the adjacent rotor lamination. According to example aspects of the invention, the connecting bodies therefore extend perpendicular to the sheet-metal plane of the rotor laminations and, thereby, also perpendicular to the magnetic field lines in the rotor lamination.
In particular, the connecting elements can be designed as raised areas at the one side of the rotor laminations and corresponding indentations at the opposite, other sides of the rotor laminations, preferably as bead profiles crimped into the sheet metal. Such raised areas and indentations or bead profiles can be easily and economically manufactured in the stamping process. A minimal axial extension of the raised areas and indentations suffices for achieving an effective mutual support of the rotor laminations.
Specifically in the case of highly effective reluctance electric motors, the desire is to design the open intermediate spaces between the metal guide webs to be as long as possible and also as wide as possible. The risk of an insufficient mechanical strength of the rotor lamination increases as a result. An arrangement of the connecting elements in the proximity of the edges of the open intermediate spaces has proven particularly advantageous in order to resolve, to the greatest extent possible, the trade-off between the most effective flux barriers possible, on the one hand, and the mechanical strength of the rotor laminations, on the other hand.
The connecting elements according to example aspects of the invention even permit sheet metal sections having slot-shaped intermediate spaces that extend predominantly in the radial direction and terminate at the peripheral edge of the rotor lamination, and so the intermediate spaces or slots transition into the air gap between the rotor and the stator. Rotor laminations, in which the sheet metal is interrupted directly at the outer edge by intermediate spaces, would be able to absorb barely higher centrifugal forces without the axial connecting elements.
In one preferred example embodiment of the rotor according to example aspects of the invention, additional support plates having a sheet metal section without intermediate spaces are inserted between the magnetically active rotor laminations. These support plates are utilized for absorbing the radial thrust forces from the adjacent rotor laminations. The mechanical forces, in particular centrifugal forces, are transferred from the metallic sections of the rotor laminations via the connecting elements onto the support plates, and so the force flow is finally completed via the support plates. The support plates have receptacles for the connecting elements.
Preferably, the support plates are arranged at regular axial intervals between the magnetically active rotor laminations. The interposition of a support plate approximately after every tenth rotor lamination has proven advantageous.
Example aspects of the present invention also provide an electric machine, in particular an electric motor, including a stator, which is mounted in a housing in a rotationally fixed manner, and including a rotor, in which, according to example aspects of the invention, connecting elements are arranged between the individual rotor laminations for transferring radial thrust forces from one rotor lamination onto the adjacent rotor lamination. The connecting elements according to example aspects of the invention come into play particularly advantageously in a permanently excited electric motor, in which permanent magnets are fitted in the open intermediate spaces of the rotor laminations.
Exemplary embodiments of the invention are described in the following with reference to the attached figures, in which:
Reference will now be made to embodiments of the invention, one or more examples of which are shown in the drawings. Each embodiment is provided by way of explanation of the invention, and not as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be combined with another embodiment to yield still another embodiment. It is intended that the present invention include these and other modifications and variations to the embodiments described herein.
The electric motor represented in
The enlarged representation in
The metal guide webs 51 guide the magnetic flux in the rotor lamination 50. The open intermediate spaces 52 act as a flux barrier for the magnetic field lines. The width of the connecting webs 53 is designed to be as small as possible in order to meet the requirement for minimal magnetic permeability. A certain minimum width of the connecting webs 53 cannot be fallen below, however, so that the arising mechanical forces, primarily the centrifugal forces acting in the radial direction, can also be absorbed in the area of the intermediate spaces 52 and, in particular, in the area of the peripheral edge of the rotor lamination 50. Nevertheless, an undesired magnetic flux arises due to the metallic connecting webs 53.
As is apparent from the associated offset cross-section in
As is apparent from
Permanent magnets 80 are fitted in the intermediate spaces 62 of the rotor laminations 60. The rotor in this case is the rotor of a permanently excited synchronous motor.
At a fast rotational speed of the electric motor, high centrifugal forces act, in particular, upon the peripheral sections of the rotor laminations 60. Due to the weakening of the sheet metal structure by the intermediate spaces 62, there is a risk that the relatively thin guide webs 61 bend radially outward under the effect of the centrifugal forces, which could result in a constriction of the air gap between the rotor and the stator (cf.
The rotor lamination 90 according to
In the further example embodiment according to
The invention was comprehensively described and explained with reference to the drawings and the description. The description and the explanation are to be understood as an example and are not to be understood as limiting. The invention is not limited to the disclosed embodiments. Other embodiments or variations result for a person skilled in the art within the scope of the utilization of the present invention and within the scope of a precise analysis of the drawings, the disclosure, and the following claims.
In the claims, the words “comprise” and “comprising” do not rule out the presence of further elements or steps. The indefinite article “a” does not rule out the presence of a plurality. A single element or a single unit can carry out the functions of several of the units mentioned in the claims. An element, a unit, an interface, a device, and a system can be partially or completely converted into hardware and/or into software. The mere mention of a few measures in multiple various dependent claims is not to be understood to mean that a combination of these measures cannot also be advantageously utilized.
Modifications and variations can be made to the embodiments illustrated or described herein without departing from the scope and spirit of the invention as set forth in the appended claims. In the claims, reference characters corresponding to elements recited in the detailed description and the drawings may be recited. Such reference characters are enclosed within parentheses and are provided as an aid for reference to example embodiments described in the detailed description and the drawings. Such reference characters are provided for convenience only and have no effect on the scope of the claims. In particular, such reference characters are not intended to limit the claims to the particular example embodiments described in the detailed description and the drawings.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 200 874.7 | Feb 2021 | DE | national |
