Rotor for an Electric Machine and Method for Producing a Rotor

Abstract

A rotor for an electric machine, in particular for a brushless DC motor, includes a hollow cylindrical main body that is rotationally fixed to a machine shaft. The main body includes a plurality of radial protrusions arranged over its casing surface in the circumferential direction and in the axial direction and offset relative to one another by a defined offset angle. Each radial protrusion is limited over an angular range, which is smaller than the offset angle. The hollow cylindrical main body is permanently connected, in particular adhered, to a hollow cylindrical body surrounding same in the circumferential direction by way of a joining process. A method for producing a rotor for an electric machine is also disclosed. The method includes (i) using rotor laminations for a rotor lamination stack of the rotor, wherein a plurality of rotor laminations have a respective at least one radial protrusion that is limited over an angular range, (ii) stacking the rotor laminations to form the rotor lamination stack in such a way that, of the plurality of rotor laminations having at least one radial protrusion, neighboring rotor laminations are rotated relative to one another about a defined offset angle that is greater than the angular range of the at least one radial protrusion, (iii) applying a joining agent, in particular an adhesive, to an outer casing of the rotor lamination stack, preferably between the radial protrusions, and/or to an inner surface of a hollow cylindrical body, and (iv) sliding the hollow cylindrical body onto the rotor lamination stack. An electric machine is also disclosed that includes a corresponding rotor, as well as an electrical processing device having a corresponding electric machine.

Claims

1. A rotor for an electric machine which is connectable to a machine shaft, comprising: a hollow-cylindrical core configured to be connected non-rotatably to the machine shaft a hollow-cylindrical body surrounding the hollow-cylindrical core, wherein the core has a plurality of radial bulges which are offset relative to one another by a defined offset angle in the circumferential direction and in the axial direction over its outer surface, wherein each radial bulge of the plurality of radial bulges is delimited over an angular range which is smaller than the offset angle, and wherein the hollow-cylindrical core is permanently connected, in particular to the hollow-cylindrical body by way of a joining process.

2. The rotor as claimed in claim 1, wherein: the hollow-cylindrical core is formed by a rotor blade stack that includes a plurality of rotor laminations, and each of the plurality of rotor laminations has at least one radial bulge and adjacent rotor laminations of the plurality of rotor laminations with at least one radial bulge are rotated relative to one another by the offset angle.

3. The rotor as claimed in claim 2, wherein each rotor lamination of the rotor blade stack has at least one radial bulge and is rotated relative to its adjacent rotor lamination by the offset angle.

4. The rotor as claimed in claim 1, wherein the offset angle corresponds to at least twice the value of the angular range of the at least one radial bulge.

5. The rotor as claimed in claim 1, wherein the radial bulges of the hollow-cylindrical core over an angular range of less than 30°, exceed a maximum radius that exists over the remaining outer surface of the hollow-cylindrical core by a height of approximately 0.01 to 5%.

6. The rotor as claimed in claim 1, wherein the hollow-cylindrical body is a magnetic ring, a protective sleeve, or a sensor ring.

7. A method for producing a rotor for an electric machine, comprising: using rotor laminations for a rotor blade stack of the rotor, wherein a plurality of rotor laminations each have at least one radial bulge delimited over an angular range, stacking the rotor laminations to form the rotor blade stack in such a way that adjacent rotor laminations of the plurality of rotor laminations with at least one radial bulge are rotated relative to one another by a defined offset angle which is larger than the angular range of the at least one radial bulge, applying a joining agent to an outer surface of the rotor blade stack and/or to an inner surface of a hollow-cylindrical body, and pushing the hollow-cylindrical body onto the rotor blade stack.

8. The method as claimed in claim 7, wherein each rotor lamination of the rotor blade stack has at least one radial bulge and is rotated relative to its adjacent rotor lamination by the offset angle.

9. The method as claimed in claim 7, wherein the pushing step includes pushing the hollow-cylindrical body onto the bulges of the rotor blade stack with a small amount of play.

10. The method as claimed in claim 7, wherein the offset angle by which the rotor lamination is rotated relative to the adjacent rotor lamination corresponds to at least twice the value of the angular range of the at least one radial bulge and is at least 30°.

11. The method as claimed in claim 7, wherein the rotor blade stack and the hollow-cylindrical body are rotated relative to each other during the joining process.

12. An electric machine with a rotor as claimed in claim 1.

13. An electric treatment device with an electric machine as claimed in claim 12.

14. The rotor as claimed in claim 1, wherein the hollow-cylindrical core is adhesively bonded to the hollow-cylindrical body by way of the joining process.

15. The rotor as claimed in claim 4, wherein the offset angle is at least 30°.

16. The rotor as claimed in claim 15, wherein the offset angle is at least 60°.

17. The rotor as claimed in claim 1, wherein the radial bulges of the hollow-cylindrical core over an angular range of less than 10° exceed a maximum radius that exists over the remaining outer surface of the hollow-cylindrical core by a height of approximately 0.02% to 2%.

18. The method of claim 7, wherein the applying step includes applying the joining agent between the radial bulges.

19. The method as claimed in claim 10, wherein the offset angle by which the rotor lamination is rotated relative to the adjacent rotor lamination is at least 60°.

20. An electric machine with a rotor produced according to the method as claimed in claim 7.

Description

[0026] In the drawings:

[0027] FIG. 1 shows a view in cross-section of a three-phase electric machine, in particular a three-phase brushless direct-current machine, with a rotor according to the prior art having four buried magnets (Figure la) and with a magnetic ring according to the prior art having four surface magnets (Figure lb),

[0028] FIG. 2 shows a circuit diagram of a driver circuit according to the prior art for controlling the electric machine according to FIG. 1,

[0029] FIG. 3 shows an exemplary embodiment of a rotor blade stack according to the invention in a perspective view;

[0030] FIG. 4 shows an exemplary embodiment of a rotor lamination according to the invention in a plan view;

[0031] FIG. 5 shows the rotor blade stack according to the invention according to FIG. 3 with the hollow-cylindrical body pushed over it in a front view, and

[0032] FIG. 6 shows the rotor blade stack according to the invention according to FIGS. 3 and 5 with the hollow-cylindrical body pushed over it in an axial section.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0033] FIGS. 1a and 1b each show a view in cross-section through a three-phase electric machine 10, in particular a three-phase brushless direct-current machine 12, with a stator 14 and a rotor 18 according to the prior art which is arranged non-rotatably on a machine shaft 16. The electric machine 10 equally take the form of an electric motor or a generator. The rotor 18 of the electric machine 10 comprises a hollow-cylindrical core 20 which, according to Figure la, has an even-numbered plurality of permanent magnets 24 which are buried in pockets 22 and alternate in polarity N, S in the circumferential direction U of the rotor 18. Figure lb shows an alternative embodiment of the rotor 18 with a hollow-cylindrical body 26, in the form of a magnetic ring, with corresponding permanent magnets 22 in the form of surface magnets 28. In each case four permanent magnets 22 are illustrated in both exemplary embodiments and themselves form two pairs of rotor poles. The stators 14 according to FIGS. 1a and 1b each have six radially inward directed stator teeth 30 which themselves each carry an individual tooth winding 32 of a stator winding 34. A stator 14 defines with its stator teeth 30 a cylindrical cavity in which the rotor 18 is arranged so that it can move in rotation relative to the stator 14. A rotating magnetic field, which entrains the permanently excited rotor 18 when the motor is running, is generated by means of the stator winding 34.

[0034] Alternatively, it is also conceivable that the rotor 18 induces a voltage in the stator winding 34 in generator mode.

[0035] An example of a power output stage 36, which is controlled with the aid of a closed- or open-loop control unit 38, is illustrated in FIG. 2. The power output stage 38 has a half-bridge 42, in the form of an inverter circuit, per phase line 40 of the stator winding 34 connected in a delta circuit. Each half-bridge 42 consists of a first power switch 44, which is connected to a high supply potential VH (high side), and a second power switch 46, which is connected to a low supply potential VL (low side). The power switches 44, 46 can take the form of semiconductor switches in the form of IGBT, IGCT, thyristors, power MOFSETs, or the like but also of a relay. The closed- or open-loop control unit 38 controls the power switches 44, 46 in order to energize in each case two phase lines 40 according to a pulse width modulation (PWM) in such a way that one of the first power switches 44 (for example, T1) of one of the three half-bridges 42 is closed, whilst the two other first power switches 44 (T3, T5) are opened, and that one of the second power switches 46 (for example, T2) of a further one of the half-bridges 42 is closed, whilst the two remaining second power switches 46 (T4, T6) are opened. In this way, in order to generate the rotating magnetic field, the first power switches 44 and the second power switches 46 can be switched alternately by means of three rotor position sensors 47, which for example take the form of Hall effect sensors, in such a way that four individual tooth windings 28 of the stator winding 30 are energized at all times such that during operation the resulting stator flux is on average oriented perpendicularly to the rotor flux. This type of circuit is known to a person skilled in the art such that no further detail needs to be described here.

[0036] According to the invention, it is then described in FIGS. 3 to 6 that the hollow-cylindrical core 20, connected non-rotatably to the motor shaft 16, of the rotor 18 has a plurality of radial bulges 48 which are offset relative to one another by a defined offset angle V in a circumferential direction U and in an axial direction A over its outer surface. According to FIG. 3, each radial bulge 48 is here delimited over an angular range W which is smaller than the offset angle V of the radial bulges 48. FIG. 3 shows the structure of the hollow-cylindrical core 20 as a rotor blade stack 52 consisting of rotor laminations 50. For this purpose, the rotor laminations 52 are accordingly stacked one above or next to another (depending on the viewing direction).

[0037] The offset angle V of two radial bulges 48 which are adjacent in the circumferential direction U corresponds at least to twice the value of the angular range W of the at least one radial bulge 48. The offset angle V is preferably at least 30°, particularly preferably approximately 60°.

[0038] With reference to the production method according to the invention of the rotor 18, a plurality of rotor laminations 50 of the rotor blade stack 52 in each case have at least one radial bulge 48 delimited over the angular range W. FIG. 4 shows such a rotor lamination 50 in a plan view. The rotor laminations 50 are then stacked to form the rotor blade stack 52 in such a way that adjacent rotor laminations 50 of the plurality of rotor laminations 50 with at least one radial bulge 48 are rotated relative to one another by the defined offset angle V. It is completely possible here, in a variant of the exemplary embodiment according to FIG. 3, to provide rotor laminations 50 with no radial bulge between rotor laminations 50 with at least one radial bulge 48. It is likewise conceivable to use rotor laminations 50 with a plurality of radial bulges 48, the respective angular range W of which is smaller than the offset angle V.

[0039] According to FIG. 5, for the procedure of joining the rotor blade stack 52 or the hollow-cylindrical core 20 to the hollow-cylindrical body 26 surrounding the latter, a joining agent 54, in particular an adhesive, is applied to the outer surface of the rotor blade stack 52 or the hollow-cylindrical core 20, preferably between the radial bulges 48, and/or to an inner surface of the hollow-cylindrical body 26, and the hollow-cylindrical body 26 according to FIG. 6 is then pushed in an axial direction A onto the rotor blade stack 52 or the hollow-cylindrical core 20 in order to permanently connect the two components such that a bonding gap 56 is formed between them. The rotor blade stack 52 and the hollow-cylindrical body 26 are here preferably rotated relative to one another during the joining process. In order to absorb any temperature-related expansions of the rotor blade stack 52 or the hollow-cylindrical core 20 as a consequence of operation of the electric machine 10 with high power demands, there is a small amount of play between the radial bulges 48 and the inner surface of the hollow-cylindrical body 26. The hollow-cylindrical body 26 usually takes the form of a magnetic ring which has the same axial structural length as the core 20. It is, however, also possible, without limiting the invention, that the hollow-cylindrical body 26 and the core 20 have different axial lengths. Thus, the hollow-cylindrical body 26 can therefore also take the form of a protective sleeve of the rotor 10, of a sensor ring, or the like.

[0040] Depending on the adhesive used and the associated optimal bonding gap 56 or joining procedure, the radial bulges 48 of the core 20 or the rotor blade stack 52 over an angular range W of less than 30°, preferably less than 20°, particularly preferably approximately 10°, exceed the maximum radius R that exists over the remaining outer surface of the core 20 or the rotor blade stack 52 by a height H of approximately 0.01% to 5%, preferably of approximately 0.02% to 2% (cf FIG. 4).

[0041] The radial bulges 48 thus, on the one hand, locally narrow the play between the components to be joined such that the possible concentricity errors are minimized directly without the additional incorporation of additional spacer particles. On the other hand, the defined bonding gap 56 is ensured in all other regions between the two components in order to ensure the curing of the adhesive and hence the mechanical resistance of the adhesive connection and to ensure axial and radial permeability of the adhesive such that it can spread unhindered in the whole bonding gap 56 during the joining procedure.

[0042] It should finally be pointed out that the invention is not limited to either the exemplary embodiment shown according to FIGS. 3 to 6 or to the illustrated form and number of the rotor laminations 50 and their radial bulges 48.