Electric Motor

Abstract

An electric motor (1), at least having: a rotor (2) with an axis of rotation (3) and an annular stator (4) surrounding the rotor (2), the stator extending along an axial direction (5) parallel to the axis of rotation (3) and having a first end face (6) and a second end face (7) pointing in opposite axial directions (5); wherein the stator (4) has exactly two stator teeth (8, 9) extending from an annular circumferential surface (10) that runs between the end faces (6, 7) of the stator (4), in a radially inward direction (11) to the rotor (2) and facing one another in relation to the axis of rotation (3), a first stator slot (12) and a second stator slot (13), which faces the first slot in relation to the axis of rotation (3), extending along the circumferential surface (10), between the stator teeth (8, 9).

Claims

1. An electric motor, at least having a rotor with a rotation axis and having an annular stator which surrounds the rotor, extends along an axial direction that is parallel to the rotation axis and respectively has a first end side and a second end side that point in opposite axial directions; wherein the stator has precisely two stator teeth which, starting from an annular circumferential surface of the stator, which circumferential surface extends between the end sides extend along a radial direction inward toward the rotor and are arranged opposite one another with respect to the rotation axis, wherein a first stator slot and a second stator slot, which is arranged opposite with respect to the rotation axis, extend along the circumferential surface between the stator teeth; wherein at least one first winding is arranged in the first stator slot and at least one second winding is arranged in the second stator slot, wherein each winding extends over the end sides and on the outside and on the inside in the radial direction around the annular circumferential surface.

2. The electric motor as claimed in claim 1, wherein the first winding and the second winding are arranged in relation to one another and electrically connected to one another such that a magnetic flux, which can be generated by the respective winding during operation, is directed through the circumferential surface along opposite circumferential directions in the region of the stator slots and is added up in the region of the stator teeth and can be conducted across the stator teeth and the rotor along the radial direction.

3. The electric motor as claimed in claim 2, wherein the at least one first winding and the at least one second winding are connected to one another in parallel.

4. The electric motor as claimed in claim 2, wherein the at least one first winding and the at least one second winding are connected to one another in series.

5. The electric motor as claimed in claim 1, wherein a plurality of windings are arranged in each stator slot, wherein at least the windings of one stator slot are connected to one another in parallel or in series.

6. The electric motor as claimed in claim 1, wherein at least one stator tooth, starting from the annular circumferential surface, extends along a radial direction inward toward the rotor and as far as an inner circumferential surface of the stator tooth and, along this extent, has a tapered portion with respect to a circumferential direction.

7. The electric motor as claimed in claim 1, wherein a smallest distance between an outer circumferential surface of the rotor and an inner circumferential surface of the stator teeth is between 5 and 20 millimeters.

8. The electric motor as claimed claim 1, wherein at least one of the stator teeth extends beyond the at least one end side along the axial direction and forms a projection.

9. The electric motor as claimed in claim 1, wherein the rotor has a structure for conveying a fluid along the axial direction through an intermediate space formed between the rotor and the stator.

10. An arrangement, at least comprising an electric motor as claimed in claim 1, and at least one voltage source, wherein the first winding and the second winding are arranged in relation to one another and connected such that an electric current can flow through them in opposite directions.

Description

[0060] The invention and the technical field will be discussed in more detail below on the basis of the figures. It is pointed out that the invention is not intended to be restricted by the exemplary embodiments shown. In particular, unless explicitly presented otherwise, it is also possible for partial aspects of the substantive matter discussed in the figures to be extracted and combined with other constituent parts and knowledge from the present description and/or figures. The same reference signs are used to denote identical objects, such that, where appropriate, explanations from other figures can be taken into consideration in a supplementary manner. In the figures, in each case schematically:

[0061] FIG. 1 shows a perspective view, partially in section, of an arrangement comprising an electric motor;

[0062] FIG. 2 shows the electric motor of the arrangement according to FIG. 1 in a view along the rotation axis;

[0063] FIG. 3 shows the electric motor according to FIG. 2 in a view along the rotation axis with a course of the magnetic flux;

[0064] FIG. 4 shows a perspective view of the electric motor according to FIGS. 2 and 3; and

[0065] FIG. 5 shows a graph.

[0066] FIG. 1 shows a perspective view, partially in section, of an arrangement 25 comprising an electric motor 1. FIG. 2 shows the electric motor 1 of the arrangement 25 according to FIG. 1 in a view along the rotation axis 3. FIG. 3 shows the electric motor 1 according to FIG. 2 in a view along the rotation axis 3 with a course of the magnetic flux 30. FIG. 4 shows a perspective view of the electric motor 1 according to FIGS. 2 and 3. FIGS. 1 to 4 will be described together in the text which follows.

[0067] The electric motor 1 comprises a rotor 2 with a rotation axis 3 and comprises an annular stator 4 which surrounds the rotor 2 and is arranged coaxially to the rotor 2. The stator 4 extends along an axial direction 5 that is parallel to the rotation axis 3 and respectively has a first end side 6 and a second end side 7 that point in opposite axial directions 5. The stator 4 has precisely two stator teeth 8, 9 which, starting from an annular circumferential surface 10 of the stator 4, which circumferential surface extends between the end sides 5, 6, extend along a radial direction 11 inward toward the rotor 2 and are arranged opposite one another with respect to the rotation axis 3 (that is to say offset in relation to one another through 180 angular degrees in a circumferential direction 27). A first stator slot 12 and a second stator slot 13, which is arranged opposite with respect to the rotation axis 3, extend along the circumferential surface 10 between the first stator tooth 8 and the second stator tooth 9. A plurality of first windings 14 are arranged in the first stator slot 12 and a plurality of second windings 15 are arranged in the second stator slot 13, wherein each winding 14 extends over the end sides 6, 7 and on the outside and on the inside in the radial direction 11 around the circumferential surface 10. In FIGS. 1 to 3, the parts of each of the windings 14, 15 that extend along the end sides 6, 7 along the radial direction 11 are cut away and therefore not illustrated. The complete windings 14, 15 are illustrated only in FIG. 4.

[0068] The windings 14, 15 do not extend around the stator teeth 8, 9, but rather only around the annular circumferential surface 10. Individual windings 14, 15 are arranged adjacent to one another along the circumferential direction 27.

[0069] The first winding 14 and the second windings 14, 15 are arranged in relation to one another and electrically connected to one another such that a magnetic flux 30, which can be generated by the respective winding 14, 15 during operation of the electric motor 1, is directed through the circumferential surface 10 (the main body of the stator 4) along opposite circumferential directions 27 in the region of the stator slots 12, 13 and is added up in the region of the stator teeth 8, 9 and can be conducted across the stator teeth 8, 9 and the rotor 2 along the radial direction 11 (see FIGS. 1, 3 and 4).

[0070] Here, the first windings 14 and the second windings 15 are connected to one another in parallel. The first windings 14 and the second windings 15 are windings 14, 15 that are independent of one another.

[0071] A plurality of windings 14, 15 are arranged in each stator slot 12, 13, wherein the windings 14, 15 of one stator slot 12, 13 (that is to say first windings 14 in the first stator slot 12 or second windings 15 in the second stator slot 13) are connected to one another in series (see indication in FIG. 1). Therefore, here, the first windings 14 are connected to one another in series. Furthermore, the second windings 15 are connected to one another in series. The first windings 14 and the second windings 15 are connected to one another in parallel.

[0072] Here, an identical number of windings 14, 15 are arranged in the two stator slots 12, 13.

[0073] One winding 14, 15 extends at least along the axial direction 5 along the circumferential surfaces 10 (that is to say on the outside and on the inside of the circumferential surface 10) and along the radial direction 11 beyond the end sides 6, 7 of the annular stator 4 and in so doing over the end sides 6, 7 and in the radial direction 11 on the outside and on the inside around the circumferential surface 10.

[0074] The arrangement of the windings 14, 15 through which an electric current 16 flows in opposite directions in stator slots 12, 13 that are separated from one another by the two stator teeth 8, 9 allows the magnetic field lines (or the magnetic flux 30) to be conducted along the circumferential direction 27 through the main body of the stator 4 and through the winding 14, 15 toward the stator tooth 8, 9. At the first stator tooth 8, the magnetic field lines (the magnetic flux 30) exit from the windings 14, 15 of the opposite stator slots 12, 13 and are guided along the radial direction 11 through the first stator tooth 8 toward the rotor 2 and across the rotor 2 toward the second stator tooth 9. At this second stator tooth 9, the magnetic field lines (the magnetic flux 30) are guided toward the main body of the stator 4 and there passed on through the windings 14, 15 and through the main body of the stator 4 in the circumferential direction 27. The different polarized ends of each winding 14, 15 or of the electrical conductor that forms the at least one winding 14, 15 in the respective stator slot 12, 13 are therefore at a maximum distance from one another, and therefore a stray field is as small as possible. One end of the electrical conductor of a stator slot is arranged, in particular, in the immediate vicinity of one stator tooth 8, 9 and the other end is arranged in the immediate vicinity of the other stator tooth 9, 8 (see FIG. 1).

[0075] In this embodiment of an electric motor 1, a stray field can be kept small, wherein an air gap or distance 18 between the stator tooth 8, 9 and the rotor 2 can be designed to be particularly large. Therefore, the diameter of the rotor 2 can be designed to be small, and therefore the intermediate space 24 of the motor 1 can be realized with a large throughflow cross section.

[0076] The stator teeth 8, 9, starting from an annular circumferential surface 10 of the stator 4, which circumferential surface extends between the end sides 6, 7, extend along a radial direction 11 inward toward the rotor 2 as far as an inner circumferential surface 20 of the stator tooth 8, 9. Along this extent 33, the stator tooth 8, 9 has a tapered portion 34 with respect to the circumferential direction 27, i.e. a width of the stator tooth 8, 9, which width extends in the circumferential direction 27, is at minimum between the circumferential surface 10 of the stator 4, which circumferential surface points inward in the radial direction 11, and the inner circumferential surface 20 of the stator tooth 8, 9.

[0077] The inner circumferential surface 20 of the stator teeth 8, 9 is of wider design along the circumferential direction 27 than the region of the stator tooth 8, 9 between the circumferential surface 10 of the stator 4 and the tapered portion 34.

[0078] The stator tooth 8, 9 extends along the radial direction 11 and, starting from the circumferential surface 10 of the stator 4, over a first section 35 toward the tapered portion 34 and, starting from the tapered portion 34, over a second section 36 toward the inner circumferential surface 20.

[0079] The second section 36 extends in the circumferential direction 27 over a second angular range 38 of approximately 90 angular degrees which exceeds a greatest first angular range 37 of approximately 30 angular degrees of the first section 35 by approximately 200%. The angular range 37, 38 is determined starting from a rotation axis 3 of the motor 1.

[0080] The first section 35 as far as the tapered portion 34 extends starting from the circumferential surface 10 of the stator 4 and along the radial direction 11 inward beyond the windings 14, 15.

[0081] The first section 35 comprises approximately 75% of the extent 33 of the stator tooth 8, 9 along the radial direction 11.

[0082] The two stator slots 12, 13 each extend over a third angular range 39 of approximately 150 angular degrees along the circumferential direction 27.

[0083] The at least one winding 14, 15, which extends around the circumferential surface 10 of the stator 4 and is arranged only in one stator slot 12, 13, extends over a proportion of approximately 97% of this third angular range 39.

[0084] The rotor 2 has (next to one another along the circumferential direction 27) two poles 17 of a permanent magnet, which two poles are respectively magnetized in the radial direction 11 (see FIG. 2). The poles 17 are arranged offset in relation to one another through 180 angular degrees along the circumferential direction 27 and point in opposite radial directions 11. The poles 17 are separated from one another by a boundary which extends transversely to an extent 33 of the stator teeth 8, 9 here (dashed line in FIG. 2).

[0085] A smallest distance 18 between an outer circumferential surface 19 of the rotor 2 and an inner circumferential surface 20 of the stator teeth 8, 9 is at least 5 millimeters.

[0086] FIGS. 1 and 4 show that the stator teeth 8, 9 extend beyond the two end sides 6, 7 along the axial direction 5 and in so doing form a projection 40 on each end side 6, 7. This projection 40 extends over the entire extent 33 of the respective stator tooth 8, 9 along the radial direction 11. Therefore, the inner circumferential surface 20 of the respective stator tooth 8, 9, which inner circumferential surface is situated opposite the rotor 2, can be increased in size, so that, with a given electric current, a magnetic flux density in the region of the inner circumferential surface 20 of the stator teeth 8, 9 can be reduced and a magnetic reluctance can be lowered.

[0087] A bearing 21 of the rotor 2 is arranged outside the stator 4 along the axial direction 5. The rotor 2 (but in particular not the poles 17 of the magnet) extends beyond the extent of the stator 4, that is to say at least beyond an end side 6, 7, here the first end side 6, along the axial direction 5. The poles 17 may possibly also extend beyond the extent of the stator 4, so that a possible torque can be increased.

[0088] The rotor 2 has a structure 22 for conveying a fluid 23 along the axial direction 5 through an intermediate space 24 formed between the rotor 2 and the stator 4. During operation of the motor 1, the structure 23 displaces the fluid 23 in the axial direction 5, so that a fluid flow through the intermediate space 24 can be generated.

[0089] The arrangement 25 illustrated in FIG. 1 comprises the motor 1 and a voltage source 26. The voltage source 26 is, in particular, a sinusoidal source (and not a DC source) or a switchable voltage source or power electronics system. The plurality of first windings 14 and the plurality of second windings 15 are arranged in relation to one another and connected such that an electric current 16 can flow through them in opposite directions, so that a magnetic flux 30, starting from the poles 17 of the magnet, is conducted across the stator teeth 8, 9 in the radial direction 11 into the circumferential surface 10 of the stator 4 and through the circumferential surface 10 of the stator 4 along the circumferential direction 27.

[0090] FIG. 5 shows a graph. A rotation speed 29 in revolutions per minute of the electric motor 1 is plotted on the horizontal axis. A torque 28, which can be generated by the electric motor 1, in Newton meters is plotted on the vertical axis. The first profile 31 shows the torque 28 of an electric motor 1 of different construction. The second profile 32 shows the achievable torque 28 of the electric motor 1 described here, which achievable torque is higher at almost all operating points.

LIST OF REFERENCE SIGNS

[0091] 1 Motor [0092] 2 Rotor [0093] 3 Rotation axis [0094] 4 Stator [0095] 5 Axial direction [0096] 6 First end side [0097] 7 Second end side [0098] 8 First stator tooth [0099] 9 Second stator tooth [0100] 10 Circumferential surface [0101] 11 Radial direction [0102] 12 First stator slot [0103] 13 Second stator slot [0104] 14 First winding [0105] 15 Second winding [0106] 16 Current [amperes], that is to say [A] [0107] 17 Pole [0108] 18 Distance [0109] 19 Outer circumferential surface [0110] 20 Inner circumferential surface [0111] 21 Bearing [0112] 22 Structure [0113] 23 Fluid [0114] 24 Intermediate space [0115] 25 Arrangement [0116] 26 Voltage source [0117] 27 Circumferential direction [0118] 28 Torque [Newton meters], that is to say [Nm] [0119] 29 Rotation speed [revolutions per minute], that is to say [rpm] [0120] 30 Magnetic flux [Tesla square meters], that is to say [T*m.sup.2] [0121] 31 First profile [0122] 32 Second profile [0123] 33 Extent [0124] 34 Tapered portion [0125] 35 First section [0126] 36 Second section [0127] 37 First angular range [0128] 38 Second angular range [0129] 39 Third angular range [0130] 40 Projection