electric machine

Abstract

Electric machine (1), for use in an electrically powered motor vehicle, comprising a rotor (20) comprising a rotor core arranged on a rotor shaft (30), and a stator (10) surrounding the rotor (20) comprising a stator core formed from stator laminations (13a, 13b, 13c, ...) and support stator laminations (13x, 13y, 13z), wherein the single rotor shaft (30) is supported by the stator (10) such that the rotor core of the rotor (20) is formed in the axial direction from two partial cores (21, 22) with approximately the same dimensions, which are configured such that they can be connected to the rotor shaft (30) in different ways, are each separately and rotationally fixed to the rotor shaft (30) and carry a radial bearing (40) arranged on the rotor shaft (30) between them, the stator core (10) having a fixed connecting finger (13') has, which is located between the two subnuclei (21,22) extends substantially orthogonally to the rotor axis (30) and contacts the radial bearing (40) and is extended axially between the sub-cores (21, 22) to form the connecting finger (13') in the area to the radial bearing (40), and the support stator laminations (13x, 13y, 13z) are provided for the axial area between the sub-cores (21, 22) to form the connecting finger (13').

Description

[0001] The invention relates to an electric machine for use in an electrically powered motor vehicle, for example a hybrid or electric vehicle.

[0002] Such electric machines are known, for example, from US 7,843,100 B2 or DE 697 35 741 T2. They have a rotor arranged radially within a stationary stator. Because the two are separated by a radial gap, the rotor can rotate within the stator. The rotor comprises a rotor core rigidly connected to a rotor shaft, which has recesses in which permanent magnets are arranged. The stator comprises a stator core with slots in which wire windings are arranged. Typically, the rotor core and stator core are made of ferrous metal. When current is energized, a magnetic force acts between the permanent magnets of the rotor and the wire windings of the stator, which rotates the rotor relative to the stator if the rotor shaft is appropriately supported.

[0003] Furthermore, electric machines are known in which two completely separate rotors are arranged within a common stator; see, for example, US 5,172,784 A and JP 2011-188567 A. Such electric machines do not have a single rotor axis with a corresponding rotor core, but rather two separate rotor axes. Each of the two rotor axes carries its own rotor core, forming two separate rotors. An axial bearing or thrust bearing is arranged between the two rotor axes to allow independent rotation of the two rotor axes or rotors within the stator. This arrangement is intended, in particular, to provide a simple means of controlling the left and right wheels of a vehicle's axle independently.However, the relatively large pressure forces occurring here between the two rotor axes must be absorbed by a thrust bearing which, due to the limited space in the stator, can only be dimensioned relatively small.

[0004] From US 3 506 861 A and DE 693 13 744 T2, an electric machine is known in which two rotors are each connected to the single rotor axis.

[0005] US 6 225 719 B1 discloses a method for manufacturing an electric machine in which two rotor cores, each having recesses in which permanent magnets are arranged, and a stator with a core is provided in whose slots wire windings are arranged and which is formed from stator laminations and support stator laminations which form a fixed connecting finger which contacts the radial bearing.

[0006] Pressing and splined connection of rotor cores to the rotor shaft are alternative design measures for fastening rotor cores to a rotor shaft known to those skilled in the art from DE 10 2007 060 011 A1 and JP 2004 - 248 443 A.

[0007] When using an electric motor in an electrically powered vehicle, a high top speed and rapid response to changes in speed, i.e., good acceleration, are desirable. For this purpose, it is advantageous to keep the rotor of the electric motor relatively small in radial dimensions. On the other hand, the electric motor must be able to provide sufficient torque to reliably propel the vehicle, especially when loaded. This requires electric motors with correspondingly large dimensions. To prevent the radial dimensions of the electric motor from becoming too large, its axial dimensions must be increased. However, this presents the problem that, particularly at high speeds, the rotor shaft tends to deflect.This creates the risk that the distance between the rotor and stator will be reduced to such an extent that the rotor, with its radially outer area, will touch the stator in its radially inner area. Since this would lead to serious damage to the electric motors, such contact must be prevented at all costs.

[0008] According to the invention, the rotor axis is therefore supported on the stator in such a way that the rotor core is formed in the axial direction from at least two sub-cores, which are each separately and rotationally fixed to the same, single rotor axis and carry a radial bearing arranged on the rotor axis between them, wherein the stator core has a fixed connecting finger which extends between the two sub-cores and contacts the radial bearing.

[0009] The support of the rotor shaft via the connecting finger on the stator, as described in the invention, reliably prevents deflection of the rotor shaft, while the radial bearing continues to ensure undisturbed rotation of the rotor relative to the stator. Even at high speeds of the electric machine, i.e., at rapid rotation of the rotor shaft, a suitably dimensioned support according to the invention reliably counteracts any centrifugal force that may occur.

[0010] According to the invention, the radial or rotary bearing is arranged on the single rotor axis of the electric machine to allow rotation of the rotor axis relative to the stationary connecting finger of the stator and to reliably suppress movements in the radial direction. This distinguishes the electric machine according to the invention from those of US 5,172,784 A and JP 2011-188567 A, where an axial or thrust bearing is provided instead. This is because, in the latter case, there is no support of a single rotor axis against a stationary stator, but rather mutual support between two rotor axes that rotate independently of each other.

[0011] The radial bearing provided according to the invention can be designed either as a plain bearing or as a rolling bearing. While in a plain bearing the stationary connecting finger of the stator core has direct contact with the single rotor axis, in a rolling bearing the two support each other via rolling elements. Depending on the intended use and / or size of the electric machine, various implementations are possible, such as low-friction material pairings, lubrication, or special rolling elements.

[0012] According to the invention, both sub-cores of the rotor core have approximately the same dimensions. This allows the radial bearing to be positioned almost centrally on the single rotor axis, which, due to the symmetry, enables particularly reliable support.

[0013] The sub-cores are configured so that they can be connected to the single rotor shaft in different ways. This can simplify the manufacturing of the electric machine according to the invention. In particular, it is provided that at least one of the sub-cores can be pressed onto the single rotor shaft. This is preferably the sub-core that is first connected to the rotor shaft in a rotationally fixed manner. A further sub-core can then be provided for mounting via a splined connection, preferably after a connecting finger of the stator core has contacted a corresponding radial bearing.

[0014] In a preferred embodiment of the invention, the connecting finger(s) between the radial bearing and the stator core are aligned orthogonally to the single rotor axis. By eliminating inclined supports, i.e., those deviating from the orthogonal axis, the usable volume of the sub-cores can be maximized. This allows for a particularly space-saving support arrangement. A connecting finger can nevertheless be designed to be sufficiently stable, for example, by being constructed as a solid circular arc between the single rotor axis and the stator core. Alternatively, connecting fingers can also be configured as a plurality of struts that are orthogonal to the single rotor axis, for example, made of a particularly strong metal alloy.

[0015] According to the invention, the stator core is extended axially in the area between two sub-cores up to the radial bearing in order to form a connecting finger. By essentially integrating the connecting finger into the stator core, the manufacturing of the electric machine according to the invention is particularly simple.

[0016] The connecting finger is then efficiently integrated into the stator core by using support stator laminations, as specially designed stator laminations, for that area of ​​the stator core which is provided in the axial direction between the sub-cores of the rotor, in order to form a connecting finger for support on the radial bearing.

[0017] The invention will now be described in more detail with reference to a drawing. The single figure shows a preferred embodiment of the invention.

[0018] The diagram shows an electric machine 1 comprising a stationary stator 10 and a rotatable rotor 20 therein. The rotor 20 is non-rotatably connected to a single, continuous rotor shaft 30. The rotor shaft 30 is supported in two radial bearings 31, 32, which are designed as rolling bearings. The outer rings of the rolling bearings, like the stator 10, are stationary. For this purpose, they are connected in a suitable manner, not shown in detail, for example to a housing of the electric machine 1.

[0019] The stator 10 of the electric machine 1 comprises a plurality of individual stator laminations 13a, 13b, 13c, .... These stator laminations are stacked in a known manner and then fixed together, for example by welding. Subsequently, corresponding wire windings are inserted into slots (not shown in detail). Only the axially projecting winding heads 11, 12 of these wire windings are shown.

[0020] Furthermore, the electric machine 1 comprises a rotor 20 with two sub-cores 21 and 22. Both sub-cores 21 and 22 are rotationally fixed to the same rotor axis 30. Each rotor core comprises a plurality of individual rotor laminations with recesses in which permanent magnets are arranged (not shown). An axial gap is provided between the two sub-cores 21 and 22, extending over the entire cross-sectional area of ​​the sub-cores 21 and 22. In other words, an annular air gap lies between the two sub-cores 21 and 22, extending from the rotor axis 30 to the stator 10.

[0021] A connecting finger 13' now extends through this air gap. This finger is formed by three support stator laminations 13x, 13y, 13z. The three support stator laminations 13x, 13y, 13z have the same outer contour in the radial direction as the other stator laminations 13a, 13b, 13c, ..., but have a much smaller inner diameter. The inner diameter of the stator laminations 13a, 13b, 13c, ... is dimensioned such that it provides sufficient radial space to accommodate a partial core 21, 22, and also a corresponding radial gap to it. In contrast, the inner diameter of the three support stator laminations 13x, 13y, 13z is chosen so that it extends to near the rotor axis 30. This is easily possible by arranging the three support stator laminations 13x, 13y, 13z in the axial direction such that they are positioned just between the two sub-cores 21, 22, i.e. in the area of ​​the corresponding air gap.In particular, the axial distance between the sub-cores 21 and 22 and the thickness of the three support stator laminations 13x, 13y, 13z are selected such that sufficient axial clearance remains between an outer support stator lamination and the surface of a sub-core. In other words, there is sufficient space between the left side of the support stator lamination 13x and the sub-core 21, and between the right side of the support stator lamination 13z and the sub-core 22, for unimpeded rotation of the rotor 20 on the single rotor axis 30 in the stator 10 with the connecting finger 13'.

[0022] A rotary bearing, or radial bearing, is provided on the single rotor shaft 30, and is designed here as a rolling bearing 40. The inner ring 41 of the rolling bearing 40 is non-rotatably connected to the rotor shaft 30. The outer ring 42 of the rolling bearing 40 is non-rotatably connected to the connecting finger 13' formed by the three support stator laminations 13x, 13y, 13z. Rolling elements (not shown) are provided between the inner ring 41 and the outer ring 42 to allow unimpeded rotation of the inner ring 41, and thus of the rotor shaft 30 or the rotor 20, relative to the outer ring 42, and thus of the stationary stator 10 or the connecting finger 13'. By connecting the outer ring 42 to the support stator laminations 13x, 13y, 13z in a rotationally fixed manner, it is as stationary as the stator 10 itself. This allows the rotor axis 30 with the rotor 20 to rotate freely relative to the stator 10.

[0023] Even at high speeds of the electric machine 1, the single rotor axis 30 no longer deflects. This is because the centrifugal forces acting on the rotor axis 30 are now counteracted by the support in the form of the connecting finger 13' formed from the support stator laminations 13x, 13y, 13z and the radial bearing 40. By absorbing the centrifugal forces, this support prevents deflection of the rotor axis 30, even at high speeds of the electric machine 1.

[0024] For the simplified manufacture of the illustrated electric machine 1, the first, left-hand core section 21 is pressed onto the single rotor shaft 30 in a known manner. The stator 10 is then connected to the outer ring 42 of the rotary bearing 40 in a rotationally fixed manner by means of the support stator laminations 13x, 13y, 13z. Since the protruding stator 10 now makes it difficult to mount the second, right-hand core section 22 of the electric machine 1, this core section 22 is mounted using a splined connection 23. This results in a rotationally fixed fit of the second, right-hand core section 22 on the rotor shaft 30. The remaining steps for the manufacture of the electric machine 1 are again carried out in a known manner. In particular, bearings 31, 32 are mounted, which allow for unimpeded rotation of the single rotor shaft 30.

Claims

[1] Electric machine (1), for use in an electrically powered motor vehicle, comprising a rotor (20) comprising a rotor core arranged on a rotor shaft (30), and a stator (10) surrounding the rotor (20) comprising a stator core formed from stator laminations (13a, 13b, 13c, ...) and support stator laminations (13x, 13y, 13z), wherein the single rotor shaft (30) is supported by the stator (10) such that the rotor core of the rotor (20) is formed in the axial direction from two partial cores (21, 22) with approximately the same dimensions, which are configured such that they can be connected to the rotor shaft (30) in different ways, are each separately and rotationally fixed to the rotor shaft (30) and carry a radial bearing (40) arranged on the rotor shaft (30) between them, the stator core (10) has a fixed connecting finger (13') that is located between the two sub-cores (21,22) extends substantially orthogonally to the rotor axis (30) and contacts the radial bearing (40) and is extended axially between the sub-cores (21, 22) to form the connecting finger (13') in the area to the radial bearing (40), and the support stator laminations (13x, 13y, 13z) are provided for the axial area between the sub-cores (21, 22) to form the connecting finger (13'). [2] Method for manufacturing an electric machine (1) according to claim 1, comprising the steps: - Provision of a first partial core (21) and a second partial core (22) of a rotor (20), wherein the partial cores (21, 22) each have recesses in which permanent magnets are arranged; - Provision of a stator (10) comprising a stator core (13) having slots in which wire windings are arranged, wherein the stator core (13) is formed from stator laminations (13a, 13b, 13c, ...) and support stator laminations (13x, 13y, 13z), and wherein the support stator laminations (13x, 13y, 13z) form a connecting finger (13'); - Providing a single, continuous rotor shaft (30) which has a radial bearing (40); - Pressing the first partial core (21) together with the rotor axis (30); - Contacting the connecting finger (13') with the radial bearing (40); - Interlocking teeth (23) of the second sub-core (22) with the rotor axis (30).

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