DE102012101822A1 - Rotor and electric machine - Google Patents

Abstract

The present invention specifies a rotor for an electrical machine, which rotor comprises two rotor elements (2, 3) which each comprise at least one flux barrier (4, 5, 4', 5'). The at least one flux barrier (4', 5') of the at least one second rotor element (3) is displaced in the circumferential direction in relation to the at least one flux barrier (4, 5) of the first rotor element (2). The two rotor elements (2, 3) are combined with one another axially and/or in the circumferential direction. The invention also describes an electrical machine having the rotor.

Description

The present invention relates to a rotor for an electric machine. Furthermore, the invention relates to an electrical machine with such a rotor.

Electric machines include a stator and a rotor movable relative thereto. Depending on the relative movement, a distinction is made between rotating machines and linear machines. Electrical machines can work by motor or generator, converting electrical energy into rotational energy or translational energy, or vice versa.

For example, in synchronous machines with permanent magnets arranged in the rotor, but also in synchronous reluctance machines, a ripple of the torque of the machine may occur, which is normally undesirable. Such torque fluctuations can be the cause of vibration, noise, and speed fluctuations, as well as problems with control. In permanent-magnet synchronous machines, a distinction is made between the torque ripple and the cogging torque, while in reluctance machines the torque ripple is significant.

This torque ripple may result from the interaction between the magnetic flux due to stator currents and the magnetic flux of the rotor. In permanent magnet synchronous machines, the torque ripple is the result of the interaction of higher harmonics of the air gap flux density generated by rotor magnets and the stator current. Finally, the cogging torque is the result of an interaction between the magnetic flux resulting from magnets and the stator geometry, since a variable reluctance depends on the angular position of the rotor.

For example, in automotive applications, torque ripple and cogging torque should be less than 5% and 0.5% of rated torque, respectively. Various approaches have been described to reduce these unwanted cogging torques or torque ripple. However, previously known approaches are usually associated with a reduced efficiency of the machine and / or higher manufacturing costs.

In the patent application DE 10 2010 032 764 a stator for an electrical machine is specified, which comprises at least two parts, which each have grooves for receiving electrical windings. The slot openings of the two stators are shifted from each other in the circumferential direction. The stators are combined with each other axially and / or circumferentially. This approach leads to an effective reduction of the cogging torque of the electric machine, largely without the above-described disadvantages of hitherto known approaches. This approach requires a change in the geometry of the stator.

Object of the present invention is to provide a rotor and a machine with this rotor, in which the torque ripple is significantly reduced.

The object is achieved with the objects of the independent claims. Advantageous embodiments and further developments are specified in the dependent claims.

In one embodiment, the rotor for an electric machine comprises a first and a second sub-rotor. These each have at least one magnet and at least one flux barrier associated with the magnet. The flux barrier is designed to inhibit the magnetic flux in the rotor. The flow barrier of the at least one second sub-rotor is arranged displaced with respect to the at least one flow barrier of the first sub-rotor in the circumferential direction of the rotor. The two part rotors are combined with each other in the axial direction and / or in the circumferential direction.

An asymmetrical displacement of the flow barriers in the sub-rotors relative to one another correspondingly results in a relative shift of the location of the minimum reluctance of the sub-rotors. This in turn results in a relative displacement of the torque ripple components generated by the respective sub-rotors. Combining the sub-rotors as proposed, the torque ripple components of the sub-rotors can be mutually compensated and the overall torque ripple of such a rotor can be significantly reduced, up to an extinction.

The flow barriers of the rotor can be designed, for example, as air-filled cavities of the rotor.

Preferably, the flow barriers directly adjoin the magnets in the circumferential direction on opposite sides.

Displacement, in one embodiment, means that a flux barrier that attaches to a magnet is circumferentially expanded, that is, enlarged, while the opposing flux barrier on that magnet can be reduced by the corresponding amount.

As indicated above, the displacement of the flux barriers relative to one another is designed such that the minimum of the reluctance of the rotor is shifted relative to one another, that is to say in comparison with the two sub-rotors.

Rotors of electric machines can be described with the d-q axis theory. The d-axis lies in the middle of a rotor pole, and the q-axis lies between two rotor poles. The q-axis is shifted by 90 ° with respect to the d-axis.

In permanent magnet excited machines, for example with buried or buried magnets in the rotor, the d-axis represents the location with the highest reluctance and the q-axis represents the location with the least reluctance.

Also in synchronous reluctance machines, the d-axis represents the region of highest reluctance and the q-axis represents the region of least reluctance.

As discussed above, circumferential flow barriers asymmetrically shifted to the right or left will cause the region of minimum reluctance of the rotor to also shift to the left and to the right in the circumferential direction, respectively. Flow barriers are preferably regions of non-magnetic and non-electrical material, such as air. They can be realized, for example, as a cavity in the rotor laminated core. This cavity is preferably adjacent to the magnet and is otherwise enclosed by the iron of the rotor.

In the d-q axis theory, the described shift in the region of minimum reluctance of the rotor is such that the q-axis also shifts and lies in the middle of the minimum of the range of minimum rotor reluctance. In other words, the asymmetric displacement of the flux barriers results in the q-axis being shifted by an angle α.

It is proposed to disassemble the rotor in at least two sub-rotors, wherein in a rotor, the q-axis is shifted by a certain angle to the right, and the other rotor by a certain angle to the left. Instead of the terms right and left, the terms clockwise and counterclockwise can alternatively be used.

In this way, since the displacement of the q-axis is also accompanied by a shift of the components of the torque ripple of the sub-rotors, it is possible to significantly reduce the overall torque ripple of the rotor, up to an extinction of these residual ripple components of the torque.

In one embodiment, the shift angles of the q-axes of the sub-rotors are equal in magnitude to a rotor with conventional flux-barriers, but have a different sign.

In one embodiment, the sub-rotors each have at least one north magnetic pole and one south magnetic pole. The north pole and the south pole each have opposing flux barriers, wherein the opposing flux barriers of the north pole as well as the south pole with respect to a respective axis of symmetry of a conventional rotor are asymmetrical.

Partial rotors are preferably combined with each other, which apart from the described asymmetric displacement of the flow barriers have the same structure, in particular the same rotor geometry. When the sub-rotors are combined in the axial direction, the sub-rotors can even have a completely identical construction, but are not combined axially in the same sense, but one of the sub-rotors is combined in the reverse direction with the other.

Preferably, the first and the second part rotor, in the embodiment with permanent magnets, at least one of the following types: grooved magnets, buried magnets, such as buried tangential magnets or buried V magnets, or a buried multi-layer structure. Preferably cuboid magnets are used.

Alternatively or additionally, the rotor may be designed as a reluctance rotor, in which case the first and second part-rotors are also designed as reluctance rotors.

In another embodiment, an electric machine is provided with a stator and a rotor described above. The stator may be designed to receive electrical windings, for example in stator slots. In this case, the stator may be provided for receiving an electrical three-phase system, but other current systems are possible.

The invention will be explained in more detail below with reference to several exemplary embodiments with reference to drawings.

Showing:

1 An embodiment of an electrical machine with a first part rotor according to the proposed principle,

2 An embodiment of an electric machine with a second part rotor according to the proposed principle,

3 an embodiment of a rotor, in which the first and second part-rotor according to 1 and 2 are axially combined with each other,

4 a conventional rotor with V-shaped buried magnets,

5A and 5B Embodiments of the magnetic flux lines of respective sections of the examples of 1 and 2 .

6 an example of a graph of torque curves,

7A and 7B Embodiments of two partial rotors with buried tangential magnets according to the proposed principle, and

8A and 8B Embodiments of two executed as a reluctance rotor part rotors according to the proposed principle.

1 shows an embodiment of an electric machine with a stator 1 and a rotor, wherein in 1 a first part rotor 2 is shown. The first part rotor 2 has buried V-shaped arranged magnetic poles, which are formed as north pole N and south pole S. Overall, two magnetic pole pairs, that is a total of four buried magnets S, N are provided, opposite magnets are each of the same polarity. At the respective opposite ends of the legs of the V-shaped magnets each includes a flow barrier 4 . 5 which is realized as an air-filled cavity. In each case, in the circumferential direction in the clockwise direction of the respective magnet S, N starting, the magnetic flux barrier 5 enlarged while the river barrier 4 is reduced counterclockwise starting from the magnets. This results in an asymmetrical distribution of the flux barriers 4 . 5 at the respective buried V-shaped magnets S, N.

In other words, the river barriers are 4 . 5 each cavities in the iron core of the rotor, which connect to the permanent magnets S, N.

If one considers the electric machine in a dq-axis representation with a d-axis and a q-axis perpendicular thereto in the electrical angle, then the d-axis passes through the center of a rotor pole N, while the q-axis is electrically perpendicular to it and in the middle between the north pole N and an adjacent south pole S runs. Due to the fact that in the example two pole pairs are provided, the geometric angle is not 90 °, but only half of it, namely 45 ° between the d-axis and q-axis. At the same time, the d-axis represents the region of highest reluctance of the rotor, while the q-axis represents the region of least reluctance. This ideal angle of 45 ° applies to symmetrical arrangement of the flow barriers, as later in 4 shown. At the present 1 However, there is a shift of the q-axis by an angle α _r clockwise. This is related to the shift of the region of least reluctance in the rotor by the same angle α _r due to the asymmetry of the flux barriers 4 . 5 ,

2 shows an electric machine with a second part rotor 3 on an embodiment. The structure and geometry of the two part rotors of 1 and 2 are completely identical, only apart from the asymmetry of the river barriers, which at the 2 not clockwise but counterclockwise. This results in the example of 2 a shift of the q-axis counterclockwise, by an angle α _r . The displacement angle α _{r of} the examples of 1 and 2 is equal in size, but in opposite directions.

Combine the part rotors 2 . 3 according to 1 and 2 axially behind one another to form a common rotor, the result is a rotor according to the embodiment of FIG 3 , Here is the second part rotor 3 according to 2 in 3 behind the first part-rotor of 1 shown. The stator 1 is in the presentation of 3 the sake of clarity not shown. It can be seen that the resulting q-axis of the entire rotor of 3 , which is due to superimposition of the q-axis q1 of the first sub-rotor 2 and the q-axis q2 of the second sub-rotor 3 results, just again at an angle of electrical 90 ° to the d-axis of the overall rotor is. The d-axis of the total rotor is identical to the d1-axis of the first part-rotor and the d2-axis of the second part-rotor. Function and advantages of this embodiment will be described later with reference to 6 explained.

4 shows a conventional rotor with V-shaped buried magnets S, N and symmetrically at their outer leg ends subsequent flow barriers.

It can be seen that in the conventional rotor of 4 the same angle between the d-axis and q-axis as in the combination of part rotors with circumferentially shifted flow barriers according to 3 result.

5A and 5B show the field lines of the magnetic flux in the rotor and stator, wherein 5A an exemplary excerpt from 1 and 5B an exemplary excerpt from 2 with respect to rotor and stator geometry. It clearly shows the effect of each locally enlarged river barriers 5 . 5 ' locally reducing the magnetic flux significantly. This effect ultimately results in the shift of the region of minimum reluctance, which can be illustrated by the respective displacement of the q-axis by an angle α _r .

The effect of combining the part rotors according to 3 is based on the graph of 6 vividly. In the diagram of 6 the electromagnetic torque T is shown, wherein the torque is plotted against the rotor position in electrical degrees. The curve marked X denotes the torque curve of the electric machine of 1 if the rotor is only from the first part rotor 2 is formed, while the torque curve denoted by O represents the torque of the engine when the rotor with only the second part rotor 3 from 2 is formed. It can be seen that each of these torque curves X, O taken by itself has a high torque ripple.

The resulting torque curve - is shown in dashed lines and applies to the overall arrangement according to 3 to. In this case, the total rotor is half of the part rotors 2 and 3 educated. It can be clearly seen that the proposed combination of part rotors 2 . 3 with circumferentially displaced flux barriers, the total torque ripple is significantly reduced. This is accompanied by a significant reduction in the consequences of a high torque ripple, for example, a significant reduction of vibrations of the electric machine during operation and the operating noise and ultimately a significant improvement in the efficiency.

Thus, the electrical machine described is suitable, for example, especially for the automotive sector.

7A and 7B show on the basis of respective examples of two part rotors another embodiment of the proposed principle with buried, tangential permanent magnet. The embodiment is based in its structure, the operation and the advantageous operation on that according to the 1 to 3 and will not be described again. Here, however, instead of the V-shaped magnets are introduced in a tangential design in the sub-rotors. The tangential magnets S, N in turn close flow barriers 4 . 4 ' . 5 . 5 ' which, in the two part rotors according to 7A and 7B are in turn shifted in different directions of rotation, so that the above-explained asymmetry with the corresponding axis displacement of the q-axes of the part rotors q1, q2 results. These part rotors according to 7A and 7B can in turn be combined axially with one another to form an overall rotor having the advantages explained above and a reduced torque ripple.

8A and 8B show partial rotors according to an application of the proposed principle to a pure reluctance rotor without permanent magnets. The regions of missing iron, ie air, which are provided in a conventional reluctance rotor, enter into asymmetrically formed flow barriers at the respective ends of the V-shaped regions. This asymmetry in the circumferential direction results according to the first part-rotor 8A again a shift of the q-axis clockwise to the axis q1, while in the second part-rotor according to 8B a counterclockwise displacement, again by the same angular amount, is provided so that the new q-axis q2 results.

These part rotors according to 8A and 8B can in turn be combined axially with one another to form an overall rotor having the advantages explained above and a reduced torque ripple.

The electric machine described requires no changes to the stator. It is sufficient to carry out the measures described in the rotor. The asymmetrical design of the river barriers 4 . 5 can be done in a simple manner by punching the laminated core of the rotor, wherein for the realization of the exemplary embodiment of 3 only a single punching tool is required because the rotors of 1 and 2 by turning the laminated cores and mutually rotated axial combining according to 3 can be manufactured very inexpensively.

Of course, it is within the scope of expert action, instead of the axial combination shown to make a combination of the part rotors in the circumferential direction, for example, with two part rotors, each covering 180 ° geometrically and can be realized as a half cylinder.

It is also within the scope of expert action, instead of the shown buried V-shaped permanent magnets or buried tangential magnets, other Rotortopologien too use, such as magnets used in grooves or buried multilayer magnets. In addition, the proposed principle is not limited to buried permanent magnets, but can for example be used advantageously in multilayer reluctance rotortopologies.

LIST OF REFERENCE NUMBERS

1

 stator

2

 first part rotor

3

 second part rotor

4

 reduced river barrier

4 '

 reduced river barrier

5

 enlarged river barrier

5 '

 enlarged river barrier

d

 d-axis

d1

 axis

d2

 axis

q

 q-axis

q1

 axis

q2

 axis

N

 North Pole

S

 South Pole

α _r

 Displacement angle of the q-axis

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102010032764 [0006]

Claims (10)

Rotor for an electric machine, the rotor comprising: - a first part rotor ( 2 ) and at least one second sub-rotor ( 3 ), each having at least one flow barrier ( 4 . 4 ' . 5 . 5 ' ), wherein the at least one flow barrier ( 4 ' . 5 ' ) of the at least one second sub-rotor ( 3 ) with respect to the at least one flow barrier ( 4 . 5 ) of the first part rotor ( 2 ) is displaced in the circumferential direction and - the two part rotors ( 2 . 3 ) are combined with each other axially and / or in the circumferential direction. Rotor according to claim 1, characterized in that the displacement of the at least one flow barrier ( 4 ' . 5 ' ) of the at least one second sub-rotor ( 3 ) with respect to the at least one flow barrier ( 4 . 5 ) of the first part rotor ( 2 ) is designed such that a minimum of the rotor reluctance of the second sub-rotor ( 3 ) relative to a minimum of the rotor reluctance of the first sub-rotor ( 2 ) is shifted. Rotor according to claim 1 or 2, characterized in that the displacement of the at least one flux barrier ( 4 ' . 5 ' ) of the at least one second sub-rotor ( 3 ) with respect to the at least one flow barrier ( 4 . 5 ) of the first part rotor ( 2 ) is formed such that the q-axis (q2) of the second sub-rotor ( 3 ) relative to the q-axis (q1) of the first sub-rotor ( 2 ), each related to a common d-axis (d), is shifted. Rotor according to one of claims 1 to 3, characterized in that the first part rotor ( 2 ) and the at least one second sub-rotor ( 3 ) each comprise at least one magnet (S, N), each of which has at least one flux barrier ( 4 . 4 ' . 5 . 5 ' ) of the first or at least one second sub-rotor ( 2 . 3 ) assigned. Rotor according to claim 4, characterized in that - the first and the second part-rotor ( 2 . 3 ) each comprise at least one magnetic north pole (N) and one magnetic south pole (S), each having an axis of symmetry, - the north pole and the south pole respectively opposing flux barriers ( 4 . 4 ' . 5 . 5 ' ), the opposing flow barriers ( 4 . 4 ' . 5 . 5 ' ) of the north pole (N) with respect to its symmetry axis are asymmetrical and / or - wherein the opposing flux barriers ( 4 . 4 ' . 5 . 5 ' ) of the south pole (S) are formed asymmetrically with respect to its axis of symmetry. Rotor according to one of claims 1 to 3, characterized in that the first and the second partial rotor ( 2 . 3 ) are each formed as a reluctance rotor. Rotor according to one of claims 1 to 6, wherein the at least one flow barrier ( 4 ' . 5 ' ) of the at least one second sub-rotor ( 3 ) with respect to the at least one flow barrier ( 4 . 5 ) of the first part rotor ( 2 ) is displaced in the circumferential direction such that the torque ripple of the sub-rotors mutually compensated and / or the torque ripple is reduced. Rotor according to one of claims 1 to 7, in which the at least two partial rotors ( 2 . 3 ), apart from the displacement of the river barriers ( 4 . 4 ' . 5 . 5 ' ), have the same structure, in particular the same geometry. Rotor according to one of claims 1 to 8, characterized in that the first and the second part rotor ( 2 . 3 ) Have permanent magnets of at least one of the following types: - magnets used in grooves, - buried tangential magnets, - buried V magnets, - buried multilayer structure. Electric machine with a rotor according to one of claims 1 to 9 and further comprising: a stator ( 1 ), wherein the rotor ( 2 . 3 ) is movable relative to the stator.

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