WO2015172916A1

WO2015172916A1 - Heat-treated rotor for a permanent magnet electric machine

Info

Publication number: WO2015172916A1
Application number: PCT/EP2015/055601
Authority: WO
Inventors: Gerd Kirsten; Mario Matic
Original assignee: Robert Bosch Gmbh
Priority date: 2014-05-12
Filing date: 2015-03-18
Publication date: 2015-11-19
Also published as: DE102014208866A1

Abstract

A rotor (18) for an electric machine (10) excited by permanent magnets comprises a lamination stack (20) which consists of a plurality of laminations (22), the lamination stack (20) having at least one axial opening (24) for accommodating at least one permanent magnet (12). On its exterior circumference (26), the lamination stack (20) has an axial region (28) for modifying a magnetic flux through the rotor (18). Said region has a material of the lamination stack (20) with modified magnetic properties, said axial region (28) being produced by heat-treating the lamination stack (20).

Description

description

Heat-treated rotor for an electric machine excited by permanent magnets

Field of the invention

The invention relates to a rotor for a permanent magnet excited electric machine and a method for manufacturing a rotor.

Background of the invention

In particular, in permanent-magnet synchronous machines, as used for some time in hybrid vehicles are used to improve the operating characteristics (such as cogging torque, field weakening, reducing the no-load losses, increasing reluctance torque) in the arrangement of the

Permanent magnets in the rotor yoke are used as so-called buried magnets (IPM) cavities and depressions as flux barriers for the magnetic flux through the rotor. These flux barriers are usually located between the magnets and the rotor surface.

The effect of the flux barriers is to create targeted areas in the rotor, which are less conductive for the magnetic field than the sheets of the rotor, which is usually composed of a plurality of sheets.

Furthermore, the losses in a machine excited by permanent magnets can be increased by a specific design of the rotor outer geometry

Speeds are reduced. In this case depressions can be introduced in the otherwise circular shape of the rotor, which by skillful Designing the shape and position Avoid harmonics in the operation of the machine and thus increase the efficiency of the machine.

Laminated packages of a rotor are often produced by stamped packaging. This can be at high speeds and the associated vibrations

(For example, in the vehicle) the problem arise that especially the

End laminations of the laminated core can detach from the rest of the package, since the strength of the stand paketierpunkte is not sufficient.

Summary of the invention

With the invention, a smooth-running, stable, inexpensive electric machine can be provided with high efficiency.

These advantages can be achieved with the subject matter of the independent claims. Further embodiments of the invention will become apparent from the dependent claims and from the following description. One aspect of the invention relates to a rotor for an electric machine excited by permanent magnets, for example an electric motor and / or an electric generator. The electric machine may be, for example, a component of a drive of an electric vehicle or hybrid vehicle. In general, the electric machine will have a rotor surrounding the stator, which is accommodated in a housing in which the rotor is rotatably mounted.

According to one embodiment of the invention, the rotor comprises a laminated core of a plurality of laminations, wherein the laminated core has at least one axial opening for receiving at least one permanent magnet. It should be understood that "axially" here and below means parallel to the axis of rotation of the rotor.

The laminated core has on its outer circumference an axis of rotation relative to the axial region for changing a magnetic flux through the Rotor having a material of the laminated core with altered magnetic properties, which are produced by a heat treatment of the laminated core. Normally, the material of the laminated core or of the laminations has certain magnetic properties which can already be set when producing the laminations. This can

For example, done with a certain crystal structure in the material of the laminations. Through a heat treatment, the crystal structure can now be changed in such a way that, for example, the magnetic permeability decreases.

In this way, river barriers without the sometimes very small

Cavities, recesses and indentations are produced when punching the slats. Punching tools usually make a big

Cost factor in lamellae and any simplification of the geometry can reduce the cost of the cutting tool or increase the tool life.

With the permanent magnets, a magnetic flux can be generated in the rotor, which can be deflected by the heat-treated areas. With the heat-treated region, a flux barrier for the magnetic flux through the rotor can be generated, with which the magnetic flux in the rotor can be modeled in the desired manner. The properties of the

Rotor laminations at the necessary points can be deteriorated on the outer circumference of the rotor by targeted heat treatment, so as to achieve a similar effect as with the conventional wells.

For example, the axial region can be arranged in the vicinity or in the radial direction over the opening for the permanent magnet and change the magnetic flux there.

The axial range is usually a predefined (through the

Heat treatment adjustable) have radial depth. For example, the <radial depth may be more than 1, 2 or 3% of the radius of the stator.

According to one embodiment of the invention, the laminated core per opening has at least two axial regions with altered magnetic properties. The two areas can have different radial depths exhibit.

Normally, several permanent magnets are arranged in pairs. The two magnets of a pair can be in a straight shape or for

Increasing the magnetic flux can be arranged as so-called V-magnets, U-magnets or Dovetail magnets.

According to one embodiment of the invention, the outer circumference of the rotor is circular in cross section. For example, a cylindrical rotor may have the heat treated areas without apertures and / or depressions for redirecting a magnetic flux.

According to one embodiment of the invention, the outer circumference of the rotor has an axial recess for varying an electromagnetic flux through the rotor. The axial region can be arranged in the depression.

Alternatively or additionally, the axial recess can also be used to change the mechanical properties of the rotor. For example, the axial recess can be produced when punching the laminations.

According to one embodiment of the invention, an axial elevation is arranged in the axial recess, on which a weld seam is arranged. The structural design of a weld can have an influence on the quality of the weld. For electric sheets, it may be useful to

Select weld on an increase, since in this way the

Outgassing / burnout of the insulating lacquer layers can be facilitated. This can result in a reduction of pores and ejection during welding and thus a positive influence on the mechanical strength of the produced sheet metal composite. In order to implement such a design of the weld in a rotor, the laminated core can be arched, i. have an axial recess.

According to one embodiment of the invention, the laminated core has been heat treated by creating a weld. The heat treatment of the axial region can take place simultaneously with the production of a weld seam. Thus, below the weld, an axial region with changed magnetic properties are located.

According to one embodiment of the invention, the laminations are made of an electrical sheet produced by rolling and / or by heat treatment. The electrical sheet can be rolled and heat-treated in a preferred direction.

Another aspect of the invention relates to a method of manufacturing a rotor of a permanent magnet excited electric machine, such as a motor, as described above and below. It should be understood that features of the method as described above and below may also be features of the device and vice versa.

According to one embodiment of the invention, the method comprises:

Providing a laminated core of a plurality of laminations, the at least one axial opening for receiving at least one

Having permanent magnets, and heat-treating the laminated core at its outer periphery in an axial region, so that the region has changed magnetic properties, by which an electromagnetic flux is changed by the rotor.

According to one embodiment of the invention, the heat treatment is carried out at a temperature below the melting point of the material of the laminations. In this way, although the magnetic properties of the

Material of the laminations are changed, but there is no need

Weld produced.

According to one embodiment of the invention, the heat treatment is carried out at a temperature above the melting point and is in the axial

Area creates a weld. Simultaneously with the creation of a weld, an axial region with altered magnetic

Properties are generated.

According to one embodiment of the invention, the heat treatment is carried out with a laser beam, for example a laser beam for laser welding, carried out. The treatment can be done for example with an industrial laser, which either briefly heats or melts the corresponding locations on the rotor circumference. With the laser and the laminations can be welded in the axial direction to solidify the laminated core of the rotor. The laser between the laser source can be a continuous wave laser (cw) or a pulsed laser. Also, the laser can only use a laser for

Heat treatment (for example, an infrared laser).

For the laser, a focus diameter smaller than 600 μηη, for example, less than 300 μηη, at high process speeds of more than 1 m / min are suitable. In this way, for example, a load-bearing weld seam having a welding depth of, for example, less than 1 mm, for example less than 0.5 mm, can be produced under controlled thermal influence of the laminated core.

Brief description of the figures

Embodiments of the invention will now be described in detail with reference to the accompanying drawings.

Fig. 1 shows a schematic side view of an electric machine with a rotor according to an embodiment of the invention. Fig. 2 shows a schematic section of a rotor according to a

Embodiment of the invention in cross section.

Fig. 3 shows a schematic section of a rotor according to another embodiment of the invention in cross section.

4 shows a schematic section of a rotor according to a further embodiment of the invention in cross section.

Fig. 5 shows a schematic section of a rotor according to another embodiment of the invention in cross section. Fig. 6 shows a schematic section of a rotor according to another embodiment of the invention in cross section.

Basically, identical or similar parts are the same

Provided with reference numerals.

Detailed description of embodiments

Fig. 1 shows a rotary electric machine 10, such as a generator or electric motor. The electric machine 10 can by a

Permanent magnets 12 be excited synchronous machine. In the housing 14 of the electric machine 10, a stator 16 which can be excited by electric current is arranged, which surrounds a rotor 18 which is mounted rotatably about the axis A in the housing 14 and in the stator 16.

The rotor 18 includes a substantially cylindrical laminated core 20, which consists of a plurality of stacked laminations 22nd

is composed. In the rotor 18 is a plurality of axial openings 24 in which the permanent magnets 12 are arranged.

For example, the laminations 22 may be stamped out of an electrical sheet and possibly coated with an insulating layer. When punching, the shape of the outer periphery 26 of the rotor 18 and the openings 24 can be generated.

Above each permanent magnet 12, i. between the permanent magnet 12 and the outer periphery 26, there is an axial, for example

strip-shaped or weld-shaped area 28, in which the material of the laminations 22 has been changed by means of heat treatment such that it compared to the rest of the laminated core 20 has changed magnetic properties.

For example, the regions 28 may be created by sweeping the rotor 18 with a laser for laser welding. The regions 28 are formed from zones of the laminated core 20. To change the magnetic Properties of the electric sheet of the laminations 22, the rotor 18 is swept over, for example, in the axial direction with the laser.

FIG. 2 shows a detail of a cross section through the rotor 18 from FIG. 1. The rotor 18 has a circular cross-section

Outer circumference 26 with radius R on, in which the axial regions 28 are introduced. The openings 24 and the permanent magnets 12 have a

rectangular cross section on. As is apparent from Fig. 2, the

Openings 24 and the permanent magnets 12 may be arranged obliquely to each other, so that together they form a V-shaped arrangement.

FIG. 3 shows a further embodiment of the rotor 18 analogous to FIG. 2, in which a plurality of axial regions 28, 28 'are provided per opening 24 or permanent magnet 12. The axial region 28 'has a higher penetration depth than the axial region 28. The penetration depth of the axial regions 28 'can be determined, for example, by the height of the temperature and the duration of the

Heat treatment can be adjusted. The axial region 28 'is not located above the permanent magnet 12, but in the pole gap between two permanent magnets 12 (only one of the permanent magnets is visible). An embodiment where axial regions 28 'are only in pole gaps is also conceivable.

Fig. 4, as well as the following figures, show an embodiment of the rotor 18, wherein the outer circumference 26 axial recesses 30 and

Has bulges. These form together with the permanent magnets 12 a so-called sine pole. The axial recesses 30 are defined by different radii Rl (for the maximum distance to the axis of rotation A) and R2 (for the curvature forming the axial recesses). In the region of the recesses 30, therefore, the radius R 1 of the rotor 18 is deviated. The recesses 30 are thus in relation to the circular shape of the rotor 18 with the

Radius Rl deepened.

In this case, the axial regions 28 are located in a region of the depressions 30 which lie radially closest to the axis of rotation A, ie at their lowest point. FIG. 5 shows an embodiment in which one of the regions 28 is covered by an axial weld seam 32. When welding the weld 32 was also a targeted heat treatment of the material under the

Weld 32 performed, which has led to the area 28.

It is also shown in FIG. 5 that the openings 24 or the permanent magnets 12 can be arranged in different ways and relative to one another. For example, as shown, the openings 24 and the

Permanent magnets 12 should be aligned parallel or straight to each other. V-shaped permanent magnets 12 may have a larger volume than parallel aligned permanent magnets 12.

FIG. 6 shows an embodiment of a rotor 20 in which an axial elevation 34 is provided in the recess 32. For example, the increase 34 can already be generated when punching the laminations 22.

The elevation 34 can be used on her back

Weld 32 to attach, which can result from the increase 34 advantages in welding, such as simplified outgassing.

Further, in the elevation 34 and below, a region 28 with altered magnetic properties can be generated.

In addition, it should be understood that "comprising" does not exclude other elements or steps and "a" or "an" does not exclude a plurality. "Further, it should be noted that features or steps described with reference to one of the above embodiments also in combination with other features or steps of others described above

Embodiments can be used. Reference numerals in the

Claims are not intended to be limiting.

Claims

Rotor (18) for a permanent magnet excited electrical machine (10),

wherein the rotor (18) comprises a laminated core (20) of a plurality of

Laminations (22) comprises;

wherein the laminated core (20) at least one axial opening (24) for

Receiving at least one permanent magnet (12);

characterized in that

the laminated core (20) has on its outer circumference (26) an axial region (28) for changing a magnetic flux through the rotor (18), which changed a material of the laminated core (20)

magnetic properties, wherein the axial region (28) is produced by a heat treatment of the laminated core (20).

Rotor (18) according to claim 1,

wherein the laminated core (20) per opening (24) has at least two axial regions (28, 28 ') with altered magnetic properties.

Rotor (18) according to claim 1 or 2,

wherein the outer periphery (26) of the rotor (18) is circular. Rotor (18) according to claim 1 or 2,

wherein the outer periphery (26) of the rotor (18) has an axial recess (30) for varying electromagnetic flux through the rotor (18) and the axial portion (28) is disposed in the axial recess (30).

5. Rotor (18) according to claim 4,

wherein in the axial recess (30) an axial elevation (34) is arranged, on which a weld (32) is arranged. A rotor (18) according to any one of the preceding claims, wherein the laminated core (20) is heat treated by creating a weld (32).

Rotor (18) according to one of the preceding claims,

wherein the laminations (22) consists of a by rolling and / or by

Heat treatment produced electrical steel are produced.

A method of manufacturing a rotor (18) of an electric machine (10) excited by permanent magnets (12), the method comprising:

Providing a laminated core (20) of a plurality of laminations (22) having at least one axial opening (24) for receiving at least one permanent magnet (12);

Heat treating the laminated core (20) at its outer periphery (26) in an axial region (28) so that the region (28) changed

has magnetic properties by which an electromagnetic flux through the rotor (18) is changed.

Method according to claim 8,

wherein the heat treatment is performed at a temperature lower than the melting point of the material of the laminations (22); or

wherein the heat treatment is performed at a temperature above the melting point of the laminations (22) and a weld is produced in the axial region (28).

0. Method according to claim 8 or 9,

wherein the heat treatment is performed with a laser beam.