EP3759800A1

EP3759800A1 - Electric motor

Info

Publication number: EP3759800A1
Application number: EP19706621.0A
Authority: EP
Inventors: Sunny Zhang; Thomas Susemihl; Kevin Steinert
Original assignee: Brose Fahrzeugteile SE and Co KG
Current assignee: Brose Fahrzeugteile SE and Co KG
Priority date: 2018-02-27
Filing date: 2019-02-22
Publication date: 2021-01-06
Also published as: WO2019166333A1; MA52409A; CN111954971A; US20200403469A1; DE102018202943A1

Abstract

The invention relates to a brushless electric motor (6) having a stator (4) and having a rotor (2) which is drive-connected to a rotating element (28), wherein the rotor (2) has a permanent-magnet rotor magnet (2a) which is magnetized in the manner of a Halbach arrangement, wherein the rotor magnet (2a) is an injection-moulded part containing embedded magnetically anisotropic magnet material, which injection-moulded part is formed at least partially from a ferrite, and wherein the rotor (2) is integrated into the rotating element (28) or is joined to said rotating element.

Description

description

The invention relates to a brushless electric motor with a stator and with a rotor, which is in drive connection with a rotary element, wherein the rotor has a permanent magnetic rotor magnet (ring magnet), which is magnetized in the manner of a Halbach arrangement. A brushless electric motor typically comprises a rotor (rotor), which is rotatably mounted against a fixed stator. For example, the stator in this case has a rotating field winding, by means of which a magnetic rotating field is generated when subjected to an alternating current. The rotor in this case has permanent magnets whose magnetic field interacts with the rotating field of the stator, so that the rotor is rotationally driven.

These permanent magnets are produced, for example, from a powder of a magnetic material, such as a neodymium alloy or a ferrite, by means of a sintered process. In this case, the intended magnetization of the permanent magnets during their production is achieved by means of an applied exciter magnetic field. The permanent magnets are then introduced into the rotor, wherein these are arranged, for example, spoke-shaped in the rotor. In summary, such a production of permanent magnets in a comparatively complex manner and is therefore costly. In addition, due to the multi-part structure of the rotor and / or the manufacture of the rotor in several steps, a total tolerance of the rotor is comparatively high, which adversely affects a motor statics and an acoustic behavior of the motor. As an alternative to the spoke-like arrangement of the permanent magnets (magnetic segments) of the rotor, rotors are used, for example, which have a magnetization in the manner of a Halbach arrangement (Halbach array, Halbach magnetization). In such an arrangement, the magnetic field is amplified on one side of the assembly, while it is reduced on the opposite side. With a corresponding orientation of the permanent magnets, a sinusoidal field strength profile results on the side facing the stator, whereby in particular a cogging torque is reduced. On the opposite side of this page, however, the field strength is substantially equal to zero, so that no magnetic inference is necessary.

By way of example, the rotors with a Halbach magnetization are produced by means of individually prefabricated, anisotropic permanent magnets in a corresponding orientation. As an alternative to this embodiment with several anisotropic permanent magnets, a Haibach magnetization can be realized by means of an isotropic ring magnet, on which the Halbach magnetization is impressed. For example, from DE 10 2013 007 563 A1 a rotor with a rotor magnet is known, which is formed from a plurality of ring magnet segments produced by injection molding. In the assembly state, the rotor magnet has a Halbach magnetization with several magnetic poles on the circumference. In this case, the ring magnet segments consist of a magnetically anisotropic magnetic material, which is acted upon during the injection molding process with a correspondingly shaped magnetic field in order to achieve the intended magnetization.

The invention has for its object to provide an electric motor with an improved magnetic flux flow in between the rotor and the stator of the electric motor and improved Flußablaufanfälligkeit. In addition, this electric motor should be cost-effective to produce. This object is achieved by the features of claim 1. Advantageous developments and refinements are the subject of the subclaims. For this purpose, the brushless electric motor comprises a stator and a rotor, which is in driving connection with a rotary element. In this case, the rotor to a permanent magnetic rotor magnet (ring magnet), which is magnetized in the manner of a Halbach arrangement (Halbacharray). This rotor magnet is an injection molded part with embedded magnetically anisotropic magnetic material, wherein the magnetically anisotropic magnetic material is at least partially formed from a ferrite. Hereinafter, the magnetically anisotropic magnetic material is also referred to simply as magnetic material. Furthermore, the rotor is integrated in the rotary element or joined with this. The rotor magnet has a Haibach magnetization with a number of magnetic poles. This magnetization is achieved in particular by means of a magnetic pre-alignment in the production of the magnet. For example, the rotor magnet in this case has 6 to 20 magnetic poles, in particular 8 to 20 magnetic poles or preferably 10 to 20 magnetic poles.

Preferably, the magnetically anisotropic magnetic material is plastic bonded. The plastic is a binding material in which magnetically anisotropic, in particular powdery, magnetic material is incorporated. The binder used for this purpose, for example, a plastic such as nylon, polyphenylene sulfide or polyamide.

Particularly preferably, the ferrite is a hard ferrite. For example, as an alternative to ferrite, a magnetically anisotropic alloy of neodymium-iron-boron (NdFeB) is used as the magnetic material. However, a magnet with ferrite as magnetically anisotropic magnetic material is comparatively more cost-saving and more temperature-stable than a magnet with an alloy of neodymium-iron-boron. To join the rotor to the rotary element, a joining contour or joining elements, such as, for example, screw domes or hot clinching domes, are preferably provided on the rotor. This is or are preferably integrally formed on the rotor magnet by means of a multi-component injection molding process.

Thus, the rotor magnet and provided for joining joint contour and the joining elements are made in one piece. The rotor can thus be produced and also produced in a single production step and in particular in the intended final form, which advantageously saves further production steps and production costs. Compared to a rotor which is made of individual components and therefore has a comparatively high tolerance chain in the assembly state of the individual components, such a tolerance chain is comparatively small in the case of the integrally formed rotor by means of the multi-component injection molding process, which is why running properties and acoustics of the electric motor are improved.

Additionally or alternatively, for example by means of the injection molding process, the rotor is designed such that it has ventilation holes, which run in particular in the axial direction with respect to a motor axis. In this way, an air flow is made possible via a motor mount carrying the electric motor. This air flow serves, for example, for cooling an engine electronics arranged in or on the engine mount. Furthermore, in the case of a rotor formed by means of the injection molding method, no rotor lamination is necessary, which is why costs are also saved particularly advantageously, the weight of the rotor is reduced and a comparatively high (torque) density of the (motor) acting on the rotor by means of the rotating field. Torque is reached.

For example, additionally or alternatively, by means of the injection molding process designed as an internal rotor rotor is annular. In other words, the trained as an internal rotor (coreless) rotor is recessed centrally. Such a rotor is then expediently joined to the rotary element by means of the joining contour or by means of the joining elements. In this case, the rotary member is accordingly, example, by means of a bearing shaft of a motor mount, rotatably mounted. Advantage- Of course, due to this recess a space is provided, which is used for example for cooling or electronics and / or allows alternative designs for cooling ducts. In summary, due to the injection molding process, the geometry of the rotor and in particular of the rotor magnet can be adapted and adapted comparatively easily to specifications resulting from the installation space and / or an intended functionality, such as, for example, the ventilation holes. In a suitable embodiment, the rotor magnet at room temperature (20 ° C) has a remanence between 0.2 T and 0.5 T and a coercive field strength of the magnetic polarization (H _C J) between 150 kA / m and 1000 kA / m.

Furthermore, the rotor has a sinusoidal flux density profile on its side facing the stator. In this case, a maximum flux density (flux density amplitude) between 1.2 times and 1.5 times the remanence of the rotor magnet is achieved. On the opposite side of this side, the flow density is essentially zero. In other words, the rotor magnet has a magnetization in the manner of a Haibach arrangement such that the maximum flux density at the circumference of the rotor is 1.2 times to 1.5 times greater

Remanence reached. The (magnetic) flux density amplitude of the sinusoidal profile of the magnetic flux density is preferably between 0.32 T and 0.7 T. The rotor, which is magnetized in the manner of a Halbach arrangement, has a sinusoidal magnetic field intensity profile with respect to a radial direction, ie perpendicular to the motor axis, at its side facing the stator and correspondingly in an air gap formed between the rotor and the stator. This results in a sinusoidal electromotive force (EMF) along the circumferential direction of the rotor. In particular, due to the manufacture of the rotor by means of the injection molding process and the correspondingly impressed magnetization, a sinusoidal EMF is without or at least with comparatively few and / or weakly formed harmonics realized. Because of this, a comparatively low torque impedance and a comparatively low iron loss occur, which is why the engine efficiency is advantageously improved. The running properties of the electric motor are thus improved. In addition, the sinusoidal shape of the magnetic field strength curve reduces a cogging torque of the rotor. Furthermore, a radial force acting on the stator teeth is reduced in this way, so that a deformation of the stator and a concomitant deterioration of the engine acoustics are avoided. In summary, the magnetic flux flow between the rotor and the stator of the electric motor and its Flussablaufanfälligkeit are improved.

The motor torque acting on the rotor by means of the rotating field is proportional to the square of the diameter of the rotor. In other words, so the engine torque increases with increasing rotor diameter. According to an advantageous embodiment, the rotor is designed as an outer rotor. Consequently, the motor torque is greater in this way in comparison to a designed as an internal rotor electric motor with the same size of the electric motor. Furthermore, in the case of an embodiment of the rotor as an outer rotor, integration thereof into the rotary element is facilitated if the rotary element comprises the rotor and the stator on the outside in the radial direction and / or is arranged there.

In order to integrate the rotor into the rotary element, the rotor and the rotary element are, according to an advantageous development, an injection-molded part formed in one piece (in one piece). In particular, the injection-molded part is produced for this purpose in a multi-component injection molding process. Thus, the rotor is not in drive connection by means of a shaft with a rotary element, but rather drives the rotary element directly (directly) rotationally during its rotation about the motor axis.

The advantages mentioned in connection with the design, in which the joining contour or the joining elements and the rotor magnet are formed in one piece, apply here analogously. For example, the rotor and the rotary element in one piece, which saves production costs and improves the running properties of the electric motor. Furthermore, for example, the rotary element with integrated rotor is designed by means of the multi-component injection molding process such that the rotor and / or the rotary element has ventilation holes.

According to an expedient embodiment, the rotary element with integrated rotor is mounted rotatably via a bearing system on the bearing shaft of the motor carrier. The stator is connected to the engine mount (held, fastened). In a suitable embodiment, the rotary element is the hub of a fan. The hub has the storage system. Furthermore, the rotor is formed on the inside of the hub. Such a hub suitably includes the rotor and stator externally with respect to the radial direction. Thus, an integration of the rotor formed as an outer rotor on the inside of the hub comprising the outer rotor can be realized comparatively easily.

Embodiments of the invention will be explained in more detail with reference to a drawing. Show:

1 shows a schematic representation of the field line course of a magnetic field between a rotor magnet of a rotor and a stator of an electric motor, wherein the rotor is designed as an external rotor and has a magnetization in the manner of a Haibach arrangement,

2 is a schematic sectional view of a hub of a fan with a bearing system, wherein the rotor formed as an outer rotor is integrated into the hub, and wherein the hub and the rotor are rotatably mounted on a bearing shaft of an engine mount by means of the bearing system,

3 shows schematically an alternative embodiment of the electric motor, in which the rotor formed as an internal rotor is joined to the hub of the fan,

FIG. 4a is a sectional view of a second alternative embodiment of the electric motor, in which the rotor magnet of the rotor designed as an external rotor is joined to a rotor cup, and FIG Fig. 4b in a plan view of the rotor magnet of the rotor of FIG. 4a, wherein the rotor magnet for joining with the rotor pot has a number of shoulders and pin-like pins. Corresponding parts are provided with the same reference numbers in all figures.

1 schematically shows a field line course of a magnetic field between a rotor magnet 2 a of a rotor 2, which is rotatably mounted about a motor axis M extending in the axial direction A, and a stator 4 of a brushless electric motor 6 improved visibility availability of the field line history only partially shown. Thus, FIG. 1 shows only one half of the rotor 2 and the stator 4, wherein the half of the rotor 2 and the stator 4, not shown, is mirror-symmetrical with respect to a plane E, through which the motor axis M runs, and which is perpendicular to the plane of the drawing is oriented.

The stator 4 has an annular stator yoke 8, from which stator teeth 10 extend from the motor axis M to the rotor 2 in a star-shaped manner, ie in a radial direction R oriented perpendicular to the axial direction A. The rotor 2 is thus arranged on the outside of the stator 4. In other words, the rotor 2 is formed as an outer rotor (external rotor).

Between the stator teeth 10, stator slots 12 are formed, in which a stator winding not shown in detail, in particular designed as coils, is accommodated. The stator teeth have a T-shape. Thus, these are extended on their sides facing the rotor 2 free end on both sides to form pole pockets 14 in a circumferential direction (azimuthally), which is oriented perpendicular to the axial direction A and to the radial direction R.

The rotor magnet 2a is magnetized in the manner of a Flalbach arrangement. Flierzu the rotor magnet 2a is formed as an injection molded part, in which magnetically anisotropic magnetic material is embedded, wherein the magnetic material at least partially formed of a ferrite. In this case, the rotor magnet has fourteen magnetic poles. Due to the Halbachmagetisierung the magnetic field lines are guided substantially within the rotor 2. Consequently, no iron yoke for the rotor 2 is necessary. In contrast, a magnetic inference in the stator 4 takes place through the stator yoke 8.

The magnetic field lines are oriented substantially along the radial direction R in an air-motor gap 16 formed between the rotor 2 and the stator 4. The magnetic field has a sinusoidal profile of the flux density along the circumference of the rotor 2, that is to say in the circumferential direction U, at its (inner) side 18 facing the stator 4, while the side 20 opposite this side, that is the Outside, the flux density is substantially zero. In particular, the rotor magnet has a remanence of 0.28 T and a coercive force of magnetic polarization (H _C J) of 200 KA / m. In particular, by the choice of the magnetic material, its density in the rotor magnet 2a, the number of poles and the magnetization orientation, it is possible that the maximum flux density is 1, 2 to 1, 5 times the remanence. In Fig. 2, the electric motor 6 is shown in a schematic sectional view, wherein the sectional plane is clamped by means of the axial direction A and by means of the radial direction R and wherein the motor axis is in this sectional plane. The stator 4 is fastened or connected to a motor mount 22. The motor mount 22 has centrally a bearing shaft 24 extending in the axial direction A. By means of a bearing system 26, a rotary member 28 is rotatably mounted about the motor axis M. In this case, the rotary member 28, the bearing system 26 or is at least partially formed by means of this. The rotary member 28 is formed as a hub of a fan. The rotor 2 is integrated in the rotary element 28. For this purpose, the rotor 2 and the rotary element 28 are a one-piece (monolithic) injection-molded part. For this purpose, the rotary element 28 with the rotor 2 integrated in this way is produced by means of a multi-component injection molding process. The hub includes while the rotor 2 on the outside. In other words, the rotor 2 is integrally formed on the inner side 30 of the rotary element 28, ie, on the side facing the stator 4 and perpendicular to the radial direction R, for integrating the rotor 2 into the rotary element 28. In this way, the rotor 2 is in drive connection with the rotary element 28 designed as a hub of the fan wheel.

3, an alternative embodiment of the electric motor 6 is sketched, in which the rotor 2 is formed as an internal rotor. Analogously to the embodiment according to FIG. 2, the stator 4 is connected to the motor mount 22, wherein the motor mount 22 centrally has the bearing shaft 24 extending in the axial direction A.

In comparison to the embodiment of FIG. 2, in which the bearing shaft 24 by means of the bearing system 26 designed as a hub rotary member 28 is mounted, here the rotor 2 has a rotor core 2c, which includes the bearing system 26 of this at least partially forms. By means of the bearing system 26, the rotor 2 on the bearing shaft 24 of the motor mount 22 is rotatably mounted (rotationally). In this case, the ring-shaped rotor magnet 2a surrounds the rotor core on the outside with respect to the radial direction R. The hub of the fan wheel is hereby joined to the rotor 2 by means of its joining elements 2b. By way of example, the joining elements 2b are designed as screw domes formed as part of the manufacture of the rotor 2 by means of the multi-component injection molding process or as latching contours or as a pin-shaped joining contour which, in the course of hot compression or hot caulking, has a corresponding contour of the hub - is added.

Fig. 4a shows a second alternative embodiment of the electric motor 6, wherein the rotor 2 is formed as an external rotor. In this case, the rotor magnet 2 a of the rotor 2 is rotatably mounted on the bearing shaft 24 via the bearing system 26 by means of a rotor pot 2 d. The rotor pot 2d is, for example, an injection-molded part or alternatively a component produced by means of milling, with aluminum in particular being used as the material for the rotor pot 2d. The rotor pot also has continuous recesses 22 in the axial direction, which, for example, se are each realized by means of a bore. In this way, an air flow (draft) for cooling the stator 4 or arranged on the motor mount 22 (motor) electronics 34. The rotor pot 2d has joining elements 2b for joining with the rotary member 28, not shown, which is formed here, for example, as a screw are.

As shown in FIG. 4b, the rotor magnet 2a has joining pins 36 for its joining to the rotor pot 2d, which pins are seated in corresponding receptacles 38. By way of example, the joining pins are held on the side facing away from the rotor magnet 2a by means of a securing ring (not shown in further detail) or, alternatively, the joining takes place by means of laser welding or hot-caulking. In summary, the rotor magnet 2 a is joined by means of the rotor pot 2 d to the rotary element 28 (not shown further). In order in particular to compensate for a play between the joining pin 36 and the corresponding receptacle and to realize a secure mounting of the magnet in the tangential direction (azimuthally, in the circumferential direction U), the rotor 2a has a parallelepiped recess to form contact shoulders 40, in wel - a flap 42 of the rotor pot with respect to the radial direction R and the circumferential direction U is positively seated. The plane IV represents the sectional plane according to FIG. 4a.

The invention is not limited to the embodiments described above. Rather, other variants of the invention can be derived therefrom by the person skilled in the art without departing from the subject matter of the invention. In particular, all the individual features described in connection with the exemplary embodiments can also be combined with one another in other ways without leaving the subject matter of the invention. LIST OF REFERENCE NUMBERS

2 rotor

2a rotor magnet

2b joining element

2c rotor core

2d rotor pot

4 stator

6 electric motor

8 stator yoke

10 stator tooth

12 stator slot

14 pole ash

16 gap

18 inside of the rotor

20 outside of the rotor 22 engine mount

24 bearing stock

26 storage system

28 rotary element

30 inside of the rotary member 32 recess

34 electronics

36 joining pin

38 recording

40 contact shoulder

42 tab

A axial direction

E symmetry plane

M motor axle

R radial direction

U circumferential direction

Claims

claims

1. Brushless electric motor (6), comprising a stator (4) and a rotor (2) which is in driving connection with a rotary element (28), - wherein the rotor (2) has a permanent magnet rotor magnet (2a), which according to Art a Halbach arrangement is magnetized,

- wherein the rotor magnet (2 a) is an injection molded part with embedded magnetically anisotropic magnetic material, which is at least partially formed from a ferrite, and

- Wherein the rotor (2) in the rotary member (28) is integrated or joined with this.

2. brushless electric motor (6) according to claim 1,

- characterized,

- That the rotor magnet (2a) has a remanence between 0.2 T and 0.5 T, and a coercive field strength of the magnetic polarization (H _C J) between 150 kA / m and 1000 kA / m.

3. brushless electric motor (6) according to claim 1 or 2,

characterized,

that the rotor (2) on its side (18) facing the stator (4) has a sinusoidal flux density course along its circumference, with a maximum flux density between 1.2 times and 1.5 times the remanence is reached, and wherein the flux density of the rotor (2) on the side opposite this side (18) (20) is substantially equal to zero.

4. Brushless electric motor (6) according to one of claims 1 to 3,

characterized,

the rotor (2) is designed as an outer rotor.

5. brushless electric motor (6) according to claim 4,

characterized, the rotor (2) and the rotary element (28) are an integrally formed injection-molded part.

6. Brushless electric motor (6) according to claim 5,

characterized,

in that the rotary element (28) with integrated rotor (2) is mounted for rotation by way of a bearing system (26) on a bearing shaft (24) of a motor carrier (22) to which the stator (4) is connected.

7. Brushless electric motor (6) according to claim 6,

characterized,

the rotary element (28) is the hub of a fan wheel, the hub having the bearing system (26), and the rotor (2) being integrally formed on its inner side (30).