Rotor for an electric machine with a magnet having projections

Abstract

The invention relates to a rotor (1) for an electric machine (18), having a rotor laminated core (2) comprising a plurality of rotor laminations (3) stacked in the axial direction, which have a plurality of recesses that are arranged distributed in the circumferential direction, forming magnet pockets (6, 7, 8) and in each of which a magnet (9, 13, 15) is inserted, wherein a magnet (9, 13, 15) has at least two projections (11, 14, 16) on an outer side (10). The invention also relates to an electric machine (18) having such a rotor (1), and a vehicle (17) having the electric machine (18).

Description

[0001] Rotor for an electrical machine with a magnet having projections

[0002] The invention relates to a rotor for an electrical machine, comprising a rotor core comprising a plurality of rotor cores stacked in the axial direction, which have a plurality of recesses arranged circumferentially and forming magnetic pockets, each of which contains a magnet. The axial direction runs parallel to the rotational axis of the rotor.

[0003] Electric machines with such a rotor are increasingly being used in electrically powered vehicles or hybrid vehicles. The electric machine is predominantly used as an electric motor to drive a wheel or axle of the vehicle. The electric motor can be designed as a synchronous motor or an asynchronous motor, among other types.

[0004] The electric motor is usually mechanically coupled to a gearbox for speed adjustment. In addition, the electric motor is usually electrically connected to an inverter, which converts a direct current supplied by a battery into an alternating current (AC) for operating the electric machine, particularly a multiphase alternating current.

[0005] The stator of an electrical machine consists of a stator core and stator windings. When a current is applied to the stator windings, a rotating electric field is generated, which causes the rotor to rotate.

[0006] The rotor lamination stack consists of a large number of axially stacked or aligned rotor laminations. Some rotor laminations contain recesses that form magnet pockets. After the magnets are inserted into the magnet pockets, a liquid potting compound is typically poured into the rotor lamination stack, which is then cured by applying heat. Care must be taken to ensure that the rotor lamination stack, consisting of stacked rotor laminations, is sealed to prevent leakage of the potting compound. The tolerances of the magnet pockets and the magnets are selected so that the magnets can be inserted into the magnet pockets without jamming or jamming.

[0007] The goal is to position the magnets as radially outward as possible in the magnetic pockets, as this maximizes the electromagnetic force. However, due to the tolerances required for magnet assembly, it may happen that a magnet is located in a radially inner position or that the position is undefined. Therefore, there is a need for a rotor in which the magnets are positioned radially outward in the magnetic pockets. This radial direction is perpendicular to the rotor's rotation axis.

[0008] The invention is therefore based on the object of providing a rotor in which the magnets in the magnetic pockets are positioned radially outwards.

[0009] This object is achieved with a rotor having the features of claim 1.

[0010] In the rotor according to the invention, a magnet has at least two projections on one outer side. The outer side can be one of the longer outer sides of the magnet. The size of the projections and the size of the magnet are matched to the size of the recess or to the size of the magnetic pocket that accommodates the magnet, so that the magnet can be positioned in the magnetic pocket without play. In particular, the magnet touches an inner side of the recess with the two projections on its outer side, so that its position is fixed. This has the advantage that complex potting with a potting compound can be dispensed with. The rotor according to the invention is thus characterized by a shortened production time compared to the prior art. Within the scope of the invention, it is preferred that the at least two projections on the outer side of the magnet are directed radially inward.The magnet is inserted into the recess with the projections facing the rotor's rotational axis. This ensures that the magnet is positioned as radially outward as possible. However, it is also possible for both projections to face radially outward.

[0011] In the present application, it is preferred for a magnet to have two or more projections on its exterior. However, it is also possible to provide only a single such projection. To prevent the magnet from tilting, it is also possible for the projection to extend over a larger area of ​​the exterior of the magnet.

[0012] On the other hand, a magnet can also have more than two such projections, for example three, four, five, six, seven, eight, nine, ten, eleven or twelve projections located on the same outer side of the magnet.

[0013] A further development of the invention provides that the at least two projections are designed such that an outer side of the magnet opposite the projections rests flush against an inner side of the magnet pocket. This improves the hold of the magnet in the magnet pocket, preventing it from slipping. In particular, the magnet can thus securely maintain a radially outermost position in the magnet pocket.

[0014] It can also be provided that the two projections arranged on the outside of the magnet are spaced from an edge of the magnet. The two projections can in particular be offset from one edge towards the center of the outside. Alternatively, however, the projections can also be placed directly on an edge of the magnet. In particular, the projections can each border on an edge of the magnet or touch the edge. It is also within the scope of the invention for a projection to have a semicircular, triangular, or rectangular cross-section. With regard to its three-dimensional shape, a projection can be designed as a hemisphere, three-sided pyramid, four-sided pyramid, or cuboid.

[0015] It is particularly preferred that the shape and size of the projections be selected such that a magnet is held frictionally in the magnetic pocket. The friction between the magnet and the inside of the magnetic pocket securely holds the magnet in the desired position.

[0016] The rotor according to the invention can also be designed such that the rotor core is divided into several core segments in the axial direction, with two adjacent core segments being rotated relative to each other in the circumferential direction. The rotation is typically a few degrees. This measure counteracts the development of a cogging torque.

[0017] In the rotor according to the invention, a projection can preferably extend over the entire axial length or over part of the axial length of the magnet. The axial length of the magnet refers to the length of the magnet accommodated in the magnet pocket along the rotor's rotational axis.

[0018] Preferably, the projections can each be arranged at a corner of the magnet. Care must be taken to ensure that the projections do not collide with the contour of the magnetic pocket, so that the magnet can be easily inserted into the magnetic pocket. To achieve this, the corners and radii of the magnet and magnetic pocket can be designed and dimensioned accordingly.

[0019] In a magnet pocket of the rotor core, preferably several magnets are arranged one behind the other in the axial direction. The invention also relates to an electric machine with a rotor of the type described and a stator, relative to which the rotor is rotatably mounted. The rotor may have a rotor shaft, and the stator may have stator windings. The rotor core may be connected to the rotor shaft in a rotationally fixed manner, for example, by screwing or pressing. The rotor core may be stamped, for example, by inserting metal rods through the rotor core and pressing them together on both sides.

[0020] The rotor core may also have end plates, each arranged on an axial side of the rotor core. The end plates may be bolted to the rotor core using through-bolts. Alternatively, the end plates may be attached to the rotor core in another way, for example, by bonding or stamping.

[0021] The invention also relates to a vehicle having at least one such electric machine by which it can be driven.

[0022] The invention is explained below using an exemplary embodiment with reference to the drawings. The drawings are schematic representations and show:

[0023] Fig. 1 is a sectional view of a rotor according to the invention;

[0024] Fig. 2 is a plan view of a rotor lamination;

[0025] Fig. 3 shows a detail of a rotor lamination with a magnet inserted in a magnet pocket;

[0026] Fig. 4 shows a further embodiment of a rotor lamination with a magnet inserted in a magnetic pocket; Fig. 5 shows a further embodiment of a rotor lamination with a magnet inserted in a magnetic pocket; and

[0027] Fig. 6 shows a vehicle with an electric machine according to the invention.

[0028] Fig. 1 is a sectional view of a rotor 1 for an electrical machine. The rotor 1 comprises a rotor core 2 consisting of a plurality of rotor laminations 3 stacked in the axial direction. The rotor laminations 3 have a central opening into which a rotor shaft 4 is pressed in a rotationally fixed manner.

[0029] In Fig. 1, it can be seen that the rotor core 2 has through-holes 5. Magnetic pockets 6 are arranged on the outer circumference of the rotor core 2, into which, in the assembled state, several magnets are inserted one above the other in the axial direction.

[0030] Fig. 2 shows a schematic plan view of an individual rotor lamination 3, which does not necessarily correspond in terms of details to the rotor laminations of the rotor lamination stack 2 shown in Fig. 1. The rotor lamination 3 comprises magnetic pockets 6, 7 distributed over the circumference for magnets that differ in size and shape. The shape and number of magnetic pockets can vary with the number of magnetic poles of the rotor. The magnetic pockets 6, 7 are arranged in pairs. The rotor lamination 3 also comprises through openings 5 ​​arranged between the larger magnetic pockets 6, which serve for screwing the rotor lamination stack 2. Alternatively, end plates can be attached to a rotor lamination stack by means of adhesive bonding or punching.

[0031] Fig. 3 is a plan view showing a detail of a rotor lamination stack 2 near the outer circumference. The rotor lamination stack 2, consisting of stacked rotor laminations, has a magnet pocket 8 into which a magnet 9 is inserted. The magnet 9 has the basic shape of a cuboid; on its radially inward-facing outer side 10, two projections 11 are formed, which have a triangular cross-section. Both projections 11 are spaced from an edge of the magnet 9 to the center of the outer side 10. In the illustrated embodiment, the projections 11 extend over the entire axial length of the magnet 9. The size of the magnet 9 having the projections 11 and the size of the magnet pocket 8 are coordinated with one another, taking tolerances into account, such that a magnet 9 inserted into the magnet pocket 8 is held there with frictional engagement. On the one hand, the projections 11 touch a first inner side of the magnet pocket 8.The opposite outer side 12 of the magnet 9 touches a second inner side of the magnetic pocket 8. The magnets 9 can be inserted into the magnetic pockets 8 with little force and are automatically held in this position. Additional positioning, for example, by applying a potting compound, is optional.

[0032] In a further manufacturing step, the previously unmagnetized magnet can be magnetized with an external magnetic field. This increases the magnetic attraction of the magnet 9 on the outer surface 12 and its tendency to adhere precisely to that surface.

[0033] Fig. 4 is a view similar to Fig. 3 and shows another embodiment of a rotor core 2 with a magnet 13 inserted into a magnet pocket 8, the projections 14 of which are formed as hemispheres. In this embodiment, the projections 14 are located directly on an edge of the outer side of the magnet 13. The projections 14 cause the magnet 13 to be located at its radially outermost position, so that the magnetic field acting outside the rotor is maximized.

[0034] Fig. 5 is a view similar to Figs. 3 and 4 and shows a rotor core 2 with a magnet 15 whose projections 16 are rectangular. The projections 16 are supported on the radially inner inside of the magnet pocket 8. The outer side of the magnet 15 lies flat against the radially outer inside of the magnet pocket 8. Fig. 6 shows a vehicle 17 with an electric machine 18 with a rotor 1 having a rotor shaft 19, and with a stator 20 surrounding the rotor 1, which has stator windings. The electric machine 18 serves to drive an axle of the vehicle 17.

[0035] List of reference symbols

[0036] 1 rotor

[0037] 2 rotor lamination pack

[0038] 3 rotor sheet

[0039] 4 Rotor shaft

[0040] 5 passage opening

[0041] 6 magnetic pockets

[0042] 7 magnetic pocket

[0043] 8 magnetic pocket

[0044] 9 Magnet

[0045] 10 Outside

[0046] 11 lead

[0047] 12 Outside

[0048] 13 Magnet

[0049] 14 lead

[0050] 15 Magnet

[0051] 16 lead

[0052] 17 vehicles

[0053] 18 electric machine

[0054] 19 Rotor shaft

[0055] 20 Stator

Claims

Patent claims 1. Rotor (1) for an electrical machine (18), with a rotor lamination stack (2) comprising a plurality of rotor laminations (3) stacked in the axial direction, which have a plurality of recesses arranged distributed in the circumferential direction and forming magnetic pockets (6, 7, 8), in each of which a magnet (9, 13, 15) is inserted, characterized in that a magnet (9, 13, 15) has at least two projections (11, 14, 16) on an outer side (10).

2. Rotor according to claim 1, wherein the at least two projections (11, 14, 16) are directed radially inward or radially outward.

3. Rotor according to claim 1 or 2, wherein the at least two projections (11, 14, 16) are designed such that an outer side (12) of the magnet (9, 13, 15) opposite the projections (11, 14, 16) lies flush with an inner side of the magnet pocket (6, 7, 8).

4. Rotor according to one of the preceding claims, wherein the two projections (11, 14, 16) arranged on the outer side (10) are either spaced from an edge of the magnet or adjoin an edge of the magnet (9, 13, 15).

5. Rotor according to one of the preceding claims, wherein a projection (11, 14, 16) has a semicircular or triangular or rectangular cross-section.

6. Rotor according to one of the preceding claims, wherein the shape and size of the projections (11, 14, 16) are selected such that a magnet (9, 13, 15) is held in the magnet pocket (6, 7, 8) by frictional engagement.

7. Rotor according to one of the preceding claims, wherein the rotor laminated core (2) is divided in the axial direction into several laminated core segments and two adjacent laminated core segments are twisted relative to each other in the circumferential direction.

8. Rotor according to one of the preceding claims, wherein a projection (11, 14, 16) extends over the entire axial length or over part of the axial length of the magnet (9, 13, 15).

9. Rotor according to one of the preceding claims, wherein the projections (11, 14, 16) are each arranged at a corner of the magnet (9, 13, 15).

10. Rotor according to one of the preceding claims, wherein a plurality of magnets (9, 13, 15) are arranged one behind the other in the axial direction in a magnet pocket.

11. Electrical machine (18) comprising a rotor (1) according to one of claims 1 to 10 and a stator (20) relative to which the rotor (1) is rotatably mounted.

12. Vehicle (17) having at least one electric machine (18) according to claim 11 by which it can be driven.

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