Rotor for an electric machine

Abstract

The present invention relates to a rotor (10) for an electrical machine, in particular for an electric motor, comprising a main body (1), a shaft (2) extending along an axis (X), a stack (3) of rotor laminations having an outer zone (4) with a plurality of magnet pockets (5) receiving a plurality of permanent magnets (6), the outer zone (4) having a circumferential outer wall (7) with a periodically varying thickness defining a plurality of minimum thickness walls (8) on each end of the permanent magnets (6) and these minimum thickness walls (8) are heat-shrinked by forming an axial shrink line (9) along the circumferential outer wall (7) in order to hold the permanent magnets (6) in their respective magnet pockets (5). The invention also relates to a method for manufacturing such a rotor (10). Figure for abstract: Figure 1

Description

Title of the invention: Rotor for an electric machine

[0001] The invention relates to a rotor for an electric machine, in particular an electric motor.

[0002] The rotor is particularly intended for use in an electric motor which drives a hydraulic pump, such as used in motor vehicles to provide a volumetric flow of hydraulic oil which is supplied to a clutch actuator, a gearbox actuator, a clutch cooling system, a gearbox lubrication system or the like.

[0003] Rotors are known having a stack of rotor laminations mounted on a metal shaft, in which permanent magnets are held. Such rotors require manufacturing effort, but are distinguished by a strong magnetic field strength.

[0004] One of the technical problems associated with these types of rotor is the fixing of the permanent magnets in the pockets.

[0005] It is known to hold these permanent magnets in their respective pockets with glue or by making complex shapes, additional ribs for example, which increases production costs.

[0006] Conventional assembly processes for permanent magnets always require a gap between the magnet and the stacking pocket. This causes magnetic losses. Known solutions with a tight fit between the magnet and the ribs cause debris during the pressing process and the magnet coating can be damaged.

[0007] The invention aims to provide a rotor comprising a stack of rotor laminations which can be produced with less effort and with good retention of the permanent magnets.

[0008] This object is achieved according to the invention by a rotor for an electrical machine, in particular for an electric motor, comprising a single-piece main body, a shaft extending along an axis, a stack of rotor laminations having an outer zone with a plurality of magnet pockets receiving a plurality of permanent magnets, the outer zone having a circumferential outer wall with a periodically varying thickness defining a plurality of walls of minimum thickness on each end of the permanent magnets and these walls of minimum thickness are heat-shrunk by forming an axial retraction line along the circumferential outer wall in order to maintain the permanent magnets in their respective magnet pockets.

[0009] The invention is based on the basic concept of deformation of the stack of sheets rotors by heat shrinking such as laser shrinking, flame shrinking or welding shrinking in order to deform the magnet pockets and hold the permanent magnets in their respective magnet pockets.

[0010] By axial retraction line is meant a continuous elongated line which is not necessarily straight, the line may for example be curved, broken or polygonal.

[0011] According to a configuration of the invention, each magnet pocket has an opening at each of its ends and each wall of minimal thickness is located relative to these openings. Thin areas of stacked rotor laminations are heat-shrinked, gaps between the permanent magnets and the magnet pockets are eliminated. Magnets are fixed without additional measures and magnetic losses in the gaps are eliminated.

[0012] According to one configuration of the invention, the stack of rotor laminations is integrated into a main body.

[0013] According to one configuration of the invention, the main body is formed from a single piece and made of plastic material.

[0014] According to one configuration of the invention, the shaft is injection molded into the main body by complementary shapes.

[0015] According to a configuration of the invention, the stack of rotor laminations is provided with a formation with axial geometric positioning along the circumferential outer wall.

[0016] The aforementioned object is also achieved according to the invention by providing a method of manufacturing a rotor for an electric machine, in particular for an electric motor, by means of the following steps: i. assembly of a stack of rotor laminations having a number of magnet pockets and a circumferential outer wall, ii. inserting a permanent magnet into each magnet pocket, iii. placing the stack of rotor laminations having permanent magnets in a heat source device, iv. forming a plurality of axial retraction lines along the circumferential outer wall with the heat source device to hold the permanent magnets in their respective magnet pockets.

[0017] According to one configuration of the invention, the heat source device is a laser source or a plurality of laser sources.

[0018] According to one configuration of the invention, the laser source has a focal point and the axial retraction line is created with relative axial movement between the laser source and the stack of rotor laminations.

[0019] According to a variant, the laser source has a line and the axial retraction line is created without relative movement between the laser source and the stack of ro- sheets. toric.

[0020] According to another variant, the heat source device is a welding source, such as TIG welding or plasma arc welding.

[0021] The invention will be described below on the basis of an embodiment illustrated in the accompanying drawings. In the drawings:

[0022] [Fig.l] illustrates a perspective view of the rotor according to the invention;

[0023] [Fig.2] illustrates a specific view of the axial retraction lines of the rotor according to the invention;

[0024] [Fig.3] illustrates a specific top view of the rotor according to the invention and focused on a magnet pocket;

[0025] [Fig.4] illustrates a step-by-step diagram of the method of manufacturing a rotor according to the invention.

[0026] With reference to [Fig.l] to [Fig.3], a rotor 10 according to the invention is shown. It is intended to be used in conjunction with a stator of an electric motor and to drive a hydraulic pump as used in the drive train of a motor vehicle, for example to switch an actuator or to lubricate or cool components.

[0027] The rotor 10 comprises a main body 1 in the form of a pot or cup which is made of plastic material. The main body 1 is in particular injection molded.

[0028] The main body 1 has an end wall at one axial end, which forms the bottom of the "cup". In the end wall, a rotor shaft 2 is held by form-fitting. In the end wall, through openings are provided, which serve for the flow of the hydraulic fluid.

[0029] A plurality of rotor laminations are received on the main body 1, which together form a stack 3.

[0030] The stack 3 formed by the rotor laminations is received on the main body 1 in such a way that it extends along the inner circumference of the stack 15 in the manner of a sleeve and forms a collar at each axial end. The collar ensures that the rotor laminations are firmly held together in the axial direction.

[0031] The rotor 10 has a generally cylindrical shape, the stack 3 of rotor laminations has an external zone 4 with a plurality of magnet pockets 5 receiving a plurality of permanent magnets 6.

[0032] The stack 3 of rotor laminations is provided with a plurality of axially geometrically positioned formations 11 along the circumferential outer wall 7.

[0033] As can be seen in particular in [Fig. 2], the magnet pockets 5 have an elongated cross-section when viewed in section or end. Each magnet pocket 5 has an opening 12 at each of its ends.

[0034] The external zone 4 has a circumferential external wall 7 of thickness varying periodically defining a plurality of walls of maximum thickness defined by a width W2 and a plurality of walls of minimum thickness 8 defined by a width Wl, W1 being less than W2.

[0035] Each wall of minimum thickness 8 of the circumferential outer wall 7 is located relative to the openings 12. Each wall of maximum thickness of the circumferential outer wall 7 is located relative to the magnet pockets 5.

[0036] All the minimum thickness walls 8 are heat-shrinked forming an axial shrink line 9 along the circumferential outer wall 7 to hold the permanent magnets 6 in their respective magnet pockets 5. The axial shrink line 9 is a straight line extending axially along the outer area 4 of the circumferential outer wall 7.

[0037] The shrink line 9 creates a deformation of the stack 3 with flame straightening or welding shrinkage in order to deform the magnet pockets 5 and hold the permanent magnets 6 in their respective magnet pockets 5. Preferably, the deformation of the stack 3 is obtained by laser shrinkage.

[0038] The deformation causes a reduction in the widths of the magnet pockets 5 to eliminate permanent magnet assembly spaces 6 avoiding magnetic losses.

[0039] [Fig.4] shows the manufacturing process of the rotor 10 described above with the following steps: i. assembly of the stack 3 of rotor laminations having a number of magnet pockets 5 and a circumferential outer wall 7, ii. inserting the permanent magnets 6 into each of the magnet pockets 5, iii. placing the stack 3 of rotor laminations equipped with the permanent magnets 6 in a heat source device, iv. forming a plurality of axial retraction lines 9 along the circumferential outer wall 7 with the heat source device in order to hold the permanent magnets 6 in their respective magnet pockets 5.

[0040] Axial retraction lines 9 can be created one by one with a single-source laser. Alternatively, the lines can be created simultaneously with a multi-source laser. The plurality of laser sources can be obtained with only one laser source and an optical device dividing the laser source into a plurality of laser sources.

[0041] Each permanent magnet 6 is assigned two axial retraction lines 9 on either side of the permanent magnet 6 relative to the opening 12. In the illustrated embodiment, this is equivalent to the creation 16 of axial retraction lines 9.

[0042] The laser source has a focal point and each axial retraction line 9 is created with relative axial movement along the rotor between the laser source and the stack 3 of rotor laminations. In other words, all points move simultaneously along the rotor axis.

[0043] The variant with movable laser focal points does not require additional clamping jigs, the surrounding material prevents expansion.

[0044] According to a variant, the laser source creates a line and each axial retraction line 9 is created without relative movement between the laser source and the stack 3 of rotor laminations. The line can be created by an optical device from the laser source.

[0045] The variant with linear focusing and without movement requires clamping to avoid radial expansion when the part is heated.

Claims

Claims

1. Rotor (10) for an electrical machine, in particular for an electric motor, comprising a main body (1), a shaft (2) extending along an axis (X), a stack (3) of rotor laminations having an outer zone (4) with a plurality of magnet pockets (5) receiving a plurality of permanent magnets (6), the outer zone (4) having a circumferential outer wall (7) with a periodically varying thickness defining a plurality of minimum thickness walls (8) on each end of the permanent magnets (6) and these minimum thickness walls (8) are heat-shrinked by forming an axial shrink line (9) along the circumferential outer wall (7) in order to maintain the permanent magnets (6) in their respective magnet pockets (5).

2. Rotor (10) according to claim 1, characterized in that each magnet pocket (5) has an opening (12) at each of its ends and each wall of minimum thickness (8) is located relative to these openings (12).

3. Rotor (10) according to claim 1 or 2, characterized in that the stack (3) of rotor laminations is integrated into the main body (1).

4. Rotor (10) according to any one of the preceding claims, characterized in that the main body (1) is made of a single piece and of plastic material.

5. Rotor (10) according to any one of the preceding claims, characterized in that the shaft (2) is injection molded into the main body (1) by form-fitting.

6. Rotor (10) according to any one of the preceding claims, characterized in that the stack (3) of rotor laminations is provided with at least one axially geometrically positioned formation (11) along the circumferential outer wall (7).

7. A method of manufacturing a rotor (10) for an electrical machine, in particular for an electric motor, by means of the following steps: (i) assembling a stack (3) of rotor laminations having a number of magnet pockets (5) and a circumferential outer wall (7), (ii) inserting a permanent magnet (6) into each magnet pocket (5), (iii) placing the stack (3) of rotor laminations equipped with the permanent magnets (6) in a heat source device, (iv) forming a plurality of axial retraction lines (9) along the circumferential outer wall (7) with the heat source device to hold the permanent magnets (6) in their respective magnet pockets (5).

8. Method according to claim 7, characterized in that the heat source device is a laser source or a plurality of laser sources.

9. Method according to claim 8, characterized in that the laser source has a focal point and the axial retraction line (9) is created with a relative axial movement between the laser source and the stack (3) of rotor laminations.

10. Method according to claim 8, characterized in that the laser source has a line and the axial retraction line (9) is created without relative movement between the laser source and the stack (3) of rotor laminations.

11. A method according to claim 7, characterized in that the heat source device is a welding source, such as TIG welding or plasma arc welding.

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