DE102022116139B4 - Rotor for an electrical machine and method for its manufacture - Google Patents

Abstract

Rotor (10) for an electrical machine, having the following features:
- the rotor (10) comprises an inner laminated core (12) and an outer laminated core (14),
- the rotor (10) contains an inner magnet (13) aligned along a secant of its cross-section and a further inner magnet (13),
- the inner magnets (13) are aligned at an obtuse angle to each other and symmetrically to a radius of the cross-section and
- the rotor (10) has a cavity extending between the inner magnets (13) and carries an outer magnet (15) and a bandage (11) spanning the outer magnet (15), characterized by the following features:
- the rotor (10) has a pre-tensioning element (20) arranged radially below the outer magnet (15) for tightening the bandage (11), namely a wedge (20) directed towards the outer magnet (15) within the cavity, and
- the inner magnet (13) is embedded between the laminated cores (12, 14) in such a way that the wedge (20) acts on the bandage (11) via the inner magnet (13).

Description

The present invention relates to a rotor for an electrical machine. The present invention also relates to a corresponding manufacturing method, a corresponding electrical machine and a corresponding motor vehicle.

State of the art

IEC 60034-16-1 standardizes different types of excitation for single-phase and three-phase synchronous machines. Synchronous machines with small to medium power, such as those used as servo motors in automotive engineering, are predominantly permanently excited according to the state of the art (permanently excited synchronous machine, PSM). The magnets used for this purpose can be placed on or in the rotor's laminated cores in a variety of ways.

Magnets that are either surface-mounted or embedded ("buried") are well known and are often arranged in a star shape in the rotor to concentrate the flux. To further increase the flux density in the air gap, rare earth magnets in particular are often arranged in a V shape under a pole. In the pursuit of a compromise between the lowest possible magnetic edge scattering and manageable tensile and shear stresses, both configurations are sometimes combined.

To secure the surface magnets of fast-rotating rotors, these are usually reinforced to absorb the centrifugal force acting on the magnets during operation. In high-performance motors, thin-walled bandages made of fiber-reinforced plastic are used instead of metal sleeves to avoid eddy currents in the reinforcement.

In the design and manufacture of bandaged rotors, a deliberately defined overlap of the laminated core and rotor bandage components is required with regard to operational functionality.

The drum must therefore always be “tensioned” for operation under all load collectives.

The required preload is achieved according to the state of the art by means of a geometric transition or press fit. The overlap between the laminated core and the bandage is typically less than 1 percent of the rotor diameter.

This makes the joining process a challenge, as the components must be joined below ambient temperature or under contact (with high demands on the respective surfaces) for damage-free and contact-free assembly. To do this, the laminated core is cooled strongly - for example with nitrogen - and its outer surface is finely ground.

US 2014 / 0 009 024 A1 discloses a rotor of an electric motor, wherein the rotor has a rotor base body, a plurality of magnets arranged on an outer peripheral surface of the rotor base body and a bandage.

DE 10 2004 046 440 A1 discloses a rotor of an electric motor, having a rotor base body, a plurality of magnets arranged on an outer peripheral surface of the rotor base body and a bandage, wherein a clamping device is provided for aligning the rotor base body on a rotor shaft.

US 2016 / 0 028 282 A1 discloses a rotor of an electric motor, wherein the rotor has a rotor base body, a plurality of magnets arranged on an outer circumferential surface of the rotor base body and a bandage, wherein an end element is arranged on at least one axial end of the rotor base body, which end element is arranged radially between the bandage and an edge magnet.

DE 102 16 856 A1 discloses a rotor of an electric motor, wherein the rotor has a rotor base body, a plurality of magnets arranged on an outer peripheral surface of the rotor base body and a bandage, wherein a locking ring is provided for fixing each of the two axial ends of the bandage.

Further state of the art is provided in the publications DE 10 2005 041 676 A1 , DE 10 2017 223 042 A1 , DE 10 2010 022 702 A1 , DE 10 2010 062 393 B4 , DE 10 2013 102 822 A1 , WO 2014/ 125 433 A2 , DE 10 2019 117 686 A1 , DE 101 31 474 A1 , JP 2013- 116 002 A , DE 11 2010 005 756 T5 and CN 2 05 377 495 U out.

disclosure of the invention

The invention provides a rotor, a method for its manufacture, an electric machine and a motor vehicle according to the independent claims.

The invention is based on the idea of providing a generic rotor with additional components or supplementary geometric features on existing components to generate the radial preload.

This approach provides rotors according to the invention with high operational stability and speed.

Further advantageous embodiments of the invention are specified in the dependent patent claims. Thus, the said components can optionally already be present as punched tabs or other spring elements on the components used or can be introduced by additional radially or axially introduced elements as part of pre- or post-processing during assembly.

One advantage of this approach is the reduction of complex preliminary processes - such as grinding the outer diameter of the rotor laminations - and cold-hot processes in production. The manufacture of a rotor according to the invention is achieved in a sustainable manner through resource-saving processes.

Short description of the drawings

• 1 zeigt den Stand der Technik.
• 2 zeigt erfindungsgemäße Ausprägungen an vorhandenen Bauteilen.
• 3 zeigt erfindungsgemäße Zusatzbauteile zum Einsetzen vor, während oder nach der Montage.

Embodiments of the invention are illustrated in the drawings and are described in more detail below.

• 1 shows the state of the art.
• 2 shows inventive features on existing components.
• 3 shows additional components according to the invention for insertion before, during or after assembly.

embodiments of the invention

1 shows the segment of a bandaged rotor (10) in its cross-section, which is composed of an inner (12) and outer laminated core (14) that embed two magnets (13) that are aligned at an obtuse angle to each other and symmetrically to the rotor radius. Together, the magnets (13) thus describe the shape of the letter "V". The outer laminated core (14) also carries an outer magnet (15), which in turn is covered by the bandage (11) of the rotor (10).

The term "bandage" should be interpreted in a broad sense, which includes reinforcements wound directly onto the rotor (10) as well as inherently strong components for fixing the loose outer sheet stack (14) and magnets (15). If this bandage (11) does not fit tightly onto the rotor (10), there is insufficient strength and failure occurs when it rotates quickly, as the illustration clearly shows. This type of component design therefore presents the expert with the challenge of generating a pre-stress in the bandage (11).

2 illustrates the corresponding segment of a rotor (10) according to the invention, which faces this challenge. For this purpose, the electrical sheets of the laminated cores (12, 14) were cut or punched by laser during production in such a way that they each have a tab (20) on their surface facing the inner magnet (13), which is received in a corresponding groove in the same. The tabs (20) shown here in the unstressed state after punching or cutting are tensioned during assembly so that after final assembly they tighten the bandage (11) over the inner magnet (13).

3 highlights a variation of this principle, in which instead of the molded tabs (20 - 2 ) a wedge (20) manufactured independently of the laminated cores (12, 14) serves as a prestressing element, which - pointing radially outwards with respect to the rotor (10) and thus in the direction of the outer magnet (15) - is arranged in the cavity between the inner magnets (13) and thus at the apex of the letter "V" formed by the latter. Such a wedge (20) can optionally be inserted during assembly or subsequently inserted lengthwise into the cavity of the rotor (10) without departing from the scope of the invention.

Claims (6)

Rotor (10) for an electrical machine, having the following features: - the rotor (10) comprises an inner laminated core (12) and an outer laminated core (14), - the rotor (10) contains an inner magnet (13) aligned along a secant of its cross section and a further inner magnet (13), - the inner magnets (13) are aligned at an obtuse angle to one another and symmetrically to a radius of the cross section and - the rotor (10) has a cavity extending between the inner magnets (13) and carries an outer magnet (15) and a bandage (11) spanning the outer magnet (15), characterized by the following features: - the rotor (10) has a prestressing element (20) arranged radially below the outer magnet (15) for tightening the bandage (11), namely a wedge (20) directed towards the outer magnet (15) within the cavity, and - the inner magnet (13) is arranged between the Embedded in laminated cores (12, 14) such that the wedge (20) acts on the bandage (11) via the inner magnet (13). Method for producing a rotor (10) according to claim 1 , characterized by the following Features: - Electrical sheet is cut or punched and assembled to form the sheet packages (12, 14) and - the sheet packages (12, 14) and magnets are assembled and reinforced with the bandage (11). procedure according to claim 2 , characterized by the following features: - the wedge (20) is formed during cutting or punching on the electrical sheet and - the wedge (20) is tensioned during assembly. procedure according to claim 2 , characterized by the following features: - the wedge (20) is manufactured independently of the laminated cores (12, 14) and - the wedge (20) is inserted during assembly or inserted lengthwise into a cavity of the rotor (10) remaining after assembly. Electric machine with a rotor (10) according to claim 1 . Motor vehicle with an electric machine according to claim 5 .

Images