WO2018103969A1

WO2018103969A1 - Permanent magnet synchronous electric motor

Info

Publication number: WO2018103969A1
Application number: PCT/EP2017/077942
Authority: WO
Inventors: Burcu DURAK; Merve Ayca TELEMEZ; Caglar ACAR; Hakan Gedik; Ipek DOKUMCU
Original assignee: Arcelik Anonim Sirketi
Priority date: 2016-12-08
Filing date: 2017-11-01
Publication date: 2018-06-14
Also published as: EP3552302A1; TR201618100A2

Abstract

The present invention relates to a permanent magnet synchronous electric motor (1) comprising a stator (2); a cylindrical rotor (3) that is composed of stacked magnetic steel laminations and that has annular and planar front and rear surfaces; a shaft (5) that is snap-fitted into the shaft hole (4) arranged at the center of the rotor (3); a plurality of magnet coupling holes (7) that are disposed around the shaft hole (4), that extend towards the interior of the rotor (3) in the axial direction from the annular surface of the rotor (3) and wherein magnets (6) providing synchronous operation are disposed; and a plurality of slots (11) that extend in the rotor (3) all around and in the axial direction in the area close to the cylindrical side surface of the rotor (3) and wherein aluminum is injected in the injection mold during the production of the rotor (3).

Description

PERMANENT MAGNET SYNCHRONOUS ELECTRIC MOTOR

The present invention relates to an electric motor wherein permanent magnets are disposed in the rotor. Especially in industrial embodiments where high start-up moment and high operation efficiency are important, electric motors that have the asynchronous motor feature at the start-up and the synchronous motor feature in continuous operation are used. This type of electric motor is known as permanent magnet synchronous motors. In the electric motor, permanent magnets that are embedded in the rotor are used in addition to the aluminum magnetic cage (squirrel cage) structure in the rotor slots. The electric motor starts up asynchronously by means of the magnetic cage disposed in the rotor and operates synchronously after the start-up by means of the permanent magnets disposed in the rotor. Reaching high temperatures while the aluminum material is being injected into the rotor slots and the magnets embedded in the rotor losing their magnetic features due to high temperature create problems in the production of this type of rotor. The magnets are disposed in the rotor after the aluminum injection process in order to solve this problem. Especially in the high speed electric motors, the magnets need to be fixed against the risk of breaking away their coupling holes, before causing magnetic flux irregularities and any harm to the rotor balance after being placed in the rotor.

The International Patent Applications No. WO2008012269 (A1), WO2008012270 (A1), and WO2008012271 (A1) relate to a permanent magnet synchronous electric motor where the magnets that are disposed in the rotor by being embedded are prevented from dislodging.

The aim of the present invention is the realization of a permanent magnet synchronous electric motor that has an easy-to-produce low-cost rotor, with improved start-up and operation efficiency.

In the electric motor realized in order to attain the aim of the present invention, an external circlip that prevents the magnets from dislodging from the coupling holes thereof is attached to a circlip channel (adjacent to the rotor package) that is disposed on the rotor shaft and that is disposed right in front of a annular surface of the rotor package composed of laminations. The external circlip comprises magnet retaining extensions that extend outwards in the radial direction from the side thereof, that partially cover the magnet coupling holes and that prevent the magnets from dislodging from the coupling holes thereof by bearing against the magnets.

Figure 1 – is the schematic view of an electric motor.

Figure 2 - is the exploded view of a rotor, magnets to be attached to the rotor, and an external circlip having magnet retaining extensions.

Figure 3 - is the perspective view of an external circlip comprising magnet retaining extensions.

Figure 4 - is the front schematic view of the rotor, wherein the external circlip having the magnet retaining extensions is attached.

Figure 5 - is the perspective view of the rotor, wherein the external circlip having the magnet retaining extensions is attached.

Figure 6 - is the front schematic view of the rotor, wherein the external circlip having the magnet retaining extensions extending in the radial direction is attached in an embodiment of the present invention.

The elements in the figures are numbered as follows:

Electric motor
Stator
Rotor
Shaft hole
Shaft
Magnet
Magnet coupling hole
Circlip channel
Retaining extension
External circlip
Slot

The electric motor (1) comprises a stator (2); a cylindrical rotor (3) that is composed of stacked magnetic steel laminations and that has annular and planar front and rear surfaces; a shaft (5) that is snap-fitted into the shaft hole (4) arranged at the center of the rotor (3); a plurality of magnet coupling holes (7) that are disposed around the shaft hole (4), that extend towards the interior of the rotor (3) in the axial direction from the annular surface of the rotor (3) and wherein magnets (6) providing synchronous operation are disposed; and a plurality of slots (11) that extend in the rotor (3) all around and in the axial direction in the area close to the cylindrical side surface of the rotor (3) and wherein aluminum is injected in the injection mold during the production of the rotor (3).

The electric motor (1) of the present invention comprises

- a circlip channel (8) that is bored on the shaft (5) and that is adjacent to the annular rotor (3) surface where the magnets (6) are disposed into the magnet coupling holes (7), and

- an external circlip (10) that extends on the annular rotor (3) surface, that bears against the magnets (6) by at least partially covering the magnet coupling holes (7) and that has at least one magnet retaining extension (9) that prevents the magnets (6) from dislodging from the magnet coupling holes (7) by preventing the movement of the magnets (6) in the axial direction.

The magnet retaining extensions (9) are produced as a single piece with the external circlip (10) from the spring steel and extend outwards in the radial direction from the side of the external circlip (10).

While the rotor is being produced (3), the laminations whereon the shaft hole (4), the slots (11), and the magnet coupling holes (7) are disposed are fixed by being stacked and then placed into the aluminum injection mold, and aluminum is injected into the slots (11) from an annular surface of the core of the rotor (3). The aluminum material is prevented from entering the magnet coupling holes (7) and the shaft hole (4) by means of various methods while aluminum is being injected into the core of the rotor (3). The magnets (6) are disposed into the magnet coupling holes (7) after the aluminum injection process, and thus the magnets (6) are prevented from being affected from high temperature. After the magnets (6) are disposed, by using circlip pliers the external circlip (10) is attached to the circlip channel (8) arranged in the shaft (5) that is previously attached to the rotor (3). The magnet retaining extensions (9) integrated with the external circlip (10) extend on the annular surface of the rotor (3) so as to at least partially cover the magnet coupling holes (7), and bear against the magnets (6) so as to prevent the same from dislodging.

In an embodiment of the present invention, the external circlip (10) comprises at least one T-shaped magnet retaining extension (9) that bears against the magnets (6) with the arms that constitute the T-shape.

In this embodiment, the electric motor (1) comprises four magnet coupling holes (7) with rectangular cross-sections that are arranged around the shaft hole (4) and four magnets (6) with rectangular cross-sections that are disposed into the magnet coupling holes (7), and the external circlip (10) comprises two T-shaped magnet retaining extensions (9), each bearing against two magnets (6).

In another embodiment of the present invention, the electric motor (1) comprises four magnet coupling holes (7) with rectangular cross-sections that are arranged around the shaft hole (4) and four magnets (6) with rectangular cross-sections that are disposed into the magnet coupling holes (7), and the external circlip (10) comprises four bar-shaped magnet retaining extensions (9) that extend outwards in the radial direction, each bearing against at least one magnet (6).

In the embodiment of the present invention, the magnets (6) that are disposed by being embedded to the rotor (3) are prevented from dislodging from the magnet coupling holes (7) during the operation of the electric motor (1) at high rotational speeds. An external circlip (10) that is produced from spring steel and around which magnet retaining extensions (9) are added is used in order to keep the magnets (6) in the magnet coupling holes (7). The external circlip (10) is easily mounted by using circlip pliers, and material and labor savings in the production of the electric motor (1) are provided.

Claims

An electric motor (1) comprising a stator (2); a rotor (3); a shaft (5) that is snap-fitted into a shaft hole (4) arranged at the center of the rotor (3), and a plurality of magnet coupling holes (7) that are arranged around the shaft hole (4), that extend towards the interior of the rotor (3) in the axial direction from the annular surface of the rotor (3) and wherein magnets (6) are disposed; characterized by

- a circlip channel (8) that is bored on the shaft (5) and that is adjacent to the annular rotor (3) surface where the magnets (6) are disposed into the magnet coupling holes (7), and

- an external circlip (10) that arranged on the circlip channel (8) and extends on the annular rotor (3) surface, that bears against the magnets (6) by at least partially covering the magnet coupling holes (7) and that has at least one magnet retaining extension (9) that prevents the magnets (6) from dislodging from the magnet coupling holes (7).
An electric motor (1) as in Claim 1, characterized by the magnet retaining extensions (9) that are produced as a single piece with the external circlip (10) from spring steel.
An electric motor (1) as in Claim 1 or 2, characterized by at least one T-shaped magnet retaining extension (9) that bears against the magnets (6) with the arms that constitute the T-shape.
An electric motor (1) as in Claim 3, characterized by four magnet coupling holes (7) with rectangular cross-sections that are arranged around the shaft hole (4), four magnets (6) with rectangular cross-sections that are disposed into the magnet coupling holes (7), and two T-shaped magnet retaining extensions (9), each bearing against two magnets (6).
An electric motor (1) as in Claim 1 or 2, characterized by the magnet retaining extensions (9) that extend outwards in the radial direction from the side of the outer external circlip (10).
An electric motor (1) as in Claim 5, characterized by four magnet coupling holes (7) with rectangular cross-sections that are arranged around the shaft hole (4), four magnets (6) with rectangular cross-sections that are disposed into the magnet coupling holes (7); and four bar-shaped magnet retaining extensions (9) that extend outwards in the radial direction, each bearing against at least one magnet (6).