DE8612858U1 - Permanent magnet rotors for electric motors - Google Patents

Description

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Bauer magnetic rotors for electric motors

The invention relates to a permanent magnet rotor for electric motors, which consists of two parts that can rotate relative to one another about the rotor axis and can be coupled to one another, one part of which is mechanically connected to the rotor shaft for rotational drive and one of the parts of which carries permanent magnets.

Such a rotor is known from DE-GM 73 44 638. A slip clutch is connected between the two parts that rotate against each other, the transferable torque of which is greater than the static load torque and smaller than the starting torque of the motor. If such a rotor is installed in a synchronous motor, it can start immediately with the part containing the permanent magnets. The other part, which is firmly connected to the rotor shaft, is gradually accelerated to the nominal speed by the first rotor part via the slip clutch. Since the coupling of the two rotor parts that move against each other around the rotor axis is mechanical in the known rotor, gradual wear occurs on the coupling surfaces. The friction that occurs also causes heat to develop and the efficiency of the motor to deteriorate.

To ensure that the rotor part containing the permanent magnets, which is rotatably mounted on the shaft, has as low a moment of inertia as possible, an inner ring made of plastic is provided between the permanent magnets and the rotor shaft.

This reduces the moment of inertia, but due to the lack of feedback between the permanent magnets and the rotor shaft, the efficiency deteriorates at the same time.

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The invention is therefore based on the object of

Permanent magnet rotor for electric motors of the type mentioned above
type^ in which less wear occurs due to improved starting conditions«

This object is achieved according to the invention in that the

Rotor in the form of a magnetic central rotary coupling |

is formed with two concentrically and coaxially arranged |

mutually rotatable parts, of which a«? iüx'C duration·= &egr;

1Ö magnet and the other the magnetic return I

The two parts are therefore magnetic

This eliminates the need for a mechanical coupling and J ₅

also the associated wear and tear. The heat development |

due to friction is reduced. I

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It is advantageous for the part not connected to the shaft by means of sliding or rolling bearings to be connected to the |

4 shaft connected. This enables a particularly simple |

f arrangement. |

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The permanent magnet rotor according to the invention can be used in both j brushless DC motors and synchronous motors

be used. Particularly for use in , !

Synchronous motors, it is advantageous if the continuous '■■

magnets containing part of the rotor can be rotated on and off *·'

is mounted above the shaft and the part of the rotor with the magnetic return is firmly connected to the shaft. This makes starting the motor particularly easy.

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During the start-up phase, the magnetic return only works with
a weak torque, which is caused by hysteresis or eddy current losses, on the rotating permanent magnet system of one rotor part. This torque.

can be kept very small and the efficiency can

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be improved, If the return path is a sheet metal package made of

made of low-loss soft iron. j|

Two embodiments of the invention are shown in the drawings |

tions and are described in more detail below. They show*

Fig. 1 shows a permanent magnet rotor according to the invention in

TcIiSCuüi L.t j ucl uciii uSS uxc uaUSrüiäguSi/S uTSgSH-de The rotor part is firmly connected to the shaft,

Fig. 2 shows a further embodiment of the invention in partial section, in which the rotor part with the yoke is rigidly connected to the rotor shaft and

Fig. 3 is a cross-section along the line &Idigr;&Idigr;&Igr;-&Igr;&Idigr;&Igr; in Fig. 2.

The permanent magnet rotor shown in Fig. 1 consists of a part A connected to the rotor shaft 5 and a part B that can rotate relative to it. Two roller bearings 6 are arranged on the rotor shaft 5, via which the part B carrying the soft iron yoke 4 is rotatably mounted on the rotor shaft 5. For example, shell-shaped permanent magnets 1 are arranged concentrically around the hollow cylindrical soft iron yoke 4 on a thin support tube 2 on part A. The permanent magnets 1, which can also be replaced by a radially magnetized ring, and the support tube 2 are rigidly connected to the rotor shaft 5 via two support disks 3 arranged at the ends of the support tube 2. In order to make the weight of the parts rigidly connected to the rotor shaft 5 as low as possible, the support disks 3 can advantageously be made of light metal or plastic and additionally have weight-saving openings 9.

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In the start-up phase of an electric motor having the permanent magnet rotor according to the invention, initially only the permanent magnets 1, the support tube 2, the support disks 3 and the rotor shaft 5 connected to them are accelerated. The relatively heavy yoke 4 is gradually accelerated by the rotating magnetic field which penetrates into the soft iron yoke 4 until it reaches the speed of the rotor shaft 5. The

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The magnetic return 4, which can be kept very small anyway, is completely eliminated when the magnetic return 4 reaches the speed of the rotor shaft 5.

Compared to a permanent magnet rotor with a return path 4 rigidly coupled to the rotor shaft 5, the moment of inertia of the rotor according to the invention in the embodiment of Fig. 1 is reduced by a factor of 2 to 3.

Another embodiment of the invention is shown in Fig. 2.

This design is particularly important for synchronous motors, since the effective moment of inertia of the rotor is further reduced when starting. In this design, the bowl-shaped permanent magnets 1 are attached to the thin support tube 2, just as in the previous example, and are connected to support disks 3 arranged at the ends of the support tube 2. In this example, however, the support disks 3 are rotatably mounted on the rotor shaft 5 via roller bearings 7. The magnetic yoke arranged concentrically within the cavity consisting of the permanent magnets 1, the tube 2 and the support disks 3 is rigidly connected to the rotor shaft 5. When starting up an electric motor with such a rotor, the permanent magnet system 1 reaches the nominal speed very quickly, but the rotor shaft 5 with the yoke 4 rigidly connected to it only accelerates relatively slowly. Therefore

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you can only take a torque from the motor shaft that corresponds to a kind of "asynchronous" torque transmitted from the permanent magnet system to the feedback loop. With this torque, which is approximately constant regardless of the speed, a synchronous motor equipped with it accelerates masses of any size, just like any "hysteresis motor". Compared to the classic hysteresis motor, however, it has the great advantage that the magnetization of the magnetic circuit

L/auci uia5licoc <7i &khgr; uxg &ugr; uiiu iiiuuu uui uli ux? uuaiiuci'~ winding. This results in a significantly higher torque than with a hysteresis motor of the same size.

Fig. 3 shows a cross section along the line III-III of Fig. 2. The air gap 8 between the permanent magnets 1 or the thin support tube 2 and the ferromagnetic yoke 4 can be seen particularly well. Through this yoke, the magnetic field generated by the permanent magnets extends across the air gap into the soft iron yoke 4 and thus enables the yoke part to be driven along in rotation.

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Claims (4)

. COHAUSZ& "fLÖRACK PATRON WALTSBORO SCHUMANNSTR. 97 D-4OOO DÜSSELDORF 1 Telephone: (0211) Ü83346 · Fax: (0211) 6790871 · Telex: 8585513 cop d PATENT ATTORNEYS: DipL-lng. W COHAUSZ ■ DipL-lng. R KNAUF - DipL-lng. K a COHAUSZ · DtpL-liig. D. K WERNER ■ Dn rer. nat a REDIES 9. ~May 1985 WE/SCH/KA 46079 Expectations 1. Permanent magnet rotor for electric motors, which consists of two parts that can rotate against each other around the rotor axis and can be coupled together, one of which is mechanically connected to the rotor shaft for rotational drive and one of which carries permanent magnets, characterized in that it is designed in the manner of a magnetic central rotary coupling. 2. Rotor according to claim 1, characterized in that the part (B) not connected to the shaft (5) for rotational movement is supported on the shaft (5) via plain or roller bearings (£·). 3· Rotor according to claim 1 or 2, 2Q characterized in that the part of the rotor having the permanent magnets (1) is rotatably mounted on and opposite the shaft (5) and the part of the rotor having the magnetic yoke (4) is firmly connected to the shaft (5). 25 4. Rotor according to one of claims 1 to 3, characterized in that the return path (k) is designed as a laminated core made of low-loss soft iron. 30 ■ II * * Ml