GB2205002A

GB2205002A - Permanent magnet rotor for a dynamo-electric machine

Info

Publication number: GB2205002A
Application number: GB08710990A
Authority: GB
Inventors: Alan Burrows Turner; Toshiyuki Kondo; Katsuhiro Mori
Original assignee: Aisin Seiki Co Ltd
Current assignee: Aisin Corp
Priority date: 1987-05-08
Filing date: 1987-05-08
Publication date: 1988-11-23
Anticipated expiration: 2007-05-08
Also published as: JPS6426350A; GB8710990D0; GB2205002B

Abstract

A rotating part 10 for a high speed synchronous generator comprises a portion 13 provided with an inner layer 14, an inner retainer ring 15, an outer layer 16 and an outer retainer ring 17. The layers 14, 16 are made up of magnetic and non-magnetic portions. The rings 15, 17 are of magnetic material. The greater strength of the non-magnetic portions reduces the centrifugal forces on the magnetic portions. The rotating part includes a core 11 of magnetic material and side walls 12 of non-magnetic material. <IMAGE>

Description

Dynamo-Electric Machines DESCRIPTION: Technical Field The invention relates to rotating parts for high speed dynamo-electric machines, that is electric power generators and motors.

Background Art Rotating parts of dynamo-electric machines cannot be rotated at high speed owing to the low tensile strength of permanent magnetic materials. The tensile stress induced by the centrigual force exceeds the limit permitted for the material.

The Invention According to the invention, there is provided a rotating part for a dynamo-electric machine. which comprises an annular permanent magnet' and a retainer ring of magnetic material for securing the permanent magnet. The rotating part generally includes a core portion of magnetic material inside the permanent magnet and preferably also a side wall made of a non-magnetic material A number of annular permanent magnets may be provided side by side and separated by non-magnetic rings. More than one layer of such permanent magnets may be provided. and if the magnets in both layers are separated by non-magnetic rings the rings should be equi-distantly spaced along the axis of the rotating part, so that the pressure of the retainer rings securing the magnets is transferred through the non-magnetic rings.

The material for securing the outer circumferential portion may be of high strength, and so make it possible to produce a machine of small size and light weight which is efficient and suitable for high speed operation. For example, a gas turbine can be directly connected to a high speed generator that is without a gear box to decrease the rotational speed of the engine. Thus the power loss in the gear box is avoided. The outer circumferential portion of the permanent magnet is exposed, so that the clearance between the permanent magnet and a stator can be small, making for generating efficiency.

Drawings Figure 1 is a longitudinal section through a rotating part according to the invention; Figure 2 is a cross section along II-II in Figure 1; and Figure 3 is an enlarged view of an outer circumferential portion in Figure 1.

Best Mode Figures 1 and 2 show a rotating part 10 for a high speed synchronous generator which comprises also a stator (not shown). The part 10 includes a core 11, a side wall 12 and an outer circumferential portion 13. The core 11 is made of a magnetic material such as a high strength magnetic alloy. The side wall 12 is made of a non-magnetic material such as a high strength non-magnetic alloy or a carbon fibre reinforced plastics material. The outer circumferential portion 13 is provided on its outside with an inner layer 14, an inner retainer ring 15, an outer layer 16 and an outer retainer ring 17. The members are circumferentially located one on top of another.

As clearly shown in Figure 3, the inner layer 14 includes a permanent magnet portion 18 and a light weight non-magnetic material portion 19 which are axially alternately arranged.

The permanent magnet portion 18 is made of a high magnetic neodymium-iron-boron magnet, while the light weight non-magnetic material portion 19 is made of a high modulus carbon fibre reinforced plastics material. The inner retainer ring 15 is made of a magnetic material such as a high strength magnetic alloys and is located on the outer circumference of the inner layer 14. The outer layer 16 includes a permanent magnet portion 20 and a light weight non-magnetic portion 21 which are axially alternately arrange in the same way as the inner layer 14. The permanent magnet portions 18, 20 and the light weight non-magnetic portions 19, 21 are axially located at the same position. The outer retainer ring 17 is made of a magnetic material such as a high strength magnetic alloy and is located on the outer circumference of the outer layer 16.

If the side walls 12 and the non-magnetic portions 19, 21 are made of a high modulus carbon fibre reinforced plastics material, the plastics material is wound circumferentially and fixed by an adhesive. The magnetic material of the outer retainer ring 17 is exposed. Upon the high speed rotation of the rotating part 10, each member of the outer circumferential portion 13 is subjected to very high and possibly damaging tensile stress. The permanent magnet portion 18 of the inner layer 14 is supported by the inner retainer ring 15. The inner retainer ring 15 is secured by the light weight non-magnetic material 21, while the permanent magnet portion 20 of the outer layer 16 is secured by the outer retainer ring 17, so that each member of the outer circumferential portion 13 is protected from damage. The non-magnetic material portions 19, 21 of the layers 14, 16 are light weights so that the centrifugal forces acting on the inner and outer retainer rings 15, 17 are small and dangerous loading and possible damage to the rings 15, 17 is avoided. The inner retainer ring 15 is interposed between the permanent magnet portions 18, 20 and supported by the portion 21 of the outer layer 16, so the centrifugal force of the permanent magnet portion 18 does not act on the permanent magnet portion 20 of the outer layer 16 and the outer retainer ring 17. Thus dangerous loading and possible damage to the outer retainer ring 17 is avoided.

The outer retainer ring li is made of magnetic material and is exposed, so the distance between the magnetic material of the rotating part 10 and the stator can be small, and the efficiency of the generator high.

Claims

1. A rotating part for a dynamo-electric machine, which comprises an annular permanent magnet, and a retainer ring of magnetic material for securing the permanent magnet.

2. A rotating part according to claim 1 which includes a core portion of magnetic material inside the permanent magnet and also a side wall made of a non-magnetic material.

3. A rotating part according to claim 1 or claim 2 in which a number of annular permanent magnets are provided side by side and separated by non-magnetic'rings.

4. A rotating part according to claim 3 in which more than one layer of such permanent magnets is provided.

5. A rotating part according to claim 4 in which the magnets are separated by non-magnetic rings, and the rings are equi-distantl spaced along the axis of the rotating part.

6. A rotating part for a dynamo-electric machine as herein described with reference to the drawings.

7. A dynamo-electric machine having a rotating part according to any preceding claim.