WO1989003606A1 - A reinforced permanent magnet device - Google Patents

A reinforced permanent magnet device Download PDF

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Publication number
WO1989003606A1
WO1989003606A1 PCT/EP1988/000917 EP8800917W WO8903606A1 WO 1989003606 A1 WO1989003606 A1 WO 1989003606A1 EP 8800917 W EP8800917 W EP 8800917W WO 8903606 A1 WO8903606 A1 WO 8903606A1
Authority
WO
WIPO (PCT)
Prior art keywords
permanent magnet
caps
magnet member
edges
periphery
Prior art date
Application number
PCT/EP1988/000917
Other languages
French (fr)
Inventor
Claude Oudet
Pierre Gandel
Original Assignee
Portescap
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Portescap filed Critical Portescap
Publication of WO1989003606A1 publication Critical patent/WO1989003606A1/en

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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
    • H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
    • H02K21/24—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets axially facing the armatures, e.g. hub-type cycle dynamos
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/22—Rotating parts of the magnetic circuit
    • H02K1/27—Rotor cores with permanent magnets
    • H02K1/2793—Rotors axially facing stators
    • H02K1/2795—Rotors axially facing stators the rotor consisting of two or more circumferentially positioned magnets
    • H02K1/2796—Rotors axially facing stators the rotor consisting of two or more circumferentially positioned magnets where both axial sides of the rotor face a stator
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F7/00—Magnets
    • H01F7/02—Permanent magnets [PM]
    • H01F7/0205—Magnetic circuits with PM in general
    • H01F7/0221—Mounting means for PM, supporting, coating, encapsulating PM

Definitions

  • the present invention relates to a permanent magnet device comprising a permanent magnet member having two plane parallel surfaces and having, between these two plane surfaces, a very small thickness in comparison with its dimensions in said plane surfaces.
  • Flat permanent magnet members of a very small thickness are used, for example, in synchronous electric motors with a rotor comprising a magnetized disc such as described, for example, in US Patent No 4'330'727.
  • Such permanent magnet members are generally made from a material having a high residual flux density and a substantially linear demagnetization characteristic such as samarium-cobalt or other materials based on rare earths, generally produced in a sintered form. Such materials are very fragile, so that their handling during the manufacture of the motor often results in rejects. Deteriorations of these materials can also occur during the utilisation of the motor, in particular under the effect of corrosive vapours.
  • the invention is aimed at remedying this drawback and at providing a permanent magnet device, wherein the permanent magnet member is physically protected, so as to become substantially unbreakable.
  • Another purpose of the invention is to protect the magnet against the effect of chemical agents and, in particular, against corrosion.
  • the permanent magnet member can have the shape of an annular disc and be mounted between two coaxial rim members made of an amagnetic material extending on inner annular portions of each plane surface of the disc.
  • one of the rim member consists of a nut screwed on an axial cylindrical part integral with the other rim member.
  • the device can comprise a ring made of an amagnetic material of the same thickness as said annular disc, placed and fastened inside the latter and covered with said reinforcing caps, and at least one pin can be inserted_into a hole bored through the rim members, the caps and the ring in a direction parallel to, the axis of the device.
  • Figure 1 is a partial cross-sectional view of an annular permanent magnet member and of two caps before their fastening
  • Figure 4 is a top view of an annular permanent magnet member provided with reinforcing caps with toothed edges; and Figure 5 is a side view of the structure according to Figure 4 with the two reinforcing caps before their fastening.
  • Figure 1 shows a permanent magnet member made of rare earth, having an annular shape, the thickness of said member being very small in comparison with its diameter. This thickness can be comprised, for example, between 0.3 and 1.2 mm.
  • Two reinforcing caps are stuck one on each plane surface of the member 1. These caps are made of a non-magnetic steel having a high limit of elasticity, such as the spring steel sold by Creusot Loire under the trademark PHYNOX. It should be noted that the steels, which are preferably used for making the reinforcing caps, have about the same dilatation coefficient as the permanent magnet material and the values of their modulus of elasticity are of the same order as those of the latter.
  • the caps are of an extremely small thickness, in the order of 0.05 mm, and they are made by stamping, which is made possible by the very small depth of stamping required in this case, i.e. at most half the thickness of the permanent magnet member.
  • the fastening of the caps to the permanent magnet member is carried out through an appropriate sticking operation, including preferably heating between two plates subjected to a certain pressure.
  • the edges of the caps are preferably welded against each other at location 4, as shown in Figure 2.
  • the reinforced permanent magnet device as according to the example of Figure 2, turns out to be substantially unbreakable and to be also well protected against attack from acid vapours or from other detrimental effects of the environment.
  • FIG. 3 shows the mounting of a reinforced permanent magnet structure in a rotor of a synchronous motor of the aforementioned type.
  • the permanent magnet member and the reinforcing caps are designated by the same reference numerals as previously, the caps in this example covering also the plane surfaces of an annular ring 5 disposed and stuck by its periphery 9 inside the central opening of the annular disc-shaped member 1.
  • Two rim members 6 and 7, made of aluminum or of an amagnetic stainless steel, are applied on respective plane inner annular portions on both sides of the permanent magnet member with its reinforcing caps, the rim member 7 being, for example, a very finely threaded nut screwed on a central cylindrical part 10 integral with the rim member 6.
  • the permanent magnet member is thus perfectly well held between the rim members without any possibility of rotating with respect to the latter and, further, the nut is prevented from becoming loose.

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Permanent Field Magnets Of Synchronous Machinery (AREA)

Abstract

A permanent magnet device comprises a permanent magnet member (1), for example in the shape of a flat thin annular disc, and two reinforcing caps (2, 3) of spring steel of a very small thickness, stuck to the disc and welded by their edges to each other. The resulting device appears to be practically unbreakable as well as protected against corrosion and possible other detrimental effects of the environment, in particular when used as a rotor in an electric motor.

Description

A REINFORCED PERMANENT MAGNET DEVICE
The present invention relates to a permanent magnet device comprising a permanent magnet member having two plane parallel surfaces and having, between these two plane surfaces, a very small thickness in comparison with its dimensions in said plane surfaces.
Flat permanent magnet members of a very small thickness are used, for example, in synchronous electric motors with a rotor comprising a magnetized disc such as described, for example, in US Patent No 4'330'727.
Such permanent magnet members are generally made from a material having a high residual flux density and a substantially linear demagnetization characteristic such as samarium-cobalt or other materials based on rare earths, generally produced in a sintered form. Such materials are very fragile, so that their handling during the manufacture of the motor often results in rejects. Deteriorations of these materials can also occur during the utilisation of the motor, in particular under the effect of corrosive vapours.
The invention is aimed at remedying this drawback and at providing a permanent magnet device, wherein the permanent magnet member is physically protected, so as to become substantially unbreakable. Another purpose of the invention is to protect the magnet against the effect of chemical agents and, in particular, against corrosion.
For this purpose, the device according to the invention comprises a permanent magnet member encapsulated between reinforcing caps made of a substantially non-magnetic steel of a very small thickness in comparison with the thickness of the permanent magnet member. These reinforcing caps are preferably stuck on the plane surfaces of the permanent magnet member, and their lateral edges covering the lateral surface or surfaces of said member can be welded to each other along the periphery of the same. These edges can also be cut out in the shape of teeth and bent along the periphery of said permanent magnet member so as to cover the same at least partly, but preferably in its totality.
In a motor device of the aforementioned type, the permanent magnet member can have the shape of an annular disc and be mounted between two coaxial rim members made of an amagnetic material extending on inner annular portions of each plane surface of the disc. According to one preferred embodiment, one of the rim member consists of a nut screwed on an axial cylindrical part integral with the other rim member. Further, the device can comprise a ring made of an amagnetic material of the same thickness as said annular disc, placed and fastened inside the latter and covered with said reinforcing caps, and at least one pin can be inserted_into a hole bored through the rim members, the caps and the ring in a direction parallel to, the axis of the device.
The invention will be better understood in the light of the following description of embodiments given by way of example and illustrated in the attached drawings, wherein:
Figure 1 is a partial cross-sectional view of an annular permanent magnet member and of two caps before their fastening;
Figure 2 is a partial axial cross-sectional view of an annular encapsulated permanent magnet member;
Figure 3 is a partial axial cross-sectional view of a rotor comprising an encapsulated permanent magnet member;
Figure 4 is a top view of an annular permanent magnet member provided with reinforcing caps with toothed edges; and Figure 5 is a side view of the structure according to Figure 4 with the two reinforcing caps before their fastening.
Figure 1 shows a permanent magnet member made of rare earth, having an annular shape, the thickness of said member being very small in comparison with its diameter. This thickness can be comprised, for example, between 0.3 and 1.2 mm. Two reinforcing caps are stuck one on each plane surface of the member 1. These caps are made of a non-magnetic steel having a high limit of elasticity, such as the spring steel sold by Creusot Loire under the trademark PHYNOX. It should be noted that the steels, which are preferably used for making the reinforcing caps, have about the same dilatation coefficient as the permanent magnet material and the values of their modulus of elasticity are of the same order as those of the latter. The caps are of an extremely small thickness, in the order of 0.05 mm, and they are made by stamping, which is made possible by the very small depth of stamping required in this case, i.e. at most half the thickness of the permanent magnet member.
The fastening of the caps to the permanent magnet member is carried out through an appropriate sticking operation, including preferably heating between two plates subjected to a certain pressure. The edges of the caps are preferably welded against each other at location 4, as shown in Figure 2. The reinforced permanent magnet device, as according to the example of Figure 2, turns out to be substantially unbreakable and to be also well protected against attack from acid vapours or from other detrimental effects of the environment.
Figure 3 shows the mounting of a reinforced permanent magnet structure in a rotor of a synchronous motor of the aforementioned type. The permanent magnet member and the reinforcing caps are designated by the same reference numerals as previously, the caps in this example covering also the plane surfaces of an annular ring 5 disposed and stuck by its periphery 9 inside the central opening of the annular disc-shaped member 1. Two rim members 6 and 7, made of aluminum or of an amagnetic stainless steel, are applied on respective plane inner annular portions on both sides of the permanent magnet member with its reinforcing caps, the rim member 7 being, for example, a very finely threaded nut screwed on a central cylindrical part 10 integral with the rim member 6. The permanent magnet member is thus perfectly well held between the rim members without any possibility of rotating with respect to the latter and, further, the nut is prevented from becoming loose.
Figures 4 and 5 illustrate another configuration of the caps allowing their manufacture by bending of their edges. As shown in Figure 5, both caps 21 and 31 have on their edge cut out and bent teeth, the .height of which can amount to the thickness of the magnet. The two caps assembled with the permanent magnet member can, for example, be offset with respect to each other so as to cover the totality of the lateral surface of the permanent magnet member 1 onto which they are stuck directly or indirectly, an outer tooth being stuck on an inner tooth, and the latter being stuck to the magnet member. According to an alternative embodiment, not represented, the teeth can have a substantially complementary shape and thereby cover substantially the totality of the lateral surface of the permanent magnet member without overlapping.

Claims

1. A permanent magnet device, comprising a permanent magnet member having two plane parallel surfaces and having a very small thickness in comparison with its dimensions in said plane surfaces, wherein said permanent magnet member is encapsulated between reinforcing caps made of a substantially non-magnetic steel of a very small thickness in comparison with the thickness of the magnet.
2. A device according to claim 1, wherein said reinforcing caps are stuck on the plane surfaces of said permanent member.
3. A device according to claim 1, wherein said caps have edges covering the lateral surface or surfaces of said permanent magnet member.
4. A device according to claim 2, wherein said caps have edges covering the lateral surface or surfaces of said permanent magnet member.
5. A device according to claim 3, Wherein said edges are joined together along the periphery of said permanent magnet member by welding.
6. A device according to claim 4, wherein said edges are joined together along the periphery of said permanent magnet member by welding.
7. A device according to claim 1, wherein said edges of the caps have cut out teeth bent along the periphery of said permanent magnet member so as to cover the latter at least partly.
8. A device according to claim 2, wherein said edges of the caps have cut out teeth bent along the periphery of said permanent magnet member so as to cover the latter at least partly.
9. A device according to claim 1, wherein said permanent magnet member has the shape of an annular disc.
10. A device according to claim 9, wherein said reinforcing caps are stuck on the plane surfaces of said permanent member.
11. A device according to claim 9, wherein said caps have edges covering the lateral surface or surfaces of said permanent magnet member.
12. A device according to claim 10, wherein said caps have edges covering the lateral surface or surfaces of said permanent magnet member.
13. A device according to claim 11, wherein said edges are joined together along the periphery of said permanent magnet member by welding.
14. A device according to claim 12, wherein said edges are joined together along the periphery of said permanent magnet member by welding.
15. A device according to claim 9, wherein said edges of the caps have cut out teeth bent along the periphery of said permanent magnet member so as to cover the latter at least partly.
16. A device according to claim 10, wherein said edges of the caps have cut out teeth bent along the periphery of said permanent magnet member so as to cover the latter at least partly.
17. A device according to claim 9, wherein said disc is mounted between two coaxial rim members made of an amagnetic material extending over respective annular inner portions of the plane surfaces of said disc.
18. A device according to claim 17, wherein one of said rim members is formed by a nut screwed on an axial cylindrical part integral with the other rim member.
19. A device according to claim 17, comprising a ring made of an amagnetic material and having the same thickness as said disc, said ring being placed and fastened coaxially inside said annular disc and being covered by said reinforced caps, at least one pin being inserted into a hole bored through said rim members, said caps and said ring in a direction parallel to the axis of the device.
20. A device according to claim 18, comprising a ring made of an amagnetic material and having the same thickness as said disc, said ring being placed and fastened coaxially inside said annular disc and being covered by said reinforced caps, at least one pin being inserted into a hole bored through said rim members, said caps and said ring in a direction parallel to the axis of the device.
PCT/EP1988/000917 1987-10-16 1988-10-11 A reinforced permanent magnet device WO1989003606A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CH4073/87A CH674278A5 (en) 1987-10-16 1987-10-16
CH4073/87-2 1987-10-16

Publications (1)

Publication Number Publication Date
WO1989003606A1 true WO1989003606A1 (en) 1989-04-20

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Application Number Title Priority Date Filing Date
PCT/EP1988/000917 WO1989003606A1 (en) 1987-10-16 1988-10-11 A reinforced permanent magnet device

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WO (1) WO1989003606A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2483967B (en) * 2010-09-23 2014-12-31 Dyson Technology Ltd A reinforced rotor magnet and method of manufacturing the same
EP3091640A1 (en) * 2015-05-05 2016-11-09 Robert Bosch Gmbh Rotor for axial flow machine

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB0518787D0 (en) * 2005-09-15 2005-10-26 Khoo Wee K Reinforced discs for magnetic bearings and electrical machines

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2437142A (en) * 1946-06-11 1948-03-02 Gen Electric Shaded-pole synchronous motor
US3121814A (en) * 1957-12-12 1964-02-18 L R Power Corp Dynamoelectric machine
US3482131A (en) * 1966-09-27 1969-12-02 Garrett Corp Polyphase alternator winding arrangement
FR2057163A5 (en) * 1969-08-04 1971-05-21 Transformateur
WO1985001619A1 (en) * 1983-10-03 1985-04-11 Micro-Electric Ag Alternating current synchronous servomotor
GB2174252A (en) * 1985-03-21 1986-10-29 Bosch Gmbh Robert Brushless synchronous machine with axial air gap
JPH06146154A (en) * 1992-11-05 1994-05-27 Kiyoshi Kawai Tufting machine

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2437142A (en) * 1946-06-11 1948-03-02 Gen Electric Shaded-pole synchronous motor
US3121814A (en) * 1957-12-12 1964-02-18 L R Power Corp Dynamoelectric machine
US3482131A (en) * 1966-09-27 1969-12-02 Garrett Corp Polyphase alternator winding arrangement
FR2057163A5 (en) * 1969-08-04 1971-05-21 Transformateur
WO1985001619A1 (en) * 1983-10-03 1985-04-11 Micro-Electric Ag Alternating current synchronous servomotor
GB2174252A (en) * 1985-03-21 1986-10-29 Bosch Gmbh Robert Brushless synchronous machine with axial air gap
JPH06146154A (en) * 1992-11-05 1994-05-27 Kiyoshi Kawai Tufting machine

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Patent Abstracts of Japan, vol. 10, no. 205 (E-420) (2261) 17 July 1986 & JP-A-6146154 (MATSUSHITA) 6 March 1986, *
Patent Abstracts of Japan, vol. 6, no. 182 (E-131) (1060) 18 September 1982 & JP-A-5797354 (HITACHI) 17 June 1982 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2483967B (en) * 2010-09-23 2014-12-31 Dyson Technology Ltd A reinforced rotor magnet and method of manufacturing the same
EP3091640A1 (en) * 2015-05-05 2016-11-09 Robert Bosch Gmbh Rotor for axial flow machine

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Publication number Publication date
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