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)

Applications Claiming Priority (2)

Publications (1)

Family

ID=4269310

Family Applications (1)

Country Status (2)

Cited By (2)

Families Citing this family (1)

Citations (7)

• 1987
  • 1987-10-16 CH CH4073/87A patent/CH674278A5/fr not_active IP Right Cessation
• 1988
  • 1988-10-11 WO PCT/EP1988/000917 patent/WO1989003606A1/en unknown

Patent Citations (7)

Non-Patent Citations (2)

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