Electrical generator or motor structure – Dynamoelectric – Reciprocating
Patent
1989-08-23
1992-05-19
Stephan, Steven L.
Electrical generator or motor structure
Dynamoelectric
Reciprocating
H02K 3300
Patent
active
051151588
DESCRIPTION:
BRIEF SUMMARY
As known an orbiting artificial satellite is exposed to temperatures between approximately +150.degree. C. and -180.degree. C. according to whether it is in sunlight or shadow. This explains the need to provide thermal protection for onboard equipment that cannot withstand such temperature differences.
Such thermal protection can be provided in various ways, and mention may be made of two types of system: super-insulator; flowing through heat exchangers.
Associated with these heat exchangers are heat shields which cover or uncover the heat exchangers to modulate radiation from them to the exterior of the satellite.
A Maltese cross shaped heat shield may be used and rotated from 0.degree. to 45.degree. and from 45.degree. to 0.degree. relative to a fixed reference to cover or uncover heat exchangers and so modulate their radiation.
Previously the heat shield was rotated by a spiral-shape bimetallic strip, peripheral abutment members immobilising the shield in the open or closed position.
This solution has the undoubted advantage of being simple and of not consuming any energy, but its major disadvantage is that it does not provide for precise (if any) regulation because the bearings used for the rotation movement often have hard spots, especially after having been subjected to the vibrations of launching the vector placing the satellite in orbit.
Given these shortcomings, a new device based on "all or nothing" rotation by means of a brushless torque motor has been developed.
The problem was to find a system to damp the impacts at the end of opening or closing movements and to guarantee the open or closed position without consuming energy.
In accordance with the invention damping of the movements is provided by elastic abutment members made from an amagnetic material, the motor torque being maintained until the motor stops completely, whereas the locking without expenditure of energy is obtained by shunting part of the magnetic field of the rotor to a magnetic tooth judiciously disposed on the stator.
The advantage of a system of this kind is that the farther the rotor moves away from the tooth the smaller is the locking force, reducing very quickly to zero since the change in the force is inversely proportional to the square of the airgap.
In other words, the present invention therefore concerns a magnetic locking abutment member device which associated with a torque motor enables optimum operation of a heat shield.
More generally, the present invention concerns an electric motor comprising magnetic locking abutment members yielding highly accurate abutment positioning and maintaining this position without expenditure of energy.
This is why the magnetic locking abutment member device in accordance with the invention is applicable in a particularly advantageous way to brushless direct current torque motors.
In this application the motor is of a type comprising: a magnetic material stator member surrounded over part of its length by at least one winding and a mobile member carrying at least one permanent magnet generating a magnetic flux which is closed in said stator member.
The invention therefore proposes an electric motor comprising: and having two ends adapted to lie along sections of the stator member to define with these sections two constant airgaps by virtue of which the magnetic flux of the permanent magnet is closed within said stator member between these sections, stator member a particular range of movement for said ends of the mobile member between two abutment configurations, one of these ends facing said winding for any position of the mobile member, each of the abutment members being provided with a magnetic material portion linked to the stator member and defining, when one of the ends is in contact with the abutment member, an airgap (E) through which some of the magnetic flux from the magnet passes into said magnetic material portion, the mobile member coming into one or the other of said abutment configurations according to the direction of the direct current applied to the winding and re
REFERENCES:
patent: 3634857 (1972-01-01), Pihl
patent: 3970980 (1976-06-01), Nelson
patent: 4059775 (1977-11-01), Warmka
patent: 4227164 (1980-10-01), Kitahara
patent: 4577832 (1986-03-01), Sogabe
patent: 4642539 (1987-02-01), Hinds
Joly Jean-Louis
Vaillant De Guelis Hubert
Aerospatiale - Societe Nationale Industrielle
Stephan Steven L.
To Ed
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