Electrical generator or motor structure – Dynamoelectric – Rotary
Patent
1996-05-03
1999-10-26
Ramirez, Nestor
Electrical generator or motor structure
Dynamoelectric
Rotary
F16C 3906
Patent
active
059734302
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for mounting and driving a textile spindle, comprising a tube which is mounted relative to a frame by means of first and second radial bearings and which is rotated by means of an electric motor.
BACKGROUND OF THE PRIOR ART
Various types of spindle are known that are required to rotate at high speed, in particular textile spindles for spinning. An example of such a spindle comprises a vertical tube that may have an inside diameter of the order of 30 mm to 40 mm, that is mounted in a frame inside a housing with predetermined clearance so as to allow the tube to rotate without making contact with the wall of the housing. The top portion of the tube is extended by a portion of smaller diameter mounted on conventional bearings such as ball bearings, and it is rotated by an electric motor. A thread to be put into the form of a spool is inserted into the tube within which it can be driven by centrifugal force against the inside wall of the tube so as to make up a spool of thread inside the tube, which spool is subsequently extracted from the tube via the opening at the bottom. The tube is rotated by the motor at rotary speeds of about 300 revolutions per second (rps), for example.
Spindles of this type, fitted with a mechanical suspension based on ball bearings and mounted in a cantilever configuration are subjected to instabilities of rotation that lead to disturbances in the centrifugal effect and that reduce the lifetime of the device. In addition, the dimensions of the spindle and its speed of rotation are limited by the mechanical suspension used, thereby reducing production capacities and rates.
SUMMARY OF THE INVENTION
The present invention seeks to remedy the above-specified drawbacks and to enable rotary tubular members such as spindles to be mounted in such a manner that reliability, lifetime, and production capacity are increased.
Another object of the invention is to provide a spindle mounting having a minimum of disturbance to the centrifugal effect and in which aerodynamic friction losses are also very greatly reduced.
These objects are achieved by a device for mounting and driving a spindle, in particular a textile spindle comprising a tube mounted relative to a frame by means of first and second radial bearings and rotated by means of an electric motor, relative to the frame which is in the form of a casing, by means of first and second axial-flux radial active magnetic bearings disposed respectively at a first end of the tube and at a second end thereof, with said electric motor being disposed between them, in that each of the radial active magnetic bearings comprises a stator magnetic circuit made up of four axial-flux slot-free touching elements distributed around the tube, and in that means are provided to create a reduced pressure of the order of a few hundreds of Pascals to a few thousands of Pascals inside the spindle in the air gaps of the radial magnetic bearings and of the electric motor.
Because of the absence of mechanical contact between the tube and the frame, due to using an active magnetic suspension, the spindle of the invention presents increased reliability and lifetime. The suction created in the air gap of the radial magnetic bearings and of the electric motor contributes to significantly reducing aerodynamic friction losses, even at high speeds of rotation of about 800 rps to 1,000 rps, for example.
In spite of using a tubular rotor that is solid, i.e. not laminated, the electromagnetic losses in the rotor co-operating with the radial magnetic bearings are very small because of the use of axial-flux stator magnetic circuits made up of a plurality of slot-free elements that touch.
According to a particularly advantageous characteristic that simplifies assembly, each stator magnetic circuit comprising four touching elements of the radial active magnetic bearings is made up of two subassemblies each comprising four touching elements, the subassemblies being united in a radial join plane and being held toget
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Von Winfreid Horsemann, Prezessregelung beim Innenrundschleifen mit aktiv magnetgelagerten Spindeln', VDI--Zeitschrift, vol. 132, No. 12, Dec. 1990, pp. 77-79.
Mullins Burton S.
Ramirez Nestor
Societe de Mecanique Magnetique
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