Back to results
US 4,734,606 AGranted
Electric motor with ferrofluid bearing
OwnerChester S. Hajecinventor
Life of this patent
Estimating the term…
Abstract
An electric motor including an integral ferrofluid bearing provides significant reduction in non-repeatable runout, stray flux, and audible noise over conventional motors using ball bearings. The motor includes a hub and a base, with the base attached to a tapered magnetically permeable shaft which defines an inner bearing race, and the hub attached to an internally tapered, magnetically permeable sleeve which defines an outer bearing race. Permanent magnets surround and are rotatable with the sleeve to provide mangetic fields which interact with the stator winding to cause rotation of the hub and sleeve. In addition, the permanent magnets form magnetic flux paths with the shaft and the sleeve to maintain ferrofluid lubricant between the inner and outer bearing races.
Claims46
An electric motor comprising:
- a base;
- a hub for rotation about an axis;
- a magnetically permeable shaft attached to the base for defining the axis;
- the shaft defining an inner bearing race;
- a magnetically permeable sleeve attached to the hub and coaxially positioned with the shaft, the sleeve defining an outer bearing race spaced from the inner bearing race of the shaft to define a first gap therebetween;
- a ferrofluid lubricant;
- stator winding means supported by the base for providing magnetic fields for causing rotation of the hub;
- and
- permanent magnet means rotatable with the sleeve;
- separated from the stator winding means by an air gap, for providing magnetic fields which interact with the magnetic fields provided by the stator winding means to cause rotation of the hub, the permanent magnet means, the shaft and the sleeve forming a magnetic flux path for maintaining the ferrofluid within the gap.
7 more elements
An electric motor comprising:
- a base;
- a hub for rotation about an axis;
- a magnetically permeable shaft attached to the base for defining the axis, the shaft defining an inner bearing race and having an end surface at a first end of the shaft which is generally perpendicular to the axis;
- a magnetically permeable sleeve attached to the hub and coaxially positioned with the shaft, the sleeve defining an outer bearing race spaced from the inner bearing race of the shaft to define a first gap therebetween, the inner bearing race including a tapered exterior surface and the outer bearing race including a generally parallel tapered interior surface;
- a ferrofluid lubricant;
- stator winding means supported by the base for providing magnetic fields for causing rotation of the hub;
- and
- permanent magnet means rotatable with the sleeve, separated from the stator winding means by an air gap, for providing magnetic fields which interact with the magnetic fields provided by the stator winding means to cause rotation of the hub, the permanent magnet means, the shaft and the sleeve forming a magnetic flux path for maintaining the ferrofluid within the gap.
5 more elements
An electric motor comprising:
- a base;
- a hub for rotation about an axis;
- a magnetically permeable shaft attached to the base for defining the axis;
- the shaft defining an inner bearing race;
- a magnetically permeable sleeve attached to the hub and coaxially positioned with the shaft, the sleeve defining an outer bearing race spaced from the inner bearing race of the shaft to define a first gap therebetween, the inner bearing race including a tapered exterior surface and the outer bearing race including a generally parallel tapered interior surface;
- means for adjusting relative axial positions of the sleeve and shaft to vary size of the first gap between the tapered surface;
- a ferrofluid lubricant;
- stator winding means supported by the base for providing magnetic fields for causing rotation of the hub;
- and
- permanent magnet means rotatable with the sleeve, separated from the stator winding means by an air gap, for providing magnetic fields which interact with the magnetic fields provided by the stator winding means to cause rotation of the hub, the permanent magnet means, the shaft and the sleeve forming a magnetic flux path for maintaining the ferrofluid within the gap.
7 more elements
An electric motor comprising:
- a base;
- a hub for rotation about an axis;
- a magnetically permeable shaft attached to the base for defining the axis;
- the shaft defining an inner bearing race and having an internal axial bore;
- a magnetically permeable sleeve attached to the hub and coaxially positioned with the shaft, the sleeve defining an outer bearing race spaced from the inner bearing race of the shaft to define a first gap therebetween;
- a ferrofluid lubricant;
- stator winding means supported by the base for providing magnetic fields for causing rotation of the hub;
- and
- permanent magnet means rotatable with the sleeve, separated from the stator winding means by an air gap, for providing magnetic fields which interact with the magnetic fields provided by the stator winding means to cause rotation of the hub, the permanent magnet means, the shaft and the sleeve forming a magnetic flux path for maintaining the ferrofluid within the gap.
6 more elements
An electric motor comprising:
- a base;
- a hub for rotation about an axis having a first closed end, a second open end and a generally cylindrical side wall;
- a magnetic shield coating on interior surfaces of the hub;
- a magnetically permeable shaft attached to the base for defining the axis;
- the shaft defining an inner bearing race;
- a magnetically permeable sleeve attached to the hub and coaxially positioned with the shaft, the sleeve defining an outer bearing race spaced from the inner bearing race of the shaft to define a first gap therebetween;
- a ferrofluid lubricant;
- stator winding means supported by the base for providing magnetic fields for causing rotation of the hub;
- permanent magnet means rotatable with the sleeve, separated from the stator winding means by an air gap, for providing magnetic fields which interact with the magnetic fields provided by the stator winding means to cause rotation of the hub, the permanent magnet means, the shaft and the sleeve forming a magnetic flux path for maintaining the ferrofluid within the gap, and the hub and the base defining an essentially closed interior in which the shaft, sleeve, ferrofluid lubricant, permanent magnet means and stator winding means are located.
6 more elements
An electric motor comprising:
- a base;
- a hub for rotation about an axis having a first closed end, a second open end and a generally cylindrical sidewall, the second open end of the hub being positioned adjacent the base;
- a first set of annular ribs and grooves on the hub and a second complementary set of ribs and groves on the base which together define a labyrinth passage between the interior and an exterior which surrounds the motor;
- a magnetically permeable shaft attached to the base for defining the axis;
- the shaft defining an inner bearing race;
- a magnetically permeable sleeve attached to the hub and coaxially positioned with the shaft, the sleeve defining an outer bearing race spaced from the inner bearing race of the shaft to define a first gap therebetween;
- a ferrofluid lubricant;
- stator winding means supported by the base for providing magnetic fields for causing rotation of the hub;
- and
- permanent magnet means rotatable with the sleeve, separated from the stator winding means by an air gap, for providing magnetic fields which interact with the magnetic fields provided by the stator winding means to cause rotation of the hub, the permanent magnet means, the shaft and the sleeve forming a magnetic flux path for maintaining the ferrofluid within the gap, and the hub and the base defining an essentially closed interior in which the shaft, sleeve, ferrofluid lubricant, permanent magnet means and stator winding means are located.
7 more elements
An electric motor comprising:
- a base;
- a hub for rotation about an axis having a first closed end, a second open end and a generally cylindrical sidewall;
- a magnetically permeable shaft attached to the base for defining the axis;
- the shaft defining an inner bearing race;
- a magnetically permeable sleeve attached to the hub and coaxially positioned with the shaft, the sleeve defining an outer bearing race spaced from the inner bearing race of the shaft to define a first gap therebetween;
- a ferrofluid lubricant;
- stator winding means supported by the base for providing magnetic fields for causing rotation of the hub;
- permanent magnet means rotatable with the sleeve, separated from the stator winding means by an air gap, for providing magnetic fields which interact with the stator winding means to cause rotation of the hub, the permanent magnet means, the shaft and the sleeve forming a magnetic flux path for maintaining the ferrofluid within the gap, and the hub and the base defining an essentially closed interior in which the shaft, sleeve, ferrofluid lubricant, permanent magnet means and stator winding means are located;
- means for supporting the stator winding means at a position between the permanent magnet means and the side wall of the hub, the stator winding means being separated from the permanent magnet means by a first air gap and separated from the side wall of the hub by a second air gap, the means for supporting the stator winding means being located on the base.
6 more elements
An electric motor comprising:
- a first member;
- a second member;
- an externally tapered shaft attached to the first member and defining an axis of rotation;
- an internally tapered sleeve attached to the second member and coaxially positioned with respect to the externally tapered shaft to define a first gap therebetween which is a function of relative axial position of the internally tapered sleeve and externally tapered shaft;
- means for adjusting relative axial positions of the internally tapered sleeve and externally tapered shaft to vary size of the first gap;
- means for maintaining a ferrofluid lubricant in the first gap;
- and
- means for causing rotation of one of the first and second members about the axis.
5 more elements
An electric motor comprising:
- a first member;
- a second member;
- an externally tapered shaft attached to the first member and defining an axis of rotation and having an end surface at a first end of the externally tapered shaft which is generally perpendicular to the axis of rotation;
- an internally tapered sleeve attached to the second member and coaxially positioned with respect to the externally tapered shaft to define a first gap therebetween which is a function of relative axial position of the internally tapered sleeve and externally tapered shaft;
- a thrust bearing cap connected to the sleeve and having a surface generally parallel to the end surface to define a second gap;
- means for maintaining a ferrofluid lubricant in the first gap;
- and
- means for causing rotation of one of the first and second members about the axis.
5 more elements
An electric motor comprising:
- a first member;
- a second member;
- an externally tapered shaft attached to the first member and defining an axis of rotation, the externally tapered shaft having an internal axial bore;
- an internally tapered sleeve attached to the second member and coaxially positioned with respect to the externally tapered shaft to define a first gap therebetween which is a function of relative axial position of the internally tapered sleeve and externally tapered shaft;
- means for maintaining a ferrofluid lubricant in the first gap;
- and
- means for causing rotation on one of the first and second members about the axis.
4 more elements
Dependencies are inferred from the claim text.