Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-07-21
2001-12-04
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S596000, C310S043000, C264S272190, C156S089120
Reexamination Certificate
active
06324745
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to rotor assemblies for use in rotating machines, and more specifically to rotor assemblies for use in rotating machines suitable for operation while immersed in an operating fluid.
BACKGROUND OF THE INVENTION
Rotating machines are commonly used to drive rotational loads such as pump impellers. In certain applications, the process fluid pumped by the impeller is not compatible with elements of the rotating machine. In such applications, the rotating machine must be isolated from the process fluid. Otherwise, the elements of the rotating machine must be constructed of materials compatible with the fluid. This specification describes a rotating machine adapted for use in an electro-hydraulic power steering unit, however other applications are contemplated.
In typical power steering pump designs, the motor drive has two endshields and uses ball bearings to reduce friction generated by rotation of the shaft. The motor is generally separated from the fluid by a seal on the shaft. The use of a ball bearing motor in the presence of hydraulic fluid limits the life expectancy of the ball bearings. Leakage of the hydraulic fluid past the shaft seal will contaminate the bearing lubricant, leading to the eventual demise of the ball bearings. It is therefore desirable for a rotating machine adapted for use in a pump application to be compatible with the process fluid being pumped. It s further desirable for a rotating machine adapted for use in a pump application to be capable of being immersed in the process fluid, thus obviating the need for a seal between the rotating machine and the pump.
In rotating machines using permanent magnet motors, it is common to attach permanent magnets on a rotor member to form a rotor assembly. The permanent magnets may be attached by retaining members or adhesives. In the process of attaching the magnets, the thickness and uniformity of the adhesive layer greatly determines the shear strength of the adhesive. It is desirable to control the thickness and uniformity of the adhesive layer to ensure adequate adhesion. It is also desirable to provide a back-up retention means should the adhesive layer fail.
Another important aspect in the assembly of a rotating machine lies in assuring alignment between the stator of the machine and the position sensors used to indicate the relative position of the rotor during operation and control of the machine. Typically Hall effect sensors are placed near the rotor to sense magnetic field changes caused by the interaction between the magnets on the rotor and the stator poles, thus allowing the control electronics to time the switching on and off of the phase windings to control machine torque and speed. The alignment of the sensors relative the stator is crucial to this timing process. Typically, the sensors are adjusted after fabrication of the rotating machine to ensure the proper timing. It is desirable for a rotating machine to have features which align the stator poles relative to the position sensors during the assembly process, thus obviating the need for further adjustment after assembly has been completed.
SUMMARY OF THE INVENTION
The present invention in a broad aspect addresses the problems and shortcomings mentioned above. More specifically, an, aspect of the invention is seen in a rotor assembly for a rotating machine, comprising a substantially cylindrical main rotor body having an outer surface. A plurality of longitudinal ribs project from the outer surface of the main rotor body. A plurality of primary recesses are defined by adjacent ribs, and a secondary recess is defined in the outer surface within at least one primary recess. A magnet is positioned within at least one primary recess, and a layer of adhesive between the magnet and the outer surface of the main rotor body substantially fills the secondary recess.
Another aspect of the invention is seen in a rotor assembly for a rotating machine, comprising a substantially cylindrical main rotor body having an outer surface. A plurality of longitudinal ribs project from the outer surface of the main rotor body. A is plurality of primary recesses are defined by adjacent ribs, and a magnet is positioned within at least one primary recess. A star-shaped retainer is located at at least one end of the main rotor body. The star-shaped retainer comprises a circular member including a plurality of radial projections extending outwardly from the circular member. The number of projections correspond to the number of ribs defined in the outer surface of the main rotor body. Each projection exhibits a termination that engages a surface of the adjacent magnets.
A further aspect of the invention is seen in a rotor assembly for a rotating machine, comprising a substantially cylindrical main rotor body having an outer surface. A plurality of longitudinal ribs project from the outer surface of the main rotor body. A plurality of primary recesses are defined by adjacent ribs, and a magnet is positioned within at least one primary recess. An elongated retaining member, is positioned over a rib and connected to the rotor body at each end thereof. A surface of the elongated retaining member engages a corresponding surface of the adjacent magnet.
An aspect of the invention is seen in a rotor assembly for a rotating machine, comprising, a substantially cylindrical main rotor body having an outer surface, a plurality of longitudinal ribs projecting from the outer surface of the main rotor body, a plurality of primary recesses defined by adjacent ribs, a magnet positioned within at least one primary recess, and a layer of encapsulation material positioned about the main rotor body and the at least one magnet.
Still another aspect of the invention is seen in a method of assembling a rotor assembly for a rotating machine. The rotor assembly comprises a main rotor body having an outer surface, a plurality of longitudinal ribs defined in the outer surface, a plurality of primary recesses defined by adjacent ribs, and a secondary recess defined in the outer surface within at least one of the plurality of primary recesses. The method comprises providing an adhesive layer within at least one primary recess and substantially filling the secondary recess with adhesive, positioning a magnet within at least one primary recess, and compressing the magnet against the main rotor body such that the adhesive is extruded from the primary recess.
Another aspect of the invention is seen in a method of assembling a rotor assembly for a rotating machine. The rotor assembly comprises a main rotor body having an outer surface, a plurality of longitudinal ribs defined in the outer surface, and a plurality of magnet recesses defined by adjacent ribs. The method comprises positioning a magnet within at least one magnet recess, and attaching a star-shaped retainer to at least one end of the main rotor body. The star-shaped retainer comprises a circular member with a plurality of radial projections extending outwardly therefrom. The number of projections is equal to the number of ribs. Each projection has a termination which is deformed to engage a surface of the adjacent magnet to retain the magnet in the magnet recess.
Yet another aspect of the invention is seen in a method of assembling a rotor assembly for a rotating machine, the rotor assembly comprising a main rotor body having an outer surface; a plurality of longitudinal ribs defined in the outer surface, and a plurality of magnet recesses defined by adjacent ribs. The method comprises positioning a magnet within at least one magnet recess, locating an elongated retaining member over at least one of the ribs such that a lower surface of the elongated retaining member engages a surface of the adjacent magnet, and deforming first and second ends of the elongated retaining members to engage the main rotor body at first and second ends thereof to secure the adjacent magnet to the main rotor body.
An aspect of the invention is seen in a method of assembling a rotor assembly for a rotating m
Gavello Mauro
Heilman Ray D.
Poag Andrew F.
Tevaarwerk Joseph L.
Chang Rick Kiltae
Emerson Electric Co.
Howrey Simon Arnold & White , LLP
Young Lee
LandOfFree
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