Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2004-02-18
2004-10-19
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
Reexamination Certificate
active
06806617
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to alternators for automotive vehicles, and more particularly relates to rotors used in such alternators.
BACKGROUND OF THE INVENTION
Currently, the majority of all vehicles driven today use front-end accessory drive alternators that contain Lundell style rotors, also known as “claw pole” rotors. The rotor provides the alternators magnetic field and rotates within the machine. The rotor includes a coil assembly having a field coil made up of an insulated copper wire or wires wrapped around an electrically insulating bobbin. The bobbin surrounds a steel hub, and insulates the field coil from the steel pole pieces which sandwich the field coil to form north and south poles. The magnetic field is generated when the field coil is energized and a current flows through the wires.
These alternators provide DC output current to charge batteries and support other electronic devices in vehicles. Modern automobiles include increasing amounts of electric demands such as for on screen displays, DVD players, radios, seat warmers and the like. Accordingly, more electric output power is required from the alternator especially at low or idle engine speeds (i.e. 400 rpm to 550 rpm). At the same time, the mass and volume of the alternator is expected to be the same or even smaller for vehicle efficiency considerations. Accordingly, there exists a need to provide an alternator that has increased electric output while minimizing the mass and volume of the alternator.
BRIEF SUMMARY OF THE INVENTION
One embodiment of the invention provides a rotor assembly for an alternator having a rotor shaft, a field coil wound on an insulative bobbin, and pair of poles mounted on the shaft around the field coil and bobbin. Each of the poles includes a pole core and a plurality of pole fingers. The plurality of pole fingers each have an inner surface facing the field coil. The plurality of pole fingers and their inner surface is structured to increase the electric output power of the alternator while decreasing the mass and volume of the alternator pole fingers, thereby increasing the alternator maximum speed by reducing the deflection of the claw pole fingers.
The inner surface of the inner plurality of pole fingers may be structured to have a first portion disposed at a first angle relative to the rotor shaft and a second portion disposed at a second angle relative to the rotor shaft. The first and second angles are different, the first angle preferably being less than the second angle. The first angle is preferably less than 18° and most preferably about 15°, while the second angle is preferably greater than 18° and most preferably is approximately 24°.
The field coil extends along at least a portion of the inner surface of the pole fingers. Preferably, the field coil extends along the first portion and along at least a part of the second portion of the inner surface. An outer surface of the field coil is shaped to correspond to the inner surfaces of the plurality of pole fingers. For example, the outer surface of a portion of the field coil may have third and fourth portions disposed at angles corresponding to the first and second portions of the inner surface. The plurality of pole fingers preferably exert a force on the field coil and deform the field coil into a corresponding shape.
Another embodiment provides a rotor assembly for an alternator comprising a rotor shaft, a field coil wound on an insulative bobbin, and a pair of poles mounted on the shaft around the field coil and bobbin. Each of the poles includes a pole core and a plurality of pole fingers. The plurality of pole fingers each have a pole root, a pole tip, and an inner surface facing the field coil. The inner surface has a curved shape increasing in slope from the pole root to the pole tip. The curved shape may be parabolic, exponential, or any other curve shape of increasing slope. The field coil preferably has an outer surface corresponding to the curved inner surface of the plurality of pole fingers, and the field coil is deformed by the pole fingers and extends along at least a portion of the inner surface of the pole fingers beyond the axial center of the two pole pieces.
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Chen Hanyang Ben
York Michael Timothy
Brinks Hofer Gilson & Lione
Nguyen Tran
Visteon Global Technologies Inc.
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