Grounding mechanism for electric motor
First Claim
1. An electric motor comprising:
- a rotor including a rotor core and a rotor shaft having the rotor core mounted thereon, the rotor shaft having a longitudinal shaft axis, an axial shaft end, and a cylindrical inner surface defining an axially extending bore having a bore opening located at the axial shaft end;
a stator positioned about the rotor and configured to connect with an electrical power supply for inducing a torque on the rotor;
an electric motor housing defining a bearing bore receiving the axial shaft end of the rotor shaft therein;
a bearing mounted on the rotor shaft adjacent the axial shaft end and positioned within the bearing bore to rotatably support the rotor shaft within the electric motor housing, the bearing forming a relatively high resistance electrical circuit segment between the rotor shaft and the electric motor housing; and
an electrical grounding mechanism including a grounding member mounted to the electric motor housing and extending into the axially extending bore, and an electrical grounding ring having an outer periphery contacting the cylindrical inner surface of the rotor shaft and an inner periphery contacting the grounding member, the electrical grounding ring having an inertia insensitive configuration and forming a relatively low resistance electrical circuit segment between the rotor shaft and the electric motor housing.
1 Assignment
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Accused Products
Abstract
An electric motor such as an AC induction electric motor includes a rotor having a rotor core and a rotor shaft. The rotor shaft defines an axially extending bore which has an electrical grounding ring positioned therein. The electrical grounding ring has an inertia insensitive configuration and forms a relatively low resistance electrical circuit segment between the rotor shaft and an electric motor housing to ground the electric motor rotor. The electric motor includes an oil lubricated bearing for the rotor shaft, and a sealing member such as a lip seal is positioned within the axially extending bore to inhibit lubricating oil intrusion therein. A non-rotating stub shaft may be mounted in the housing and extends into the axially extending bore to fluidly seal with the sealing member and electrically connect with the electrical grounding ring, which is fixed to rotate with the rotor shaft.
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Citations
20 Claims
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1. An electric motor comprising:
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a rotor including a rotor core and a rotor shaft having the rotor core mounted thereon, the rotor shaft having a longitudinal shaft axis, an axial shaft end, and a cylindrical inner surface defining an axially extending bore having a bore opening located at the axial shaft end; a stator positioned about the rotor and configured to connect with an electrical power supply for inducing a torque on the rotor; an electric motor housing defining a bearing bore receiving the axial shaft end of the rotor shaft therein; a bearing mounted on the rotor shaft adjacent the axial shaft end and positioned within the bearing bore to rotatably support the rotor shaft within the electric motor housing, the bearing forming a relatively high resistance electrical circuit segment between the rotor shaft and the electric motor housing; and an electrical grounding mechanism including a grounding member mounted to the electric motor housing and extending into the axially extending bore, and an electrical grounding ring having an outer periphery contacting the cylindrical inner surface of the rotor shaft and an inner periphery contacting the grounding member, the electrical grounding ring having an inertia insensitive configuration and forming a relatively low resistance electrical circuit segment between the rotor shaft and the electric motor housing. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A rotor for an electric motor comprising:
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a rotor shaft defining a longitudinal shaft axis and having a first axial shaft end, a second axial shaft end and a bearing mounting interface adjacent the first axial shaft end, the rotor shaft further including a cylindrical inner surface defining an axially extending bore having a bore opening located at the first axial shaft end; a rotor core mounted on the rotor shaft between the first axial shaft end and the second axial shaft end; and an electrical grounding ring positioned within the axially extending bore and having an outer periphery which includes a cylindrical outer surface electrically connecting the grounding ring with the rotor shaft and an inner periphery which includes an electrical contact interface; wherein the electrical grounding ring is fixed to rotate with the rotor via a press fit with the rotor shaft, the electrical grounding ring further having an inertia insensitive configuration adapted to maintain contact between the electrical contact interface and a non-rotating grounding member during rotation of the rotor. - View Dependent Claims (11, 12, 13, 14, 15)
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16. A method of making an electric motor comprising:
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assembling a rotor for the electric motor at least in part via mounting a rotor core between a first axial shaft end and a second axial shaft end of a rotor shaft having a cylindrical inner surface defining an axially extending bore which includes a bore opening located at the first axial shaft end; establishing an electrical ground circuit segment for the rotor at least in part via positioning an electrical grounding ring in the axially extending bore which includes an inertia insensitive configuration adapted to maintain contact between the electrical grounding ring and a non-rotating grounding member during rotor rotation; and positioning a sealing member within the axially extending bore at a location which is axially outward of the electrical grounding ring, the sealing member including an outer surface contacting the cylindrical inner surface of the rotor shaft and fluidly sealing therewith and an inner surface adapted to fluidly seal with the non-rotating grounding member during rotor rotation. - View Dependent Claims (17, 18)
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19. A rotor assembly for an electric motor comprising:
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an electrical circuit segment configured to ground the electric motor, the electrical circuit segment including a rotor shaft of a rotor for the electric motor, the rotor shaft defining a longitudinal axis and having an axial shaft end, a cylindrical outer surface with a bearing mounting interface configured for mounting an oil lubricated bearing thereon and a cylindrical inner surface defining an axially extending bore having a bore opening located at the axial shaft end; the electrical circuit segment further including an electrical grounding ring fixed to rotate with the rotor shaft at an axially inward location within the axially extending bore and having an outer periphery which includes a cylindrical outer surface electrically connecting the grounding ring with the rotor shaft and an inner periphery which includes an electrical contact interface, the electrical grounding ring further having an inertia insensitive configuration; a sealing member configured to inhibit intrusion of bearing lubricating oil into the axially extending bore, the sealing member being fixed to rotate with the rotor shaft at an axially outward location within the axially extending bore; and a stub shaft coaxial with the rotor shaft and extending into the axially extending bore, the stub shaft being configured to electrically connect the electrical circuit segment with a housing for the electric motor, the stub shaft having a first axial stub shaft segment contacting the electrical grounding ring and a second axial stub shaft segment contacting the sealing member.
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20. A grounding mechanism for an electric motor rotor comprising:
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a stub shaft defining a longitudinal axis and having a first axial end, a second axial end and a plurality of axial stub shaft segments including a mounting segment adjoining the first axial end which is adapted for press fitting within an electric motor housing, an electrical grounding segment adjoining the second axial end and a sealing segment extending between the mounting segment and the grounding segment, wherein the mounting segment includes a first diameter, the grounding segment includes a second diameter greater than the first diameter and the sealing segment includes a third diameter greater than the first diameter and greater than the second diameter; an electrical grounding ring positionable about the stub shaft and adapted to press fit within an axially extending bore defined by a rotor shaft of an electric motor, the electrical grounding ring including an outer periphery having a cylindrical outer surface adapted to contact the rotor shaft within the axially extending bore, and an inner periphery including an electrical contact interface configured to electrically connect the electrically grounding ring with the stub shaft via contacting the stub shaft circumferentially about the grounding segment; and a sealing member positionable about the stub shaft and also adapted to press fit within an axially extending bore defined by a rotor shaft of an electric motor, the sealing member including a cylindrical outer surface, and a sealing lip extending radially inwardly and configured to form a fluid seal with the stub shaft via contacting the stub shaft circumferentially about the sealing segment.
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Specification