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Electric motor having fluid circulation system and methods for cooling an electric motor

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Electric motor having fluid circulation system and methods for cooling an electric motor


An electric motor having a housing, a stator mounted in the housing, and a rotor mounted in the housing for rotation relative to the stator about a central axis. A plurality of fluid flow passages extend through the rotor between opposite ends. An electro-magnetic drive system is adapted for driving rotation of the rotor relative to the stator. A fluid circulation system is in fluid communication with the fluid flow passages for providing fluid flow from the first end of the rotor to the second end of the rotor through at least one of the fluid flow passages and fluid flow from the second end of the rotor to the first end of the rotor through at least one other of the fluid flow passages. The rotor and components of the fluid circulation system can be assembled to make a rotor assembly

Browse recent Nidec Motor Corporation patents - St. Louis, MO, US
Inventors: Stephen M. Ruffing, Ronald W. Schmidt, Kenneth R. Friedman
USPTO Applicaton #: #20120256504 - Class: 310 61 (USPTO) - 10/11/12 - Class 310 


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The Patent Description & Claims data below is from USPTO Patent Application 20120256504, Electric motor having fluid circulation system and methods for cooling an electric motor.

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CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 12/402,138, filed Mar. 11, 2009, the entire disclosure of which is hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates generally to electric motors, and more particularly to systems and methods for cooling an electric motor.

BACKGROUND

Electric motors generally include a stator and rotor mounted for rotation relative to the stator. An electromagnetic drive system including a plurality of magnets and/or electromagnets on the rotor and stator is used to drive rotation of the rotor relative to the stator. The rotor is connected to an output shaft so that as the drive system rotates the rotor the output shaft rotates. Operation of the motor, particularly under a load, generates heat. In some cases, one end of the motor (e.g., the driving end) reaches a higher temperature than the other due to this heat generation. The electromagnetic drive system also generates heat. Heat associated with operation of the motor can promote premature breakdown of lubricants (e.g., in the bearings), damage the electromagnetic drive system, and otherwise interfere with desired operation of the motor.

Some electric motors include passive cooling features, such as cooling fins and the like, to facilitate heat transfer out of the motor. Some electric motors include active cooling systems, such as a forced air ventilation systems. For example, a fan can be attached to the output shaft so rotation of the output shaft rotates the fan to generate air flow to cool the motor. Active cooling systems and passive cooling features such as cooling fins can be used in combination.

A motor\'s stator and rotor are commonly mounted in a housing. The housing provides a frame for anchoring the mounted rotor and stator and holding the stator fixed relative to the housing. The housing can also be a barrier preventing people (or other objects) from contacting parts of the motor inside the housing. In some cases the stator and rotor are totally enclosed by and sealed within the housing in order to limit the potential for dust and other debris to interact with the rotor or stator and thereby interfere with operation of the motor. A fan can be used to cool a totally enclosed motor (e.g., by directing air over the housing), in which case the motor may be referred to as Totally Enclosed Fan-Cooled (TEFC). The drive end of a TEFC motor is typically hotter than the opposite end because the fan is installed opposite the drive end. Sometimes, an internal air circuit is used to improve heat distribution in the motor by interchanging air from one end of the motor to the other. For example, in one conventional TEFC motor, a fan pumps air from one end of the housing to the other through passages in the rotor. Air is returned to the first end of the housing through passages in the stator and/or housing.

SUMMARY

In one embodiment, an electric motor includes a housing and a stator mounted in the housing. A rotor is mounted in the housing for rotational movement relative to the stator about a central axis. The rotor has first and second opposite ends and a plurality of fluid flow passages through the rotor between the first and second ends. An electro-magnetic drive system is adapted to drive rotation of the rotor relative to the stator. A fluid circulation system is adapted to produce fluid flow in the housing. The fluid flow includes fluid flow from the first end of the rotor to the second end of the rotor through at least one of the fluid flow passages and fluid flow from the second end of the rotor to the first end of the rotor through at least one other of the fluid flow passages.

Another aspect of the invention is a rotor assembly for an electric motor. The rotor assembly includes a rotor having a central axis and first and second opposite ends. The rotor defines at least in part a plurality of openings at each end and a plurality of fluid flow passages between the first and second ends. Each of said fluid flow passages extends between at least one of said openings at the first end and at least one of said openings at the second end. A hub is fixedly secured to the rotor adjacent one of the first and second ends. The hub includes an outward-facing surface having one or more outward-facing channels and an inward-facing surface defining at least in part one or more conduits through the hub. The conduits and outward-facing channels are aligned with and adjacent a respective one of said openings. The assembly has an impeller having a peripheral edge margin, an inlet radially inward from the peripheral edge margin, and an outlet radially outward from the inlet. The impeller is fixedly secured to at least one of the hub and the rotor and adapted to propel a fluid radially outward from the inlet to the outlet when the rotor assembly is rotated about said central axis. The impeller is positioned relative to the hub so the outward-facing channel of the hub is adjacent the impeller inlet and the inward-facing surface of the conduit substantially prevents fluid flow directly to the impeller inlet from the opening that is aligned with the conduit.

Another aspect of the invention is a method of cooling an electric motor having a housing, a stator in the housing, a rotor having first and second opposite ends mounted in the housing for rotational movement relative to the stator, and an electro-magnetic drive system adapted to drive rotation of the rotor relative to the stator. A fluid is pumped from the first end of the rotor through a first fluid flow passage through the rotor to the second end of the rotor. The fluid is pumped from the second end of the rotor through a second fluid flow passage in the rotor to the first end of the rotor.

Other objects and features will be in part apparent and in part pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective illustrating one embodiment of a motor of the present invention in cross section;

FIG. 2 is an elevation of the motor in cross section;

FIG. 3 is a perspective of a rotor assembly of the motor with parts removed to illustrate bi-directional fluid flow through the rotor;

FIG. 4 is a perspective of the rotor assembly sectioned along planes including the lines 4-4 on FIG. 6 and illustrating one of multiple possible paths for fluid flow back and forth through the rotor;

FIG. 5 is a side elevation of the rotor assembly with an end plate removed to show blades of an impeller and fluid flow passages through the rotor;

FIG. 6 is a side elevation similar to FIG. 5, but including the end plate;

FIG. 7 is an exploded perspective of the rotor assembly;

FIG. 8 is an exploded perspective of components of a fluid circulation system of the rotor assembly;

FIG. 9 is a side elevation of a hub of the fluid circulation system; and



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Stator arrangement
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stats Patent Info
Application #
US 20120256504 A1
Publish Date
10/11/2012
Document #
13431252
File Date
03/27/2012
USPTO Class
310 61
Other USPTO Classes
International Class
/
Drawings
11



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