Patent Application
20120074801
1. Field of the Invention
The present invention relates to an interior permanent magnet synchronous motor having a rotor configuration permitting an increased flow of air or other fluid between the rotor and a stator of the motor for improved heat transfer.
2. Description of Related Art
U.S. Pat. No. 5,051,634 to Overton discloses an electric motor including a steel shaft surrounded by an iron sleeve on which four permanent magnets are mounted. A banding surrounds the rotor structure to hold the magnets in place. To effect a transfer of heat from windings of the motor to the motor housing, a heat spike is added into each stator slot of the motor.
U.S. Patent Application Publication 2008/0030108 to Trago et al. discloses a stepper motor having a rotor shaft with front and rear rotor segments disposed thereon. An aluminum housing and aluminum endbells conduct heat generated in the motor into a faceplate for improved performance.
The disclosures of U.S. Pat. No. 5,051,634 to Overton and U.S. Patent Application Publication 2008/0030108 to Trago et al. are both incorporated herein by reference in their entireties as non-essential subject matter.
According to the present invention, an interior permanent magnet synchronous motor (IPMSM) has bridges, between the magnet layers of each pole and between poles, that are inset from the outer diameter of the rotor. Setting the bridges in from the outer diameter of the rotor provides an increased cross-sectional area in an air gap region, which increases the airflow from a fan and provides increased heat transfer from the winding and the rotor to the airflow, thereby cooling the motor with greater effect.
By way of the present invention, a rotor arrangement with decreased fluid flow impedance and improved rotary motor cooling is mountable on a shaft for rotation relative to a stator of a rotary motor arrangement The rotor arrangement has a plurality of laminations joined together to form a multilayer laminated rotor with a plurality of magnet receptacles. Each of the laminations has a solid central section surrounding an opening within which the shaft is receivable, spokes extending substantially radially outwardly from said solid central section, ribs interposed between adjacent spokes, and bridges interconnecting the spokes and ribs. At least some of the bridges are inset from an outer diameter of the lamination toward the solid central section to decrease fluid flow impedance and improve rotary motor cooling. In one configuration of the rotor arrangement, each lamination has an unobstructed channel for fluid on its outer circumference that is centrally located between the spokes, while, in another configuration, each lamination has a center pole tip on its outer circumference that is centrally located between the spokes.
In one preferred arrangement, the bridges extend approximately circumferentially. Additional, radially extending bridges may be provided to interconnect the solid central section and a plurality of the ribs. The ribs and the spokes can have protrusions defined thereon to properly position magnet elements between the protrusions and the outer bridges.
A lamina 40 used in production of a rotor according to the present invention is shown in plan view in
Each lamina 40 may have a unitary, one piece construction, as shown, with a solid central section 46, in which the shaft opening 42 is provided, and a multiplicity of spokes 48 extending radially outward from the solid central section 46. A plurality of nested ribs 50 are received between adjacent spokes 48. The ribs 50 and the spokes 48 are interconnected by way of outer, approximately circumferentially extending bridges 52 and inner, approximately radially extending bridges 54, so that each rotor lamina 40, as a whole, is an integral element. In
The rotor 44 thus is formed as a multilayer IPM (interior permanent magnet) rotor, with outer bridges 52 that are inset from the outer diameter of the rotor 44. These bridges 52 of laminate material are not on the rotor outer diameter, as is traditional for multilayer IPM designs, but rather inset toward the inner diameter or solid central section 46 of the rotor 44. Insetting the bridges 52 in this way allows for recesses 64, which add significant cross-sectional area at the rotor outer diameter that is contiguous with the air or other fluid gap, within which cooling air or other fluid can flow. This area allows for a lower impedance path for fluid flow from a shaft mounted fan, and, therefore, provides improved cooling of the motor windings, which form the hottest part of the motor. Setting the outer bridges 52 in from the outer diameter of the rotor 44, in other words, provides an increased cross-sectional area in an air gap region, which increases the airflow from a fan (not shown) and provides increased heat transfer from the winding and the rotor to the airflow, thereby cooling the motor with greater effect. Air flow, of course, will also occur through passages 66 remaining between the magnet receptacles 60 and the radially extending bridges 54.
Each lamination of the rotor 44 illustrated in
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, and the invention should be construed to include everything within the scope of the invention ultimately claimed.
This application claims priority under 35 U.S.C. §119(e) to U.S. provisional application Ser. No. 61/386,811, filed Sep. 27, 2010, the entire disclosure of which is incorporated by this reference into the present U.S. patent application.
| Number | Date | Country | |
|---|---|---|---|
| 61386811 | Sep 2010 | US |
