Motor stator with lift capability and reduced cogging characteristics

• US 8,659,205 B2
• Filed: 06/27/2008
• Issued: 02/25/2014
• Est. Priority Date: 06/27/2007
• Status: Active Grant

• Current Assignee: Brooks Automation Ltd. (United Kingdom) (Azenta, Inc.)
• Original Assignee: Brooks Automation Incorporated (Azenta, Inc.)
• Inventors: Moura, Jairo, Hosek, Martin, Krishnasamy, Jay
• Primary Examiner(s): Nguyen, Tran
• Assistant Examiner(s): Andrews, Michael
• Application Number:
  US12/163,993
• Publication Number:
  US 20090033173A1
• Time in Patent Office: 2,069 Days
• Field of Search: 310/156.55, 310/156.57, 310/254, 310/156.38, 310/156.45, 310/156.75, 310/156.76, 310/216.069, 310/254.1
• US Class Current: 310/254.1
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
• CPC Class Codes: H02K 7/09 with magnetic bearings

Abstract

A motor includes a stator and a rotor, equipped to be movable in at least a first direction relative to the stator, the rotor operably interfacing the stator so that a motor force is generated in a first direction, where the stator comprises an anti-cogging element configured to generate anti-cogging forces on the rotor in at least the first direction and a second direction at an angle to the first direction.

Claims

1. A motor comprising:

a stator including a surface; and

a rotor equipped to be movable in at least a first direction relative to the stator, the rotor operably interfacing the stator so that a motor force is generated in a first direction, the rotor including permanent magnets,

the stator comprising a plurality of elements disposed in the surface and configured to interface with the permanent magnets such that spacing of the permanent magnets and at least one element is configured such that leading edges of individual magnets of a pair of the permanent magnets approach a first transition between the surface and the one element and a second transition between the one element and the surface substantially simultaneously to generate anti-cogging forces on the rotor in at least the first direction and a second direction at an angle to the first direction,

wherein the first and second transitions each comprise a first transition portion located a first distance from a radial center of the rotor and a second transition portion located a second distance from the radial center of the rotor, the first distance being different from the second distance,

wherein a third distance between the first transition portion of the first transition and the second transition portion of the second transition is substantially a pitch of permanent magnets of the same polarity divided by 2, and

wherein a pitch of adjacent elements is an integer multiple of the pitch of permanent magnets of the same polarity.

2. The motor of claim 1, comprising a synchronous brushless motor.

3. The motor of claim 1, wherein the at least one element is configured to generate anti-cogging forces on the rotor in at least a third direction at an angle to the first and second directions.

4. The motor of claim 1, wherein the at least one element comprises:

at least a first recess extending inward from an inner surface of the stator; and

at least two transition areas extending from the inner surface to the first recess,

wherein a distance between the at least two transition areas is approximately nP/2 where n is any integer and P is the pitch between magnets of the same polarity interfacing with the stator.

5. The motor of claim 4, wherein the at least one element includes at least a second recess extending inward from an inner surface of the stator, wherein a distance between the first and second recesses is approximately nP/2 +mP/4, where n is any integer and m is an odd number.

6. The motor of claim 4, wherein at least one of the transition areas is angled with respect to the inner surface.

7. The motor of claim 4, wherein at least one of the transition areas has a surface concave with respect to the inner surface.

8. The motor of claim 4, wherein at least one of the transition areas has a surface convex with respect to the inner surface.

9. The motor of claim 4, wherein at least one of the transition areas recedes from the inner surface and the first recess.

10. The motor of claim 4, wherein at least one of the transition areas defines a compound angle between the inner surface and the first recess.