Browse Prior Art Database

Linear Stepper Motor with an Anisotropic Bar

IP.com Disclosure Number: IPCOM000087697D
Original Publication Date: 1977-Mar-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Chai, HD: AUTHOR [+2]

Abstract

A variable reluctance linear stepper motor comprises magnetic E cores 10 and 11 located above and below a toothed magnetic bar 12. The E cores 10 and 11 are supported by bearings (not shown) riding on the opposite surfaces of bar 12 so that the faces of the poles of the E cores are separated by top air gap 13 and bottom air gap 14, respectively. Teeth are formed in the faces of the poles having the spacing and size relative to the teeth of the stator bar 12 to effect stepwise motion in the direction of the longitudinal axis 15 of the bar 12. A complete description of such a motor is contained in U. S. Patent 3,867,676.

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Linear Stepper Motor with an Anisotropic Bar

A variable reluctance linear stepper motor comprises magnetic E cores 10 and 11 located above and below a toothed magnetic bar 12. The E cores 10 and 11 are supported by bearings (not shown) riding on the opposite surfaces of bar 12 so that the faces of the poles of the E cores are separated by top air gap 13 and bottom air gap 14, respectively. Teeth are formed in the faces of the poles having the spacing and size relative to the teeth of the stator bar 12 to effect stepwise motion in the direction of the longitudinal axis 15 of the bar 12. A complete description of such a motor is contained in U. S. Patent 3,867,676.

In the event the dimensions of the top air gap 13 and the bottom air gap 14 are not identical when the motor is assembled, there will be an imbalance in the normal force which adds wear to the bearings. The imbalance is caused by the difference in the flux through the E cores 10 and 11, which may be expressed by the following equation: Delta Phi = Phi(B) - Phi(T). In addition to a normal force which is not equal to zero, there are reluctance forces in the top and bottom E cores 10 and 11 which are different and which induce coupling of the E core assembly.

The coupling effect and normal force imbalance can be minimized by constructing the motor bar 12 with one or more laminations of magnetic material which has an anisotropic grain orientation. This type of material provides a low reluctance path perpendi...