Magnetically shielded linear motors, and stage apparatus comprising same
AssigneeKabushiki Kaisha Yaskawa Denki
InventorsRyuichirou Tominaga, Masafumi Tamai, Keiichi Tanaka
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Abstract
Stage apparatus are disclosed that provide high-accuracy positioning and movements of a stage platform, while generating reduced stray magnetic-field fluctuations and perturbations. The stage apparatus include at least one linear motor having a stator and a moving coil. Each stator includes a yoke that includes linear arrays of permanent magnets relative to which the moving coil, attached to the stage platform, moves inside a linearly extended coil gap in the yoke. A magnetic-shield plate extends around all outer surfaces and edges of the yoke as well adjacent the coil gap. The magnetic-shield plate is made of a magnetic material having high magnetic permeability.
Claims14
A linear motor, comprising:
- a stator, including a yoke extending in a longitudinal direction and having a U-shaped transverse profile, the stator comprising two parallel linear arrays of permanent magnets mounted to respective inner walls of the yoke and facing each other across a coil-race gap that extends in the longitudinal direction, the yoke having outer surfaces as well as edge regions located adjacent the coil-race gap;
- a moving coil situated inside the coil-race gap so as to move, when the moving coil is electrically energized, in the longitudinal direction relative to the arrays of permanent magnets;
- and
- a magnetic shield extending around, with an intervening space, the outer surfaces of the yoke as well as the edge regions adjacent the coil-race gap, and extending in the longitudinal direction along the length of the yoke.
A stage apparatus, comprising:
- a guide member extending in a longitudinal direction;
- a slider that is guided by the guide member by a non-contacting air bearing situated between the slider and the guide member;
- a stage platform mounted to the slider;
- and
- a first linear motor that actuates movement of the slider in the longitudinal direction relative to the guide member, the first linear motor comprising (a) a stator, including a yoke extending in the longitudinal direction and having a U-shaped transverse profile, the stator comprising two parallel linear arrays of permanent magnets mounted to respective inner walls of the yoke and facing each other across a coil-race gap that extends in the longitudinal direction, the yoke and respective sets of permanent magnets forming individual magnetic loops in the stator, the yoke having outer surfaces as well as edge regions located adjacent the coil-race gap;
- (b) a moving coil situated inside the coil-race gap so as to move, when the moving coil is electrically energized, in the longitudinal direction relative to the arrays of permanent magnets;
- and (c) a magnetic shield extending around, with an intervening space, the outer surfaces of the yoke as well as the edge regions adjacent the coil-race gap, and extending in the longitudinal direction along the length of the yoke.
With respect to a linear motor including (a) a stator, including a yoke extending in a longitudinal direction and having a U-shaped transverse profile, the stator comprising two parallel linear arrays of permanent magnets mounted to respective inner walls of the yoke and facing each other across a coil-race gap that extends in the longitudinal direction, the yoke having outer surfaces as well as edge regions located adjacent the coil-race gap;
- and (b) a moving coil situated inside the coil-race gap so as to move, when the moving coil is electrically energized, in the longitudinal direction relative to the arrays of permanent magnets, a method for magnetically shielding the linear motor, the method comprising forming a magnetic shield extending around, with an intervening space, the outer surfaces of the yoke as well as the edge regions adjacent the coil-race gap, and extending in the longitudinal direction along the length of the yoke.
Dependencies are inferred from the claim text.