| 摘要 |
<p>A permanent magnet direct current motor includes two annular rigid magnets which are held within a cylindrical casing by a spacer formed of a rigid mild steel insert. The rigid insert is disposed between two free edges of the magnets. An additional spacer in the form of a resiliently deformable "U"-shaped spring is disposed between a second set of two free edges of the magnets. The mild steel insert has two oppositely-directed lateral extensions disposed in contact with each of the magnets and the closed end of the casing to locate the magnets longitudinally within the casing. The insert also has a first locating member adjacent the open end of the casing for engagement with a second complementary locating member in an end cap for closing the open end of the casing to locate the end cap angularly relative to the casing and thereby provide optimal commutation. The complementary locating member may include an electrically conductive member which contacts the insert to provide an earth connection within the end cap. Moreover, the insert serves as a magnetic shunt between the magnets so that upon magnetization of the magnets, the axis of the magnetic field lies in a second plane spaced from the longitudinal axis in the direction towards the insert, thus reducing radial vibration of the rotor and noise during operation.</p> |
