Permanent magnet motor having teeth with fingers
View Patent ↗A permanent magnet-type stepping motor broadly includes: a movable member (e.g., a rotor) having a number of magnetic poles on a surface thereof, with adjacent poles being of opposite polarity, the number of poles being a function of a constant, the number of phases and a desired step interval; and a stationary member (e.g., a stator) having a number of equally-spaced teeth arranged to face toward said movable member surface, each of said teeth having a plurality of fingers arranged to face toward said movable member surface, the number of said teeth being a whole integer that is a function of a constant, the number of said poles, the number of said fingers on each stator tooth, and the number of phases.
1. A permanent magnet-type stepping motor having a motor driver, a movable member and a stationary member, comprising:
a number of circumferentially spaced magnetic poles on a surface of one of said members, with adjacent poles being of opposite polarity, the number of poles being a function of a constant, the number of phases and a desired step interval;
said magnetic poles having a separation region between adjacent magnetic poles;
a number of equally-spaced teeth on the other of said members, said teeth being arranged to face toward said one member surface, each of said teeth having a plurality of circumferentially spaced fingers arranged to face toward said one member surface, the number of said teeth being a whole integer that is a function of a constant, the number of said poles, the number of fingers on each stator tooth, and the number of phases;
wherein said fingers are spaced from one another such that the fingers on any given tooth will align with poles of the same polarity;
wherein said one member is a rotor having an outer surface, said other member is a stator, said desired step interval is a desired step angle, and said teeth are spaced circularly about said stator to face toward said rotor outer surface;
wherein the number of said rotor poles is an even integer determined from the equation:
step
angle
=
(
drive
number
)
×
360
°
(
no
.
of
phases
)
×
(
no
.
of
rotor
poles
)
where the drive number is 1 for a bipolar drive and 2 for a unipolar drive; and
wherein the maximum number of stator teeth (m) per phase is determined by the equation:
m
≤
int
(
no
.
of
rotor
poles
[
2
×
(
no
.
of
fingers
per
stator
tooth
)
-
1
]
×
(
no
.
of
phases
)
)
,
where the expression, int(x), is the integer function that returns the integer portion of its argument (x).
2. A permanent magnet-type stepping motor as set forth in claim 1 wherein said rotor comprises solid soft magnetic steels, or is laminated with electrical steel laminations.
3. A permanent magnet-type stepping motor as set forth in claim 1 wherein said teeth are spaced equally about said stator.
4. A permanent magnet-type stepping motor as set forth in claim 1 and having two phases A and B, and wherein said rotor and stator are configured and arranged such that when the phase A fingers on the stator teeth align with the rotor poles, each phase B finger will align with the center of two neighboring rotor poles.
5. A permanent magnet-type stepping motor as set forth in claim 1 and having three phases A, B, and C, and wherein said rotor and stator are configured and arranged such that when the phase A stator fingers align with the rotor poles of one polarity, each phase B and phase C stator finger will align with rotor poles of the opposite polarity.
6. A permanent magnet-type stepping motor as set forth in claim 5 wherein if each phase B stator finger aligns with the leading edge of an associated rotor pole, each phase C finger aligns with the trailing edge of an associated rotor pole.
7. A permanent magnet-type stepping motor as set forth in claim 5 wherein if each phase B stator finger aligns with the trailing edge of an associated rotor pole, each phase C finger aligns with the leading edge of an associated rotor pole.
8. A permanent magnet-type stepping motor as set forth in claim 1 wherein said rotor and stator are configured and arranged such that for a four-phase motor having phases A, B, C and D, when the phase A fingers on the stator teeth align with the rotor poles, each phase B finger will align with the center of two neighboring poles, each phase C finger will align with a pole opposite to those aligned with phase A, and each phase D finger will align with a pole opposite those aligned with phase B.
9. A permanent magnet-type stepping motor as set forth in claim 1 wherein the number of poles is 80.
10. A permanent magnet-type stepping motor as set forth in claim 1 wherein the number of poles is 120.
11. A permanent magnet-type stepping motor as set forth in claim 1 wherein the number of said fingers on each said tooth is two.
12. A permanent magnet-type stepping motor as set forth in claim 1 wherein the number of said fingers on each said tooth is three.
13. A permanent magnet-type stepping motor as set forth in claim 1 wherein the number of said fingers on each said tooth is four.
14. A permanent magnet-type stepping motor as set forth in claim 1 wherein said separation region comprises an air gap.
15. A permanent magnet-type stepping motor as set forth in claim 1 wherein said separation region comprises soft magnetic steel or steel laminations.