Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2001-07-13
2004-08-10
Le, Dang (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S156010, C310S156080, C310S156340, C310S156660, C310S156690, C310S257000
Reexamination Certificate
active
06774512
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a claw-pole permanent-magnet stepping motor. More particularly, the present invention relates to a claw-pole permanent-magnet stepping motor that minimizes external flux leakage, minimizes magnetic circuit obstructions common in low profile designs, and reduces costs.
2. Description of the Related Art
A claw-pole permanent-magnet stepping motor is a type of hybrid stepping motor. Magnetic parts known as claw poles, form a phase A inductor and a phase B inductor in the claw-pole permanent-magnet stepping motor. Claw poles are widely used in commercial devices since they can be produced inexpensively and accurately with plate-pressing technology.
Referring now to
FIG. 5
, a conventional claw-pole permanent-magnet stepping motor
100
includes a permanent magnet
103
secured to a rotor
102
. Permanent magnet
103
is constructed and magnetized to form multiple radial poles, as shown.
Rotor
102
is rotationally supported by a bottom bearing, not shown, and secured to a case unit
113
. Rotor
102
, is supported at a top by a bearing
115
secured to a securing member
114
on a case unit
112
. Case units
112
113
are formed from a magnetic material.
Case units
112
,
113
respectively house a phase A inductor and a phase B inductor arranged symmetrically about rotor
102
. The phase A inductor and the phase B inductor are formed from separate claw poles
104
,
105
,
106
,
107
. A coil
108
wraps around claw poles
104
and
105
. A coil
109
wraps around claw poles
106
and
107
A diameter L1 is defined on the arcuate section of case units
112
,
113
. A total case unit length L2 is defined along rotor
102
. Diameter L1 and length L2 are designed to form roughly a 2:1 ratio, as shown.
During operation, power is alternately applied to the phase A inductor and the phase B inductor. As a result, magnetic attraction, based on the arrangement of teeth, takes place between permanent magnet
103
and claw poles
104
,
105
,
106
,
107
. The magnetic attraction drives a stepping operation that provides rotational torque.
It should be understood that claw-pole permanent-magnet stepping motor
100
cannot be used in devices that impose restrictions on outer diameter L1 of case units
112
,
113
.
Additionally, devices employing claw-pole permanent-magnet stepping motor
100
must provide a wide attachment area since motor
100
is secured to the device using bolts and nuts via a set of securing holes
114
a
,
114
a
formed on securing member
114
of case unit
112
.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the present invention to provide a claw-pole permanent-magnet stepping motor that overcomes the issues described above.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that may be attached or internally disposed in devices that impose outer dimension restrictions on a case unit.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that eliminates magnetic circuit obstructions that accompany low-profile designs.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that limits external flux leakage.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that employs a case unit that can be produced simply and with high precision.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor that includes a case unit formed with a lateral cross-section shaped roughly as an oval shape with flat sides, flat side walls, and continuously formed thick arcuate sections.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor where a total length of a case unit along the longitudinal axis of the rotor to a diameter of arcuate sections of a pair of case units is a ratio of at least 1:1 and preferably a ratio of 2:1.
It is another object of the present invention to provide a claw-pole permanent-magnet stepping motor where a permanent magnet faces a phase A inductor and a phase B inductor to provide adequate rotational torque during operation.
Briefly stated, the present invention relates to a claw-pole permanent-magnet stepping motor that includes a pair of cases containing two or more inductors in symmetrical arrangement with multiple claw poles. The case unit has an oval shape having thin flat side walls or thin stepped side walls and connecting thick arcuate surfaces operating to resist external flux leakage from the motor and eliminating magnetic circuit obstructions. The cases, side walls, and inductors allow the motor to have a width to length ratio from about one to one to about one to two thus allowing a reduction in size and a low profile design while retaining output torque.
According to an embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, comprising: a first and a second case unit having a total length, a rotor having at least a first and a second permanent magnet, the first and the second case units having a shape supporting the rotor, a third and a fourth arcuate section on each the first and the second case units, a fifth and a sixth side wall section joining each respective the third and forth arcuate sections in a continuous flattened-oval shape about the rotor, the third and the forth arcuate sections each having a first diameter, and a ratio of the total length to the first diameter is at least 1:1, whereby the claw-pole permanent magnet stepping motor has a reduced size, eliminates magnetic circuit obstructions, and prevents external flux leakage to allow use with magnetic devices while providing an adequate rotational torque.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: the ratio is preferably 2:1 whereby the claw-pole permanent magnet stepping motor has a reduced size while providing adequate rotational torque despite the ratio.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: the third and the fourth arcuate sections each have a first thickness, the fifth and the sixth wall sections each have a second thickness, and the first thickness being greater than the second thickness, whereby size is reduced, magnetic circuit obstructions are eliminated, and external flux leakage is minimized.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, wherein: the fifth and the sixth sections each having a planar shape and being closer to the rotor than the third and the fourth arcuate sections, and the at least first case unit having a flattened-oval cross section, whereby the claw-pole permanent magnet stepping motor has a reduced size.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, further comprising: a first thin wall section on each the fifth and the sixth sections orthogonal each the third and the fourth arcuate sections, the first thin wall section having a third thickness, and the third thickness being less than the second thickness, whereby the claw-pole permanent magnet stepping motor may be made with an increased torque while retaining a same external size.
According to another embodiment of the present invention there is provided a claw-pole permanent-magnet stepping motor, further comprising: a first metal bearing in the first case unit, a second metal bearing in the second case unit, the rotor supported between the first and the second metal bearings, a plurality of poles on the first and second permanent magnets, a first and a second phase inductor in each respective the first and the second unit case opposite each respective the first and second permanent magnet, the first and the second phase inductors disposed symmetrically in each resp
Sadamitsu Toshio
Saitou Katumi
Takagi Masaaki
Darby & Darby
Elkassabgi H.
Le Dang
Nidec Copel Corporation
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