Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2000-01-26
2001-11-13
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S261100, C310S269000
Reexamination Certificate
active
06316850
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a small-sized motor and particularly to a small-sized motor that suppresses vibration to thereby prevent emergence of a resonance peak.
BACKGROUND ART
A small-sized motor—which includes a cylindrical, metallic casing and magnets mounted on the inner surface of the casing and serving as stator-side magnetic poles—has been used to drive electric equipment for use in an automobile. Rotor-side magnetic poles of such a small-sized motor are of an odd or even number. For example, as shown in
FIG. 8
, in the case of a small-sized motor including right-hand and left-hand magnets
1
forming two stator-side magnetic poles, and a 5-pole, laminated core
8
forming rotor-side magnetic poles of an odd number, when one rotor-side magnetic pole is positioned on the X axis, the five rotor-side magnetic poles become asymmetrical with respect to the Y axis. However, when, as a result of rotational progress, one rotor-side magnetic pole comes to be positioned on the Y axis, the rotor-side magnetic poles become symmetrical with respect to the Y axis, as shown in FIG.
9
. Repeatedly becoming symmetrical and asymmetrical according to rotation as viewed from the stationary-side magnetic poles, a rotor having an odd number of poles is not advantageous in terms of vibration.
By contrast, when two magnet-type magnetic poles are combined with a rotor having an even number of poles, for example, 6 poles, the rotor becomes symmetrical in any rotational position. Thus, the rotor having an even number of poles is advantageous in terms of vibration. However, when a small-sized motor employing a rotor having an odd number of poles and that employing a rotor having an even number of poles are compared under substantially the same conditions (motor size, voltage, and current, among others), the rotor having an odd number of poles is conventionally known to exhibit a larger torque. The small-sized motor employing a rotor having an even number of poles may raise a cogging problem.
A motor employing a rotor having an odd number of poles is advantageously applicable to fields requiring a large torque, and, at the same time, is required to suppress an inherent vibration problem. Conventionally, the profile of a laminated core has not been considered from the viewpoint of suppression of vibration. Specifically, the profile of the conventional laminated core shown in
FIGS. 8 and 9
; i.e., the width of arm portions
16
, the thickness t of wing portions
17
, and the distance between the adjacent wing portions
17
, constituting salient magnetic poles of the rotor have not been considered from the viewpoint of suppression of vibration.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide a small-sized motor capable of solving a problem of a rotor having an odd number of poles in that vibration is likely to arise, to thereby suppress vibration while maintaining a feature of the rotor that a large torque can be produced.
A small-sized motor of the present invention comprises a casing
2
having a closed-bottomed cylindrical shape and including a magnet
1
attached to an inner surface thereof; a casing cover
5
fitted to the casing
2
so as to close an opening portion of the casing
2
and including a brush attached thereto; and a rotor including a shaft
7
, a laminated core
8
forming salient magnetic poles of an odd number and mounted on the shaft
7
, windings
9
, each being wound around a plurality of salient magnetic poles, and a commutator
10
mounted on the shaft
7
. Each salient magnetic pole includes an arm portion
16
and wing portions
17
, which are integrated with ends of the arm portion
16
and circumferentially extends symmetrically with respect to the arm portion
16
. Core laminations of the laminated core
8
are blanked from a silicon steel sheet through press-working. When the core laminations each have a thickness u, the core
8
has a diameter D, and the wing portion
17
has a thickness t as measured at its root in a radial direction, the thickness t falls within a range the upper limit of which is 5.5% the core diameter D and the lower limit of which is the core-lamination thickness u. Through employment of such a range of the thickness t, vibration can be suppressed.
According to the small-sized motor of the present invention, the distance v between adjacent ends of the wing portions
17
is selected so as to be not less than 1.2 times a wire diameter of winding and such that [distance v/diameter D×(the number of poles)] is not greater than 0.22, thereby effectively suppressing vibration further.
According to the small-sized motor of the present invention, the ratio of the width w of the arm portion
16
to the core diameter D is 0.14 to 0.16, thereby effectively suppressing vibration further.
REFERENCES:
patent: 4616151 (1986-10-01), Pryjmak
patent: 4881002 (1989-11-01), Yamaguchi
patent: 5528096 (1996-06-01), Orii et al.
patent: 5982055 (1999-11-01), Matsushita et al.
Mabuchi Motor Co. Ltd.
McGlew and Tutle, P.C.
Waks Joseph
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