Motor

Details Motor Motor

2002-09-27

2004-03-30

Mullins, Burton S. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S090000, C310S254100

Reexamination Certificate

active

06713915

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to motors that are used in industrial equipment and home electric appliances. More particularly, the present invention relates to the structure of motors and motor cases that shorten the overall length of the motors.
2. Description of Related Art
FIGS. 6 and 7
show a typical conventional motor M. The conventional motor M is generally structured with a stator S disposed in a motor case
100
and a rotor R that is freely, rotatably supported within the stator S. The stator S is equipped with a stator core
5
and excitation coils
6
. The stator core
5
has a plurality of salient poles disposed at generally equal angles and radially extending toward the center, and each of the excitation coils
6
is wound in generally the same width on each of the salient poles. The stator core
5
is provided with a shaft hole at its center through which a rotary shaft
2
composing the rotor R is passed. The shaft hole is provided opposite to a driving magnet
3
that is affixed to an outer circumference of the rotary shaft
2
of the rotor R.
The rotary shaft
2
is freely, rotatably supported by a pair of bearings
41
and
42
that are provided at both end sides, respectively, of the motor case
100
. One end of the rotary shaft
2
outwardly protrudes from the motor case
100
to form an output shaft section
2
a.
The motor case
100
has a cup shape, and is formed from a first case
110
that houses the stator S and a part of the rotor R, and a second case
120
that retains the bearing
42
and covers an opening section of the first case
110
. A bearing retaining section
114
is formed in the first case
110
in a manner that the bearing retaining section
114
outwardly protrudes in the axial direction from a bottom surface section
112
of the first case
110
. The bearing retaining section
114
retains the first bearing
41
on its inside. Also, a bearing retaining section
124
is similarly formed in the second case
120
in a manner that the bearing retaining section
124
outwardly protrudes in the axial direction from a bottom surface section
122
of the second case
120
. The second bearing
42
is retained inside the bearing retaining section
124
.
In recent years in particular, the miniaturization of industrial equipment and home electric appliances has been greatly advanced, and in this connection, there is a greater demand in reducing the size of motors themselves. However, since the conventional motor M described above has a structure in which the bearing retaining section
114
protrudes from the bottom surface section
112
, which elongates the overall length of the motor M. This prevents miniaturization of the motor M.
Conventionally, some measures to shorten the overall length of motors have been proposed. For example, after the excitation coils
6
are wound on the salient poles of the stator core
5
, end faces of the excitation coils
6
are press-formed, or the number of turns of the excitation coils
6
is reduced, to lower the height of the excitation coils
6
in the axial direction.
However, when the end faces of the excitation coils
6
are to be press-formed, additional work is required after the excitation coils
6
are wound, and there is a possibility of severing the excitation coils
6
. When the number of turns of the excitation coils
6
is reduced, there may be a problem in that the designed motor performance may not be attained.
SUMMARY OF THE INVENTION
The present invention has been made in view of the problems described above. Accordingly, the present invention relates to providing motors that can realize miniaturization of motors by shortening the overall length of the motors.
In accordance with an embodiment of the present invention, a motor includes a case body having a bottom surface section, a recessed concave section that is located inside the bottom surface section in a radial direction and recedes inwardly in an axial direction at a location opposite to an excitation coil provided within the case body, and a bearing retaining section that is formed inside the recessed concave section in the radial direction, wherein at least one part of the bearing retaining section is located inside in the axial direction than the bottom surface section.
In accordance with the present invention, the bearing retaining section is disposed inside the recessed concave section in the radial direction that is located opposite to the excitation coil and inside the bottom surface section of the case body the radial direction of. As a result, the bearing can be located more interior in the axial direction than the bottom surface section. Consequently, the amount of protrusion of the bearing retaining section that may protrude from the bottom surface section of the case body is suppressed to a small level, and thus the overall length of the motor can be shortened.
Also, in the present invention, the excitation coil may be wound in a manner that the number of turns of the excitation coil becomes greater toward outside in the radial direction such that an end face of the excitation coil is inclined inwardly in the axial direction, and the recessed concave section may have a sloped surface section that is concaved inwardly in the axial direction and extends along the inclined end face of the excitation coil.
In one embodiment, each of the salient poles of the stator core may be formed from a base section that is located on the outer circumferential side of the stator core, an extended section that is to be located opposite to the driving magnet on the inner circumferential side of the stator core and a rib section that connects the base section and the extended section. The width of the base section may be wider in the circumferential direction than the width of the extended section. By using such a structure of the stator core, the configuration of excitation coil whose number of turns becomes greater in the radial direction toward the outer periphery of the stator core can be more rationally achieved.
With the structure described above, the excitation coil can be wound on the salient pole of the stator core in the amount necessary to provide its intended function without creating waste spaces in the circumferential direction, and the end face of the excitation coils become inclined in the axial direction. As a result, the recessed concave section of the case body can be inwardly concaved along the inclined end faces of the excitation coils, and spaces along the axial direction of the case body can be effectively utilized to reduce the amount of protrusion of the bearing retaining section. As a consequence, while the necessary number of turns for the excitation coil is maintained, the overall length of the motor can be shortened.
In accordance with an embodiment of the present invention, the stator core may be divided in the circumferential direction for each of the salient poles; in other words, the stator core may be formed from a plurality of divided cores that are circularly arranged in a ring shape. The excitation coil may be wound on each of the divided cores. By so doing, the coil winding work on each of the salient poles becomes simpler, and a motor with good volume efficiency as a whole and high occupancy rate of the excitation coils can be structured.
Furthermore, in accordance with an embodiment of the present invention, the case body may have two sides that interpose the stator core in the axial direction, and each of the sides may have the bottom surface section, the recessed concave section and the bearing retaining section, and each of the bearing retaining sections may retain a bearing, wherein at least a part of each of the bearings may be located more interior in the axial direction than the bottom surface section.
With the structure of described above, at least a part of each of the bearings retained at both of the two sides in the axial direction of the case body is located more inside in the axial direction than the bottom surface sections. As a result, the

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